Quarkonium production in an improved color evaporation model

DOE PAGES

Ma, Yan-Qing; Vogt, Ramona

2016-12-27

In this paper, we propose an improved version of the color evaporation model to describe heavy quarkonium production. In contrast to the traditional color evaporation model, we impose the constraint that the invariant mass of the intermediate heavy quark-antiquark pair be larger than the mass of produced quarkonium. We also introduce a momentum shift between the heavy quark-antiquark pair and the quarkonium. Finally, numerical calculations show that our model can describe the charmonium yields as well as the ratio of ψ' over J/ψ better than the traditional color evaporation model.

Resolving an ostensible inconsistency in calculating the evaporation rate of sessile drops.

PubMed

Chini, S F; Amirfazli, A

2017-05-01

This paper resolves an ostensible inconsistency in the literature in calculating the evaporation rate for sessile drops in a quiescent environment. The earlier models in the literature have shown that adapting the evaporation flux model for a suspended spherical drop to calculate the evaporation rate of a sessile drop needs a correction factor; the correction factor was shown to be a function of the drop contact angle, i.e. f(θ). However, there seemed to be a problem as none of the earlier models explicitly or implicitly mentioned the evaporation flux variations along the surface of a sessile drop. The more recent evaporation models include this variation using an electrostatic analogy, i.e. the Laplace equation (steady-state continuity) in a domain with a known boundary condition value, or known as the Dirichlet problem for Laplace's equation. The challenge is that the calculated evaporation rates using the earlier models seemed to differ from that of the recent models (note both types of models were validated in the literature by experiments). We have reinvestigated the recent models and found that the mathematical simplifications in solving the Dirichlet problem in toroidal coordinates have created the inconsistency. We also proposed a closed form approximation for f(θ) which is valid in a wide range, i.e. 8°≤θ≤131°. Using the proposed model in this study, theoretically, it was shown that the evaporation rate in the CWA (constant wetted area) mode is faster than the evaporation rate in the CCA (constant contact angle) mode for a sessile drop. Copyright © 2016 Elsevier B.V. All rights reserved.

On the Evaporation Kinetics and Phase of Laboratory and Ambient Secondary Organic Aerosol

NASA Astrophysics Data System (ADS)

Zelenyuk, A.; Vaden, T.; Imre, D. G.; Beránek, J.; Shrivastava, M.

2010-12-01

Field measurements of secondary organic aerosol (SOA) find significantly higher mass loads than predicted by models, sparking intense effort that is focused on finding additional SOA sources, but leaves many of the fundamental assumptions that are used by models unchallenged. Current air-quality models use absorptive partitioning theory assuming SOA particles are liquid droplets that form instantaneous reversible equilibrium with gas phase. Further, they ignore the effects of adsorption of spectator organic species during SOA formation on SOA properties and fate. Using an accurate and highly sensitive experimental approach for studying evaporation kinetics of size-selected single SOA particles, we characterized room-temperature evaporation kinetics of laboratory generated α-pinene SOA and ambient atmospheric SOA. The experimental setup was first tested by measuring the evaporation kinetics of single component organic particles of known vapor pressure. We show that, as expected for liquid droplets, smaller particles evaporate faster, and that these data yield the correct vapor pressure. We then study the evaporation kinetics of α-pinene SOA and find that evaporation proceeds in two stages: a fast stage, during which 50% of the particle volume evaporates in ~100 minutes, followed by a slower stage, when additional 25% evaporate in 1400 minutes, which is in sharp contrast to the ~10 minutes timescale predicted by current kinetic models. α-pinene SOA formed in the presence of “spectator” hydrophobic organic vapors like dioctyl phthalate, dioctyl sebacate, pyrene, or their mixture, were shown to adsorb noticeable amounts of these organics, forming what we term here ‘coated’ SOA particles. We show that these adsorbed coatings reduce evaporation rates of SOA particles. Moreover, aging of coated SOA particles dramatically reduces evaporation rates, and in some cases nearly stops it. For example, aging of SOA with adsorbed pyrene reduces evaporation rate to the point that only ~11% of the particle volume evaporates within 24 hrs. For all cases studied in this work, SOA evaporation behavior is size-independent and does not follow the evaporation kinetics of liquid droplets, which is in sharp contrast with model assumptions. To address the question of how closely the laboratory observations described above reflect reality in the atmosphere we characterized the evaporation kinetics of size-selected atmospheric SOA particles sampled in-situ during the recent Carbonaceous Aerosols and Radiative Effects Study (CARES) field campaign. We find that the evaporation of ambient SOA is very similar to that of coated and aged laboratory-generated α-pinene SOA. Ambient SOA particles in Sacramento, CA lose between 17% and 25% of their volume in 6 hours. Like laboratory SOA, their evaporation is size-independent and does not follow the kinetics of liquid droplets. The findings about SOA phase, evaporation rates, and the importance of spectator gases and aging - all indicate the need to reformulate the way SOA formation and evaporation are treated by models.

Isotopic modeling of the sub-cloud evaporation effect in precipitation.

PubMed

Salamalikis, V; Argiriou, A A; Dotsika, E

2016-02-15

In dry and warm environments sub-cloud evaporation influences the falling raindrops modifying their final stable isotopic content. During their descent from the cloud base towards the ground surface, through the unsaturated atmosphere, hydrometeors are subjected to evaporation whereas the kinetic fractionation results to less depleted or enriched isotopic signatures compared to the initial isotopic composition of the raindrops at cloud base. Nowadays the development of Generalized Climate Models (GCMs) that include isotopic content calculation modules are of great interest for the isotopic tracing of the global hydrological cycle. Therefore the accurate description of the underlying processes affecting stable isotopic content can improve the performance of iso-GCMs. The aim of this study is to model the sub-cloud evaporation effect using a) mixing and b) numerical isotope evaporation models. The isotope-mixing evaporation model simulates the isotopic enrichment (difference between the ground and the cloud base isotopic composition of raindrops) in terms of raindrop size, ambient temperature and relative humidity (RH) at ground level. The isotopic enrichment (Δδ) varies linearly with the evaporated raindrops mass fraction of the raindrop resulting to higher values at drier atmospheres and for smaller raindrops. The relationship between Δδ and RH is described by a 'heat capacity' model providing high correlation coefficients for both isotopes (R(2)>80%) indicating that RH is an ideal indicator of the sub-cloud evaporation effect. Vertical distribution of stable isotopes in falling raindrops is also investigated using a numerical isotope-evaporation model. Temperature and humidity dependence of the vertical isotopic variation is clearly described by the numerical isotopic model showing an increase in the isotopic values with increasing temperature and decreasing RH. At an almost saturated atmosphere (RH=95%) sub-cloud evaporation is negligible and the isotopic composition hardly changes even at high temperatures while at drier and warm conditions the enrichment of (18)Ο reaches up to 20‰, depending on the raindrop size and the initial meteorological conditions. Copyright © 2015 Elsevier B.V. All rights reserved.

Relationship between a solar drying model of red pepper and the kinetics of pure water evaporation (1)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Passamai, V.; Saravia, L.

1997-05-01

Drying of red pepper under solar radiation was investigated, and a simple model related to water evaporation was developed. Drying experiments at constant laboratory conditions were undertaken where solar radiation was simulated by a 1,000 W lamp. In this first part of the work, water evaporation under radiation is studied and laboratory experiments are presented with two objectives: to verify Penman`s model of evaporation under radiation, and to validate the laboratory experiments. Modifying Penman`s model of evaporation by introducing two drying conductances as a function of water content, allows the development of a drying model under solar radiation. In themore » second part of this paper, the model is validated by applying it to red pepper open air solar drying experiments.« less

Boundary conditions for a one-sided numerical model of evaporative instabilities in sessile drops of ethanol on heated substrates

NASA Astrophysics Data System (ADS)

Semenov, Sergey; Carle, Florian; Medale, Marc; Brutin, David

2017-12-01

The work is focused on obtaining boundary conditions for a one-sided numerical model of thermoconvective instabilities in evaporating pinned sessile droplets of ethanol on heated substrates. In the one-sided model, appropriate boundary conditions for heat and mass transfer equations are required at the droplet surface. Such boundary conditions are obtained in the present work based on a derived semiempirical theoretical formula for the total droplet's evaporation rate, and on a two-parametric nonisothermal approximation of the local evaporation flux. The main purpose of these boundary conditions is to be applied in future three-dimensional (3D) one-sided numerical models in order to save a lot of computational time and resources by solving equations only in the droplet domain. Two parameters, needed for the nonisothermal approximation of the local evaporation flux, are obtained by fitting computational results of a 2D two-sided numerical model. Such model is validated here against parabolic flight experiments and the theoretical value of the total evaporation rate. This study combines theoretical, experimental, and computational approaches in convective evaporation of sessile droplets. The influence of the gravity level on evaporation rate and contributions of different mechanisms of vapor transport (diffusion, Stefan flow, natural convection) are shown. The qualitative difference (in terms of developing thermoconvective instabilities) between steady-state and unsteady numerical approaches is demonstrated.

Factors controlling the evaporation of secondary organic aerosol from α‐pinene ozonolysis

PubMed Central

Pajunoja, Aki; Tikkanen, Olli‐Pekka; Buchholz, Angela; Faiola, Celia; Väisänen, Olli; Hao, Liqing; Kari, Eetu; Peräkylä, Otso; Garmash, Olga; Shiraiwa, Manabu; Ehn, Mikael; Lehtinen, Kari; Virtanen, Annele

2017-01-01

Abstract Secondary organic aerosols (SOA) forms a major fraction of organic aerosols in the atmosphere. Knowledge of SOA properties that affect their dynamics in the atmosphere is needed for improving climate models. By combining experimental and modeling techniques, we investigated the factors controlling SOA evaporation under different humidity conditions. Our experiments support the conclusion of particle phase diffusivity limiting the evaporation under dry conditions. Viscosity of particles at dry conditions was estimated to increase several orders of magnitude during evaporation, up to 109 Pa s. However, at atmospherically relevant relative humidity and time scales, our results show that diffusion limitations may have a minor effect on evaporation of the studied α‐pinene SOA particles. Based on previous studies and our model simulations, we suggest that, in warm environments dominated by biogenic emissions, the major uncertainty in models describing the SOA particle evaporation is related to the volatility of SOA constituents. PMID:28503004

Analytical Model for Diffusive Evaporation of Sessile Droplets Coupled with Interfacial Cooling Effect.

PubMed

Nguyen, Tuan A H; Biggs, Simon R; Nguyen, Anh V

2018-05-30

Current analytical models for sessile droplet evaporation do not consider the nonuniform temperature field within the droplet and can overpredict the evaporation by 20%. This deviation can be attributed to a significant temperature drop due to the release of the latent heat of evaporation along the air-liquid interface. We report, for the first time, an analytical solution of the sessile droplet evaporation coupled with this interfacial cooling effect. The two-way coupling model of the quasi-steady thermal diffusion within the droplet and the quasi-steady diffusion-controlled droplet evaporation is conveniently solved in the toroidal coordinate system by applying the method of separation of variables. Our new analytical model for the coupled vapor concentration and temperature fields is in the closed form and is applicable for a full range of spherical-cap shape droplets of different contact angles and types of fluids. Our analytical results are uniquely quantified by a dimensionless evaporative cooling number E o whose magnitude is determined only by the thermophysical properties of the liquid and the atmosphere. Accordingly, the larger the magnitude of E o , the more significant the effect of the evaporative cooling, which results in stronger suppression on the evaporation rate. The classical isothermal model is recovered if the temperature gradient along the air-liquid interface is negligible ( E o = 0). For substrates with very high thermal conductivities (isothermal substrates), our analytical model predicts a reversal of temperature gradient along the droplet-free surface at a contact angle of 119°. Our findings pose interesting challenges but also guidance for experimental investigations.

Comparison of techniques for estimating annual lake evaporation using climatological data

USGS Publications Warehouse

Andersen, M.E.; Jobson, H.E.

1982-01-01

Mean annual evaporation estimates were determined for 30 lakes by use of a numerical model (Morton, 1979) and by use of an evaporation map prepared by the U.S. Weather Service (Kohler et al., 1959). These estimates were compared to the reported value of evaporation determined from measurements on each lake. Various lengths of observation and methods of measurement were used among the 30 lakes. The evaporation map provides annual evaporation estimates which are more consistent with observations than those determined by use of the numerical model. The map cannot provide monthly estimates, however, and is only available for the contiguous United States. The numerical model can provide monthly estimates for shallow lakes and is based on monthly observations of temperature, humidity, and sunshine duration.

Evaluation of evaporation coefficient for micro-droplets exposed to low pressure: A semi-analytical approach

NASA Astrophysics Data System (ADS)

Chakraborty, Prodyut R.; Hiremath, Kirankumar R.; Sharma, Manvendra

2017-02-01

Evaporation rate of water is strongly influenced by energy barrier due to molecular collision and heat transfer limitations. The evaporation coefficient, defined as the ratio of experimentally measured evaporation rate to that maximum possible theoretical limit, varies over a conflicting three orders of magnitude. In the present work, a semi-analytical transient heat diffusion model of droplet evaporation is developed considering the effect of change in droplet size due to evaporation from its surface, when the droplet is injected into vacuum. Negligible effect of droplet size reduction due to evaporation on cooling rate is found to be true. However, the evaporation coefficient is found to approach theoretical limit of unity, when the droplet radius is less than that of mean free path of vapor molecules on droplet surface contrary to the reported theoretical predictions. Evaporation coefficient was found to reduce rapidly when the droplet under consideration has a radius larger than the mean free path of evaporating molecules, confirming the molecular collision barrier to evaporation rate. The trend of change in evaporation coefficient with increasing droplet size predicted by the proposed model will facilitate obtaining functional relation of evaporation coefficient with droplet size, and can be used for benchmarking the interaction between multiple droplets during evaporation in vacuum.

Using Historical Precipitation, Temperature, and Runoff Observations to Evaluate Evaporation Formulations in Land Surface Models

NASA Technical Reports Server (NTRS)

Koster, Randal D.; Mahanama, P. P.

2012-01-01

Key to translating soil moisture memory into subseasonal precipitation and air temperature forecast skill is a realistic treatment of evaporation in the forecast system used - in particular, a realistic treatment of how evaporation responds to variations in soil moisture. The inherent soil moisture-evaporation relationships used in today's land surface models (LSMs), however, arguably reflect little more than guesswork given the lack of evaporation and soil moisture data at the spatial scales represented by regional and global models. Here we present a new approach for evaluating this critical aspect of LSMs. Seasonally averaged precipitation is used as a proxy for seasonally-averaged soil moisture, and seasonally-averaged air temperature is used as a proxy for seasonally-averaged evaporation (e.g., more evaporative cooling leads to cooler temperatures) the relationship between historical precipitation and temperature measurements accordingly mimics in certain important ways nature's relationship between soil moisture and evaporation. Additional information on the relationship is gleaned from joint analysis of precipitation and streamflow measurements. An experimental framework that utilizes these ideas to guide the development of an improved soil moisture-evaporation relationship is described and demonstrated.

Thermal Management Optimization of a Thermoelectric-Integrated Methanol Evaporator Using a Compact CFD Modeling Approach

NASA Astrophysics Data System (ADS)

Gao, Xin; Chen, Min; Snyder, G. Jeffrey; Andreasen, Søren Juhl; Kær, Søren Knudsen

2013-07-01

To better manage the magnitude and direction of the heat flux in an exchanger-based methanol evaporator of a fuel cell system, thermoelectric (TE) modules can be deployed as TE heat flux regulators (TERs). The performance of the TE-integrated evaporator is strongly influenced by its heat exchange structure. The structure transfers the fuel cell exhaust heat to the evaporation chamber to evaporate the methanol, where TE modules are installed in between to facilitate the heat regulation. In this work, firstly, a numerical study is conducted to determine the working currents and working modes of the TERs under the system working condition fluctuations and during the system cold start. A three-dimensional evaporator model is generated in ANSYS FLUENT® by combining a compact TE model with various heat exchange structure geometries. The compact TE model can dramatically improve the computational efficiency, and uses a different material property acquisition method based on module manufacturers' datasheets. Secondly, a simulation study is carried out on the novel evaporator to minimize its thermal resistance and to assess the evaporator pressure drop. The factors studied include the type of fins in the heat exchange structure, the thickness of the fins, the axial conduction penalty, etc. Results show that the TE-integrated evaporator can work more efficiently and smoothly during both load fluctuations and system cold start, offering superior performance.

Analysis of a resistance-energy balance method for estimating daily evaporation from wheat plots using one-time-of-day infrared temperature observations

NASA Technical Reports Server (NTRS)

Choudhury, B. J.; Idso, S. B.; Reginato, R. J.

1986-01-01

Accurate estimates of evaporation over field-scale or larger areas are needed in hydrologic studies, irrigation scheduling, and meteorology. Remotely sensed surface temperature might be used in a model to calculate evaporation. A resistance-energy balance model, which combines an energy balance equation, the Penman-Monteith (1981) evaporation equation, and van den Honert's (1948) equation for water extraction by plant roots, is analyzed for estimating daily evaporation from wheat using postnoon canopy temperature measurements. Additional data requirements are half-hourly averages of solar radiation, air and dew point temperatures, and wind speed, along with reasonable estimates of canopy emissivity, albedo, height, and leaf area index. Evaporation fluxes were measured in the field by precision weighing lysimeters for well-watered and water-stressed wheat. Errors in computed daily evaporation were generally less than 10 percent, while errors in cumulative evaporation for 10 clear sky days were less than 5 percent for both well-watered and water-stressed wheat. Some results from sensitivity analysis of the model are also given.

Remotely monitoring evaporation rate and soil water status using thermal imaging and "three-temperatures model (3T Model)" under field-scale conditions.

PubMed

Qiu, Guo Yu; Zhao, Ming

2010-03-01

Remote monitoring of soil evaporation and soil water status is necessary for water resource and environment management. Ground based remote sensing can be the bridge between satellite remote sensing and ground-based point measurement. The primary object of this study is to provide an algorithm to estimate evaporation and soil water status by remote sensing and to verify its accuracy. Observations were carried out in a flat field with varied soil water content. High-resolution thermal images were taken with a thermal camera; soil evaporation was measured with a weighing lysimeter; weather data were recorded at a nearby meteorological station. Based on the thermal imaging and the three-temperatures model (3T model), we developed an algorithm to estimate soil evaporation and soil water status. The required parameters of the proposed method were soil surface temperature, air temperature, and solar radiation. By using the proposed method, daily variation in soil evaporation was estimated. Meanwhile, soil water status was remotely monitored by using the soil evaporation transfer coefficient. Results showed that the daily variation trends of measured and estimated evaporation agreed with each other, with a regression line of y = 0.92x and coefficient of determination R(2) = 0.69. The simplicity of the proposed method makes the 3T model a potentially valuable tool for remote sensing.

Improving terrestrial evaporation estimates over continental Australia through assimilation of SMOS soil moisture

NASA Astrophysics Data System (ADS)

Martens, B.; Miralles, D.; Lievens, H.; Fernández-Prieto, D.; Verhoest, N. E. C.

2016-06-01

Terrestrial evaporation is an essential variable in the climate system that links the water, energy and carbon cycles over land. Despite this crucial importance, it remains one of the most uncertain components of the hydrological cycle, mainly due to known difficulties to model the constraints imposed by land water availability on terrestrial evaporation. The main objective of this study is to assimilate satellite soil moisture observations from the Soil Moisture and Ocean Salinity (SMOS) mission into an existing evaporation model. Our over-arching goal is to find an optimal use of satellite soil moisture that can help to improve our understanding of evaporation at continental scales. To this end, the Global Land Evaporation Amsterdam Model (GLEAM) is used to simulate evaporation fields over continental Australia for the period September 2010-December 2013. SMOS soil moisture observations are assimilated using a Newtonian Nudging algorithm in a series of experiments. Model estimates of surface soil moisture and evaporation are validated against soil moisture probe and eddy-covariance measurements, respectively. Finally, an analogous experiment in which Advanced Microwave Scanning Radiometer (AMSR-E) soil moisture is assimilated (instead of SMOS) allows to perform a relative assessment of the quality of both satellite soil moisture products. Results indicate that the modelled soil moisture from GLEAM can be improved through the assimilation of SMOS soil moisture: the average correlation coefficient between in situ measurements and the modelled soil moisture over the complete sample of stations increased from 0.68 to 0.71 and a statistical significant increase in the correlations is achieved for 17 out of the 25 individual stations. Our results also suggest a higher accuracy of the ascending SMOS data compared to the descending data, and overall higher quality of SMOS compared to AMSR-E retrievals over Australia. On the other hand, the effect of soil moisture data assimilation on the evaporation fields is very mild, and difficult to assess due to the limited availability of eddy-covariance data. Nonetheless, our continental-scale simulations indicate that the assimilation of soil moisture can have a substantial impact on the estimated dynamics of evaporation in water-limited regimes. Progressing towards our goal of using satellite soil moisture to increase understanding of global land evaporation, future research will focus on the global application of this methodology and the consideration of multiple evaporation models.

Dynamics of contact line depinning during droplet evaporation based on thermodynamics.

PubMed

Yu, Dong In; Kwak, Ho Jae; Doh, Seung Woo; Ahn, Ho Seon; Park, Hyun Sun; Kiyofumi, Moriyama; Kim, Moo Hwan

2015-02-17

For several decades, evaporation phenomena have been intensively investigated for a broad range of applications. However, the dynamics of contact line depinning during droplet evaporation has only been inductively inferred on the basis of experimental data and remains unclear. This study focuses on the dynamics of contact line depinning during droplet evaporation based on thermodynamics. Considering the decrease in the Gibbs free energy of a system with different evaporation modes, a theoretical model was developed to estimate the receding contact angle during contact line depinning as a function of surface conditions. Comparison of experimentally measured and theoretically modeled receding contact angles indicated that the dynamics of contact line depinning during droplet evaporation was caused by the most favorable thermodynamic process encountered during constant contact radius (CCR mode) and constant contact angle (CCA mode) evaporation to rapidly reach an equilibrium state during droplet evaporation.

Evaporation thermal anslysis of Swallow-tailed Axial-grooved Heat Pipe

NASA Astrophysics Data System (ADS)

Zhang, Renping

2018-03-01

A detailed mathematical model that describes evaporating characteristics through thin liquid film at the evaporator section of swallow-tailed axial-grooved heat pipe was developed. The numerical simulation results about thin film profile, liquid-vapour interface temperature, evaporating rate and heat flux at the evaporating thin film region were given by the current investigation and the effect of superheat on the liquid-vapour interface temperature, evaporating mass rate and heat flux was discussed. Meanwhile, thermal model of the meniscus region at the evaporating section was developed to calculate the rate of heat transfer. The ratio of the heat conduction in the evaporating thin liquid film region and total heat rate were also discussed. It is indicated that the thickness of thin liquid film rises in a nearly linear fashion. The disjoining pressure can be neglected with increasing the liquid film thickness, tends to be negligibly small. The heat transfer rate at the intrinsic meniscus cannot be compared with that of the evaporating liquid film region.

Measurements of evaporation from a mine void lake and testing of modelling approaches

NASA Astrophysics Data System (ADS)

McJannet, David; Hawdon, Aaron; Van Niel, Tom; Boadle, Dave; Baker, Brett; Trefry, Mike; Rea, Iain

2017-12-01

Pit lakes often form in the void that remains after open cut mining operations cease. As pit lakes fill, hydrological and geochemical processes interact and these need to be understood for appropriate management actions to be implemented. Evaporation is important in the evolution of pit lakes as it acts to concentrate various constituents, controls water level and changes the thermal characteristics of the water body. Despite its importance, evaporation from pit lakes is poorly understood. To address this, we used an automated floating evaporation pan and undertook measurements at a pit lake over a 12 month period. We also developed a new procedure for correcting floating pan evaporation estimates to lake evaporation estimates based on surface temperature differences. Total annual evaporation was 2690 mm and reflected the strong radiation inputs, high temperatures and low humidity experienced in this region. Measurements were used to test the performance of evaporation estimates derived using both pan coefficient and aerodynamic modelling techniques. Daily and monthly evaporation estimates were poorly reproduced using pan coefficient techniques and their use is not recommended for such environments. Aerodynamic modelling was undertaken using a range of input datasets that may be available to those who manage pit lake systems. Excellent model performance was achieved using over-water or local over-land meteorological observations, particularly when the sheltering effects of the pit were considered. Model performance was reduced when off-site data were utilised and differences between local and off-site vapor pressure and wind speed were found to be the major cause.

Daily pan evaporation modelling using a neuro-fuzzy computing technique

NASA Astrophysics Data System (ADS)

Kişi, Özgür

2006-10-01

SummaryEvaporation, as a major component of the hydrologic cycle, is important in water resources development and management. This paper investigates the abilities of neuro-fuzzy (NF) technique to improve the accuracy of daily evaporation estimation. Five different NF models comprising various combinations of daily climatic variables, that is, air temperature, solar radiation, wind speed, pressure and humidity are developed to evaluate degree of effect of each of these variables on evaporation. A comparison is made between the estimates provided by the NF model and the artificial neural networks (ANNs). The Stephens-Stewart (SS) method is also considered for the comparison. Various statistic measures are used to evaluate the performance of the models. Based on the comparisons, it was found that the NF computing technique could be employed successfully in modelling evaporation process from the available climatic data. The ANN also found to perform better than the SS method.

An analytical model accounting for tip shape evolution during atom probe analysis of heterogeneous materials.

PubMed

Rolland, N; Larson, D J; Geiser, B P; Duguay, S; Vurpillot, F; Blavette, D

2015-12-01

An analytical model describing the field evaporation dynamics of a tip made of a thin layer deposited on a substrate is presented in this paper. The difference in evaporation field between the materials is taken into account in this approach in which the tip shape is modeled at a mesoscopic scale. It was found that the non-existence of sharp edge on the surface is a sufficient condition to derive the morphological evolution during successive evaporation of the layers. This modeling gives an instantaneous and smooth analytical representation of the surface that shows good agreement with finite difference simulations results, and a specific regime of evaporation was highlighted when the substrate is a low evaporation field phase. In addition, the model makes it possible to calculate theoretically the tip analyzed volume, potentially opening up new horizons for atom probe tomographic reconstruction. Copyright © 2015 Elsevier B.V. All rights reserved.

Detailed finite element method modeling of evaporating multi-component droplets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Diddens, Christian, E-mail: C.Diddens@tue.nl

The evaporation of sessile multi-component droplets is modeled with an axisymmetic finite element method. The model comprises the coupled processes of mixture evaporation, multi-component flow with composition-dependent fluid properties and thermal effects. Based on representative examples of water–glycerol and water–ethanol droplets, regular and chaotic examples of solutal Marangoni flows are discussed. Furthermore, the relevance of the substrate thickness for the evaporative cooling of volatile binary mixture droplets is pointed out. It is shown how the evaporation of the more volatile component can drastically decrease the interface temperature, so that ambient vapor of the less volatile component condenses on the droplet.more » Finally, results of this model are compared with corresponding results of a lubrication theory model, showing that the application of lubrication theory can cause considerable errors even for moderate contact angles of 40°. - Graphical abstract:.« less

Planetary population synthesis coupled with atmospheric escape: a statistical view of evaporation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jin, Sheng; Ji, Jianghui; Mordasini, Christoph

2014-11-01

We apply hydrodynamic evaporation models to different synthetic planet populations that were obtained from a planet formation code based on the core-accretion paradigm. We investigated the evolution of the planet populations using several evaporation models, which are distinguished by the driving force of the escape flow (X-ray or EUV), the heating efficiency in energy-limited evaporation regimes, or both. Although the mass distribution of the planet populations is barely affected by evaporation, the radius distribution clearly shows a break at approximately 2 R {sub ⊕}. We find that evaporation can lead to a bimodal distribution of planetary sizes and to anmore » 'evaporation valley' running diagonally downward in the orbital distance—planetary radius plane, separating bare cores from low-mass planets that have kept some primordial H/He. Furthermore, this bimodal distribution is related to the initial characteristics of the planetary populations because low-mass planetary cores can only accrete small primordial H/He envelopes and their envelope masses are proportional to their core masses. We also find that the population-wide effect of evaporation is not sensitive to the heating efficiency of energy-limited description. However, in two extreme cases, namely without evaporation or with a 100% heating efficiency in an evaporation model, the final size distributions show significant differences; these two scenarios can be ruled out from the size distribution of Kepler candidates.« less

Physically based approaches incorporating evaporation for early warning predictions of rainfall-induced landslides

NASA Astrophysics Data System (ADS)

Reder, Alfredo; Rianna, Guido; Pagano, Luca

2018-02-01

In the field of rainfall-induced landslides on sloping covers, models for early warning predictions require an adequate trade-off between two aspects: prediction accuracy and timeliness. When a cover's initial hydrological state is a determining factor in triggering landslides, taking evaporative losses into account (or not) could significantly affect both aspects. This study evaluates the performance of three physically based predictive models, converting precipitation and evaporative fluxes into hydrological variables useful in assessing slope safety conditions. Two of the models incorporate evaporation, with one representing evaporation as both a boundary and internal phenomenon, and the other only a boundary phenomenon. The third model totally disregards evaporation. Model performances are assessed by analysing a well-documented case study involving a 2 m thick sloping volcanic cover. The large amount of monitoring data collected for the soil involved in the case study, reconstituted in a suitably equipped lysimeter, makes it possible to propose procedures for calibrating and validating the parameters of the models. All predictions indicate a hydrological singularity at the landslide time (alarm). A comparison of the models' predictions also indicates that the greater the complexity and completeness of the model, the lower the number of predicted hydrological singularities when no landslides occur (false alarms).

Parameter prediction based on Improved Process neural network and ARMA error compensation in Evaporation Process

NASA Astrophysics Data System (ADS)

Qian, Xiaoshan

2018-01-01

The traditional model of evaporation process parameters have continuity and cumulative characteristics of the prediction error larger issues, based on the basis of the process proposed an adaptive particle swarm neural network forecasting method parameters established on the autoregressive moving average (ARMA) error correction procedure compensated prediction model to predict the results of the neural network to improve prediction accuracy. Taking a alumina plant evaporation process to analyze production data validation, and compared with the traditional model, the new model prediction accuracy greatly improved, can be used to predict the dynamic process of evaporation of sodium aluminate solution components.

Study of the effect of wind speed on evaporation from soil through integrated modeling of the atmospheric boundary layer and shallow subsurface.

PubMed

Davarzani, Hossein; Smits, Kathleen; Tolene, Ryan M; Illangasekare, Tissa

2014-01-01

In an effort to develop methods based on integrating the subsurface to the atmospheric boundary layer to estimate evaporation, we developed a model based on the coupling of Navier-Stokes free flow and Darcy flow in porous medium. The model was tested using experimental data to study the effect of wind speed on evaporation. The model consists of the coupled equations of mass conservation for two-phase flow in porous medium with single-phase flow in the free-flow domain under nonisothermal, nonequilibrium phase change conditions. In this model, the evaporation rate and soil surface temperature and relative humidity at the interface come directly from the integrated model output. To experimentally validate numerical results, we developed a unique test system consisting of a wind tunnel interfaced with a soil tank instrumented with a network of sensors to measure soil-water variables. Results demonstrated that, by using this coupling approach, it is possible to predict the different stages of the drying process with good accuracy. Increasing the wind speed increases the first stage evaporation rate and decreases the transition time between two evaporative stages (soil water flow to vapor diffusion controlled) at low velocity values; then, at high wind speeds the evaporation rate becomes less dependent on the wind speed. On the contrary, the impact of wind speed on second stage evaporation (diffusion-dominant stage) is not significant. We found that the thermal and solute dispersion in free-flow systems has a significant influence on drying processes from porous media and should be taken into account.

Study of the effect of wind speed on evaporation from soil through integrated modeling of the atmospheric boundary layer and shallow subsurface

PubMed Central

Davarzani, Hossein; Smits, Kathleen; Tolene, Ryan M; Illangasekare, Tissa

2014-01-01

In an effort to develop methods based on integrating the subsurface to the atmospheric boundary layer to estimate evaporation, we developed a model based on the coupling of Navier-Stokes free flow and Darcy flow in porous medium. The model was tested using experimental data to study the effect of wind speed on evaporation. The model consists of the coupled equations of mass conservation for two-phase flow in porous medium with single-phase flow in the free-flow domain under nonisothermal, nonequilibrium phase change conditions. In this model, the evaporation rate and soil surface temperature and relative humidity at the interface come directly from the integrated model output. To experimentally validate numerical results, we developed a unique test system consisting of a wind tunnel interfaced with a soil tank instrumented with a network of sensors to measure soil-water variables. Results demonstrated that, by using this coupling approach, it is possible to predict the different stages of the drying process with good accuracy. Increasing the wind speed increases the first stage evaporation rate and decreases the transition time between two evaporative stages (soil water flow to vapor diffusion controlled) at low velocity values; then, at high wind speeds the evaporation rate becomes less dependent on the wind speed. On the contrary, the impact of wind speed on second stage evaporation (diffusion-dominant stage) is not significant. We found that the thermal and solute dispersion in free-flow systems has a significant influence on drying processes from porous media and should be taken into account. PMID:25309005

The effects of surface evaporation parameterizations on climate sensitivity to solar constant variations

NASA Technical Reports Server (NTRS)

Chou, S.-H.; Curran, R. J.; Ohring, G.

1981-01-01

The effects of two different evaporation parameterizations on the sensitivity of simulated climate to solar constant variations are investigated by using a zonally averaged climate model. One parameterization is a nonlinear formulation in which the evaporation is nonlinearly proportional to the sensible heat flux, with the Bowen ratio determined by the predicted vertical temperature and humidity gradients near the earth's surface (model A). The other is the formulation of Saltzman (1968) with the evaporation linearly proportional to the sensible heat flux (model B). The computed climates of models A and B are in good agreement except for the energy partition between sensible and latent heat at the earth's surface. The difference in evaporation parameterizations causes a difference in the response of temperature lapse rate to solar constant variations and a difference in the sensitivity of longwave radiation to surface temperature which leads to a smaller sensitivity of surface temperature to solar constant variations in model A than in model B. The results of model A are qualitatively in agreement with those of the general circulation model calculations of Wetherald and Manabe (1975).

40 CFR 86.1811-09 - Emission standards for light-duty vehicles, light-duty trucks and medium-duty passenger vehicles.

Code of Federal Regulations, 2014 CFR

2014-07-01

... Diurnal Plus Hot Soak Evaporative Emission Standards: Non-Gasoline Portion of Multi-Fueled Vehicles Model...) Evaporative emission in-use standards. (1) For LDVs and LLDTs certified prior to the 2012 model year, the Tier... the 2011 model year must meet the Tier 2 LDV/LLDT evaporative emission standards (Table S04-3) in-use...

Evaporation in Capillary Porous Media at the Perfect Piston-Like Invasion Limit: Evidence of Nonlocal Equilibrium Effects

NASA Astrophysics Data System (ADS)

Attari Moghaddam, Alireza; Prat, Marc; Tsotsas, Evangelos; Kharaghani, Abdolreza

2017-12-01

The classical continuum modeling of evaporation in capillary porous media is revisited from pore network simulations of the evaporation process. The computed moisture diffusivity is characterized by a minimum corresponding to the transition between liquid and vapor transport mechanisms confirming previous interpretations. Also the study suggests an explanation for the scattering generally observed in the moisture diffusivity obtained from experimental data. The pore network simulations indicate a noticeable nonlocal equilibrium effect leading to a new interpretation of the vapor pressure-saturation relationship classically introduced to obtain the one-equation continuum model of evaporation. The latter should not be understood as a desorption isotherm as classically considered but rather as a signature of a nonlocal equilibrium effect. The main outcome of this study is therefore that nonlocal equilibrium two-equation model must be considered for improving the continuum modeling of evaporation.

Analysis of the convective evaporation of nondilute clusters of drops

NASA Technical Reports Server (NTRS)

Bellan, J.; Harstad, K.

1987-01-01

The penetration distance of an outer flow into a drop cluster volume is the critical, evaporation mode-controlling parameter in the present model for nondilute drop clusters' convective evaporation. The model is found to perform well for such low penetration distances as those obtained for dense clusters in hot environments and low relative velocities between the outer gases and the cluster. For large penetration distances, however, the predictive power of the model deteriorates; in addition, the evaporation time is found to be a weak function of the initial relative velocity and a strong function of the initial drop temperature. The results generally show that the interior drop temperature was transient throughout the drop lifetime, although temperature nonuniformities persisted up to the first third of the total evaporation time at most.

Modeling Evaporation of Drops of Different Kerosenes

NASA Technical Reports Server (NTRS)

Bellan, Josette; Harstad, Kenneth

2007-01-01

A mathematical model describes the evaporation of drops of a hydrocarbon liquid composed of as many as hundreds of chemical species. The model is intended especially for application to any of several types of kerosenes commonly used as fuels. The concept of continuous thermodynamics, according to which the chemical composition of the evaporating multicomponent liquid is described by use of a probability distribution function (PDF). However, the present model is more generally applicable than is its immediate predecessor.

Evaporation and Accompanying Isotopic Fractionation of Sulfur from FE-S Melt During Shock Wave Heating

NASA Technical Reports Server (NTRS)

Tachibana, S.; Huss, G. R.; Miura, H.; Nakamoto, T.

2004-01-01

Chondrules probably formed by melting and subsequent cooling of solid precursors. Evaporation during chondrule melting may have resulted in depletion of volatile elements in chondrules. It is known that kinetic evaporation, especially evaporation from a melt, often leads to enrichment of heavy isotopes in an evaporation residue. However, no evidence for a large degree of heavy-isotope enrichment has been reported in chondrules for K, Mg, Si, and Fe (as FeO). The lack of isotopic fractionation has also been found for sulfur in troilites (FeS) within Bishunpur (LL3.1) and Semarkona (LL3.0) chondrules by an ion microprobe study. The largest fractionation, found in only one grain, was 2.7 +/- 1.4 %/amu, while all other troilite grains showed isotopic fractionations of <1 %/amu. The suppressed isotopic fractionation has been interpreted as results of (i) rapid heating of precursors at temperatures below the silicate solidus and (ii) diffusion-controlled evaporation through a surrounding silicate melt at temperatures above the silicate solidus. The kinetic evaporation model suggests that a rapid heating rate of >10(exp 4)-10(exp 6) K/h for a temperature range of 1000-1300 C is required to explain observed isotopic fractionations. Such a rapid heating rate seems to be difficult to be achieved in the X-wind model, but can be achieved in shock wave heating models. In this study, we have applied the sulfur evaporation model to the shock wave heating conditions of to evaluate evaporation of sulfur and accompanying isotopic fractionation during shock wave heating at temperatures below the silicate solidus.

Estimation of open water evaporation using land-based meteorological data

NASA Astrophysics Data System (ADS)

Li, Fawen; Zhao, Yong

2017-10-01

Water surface evaporation is an important process in the hydrologic and energy cycles. Accurate simulation of water evaporation is important for the evaluation of water resources. In this paper, using meteorological data from the Aixinzhuang reservoir, the main factors affecting water surface evaporation were determined by the principal component analysis method. To illustrate the influence of these factors on water surface evaporation, the paper first adopted the Dalton model to simulate water surface evaporation. The results showed that the simulation precision was poor for the peak value zone. To improve the model simulation's precision, a modified Dalton model considering relative humidity was proposed. The results show that the 10-day average relative error is 17.2%, assessed as qualified; the monthly average relative error is 12.5%, assessed as qualified; and the yearly average relative error is 3.4%, assessed as excellent. To validate its applicability, the meteorological data of Kuancheng station in the Luan River basin were selected to test the modified model. The results show that the 10-day average relative error is 15.4%, assessed as qualified; the monthly average relative error is 13.3%, assessed as qualified; and the yearly average relative error is 6.0%, assessed as good. These results showed that the modified model had good applicability and versatility. The research results can provide technical support for the calculation of water surface evaporation in northern China or similar regions.

GLEAM version 3: Global Land Evaporation Datasets and Model

NASA Astrophysics Data System (ADS)

Martens, B.; Miralles, D. G.; Lievens, H.; van der Schalie, R.; de Jeu, R.; Fernandez-Prieto, D.; Verhoest, N.

2015-12-01

Terrestrial evaporation links energy, water and carbon cycles over land and is therefore a key variable of the climate system. However, the global-scale magnitude and variability of the flux, and the sensitivity of the underlying physical process to changes in environmental factors, are still poorly understood due to limitations in in situ measurements. As a result, several methods have risen to estimate global patterns of land evaporation from satellite observations. However, these algorithms generally differ in their approach to model evaporation, resulting in large differences in their estimates. One of these methods is GLEAM, the Global Land Evaporation: the Amsterdam Methodology. GLEAM estimates terrestrial evaporation based on daily satellite observations of meteorological variables, vegetation characteristics and soil moisture. Since the publication of the first version of the algorithm (2011), the model has been widely applied to analyse trends in the water cycle and land-atmospheric feedbacks during extreme hydrometeorological events. A third version of the GLEAM global datasets is foreseen by the end of 2015. Given the relevance of having a continuous and reliable record of global-scale evaporation estimates for climate and hydrological research, the establishment of an online data portal to host these data to the public is also foreseen. In this new release of the GLEAM datasets, different components of the model have been updated, with the most significant change being the revision of the data assimilation algorithm. In this presentation, we will highlight the most important changes of the methodology and present three new GLEAM datasets and their validation against in situ observations and an alternative dataset of terrestrial evaporation (ERA-Land). Results of the validation exercise indicate that the magnitude and the spatiotemporal variability of the modelled evaporation agree reasonably well with the estimates of ERA-Land and the in situ observations. It is also shown that the performance of the revised model is higher compared to the original one.

GLACE: The Global Land-Atmosphere Coupling Experiment Part 2: Analysis

NASA Technical Reports Server (NTRS)

Guo, Zhichang; Dirmeyer, Paul A.; Koster, Randal D.; Bonan, Gordon; Chan, Edmond; Cox, Peter; Gordon, C. T.; Kanae, Shinjiro; Kowalczyk, Eva; Lawrence, David

2005-01-01

The twelve weather and climate models participating in the Global Land-Atmosphere Coupling Experiment (GLACE) show both a wide variation in the strength of land-atmosphere coupling and some intriguing commonalities. In this paper, we address the causes of variations in coupling strength - both the geographic variations within a given model and the model-to-model differences. The ability of soil moisture to affect precipitation is examined in two stages, namely, the ability of the soil moisture to affect evaporation, and the ability of evaporation to affect precipitation. Most of the differences between the models and within a given model are found to be associated with the first stage - an evaporation rate that varies strongly and consistently with soil moisture tends to lead to a higher coupling strength. The first stage differences reflect identifiable differences in model parameterization and model climate. Intermodel differences in the evaporation-precipitation connection, however, also play a key role.

Modeling evaporation using models that are not boundary-layer regulated.

PubMed

Fingas, Merv F

2004-02-27

Experimentation shows that oil is not strictly air boundary-layer regulated. The fact that oil evaporation is not strictly boundary-layer regulated implies that a simplistic evaporation equation suffices to describe the process. The following processes do not require consideration: wind velocity, turbulence level, area, thickness, and scale size. The factors important to evaporation are time and temperature. The equation parameters found experimentally for the evaporation of oils can be related to commonly available distillation data for the oil. Specifically, it has been found that the distillation percentage at 180 degrees C correlates well with the equation parameters. Relationships have been developed enabling calculation of evaporation equations directly from distillation data: percentage evaporated = 0.165 (%D)ln(t) where %D is the percentage (by weight) distilled at 180 degrees C and t is the time in minutes. These equations were combined with the equations generated to account for the temperature variations: percentage evaporated = [0.165(%D)+0.045(T-15))ln(t) The results have application in oil spill prediction and modeling. The simple equations can be applied using readily available data such as sea temperature and time. Old equations required oil vapour pressure, specialized distillation data, spill area, wind speed, and mass transfer coefficients, all of which are difficult to obtain.

Mapping energetics of atom probe evaporation events through first principles calculations.

PubMed

Peralta, Joaquín; Broderick, Scott R; Rajan, Krishna

2013-09-01

The purpose of this work is to use atomistic modeling to determine accurate inputs into the atom probe tomography (APT) reconstruction process. One of these inputs is evaporation field; however, a challenge occurs because single ions and dimers have different evaporation fields. We have calculated the evaporation field of Al and Sc ions and Al-Al and Al-Sc dimers from an L1₂-Al₃Sc surface using ab initio calculations and with a high electric field applied to the surface. The evaporation field is defined as the electric field at which the energy barrier size is calculated as zero, corresponding to the minimum field that atoms from the surface can break their bonds and evaporate from the surface. The evaporation field of the surface atoms are ranked from least to greatest as: Al-Al dimer, Al ion, Sc ion, and Al-Sc dimer. The first principles results were compared with experimental data in the form of an ion evaporation map, which maps multi-ion evaporations. From the ion evaporation map of L1₂-Al₃Sc, we extract relative evaporation fields and identify that an Al-Al dimer has a lower evaporation field than an Al-Sc dimer. Additionally, comparatively an Al-Al surface dimer is more likely to evaporate as a dimer, while an Al-Sc surface dimer is more likely to evaporate as single ions. These conclusions from the experiment agree with the ab initio calculations, validating the use of this approach for modeling APT energetics. Copyright © 2013 Elsevier B.V. All rights reserved.

Thermal management of metallic surfaces: evaporation of sessile water droplets on polished and patterned stainless steel

NASA Astrophysics Data System (ADS)

Czerwiec, T.; Tsareva, S.; Andrieux, A.; Bortolini, G. A.; Bolzan, P. H.; Castanet, G.; Gradeck, M.; Marcos, G.

2017-10-01

This communication focus on the evaporation of sessile water droplets on different states of austenitic stainless steel surfaces: mirror polished, mirror polished and aged and patterned by sputtering. The evolution of the contact angle and of the droplet diameter is presented as a function of time at room temperature. For all the surface states, a constant diameter regime (CCR) is observed. An important aging effect on the contact angle is measured on polished surfaces due to atmospheric contamination. The experimental observations are compared to a quasi-static evaporation model assuming spherical caps. The evolution of the droplet volume as a function of time is almost linear with the evaporation time for all the observed surfaces. This is in accordance with the model prediction for the CCR mode for small initial contact angles. In our experiments, the evaporation time is found to be linearly dependent on the initial contact angle. This dependence is not correctly described by the evaporation model

Start-up Characteristics of Swallow-tailed Axial-grooved Heat Pipe under the conditions of Multiple Heat Sources

NASA Astrophysics Data System (ADS)

Zhang, Renping

2017-12-01

A mathematical model was developed for predicting start-up characteristics of Swallow-tailed Axial-grooved Heat Pipe under the conditions of Multiple Heat Sources. The effects of heat capacitance of heat source, liquid-vapour interfacial evaporation-condensation heat transfer, shear stress at the interface was considered in current model. The interfacial evaporating mass flow rate is based on the kinetic analysis. Time variations of evaporating mass rate, wall temperature and liquid velocity are studied from the start-up to steady state. The calculated results show that wall temperature demonstrates step transition at the junction between the heat source and non-existent heat source on the evaporator. The liquid velocity changes drastically at the evaporator section, however, it has slight variation at the evaporator section without heat source. When the effect of heat source is ignored, the numerical temperature demonstrates a quicker response. With the consideration of capacitance of the heat source, the data obtained from the proposed model agree well with the experimental results.

Simulation of lake ice and its effect on the late-Pleistocene evaporation rate of Lake Lahontan

USGS Publications Warehouse

Hostetler, S.W.

1991-01-01

A model of lake ice was coupled with a model of lake temperature and evaporation to assess the possible effect of ice cover on the late-Pleistocene evaporation rate of Lake Lahontan. The simulations were done using a data set based on proxy temperature indicators and features of the simulated late-Pleistocene atmospheric circulation over western North America. When a data set based on a mean-annual air temperature of 3?? C (7?? C colder than present) and reduced solar radiation from jet-stream induced cloud cover was used as input to the model, ice cover lasting ??? 4 months was simulated. Simulated evaporation rates (490-527 mm a-1) were ??? 60% lower than the present-day evaporation rate (1300 mm a-1) of Pyramid Lake. With this reduced rate of evaporation, water inputs similar to the 1983 historical maxima that occurred in the Lahontan basin would have been sufficient to maintain the 13.5 ka BP high stand of Lake Lahontan. ?? 1991 Springer-Verlag.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, Yan-Qing; Vogt, Ramona

In this paper, we propose an improved version of the color evaporation model to describe heavy quarkonium production. In contrast to the traditional color evaporation model, we impose the constraint that the invariant mass of the intermediate heavy quark-antiquark pair be larger than the mass of produced quarkonium. We also introduce a momentum shift between the heavy quark-antiquark pair and the quarkonium. Finally, numerical calculations show that our model can describe the charmonium yields as well as the ratio of ψ' over J/ψ better than the traditional color evaporation model.

Using a basin-scale hydrological model to estimate crop transpiration and soil evaporation

NASA Astrophysics Data System (ADS)

Kite, G.

2000-03-01

Increasing populations and expectations, declining crop yields and the resulting increased competition for water necesitate improvements in irrigation management and productivity. A key factor in defining agricultural productivity is to be able to simulate soil evaporation and crop transpiration. In agribusiness terms, crop transpiration is a useful process while soil and open-water evaporations are wasteful processes. In this study a distributed hydrological model was used to compute daily evaporation and transpiration for a variety of crops and other land covers within the 17,200 km 2 Gediz Basin in western Turkey. The model, SLURP, describes the complete hydrological cycle for each land cover within a series of sub-basins including all dams, reservoirs, regulators and irrigation schemes in the basin. The sub-basins and land covers are defined by analysing a digital elevation model and NOAA AVHRR satellite data. In this study, the model uses the FAO implementation of the Penman-Monteith equation to simulate soil evaporation and crop transpiration. The results of the model runs provide time series of data on streamflow at many points along the river system, abstractions and return flows from crops within the irrigation schemes and areally distributed soil evaporation and crop transpiration across the entire basin on each day of an 11 year period. The results show that evaporation and transpiration vary widely across the basin on any one day and over the irrigation season and can be used to evaluate the effectiveness of the various irrigation strategies used in the basin. The advantages of using such a model as compared to deriving evapotranspiration from satellite data are that the model obtains results for each day of an indefinitely long period, as opposed to occasional snapshots, and can also be used to simulate alternate scenarios.

An abstract approach to evaporation models in rarefied gas dynamics

NASA Astrophysics Data System (ADS)

Greenberg, W.; van der Mee, C. V. M.

1984-03-01

Strong evaporation models involving 1D stationary problems with linear self-adjoint collision operators and solutions in abstract Hilbert spaces are investigated analytically. An efficient algorithm for locating the transition from existence to nonexistence of solutions is developed and applied to the 1D and 3D BGK model equations and the 3D BGK model in moment form, demonstrating the nonexistence of stationary evaporation states with supersonic drift velocities. Applications to similar models in electron and phonon transport, radiative transfer, and neutron transport are suggested.

Theoretical and experimental researches of the liquid evaporation during thermal vacuum influences

NASA Astrophysics Data System (ADS)

Trushlyakov, V.; Panichkin, A.; Prusova, O.; Zharikov, K.; Dron, M.

2018-01-01

The mathematical model of the evaporation process of model liquid with the free surface boundary conditions of the "mirror" type under thermal vacuum influence and the numerical estimates of the evaporation process parameters are developed. An experimental stand, comprising a vacuum chamber, an experimental model tank with a heating element is designed; the experimental data are obtained. A comparative analysis of numerical and experimental results showed their close match.

Evaporation of Sunscreen Films: How the UV Protection Properties Change.

PubMed

Binks, Bernard P; Brown, Jonathan; Fletcher, Paul D I; Johnson, Andrew J; Marinopoulos, Ioannis; Crowther, Jonathan M; Thompson, Michael A

2016-06-01

We have investigated the evaporation of thin sunscreen films and how the light absorption and the derived sun protection factor (SPF) change. For films consisting of solutions of common UV filters in propylene glycol (PG) as solvent, we show how evaporation generally causes three effects. First, the film area can decrease by dewetting leading to a transient increase in the average film thickness. Second, the film thins by evaporative loss of the solvent. Third, precipitation of the UV filter occurs when solvent loss causes the solubility limit to be reached. These evaporation-induced changes cause the UV absorbance of the film to decrease with resultant loss of SPF over the time scale of the evaporation. We derive an approximate model which accounts semiquantitatively for the variation of SPF with evaporation. Experimental results for solutions of different UV filters on quartz, different skin mimicking substrates, films with added nanoparticles, films with an added polymer and films with fast-evaporating decane as solvent (instead of slow evaporating PG) are discussed and compared with model calculations. Addition of either nanoparticles or polymer suppress film dewetting. Overall, it is hoped that the understanding gained about the mechanisms whereby film evaporation affects the SPF will provide useful guidance for the formulation of more effective sunscreens.

Water evaporation: a transition path sampling study.

PubMed

Varilly, Patrick; Chandler, David

2013-02-07

We use transition path sampling to study evaporation in the SPC/E model of liquid water. On the basis of thousands of evaporation trajectories, we characterize the members of the transition state ensemble (TSE), which exhibit a liquid-vapor interface with predominantly negative mean curvature at the site of evaporation. We also find that after evaporation is complete, the distributions of translational and angular momenta of the evaporated water are Maxwellian with a temperature equal to that of the liquid. To characterize the evaporation trajectories in their entirety, we find that it suffices to project them onto just two coordinates: the distance of the evaporating molecule to the instantaneous liquid-vapor interface and the velocity of the water along the average interface normal. In this projected space, we find that the TSE is well-captured by a simple model of ballistic escape from a deep potential well, with no additional barrier to evaporation beyond the cohesive strength of the liquid. Equivalently, they are consistent with a near-unity probability for a water molecule impinging upon a liquid droplet to condense. These results agree with previous simulations and with some, but not all, recent experiments.

Implications of climate change for evaporation from bare soils in a Mediterranean environment.

PubMed

Aydin, Mehmet; Yano, Tomohisa; Evrendilek, Fatih; Uygur, Veli

2008-05-01

The purpose of this study was to predict quantitative changes in evaporation from bare soils in the Mediterranean climate region of Turkey in response to the projections of a regional climate model developed in Japan (hereafter RCM). Daily RCM data for the estimation of reference evapotranspiration (ETr) and soil evaporation were obtained for the periods of 1994--2003 and 2070--2079. Potential evaporation (Ep) from bare soils was calculated using the Penman-Monteith equation with a surface resistance of zero. Simulation of actual soil evaporation (Ea) was carried out using Aydin model (Aydin et al., Ecological Modelling 182:91-105, 2005) combined with Aydin and Uygur (2006, A model for estimating soil water potential of bare fields. In Proceedings of the 18th International Soil Meeting (ISM) on Soils Sustaining Life on Earth, Managing Soil and Technology, Sanliurfa, 477-480pp.) model of predicting soil water potential at the top surface layer of a bare soil, after performances of Aydin model (R2 = 94.0%) and Aydin and Uygur model (R2 = 97.6) were tested. The latter model is based on the relations among potential soil evaporation, hydraulic diffusivity, and soil wetness, with some simplified assumptions. Input parameters of the model are simple and easily obtainable such as climatic parameters used to compute the potential soil evaporation, average diffusivity for the drying soil, and volumetric water content at field capacity. The combination of Aydin and Aydin and Uygur models appeared to be useful in estimating water potential of soils and Ea from bare soils, with only a few parameters. Unlike ETr and Ep projected to increase by 92 and 69 mm (equivalent to 8.0 and 7.3% increases) due to the elevated evaporative demand of the atmosphere, respectively, Ea from bare soils is projected to reduce by 50 mm (equivalent to a 16.5% decrease) in response to a decrease in rainfall by 46% in the Mediterranean region of Turkey by the 2070s predicted by RCM, and consequently, to decreased soil wetness in the future.

GLEAM v3: updated land evaporation and root-zone soil moisture datasets

NASA Astrophysics Data System (ADS)

Martens, Brecht; Miralles, Diego; Lievens, Hans; van der Schalie, Robin; de Jeu, Richard; Fernández-Prieto, Diego; Verhoest, Niko

2016-04-01

Evaporation determines the availability of surface water resources and the requirements for irrigation. In addition, through its impacts on the water, carbon and energy budgets, evaporation influences the occurrence of rainfall and the dynamics of air temperature. Therefore, reliable estimates of this flux at regional to global scales are of major importance for water management and meteorological forecasting of extreme events. However, the global-scale magnitude and variability of the flux, and the sensitivity of the underlying physical process to changes in environmental factors, are still poorly understood due to the limited global coverage of in situ measurements. Remote sensing techniques can help to overcome the lack of ground data. However, evaporation is not directly observable from satellite systems. As a result, recent efforts have focussed on combining the observable drivers of evaporation within process-based models. The Global Land Evaporation Amsterdam Model (GLEAM, www.gleam.eu) estimates terrestrial evaporation based on daily satellite observations of meteorological drivers of terrestrial evaporation, vegetation characteristics and soil moisture. Since the publication of the first version of the model in 2011, GLEAM has been widely applied for the study of trends in the water cycle, interactions between land and atmosphere and hydrometeorological extreme events. A third version of the GLEAM global datasets will be available from the beginning of 2016 and will be distributed using www.gleam.eu as gateway. The updated datasets include separate estimates for the different components of the evaporative flux (i.e. transpiration, bare-soil evaporation, interception loss, open-water evaporation and snow sublimation), as well as variables like the evaporative stress, potential evaporation, root-zone soil moisture and surface soil moisture. A new dataset using SMOS-based input data of surface soil moisture and vegetation optical depth will also be distributed. The most important updates in GLEAM include the revision of the soil moisture data assimilation system, the evaporative stress functions and the infiltration of rainfall. In this presentation, we will highlight the changes of the methodology and present the new datasets, their validation against in situ observations and the comparisons against alternative datasets of terrestrial evaporation, such as GLDAS-Noah, ERA-Interim and previous GLEAM datasets. Preliminary results indicate that the magnitude and the spatio-temporal variability of the evaporation estimates have been slightly improved upon previous versions of the datasets.

Externally Induced Evaporation of Young Stellar Disks in Orion

NASA Technical Reports Server (NTRS)

Johnstone, D.; Hollenbach, D.; Shu, F.

1996-01-01

In this paper we propose a model for the evaporation of disks around young low-mass stars by external sources of high energy photons. Two evaporation techniques are possible. Lyman continuum radiation can ionize hydrogen at the disk surface powering a steady thermal ionized disk-wind, or FUV radiation can heat the disk through photo-electric grain processes powering a slower thermal neutral disk-wind. Applying these two models to the evaporating objects in the Trapezium produces a satisfactory solution to both the mass-loss rate and size of the ionized envelopes.

An evaluation of models of bare soil evaporation formulated with different land surface boundary conditions and assumptions

NASA Astrophysics Data System (ADS)

Smits, Kathleen M.; Ngo, Viet V.; Cihan, Abdullah; Sakaki, Toshihiro; Illangasekare, Tissa H.

2012-12-01

Bare soil evaporation is a key process for water exchange between the land and the atmosphere and an important component of the water balance. However, there is no agreement on the best modeling methodology to determine evaporation under different atmospheric boundary conditions. Also, there is a lack of directly measured soil evaporation data for model validation to compare these methods to establish the validity of their mathematical formulations. Thus, a need exists to systematically compare evaporation estimates using existing methods to experimental observations. The goal of this work is to test different conceptual and mathematical formulations that are used to estimate evaporation from bare soils to critically investigate various formulations and surface boundary conditions. Such a comparison required the development of a numerical model that has the ability to incorporate these boundary conditions. For this model, we modified a previously developed theory that allows nonequilibrium liquid/gas phase change with gas phase vapor diffusion to better account for dry soil conditions. Precision data under well-controlled transient heat and wind boundary conditions were generated, and results from numerical simulations were compared with experimental data. Results demonstrate that the approaches based on different boundary conditions varied in their ability to capture different stages of evaporation. All approaches have benefits and limitations, and no one approach can be deemed most appropriate for every scenario. Comparisons of different formulations of the surface boundary condition validate the need for further research on heat and vapor transport processes in soil for better modeling accuracy.

A comprehensive analysis of the evaporation of a liquid spherical drop.

PubMed

Sobac, B; Talbot, P; Haut, B; Rednikov, A; Colinet, P

2015-01-15

In this paper, a new comprehensive analysis of a suspended drop of a pure liquid evaporating into air is presented. Based on mass and energy conservation equations, a quasi-steady model is developed including diffusive and convective transports, and considering the non-isothermia of the gas phase. The main original feature of this simple analytical model lies in the consideration of the local dependence of the physico-chemical properties of the gas on the gas temperature, which has a significant influence on the evaporation process at high temperatures. The influence of the atmospheric conditions on the interfacial evaporation flux, molar fraction and temperature is investigated. Simplified versions of the model are developed to highlight the key mechanisms governing the evaporation process. For the conditions considered in this work, the convective transport appears to be opposed to the evaporation process leading to a decrease of the evaporation flux. However, this effect is relatively limited, the Péclet numbers happening to be small. In addition, the gas isothermia assumption never appears to be valid here, even at room temperature, due to the large temperature gradient that develops in the gas phase. These two conclusions are explained by the fact that heat transfer from the gas to the liquid appears to be the step limiting the evaporation process. Regardless of the complexity of the developed model, yet excluding extremely small droplets, the square of the drop radius decreases linearly over time (R(2) law). The assumptions of the model are rigorously discussed and general criteria are established, independently of the liquid-gas couple considered. Copyright © 2014 Elsevier Inc. All rights reserved.

Evaporation of Cu, Sn, and S from Fe-C-Cu-Sn-S Liquid Alloys in the Temperature Range from 1513 K to 1873 K (1240 °C to 1600 °C)

NASA Astrophysics Data System (ADS)

Tafwidli, Fahmi; Choi, Moo-Eob; Yi, Sang-Ho; Kang, Youn-Bae

2018-02-01

Evaporation of Cu or Sn from liquid iron alloys containing C and S was experimentally investigated. The initial C concentration, [pct C]0, in the liquid alloy was varied from zero to C saturation, and the evaporation temperature was varied from 1513 K to 1773 K (1240 °C to 1500 °C). Along with the report by one of the present authors, the evaporation mechanism of Cu and Sn from liquid Fe-C-S alloy is proposed, after a modification from the previous mechanism. It was proposed that Cu and Sn evaporate as Cu(g) and Sn(g) and also evaporate as CuS(g) and SnS(g), which are more volatile species. Therefore, availability of S in the alloy affects the overall evaporation rate of Cu and Sn. At the same time, C in the alloy also forms volatile carbosulfides CS(g) and CS2(g), thereby competing with Cu and Sn. Moreover, C increases the activity coefficients of Cu, Sn, and S. This increases the thermodynamic driving force for the formation of CuS(g) and SnS(g). Therefore, increasing [pct C] partly accelerates the evaporation rate of Cu and Sn by increasing the activity coefficient but partly decelerates the evaporation rate by lowering the available S content. S partly accelerates the evaporation rate by increasing the available S for the sulfide gas species but partly decelerates the evaporation rate due to the surface poisoning effect. Increasing the reaction temperature increases the overall evaporation rate. All these facts were taken into account in order to develop an evaporation rate model. This model was extended from the present authors' previous one by taking into account (1) CS(g), S(g), and CS2(g) (therefore, the following species were considered as dominant evaporating species: Cu(g), CuS(g), Sn(g), SnS(g), S(g), CS(g), and CS2(g)); (2) the effect of C and temperature on the activity coefficients of Cu, Sn, and S; (3) the effect of C and temperature on the density of the liquid alloy; and (4) the effect of temperature on the S adsorption coefficient. This revised evaporation model was used in order to explain the experimental data, and it showed good agreement. In particular, it was found that the temperature showed a significant effect on the evaporation rate, and the effect of temperature and C content on the activity coefficients of Cu, Sn, and S also significantly affected the evaporation rate. The chemical reaction rate constant of the individual evaporation reaction ( kiR ) and residual rate constant ( kir ) could be obtained as a function of temperature. The activation energy of each evaporation reaction was derived and discussed. The evaporation rate model can be applied in order to predict the content of Cu and Sn remaining in liquid iron under various conditions of temperature and [pct C].

Evaporation of Cu, Sn, and S from Fe-C-Cu-Sn-S Liquid Alloys in the Temperature Range from 1513 K to 1873 K (1240 °C to 1600 °C)

NASA Astrophysics Data System (ADS)

Tafwidli, Fahmi; Choi, Moo-Eob; Yi, Sang-Ho; Kang, Youn-Bae

2018-06-01

Evaporation of Cu or Sn from liquid iron alloys containing C and S was experimentally investigated. The initial C concentration, [pct C]0, in the liquid alloy was varied from zero to C saturation, and the evaporation temperature was varied from 1513 K to 1773 K (1240 °C to 1500 °C). Along with the report by one of the present authors, the evaporation mechanism of Cu and Sn from liquid Fe-C-S alloy is proposed, after a modification from the previous mechanism. It was proposed that Cu and Sn evaporate as Cu(g) and Sn(g) and also evaporate as CuS(g) and SnS(g), which are more volatile species. Therefore, availability of S in the alloy affects the overall evaporation rate of Cu and Sn. At the same time, C in the alloy also forms volatile carbosulfides CS(g) and CS2(g), thereby competing with Cu and Sn. Moreover, C increases the activity coefficients of Cu, Sn, and S. This increases the thermodynamic driving force for the formation of CuS(g) and SnS(g). Therefore, increasing [pct C] partly accelerates the evaporation rate of Cu and Sn by increasing the activity coefficient but partly decelerates the evaporation rate by lowering the available S content. S partly accelerates the evaporation rate by increasing the available S for the sulfide gas species but partly decelerates the evaporation rate due to the surface poisoning effect. Increasing the reaction temperature increases the overall evaporation rate. All these facts were taken into account in order to develop an evaporation rate model. This model was extended from the present authors' previous one by taking into account (1) CS(g), S(g), and CS2(g) (therefore, the following species were considered as dominant evaporating species: Cu(g), CuS(g), Sn(g), SnS(g), S(g), CS(g), and CS2(g)); (2) the effect of C and temperature on the activity coefficients of Cu, Sn, and S; (3) the effect of C and temperature on the density of the liquid alloy; and (4) the effect of temperature on the S adsorption coefficient. This revised evaporation model was used in order to explain the experimental data, and it showed good agreement. In particular, it was found that the temperature showed a significant effect on the evaporation rate, and the effect of temperature and C content on the activity coefficients of Cu, Sn, and S also significantly affected the evaporation rate. The chemical reaction rate constant of the individual evaporation reaction ( kiR ) and residual rate constant ( kir ) could be obtained as a function of temperature. The activation energy of each evaporation reaction was derived and discussed. The evaporation rate model can be applied in order to predict the content of Cu and Sn remaining in liquid iron under various conditions of temperature and [pct C].

Modeling Pan Evaporation for Kuwait by Multiple Linear Regression

PubMed Central

Almedeij, Jaber

2012-01-01

Evaporation is an important parameter for many projects related to hydrology and water resources systems. This paper constitutes the first study conducted in Kuwait to obtain empirical relations for the estimation of daily and monthly pan evaporation as functions of available meteorological data of temperature, relative humidity, and wind speed. The data used here for the modeling are daily measurements of substantial continuity coverage, within a period of 17 years between January 1993 and December 2009, which can be considered representative of the desert climate of the urban zone of the country. Multiple linear regression technique is used with a procedure of variable selection for fitting the best model forms. The correlations of evaporation with temperature and relative humidity are also transformed in order to linearize the existing curvilinear patterns of the data by using power and exponential functions, respectively. The evaporation models suggested with the best variable combinations were shown to produce results that are in a reasonable agreement with observation values. PMID:23226984

Development of an Evaporation Sub-model and Simulation of Multiple Droplet Impingement in Volume of Fluid Method

NASA Astrophysics Data System (ADS)

Potham, Sathya Prasad

Droplet collision and impingement on a substrate are widely observed phenomenon in many applications like spray injection of Internal Combustion Engines, spray cooling, spray painting and atomizers used in propulsion applications. Existing Lagrangian models do not provide a comprehensive picture of the outcome of these events and may involve model constants requiring experimental data for validation. Physics based models like Volume of Fluid (VOF) method involve no parametric tuning and are more accurate. The aim of this thesis is to extend the basic VOF method with an evaporation sub-model and implement in an open source Computational Fluid Dynamics (CFD) software, OpenFOAM. The new model is applied to numerically study the evaporation of spherical n-heptane droplets impinging on a hot wall at atmospheric pressure and a temperature above the Leidenfrost temperature. An additional vapor phase is introduced apart from the liquid and gas phases to understand the mixing and diffusion of vapor and gas phases. The evaporation model is validated quantitatively and qualitatively with fundamental problems having analytical solutions and published results. The effect of droplet number and arrangement on evaporation is studied by three cases with one (Case 1), two (Case 2) and four (Case 3) droplets impinging on hot wall in film boiling regime at a fixed temperature of wall and a constant non-dimensional distance between droplets. Droplet lift and spread, surface temperature, heat transfer, and evaporation rate are examined. It was observed that more liquid mass evaporated in Case 1 compared to the other cases. Droplet levitation begins early in Case 1 and very high levitation observed was partially due to contraction of its shape from elongated to a more circular form. Average surface temperature was also considerably reduced in Case 1 due to high droplet levitation.

The impact of non-isothermal soil moisture transport on evaporation fluxes in a maize cropland

NASA Astrophysics Data System (ADS)

Shao, Wei; Coenders-Gerrits, Miriam; Judge, Jasmeet; Zeng, Yijian; Su, Ye

2018-06-01

The process of evaporation interacts with the soil, which has various comprehensive mechanisms. Multiphase flow models solve air, vapour, water, and heat transport equations to simulate non-isothermal soil moisture transport of both liquid water and vapor flow, but are only applied in non-vegetated soils. For (sparsely) vegetated soils often energy balance models are used, however these lack the detailed information on non-isothermal soil moisture transport. In this study we coupled a multiphase flow model with a two-layer energy balance model to study the impact of non-isothermal soil moisture transport on evaporation fluxes (i.e., interception, transpiration, and soil evaporation) for vegetated soils. The proposed model was implemented at an experimental agricultural site in Florida, US, covering an entire maize-growing season (67 days). As the crops grew, transpiration and interception became gradually dominated, while the fraction of soil evaporation dropped from 100% to less than 20%. The mechanisms of soil evaporation vary depending on the soil moisture content. After precipitation the soil moisture content increased, exfiltration of the liquid water flow could transport sufficient water to sustain evaporation from soil, and the soil vapor transport was not significant. However, after a sufficient dry-down period, the soil moisture content significantly reduced, and the soil vapour flow significantly contributed to the upward moisture transport in topmost soil. A sensitivity analysis found that the simulations of moisture content and temperature at the soil surface varied substantially when including the advective (i.e., advection and mechanical dispersion) vapour transport in simulation, including the mechanism of advective vapour transport decreased soil evaporation rate under wet condition, while vice versa under dry condition. The results showed that the formulation of advective soil vapor transport in a soil-vegetation-atmosphere transfer continuum can affect the simulated evaporation fluxes, especially under dry condition.

Tear-Film Evaporation Rate from Simultaneous Ocular-Surface Temperature and Tear-Breakup Area.

PubMed

Dursch, Thomas J; Li, Wing; Taraz, Baseem; Lin, Meng C; Radke, Clayton J

2018-01-01

A corneal heat-transfer model is presented to quantify simultaneous measurements of fluorescein tear-breakup area (TBA) and ocular-surface temperature (OST). By accounting for disruption of the tear-film lipid layer (TFLL), we report evaporation rates through lipid-covered tear. The modified heat-transfer model provides new insights into evaporative dry eye. A quantitative analysis is presented to assess human aqueous tear evaporation rate (TER) through intact TFLLs from simultaneous in vivo measurement of time-dependent infrared OST and fluorescein TBA. We interpret simultaneous OST and TBA measurements using an extended heat-transfer model. We hypothesize that TBAs are ineffectively insulated by the TFLL and therefore exhibit higher TER than does that for a well-insulting TFLL-covered tear. As time proceeds, TBAs increase in number and size, thereby increasing the cornea area-averaged TER and decreasing OST. Tear-breakup areas were assessed from image analysis of fluorescein tear-film-breakup video recordings and are included in the heat-transfer description of OST. Model-predicted OSTs agree well with clinical experiments. Percent reductions in TER of lipid-covered tear range from 50 to 95% of that for pure water, in good agreement with literature. The physical picture of noninsulating or ruptured TFLL spots followed by enhanced evaporation from underlying cooler tear-film ruptures is consistent with the evaporative-driven mechanism for local tear rupture. A quantitative analysis is presented of in vivo TER from simultaneous clinical measurement of transient OST and TBA. The new heat-transfer model accounts for increased TER through expanding TBAs. Tear evaporation rate varies strongly across the cornea because lipid is effectively missing over tear-rupture troughs. The result is local faster evaporation compared with nonruptured, thick lipid-covered tear. Evaporative-driven tear-film ruptures deepen to a thickness where fluorescein quenching commences and local salinity rises to uncomfortable levels. Mitigation of tear-film rupture may therefore reduce dry eye-related symptoms.

MOVES2014: Evaporative Emissions Report

EPA Science Inventory

Vehicle evaporative emissions are now modeled in EPA’s MOVES according to physical processes, permeation, tank vapor venting, liquid leaks, and refueling emissions. With this update, the following improvements are being incorporated into MOVES evaporative emissions methodology, a...

CFD Analysis of Evaporation-Condensation Phenomenon In an Evaporation Chamber of Natural Vacuum Solar Desalination

NASA Astrophysics Data System (ADS)

Ambarita, H.; Ronowikarto, A. D.; Siregar, R. E. T.; Setyawan, E. Y.

2018-01-01

Desalination technologies is one of solutions for water scarcity. With using renewable energy, like solar energy, wind energy, and geothermal energy, expected will reduce the energy demand. This required study on the modeling and transport parameters determination of natural vacuum solar desalination by using computational fluid dynamics (CFD) method to simulate the model. A three-dimensional case, two-phase model was developed for evaporation-condensation phenomenon in natural vacuum solar desalination. The CFD simulation results were compared with the avalaible experimental data. The simulation results shows inthat there is a phenomenon of evaporation-condensation in an evaporation chamber. From the simulation, the fresh water productivity is 2.21 litre, and from the experimental is 2.1 litre. This study shows there’s an error of magnitude 0.4%. The CFD results also show that, vacuum pressure will degrade the saturation temperature of sea water.

Application of thermal model for pan evaporation to the hydrology of a defined medium, the sponge

NASA Technical Reports Server (NTRS)

Trenchard, M. H.; Artley, J. A. (Principal Investigator)

1981-01-01

A technique is presented which estimates pan evaporation from the commonly observed values of daily maximum and minimum air temperatures. These two variables are transformed to saturation vapor pressure equivalents which are used in a simple linear regression model. The model provides reasonably accurate estimates of pan evaporation rates over a large geographic area. The derived evaporation algorithm is combined with precipitation to obtain a simple moisture variable. A hypothetical medium with a capacity of 8 inches of water is initialized at 4 inches. The medium behaves like a sponge: it absorbs all incident precipitation, with runoff or drainage occurring only after it is saturated. Water is lost from this simple system through evaporation just as from a Class A pan, but at a rate proportional to its degree of saturation. The contents of the sponge is a moisture index calculated from only the maximum and minium temperatures and precipitation.

Insights into Mechanistic Models for Evaporation of Organic Liquids in the Environment Obtained by Position-Specific Carbon Isotope Analysis.

PubMed

Julien, Maxime; Nun, Pierrick; Robins, Richard J; Remaud, Gérald S; Parinet, Julien; Höhener, Patrick

2015-11-03

Position-specific isotope effects (PSIEs) have been measured by isotope ratio monitoring (13)C nuclear magnetic resonance spectrometry during the evaporation of 10 liquids of different polarities under 4 evaporation modes (passive evaporation, air-vented evaporation, low pressure evaporation, distillation). The observed effects are used to assess the validity of the Craig-Gordon isotope model for organic liquids. For seven liquids the overall isotope effect (IE) includes a vapor-liquid contribution that is strongly position-specific in polar compounds but less so in apolar compounds and a diffusive IE that is not position-specific, except in the alcohols, ethanol and propan-1-ol. The diffusive IE is diminished under forced evaporation. The position-specific isotope pattern created by liquid-vapor IEs is manifest in five liquids, which have an air-side limitation for volatilization. For the alcohols, undefined processes in the liquid phase create additional PSIEs. Three other liquids with limitations on the liquid side have a lower, highly position-specific, bulk diffusive IE. It is concluded that evaporation of organic pollutants creates unique position-specific isotope patterns that may be used to assess the progress of remediation or natural attenuation of pollution and that the Craig-Gordon isotope model is valid for the volatilization of nonpolar organic liquids with air-side limitation of the volatilization rate.

Experimental and Numerical Study of the Evaporation of Water at Low Pressures.

PubMed

Kazemi, Mohammad Amin; Nobes, David S; Elliott, Janet A W

2017-05-09

Although evaporation is considered to be a surface phenomenon, the rate of molecular transport across a liquid-vapor boundary is strongly dependent on the coupled fluid dynamics and heat transfer in the bulk fluids. Recent experimental thermocouple measurements of the temperature field near the interface of evaporating water into its vapor have begun to show the role of heat transfer in evaporation. However, the role of fluid dynamics has not been explored sufficiently. Here, we have developed a mathematical model to describe the coupling of the heat, mass, and momentum transfer in the fluids with the transport phenomena at the interface. The model was used to understand the experimentally obtained velocity field in the liquid and temperature profiles in the liquid and vapor, in evaporation from a concave meniscus for various vacuum pressures. By using the model, we have shown that an opposing buoyancy flow suppressed the thermocapillary flow in the liquid during evaporation at low pressures in our experiments. As such, in the absence of thermocapillary convection, the evaporation is controlled by heat transfer to the interface, and the predicted behavior of the system is independent of choosing between the existing theoretical expressions for evaporation flux. Furthermore, we investigated the temperature discontinuity at the interface and confirmed that the discontinuity strongly depends on the heat flux from the vapor side, which depends on the geometrical shape of the interface.

Numerical Modeling of Turbulence Effects within an Evaporating Droplet in Atomizing Sprays

NASA Technical Reports Server (NTRS)

Balasubramanyam, M. S.; Chen, C. P.; Trinh, H. P.

2006-01-01

A new approach to account for finite thermal conductivity and turbulence effects within atomizing liquid sprays is presented in this paper. The model is an extension of the T-blob and T-TAB atomization/spray model of Trinh and Chen (2005). This finite conductivity model is based on the two-temperature film theory, where the turbulence characteristics of the droplet are used to estimate the effective thermal diffhsivity within the droplet phase. Both one-way and two-way coupled calculations were performed to investigate the performance of this model. The current evaporation model is incorporated into the T-blob atomization model of Trinh and Chen (2005) and implemented in an existing CFD Eulerian-Lagrangian two-way coupling numerical scheme. Validation studies were carried out by comparing with available evaporating atomization spray experimental data in terms of jet penetration, temperature field, and droplet SMD distribution within the spray. Validation results indicate the superiority of the finite-conductivity model in low speed parallel flow evaporating spray.

Simultaneous Evaporation of Cu and Sn from Liquid Steel

NASA Astrophysics Data System (ADS)

Jung, Sung-Hoon; Kang, Youn-Bae

2016-08-01

In order to understand evaporation refining of tramp elements in molten ferrous scrap, Cu and Sn, a series of experiments were carried out using liquid-gas reaction in a levitation melting equipment. Effect of S and C, which are abundant in hot metal from ironmaking process, was examined and analyzed by employing a comprehensive evaporation kinetic model developed by the present authors (Jung et al. in Metall Mater Trans B 46B:250-258, 2014; Jung et al. in Metall Mater Trans B 46B:259-266, 2014; Jung et al. in Metall Mater Trans B 46B:267-277, 2014; Jung and Kang in Metall Mater Trans B 10.1007/s11663-016-0601-5, 2016). Evaporation of Cu and Sn were treated by evaporation of individual species such as Cu(g), CuS(g), Sn(g), and SnS(g), along with CS2(g). Decrease of Cu and Sn content in liquid steel was in good agreement with the model prediction. Optimum conditions of steel composition for the rapid evaporation of Cu and Sn were proposed by utilizing the model predictions.

Spatial–temporal changes in potential evaporation patterns based on the Cloud model and their possible causes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Yuelu; Huang, Shengzhi; Chang, Jianxia

It is of importance to comprehensively investigate the spatial-temporal changes in potential evaporation patterns, which helps guide the long-term water resource allocation and irrigation managements. In this study, the Cloud model was adopted to quantify the average, uniformity, and stability of annual potential evaporation in the Wei River Basin (WRB), a typical arid and semi-arid region in China.. The cross wavelet analysis was then applied to explore the correlations between potential evaporation and Arctic Oscillation (AO)/El Niño Southern Oscillation (ENSO) with an aim to determine the possible causes of potential evaporation variations. Results indicated that: (1) the average of annualmore » potential evaporation in the WRB first declined and then increased, which was similar with its stability, whilst its dispersion degree exhibited a decreasing trend, implying that potential evaporation has a small inter-annual variation; (2) the average of potential evaporation in the western basin was obviously smaller than that in the other areas, while its uniformity and stability in the Guanzhong plain and the Loess Plateau areas are larger than those in other areas, particularly in the western basin where the uniformity and stability are the smallest; (3) both AO and ENSO exhibited strong correlations with potential evaporation variations, indicating that both AO and ENSO have played an important role in the annual potential evaporation variations in the WRB.« less

Effects of Topography-driven Micro-climatology on Evaporation

NASA Astrophysics Data System (ADS)

Adams, D. D.; Boll, J.; Wagenbrenner, N. S.

2017-12-01

The effects of spatial-temporal variation of climatic conditions on evaporation in micro-climates are not well defined. Current spatially-based remote sensing and modeling for evaporation is limited for high resolutions and complex topographies. We investigated the effect of topography-driven micro-climatology on evaporation supported by field measurements and modeling. Fourteen anemometers and thermometers were installed in intersecting transects over the complex topography of the Cook Agronomy Farm, Pullman, WA. WindNinja was used to create 2-D vector maps based on recorded observations for wind. Spatial analysis of vector maps using ArcGIS was performed for analysis of wind patterns and variation. Based on field measurements, wind speed and direction show consequential variability based on hill-slope location in this complex topography. Wind speed and wind direction varied up to threefold and more than 45 degrees, respectively for a given time interval. The use of existing wind models enables prediction of wind variability over the landscape and subsequently topography-driven evaporation patterns relative to wind. The magnitude of the spatial-temporal variability of wind therefore resulted in variable evaporation rates over the landscape. These variations may contribute to uneven crop development patterns observed during the late growth stages of the agricultural crops at the study location. Use of hill-slope location indexes and appropriate methods for estimating actual evaporation support development of methodologies to better define topography-driven heterogeneity in evaporation. The cumulative effects of spatially-variable climatic factors on evaporation are important to quantify the localized water balance and inform precision farming practices.

Interactions of bluff-body obstacles with turbulent airflows affecting evaporative fluxes from porous surfaces

NASA Astrophysics Data System (ADS)

Haghighi, Erfan; Or, Dani

2015-11-01

Bluff-body obstacles interacting with turbulent airflows are common in many natural and engineering applications (from desert pavement and shrubs over natural surfaces to cylindrical elements in compact heat exchangers). Even with obstacles of simple geometry, their interactions within turbulent airflows result in a complex and unsteady flow field that affects surface drag partitioning and transport of scalars from adjacent evaporating surfaces. Observations of spatio-temporal thermal patterns on evaporating porous surfaces adjacent to bluff-body obstacles depict well-defined and persistent zonation of evaporation rates that were used to construct a simple mechanistic model for surface-turbulence interactions. Results from evaporative drying of sand surfaces with isolated cylindrical elements (bluff bodies) subjected to constant turbulent airflows were in good agreement with model predictions for localized exchange rates. Experimental and theoretical results show persistent enhancement of evaporative fluxes from bluff-rough surfaces relative to smooth flat surfaces under similar conditions. The enhancement is attributed to formation of vortices that induce a thinner boundary layer over part of the interacting surface footprint. For a practical range of air velocities (0.5-4.0 m/s), low-aspect ratio cylindrical bluff elements placed on evaporating sand surfaces enhanced evaporative mass losses (relative to a flat surface) by up to 300% for high density of elements and high wind velocity, similar to observations reported in the literature. Concepts from drag partitioning were used to generalize the model and upscale predictions to evaporation from surfaces with multiple obstacles for potential applications to natural bluff-rough surfaces.

Simulations of Evaporating Multicomponent Fuel Drops

NASA Technical Reports Server (NTRS)

Bellan, Josette; Le Clercq, Patrick

2005-01-01

A paper presents additional information on the subject matter of Model of Mixing Layer With Multicomponent Evaporating Drops (NPO-30505), NASA Tech Briefs, Vol. 28, No. 3 (March 2004), page 55. To recapitulate: A mathematical model of a three-dimensional mixing layer laden with evaporating fuel drops composed of many chemical species has been derived. The model is used to perform direct numerical simulations in continuing studies directed toward understanding the behaviors of sprays of liquid petroleum fuels in furnaces, industrial combustors, and engines. The model includes governing equations formulated in an Eulerian and a Lagrangian reference frame for the gas and drops, respectively, and incorporates a concept of continuous thermodynamics, according to which the chemical composition of a fuel is described by use of a distribution function. In this investigation, the distribution function depends solely on the species molar weight. The present paper reiterates the description of the model and discusses further in-depth analysis of the previous results as well as results of additional numerical simulations assessing the effect of the mass loading. The paper reiterates the conclusions reported in the cited previous article, and states some new conclusions. Some new conclusions are: 1. The slower evaporation and the evaporation/ condensation process for multicomponent-fuel drops resulted in a reduced drop-size polydispersity compared to their single-component counterpart. 2. The inhomogeneity in the spatial distribution of the species in the layer increases with the initial mass loading. 3. As evaporation becomes faster, the assumed invariant form of the molecular- weight distribution during evaporation becomes inaccurate.

Using isotopes to quantify evaporation and non-stationary transit times distributions in lake water budgets

NASA Astrophysics Data System (ADS)

Smith, A. A.; Tetzlaff, D.; Soulsby, C.

2017-12-01

Evaporative fluxes from northern lakes are essential components of catchment water balances, providing large supplies of water to the atmosphere, and affecting downstream water availability. However, measurement of lake evaporation is difficult in many catchments due to remoteness and inaccessibility. Evaporative flux may also influence mean transit times of lakes and catchments, identified through water- and tracer mass-balance. We combined stable water isotopes (δ2H and δ18O), transit, and residence time distributions in a non-stationary transit time model to estimate the evaporative flux from two lakes in the Scottish Highlands. The lakes were in close proximity to each other ( 2km), shallow (mean depth, 1.5 m) with one large (0.88km2) and one small (0.4km2). Model calibration used measurements of precipitation, air temperature, water level, and isotopic stream compositions of lake inflow and outflows. Evaporation flux was identified using lake fractionation of δ2H and δ18O. Mixing patterns of the lakes and their respective outlet isotopic compositions were accounted for by comparing three probability distributions for discharge and evaporation. We found that the evaporation flux was strongly influenced by these discharge and evaporation distributions. Decreased mixing within the lake resulted in greater evaporation fluxes. One of the three distributions yielded similar mean daily evaporation and uncertainty for both lakes (max 5mm/day), while evaporation using the other two distributions was inconsistent between the lakes. Importantly, our approach also estimated distributions of evaporation age, which were significantly different between the lakes, reflecting a combination of inflow stream magnitude and the mixing regimes. The mean evaporation flux age of the large lake was 160 days, and 14 days for the small lake. Our integrated approach of stable isotopes, time variant transit time distributions has shown to be a useful tool for quantifying evaporative fluxes and closing the water balance, while simultaneously providing useful transit times of fluxes for lake dominated catchments.

Modelling of influential parameters on a continuous evaporation process by Doehlert shells

PubMed Central

Porte, Catherine; Havet, Jean-Louis; Daguet, David

2003-01-01

The modelling of the parameters that influence the continuous evaporation of an alcoholic extract was considered using Doehlert matrices. The work was performed with a wiped falling film evaporator that allowed us to study the influence of the pressure, temperature, feed flow and dry matter of the feed solution on the dry matter contents of the resulting concentrate, and the productivity of the process. The Doehlert shells were used to model the influential parameters. The pattern obtained from the experimental results was checked allowing for some dysfunction in the unit. The evaporator was modified and a new model applied; the experimental results were then in agreement with the equations. The model was finally determined and successfully checked in order to obtain an 8% dry matter concentrate with the best productivity; the results fit in with the industrial constraints of subsequent processes. PMID:18924887

Spatial and temporal connections in groundwater contribution to evaporation

NASA Astrophysics Data System (ADS)

Lam, A.; Karssenberg, D.; van den Hurk, B. J. J. M.; Bierkens, M. F. P.

2011-02-01

In climate models, lateral terrestrial water fluxes are usually neglected. We estimated the contribution of vertical and lateral groundwater fluxes to the land surface water budget at a subcontinental scale, by modelling convergence of groundwater and surfacewater fluxes. We present a hydrological model of the entire Danube Basin at 5 km resolution, and use it to show the importance of groundwater for the surface climate. The contribution of groundwater to evaporation is significant, and can be upwards of 30% in summer. We show that this contribution is local by presenting the groundwater travel times and the magnitude of groundwater convergence. Throughout the Danube Basin the lateral fluxes of groundwater are negligible when modelling at this scale and resolution. Also, it is shown that the contribution of groundwater to evaporation has important temporal characteristics. An experiment with the same model shows that a wet episode influences groundwaters contribution to summer evaporation for several years afterwards. This indicates that modelling groundwater flow has the potential to augment the multi-year memory of climate models.

Evaporation kinetics of surfactant solution droplets on rice (Oryza sativa) leaves

PubMed Central

Cao, Li-Dong; Zheng, Li; Xu, Jun; Li, Feng-Min; Huang, Qi-Liang

2017-01-01

The dynamics of evaporating sessile droplets on hydrophilic or hydrophobic surfaces is widely studied, and many models for these processes have been developed based on experimental evidence. However, few research has been explored on the evaporation of sessile droplets of surfactant or pesticide solutions on target crop leaves. Thus, in this paper the impact of surfactant concentrations on contact angle, contact diameter, droplet height, and evolution of the droplets’ evaporative volume on rice leaf surfaces have been investigated. The results indicate that the evaporation kinetics of surfactant droplets on rice leaves were influenced by both the surfactant concentrations and the hydrophobicity of rice leaf surfaces. When the surfactant concentration is lower than the surfactant CMC (critical micelle concentration), the droplet evaporation time is much longer than that of the high surfactant concentration. This is due to the longer existence time of a narrow wedge region under the lower surfactant concentration, and such narrow wedge region further restricts the droplet evaporation. Besides, our experimental data are shown to roughly collapse onto theoretical curves based on the model presented by Popov. This study could supply theoretical data on the evaporation of the adjuvant or pesticide droplets for practical applications in agriculture. PMID:28472108

Influence of three different concentration techniques on evaporation rate, color and phenolics content of blueberry juice.

PubMed

Elik, Aysel; Yanık, Derya Koçak; Maskan, Medeni; Göğüş, Fahrettin

2016-05-01

The present study was undertaken to assess the effects of three different concentration processes open-pan, rotary vacuum evaporator and microwave heating on evaporation rate, the color and phenolics content of blueberry juice. Kinetics model study for changes in soluble solids content (°Brix), color parameters and phenolics content during evaporation was also performed. The final juice concentration of 65° Brix was achieved in 12, 15, 45 and 77 min, for microwave at 250 and 200 W, rotary vacuum and open-pan evaporation processes, respectively. Color changes associated with heat treatment were monitored using Hunter colorimeter (L*, a* and b*). All Hunter color parameters decreased with time and dependently studied concentration techniques caused color degradation. It was observed that the severity of color loss was higher in open-pan technique than the others. Evaporation also affected total phenolics content in blueberry juice. Total phenolics loss during concentration was highest in open-pan technique (36.54 %) and lowest in microwave heating at 200 W (34.20 %). So, the use of microwave technique could be advantageous in food industry because of production of blueberry juice concentrate with a better quality and short time of operation. A first-order kinetics model was applied to modeling changes in soluble solids content. A zero-order kinetics model was used to modeling changes in color parameters and phenolics content.

Estimate of rain evaporation rates from dual-wavelength lidar measurements: comparison against a model analytical solution

NASA Astrophysics Data System (ADS)

Lolli, Simone; Di Girolamo, Paolo; Demoz, Belay; Li, Xiaowen; Welton, Ellsworth J.

2018-04-01

Rain evaporation significantly contributes to moisture and heat cloud budgets. In this paper, we illustrate an approach to estimate the median volume raindrop diameter and the rain evaporation rate profiles from dual-wavelength lidar measurements. These observational results are compared with those provided by a model analytical solution. We made use of measurements from the multi-wavelength Raman lidar BASIL.

Large Eddy Simulation of jets laden with evaporating drops

NASA Technical Reports Server (NTRS)

Leboissetier, A.; Okong'o, N.; Bellan, J.

2004-01-01

LES of a circular jet laden with evaporating liquid drops are conducted to assess computational-drop modeling and three different SGS-flux models: the Scale Similarity model (SSC), using a constant coefficient calibrated on a temporal mixing layer DNS database, and dynamic-coefficient Gradient and Smagorinsky models.

Thin stillage fractionation using ultrafiltration: resistance in series model.

PubMed

Arora, Amit; Dien, Bruce S; Belyea, Ronald L; Wang, Ping; Singh, Vijay; Tumbleson, M E; Rausch, Kent D

2009-02-01

The corn based dry grind process is the most widely used method in the US for fuel ethanol production. Fermentation of corn to ethanol produces whole stillage after ethanol is removed by distillation. It is centrifuged to separate thin stillage from wet grains. Thin stillage contains 5-10% solids. To concentrate solids of thin stillage, it requires evaporation of large amounts of water and maintenance of evaporators. Evaporator maintenance requires excess evaporator capacity at the facility, increasing capital expenses, requiring plant slowdowns or shut downs and results in revenue losses. Membrane filtration is one method that could lead to improved value of thin stillage and may offer an alternative to evaporation. Fractionation of thin stillage using ultrafiltration was conducted to evaluate membranes as an alternative to evaporators in the ethanol industry. Two regenerated cellulose membranes with molecular weight cut offs of 10 and 100 kDa were evaluated. Total solids (suspended and soluble) contents recovered through membrane separation process were similar to those from commercial evaporators. Permeate flux decline of thin stillage using a resistance in series model was determined. Each of the four components of total resistance was evaluated experimentally. Effects of operating variables such as transmembrane pressure and temperature on permeate flux rate and resistances were determined and optimum conditions for maximum flux rates were evaluated. Model equations were developed to evaluate the resistance components that are responsible for fouling and to predict total flux decline with respect to time. Modeling results were in agreement with experimental results (R(2) > 0.98).

Near-infrared hyperspectral imaging of water evaporation dynamics for early detection of incipient caries.

PubMed

Usenik, Peter; Bürmen, Miran; Fidler, Aleš; Pernuš, Franjo; Likar, Boštjan

2014-10-01

Incipient caries is characterized as demineralization of the tooth enamel reflecting in increased porosity of enamel structure. As a result, the demineralized enamel may contain increased amount of water, and exhibit different water evaporation dynamics than the sound enamel. The objective of this paper is to assess the applicability of water evaporation dynamics of sound and demineralized enamel for detection and quantification of incipient caries using near-infrared hyperspectral imaging. The time lapse of water evaporation from enamel samples with artificial and natural caries lesions of different stages was imaged by a near-infrared hyperspectral imaging system. Partial least squares regression was used to predict the water content from the acquired spectra. The water evaporation dynamics was characterized by a first order logarithmic drying model. The calculated time constants of the logarithmic drying model were used as the discriminative feature. The conducted measurements showed that demineralized enamel contains more water and exhibits significantly faster water evaporation than the sound enamel. By appropriate modelling of the water evaporation process from the enamel surface, the contrast between the sound and demineralized enamel observed in the individual near infrared spectral images can be substantially enhanced. The presented results indicate that near-infrared based prediction of water content combined with an appropriate drying model presents a strong foundation for development of novel diagnostic tools for incipient caries detection. The results of the study enhance the understanding of the water evaporation process from the sound and demineralized enamel and have significant implications for the detection of incipient caries by near-infrared hyperspectral imaging. Copyright © 2014 Elsevier Ltd. All rights reserved.

Volatility of organic aerosol: evaporation of ammonium sulfate/succinic acid aqueous solution droplets.

PubMed

Yli-Juuti, Taina; Zardini, Alessandro A; Eriksson, Axel C; Hansen, Anne Maria K; Pagels, Joakim H; Swietlicki, Erik; Svenningsson, Birgitta; Glasius, Marianne; Worsnop, Douglas R; Riipinen, Ilona; Bilde, Merete

2013-01-01

Condensation and evaporation modify the properties and effects of atmospheric aerosol particles. We studied the evaporation of aqueous succinic acid and succinic acid/ammonium sulfate droplets to obtain insights on the effect of ammonium sulfate on the gas/particle partitioning of atmospheric organic acids. Droplet evaporation in a laminar flow tube was measured in a Tandem Differential Mobility Analyzer setup. A wide range of droplet compositions was investigated, and for some of the experiments the composition was tracked using an Aerosol Mass Spectrometer. The measured evaporation was compared to model predictions where the ammonium sulfate was assumed not to directly affect succinic acid evaporation. The model captured the evaporation rates for droplets with large organic content but overestimated the droplet size change when the molar concentration of succinic acid was similar to or lower than that of ammonium sulfate, suggesting that ammonium sulfate enhances the partitioning of dicarboxylic acids to aqueous particles more than currently expected from simple mixture thermodynamics. If extrapolated to the real atmosphere, these results imply enhanced partitioning of secondary organic compounds to particulate phase in environments dominated by inorganic aerosol.

Volatility of Organic Aerosol: Evaporation of Ammonium Sulfate/Succinic Acid Aqueous Solution Droplets

PubMed Central

2013-01-01

Condensation and evaporation modify the properties and effects of atmospheric aerosol particles. We studied the evaporation of aqueous succinic acid and succinic acid/ammonium sulfate droplets to obtain insights on the effect of ammonium sulfate on the gas/particle partitioning of atmospheric organic acids. Droplet evaporation in a laminar flow tube was measured in a Tandem Differential Mobility Analyzer setup. A wide range of droplet compositions was investigated, and for some of the experiments the composition was tracked using an Aerosol Mass Spectrometer. The measured evaporation was compared to model predictions where the ammonium sulfate was assumed not to directly affect succinic acid evaporation. The model captured the evaporation rates for droplets with large organic content but overestimated the droplet size change when the molar concentration of succinic acid was similar to or lower than that of ammonium sulfate, suggesting that ammonium sulfate enhances the partitioning of dicarboxylic acids to aqueous particles more than currently expected from simple mixture thermodynamics. If extrapolated to the real atmosphere, these results imply enhanced partitioning of secondary organic compounds to particulate phase in environments dominated by inorganic aerosol. PMID:24107221

Nanosecond laser ablation of target Al in a gaseous medium: explosive boiling

NASA Astrophysics Data System (ADS)

Mazhukin, V. I.; Mazhukin, A. V.; Demin, M. M.; Shapranov, A. V.

2018-03-01

An approximate mathematical description of the processes of homogeneous nucleation and homogeneous evaporation (explosive boiling) of a metal target (Al) under the influence of ns laser radiation is proposed in the framework of the hydrodynamic model. Within the continuum approach, a multi-phase, multi-front hydrodynamic model and a computational algorithm are designed to simulate nanosecond laser ablation of the metal targets immersed in gaseous media. The proposed approach is intended for modeling and detailed analysis of the mechanisms of heterogeneous and homogeneous evaporation and their interaction with each other. It is shown that the proposed model and computational algorithm allow modeling of interrelated mechanisms of heterogeneous and homogeneous evaporation of metals, manifested in the form of pulsating explosive boiling. Modeling has shown that explosive evaporation in metals is due to the presence of a near-surface temperature maximum. It has been established that in nanosecond pulsed laser ablation, such exposure regimes can be implemented in which phase explosion is the main mechanism of material removal.

Effect of DOC on evaporation from small Wisconsin lakes

NASA Astrophysics Data System (ADS)

Watras, C. J.; Morrison, K. A.; Rubsam, J. L.

2016-09-01

Evaporation (E) dominates the loss of water from many small lakes, and the balance between precipitation and evaporation (P-E) often governs water levels. In this study, evaporation rates were estimated for three small Wisconsin lakes over several years using 30-min data from floating evaporation pans (E-pans). Measured E was then compared to the output of mass transfer models driven by local conditions over daily time scales. The three lakes were chosen to span a range of dissolved organic carbon (DOC) concentrations (3-20 mg L-1), a solute that imparts a dark, tea-stain color which absorbs solar energy and limits light penetration. Since the lakes were otherwise similar, we hypothesized that a DOC-mediated increase in surface water temperature would translate directly to higher rates of evaporation thereby informing climate response models. Our results confirmed a DOC effect on surface water temperature, but that effect did not translate to enhanced evaporation. Instead the opposite was observed: evaporation rates decreased as DOC increased. Ancillary data and prior studies suggest two explanatory mechanisms: (1) disproportionately greater radiant energy outflux from high DOC lakes, and (2) the combined effect of wind speed (W) and the vapor pressure gradient (es - ez), whose product [W(es - ez)] was lowest on the high DOC lake, despite very low wind speeds (<1.5 m s-1) and steep forested uplands surrounding all three lakes. Agreement between measured (E-pan) and modeled evaporation rates was reasonably good, based on linear regression results (r2: 0.6-0.7; slope: 0.5-0.7, for the best model). Rankings based on E were similar whether determined by measured or modeled criteria (high DOC < low DOC). Across the 3 lakes and 4 years, E averaged ∼3 mm d-1 (C.V. 9%), but statistically significant differences between lakes resulted in substantial differences in cumulative E that were consistent from year to year. Daily water budgets for these lakes show that inputs were dominated by P and outputs by E; and our findings indicate that subtle changes in the variables that drive E can have measurable effects on water levels by shifting the balance between P and E.

Solar geoengineering, atmospheric water vapor transport, and land plants

NASA Astrophysics Data System (ADS)

Caldeira, Ken; Cao, Long

2015-04-01

This work, using the GeoMIP database supplemented by additional simulations, discusses how solar geoengineering, as projected by the climate models, affects temperature and the hydrological cycle, and how this in turn is related to projected changes in net primary productivity (NPP). Solar geoengineering simulations typically exhibit reduced precipitation. Solar geoengineering reduces precipitation because solar geoengineering reduces evaporation. Evaporation precedes precipitation, and, globally, evaporation equals precipitation. CO2 tends to reduce evaporation through two main mechanisms: (1) CO2 tends to stabilize the atmosphere especially over the ocean, leading to a moister atmospheric boundary layer over the ocean. This moistening of the boundary layer suppresses evaporation. (2) CO2 tends to diminish evapotranspiration, at least in most land-surface models, because higher atmospheric CO2 concentrations allow leaves to close their stomata and avoid water loss. In most high-CO2 simulations, these effects of CO2 which tend to suppress evaporation are masked by the tendency of CO2-warming effect to increase evaporation. In a geoengineering simulation, with the warming effect of CO2 largely offset by the solar geoengineering, the evaporation suppressing characteristics of CO2 are no longer masked and are clearly exhibited. Decreased precipitation in solar geoengineering simulations is a bit like ocean acidification - an effect of high CO2 concentrations that is not offset by solar geoengineering. Locally, precipitation ultimately either evaporates (much of that through the leaves of plants) or runs off through groundwater to streams and rivers. On long time scales, runoff equals precipitation minus evaporation, and thus, water runoff generated at a location is equal to the net atmospheric transport of water to that location. Runoff typically occurs where there is substantial soil moisture, at least seasonally. Locations where there is enough water to maintain runoff are typically locations where there is sufficient water to maintain plant growth. This work aims at: (i) Identifying the geographical distribution of sensitivity of modeled-NPP to changes in CO2, temperature, and various parameters related to the hydrological cycle; (ii) Geographically partitioning changes in modeled-NPP to changes in CO2, temperature, and hydrological variables (and a non-linear interaction term).

Diffusion Of Mass In Evaporating Multicomponent Drops

NASA Technical Reports Server (NTRS)

Bellan, Josette; Harstad, Kenneth G.

1992-01-01

Report summarizes study of diffusion of mass and related phenomena occurring in evaporation of dense and dilute clusters of drops of multicomponent liquids intended to represent fuels as oil, kerosene, and gasoline. Cluster represented by simplified mathematical model, including global conservation equations for entire cluster and conditions on boundary between cluster and ambient gas. Differential equations of model integrated numerically. One of series of reports by same authors discussing evaporation and combustion of sprayed liquid fuels.

Accounting for rainfall evaporation using dual-polarization radar and mesoscale model data

NASA Astrophysics Data System (ADS)

Pallardy, Quinn; Fox, Neil I.

2018-02-01

Implementation of dual-polarization radar should allow for improvements in quantitative precipitation estimates due to dual-polarization capability allowing for the retrieval of the second moment of the gamma drop size distribution. Knowledge of the shape of the DSD can then be used in combination with mesoscale model data to estimate the motion and evaporation of each size of drop falling from the height at which precipitation is observed by the radar to the surface. Using data from Central Missouri at a range between 130 and 140 km from the operational National Weather Service radar a rain drop tracing scheme was developed to account for the effects of evaporation, where individual raindrops hitting the ground were traced to the point in space and time where they interacted with the radar beam. The results indicated evaporation played a significant role in radar rainfall estimation in situations where the atmosphere was relatively dry. Improvements in radar estimated rainfall were also found in these situations by accounting for evaporation. The conclusion was made that the effects of raindrop evaporation were significant enough to warrant further research into the inclusion high resolution model data in the radar rainfall estimation process for appropriate locations.

Trends in evaporation loss over the UK: 1962 to 2013

NASA Astrophysics Data System (ADS)

Blyth, Eleanor; Robinson, Emma; Martinez de la Torre, Alberto

2017-04-01

Many models of hydrology assume that an increase in air temperature will result in an increase in evaporation. However, there are some processes involved in transpiration (evaporation through the vegetation) that make the relationship more complicated: in a bid to conserve water, vegetation will reduce their stomata in response to drier soils and warmer drier air which leads to lower transpiration rates despite higher evaporative demands. In addition, the vegetation responds to increases in atmospheric carbon dioxide by closing their stomata, and this further reduces the transpiration. The JULES (Joint UK Land Environment Simulator) model, used widely in the UK to study the impacts of climate change on the environment, includes many of the processes that are likely to affect changes in water loss and its impact on large scale hydrology. A new assessment of the UK wide water balance for the last 52 years (1961 to 2013) at a 1km grid-scale has been made using this model in a system called CHESS (Climate Hydrology and Ecology research Support System). Some data is available to check the overall water balance. For instance, river flow data can be used at an annual time scale to capture the water balance, while evaporation data from flux towers can be used at some locations around the UK for the few years that it is available to evaluate the seasonal variations of evaporation. Both of these methods provide imperfect but useful evidence. Here we present the results of the modelling exercise and the evaluation: long term increasing evaporation loss trends are clearly present in the model output and these are discussed with respect to the different drivers of change.

Modelling the evaporation of a tear film over a contact lens.

PubMed

Talbott, Kevin; Xu, Amber; Anderson, Daniel M; Seshaiyer, Padmanabhan

2015-06-01

A contact lens (CL) separates the tear film into a pre-lens tear film (PrLTF), the fluid layer between the CL and the outside environment, and a post-lens tear film (PoLTF), the fluid layer between the CL and the cornea. We examine a model for evaporation of a PrLTF on a modern permeable CL allowing fluid transfer between the PrLTF and the PoLTF. Evaporation depletes the PrLTF, and continued evaporation causes depletion of the PoLTF via fluid loss through the CL. Governing equations include Navier-Stokes, heat and Darcy's equations for the fluid flow and heat transfer in the PrLTF and porous layer. The PoLTF is modelled by a fixed pressure condition on the posterior surface of the CL. The original model is simplified using lubrication theory for the PrLTF and CL applied to a sagittal plane through the eye. We obtain a partial differential equation (PDE) for the PrLTF thickness that is first-order in time and fourth-order in space. This model incorporates evaporation, conjoining pressure effects in the PrLTF, capillarity and heat transfer. For a planar film, we find that this PDE can be reduced to an ordinary differential equation (ODE) that can be solved analytically or numerically. This reduced model allows for interpretation of the various system parameters and captures most of the basic physics contained in the model. Comparisons of ODE and PDE models, including estimates for the loss of fluid through the lens due to evaporation, are given. © The Authors 2014. Published by Oxford University Press on behalf of the Institute of Mathematics and its Applications. All rights reserved.

Projecting and attributing future changes of evaporative demand over China in CMIP5 climate models

NASA Astrophysics Data System (ADS)

Liu, Wenbin; Sun, Fubao

2017-04-01

Atmospheric evaporative demand plays a pivotal role in global water and energy budgets and its change is very important for drought monitoring, irrigation scheduling and water resource management under a changing environment. Here, we first projected and attributed future changes of pan evaporation (E_pan), a measurable indictor for atmospheric evaporative demand, over China through a physical- based approach, namely PenPan model, forced with outputs form twelve state-of-the-art Coupled Model Intercomparison Project Phase 5 (CMIP5) climate models. An equidistant quantile mapping method was also used to correct the biases in GCMs outputs to reduce uncertainty in〖 E〗_pan projection. The results indicated that the E_panwould increase during the periods 2021-2050 and 2071-2100 relative to the baseline period 1971-2000 under the Representative Concentration Pathway (RCP) 4.5 and 8.5 scenarios, which can mainly be attributed to the projected increase in air temperature and vapour pressure deficit over China. The percentage increase of E_pan is relatively larger in eastern China than that in western China, which is due to the spatially inconsistent increases in air temperature, net radiation, wind speed and vapour pressure deficit over China. The widely reported "pan evaporation paradox" was not well reproduced for the period 1961-2000 in the climate models, before or after bias correction, suggesting discrepancy between observed and modeled trends. With that caveat, we found that the pan evaporation has been projected to increase at a rate of 117 167 mm/yr per K (72 80 mm/yr per K) over China using the multiple GCMs under the RCP4.5 (RCP8.5) scenario with increased greenhouse gases and the associated warming of the climate system. References: Liu W, and Sun F, 2017. Projecting and attributing future changes of evaporative demand over China in CMIP5 climate models, Journal of Hydrometeorology, doi: 10.1175/JHM-D-16-0204.1

Understanding the role of monolayers in retarding evaporation from water storage bodies

NASA Astrophysics Data System (ADS)

Fellows, Christopher M.; Coop, Paul A.; Lamb, David W.; Bradbury, Ronald C.; Schiretz, Helmut F.; Woolley, Andrew J.

2015-03-01

Retardation of evaporation by monomolecular films by a 'barrier model' does not explain the effect of air velocity on relative evaporation rates in the presence and absence of such films. An alternative mechanism for retardation of evaporation attributes reduced evaporation to a reduction of surface roughness, which in turn increases the effective vapour pressure of water above the surface. Evaporation suppression effectiveness under field conditions should be predictable from measurements of the surface dilational modulus of monolayers and research directed to optimising this mechanism should be more fruitful than research aimed at optimising a monolayer to provide an impermeable barrier.

A Computer Model of the Evaporator for the Development of an Automatic Control System

NASA Astrophysics Data System (ADS)

Kozin, K. A.; Efremov, E. V.; Kabrysheva, O. P.; Grachev, M. I.

2016-08-01

For the implementation of a closed nuclear fuel cycle it is necessary to carry out a series of experimental studies to justify the choice of technology. In addition, the operation of the radiochemical plant is impossible without high-quality automatic control systems. In the technologies of spent nuclear fuel reprocessing, the method of continuous evaporation is often used for a solution conditioning. Therefore, the effective continuous technological process will depend on the operation of the evaporation equipment. Its essential difference from similar devices is a small size. In this paper the method of mathematic simulation is applied for the investigation of one-effect evaporator with an external heating chamber. Detailed modelling is quite difficult because the phase equilibrium dynamics of the evaporation process is not described. Moreover, there is a relationship with the other process units. The results proved that the study subject is a MIMO plant, nonlinear over separate control channels and not selfbalancing. Adequacy was tested using the experimental data obtained at the laboratory evaporation unit.

Suppression of the sonic heat transfer limit in high-temperature heat pipes

NASA Astrophysics Data System (ADS)

Dobran, Flavio

1989-08-01

The design of high-performance heat pipes requires optimization of heat transfer surfaces and liquid and vapor flow channels to suppress the heat transfer operating limits. In the paper an analytical model of the vapor flow in high-temperature heat pipes is presented, showing that the axial heat transport capacity limited by the sonic heat transfer limit depends on the working fluid, vapor flow area, manner of liquid evaporation into the vapor core of the evaporator, and lengths of the evaporator and adiabatic regions. Limited comparisons of the model predictions with data of the sonic heat transfer limits are shown to be very reasonable, giving credibility to the proposed analytical approach to determine the effect of various parameters on the axial heat transport capacity. Large axial heat transfer rates can be achieved with large vapor flow cross-sectional areas, small lengths of evaporator and adiabatic regions or a vapor flow area increase in these regions, and liquid evaporation in the evaporator normal to the main flow.

On the remote measurement of evaporation rates from bare wet soil under variable cloud cover

NASA Technical Reports Server (NTRS)

Auer, S.

1976-01-01

Evaporation rates from a natural wet soil surface are calculated from an energy balance equation at 0.1-hour intervals. A procedure is developed for calculating the heat flux through the soil surface from a harmonic analysis of the surface temperature curve. The evaporation integrated over an entire 24-hour period is compared with daily evaporation rates obtained from published models.

Simple analytical model of evapotranspiration in the presence of roots.

PubMed

Cejas, Cesare M; Hough, L A; Castaing, Jean-Christophe; Frétigny, Christian; Dreyfus, Rémi

2014-10-01

Evaporation of water out of a soil involves complicated and well-debated mechanisms. When plant roots are added into the soil, water transfer between the soil and the outside environment is even more complicated. Indeed, plants provide an additional process of water transfer. Water is pumped by the roots, channeled to the leaf surface, and released into the surrounding air by a process called transpiration. Prediction of the evapotranspiration of water over time in the presence of roots helps keep track of the amount of water that remains in the soil. Using a controlled visual setup of a two-dimensional model soil consisting of monodisperse glass beads, we perform experiments on actual roots grown under different relative humidity conditions. We record the total water mass loss in the medium and the position of the evaporating front that forms within the medium. We then develop a simple analytical model that predicts the position of the evaporating front as a function of time as well as the total amount of water that is lost from the medium due to the combined effects of evaporation and transpiration. The model is based on fundamental principles of evaporation fluxes and includes empirical assumptions on the quantity of open stomata in the leaves, where water transpiration occurs. Comparison between the model and experimental results shows excellent prediction of the position of the evaporating front as well as the total mass loss from evapotranspiration in the presence of roots. The model also provides a way to predict the lifetime of a plant.

Advances in the two-source energy balance model:Partioning of evaporation and transpiration for row crops

USDA-ARS?s Scientific Manuscript database

Accurate partitioning of the evaporation (E) and transpiration (T) components of evapotranspiration (ET) in remote sensing models is important for evaluating strategies aimed at increasing crop water productivity. The two-source energy balance (TSEB) model solves the energy balance of the soil-plant...

Simultaneous ion and neutral evaporation in aqueous nanodrops: experiment, theory, and molecular dynamics simulations.

PubMed

Higashi, Hidenori; Tokumi, Takuya; Hogan, Christopher J; Suda, Hiroshi; Seto, Takafumi; Otani, Yoshio

2015-06-28

We use a combination of tandem ion mobility spectrometry (IMS-IMS, with differential mobility analyzers), molecular dynamics (MD) simulations, and analytical models to examine both neutral solvent (H2O) and ion (solvated Na(+)) evaporation from aqueous sodium chloride nanodrops. For experiments, nanodrops were produced via electrospray ionization (ESI) of an aqueous sodium chloride solution. Two nanodrops were examined in MD simulations: a 2500 water molecule nanodrop with 68 Na(+) and 60 Cl(-) ions (an initial net charge of z = +8), and (2) a 1000 water molecule nanodrop with 65 Na(+) and 60 Cl(-) ions (an initial net charge of z = +5). Specifically, we used MD simulations to examine the validity of a model for the neutral evaporation rate incorporating both the Kelvin (surface curvature) and Thomson (electrostatic) influences, while both MD simulations and experimental measurements were compared to predictions of the ion evaporation rate equation of Labowsky et al. [Anal. Chim. Acta, 2000, 406, 105-118]. Within a single fit parameter, we find excellent agreement between simulated and modeled neutral evaporation rates for nanodrops with solute volume fractions below 0.30. Similarly, MD simulation inferred ion evaporation rates are in excellent agreement with predictions based on the Labowsky et al. equation. Measurements of the sizes and charge states of ESI generated NaCl clusters suggest that the charge states of these clusters are governed by ion evaporation, however, ion evaporation appears to have occurred with lower activation energies in experiments than was anticipated based on analytical calculations as well as MD simulations. Several possible reasons for this discrepancy are discussed.

Aqueous Chemical Modeling of Sedimentation on Early Mars with Application to Surface-Atmosphere Evolution

NASA Technical Reports Server (NTRS)

Catling, David C.

2004-01-01

This project was to investigate models for aqueous sedimentation on early Mars from fluid evaporation. Results focused on three specific areas: (1) First, a fluid evaporation model incorporating iron minerals was developed to compute the evaporation of a likely solution on early Mars derived from the weathering of mafic rock. (2) Second, the fluid evaporation model was applied to salts within Martian meteorites, specifically salts in the nakhlites and ALH84001. Evaporation models were found to be consistent with the mineralogy of salt assemblages-anhydrite, gypsum, Fe-Mg-Ca carbonates, halite, clays-- and the concentric chemical fractionation of Ca-to Mg-rich carbonate rosettes in ALH84001. We made progress in further developing our models of fluid concentration by contributing to updating the FREZCHEM model. (3) Third, theoretical investigation was done to determine the thermodynamics and kinetics involved in the formation of gray, crystalline hematite. This mineral, of probable ancient aqueous origin, has been observed in several areas on the surface of Mars by the Thermal Emission Spectrometer on Mars Global Surveyor. The "Opportunity" Mars Exploration Rover has also detected gray hematite at its landing site in Meridiani Planum. We investigated how gray hematite can be formed via atmospheric oxidation, aqueous precipitation and subsequent diagenesis, or hydrothermal processes. We also studied the geomorphology of the Aram Chaos hematite region using Mars Orbiter Camera (MOC) images.

Spectral model for long-term computation of thermodynamics and potential evaporation in shallow wetlands

NASA Astrophysics Data System (ADS)

de la Fuente, Alberto; Meruane, Carolina

2017-09-01

Altiplanic wetlands are unique ecosystems located in the elevated plateaus of Chile, Argentina, Peru, and Bolivia. These ecosystems are under threat due to changes in land use, groundwater extractions, and climate change that will modify the water balance through changes in precipitation and evaporation rates. Long-term prediction of the fate of aquatic ecosystems imposes computational constraints that make finding a solution impossible in some cases. In this article, we present a spectral model for long-term simulations of the thermodynamics of shallow wetlands in the limit case when the water depth tends to zero. This spectral model solves for water and sediment temperature, as well as heat, momentum, and mass exchanged with the atmosphere. The parameters of the model (water depth, thermal properties of the sediments, and surface albedo) and the atmospheric downscaling were calibrated using the MODIS product of the land surface temperature. Moreover, the performance of the daily evaporation rates predicted by the model was evaluated against daily pan evaporation data measured between 1964 and 2012. The spectral model was able to correctly represent both seasonal fluctuation and climatic trends observed in daily evaporation rates. It is concluded that the spectral model presented in this article is a suitable tool for assessing the global climate change effects on shallow wetlands whose thermodynamics is forced by heat exchanges with the atmosphere and modulated by the heat-reservoir role of the sediments.

Predicting the weathering of fuel and oil spills: A diffusion-limited evaporation model.

PubMed

Kotzakoulakis, Konstantinos; George, Simon C

2018-01-01

The majority of the evaporation models currently available in the literature for the prediction of oil spill weathering do not take into account diffusion-limited mass transport and the formation of a concentration gradient in the oil phase. The altered surface concentration of the spill caused by diffusion-limited transport leads to a slower evaporation rate compared to the predictions of diffusion-agnostic evaporation models. The model presented in this study incorporates a diffusive layer in the oil phase and predicts the diffusion-limited evaporation rate. The information required is the composition of the fluid from gas chromatography or alternatively the distillation data. If the density or a single viscosity measurement is available the accuracy of the predictions is higher. Environmental conditions such as water temperature, air pressure and wind velocity are taken into account. The model was tested with synthetic mixtures, petroleum fuels and crude oils with initial viscosities ranging from 2 to 13,000 cSt. The tested temperatures varied from 0 °C to 23.4 °C and wind velocities from 0.3 to 3.8 m/s. The average absolute deviation (AAD) of the diffusion-limited model ranged between 1.62% and 24.87%. In comparison, the AAD of a diffusion-agnostic model ranged between 2.34% and 136.62% against the same tested fluids. Copyright © 2017 Elsevier Ltd. All rights reserved.

Towards a sharp-interface volume-of-fluid methodology for modeling evaporation

NASA Astrophysics Data System (ADS)

Pathak, Ashish; Raessi, Mehdi

2017-11-01

In modeling evaporation, the diffuse-interface (one-domain) formulation yields inaccurate results. Recent efforts approaching the problem via a sharp-interface (two-domain) formulation have shown significant improvements. The reasons behind their better performance are discussed in the present work. All available sharp-interface methods, however, exclusively employ the level-set. In the present work, we develop a sharp-interface evaporation model in a volume-of-fluid (VOF) framework in order to leverage its mass-conserving property as well as its ability to handle large topographical changes. We start with a critical review of the assumptions underlying the mathematical equations governing evaporation. For example, it is shown that the assumption of incompressibility can only be applied in special circumstances. The famous D2 law used for benchmarking is valid exclusively to steady-state test problems. Transient is present over significant lifetime of a micron-size droplet. Therefore, a 1D spherical fully transient model is developed to provide a benchmark transient solution. Finally, a 3D Cartesian Navier-Stokes evaporation solver is developed. Some preliminary validation test-cases are presented for static and moving drop evaporation. This material is based upon work supported by the Department of Energy, Office of Energy Efficiency and Renewable Energy and the Department of Defense, Tank and Automotive Research, Development, and Engineering Center, under Award Number DEEE0007292.

A sensitivity study of the effects of evaporation/condensation accommodation coefficients on transient heat pipe modeling

NASA Astrophysics Data System (ADS)

Hall, Michael L.; Doster, J. Michael

1990-03-01

The dynamic behavior of liquid metal heat pipe models is strongly influenced by the choice of evaporation and condensation modeling techniques. Classic kinetic theory descriptions of the evaporation and condensation processes are often inadequate for real situations; empirical accommodation coefficients are commonly utilized to reflect nonideal mass transfer rates. The complex geometries and flow fields found in proposed heat pipe systems cause considerable deviation from the classical models. the THROHPUT code, which has been described in previous works, was developed to model transient liquid metal heat pipe behavior from frozen startup conditions to steady state full power operation. It is used here to evaluate the sensitivity of transient liquid metal heat pipe models to the choice of evaporation and condensation accommodation coefficients. Comparisons are made with experimental liquid metal heat pipe data. It is found that heat pipe behavior can be predicted with the proper choice of the accommodation coefficients. However, the common assumption of spatially constant accommodation coefficients is found to be a limiting factor in the model.

Application of Modular Modeling System to Predict Evaporation, Infiltration, Air Temperature, and Soil Moisture

NASA Technical Reports Server (NTRS)

Boggs, Johnny; Birgan, Latricia J.; Tsegaye, Teferi; Coleman, Tommy; Soman, Vishwas

1997-01-01

Models are used for numerous application including hydrology. The Modular Modeling System (MMS) is one of the few that can simulate a hydrology process. MMS was tested and used to compare infiltration, soil moisture, daily temperature, and potential and actual evaporation for the Elinsboro sandy loam soil and the Mattapex silty loam soil in the Microwave Radiometer Experiment of Soil Moisture Sensing at Beltsville Agriculture Research Test Site in Maryland. An input file for each location was created to nut the model. Graphs were plotted, and it was observed that the model gave a good representation for evaporation for both plots. In comparing the two plots, it was noted that infiltration and soil moisture tend to peak around the same time, temperature peaks in July and August and the peak evaporation was observed on September 15 and July 4 for the Elinsboro Mattapex plot respectively. MMS can be used successfully to predict hydrological processes as long as the proper input parameters are available.

Development and application of Geobacillus stearothermophilus growth model for predicting spoilage of evaporated milk.

PubMed

Kakagianni, Myrsini; Gougouli, Maria; Koutsoumanis, Konstantinos P

2016-08-01

The presence of Geobacillus stearothermophilus spores in evaporated milk constitutes an important quality problem for the milk industry. This study was undertaken to provide an approach in modelling the effect of temperature on G. stearothermophilus ATCC 7953 growth and in predicting spoilage of evaporated milk. The growth of G. stearothermophilus was monitored in tryptone soy broth at isothermal conditions (35-67 °C). The data derived were used to model the effect of temperature on G. stearothermophilus growth with a cardinal type model. The cardinal values of the model for the maximum specific growth rate were Tmin = 33.76 °C, Tmax = 68.14 °C, Topt = 61.82 °C and μopt = 2.068/h. The growth of G. stearothermophilus was assessed in evaporated milk at Topt in order to adjust the model to milk. The efficiency of the model in predicting G. stearothermophilus growth at non-isothermal conditions was evaluated by comparing predictions with observed growth under dynamic conditions and the results showed a good performance of the model. The model was further used to predict the time-to-spoilage (tts) of evaporated milk. The spoilage of this product caused by acid coagulation when the pH approached a level around 5.2, eight generations after G. stearothermophilus reached the maximum population density (Nmax). Based on the above, the tts was predicted from the growth model as the sum of the time required for the microorganism to multiply from the initial to the maximum level ( [Formula: see text] ), plus the time required after the [Formula: see text] to complete eight generations. The observed tts was very close to the predicted one indicating that the model is able to describe satisfactorily the growth of G. stearothermophilus and to provide realistic predictions for evaporated milk spoilage. Copyright © 2016 Elsevier Ltd. All rights reserved.

Modeling Evaporation and Particle Assembly in Colloidal Droplets.

PubMed

Zhao, Mingfei; Yong, Xin

2017-06-13

Evaporation-induced assembly of nanoparticles in a drying droplet is of great importance in many engineering applications, including printing, coating, and thin film processing. The investigation of particle dynamics in evaporating droplets can provide fundamental hydrodynamic insight for revealing the processing-structure relationship in the particle self-organization induced by solvent evaporation. We develop a free-energy-based multiphase lattice Boltzmann method coupled with Brownian dynamics to simulate evaporating colloidal droplets on solid substrates with specified wetting properties. The influence of interface-bound nanoparticles on the surface tension and evaporation of a flat liquid-vapor interface is first quantified. The results indicate that the particles at the interface reduce surface tension and enhance evaporation flux. For evaporating particle-covered droplets on substrates with different wetting properties, we characterize the increase of evaporate rate via measuring droplet volume. We find that droplet evaporation is determined by the number density and circumferential distribution of interfacial particles. We further correlate particle dynamics and assembly to the evaporation-induced convection in the bulk and on the surface of droplet. Finally, we observe distinct final deposits from evaporating colloidal droplets with bulk-dispersed and interface-bound particles. In addition, the deposit pattern is also influenced by the equilibrium contact angle of droplet.

Relationship between a solar drying model of red pepper and the kinetics of pure water evaporation (2)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Passamai, V.; Saravia, L.

1997-05-01

In part one, a simple drying model of red pepper related to water evaporation was developed. In this second part the drying model is applied by means of related experiments. Both laboratory and open air drying experiments were carried out to validate the model and simulation results are presented.

Isotope effects accompanying evaporation of water from leaky containers.

PubMed

Rozanski, Kazimierz; Chmura, Lukasz

2008-03-01

Laboratory experiments aimed at quantifying isotope effects associated with partial evaporation of water from leaky containers have been performed under three different settings: (i) evaporation into dry atmosphere, performed in a dynamic mode, (ii) evaporation into dry atmosphere, performed in a static mode, and (iii) evaporation into free laboratory atmosphere. The results demonstrate that evaporative enrichment of water stored in leaky containers can be properly described in the framework of the Craig-Gordon evaporation model. The key parameter controlling the degree of isotope enrichment is the remaining fraction of water in the leaking containers. Other factors such as temperature, relative humidity, or extent of kinetic fractionation play only minor roles. Satisfactory agreement between observed and predicted isotope enrichments for both (18)O and (2)H in experiments for the case of evaporation into dry atmosphere could be obtained only when molecular diffusivity ratios of isotope water molecules as suggested recently by Cappa et al. [J. Geophys. Res., 108, 4525-4535, (2003).] were adopted. However, the observed and modelled isotope enrichments for (2)H and (18)O could be reconciled also for the ratios of molecular diffusivities obtained by Merlivat [J. Chem. Phys., 69, 2864-2871 (1978).], if non-negligible transport resistance in the viscous liquid sub-layer adjacent to the evaporating surface is considered. The evaporation experiments revealed that the loss of mass of water stored in leaky containers in the order of 1%, will lead to an increase of the heavy isotope content in this water by ca. 0.35 and 1.1 per thousand, for delta (18)O and delta (2)H, respectively.

Application of the Generalized Nonlinear Complementary Relationship for Estimating Evaporation in North China

NASA Astrophysics Data System (ADS)

Yu, M.; Wu, B.

2017-12-01

As an important part of the coupled Eco-Hydrological processes, evaporation is the bond for exchange of energy and heat between the surface and the atmosphere. However, the estimation of evaporation remains a challenge compared with other main hydrological factors in water cycle. The complementary relationship which proposed by Bouchet (1963) has laid the foundation for various approaches to estimate evaporation from land surfaces, the essence of the principle is a relationship between three types of evaporation in the environment. It can simply implemented with routine meteorological data without the need for resistance parameters of the vegetation and bare land, which are difficult to observed and complicated to estimate in most surface flux models. On this basis the generalized nonlinear formulation was proposed by Brutsaert (2015). The daily evaporation can be estimated once the potential evaporation (Epo) and apparent potential evaporation (Epa) are known. The new formulation has a strong physical basis and can be expected to perform better under natural water stress conditions, nevertheless, the model has not been widely validated over different climate types and underlying surface patterns. In this study, we attempted to apply the generalized nonlinear complementary relationship in North China, three flux stations in North China are used for testing the universality and accuracy of this model against observed evaporation over different vegetation types, including Guantao Site, Miyun Site and Huailai Site. Guantao Site has double-cropping systems and crop rotations with summer maize and winter wheat; the other two sites are dominated by spring maize. Detailed measurements of meteorological factors at certain heights above ground surface from automatic weather stations offered necessary parameters for daily evaporation estimation. Using the Bowen ratio, the surface energy measured by the eddy covariance systems at the flux stations is adjusted on a daily scale to satisfy the surface energy closure. After calibration the estimated daily evaporation are in good agreement with EC-measured flux data with a mean correlation coefficient in excess of 0.85. The results indicate that the generalized nonlinear complementary relationship can be applied in plant growing and non-growing season in North China.

/sup 18/O + /sup 12/C fusion-evaporation reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heusch, B; Beck, C; Coffin, J P

1980-01-01

A study of the /sup 18/O + /sup 12/C fusion evaporation reaction has been undertaken for 2 reasons: to make a systematic study of the formation cross section for each individual evaporation residue over a broad excitation energy region in the compound nucleus /sup 30/Si:30 to 62 MeV; and to compare all results to fusion-evaporation calculations done in the framework of the Hauser-Feschbach statistical model.

Model for determining vapor equilibrium rates in the hanging drop method for protein crystal growth

NASA Technical Reports Server (NTRS)

Baird, James K.; Frieden, Richard W.; Meehan, E. J., Jr.; Twigg, Pamela J.; Howard, Sandra B.; Fowlis, William A.

1987-01-01

An engineering analysis of the rate of evaporation of solvent in the hanging drop method of protein crystal growth is presented. Results are applied to 18 drop and well arrangements commonly encountered in the laboratory. The chemical nature of the salt, drop size and shape, drop concentration, well size, well concentration, and temperature are taken into account. The rate of evaporation increases with temperature, drop size, and the salt concentration difference between the drop and the well. The evaporation in this model possesses no unique half-life. Once the salt in the drop achieves 80 percent of its final concentration, further evaporation suffers from the law of diminishing returns.

Measurements of clothing evaporative resistance using a sweating thermal manikin: an overview

PubMed Central

WANG, Faming

2017-01-01

Evaporative resistance has been widely used to describe the evaporative heat transfer property of clothing. It is also a critical variable in heat stress models for predicting human physiological responses in various environmental conditions. At present, sweating thermal manikins provide a fast and cost-effective way to determine clothing evaporative resistance. Unfortunately, the measurement repeatability and reproducibility of evaporative resistance are rather low due to the complicated moisture transfer processes through clothing. This review article presents a systematical overview on major influential factors affecting the measurement precision of clothing evaporative resistance measurements. It also illustrates the state-of-the-art knowledge on the development of test protocol to measure clothing evaporative resistance by means of a sweating manikin. Some feasible and robust test procedures for measurement of clothing evaporative resistance using a sweating manikin are described. Recommendations on how to improve the measurement accuracy of clothing evaporative resistance are addressed and expected future trends on development of advanced sweating thermal manikins are finally presented. PMID:28566566

Mathematical model of compact type evaporator

NASA Astrophysics Data System (ADS)

Borovička, Martin; Hyhlík, Tomáš

2018-06-01

In this paper, development of the mathematical model for evaporator used in heat pump circuits is covered, with focus on air dehumidification application. Main target of this ad-hoc numerical model is to simulate heat and mass transfer in evaporator for prescribed inlet conditions and different geometrical parameters. Simplified 2D mathematical model is developed in MATLAB SW. Solvers for multiple heat and mass transfer problems - plate surface temperature, condensate film temperature, local heat and mass transfer coefficients, refrigerant temperature distribution, humid air enthalpy change are included as subprocedures of this model. An automatic procedure of data transfer is developed in order to use results of MATLAB model in more complex simulation within commercial CFD code. In the end, Proper Orthogonal Decomposition (POD) method is introduced and implemented into MATLAB model.

Modeling of liquid and gas flows in the horizontal layer with evaporation

NASA Astrophysics Data System (ADS)

Lyulin, Yuri; Rezanova, Ekaterina

2017-10-01

Mathematical modeling of two-layer flows in the "ethanol-nitrogen" system on the basis of the exact solutions of a special type is carried out. The influence of the gas flow, temperature and Soret effect on the flow patterns and evaporating processes at the interface is investigated. The results of comparison of the experimental and theoretical data are presented; the dependence of the evaporation intensity at interface of the gas flow rate and temperature is studied.

Non-equilibrium ionization around clouds evaporating in the interstellar medium

NASA Technical Reports Server (NTRS)

Ballet, J.; Luciani, J. F.; Mora, P.

1986-01-01

It is of prime importance for global models of the interstellar medium to know whether dense clouds do or do not evaporate in the hot coronal gas. The rate of mass exchanges between phases depends very much on that. McKee and Ostriker's model, for instance, assumes that evaporation is important enough to control the expansion of supernova remnants, and that mass loss obeys the law derived by Cowie and McKee. In fact, the geometry of the magnetic field is nearly unknown, and it might totally inhibit evaporation, if the clouds are not regularly connected to the hot gas. Up to now, the only test of the theory is the U.V. observation (by the Copernicus and IUE satellites) of absorption lines of ions such as OVI or NV, that exist at temperatures of a few 100,000 K typical of transition layers around evaporating clouds. Other means of testing the theory are discussed.

Advances in the two-source energy balance model: Partioning of evaporation and transpiration for row crops for cotton

USDA-ARS?s Scientific Manuscript database

Accurate partitioning of the evaporation (E) and transpiration (T) components of evapotranspiration (ET) in remote sensing models is important for evaluating strategies aimed at increasing crop water productivity. The two-source energy balance (TSEB) model solves the energy balance of the soil-plant...

Evaporation from a temperate closed-basin lake and its impact on present, past, and future water level

NASA Astrophysics Data System (ADS)

Xiao, Ke; Griffis, Timothy J.; Baker, John M.; Bolstad, Paul V.; Erickson, Matt D.; Lee, Xuhui; Wood, Jeffrey D.; Hu, Cheng; Nieber, John L.

2018-06-01

Lakes provide enormous economic, recreational, and aesthetic benefits to citizens. These ecosystem services may be adversely impacted by climate change. In the Twin Cities Metropolitan Area of Minnesota, USA, many lakes have been at historic low levels and water augmentation strategies have been proposed to alleviate the problem. White Bear Lake (WBL) is a notable example. Its water level declined 1.5 m during 2003-2013 for reasons that are not fully understood. This study examined current, past, and future lake evaporation to better understand how climate will impact the water balance of lakes within this region. Evaporation from WBL was measured from July 2014 to February 2017 using two eddy covariance (EC) systems to provide better constraints on the water budget and to investigate the impact of evaporation on lake level. The estimated annual evaporation losses for years 2014 through 2016 were 559 ± 22 mm, 779 ± 81 mm, and 766 ± 11 mm, respectively. The higher evaporation in 2015 and 2016 was caused by the combined effects of larger average daily evaporation and a longer ice-free season. The EC measurements were used to tune the Community Land Model 4 - Lake, Ice, Snow and Sediment Simulator (CLM4-LISSS) to estimate lake evaporation over the period 1979-2016. Retrospective analyses indicate that WBL evaporation increased during this time by about 3.8 mm year-1, which was driven by increased wind speed and lake-surface vapor pressure gradient. Using a business-as-usual greenhouse gas emission scenario (RCP8.5), lake evaporation was modeled forward in time from 2017 to 2100. Annual evaporation is expected to increase by 1.4 mm year-1 over this century, largely driven by lengthening ice-free periods. These changes in ice phenology and evaporation will have important implications for the regional water balance, and water management and water augmentation strategies that are being proposed for these Metropolitan lakes.

Dynamic Roughness Ratio-Based Framework for Modeling Mixed Mode of Droplet Evaporation.

PubMed

Gunjan, Madhu Ranjan; Raj, Rishi

2017-07-18

The spatiotemporal evolution of an evaporating sessile droplet and its effect on lifetime is crucial to various disciplines of science and technology. Although experimental investigations suggest three distinct modes through which a droplet evaporates, namely, the constant contact radius (CCR), the constant contact angle (CCA), and the mixed, only the CCR and the CCA modes have been modeled reasonably. Here we use experiments with water droplets on flat and micropillared silicon substrates to characterize the mixed mode. We visualize that a perfect CCA mode after the initial CCR mode is an idealization on a flat silicon substrate, and the receding contact line undergoes intermittent but recurring pinning (CCR mode) as it encounters fresh contaminants on the surface. The resulting increase in roughness lowers the contact angle of the droplet during these intermittent CCR modes until the next depinning event, followed by the CCA mode of evaporation. The airborne contaminants in our experiments are mostly loosely adhered to the surface and travel along with the receding contact line. The resulting gradual increase in the apparent roughness and hence the extent of CCR mode over CCA mode forces appreciable decrease in the contact angle observed during the mixed mode of evaporation. Unlike loosely adhered airborne contaminants on flat samples, micropillars act as fixed roughness features. The apparent roughness fluctuates about the mean value as the contact line recedes between pillars. Evaporation on these surfaces exhibits stick-jump motion with a short-duration mixed mode toward the end when the droplet size becomes comparable to the pillar spacing. We incorporate this dynamic roughness into a classical evaporation model to accurately predict the droplet evolution throughout the three modes, for both flat and micropillared silicon surfaces. We believe that this framework can also be extended to model the evaporation of nanofluids and the coffee-ring effect, among others.

Spatial and temporal connections in groundwater contribution to evaporation

NASA Astrophysics Data System (ADS)

Lam, A.; Karssenberg, D.; van den Hurk, B. J. J. M.; Bierkens, M. F. P.

2011-08-01

In climate models, lateral terrestrial water fluxes are usually neglected. We estimated the contribution of vertical and lateral groundwater fluxes to the land surface water budget at a subcontinental scale, by modeling convergence of groundwater and surfacewater fluxes. We present a hydrological model of the entire Danube Basin at 5 km resolution, and use it to show the importance of groundwater for the surface climate. Results show that the contribution of groundwater to evaporation is significant, and can locally be higher than 30 % in summer. We demonstrate through the same model that this contribution also has important temporal characteristics. A wet episode can influence groundwater contribution to summer evaporation for several years afterwards. This indicates that modeling groundwater flow has the potential to augment the multi-year memory of climate models. We also show that the groundwater contribution to evaporation is local by presenting the groundwater travel times and the magnitude of groundwater convergence. Throughout the Danube Basin the lateral fluxes of groundwater are negligible when modeling at this scale and resolution. This suggests that groundwater can be adequately added in land surface models by including a lower closed groundwater reservoir of sufficient size with two-way interaction with surface water and the overlying soil layers.

Interannual to Decadal Variability of Ocean Evaporation as Viewed from Climate Reanalyses

NASA Technical Reports Server (NTRS)

Robertson, Franklin R.; Bosilovich, Michael G.; Roberts, Jason B.; Wang, Hailan

2015-01-01

Questions we'll address: Given the uncoupled framework of "AMIP" (Atmosphere Model Inter-comparison Project) experiments, what can they tell us regarding evaporation variability? Do Reduced Observations Reanalyses (RedObs) using Surface Fluxes and Clouds (SFC) pressure (and wind) provide a more realistic picture of evaporation variability? What signals of interannual variability (e.g. El Nino/Southern Oscillation (ENSO)) and decadal variability (Interdecadal Pacific Oscillation (IPO)) are detectable with this hierarchy of evaporation estimates?

Evaluation of a locally homogeneous model of spray evaporation

NASA Technical Reports Server (NTRS)

Shearer, A. J.; Faeth, G. M.

1979-01-01

A model of spray evaporation which employs a second-order turbulence model in conjunction with the locally homogeneous flow approximation, which implies infinitely fast interphase transport rates is presented. Measurements to test the model were completed for single phase constant and variable density jets, as well as an evaporating spray in stagnant air. Profiles of mean velocity, composition, temperature and drop size distribution as well as velocity fluctuations and Reynolds stress, were measured within the spray. Predictions were in agreement with measurements in single phase flows and also with many characteristics of the spray, e.g. flow width, radial profiles of mean and turbulent quantities, and the axial rate of decay of mean velocity and mixture fraction.

The beam-driven chromospheric evaporation model of solar flares - A model not supported by observations from nonimpulsive large flares

NASA Technical Reports Server (NTRS)

Feldman, U.

1990-01-01

Most large solar flares exhibit hard X-ray emission which is usually impulsive, as well as thermal soft X-ray emission, which is gradual. The beam-driven chromospheric evaporation model of solar flares was proposed to explain the origin of the soft X-ray emitting flare plasma. A careful evaluation of the issue under discussion reveals contradictions between predictions from the theoretical chromospheric evaporation model and actual observations from a set of large X- and M-type flares. It is shown that although the soft X-ray and hard X-ray emissions are a result of the same flare, one is not a result of the other.

Study of the Effect of Turbulence and Large Obstacles on the Evaporation from Bare Soil Surface through Coupled Free-flow and Porous-medium Flow Model

NASA Astrophysics Data System (ADS)

Gao, B.; Smits, K. M.

2017-12-01

Evaporation is a strongly coupled exchange process of mass, momentum and energy between the atmosphere and the soil. Several mechanisms influence evaporation, such as the atmospheric conditions, the structure of the soil surface, and the physical properties of the soil. Among the previous studies associated with evaporation modeling, most efforts use uncoupled models which simplify the influences of the atmosphere and soil through the use of resistance terms. Those that do consider the coupling between the free flow and porous media flow mainly consider flat terrain with grain-scale roughness. However, larger obstacles, which may form drags or ridges allowing normal convective air flow through the soil, are common in nature and may affect the evaporation significantly. Therefore, the goal of this work is to study the influence of large obstacles such as wavy surfaces on the flow behavior within the soil and exchange processes to the atmosphere under turbulent free-flow conditions. For simplicity, the soil surface with large obstacles are represented by a simple wavy surface. To do this, we modified a previously developed theory for two-phase two-component porous-medium flow, coupling it to single-phase two-component turbulent flow to simulate and analyze the evaporation from wavy soil surfaces. Detailed laboratory scale experiments using a wind tunnel interfaced with a porous media tank were carried out to test the modeling results. The characteristics of turbulent flow across a permeable wavy surface are discussed. Results demonstrate that there is an obvious recirculation zone formed at the surface, which is special because of the accumulation of water vapor and the thicker boundary layer in this area. In addition, the influences of both the free flow and porous medium on the evaporation are also analyzed. The porous medium affects the evaporation through the amount of water it can provide to the soil surface; while the atmosphere influences the evaporation through the gradients formed within the boundary layer. This study gives a primary cognition on the evaporation from bare soil surface with obstacles. Ongoing work will include a deep understanding of the mechanisms which may provide the basis for land-atmosphere study on field scale.

A High Performance Impedance-based Platform for Evaporation Rate Detection.

PubMed

Chou, Wei-Lung; Lee, Pee-Yew; Chen, Cheng-You; Lin, Yu-Hsin; Lin, Yung-Sheng

2016-10-17

This paper describes the method of a novel impedance-based platform for the detection of the evaporation rate. The model compound hyaluronic acid was employed here for demonstration purposes. Multiple evaporation tests on the model compound as a humectant with various concentrations in solutions were conducted for comparison purposes. A conventional weight loss approach is known as the most straightforward, but time-consuming, measurement technique for evaporation rate detection. Yet, a clear disadvantage is that a large volume of sample is required and multiple sample tests cannot be conducted at the same time. For the first time in literature, an electrical impedance sensing chip is successfully applied to a real-time evaporation investigation in a time sharing, continuous and automatic manner. Moreover, as little as 0.5 ml of test samples is required in this impedance-based apparatus, and a large impedance variation is demonstrated among various dilute solutions. The proposed high-sensitivity and fast-response impedance sensing system is found to outperform a conventional weight loss approach in terms of evaporation rate detection.

Contributions of local terrestrial evaporation and transpiration to precipitation using δ18O and D-excess as a proxy in Shiyang inland river basin in China

NASA Astrophysics Data System (ADS)

Zongxing, Li; Qi, Feng; Wang, Q. J.; Yanlong, Kong; Aifang, Cheng; Song, Yong; Yongge, Li; Jianguo, Li; Xiaoyan, Guo

2016-11-01

Moisture recycling by terrestrial evaporation and transpiration has recently been confirmed as an important source of precipitation, but little is known of this contribution in inland river basins of China. This study determines the fractions contributed by terrestrial evaporation and transpiration to precipitation in the Shiyang river basin, located in Gansu province of northwestern China. The basin has an area of 4.16 × 104 km2 and mean annual precipitation of 300 mm/yr. Hundreds of samples of precipitation, surface water, plant stem water and soil water were collected and analyzed for their isotopic compositions. The Craig-Gordon model and a three-end-member mixing model were used to partition precipitation into water sourced from evaporation, transpiration and advection. On average, evaporation, transpiration and advection were responsible for 9%, 14% and 77%, respectively, of precipitation, and the contribution from terrestrial evaporation and transpiration also increased with elavation; they also varied with season, being highest in August. The significant contribution from transpiration highlights the importance of vegetation conservation in this ecologically fragile basin.

A catchment scale water balance model for FIFE

NASA Technical Reports Server (NTRS)

Famiglietti, J. S.; Wood, E. F.; Sivapalan, M.; Thongs, D. J.

1992-01-01

A catchment scale water balance model is presented and used to predict evaporation from the King's Creek catchment at the First ISLSCP Field Experiment site on the Konza Prairie, Kansas. The model incorporates spatial variability in topography, soils, and precipitation to compute the land surface hydrologic fluxes. A network of 20 rain gages was employed to measure rainfall across the catchment in the summer of 1987. These data were spatially interpolated and used to drive the model during storm periods. During interstorm periods the model was driven by the estimated potential evaporation, which was calculated using net radiation data collected at site 2. Model-computed evaporation is compared to that observed, both at site 2 (grid location 1916-BRS) and the catchment scale, for the simulation period from June 1 to October 9, 1987.

Integration of satellite-induced fluorescence and vegetation optical depth to improve the retrieval of land evaporation

NASA Astrophysics Data System (ADS)

Pagán, B. R.; Martens, B.; Maes, W. H.; Miralles, D. G.

2017-12-01

Global satellite-based data sets of land evaporation overcome limitations in coverage of in situ measurements while retaining some observational nature. Although their potential for real world applications are promising, their value during dry conditions is still poorly understood. Most evaporation retrieval algorithms are not directly sensitive to soil moisture. An exception is the Global Land Evaporation Amsterdam Model (GLEAM), which uses satellite surface soil moisture and precipitation to account for land water availability. The existing methodology may greatly benefit from the optimal integration of novel observations of the land surface. Microwave vegetation optical depth (VOD) and near-infrared solar-induced fluorescence (SIF) are expected to reflect different aspects of evaporative stress. While the former is considered to be a proxy of vegetation water content, the latter is indicative of the activity of photosynthetic machinery. As stomata regulate both photosynthesis and transpiration, we expect a relationship between SIF and transpiration. An important motivation to incorporate observations in land evaporation calculations is that plant transpiration - usually the largest component of the flux - is extremely challenging to model due to species-dependent responses to drought. Here we present an innovative integration of VOD and SIF into the GLEAM evaporative stress function. VOD is utilized as a measurement of isohydricity to improve the representation of species specific drought responses. SIF is used for transpiration modelling, a novel application, and standardized by incoming solar radiation to better account for radiation-limited periods. Results are validated with global FLUXNET and International Soil Moisture Network data and demonstrate that the incorporation of VOD and SIF can yield accurate estimates of transpiration over large-scales, which are essential to further understand ecosystem-atmosphere feedbacks and the response of terrestrial hydrology and ecology to meteorological drought. The resulting retrievals of land evaporation can be used to benchmark climate model representation of turbulent fluxes, at a time when these models still consider water stress rudimentarily, and typically assume the same sensitivity for all vegetation types to drought stress.

A cloud-evaporation parameterization for general ciculation models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schlesinger, M.E.; Oh, J.H.

1993-04-01

An evaporation-zone (EZ) model for cloud evaporation is developed. In this model a cloud consists of I [open quotes]cloudlets,[close quotes] each comprising cloud droplets with radii from zero to r[sub max], the latter value depending on the drop size distribution (DSD). Evaporation occurs only within the EZ comprised of J[le]I cloudlets. When the cloudlet at cloud edge evaporates, the EZ progresses one cloudlet into the cloud's interior. This eventually results in evaporation of the cloud in time t[sub E] = K(H/h)r[sup 2][sub max](1[minus]S[sub e])[sup [minus]1] where H is the cloud thickness, h the EZ thickness, S[sub e] the environmental saturationmore » ratio, and K a constant. Values of t[sub E](1[minus]S[sub e]) versus h are presented for eight observed DSDs. For use in atmospheric general circulation models (GCMs), the cloud evaporation process is represented by dm/dt=[minus](1[minus]S[sub e])m/[tau], where m is the cloud-water mixing ratio and [tau]=K(H/h)r[sup 2][sub max]n[sup [minus]1]. With parameter n chosen sufficiently large, a GCM cloud will evaporate virtually entirely in time t[sub E], for example, 99.3% for n = 5. Values of [tau] for use in the multilayer atmospheric CRCM have been determined by performing ten perpetual-January simulations and ten perpetual-July simulations, each set of ten for prescribed pairs of [tau] values for stratiform ([tau][sub s]) and cumuloform ([tau][sub c]) clouds. An optimum choice of [tau][sub s] and [tau][sub c], based on minimizing the errors of the model's simulated cloudiness, planetary albedo, outgoing longwave radiation, and precipitation, is [tau][sub s]=[tau][sub c] = 3 min. This corresponds to t[sub E](1-S[sub e]) = 15 min for both stratiform and cumuloform clouds; hence, to an EZ thickness of about 0.6-0.8 m for stratus, stratocumulus, and altostratus clouds, 2-3 m for nimbostratus and cumulus clouds, and 17 m for cumulonimbus clouds. 18 refs., 6 figs.« less

Modeling comprehensive chemical composition of weathered oil following a marine spill to predict ozone and potential secondary aerosol formation and constrain transport pathways

NASA Astrophysics Data System (ADS)

Drozd, Greg T.; Worton, David R.; Aeppli, Christoph; Reddy, Christopher M.; Zhang, Haofei; Variano, Evan; Goldstein, Allen H.

2015-11-01

Releases of hydrocarbons from oil spills have large environmental impacts in both the ocean and atmosphere. Oil evaporation is not simply a mechanism of mass loss from the ocean, as it also causes production of atmospheric pollutants. Monitoring atmospheric emissions from oil spills must include a broad range of volatile organic compounds (VOC), including intermediate-volatile and semivolatile compounds (IVOC, SVOC), which cause secondary organic aerosol (SOA) and ozone production. The Deepwater Horizon (DWH) disaster in the northern Gulf of Mexico during Spring/Summer of 2010 presented a unique opportunity to observe SOA production due to an oil spill. To better understand these observations, we conducted measurements and modeled oil evaporation utilizing unprecedented comprehensive composition measurements, achieved by gas chromatography with vacuum ultraviolet time of flight mass spectrometry (GC-VUV-HR-ToFMS). All hydrocarbons with 10-30 carbons were classified by degree of branching, number of cyclic rings, aromaticity, and molecular weight; these hydrocarbons comprise ˜70% of total oil mass. Such detailed and comprehensive characterization of DWH oil allowed bottom-up estimates of oil evaporation kinetics. We developed an evaporative model, using solely our composition measurements and thermodynamic data, that is in excellent agreement with published mass evaporation rates and our wind-tunnel measurements. Using this model, we determine surface slick samples are composed of oil with a distribution of evaporative ages and identify and characterize probable subsurface transport of oil.

Evaporation suppression from water reservoirs using floating covers: Lab scale observations and model predictions

NASA Astrophysics Data System (ADS)

Or, D.; Lehmann, P.; Aminzadeh, M.; Sommer, M.; Wey, H.; Wunderli, H.; Breitenstein, D.

2016-12-01

The competition over dwindling fresh water resources is expected to intensify with projected increase in human population in arid regions, expansion of irrigated land and changes in climate and drought patterns. The volume of water stored in reservoirs would also increase to mitigate seasonal shortages due to rainfall variability and to meet irrigation water needs. By some estimates up to half of the stored water is lost to evaporation thereby exacerbating the water scarcity problem. Recently, there is an upsurge in the use of self-assembling floating covers to suppress evaporation, yet the design, and implementation remain largely empirical. Studies have shown that evaporation suppression is highly nonlinear, as also known from a century of research on gas exchange from plant leaves (that often evaporate as free water surfaces through stomata that are only 1% of leaf area). We report a systematic evaluation of different cover types and external drivers (radiation, wind, wind+radiation) on evaporation suppression and energy balance of a 1.4 m2 basin placed in a wind-tunnel. Surprisingly, evaporation suppression by black and white floating covers (balls and plates) were similar despite significantly different energy balance regimes over the cover surfaces. Moreover, the evaporation suppression efficiency was a simple function of the uncovered area (square root of the uncovered fraction) with linear relations with the covered area in some cases. The thermally decoupled floating covers offer an efficient solution to the evaporation suppression with limited influence of the surface energy balance (water temperature for black and white covers was similar and remained nearly constant). The results will be linked with a predictive evaporation-energy balance model and issues of spatial scales and long exposure times will be studied.

The precipitation of gypsum, celestine, and barite and coprecipitation of radium during seawater evaporation

NASA Astrophysics Data System (ADS)

Rosenberg, Yoav Oved; Sade, Ziv; Ganor, Jiwchar

2018-07-01

While the precipitation paths of the major ions (i.e., Ca2+, Na+, K+, Cl- and SO42-) during seawater evaporation have been extensively studied, the precipitation of minor solutes from evaporated seawater was not thoroughly studied. The present study aims to achieve a quantitative understanding of Sr2+, Ba2+ and Ra2+ removal from evaporated seawater, by exploring in-situ evaporation of seawater in a series of ponds of a salt plant. Seawater samples, at various degrees of evaporation, were collected and analyzed for their solute concentrations. Mass balance and thermodynamic calculations were performed for each sample, revealing that the evaporated seawater remained oversaturated with respect to the three sulphate minerals: gypsum, celestine and barite, for a considerable period before precipitation commenced. In view of this observation, the results are discussed within the framework of the classical nucleation theory. It is hypothesized that the precipitation of these minerals is kinetically hindered by surface area starvation which, in turn, causes the nucleation of these minerals to be the rate determining step. The removal of Ra commences in concordance with the precipitation of Sr and Ba, suggesting that Ra removal is controlled by the formation of a solid solution. Although a ternary solid solution of RaxBaySr1-x-ySO4 actually precipitates, the removal of Ra was modeled by the precipitation of a binary solid solution of RaxBa1-xSO4. Using empirical law from the literature, the removal of Ra could be modeled fairly well. The model suggests that the removal of Ra in evaporated seawater is hindered in comparison to low ionic strength solutions. This inhibition is a result of: 1. The high ionic strength (up to 10.8 mol kg-1); and 2. Precipitation kinetics that may be quantified by the degree of supersaturation with respect to end-member barite in the evaporated seawater (up to 51).

Design of a solar energy assisted air conditioning system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Varlet, J.L.P.; Johnson, B.R.; Vora, J.N.

1976-03-24

Energy consumption in air conditioning systems can be reduced by reducing the water content of air before cooling. This reduction in humidity can be accomplished by contacting the humid air with a hygroscopic solution in a spray tower. The hydroscopic solution, diluted by water from the air, can be reconcentrated in a solar evaporator. A solar evaporator for this purpose was evaluated by formulating simultaneous energy and mass balances for forced air convection through the evaporator. Temperatures in the evaporator were calculated by numerical integration of the mathematical model. The calculations indicated that the salt solution cannot be reconcentrated inmore » a forced convection evaporator because of the large energy losses associated with the air stream passing through the evaporator.« less

A multi-component evaporation model for beam melting processes

NASA Astrophysics Data System (ADS)

Klassen, Alexander; Forster, Vera E.; Körner, Carolin

2017-02-01

In additive manufacturing using laser or electron beam melting technologies, evaporation losses and changes in chemical composition are known issues when processing alloys with volatile elements. In this paper, a recently described numerical model based on a two-dimensional free surface lattice Boltzmann method is further developed to incorporate the effects of multi-component evaporation. The model takes into account the local melt pool composition during heating and fusion of metal powder. For validation, the titanium alloy Ti-6Al-4V is melted by selective electron beam melting and analysed using mass loss measurements and high-resolution microprobe imaging. Numerically determined evaporation losses and spatial distributions of aluminium compare well with experimental data. Predictions of the melt pool formation in bulk samples provide insight into the competition between the loss of volatile alloying elements from the irradiated surface and their advective redistribution within the molten region.

Understanding land surface evapotranspiration with satellite multispectral measurements

NASA Technical Reports Server (NTRS)

Menenti, M.

1993-01-01

Quantitative use of remote multispectral measurements to study and map land surface evapotranspiration has been a challenging issue for the past 20 years. Past work is reviewed against process physics. A simple two-layer combination-type model is used which is applicable to both vegetation and bare soil. The theoretic analysis is done to show which land surface properties are implicitly defined by such evaporation models and to assess whether they are measurable as a matter of principle. Conceptual implications of the spatial correlation of land surface properties, as observed by means of remote multispectral measurements, are illustrated with results of work done in arid zones. A normalization of spatial variability of land surface evaporation is proposed by defining a location-dependent potential evaporation and surface temperature range. Examples of the application of remote based estimates of evaporation to hydrological modeling studies in Egypt and Argentina are presented.

On the Effect of Energy Conservation on Black Hole Evaporation

NASA Astrophysics Data System (ADS)

Torres, R.; Fayos, F.; Lorente-Espín, O.

2013-06-01

We consider the emission of Hawking radiation by black holes as a consequence of a tunneling process. By requiring energy conservation in the derivation of the emission rate we get a well-known deviation from an exact thermal spectrum. A model that takes into account the implications of energy conservation, as well as the back-scattered radiation, is then constructed in order to describe the evolution of black holes as they evaporate. The evaporation process in this model is compared with the results in the standard "thermal" approximation. This allows us to point out the relevance that energy conservation might have in the last stages of black hole evaporation. We also comment about the possible implications of energy conservation in the information loss paradox.

Switching moving boundary models for two-phase flow evaporators and condensers

NASA Astrophysics Data System (ADS)

Bonilla, Javier; Dormido, Sebastián; Cellier, François E.

2015-03-01

The moving boundary method is an appealing approach for the design, testing and validation of advanced control schemes for evaporators and condensers. When it comes to advanced control strategies, not only accurate but fast dynamic models are required. Moving boundary models are fast low-order dynamic models, and they can describe the dynamic behavior with high accuracy. This paper presents a mathematical formulation based on physical principles for two-phase flow moving boundary evaporator and condenser models which support dynamic switching between all possible flow configurations. The models were implemented in a library using the equation-based object-oriented Modelica language. Several integrity tests in steady-state and transient predictions together with stability tests verified the models. Experimental data from a direct steam generation parabolic-trough solar thermal power plant is used to validate and compare the developed moving boundary models against finite volume models.

Developing Mathematical Provisions for Assessment of Liquid Hydrocarbon Emissions in Emergency Situations

NASA Astrophysics Data System (ADS)

Zemenkova, M. Yu; Zemenkov, Yu D.; Shantarin, V. D.

2016-10-01

The paper reviews the development of methodology for calculation of hydrocarbon emissions during seepage and evaporation to monitor the reliability and safety of hydrocarbon storage and transportation. The authors have analyzed existing methods, models and techniques for assessing the amount of evaporated oil. Models used for predicting the material balance of multicomponent two-phase systems have been discussed. The results of modeling the open-air hydrocarbon evaporation from an oil spill are provided and exemplified by an emergency pit. Dependences and systems of differential equations have been obtained to assess parameters of mass transfer from the open surface of a liquid multicomponent mixture.

Probing loop quantum gravity with evaporating black holes.

PubMed

Barrau, A; Cailleteau, T; Cao, X; Diaz-Polo, J; Grain, J

2011-12-16

This Letter aims at showing that the observation of evaporating black holes should allow the usual Hawking behavior to be distinguished from loop quantum gravity (LQG) expectations. We present a full Monte Carlo simulation of the evaporation in LQG and statistical tests that discriminate between competing models. We conclude that contrarily to what was commonly thought, the discreteness of the area in LQG leads to characteristic features that qualify evaporating black holes as objects that could reveal quantum gravity footprints. © 2011 American Physical Society

Global lake evaporation accelerated by changes in surface energy allocation in a warmer climate

NASA Astrophysics Data System (ADS)

Wang, Wei; Lee, Xuhui; Xiao, Wei; Liu, Shoudong; Schultz, Natalie; Wang, Yongwei; Zhang, Mi; Zhao, Lei

2018-06-01

Lake evaporation is a sensitive indicator of the hydrological response to climate change. Variability in annual lake evaporation has been assumed to be controlled primarily by the incoming surface solar radiation. Here we report simulations with a numerical model of lake surface fluxes, with input data based on a high-emissions climate change scenario (Representative Concentration Pathway 8.5). In our simulations, the global annual lake evaporation increases by 16% by the end of the century, despite little change in incoming solar radiation at the surface. We attribute about half of this projected increase to two effects: periods of ice cover are shorter in a warmer climate and the ratio of sensible to latent heat flux decreases, thus channelling more energy into evaporation. At low latitudes, annual lake evaporation is further enhanced because the lake surface warms more slowly than the air, leading to more long-wave radiation energy available for evaporation. We suggest that an analogous change in the ratio of sensible to latent heat fluxes in the open ocean can help to explain some of the spread among climate models in terms of their sensitivity of precipitation to warming. We conclude that an accurate prediction of the energy balance at the Earth's surface is crucial for evaluating the hydrological response to climate change.

Evaporation from a temperate closed-basin lake and its impact on present, past, and future water level

NASA Astrophysics Data System (ADS)

Xiao, K.; Griffis, T. J.; Baker, J. M.; Bolstad, P. V.; Erickson, M. D.; Lee, X.; Wood, J. D.; Hu, C.

2017-12-01

Lakes provide enormous economic, recreational, and aesthetic benefits to citizens. These ecosystem services may be adversely impacted by climate change. In the Twin Cities Metropolitan Area of Minnesota, USA, many lakes have been at historic low levels and water augmentation strategies have been proposed to alleviate the problem. For example, the water level of White Bear Lake (WBL) declined 1.5 m during 2003-2013 for reasons that are not fully understood. This study examined current, past, and future lake evaporation to better understand how climate will impact the water balance of lakes within this region. Evaporation from WBL was measured from July 2014 to February 2017 using two eddy covariance (EC) systems to provide better constraints on the water budget and to investigate the impact of evaporation on lake level. The annual evaporation for years 2014 through 2016 were 559±22 mm, 779±81 mm, and 766±11 mm, respectively. The larger evaporation in 2015 and 2016 was caused by the combined effects of larger average daily evaporation and a longer ice-free season. The EC measurements were used to tune the Community Land Model 4 - Lake, Ice, Snow and Sediment Simulator (CLM4-LISSS) to estimate lake evaporation over the period 1979-2016. Retrospective analyses indicated that WBL evaporation increased by about 3.8 mm yr-1. Mass balance analysis implied that the lake level declines at WBL during 1986-1990 and 2003-2012 were mainly caused by the coupled low precipitation and high evaporation. Using a business-as-usual greenhouse gas emission scenario (RCP8.5), lake evaporation was modeled forward in time from 2017 to 2100. Annual evaporation is expected to increase by 1.4 mm yr-1 over this century, which is largely driven by lengthening ice-free periods. These changes in ice phenology and evaporation will have important implications for the regional water balance, and water management and water augmentation strategies that are being proposed for these Metropolitan lakes.

Numerical Analysis of the Heat Transfer Characteristics within an Evaporating Meniscus

NASA Astrophysics Data System (ADS)

Ball, Gregory

A numerical analysis was performed as to investigate the heat transfer characteristics of an evaporating thin-film meniscus. A mathematical model was used in the formulation of a third order ordinary differential equation. This equation governs the evaporating thin-film through use of continuity, momentum, energy equations and the Kelvin-Clapeyron model. This governing equation was treated as an initial value problem and was solved numerically using a Runge-Kutta technique. The numerical model uses varying thermophysical properties and boundary conditions such as channel width, applied superheat, accommodation coefficient and working fluid which can be tailored by the user. This work focused mainly on the effects of altering accommodation coefficient and applied superheat. A unified solution is also presented which models the meniscus to half channel width. The model was validated through comparison to literature values. In varying input values the following was determined; increasing superheat was found to shorten the film thickness and greatly increase the interfacial curvature overshoot values. The effect of decreasing accommodation coefficient lengthened the thin-film and retarded the evaporative effects.

A theoretical study of the spheroidal droplet evaporation in forced convection

NASA Astrophysics Data System (ADS)

Li, Jie; Zhang, Jian

2014-11-01

In many applications, the shape of a droplet may be assumed to be an oblate spheroid. A theoretical study is conducted on the evaporation of an oblate spheroidal droplet under forced convection conditions. Closed-form analytical expressions of the mass evaporation rate for an oblate spheroid are derived, in the regime of controlled mass-transfer and heat-transfer, respectively. The variation of droplet size during the evaporation process is presented in the regime of shrinking dynamic model. Comparing with the droplets having the same surface area, an increase in the aspect ratio enhances the mass evaporation rate and prolongs the burnout time.

Method for improving accuracy in full evaporation headspace analysis.

PubMed

Xie, Wei-Qi; Chai, Xin-Sheng

2017-05-01

We report a new headspace analytical method in which multiple headspace extraction is incorporated with the full evaporation technique. The pressure uncertainty caused by the solid content change in the samples has a great impact to the measurement accuracy in the conventional full evaporation headspace analysis. The results (using ethanol solution as the model sample) showed that the present technique is effective to minimize such a problem. The proposed full evaporation multiple headspace extraction analysis technique is also automated and practical, and which could greatly broaden the applications of the full-evaporation-based headspace analysis. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Evaporative segregation in 80% Ni-20% Cr and 60% Fe-40% Ni alloys

NASA Technical Reports Server (NTRS)

Gupta, K. P.; Mukherjee, J. L.; Li, C. H.

1974-01-01

An analytical approach is outlined to calculate the evaporative segregation behavior in metallic alloys. The theoretical predictions are based on a 'normal' evaporation model and have been examined for Fe-Ni and Ni-Cr alloys. A fairly good agreement has been found between the predicted values and the experimental results found in the literature.

Measured and simulated soil water evaporation from four Great Plains soils

USDA-ARS?s Scientific Manuscript database

The amount of soil water lost during stage one and stage two soil water evaporation is of interest to crop water use modelers. The ratio of measured soil surface temperature (Ts) to air temperature (Ta) was tested as a signal for the transition in soil water evaporation from stage one to stage two d...

OPTIMAL ELECTRON ENERGIES FOR DRIVING CHROMOSPHERIC EVAPORATION IN SOLAR FLARES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reep, J. W.; Bradshaw, S. J.; Alexander, D., E-mail: jr665@cam.ac.uk, E-mail: stephen.bradshaw@rice.edu, E-mail: dalex@rice.edu

2015-08-01

In the standard model of solar flares, energy deposition by a beam of electrons drives strong chromospheric evaporation leading to a significantly denser corona and much brighter emission across the spectrum. Chromospheric evaporation was examined in great detail by Fisher et al., who described a distinction between two different regimes, termed explosive and gentle evaporation. In this work, we examine the importance of electron energy and stopping depths on the two regimes and on the atmospheric response. We find that with explosive evaporation, the atmospheric response does not depend strongly on electron energy. In the case of gentle evaporation, lowermore » energy electrons are significantly more efficient at heating the atmosphere and driving up-flows sooner than higher energy electrons. We also find that the threshold between explosive and gentle evaporation is not fixed at a given beam energy flux, but also depends strongly on the electron energy and duration of heating. Further, at low electron energies, a much weaker beam flux is required to drive explosive evaporation.« less

Understanding Atom Probe Tomography of Oxide-Supported Metal Nanoparticles by Correlation with Atomic-Resolution Electron Microscopy and Field Evaporation Simulation.

PubMed

Devaraj, Arun; Colby, Robert; Vurpillot, François; Thevuthasan, Suntharampillai

2014-04-17

Oxide-supported metal nanoparticles are widely used in heterogeneous catalysis. The increasingly detailed design of such catalysts necessitates three-dimensional characterization with high spatial resolution and elemental selectivity. Laser-assisted atom probe tomography (APT) is uniquely suited to the task but faces challenges with the evaporation of metal/insulator systems. Correlation of APT with aberration-corrected scanning transmission electron microscopy (STEM), for Au nanoparticles embedded in MgO, reveals preferential evaporation of the MgO and an inaccurate assessment of nanoparticle composition. Finite element field evaporation modeling is used to illustrate the evolution of the evaporation front. Nanoparticle composition is most accurately predicted when the MgO is treated as having a locally variable evaporation field, indicating the importance of considering laser-oxide interactions and the evaporation of various molecular oxide ions. These results demonstrate the viability of APT for analysis of oxide-supported metal nanoparticles, highlighting the need for developing a theoretical framework for the evaporation of heterogeneous materials.

The Effect of Dynamic Evaporation Rates on the Mobility of Pharmaceuticals in Unsaturated Environments

NASA Astrophysics Data System (ADS)

Normile, H.; Papelis, C.; Kibbey, T. C. G.

2015-12-01

The focus of this work was on investigating how dynamic rates of evaporation affect the fate and transport of pharmaceutical compounds in unsaturated porous media. The environmental processes of saturation and evaporation control local concentrations of contaminants in pore water of porous media. Specifically, the rate of evaporation can affect the identity and extent of solid formation of a pharmaceutical compound. A range of experiments with different evaporation rates were conducted on sand columns saturated with a solution of ciprofloxacin, a fluoroquinolone antibiotic. Experiments were designed to simulate increased and decreased pore-water concentrations of a compound due to evaporation and resaturation, respectively. Results suggest that varied rates of evaporation cause differences in compound adsorption behavior. This result has significant implications for understanding fate and transport within the unsaturated zone. Preliminary models exploring the impact on contaminant mobility are discussed.

A size-composition resolved aerosol model for simulating the dynamics of externally mixed particles: SCRAM (v 1.0)

NASA Astrophysics Data System (ADS)

Zhu, S.; Sartelet, K. N.; Seigneur, C.

2015-06-01

The Size-Composition Resolved Aerosol Model (SCRAM) for simulating the dynamics of externally mixed atmospheric particles is presented. This new model classifies aerosols by both composition and size, based on a comprehensive combination of all chemical species and their mass-fraction sections. All three main processes involved in aerosol dynamics (coagulation, condensation/evaporation and nucleation) are included. The model is first validated by comparison with a reference solution and with results of simulations using internally mixed particles. The degree of mixing of particles is investigated in a box model simulation using data representative of air pollution in Greater Paris. The relative influence on the mixing state of the different aerosol processes (condensation/evaporation, coagulation) and of the algorithm used to model condensation/evaporation (bulk equilibrium, dynamic) is studied.

Isothermal evaporation process simulation using the Pitzer model for the Quinary system LiCl–NaCl–KCl–SrCl 2–H 2O at 298.15 K

DOE PAGES

Meng, Lingzong; Gruszkiewicz, Miroslaw S.; Deng, Tianlong; ...

2015-08-05

In this study, the Pitzer thermodynamic model for solid-liquid equilibria in the quinary system LiCl–NaCl–KCl–SrCl 2–H 2O at 298.15 K was constructed by selecting the proper parameters for the subsystems in the literature. The solubility data of the systems NaCl–SrCl 2–H 2O, KCl–SrCl 2–H 2O, LiCl–SrCl 2–H 2O, and NaCl–KCl–SrCl 2–H 2O were used to evaluate the model. Good agreement between the experimental and calculated solubilities shows that the model is reliable. The Pitzer model for the quinary system at 298.15 K was then used to calculate the component solubilities and conduct computer simulation of isothermal evaporation of the mothermore » liquor for the oilfield brine from Nanyishan district in the Qaidam Basin. The evaporation-crystallization path and sequence of salt precipitation, change in concentration and precipitation of lithium, sodium, potassium, and strontium, and water activities during the evaporation process were demonstrated. The salts precipitated from the brine in the order : KCl, NaCl, SrCl 2∙6H 2O, SrCl 2∙2H 2O, and LiCl∙H 2O. The entire evaporation process may be divided into six stages. In each stage the variation trends for the relationships between ion concentrations or water activities and the evaporation ratio are different. This result of the simulation of brines can be used as a theoretical reference for comprehensive exploitation and utilization of this type of brine resources.« less

Controls on surface soil drying rates observed by SMAP and simulated by the Noah land surface model

NASA Astrophysics Data System (ADS)

Shellito, Peter J.; Small, Eric E.; Livneh, Ben

2018-03-01

Drydown periods that follow precipitation events provide an opportunity to assess controls on soil evaporation on a continental scale. We use SMAP (Soil Moisture Active Passive) observations and Noah simulations from drydown periods to quantify the role of soil moisture, potential evaporation, vegetation cover, and soil texture on soil drying rates. Rates are determined using finite differences over intervals of 1 to 3 days. In the Noah model, the drying rates are a good approximation of direct soil evaporation rates, and our work suggests that SMAP-observed drying is also predominantly affected by direct soil evaporation. Data cover the domain of the North American Land Data Assimilation System Phase 2 and span the first 1.8 years of SMAP's operation. Drying of surface soil moisture observed by SMAP is faster than that simulated by Noah. SMAP drying is fastest when surface soil moisture levels are high, potential evaporation is high, and when vegetation cover is low. Soil texture plays a minor role in SMAP drying rates. Noah simulations show similar responses to soil moisture and potential evaporation, but vegetation has a minimal effect and soil texture has a much larger effect compared to SMAP. When drying rates are normalized by potential evaporation, SMAP observations and Noah simulations both show that increases in vegetation cover lead to decreases in evaporative efficiency from the surface soil. However, the magnitude of this effect simulated by Noah is much weaker than that determined from SMAP observations.

Evaporation suppression from reservoirs using floating covers: Lab scale wind-tunnel observations and mechanistic model predictions

NASA Astrophysics Data System (ADS)

Or, Dani; Lehmann, Peter; Aminzadeh, Milad; Sommer, Martina; Wey, Hannah; Krentscher, Christiane; Wunderli, Hans; Breitenstein, Daniel

2017-04-01

The competition over dwindling fresh water resources is expected to intensify with projected increase in human population in arid regions, expansion of irrigated land and changes in climate and drought patterns. The volume of water stored in reservoirs would also increase to mitigate seasonal shortages due to rainfall variability and to meet irrigation water needs. By some estimates up to half of the stored water is lost to evaporation, thereby exacerbating the water scarcity problem. Recently, there is an upsurge in the use of self-assembling floating covers to suppress evaporation, yet the design and implementation remain largely empirical. We report a systematic experimental evaluation of different cover types and external drivers (radiation, wind, wind plus radiation) on evaporation suppression and energy balance of a 1.4 m2 basin placed in a wind-tunnel. Surprisingly, evaporation suppression by black and white floating covers (balls and plates) were similar despite significantly different energy balance regimes over the cover surfaces. Moreover, the evaporation suppression efficiency was a simple function of the uncovered area (square root of the uncovered fraction) with linear relations with the covered area in some cases. The thermally decoupled floating covers offer an efficient solution to the evaporation suppression with limited influence of the surface energy balance (water temperature for black and white covers was similar and remained nearly constant). The results will be linked with a predictive evaporation-energy balance model and issues of spatial scales and long exposure times will be studied.

Study of the Effect of Wind Speed on Evaporation from Soil Through Integrated Modeling of Atmospheric Boundary Layer and Shallow Subsurface

NASA Astrophysics Data System (ADS)

Smits, K. M.; Davarzani, H.; Illangasekare, T. H.

2012-12-01

The study of the interaction between the land and atmosphere is paramount to our understanding of many emerging problems to include climate change and the movement of green house gases such as possible leaking of sequestered CO2. Soil moisture distribution in the shallow subsurface becomes a critical factor in these problems. The heat and mass flux in the form of soil evaporation across the land surface couples the atmospheric boundary layer to the shallow subsurface. The coupling between land and the atmosphere leads to highly dynamic interactions between the porous media properties, transport processes and boundary conditions, resulting in dynamic evaporative behavior. However, the coupling at the land-atmospheric interface is rarely considered in most current models and their validation for practical applications. This is due to the complexity of the problem in field scenarios and the scarcity of field or laboratory data capable of testing and refining coupled energy and mass transfer theories. In most efforts to compute evaporation from soil, only indirect coupling is provided to characterize the interaction between non-isothermal multiphase flows under realistic atmospheric conditions even though heat and mass flux are controlled by the coupled dynamics of the land and the atmospheric boundary layer. In earlier drying modeling concepts, imposing evaporation flux (kinetic of relative humidity) and temperature as surface boundary condition is often needed. With the goal of improving our understanding of the land/atmospheric coupling, we developed a model based on the coupling of Navier-Stokes free flow and Darcy flow in porous medium. The model consists of the coupled equations of mass conservation for the liquid phase (water) and gas phase (water vapor and air) in porous medium with gas phase (water vapor and air) in free flow domain under non-isothermal, non-equilibrium conditions. The boundary conditions at the porous medium-free flow medium interface include dynamical, thermal and solutal equilibriums, and using the Beavers-Joseph slip boundary condition. What is unique about this model is that the evaporation rate and soil surface temperature conditions come directly from the model output. In order to experimentally validate the numerical results, we developed and used a unique two dimensional wind tunnel placed above a soil tank equipped with a network of different sensors. A series of experiments under varying boundary conditions were performed. Precision data under well-controlled transient heat and wind boundary conditions was generated. Results from numerical simulations were compared with experimental data. Results demonstrate that the coupling concept can predict the different stages of the drying process in porous media with good accuracy. Increasing the wind speed increases the first stage evaporation rate and decreases the transition time at low velocity values; then, at high values of wind speed the evaporation rate becomes less dependent of flow in free fluid. In the opposite, the impact of the wind speed on the second stage evaporation (diffusion dominant stage) is not significant. The proposed theoretical model can be used to predict the evaporation process where a porous medium flow is coupled to a free flow for different practical applications.

Exploring the correlation between annual precipitation and potential evaporation

NASA Astrophysics Data System (ADS)

Chen, X.; Buchberger, S. G.

2017-12-01

The interdependence between precipitation and potential evaporation is closely related to the classic Budyko framework. In this study, a systematic investigation of the correlation between precipitation and potential evaporation at the annual time step is conducted at both point scale and watershed scale. The point scale precipitation and potential evaporation data over the period of 1984-2015 are collected from 259 weather stations across the United States. The watershed scale precipitation data of 203 watersheds across the United States are obtained from the Model Parameter Estimation Experiment (MOPEX) dataset from 1983 to 2002; and potential evaporation data of these 203 watersheds in the same period are obtained from a remote-sensing algorithm. The results show that majority of the weather stations (77%) and watersheds (79%) exhibit a statistically significant negative correlation between annual precipitation and annual potential evaporation. The aggregated data cloud of precipitation versus potential evaporation follows a curve based on the combination of the Budyko-type equation and Bouchet's complementary relationship. Our result suggests that annual precipitation and potential evaporation are not independent when both Budyko's hypothesis and Bouchet's hypothesis are valid. Furthermore, we find that the wet surface evaporation, which is controlled primarily by short wave radiation as defined in Bouchet's hypothesis, exhibits less dependence on precipitation than the potential evaporation. As a result, we suggest that wet surface evaporation is a better representation of energy supply than potential evaporation in the Budyko framework.

Spontaneous parametric down conversion with a depleted pump as an analogue for black hole evaporation/particle production

NASA Astrophysics Data System (ADS)

Alsing, P. M.; Fanto, M. L.

2016-05-01

In this work we argue that black hole evaporation/particle production has a very close analogy to the laboratory process of spontaneous parametric down conversion, when the pump is allowed to deplete. We present an analytical formulation of the recent one-shot decoupling model that was numerically analyzed in Bradler and Adami Phys. Rev. Lett. 116, 101301 (2016) [arXiv:1505.0284]. We compute the resulting "Page Information" curves, which describe the rate at which information escapes form the black hole as it evaporates, for the reduced density matrices for the evaporating black hole internal degrees of freedom, and emitted Hawking radiation pairs entangled across the horizon. The present work reviews and attempts to elucidate the trilinear Hamiltonian models for black hole evaporation/particle production recently investigated by the authors in Class. Quant. Grav 32, 075010 (2015) [arXiv:1408.4491] and Class. Quant. Grav 33, 015005 (2016) [arXiv:1507.00429].

Desiccation of a Sessile Drop of Blood: Cracks Formation and Delamination

NASA Astrophysics Data System (ADS)

Sobac, Benjamin; Brutin, David

2011-11-01

The evaporation of drops of biological fluids has been studied since few years du to several applications in medical fields such as medical tests, drug screening, biostabilization... The evaporation of a drop of whole blood leads to the formation of final typical pattern of cracks. Flow motion, adhesion, gelation and fracturation all occur during the evaporation of this complex matter. During the drying, a sol-gel transition develops. The drying kinetics is explained by a simple model of evaporation taking account of the evolution of the gelation front. The system solidifies and when stresses are too important, cracks nucleate. The cracks formation and the structure of the crack pattern are investigated. The initial crack spacing is found in good agreement with the implementation in open geometry of the model of cracks formation induced by evaporation proposed by Allain and Limat. Finally, the drop is still drying after the end of the formation of cracks which leads, like in the situation of colloid suspensions, to the observation of a delamination phenomenon.

The structure of evaporating and combusting sprays: Measurements and predictions

NASA Technical Reports Server (NTRS)

Shuen, J. S.; Solomon, A. S. P.; Faeth, F. M.

1983-01-01

The structure of particle-laden jets and nonevaporating and evaporating sprays was measured in order to evaluate models of these processes. Three models are being evaluated: (1) a locally homogeneous flow model, where slip between the phases is neglected and the flow is assumed to be in local thermodynamic equilibrium; (2) a deterministic separated flow model, where slip and finite interphase transport rates are considered but effects of particle/drop dispersion by turbulence and effects of turbulence on interphase transport rates are ignored; and (3) a stochastic separated flow model, where effects of interphase slip, turbulent dispersion and turbulent fluctuations are considered using random sampling for turbulence properties in conjunction with random-walk computations for particle motion. All three models use a k-e-g turbulence model. All testing and data reduction are completed for the particle laden jets. Mean and fluctuating velocities of the continuous phase and mean mixture fraction were measured in the evaporating sprays.

A New Experiment for Investigating Evaporation and Condensation of Cryogenic Propellants.

PubMed

Bellur, K; Médici, E F; Kulshreshtha, M; Konduru, V; Tyrewala, D; Tamilarasan, A; McQuillen, J; Leao, J; Hussey, D S; Jacobson, D L; Scherschligt, J; Hermanson, J C; Choi, C K; Allen, J S

2016-03-01

Passive and active technologies have been used to control propellant boil-off, but the current state of understanding of cryogenic evaporation and condensation in microgravity is insufficient for designing large cryogenic depots critical to the long-term space exploration missions. One of the key factors limiting the ability to design such systems is the uncertainty in the accommodation coefficients (evaporation and condensation), which are inputs for kinetic modeling of phase change. A novel, combined experimental and computational approach is being used to determine the accommodation coefficients for liquid hydrogen and liquid methane. The experimental effort utilizes the Neutron Imaging Facility located at the National Institute of Standards and Technology (NIST) in Gaithersburg, Maryland to image evaporation and condensation of hydrogenated propellants inside of metallic containers. The computational effort includes numerical solution of a model for phase change in the contact line and thin film regions as well as an CFD effort for determining the appropriate thermal boundary conditions for the numerical solution of the evaporating and condensing liquid. Using all three methods, there is the possibility of extracting the accommodation coefficients from the experimental observations. The experiments are the first known observation of a liquid hydrogen menisci condensing and evaporating inside aluminum and stainless steel cylinders. The experimental technique, complimentary computational thermal model and meniscus shape determination are reported. The computational thermal model has been shown to accurately track the transient thermal response of the test cells. The meniscus shape determination suggests the presence of a finite contact angle, albeit very small, between liquid hydrogen and aluminum oxide.

A New Experiment for Investigating Evaporation and Condensation of Cryogenic Propellants

PubMed Central

Bellur, K.; Médici, E. F.; Kulshreshtha, M.; Konduru, V.; Tyrewala, D.; Tamilarasan, A.; McQuillen, J.; Leao, J.; Hussey, D. S.; Jacobson, D. L.; Scherschligt, J.; Hermanson, J. C.; Choi, C. K.; Allen, J. S.

2016-01-01

Passive and active technologies have been used to control propellant boil-off, but the current state of understanding of cryogenic evaporation and condensation in microgravity is insufficient for designing large cryogenic depots critical to the long-term space exploration missions. One of the key factors limiting the ability to design such systems is the uncertainty in the accommodation coefficients (evaporation and condensation), which are inputs for kinetic modeling of phase change. A novel, combined experimental and computational approach is being used to determine the accommodation coefficients for liquid hydrogen and liquid methane. The experimental effort utilizes the Neutron Imaging Facility located at the National Institute of Standards and Technology (NIST) in Gaithersburg, Maryland to image evaporation and condensation of hydrogenated propellants inside of metallic containers. The computational effort includes numerical solution of a model for phase change in the contact line and thin film regions as well as an CFD effort for determining the appropriate thermal boundary conditions for the numerical solution of the evaporating and condensing liquid. Using all three methods, there is the possibility of extracting the accommodation coefficients from the experimental observations. The experiments are the first known observation of a liquid hydrogen menisci condensing and evaporating inside aluminum and stainless steel cylinders. The experimental technique, complimentary computational thermal model and meniscus shape determination are reported. The computational thermal model has been shown to accurately track the transient thermal response of the test cells. The meniscus shape determination suggests the presence of a finite contact angle, albeit very small, between liquid hydrogen and aluminum oxide. PMID:28154426

Numerical study of droplet evaporation in an acoustic levitator

NASA Astrophysics Data System (ADS)

Bänsch, Eberhard; Götz, Michael

2018-03-01

We present a finite element method for the simulation of all relevant processes of the evaporation of a liquid droplet suspended in an acoustic levitation device. The mathematical model and the numerical implementation take into account heat and mass transfer across the interface between the liquid and gaseous phase and the influence of acoustic streaming on this process, as well as the displacement and deformation of the droplet due to acoustic radiation pressure. We apply this numerical method to several theoretical and experimental examples and compare our results with the well-known d2-law for the evaporation of spherical droplets and with theoretical predictions for the acoustic streaming velocity. We study the influence of acoustic streaming on the distribution of water vapor and temperature in the levitation device, with special attention to the vapor distribution in the emerging toroidal vortices. We also compare the evaporation rate of a droplet with and without acoustic streaming, as well as the evaporation rates in dependence of different temperatures and sound pressure levels. Finally, a simple model of protein inactivation due to heat damage is considered and studied for different evaporation settings and their respective influence on protein damage.

Evaporation-induced patterns from droplets containing motile and nonmotile bacteria.

PubMed

Nellimoottil, Tittu Thomas; Rao, Pinjala Nagaraju; Ghosh, Siddhartha Sankar; Chattopadhyay, Arun

2007-08-14

In this letter, we report the observations of specific pattern formation from the evaporation of aqueous droplets containing motile and nonmotile bacteria. We found that when motile bacteria were present the droplet evaporated into disclike patterned deposits of bacteria. However, when the bacteria were made nonmotile by treatment with liquid nitrogen, the droplet evaporated into ringlike deposits. We also observed that bacteria with higher motility produced more uniformly deposited disclike patterns. Furthermore, we propose a model with numerical simulations to explain the mechanism of formation of these patterns. The model is based on the advective fluid flow from the center of the droplet toward the edge due to enhanced evaporation from the edge of the pinned droplet in comparison to that from the free surface. For the case of motile bacteria, we have added another velocity parameter toward the axis of the droplet and directed against the fluid flow in order to account for the disclike pattern formation. The numerical simulations match the experimental observations well. The present work, by qualitative and quantitative understanding of the evaporation of bacteria droplets, demonstrates that the inherent bacterial motility is primarily responsible for the formation of these differential patterns.

"Efficiency Space" - A Framework for Evaluating Joint Evaporation and Runoff Behavior

NASA Technical Reports Server (NTRS)

Koster, Randal

2014-01-01

At the land surface, higher soil moisture levels generally lead to both increased evaporation for a given amount of incoming radiation (increased evaporation efficiency) and increased runoff for a given amount of precipitation (increased runoff efficiency). Evaporation efficiency and runoff efficiency can thus be said to vary with each other, motivating the development of a unique hydroclimatic analysis framework. Using a simple water balance model fitted, in different experiments, with a wide variety of functional forms for evaporation and runoff efficiency, we transform net radiation and precipitation fields into fields of streamflow that can be directly evaluated against observations. The optimal combination of the functional forms the combination that produces the most skillful stream-flow simulations provides an indication for how evaporation and runoff efficiencies vary with each other in nature, a relationship that can be said to define the overall character of land surface hydrological processes, at least to first order. The inferred optimal relationship is represented herein as a curve in efficiency space and should be valuable for the evaluation and development of GCM-based land surface models, which by this measure are often found to be suboptimal.

An Experimental and Modeling Study of Evaporation from Bare Soils Subjected to Natural Boundary Conditions at the Land-Atmospheric Interface

NASA Astrophysics Data System (ADS)

Smits, K. M.; Ngo, V. V.; Cihan, A.; Sakaki, T.; Illangasekare, T. H.; kathleen m smits

2011-12-01

Bare soil evaporation is a key process for water exchange between the land and the atmosphere and an important component of the water balance in semiarid and arid regions. However, there is no agreement on the best methodology to determine evaporation under different boundary conditions. Because it is difficult to measure evaporation from soil,with the exception of using lysimeters, numerous formulations have been proposed to establish a relationship between the rate of evaporation and soil moisture and/or soil temperature and thermal properties. Different formulations vary in how they partition available energy and include, among others, a classical bulk aerodynamic formulation which requires knowledge of the relative humidity at the soil surface and a more non-traditional heat balance method which requires knowledge of soil temperature and soil thermal properties. A need exists to systematically compare existing methods to experimental data under highly controlled conditions not achievable in the field. The goal of this work is to perform controlled experiments under transient conditions of soil moisture, temperature and wind at the land/atmospheric interface to test different conceptual and mathematical formulations for evaporation rate estimates and to develop appropriate numerical models to be used in simulations. In this study, to better understand the coupled water-vapor-heat flow processes in the shallow subsurface near the land surface, we modified a previously developed theory that allows non-equilibrium liquid/gas phase change with gas phase vapor diffusion to better account for evaporation under dry soil conditions. This theory was used to compare estimates of evaporation based on different formulations of the bulk aerodynamic and heat balance methods. In order to experimentally validate the numerical formulations/code, we performed a series of two-dimensional physical model experiments under varying boundary conditions using test sand for which the hydraulic and thermal properties were well characterized. We developed a unique two dimensional cell apparatus equipped with a network of sensors for automated and continuous monitoring of soil moisture, soil and air temperature and relative humidity, and wind velocity. Precision data under well-controlled transient heat and wind boundary conditions was generated. Results from numerical simulations were compared with experimental data. Results demonstrate the importance of properly characterizing soil thermal properties and accounting for dry soil conditions to properly estimate evaporation. Initial comparisons of various formulations of evaporation demonstrate the need for joint evaluation of heat and mass transfer for better modeling accuracy. Detailed comparisons are still underway. This knowledge is applicable to many current hydrologic and environmental problems to include climate modeling and the simulation of contaminant transport and volatilization in the shallow subsurface.

On the physical basis of a theory of human thermoregulation.

NASA Technical Reports Server (NTRS)

Iberall, A. S.; Schindler, A. M.

1973-01-01

Theoretical study of the physical factors which are responsible for thermoregulation in nude resting humans in a physical steady state. The behavior of oxidative metabolism, evaporative and convective thermal fluxes, fluid heat transfer, internal and surface temperatures, and evaporative phase transitions is studied by physiological/physical modeling techniques. The modeling is based on the theories that the body has a vital core with autothermoregulation, that the vital core contracts longitudinally, that the temperature of peripheral regions and extremities decreases towards the ambient, and that a significant portion of the evaporative heat may be lost underneath the skin. A theoretical basis is derived for a consistent modeling of steady-state thermoregulation on the basis of these theories.

Evaporation channel as a tool to study fission dynamics

NASA Astrophysics Data System (ADS)

Di Nitto, A.; Vardaci, E.; La Rana, G.; Nadtochy, P. N.; Prete, G.

2018-03-01

The dynamics of the fission process is expected to affect the evaporation residue cross section because of the fission hindrance due to the nuclear viscosity. Systems of intermediate fissility constitute a suitable environment for testing such hypothesis since they are characterized by evaporation residue cross sections comparable or larger than the fission ones. Observables related to emitted charged particles, due to their relatively high emission probability, can be used to put stringent constraints on models describing the excited nucleus decay and to recognize the effects of fission dynamics. In this work model simulations are compared with the experimental data collected via the 32S +100 Mo reaction at Elab = 200 MeV. Consequently we pointed out, exploring an extended set of evaporation channel observables, the limits of the statistical model and the large improvement obtained with a dynamical model. Moreover we stress the importance of using an apparatus covering a large fraction of 4π to extract observables. Finally, we discuss the opportunity to measure more sensitive observables by a new detection device in operation at LNL.

A Thermal Analysis of a Hot-Wire Probe for Icing Applications

NASA Technical Reports Server (NTRS)

Struk, Peter M.; Rigby, David L.; Venkataraman, Krishna

2014-01-01

This paper presents a steady-state thermal model of a hot-wire instrument applicable to atmospheric measurement of water content in clouds. In this application, the power required to maintain the wire at a given temperature is used to deduce the water content of the cloud. The model considers electrical resistive heating, axial conduction, convection to the flow, radiation to the surroundings, as well as energy loss due to the heating, melting, and evaporation of impinging liquid and or ice. All of these parameters can be varied axially along the wire. The model further introduces a parameter called the evaporation potential which locally gauges the maximum fraction of incoming water that evaporates. The primary outputs of the model are the steady-state power required to maintain a spatially-average constant temperature as well as the variation of that temperature and other parameters along the wire. The model is used to understand the sensitivity of the hot-wire performance to various flow and boundary conditions including a detailed comparison of dry air and wet (i.e. cloud-on) conditions. The steady-state power values are compared to experimental results from a Science Engineering Associates (SEA) Multi-Element probe, a commonly used water-content measurement instrument. The model results show good agreement with experiment for both dry and cloud-on conditions with liquid water content. For ice, the experimental measurements under read the actual water content due to incomplete evaporation and splashing. Model results, which account for incomplete evaporation, are still higher than experimental results where the discrepancy is attributed to splashing mass-loss which is not accounted in the model.

Numerical modeling of heat and mass transport processes in an evaporative thermal protection system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bobrov, I.N.; Kuryachii, A.P.

1992-08-01

We propose a mathematical model of heat and mass transport processes in a moist, porous material subject to capillary action. The material is in contact with a heated surface, and the processes take place while the liquid is evaporating in a cavity with a drainage hole. A sample calculation based on the model is presented. 45 refs., 4 figs.

Evolution of vaporizing pulsars

NASA Technical Reports Server (NTRS)

Mccormick, P.

1994-01-01

We construct evolutional scenarios for LMXB's using a simplified stellar model. We discuss the origin and evolution of short-period, low mass binary pulsars with evaporating companions. We suggest that these systems descend from low-mass X-ray binaries and that angular momentum loss mainly due to evaporative wind drives their evolution. We derive limits on the energy and angular momentum carried away by the wind based on the observed low eccentricity. In our model the companion remains near contact, and its quasiadiabatic expansion causes the binary to expand. Short-term oscillations of the orbital period may occur if the Roche-lobe overflow forms an evaporating disk.

Approximate solution to the Callan-Giddings-Harvey-Strominger field equations for two-dimensional evaporating black holes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ori, Amos

2010-11-15

Callan, Giddings, Harvey, and Strominger (CGHS) previously introduced a two-dimensional semiclassical model of gravity coupled to a dilaton and to matter fields. Their model yields a system of field equations which may describe the formation of a black hole in gravitational collapse as well as its subsequent evaporation. Here we present an approximate analytical solution to the semiclassical CGHS field equations. This solution is constructed using the recently introduced formalism of flux-conserving hyperbolic systems. We also explore the asymptotic behavior at the horizon of the evaporating black hole.

Instability and dynamics of volatile thin films

NASA Astrophysics Data System (ADS)

Ji, Hangjie; Witelski, Thomas P.

2018-02-01

Volatile viscous fluids on partially wetting solid substrates can exhibit interesting interfacial instabilities and pattern formation. We study the dynamics of vapor condensation and fluid evaporation governed by a one-sided model in a low-Reynolds-number lubrication approximation incorporating surface tension, intermolecular effects, and evaporative fluxes. Parameter ranges for evaporation-dominated and condensation-dominated regimes and a critical case are identified. Interfacial instabilities driven by the competition between the disjoining pressure and evaporative effects are studied via linear stability analysis. Transient pattern formation in nearly flat evolving films in the critical case is investigated. In the weak evaporation limit unstable modes of finite-amplitude nonuniform steady states lead to rich droplet dynamics, including flattening, symmetry breaking, and droplet merging. Numerical simulations show that long-time behaviors leading to evaporation or condensation are sensitive to transitions between filmwise and dropwise dynamics.

Optimized evaporation technique for leachate treatment: Small scale implementation.

PubMed

Benyoucef, Fatima; Makan, Abdelhadi; El Ghmari, Abderrahman; Ouatmane, Aziz

2016-04-01

This paper introduces an optimized evaporation technique for leachate treatment. For this purpose and in order to study the feasibility and measure the effectiveness of the forced evaporation, three cuboidal steel tubs were designed and implemented. The first control-tub was installed at the ground level to monitor natural evaporation. Similarly, the second and the third tub, models under investigation, were installed respectively at the ground level (equipped-tub 1) and out of the ground level (equipped-tub 2), and provided with special equipment to accelerate the evaporation process. The obtained results showed that the evaporation rate at the equipped-tubs was much accelerated with respect to the control-tub. It was accelerated five times in the winter period, where the evaporation rate was increased from a value of 0.37 mm/day to reach a value of 1.50 mm/day. In the summer period, the evaporation rate was accelerated more than three times and it increased from a value of 3.06 mm/day to reach a value of 10.25 mm/day. Overall, the optimized evaporation technique can be applied effectively either under electric or solar energy supply, and will accelerate the evaporation rate from three to five times whatever the season temperature. Copyright © 2016. Published by Elsevier Ltd.

Seasonal and Interannual Variations of Evaporation and their Relations with Precipitation, Net Radiation, and Net Carbon Accumulation for the Gediz Basin Area

NASA Technical Reports Server (NTRS)

Choudhury, Bhaskar J.

1999-01-01

A model combining the rate of carbon assimilation with water and energy balance equations has been run using satellite and ancillary data for a period of 60 months (January 1986 to December 1990). Calculations for the Gediz basin area give mean annual evaporation as 395 mm, which is composed of 45% transpiration, 42% soil evaporation and 13% interception. The coefficient of interannual variation of evaporation is found to be 6%, while that for precipitation and net radiation are, respectively, 16% and 2%, illustrating that net radiation has an important effect in modulating interannual variation of evaporation. The mean annual water use efficiency (i.e., the ratio of net carbon accumulation and total evaporation) is ca. 1 g/sq m/mm, and has a coefficient of interannual variation of 5%. A comparison of the mean water use efficiency with field observations suggests that evaporation over the area is utilized well for biomass production. The reference crop evaporation for irrigated areas has annual mean and coefficient of variation as, respectively, 1176 mm and 3%. The total evaporation during three summer months of peak evaporation (June-August) is estimated to be about 575 mm for irrigated crops like maize and cotton. Seasonal variations of the fluxes are presented.

Spin distributions and cross sections of evaporation residues in the 28Si+176Yb reaction

NASA Astrophysics Data System (ADS)

Sudarshan, K.; Tripathi, R.; Sodaye, S.; Sharma, S. K.; Pujari, P. K.; Gehlot, J.; Madhavan, N.; Nath, S.; Mohanto, G.; Mukul, I.; Jhingan, A.; Mazumdar, I.

2017-02-01

Background: Non-compound-nucleus fission in the preactinide region has been an active area of investigation in the recent past. Based on the measurements of fission-fragment mass distributions in the fission of 202Po, populated by reactions with varying entrance channel mass asymmetry, the onset of non-compound-nucleus fission was proposed to be around ZpZt˜1000 [Phys. Rev. C 77, 024606 (2008), 10.1103/PhysRevC.77.024606], where Zp and Zt are the projectile and target proton numbers, respectively. Purpose: The present paper is aimed at the measurement of cross sections and spin distributions of evaporation residues in the 28Si+176Yb reaction (ZpZt=980 ) to investigate the fusion hindrance which, in turn, would give information about the contribution from non-compound-nucleus fission in this reaction. Method: Evaporation-residue cross sections were measured in the beam energy range of 129-166 MeV using the hybrid recoil mass analyzer (HYRA) operated in the gas-filled mode. Evaporation-residue cross sections were also measured by the recoil catcher technique followed by off-line γ -ray spectrometry at few intermediate energies. γ -ray multiplicities of evaporation residues were measured to infer about their spin distribution. The measurements were carried out using NaI(Tl) detector-based 4π-spin spectrometer from the Tata Institute of Fundamental Research, Mumbai, coupled to the HYRA. Results: Evaporation-residue cross sections were significantly lower compared to those calculated using the statistical model code pace2 [Phys. Rev. C 21, 230 (1980), 10.1103/PhysRevC.21.230] with the coupled-channel fusion model code ccfus [Comput. Phys. Commun. 46, 187 (1987), 10.1016/0010-4655(87)90045-2] at beam energies close to the entrance channel Coulomb barrier. At higher beam energies, experimental cross sections were close to those predicted by the model. Average γ -ray multiplicities or angular momentum values of evaporation residues were in agreement with the calculations of the code ccfus + pace2 within the experimental uncertainties at all the beam energies. Conclusions: Deviation of evaporation-residue cross sections from the "fusion + statistical model" predictions at beam energies close to the entrance channel Coulomb barrier indicates fusion hindrance at these beam energies which would lead to non-compound-nucleus fission. However, reasonable agreement of average angular momentum values of evaporation residues at these beam energies with those calculated using the coupled-channel fusion model with the statistical model codes ccfus + pace2 suggests that fusion suppression at beam energies close to the entrance channel Coulomb barrier where populated l waves are low is not l dependent.

Potential for natural evaporation as a reliable renewable energy resource.

PubMed

Cavusoglu, Ahmet-Hamdi; Chen, Xi; Gentine, Pierre; Sahin, Ozgur

2017-09-26

About 50% of the solar energy absorbed at the Earth's surface drives evaporation, fueling the water cycle that affects various renewable energy resources, such as wind and hydropower. Recent advances demonstrate our nascent ability to convert evaporation energy into work, yet there is little understanding about the potential of this resource. Here we study the energy available from natural evaporation to predict the potential of this ubiquitous resource. We find that natural evaporation from open water surfaces could provide power densities comparable to current wind and solar technologies while cutting evaporative water losses by nearly half. We estimate up to 325 GW of power is potentially available in the United States. Strikingly, water's large heat capacity is sufficient to control power output by storing excess energy when demand is low, thus reducing intermittency and improving reliability. Our findings motivate the improvement of materials and devices that convert energy from evaporation.The evaporation of water represents an alternative source of renewable energy. Building on previous models of evaporation, Cavusoglu et al. show that the power available from this natural resource is comparable to wind and solar power, yet it does not suffer as much from varying weather conditions.

Dynamics of Soil Water Evaporation during Soil Drying: Laboratory Experiment and Numerical Analysis

PubMed Central

Han, Jiangbo; Zhou, Zhifang

2013-01-01

Laboratory and numerical experiments were conducted to investigate the evolution of soil water evaporation during a continuous drying event. Simulated soil water contents and temperatures by the calibrated model well reproduced measured values at different depths. Results show that the evaporative drying process could be divided into three stages, beginning with a relatively high evaporation rate during stage 1, followed by a lower rate during transient stage and stage 2, and finally maintaining a very low and constant rate during stage 3. The condensation zone was located immediately below the evaporation zone in the profile. Both peaks of evaporation and condensation rate increased rapidly during stage 1 and transition stage, decreased during stage 2, and maintained constant during stage 3. The width of evaporation zone kept a continuous increase during stages 1 and 2 and maintained a nearly constant value of 0.68 cm during stage 3. When the evaporation zone totally moved into the subsurface, a dry surface layer (DSL) formed above the evaporation zone at the end of stage 2. The width of DSL also presented a continuous increase during stage 2 and kept a constant value of 0.71 cm during stage 3. PMID:24489492

Dynamics of soil water evaporation during soil drying: laboratory experiment and numerical analysis.

PubMed

Han, Jiangbo; Zhou, Zhifang

2013-01-01

Laboratory and numerical experiments were conducted to investigate the evolution of soil water evaporation during a continuous drying event. Simulated soil water contents and temperatures by the calibrated model well reproduced measured values at different depths. Results show that the evaporative drying process could be divided into three stages, beginning with a relatively high evaporation rate during stage 1, followed by a lower rate during transient stage and stage 2, and finally maintaining a very low and constant rate during stage 3. The condensation zone was located immediately below the evaporation zone in the profile. Both peaks of evaporation and condensation rate increased rapidly during stage 1 and transition stage, decreased during stage 2, and maintained constant during stage 3. The width of evaporation zone kept a continuous increase during stages 1 and 2 and maintained a nearly constant value of 0.68 cm during stage 3. When the evaporation zone totally moved into the subsurface, a dry surface layer (DSL) formed above the evaporation zone at the end of stage 2. The width of DSL also presented a continuous increase during stage 2 and kept a constant value of 0.71 cm during stage 3.

Optimized evaporation from a microchannel heat sink

NASA Astrophysics Data System (ADS)

Monazami, Reza; Haj-Hariri, Hossein

2011-11-01

Two-phase heat transfer devices, benefiting the unique thermal capacities of phase- change, are considered as the top choice for a wide range of applications involving cooling and temperature control. Evaporation and condensation in these devices usually take place on porous structures. It is widely accepted that they improve the evaporation rates and the overall performance of the device. The liquid menisci formed on the pores of a porous material can be viewed as the active sites of evaporation. Therefore, quantifying the rate of evaporation from a single pore can be used to calculate the total evaporation taking place in the evaporator given the density and the average size of the pores. A microchannel heat sink can be viewed as an structured porous material. In this work, an analytical model is developed to predict the evaporation rate from a liquid meniscus enclosed in a microchannel. The effects of the wall superheat and the width of the channel on the evaporation profile through the meniscus are studied. The results suggest that there is an optimum size for the width of the channel in order to maximize the thermal energy absorbed by the unit area of the heat sink as an array of microchannels.

Global root zone storage capacity from satellite-based evaporation

NASA Astrophysics Data System (ADS)

Wang-Erlandsson, Lan; Bastiaanssen, Wim G. M.; Gao, Hongkai; Jägermeyr, Jonas; Senay, Gabriel B.; van Dijk, Albert I. J. M.; Guerschman, Juan P.; Keys, Patrick W.; Gordon, Line J.; Savenije, Hubert H. G.

2016-04-01

This study presents an "Earth observation-based" method for estimating root zone storage capacity - a critical, yet uncertain parameter in hydrological and land surface modelling. By assuming that vegetation optimises its root zone storage capacity to bridge critical dry periods, we were able to use state-of-the-art satellite-based evaporation data computed with independent energy balance equations to derive gridded root zone storage capacity at global scale. This approach does not require soil or vegetation information, is model independent, and is in principle scale independent. In contrast to a traditional look-up table approach, our method captures the variability in root zone storage capacity within land cover types, including in rainforests where direct measurements of root depths otherwise are scarce. Implementing the estimated root zone storage capacity in the global hydrological model STEAM (Simple Terrestrial Evaporation to Atmosphere Model) improved evaporation simulation overall, and in particular during the least evaporating months in sub-humid to humid regions with moderate to high seasonality. Our results suggest that several forest types are able to create a large storage to buffer for severe droughts (with a very long return period), in contrast to, for example, savannahs and woody savannahs (medium length return period), as well as grasslands, shrublands, and croplands (very short return period). The presented method to estimate root zone storage capacity eliminates the need for poor resolution soil and rooting depth data that form a limitation for achieving progress in the global land surface modelling community.

Evaporation of LOX under supercritical and subcritical conditions

NASA Technical Reports Server (NTRS)

Yang, A. S.; Hsieh, W. H.; Kuo, K. K.; Brown, J. J.

1993-01-01

The evaporation of LOX under supercritical and subcritical conditions was studied experimentally and theoretically. In experiments, the evaporation rate and surface temperature were measured for LOX strand vaporizing in helium environments at pressures ranging from 5 to 68 atmospheres. Gas sampling and chromatography analysis were also employed to profile the gas composition above the LOX surface for the purpose of model validation. A comprehensive theoretical model was formulated and solved numerically to simulate the evaporation process of LOX at high pressures. The model was based on the conservation equations of mass, momentum, energy, and species concentrations for a multicomponent system, with consideration of gravitational body force, solubility of ambient gases in liquid, and variable thermophysical properties. Good agreement between predictions and measured oxygen mole fraction profiles was obtained. The effect of pressure on the distribution of the Lewis number, as well as the effect of variable diffusion coefficient, were further examined to elucidate the high-pressure transport behavior exhibited in the LOX vaporization process.

An evaporative and engine-cycle model for fuel octane sensitivity prediction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moran, D.P.; Taylor, A.B.

The Motor Octane Number (MON) ranks fuels by their chemical resistance to knock. Evaporative cooling coupled with fuel chemistry determine Research Octane Number (RON) antiknock ratings. It is shown in this study that fuel Octane sensitivity (numerically RON minus MON) is liked to an important difference between the two test methods; the RON test allows each fuel`s evaporative cooling characteristics to affect gas temperature, while the MON test generally eliminates this effect by pre-evaporation. In order to establish RON test charge temperatures, a computer model of fuel evaporation was adapted to Octane Engine conditions, and simulations were compared with realmore » Octane Test Engine measurements including droplet and gas temperatures. A novel gas temperature probe yielded data that corresponded well with model predictions. Tests spanned single component fuels and blends of isomers, n-paraffins, aromatics and alcohols. Commercially available automotive and aviation gasolines were also tested. A good correlation was observed between the computer predictions and measured temperature data across the range of pure fuels and blends. A numerical method to estimate the effect of precombustion temperature differences on Octane sensitivity was developed and applied to analyze these data, and was found to predict the widely disparate sensitivities of the tested fuels with accuracy. Data are presented showing mixture temperature histories of various tested fuels, and consequent sensitivity predictions. It is concluded that a fuel`s thermal-evaporative behavior gives rise to fuel Octane sensitivity as measured by differences between the RON and MON tests. This is demonstrated by the success, over a wide range of fuels, of the sensitivity predictor method describes. Evaporative cooling, must therefore be regarded as an important parameter affecting the general road performance of automobiles.« less

Brief Communication: A Simplified Approach to Transient Convective Droplet Evaporation and Burning

NASA Technical Reports Server (NTRS)

Madooglu, K.; Karagozian, A. R.

1994-01-01

Empirical correlations for evaporation rates from single fuel droplets have existed since the 1930s. These correlations, which will be referred to in this article as Froessling/Ranz-Marshall types of correlations, are appropriate to the special cases of steady-state evaporation in the absence of chemical reaction. In a previous article by the authors, the quasi-steady evaporation and burning processes associated with a fuel drop in a convective environment are examined through a droplet model based on the boundary layer approach. For droplet Reynolds numbers of practical interest, this model produces very reasonable steady state as well as quasi-time-dependent droplet simulations, requiring relatively short computational times and yielding good agreement with the above-mentioned empirical correlations. The steady-state case, however, is usually relevant to practical combustor situations only when the drop has reached a nearly uniform temperature since the heating process of the drop cannot be considered to be quasi-steady. In the present study, the transient heating process of the droplet interior during evaporation and/or burning is taken into account, and thus calculations pertaining to the entire life-time of the droplet are carried out. It is of particular interest here to obtain simplified correlations to describe the transient behavior of evaporating and burning droplets; these may be incorporated with greater ease into spray calculations. Accordingly, we have chosen to use stagnation conditions in the present model in a modification of the Froessling/Ranz-Marshall correlations. These modified correlations, incorporating an effective transfer number, produce a fairly accurate representation of droplet evaporation and burning, while requiring only one tenth the computational effort used in a full boundary layer solution.

Monthly evaporation forecasting using artificial neural networks and support vector machines

NASA Astrophysics Data System (ADS)

Tezel, Gulay; Buyukyildiz, Meral

2016-04-01

Evaporation is one of the most important components of the hydrological cycle, but is relatively difficult to estimate, due to its complexity, as it can be influenced by numerous factors. Estimation of evaporation is important for the design of reservoirs, especially in arid and semi-arid areas. Artificial neural network methods and support vector machines (SVM) are frequently utilized to estimate evaporation and other hydrological variables. In this study, usability of artificial neural networks (ANNs) (multilayer perceptron (MLP) and radial basis function network (RBFN)) and ɛ-support vector regression (SVR) artificial intelligence methods was investigated to estimate monthly pan evaporation. For this aim, temperature, relative humidity, wind speed, and precipitation data for the period 1972 to 2005 from Beysehir meteorology station were used as input variables while pan evaporation values were used as output. The Romanenko and Meyer method was also considered for the comparison. The results were compared with observed class A pan evaporation data. In MLP method, four different training algorithms, gradient descent with momentum and adaptive learning rule backpropagation (GDX), Levenberg-Marquardt (LVM), scaled conjugate gradient (SCG), and resilient backpropagation (RBP), were used. Also, ɛ-SVR model was used as SVR model. The models were designed via 10-fold cross-validation (CV); algorithm performance was assessed via mean absolute error (MAE), root mean square error (RMSE), and coefficient of determination (R 2). According to the performance criteria, the ANN algorithms and ɛ-SVR had similar results. The ANNs and ɛ-SVR methods were found to perform better than the Romanenko and Meyer methods. Consequently, the best performance using the test data was obtained using SCG(4,2,2,1) with R 2 = 0.905.

Evaporation Flux Distribution of Drops on a Hydrophilic or Hydrophobic Flat Surface by Molecular Simulations.

PubMed

Xie, Chiyu; Liu, Guangzhi; Wang, Moran

2016-08-16

The evaporation flux distribution of sessile drops is investigated by molecular dynamic simulations. Three evaporating modes are classified, including the diffusion dominant mode, the substrate heating mode, and the environment heating mode. Both hydrophilic and hydrophobic drop-substrate interactions are considered. To count the evaporation flux distribution, which is position dependent, we proposed an azimuthal-angle-based division method under the assumption of spherical crown shape of drops. The modeling results show that the edge evaporation, i.e., near the contact line, is enhanced for hydrophilic drops in all the three modes. The surface diffusion of liquid molecular absorbed on solid substrate for hydrophilic cases plays an important role as well as the space diffusion on the enhanced evaporation rate at the edge. For hydrophobic drops, the edge evaporation flux is higher for the substrate heating mode, but lower than elsewhere of the drop for the diffusion dominant mode; however, a nearly uniform distribution is found for the environment heating mode. The evidence shows that the temperature distribution inside drops plays a key role in the position-dependent evaporation flux.

Effects of Gravel Mulch Properties and Thickness on Evaporation from Underlying Soil

NASA Astrophysics Data System (ADS)

Li, Z.; Smits, K. M.

2017-12-01

Evaporation is the process of mass and heat transfer between the atmosphere and the shallow subsurface, and it is critical to many natural and industrial applications. In arid areas with very little rainfall, gravel has been widely used as a mulch layer to suppress evaporation from the underlying soil. The properties of mulch layers have a significant effect on the evaporation process, and the effect of grain size and mulch thickness has been previously studied experimentally. However, there is debate on the effect of the gravel mulch hydraulic properties on the evaporation suppression and role of the gravel mulch layer just after precipitation has not been discussed. The goal of this work is to investigate in more depth the impact of the gravel mulch hydraulic properties and the thickness of the mulch layer on evaporation from underlying soil with the combination of experiments and theoretical models. For this work, we developed a fully coupled numerical model of layered porous media that solves for heat, liquid water and water vapor flux under both wet and dry soil conditions. Various mulch layers with different texture and thickness were employed in the numerical simulation to study the effect of the hydraulic properties and thickness on the underlying soil evaporation. The water and heat transport in the soil and across the soil-atmosphere interface were presented and analyzed. In addition, results from numerical simulations were also compared with a series of mulch layer experiments performed using bench-scale porous media tanks interfaced with an open-return wind tunnel. Results demonstrated that gravel mulch is effective in significantly delaying and suppressing evaporation from underlying soil, and the evaporation behavior varies from different mulch types and thicknesses. The reason for evaporation suppression is that the gravel mulch retards the evaporation from the underlying soil first, and then cuts the hydraulic connection between the drying front and the atmosphere. The delaying time and evaporation reduction increases with the decrease of the grain size and increase of the air entry value of the gravel mulch, in which the air entry value is the primary factor. Thicker mulch layers have a better performance in both retarding and preventing evaporation from the underlying soil.

Pressurization of a Flightweight, Liquid Hydrogen Tank: Evaporation and Condensation at a Liquid Vapor Interface

NASA Technical Reports Server (NTRS)

Stewart, Mark E.

2017-01-01

Evaporation and condensation at a liquidvapor interface is important for long-term, in-space cryogenic propellant storage. Yet the current understanding of interfacial physics does not predict behavior or evaporation condensation rates. The proposed paper will present a physical model, based on the 1-D Heat equation and Schrages equation which demonstrates thin thermal layers at the fluidvapor interface.

Numerical study of the influence of water evaporation on radiofrequency ablation.

PubMed

Zhu, Qing; Shen, Yuanyuan; Zhang, Aili; Xu, Lisa X

2013-12-10

Radiofrequency ablation is a promising minimal invasive treatment for tumor. However, water loss due to evaporation has been a major issue blocking further RF energy transmission and correspondently eliminating the therapeutic outcome of the treatment. A 2D symmetric cylindrical mathematical model coupling the transport of the electrical current, heat, and the evaporation process in the tissue, has been developed to simulate the treatment process and investigate the influence of the excessive evaporation of the water on the treatment. Our results show that the largest specific absorption rate (QSAR) occurs at the edge of the circular surface of the electrode. When excessive evaporation takes place, the water dehydration rate in this region is the highest, and after a certain time, the dehydrated tissue blocks the electrical energy transmission in the radial direction. It is found that there is an interval as long as 65 s between the beginning of the evaporation and the increase of the tissue impedance. The model is further used to investigate whether purposely terminating the treatment for a while allowing diffusion of the liquid water into the evaporated region would help. Results show it has no obvious improvement enlarging the treatment volume. Treatment with the cooled-tip electrode is also studied. It is found that the cooling conditions of the inside agent greatly affect the water loss pattern. When the convection coefficient of the cooling agent increases, excessive evaporation will start from near the central axis of the tissue cylinder instead of the edge of the electrode, and the coagulation volume obviously enlarges before a sudden increase of the impedance. It is also found that a higher convection coefficient will extend the treatment time. Though the sudden increase of the tissue impedance could be delayed by a larger convection coefficient; the rate of the impedance increase is also more dramatic compared to the case with smaller convection coefficient. The mathematical model simulates the water evaporation and diffusion during radiofrequency ablation and may be used for better clinical design of radiofrequency equipment and treatment protocol planning.

Evaporation and abstraction determined from stable isotopes during normal flow on the Gariep River, South Africa

NASA Astrophysics Data System (ADS)

Diamond, Roger E.; Jack, Sam

2018-04-01

Changes in the stable isotope composition of water can, with the aid of climatic parameters, be used to calculate the quantity of evaporation from a water body. Previous workers have mostly focused on small, research catchments, with abundant data, but of limited scope. This study aimed to expand such work to a regional or sub-continental scale. The first full length isotope survey of the Gariep River quantifies evaporation on the river and the man-made reservoirs for the first time, and proposes a technique to calculate abstraction from the river. The theoretically determined final isotope composition for an evaporating water body in the given climate lies on the empirically determined local evaporation line, validating the assumptions and inputs to the Craig-Gordon evaporation model that was used. Evaporation from the Gariep River amounts to around 20% of flow, or 40 m3/s, of which about half is due to evaporation from the surface of the Gariep and Vanderkloof Reservoirs, showing the wastefulness of large surface water impoundments. This compares well with previous estimates based on evapotranspiration calculations, and equates to around 1300 GL/a of water, or about the annual water consumption of Johannesburg and Pretoria, where over 10 million people reside. Using similar evaporation calculations and applying existing transpiration estimates to a gauged length of river, the remaining quantity can be attributed to abstraction, amounting to 175 L/s/km in the lower middle reaches of the river. Given that high water demand and climate change are global problems, and with the challenges of maintaining water monitoring networks, stable isotopes are shown to be applicable over regional to national scales for modelling hydrological flows. Stable isotopes provide a complementary method to conventional flow gauging for understanding hydrology and management of large water resources, particularly in arid areas subject to significant evaporation.

Sensitivity of Spacebased Microwave Radiometer Observations to Ocean Surface Evaporation

NASA Technical Reports Server (NTRS)

Liu, Timothy W.; Li, Li

2000-01-01

Ocean surface evaporation and the latent heat it carries are the major components of the hydrologic and thermal forcing on the global oceans. However, there is practically no direct in situ measurements. Evaporation estimated from bulk parameterization methods depends on the quality and distribution of volunteer-ship reports which are far less than satisfactory. The only way to monitor evaporation with sufficient temporal and spatial resolutions to study global environment changes is by spaceborne sensors. The estimation of seasonal-to-interannual variation of ocean evaporation, using spacebased measurements of wind speed, sea surface temperature (SST), and integrated water vapor, through bulk parameterization method,s was achieved with reasonable success over most of the global ocean, in the past decade. Because all the three geophysical parameters can be retrieved from the radiance at the frequencies measured by the Scanning Multichannel Microwave Radiometer (SMMR) on Nimbus-7, the feasibility of retrieving evaporation directly from the measured radiance was suggested and demonstrated using coincident brightness temperatures observed by SMMR and latent heat flux computed from ship data, in the monthly time scale. However, the operational microwave radiometers that followed SMMR, the Special Sensor Microwave/Imager (SSM/I), lack the low frequency channels which are sensitive to SST. This low frequency channels are again included in the microwave imager (TMI) of the recently launched Tropical Rain Measuring Mission (TRMM). The radiance at the frequencies observed by both TMI and SSM/I were simulated through an atmospheric radiative transfer model using ocean surface parameters and atmospheric temperature and humidity profiles produced by the reanalysis of the European Center for Medium Range Weather Forecast (ECMWF). From the same ECMWF data set, coincident evaporation is computed using a surface layer turbulent transfer model. The sensitivity of the radiance to evaporation over various seasons and geographic locations are examined. The microwave frequencies with radiance that are significant correlated with evaporation are identify and capability of estimating evaporation directly from TMI will be discussed.

Final Summary of Research Report to the National Aeronautics and Space Administration Origins of Solar Systems Program

NASA Technical Reports Server (NTRS)

O'D. Alexander, Conel

2003-01-01

The chondrites are aggregates of components (e.g. chondrules, chondrule rims and matrix) that formed in the nebula but, at present, there is no consensus on how any of these components formed or whether their formation produced or post dated the chemical fractionations between the chondrites. Chondrites are, at present, the most primitive Solar System objects available for laboratory study and the conditions under which their principle components formed would provide the most direct constraints for models of nebula formation and evolution. The conditions under which chondrules formed is of particular importance because, if their relative abundance in chondrites approximates that in the nebula, they are the products of one of the most energetic and pervasive processes that operated in the early Solar System. The goal of this proposal was to combine theoretical modeling with a comprehensive study of the elemental and isotopic compositions of the major components in unequilibrated ordinary chondrites (UOCs), with the aim of determining the conditions in the nebula at the time of their formation. The isotopes of volatile and moderately volatile elements should be particularly revealing of conditions during chondrule formation, as evaporation under most conditions would lead to isotopic mass fractionation. Modeling of chondrule and matrix formation requires the development of a kinetic model of evaporation and condensation, and calibration of this model against experiments. Cosmic spherules present an opportunity to test our evaporation models under flash heating conditions that would be difficult to simulate experimentally. However, there is surprisingly little known about the isotopic compositions of silicate cosmic spherules, and a number of questions need to be addressed. Is the range of compositions they exhibit due to evaporation? If they are, are the relative volatilities consistent with the models/experiments and are the isotopic fractionations consistent with Rayleigh conditions? For instance, do the alkalis and S evaporate prior to significant melting so that conditions did not meet the Rayleigh criteria of rapid diffusion? If so, their isotopic fractionation might be considerably suppressed. Could this mechanism of K loss apply to chondrule formation? The Fe isotopic fractionation during evaporation of silicates has not been measured, so cosmic spherules might provide a clue to whether FeO diffusion is fast enough to maintain Rayleigh conditions during evaporation. And so on.

Climate change impact on the annual water balance in the northwest Florida coastal

NASA Astrophysics Data System (ADS)

Alizad, K.; Wang, D.; Alimohammadi, N.; Hagen, S. C.

2012-12-01

As the largest tributary to the Apalachicola River, the Chipola River originates in southern Alabama, flows through Florida Panhandle and ended to Gulf of Mexico. The Chipola watershed is located in an intermediate climate environment with aridity index around one. Watershed provides habitat for a number of threatened and endangered animal and plant species. However, climate change affects hydrologic cycle of Chipola River watershed at various temporal and spatial scales. Studying the effects of climate variations is of great importance for water and environmental management purposes in this catchment. This research is mainly focuses on assessing climate change impact on the partitioning pattern of rainfall from mean annual to inter-annual and to seasonal scales. At the mean annual scale, rainfall is partitioned into runoff and evaporation assuming negligible water storage changes. Mean annual runoff is controlled by both mean annual precipitation and potential evaporation. Changes in long term mean runoff caused by variations of long term mean precipitation and potential evaporation will be evaluated based on Budyko hypothesis. At the annual scale, rainfall is partitioned into runoff, evaporation, and storage change. Inter-annual variability of runoff and evaporation are mainly affected by the changes of mean annual climate variables as well as their inter-annual variability. In order to model and evaluate each component of water balance at the annual scale, parsimonious but reliable models, are developed. Budyko hypothesis on the existing balance between available water and energy supply is reconsidered and redefined for the sub-annual time scale and reconstructed accordingly in order to accurately model seasonal hydrologic balance of the catchment. Models are built in the seasonal time frame with a focus on the role of storage change in water cycle. Then for Chipola catchment, models are parameterized based on a sufficient time span of historical data and the their coefficients are quantified. For necessary future predictions, data obtained from climate regional models starting 2040 to 2069 will be utilized. To accommodate the inherent uncertainty of climate projections, an ensemble of regional climate models will be used to assess changes of rainfall and potential evaporation. Then, the climate change impact on seasonal and annual runoff, evaporation, and water storage changes will be projected.

On the kinetics of body versus end evaporation and addition of supramolecular polymers.

PubMed

Tiwari, Nitin S; van der Schoot, Paul

2017-06-01

The kinetics of the self-assembly of supramolecular polymers is dictated by how monomers, dimers, trimers etc., attach to and detach from each other. It is for this reasons that researchers have proposed a plethora of pathways to explain the kinetics of various self-assembling supramolecules, including sulfur, linear micelles, living polymers and protein fibrils. Recent observations hint at the importance of a hitherto ignored molecular aggregation pathway that we refer to as "body evaporation and addition". In this pathway, monomers can enter at or dissociate from any point along the backbone of the polymer. In this paper, we compare predictions for the well-established end evaporation and addition pathway with those that we obtained for the newly proposed body evaporation and addition model. We quantify the lag time, characteristic of nucleated reversible polymerisation, in terms of the time it takes to obtain half of the steady-state polymerised fraction and the apparent growth rate at that point, and obtain power laws for both as a function of the total monomer concentration. We find, perhaps not entirely unexpectedly, that the body evaporation and addition pathway speeds up the relaxation of the polymerised monomeric mass relative to that of the end evaporation and addition. However, the presence of the body evaporation and addition pathway does not affect the dependence of the lag time on the total monomer concentration and it remains the same as that for the case of end evaporation and addition. The scaling of the lag time with the forward rate is different for the two models, suggesting that they may be distinguished experimentally.

Climate, interseasonal storage of soil water, and the annual water balance

USGS Publications Warehouse

Milly, P.C.D.

1994-01-01

The effects of annual totals and seasonal variations of precipitation and potential evaporation on the annual water balance are explored. It is assumed that the only other factor of significance to annual water balance is a simple process of water storage, and that the relevant storage capacity is the plant-available water-holding capacity of the soil. Under the assumption that precipitation and potential evaporation vary sinusoidally through the year, it is possible to derive an analytic solution of the storage problem, and this yields an expression for the fraction of precipitation that evaporates (and the fraction that runs off) as a function of three dimensionless numbers: the ratio of annual potential evaporation to annual precipitation (index of dryness); an index of the seasonality of the difference between precipitation and potential evaporation; and the ratio of plant-available water-holding capacity to annual precipitation. The solution is applied to the area of the United States east of 105??W, using published information on precipitation, potential evaporation, and plant-available water-holding capacity as inputs, and using an independent analysis of observed river runoff for model evaluation. The model generates an areal mean annual runoff of only 187 mm, which is about 30% less than the observed runoff (263 mm). The discrepancy is suggestive of the importance of runoff-generating mechanisms neglected in the model. These include intraseasonal variability (storminess) of precipitation, spatial variability of storage capacity, and finite infiltration capacity of land. ?? 1994.

Comparative Measurements of Condensation and Evaporation In The Alpine Regions of Thegiant Mountains, Poland and The Dischma, E. Switzerland

NASA Astrophysics Data System (ADS)

de Jong, C.; Mundelius, M.; Migala, K.

During the summers of 1998, 1999 and 2001, two basins were instrumented for detailed comparative measurements of evaporation, transpiration and condensation. The catchments of the Reifträger, situated in the Giant Mountains of Poland and the Dischma, situated in the Kanton Graubünden in Eastern Switzerland range in altitude between 850 - 1410 m and 1600 - 3100 m respectively. All hydrological and meteorological measurements were carried out above the treeline. Both regions consist mainly of dwarf shrubs with dwarf pines, ferns, and moors dominating in the Reifträger and alpine pasture and dwarf shrubs in the Dischma. Automatic we ighing lysimeters and evaporation pans recorded evaporation, transpiration, condensation and rainfall data at 10 minute intervals over different slope profiles. On the Reifträger, condensation occurs between 05:00-07:00 and is followed by the onset of evaporation. Evaporation stagnates nearly entirely between 11:00-12:00 but it is subsequently reinitiated due to rapidly increasing wind speeds, reaching a maximum at 14:00. Evaporation continues until 18:00, followed by some nighttime evaporation in the early morning hours. Unlike the Reifträger, the Dischma has two daily maxima for evaporation and transpiration, again preceded in the morning hours by intensive condensation. In the Dischma, evaporation and transpiration is variable according to valley side but the first maximum usually occurs at 15:00 followed by a second maximum between 18:00-19:00 after sunset. The differences in the timing and pattern of evaporation and transpiration of the two catchments can be explained by influence of fog on the Reifträger compared to the regular exchange of moist and dry air from the glacier in the Dischma. In both cases, evaporation is delayed relative to radiation so that there is an evaporation lag of approximately 30 - 50 minutes on the Reifträger and up to 2 hours in the Dischma. Evaporation should therefore be modelled through a function of the temperature profile and wind distribution i.e. with a well-developed advection term. In both cases, transpiration exceeds evaporation, with about 70% for the Reifträger and 30% for the Dischma. The Reifträger has a dynamic local wind system that, together with temperature, has a significant influence on evaporation and transpiration. As the name suggests, the Reifträger experiences up to 124 days per year with 24 hours of fog. Although barely any evaporation or radiation is recorded on such days, the highest transpiration rates are observed due to windy conditions with relatively high temperatures. In the Dischma the strong influence of winds is also very significant for evaporation and transpiration, with some daily maxima occurring after sunset under the influence of warm, dry katabatic winds descending from the high altitudes. As such, condensation is a limiting factor for evaporation on clear days, but there may be an intensive interrelationship between condensation and evaporation on cloudy, humid days. Condensation during the night time replaces about 15% of the water evaporated during the daytime for the Polish example and 25 % for the Swiss example. This is strongly dependant on the capacity of the vegetation layer to absorb moisture. If the water balance is to be modelled accurately, it is advisable to measure evaporation, transpiration as well as discharge precisely to obtain a good estimate of both condensation and precipitation.

Sequential evaporation of water molecules from protonated water clusters: measurement of the velocity distributions of the evaporated molecules and statistical analysis.

PubMed

Berthias, F; Feketeová, L; Abdoul-Carime, H; Calvo, F; Farizon, B; Farizon, M; Märk, T D

2018-06-22

Velocity distributions of neutral water molecules evaporated after collision induced dissociation of protonated water clusters H+(H2O)n≤10 were measured using the combined correlated ion and neutral fragment time-of-flight (COINTOF) and velocity map imaging (VMI) techniques. As observed previously, all measured velocity distributions exhibit two contributions, with a low velocity part identified by statistical molecular dynamics (SMD) simulations as events obeying the Maxwell-Boltzmann statistics and a high velocity contribution corresponding to non-ergodic events in which energy redistribution is incomplete. In contrast to earlier studies, where the evaporation of a single molecule was probed, the present study is concerned with events involving the evaporation of up to five water molecules. In particular, we discuss here in detail the cases of two and three evaporated molecules. Evaporation of several water molecules after CID can be interpreted in general as a sequential evaporation process. In addition to the SMD calculations, a Monte Carlo (MC) based simulation was developed allowing the reconstruction of the velocity distribution produced by the evaporation of m molecules from H+(H2O)n≤10 cluster ions using the measured velocity distributions for singly evaporated molecules as the input. The observed broadening of the low-velocity part of the distributions for the evaporation of two and three molecules as compared to the width for the evaporation of a single molecule results from the cumulative recoil velocity of the successive ion residues as well as the intrinsically broader distributions for decreasingly smaller parent clusters. Further MC simulations were carried out assuming that a certain proportion of non-ergodic events is responsible for the first evaporation in such a sequential evaporation series, thereby allowing to model the entire velocity distribution.

Diffusion-controlled magnesium isotopic fractionation of a single crystal forsterite evaporated from the solid state

NASA Technical Reports Server (NTRS)

Wang, Jianhua; Davis, Andrew M.; Hashimoto, Akihiko; Clayton, Robert N.

1993-01-01

Though the origin of calcium- and aluminum-rich inclusions (CAI's) in carbonaceous chondrites is till a disputed issue, evaporation is no doubt one of the most important processes for the formation of CAI's in the early solar nebula. The mechanism for production of large isotopic mass fractionation effects in magnesium, silicon, oxygen, and chromium in CAI's can be better understood by examining isotopic fractionation during the evaporation of minerals. New evaporation experiments were performed on single-crystal forsterite. The magnesium isotopic distribution near the evaporating surfaces of the residues using a modified AEI IM-20 ion microprobe to obtain rastered beam depth profiles was measured. A theoretical model was used to explain the profiles and allowed determination of the diffusion coefficient of Mg(++) in forsterite at higher temperatures than previous measurements. The gas/solid isotopic fractionation factor for magnesium for evaporation from solid forsterite was also determined and found to be nearly the same as that for evaporation of liquid Mg2SiO4.

Study of the effect of wind speed on evaporation from soil through integrated modeling of atmospheric boundary layer and shallow subsurface

NASA Astrophysics Data System (ADS)

Davarzani, Hossein; Smits, Kathleen; Tolene, Ryan; Illangasekare, Tissa

2013-04-01

The study of the interaction between the land and atmosphere is paramount to our understanding of many emerging problems to include climate change, the movement of green house gases such as possible leaking of sequestered CO2 and the accurate detection of buried objects such as landmines. Soil moisture distribution in the shallow subsurface becomes a critical factor in all these problems. The heat and mass flux in the form of soil evaporation across the land surface couples the atmospheric boundary layer to the shallow subsurface. The coupling between land and the atmosphere leads to highly dynamic interactions between the porous media properties, transport processes and boundary conditions, resulting in dynamic evaporative behavior. However, the coupling at the land-atmospheric interface is rarely considered in most current models and their validation for practical applications. This is due to the complexity of the problem in field scenarios and the scarcity of field or laboratory data capable of testing and refining coupled energy and mass transfer theories. In most efforts to compute evaporation from soil, only indirect coupling is provided to characterize the interaction between non-isothermal multiphase flows under realistic atmospheric conditions even though heat and mass flux are controlled by the coupled dynamics of the land and the atmospheric boundary layer. In earlier drying modeling concepts, imposing evaporation flux (kinetic of relative humidity) and temperature as surface boundary condition is often needed. With the goal of improving our understanding of the land/atmospheric coupling, we developed a model based on the coupling of Navier-Stokes free flow and Darcy flow in porous medium. The model consists of the coupled equations of mass conservation for the liquid phase (water) and gas phase (water vapor and air) in porous medium with gas phase (water vapor and air) in free flow domain under non-isothermal, non-equilibrium conditions. The boundary conditions at the porous medium-free flow medium interface include dynamical, thermal and solutal equilibriums, and using the Beavers-Joseph slip boundary condition. What is unique about this model is that the evaporation rate and soil surface temperature conditions come directly from the model output. In order to experimentally validate the numerical results, we developed and used a unique two dimensional wind tunnel placed above a soil tank equipped with a network of different sensors. A series of experiments under varying boundary conditions, using a test sand for which the hydraulic and thermal properties were well characterized, were performed. Precision data for soil moisture, soil and air temperature and relative humidity, and also wind velocity under well-controlled transient heat and wind boundary conditions was generated. Results from numerical simulations were compared with experimental data. Results demonstrate that the coupling concept can predict the different stages of the drying process in porous media with good accuracy. Increasing the wind speed increases the first stage evaporation rate and decreases the transition time at low velocity values; then, at high values of wind speed the evaporation rate becomes less dependent of flow in free fluid. In the opposite, the impact of the wind speed on the second stage evaporation (diffusion dominant stage) is not significant. The proposed theoretical model can be used to predict the evaporation process where a porous medium flow is coupled to a free flow for different practical applications.

Thermal and Hydrologic Signatures of Soil Controls on Evaporation: A Combined Energy and Water Balance Approach with Implications for Remote Sensing of Evaporation

NASA Technical Reports Server (NTRS)

Salvucci, Guido D.

2000-01-01

The overall goal of this research is to examine the feasibility of applying a newly developed diagnostic model of soil water evaporation to large land areas using remotely sensed input parameters. The model estimates the rate of soil evaporation during periods when it is limited by the net transport resulting from competing effects of capillary rise and drainage. The critical soil hydraulic properties are implicitly estimated via the intensity and duration of the first stage (energy limited) evaporation, removing a major obstacle in the remote estimation of evaporation over large areas. This duration, or 'time to drying' (t(sub d)) is revealed through three signatures detectable in time series of remote sensing variables. The first is a break in soil albedo that occurs as a small vapor transmission zone develops near the surface. The second is a break in either surface to air temperature differences or in the diurnal surface temperature range, both of which indicate increased sensible heat flux (and/or storage) required to balance the decrease in latent heat flux. The third is a break in the temporal pattern of near surface soil moisture. Soil moisture tends to decrease rapidly during stage I drying (as water is removed from storage), and then become more or less constant during soil limited, or 'stage II' drying (as water is merely transmitted from deeper soil storage). The research tasks address: (1) improvements in model structure, including extensions to transpiration and aggregation over spatially variable soil and topographic landscape attributes; and (2) applications of the model using remotely sensed input parameters.

Thermal and Hydrologic Signatures of Soil Controls on Evaporation: A Combined Energy and Water Balance Approach with Implications for Remote Sensing of Evaporation

NASA Technical Reports Server (NTRS)

Salvucci, Guido D.

1997-01-01

The overall goal of this research is to examine the feasibility of applying a newly developed diagnostic model of soil water evaporation to large land areas using remotely sensed input parameters. The model estimates the rate of soil evaporation during periods when it is limited by the net transport resulting from competing effects of capillary rise and drainage. The critical soil hydraulic properties are implicitly estimated via the intensity and duration of the first stage (energy limited) evaporation, removing a major obstacle in the remote estimation of evaporation over large areas. This duration, or "time to drying" (t(sub d)), is revealed through three signatures detectable in time series of remote sensing variables. The first is a break in soil albedo that occurs as a small vapor transmission zone develops near the surface. The second is a break in either surface to air temperature differences or in the diurnal surface temperature range, both of which indicate increased sensible heat flux (and/or storage) required to balance the decrease in latent heat flux. The third is a break in the temporal pattern of near surface soil moisture. Soil moisture tends to decrease rapidly during stage 1 drying (as water is removed from storage), and then become more or less constant during soil limited, or "stage 2" drying (as water is merely transmitted from deeper soil storage). The research tasks address: (1) improvements in model structure, including extensions to transpiration and aggregation over spatially variable soil and topographic landscape attributes; and (2) applications of the model using remotely sensed input parameters.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barbante, Paolo; Frezzotti, Aldo; Gibelli, Livio

The unsteady evaporation of a thin planar liquid film is studied by molecular dynamics simulations of Lennard-Jones fluid. The obtained results are compared with the predictions of a diffuse interface model in which capillary Korteweg contributions are added to hydrodynamic equations, in order to obtain a unified description of the liquid bulk, liquid-vapor interface and vapor region. Particular care has been taken in constructing a diffuse interface model matching the thermodynamic and transport properties of the Lennard-Jones fluid. The comparison of diffuse interface model and molecular dynamics results shows that, although good agreement is obtained in equilibrium conditions, remarkable deviationsmore » of diffuse interface model predictions from the reference molecular dynamics results are observed in the simulation of liquid film evaporation. It is also observed that molecular dynamics results are in good agreement with preliminary results obtained from a composite model which describes the liquid film by a standard hydrodynamic model and the vapor by the Boltzmann equation. The two mathematical model models are connected by kinetic boundary conditions assuming unit evaporation coefficient.« less

Evaporation And Ignition Of Dense Fuel Sprays

NASA Technical Reports Server (NTRS)

Bellan, Josette; Harstad, Kenneth G.

1988-01-01

Simple theoretical model makes useful predictions of trends. Pair of reports presents theoretical model of evaporation and ignition of sprayed liquid fuel. Developed as part of research in combustion of oil and liquid fuels derived from coal, tar sand, and shale in furnace. Work eventually contributes to increase efficiency of combustion and decrease pollution generated by burning of such fuels.

EVAPORATION OF ICY PLANETESIMALS DUE TO BOW SHOCKS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tanaka, Kyoko K.; Yamamoto, Tetsuo; Tanaka, Hidekazu

2013-02-20

We present the novel concept of evaporation of planetesimals as a result of bow shocks associated with planetesimals orbiting with supersonic velocities relative to the gas in a protoplanetary disk. We evaluate the evaporation rates of the planetesimals based on a simple model describing planetesimal heating and evaporation by the bow shock. We find that icy planetesimals with radius {approx}>100 km evaporate efficiently even outside the snow line in the stage of planetary oligarchic growth, where strong bow shocks are produced by gravitational perturbations from protoplanets. The obtained results suggest that the formation of gas giant planets is suppressed owingmore » to insufficient accretion of icy planetesimals onto the protoplanet within the {approx}<5 AU disk region.« less

Structural and evaporative evolutions in desiccating sessile drops of blood

NASA Astrophysics Data System (ADS)

Sobac, B.; Brutin, D.

2011-07-01

We report an experimental investigation of the drying of a deposited drop of whole blood. Flow motion, adhesion, gelation, and fracturation all occur during the evaporation of this complex matter, leading to a final typical pattern. Two distinct regimes of evaporation are highlighted: the first is driven by convection, diffusion, and gelation in a liquid phase, whereas the second, with a much slower rate of evaporation, is characterized by the mass transport of the liquid left over in the gellified biocomponent matter. A diffusion model of the drying process allows a prediction of the transition between these two regimes of evaporation. Moreover, the formation of cracks and other events occurring during the drying are examined and shown to be driven by critical solid mass concentrations.

Evaporative cooling of microscopic water droplets in vacuo: Molecular dynamics simulations and kinetic gas theory

DOE PAGES

Schlesinger, Daniel; Sellberg, Jonas A.; Nilsson, Anders; ...

2016-03-22

In the present study, we investigate the process of evaporative cooling of nanometer-sized droplets in vacuum using molecular dynamics simulations with the TIP4P/2005 water model. The results are compared to the temperature evolution calculated from the Knudsen theory of evaporation which is derived from kinetic gas theory. The calculated and simulation results are found to be in very good agreement for an evaporation coefficient equal to unity. Lastly, our results are of interest to experiments utilizing droplet dispensers as well as to cloud micro-physics.

Enhanced Evaporation and Condensation in Tubes

NASA Astrophysics Data System (ADS)

Honda, Hiroshi

A state-of-the-art review of enhanced evaporation and condensation in horizontal microfin tubes and micro-channels that are used for air-conditioning and refrigeration applications is presented. The review covers the effects of flow pattern and geometrical parameters of the tubes on the heat transfer performance. Attention is paid to the effect of surface tension which leads to enhanced evaporation and condensation in the microfin tubes and micro-channels. A review of prior efforts to develop empirical correlations of the heat transfer coefficient and theoretical models for evaporation and condensation in the horizontal microfin tubes and micro-channels is also presented.

[Measurement and estimation methods and research progress of snow evaporation in forests].

PubMed

Li, Hui-Dong; Guan, De-Xin; Jin, Chang-Jie; Wang, An-Zhi; Yuan, Feng-Hui; Wu, Jia-Bing

2013-12-01

Accurate measurement and estimation of snow evaporation (sublimation) in forests is one of the important issues to the understanding of snow surface energy and water balance, and it is also an essential part of regional hydrological and climate models. This paper summarized the measurement and estimation methods of snow evaporation in forests, and made a comprehensive applicability evaluation, including mass-balance methods (snow water equivalent method, comparative measurements of snowfall and through-snowfall, snow evaporation pan, lysimeter, weighing of cut tree, weighing interception on crown, and gamma-ray attenuation technique) and micrometeorological methods (Bowen-ratio energy-balance method, Penman combination equation, aerodynamics method, surface temperature technique and eddy covariance method). Also this paper reviewed the progress of snow evaporation in different forests and its influencal factors. At last, combining the deficiency of past research, an outlook for snow evaporation rearch in forests was presented, hoping to provide a reference for related research in the future.

Modeling solvent evaporation during thin film formation in phase separating polymer mixtures

DOE PAGES

Cummings, John; Lowengrub, John S.; Sumpter, Bobby G.; ...

2018-02-09

Preparation of thin films by dissolving polymers in a common solvent followed by evaporation of the solvent has become a routine processing procedure. However, modeling of thin film formation in an evaporating solvent has been challenging due to a need to simulate processes at multiple length and time scales. In this paper, we present a methodology based on the principles of linear non-equilibrium thermodynamics, which allows systematic study of various effects such as the changes in the solvent properties due to phase transformation from liquid to vapor and polymer thermodynamics resulting from such solvent transformations. The methodology allows for themore » derivation of evaporative flux and boundary conditions near each surface for simulations of systems close to the equilibrium. We apply it to study thin film microstructural evolution in phase segregating polymer blends dissolved in a common volatile solvent and deposited on a planar substrate. Finally, effects of the evaporation rates, interactions of the polymers with the underlying substrate and concentration dependent mobilities on the kinetics of thin film formation are studied.« less

Modeling solvent evaporation during thin film formation in phase separating polymer mixtures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cummings, John; Lowengrub, John S.; Sumpter, Bobby G.

Preparation of thin films by dissolving polymers in a common solvent followed by evaporation of the solvent has become a routine processing procedure. However, modeling of thin film formation in an evaporating solvent has been challenging due to a need to simulate processes at multiple length and time scales. In this paper, we present a methodology based on the principles of linear non-equilibrium thermodynamics, which allows systematic study of various effects such as the changes in the solvent properties due to phase transformation from liquid to vapor and polymer thermodynamics resulting from such solvent transformations. The methodology allows for themore » derivation of evaporative flux and boundary conditions near each surface for simulations of systems close to the equilibrium. We apply it to study thin film microstructural evolution in phase segregating polymer blends dissolved in a common volatile solvent and deposited on a planar substrate. Finally, effects of the evaporation rates, interactions of the polymers with the underlying substrate and concentration dependent mobilities on the kinetics of thin film formation are studied.« less

Analysis of a Free Surface Film from a Controlled Liquid Impinging Jet over a Rotating Disk Including Conjugate Effects, with and without Evaporation

NASA Technical Reports Server (NTRS)

Sankaran, Subramanian (Technical Monitor); Rice, Jeremy; Faghri, Amir; Cetegen, Baki M.

2005-01-01

A detailed analysis of the liquid film characteristics and the accompanying heat transfer of a free surface controlled liquid impinging jet onto a rotating disk are presented. The computations were run on a two-dimensional axi-symmetric Eulerian mesh while the free surface was calculated with the volume of fluid method. Flow rates between 3 and 15 1pm with rotational speeds between 50 and 200 rpm are analyzed. The effects of inlet temperature on the film thickness and heat transfer are characterized as well as evaporative effects. The conjugate heating effect is modeled, and was found to effect the heat transfer results the most at both the inner and outer edges of the heated surface. The heat transfer was enhanced with both increasing flow rate and increasing rotational speeds. When evaporative effects were modeled, the evaporation was found to increase the heat transfer at the lower flow rates the most because of a fully developed thermal field that was achieved. The evaporative effects did not significantly enhance the heat transfer at the higher flow rates.

Pressurization of a Flightweight, Liquid Hydrogen Tank: Evaporation and Condensation at a Liquid Vapor Interface

NASA Technical Reports Server (NTRS)

Stewart, Mark

2017-01-01

Evaporation and condensation at a liquid-vapor interface is important for long-term, in-space cryogenic propellant storage. Yet the current understanding of inter-facial physics does not consistently predict behavior of evaporation or condensation rates. The proposed paper will present a physical model, based on the 1-D Heat equation and Schrage's equation, which demonstrates thin thermal layers at the fluid vapor interface.

Carbon-Water-Energy Relations for Selected River Basins

NASA Technical Reports Server (NTRS)

Choudhury, B. J.

1998-01-01

A biophysical process-based model was run using satellite, assimilated and ancillary data for four years (1987-1990) to calculate components of total evaporation (transpiration, interception, soil and snow evaporation), net radiation, absorbed photosynthetically active radiation and net primary productivity over the global land surface. Satellite observations provided fractional vegetation cover, solar and photosynthetically active radiation incident of the surface, surface albedo, fractional cloud cover, air temperature and vapor pressure. The friction velocity and surface air pressure are obtained from a four dimensional data assimilation results, while precipitation is either only surface observations or a blended product of surface and satellite observations. All surface and satellite data are monthly mean values; precipitation has been disaggregated into daily values. All biophysical parameters of the model are prescribed according to published records. From these global land surface calculations results for river basins are derived using digital templates of basin boundaries. Comparisons with field observations (micrometeorologic, catchment water balance, biomass production) and atmospheric water budget analysis for monthly evaporation from six river basins have been done to assess errors in the calculations. Comparisons are also made with previous estimates of zonal variations of evaporation and net primary productivity. Efficiencies of transpiration, total evaporation and radiation use, and evaporative fraction for selected river basins will be presented.

Calculation of surface temperature and surface fluxes in the GLAS GOM

NASA Technical Reports Server (NTRS)

Sud, Y. C.; Abeles, J. A.

1981-01-01

Because the GLAS model's surface fluxes of sensible and latent heat exhibit strong 2 delta t oscillations at the individual grid points as well as in the zonal hemispheric averages and because a basic weakness of the GLAS model lower evaporation over oceans and higher evaporation over land in a typical monthly simulation, the GLAS model PBL parameterization was changed to calculate the mixed layer temperature gradient by solution of a quadratic equation for a stable PBL and by a curve fit relation for an unstable PBL. The new fluxes without any 2 delta t oscillation. Also, the geographical distributions of the surface fluxes are improved. The parameterization presented is incorporated into the new GLAS climate model. Some results which compare the evaporation over land and ocean between old and new calculations are appended.

On the theory relating changes in area-average and pan evaporation (Invited)

NASA Astrophysics Data System (ADS)

Shuttleworth, W.; Serrat-Capdevila, A.; Roderick, M. L.; Scott, R.

2009-12-01

Theory relating changes in area-average evaporation with changes in the evaporation from pans or open water is developed. Such changes can arise by Type (a) processes related to large-scale changes in atmospheric concentrations and circulation that modify surface evaporation rates in the same direction, and Type (b) processes related to coupling between the surface and atmospheric boundary layer (ABL) at the landscape scale that usually modify area-average evaporation and pan evaporation in different directions. The interrelationship between evaporation rates in response to Type (a) changes is derived. They have the same sign and broadly similar magnitude but the change in area-average evaporation is modified by surface resistance. As an alternative to assuming the complementary evaporation hypothesis, the results of previous modeling studies that investigated surface-atmosphere coupling are parameterized and used to develop a theoretical description of Type (b) coupling via vapor pressure deficit (VPD) in the ABL. The interrelationship between appropriately normalized pan and area-average evaporation rates is shown to vary with temperature and wind speed but, on average, the Type (b) changes are approximately equal and opposite. Long-term Australian pan evaporation data are analyzed to demonstrate the simultaneous presence of Type (a) and (b) processes, and observations from three field sites in southwestern USA show support for the theory describing Type (b) coupling via VPD. England's victory over Australia in 2009 Ashes cricket test match series will not be mentioned.

The Sites of Evaporation within Leaves.

PubMed

Buckley, Thomas N; John, Grace P; Scoffoni, Christine; Sack, Lawren

2017-03-01

The sites of evaporation within leaves are unknown, but they have drawn attention for decades due to their perceived implications for many factors, including patterns of leaf isotopic enrichment, the maintenance of mesophyll water status, stomatal regulation, and the interpretation of measured stomatal and leaf hydraulic conductances. We used a spatially explicit model of coupled water and heat transport outside the xylem, MOFLO 2.0, to map the distribution of net evaporation across leaf tissues in relation to anatomy and environmental parameters. Our results corroborate earlier predictions that most evaporation occurs from the epidermis at low light and moderate humidity but that the mesophyll contributes substantially when the leaf center is warmed by light absorption, and more so under high humidity. We also found that the bundle sheath provides a significant minority of evaporation (15% in darkness and 18% in high light), that the vertical center of amphistomatous leaves supports net condensation, and that vertical temperature gradients caused by light absorption vary over 10-fold across species, reaching 0.3°C. We show that several hypotheses that depend on the evaporating sites require revision in light of our findings, including that experimental measurements of stomatal and hydraulic conductances should be affected directly by changes in the location of the evaporating sites. We propose a new conceptual model that accounts for mixed-phase water transport outside the xylem. These conclusions have far-reaching implications for inferences in leaf hydraulics, gas exchange, water use, and isotope physiology. © 2017 American Society of Plant Biologists. All Rights Reserved.

Regulatory off-gas analysis from the evaporation of Hanford simulated waste spiked with organic compounds.

PubMed

Saito, Hiroshi H; Calloway, T Bond; Ferrara, Daro M; Choi, Alexander S; White, Thomas L; Gibson, Luther V; Burdette, Mark A

2004-10-01

After strontium/transuranics removal by precipitation followed by cesium/technetium removal by ion exchange, the remaining low-activity waste in the Hanford River Protection Project Waste Treatment Plant is to be concentrated by evaporation before being mixed with glass formers and vitrified. To provide a technical basis to permit the waste treatment facility, a relatively organic-rich Hanford Tank 241-AN-107 waste simulant was spiked with 14 target volatile, semi-volatile, and pesticide compounds and evaporated under vacuum in a bench-scale natural circulation evaporator fitted with an industrial stack off-gas sampler at the Savannah River National Laboratory. An evaporator material balance for the target organics was calculated by combining liquid stream mass and analytical data with off-gas emissions estimates obtained using U.S. Environmental Protection Agency (EPA) SW-846 Methods. Volatile and light semi-volatile organic compounds (<220 degrees C BP, >1 mm Hg vapor pressure) in the waste simulant were found to largely exit through the condenser vent, while heavier semi-volatiles and pesticides generally remain in the evaporator concentrate. An OLI Environmental Simulation Program (licensed by OLI Systems, Inc.) evaporator model successfully predicted operating conditions and the experimental distribution of the fed target organics exiting in the concentrate, condensate, and off-gas streams, with the exception of a few semi-volatile and pesticide compounds. Comparison with Henry's Law predictions suggests the OLI Environmental Simulation Program model is constrained by available literature data.

The Sites of Evaporation within Leaves1[OPEN

PubMed Central

Sack, Lawren

2017-01-01

The sites of evaporation within leaves are unknown, but they have drawn attention for decades due to their perceived implications for many factors, including patterns of leaf isotopic enrichment, the maintenance of mesophyll water status, stomatal regulation, and the interpretation of measured stomatal and leaf hydraulic conductances. We used a spatially explicit model of coupled water and heat transport outside the xylem, MOFLO 2.0, to map the distribution of net evaporation across leaf tissues in relation to anatomy and environmental parameters. Our results corroborate earlier predictions that most evaporation occurs from the epidermis at low light and moderate humidity but that the mesophyll contributes substantially when the leaf center is warmed by light absorption, and more so under high humidity. We also found that the bundle sheath provides a significant minority of evaporation (15% in darkness and 18% in high light), that the vertical center of amphistomatous leaves supports net condensation, and that vertical temperature gradients caused by light absorption vary over 10-fold across species, reaching 0.3°C. We show that several hypotheses that depend on the evaporating sites require revision in light of our findings, including that experimental measurements of stomatal and hydraulic conductances should be affected directly by changes in the location of the evaporating sites. We propose a new conceptual model that accounts for mixed-phase water transport outside the xylem. These conclusions have far-reaching implications for inferences in leaf hydraulics, gas exchange, water use, and isotope physiology. PMID:28153921

Transcriptome sequencing reveals e-cigarette vapor and mainstream-smoke from tobacco cigarettes activate different gene expression profiles in human bronchial epithelial cells

PubMed Central

Shen, Yifei; Wolkowicz, Michael J.; Kotova, Tatyana; Fan, Lonjiang; Timko, Michael P.

2016-01-01

Electronic cigarettes (e-cigarettes) generate an aerosol vapor (e-vapor) thought to represent a less risky alternative to main stream smoke (MSS) of conventional tobacco cigarettes. RNA-seq analysis was used to examine the transcriptomes of differentiated human bronchial epithelial (HBE) cells exposed to air, MSS from 1R5F tobacco reference cigarettes, and e-vapor with and without added nicotine in an in vitro air-liquid interface model for cellular exposure. Our results indicate that while e-vapor does not elicit many of the cell toxicity responses observed in MSS-exposed HBE cells, e-vapor exposure is not benign, but elicits discrete transcriptomic signatures with and without added nicotine. Among the cellular pathways with the most significantly enriched gene expression following e-vapor exposure are the phospholipid and fatty acid triacylglycerol metabolism pathways. Our data suggest that alterations in cellular glycerophopholipid biosynthesis are an important consequences of e-vapor exposure. Moreover, the presence of nicotine in e-vapor elicits a cellular response distinct from e-vapor alone including alterations of cytochrome P450 function, retinoid metabolism, and nicotine catabolism. These studies establish a baseline for future analysis of e-vapor and e-vapor additives that will better inform the FDA and other governmental bodies in discussions of the risks and future regulation of these products. PMID:27041137

Water-evaporation reduction by duplex films: application to the human tear film.

PubMed

Cerretani, Colin F; Ho, Nghia H; Radke, C J

2013-09-01

Water-evaporation reduction by duplex-oil films is especially important to understand the physiology of the human tear film. Secreted lipids, called meibum, form a duplex film that coats the aqueous tear film and purportedly reduces tear evaporation. Lipid-layer deficiency is correlated with the occurrence of dry-eye disease; however, in-vitro experiments fail to show water-evaporation reduction by tear-lipid duplex films. We review the available literature on water-evaporation reduction by duplex-oil films and outline the theoretical underpinnings of spreading and evaporation kinetics that govern behavior of these systems. A dissolution-diffusion model unifies the data reported in the literature and identifies dewetting of duplex films into lenses as a key challenge to obtaining significant evaporation reduction. We develop an improved apparatus for measuring evaporation reduction by duplex-oil films including simultaneous assessment of film coverage, stability, and temperature, all under controlled external mass transfer. New data reported in this study fit into the larger body of work conducted on water-evaporation reduction by duplex-oil films. Duplex-oil films of oxidized mineral oil/mucin (MOx/BSM), human meibum (HM), and bovine meibum (BM) reduce water evaporation by a dissolution-diffusion mechanism, as confirmed by agreement between measurement and theory. The water permeability of oxidized-mineral-oil duplex films agrees with those reported in the literature, after correction for the presence of mucin. We find that duplex-oil films of bovine and human meibum at physiologic temperature reduce water evaporation only 6-8% for a 100-nm film thickness pertinent to the human tear film. Comparison to in-vivo human tear-evaporation measurements is inconclusive because evaporation from a clean-water surface is not measured and because the mass-transfer resistance is not characterized. Copyright © 2013 Elsevier B.V. All rights reserved.

Reconstructing Heat Fluxes Over Lake Erie During the Lake Effect Snow Event of November 2014

NASA Astrophysics Data System (ADS)

Fitzpatrick, L.; Fujisaki-Manome, A.; Gronewold, A.; Anderson, E. J.; Spence, C.; Chen, J.; Shao, C.; Posselt, D. J.; Wright, D. M.; Lofgren, B. M.; Schwab, D. J.

2017-12-01

The extreme North American winter storm of November 2014 triggered a record lake effect snowfall (LES) event in southwest New York. This study examined the evaporation from Lake Erie during the record lake effect snowfall event, November 17th-20th, 2014, by reconstructing heat fluxes and evaporation rates over Lake Erie using the unstructured grid, Finite-Volume Community Ocean Model (FVCOM). Nine different model runs were conducted using combinations of three different flux algorithms: the Met Flux Algorithm (COARE), a method routinely used at NOAA's Great Lakes Environmental Research Laboratory (SOLAR), and the Los Alamos Sea Ice Model (CICE); and three different meteorological forcings: the Climate Forecast System version 2 Operational Analysis (CFSv2), Interpolated observations (Interp), and the High Resolution Rapid Refresh (HRRR). A few non-FVCOM model outputs were also included in the evaporation analysis from an atmospheric reanalysis (CFSv2) and the large lake thermodynamic model (LLTM). Model-simulated water temperature and meteorological forcing data (wind direction and air temperature) were validated with buoy data at three locations in Lake Erie. The simulated sensible and latent heat fluxes were validated with the eddy covariance measurements at two offshore sites; Long Point Lighthouse in north central Lake Erie and Toledo water crib intake in western Lake Erie. The evaluation showed a significant increase in heat fluxes over three days, with the peak on the 18th of November. Snow water equivalent data from the National Snow Analyses at the National Operational Hydrologic Remote Sensing Center showed a spike in water content on the 20th of November, two days after the peak heat fluxes. The ensemble runs presented a variation in spatial pattern of evaporation, lake-wide average evaporation, and resulting cooling of the lake. Overall, the evaporation tended to be larger in deep water than shallow water near the shore. The lake-wide average evaporations from CFSv2 and LLTM are significantly smaller than those from FVCOM. The variation among the nine FVCOM runs resulted in the 3D mean water temperature cooling in a range from 3 degrees C to 5 degrees C (6-10 EJ loss in heat content), implication for impacts on preconditioning for the upcoming ice season.

Self-wrapping of an ouzo drop induced by evaporation on a superamphiphobic surface.

PubMed

Tan, Huanshu; Diddens, Christian; Versluis, Michel; Butt, Hans-Jürgen; Lohse, Detlef; Zhang, Xuehua

2017-04-12

Evaporation of multi-component drops is crucial to various technologies and has numerous potential applications because of its ubiquity in nature. Superamphiphobic surfaces, which are both superhydrophobic and superoleophobic, can give a low wettability not only for water drops but also for oil drops. In this paper, we experimentally, numerically and theoretically investigate the evaporation process of millimetric sessile ouzo drops (a transparent mixture of water, ethanol, and trans-anethole) with low wettability on a superamphiphobic surface. The evaporation-triggered ouzo effect, i.e. the spontaneous emulsification of oil microdroplets below a specific ethanol concentration, preferentially occurs at the apex of the drop due to the evaporation flux distribution and volatility difference between water and ethanol. This observation is also reproduced by numerical simulations. The volume decrease of the ouzo drop is characterized by two distinct slopes. The initial steep slope is dominantly caused by the evaporation of ethanol, followed by the slower evaporation of water. At later stages, thanks to Marangoni forces the oil wraps around the drop and an oil shell forms. We propose an approximate diffusion model for the drying characteristics, which predicts the evaporation of the drops in agreement with experiment and numerical simulation results. This work provides an advanced understanding of the evaporation process of ouzo (multi-component) drops.

Nonanalytic microscopic phase transitions and temperature oscillations in the microcanonical ensemble: An exactly solvable one-dimensional model for evaporation

NASA Astrophysics Data System (ADS)

Hilbert, Stefan; Dunkel, Jörn

2006-07-01

We calculate exactly both the microcanonical and canonical thermodynamic functions (TDFs) for a one-dimensional model system with piecewise constant Lennard-Jones type pair interactions. In the case of an isolated N -particle system, the microcanonical TDFs exhibit (N-1) singular (nonanalytic) microscopic phase transitions of the formal order N/2 , separating N energetically different evaporation (dissociation) states. In a suitably designed evaporation experiment, these types of phase transitions should manifest themselves in the form of pressure and temperature oscillations, indicating cooling by evaporation. In the presence of a heat bath (thermostat), such oscillations are absent, but the canonical heat capacity shows a characteristic peak, indicating the temperature-induced dissociation of the one-dimensional chain. The distribution of complex zeros of the canonical partition may be used to identify different degrees of dissociation in the canonical ensemble.

Development of water movement model as a module of moisture content simulation in static pile composting.

PubMed

Seng, Bunrith; Kaneko, Hidehiro; Hirayama, Kimiaki; Katayama-Hirayama, Keiko

2012-01-01

This paper presents a mathematical model of vertical water movement and a performance evaluation of the model in static pile composting operated with neither air supply nor turning. The vertical moisture content (MC) model was developed with consideration of evaporation (internal and external evaporation), diffusion (liquid and vapour diffusion) and percolation, whereas additional water from substrate decomposition and irrigation was not taken into account. The evaporation term in the model was established on the basis of reference evaporation of the materials at known temperature, MC and relative humidity of the air. Diffusion of water vapour was estimated as functions of relative humidity and temperature, whereas diffusion of liquid water was empirically obtained from experiment by adopting Fick's law. Percolation was estimated by following Darcy's law. The model was applied to a column of composting wood chips with an initial MC of 60%. The simulation program was run for four weeks with calculation span of 1 s. The simulated results were in reasonably good agreement with the experimental results. Only a top layer (less than 20 cm) had a considerable MC reduction; the deeper layers were comparable to the initial MC, and the bottom layer was higher than the initial MC. This model is a useful tool to estimate the MC profile throughout the composting period, and could be incorporated into biodegradation kinetic simulation of composting.

Modelling rainfall interception by a lowland tropical rain forest in northeastern Puerto Rico

NASA Astrophysics Data System (ADS)

Schellekens, J.; Scatena, F. N.; Bruijnzeel, L. A.; Wickel, A. J.

1999-12-01

Recent surveys of tropical forest water use suggest that rainfall interception by the canopy is largest in wet maritime locations. To investigate the underlying processes at one such location—the Luquillo Experimental Forest in eastern Puerto Rico—66 days of detailed throughfall and above-canopy climatic data were collected in 1996 and analysed using the Rutter and Gash models of rainfall interception. Throughfall occurred on 80% of the days distributed over 80 rainfall events. Measured interception loss was 50% of gross precipitation. When Penman-Monteith based estimates for the wet canopy evaporation rate (0.11 mm h -1 on average) and a canopy storage of 1.15 mm were used, both models severely underestimated measured interception loss. A detailed analysis of four storms using the Rutter model showed that optimizing the model for the wet canopy evaporation component yielded much better results than increasing the canopy storage capacity. However, the Rutter model failed to properly estimate throughfall amounts during an exceptionally large event. The analytical model, on the other hand, was capable of representing interception during the extreme event, but once again optimizing wet canopy evaporation rates produced a much better fit than optimizing the canopy storage capacity. As such, the present results support the idea that it is primarily a high rate of evaporation from a wet canopy that is responsible for the observed high interception losses.

Evaluating soil moisture constraints on surface fluxes in land surface models globally

NASA Astrophysics Data System (ADS)

Harris, Phil; Gallego-Elvira, Belen; Taylor, Christopher; Folwell, Sonja; Ghent, Darren; Veal, Karen; Hagemann, Stefan

2016-04-01

Soil moisture availability exerts a strong control over land evaporation in many regions. However, global climate models (GCMs) disagree on when and where evaporation is limited by soil moisture. Evaluation of the relevant modelled processes has suffered from a lack of reliable, global observations of land evaporation at the GCM grid box scale. Satellite observations of land surface temperature (LST) offer spatially extensive but indirect information about the surface energy partition and, under certain conditions, about soil moisture availability on evaporation. Specifically, as soil moisture decreases during rain-free dry spells, evaporation may become limited leading to increases in LST and sensible heat flux. We use MODIS Terra and Aqua observations of LST at 1 km from 2000 to 2012 to assess changes in the surface energy partition during dry spells lasting 10 days or longer. The clear-sky LST data are aggregated to a global 0.5° grid before being composited as a function dry spell day across many events in a particular region and season. These composites are then used to calculate a Relative Warming Rate (RWR) between the land surface and near-surface air. This RWR can diagnose the typical strength of short term changes in surface heat fluxes and, by extension, changes in soil moisture limitation on evaporation. Offline land surface model (LSM) simulations offer a relatively inexpensive way to evaluate the surface processes of GCMs. They have the benefits that multiple models, and versions of models, can be compared on a common grid and using unbiased forcing. Here, we use the RWR diagnostic to assess global, offline simulations of several LSMs (e.g., JULES and JSBACH) driven by the WATCH Forcing Data-ERA Interim. Both the observed RWR and the LSMs use the same 0.5° grid, which allows the observed clear-sky sampling inherent in the underlying MODIS LST to be applied to the model outputs directly. This approach avoids some of the difficulties in analysing free-running simulations in which land and atmosphere are coupled and, as such, it provides a flexible intermediate step in the assessment of surface processes in GCMs.

Multi-layer solid-phase extraction and evaporation-enrichment methods for polar organic chemicals from aqueous matrices.

PubMed

Köke, Niklas; Zahn, Daniel; Knepper, Thomas P; Frömel, Tobias

2018-03-01

Analysis of polar organic chemicals in the aquatic environment is exacerbated by the lack of suitable and widely applicable enrichment methods. In this work, we assessed the suitability of a novel combination of well-known solid-phase extraction (SPE) materials in one cartridge as well as an evaporation method and for the enrichment of 26 polar model substances (predominantly log D < 0) covering a broad range of physico-chemical properties in three different aqueous matrices. The multi-layer solid-phase extraction (mlSPE) and evaporation method were investigated for the recovery and matrix effects of the model substances and analyzed with hydrophilic interaction liquid chromatography-tandem mass spectrometry (HILIC-MS/MS). In total, 65% of the model substances were amenable (> 10% recovery) to the mlSPE method with a mean recovery of 76% while 73% of the model substances were enriched with the evaporation method achieving a mean recovery of 78%. Target and non-target screening comparison of both methods with a frequently used reversed-phase SPE method utilizing "hydrophilic and lipophilic balanced" (HLB) material was performed. Target analysis showed that the mlSPE and evaporation method have pronounced advantages over the HLB method since the HLB material retained only 30% of the model substances. Non-target screening of a ground water sample with the investigated enrichment methods showed that the median retention time of all detected features on a HILIC system decreased in the order mlSPE (3641 features, median t R 9.7 min), evaporation (1391, 9.3 min), HLB (4414, 7.2 min), indicating a higher potential of the described methods to enrich polar analytes from water compared with HLB-SPE. Graphical abstract Schematic of the method evaluation (recovery and matrix effects) and method comparison (target and non-target analysis) of the two investigated enrichment methods for very polar chemicals in aqueousmatrices.

The Evaporative Function of Cockroach Hygroreceptors

PubMed Central

Tichy, Harald; Kallina, Wolfgang

2013-01-01

Insect hygroreceptors associate as antagonistic pairs of a moist cell and a dry cell together with a cold cell in small cuticular sensilla on the antennae. The mechanisms by which the atmospheric humidity stimulates the hygroreceptive cells remain elusive. Three models for humidity transduction have been proposed in which hygroreceptors operate either as mechanical hygrometers, evaporation detectors or psychrometers. Mechanical hygrometers are assumed to respond to the relative humidity, evaporation detectors to the saturation deficit and psychrometers to the temperature depression (the difference between wet-bulb and dry-bulb temperatures). The models refer to different ways of expressing humidity. This also means, however, that at different temperatures these different types of hygroreceptors indicate very different humidity conditions. The present study tested the adequacy of the three models on the cockroach’s moist and dry cells by determining whether the specific predictions about the temperature-dependence of the humidity responses are indeed observed. While in previous studies stimulation consisted of rapid step-like humidity changes, here we changed humidity slowly and continuously up and down in a sinusoidal fashion. The low rates of change made it possible to measure instantaneous humidity values based on UV-absorption and to assign these values to the hygroreceptive sensillum. The moist cell fitted neither the mechanical hygrometer nor the evaporation detector model: the temperature dependence of its humidity responses could not be attributed to relative humidity or to saturation deficit, respectively. The psychrometer model, however, was verified by the close relationships of the moist cell’s response with the wet-bulb temperature and the dry cell’s response with the dry-bulb temperature. Thus, the hygroreceptors respond to evaporation and the resulting cooling due to the wetness or dryness of the air. The drier the ambient air (absolutely) and the higher the temperature, the greater the evaporative temperature depression and the power to desiccate. PMID:23342058

The evaporative function of cockroach hygroreceptors.

PubMed

Tichy, Harald; Kallina, Wolfgang

2013-01-01

Insect hygroreceptors associate as antagonistic pairs of a moist cell and a dry cell together with a cold cell in small cuticular sensilla on the antennae. The mechanisms by which the atmospheric humidity stimulates the hygroreceptive cells remain elusive. Three models for humidity transduction have been proposed in which hygroreceptors operate either as mechanical hygrometers, evaporation detectors or psychrometers. Mechanical hygrometers are assumed to respond to the relative humidity, evaporation detectors to the saturation deficit and psychrometers to the temperature depression (the difference between wet-bulb and dry-bulb temperatures). The models refer to different ways of expressing humidity. This also means, however, that at different temperatures these different types of hygroreceptors indicate very different humidity conditions. The present study tested the adequacy of the three models on the cockroach's moist and dry cells by determining whether the specific predictions about the temperature-dependence of the humidity responses are indeed observed. While in previous studies stimulation consisted of rapid step-like humidity changes, here we changed humidity slowly and continuously up and down in a sinusoidal fashion. The low rates of change made it possible to measure instantaneous humidity values based on UV-absorption and to assign these values to the hygroreceptive sensillum. The moist cell fitted neither the mechanical hygrometer nor the evaporation detector model: the temperature dependence of its humidity responses could not be attributed to relative humidity or to saturation deficit, respectively. The psychrometer model, however, was verified by the close relationships of the moist cell's response with the wet-bulb temperature and the dry cell's response with the dry-bulb temperature. Thus, the hygroreceptors respond to evaporation and the resulting cooling due to the wetness or dryness of the air. The drier the ambient air (absolutely) and the higher the temperature, the greater the evaporative temperature depression and the power to desiccate.

Modelling of evaporation of a dispersed liquid component in a chemically active gas flow

NASA Astrophysics Data System (ADS)

Kryukov, V. G.; Naumov, V. I.; Kotov, V. Yu.

1994-01-01

A model has been developed to investigate evaporation of dispersed liquids in chemically active gas flow. Major efforts have been directed at the development of algorithms for implementing this model. The numerical experiments demonstrate that, in the boundary layer, significant changes in the composition and temperature of combustion products take place. This gives the opportunity to more correctly model energy release processes in combustion chambers of liquid-propellant rocket engines, gas-turbine engines, and other power devices.

Analysis of models for two solution crystal growth problems

NASA Technical Reports Server (NTRS)

Fehribach, Joseph D.; Rosenberger, Franz

1989-01-01

Two diffusive solution crystal growth models are considered which are characterized by two phases separated by an interface, a lack of convective mixing in either phase, and the presence of diffusion components differing widely in diffusivity. The first model describes precipitant-driven solution crystal growth and the second model describes a hanging drop evaporation problem. It is shown that for certain proteins sharp concentration gradients may develop in the drop during evaporation, while under the same conditions the concentrations of other proteins remain uniform.

40 CFR 86.1811-09 - Emission standards for light-duty vehicles, light-duty trucks and medium-duty passenger vehicles.

Code of Federal Regulations, 2012 CFR

2012-07-01

... standards for all LDVs, LDTs and MDPVs. This section applies to 2009 and later model year LDVs, LDTs and... the 2012 model year, the Tier 2 LDV/LLDT evaporative emissions standards in Table S04-3 of § 86.1811.../LLDT standards in Table S09-1 in the 2011 model year must meet the Tier 2 LDV/LLDT evaporative emission...

Tracing Water Sources and Quantifying Evaporation in the Brazos River, Central Texas

NASA Astrophysics Data System (ADS)

VanPlantinga, A.; Hunt, L. E.; Winning, D.; Robertson, J.; Stockert, E.; Roark, E.; Grossman, E. L.

2013-12-01

Situated in the subtropical dry zone, Central Texas is sensitive to the effects of climate change, notably drought; furthermore, developments over the last century in agriculture, urban infrastructure, and river engineering have altered the landscape extensively. This study models water source mixing and seasonal variation in evaporation in Brazos River waters in Central Texas. The Brazos River from Waco to College Station, Texas is generally characterized as having dissolved salt load derived mostly from Lake Whitney (a flood-control and hydroelectric storage reservoir) and groundwater baseflow from the adjacent shallow alluvial aquifer. Brazos River water δ18O, δD, and conductivity were measured bi-weekly in Brazos County, Texas from January 2012 through August 2013. Conductivity, δ18O, and δD vary seasonally and are positively correlated. The Brazos River δ18O-δD data from Brazos County fall along a local evaporation line (δD = 5.66 * δ18O - 2.47, r2 = 0.95) that intersects and surpasses values for Lake Whitney. In contrast, the δ18O-conductivity trend for the Brazos River does not intersect data for Lake Whitney. These observations suggest mixing with an evaporated water source of lower conductivity. The relative contribution of other Brazos River water sources is uncertain. Percent evaporation of original rain sampled as Brazos River water was estimated using a Rayleigh distillation model and the method of Gonfiantini (1986) while assuming 1) a closed system with an atmospheric exchange component, and 2) δ18O and δD values of local rain are -5.33‰ and -32.6‰, respectively. Modeled percent evaporation of original rain varies from winter (JFM; 1%-20%) to spring (AMJ; 9-25%) to summer (JAS; 16-33%), to fall (OND; 15-24%). Rayleigh distillation modeling estimates are consistently higher (~5%) than those estimated by Gonfiantini's method. A simple mass-balance model predicts that Brazos River water percent evaporation and δ18O enrichment are 2.8% and 0.40‰ respectively for low flow in Brazos County (200 cubic feet per second or cfs) and 0.9% and 0.12‰ respectively for high flow (1000 cfs). This implies that a small percentage of evaporation of original rain in the Brazos River could be attributed to the alluvial aquifer. Thus, we believe that the alluvial aquifer is not dominating the Brazos River water supply as much as previously thought, even in times of low flow. Other surface waters more evaporatively enriched in 18O, specifically those derived from the network of local reservoirs and tributaries, likely influence the Brazos River more than previously thought.

An analytic solution of the stochastic storage problem applicable to soil water

USGS Publications Warehouse

Milly, P.C.D.

1993-01-01

The accumulation of soil water during rainfall events and the subsequent depletion of soil water by evaporation between storms can be described, to first order, by simple accounting models. When the alternating supplies (precipitation) and demands (potential evaporation) are viewed as random variables, it follows that soil-water storage, evaporation, and runoff are also random variables. If the forcing (supply and demand) processes are stationary for a sufficiently long period of time, an asymptotic regime should eventually be reached where the probability distribution functions of storage, evaporation, and runoff are stationary and uniquely determined by the distribution functions of the forcing. Under the assumptions that the potential evaporation rate is constant, storm arrivals are Poisson-distributed, rainfall is instantaneous, and storm depth follows an exponential distribution, it is possible to derive the asymptotic distributions of storage, evaporation, and runoff analytically for a simple balance model. A particular result is that the fraction of rainfall converted to runoff is given by (1 - R−1)/(eα(1−R−1) − R−1), in which R is the ratio of mean potential evaporation to mean rainfall and a is the ratio of soil water-holding capacity to mean storm depth. The problem considered here is analogous to the well-known problem of storage in a reservoir behind a dam, for which the present work offers a new solution for reservoirs of finite capacity. A simple application of the results of this analysis suggests that random, intraseasonal fluctuations of precipitation cannot by themselves explain the observed dependence of the annual water balance on annual totals of precipitation and potential evaporation.

Pinning of the Contact Line during Evaporation on Heterogeneous Surfaces: Slowdown or Temporary Immobilization? Insights from a Nanoscale Study.

PubMed

Zhang, Jianguo; Müller-Plathe, Florian; Leroy, Frédéric

2015-07-14

The question of the effect of surface heterogeneities on the evaporation of liquid droplets from solid surfaces is addressed through nonequilibrium molecular dynamics simulations. The mechanism behind contact line pinning which is still unclear is discussed in detail on the nanoscale. Model systems with the Lennard-Jones interaction potential were employed to study the evaporation of nanometer-sized cylindrical droplets from a flat surface. The heterogeneity of the surface was modeled through alternating stripes of equal width but two chemical types. The first type leads to a contact angle of 67°, and the other leads to a contact angle of 115°. The stripe width was varied between 2 and 20 liquid-particle diameters. On the surface with the narrowest stripes, evaporation occurred at constant contact angle as if the surface was homogeneous, with a value of the contact angle as predicted by the regular Cassie-Baxter equation. When the width was increased, the contact angle oscillated during evaporation between two boundaries whose values depend on the stripe width. The evaporation behavior was thus found to be a direct signature of the typical size of the surface heterogeneity domains. The contact angle both at equilibrium and during evaporation could be predicted from a local Cassie-Baxter equation in which the surface composition within a distance of seven fluid-particle diameters around the contact line was considered, confirming the local nature of the interactions that drive the wetting behavior of droplets. More importantly, we propose a nanoscale explanation of pinning during evaporation. Pinning should be interpreted as a drastic slowdown of the contact line dynamics rather than a complete immobilization of it during a transition between two contact angle boundaries.

Evaporation kinetics of sessile water droplets on micropillared superhydrophobic surfaces.

PubMed

Xu, Wei; Leeladhar, Rajesh; Kang, Yong Tae; Choi, Chang-Hwan

2013-05-21

Evaporation modes and kinetics of sessile droplets of water on micropillared superhydrophobic surfaces are experimentally investigated. The results show that a constant contact radius (CCR) mode and a constant contact angle (CCA) mode are two dominating evaporation modes during droplet evaporation on the superhydrophobic surfaces. With the decrease in the solid fraction of the superhydrophobic surfaces, the duration of a CCR mode is reduced and that of a CCA mode is increased. Compared to Rowan's kinetic model, which is based on the vapor diffusion across the droplet boundary, the change in a contact angle in a CCR (pinned) mode shows a remarkable deviation, decreasing at a slower rate on the superhydrophobic surfaces with less-solid fractions. In a CCA (receding) mode, the change in a contact radius agrees well with the theoretical expectation, and the receding speed is slower on the superhydrophobic surfaces with lower solid fractions. The discrepancy between experimental results and Rowan's model is attributed to the initial large contact angle of a droplet on superhydrophobic surfaces. The droplet geometry with a large contact angle results in a narrow wedge region of air along the contact boundary, where the liquid-vapor diffusion is significantly restricted. Such an effect becomes minor as the evaporation proceeds with the decrease in a contact angle. In both the CCR and CCA modes, the evaporative mass transfer shows the linear relationship between mass(2/3) and evaporation time. However, the evaporation rate is slower on the superhydrophobic surfaces, which is more significant on the surfaces with lower solid fractions. As a result, the superhydrophobic surfaces slow down the drying process of a sessile droplet on them.

Maximum Entropy Production Modeling of Evapotranspiration Partitioning on Heterogeneous Terrain and Canopy Cover: advantages and limitations.

NASA Astrophysics Data System (ADS)

Gutierrez-Jurado, H. A.; Guan, H.; Wang, J.; Wang, H.; Bras, R. L.; Simmons, C. T.

2015-12-01

Quantification of evapotranspiration (ET) and its partition over regions of heterogeneous topography and canopy poses a challenge using traditional approaches. In this study, we report the results of a novel field experiment design guided by the Maximum Entropy Production model of ET (MEP-ET), formulated for estimating evaporation and transpiration from homogeneous soil and canopy. A catchment with complex terrain and patchy vegetation in South Australia was instrumented to measure temperature, humidity and net radiation at soil and canopy surfaces. Performance of the MEP-ET model to quantify transpiration and soil evaporation was evaluated during wet and dry conditions with independently and directly measured transpiration from sapflow and soil evaporation using the Bowen Ratio Energy Balance (BREB). MEP-ET transpiration shows remarkable agreement with that obtained through sapflow measurements during wet conditions, but consistently overestimates the flux during dry periods. However, an additional term introduced to the original MEP-ET model accounting for higher stomatal regulation during dry spells, based on differences between leaf and air vapor pressure deficits and temperatures, significantly improves the model performance. On the other hand, MEP-ET soil evaporation is in good agreement with that from BREB regardless of moisture conditions. The experimental design allows a plot and tree scale quantification of evaporation and transpiration respectively. This study confirms for the first time that the MEP-ET originally developed for homogeneous open bare soil and closed canopy can be used for modeling ET over heterogeneous land surfaces. Furthermore, we show that with the addition of an empirical function simulating the plants ability to regulate transpiration, and based on the same measurements of temperature and humidity, the method can produce reliable estimates of ET during both wet and dry conditions without compromising its parsimony.

Target fragments in collisions of 1.8 GeV/nucleon Fe-56 nuclei with photoemulsion nuclei, and the cascade-evaporation model

NASA Technical Reports Server (NTRS)

Dudkin, V. E.; Kovalev, E. E.; Nefedov, N. A.; Antonchik, V. A.; Bogdanov, S. D.; Ostroumov, V. I.; Benton, E. V.; Crawford, H. J.

1995-01-01

Nuclear photographic emulsion is used to study the dependence of the characteristics of target-nucleus fragments on the masses and impact parameters of interacting nuclei. The data obtained are compared in all details with the calculation results made in terms of the Dubna version of the cascade-evaporation model (DCM).

A numerical model for the movement of H 2O, H 218O, and 2HHO in the unsaturated zone

NASA Astrophysics Data System (ADS)

Shurbaji, Abdel-Rahman M.; Phillips, Fred M.

1995-09-01

Vertical profiles of H 218O and 2HHO concentrations have yielded useful information on evaporation and infiltration processes in soils. However, in the field, quantitative interpretation of such profiles has been limited by the restrictions inherent in the quasi-steady-state and transient analytical models available to describe the physical processes. This study presents a flexible numerical model that simulates transient fluxes of heat, liquid water, water vapor, and isotopic species. The model can simulate both infiltration and evaporation under fluctuating meteorological conditions and thus should be useful in reproducing changes in field isotope profiles. A transition factor is introduced in the isotope transport equation. This factor combines hydrologic and isotopic parameters and changes slowly with depth in the soil profile but strongly in the evaporation zone, owing to the rapid change in the dominant phase of water from liquid to vapor. Using the transition factor in the isotope transport equation facilitates obtaining the typical shape of the isotope profile (bulge at the evaporation zone). This factor also facilitates producing broad isotope enrichment peaks that may be seen in very dry soils.

Does the Budyko curve reflect a maximum power state of hydrological systems? A backward analysis

NASA Astrophysics Data System (ADS)

Westhoff, Martijn; Zehe, Erwin; Archambeau, Pierre; Dewals, Benjamin

2016-04-01

Almost all catchments plot within a small envelope around the Budyko curve. This apparent behaviour suggests that organizing principles may play a role in the evolution of catchments. In this paper we applied the thermodynamic principle of maximum power as the organizing principle. In a top-down approach we derived mathematical formulations of the relation between relative wetness and gradients driving runoff and evaporation for a simple one-box model. We did this in an inverse manner such that when the conductances are optimized with the maximum power principle, the steady state behaviour of the model leads exactly to a point on the asymptotes of the Budyko curve. Subsequently, we added dynamics in forcing and actual evaporations, causing the Budyko curve to deviate from the asymptotes. Despite the simplicity of the model, catchment observations compare reasonably well with the Budyko curves subject to observed dynamics in rainfall and actual evaporation. Thus by constraining the - with the maximum power principle optimized - model with the asymptotes of the Budyko curve we were able to derive more realistic values of the aridity and evaporation index without any parameter calibration. Future work should focus on better representing the boundary conditions of real catchments and eventually adding more complexity to the model.

Does the Budyko curve reflect a maximum-power state of hydrological systems? A backward analysis

NASA Astrophysics Data System (ADS)

Westhoff, M.; Zehe, E.; Archambeau, P.; Dewals, B.

2016-01-01

Almost all catchments plot within a small envelope around the Budyko curve. This apparent behaviour suggests that organizing principles may play a role in the evolution of catchments. In this paper we applied the thermodynamic principle of maximum power as the organizing principle. In a top-down approach we derived mathematical formulations of the relation between relative wetness and gradients driving run-off and evaporation for a simple one-box model. We did this in an inverse manner such that, when the conductances are optimized with the maximum-power principle, the steady-state behaviour of the model leads exactly to a point on the asymptotes of the Budyko curve. Subsequently, we added dynamics in forcing and actual evaporation, causing the Budyko curve to deviate from the asymptotes. Despite the simplicity of the model, catchment observations compare reasonably well with the Budyko curves subject to observed dynamics in rainfall and actual evaporation. Thus by constraining the model that has been optimized with the maximum-power principle with the asymptotes of the Budyko curve, we were able to derive more realistic values of the aridity and evaporation index without any parameter calibration. Future work should focus on better representing the boundary conditions of real catchments and eventually adding more complexity to the model.

The Surface Energy Balance at Local and Regional Scales-A Comparison of General Circulation Model Results with Observations.

NASA Astrophysics Data System (ADS)

Garratt, J. R.; Krummel, P. B.; Kowalczyk, E. A.

1993-06-01

Aspects of the mean monthly energy balance at continental surfaces are examined by appeal to the results of general circulation model (GCM) simulations, climatological maps of surface fluxes, and direct observations. Emphasis is placed on net radiation and evaporation for (i) five continental regions (each approximately 20°×150°) within Africa, Australia, Eurasia, South America, and the United States; (ii) a number of continental sites in both hemispheres. Both the mean monthly values of the local and regional fluxes and the mean monthly diurnal cycles of the local fluxes are described. Mostly, GCMs tend to overestimate the mean monthly levels of net radiation by about 15% -20% on an annual basis, for observed annual values in the range 50 to 100 Wm2. This is probably the result of several deficiencies, including (i) continental surface albedos being undervalued in a number of the models, resulting in overestimates of the net shortwave flux at the surface (though this deficiency is steadily being addressed by modelers); (ii) incoming shortwave fluxes being overestimated due to uncertainties in cloud schemes and clear-sky absorption; (iii) land-surface temperatures being under-estimated resulting in an underestimate of the outgoing longwave flux. In contrast, and even allowing for the poor observational base for evaporation, there is no obvious overall bias in mean monthly levels of evaporation determined in GCMS, with one or two exceptions. Rather, and far more so than with net radiation, there is a wide range in values of evaporation for all regions investigated. For continental regions and at times of the year of low to moderate rainfall, there is a tendency for the simulated evaporation to be closely related to the precipitation-this is not surprising. In contrast, for regions where there is sufficient or excessive rainfall, the evaporation tends to follow the behavior of the net radiation. Again, this is not surprising given the close relation between potential evaporation and net radiation, as discussed by Priestley and Taylor. Finally, the introduction into GCMs of an `improved' surface scheme (incorporating more realistic representations of soil and canopy processes and revised albedos) does tend to improve the calculations of both regional net radiation and evaporation.

Evaporation variability of Nam Co Lake in the Tibetan Plateau and its role in recent rapid lake expansion

NASA Astrophysics Data System (ADS)

Ma, Ning; Szilagyi, Jozsef; Niu, Guo-Yue; Zhang, Yinsheng; Zhang, Teng; Wang, Binbin; Wu, Yanhong

2016-06-01

Previous studies have shown that the majority of the lakes in the Tibetan Plateau (TP) started to expand rapidly since the late 1990s. However, the causes are still not well known. For Nam Co, being a closed lake with no outflow, evaporation (EL) over the lake surface is the only way water may leave the lake. Therefore, quantifying EL is key for investigating the mechanism of lake expansion in the TP. EL can be quantified by Penman- and/or bulk-transfer-type models, requiring only net radiation, temperature, humidity and wind speed for inputs. However, interpolation of wind speed data may be laden with great uncertainty due to extremely sparse ground meteorological observations, the highly heterogeneous landscape and lake-land breeze effects. Here, evaporation of Nam Co Lake was investigated within the 1979-2012 period at a monthly time-scale using the complementary relationship lake evaporation (CRLE) model which does not require wind speed data. Validations by in-situ observations of E601B pan evaporation rates at the shore of Nam Co Lake as well as measured EL over an adjacent small lake using eddy covariance technique suggest that CRLE is capable of simulating EL well since it implicitly considers wind effects on evaporation via its vapor transfer coefficient. The multi-year average of annual evaporation of Nam Co Lake is 635 mm. From 1979 to 2012, annual evaporation of Nam Co Lake expressed a very slight decreasing trend. However, a more significant decrease in EL occurred during 1998-2008 at a rate of -12 mm yr-1. Based on water-level readings, this significant decrease in lake evaporation was found to be responsible for approximately 4% of the reported rapid water level increase and areal expansion of Nam Co Lake during the same period.

[Influence of below-cloud secondary evaporation on stable isotope composition in precipitation in Northwest China.

PubMed

Liu, Jie Yao; Zhang, Fu Ping; Feng, Qi; Li, Zong Xing; Zhu, Yi Wen; Nie, Shuo; Li, Ling

2018-05-01

The precipitation isotope data and meteorological data of eight stations provided by GNIP (Global Network for Isotopes in Precipitation) and two stations from the present study, combined with HYSPLIT model and water droplet evaporation model were used to examine the spatial and temporal distribution of precipitation δ 18 O and d values in Northwest China. The secondary evaporative effect of existence was evaluated and then quantitatively discussed, with the sensitive factors of secondary evaporative effect being considered. The results showed that during the summer monsoon, the δ 18 O and d values decreased from south to north in Xinjiang, while the δ 18 O value increased but d values decreased from south to north and from east to west of Shaanxi-Gansu-Ningxia region. During the winter monsoon, the δ 18 O value decreased from east to west in whole Northwest region, while the d value increased from south to north in Xinjiang, decreased from south to north and increased slightly from east to west in Shanxi-Gansu-Ningxia. The slope and intercept (6.80, -0.07) of the atmospheric precipitation line in the summer monsoon period was significantly lower than that of annual mean (7.27, 3.37) and winter monsoon period (7.46, 6.07), indicating that the secondary evaporation was stronger during the summer monsoon. The evaporation ratio in the summer monsoon was 4.49%, which was higher than 3.65% in the winter monsoon. However, the evaporation ratio of the winter monsoon was higher than the summer monsoon around of Loess Plateau, which might closely relate to the increasing drought of the Loess Plateau in recent years. Finally, the intensity of secondary evaporation decreased with increasing relative humidity, precipitation and vapor pressure but increased with increasing temperature (greater than 0 ℃). The influences of those factors (humidity, precipitation, temperature and vapor pressure) on the secondary evaporation were dependent on the differences of ranges.

Ionic solubility and solutal advection governed augmented evaporation kinetics of salt solution pendant droplets

NASA Astrophysics Data System (ADS)

Jaiswal, Vivek; Harikrishnan, A. R.; Khurana, Gargi; Dhar, Purbarun

2018-01-01

The presence of dispersed inclusions is known to modify the interfacial characteristics in liquids by adsorption-desorption of the ions at interfaces. The present article reports the influencing role of dissolved ions in a polar fluid on its evaporation dynamics. The evaporation dynamics of pendant droplets of aqueous solutions of variant simple salts and concentrations have been experimentally studied. The presence of salts is observed to enhance the evaporation rate (obeying the classical D2 law), and the enhancement has been found to hold a direct proportionality to the concentration of the dissolved salt. Furthermore, it is observed that the degree of enhancement in the evaporation rate is also directly proportional to the solubility of the salt in question. The phenomenon is explained based on the chemical kinetics and thermodynamics of hydration of the ionic species in the polar fluid. The classical evaporation rate constant formulation is found to be inadequate in modeling the enhanced species transport. Additional probing via particle image velocimetry reveals augmented internal circulation within the evaporating salt based drops compared to pure water. Mapping the dynamic surface tension reveals that a salt concentration gradient is generated between the bulk and periphery of the droplet and it could be responsible for the internal advection cells visualized. A thermo-solutal Marangoni and Rayleigh convection based mathematical formulation has been put forward, and it is shown that the enhanced solute-thermal convection could play a major role in enhanced evaporation. The internal circulation mapped from experiments is found to be in good quantitative agreement with the model predictions. Scaling analysis further reveals that the stability of the solutal Marangoni convection surpasses the thermal counterpart with higher salt concentration and solubility. The present article sheds insight into the possible domineering role of conjugate thermohydraulic and mass transport phenomena on the evaporation kinetics aqueous droplets with ionic inclusions.

Estimation of refueling emissions based on theoretical model and effects of E10 fuel on refueling and evaporative emissions from gasoline cars.

PubMed

Yamada, Hiroyuki; Inomata, Satoshi; Tanimoto, Hiroshi; Hata, Hiroo; Tonokura, Kenichi

2018-05-01

The effects of Reid vapor pressure (RVP) on refueling emissions and the effects of ethanol 10% (E10) fuel on refueling and evaporative emissions were observed using six cars and seven fuels. The results indicated that refueling emissions can be reproduced by a simple theoretical model in which fuel vapor in the empty space in the tank is pushed out by the refueling process. In this model, the vapor pressures of fuels can be estimated by the Clausius-Clapeyron equation as a function of temperature. We also evaluated E10 fuel in terms of refueling and evaporative emissions, excluding the effect of contamination of ethanol in the canister. E10 fuel had no effect on the refueling emissions in cases without onboard refueling vapor recovery. E10 showed increased permeation emissions in evaporative emissions because of the high permeability of ethanol. And with E10 fuel, breakthrough emissions appeared earlier but broke through slower than normal fuel. Finally, canisters could store more fuel vapor with E10 fuel. Copyright © 2017 Elsevier B.V. All rights reserved.

Evaporation effects in a shock-driven multiphase instability with a spherical interface

NASA Astrophysics Data System (ADS)

Paudel, Manoj; Dahal, Jeevan; McFarland, Jacob

2017-11-01

This talk presents results from 3D numerical simulations of a shock driven instability of a gas-particle system with a spherical interface. Two cases, one with an evaporating particle cloud and another with a gas only approximation of this particle cloud, were run in the hydrodynamics code FLASH, developed at University of Chicago. It is shown that the gas only approximation, a classical Richtmyer Meshkov instability, cannot replicate effects from particles like, lag, clustering, and evaporation. Instead, both gas hydrodynamics and particle properties influence one another and are coupled. Results are presented to highlight the coupling of interface evolution and particle evaporation. Qualitative and quantitative differences in the RMI and SDMI are presented by studying the change in gas properties like density and vorticity within the interface. Similarly, the effect of gas hydrodynamics on particles distribution and evaporation is studied. Particle evaporation rates are compared with 1D models and show poor agreement. The variation in evaporation rates for similar sized particles and the role of gas hydrodynamics in these variation is explored.

Droplet evaporation on a horizontal substrate under gravity field by mesoscopic modeling.

PubMed

Xie, Chiyu; Zhang, Jianying; Bertola, Volfango; Wang, Moran

2016-02-01

The evaporation of water drop deposited on a horizontal substrate is investigated using a lattice Boltzmann method (LBM) for multiphase flows with a large-density ratio. To account for the variation of evaporation flux distribution along the drop interface, a novel evaporation scheme is introduced into the LBM framework, and validated by comparison with experimental data. We aim at discovering the effect of gravity on the evaporating drop in detail, and various evaporation conditions are considered as well as different wetting properties of the substrates. An effective diameter is introduced as an indicator of the critical drop size under which gravity is negligible. Our results show that such critical diameter is much smaller than the capillary length, which has been widely accepted as the critical size in previous and current works. The critical diameter is found to be almost independent of the evaporation conditions and the surface wettability. A correlation between this critical diameter and the capillary length is also proposed for easy use in applications. Copyright © 2015 Elsevier Inc. All rights reserved.

Investigating evaporation of melting ice particles within a bin melting layer model

NASA Astrophysics Data System (ADS)

Neumann, Andrea J.

Single column models have been used to help develop algorithms for remote sensing retrievals. Assumptions in the single-column models may affect the assumptions of the remote sensing retrievals. Studies of the melting layer that use single column models often assume environments that are near or at water saturation. This study investigates the effects of evaporation upon melting particles to determine whether the assumption of negligible mass loss still holds within subsaturated melting layers. A single column, melting layer model is modified to include the effects of sublimation and evaporation upon the particles. Other changes to the model include switching the order in which the model loops over particle sizes and model layers; including a particle sedimentation scheme; adding aggregation, accretion, and collision and coalescence processes; allowing environmental variables such as the water vapor diffusivity and the Schmidt number to vary with the changes in the environment; adding explicitly calculated particle temperature, changing the particle terminal velocity parameterization; and using a newly-derived effective density-dimensional relationship for use in particle mass calculations. Simulations of idealized melting layer environments show that significant mass loss due to evaporation during melting is possible within subsaturated environments. Short melting distances, accelerating particle fall speeds, and short melting times help constrain the amount of mass lost due to evaporation while melting is occurring, even in subsaturated profiles. Sublimation prior to melting can also be a significant source of mass loss. The trends shown on the particle scale also appear in the bulk distribution parameters such as rainfall rate and ice water content. Simulations incorporating observed melting layer environments show that significant mass loss due to evaporation during the melting process is possible under certain environmental conditions. A profile such as the first melting layer profile on 10 May 2011 from the Midlatitude Continental Convective Clouds Experiment (MC3E) that is neither too saturated nor too subsaturated is possible and shows considerable mass loss for all particle sizes. Most melting layer profiles sampled during MC3E were too saturated for more than a dozen or two of the smallest particle sizes to experience significant mass loss. The aggregation, accretion, and collision and coalescence processes also countered significant mass loss at the largest particles sizes because these particles are efficient at collecting smaller particles due to their relative large sweep-out area. From these results, it appears that the assumption of negligible mass loss due to evaporation while melting is occurring is not always valid. Studies that use large, low-density snowflakes and high RH environments can safely use the assumption of negligible mass loss. Studies that use small ice particles or low RH environments (RH less than about 80%) cannot use the assumption of negligible mass loss due to evaporation. Retrieval algorithms may be overestimating surface precipitation rates and intensities in subsaturated environments due to the assumptions of negligible mass loss while melting and near-saturated melting layer environments.

Estimating evaporation with thermal UAV data and two-source energy balance models

NASA Astrophysics Data System (ADS)

Hoffmann, H.; Nieto, H.; Jensen, R.; Guzinski, R.; Zarco-Tejada, P.; Friborg, T.

2016-02-01

Estimating evaporation is important when managing water resources and cultivating crops. Evaporation can be estimated using land surface heat flux models and remotely sensed land surface temperatures (LST), which have recently become obtainable in very high resolution using lightweight thermal cameras and Unmanned Aerial Vehicles (UAVs). In this study a thermal camera was mounted on a UAV and applied into the field of heat fluxes and hydrology by concatenating thermal images into mosaics of LST and using these as input for the two-source energy balance (TSEB) modelling scheme. Thermal images are obtained with a fixed-wing UAV overflying a barley field in western Denmark during the growing season of 2014 and a spatial resolution of 0.20 m is obtained in final LST mosaics. Two models are used: the original TSEB model (TSEB-PT) and a dual-temperature-difference (DTD) model. In contrast to the TSEB-PT model, the DTD model accounts for the bias that is likely present in remotely sensed LST. TSEB-PT and DTD have already been well tested, however only during sunny weather conditions and with satellite images serving as thermal input. The aim of this study is to assess whether a lightweight thermal camera mounted on a UAV is able to provide data of sufficient quality to constitute as model input and thus attain accurate and high spatial and temporal resolution surface energy heat fluxes, with special focus on latent heat flux (evaporation). Furthermore, this study evaluates the performance of the TSEB scheme during cloudy and overcast weather conditions, which is feasible due to the low data retrieval altitude (due to low UAV flying altitude) compared to satellite thermal data that are only available during clear-sky conditions. TSEB-PT and DTD fluxes are compared and validated against eddy covariance measurements and the comparison shows that both TSEB-PT and DTD simulations are in good agreement with eddy covariance measurements, with DTD obtaining the best results. The DTD model provides results comparable to studies estimating evaporation with similar experimental setups, but with LST retrieved from satellites instead of a UAV. Further, systematic irrigation patterns on the barley field provide confidence in the veracity of the spatially distributed evaporation revealed by model output maps. Lastly, this study outlines and discusses the thermal UAV image processing that results in mosaics suited for model input. This study shows that the UAV platform and the lightweight thermal camera provide high spatial and temporal resolution data valid for model input and for other potential applications requiring high-resolution and consistent LST.

Evaluation of a Consistent LES/PDF Method Using a Series of Experimental Spray Flames

NASA Astrophysics Data System (ADS)

Heye, Colin; Raman, Venkat

2012-11-01

A consistent method for the evolution of the joint-scalar probability density function (PDF) transport equation is proposed for application to large eddy simulation (LES) of turbulent reacting flows containing evaporating spray droplets. PDF transport equations provide the benefit of including the chemical source term in closed form, however, additional terms describing LES subfilter mixing must be modeled. The recent availability of detailed experimental measurements provide model validation data for a wide range of evaporation rates and combustion regimes, as is well-known to occur in spray flames. In this work, the experimental data will used to investigate the impact of droplet mass loading and evaporation rates on the subfilter scalar PDF shape in comparison with conventional flamelet models. In addition, existing model term closures in the PDF transport equations are evaluated with a focus on their validity in the presence of regime changes.

Evaporation Mechanism of Cu from Liquid Fe Containing C and S

NASA Astrophysics Data System (ADS)

Jung, Sung-Hoon; Kang, Youn-Bae

2016-08-01

A number of liquid-gas experiments were carried out in order to elucidate evaporation mechanism of Cu from liquid Fe containing C and S. Rate of Cu evaporation in liquid Fe droplets at 1873 K (1600 °C) was determined using electromagnetic levitation equipment. Evaporation rate of the Cu under various conditions (flow rate of gas mixtures, initial C, and S concentrations) was examined. It was found from a series of kinetic analyses of the experimental data that Cu evaporates in forms of Cu(g) and CuS(g). As was reported for the Sn evaporation from liquid iron (Jung et al. Met. Mater. Trans. 46B, 250-258, 2014), S plays two roles for the evaporation of Cu: accelerating the rate by forming CuS(g) and decelerating the rate by blocking evaporation sites. As a result of these combinatorial effects, the evaporation of Cu is decelerated at low S content, but is accelerated at high S content. Based on the elucidated mechanism, an evaporation model equation for Cu was developed in the present study, which takes into account (1) evaporation of Cu in the two forms (Cu(g) and CuS(g)), (2) surface blocking by S using ideal Langmuir adsorption, and (3) effect of C. The obtained rate constant of a reaction Cu i + S i = CuS i (g), k CuS R , is 1.37 × 10-9 m4 mol-1 s-1, and the residual rate constant, k CuS r , is 4.11 × 10-10 m4 mol-1 s-1 at 1873 K (1600 °C). Both of them were found to be one order lower than those for Sn evaporation.

Modifications in the land surface model ORCHIDEE and application in the Tarim basin

NASA Astrophysics Data System (ADS)

Zhou, Xudong; Polcher, Jan; Yang, Tao; Nguyen Quang, Trung; Hirabayashi, Yukiko

2017-04-01

Land surface modeling in regions mixing high mountains and arid deserts remains a great challenge due to the inadequate representations of physical processes in atmospheric forcings , runoff generation, evaporation and river routing. A few key improvements were analyzed within ORCHIDEE (Organising Carbon and Hydrology in Dynamic Ecosystems) to better understand these limitations as well as quantify their influence on the water cycle over Tarim basin (TRB). The TRB is a representative endorheic basin in center Asia, with glacier and snow melting, limited precipitation but strong evaporation, high spatial heterogeneity and intensive human interference, thus challenging any land surface model. National observations on daily precipitation from China Meteorological Administration (CMA) were used to correct precipitation inputs on the basis of WATCH forcing datasets. The independent glacier melting simulation by HYOGA2 was added to the forcing to overcome the lack of glacier module in ORCHIDEE. Improvements in the snow scheme provided more accurate simulations of the soil temperature which restrict the infiltration process when the soil is frozen. In addition, a novel routing scheme with finer spatial resolution from 50km to 1km was developed based on HydroSHED map. It improves the descriptions of catchments boundaries, the flow direction and the water residence time within sub-basins that make significant difference especially for the mountainous area and flat plains. Model results with these modifications were compared through various atmospheric and hydrological variables (i.e. evaporation, soil moisture, runoff and discharge). In conclusion, the correction by the precipitation observations and involvement of glacier melting simulations increase the water input to the basin by 37.2% and 8.4% respectively, which in turn increases evaporation, soil moisture and runoff to different extents. The new snow and soil freezing scheme advance in time the spring high-water in the hydrograph and induce a decreasing in the flow peaks during summer. The changes reduce the annual evaporation by 6.7%, with the ratio between evaporation and precipitation decreasing from 0.73 to 0.68. All the modifications improve the model performance in terms of the similarity between modeled discharge and the observations. However, large biases still exist which could be attributed to the human influence (i.e. irrigation or dams regulation which are not included in the current model) and other modules in ORCHIDEE. Further efforts should be made to optimize evaporation estimation as well as the relevant human processes.

The Space Shuttle Orbiter molecular environment induced by the supplemental flash evaporator system

NASA Technical Reports Server (NTRS)

Ehlers, H. K. F.

1985-01-01

The water vapor environment of the Space Shuttle Orbiter induced by the supplemental flash evaporator during the on-orbit flight phase has been analyzed based on Space II model predictions and orbital flight measurements. Model data of local density, column density, and return flux are presented. Results of return flux measurements with a mass spectrometer during STS-2 and of direct flux measurements during STS-4 are discussed and compared with model predictions.

Parametric study of thin film evaporation from nanoporous membranes

NASA Astrophysics Data System (ADS)

Wilke, Kyle L.; Barabadi, Banafsheh; Lu, Zhengmao; Zhang, TieJun; Wang, Evelyn N.

2017-10-01

The performance and lifetime of advanced electronics are often dictated by the ability to dissipate heat generated within the device. Thin film evaporation from nanoporous membranes is a promising thermal management approach, which reduces the thermal transport distance across the liquid film while also providing passive capillary pumping of liquid to the evaporating interface. In this work, we investigated the dependence of thin film evaporation from nanoporous membranes on a variety of geometric parameters. Anodic aluminum oxide membranes were used as experimental templates, where pore radii of 28-75 nm, porosities of 0.1-0.35, and meniscus locations down to 1 μm within the pore were tested. We demonstrated different heat transfer regimes and observed more than an order of magnitude increase in dissipated heat flux by operating in the pore-level evaporation regime. The pore diameter had little effect on pore-level evaporation performance due to the negligible conduction resistance from the pore wall to the evaporating interface. The dissipated heat flux scaled with porosity as the evaporative area increased. Furthermore, moving the meniscus as little as 1 μm into the pore decreased the dissipated heat flux by more than a factor of two due to the added resistance to vapor escaping the pore. The experimental results elucidate thin film evaporation from nanopores and confirm findings of recent modeling efforts. This work also provides guidance for the design of future thin film evaporation devices for advanced thermal management. Furthermore, evaporation from nanopores is relevant to water purification, chemical separations, microfluidics, and natural processes such as transpiration.

Lysozyme pattern formation in evaporating droplets

NASA Astrophysics Data System (ADS)

Gorr, Heather Meloy

Liquid droplets containing suspended particles deposited on a solid, flat surface generally form ring-like structures due to the redistribution of solute during evaporation (the "coffee ring effect"). The forms of the deposited patterns depend on complex interactions between solute(s), solvent, and substrate in a rapidly changing, far from equilibrium system. Solute self-organization during evaporation of colloidal sessile droplets has attracted the attention of researchers over the past few decades due to a variety of technological applications. Recently, pattern formation during evaporation of various biofluids has been studied due to potential applications in medical screening and diagnosis. Due to the complexity of 'real' biological fluids and other multicomponent systems, a comprehensive understanding of pattern formation during droplet evaporation of these fluids is lacking. In this PhD dissertation, the morphology of the patterns remaining after evaporation of droplets of a simplified model biological fluid (aqueous lysozyme solutions + NaCl) are examined by atomic force microscopy (AFM) and optical microscopy. Lysozyme is a globular protein found in high concentration, for example, in human tears and saliva. The drop diameters, D, studied range from the micro- to the macro- scale (1 microm -- 2 mm). In this work, the effect of evaporation conditions, solution chemistry, and heat transfer within the droplet on pattern formation is examined. In micro-scale deposits of aqueous lysozyme solutions (1 microm < D < 50 microm), the protein motion and the resulting dried residue morphology are highly influenced by the decreased evaporation time of the drop. The effect of electrolytes on pattern formation is also investigated by adding varying concentrations NaCl to the lysozyme solutions. Finally, a novel pattern recognition program is described and implemented which classifies deposit images by their solution chemistries. The results presented in this PhD dissertation provide insight into the evaporative behavior and pattern formation in droplets of simplified model biological fluids (aqueous lysozyme + NaCl). The patterns that form depend sensitively on the evaporation conditions, characteristic time and length scales, and the physiochemical properties of the solutions. The patterns are unique, dependent on solution chemistry, and may therefore act as a "fingerprint" in identifying fluid properties.

KEPLER PLANETS: A TALE OF EVAPORATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Owen, James E.; Wu, Yanqin, E-mail: jowen@cita.utoronto.ca, E-mail: wu@astro.utoronto.ca

2013-10-01

Inspired by the Kepler mission's planet discoveries, we consider the thermal contraction of planets close to their parent star, under the influence of evaporation. The mass-loss rates are based on hydrodynamic models of evaporation that include both X-ray and EUV irradiation. We find that only low mass planets with hydrogen envelopes are significantly affected by evaporation, with evaporation being able to remove massive hydrogen envelopes inward of ∼0.1 AU for Neptune-mass objects, while evaporation is negligible for Jupiter-mass objects. Moreover, most of the evaporation occurs in the first 100 Myr of stars' lives when they are more chromospherically active. Wemore » construct a theoretical population of planets with varying core masses, envelope masses, orbital separations, and stellar spectral types, and compare this population with the sizes and densities measured for low-mass planets, both in the Kepler mission and from radial velocity surveys. This exercise leads us to conclude that evaporation is the driving force of evolution for close-in Kepler planets. In fact, some 50% of the Kepler planet candidates may have been significantly eroded. Evaporation explains two striking correlations observed in these objects: a lack of large radius/low density planets close to the stars and a possible bimodal distribution in planet sizes with a deficit of planets around 2 R{sub ⊕}. Planets that have experienced high X-ray exposures are generally smaller than this size, and those with lower X-ray exposures are typically larger. A bimodal planet size distribution is naturally predicted by the evaporation model, where, depending on their X-ray exposure, close-in planets can either hold on to hydrogen envelopes ∼0.5%-1% in mass or be stripped entirely. To quantitatively reproduce the observed features, we argue that not only do low-mass Kepler planets need to be made of rocky cores surrounded with hydrogen envelopes, but few of them should have initial masses above 20 M{sub ⊕} and the majority of them should have core masses of a few Earth masses.« less

Mass accommodation of water: bridging the gap between molecular dynamics simulations and kinetic condensation models.

PubMed

Julin, Jan; Shiraiwa, Manabu; Miles, Rachael E H; Reid, Jonathan P; Pöschl, Ulrich; Riipinen, Ilona

2013-01-17

The condensational growth of submicrometer aerosol particles to climate relevant sizes is sensitive to their ability to accommodate vapor molecules, which is described by the mass accommodation coefficient. However, the underlying processes are not yet fully understood. We have simulated the mass accommodation and evaporation processes of water using molecular dynamics, and the results are compared to the condensation equations derived from the kinetic gas theory to shed light on the compatibility of the two. Molecular dynamics simulations were performed for a planar TIP4P-Ew water surface at four temperatures in the range 268-300 K as well as two droplets, with radii of 1.92 and 4.14 nm at T = 273.15 K. The evaporation flux from molecular dynamics was found to be in good qualitative agreement with that predicted by the simple kinetic condensation equations. Water droplet growth was also modeled with the kinetic multilayer model KM-GAP of Shiraiwa et al. [Atmos. Chem. Phys. 2012, 12, 2777]. It was found that, due to the fast transport across the interface, the growth of a pure water droplet is controlled by gas phase diffusion. These facts indicate that the simple kinetic treatment is sufficient in describing pure water condensation and evaporation. The droplet size was found to have minimal effect on the value of the mass accommodation coefficient. The mass accommodation coefficient was found to be unity (within 0.004) for all studied surfaces, which is in agreement with previous simulation work. Additionally, the simulated evaporation fluxes imply that the evaporation coefficient is also unity. Comparing the evaporation rates of the mass accommodation and evaporation simulations indicated that the high collision flux, corresponding to high supersaturation, present in typical molecular dynamics mass accommodation simulations can under certain conditions lead to an increase in the evaporation rate. Consequently, in such situations the mass accommodation coefficient can be overestimated, but in the present cases the corrected values were still close to unity with the lowest value at ≈0.99.

Mass Accommodation of Water: Bridging the Gap Between Molecular Dynamics Simulations and Kinetic Condensation Models

PubMed Central

2012-01-01

The condensational growth of submicrometer aerosol particles to climate relevant sizes is sensitive to their ability to accommodate vapor molecules, which is described by the mass accommodation coefficient. However, the underlying processes are not yet fully understood. We have simulated the mass accommodation and evaporation processes of water using molecular dynamics, and the results are compared to the condensation equations derived from the kinetic gas theory to shed light on the compatibility of the two. Molecular dynamics simulations were performed for a planar TIP4P-Ew water surface at four temperatures in the range 268–300 K as well as two droplets, with radii of 1.92 and 4.14 nm at T = 273.15 K. The evaporation flux from molecular dynamics was found to be in good qualitative agreement with that predicted by the simple kinetic condensation equations. Water droplet growth was also modeled with the kinetic multilayer model KM-GAP of Shiraiwa et al. [Atmos. Chem. Phys.2012, 117, 2777]. It was found that, due to the fast transport across the interface, the growth of a pure water droplet is controlled by gas phase diffusion. These facts indicate that the simple kinetic treatment is sufficient in describing pure water condensation and evaporation. The droplet size was found to have minimal effect on the value of the mass accommodation coefficient. The mass accommodation coefficient was found to be unity (within 0.004) for all studied surfaces, which is in agreement with previous simulation work. Additionally, the simulated evaporation fluxes imply that the evaporation coefficient is also unity. Comparing the evaporation rates of the mass accommodation and evaporation simulations indicated that the high collision flux, corresponding to high supersaturation, present in typical molecular dynamics mass accommodation simulations can under certain conditions lead to an increase in the evaporation rate. Consequently, in such situations the mass accommodation coefficient can be overestimated, but in the present cases the corrected values were still close to unity with the lowest value at ≈0.99. PMID:23253100

Experiments and Modeling of Evaporating/Condensing Menisci

NASA Technical Reports Server (NTRS)

Plawsky, Joel; Wayner, Peter C., Jr.

2013-01-01

Discuss the Constrained Vapor Bubble (CVB) experiment and how it aims to achieve a better understanding of the physics of evaporation and condensation and how they affect cooling processes in microgravity using a remotely controlled microscope and a small cooling device.

Isotope effects in the evaporation of water: a status report of the Craig-Gordon model.

PubMed

Horita, Juske; Rozanski, Kazimierz; Cohen, Shabtai

2008-03-01

The Craig-Gordon model (C-G model) [H. Craig, L.I. Gordon. Deuterium and oxygen 18 variations in the ocean and the marine atmosphere. In Stable Isotopes in Oceanographic Studies and Paleotemperatures, E. Tongiorgi (Ed.), pp. 9-130, Laboratorio di Geologia Nucleare, Pisa (1965).] has been synonymous with the isotope effects associated with the evaporation of water from surface waters, soils, and vegetations, which in turn constitutes a critical component of the global water cycle. On the occasion of the four decades of its successful applications to isotope geochemistry and hydrology, an attempt is made to: (a) examine its physical background within the framework of modern evaporation models, (b) evaluate our current knowledge of the environmental parameters of the C-G model, and (c) comment on a general strategy for the use of these parameters in field applications. Despite its simplistic representation of evaporation processes at the water-air interface, the C-G model appears to be adequate to provide the isotopic composition of the evaporation flux. This is largely due to its nature for representing isotopic compositions (a ratio of two fluxes of different isotopic water molecules) under the same environmental conditions. Among many environmental parameters that are included in the C-G model, accurate description and calculations are still problematic of the kinetic isotope effects that occur in a diffusion-dominated thin layer of air next to the water-air interface. In field applications, it is of importance to accurately evaluate several environmental parameters, particularly the relative humidity and isotopic compositions of the 'free-atmosphere', for a system under investigation over a given time-scale of interest (e.g., hourly to daily to seasonally). With a growing interest in the studies of water cycles of different spatial and temporal scales, including paleoclimate and water resource studies, the importance and utility of the C-G model is also likely to grow in the future.

Comment on self-consistent model of black hole formation and evaporation

NASA Astrophysics Data System (ADS)

Ho, Pei-Ming

2015-08-01

In an earlier work, Kawai et al. proposed a model of black-hole formation and evaporation, in which the geometry of a collapsing shell of null dust is studied, including consistently the back reaction of its Hawking radiation. In this note, we illuminate the implications of their work, focusing on the resolution of the information loss paradox and the problem of the firewall.

Evaporation of 2-dimensional black holes

NASA Astrophysics Data System (ADS)

Ramazanoglu, Fethi M.

We present a detailed analysis of results from a new study of the quantum evaporation of Callan-Giddings-Harvey-Strominger (CGHS) black holes within the mean-field approximation. The CGHS model is a two dimensional model of quantum gravity which has been extensively investigated in the last two decades. Moreover, Ashtekar, Taveras and Varadarajan have recently proposed a solution to the information loss paradox within the context of this model, which has rekindled the interest in it. However, many aspects of black hole evaporation in this model has been overlooked because of lack of a solution for black holes with macroscopic mass. We show that this was due to, in part, limited numerical precision and, in part, misinterpretation of certain properties and symmetries of the model. By addressing these issues, we were, for the first time, able to numerically evolve macroscopic-mass black hole spacetimes of the CGHS model within the mean-field approximation, up to the vicinity of the singularity. Our calculations show that, while some of the assumptions underlying the standard evaporation paradigm are borne out, several are not. One of the anticipated properties we confirm is that the semi-classical space-time is asymptotically flat at right future null infinity, I+R , yet incomplete in the sense that null observers reach a future Cauchy horizon in finite affine time. Unexpected behavior includes that the Bondi mass traditionally used in the literature can become negative even when the area of the horizon is macroscopic; an improved Bondi mass remains positive until the end of semi-classical evaporation, yet the final value can be arbitrarily large relative to the Planck mass; and the flux of the quantum radiation at I+R is non-thermal even when the horizon area is large compared to the Planck scale. Furthermore, if the black hole is initially macroscopic, the evaporation process exhibits remarkable universal properties, which offer problems to attack to the mathematical relativity and geometric analysis communities. Our results also provide support for the full quantum scenario developed by Ashtekar et al.

Evaporation-Driven Charge Redistribution and Current Generation for Energy Harvesting Applications

DTIC Science & Technology

2008-12-01

has occurred and the system has a net positive energy gain, ∆Ecycle, as given by equation (5). 2 2 1 outstorecycle VCE =∆ (5) 5.5 Voltage...then the energy gained using the constant charge model can be represented by equation ( 2 ). minmaxminmax )( 2 1 VVCCE −=∆ ( 2 ) 3. DEVICE...evaporation. Evaporation can be the caused by changes in multiple environmental conditions such as: ( 1 ) percent relative humidity, ( 2 ) temperature, (3

Evaporation from a partially wet forest canopy

NASA Technical Reports Server (NTRS)

Hancock, N. H.; Sellers, P. J.; Crowther, J. M.

1983-01-01

The results of experimental studies of water storage in a Sitka-spruce canopy are presented and analyzed in terms of model simulations of evaporation. Wet-branch cantilever deflection was measured along with meteorological data on three days in August, 1976, to determine the relationship of canopy evaporation to wind speed and (hence) aerodynamic resistance. Two versions of a simple unilayer model of sensible and latent heat transport from a partially wet canopy were tested in the data analysis: model F1 forbids the exchange of heat between wet and dry foliage surfaces; model F2 assumes that this exchange is highly efficient. Model F1 is found to give results consistent with the rainfall-interception model of Rutter et al. (1971, 1975, 1977), but model F2 gives results which are more plausible and correspond to the multilayer simulations of Sellers and Lockwood (1981) and the experimental findings of Hancock and Crowther (1979). It is inferred that the role of eddy diffusivity for water vapor is enhanced relative to momentum transport, and that the similarity hypothesis used in conventional models may fail in the near vicinity of a forest canopy.

Example of a Fluid-Phase Change Examined with MD Simulation: Evaporative Cooling of a Nanoscale Droplet.

PubMed

Ao, Takashi; Matsumoto, Mitsuhiro

2017-10-24

We carried out a series of molecular dynamics simulations in order to examine the evaporative cooling of a nanoscale droplet of a Lennard-Jones liquid. After thermally equilibrating a droplet at a temperature T ini /T t ≃ 1.2 (T t is the triple-point temperature), we started the evaporation into vacuum by removing vaporized particles and monitoring the change in droplet size and the temperature inside. As free evaporation proceeds, the droplet reaches a deep supercooled liquid state of T/T t ≃ 0.7. The temperature was found to be uniform in spite of the fast evaporative cooling on the surface. The time evolution of the evaporating droplet properties was satisfactorily explained with a simple one-dimensional phase-change model. After a sufficiently long run, the supercooled droplet was crystallized into a polycrystalline fcc structure. The crystallization is a stochastic nucleation process. The time and the temperature of inception were evaluated over 42 samples, which indicate the existence of a stability limit.

Effects of Chemistry on Vertical Dust Motion in Early Protoplanetary Disks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miyazaki, Yoshinori; Korenaga, Jun

We propose the possibility of a new phenomenon affecting the settling of dust grains at the terrestrial region in early protoplanetary disks. Sinking dust grains evaporate in a hot inner region during the early stage of disk evolution, and the effects of condensation and evaporation on vertical dust settling can be significant. A 1D dust settling model considering both physical and chemical aspects is presented in this paper. Modeling results show that dust grains evaporate as they descend into the hotter interior and form a condensation front, above which dust-composing major elements, Mg, Si, and Fe, accumulate, creating a largemore » temperature gradient. Repeated evaporation at the front inhibits grain growth, and small grain sizes elevate the opacity away from the midplane. Self-consistent calculations, including radiative heat transfer and condensation theory, suggest that the mid-disk temperature could be high enough for silicates to remain evaporated longer than previous estimates. The formation of a condensation front leads to contrasting settling behaviors between highly refractory elements, such as Al and Ca, and moderately refractory elements, such as Mg, Si, and Fe, suggesting that elemental abundance in planetesimals may not be a simple function of volatility.« less

A model of the evaporation of binary-fuel clusters of drops

NASA Technical Reports Server (NTRS)

Harstad, K.; Bellan, J.

1991-01-01

A formulation has been developed to describe the evaporation of dense or dilute clusters of binary-fuel drops. The binary fuel is assumed to be made of a solute and a solvent whose volatility is much lower than that of the solute. Convective flow effects, inducing a circulatory motion inside the drops, are taken into account, as well as turbulence external to the cluster volume. Results obtained with this model show that, similar to the conclusions for single isolated drops, the evaporation of the volatile is controlled by liquid mass diffusion when the cluster is dilute. In contrast, when the cluster is dense, the evaporation of the volatile is controlled by surface layer stripping, that is, by the regression rate of the drop, which is in fact controlled by the evaporation rate of the solvent. These conclusions are in agreement with existing experimental observations. Parametric studies show that these conclusions remain valid with changes in ambient temperature, initial slip velocity between drops and gas, initial drop size, initial cluster size, initial liquid mass fraction of the solute, and various combinations of solvent and solute. The implications of these results for computationally intensive combustor calculations are discussed.

Analysis of 2H-Evaporator Acid Cleaning Samples

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hay, M.; Diprete, D.; Edwards, T.

The 2H-Evaporator acid cleaning solution samples were analyzed by SRNL to determine a composition for the scale present in the evaporator before recent acid cleaning. Composite samples were formed from the solution samples from the two acid cleaning cycles. The solution composition was converted to a weight percent scale solids basis under an assumed chemical composition. The scale composition produced from the acid cleaning solution samples indicates a concentration of 6.85 wt% uranium. An upper bound, onesided 95% confidence interval on the weight percent uranium value may be given as 6.9 wt% + 1.645 × 0.596 wt% = 7.9 wt%.more » The comparison of the composition from the current acid cleaning solutions with the composition of recent scale samples along with the thermodynamic modeling results provides reasonable assurance that the sample results provide a good representation of the overall scale composition in the evaporator prior to acid cleaning. The small amount of scale solids dissolved in the 1.5 M nitric acid during the evaporator cleaning process likely produced only a small amount of precipitation based on modeling results and the visual appearance of the samples.« less

Effects of Chemistry on Vertical Dust Motion in Early Protoplanetary Disks

NASA Astrophysics Data System (ADS)

Miyazaki, Yoshinori; Korenaga, Jun

2017-11-01

We propose the possibility of a new phenomenon affecting the settling of dust grains at the terrestrial region in early protoplanetary disks. Sinking dust grains evaporate in a hot inner region during the early stage of disk evolution, and the effects of condensation and evaporation on vertical dust settling can be significant. A 1D dust settling model considering both physical and chemical aspects is presented in this paper. Modeling results show that dust grains evaporate as they descend into the hotter interior and form a condensation front, above which dust-composing major elements, Mg, Si, and Fe, accumulate, creating a large temperature gradient. Repeated evaporation at the front inhibits grain growth, and small grain sizes elevate the opacity away from the midplane. Self-consistent calculations, including radiative heat transfer and condensation theory, suggest that the mid-disk temperature could be high enough for silicates to remain evaporated longer than previous estimates. The formation of a condensation front leads to contrasting settling behaviors between highly refractory elements, such as Al and Ca, and moderately refractory elements, such as Mg, Si, and Fe, suggesting that elemental abundance in planetesimals may not be a simple function of volatility.

The study on the interdependence of spray characteristics and evaporation history of fuel spray in high temperature air crossflow

NASA Astrophysics Data System (ADS)

Zhu, J. Y.; Chin, J. S.

1986-06-01

A numerical calculation method is used to predict the variation of the characteristics of fuel spray moving in a high temperature air crossflow, mainly, Sauter mean diameter SMD, droplet size distribution index N of Rosin-Rammler distribution and evaporation percentage changing with downstream distance X from the nozzle. The effect of droplet heat-up period evaporation process and forced convection are taken into full account; thus, the calculation model is a very good approximation to the process of spray evaporation in a practical combustor, such as ramjet, aero-gas turbine, liquid propellant rocket, diesel and other liquid fuel-powered combustion devices. The changes of spray characteristics N, SMD and spray evaporation percentage with air velocity, pressure, temperature, fuel injection velocity, and the initial spray parameters are presented.

Autodyne effect in a single-mode Er fibre laser and the possibility of its usage for recognising the evaporated biotissue type

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dmitriev, A K; Konovalov, A N; Ul'yanov, V A

2015-12-31

The autodyne signal arising in an Er fibre laser in the course of evaporating biological models of different types is studied and the possibility of recognising the biotissue type using the method of autodyne detection of the backscattered Doppler signal is assessed. In the experiments we modelled the process of surgical intervention using the contact (hole perforation with the Er laser fibre) and noncontact (surface evaporation with the focused radiation) regimes of impact on different biological models. The amplitude – frequency characteristic of the autodyne detection for the Er fibre laser is measured and the initial spectra of the backscatteredmore » Doppler signal arising under the action of laser radiation on the samples of biological models are obtained. The experiments have shown that the spectra of the backscattered Doppler signal, arising in the course of the contact and noncontact action of the Er fibre laser on different biological models, demonstrate clear-cut distinctions. (control of laser radiation parameters)« less

Evaluation of a locally homogeneous model of spray evaporation

NASA Technical Reports Server (NTRS)

Shearer, A. J.; Faeth, G. M.; Tamura, H.

1978-01-01

Measurements were conducted on an evaporating spray in a stagnant environment. The spray was formed using an air-atomizing injector to yield a Sauter mean diameter of the order of 30 microns. The region where evaporation occurred extended approximately 1 m from the injector for the test conditions. Profiles of mean velocity, temperature, composition, and drop size distribution, as well as velocity fluctuations and Reynolds stress, were measured. The results are compared with a locally homogeneous two-phase flow model which implies no velocity difference and thermodynamic equilibrium between the phases. The flow was represented by a k-epsilon-g turbulence model employing a clipped Gaussian probability density function for mixture fraction fluctuations. The model provides a good representation of earlier single-phase jet measurements, but generally overestimates the rate of development of the spray. Using the model predictions to represent conditions along the centerline of the spray, drop life-history calculations were conducted which indicate that these discrepancies are due to slip and loss of thermodynamic equilibrium between the phases.

Remarks on non-singular black holes

NASA Astrophysics Data System (ADS)

Frolov, Valeri P.

2018-01-01

We briefly discuss non-singular black hole models, with the main focus on the properties of non-singular evaporating black holes. Such black holes possess an apparent horizon, however the event horizon may be absent. In such a case, the information from the black hole interior may reach the external observer after the complete evaporation of the black hole. This model might be used for the resolution of the information loss puzzle. However, as we demonstrate, in a general case the quantum radiation emitted from the black hole interior, calculated in the given black hole background, is very large. This outburst of the radiation is exponentially large for models with the redshift function α = 1. We show that it can be suppressed by including a non-trivial redshift function. However, even this suppression is not enough to guarantee self-consistency of the model. This problem is a manifestation of a general problem, known as the "mass inflation". We briefly comment on possible ways to overcome this problem in the models of non-singular evaporating black holes.

New Correlation Methods of Evaporation Heat Transfer in Horizontal Microfine Tubes

NASA Astrophysics Data System (ADS)

Makishi, Osamu; Honda, Hiroshi

A stratified flow model and an annular flow model of evaporation heat transfer in horizontal microfin tubes have been proposed. In the stratified flow model, the contributions of thin film evaporation and nucleate boiling in the groove above a stratified liquid were predicted by a previously reported numerical analysis and a newly developed correlation, respectively. The contributions of nucleate boiling and forced convection in the stratified liquid region were predicted by the new correlation and the Carnavos equation, respectively. In the annular flow model, the contributions of nucleate boiling and forced convection were predicted by the new correlation and the Carnavos equation in which the equivalent Reynolds number was introduced, respectively. A flow pattern transition criterion proposed by Kattan et al. was incorporated to predict the circumferential average heat transfer coefficient in the intermediate region by use of the two models. The predictions of the heat transfer coefficient compared well with available experimental data for ten tubes and four refrigerants.

Humidity-insensitive water evaporation from molecular complex fluids.

PubMed

Salmon, Jean-Baptiste; Doumenc, Frédéric; Guerrier, Béatrice

2017-09-01

We investigated theoretically water evaporation from concentrated supramolecular mixtures, such as solutions of polymers or amphiphilic molecules, using numerical resolutions of a one-dimensional model based on mass transport equations. Solvent evaporation leads to the formation of a concentrated solute layer at the drying interface, which slows down evaporation in a long-time-scale regime. In this regime, often referred to as the falling rate period, evaporation is dominated by diffusive mass transport within the solution, as already known. However, we demonstrate that, in this regime, the rate of evaporation does not also depend on the ambient humidity for many molecular complex fluids. Using analytical solutions in some limiting cases, we first demonstrate that a sharp decrease of the water chemical activity at high solute concentration leads to evaporation rates which depend weakly on the humidity, as the solute concentration at the drying interface slightly depends on the humidity. However, we also show that a strong decrease of the mutual diffusion coefficient of the solution enhances considerably this effect, leading to nearly independent evaporation rates over a wide range of humidity. The decrease of the mutual diffusion coefficient indeed induces strong concentration gradients at the drying interface, which shield the concentration profiles from humidity variations, except in a very thin region close to the drying interface.

Streamer Evaporation

NASA Technical Reports Server (NTRS)

Suess, S. T.; Wang, A.-H.; Wu, S. T.; Nerney, S. F.

1998-01-01

Evaporation is the consequence of heating near the top of streamers in ideal Magnetohydrodynamics (MHD) models, where the plasma is weakly contained by the magnetic field. Heating causes slow opening of field lines and release of new solar wind. It was discovered in simulations and, due to the absence of loss mechanisms, the ultimate end point is the complete evaporation of the streamer. Of course streamers do not behave in this way because there are losses by thermal conduction and radiation. Physically, heating is also expected to depend on ambient conditions. We use our global MHD model with thermal conduction to examine the effect of changing the heating scale height. We also apply and extend an analytic model of streamers developed by Pneuman (1968) to show that steady streamers are unable to contain plasma for temperatures near the cusp greater than approximately 2 x 10(exp 6) K.

Design, development and test of a capillary pump loop heat pipe

NASA Technical Reports Server (NTRS)

Kroliczek, E. J.; Ku, J.; Ollendorf, S.

1984-01-01

The development of a capillary pump loop (CPL) heat pipe, including computer modeling and breadboard testing, is presented. The computer model is a SINDA-type thermal analyzer, combined with a pressure analyzer, which predicts the transients of the CPL heat pipe during operation. The breadboard is an aluminum/ammonia transport system which contains multiple parallel evaporator and condenser zones within a single loop. Test results have demonstrated the practicality and reliability of such a design, including heat load sharing among evaporators, liquid inventory/temperature control feature, and priming under load. Transport capability for this system is 65 KW-M with individual evaporator pumps managing up to 1.7 KW at a heat flux of 15 W/sq cm. The prediction of the computer model for heat transport capabilities is in good agreement with experimental results.

Modelling component evaporation and composition change of traffic-induced ultrafine particles during travel from street canyon to urban background.

PubMed

Nikolova, Irina; MacKenzie, A Rob; Cai, Xiaoming; Alam, Mohammed S; Harrison, Roy M

2016-07-18

We developed a model (CiTTy-Street-UFP) of traffic-related particle behaviour in a street canyon and in the nearby downwind urban background that accounts for aerosol dynamics and the variable vapour pressure of component organics. The model simulates the evolution and fate of traffic generated multicomponent ultrafine particles (UFP) composed of a non-volatile core and 17 Semi-Volatile Organic Compounds (SVOC, modelled as n-alkane proxies). A two-stage modelling approach is adopted: (1) a steady state simulation inside the street canyon is achieved, in which there exists a balance between traffic emissions, condensation/evaporation, deposition, coagulation and exchange with the air above roof-level; and (2) a continuing simulation of the above-roof air parcel advected to the nearby urban park during which evaporation is dominant. We evaluate the component evaporation and associated composition changes of multicomponent organic particles in realistic atmospheric conditions and compare our results with observations from London (UK) in a street canyon and an urban park. With plausible input conditions and parameter settings, the model can reproduce, with reasonable fidelity, size distributions in central London in 2007. The modelled nucleation-mode peak diameter, which is 23 nm in the steady-state street canyon, decreases to 9 nm in a travel time of just 120 s. All modelled SVOC in the sub-10 nm particle size range have evaporated leaving behind only non-volatile material, whereas modelled particle composition in the Aitken mode contains SVOC between C26H54 and C32H66. No data on particle composition are available in the study used for validation, or elsewhere. Measurements addressing in detail the size resolved composition of the traffic emitted UFP in the atmosphere are a high priority for future research. Such data would improve the representation of these particles in dispersion models and provide the data essential for model validation. Enhanced knowledge of the chemical composition of nucleation-mode particles from diesel engine exhaust is needed to predict both their atmospheric behaviour and their implications for human health.

Pan evaporation prediction using a hybrid multilayer perceptron-firefly algorithm (MLP-FFA) model: case study in North Iran

NASA Astrophysics Data System (ADS)

Ghorbani, M. A.; Deo, Ravinesh C.; Yaseen, Zaher Mundher; H. Kashani, Mahsa; Mohammadi, Babak

2017-08-01

An accurate computational approach for the prediction of pan evaporation over daily time horizons is a useful decisive tool in sustainable agriculture and hydrological applications, particularly in designing the rural water resource systems, water use allocations, utilization and demand assessments, and the management of irrigation systems. In this study, a hybrid predictive model (Multilayer Perceptron-Firefly Algorithm (MLP-FFA)) based on the FFA optimizer that is embedded within the MLP technique is developed and evaluated for its suitability for the prediction of daily pan evaporation. To develop the hybrid MLP-FFA model, the pan evaporation data measured between 2012 and 2014 for two major meteorological stations (Talesh and Manjil) located at Northern Iran are employed to train and test the predictive model. The ability of the hybrid MLP-FFA model is compared with the traditional MLP and support vector machine (SVM) models. The results are evaluated using five performance criteria metrics: root mean square error (RMSE), mean absolute error (MAE), Nash-Sutcliffe efficiency (NS), and the Willmott's Index (WI). Taylor diagrams are also used to examine the similarity between the observed and predicted pan evaporation data in the test period. Results show that an optimal MLP-FFA model outperforms the MLP and SVM model for both tested stations. For Talesh, a value of WI = 0.926, NS = 0.791, and RMSE = 1.007 mm day-1 is obtained using MLP-FFA model, compared with 0.912, 0.713, and 1.181 mm day-1 (MLP) and 0.916, 0.726, and 1.153 mm day-1 (SVM), whereas for Manjil, a value of WI = 0.976, NS = 0.922, and 1.406 mm day-1 is attained that contrasts 0.972, 0.901, and 1.583 mm day-1 (MLP) and 0.971, 0.893, and 1.646 mm day-1 (SVM). The results demonstrate the importance of the Firefly Algorithm applied to improve the performance of the MLP-FFA model, as verified through its better predictive performance compared to the MLP and SVM model.

The effects of ground hydrology on climate sensitivity to solar constant variations

NASA Technical Reports Server (NTRS)

Chou, S. H.; Curran, R. J.; Ohring, G.

1979-01-01

The effects of two different evaporation parameterizations on the climate sensitivity to solar constant variations are investigated by using a zonally averaged climate model. The model is based on a two-level quasi-geostrophic zonally averaged annual mean model. One of the evaporation parameterizations tested is a nonlinear formulation with the Bowen ratio determined by the predicted vertical temperature and humidity gradients near the earth's surface. The other is the linear formulation with the Bowen ratio essentially determined by the prescribed linear coefficient.

A Kolmogorov-Brutsaert Structure Function Model for Evaporation from a Rough Surface into a Turbulent Atmosphere

NASA Astrophysics Data System (ADS)

Katul, Gabriel; Liu, Heping

2017-04-01

In his 1881 acceptance letter of the Rumford Medal, Gibbs declared that "One of the principal objects of theoretical research is to find the point of view from which the subject appears in the greatest simplicity". Guided by this quotation, the subject of evaporation into the atmosphere from rough surfaces by turbulence offered in a 1965 study by Brutsaert is re-examined. Brutsaert proposed a model that predicted mean evaporation rate E from rough surfaces to scale with the 3/4 power-law of the friction velocity (u∗) and the square-root of molecular diffusivity (Dm) for water vapor. This result was supported by a large corpus of experiments and spawned a number of studies on inter-facial transfer of scalars, evaporation from porous media at single and multiple pore scales, bulk evaporation from bare soil surfaces, as well as isotopic fractionation in hydrological applications. It also correctly foreshadowed the much discussed 1/4 'universal' scaling of liquid transfer coefficients of sparingly soluble gases in air-sea exchange studies. In arriving at these results, a number of assumptions were made regarding the surface renewal rate describing the contact durations between eddies and the evaporating surface, the diffusional mass process from the surface into eddies, and the cascade of turbulent kinetic energy sustaining the eddy renewal process itself. The anzats explored here is that E ˜√Dm-u∗3/4 is a direct outcome of the Kolmogorov scaling for inertial subrange eddies modified to include viscous-cutoff thereby by-passing the need for a surface renewal assumption. It is demonstrated that Brutsaert's model for E may be more general than its original derivation assumed. Extensions to canopy surfaces as well as other scalars with different molecular Schmidt numbers are also featured.

A Method for a Multi-Platform Approach to Generate Gridded Surface Evaporation

NASA Astrophysics Data System (ADS)

Badger, A.; Livneh, B.; Small, E. E.; Abolafia-Rosenzweig, R.

2017-12-01

Evapotranspiration is an integral component of the surface water balance. While there are many estimates of evapotranspiration, there are fewer estimates that partition evapotranspiration into evaporation and transpiration components. This study aims to generate a CONUS-scale, observationally-based soil evaporation dataset by using the time difference of surface soil moisture by Soil Moisture Active Passive (SMAP) satellite with adjustments for transpiration and a bottom flux out of the surface layer. In concert with SMAP, the Moderate-Resolution Imaging Spectroradiometer (MODIS) satellite, North American Land Data Assimilation Systems (NLDAS) and the Hydrus-1D model are used to fully analyze the surface water balance. A biome specific estimate of the total terrestrial ET is calculated through a variation of the Penman-Monteith equation with NLDAS forcing and NLDAS Noah Model output for meteorological variables. A root density restriction and SMAP-based soil moisture restriction are applied to obtain terrestrial transpiration estimates. By forcing Hydrus-1D with NLDAS meteorology and our terrestrial transpiration estimates, an estimate of the flux between the soil surface and root zone layers (qbot) will dictate the proportion of water that is available for soil evaporation. After constraining transpiration and the bottom flux from the surface layer, we estimate soil evaporation as the residual of the surface water balance. Application of this method at Fluxnet sites shows soil evaporation estimates of approximately 0­3 mm/day and less than ET estimates. Expanding this methodology to produce a gridded product for CONUS, and eventually a global-scale product, will enable a better understanding of water balance processes and contribute a dataset to validate land-surface model's surface flux processes.

High throughput research and evaporation rate modeling for solvent screening for ethylcellulose barrier membranes in pharmaceutical applications.

PubMed

Schoener, Cody A; Curtis-Fisk, Jaime L; Rogers, True L; Tate, Michael P

2016-10-01

Ethylcellulose is commonly dissolved in a solvent or formed into an aqueous dispersion and sprayed onto various dosage forms to form a barrier membrane to provide controlled release in pharmaceutical formulations. Due to the variety of solvents utilized in the pharmaceutical industry and the importance solvent can play on film formation and film strength it is critical to understand how solvent can influence these parameters. To systematically study a variety of solvent blends and how these solvent blends influence ethylcellulose film formation, physical and mechanical film properties and solution properties such as clarity and viscosity. Using high throughput capabilities and evaporation rate modeling, thirty-one different solvent blends composed of ethanol, isopropanol, acetone, methanol, and/or water were formulated, analyzed for viscosity and clarity, and narrowed down to four solvent blends. Brookfield viscosity, film casting, mechanical film testing and water permeation were also completed. High throughput analysis identified isopropanol/water, ethanol, ethanol/water and methanol/acetone/water as solvent blends with unique clarity and viscosity values. Evaporation rate modeling further rank ordered these candidates from excellent to poor interaction with ethylcellulose. Isopropanol/water was identified as the most suitable solvent blend for ethylcellulose due to azeotrope formation during evaporation, which resulted in a solvent-rich phase allowing the ethylcellulose polymer chains to remain maximally extended during film formation. Consequently, the highest clarity and most ductile films were formed. Employing high throughput capabilities paired with evaporation rate modeling allowed strong predictions between solvent interaction with ethylcellulose and mechanical film properties.

Evaluating the Effect of Ground Temperature on Phreatic Evaporation in Bare Soil Area

NASA Astrophysics Data System (ADS)

Manting, S.; Wang, B.; Liu, P.

2017-12-01

Phreatic water evaporation is an important link in water conversion, and it is also the main discharge of shallow groundwater. The influencing factors of phreatic evaporation intensity include meteorological elements, soil lithology, ground temperature, water table depth and plant growth status, etc. However, the effect of ground temperature on phreatic evaporation is neglected in the traditional phreatic evaporation study, while from the principle of water vapor conversion, the ground temperature is the main energy controlling the process. Taking the homogeneous sand in bare soil area for example, the effect of different temperature difference between ground temperature and air temperature on phreatic evaporation was studied by constructing soil column experiment and Hydrus numerical simulation model. Based on analysis of the process and trend of soil water content in different depths, the influence mechanism of ground temperature on phreatic evaporation was discussed quantitatively. The experimental results show that the change trend of daily evaporation is basically the same. But considering the effect of ground temperature the evaporation amount is significantly larger than that of without considering the temperature. When the temperature (-2.3 ° 13.6 °) is lower than the ground temperature (20 °), the average value of evaporation increased by about 33.7%; When the temperature (22 ° -33.2 °) is higher than the ground temperature (20 °), the average increase of evaporation is about 10.08%. The effect of ground temperature on the evaporation is very significant in winter and summer. Soil water content increased with the increase of water table depth, while the soil water content at the same depth was different due to the temperature difference, and the soil water content was also different. The larger the temperature difference, the greater the difference of soil water content. The slope of the trend line of the phreatic evaporation is also increased accordingly. That is, under the influence of ground temperature, water vapor conversion rate increased, resulting in increased soil moisture and increased phreatic evaporation. Therefore, considering the ground temperature, it has important theoretical and practical value for scientific understanding and revealing the phreatic evaporation process.

A simplified model of precipitation enhancement over a heterogeneous surface

NASA Astrophysics Data System (ADS)

Cioni, Guido; Hohenegger, Cathy

2018-06-01

Soil moisture heterogeneities influence the onset of convection and subsequent evolution of precipitating systems through the triggering of mesoscale circulations. However, local evaporation also plays a role in determining precipitation amounts. Here we aim at disentangling the effect of advection and evaporation on precipitation over the course of a diurnal cycle by formulating a simple conceptual model. The derivation of the model is inspired by the results of simulations performed with a high-resolution (250 m) large eddy simulation model over a surface with varying degrees of heterogeneity. A key element of the conceptual model is the representation of precipitation as a weighted sum of advection and evaporation, each weighed by its own efficiency. The model is then used to isolate the main parameters that control precipitation variations over a spatially drier patch. It is found that these changes surprisingly do not depend on soil moisture itself but instead purely on parameters that describe the atmospheric initial state. The likelihood for enhanced precipitation over drier soils is discussed based on these parameters. Additional experiments are used to test the validity of the model.

Modeling acid-gas generation from boiling chloride brines

PubMed Central

2009-01-01

Background This study investigates the generation of HCl and other acid gases from boiling calcium chloride dominated waters at atmospheric pressure, primarily using numerical modeling. The main focus of this investigation relates to the long-term geologic disposal of nuclear waste at Yucca Mountain, Nevada, where pore waters around waste-emplacement tunnels are expected to undergo boiling and evaporative concentration as a result of the heat released by spent nuclear fuel. Processes that are modeled include boiling of highly concentrated solutions, gas transport, and gas condensation accompanied by the dissociation of acid gases, causing low-pH condensate. Results Simple calculations are first carried out to evaluate condensate pH as a function of HCl gas fugacity and condensed water fraction for a vapor equilibrated with saturated calcium chloride brine at 50-150°C and 1 bar. The distillation of a calcium-chloride-dominated brine is then simulated with a reactive transport model using a brine composition representative of partially evaporated calcium-rich pore waters at Yucca Mountain. Results show a significant increase in boiling temperature from evaporative concentration, as well as low pH in condensates, particularly for dynamic systems where partial condensation takes place, which result in enrichment of HCl in condensates. These results are in qualitative agreement with experimental data from other studies. Conclusion The combination of reactive transport with multicomponent brine chemistry to study evaporation, boiling, and the potential for acid gas generation at the proposed Yucca Mountain repository is seen as an improvement relative to previously applied simpler batch evaporation models. This approach allows the evaluation of thermal, hydrological, and chemical (THC) processes in a coupled manner, and modeling of settings much more relevant to actual field conditions than the distillation experiment considered. The actual and modeled distillation experiments do not represent expected conditions in an emplacement drift, but nevertheless illustrate the potential for acid-gas generation at moderate temperatures (<150°C). PMID:19917082

A New Finite-Conductivity Droplet Evaporation Model Including Liquid Turbulence Effect

NASA Technical Reports Server (NTRS)

Balasubramanyam, M. S.; Chen, C. P.; Trinh, H. P.

2006-01-01

A new approach to account for finite thermal conductivity and turbulence effects within atomizing droplets of an evaporating spray is presented in this paper. The model is an extension of the T-blob and T-TAB atomization/spray model of Trinh and Chen [9]. This finite conductivity model is based on the two-temperature film theory in which the turbulence characteristics of the droplet are used to estimate the effective thermal diffusivity for the liquid-side film thickness. Both one-way and two-way coupled calculations were performed to investigate the performance cf this model against the published experimental data.

Atmospheric pressure arc discharge with ablating graphite anode

NASA Astrophysics Data System (ADS)

Nemchinsky, V. A.; Raitses, Y.

2015-06-01

The anodic carbon arc discharge is used to produce carbon nanoparticles. Recent experiments with the carbon arc at atmospheric pressure helium demonstrated the enhanced ablation rate for narrow graphite anodes resulting in high deposition rates of carbonaceous products on the copper cathode (Fetterman et al 2008 Carbon 46 1322-6). The proposed model explains these results with interconnected steady-state models of the cathode and the anode processes. When considering cathode functioning, the model predicts circulation of the particles in the near-cathode region: evaporation of the cathode material, ionization of evaporated atoms and molecules in the near-cathode plasma, return of the resulting ions to the cathode, surface recombination of ions and electrons followed again by cathode evaporation etc. In the case of the low anode ablation rate, the ion acceleration in the cathode sheath provides the major cathode heating mechanism. In the case of an intensive anode ablation, an additional cathode heating is due to latent fusion heat of the atomic species evaporated from the anode and depositing at the cathode. Using the experimental arc voltage as the only input discharge parameter, the model allows us to calculate the anode ablation rate. A comparison of the results of calculations with the available experimental data shows reasonable agreement.

Evaporation of Particle-Stabilized Emulsion Sunscreen Films.

PubMed

Binks, Bernard P; Fletcher, Paul D I; Johnson, Andrew J; Marinopoulos, Ioannis; Crowther, Jonathan M; Thompson, Michael A

2016-08-24

We recently showed (Binks et al., ACS Appl. Mater. Interfaces, 2016, DOI: 10.1021/acsami.6b02696) how evaporation of sunscreen films consisting of solutions of molecular UV filters leads to loss of UV light absorption and derived sun protection factor (SPF). In the present work, we investigate evaporation-induced effects for sunscreen films consisting of particle-stabilized emulsions containing a dissolved UV filter. The emulsions contained either droplets of propylene glycol (PG) in squalane (SQ), droplets of SQ in PG or droplets of decane in PG. In these different emulsion types, the SQ is involatile and shows no evaporation, the PG is volatile and evaporates relatively slowly, whereas the decane is relatively very volatile and evaporates quickly. We have measured the film mass and area, optical micrographs of the film structure, and the UV absorbance spectra during evaporation. For emulsion films containing the involatile SQ, evaporation of the PG causes collapse of the emulsion structure with some loss of specular UV absorbance due to light scattering. However, for these emulsions with droplets much larger than the wavelength of light, the light is scattered only at small forward angles so does not contribute to the diffuse absorbance and the film SPF. The UV filter remains soluble throughout the evaporation and thus the UV absorption by the filter and the SPF remain approximately constant. Both PG-in-SQ and SQ-in-PG films behave similarly and do not show area shrinkage by dewetting. In contrast, the decane-in-PG film shows rapid evaporative loss of the decane, followed by slower loss of the PG resulting in precipitation of the UV filter and film area shrinkage by dewetting which cause the UV absorbance and derived SPF to decrease. Measured UV spectra during evaporation are in reasonable agreement with spectra calculated using models discussed here.

Dynamics of Soil Water Evaporation during Soil Drying in the Presence of a Shallow Water Table: Laboratory Experiment and Numerical Analysis

NASA Astrophysics Data System (ADS)

Han, J.; Lin, J.; Liu, P.; Li, W.

2017-12-01

Evaporation from a porous medium plays a key role in hydrological, agricultural, environmental, and engineering applications. Laboratory and numerical experiments were conducted to investigate the evolution of soil water evaporation during a continuous drying event. Simulated soil water contents and temperatures by the calibrated model well reproduced measured values at different depths. Results show that the evaporative drying process could be divided into three stages, beginning with a relatively high evaporation rate during stage 1, followed by a lower rate during transient stage and stage 2, and finally maintaining a very low and constant rate during stage 3. The condensation zone was located immediately below the evaporation zone in the profile. Both peaks of evaporation and condensation rate increased rapidly during stage 1 and transition stage, decreased during stage 2, and maintained constant during stage 3. The width of evaporation zone kept a continuous increase during stages 1 and 2 and maintained a nearly constant value of 0.68 cm during stage 3. When the evaporation zone totally moved into the subsurface, a dry surface layer (DSL) formed above the evaporation zone at the end of stage 2. The width of DSL also presented a continuous increase during stage 2 and kept a constant value of 0.71 cm during stage 3. Although the magnitude of condensation zone was much smaller than that for the evaporation zone, the importance of the contribution of condensation zone to soil water dynamics should not be underestimated. Results from our experiment and numerical simulation show that this condensation process resulted in an unexpected and apparent water content increase in the middle of vadose zone profile.

Numerical Simulation of the Effects of Water Surface in Building Environment

NASA Astrophysics Data System (ADS)

Li, Guangyao; Pan, Yuqing; Yang, Li

2018-03-01

Water body could affect the thermal environment and airflow field in the building districts, because of its special thermal characteristics, evaporation and flat surface. The thermal influence of water body in Tongji University Jiading Campus front area was evaluated. First, a suitable evaporation model was selected and then was applied to calculate the boundary conditions of the water surface in the Fluent software. Next, the computational fluid dynamics (CFD) simulations were conducted on the models both with and without water, following the CFD practices guidelines. Finally, the outputs of the two simulations were compared with each other. Results showed that the effect of evaporative cooling from water surface strongly depends on the wind direction and temperature decrease was about 2∼5°C. The relative humidity within the enclosing area was affected by both the building arrangement and surrounding water. An increase of about 0.1∼0.2m/s of wind speed induced by the water evaporation was observed in the open space.

Entanglement entropy production in gravitational collapse: covariant regularization and solvable models

NASA Astrophysics Data System (ADS)

Bianchi, Eugenio; De Lorenzo, Tommaso; Smerlak, Matteo

2015-06-01

We study the dynamics of vacuum entanglement in the process of gravitational collapse and subsequent black hole evaporation. In the first part of the paper, we introduce a covariant regularization of entanglement entropy tailored to curved spacetimes; this regularization allows us to propose precise definitions for the concepts of black hole "exterior entropy" and "radiation entropy." For a Vaidya model of collapse we find results consistent with the standard thermodynamic properties of Hawking radiation. In the second part of the paper, we compute the vacuum entanglement entropy of various spherically-symmetric spacetimes of interest, including the nonsingular black hole model of Bardeen, Hayward, Frolov and Rovelli-Vidotto and the "black hole fireworks" model of Haggard-Rovelli. We discuss specifically the role of event and trapping horizons in connection with the behavior of the radiation entropy at future null infinity. We observe in particular that ( i) in the presence of an event horizon the radiation entropy diverges at the end of the evaporation process, ( ii) in models of nonsingular evaporation (with a trapped region but no event horizon) the generalized second law holds only at early times and is violated in the "purifying" phase, ( iii) at late times the radiation entropy can become negative (i.e. the radiation can be less correlated than the vacuum) before going back to zero leading to an up-down-up behavior for the Page curve of a unitarily evaporating black hole.

Non-isothermal processes during the drying of bare soil: Model Development and Validation

NASA Astrophysics Data System (ADS)

Sleep, B.; Talebi, A.; O'Carrol, D. M.

2017-12-01

Several coupled liquid water, water vapor, and heat transfer models have been developed either to study non-isothermal processes in the subsurface immediately below the ground surface, or to predict the evaporative flux from the ground surface. Equilibrium phase change between water and gas phases is typically assumed in these models. Recently, a few studies have questioned this assumption and proposed a coupled model considering kinetic phase change. However, none of these models were validated against real field data. In this study, a non-isothermal coupled model incorporating kinetic phase change was developed and examined against the measured data from a green roof test module. The model also incorporated a new surface boundary condition for water vapor transport at the ground surface. The measured field data included soil moisture content and temperature at different depths up to the depth of 15 cm below the ground surface. Lysimeter data were collected to determine the evaporation rates. Short and long wave radiation, wind velocity, air ambient temperature and relative humidity were measured and used as model input. Field data were collected for a period of three months during the warm seasons in south eastern Canada. The model was calibrated using one drying period and then several other drying periods were simulated. In general, the model underestimated the evaporation rates in the early stage of the drying period, however, the cumulative evaporation was in good agreement with the field data. The model predicted the trends in temperature and moisture content at the different depths in the green roof module. The simulated temperature was lower than the measured temperature for most of the simulation time with the maximum difference of 5 ° C. The simulated moisture content changes had the same temporal trend as the lysimeter data for the events simulated.

Probing the Evaporation Dynamics of Ethanol/Gasoline Biofuel Blends Using Single Droplet Manipulation Techniques.

PubMed

Corsetti, Stella; Miles, Rachael E H; McDonald, Craig; Belotti, Yuri; Reid, Jonathan P; Kiefer, Johannes; McGloin, David

2015-12-24

Using blends of bioethanol and gasoline as automotive fuel leads to a net decrease in the production of harmful emission compared to the use of pure fossil fuel. However, fuel droplet evaporation dynamics change depending on the mixing ratio. Here we use single particle manipulation techniques to study the evaporation dynamics of ethanol/gasoline blend microdroplets. The use of an electrodynamic balance enables measurements of the evaporation of individual droplets in a controlled environment, while optical tweezers facilitate studies of the behavior of droplets inside a spray. Hence, the combination of both methods is perfectly suited to obtain a complete picture of the evaporation process. The influence of adding varied amounts of ethanol to gasoline is investigated, and we observe that droplets with a greater fraction of ethanol take longer to evaporate. Furthermore, we find that our methods are sensitive enough to observe the presence of trace amounts of water in the droplets. A theoretical model, predicting the evaporation of ethanol and gasoline droplets in dry nitrogen gas, is used to explain the experimental results. Also a theoretical estimation of the saturation of the environment, with other aerosols, in the tweezers is carried out.

Technical Performance and Economic Evaluation of Evaporative and Membrane-Based Concentration for Biomass-Derived Sugars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sievers, David A.; Stickel, Jonathan J.; Grundl, Nicholas J.

Several conversion pathways of lignocellulosic biomass to advanced biofuels require or benefit from using concentrated sugar syrups of 600 g/L or greater. And while concentration may seem straightforward, thermal sugar degradation and energy efficiency remain major concerns. This study evaluated the trade-offs in product recovery, energy consumption, and economics between evaporative and membrane-based concentration methods. The degradation kinetics of xylose and glucose were characterized and applied to an evaporator process simulation. Though significant sugar loss was predicted for certain scenarios due to the Maillard reaction, industrially common falling-film plate evaporators offer short residence times (<5 min) and are expected tomore » limit sugar losses. Membrane concentration experiments characterized flux and sugar rejection, but diminished flux occurred at >100 g/L. A second step using evaporation is necessary to achieve target concentrations. Techno-economic process model simulations evaluated the overall economics of concentrating a 35 g/L sugar stream to 600 g/L in a full-scale biorefinery. A two-step approach of preconcentrating using membranes and finishing with an evaporator consumed less energy than evaporation alone but was more expensive because of high capital expenses of the membrane units.« less

Technical Performance and Economic Evaluation of Evaporative and Membrane-Based Concentration for Biomass-Derived Sugars

DOE PAGES

Sievers, David A.; Stickel, Jonathan J.; Grundl, Nicholas J.; ...

2017-09-18

Several conversion pathways of lignocellulosic biomass to advanced biofuels require or benefit from using concentrated sugar syrups of 600 g/L or greater. And while concentration may seem straightforward, thermal sugar degradation and energy efficiency remain major concerns. This study evaluated the trade-offs in product recovery, energy consumption, and economics between evaporative and membrane-based concentration methods. The degradation kinetics of xylose and glucose were characterized and applied to an evaporator process simulation. Though significant sugar loss was predicted for certain scenarios due to the Maillard reaction, industrially common falling-film plate evaporators offer short residence times (<5 min) and are expected tomore » limit sugar losses. Membrane concentration experiments characterized flux and sugar rejection, but diminished flux occurred at >100 g/L. A second step using evaporation is necessary to achieve target concentrations. Techno-economic process model simulations evaluated the overall economics of concentrating a 35 g/L sugar stream to 600 g/L in a full-scale biorefinery. A two-step approach of preconcentrating using membranes and finishing with an evaporator consumed less energy than evaporation alone but was more expensive because of high capital expenses of the membrane units.« less

Climate change reduces water availability for agriculture by decreasing non-evaporative irrigation losses

NASA Astrophysics Data System (ADS)

Malek, Keyvan; Adam, Jennifer C.; Stöckle, Claudio O.; Peters, R. Troy

2018-06-01

Irrigation efficiency plays an important role in agricultural productivity; it affects farm-scale water demand, and the partitioning of irrigation losses into evaporative and non-evaporative components. This partitioning determines return flow generation and thus affects water availability. Over the last two decades, hydrologic and agricultural research communities have significantly improved our understanding of the impacts of climate change on water availability and food productivity. However, the impacts of climate change on the efficiency of irrigation systems, particularly on the partitioning between evaporative and non-evaporative losses, have received little attention. In this study, we incorporated a process-based irrigation module into a coupled hydrologic/agricultural modeling framework (VIC-CropSyst). To understand how climate change may impact irrigation losses, we applied VIC-CropSyst over the Yakima River basin, an important agricultural region in Washington State, U.S. We compared the historical period of 1980-2010 to an ensemble of ten projections of climate for two future periods: 2030-2060 and 2060-2090. Results averaged over the watershed showed that a 9% increase in evaporative losses will be compensated by a reduction of non-evaporative losses. Therefore, overall changes in future efficiency are negligible (-0.4%) while the Evaporative Loss Ratio (ELR) (defined as the ratio of evaporative to non-evaporative irrigation losses) is enhanced by 10%. This higher ELR is associated with a reduction in return flows, thus negatively impacting downstream water availability. Results also indicate that the impact of climate change on irrigation losses depend on irrigation type and climate scenarios.

Artificial Intelligence Techniques for Predicting and Mapping Daily Pan Evaporation

NASA Astrophysics Data System (ADS)

Arunkumar, R.; Jothiprakash, V.; Sharma, Kirty

2017-09-01

In this study, Artificial Intelligence techniques such as Artificial Neural Network (ANN), Model Tree (MT) and Genetic Programming (GP) are used to develop daily pan evaporation time-series (TS) prediction and cause-effect (CE) mapping models. Ten years of observed daily meteorological data such as maximum temperature, minimum temperature, relative humidity, sunshine hours, dew point temperature and pan evaporation are used for developing the models. For each technique, several models are developed by changing the number of inputs and other model parameters. The performance of each model is evaluated using standard statistical measures such as Mean Square Error, Mean Absolute Error, Normalized Mean Square Error and correlation coefficient (R). The results showed that daily TS-GP (4) model predicted better with a correlation coefficient of 0.959 than other TS models. Among various CE models, CE-ANN (6-10-1) resulted better than MT and GP models with a correlation coefficient of 0.881. Because of the complex non-linear inter-relationship among various meteorological variables, CE mapping models could not achieve the performance of TS models. From this study, it was found that GP performs better for recognizing single pattern (time series modelling), whereas ANN is better for modelling multiple patterns (cause-effect modelling) in the data.

A simple model of chromospheric evaporation and condensation driven conductively in a solar flare

DOE Office of Scientific and Technical Information (OSTI.GOV)

Longcope, D. W.

2014-11-01

Magnetic energy released in the corona by solar flares reaches the chromosphere where it drives characteristic upflows and downflows known as evaporation and condensation. These flows are studied here for the case where energy is transported to the chromosphere by thermal conduction. An analytic model is used to develop relations by which the density and velocity of each flow can be predicted from coronal parameters including the flare's energy flux F. These relations are explored and refined using a series of numerical investigations in which the transition region (TR) is represented by a simplified density jump. The maximum evaporation velocity,more » for example, is well approximated by v{sub e} ≅ 0.38(F/ρ{sub co,} {sub 0}){sup 1/3}, where ρ{sub co,} {sub 0} is the mass density of the pre-flare corona. This and the other relations are found to fit simulations using more realistic models of the TR both performed in this work, and taken from a variety of previously published investigations. These relations offer a novel and efficient means of simulating coronal reconnection without neglecting entirely the effects of evaporation.« less

Externally Induced Evaporation of Young Stellar Disks: The Case for HST 10 in Orion's Trapezium.

NASA Astrophysics Data System (ADS)

Johnstone, D.; Hollenbach, D.; Storzer, H.; Bally, J.; Sutherland, R.

1996-12-01

The Trapezium region in Orion is composed of a few high-mass stars, responsible for the ionization of the surrounding gas, and a plethora of low-mass stars with disks. Observations at infrared, optical, and radio wavelengths have led to the discovery of extended ionized envelopes around many of the young low-mass stars requiring evaporation rates dot M ~ 10(-7) Modot/yr. In this poster we explain these observations through a model for the evaporation of disks around young low-mass stars by an external source of high energy photons. In particular, the externally produced ultraviolet continuum longward of the Lyman limit is used to heat the disk surface and produce a warm neutral flow. The model results in an offset ionization front, where the neutral flow encounters Lyman continuum radiation, and a mass-loss rate which is fixed due to the self-regulating nature of FUV heating. Applying this model to the Trapezium region evaporating objects, particularly HST 10, produces a satisfactory solution to both the mass-loss rate and the size of the ionized envelopes. The resulting short destruction times for these disks constrain the gestation period for planet embryos around stars in dense clusters.

Validating a new device for measuring tear evaporation rates.

PubMed

Rohit, Athira; Ehrmann, Klaus; Naduvilath, Thomas; Willcox, Mark; Stapleton, Fiona

2014-01-01

To calibrate and validate a commercially available dermatology instrument to measure tear evaporation rate of contact lens wearers. A dermatology instrument was modified by attaching a swim goggle cup such that the cup sealed around the eye socket. Results for the unmodified instrument are dependent on probe area and enclosed volume. Calibration curves were established using a model eye, to account for individual variations in chamber volume and exposed area. Fifteen participants were recruited and the study included a contact lens wear and a no contact lens wear stage. Day and diurnal variation of the measurements were assessed by taking the measurement three times a day over 2 days. The coefficient of repeatability of the measurement was calculated and a linear mixed model assessed the influence of humidity, temperature, contact lens wear, day and diurnal variations on tear evaporation rate. The associations between variables were assessed using Pearson correlation coefficient. Absolute evaporation rates with and without contact lens wear were calculated based on the new calibration. The measurements were most repeatable during the evening with no lens wear (COR = 49 g m⁻² h) and least repeatable during the evening with contact lens wear (COR = 93 g m⁻² h). Humidity (p = 0.007), and contact lens wear (p < 0.01), significantly affected the tear evaporation rate. However, temperature (p = 0.54) diurnal variation (p = 0.85) and different days (p = 0.65) had no significant effect after controlling for humidity. Tear evaporation rates can be measured using a modified dermatology instrument. Measurements were higher and more variable with lens wear consistent with previous literature. Control of environmental conditions is important as a higher humidity results in a reduced evaporation rate. © 2013 The Authors Ophthalmic & Physiological Optics © 2013 The College of Optometrists.

Entrainment and cloud evaporation deduced from the stable isotope chemistry of clouds during ORACLES

NASA Astrophysics Data System (ADS)

Noone, D.; Henze, D.; Rainwater, B.; Toohey, D. W.

2017-12-01

The magnitude of the influence of biomass burning aerosols on cloud and rain processes is controlled by a series of processes which are difficult to measure directly. A consequence of this limitation is the emergence of significant uncertainty in the representation of cloud-aerosol interactions in models and the resulting cloud radiative forcing. Interaction between cloud and the regional atmosphere causes evaporation, and the rate of evaporation at cloud top is controlled in part by entrainment of air from above which exposes saturated cloud air to drier conditions. Similarly, the size of cloud droplets also controls evaporation rates, which in turn is linked to the abundance of condensation nuclei. To quantify the dependence of cloud properties on biomass burning aerosols the dynamic relationship between evaporation, drop size and entrainment on aerosol state, is evaluated for stratiform clouds in the southeast Atlantic Ocean. These clouds are seasonally exposed to biomass burning plumes from agricultural fires in southern Africa. Measurements of the stable isotope ratios of cloud water and total water are used to deduce the disequilibrium responsible for evaporation within clouds. Disequilibrium is identified by the relationship between hydrogen and oxygen isotope ratios of water vapor and cloud water in and near clouds. To obtain the needed information, a custom-built, dual inlet system was deployed alongside isotopic gas analyzers on the NASA Orion aircraft as part of the Observations of Aerosols above Clouds and their Interactions (ORACLES) campaign. The sampling system obtains both total water and cloud liquid content for the population of droplets above 7 micrometer diameter. The thermodynamic modeling required to convert the observed equilibrium and kinetic isotopic is linked to evaporation and entrainment is described, and the performance of the measurement system is discussed.

Evaporation of impact water droplets in interception processes: Historical precedence of the hypothesis and a brief literature overview

NASA Astrophysics Data System (ADS)

Dunkerley, David L.

2009-10-01

SummaryIntra-storm evaporation depths exceed post-storm evaporation depths in the interception of rainfall on plant canopies. An important fraction of the intra-storm evaporation may involve the small impact (or splash) droplets produced when raindrops, and perhaps gravity drops (drips released from plant parts), collide with wet plant surfaces. This idea has been presented as a new conception by Murakami [Murakami, S., 2006. A proposal for a new forest canopy interception mechanism: splash droplet evaporation. Journal of Hydrology 319, 72-82; Murakami, S., 2007a. Application of three canopy interception models to a young stand of Japanese cypress and interpretation in terms of interception mechanism. Journal of Hydrology 342, 305-319; Murakami, S., 2007b. A follow-up for the splash droplet evaporation hypothesis of canopy interception and remaining problems: why is humidity unsaturated during rainfall? In: Proceedings of the 20th Annual Conference. Japan Society of Hydrology and Water Resources (in Japanese). < http://www.jstage.jst.go.jp/article/jshwr/20/0/20_62/_article>] but was in fact advanced by Dunin [Dunin, F.X., O'Loughlin, E.M., Reyenga, W., 1988. Interception loss from eucalypt forest: lysimeter determination of hourly rates for long term evaluation. Hydrological Processes 2, 315-329] more than 20 years ago. In addition, Dunin et al. considered that canopy ventilation might be enhanced in intense rain. This note draws attention to the historical precedence of the work of Dunin et al. and also presents a short review of literature on impact droplet production, highlighting areas where data are still required for the full exploration of the role of droplet evaporation in canopy interception. Droplet production needs to be properly parameterised and included in models of interception processes and landsurface-atmosphere interactions.

Evaporation of Lennard-Jones fluids.

PubMed

Cheng, Shengfeng; Lechman, Jeremy B; Plimpton, Steven J; Grest, Gary S

2011-06-14

Evaporation and condensation at a liquid/vapor interface are ubiquitous interphase mass and energy transfer phenomena that are still not well understood. We have carried out large scale molecular dynamics simulations of Lennard-Jones (LJ) fluids composed of monomers, dimers, or trimers to investigate these processes with molecular detail. For LJ monomers in contact with a vacuum, the evaporation rate is found to be very high with significant evaporative cooling and an accompanying density gradient in the liquid domain near the liquid/vapor interface. Increasing the chain length to just dimers significantly reduces the evaporation rate. We confirm that mechanical equilibrium plays a key role in determining the evaporation rate and the density and temperature profiles across the liquid/vapor interface. The velocity distributions of evaporated molecules and the evaporation and condensation coefficients are measured and compared to the predictions of an existing model based on kinetic theory of gases. Our results indicate that for both monatomic and polyatomic molecules, the evaporation and condensation coefficients are equal when systems are not far from equilibrium and smaller than one, and decrease with increasing temperature. For the same reduced temperature T/T(c), where T(c) is the critical temperature, these two coefficients are higher for LJ dimers and trimers than for monomers, in contrast to the traditional viewpoint that they are close to unity for monatomic molecules and decrease for polyatomic molecules. Furthermore, data for the two coefficients collapse onto a master curve when plotted against a translational length ratio between the liquid and vapor phase.

Advanced evaporator technology progress report FY 1992

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chamberlain, D.; Hutter, J.C.; Leonard, R.A.

1995-01-01

This report summarizes the work that was completed in FY 1992 on the program {open_quotes}Technology Development for Concentrating Process Streams.{close_quotes} The purpose of this program is to evaluate and develop evaporator technology for concentrating radioactive waste and product streams such as those generated by the TRUEX process. Concentrating these streams and minimizing the volume of waste generated can significantly reduce disposal costs; however, equipment to concentrate the streams and recycle the decontaminated condensates must be installed. LICON, Inc., is developing an evaporator that shows a great deal of potential for this application. In this report, concepts that need to bemore » incorporated into the design of an evaporator operated in a radioactive environment are discussed. These concepts include criticality safety, remote operation and maintenance, and materials of construction. Both solubility and vapor-liquid equilibrium data are needed to design an effective process for concentrating process streams. Therefore, literature surveys were completed and are summarized in this report. A model that is being developed to predict vapor phase compositions is described. A laboratory-scale evaporator was purchased and installed to study the evaporation process and to collect additional data. This unit is described in detail. Two new LICON evaporators are being designed for installation at Argonne-East in FY 1993 to process low-level radioactive waste generated throughout the laboratory. They will also provide operating data from a full-sized evaporator processing radioactive solutions. Details on these evaporators are included in this report.« less

An Evaporative Cooling Model for Teaching Applied Psychrometrics

ERIC Educational Resources Information Center

Johnson, Donald M.

2004-01-01

Evaporative cooling systems are commonly used in controlled environment plant and animal production. These cooling systems operate based on well defined psychrometric principles. However, students often experience considerable difficulty in learning these principles when they are taught in an abstract, verbal manner. This article describes an…

Investigating the source, transport, and isotope composition of water vapor in the planetary boundary layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Griffis, Timothy J.; Wood, Jeffrey D.; Baker, John M.

Increasing atmospheric humidity and convective precipitation over land provide evidence of intensification of the hydrologic cycle – an expected response to surface warming. The extent to which terrestrial ecosystems modulate these hydrologic factors is important to understand feedbacks in the climate system. We measured the oxygen and hydrogen isotope composition of water vapor at a very tall tower (185 m) in the upper Midwest, United States, to diagnose the sources, transport, and fractionation of water vapor in the planetary boundary layer (PBL) over a 3-year period (2010 to 2012). These measurements represent the first set of annual water vapor isotopemore » observations for this region. Several simple isotope models and cross-wavelet analyses were used to assess the importance of the Rayleigh distillation process, evaporation, and PBL entrainment processes on the isotope composition of water vapor. The vapor isotope composition at this tall tower site showed a large seasonal amplitude (mean monthly δ 18O v ranged from –40.2 to –15.9 ‰ and δ 2H v ranged from –278.7 to –113.0 ‰) and followed the familiar Rayleigh distillation relation with water vapor mixing ratio when considering the entire hourly data set. However, this relation was strongly modulated by evaporation and PBL entrainment processes at timescales ranging from hours to several days. The wavelet coherence spectra indicate that the oxygen isotope ratio and the deuterium excess ( d v) of water vapor are sensitive to synoptic and PBL processes. According to the phase of the coherence analyses, we show that evaporation often leads changes in d v, confirming that it is a potential tracer of regional evaporation. Isotope mixing models indicate that on average about 31 % of the growing season PBL water vapor is derived from regional evaporation. However, isoforcing calculations and mixing model analyses for high PBL water vapor mixing ratio events ( > 25 mmol mol –1) indicate that regional evaporation can account for 40 to 60 % of the PBL water vapor. These estimates are in relatively good agreement with that derived from numerical weather model simulations. This relatively large fraction of evaporation-derived water vapor implies that evaporation has an important impact on the precipitation recycling ratio within the region. In conclusion, based on multiple constraints, we estimate that the summer season recycling fraction is about 30 %, indicating a potentially important link with convective precipitation.« less

Investigating the source, transport, and isotope composition of water vapor in the planetary boundary layer

DOE PAGES

Griffis, Timothy J.; Wood, Jeffrey D.; Baker, John M.; ...

2016-04-25

Increasing atmospheric humidity and convective precipitation over land provide evidence of intensification of the hydrologic cycle – an expected response to surface warming. The extent to which terrestrial ecosystems modulate these hydrologic factors is important to understand feedbacks in the climate system. We measured the oxygen and hydrogen isotope composition of water vapor at a very tall tower (185 m) in the upper Midwest, United States, to diagnose the sources, transport, and fractionation of water vapor in the planetary boundary layer (PBL) over a 3-year period (2010 to 2012). These measurements represent the first set of annual water vapor isotopemore » observations for this region. Several simple isotope models and cross-wavelet analyses were used to assess the importance of the Rayleigh distillation process, evaporation, and PBL entrainment processes on the isotope composition of water vapor. The vapor isotope composition at this tall tower site showed a large seasonal amplitude (mean monthly δ 18O v ranged from –40.2 to –15.9 ‰ and δ 2H v ranged from –278.7 to –113.0 ‰) and followed the familiar Rayleigh distillation relation with water vapor mixing ratio when considering the entire hourly data set. However, this relation was strongly modulated by evaporation and PBL entrainment processes at timescales ranging from hours to several days. The wavelet coherence spectra indicate that the oxygen isotope ratio and the deuterium excess ( d v) of water vapor are sensitive to synoptic and PBL processes. According to the phase of the coherence analyses, we show that evaporation often leads changes in d v, confirming that it is a potential tracer of regional evaporation. Isotope mixing models indicate that on average about 31 % of the growing season PBL water vapor is derived from regional evaporation. However, isoforcing calculations and mixing model analyses for high PBL water vapor mixing ratio events ( > 25 mmol mol –1) indicate that regional evaporation can account for 40 to 60 % of the PBL water vapor. These estimates are in relatively good agreement with that derived from numerical weather model simulations. This relatively large fraction of evaporation-derived water vapor implies that evaporation has an important impact on the precipitation recycling ratio within the region. In conclusion, based on multiple constraints, we estimate that the summer season recycling fraction is about 30 %, indicating a potentially important link with convective precipitation.« less

Chaos in matrix models and black hole evaporation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berkowitz, Evan; Hanada, Masanori; Maltz, Jonathan

Is the evaporation of a black hole described by a unitary theory? In order to shed light on this question—especially aspects of this question such as a black hole’s negative specific heat—we consider the real-time dynamics of a solitonic object in matrix quantum mechanics, which can be interpreted as a black hole (black zero-brane) via holography. We point out that the chaotic nature of the system combined with the flat directions of its potential naturally leads to the emission of D0-branes from the black brane, which is suppressed in the large N limit. Simple arguments show that the black zero-brane,more » like the Schwarzschild black hole, has negative specific heat, in the sense that the temperature goes up when it evaporates by emitting D0-branes. While the largest Lyapunov exponent grows during the evaporation, the Kolmogorov-Sinai entropy decreases. These are consequences of the generic properties of matrix models and gauge theory. Based on these results, we give a possible geometric interpretation of the eigenvalue distribution of matrices in terms of gravity. Applying the same argument in the M-theory parameter region, we provide a scenario to derive the Hawking radiation of massless particles from the Schwarzschild black hole. In conclusion, we suggest that by adding a fraction of the quantum effects to the classical theory, we can obtain a matrix model whose classical time evolution mimics the entire life of the black brane, from its formation to the evaporation.« less

Chaos in matrix models and black hole evaporation

DOE PAGES

Berkowitz, Evan; Hanada, Masanori; Maltz, Jonathan

2016-12-19

Is the evaporation of a black hole described by a unitary theory? In order to shed light on this question—especially aspects of this question such as a black hole’s negative specific heat—we consider the real-time dynamics of a solitonic object in matrix quantum mechanics, which can be interpreted as a black hole (black zero-brane) via holography. We point out that the chaotic nature of the system combined with the flat directions of its potential naturally leads to the emission of D0-branes from the black brane, which is suppressed in the large N limit. Simple arguments show that the black zero-brane,more » like the Schwarzschild black hole, has negative specific heat, in the sense that the temperature goes up when it evaporates by emitting D0-branes. While the largest Lyapunov exponent grows during the evaporation, the Kolmogorov-Sinai entropy decreases. These are consequences of the generic properties of matrix models and gauge theory. Based on these results, we give a possible geometric interpretation of the eigenvalue distribution of matrices in terms of gravity. Applying the same argument in the M-theory parameter region, we provide a scenario to derive the Hawking radiation of massless particles from the Schwarzschild black hole. In conclusion, we suggest that by adding a fraction of the quantum effects to the classical theory, we can obtain a matrix model whose classical time evolution mimics the entire life of the black brane, from its formation to the evaporation.« less

What determines transitions between energy- and moisture-limited evaporative regimes?

NASA Astrophysics Data System (ADS)

Haghighi, E.; Gianotti, D.; Akbar, R.; Salvucci, G.; Entekhabi, D.

2017-12-01

The relationship between evaporative fraction (EF) and soil moisture (SM) has traditionally been used in atmospheric and land-surface modeling communities to determine the strength of land-atmosphere coupling in the context of the dominant evaporative regime (energy- or moisture-limited). However, recent field observations reveal that EF-SM relationship is not unique and could vary substantially with surface and/or meteorological conditions. This implies that conventional EF-SM relationships (exclusive of surface and meteorological conditions) are embedded in more complex dependencies and that in fact it is a multi-dimensional function. To fill the fundamental knowledge gaps on the important role of varying surface and meteorological conditions not accounted for by the traditional evaporative regime conceptualization, we propose a generalized EF framework using a mechanistic pore-scale model for evaporation and energy partitioning over drying soil surfaces. Nonlinear interactions among the components of the surface energy balance are reflected in a critical SM that marks the onset of transition between energy- and moisture-limited evaporative regimes. The new generalized EF framework enables physically based estimates of the critical SM, and provides new insights into the origin of land surface EF partitioning linked to meteorological input data and the evolution of land surface temperature during surface drying that affect the relative efficiency of surface energy balance components. Our results offer new opportunities to advance predictive capabilities quantifying land-atmosphere coupling for a wide range of present and projected meteorological input data.

Analysis of plasma-controlled laser evaporation of Al target in vacuum

NASA Astrophysics Data System (ADS)

Mazhukin, Vladimir I.; Nossov, Vadim V.; Smurov, Igor Y.

2004-04-01

The plasma-controlled evaporation of the Al target induced by the laser pulse with intensity of 8 x 108 W/cm2 and wavelength of 1.06 μm is analyzed with account for the two-dimensional effects. The self consistent model is applied, consisting of the heat transfer equation in condensed medium, the system of radiation gas dynamics in evaporated substance, and the Knudsen layer model at the two media boundary. It is established that the phase transition of the target surface is controlled by the two factors: the surface temperature that depends on the transmitted radiation intensity and the plasma pressure, governed by the expansion regime. The process comes through three characteristics stages -- the sonic evaporation at the beginning, the condensation during the period of plasma formation and initial expansion and, finally, the recommence of evaporation in subsonic regime after the partial brightening of the plasma. During the subsonic evaporation stage the vapor flow and the mass removal rate is much higher near the beam boundaries than in the center due to smaller plasma counter-pressure. The vapor plasma pattern is characterized by the dense hot zone near the surface where the deposition of laser energy occurs, and rapid decrease of density outside the zone due to three-dimensional expansion. The application of the laser beam of smaller radius at the same intensity leads to the formation of more rarefied and more transparent plasma, that allows to improve the mass removal efficiency.

Marangoni Effect on the Shape of Freely Receding Evaporating Sessile Droplets of Perfectly Wetting Liquids

NASA Astrophysics Data System (ADS)

Tsoumpas, Yannis; Dehaeck, Sam; Rednikov, Alexey; Colinet, Pierre

2014-11-01

Freely receding evaporating sessile droplets of perfectly wetting liquids (HFE-7100, 7200 and 7500), with small finite contact angles induced by evaporation, are studied with a Mach-Zehnder interferometer. Surprisingly, the experimentally obtained profiles turn out to deviate from the classical macroscopic static shape of a sessile droplet (as determined by gravity and capillarity), often used when modeling evaporating droplets. These deviations can be seen in two ways. Namely, either the droplet appears to be inflated as compared to the classical static shape assuming the same contact angle and contact radius, or the apparent contact angle appears lower than the classical static one assuming the same volume and contact radius. In reality, the experimental profiles exhibit a local decrease of the slope near the contact line, which we attribute to the Marangoni effect in an evaporating sessile droplet. In this case, the radially inward (along the liquid-air interface) direction of the flow delivers more liquid to the center of the droplet making it appear inflated. When the Marangoni effect is weak, as in the case of the poorly volatile HFE-7500, no significant influence is noticed on the drop shape. The experimental results are compared with the predictions of a lubrication-type theoretical model that incorporates the evaporation-induced Marangoni flow. Financial support of FP7 Marie Curie MULTIFLOW Network (PITN-GA-2008-214919), ESA/BELSPO-PRODEX, BELSPO- μMAST (IAP 7/38) & FRS-FNRS is gratefully acknowledged.

Chemical and isotopic fractionations by evaporation and their cosmochemical implications

NASA Astrophysics Data System (ADS)

Ozawa, Kazuhito; Nagahara, Hiroko

2001-07-01

A kinetic model for evaporation of a multi-component condensed phase with a fixed rate constant of the reaction is developed. A binary system with two isotopes for one of the components undergoing simple thermal histories (e.g., isothermal heating) is investigated in order to evaluate the extent of isotopic and chemical fractionations during evaporation. Diffusion in the condensed phase and the effect of back reaction from ambient gas are taken into consideration. Chemical and isotopic fractionation factors and the Péclet number for evaporation are the three main parameters that control the fractionation. Dust enrichment factor (η), the ratio of the initial dust quantity to that required for attainment of gas-dust equilibrium, is critical when back reactions become significant. Dust does not reach equilibrium with gas at η < 1. Notable chemical and isotopic fractionations usually take place under these conditions. There are two circumstances in which isotopic fractionation of a very volatile element does not accompany chemical fractionation during isothermal heating. One is free evaporation when diffusion in the condensed phase is very slow (η = 0), and the other is evaporation in the presence of ambient gas (η > 0). In the former case, a quasi-steady state in the diffusion boundary layer is maintained for isotopic fractionation but not for chemical fractionation. In the latter case, the back reaction brings the strong isotopic fractionation generated in the earlier stage of evaporation back to a negligibly small value in the later stage before complete evaporation. The model results are applied to cosmochemical fractionation of volatile elements during evaporation from a condensed phase that can be regarded as a binary solution phase. The wide range of potassium depletion without isotopic fractionation in various types of chondrules (Alexander et al., 2000) is explained by instantaneous heating followed by cooling in a closed system with various degrees of dust enrichment (η = 0.001-10) and cooling rates of less than ˜5°C/min. The extent of decoupling between isotopic and chemical fractionations of various elements in chondrules and matrix minerals may constrain the time scale and the conditions of heating and cooling processes in the early solar nebula.

Seasonal groundwater contribution to crop-water use assessed with lysimeter observations and model simulations

USGS Publications Warehouse

Luo, Y.; Sophocleous, M.

2010-01-01

Groundwater evaporation can play an important role in crop-water use where the water table is shallow. Lysimeters are often used to quantify the groundwater evaporation contribution influenced by a broad range of environmental factors. However, it is difficult for such field facilities, which are operated under limited conditions within limited time, to capture the whole spectrum of capillary upflow with regard to the inter-seasonal variability of climate, especially rainfall. Therefore, in this work, the method of combining lysimeter and numerical experiments was implemented to investigate seasonal groundwater contribution to crop-water use. Groundwater evaporation experiments were conducted through a weighing lysimeter at an agricultural experiment station located within an irrigation district in the lower Yellow River Basin for two winter wheat growth seasons. A HYDRUS-1D model was first calibrated and validated with weighing lysimeter data, and then was employed to perform scenario simulations of groundwater evaporation under different depths to water table (DTW) and water input (rainfall plus irrigation) driven by long term meteorological data. The scenario simulations revealed that the seasonally averaged groundwater evaporation amount was linearly correlated to water input for different values of DTW. The linear regression could explain more than 70% of the variability. The seasonally averaged ratio of the groundwater contribution to crop-water use varied with the seasonal water input and DTW. The ratio reached as high as 75% in the case of DTW=1.0. m and no irrigation, and as low as 3% in the case of DTW=3.0. m and three irrigation applications. The results also revealed that the ratio of seasonal groundwater evaporation to potential evapotranspiration could be fitted to an exponential function of the DTW that may be applied to estimate seasonal groundwater evaporation. In this case study of multilayered soil profile, the depth at which groundwater may evaporate at potential rate was 0.60-0.65. m, and the extinction depth of groundwater evaporation was approximately 3.8. m. ?? 2010 Elsevier B.V.

Modeling of turbulence effects on the heat and mass transfer of evaporating sprays

NASA Astrophysics Data System (ADS)

Madhanabharatam, Balasubramanyam

A large diversity of two-phase gas-liquid flows of both scientific and practical interest involves the evaporation of near spherical liquid droplets in high temperature turbulent environments. Current numerical modeling approaches are predominantly focused towards the effects of continuous phase (gas phase) turbulence on the evaporation rates of liquid fuel sprays during the evaporation process, failing to account for the inherent turbulence present in the dispersed phase (liquid phase), due to the injection of sprays at high velocities. Existing models accounting for internal turbulence effects use Direct Numerical Simulations and Large Eddy Simulations that are computationally intensive. This research provides an alternative phenomenological approach of modeling droplet internal turbulence effects through the mass and heat transfer between the droplet surface and the external gas phase within a thin film inside the droplet. This finite conductivity (F-C) model was based on the two-temperature film theory, where the turbulence characteristics of the droplet are used to estimate the effective thermal diffusivity (alphaeff) within the droplet phase. The alphaeff is estimated from the physical properties of the flow within the droplet rather than from a 'curve-fit' as done conventionally. The results of the one-way coupled study indicated that the equilibrium drop temperature predictions were higher than calculations by the infinite conductivity (I-C) model. The liquid internal turbulence has a considerable effect on the diffusivity in the primary atomization regime. The thermal boundary layer was found to be substantially thick initially, decreasing quickly to a small value, exhibiting a reasonable physical trend. The two-way coupled studies (CFD) indicated that the F-C model, slowed down the evaporation process, produced larger droplets and longer tip penetration lengths during the initial stages of injection. For a jet in a supersonic cross-flow, results indicated that jet penetration increased rapidly in the vicinity of the injector exit and then gradually increased due to increase in the drag of the air stream. A modified drag coefficient was incorporated to improve model accuracy in predictions. Overall the results obtained from the numerical calculations during this study were reasonably comparable to measured data and showed more accurate comparisons to that of the I-C model.

Development and Analysis of Desiccant Enhanced Evaporative Air Conditioner Prototype

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kozubal, E.; Woods, J.; Judkoff, R.

2012-04-01

This report documents the design of a desiccant enhanced evaporative air conditioner (DEVAP AC) prototype and the testing to prove its performance. Previous numerical modeling and building energy simulations indicate a DEVAP AC can save significant energy compared to a conventional vapor compression AC (Kozubal et al. 2011). The purposes of this research were to build DEVAP prototypes, test them to validate the numerical model, and identify potential commercialization barriers.

Mathematical modeling of processes of heat and mass transfer in channels of water evaporating coolers

NASA Astrophysics Data System (ADS)

Gulevsky, V. A.; Ryazantsev, A. A.; Nikulichev, A. A.; Menzhulova, A. S.

2018-05-01

The variety of cooling systems is dictated by a wide range of demands placed on them. This is the price, operating costs, quality of work, ecological safety, etc. These requirements in a positive sense are put into correspondence by water evaporating plate coolers. Currently, their widespread use is limited by a lack of theoretical base. To solve this problem, the best method is mathematical modeling.

Comparison of Steady State Evaporation Models for Toxic Chemical Spills: Development of a New Evaporation Model

DTIC Science & Technology

1989-11-29

for diffusivity based on theory : DVab- 0.002e6 703/2 eS/s(bPM11 t/ ,cm/s (28) ab ab 1) where DV-b a molecular diffusion coefflcient of chemical a In...24 Ugt W m -K (48)S[(/hg) + (1/h)] m- K- where ha is the coefficient of heat conduction through the ground, and hl is the liquid heat transfer

A Kolmogorov-Brutsaert structure function model for evaporation into a turbulent atmosphere

NASA Astrophysics Data System (ADS)

Katul, Gabriel; Liu, Heping

2017-05-01

In 1965, Brutsaert proposed a model that predicted mean evaporation rate E¯ from rough surfaces to scale with the 3/4 power law of the friction velocity (u∗) and the square-root of molecular diffusivity (Dm) for water vapor. In arriving at these results, a number of assumptions were made regarding the surface renewal rate describing the contact durations between eddies and the evaporating surface, the diffusional mass process from the surface into eddies, and the cascade of turbulent kinetic energy sustaining the eddy renewal process itself. The working hypothesis explored here is that E¯˜Dmu∗3/4 is a direct outcome of the Kolmogorov scaling for inertial subrange eddies modified to include viscous cutoff thereby bypassing the need for a surface renewal assumption. It is demonstrated that Brutsaert's model for E¯ may be more general than its original derivation implied.

Charge loss (or the lack thereof) for AdS black holes

NASA Astrophysics Data System (ADS)

Ong, Yen Chin; Chen, Pisin

2014-06-01

The evolution of evaporating charged black holes is complicated to model in general, but is nevertheless important since the hints to the Information Loss Paradox and its recent firewall incarnation may lie in understanding more generic geometries than that of Schwarzschild spacetime. Fortunately, for sufficiently large asymptotically flat Reissner-Nordström black holes, the evaporation process can be modeled via a system of coupled linear ordinary differential equations, with charge loss rate governed by Schwinger pair-production process. The same model can be generalized to study the evaporation of AdS Reissner-Nordström black holes with flat horizon. It was recently found that such black holes always evolve towards extremality since charge loss is inefficient. This property is completely opposite to the asymptotically flat case in which the black hole eventually loses its charges and tends towards Schwarzschild limit. We clarify the underlying reason for this different behavior.

Reconciling Isotopic Partitioning Estimates of Moisture Fluxes in Semi-arid Landscapes Through a New Modeling Approach for Evaporation

NASA Astrophysics Data System (ADS)

Kaushik, A.; Berkelhammer, M. B.; O'Neill, M.; Noone, D.

2017-12-01

The partitioning of land surface latent heat flux into evaporation and transpiration remains a challenging problem despite a basic understanding of the underlying mechanisms. Water isotopes are useful tracers for separating evaporation and transpiration contributions because E and T have distinct isotopic ratios. Here we use the isotope-based partitioning method at a semi-arid grassland tall-tower site in Colorado. Our results suggest that under certain conditions evaporation cannot be isotopically distinguished from transpiration without modification of existing partitioning techniques. Over a 4-year period, we measured profiles of stable oxygen and hydrogen isotope ratios of water vapor from the surface to 300 m and soil water down to 1 m along with standard meteorological fluxes. Using these data, we evaluated the contributions of rainfall, equilibration, surface water vapor exchange and sub-surface vapor diffusion to the isotopic composition of evapotranspiration (ET). Applying the standard isotopic approach to find the transpiration portion of ET (i.e., T/ET), we see a significant discrepancy compared with a method to constrain T/ET based on gross primary productivity (GPP). By evaluating the kinetic fractionation associated with soil evaporation and vapor diffusion we find that a significant proportion (58-84%) of evaporation following precipitation is non-fractionating. This is possible when water from isolated soil layers is being nearly completely evaporated. Non-fractionating evaporation looks isotopically like transpiration and therefore leads to an overestimation of T/ET. Including non-fractionating evaporation reconciles the isotope-based partitioning estimates of T/ET with the GPP method, and may explain the overestimation of T/ET from isotopes compared to other methods. Finally, we examine the application of non-fractionating evaporation to other boundary layer moisture flux processes such as rain evaporation, where complete evaporation of smaller drop pools may produce a similarly weaker kinetic effect.

The impact of precipitation evaporation on the atmospheric aerosol distribution in EC-Earth v3.2.0

NASA Astrophysics Data System (ADS)

de Bruine, Marco; Krol, Maarten; van Noije, Twan; Le Sager, Philippe; Röckmann, Thomas

2018-04-01

The representation of aerosol-cloud interaction in global climate models (GCMs) remains a large source of uncertainty in climate projections. Due to its complexity, precipitation evaporation is either ignored or taken into account in a simplified manner in GCMs. This research explores various ways to treat aerosol resuspension and determines the possible impact of precipitation evaporation and subsequent aerosol resuspension on global aerosol burdens and distribution. The representation of aerosol wet deposition by large-scale precipitation in the EC-Earth model has been improved by utilising additional precipitation-related 3-D fields from the dynamical core, the Integrated Forecasting System (IFS) general circulation model, in the chemistry and aerosol module Tracer Model, version 5 (TM5). A simple approach of scaling aerosol release with evaporated precipitation fraction leads to an increase in the global aerosol burden (+7.8 to +15 % for different aerosol species). However, when taking into account the different sizes and evaporation rate of raindrops following Gong et al. (2006), the release of aerosols is strongly reduced, and the total aerosol burden decreases by -3.0 to -8.5 %. Moreover, inclusion of cloud processing based on observations by Mitra et al. (1992) transforms scavenged small aerosol to coarse particles, which enhances removal by sedimentation and hence leads to a -10 to -11 % lower aerosol burden. Finally, when these two effects are combined, the global aerosol burden decreases by -11 to -19 %. Compared to the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite observations, aerosol optical depth (AOD) is generally underestimated in most parts of the world in all configurations of the TM5 model and although the representation is now physically more realistic, global AOD shows no large improvements in spatial patterns. Similarly, the agreement of the vertical profile with Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) satellite measurements does not improve significantly. We show, however, that aerosol resuspension has a considerable impact on the modelled aerosol distribution and needs to be taken into account.

Numerical investigation of spray ignition of a multi-component fuel surrogate

NASA Astrophysics Data System (ADS)

Backer, Lara; Narayanaswamy, Krithika; Pepiot, Perrine

2014-11-01

Simulating turbulent spray ignition, an important process in engine combustion, is challenging, since it combines the complexity of multi-scale, multiphase turbulent flow modeling with the need for an accurate description of chemical kinetics. In this work, we use direct numerical simulation to investigate the role of the evaporation model on the ignition characteristics of a multi-component fuel surrogate, injected as droplets in a turbulent environment. The fuel is represented as a mixture of several components, each one being representative of a different chemical class. A reduced kinetic scheme for the mixture is extracted from a well-validated detailed chemical mechanism, and integrated into the multiphase turbulent reactive flow solver NGA. Comparisons are made between a single-component evaporation model, in which the evaporating gas has the same composition as the liquid droplet, and a multi-component model, where component segregation does occur. In particular, the corresponding production of radical species, which are characteristic of the ignition of individual fuel components, is thoroughly analyzed.

Atmospheric Entry Heating of Micrometeorites Revisited: Higher Temperatures and Potential Biases

NASA Technical Reports Server (NTRS)

Love, S.; Alexander, C. M. OD.

2001-01-01

The atmospheric entry heating model of Love and Brownlee appears to have overestimated evaporation rates by as much as two orders of magnitude. Here we revisit the issue of atmospheric entry heating, using a revised prescription for evaporation rates. Additional information is contained in the original extended abstract.

Global sensitivity analysis of a local water balance model predicting evaporation, water yield and drought

NASA Astrophysics Data System (ADS)

Speich, Matthias; Zappa, Massimiliano; Lischke, Heike

2017-04-01

Evaporation and transpiration affect both catchment water yield and the growing conditions for vegetation. They are driven by climate, but also depend on vegetation, soil and land surface properties. In hydrological and land surface models, these properties may be included as constant parameters, or as state variables. Often, little is known about the effect of these variables on model outputs. In the present study, the effect of surface properties on evaporation was assessed in a global sensitivity analysis. To this effect, we developed a simple local water balance model combining state-of-the-art process formulations for evaporation, transpiration and soil water balance. The model is vertically one-dimensional, and the relative simplicity of its process formulations makes it suitable for integration in a spatially distributed model at regional scale. The main model outputs are annual total evaporation (TE, i.e. the sum of transpiration, soil evaporation and interception), and a drought index (DI), which is based on the ratio of actual and potential transpiration. This index represents the growing conditions for forest trees. The sensitivity analysis was conducted in two steps. First, a screening analysis was applied to identify unimportant parameters out of an initial set of 19 parameters. In a second step, a statistical meta-model was applied to a sample of 800 model runs, in which the values of the important parameters were varied. Parameter effect and interactions were analyzed with effects plots. The model was driven with forcing data from ten meteorological stations in Switzerland, representing a wide range of precipitation regimes across a strong temperature gradient. Of the 19 original parameters, eight were identified as important in the screening analysis. Both steps highlighted the importance of Plant Available Water Capacity (AWC) and Leaf Area Index (LAI). However, their effect varies greatly across stations. For example, while a transition from a sparse to a closed forest canopy has almost no effect on annual TE at warm and dry sites, it increases TE by up to 100 mm/year at cold-humid and warm-humid sites. Further parameters of importance describe infiltration, as well as canopy resistance and its response to environmental variables. This study offers insights for future development of hydrological and ecohydrological models. First, it shows that although local water balance is primarily controlled by climate, the vegetation and soil parameters may have a large impact on the outputs. Second, it indicates that modeling studies should prioritize a realistic parameterization of LAI and AWC, while other parameters may be set to fixed values. Third, it illustrates to which extent parameter effect and interactions depend on local climate.

Playa Soil Moisture and Evaporation Dynamics During the MATERHORN Field Program

NASA Astrophysics Data System (ADS)

Hang, Chaoxun; Nadeau, Daniel F.; Jensen, Derek D.; Hoch, Sebastian W.; Pardyjak, Eric R.

2016-06-01

We present an analysis of field data collected over a desert playa in western Utah, USA in May 2013, the most synoptically active month of the year, as part of the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) program. The results show that decreasing surface albedo, decreasing Bowen ratio and increasing net radiation with increasing soil moisture sustained a powerful positive feedback mechanism promoting large evaporation rates immediately following rain events. Additionally, it was found that, while nocturnal evaporation was negligible during dry periods, it was quite significant (up to 30 % of the daily cumulative flux) during nights following rain events. Our results further show that the highest spatial variability in surface soil moisture is found under dry conditions. Finally, we report strong spatial heterogeneities in evaporation rates following a rain event. The cumulative evaporation for the different sampling sites over a five-day period varied from ≈ 0.1 to ≈ 6.6 mm. Overall, this study allows us to better understand the mechanisms underlying soil moisture dynamics of desert playas as well as evaporation following occasional rain events.

Quantification of climatic feedbacks on the Caspian Sea level variability and impacts from the Caspian Sea on the large-scale atmospheric circulation

NASA Astrophysics Data System (ADS)

Arpe, Klaus; Tsuang, Ben-Jei; Tseng, Yu-Heng; Liu, Xin-Yu; Leroy, Suzanne A. G.

2018-05-01

With a fall of the Caspian Sea level (CSL), its size gets smaller and therefore the total evaporation over the sea is reduced. With a reduced evaporation from the sea, the fall of the CSL is weakened. This creates a negative feedback as less evaporation leads to less water losses of the Caspian Sea (CS). On the other hand, less evaporation reduces the water in the atmosphere, which may lead to less precipitation in the catchment area of the CS. The two opposite feedbacks are estimated by using an atmospheric climate model coupled with an ocean model only for the CS with different CS sizes while keeping all other forcings like oceanic sea surface temperatures (SSTs) and leaf area index the same from a global climate simulation. The investigation is concentrated on the medieval period because at that time the CSL changed dramatically from about - 30 to - 19 m below the mean ocean sea level, partly man-made. Models used for simulating the last millennium are not able to change the size of the CS dynamically so far. When results from such simulations are used to investigate the CSL variability and its causes, the present study should help to parameterize its feedbacks. A first assumption that the total evaporation from the CS will vary with the size of the CS (number of grid points representing the sea) is generally confirmed with the model simulations. The decrease of grid points from 15 to 14, 10, 8 or 7 leads to a decrease of evaporation to 96, 77, 70 and 54%. The lower decrease than initially expected from the number of grid points (93, 67, 53 and 47%) is probably due to the fact that there would also be some evaporation at grid points that run dry with a lower CSL but a cooling of the CS SST with increasing CS size in summer may be more important. The reduction of evaporation over the CS means more water for the budget of the whole catchment of the CS (an increase of the CSL) but from the gain through reduced evaporation over the CS, only 70% is found to remain in the water budget of the whole catchment area due to feedbacks with the precipitation. This suggests a high proportion of recycling of water within the CS catchment area. When using a model which does not have a correct CS size, the effect of a reduced CS area on the water budget for the whole CS catchment can be estimated by taking the evaporation over the sea multiplied by the proportional changed area. However, only 50% of that change is ending up in the water balance of the total catchment of the CS. A formula is provided. This method has been applied to estimate the CSL during the Last Glacial Maximum to be at - 30 to - 33 m. The experiments show as well that the CS has an impact on the large-scale atmospheric circulation with a widened Aleutian 500 hPa height field trough with increasing CS sizes. It is possible to validate this aspect with observational data.

Effects of water vapor density on cutaneous resistance to evaporative water loss and body temperature in green tree frogs (Hyla cinerea).

PubMed

Wygoda, Mark L; Kersten, Constance A

2013-01-01

Increased cutaneous resistance to evaporative water loss (Rc) in tree frogs results in decreased water loss rate and increased body temperature. We examined sensitivity of Rc to water vapor density (WVD) in Hyla cinerea by exposing individual frogs and agar models to four different WVD environments and measuring cutaneous evaporative water loss rate and body temperature simultaneously using a gravimetric wind tunnel measuring system. We found that water loss rate varied inversely and body temperature directly with WVD but that models were affected to a greater extent than were animals. Mean Rc was significantly different between the highest WVD environment and each of the three drier environments but did not differ among the drier environments, indicating that Rc initially increases and then reaches a plateau in response to decreasing WVD. Rc was equivalent when calculated using either WVD difference or WVD deficit as the driving force for evaporation. We also directly observed secretions from cutaneous glands while measuring body temperature and tested secretions and skin samples for the presence of lipids. We found that irregular transient body temperature depressions observed during wind tunnel trials occur due to evaporative cooling from intermittent skin secretions containing lipids, although we were unable to identify lipid-secreting glands.

Insights into Evaporative Droplet Dynamics in the High-Wind Atmospheric Boundary Layer

NASA Astrophysics Data System (ADS)

Peng, T.; Richter, D. H.

2017-12-01

Sea-spray droplets ejected into the air-sea boundary layer take part in a series of complex transport processes. To model the air-sea exchange of heat and moisture under high-wind conditions, it is important yet challenging to understand influences of evaporative droplets in the atmospheric boundary layer. We implement a high-resolution Eulerian-Lagrangian algorithm with droplets laden in a turbulent open-channel flow to reveal the dynamic and thermodynamic characteristics of evaporating sea spray. Our past numerical simulations demonstrated an overall weak modification to the total heat flux by evaporative droplets. This is due to redistributed sensible and latent heat fluxes from relatively small droplets that respond rapidly to the ambient environment or the limited residence time of larger droplets. However, droplets with a slower thermodynamic response to the environment indicate a potential to enhance the total heat flux, but this is dependent on concentration and suspension time. In the current study, we focus on correlations between the residence time and thermodynamic statistics of droplets in order to better understand how best to parameterize in large-scale models. In addition, we focus in detail on the different scales of turbulence to further characterize the range of influence that evaporating droplets have on the surrounding fluid.

Dynamics of Water Absorption and Evaporation During Methanol Droplet Combustion in Microgravity

NASA Technical Reports Server (NTRS)

Hicks, Michael C.; Dietrich, Daniel L.; Nayagam, Vedha; Williams, Forman A.

2012-01-01

The combustion of methanol droplets is profoundly influenced by the absorption and evaporation of water, generated in the gas phase as a part of the combustion products. Initially there is a water-absorption period of combustion during which the latent heat of condensation of water vapor, released into the droplet, enhances its burning rate, whereas later there is a water-evaporation period, during which the water vapor reduces the flame temperature suffciently to extinguish the flame. Recent methanol droplet-combustion experiments in ambient environments diluted with carbon dioxide, conducted in the Combustion Integrated Rack on the International Space Station (ISS), as a part of the FLEX project, provided a method to delineate the water-absorption period from the water-evaporation period using video images of flame intensity. These were obtained using an ultra-violet camera that captures the OH* radical emission at 310 nm wavelength and a color camera that captures visible flame emission. These results are compared with results of ground-based tests in the Zero Gravity Facility at the NASA Glenn Research Center which employed smaller droplets in argon-diluted environments. A simplified theoretical model developed earlier correlates the transition time at which water absorption ends and evaporation starts. The model results are shown to agree reasonably well with experiment.

Estimating net rainfall, evaporation and water storage of a bare soil from sequential L-band emissivities

NASA Technical Reports Server (NTRS)

Stroosnijder, L.; Lascano, R. J.; Newton, R. W.; Vanbavel, C. H. M.

1984-01-01

A general method to use a time series of L-band emissivities as an input to a hydrological model for continuously monitoring the net rainfall and evaporation as well as the water content over the entire soil profile is proposed. The model requires a sufficiently accurate and general relation between soil emissivity and surface moisture content. A model which requires the soil hydraulic properties as an additional input, but does not need any weather data was developed. The method is shown to be numerically consistent.

The GEWEX LandFlux project: Evaluation of model evaporation using tower-based and globally gridded forcing data

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCabe, M. F.; Ershadi, A.; Jimenez, C.

Determining the spatial distribution and temporal development of evaporation at regional and global scales is required to improve our understanding of the coupled water and energy cycles and to better monitor any changes in observed trends and variability of linked hydrological processes. With recent international efforts guiding the development of long-term and globally distributed flux estimates, continued product assessments are required to inform upon the selection of suitable model structures and also to establish the appropriateness of these multi-model simulations for global application. In support of the objectives of the Global Energy and Water Cycle Exchanges (GEWEX) LandFlux project, fourmore » commonly used evaporation models are evaluated against data from tower-based eddy-covariance observations, distributed across a range of biomes and climate zones. The selected schemes include the Surface Energy Balance System (SEBS) approach, the Priestley–Taylor Jet Propulsion Laboratory (PT-JPL) model, the Penman–Monteith-based Mu model (PM-Mu) and the Global Land Evaporation Amsterdam Model (GLEAM). Here we seek to examine the fidelity of global evaporation simulations by examining the multi-model response to varying sources of forcing data. To do this, we perform parallel and collocated model simulations using tower-based data together with a global-scale grid-based forcing product. Through quantifying the multi-model response to high-quality tower data, a better understanding of the subsequent model response to the coarse-scale globally gridded data that underlies the LandFlux product can be obtained, while also providing a relative evaluation and assessment of model performance. Using surface flux observations from 45 globally distributed eddy-covariance stations as independent metrics of performance, the tower-based analysis indicated that PT-JPL provided the highest overall statistical performance (0.72; 61 W m –2; 0.65), followed closely by GLEAM (0.68; 64 W m –2; 0.62), with values in parentheses representing the R 2, RMSD and Nash–Sutcliffe efficiency (NSE), respectively. PM-Mu (0.51; 78 W m –2; 0.45) tended to underestimate fluxes, while SEBS (0.72; 101 W m –2; 0.24) overestimated values relative to observations. A focused analysis across specific biome types and climate zones showed considerable variability in the performance of all models, with no single model consistently able to outperform any other. Results also indicated that the global gridded data tended to reduce the performance for all of the studied models when compared to the tower data, likely a response to scale mismatch and issues related to forcing quality. Rather than relying on any single model simulation, the spatial and temporal variability at both the tower- and grid-scale highlighted the potential benefits of developing an ensemble or blended evaporation product for global-scale LandFlux applications. Hence, challenges related to the robust assessment of the LandFlux product are also discussed.« less

The GEWEX LandFlux project: Evaluation of model evaporation using tower-based and globally gridded forcing data

DOE PAGES

McCabe, M. F.; Ershadi, A.; Jimenez, C.; ...

2016-01-26

Determining the spatial distribution and temporal development of evaporation at regional and global scales is required to improve our understanding of the coupled water and energy cycles and to better monitor any changes in observed trends and variability of linked hydrological processes. With recent international efforts guiding the development of long-term and globally distributed flux estimates, continued product assessments are required to inform upon the selection of suitable model structures and also to establish the appropriateness of these multi-model simulations for global application. In support of the objectives of the Global Energy and Water Cycle Exchanges (GEWEX) LandFlux project, fourmore » commonly used evaporation models are evaluated against data from tower-based eddy-covariance observations, distributed across a range of biomes and climate zones. The selected schemes include the Surface Energy Balance System (SEBS) approach, the Priestley–Taylor Jet Propulsion Laboratory (PT-JPL) model, the Penman–Monteith-based Mu model (PM-Mu) and the Global Land Evaporation Amsterdam Model (GLEAM). Here we seek to examine the fidelity of global evaporation simulations by examining the multi-model response to varying sources of forcing data. To do this, we perform parallel and collocated model simulations using tower-based data together with a global-scale grid-based forcing product. Through quantifying the multi-model response to high-quality tower data, a better understanding of the subsequent model response to the coarse-scale globally gridded data that underlies the LandFlux product can be obtained, while also providing a relative evaluation and assessment of model performance. Using surface flux observations from 45 globally distributed eddy-covariance stations as independent metrics of performance, the tower-based analysis indicated that PT-JPL provided the highest overall statistical performance (0.72; 61 W m –2; 0.65), followed closely by GLEAM (0.68; 64 W m –2; 0.62), with values in parentheses representing the R 2, RMSD and Nash–Sutcliffe efficiency (NSE), respectively. PM-Mu (0.51; 78 W m –2; 0.45) tended to underestimate fluxes, while SEBS (0.72; 101 W m –2; 0.24) overestimated values relative to observations. A focused analysis across specific biome types and climate zones showed considerable variability in the performance of all models, with no single model consistently able to outperform any other. Results also indicated that the global gridded data tended to reduce the performance for all of the studied models when compared to the tower data, likely a response to scale mismatch and issues related to forcing quality. Rather than relying on any single model simulation, the spatial and temporal variability at both the tower- and grid-scale highlighted the potential benefits of developing an ensemble or blended evaporation product for global-scale LandFlux applications. Hence, challenges related to the robust assessment of the LandFlux product are also discussed.« less

A multi-physics model for ultrasonically activated soft tissue.

PubMed

Suvranu De, Rahul

2017-02-01

A multi-physics model has been developed to investigate the effects of cellular level mechanisms on the thermomechanical response of ultrasonically activated soft tissue. Cellular level cavitation effects have been incorporated in the tissue level continuum model to accurately determine the thermodynamic states such as temperature and pressure. A viscoelastic material model is assumed for the macromechanical response of the tissue. The cavitation model based equation-of-state provides the additional pressure arising from evaporation of intracellular and cellular water by absorbing heat due to structural and viscoelastic heating in the tissue, and temperature to the continuum level thermomechanical model. The thermomechanical response of soft tissue is studied for the operational range of frequencies of oscillations and applied loads for typical ultrasonically activated surgical instruments. The model is shown to capture characteristics of ultrasonically activated soft tissue deformation and temperature evolution. At the cellular level, evaporation of water below the boiling temperature under ambient conditions is indicative of protein denaturation around the temperature threshold for coagulation of tissues. Further, with increasing operating frequency (or loading), the temperature rises faster leading to rapid evaporation of tissue cavity water, which may lead to accelerated protein denaturation and coagulation.

Global root zone storage capacity from satellite-based evaporation data

NASA Astrophysics Data System (ADS)

Wang-Erlandsson, Lan; Bastiaanssen, Wim; Gao, Hongkai; Jägermeyr, Jonas; Senay, Gabriel; van Dijk, Albert; Guerschman, Juan; Keys, Patrick; Gordon, Line; Savenije, Hubert

2016-04-01

We present an "earth observation-based" method for estimating root zone storage capacity - a critical, yet uncertain parameter in hydrological and land surface modelling. By assuming that vegetation optimises its root zone storage capacity to bridge critical dry periods, we were able to use state-of-the-art satellite-based evaporation data computed with independent energy balance equations to derive gridded root zone storage capacity at global scale. This approach does not require soil or vegetation information, is model independent, and is in principle scale-independent. In contrast to traditional look-up table approaches, our method captures the variability in root zone storage capacity within land cover type, including in rainforests where direct measurements of root depth otherwise are scarce. Implementing the estimated root zone storage capacity in the global hydrological model STEAM improved evaporation simulation overall, and in particular during the least evaporating months in sub-humid to humid regions with moderate to high seasonality. We find that evergreen forests are able to create a large storage to buffer for extreme droughts (with a return period of up to 60 years), in contrast to short vegetation and crops (which seem to adapt to a drought return period of about 2 years). The presented method to estimate root zone storage capacity eliminates the need for soils and rooting depth information, which could be a game-changer in global land surface modelling.

Evaporation characteristics of ETBE-blended gasoline.

PubMed

Okamoto, Katsuhiro; Hiramatsu, Muneyuki; Hino, Tomonori; Otake, Takuma; Okamoto, Takashi; Miyamoto, Hiroki; Honma, Masakatsu; Watanabe, Norimichi

2015-04-28

To reduce greenhouse gas emissions, which contribute to global warming, production of gasoline blended with ethyl tert-buthyl ether (ETBE) is increasing annually. The flash point of ETBE is higher than that of gasoline, and blending ETBE into gasoline will change the flash point and the vapor pressure. Therefore, it is expected that the fire hazard caused by ETBE-blended gasoline would differ from that caused by normal gasoline. The aim of this study was to acquire the knowledge required for estimating the fire hazard of ETBE-blended gasoline. Supposing that ETBE-blended gasoline was a two-component mixture of gasoline and ETBE, we developed a prediction model that describes the vapor pressure and flash point of ETBE-blended gasoline in an arbitrary ETBE blending ratio. We chose 8-component hydrocarbon mixture as a model gasoline, and defined the relation between molar mass of gasoline and mass loss fraction. We measured the changes in the vapor pressure and flash point of gasoline by blending ETBE and evaporation, and compared the predicted values with the measured values in order to verify the prediction model. The calculated values of vapor pressures and flash points corresponded well to the measured values. Thus, we confirmed that the change in the evaporation characteristics of ETBE-blended gasoline by evaporation could be predicted by the proposed model. Furthermore, the vapor pressure constants of ETBE-blended gasoline were obtained by the model, and then the distillation curves were developed. Copyright © 2015 Elsevier B.V. All rights reserved.

Evaporation-triggered microdroplet nucleation and the four life phases of an evaporating Ouzo drop

NASA Astrophysics Data System (ADS)

Tan, Huanshu; Diddens, Christian; Lv, Pengyu; Kuerten, J. G. M.; Zhang, Xuehua; Lohse, Detlef

2016-11-01

Evaporating liquid droplets are omnipresent in nature and technology, such as in inkjet printing, coating, deposition of materials, medical diagnostics, agriculture, the food industry, cosmetics, or spills of liquids. Here we show that the evaporation of such ternary mixtures can trigger a phase transition and the nucleation of microdroplets of one of the components of the mixture. As a model system, we pick a sessile Ouzo droplet (as known from daily life) and reveal and theoretically explain its four life phases: In phase I, the spherical cap-shaped droplet remains transparent while the more volatile ethanol is evaporating, preferentially at the rim of the drop because of the singularity there. This leads to a local ethanol concentration reduction and correspondingly to oil droplet nucleation there. This is the beginning of phase II, in which oil microdroplets quickly nucleate in the whole drop, leading to its milky color that typifies the so-called "Ouzo effect." Once all ethanol has evaporated, the drop, which now has a characteristic nonspherical cap shape, has become clear again, with a water drop sitting on an oil ring (phase III), finalizing the phase inversion. Finally, in phase IV, all water has evaporated, leaving behind a tiny spherical cap-shaped oil drop.

Battery-powered thin film deposition process for coating telescope mirrors in space

NASA Astrophysics Data System (ADS)

Sheikh, David A.

2016-07-01

Aluminum films manufactured in the vacuum of space may increase the broadband reflectance response of a space telescope operating in the EUV (50-nm to 115-nm) by eliminating absorbing metal-fluorides and metal-oxides, which significantly reduce aluminum's reflectance below 115-nm. Recent developments in battery technology allow small lithium batteries to rapidly discharge large amounts of energy. It is therefore conceivable to power an array of resistive evaporation filaments in a space environment, using a reasonable mass of batteries and other hardware. This paper presents modeling results for coating thickness as a function of position, for aluminum films made with a hexagonal array of battery powered evaporation sources. The model is based on measured data from a single battery-powered evaporation source.

Evaporation from soils subjected to natural boundary conditions at the land-atmospheric interface

NASA Astrophysics Data System (ADS)

Smits, K.; Illngasekare, T.; Ngo, V.; Cihan, A.

2012-04-01

Bare soil evaporation is a key process for water exchange between the land and the atmosphere and an important component of the water balance in semiarid and arid regions. However, there is no agreement on the best methodology to determine evaporation under different boundary conditions at the land surface. This becomes critical in developing models that couples land to the atmosphere. Because it is difficult to measure evaporation from soil, with the exception of using lysimeters, numerous formulations have been proposed to establish a relationship between the rate of evaporation and soil moisture and/or soil temperature and thermal properties. Different formulations vary in how they partition available energy. A need exists to systematically compare existing methods to experimental data under highly controlled conditions not achievable in the field. The goal of this work is to perform controlled experiments under transient conditions of soil moisture, temperature and wind at the land/atmospheric interface to test different conceptual and mathematical formulations for the soil surface boundary conditions to develop appropriate numerical models to be used in simulations. In this study, to better understand the coupled water-vapor-heat flow processes in the shallow subsurface near the land surface, we modified a previously developed theory by Smits et al. [2011] that allows non-equilibrium liquid/gas phase change with gas phase vapor diffusion to better account for dry soil conditions. The model did not implement fitting parameters such as a vapor enhancement factor that is commonly introduced into the vapor diffusion coefficient as an arbitrary multiplication factor. In order to experimentally test the numerical formulations/code, we performed a two-dimensional physical model experiment under varying boundary conditions using test sand for which the hydraulic and thermal properties were well characterized. Precision data under well-controlled transient heat and wind boundary conditions was generated and results from numerical simulations were compared with experimental data. Results demonstrate that the boundary condition approaches varied in their ability to capture stage 1- and stage 2- evaporation. Results also demonstrated the importance of properly characterizing soil thermal properties and accounting for dry soil conditions. The contribution of film flow to hydraulic conductivity for the layer above the drying front is dominant compared to that of capillary flow, demonstrating the importance of including film flow in modeling efforts for dry soils, especially for fine grained soils. Comparisons of different formulations of the surface boundary condition validate the need for joint evaluation of heat and mass transfer for better modeling accuracy. This knowledge is applicable to many current hydrologic and environmental problems to include climate modeling and the simulation of contaminant transport and volatilization in the shallow subsurface. Smits, K. M., A. Cihan, T. Sakaki, and T. H. Illangasekare (2011). Evaporation from soils under thermal boundary conditions: Experimental and modeling investigation to compare equilibrium- and nonequilibrium-based approaches, Water Resour. Res., 47, W05540, doi:10.1029/2010WR009533.

Evaporation-triggered microdroplet nucleation and the four life phases of an evaporating Ouzo drop.

PubMed

Tan, Huanshu; Diddens, Christian; Lv, Pengyu; Kuerten, J G M; Zhang, Xuehua; Lohse, Detlef

2016-08-02

Evaporating liquid droplets are omnipresent in nature and technology, such as in inkjet printing, coating, deposition of materials, medical diagnostics, agriculture, the food industry, cosmetics, or spills of liquids. Whereas the evaporation of pure liquids, liquids with dispersed particles, or even liquid mixtures has intensively been studied over the past two decades, the evaporation of ternary mixtures of liquids with different volatilities and mutual solubilities has not yet been explored. Here we show that the evaporation of such ternary mixtures can trigger a phase transition and the nucleation of microdroplets of one of the components of the mixture. As a model system, we pick a sessile Ouzo droplet (as known from daily life-a transparent mixture of water, ethanol, and anise oil) and reveal and theoretically explain its four life phases: In phase I, the spherical cap-shaped droplet remains transparent while the more volatile ethanol is evaporating, preferentially at the rim of the drop because of the singularity there. This leads to a local ethanol concentration reduction and correspondingly to oil droplet nucleation there. This is the beginning of phase II, in which oil microdroplets quickly nucleate in the whole drop, leading to its milky color that typifies the so-called "Ouzo effect." Once all ethanol has evaporated, the drop, which now has a characteristic nonspherical cap shape, has become clear again, with a water drop sitting on an oil ring (phase III), finalizing the phase inversion. Finally, in phase IV, all water has evaporated, leaving behind a tiny spherical cap-shaped oil drop.

Evaporation-triggered microdroplet nucleation and the four life phases of an evaporating Ouzo drop

NASA Astrophysics Data System (ADS)

Tan, Huanshu; Diddens, Christian; Lv, Pengyu; Kuerten, J. G. M.; Zhang, Xuehua; Lohse, Detlef

2016-08-01

Evaporating liquid droplets are omnipresent in nature and technology, such as in inkjet printing, coating, deposition of materials, medical diagnostics, agriculture, the food industry, cosmetics, or spills of liquids. Whereas the evaporation of pure liquids, liquids with dispersed particles, or even liquid mixtures has intensively been studied over the past two decades, the evaporation of ternary mixtures of liquids with different volatilities and mutual solubilities has not yet been explored. Here we show that the evaporation of such ternary mixtures can trigger a phase transition and the nucleation of microdroplets of one of the components of the mixture. As a model system, we pick a sessile Ouzo droplet (as known from daily life—a transparent mixture of water, ethanol, and anise oil) and reveal and theoretically explain its four life phases: In phase I, the spherical cap-shaped droplet remains transparent while the more volatile ethanol is evaporating, preferentially at the rim of the drop because of the singularity there. This leads to a local ethanol concentration reduction and correspondingly to oil droplet nucleation there. This is the beginning of phase II, in which oil microdroplets quickly nucleate in the whole drop, leading to its milky color that typifies the so-called “Ouzo effect.” Once all ethanol has evaporated, the drop, which now has a characteristic nonspherical cap shape, has become clear again, with a water drop sitting on an oil ring (phase III), finalizing the phase inversion. Finally, in phase IV, all water has evaporated, leaving behind a tiny spherical cap-shaped oil drop.

Cumulative impoundment evaporation in water resource management within the mid-Atlantic: A case study in Virginia

NASA Astrophysics Data System (ADS)

Scott, D.; Burgholzer, R.; Kleiner, J.; Brogan, C. O.; Julson, C.; Withers, E.

2017-12-01

Across the eastern United States, successful management of water resources to satisfy the competing demands for human consumption, industry, agriculture, and ecosystems requires both water quality and water quantity considerations. Over the last 2 decades, low streamflows during dry summers have increased scrutiny on water supply withdrawals. Within Virginia, a statewide hydrologic model provides quantitative assessments on impacts from proposed water withdrawals to downstream river flow. Currently, evaporative losses are only accounted for from the large reservoirs. In this study, we sought to provide a baseline estimate for the cumulative evaporation from impoundments across all of the major river basins in Virginia. Virginia provides an ideal case study for the competing water demands in the mid-Atlantic region given the unique tracking of water withdrawals throughout the river corridor. In the over 73,000 Virginia impoundments, the cumulative annual impoundment evaporation was 706 MGD, or 49% of the permitted water withdrawal. The largest reservoirs (>100 acres) represented over 400 MGD, and 136 MGD for the smaller impoundments (< 5 acres). In regions with high impoundment density, impoundment evaporation tended to be a significant fraction of the total amount of water loss (evaporation + demand), with some areas where impoundment evaporation was greater than human water demand. Seasonally, our results suggest that cumulative impoundment evaporation in some watersheds greatly impacts streamflow during low flow periods. Our results demonstrate that future water supply planning will require not only understanding evaporation within large reservoirs, but also the thousands of small impoundments across the landscape.

Evaporation-triggered microdroplet nucleation and the four life phases of an evaporating Ouzo drop

PubMed Central

Tan, Huanshu; Diddens, Christian; Lv, Pengyu; Kuerten, J. G. M.; Zhang, Xuehua; Lohse, Detlef

2016-01-01

Evaporating liquid droplets are omnipresent in nature and technology, such as in inkjet printing, coating, deposition of materials, medical diagnostics, agriculture, the food industry, cosmetics, or spills of liquids. Whereas the evaporation of pure liquids, liquids with dispersed particles, or even liquid mixtures has intensively been studied over the past two decades, the evaporation of ternary mixtures of liquids with different volatilities and mutual solubilities has not yet been explored. Here we show that the evaporation of such ternary mixtures can trigger a phase transition and the nucleation of microdroplets of one of the components of the mixture. As a model system, we pick a sessile Ouzo droplet (as known from daily life—a transparent mixture of water, ethanol, and anise oil) and reveal and theoretically explain its four life phases: In phase I, the spherical cap-shaped droplet remains transparent while the more volatile ethanol is evaporating, preferentially at the rim of the drop because of the singularity there. This leads to a local ethanol concentration reduction and correspondingly to oil droplet nucleation there. This is the beginning of phase II, in which oil microdroplets quickly nucleate in the whole drop, leading to its milky color that typifies the so-called “Ouzo effect.” Once all ethanol has evaporated, the drop, which now has a characteristic nonspherical cap shape, has become clear again, with a water drop sitting on an oil ring (phase III), finalizing the phase inversion. Finally, in phase IV, all water has evaporated, leaving behind a tiny spherical cap-shaped oil drop. PMID:27418601

Spatial and diurnal below canopy evaporation in a desert vineyard: measurements and modeling

USDA-ARS?s Scientific Manuscript database

Evaporation from the soil surface (E) can be a significant source of water loss in arid areas. In sparsely vegetated systems, E is expected to be a function of soil, climate, irrigation regime, precipitation patterns, and plant canopy development, and will therefore change dynamically at both daily ...

Clausius-Clapeyron Scaling of Convective Available Potential Energy (CAPE) in Cloud-Resolving Simulations

NASA Astrophysics Data System (ADS)

Seeley, J.; Romps, D. M.

2015-12-01

Recent work by Singh and O'Gorman has produced a theory for convective available potential energy (CAPE) in radiative-convective equilibrium. In this model, the atmosphere deviates from a moist adiabat—and, therefore, has positive CAPE—because entrainment causes evaporative cooling in cloud updrafts, thereby steepening their lapse rate. This has led to the proposal that CAPE increases with global warming because the strength of evaporative cooling scales according to the Clausius-Clapeyron (CC) relation. However, CAPE could also change due to changes in cloud buoyancy and changes in the entrainment rate, both of which could vary with global warming. To test the relative importance of changes in CAPE due to CC scaling of evaporative cooling, changes in cloud buoyancy, and changes in the entrainment rate, we subject a cloud-resolving model to a suite of natural (and unnatural) forcings. We find that CAPE changes are primarily driven by changes in the strength of evaporative cooling; the effect of changes in the entrainment rate and cloud buoyancy are comparatively small. This builds support for CC scaling of CAPE.

Evaporation of liquid droplets on solid substrates. I. Flat substrate with pinned or moving contact line

NASA Astrophysics Data System (ADS)

Amini, Amirhossein; Homsy, G. M.

2017-04-01

We study the evolution of the profile of a two-dimensional volatile liquid droplet that is evaporating on a flat heated substrate. We adopt a one-sided model with thermal control that, together with the lubrication approximation, results in an evolution equation for the local height of the droplet. Without requiring any presumption for the shape of the drop, the problem is formulated for the two modes of evaporation: a pinned contact line and a moving contact line with fixed contact angle. Numerical solutions are provided for each case. For the pinned contact line case, we observe that after a time interval the contact angle dynamics become nonlinear and, interestingly, the local contact angle goes to zero in advance of total evaporation of the drop. For the case of a moving contact line, in which the singularity at the contact line is treated by a numerical slip model, we find that the droplet nearly keeps its initial circular shape and that the contact line recedes with constant speed.

Design and performance considerations of evaporative-pad, waste-heat greenhouses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olszewski, M.

1978-01-01

Rising fuel costs and limited fuel availability have forced greenhouse operators to seek alternative means of heating their greenhouses in an effort to reduce production costs and conserve energy. One such alternative uses power plant reject heat, which is contained in the condenser cooling water, and a bank of evaporative pads to provide winter heating. The design technique used to size the evaporative pad system to meet both summer cooling and winter heating demands is described. Additionally, a computational scheme that simulates the system performance is presented. This analytical model is used to determine the greenhouse operating conditions that maintainmore » the vegetation in its thermal comfort zone. The evaporative pad model uses the Merkel total heat approximation and an experimentally derived transfer coefficient. Energy balance considerations on the vegetation provide a means of viewing optimal vegetation growth in terms of greenhouse environmental factors. In general, the results indicate that the vegetation can be maintained within its thermal comfort zone if sufficient warm water is available to the pads and the air stream flow is properly adjusted.« less

Multi-objective Optimization of Molecular Distillation Conditions for Oleic Acid from a Rich-in-Fatty Acid Model Mixture.

PubMed

Ketenoğlu, Onur; Erdoğdu, Ferruh; Tekin, Aziz

2018-01-01

Oleic acid is a commercially valuable compound and has many positive health effects. Determining optimum conditions in a physical separation process is an industrially significant point due to environmental and health related concerns. Molecular distillation avoids the use of chemicals and adverse effects of high temperature application. The objective of this study was to determine the molecular distillation conditions for oleic acid to increase its purity and distillation yield in a model fatty acid mixture. For this purpose, a short-path evaporator column was used. Evaporation temperature ranged from 110 to 190℃, while absolute pressure was from 0.05 to 5 mmHg. Results showed that elevating temperature generally increased distillation yield until a maximum evaporation temperature. Vacuum application also affected the yield at a given temperature, and amount of distillate increased at higher vacuums except the case applied at 190℃. A multi-objective optimization procedure was then used for maximizing both yield and oleic acid amounts in distillate simultaneously, and an optimum point of 177.36℃ and 0.051 mmHg was determined for this purpose. Results also demonstrated that evaporation of oleic acid was also suppressed by a secondary dominant fatty acid of olive oil - palmitic acid, which tended to evaporate easier than oleic acid at lower evaporation temperatures, and increasing temperature achieved to transfer more oleic acid to distillate. At 110℃ and 0.05 mmHg, oleic and palmitic acid concentrations in distillate were 63.67% and 24.32%, respectively. Outcomes of this study are expected to be useful for industrial process conditions.

Influence of some design parameters on the thermal performance of domestic refrigerator appliances

NASA Astrophysics Data System (ADS)

Rebora, Alessandro; Senarega, Maurizio; Tagliafico, Luca A.

2006-07-01

This paper presents a thermal study on chest-freezers, the small refrigerators used in domestic and supermarket applications. A thermal and energy model of a particular kind of these refrigerators, the “hot-wall” (or “skin condenser”) refrigerator, is developed and used to perform sensitivity and design optimisation analysis for given working temperatures and useful volume of the refrigerated cell. A finite-element heat transfer model of the refrigerator box is coupled to the complete thermodynamic model of the refrigerating plant, including real working conditions (compressor efficiency, friction pressure losses and so on). A sensitivity study of the main design parameters affecting the global refrigerator performance has been developed (for fixed working temperatures) with reference to the thickness of the metallic plates, to the evaporator and condenser tube diameters and to the evaporator tube pitch (with fixed evaporator-to-condenser tube pitch ratio). The results obtained show that the proposed sensitivity analysis can yield quite reliable results (in comparison with much more complex, albeit more accurate mathematical optimisation algorithms) using small computational resources. The great importance of 2-D heat conduction in the metallic plates is shown, evidencing how the plate thickness and the evaporator and condenser tube diameters affect the global performance of the system according to the well-known “fin efficiency” effect. The influence of the evaporator and condenser tube diameters on the friction pressure losses is also outlined. Some practical suggestions are made in conclusion, regarding the criteria which should be adopted in the thermal design of a hot-wall refrigerator.

A spray flamelet/progress variable approach combined with a transported joint PDF model for turbulent spray flames

NASA Astrophysics Data System (ADS)

Hu, Yong; Olguin, Hernan; Gutheil, Eva

2017-05-01

A spray flamelet/progress variable approach is developed for use in spray combustion with partly pre-vaporised liquid fuel, where a laminar spray flamelet library accounts for evaporation within the laminar flame structures. For this purpose, the standard spray flamelet formulation for pure evaporating liquid fuel and oxidiser is extended by a chemical reaction progress variable in both the turbulent spray flame model and the laminar spray flame structures, in order to account for the effect of pre-vaporised liquid fuel for instance through use of a pilot flame. This new approach is combined with a transported joint probability density function (PDF) method for the simulation of a turbulent piloted ethanol/air spray flame, and the extension requires the formulation of a joint three-variate PDF depending on the gas phase mixture fraction, the chemical reaction progress variable, and gas enthalpy. The molecular mixing is modelled with the extended interaction-by-exchange-with-the-mean (IEM) model, where source terms account for spray evaporation and heat exchange due to evaporation as well as the chemical reaction rate for the chemical reaction progress variable. This is the first formulation using a spray flamelet model considering both evaporation and partly pre-vaporised liquid fuel within the laminar spray flamelets. Results with this new formulation show good agreement with the experimental data provided by A.R. Masri, Sydney, Australia. The analysis of the Lagrangian statistics of the gas temperature and the OH mass fraction indicates that partially premixed combustion prevails near the nozzle exit of the spray, whereas further downstream, the non-premixed flame is promoted towards the inner rich-side of the spray jet since the pilot flame heats up the premixed inner spray zone. In summary, the simulation with the new formulation considering the reaction progress variable shows good performance, greatly improving the standard formulation, and it provides new insight into the local structure of this complex spray flame.

Modeling properties of chromospheric evaporation driven by thermal conduction fronts from reconnection shocks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brannon, Sean; Longcope, Dana

2014-09-01

Magnetic reconnection in the corona results in contracting flare loops, releasing energy into plasma heating and shocks. The hydrodynamic shocks produced in this manner drive thermal conduction fronts (TCFs) which transport energy into the chromosphere and drive upflows (evaporation) and downflows (condensation) in the cooler, denser footpoint plasma. Observations have revealed that certain properties of the transition point between evaporation and condensation (the 'flow reversal point' or FRP), such as temperature and velocity-temperature derivative at the FRP, vary between different flares. These properties may provide a diagnostic tool to determine parameters of the coronal energy release mechanism and the loopmore » atmosphere. In this study, we develop a one-dimensional hydrodynamical flare loop model with a simplified three-region atmosphere (chromosphere/transition region/corona), with TCFs initiated by shocks introduced in the corona. We investigate the effect of two different flare loop parameters (post-shock temperature and transition region temperature ratio) on the FRP properties. We find that both of the evaporation characteristics have scaling-law relationships to the varied flare parameters, and we report the scaling exponents for our model. This provides a means of using spectroscopic observations of the chromosphere as quantitative diagnostics of flare energy release in the corona.« less

Modeling of Bulk Evaporation and Condensation

NASA Technical Reports Server (NTRS)

Anghaie, S.; Ding, Z.

1996-01-01

This report describes the modeling and mathematical formulation of the bulk evaporation and condensation involved in liquid-vapor phase change processes. An internal energy formulation, for these phase change processes that occur under the constraint of constant volume, was studied. Compared to the enthalpy formulation, the internal energy formulation has a more concise and compact form. The velocity and time scales of the interface movement were obtained through scaling analysis and verified by performing detailed numerical experiments. The convection effect induced by the density change was analyzed and found to be negligible compared to the conduction effect. Two iterative methods for updating the value of the vapor phase fraction, the energy based (E-based) and temperature based (T-based) methods, were investigated. Numerical experiments revealed that for the evaporation and condensation problems the E-based method is superior to the T-based method in terms of computational efficiency. The internal energy formulation and the E-based method were used to compute the bulk evaporation and condensation processes under different conditions. The evolution of the phase change processes was investigated. This work provided a basis for the modeling of thermal performance of multi-phase nuclear fuel elements under variable gravity conditions, in which the buoyancy convection due to gravity effects and internal heating are involved.

Polycrystalline structures formed in evaporating droplets as a parameter to test the action of Zincum metallicum 30c in a wheat seed model.

PubMed

Kokornaczyk, Maria Olga; Baumgartner, Stephan; Betti, Lucietta

2016-05-01

Polycrystalline structures formed inside evaporating droplets of different biological fluids have been shown sensitive towards various influences, including ultra high dilutions (UHDs), representing so a new approach potentially useful for basic research in homeopathy. In the present study we tested on a wheat seed model Zincum metallicum 30c efficacy versus lactose 30c and water. Stressed and non-stressed wheat seeds were watered with the three treatments. Seed-leakage droplets were evaporated and the polycrystalline structures formed inside the droplet residues were analyzed for their local connected fractal dimensions (LCFDs) (measure of complexity) using the software ImageJ. We have found significant differences in LCFD values of polycrystalline structures obtained from stressed seeds following the treatments (p<0.0001); Zincum metallicum 30c lowered the structures' complexity compared to lactose 30c and water. In non-stressed seeds no significant differences were found. The droplet evaporation method (DEM) might represent a potentially useful tool in basic research in homeopathy. Furthermore our results suggest a sensitization of the stressed model towards the treatment action, which is conforming to previous findings. Copyright © 2015 The Faculty of Homeopathy. Published by Elsevier Ltd. All rights reserved.

Modeling Episodic Ephemeral Brine Lake Evaporation and Salt Crystallization on the Bonneville Salt Flats, Utah

NASA Astrophysics Data System (ADS)

Liu, T.; Harman, C. J.; Kipnis, E. L.; Bowen, B. B.

2017-12-01

Public concern about apparent reductions in the areal extent of the Bonneville Salt Flat (BSF) and perceived changes in inundation frequency has motivated renewed interest in the hydrologic and geochemical behavior of this salt playa. In this study, we develop a numerical modeling framework to simulate the relationship between hydrometeorologic variability, brine evaporation and salt crystallization processes on BSF. The BSF, locates in Utah, is the remnant of paleo-lake Bonneville, and is capped by up to 1 meter of salt deposition over a 100 km2 area. The BSF has two distinct hydrologic periods each year: a winter wet periods with standing surface brine and the summer dry periods when the brine is evaporated, exposing the surface salt crust. We develop a lumped non-linear dynamical models coupling conservation expressions from water, dissolved salt and thermal energy to investigate the seasonal and diurnal behavior of brine during the transition from standing brine to exposed salt at BSF. The lumped dynamic models capture important nonlinear and kinetic effects introduced by the high ionic concentration of the brine, including the pronounced effect of the depressed water activity coefficient on evaporation. The salt crystallization and dissolution rate is modeled as a kinetic process linearly proportional to the degree of supersaturation of brine. The model generates predictions of the brine temperature and the solute and solvent masses controlled by diurnal net radiation input and aerodynamic forcing. Two distinct mechanisms emerge as potential controls on salt production and dissolution: (1) evapo-concentration and (2) changes in solubility related to changes in brine temperature. Although the evaporation of water is responsible for ultimate disappearance of the brine each season ,variation in solubility is found to be the dominant control on diurnal cycles of salt precipitation and dissolution in the BSF case. Most salt is crystallized during nighttime, but the long-term salt production is driven by the seasonal evapo-concentration. Moreover, we find that the timing of the brine temperature fluctuations and salt production lags the diurnal net radiation input. The key controls on the magnitudes of these effects and phase lags are determined by analytical periodic analysis of linearized forms of the model.

A comparison of daily evaporation downscaled using WRFDA model and GLEAM dataset over the Iberian Peninsula.

NASA Astrophysics Data System (ADS)

José González-Rojí, Santos; Sáenz, Jon; Ibarra-Berastegi, Gabriel

2017-04-01

GLEAM dataset was presented a few years ago and since that moment, it has just been used for validation of evaporation in a few places of the world (Australia and Africa). The Iberian Peninsula is composed of different soil types and it is affected by different weather regimes, with different climate regions. It is this feature which makes it a very interesting zone for the study of the meteorological cycle, including evaporation. For that purpose, a numerical downscaling exercise over the Iberian Peninsula was run nesting the WRF model inside ERA Interim. Two model configurations were tested in two experiments spanning the period 2010-2014 after a one-year spin-up (2009). In the first experiment (N), boundary conditions drive the model. The second experiment (D) is configured the same way as the N case, but 3DVAR data assimilation is run every six hours (00Z, 06Z, 12Z and 18Z) using observations obtained from the PREPBUFR dataset. For both N and D runs and ERA Interim, the evaporation of the model runs was compared to GLEAM v3.0b and v3.0c datasets over the Iberian Peninsula, both at the daily and monthly time scales. GLEAM v3.0a was not used for validation as it uses for forcing radiation and air temperature data from ERA Interim. Results show that the experiment with data assimilation (D) improve the results obtained for N experiment. Moreover, correlations values are comparable to the ones obtained with ERA Interim. However, some negative correlation values are observed at Portuguese and Mediterranean coasts for both WRF runs. All of these problematic points are considered as urban sites by the NOAH land surface model. Because of that, the model is not able to simulate a correct evaporation value. Even with these discrepancies, better results than for ERA Interim are observed for seasonal Biases and daily RMSEs over Iberian Peninsula, obtaining the best values inland. Minimal differences are observed for the two GLEAM datasets selected.

European type-approval test procedure for evaporative emissions from passenger cars against real-world mobility data from two Italian provinces.

PubMed

Martini, Giorgio; Paffumi, Elena; De Gennaro, Michele; Mellios, Giorgos

2014-07-15

This paper presents an evaluation of the European type-approval test procedure for evaporative emissions from passenger cars based on real-world mobility data. The study relies on two large databases of driving patterns from conventional fuel vehicles collected by means of on-board GPS systems in the Italian provinces of Modena and Firenze. Approximately 28,000 vehicles were monitored, corresponding to approximately 36 million kilometres over a period of one month. The driving pattern of each vehicle was processed to derive the relation between trip length and parking duration, and the rate of occurrence of parking events against multiple evaporative cycles, defined on the basis of the type-approval test procedure as 12-hour diurnal time windows. These results are used as input for an emission simulation model, which calculates the total evaporative emissions given the characteristics of the evaporative emission control system of the vehicle and the ambient temperature conditions. The results suggest that the evaporative emission control system, fitted to the vehicles from Euro 3 step and optimised for the current type-approval test procedure, could not efficiently work under real-world conditions, resulting in evaporative emissions well above the type-approval limit, especially for small size vehicles and warm climate conditions. This calls for a revision of the type-approval test procedure in order to address real-world evaporative emissions. Copyright © 2014. Published by Elsevier B.V.

Effects of an Inhomogenous Electric Field on an Evaporating Thin Film in a Microchannel

NASA Astrophysics Data System (ADS)

Liu, Xiuliang; Hu, Chen; Li, Huafeng; Yu, Fei; Kong, Xiaming

2018-03-01

In this paper, heat transfer enhancement in an evaporating thin film along the wall of a microchannel under an imposed inhomogenous electrostatic field is analyzed. The mathematical model, based on the augmented Young-Laplace equation with the inhomogenous electrostatic field taken into consideration, is developed. The 2D inhomogenous electric field with the curved liquid-vapor interface is solved by the lattice Boltzmann method. Numerical solutions for the thin film characteristics are obtained for both constant wall temperature and uniform wall heat flux boundary conditions. The numerical results show that the liquid film becomes thinner and the heat transfer coefficient increases under an imposed electric field. Both of octane and water are chosen as the working mediums, and similar result about the enhancement of heat transfer on evaporating thin film by imposing electric field is obtained. It is found that applying an electric field on the evaporating thin film can enhance evaporative heat transfer in a microchannel.

Establishment of redox conditions during planetary collisions as an origin of chondrites

NASA Technical Reports Server (NTRS)

Tsuchiyama, A.; Kitamura, M.

1994-01-01

Collisions between a 'cometlike' body (mixtures of chondritic materials and ice) and a slightly differentiated body were proposed for shock origin of ordinary chondrites. In this model, chondrules were formed with shock melting, and matrices were formed both by fracturing of materials and by recondensation of evaporated materials. This model can explain different redox conditions of chondrite formations by ice evaporation. Although this model was originally proposed for ordinary chondrites, we assume here that the model can be extended to chondrite formation in general. In this paper, redox conditions during chondrite formation by collisions will be discussed in the light of phase diagrams for solid-vapor equilibria.

Refrigerant Performance Evaluation Including Effects of Transport Properties and Optimized Heat Exchangers.

PubMed

Brignoli, Riccardo; Brown, J Steven; Skye, H; Domanski, Piotr A

2017-08-01

Preliminary refrigerant screenings typically rely on using cycle simulation models involving thermodynamic properties alone. This approach has two shortcomings. First, it neglects transport properties, whose influence on system performance is particularly strong through their impact on the performance of the heat exchangers. Second, the refrigerant temperatures in the evaporator and condenser are specified as input, while real-life equipment operates at imposed heat sink and heat source temperatures; the temperatures in the evaporator and condensers are established based on overall heat transfer resistances of these heat exchangers and the balance of the system. The paper discusses a simulation methodology and model that addresses the above shortcomings. This model simulates the thermodynamic cycle operating at specified heat sink and heat source temperature profiles, and includes the ability to account for the effects of thermophysical properties and refrigerant mass flux on refrigerant heat transfer and pressure drop in the air-to-refrigerant evaporator and condenser. Additionally, the model can optimize the refrigerant mass flux in the heat exchangers to maximize the Coefficient of Performance. The new model is validated with experimental data and its predictions are contrasted to those of a model based on thermodynamic properties alone.

Polarization of prompt J / ψ and Υ ( 1 S ) production in the color evaporation model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheung, Vincent; Vogt, Ramona

We calculate the polarization of prompt J/ψ and Υ(1S) production using the color evaporation model at leading order. We present the polarization parameter x F as a function of center of mass energy and rapidity in p+p collisions. We also compare the x F dependence to experimental results in p+Cu and π+W collisions, and predict the x F dependence in p+Pb collisions at fixed-target energies.

Evaluation of fusion-evaporation cross-section calculations

NASA Astrophysics Data System (ADS)

Blank, B.; Canchel, G.; Seis, F.; Delahaye, P.

2018-02-01

Calculated fusion-evaporation cross sections from five different codes are compared to experimental data. The present comparison extents over a large range of nuclei and isotopic chains to investigate the evolution of experimental and calculated cross sections. All models more or less overestimate the experimental cross sections. We found reasonable agreement by using the geometrical average of the five model calculations and dividing the average by a factor of 11.2. More refined analyses are made for example for the 100Sn region.

Concerning modeling of double-stage water evaporation cooling

NASA Astrophysics Data System (ADS)

Shatskiy, V. P.; Fedulova, L. I.; Gridneva, I. V.

2018-03-01

The matter of need for setting technical norms for production, as well as acceptable microclimate parameters, such as temperature and humidity, at the work place, remains urgent. Use of certain units should be economically sound and that should be taken into account for construction, assembly, operation, technological, and environmental requirements. Water evaporation coolers are simple to maintain, environmentally friendly, and quite cheap, but the development of the most efficient solutions requires mathematical modeling of the heat and mass transfer processes that take place in them.

Selective field evaporation in field-ion microscopy for ordered alloys

NASA Astrophysics Data System (ADS)

Ge, Xi-jin; Chen, Nan-xian; Zhang, Wen-qing; Zhu, Feng-wu

1999-04-01

Semiempirical pair potentials, obtained by applying the Chen-inversion technique to a cohesion equation of Rose et al. [Phys. Rev. B 29, 2963 (1984)], are employed to assess the bonding energies of surface atoms of intermetallic compounds. This provides a new calculational model of selective field evaporation in field-ion microscopy (FIM). Based on this model, a successful interpretation of FIM image contrasts for Fe3Al, PtCo, Pt3Co, Ni4Mo, Ni3Al, and Ni3Fe is given.

Polarized heavy quarkonium production in the color evaporation model

DOE PAGES

Cheung, Vincent; Vogt, Ramona

2017-04-14

Here, we explore polarized heavy quarkonium production using the color evaporation model at leading order. We present the polarized to total yield ratio as a function of center of mass energy and rapidity in p+p collisions. At energies far above the Q¯Q production threshold, we find charmonium and bottomonium production to be longitudinally polarized (J z = 0). The quarkonium states are also longitudinally polarized at central rapidity, becoming transversely polarized (J z = ±1) at the most forward rapidities.

Polarization of prompt J / ψ and Υ ( 1 S ) production in the color evaporation model

DOE PAGES

Cheung, Vincent; Vogt, Ramona

2017-09-14

We calculate the polarization of prompt J/ψ and Υ(1S) production using the color evaporation model at leading order. We present the polarization parameter x F as a function of center of mass energy and rapidity in p+p collisions. We also compare the x F dependence to experimental results in p+Cu and π+W collisions, and predict the x F dependence in p+Pb collisions at fixed-target energies.

Water budgets of Italian and Dutch gravel pit lakes: a study using a fen as a natural evaporation pan, stable isotopes and conservative tracer modeling.

NASA Astrophysics Data System (ADS)

Nella Mollema, Pauline; Antonellini, Marco

2015-04-01

Gravel pits are excavated in aquifers to fulfill the need for construction materials. Flow-through lakes form where the gravel pits are below the water table and fill with groundwater. Their presence changes the drainage patterns, water- and hydrochemical budgets of a watershed. We have studied the water budget of two gravel pit lakes systems using stable H and O isotopes of water as well as conservative tracer (Cl) modeling. The Dutch gravel pit lakes are a fluvial fresh water system of 70 lakes along the Meuse River and the Italian gravel pit lakes are a brackish system along the Adriatic coast. Surface water evaporation from the gravel pit lakes is larger than the actual evapotranspiration of the grass land and forests that were replaced. The ratio of evaporation to total flow into the Dutch lakes was determined by using a Fen as a natural evaporation pan: the isotope content of the Tuspeel Fen, filled with rain water and sampled in a dry and warm summer period (August 2012), is representative for the limiting isotopic enrichment under local hydro meteorological conditions. The Local Evaporation line (LEL) was determined δ2 H = 4.20 δ 18O - 14.10 (R² = 0.99) and the ratio of total inflow to evaporation for three gravel pit lakes were calculated to be 22.6 for the De Lange Vlieter lake used for drinking water production, 11.3 for the Boschmolen Lake and 8.9 for the Anna's Beemd lake showing that groundwater flow is much larger than evaporation. The Italian gravel pit lakes are characterized by high salinity (TDS = 4.6-12.3 g L-1). Stable isotope data show that these latter gravel pit lakes are fed by groundwater, which is a mix between fresh Apennine River water and brackish (Holocene) Adriatic Sea water. The local evaporation line is determined: δ2H = 5.02 δ18O - 10.49. The ratio of total inflow to evaporation is 5. Conservative tracer modeling indicates that the chloride concentration in the Italian gravel pit lakes stabilizes after a short period of rapid increase, because water leaving the lake via groundwater flow, driven by the drainage system, removes part of the Cl that accumulates in the lake due to evapo-concentration. Under climate change, rising sea levels and continuing land subsidence as well as increasing precipitation would increase the need for drainage which would enhance groundwater flow through the lake. The resulting steady-state Cl concentration of the lakes could become less than the current Cl concentration. This effect would be larger than increasing evapo- concentration. Both gravel pit lake systems have a large flux of groundwater into and out of the lakes driven by evaporation and (artificial) drainage with important consequences for the water- and hydrochemical budgets of the whole watershed and in particular on freshwater quantity and groundwater salinity.

Experimental Measurements of the Water Evaporation Rate of a Physical Model

NASA Astrophysics Data System (ADS)

Turza, Róbert; Füri, Belo B.

2017-03-01

As the number of indoor swimming pools and wellness centers are currently growing, it is necessary to concentrate on the parameters of indoor environments. These parameters are necessary for the design of the HVAC systems that operate these premises. In indoor swimming-pool facilities, the energy demand is large due to ventilation losses from exhaust air. Since water evaporates from a pool's surface, exhaust air has a high water content and specific enthalpy. In this paper the results of the water evaporation rate measured from swimming pool surfaces at higher thermal water temperatures are described.

Marangoni flow in an evaporating water droplet

NASA Astrophysics Data System (ADS)

Xu, Xuefeng; Luo, Jianbin

2007-09-01

Marangoni effect has been observed in many liquids, but its existence in pure water is still a debated problem. In the present work, the Marangoni flow in evaporating water droplets has been observed by using fluorescent nanoparticles. Flow patterns indicate that a stagnation point where the surface flow, the surface tension gradient, and the surface temperature gradient change their directions exists at the droplet surface. The deduced nonmonotonic variation of the droplet surface temperature, which is different from that in some previous works, is explained by a heat transfer model considering the adsorbed thin film of the evaporating liquid droplet.

Modeling and experimental analysis of electrospinning bending region physics in determining fiber diameter for hydrophilic polymer solvent systems

NASA Astrophysics Data System (ADS)

Cai, Yunshen

Electrospinning produces submicron fibers from a wide range of polymer/solvent systems that enable a variety of different applications. In electrospinning process, a straight polymer/solvent charged jet is initially formed, followed by a circular moving jet in the shape of a cone, called the bending region. The process physics in the bending region are difficult to study since the jet diameter cannot be measured directly due to its rapid motion and small size ( microns and smaller), and due to complex coupling of multiple forces, mass transport, and changing jet geometry. Since the solutions studied are hydrophilic, they readily absorb ambient moisture. This thesis explores the role of the bending region in determining the resulting electrospun fiber diameter through a combined experimental and modeling analysis for a variety of hydrophilic polymer/solvent solutions. Electrospinning experiments were conducted over a broad range of operating conditions for 4 different polymer/solvent systems. Comparison of the final straight jet diameters to fiber diameters reveals that between 30% to 60% jet thinning occurs in the bending region. These experiments also reveal that relative humidity significantly affects the electrospinning process and final fiber diameter, even for non-aqueous solutions. A model is developed to obtain insight into the bending region process physics. Important ones include understanding the mass transport for non-aqueous hydrophilic jets (including solvent evaporation and water absorption on the jet surface, radial diffusion, and axial advection), and the coupling between the mass and force balances that determines the final fiber diameter. The absorption and evaporation physics is validated by evaporation experiments. The developed model predicts fiber diameter to within of 8%, even though the solution properties and operating conditions that determines net stretching forces and net evaporation rates vary over a large range. Model analysis reveals how the net evaporation rate affects the jet length and net stretching force, both of which ultimately determine the fiber diameter. It is also shown that the primary impact of RH on the process is through occupation of the surface states that limits solvent evaporation rate, rather than the amount of water absorbed. Correlation functions between process conditions, solution properties and the resulting fiber diameters are discussed.

Changing Demands from Riparian Evapotranspiration and Free-Water Evaporation in the Lower Colorado River Basin Under Different Climate Scenarios

NASA Astrophysics Data System (ADS)

Bunk, D. A.; Piechota, T. C.

2012-12-01

Observed and projected trends in riparian evapotranspiration (ET) and free-water evaporation are examined to improve water demand forecasting for use in modeling of lower Colorado River system reservoir operations. While most previous research has focused on the impacts of climate change and climate variability on water supply, the impacts on water demand under changing climate conditions have not been adequately addressed (NRC, 2007 and Reclamation, 2009). Increases in temperatures and changes in precipitation and wind patterns are expected to increase evaporative demands (Bates and others, 2008), potentially increasing free-water evaporation and ET from riparian vegetation; increasing infiltration rates; altering cropping patterns; and changing the temporal and spatial distribution of water deliveries. This study uses observations and projections under changing climate scenarios of hydroclimatic variables, such as temperature, wind, and precipitation, to analyze their impacts on riparian ET and free-water evaporation in the lower Colorado River mainstream downstream of Lake Mead and Hoover Dam. The projected changes in evaporative demands were assessed to determine their impacts on water supply and reservoir operations in the Colorado River basin under changing climate conditions. Based on analysis of observed and projected hydroclimatic data from the Variable Infiltration Capacity (VIC) hydrologic model, mean annual daily temperature in the lower Colorado River mainstream reach has increased by 0.8° Celsius (C) from the 30-year period ending in 1980 to period ending in 2010 and is projected to increase by an additional 1.7° C by 30-year period ending in 2060. Analysis of riparian ET derived from the ASCE Penman-Monteith method (Allen et al., 2005, from Monteith, 1965 and 1981) and Westenburg et al. (2006) and free-water evaporation derived from the Penman combination model in Dingman (2008) indicates that combined evaporative demand in the lower Colorado River mainstream increased by 14,800 acre-feet, or 1.8 percent, during the 30-year period ending in 2010, and may increase by an additional 16,600 acre-feet, or 2.0 percent, during the 30-year period ending in 2060, when compared to the period from 1951 to 1980. With this projected increase in evaporative demands, the combined storage of Lake Powell and Lake Mead are projected to decrease by a cumulative volume of 75,400 acre-feet, or 0.15 percent of total conservation capacity, based on 10-year running averages ending in years 2020 to 2060. In addition, average annual shortage volumes in the lower Colorado River basin are projected to increase by 40,000 acre-feet, or 0.30 percent, from 2013 to 2060.

Evaporation of decamethylcyclopentasiloxane (D5) from selected cosmetic products: Implications for consumer exposure modeling.

PubMed

Dudzina, Tatsiana; Garcia Hidalgo, Elena; von Goetz, Natalie; Bogdal, Christian; Hungerbuehler, Konrad

2015-11-01

Consumer exposure to leave-on cosmetics and personal care products (C&PCPs) ingredients of low or moderate volatility is often assumed to occur primarily via dermal absorption. In reality they may volatilize from skin and represent a significant source for inhalation exposure. Often, evaporation rates of pure substances from inert surfaces are used as a surrogate for evaporation from more complex product matrices. Also the influence of partitioning to skin is neglected and the resulting inaccuracies are not known. In this paper we describe a novel approach for measuring chemical evaporation rates from C&PCPs under realistic consumer exposure conditions. Series of experiments were carried out in a custom-made ventilated chamber fitted with a vapor trap to study the disposition of a volatile cosmetic ingredient, decamethylcyclopentasiloxane (D5), after its topical application on either aluminum foil or porcine skin in vitro. Single doses were applied neat and in commercial deodorant and face cream formulations at normal room (23°C) and skin temperature (32°C). The condition-specific evaporation rates were determined as the chemical mass loss per unit surface area at different time intervals over 1-1.25h post-dose. Product weight loss was monitored gravimetrically and the residual D5 concentrations were analyzed with GC/FID. The release of D5 from exposed surfaces of aluminum occurred very fast with mean rates of 0.029 mg cm(-2)min(-1) and 0.060 mg cm(-2)min(-1) at 23°C and 32°C, respectively. Statistical analysis of experimental data confirmed a significant effect of cosmetic formulations on the evaporation of D5 with the largest effect (2-fold decrease of the evaporation rate) observed for the neat face cream pair at 32°C. The developed approach explicitly considers the initial penetration and evaporation of a substance from the Stratum Corneum and has the potential for application in dermal exposure modeling, product emission tests and the formulation of C&PCPs. Copyright © 2015 Elsevier Ltd. All rights reserved.

Dead Sea evaporation by eddy covariance measurements vs. aerodynamic, energy budget, Priestley-Taylor, and Penman estimates

NASA Astrophysics Data System (ADS)

Metzger, Jutta; Nied, Manuela; Corsmeier, Ulrich; Kleffmann, Jörg; Kottmeier, Christoph

2018-02-01

The Dead Sea is a terminal lake, located in an arid environment. Evaporation is the key component of the Dead Sea water budget and accounts for the main loss of water. So far, lake evaporation has been determined by indirect methods only and not measured directly. Consequently, the governing factors of evaporation are unknown. For the first time, long-term eddy covariance measurements were performed at the western Dead Sea shore for a period of 1 year by implementing a new concept for onshore lake evaporation measurements. To account for lake evaporation during offshore wind conditions, a robust and reliable multiple regression model was developed using the identified governing factors wind velocity and water vapour pressure deficit. An overall regression coefficient of 0.8 is achieved. The measurements show that the diurnal evaporation cycle is governed by three local wind systems: a lake breeze during daytime, strong downslope winds in the evening, and strong northerly along-valley flows during the night. After sunset, the strong winds cause half-hourly evaporation rates which are up to 100 % higher than during daytime. The median daily evaporation is 4.3 mm d-1 in July and 1.1 mm d-1 in December. The annual evaporation of the water surface at the measurement location was 994±88 mm a-1 from March 2014 until March 2015. Furthermore, the performance of indirect evaporation approaches was tested and compared to the measurements. The aerodynamic approach is applicable for sub-daily and multi-day calculations and attains correlation coefficients between 0.85 and 0.99. For the application of the Bowen ratio energy budget method and the Priestley-Taylor method, measurements of the heat storage term are inevitable on timescales up to 1 month. Otherwise strong seasonal biases occur. The Penman equation was adapted to calculate realistic evaporation, by using an empirically gained linear function for the heat storage term, achieving correlation coefficients between 0.92 and 0.97. In summary, this study introduces a new approach to measure lake evaporation with a station located at the shoreline, which is also transferable to other lakes. It provides the first directly measured Dead Sea evaporation rates as well as applicable methods for evaporation calculation. The first one enables us to further close the Dead Sea water budget, and the latter one enables us to facilitate water management in the region.

Effect of sweating set rate on clothing real evaporative resistance determined on a sweating thermal manikin in a so-called isothermal condition (T manikin = T a = T r).

PubMed

Lu, Yehu; Wang, Faming; Peng, Hui; Shi, Wen; Song, Guowen

2016-04-01

The ASTM F2370 (2010) is the only standard with regard to measurement of clothing real evaporative resistance by means of a sweating manikin. However, the sweating set-point is not recommended in the standard. In this study, the effect of sweating rate on clothing real evaporative resistance was investigated on a 34-zone "Newton" sweating thermal manikin in a so-called isothermal condition (T manikin = T a = T r). Four different sweating set rates (i.e., all segments had a sweating rate of 400, 800, 1200 ml/hr ∙ m(2), respectively, and different sweating rates were assigned to different segments) were applied to determine the clothing real evaporative resistance of five clothing ensembles and the boundary air layer. The results indicated that the sweating rate did not affect the real evaporative resistance of clothing ensembles with the absence of strong moisture absorbent layers. For the clothing ensemble with tight cotton underwear, a sweating rate of lower than 400 ml/hr ∙ m(2) is not recommended. This is mainly because the wet fabric "skin" might not be fully saturated and thus led to a lower evaporative heat loss and thereby a higher real evaporative resistance. For vapor permeable clothing, the real evaporative resistance determined in the so-called isothermal condition should be corrected before being used in thermal comfort or heat strain models. However, the reduction of wet thermal insulation due to moisture absorption in different test scenarios had a limited contribution to the effect of sweating rate on the real evaporative resistance.

CHROMOSPHERIC EVAPORATION IN AN X1.0 FLARE ON 2014 MARCH 29 OBSERVED WITH IRIS AND EIS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Y.; Ding, M. D.; Qiu, J.

Chromospheric evaporation refers to dynamic mass motions in flare loops as a result of rapid energy deposition in the chromosphere. These motions have been observed as blueshifts in X-ray and extreme-ultraviolet (EUV) spectral lines corresponding to upward motions at a few tens to a few hundreds of km s{sup −1}. Past spectroscopic observations have also revealed a dominant stationary component, in addition to the blueshifted component, in emission lines formed at high temperatures (∼10 MK). This is contradictory to evaporation models predicting predominant blueshifts in hot lines. The recently launched Interface Region Imaging Spectrograph (IRIS) provides high-resolution imaging and spectroscopicmore » observations that focus on the chromosphere and transition region in the UV passband. Using the new IRIS observations, combined with coordinated observations from the EUV Imaging Spectrometer, we study the chromospheric evaporation process from the upper chromosphere to the corona during an X1.0 flare on 2014 March 29. We find evident evaporation signatures, characterized by Doppler shifts and line broadening, at two flare ribbons that are separating from each other, suggesting that chromospheric evaporation takes place in successively formed flaring loops throughout the flare. More importantly, we detect dominant blueshifts in the high-temperature Fe xxi line (∼10 MK), in agreement with theoretical predictions. We also find that, in this flare, gentle evaporation occurs at some locations in the rise phase of the flare, while explosive evaporation is detected at some other locations near the peak of the flare. There is a conversion from gentle to explosive evaporation as the flare evolves.« less

Simultaneous measurement of monocomponent droplet temperature/refractive index, size and evaporation rate with phase rainbow refractometry

NASA Astrophysics Data System (ADS)

Wu, Yingchun; Crua, Cyril; Li, Haipeng; Saengkaew, Sawitree; Mädler, Lutz; Wu, Xuecheng; Gréhan, Gérard

2018-07-01

The accurate measurements of droplet temperature, size and evaporation rate are of great importance to characterize the heat and mass transfer during evaporation/condensation processes. The nanoscale size change of a micron-sized droplet exactly describes its transient mass transfer, but is difficult to measure because it is smaller than the resolutions of current size measurement techniques. The Phase Rainbow Refractometry (PRR) technique is developed and applied to measure droplet temperature, size and transient size changes and thereafter evaporation rate simultaneously. The measurement principle of PRR is theoretically derived, and it reveals that the phase shift of the time-resolved ripple structures linearly depends on, and can directly yield, nano-scale size changes of droplets. The PRR technique is first verified through the simulation of rainbows of droplets with changing size, and results show that PRR can precisely measure droplet refractive index, absolute size, as well as size change with absolute and relative errors within several nanometers and 0.6%, respectively, and thus PRR permits accurate measurements of transient droplet evaporation rates. The evaporations of flowing single n-nonane droplet and mono-dispersed n-heptane droplet stream are investigated by two PRR systems with a high speed linear CCD and a low speed array CCD, respectively. Their transient evaporation rates are experimentally determined and quantitatively agree well with the theoretical values predicted by classical Maxwell and Stefan-Fuchs models. With the demonstration of evaporation rate measurement of monocomponent droplet in this work, PRR is an ideal tool for measurements of transient droplet evaporation/condensation processes, and can be extended to multicomponent droplets in a wide range of industrially-relevant applications.

Analysis of heat recovery of diesel engine using intermediate working fluid

NASA Astrophysics Data System (ADS)

Jin, Lei; Zhang, Jiang; Tan, Gangfeng; Liu, Huaming

2017-07-01

The organic Rankine cycle (ORC) is an effective way to recovery the engine exhaust heat. The thermal stability of the evaporation system is significant for the stable operation of the ORC system. In this paper, the performance of the designed evaporation system which combines with the intermediate fluid for recovering the exhaust waste heat from a diesel engine is evaluated. The thermal characteristics of the target diesel engine exhaust gas are evaluated based on the experimental data firstly. Then, the mathematical model of the evaporation system is built based on the geometrical parameters and the specific working conditions of ORC. Finally, the heat transfer characteristics of the evaporation system are estimated corresponding to three typical operating conditions of the diesel engine. The result shows that the exhaust temperature at the evaporator outlet increases slightly with the engine speed and load. In the evaporator, the heat transfer coefficient of the Rankine working fluid is slightly larger than the intermediate fluid. However, the heat transfer coefficient of the intermediate fluid in the heat exchanger is larger than the exhaust side. The heat transfer areas of the evaporator in both the two-phase zone and the preheated zone change slightly along with the engine working condition while the heat transfer areas of the overheated zone has changed obviously. The maximum heat transfer rate occurs in the preheating zone while the minimum value occurs in the overheating zone. In addition, the Rankine working fluid temperature at the evaporator outlet is not sensitively affected by the torque and speed of the engine and the organic fluid flow is relatively stable. It is concluded that the intermediate fluid could effectively reduce the physical changes of Rankine working fluid in the evaporator outlet due to changes in engine operating conditions.

LITERATURE REVIEW ON IMPACT OF GLYCOLATE ON THE 2H EVAPORATOR AND THE EFFLUENT TREATMENT FACILITY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adu-Wusu, K.

2012-05-10

Glycolic acid (GA) is being studied as an alternate reductant in the Defense Waste Processing Facility (DWPF) feed preparation process. It will either be a total or partial replacement for the formic acid that is currently used. A literature review has been conducted on the impact of glycolate on two post-DWPF downstream systems - the 2H Evaporator system and the Effluent Treatment Facility (ETF). The DWPF recycle stream serves as a portion of the feed to the 2H Evaporator. Glycolate enters the evaporator system from the glycolate in the recycle stream. The overhead (i.e., condensed phase) from the 2H Evaporatormore » serves as a portion of the feed to the ETF. The literature search revealed that virtually no impact is anticipated for the 2H Evaporator. Glycolate may help reduce scale formation in the evaporator due to its high complexing ability. The drawback of the solubilizing ability is the potential impact on the criticality analysis of the 2H Evaporator system. It is recommended that at least a theoretical evaluation to confirm the finding that no self-propagating violent reactions with nitrate/nitrites will occur should be performed. Similarly, identification of sources of ignition relevant to glycolate and/or update of the composite flammability analysis to reflect the effects from the glycolate additions for the 2H Evaporator system are in order. An evaluation of the 2H Evaporator criticality analysis is also needed. A determination of the amount or fraction of the glycolate in the evaporator overhead is critical to more accurately assess its impact on the ETF. Hence, use of predictive models like OLI Environmental Simulation Package Software (OLI/ESP) and/or testing are recommended for the determination of the glycolate concentration in the overhead. The impact on the ETF depends on the concentration of glycolate in the ETF feed. The impact is classified as minor for feed glycolate concentrations {le} 33 mg/L or 0.44 mM. The ETF unit operations that will have minor/major impacts are chlorination, pH adjustment, 1st mercury removal, organics removal, 2nd mercury removal, and ion exchange. For minor impacts, the general approach is to use historical process operations data/modeling software like OLI/ESP and/or monitoring/compiled process operations data to resolve any uncertainties with testing as a last resort. For major impacts (i.e., glycolate concentrations > 33 mg/L or 0.44 mM), testing is recommended. No impact is envisaged for the following ETF unit operations regardless of the glycolate concentration - filtration, reverse osmosis, ion exchange resin regeneration, and evaporation.« less

Engaging Fifth Graders in Scientific Modeling to Learn about Evaporation and Condensation

ERIC Educational Resources Information Center

Hokayem, Hayat; Schwarz, Christina

2014-01-01

Reform efforts in science education have aimed at fostering scientific literacy by helping learners meaningfully engage in scientific practices to make sense of the world. In this paper, we report on our second year of unit implementation that has investigated 34 fifth grade students' (10-year-olds) learning about evaporation and condensation…

KINETIC DISTRIBUTION MODEL OF EVAPORATION, BIOSORPTION AND BIODEGRADATION OF POLYCHLORINATED BIPHENYLS (PCBS) IN THE SUSPENSION OF PSEUDOMONAS STUTZERI. (R826652)

EPA Science Inventory

Abstract

Kinetics of distribution of PCBs in an active bacterial suspension of Pseudomonas stutzeri was studied by monitoring the evaporated amounts and the concentration remaining in the liquid medium with the biomass. To determine the biodegradation rate const...

Solar and Net Radiation for Estimating Potential Evaporation from Three Vegetation Canopies

Treesearch

D.M. Amatya; R.W. Skaggs; G.W. Cheschier; G.P. Fernandez

2000-01-01

Solar and net radiation data are frequent/y used in estimating potential evaporation (PE) from various vegetative surfaces needed for water balance and hydrologic modeling studies. Weather parameters such as air temperature, relative humidity, wind speed, solar radiation, and net radiation have been continuously monitored using automated sensors to estimate PE for...

Theoretical and computational analyses of LNG evaporator

NASA Astrophysics Data System (ADS)

Chidambaram, Palani Kumar; Jo, Yang Myung; Kim, Heuy Dong

2017-04-01

Theoretical and numerical analysis on the fluid flow and heat transfer inside a LNG evaporator is conducted in this work. Methane is used instead of LNG as the operating fluid. This is because; methane constitutes over 80% of natural gas. The analytical calculations are performed using simple mass and energy balance equations. The analytical calculations are made to assess the pressure and temperature variations in the steam tube. Multiphase numerical simulations are performed by solving the governing equations (basic flow equations of continuity, momentum and energy equations) in a portion of the evaporator domain consisting of a single steam pipe. The flow equations are solved along with equations of species transport. Multiphase modeling is incorporated using VOF method. Liquid methane is the primary phase. It vaporizes into the secondary phase gaseous methane. Steam is another secondary phase which flows through the heating coils. Turbulence is modeled by a two equation turbulence model. Both the theoretical and numerical predictions are seen to match well with each other. Further parametric studies are planned based on the current research.

Black hole evaporation: information loss but no paradox

NASA Astrophysics Data System (ADS)

Modak, Sujoy K.; Ortíz, Leonardo; Peña, Igor; Sudarsky, Daniel

2015-10-01

The process of black hole evaporation resulting from the Hawking effect has generated an intense controversy regarding its potential conflict with quantum mechanics' unitary evolution. A recent set of works by a collaboration involving one of us, have revised the controversy with the aims of, on one hand, clarifying some conceptual issues surrounding it, and, at the same time, arguing that collapse theories have the potential to offer a satisfactory resolution of the so-called paradox. Here we show an explicit calculation supporting this claim using a simplified model of black hole creation and evaporation, known as the CGHS model, together with a dynamical reduction theory, known as CSL, and some speculative, but seemingly natural ideas about the role of quantum gravity in connection with the would-be singularity. This work represents a specific realization of general ideas first discussed in Okon and Sudarsky (Found Phys 44:114-143, 2014 and a complete and detailed analysis of a model first considered in Modak et al. (Phys Rev D 91(12):124009, 2015.

Kinetic vaporization of heavy metals during fluidized bed thermal treatment of municipal solid waste.

PubMed

Yu, Jie; Sun, Lushi; Xiang, Jun; Hu, Song; Su, Sheng

2013-02-01

Heavy metals volatilization during thermal treatment of model solid waste was theoretically and experimentally investigated in a fluidized bed reactor. Lead, cadmium, zinc and copper, the most four conventional heavy metals were investigated. Particle temperature model and metal diffusion model were established to simulate the volatilization of CdCl(2) evaporation and investigate the possible influencing factors. The diffusion coefficient, porosity and particle size had significant effects on metal volatilization. The higher diffusion coefficient and porosity resulted in the higher metal evaporation. The influence of redox conditions, HCl, water and mineral matrice were also investigated experimentally. The metal volatilization can be promoted by the injection of HCl, while oxygen played a negative role. The diffusion process of heavy metals within particles also had a significant influence on kinetics of their vaporization. The interaction between heavy metals and mineral matter can decrease metal evaporation amount by forming stable metallic species. Copyright © 2012 Elsevier Ltd. All rights reserved.

Consistent simulation of droplet evaporation based on the phase-field multiphase lattice Boltzmann method

NASA Astrophysics Data System (ADS)

Safari, Hesameddin; Rahimian, Mohammad Hassan; Krafczyk, Manfred

2014-09-01

In the present article, we extend and generalize our previous article [H. Safari, M. H. Rahimian, and M. Krafczyk, Phys. Rev. E 88, 013304 (2013), 10.1103/PhysRevE.88.013304] to include the gradient of the vapor concentration at the liquid-vapor interface as the driving force for vaporization allowing the evaporation from the phase interface to work for arbitrary temperatures. The lattice Boltzmann phase-field multiphase modeling approach with a suitable source term, accounting for the effect of the phase change on the velocity field, is used to solve the two-phase flow field. The modified convective Cahn-Hilliard equation is employed to reconstruct the dynamics of the interface topology. The coupling between the vapor concentration and temperature field at the interface is modeled by the well-known Clausius-Clapeyron correlation. Numerous validation tests including one-dimensional and two-dimensional cases are carried out to demonstrate the consistency of the presented model. Results show that the model is able to predict the flow features around and inside an evaporating droplet quantitatively in quiescent as well as convective environments.

Consistent simulation of droplet evaporation based on the phase-field multiphase lattice Boltzmann method.

PubMed

Safari, Hesameddin; Rahimian, Mohammad Hassan; Krafczyk, Manfred

2014-09-01

In the present article, we extend and generalize our previous article [H. Safari, M. H. Rahimian, and M. Krafczyk, Phys. Rev. E 88, 013304 (2013)] to include the gradient of the vapor concentration at the liquid-vapor interface as the driving force for vaporization allowing the evaporation from the phase interface to work for arbitrary temperatures. The lattice Boltzmann phase-field multiphase modeling approach with a suitable source term, accounting for the effect of the phase change on the velocity field, is used to solve the two-phase flow field. The modified convective Cahn-Hilliard equation is employed to reconstruct the dynamics of the interface topology. The coupling between the vapor concentration and temperature field at the interface is modeled by the well-known Clausius-Clapeyron correlation. Numerous validation tests including one-dimensional and two-dimensional cases are carried out to demonstrate the consistency of the presented model. Results show that the model is able to predict the flow features around and inside an evaporating droplet quantitatively in quiescent as well as convective environments.

Pressurization of a Flightweight, Liquid Hydrogen Tank: Evaporation & Condensation at a Liquid/Vapor Interface

NASA Technical Reports Server (NTRS)

Stewart, Mark E. M.

2017-01-01

This paper presents an analysis and simulation of evaporation and condensation at a motionless liquid/vapor interface. A 1-D model equation, emphasizing heat and mass transfer at the interface, is solved in two ways, and incorporated into a subgrid interface model within a CFD simulation. Simulation predictions are compared with experimental data from the CPST Engineering Design Unit tank, a cryogenic fluid management test tank in 1-g. The numerical challenge here is the physics of the liquid/vapor interface; pressurizing the ullage heats it by several degrees, and sets up an interfacial temperature gradient that transfers heat to the liquid phase-the rate limiting step of condensation is heat conducted through the liquid and vapor. This physics occurs in thin thermal layers O(1 mm) on either side of the interface which is resolved by the subgrid interface model. An accommodation coefficient of 1.0 is used in the simulations which is consistent with theory and measurements. This model is predictive of evaporation/condensation rates, that is, there is no parameter tuning.

Study of the effect of soil disturbance on vapor transport through integrated modeling of the atmospheric boundary layer and shallow subsurface

NASA Astrophysics Data System (ADS)

Trautz, A.; Smits, K. M.; Cihan, A.; Wallen, B.

2014-12-01

Soil-water evaporation is one of the governing processes responsible for controlling water and energy exchanges between the land and atmosphere. Despite its wide relevance and application in many natural and manmade environments (e.g. soil tillage practices, wheel-track compaction, fire burn environments, textural layering and buried ordinances), there are very few studies of evaporation from disturbed soil profiles. The purpose of this study was to explore the effect of soil disturbance and capillary coupling on water distribution and fluxes. We modified a theory previously developed by the authors that allows for coupling single-phase (gas), two-component (air and water vapor) transfer in the atmosphere and two-phase (gas, liquid), two-component (air and water vapor) flow in porous media at the REV scale under non-isothermal, non-equilibrium conditions to better account for the hydraulic and thermal interactions within the media. Modeling results were validated and compared using precision data generated in a two-dimensional soil tank consisting of a loosely packed soil surrounded by a tightly packed soil. The soil tank was outfitted with an array of sensors for the measurement of wind velocity, soil and air temperature, relative humidity, soil moisture, and weight. Results demonstrated that, by using this coupling approach, it is possible to predict the different stages of the drying process in heterogeneous soils with good accuracy. Evaporation from a heterogeneous soil consisting of a loose and tight packing condition is larger than the homogeneous equivalent systems. Liquid water is supplied from the loosely packed soil region to the tightly packed soil regions, sustaining a longer Stage I evaporation in the tightly packed regions with overall greater evaporation rate than uniform homogeneous packing. In contrast, lower evaporation rates from the loosely packed regions are observed due to a limited liquid water supply resulting from capillary flow to the tightly packed regions and a shorter stage 1 evaporation period.

Understanding the relationship between actual and potential evapotranspirations from long- term water balance analysis and flux observation

NASA Astrophysics Data System (ADS)

Yang, D.; Yang, H.; Sun, F.

2007-12-01

Increase in air temperature and decrease in pan evaporation was found to be common worldwide during the past half century. This results in controversy in view of the changes to the hydrological cycle. Increases in precipitation have been expected due to the Clausius¡§CClapyeron relation in that the specific humidity increases exponentially with the greenhouse-gas induced temperature increasing and confirmed by measurements over northern extratropical land areas. The hydrologic cycle is expected to be intensified (or accelerated). However, the decreased pan evaporation is found to be well related to the global dimming, i.e., the decreased solar radiation induced by the pollution increasing, thus evaporation (i.e., the latent heat flux) should be steadily decreasing from the energy balance perspective. Many researchers explained that the potential evaporation (usually measured by pan) is decreased with increasing of precipitation; however, the increased soil moisture (due to precipitation increasing) can be evaporated because of extra energy available. Therefore, the actual and potential evaporation are in complementary relationship, which is expected to unify the controversy between global warming and dimming. This means that pan evaporation decrease implicates acceleration of the global hydrologic cycle, i.e., increase in the terrestrial evaporation. Based on the complementary theory, many operational formulae have been introduced to estimated actual evaporation from the potential evaporation. Our recent water balance analysis of 108 catchments in non-humid regions of China has shown that there are no general opposite trends between potential and actual evaporation in the same period. A novel phenomenon has been found that the complementary relationships in evaporation are distinctly confirmed when the annual actual and potential evaporation are plotted against annual precipitation; However, complementary relationships disappear in many catchments when actual and potential evaporations are plotted against the time (year) during the same period. This means that complementary idea cannot provide universally correct predictions on the trend of actual evaporation only from the potential one. In this research, we examine the coupled water-energy balance based on Budyko hypothesis and proposed a conceptual model for predicting the inter-annual variability of annual water balance, and the change trends of water balances due to climate changes. The wet environment evaporation was defined as the boundary condition in the Bouchet hypothesis and introduced into complementary relationship (CR), which combined the actual evaporation with potential evaporation in an equation. However, the CR was derived in a closed system where no horizontal energy advection existed. The effect of the horizontal advection on the CR in a real open system was also analyzed in this study. Using the long-term water balance analysis in the 108 study catchments and flux observation at 7 sites in Asia monsoon region, the regional and seasonal variability of the complementary relationship was examined. Key Words: climate change, evapotranspiration, water balance, flux observation, Budyko hypothesis, Bouchet hypothesis

Assimilation of Global Radar Backscatter and Radiometer Brightness Temperature Observations to Improve Soil Moisture and Land Evaporation Estimates

NASA Technical Reports Server (NTRS)

Lievens, H.; Martens, B.; Verhoest, N. E. C.; Hahn, S.; Reichle, R. H.; Miralles, D. G.

2017-01-01

Active radar backscatter (s?) observations from the Advanced Scatterometer (ASCAT) and passive radiometer brightness temperature (TB) observations from the Soil Moisture Ocean Salinity (SMOS) mission are assimilated either individually or jointly into the Global Land Evaporation Amsterdam Model (GLEAM) to improve its simulations of soil moisture and land evaporation. To enable s? and TB assimilation, GLEAM is coupled to the Water Cloud Model and the L-band Microwave Emission from the Biosphere (L-MEB) model. The innovations, i.e. differences between observations and simulations, are mapped onto the model soil moisture states through an Ensemble Kalman Filter. The validation of surface (0-10 cm) soil moisture simulations over the period 2010-2014 against in situ measurements from the International Soil Moisture Network (ISMN) shows that assimilating s? or TB alone improves the average correlation of seasonal anomalies (Ran) from 0.514 to 0.547 and 0.548, respectively. The joint assimilation further improves Ran to 0.559. Associated enhancements in daily evaporative flux simulations by GLEAM are validated based on measurements from 22 FLUXNET stations. Again, the singular assimilation improves Ran from 0.502 to 0.536 and 0.533, respectively for s? and TB, whereas the best performance is observed for the joint assimilation (Ran = 0.546). These results demonstrate the complementary value of assimilating radar backscatter observations together with brightness temperatures for improving estimates of hydrological variables, as their joint assimilation outperforms the assimilation of each observation type separately.

Evaporation of freely suspended single droplets: experimental, theoretical and computational simulations

NASA Astrophysics Data System (ADS)

Hołyst, R.; Litniewski, M.; Jakubczyk, D.; Kolwas, K.; Kolwas, M.; Kowalski, K.; Migacz, S.; Palesa, S.; Zientara, M.

2013-03-01

Evaporation is ubiquitous in nature. This process influences the climate, the formation of clouds, transpiration in plants, the survival of arctic organisms, the efficiency of car engines, the structure of dried materials and many other phenomena. Recent experiments discovered two novel mechanisms accompanying evaporation: temperature discontinuity at the liquid-vapour interface during evaporation and equilibration of pressures in the whole system during evaporation. None of these effects has been predicted previously by existing theories despite the fact that after 130 years of investigation the theory of evaporation was believed to be mature. These two effects call for reanalysis of existing experimental data and such is the goal of this review. In this article we analyse the experimental and the computational simulation data on the droplet evaporation of several different systems: water into its own vapour, water into the air, diethylene glycol into nitrogen and argon into its own vapour. We show that the temperature discontinuity at the liquid-vapour interface discovered by Fang and Ward (1999 Phys. Rev. E 59 417-28) is a rule rather than an exception. We show in computer simulations for a single-component system (argon) that this discontinuity is due to the constraint of momentum/pressure equilibrium during evaporation. For high vapour pressure the temperature is continuous across the liquid-vapour interface, while for small vapour pressures the temperature is discontinuous. The temperature jump at the interface is inversely proportional to the vapour density close to the interface. We have also found that all analysed data are described by the following equation: da/dt = P1/(a + P2), where a is the radius of the evaporating droplet, t is time and P1 and P2 are two parameters. P1 = -λΔT/(qeffρL), where λ is the thermal conductivity coefficient in the vapour at the interface, ΔT is the temperature difference between the liquid droplet and the vapour far from the interface, qeff is the enthalpy of evaporation per unit mass and ρL is the liquid density. The P2 parameter is the kinetic correction proportional to the evaporation coefficient. P2 = 0 only in the absence of temperature discontinuity at the interface. We discuss various models and problems in the determination of the evaporation coefficient and discuss evaporation scenarios in the case of single- and multi-component systems.

Evaporation loss and evaporation/transpiration partitioning from isotope-based monitoring of Canada's provincial and national river networks

NASA Astrophysics Data System (ADS)

Gibson, J. J.; Birks, S. J.; Stadnyk, T.; Delavau, C. J.

2017-12-01

Stable isotopes of water have been measured since the 1990's as part of hydrometric monitoring programs within Canada's Water Survey of Canada gauging network and Alberta's Long-Term River Network. These datasets are being applied for hydrograph separation of streamflow sources, including rain, snow, groundwater, and surface water, as well as for estimation of watershed evaporation losses and evaporation/transpiration partitioning. Here we describe an innovative isotope mass balance approach, discuss benefits and limitations of the method, and present selected results that illustrate important regional trends in the contemporary hydrology of Canada. Overall, isotopes are shown to be useful for constraining water balance variations across regions with low monitoring density. Recommendations for future activities are identified, including regional comparisons with outputs from isotope-capable distributed hydrologic models.

Simulation of Patterned Glass Film Formation in the Evaporating Colloidal Liquid under IR Heating

NASA Astrophysics Data System (ADS)

Kolegov, K. S.

2018-02-01

The paper theoretically studies the method of evaporative lithography in combination with external infrared heating. This method makes it possible to form solid microstructures of the required relief shape as a result of evaporation of the liquid film of the colloidal solution under the mask. The heated particles are sintered easier, so there are no cracks in the obtained structure, unlike the structure obtained employing the standard method of evaporative lithography. The paper puts forward a modification of the mathematical model which allows to describe not only heat and mass transfer at the initial stage of the process, but also the phase transition of colloidal solution into glass. Aqueous latex is taken as an example. The resulting final form of solid film is in good agreement with the experimental data of other authors.

Evaporation dynamics of completely wetting drops on geometrically textured surfaces

NASA Astrophysics Data System (ADS)

Mekhitarian, Loucine; Sobac, Benjamin; Dehaeck, Sam; Haut, Benoît; Colinet, Pierre

2017-10-01

This study deals with the evaporation dynamics of completely wetting and highly volatile drops deposited on geometrically textured but chemically homogeneous surfaces. The texturation consists in a cylindrical pillars array with a square pitch. The triple line dynamics and the drop shape are characterized by an interferometric method. A parametric study is realized by varying the radius and the height of the pillars (at fixed interpillar distance), allowing to distinguish three types of dynamics: i) an evaporation-dominated regime with a receding triple line; ii) a spreading-dominated regime with an initially advancing triple line; iii) a cross-over region with strong pinning effects. The overall picture is in qualitative agreement with a mathematical model showing that the selected regime mostly depends on the value of a dimensionless parameter comparing the time scales for evaporation and spreading into the substrate texture.

HCMM satellite follow-on investigation no. 25. Soil moisture and heat budget evalution in selected European zones of agricultural and environmental interest (TELLUS project)

NASA Technical Reports Server (NTRS)

1980-01-01

A simple procedure to evaluate actual evaporation was derived by linearizing the surface energy balance equation, using Taylor's expansion. The original multidimensional hypersurface could be reduced to a linear relationship between evaporation and surface temperature or to a surface relationship involving evaporation, surface temperature and albedo. This procedure permits a rapid sensitivity analysis of the surface energy balance equation as well as a speedy mapping of evaporation from remotely sensed surface temperatures and albedo. Comparison with experimental data yielded promising results. The validity of evapotranspiration and soil moisture models in semiarid conditions was tested. Wheat was the crop chosen for a continuous measurement campaign made in the south of Italy. Radiometric, micrometeorologic, agronomic and soil data were collected for processing and interpretation.

Land-atmosphere coupling and climate prediction over the U.S. Southern Great Plains

NASA Astrophysics Data System (ADS)

Williams, Ian N.; Lu, Yaqiong; Kueppers, Lara M.; Riley, William J.; Biraud, Sebastien C.; Bagley, Justin E.; Torn, Margaret S.

2016-10-01

Biases in land-atmosphere coupling in climate models can contribute to climate prediction biases, but land models are rarely evaluated in the context of this coupling. We tested land-atmosphere coupling and explored effects of land surface parameterizations on climate prediction in a single-column version of the National Center for Atmospheric Research Community Earth System Model (CESM1.2.2) and an off-line Community Land Model (CLM4.5). The correlation between leaf area index (LAI) and surface evaporative fraction (ratio of latent to total turbulent heat flux) was substantially underpredicted compared to observations in the U.S. Southern Great Plains, while the correlation between soil moisture and evaporative fraction was overpredicted by CLM4.5. To estimate the impacts of these errors on climate prediction, we modified CLM4.5 by prescribing observed LAI, increasing soil resistance to evaporation, increasing minimum stomatal conductance, and increasing leaf reflectance. The modifications improved the predicted soil moisture-evaporative fraction (EF) and LAI-EF correlations in off-line CLM4.5 and reduced the root-mean-square error in summer 2 m air temperature and precipitation in the coupled model. The modifications had the largest effect on prediction during a drought in summer 2006, when a warm bias in daytime 2 m air temperature was reduced from +6°C to a smaller cold bias of -1.3°C, and a corresponding dry bias in precipitation was reduced from -111 mm to -23 mm. The role of vegetation in droughts and heat waves is underpredicted in CESM1.2.2, and improvements in land surface models can improve prediction of climate extremes.

Evaporation-driven instability of the precorneal tear film.

PubMed

Peng, Cheng-Chun; Cerretani, Colin; Braun, Richard J; Radke, C J

2014-04-01

Tear-film instability is widely believed to be a signature of eye health. When an interblink is prolonged, randomly distributed ruptures occur in the tear film. "Black spots" and/or "black streaks" appear in 15 to 40 s for normal individuals. For people who suffer from dry eye, tear-film breakup time (BUT) is typically less than a few seconds. To date, however, there is no satisfactory quantitative explanation for the origin of tear rupture. Recently, it was proposed that tear-film breakup is related to locally high evaporative thinning. A spatial variation in the thickness of the tear-film lipid layer (TFLL) may lead to locally elevated evaporation and subsequent tear-film breakup. We examine the local-evaporation-driven tear-film-rupture hypothesis in a one-dimensional (1-D) model for the evolution of a thin aqueous tear film overriding the cornea subject to locally elevated evaporation at its anterior surface and osmotic water influx at its posterior surface. Evaporation rate depends on mass transfer both through the coating lipid layer and through ambient air. We establish that evaporation-driven tear-film breakup can occur under normal conditions but only for higher aqueous evaporation rates. Predicted roles of environmental conditions, such as wind speed and relative humidity, on tear-film stability agree with clinical observations. More importantly, locally elevated evaporation leads to hyperosmolar spots in the tear film and, hence, vulnerability to epithelial irritation. In addition to evaporation rate, tear-film instability depends on the strength of healing flow from the neighboring region outside the breakup region, which is determined by the surface tension at the tear-film surface and by the repulsive thin-film disjoining pressure. This study provides a physically consistent and quantitative explanation for the formation of black streaks and spots in the human tear film during an interblink. Copyright © 2013 Elsevier B.V. All rights reserved.

A new two-Dimensional Physical Basis for the Complementary Relation Between Terrestrial and pan Evaporation

NASA Astrophysics Data System (ADS)

Pettijohn, J. C.; Salvucci, G. D.

2008-12-01

Archived global measurements of water loss from evaporation pans constitute an important indirect measure of evaporative flux. Historical data from evaporation pans shows a decreasing trend over the last half century, but the relationship between pan evaporation and moisture-limited terrestrial evaporation is complex, leading to ambiguities in the interpretation of this data. Under energy-limited conditions, pan evaporation (Epan) and moisture-limited terrestrial evaporation (E) increase or decrease together, while in moisture- limited conditions these fluxes form a complementary relation in which increases in one rate accompany decreases in the other. This has lead to debate about the meaning of the observed trends in the context of changing climate. Here a two-dimensional numerical model of a wet pan in a drying landscape is used to demonstrate that, over a wide range of realistic atmospheric and surface conditions, the influence that changes in E have on Epan (1) are complementary and linear, (2) do not depend upon surface wind speed, and (3) are strikingly asymmetrical, in that a unit decrease in E causes approximately a five-fold increase in Epan, as found in a recent analysis of daily evaporation from US grasslands (Kahler and Brutsaert, 2006). Previous attempts to explain the CR have been based on one dimensional diffusion and energy balance arguments, leading to analytic solutions based on Penman-type bulk difference equations. But without acknowledging the spatially complex multidimensional humidity and temperature field around the pan, and specifically how these fields change as the contrast between the wet pan and the drying land surface increases, such integrated bulk difference equations are a priori incomplete (they ignore important divergence terms), and thus these explanations must be considered physically incomplete. Results of the present study improve the theoretical foundation of the CR, thus increasing the reliability with which it can be applied to estimate water balance and to understand the pan evaporation record of climate change.

Final Report: Modifications and Optimization of the Organic Rankine Cycle to Improve the Recovery of Waste Heat

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guillen, Donna Post; Zia, Jalal

2013-09-01

This research and development (R&D) project exemplifies a shared public private commitment to advance the development of energy efficient industrial technologies that will reduce the U.S. dependence upon foreign oil, provide energy savings and reduce greenhouse gas emissions. The purpose of this project was to develop and demonstrate a Direct Evaporator for the Organic Rankine Cycle (ORC) for the conversion of waste heat from gas turbine exhaust to electricity. In conventional ORCs, the heat from the exhaust stream is transferred indirectly to a hydrocarbon based working fluid by means of an intermediate thermal oil loop. The Direct Evaporator accomplishes preheating,more » evaporation and superheating of the working fluid by a heat exchanger placed within the exhaust gas stream. Direct Evaporation is simpler and up to 15% less expensive than conventional ORCs, since the secondary oil loop and associated equipment can be eliminated. However, in the past, Direct Evaporation has been avoided due to technical challenges imposed by decomposition and flammability of the working fluid. The purpose of this project was to retire key risks and overcome the technical barriers to implementing an ORC with Direct Evaporation. R&D was conducted through a partnership between the Idaho National Laboratory (INL) and General Electric (GE) Global Research Center (GRC). The project consisted of four research tasks: (1) Detailed Design & Modeling of the ORC Direct Evaporator, (2) Design and Construction of Partial Prototype Direct Evaporator Test Facility, (3) Working Fluid Decomposition Chemical Analyses, and (4) Prototype Evaluation. Issues pertinent to the selection of an ORC working fluid, along with thermodynamic and design considerations of the direct evaporator, were identified. The FMEA (Failure modes and effects analysis) and HAZOP (Hazards and operability analysis) safety studies performed to mitigate risks are described, followed by a discussion of the flammability analysis of the direct evaporator. A testbed was constructed and the prototype demonstrated at the GE GRC Niskayuna facility.« less

Investigating the Control of Ocean-Atmospheric Oscillations on Global Terrestrial Evaporation

NASA Astrophysics Data System (ADS)

Martens, B.; Waegeman, W.; Dorigo, W.; Verhoest, N.; Miralles, D. G.

2017-12-01

Intra-annual and multi-decadal variability in Earth's climate is strongly driven by periodic oscillations in the coupled state of our atmosphere and ocean. These oscillations do not only impact climate in nearby regions, but can also have an effect on the climate in remote areas, a phenomenon that is often referred to as teleconnection. Because changes in local climate immediately affect terrestrial ecosystems through a series of complex processes, ocean-atmospheric oscillations are expected to influence land evaporation; i.e. the return flux of water from land into the atmosphere. In this presentation, the effects of ocean-atmospheric oscillations on global terrestrial evaporation are analysed. We use multi-decadal, satellite-based observations of different climate variables (air temperature, radiation, precipitation) in combination with a simple supervised learning method - the Least Absolute Shrinkage and Selection Operator - to detect the impact of sixteen leading ocean-atmospheric oscillations on terrestrial evaporation. The latter is retrieved using the Global Land Evaporation Amsterdam Model (GLEAM). The analysis reveals hotspot regions in which more than 30% of the inter-annual variability in terrestrial evaporation can be explained by ocean-atmospheric oscillations. The impact is different per region and season, and can typically be attributed to a small subset of oscillations. For instance, the dynamics in terrestrial evaporation over eastern Australia are substantially impacted by both the El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) during Austral spring. Using the same learning method, but targeting terrestrial evaporation based on its local climatic drivers (air temperature, precipitation, and radiation), shows the dominant control of precipitation on terrestrial evaporation in Australia, suggesting that both ENSO and IOD affect the precipitation, in his turn influencing evaporation. The latter is confirmed by regressing precipitation to the ocean-atmospheric oscillations. The results of our study allow for a better understanding of the link between ocean-atmosphere dynamics and terrestrial bio-geochemical cycles, and may help improve the prediction of future changes in the water cycle over the continents.

Intra-event isotope and raindrop size data of tropical rain reveal effects concealed by event averaged data

NASA Astrophysics Data System (ADS)

Managave, S. R.; Jani, R. A.; Narayana Rao, T.; Sunilkumar, K.; Satheeshkumar, S.; Ramesh, R.

2016-08-01

Evaporation of rain is known to contribute water vapor, a potent greenhouse gas, to the atmosphere. Stable oxygen and hydrogen isotopic compositions (δ18O and, δD, respectively) of precipitation, usually measured/presented as values integrated over rain events or monthly mean values, are important tools for detecting evaporation effects. The slope ~8 of the linear relationship between such time-averaged values of δD and δ18O (called the meteoric water line) is widely accepted as a proof of condensation under isotopic equilibrium and absence of evaporation of rain during atmospheric fall. Here, through a simultaneous investigation of the isotopic and drop size distributions of seventeen rain events sampled on an intra-event scale at Gadanki (13.5°N, 79.2°E), southern India, we demonstrate that the evaporation effects, not evident in the time-averaged data, are significantly manifested in the sub-samples of individual rain events. We detect this through (1) slopes significantly less than 8 for the δD-δ18O relation on intra-event scale and (2) significant positive correlations between deuterium excess ( d-excess = δD - 8*δ18O; lower values in rain indicate evaporation) and the mass-weighted mean diameter of the raindrops ( D m ). An estimated ~44 % of rain is influenced by evaporation. This study also reveals a signature of isotopic equilibration of rain with the cloud base vapor, the processes important for modeling isotopic composition of precipitation. d-excess values of rain are modified by the post-condensation processes and the present approach offers a way to identify the d-excess values least affected by such processes. Isotope-enabled global circulation models could be improved by incorporating intra-event isotopic data and raindrop size dependent isotopic effects.

Rain Reevaporation, Boundary Layer Convection Interactions, and Pacific Rainfall Patterns in an AGCM

NASA Technical Reports Server (NTRS)

Bacmeister, Julio T.; Suarez, Max J.; Robertson, Franklin R.

2004-01-01

Sensitivity experiments with an atmospheric general circulation model (AGCM) show that parameterized rain re-evaporation has a large impact on simulated precipitation patterns in the tropical Pacific, especially on the configuration of the model s intertropical convergence zone (ITCZ). Weak re-evaporation leads t o the formation of a "double ITCZ" during the northern warm season. The double ITCZ is accompanied by strong coupling between precipitation and high-frequency vertical motion in the planetary boundary layer (PBL). Strong reevaporation leads to a better overall agreement of simulated precipitation with observations. The model s double ITCZ bias is reduced. At the same time, correlation between high-frequency vertical motion in the PBL and precipitation is reduced. Experiments with modified physics suggest that evaporative cooling by rain near the PBL top weakens the coupling between precipitation and vertical motion. This may reduce the model s tendency to form double ITCZs. The strength of high-frequency vertical motions in the PBL was also reduced directly through the introduction of a diffusive cumulus momentum transport (DCMT) parameterization. The DCMT had a visible impact on simulated precipitation in the tropics, but did not reduce the model s double bias in all cases.

Circulation and rainfall climatology of a 10-year (1979 - 1988) integration with the Goddard Laboratory for atmospheres general circulation model

NASA Technical Reports Server (NTRS)

Kim, J.-H.; Sud, Y. C.

1993-01-01

A 10-year (1979-1988) integration of Goddard Laboratory for Atmospheres (GLA) general circulation model (GCM) under Atmospheric Model Intercomparison Project (AMIP) is analyzed and compared with observation. The first momentum fields of circulation variables and also hydrological variables including precipitation, evaporation, and soil moisture are presented. Our goals are (1) to produce a benchmark documentation of the GLA GCM for future model improvements; (2) to examine systematic errors between the simulated and the observed circulation, precipitation, and hydrologic cycle; (3) to examine the interannual variability of the simulated atmosphere and compare it with observation; and (4) to examine the ability of the model to capture the major climate anomalies in response to events such as El Nino and La Nina. The 10-year mean seasonal and annual simulated circulation is quite reasonable compared to the analyzed circulation, except the polar regions and area of high orography. Precipitation over tropics are quite well simulated, and the signal of El Nino/La Nina episodes can be easily identified. The time series of evaporation and soil moisture in the 12 biomes of the biosphere also show reasonable patterns compared to the estimated evaporation and soil moisture.

Modeling and Simulation of Ablation-Controlled Plasmas

NASA Astrophysics Data System (ADS)

Kundrapu, Madhusudhan N.

Ablation and plasma formation in high energy laser target interactions and arc discharges are studied numerically. Each of the two processes is modeled separately due to the type of energy source and the resulting flow eld. Ablation of the target material and plasma formation are coupled to obtain evaporation rate, temperature distribution, velocity eld, and species concentration self-consistently. Laser ablation is studied in the perspective of directed energy applications, where beam size varies from few centimeters to tens of centimeters with energies extending up to 10 kW/cm2. Because of this high energy deposition, the evaporated material expands to supersonic speeds into the free space. Due to the large spot sizes and associated supersonic flow, one dimensional Euler equations are considered to be sufficient for modeling the plume. Instead, more emphasis was given to evaporation model, by introducing Knudsen layer kinetics at the plume target interface, and plasma shielding. The evaporation rate is validated with results from the experiments and simulations are carried out to nd the in fluence of laser beam frequency on evaporation rates. The evaporation model used in this work is found to be more accurate than the widely used model based on sonic speed assumption. The optimum beam wavelength for Al surfaces is found to be 850 nm. Attenuation of telemetry data by plasma is a concern for the testing of directed energy systems. Electrostatic approach for the mitigation of communication attenuation is analyzed to obtain the fluency limits up to which the approach can be implemented. It is found from sheath calculations that uninterrupted telemetry can be achieved through Al plasma for fluences below 4 J/cm2 at a background pressure of 1 atm, using a maximum bias voltage of 10 kV . Arc discharge ablation is modeled for the synthesis of nanoparticles. The electric arc generated between the electrodes, placed inside a Helium chamber, evaporates the catalyst-lled carbon anode to form a web of nanoparticles. Conservative form of Navier-Stokes equations along with energy equation and species transport are solved in cylindrical coordinates using SIMPLER algorithm. Current continuity in electric potential form is solved to obtain the potential distribution. Current is then calculated from the potential, and from axial current, magnetic eld is obtained using Ampere's law. Anode sublimation rate and current voltage characteristics are compared with experiments for arc currents varying from 10 to 100 A. Nanoparticle formation is estimated using homogeneous nucleation and surface diusion models. For an arc current of 60 A and inter-electrode gap of 4 mm with 68 Pa, the diameter of Nickel cluster is found to be 9.2 nm, which agrees with the upper limit of TEM measurements. The length of single walled nanotube is found to be 3.5 mum for this case. Parametric studies carried out by varying arc current, background pressure, and electrode gap showed moderate in uence on the growth rate. Hot chamber arc discharge method, proposed in this work, is found to be promising to maximize the growth of nanoparticles.

Hydrological balance and water transport processes of partially sealed soils

NASA Astrophysics Data System (ADS)

Timm, Anne; Wessolek, Gerd

2017-04-01

With increased urbanisation, soil sealing and its drastic effects on hydrological processes have received a lot of attention. Based on safety concerns, there has been a clear focus on urban drainage and prevention of urban floods caused by storm water events. For this reason, any kind of sealing is often seen as impermeable runoff generator that prevents infiltration and evaporation. While many hydrological models, especially storm water models, have been developed, there are only a handful of empirical studies actually measuring the hydrological balance of (partially) sealed surfaces. These challenge the general assumption of negligible infiltration and evaporation and show that these processes take place even for severe sealing such as asphalt. Depending on the material, infiltration from partially sealed surfaces can be equal to that of vegetated ones. Therefore, more detailed knowledge is needed to improve our understanding and models. In Berlin, two partially sealed weighable lysimeters were equipped with multiple temperature and soil moisture sensors in order to study their hydrological balance, as well as water and heat transport processes within the soil profile. This combination of methods affirms previous observations and offers new insights into altered hydrological processes of partially sealed surfaces at a small temporal scale. It could be verified that not all precipitation is transformed into runoff. Even for a relatively high sealing degree of concrete slabs with narrow seams, evaporation and infiltration may exceed runoff. Due to the lack of plant roots, the hydrological balance is mostly governed by precipitation events and evaporation generally occurs directly after rainfall. However, both surfaces allow for upward water transport from the upper underlying soil layers, sometimes resulting in relatively low evaporation rates on days without precipitation. The individual response of the surfaces differs considerably, which illustrates how important process orientated studies for different types of sealing material are.

Advanced Multi-phase Flow CFD Model Development for Solid Rocket Motor Flowfield Analysis

NASA Technical Reports Server (NTRS)

Liaw, Paul; Chen, Yen-Sen

1995-01-01

A Navier-Stokes code, finite difference Navier-Stokes (FDNS), is used to analyze the complicated internal flowfield of the SRM (solid rocket motor) to explore the impacts due to the effects of chemical reaction, particle dynamics, and slag accumulation on the solid rocket motor (SRM). The particulate multi-phase flowfield with chemical reaction, particle evaporation, combustion, breakup, and agglomeration models are included in present study to obtain a better understanding of the SRM design. Finite rate chemistry model is applied to simulate the chemical reaction effects. Hermsen correlation model is used for the combustion simulation. The evaporation model introduced by Spalding is utilized to include the heat transfer from the particulate phase to the gase phase due to the evaporation of the particles. A correlation of the minimum particle size for breakup expressed in terms of the Al/Al2O3 surface tension and shear force was employed to simulate the breakup of particles. It is assumed that the breakup occurs when the Weber number exceeds 6. A simple L agglomeration model is used to investigate the particle agglomeration. However, due to the large computer memory requirements for the agglomeration model, only 2D cases are tested with the agglomeration model. The VOF (Volume of Fluid) method is employed to simulate the slag buildup in the aft-end cavity of the redesigned solid rocket motor (RSRM). Monte Carlo method is employed to calculate the turbulent dispersion effect of the particles. The flowfield analysis obtained using the FDNS code in the present research with finite rate chemical reaction, particle evaporation, combustion, breakup, agglomeration, and VOG models will provide a design guide for the potential improvement of the SRM including the use of materials and the shape of nozzle geometry such that a better performance of the SRM can be achieved. The simulation of the slag buildup in the aft-end cavity can assist the designer to improve the design of the RSRM geometry.

Evaporation and transport of water isotopologues from Greenland lakes: The lake size effect

NASA Astrophysics Data System (ADS)

Feng, Xiahong; Lauder, Alex M.; Posmentier, Eric S.; Kopec, Ben G.; Virginia, Ross A.

2016-01-01

Isotopic compositions of evaporative flux from a lake are used in many hydrological and paleoclimate studies that help constrain the water budget of a lake and/or to infer changes in climate conditions. The isotopic fluxes of evaporation from a water surface are typically computed using a zero dimensional (0-D) model originally conceptualized by Craig and Gordon (1965). Such models generally have laminar and turbulent layers, assume a steady state condition, and neglect horizontal variations. In particular, the effect of advection on isotopic variations is not considered. While this classical treatment can be used for some sections of large open surface water bodies, such as an ocean or a large lake, it may not apply to relatively small water bodies where limited fetch does not allow full equilibration between air from land and the water surface. Both horizontal and vertical gradients in water vapor concentration and isotopic ratios may develop over a lake. These gradients, in turn, affect the evaporative fluxes of water vapor and its isotopic ratios, which is not adequately predicted by a 0-D model. We observed, for the first time, the vertical as well as horizontal components of vapor and isotopic gradients as relatively dry and isotopically depleted air advected over the surfaces of several lakes up to a 5 km fetch under winds of 1-5 m/s in Kangerlussuaq, Greenland. We modeled the vapor and isotopic distribution in air above the lake using a steady state 2-D model, in which vertical diffusive transport balances horizontal advection. The model was verified by our observations, and then used to calculate evaporative fluxes of vapor and its isotopic ratios. In the special case of zero wind speed, the model reduces to 1-D. Results from this 1-D model are compared with those from the 2-D model to assess the discrepancy in isotopic fluxes between advection and no advection conditions. Since wind advection above a lake alters the concentrations, gradients, and evaporative fluxes of water isotopes, it alters the water balance and isotope ratios of the lake and the relationship between them. These effects are greatest for small lakes. If wind advection is neglected in the inference of water balance from lake isotopes, an error is thus introduced, the magnitude of which depends on lake size. We refer to this as the "lake size effect". For lakes less than 500 m in length along the wind direction, the average δ18O and δD of vapor flux are at least 2‰ lower than the corresponding flux values from the 1-D model. The magnitude of the resulting relative error in water balance calculations is much greater if using δ18O than δD in mass balance calculations; the former is about eight times the latter. This result argues that water balance calculated with δD is less sensitive to the difference in lake size and/or its change over time. The 1-D model result is also compared with that from a comparable 0-D model. Since vertical vapor and isotope gradients always exist (even under no advection conditions), one may not obtain correct flux values if the relative humidity and isotopic ratios in ambient air measured at an arbitrary height are used for the 0-D model calculation. Typically, the standard meteorological measurements at 2 or 10 m would result in an underestimate of the δ18O and δD values of the vapor flux. This work has provided the first quantification on the effect of advection on isotopic fluxes of evaporation. The method of mobile vapor analysis combined with 2-D modeling can be applied to other environmental settings, in which the size of advection effect on isotopic fluxes depends upon relationships among local meteorological and hydrological variables. Our results also suggest that incorporating isotopic vapor measurements can help constrain modeled evaporation rates, which is worth exploring further in future studies.

Modeling the Bergeron-Findeisen Process Using PDF Methods With an Explicit Representation of Mixing

NASA Astrophysics Data System (ADS)

Jeffery, C.; Reisner, J.

2005-12-01

Currently, the accurate prediction of cloud droplet and ice crystal number concentration in cloud resolving, numerical weather prediction and climate models is a formidable challenge. The Bergeron-Findeisen process in which ice crystals grow by vapor deposition at the expense of super-cooled droplets is expected to be inhomogeneous in nature--some droplets will evaporate completely in centimeter-scale filaments of sub-saturated air during turbulent mixing while others remain unchanged [Baker et al., QJRMS, 1980]--and is unresolved at even cloud-resolving scales. Despite the large body of observational evidence in support of the inhomogeneous mixing process affecting cloud droplet number [most recently, Brenguier et al., JAS, 2000], it is poorly understood and has yet to be parameterized and incorporated into a numerical model. In this talk, we investigate the Bergeron-Findeisen process using a new approach based on simulations of the probability density function (PDF) of relative humidity during turbulent mixing. PDF methods offer a key advantage over Eulerian (spatial) models of cloud mixing and evaporation: the low probability (cm-scale) filaments of entrained air are explicitly resolved (in probability space) during the mixing event even though their spatial shape, size and location remain unknown. Our PDF approach reveals the following features of the inhomogeneous mixing process during the isobaric turbulent mixing of two parcels containing super-cooled water and ice, respectively: (1) The scavenging of super-cooled droplets is inhomogeneous in nature; some droplets evaporate completely at early times while others remain unchanged. (2) The degree of total droplet evaporation during the initial mixing period depends linearly on the mixing fractions of the two parcels and logarithmically on Damköhler number (Da)---the ratio of turbulent to evaporative time-scales. (3) Our simulations predict that the PDF of Lagrangian (time-integrated) subsaturation (S) goes as S-1 at high Da. This behavior results from a Gaussian mixing closure and requires observational validation.

Emissions model of waste treatment operations at the Idaho Chemical Processing Plant

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schindler, R.E.

1995-03-01

An integrated model of the waste treatment systems at the Idaho Chemical Processing Plant (ICPP) was developed using a commercially-available process simulation software (ASPEN Plus) to calculate atmospheric emissions of hazardous chemicals for use in an application for an environmental permit to operate (PTO). The processes covered by the model are the Process Equipment Waste evaporator, High Level Liquid Waste evaporator, New Waste Calcining Facility and Liquid Effluent Treatment and Disposal facility. The processes are described along with the model and its assumptions. The model calculates emissions of NO{sub x}, CO, volatile acids, hazardous metals, and organic chemicals. Some calculatedmore » relative emissions are summarized and insights on building simulations are discussed.« less

Formation of Cadmium-Sulfide Nanowhiskers via Vacuum Evaporation and Condensation in a Quasi-Closed Volume

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belyaev, A. P., E-mail: Alexei.Belyaev@pharminnotech.com; Antipov, V. V.; Rubets, V. P.

Structural and technological studies of processes in which cadmium-sulfide nanowhiskers are synthesized in a quasi-closed volume by the method of vacuum evaporation and condensation are reported. It is demonstrated that the processes are in agreement with the classical vapor–liquid–crystal model. Micrographs of the objects in different formation stages are presented.

Self-reflection and self-transmission of pulsed radiation by laser-evaporated media

NASA Astrophysics Data System (ADS)

Furzikov, Nickolay P.

1991-05-01

Analysis of the known laser-induced evaporation (thermodestruction) model predicts the quasiperiodic oscillation of the effective absorption depth between its normal value and some minute quantity consisting of a part of the incident wavelength. This prediction explains the experimental data on the polymer laser ablation depth as well as the reflection transient drop of the laserdestructed aluminum.

On Problem of Mathematical Modelling of Thermo-Physical Processes in Regenerative Water-Evaporating Coolers

NASA Astrophysics Data System (ADS)

Gulevsky, V. A.; Shatsky, V. P.; Osipov, E. I.; Menzhulova, A. S.

2018-03-01

For cooling the air environment of industrial premises water-evaporating air, conditioners are being increasingly applied. The simplicity of their construction, ecological safety and low power consumption distinguish them from the coolers of other types. Cooling the processed air is due to the loss of energy for the evaporation of moisture from the surface of the water-wetted plates that form air channels. As a result of this process, cooled air is often saturated with moisture, which limits the possibilities for the operation of the coolers of this type. In these cases, more complex coolers of indirect principle without such drawback should be applied. The most effective modification of indirect cooling is the installation of recuperative principle units. The paper presents a mathematical model of heat-mass transfer in such water-evaporating coolers. The scheme of realization of this model based on an iterative algorithm of solution of the system of finite–difference linear equations that takes into account longitudinal and transverse thermal conductivity of the heat transfer plates is suggested. The possibility of obtaining the optimal values of the redistribution of the main and auxiliary air flows through the substantiation of the aerodynamic resistance of the output grid is proved. This allows refusing the inclusion in the additional system cooling fan unit for discharging an auxiliary stream of air.

Source apportionment of VOCs in the Los Angeles area using positive matrix factorization

NASA Astrophysics Data System (ADS)

Brown, Steven G.; Frankel, Anna; Hafner, Hilary R.

Eight 3-h speciated hydrocarbon measurements were collected daily by the South Coast Air Quality Management District (SCAQMD) as part of the Photochemical Assessment Monitoring Stations (PAMS) program during the summers of 2001-03 at two sites in the Los Angeles air basin, Azusa and Hawthorne. Over 30 hydrocarbons from over 500 samples at Azusa and 600 samples at Hawthorne were subsequently analyzed using the multivariate receptor model positive matrix factorization (PMF). At Azusa and Hawthorne, five and six factors were identified, respectively, with a good comparison between predicted and measured mass. At Azusa, evaporative emissions (a median of 31% of the total mass), motor vehicle exhaust (22%), liquid/unburned gasoline (27%), coatings (17%), and biogenic emissions (3%) factors were identified. Factors identified at Hawthorne were evaporative emissions (a median of 34% of the total mass), motor vehicle exhaust (24%), industrial process losses (15%), natural gas (13%), liquid/unburned gasoline (13%), and biogenic emissions (1%). Together, the median contribution from mobile source-related factors (exhaust, evaporative emissions, and liquid/unburned gasoline) was 80% and 71% at Azusa and Hawthorne, respectively, similar to previous source apportionment results using the chemical mass balance (CMB) model. There is a difference in the distribution among mobile source factors compared to the CMB work, with an increase in the contribution from evaporative emissions, though the cause (changes in emissions or differences between models) is unknown.

Setting an Upper Limit on Gas Exchange Through Sea-Spray

NASA Astrophysics Data System (ADS)

Vlahos, P.; Monahan, E. C.; Andreas, E. L.

2016-02-01

Air-sea gas exchange parameterization is critical to understanding both climate forcing and feedbacks and is key in biogeochemistry cycles. Models based on wind speed have provided empirical estimates of gas exchange that are useful though it is likely that at high wind speeds of over 10 m/s there are important gas exchange parameters including bubbles and sea spray that have not been well constrained. Here we address the sea-spray component of gas exchange at these high wind speeds to set sn upper boundary condition for the gas exchange of the six model gases including; nobel gases helium, neon and argon, diatomic gases nitrogen and oxygen and finally, the more complex gas carbon dioxide. Estimates are based on the spray generation function of Andreas and Monahan and the gases are tested under three scenarios including 100 percent saturation and complete droplet evaporation, 100 percent saturation and a more realistic scenario in which a fraction of droplets evaporate completely, a fraction evaporate to some degree and a fraction returns to the water side without significant evaporation. Finally the latter scenario is applied to representative under saturated concentrations of the gases.

Modeling of growth, evaporation and sedimentation effects on transmission of visible and IR laser beams in artificial fogs

NASA Technical Reports Server (NTRS)

Yue, G. K.; Deepak, A.

1980-01-01

The dense polydisperse aerosol particles in a quiet chamber may spontaneously go through different microphysical processes including gravitational sedimentation, thermal coagulation, and growth or evaporation. In an earlier paper, we presented the results of a parametric study of the combined and separate effects of thermal coagulation and sedimentation on the time dependence of extinction of four visible and IR laser beams traversing an aerosol medium. As a continuation of this series of studies, the separate and combined effects of growth or evaporation and gravitational sedimentation on the time dependence of extinction of the same four visible and IR laser beams traversing in artificial fogs will be reported in this paper. The method of numerically modeling the change of water droplet size distribution with time due to growth/evaporation and the cutoff of larger aerosols due to gravitational sedimentation is described in detail. Factors governing the relative importance of these two processes are discussed. Results of this study show that the relative humidity or ambient temperature is a crucial parameter in determining the optical depth of the water droplet and aerosol media undergoing microphysical processes.

Lubrication model for evaporation of binary sessile drops

NASA Astrophysics Data System (ADS)

Williams, Adam; Sáenz, Pedro; Karapetsas, George; Matar, Omar; Sefiane, Khellil; Valluri, Prashant

2017-11-01

Evaporation of a binary mixture sessile drop from a solid substrate is a highly dynamic and complex process with flow driven both thermal and solutal Marangoni stresses. Experiments on ethanol/water drops have identified chaotic regimes on both the surface and interior of the droplet, while mixture composition has also been seen to govern drop wettability. Using a lubrication-type approach, we present a finite element model for the evaporation of an axisymmetric binary drop deposited on a heated substrate. We consider a thin drop with a moving contact line, taking also into account the commonly ignored effects of inertia which drives interfacial instability. We derive evolution equations for the film height, the temperature and the concentration field considering that the mixture comprises two ideally mixed volatile components with a surface tension linearly dependent on both temperature and concentration. The properties of the mixture such as viscosity also vary locally with concentration. We explore the parameter space to examine the resultant effects on wetting and evaporation where we find qualitative agreement with experiments in both these areas. This enables us to understand the nature of the instabilities that spontaneously emerge over the drop lifetime. EPSRC - EP/K00963X/1.

Time-Dependent Solid State Polymorphism of a Series of Donor-Acceptor Dyads

PubMed Central

Peebles, Cameron; Alvey, Paul M.; Lynch, Vincent; Iverson, Brent L.

2014-01-01

In order to exploit the use of favorable electrostatic interactions between aromatic units in directing the assembly of donor-acceptor (D-A) dyads, the present work examines the ability of conjugated aromatic D-A dyads with symmetric side chains to exhibit solid-state polymorphism as a function of time during the solid formation process. Four such dyads were synthesized and their packing in the solid-state from either slower (10-20 days) or faster (1-2 days) evaporation from solvent was investigated using single crystal X-ray analysis and powder X-ray diffraction. Two of the dyads exhibited tail-to-tail (A-A) packing upon slower evaporation from solvent and head-to-tail (D-A) packing upon faster evaporation from solvent. A combination of single crystal analysis and XRD patterns were used to create models wherein a packing model for the other two dyads is proposed. Our findings suggest that while side chain interactions in asymmetric aromatic dyads can play an important role in enforcing segregated D-A dyad assembly, slowly evaporating symmetrically substituted aromatic dyads allows for favorable electrostatic interactions between the aromatic moieties to facilitate the organization of the dyads in the solid-state. PMID:24678269

Evaporation-induced gas-phase flows at selective laser melting

NASA Astrophysics Data System (ADS)

Zhirnov, I.; Kotoban, D. V.; Gusarov, A. V.

2018-02-01

Selective laser melting is the method for 3D printing from metals. A solid part is built from powder layer-by-layer. A continuum-wave laser beam scans every powder layer to fuse powder. The process is studied with a high-speed CCD camera at the frame rate of 104 fps and the resolution up to 5 µm per pixel. Heat transfer and evaporation in the laser-interaction zone are numerically modeled. Droplets are ejected from the melt pool in the direction around the normal to the melt surface and the powder particles move in the horizontal plane toward the melt pool. A vapor jet is observed in the direction of the normal to the melt surface. The velocities of the droplets, the powder particles, and the jet flow and the mass loss due to evaporation are measured. The gas flow around the vapor jet is calculated by Landau's model of submerged jet. The measured velocities of vapor, droplets, and powder particles correlate with the calculated flow field. The obtained results show the importance of evaporation and the flow of the vapor and the ambient gas. These gas-dynamic phenomena can explain the formation of the denudated zones and the instability at high-energy input.

The life, death and afterlife of a raindrop on Titan

NASA Astrophysics Data System (ADS)

Lorenz, Ralph D.

1993-09-01

A model is presented which describes the descent rate and evaporation rate of methane raindrops on Titan. The model, using conventional aerodynamics, with raindrop distortion parameterized by the Weber number, gives excellent agreement with terrestrial raindrop data. Terminal descent velocities for drops of various sizes at different altitudes are presented, and it is found that the largest raindrops may be larger than those on Earth 9.5 mm diameter vs. 6.5 mm diameter) yet fall much more slowly (1.6 m/s vs 9.2 m/s). Under standard conditions on Titan, raindrops evaporate before they reach the ground: profiles showing the shrinking of drops due to evaporation during their descent are shown for various values of relative humidity. A 500 m increase in elevation an lead to a tenfold increase in rain mass flux, leading to increased 'washing' of highland terrain. It is pointed out that evaporating raindrops will leave behind their condensation nuclei: fall times for these are presented, and it is noted that they may significantly affect visibility in the troposphere. The effects of additional factors on raindrop behavior, such as the nonideal solubility of nitrogen in methane, are briefly considered.

Determining the virtual surface in the thermal evaporation process of magnesium fluoride from a tungsten boat for different deposition rates, to be used in precision optical components

NASA Astrophysics Data System (ADS)

Tejada Esteves, A.; Gálvez de la Puente, G.

2013-11-01

Vacuum thermal evaporation has, for some time now, been the principal method for the deposition of thin films, given, among other aspects, its simplicity, flexibility, and relatively low cost. Therefore, the development of models attempting to predict the deposition patterns of given thin film materials in different locations of a vacuum evaporation chamber are arguably important. With this in mind, we have designed one of such models for the thermal evaporation process of magnesium fluoride (MgF2), a common material used in optical thin films, originating from a tungsten boat source. For this we took several deposition samples in glass slide substrates at different locations in the vacuum chamber, considering as independent variables the mean deposition rate, and the axial and vertical distances of the source to the substrate. After a careful analysis by matrix method from the spectral transmittance data of the samples, while providing as output data the spectral transmittance, as well as the physical thickness of the films, both as functions of the aforementioned variables, the virtual surface of the source was determined.

An evaporation model of multicomponent solution drops

NASA Astrophysics Data System (ADS)

Sartori, Silvana; Liñán, Amable; Lasheras, Juan C.

2010-11-01

Solutions of polymers are widely used in the pharmaceutical industry as tablets coatings. These allow controlling the rate at which the drug is delivered, taste or appearance. The coating is performed by spraying and drying the tablets at moderate temperatures. The wetting of the coating solution on the pill's surface depends on the droplet Webber and Re numbers, angle of impact and on the rheological properties of the droplet. We present a model for the evaporation of multicomponent solutions droplets in a hot air environment with temperatures substantially lower than the boiling temperature of the solvent. As the liquid vaporizes from the surface the fluid in the drop increases in concentration, until reaching its saturation point. After saturation, precipitation occurs uniformly within the drop. As the surface regresses, a compacting front formed by the precipitate at its maximum packing density advances into the drop, while the solute continues precipitating uniformly. This porous shell grows fast due to the double effect of surface regression and precipitation. The evaporation rate is determined by the rates at which heat is transported to the droplet surface and at which liquid vapor diffuses away from it. When the drop is fully compacted, the evaporation is drastically reduced.

An evaporation model of colloidal suspension droplets

NASA Astrophysics Data System (ADS)

Sartori, Silvana; Li\\ Nán, Amable; Lasheras, Juan C.

2009-11-01

Colloidal suspensions of polymers in water or other solvents are widely used in the pharmaceutical industry to coat tablets with different agents. These allow controlling the rate at which the drug is delivered, taste or physical appearance. The coating is performed by simultaneously spraying and drying the tablets with the colloidal suspension at moderately high temperatures. The spreading of the coating on the pills surface depends on the droplet Webber and Reynolds numbers, angle of impact, but more importantly on the rheological properties of the drop. We present a model for the evaporation of a colloidal suspension droplet in a hot air environment with temperatures substantially lower than the boiling temperature of the carrier fluid. As the liquid vaporizes from the surface, a compacting front advances into the droplet faster than the liquid surface regresses, forming a shell of a porous medium where the particles reach their maximum packing density. While the surface regresses, the evaporation rate is determined by both the rate at which heat is transported to the droplet surface and the rate at which liquid vapor is diffused away from it. This regime continues until the compacting front reaches the center of the droplet, at which point the evaporation rate is drastically reduced.

Evaporation from Pinus caribaea plantations on former grassland soils under maritime tropical conditions

NASA Astrophysics Data System (ADS)

Waterloo, M. J.; Bruijnzeel, L. A.; Vugts, H. F.; Rawaqa, T. T.

1999-07-01

Wet canopy and dry canopy evaporation from young and mature plantations of Pinus caribaea on former grassland soils under maritime tropical conditions in southwestern Viti Levu, Fiji, were determined using micrometeorological and hydrological techniques. Modeled annual evaporation totals (ET) of 1926 and 1717 mm were derived for the 6- and the 15-year-old stands, respectively. Transpiration made up 72% and 70% of annual ET, and modeled rainfall interception by the trees and litter layer was 20-22% and 8-9% in the young and the mature stands respectively. Monthly ET was related to forest leaf area index and was much higher than that for the kind of tall fire-climax Pennisetum polystachyon grassland replaced by the forests. Grassland reforestation resulted in a maximum decrease in annual water yield of 1180 mm on a plot basis, although it is argued that a reduction of (at least) 500-700 mm would be more realistic at the catchment scale. The impact of reforesting grassland on the water resources in southwest Viti Levu is enhanced by its location in a maritime, seasonal climate in the outer tropics, which favors a larger difference between annual forest and grassland evaporation totals than do equatorial regions.

Estimation of Regional Evapotranspiration Using Remotely Sensed Land Surface Temperature. Part 2: Application of Equilibrium Evaporation Model to Estimate Evapotranspiration by Remote Sensing Technique. [Japan

NASA Technical Reports Server (NTRS)

Kotoda, K.; Nakagawa, S.; Kai, K.; Yoshino, M. M.; Takeda, K.; Seki, K.

1985-01-01

In a humid region like Japan, it seems that the radiation term in the energy balance equation plays a more important role for evapotranspiration then does the vapor pressure difference between the surface and lower atmospheric boundary layer. A Priestley-Taylor type equation (equilibrium evaporation model) is used to estimate evapotranspiration. Net radiation, soil heat flux, and surface temperature data are obtained. Only temperature data obtained by remotely sensed techniques are used.

Estimation of bare soil evaporation using multifrequency airborne SAR

NASA Technical Reports Server (NTRS)

Soares, Joao V.; Shi, Jiancheng; Van Zyl, Jakob; Engman, E. T.

1992-01-01

It is shown that for homogeneous areas soil moisture can be derived from synthetic aperture radar (SAR) measurements, so that the use of microwave remote sensing can given realistic estimates of energy fluxes if coupled to a simple two-layer model repesenting the soil. The model simulates volumetric water content (Wg) using classical meterological data, provided that some of the soil thermal and hydraulic properties are known. Only four parameters are necessary: mean water content, thermal conductivity and diffusitivity, and soil resistance to evaporation. They may be derived if a minimal number of measured values of Wg and surface layer temperature (Tg) are available together with independent measurements of energy flux to compare with the estimated values. The estimated evaporation is shown to be realistic and in good agreement with drying stage theory in which the transfer of water in the soil is in vapor form.

Segregation effects during solidification in weightless melts. [effects of evaporation and solidification on crystalization

NASA Technical Reports Server (NTRS)

Li, C.

1975-01-01

Computer programs are developed and used in the study of the combined effects of evaporation and solidification in space processing. The temperature and solute concentration profiles during directional solidification of binary alloys with surface evaporation were mathematically formulated. Computer results are included along with an econotechnical model of crystal growth. This model allows: prediction of crystal size, quality, and cost; systematic selection of the best growth equipment or alloy system; optimization of growth or material parameters; and a maximization of zero-gravity effects. Segregation in GaAs crystals was examined along with vibration effects on GaAs crystal growth. It was found that a unique segregation pattern and strong convention currents exist in GaAs crystal growth. Some beneficial effects from vibration during GaAs growth were discovered. The implications of the results in space processing are indicated.

The nonlinear model for emergence of stable conditions in gas mixture in force field

NASA Astrophysics Data System (ADS)

Kalutskov, Oleg; Uvarova, Liudmila

2016-06-01

The case of M-component liquid evaporation from the straight cylindrical capillary into N - component gas mixture in presence of external forces was reviewed. It is assumed that the gas mixture is not ideal. The stable states in gas phase can be formed during the evaporation process for the certain model parameter valuesbecause of the mass transfer initial equationsnonlinearity. The critical concentrations of the resulting gas mixture components (the critical component concentrations at which the stable states occur in mixture) were determined mathematically for the case of single-component fluid evaporation into two-component atmosphere. It was concluded that this equilibrium concentration ratio of the mixture components can be achieved by external force influence on the mass transfer processes. It is one of the ways to create sustainable gas clusters that can be used effectively in modern nanotechnology.

Scenario planning for water resource management in semi arid zone

NASA Astrophysics Data System (ADS)

Gupta, Rajiv; Kumar, Gaurav

2018-06-01

Scenario planning for water resource management in semi arid zone is performed using systems Input-Output approach of time domain analysis. This approach derived the future weights of input variables of the hydrological system from their precedent weights. Input variables considered here are precipitation, evaporation, population and crop irrigation. Ingles & De Souza's method and Thornthwaite model have been used to estimate runoff and evaporation respectively. Difference between precipitation inflow and the sum of runoff and evaporation has been approximated as groundwater recharge. Population and crop irrigation derived the total water demand. Compensation of total water demand by groundwater recharge has been analyzed. Further compensation has been evaluated by proposing efficient methods of water conservation. The best measure to be adopted for water conservation is suggested based on the cost benefit analysis. A case study for nine villages in Chirawa region of district Jhunjhunu, Rajasthan (India) validates the model.

Numerical simulations of sessile droplet evaporating on heated substrate

NASA Astrophysics Data System (ADS)

Chen, Xue; Chen, Paul G.; Ouazzani, Jalil; Liu, Qiusheng

2017-04-01

Motivated by the space project EFILE, a 2D axisymmetric numerical model in the framework of ALE method is developed to investigate the coupled physical mechanism during the evaporation of a pinned drop that partially wets on a heated substrate. The model accounts for mass transport in surrounding air, Marangoni convection inside the drop and heat conduction in the substrate as well as moving interface. Numerical results predict simple scaling laws for the evaporation rate which scales linearly with drop radius but follows a power-law with substrate temperature. It is highlighted that thermal effect of the substrate has a great impact on the temperature profile at the drop surface, which leads to a multicellular thermocapillary flow pattern. In particular, the structure of the multicellular flow behavior induced within a heated drop is mainly controlled by a geometric parameter (aspect ratio). A relationship between the number of thermal cells and the aspect ratio is proposed.

Performance evaluation of an evaporative pad greenhouse system for utilization of power plant reject heat

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olszewski, M.; Trezek, G.J.

1976-01-01

The overall performance of an evaporative pad greenhouse is considered in terms of the pad heat and mass transfer, the energy budget of the vegetation, and the performance of the power plant. An analytical predictive model for the pad performance was developed utilizing the Merkel total heat approximation. Data obtained from actual greenhouse performance provides an experimental verification of the pad model. Energy balance considerations on the vegetation provide a means of viewing optimal plant growth in terms of the power plant energy dissipation. In general, the results indicate that when an evaporative pad greenhouse system is used for wastemore » heat dispersal, the vegetation can be maintained within its thermal requirement zone, crop irrigation requirements are significantly reduced, and the power plant performance is comparable with conventional closed loop heat rejection systems.« less

Quantification of a greenhouse hydrologic cycle from equatorial to polar latitudes: The mid-Cretaceous water bearer revisited

USGS Publications Warehouse

Suarez, M.B.; Gonzalez, Luis A.; Ludvigson, Greg A.

2011-01-01

This study aims to investigate the global hydrologic cycle during the mid-Cretaceous greenhouse by utilizing the oxygen isotopic composition of pedogenic carbonates (calcite and siderite) as proxies for the oxygen isotopic composition of precipitation. The data set builds on the Aptian-Albian sphaerosiderite ??18O data set presented by Ufnar et al. (2002) by incorporating additional low latitude data including pedogenic and early meteoric diagenetic calcite ??18O. Ufnar et al. (2002) used the proxy data derived from the North American Cretaceous Western Interior Basin (KWIB) in a mass balance model to estimate precipitation-evaporation fluxes. We have revised this mass balance model to handle sphaerosiderite and calcite proxies, and to account for longitudinal travel by tropical air masses. We use empirical and general circulation model (GCM) temperature gradients for the mid-Cretaceous, and the empirically derived ??18O composition of groundwater as constraints in our mass balance model. Precipitation flux, evaporation flux, relative humidity, seawater composition, and continental feedback are adjusted to generate model calculated groundwater ??18O compositions (proxy for precipitation ??18O) that match the empirically-derived groundwater ??18O compositions to within ??0.5???. The model is calibrated against modern precipitation data sets.Four different Cretaceous temperature estimates were used: the leaf physiognomy estimates of Wolfe and Upchurch (1987) and Spicer and Corfield (1992), the coolest and warmest Cretaceous estimates compiled by Barron (1983) and model outputs from the GENESIS-MOM GCM by Zhou et al. (2008). Precipitation and evaporation fluxes for all the Cretaceous temperature gradients utilized in the model are greater than modern precipitation and evaporation fluxes. Balancing the model also requires relative humidity in the subtropical dry belt to be significantly reduced. As expected calculated precipitation rates are all greater than modern precipitation rates. Calculated global average precipitation rates range from 371mm/year to 1196mm/year greater than modern precipitation rates. Model results support the hypothesis that increased rainout produces ??18O-depleted precipitation.Sensitivity testing of the model indicates that the amount of water vapor in the air mass, and its origin and pathway, significantly affect the oxygen isotopic composition of precipitation. Precipitation ??18O is also sensitive to seawater ??18O and enriched tropical seawater was necessary to simulate proxy data (consistent with fossil and geologic evidence for a warmer and evaporatively enriched Tethys). Improved constraints in variables such as seawater ??18O can help improve boundary conditions for mid-Cretaceous climate simulations. ?? 2011 Elsevier B.V.

Vapor pressures and evaporation coefficients for melts of ferromagnesian chondrule-like compositions

NASA Astrophysics Data System (ADS)

Fedkin, A. V.; Grossman, L.; Ghiorso, M. S.

2006-01-01

To determine evaporation coefficients for the major gaseous species that evaporate from silicate melts, the Hertz-Knudsen equation was used to model the compositions of residues of chondrule analogs produced by evaporation in vacuum by Hashimoto [Hashimoto A. (1983) Evaporation metamorphism in the early solar nebula-evaporation experiments on the melt FeO-MgO-SiO 2-CaO-Al 2O 3 and chemical fractionations of primitive materials. Geochem. J. 17, 111-145] and Wang et al. [Wang J., Davis A. M., Clayton R. N., Mayeda T. K., Hashimoto A. (2001) Chemical and isotopic fractionation during the evaporation of the FeO-MgO-SiO 2-CaO-Al 2O 3-TiO 2 rare earth element melt system. Geochim. Cosmochim. Acta 65, 479-494], in vacuum and in H 2 by Yu et al. [Yu Y., Hewins R. H., Alexander C. M. O'D., Wang J. (2003) Experimental study of evaporation and isotopic mass fractionation of potassium in silicate melts. Geochim. Cosmochim. Acta 67, 773-786], and in H 2 by Cohen et al. [Cohen B. A., Hewins R. H., Alexander C. M. O'D. (2004) The formation of chondrules by open-system melting of nebular condensates. Geochim. Cosmochim. Acta 68, 1661-1675]. Vapor pressures were calculated using the thermodynamic model of Ghiorso and Sack [Ghiorso M. S., Sack R. O. (1995) Chemical mass transfer in magmatic processes IV. A revised and internally consistent thermodynamic model for the interpolation and extrapolation of liquid-solid equilibria in magmatic systems at elevated temperatures and pressures. Contrib. Mineral. Petrol. 119, 197-212], except for the late, FeO-free stages of the Wang et al. (2001) and Cohen et al. (2004) experiments, where the CMAS activity model of Berman [Berman R. G. (1983) A thermodynamic model for multicomponent melts, with application to the system CaO-MgO-Al 2O 3-SiO 2. Ph.D. thesis, University of British Columbia] was used. From these vapor pressures, evaporation coefficients ( α) were obtained that give the best fits to the time variation of the residue compositions. Evaporation coefficients derived for Fe (g), Mg (g), and SiO (g) from the Hashimoto (1983) experiments are similar to those found by Alexander [Alexander C. M. O'D. (2004) Erratum. Meteoritics Planet. Sci. 39, 163] in his EQR treatment of the same data and also adequately describe the FeO-bearing stages of the Wang et al. (2001) experiments. From the Yu et al. (2003) experiments at 1723 K, αNa = 0.26 ± 0.05, and αK = 0.13 ± 0.02 in vacuum, and αNa = 0.042 ± 0.020, and αK = 0.017 ± 0.002 in 9 × 10 -5 bar H 2. In the FeO-free stages of the Wang et al. (2001) experiments, αMg and αSiO are significantly different from their respective values in the FeO-bearing portions of the same experiments and from the vacuum values obtained at the same temperature by Richter [Richter F. M., Davis A. M., Ebel D. S., Hashimoto A. (2002) Elemental and isotopic fractionation of Type B calcium-, aluminum-rich inclusions: experiments, theoretical considerations, and constraints on their thermal evolution. Geochim. Cosmochim. Acta 66, 521-540] for CMAS compositions much lower in MgO. When corrected for temperature, the values of αMg and αSiO that best describe the FeO-free stages of the Wang et al. (2001) experiments also adequately describe the FeO-free stage of the Cohen et al. (2004) H 2 experiments, but αFe that best describes the FeO-bearing stage of the latter experiment differs significantly from the temperature-corrected value derived from the Hashimoto (1983) vacuum data.

Relationship between the evaporation rate and vapor pressure of moderately and highly volatile chemicals.

PubMed

van Wesenbeeck, Ian; Driver, Jeffrey; Ross, John

2008-04-01

Volatilization of chemicals can be an important form of dissipation in the environment. Rates of evaporative losses from plant and soil surfaces are useful for estimating the potential for food-related dietary residues and operator and bystander exposure, and can be used as source functions for screening models that predict off-site movement of volatile materials. A regression of evaporation on vapor pressure from three datasets containing 82 pesticidal active ingredients and co-formulants, ranging in vapor pressure from 0.0001 to >30,000 Pa was developed for this purpose with a regression correlation coefficient of 0.98.

Numerical simulation of water evaporation inside vertical circular tubes

NASA Astrophysics Data System (ADS)

Ocłoń, Paweł; Nowak, Marzena; Majewski, Karol

2013-10-01

In this paper the results of simplified numerical analysis of water evaporation in vertical circular tubes are presented. The heat transfer in fluid domain (water or wet steam) and solid domain (tube wall) is analyzed. For the fluid domain the temperature field is calculated solving energy equation using the Control Volume Method and for the solid domain using the Finite Element Method. The heat transfer between fluid and solid domains is conjugated using the value of heat transfer coefficient from evaporating liquid to the tube wall. It is determined using the analytical Steiner-Taborek correlation. The pressure changes in fluid are computed using Friedel model.

Standing crops and ecology of aquatic invertebrates in agricultural drainwater ponds in California

USGS Publications Warehouse

Euliss, N.H.; Jarvis, R.L.; Gilmer, D.S.

1991-01-01

We examined standing crops and ecology of aquatic invertebrates in agricultural drainwater evaporation ponds in California from October 1982 to March 1983 and September 1983 to March 1984. Evaporation ponds supported low diversities but high standing crops of aquatic invertebrates. A water boatman (Trichocorixa reticulata) and a midge (Tanypus grodhausi) were the most abundant invertebrates, constituting 44.9% and 51.4% of total macroinvertebrate biomass. Regression models indicated that of 6 environmental variables measured, only electrical conductivity (EC) and Julian date affected biomass and density of water boatmen. EC was the only significant correlate of midge biomass in evaporation ponds.

Determination of kinetic isotopic fractionation of water during bare soil evaporation

NASA Astrophysics Data System (ADS)

Quade, Maria; Brüggemann, Nicolas; Graf, Alexander; Rothfuss, Youri

2017-04-01

A process-based understanding of the water cycle in the atmosphere is important for improving meteorological and hydrological forecasting models. Usually only net fluxes of evapotranspiration - ET are measured, while land-surface models compute their raw components evaporation -E and transpiration -T. Isotopologues can be used as tracers to partition ET, but this requires knowledge of the isotopic kinetic fractionation factor (αK) which impacts the stable isotopic composition of water pools (e.g., soil and plant waters) during phase change and vapor transport by soil evaporation and plant transpiration. It is defined as a function of the ratio of the transport resistances in air of the less to the most abundant isotopologue. Previous studies determined αK for free evaporating water (Merlivat, 1978) or bare soil evaporation (Braud et al. 2009) at only low temporal resolution. The goal of this study is to provide estimates at higher temporal resolution. We performed a soil evaporation laboratory experiment to determine the αK by applying the Craig and Gordon (1965) model. A 0.7 m high column (0.48 m i.d.) was filled with silt loam (20.1 % sand, 14.9 % loam, 65 % silt) and saturated with water of known isotopic composition. Soil volumetric water content, temperature and the isotopic composition (δ) of the soil water vapor were measured at six different depths. At each depth microporous polypropylene tubing allowed the sampling of soil water vapor and the measurement of its δ in a non-destructive manner with high precision and accuracy as detailed in Rothfuss et al. (2013). In addition, atmospheric water vapor was sampled at seven different heights up to one meter above the surface for isotopic analysis. Results showed that soil and atmospheric δ profiles could be monitored at high temporal and vertical resolutions during the course of the experiment. αK could be calculated by using an inverse modeling approach and the Keeling (1958) plot method at high temporal resolution over a long period. We observed an increasing δ in the evaporating water vapor due to more enriched surface water. This leads to a higher transport resistances and an increasing αK. References Braud, I., Bariac, T., Biron, P., and Vauclin, M.: Isotopic composition of bare soil evaporated water vapor. Part II: Modeling of RUBIC IV experimental results, J. Hydrol., 369, 17-29. Craig, H. et al., 1965. Deuterium and oxygen 18 variations in the ocean and marine atmosphere. In: E. Tongiogi (Editor), Stable Isotopes in Oceanographic Studies and Paleotemperatures. V. Lishi, Spoleto, Italy, pp. 9-130. Keeling, C. D.: The Concentration and Isotopic Abundances of Atmospheric Carbon Dioxide in Rural Areas, Geochim. Cosmochim. Acta, 13, 322-334. Merlivat, L., 1978. Molecular Diffusivities of H216O, HD16O, and H218O in Gases. J Chem Phys, 69, 2864-2871. Rothfuss, Y. et al., 2013. Monitoring water stable isotopic composition in soils using gas-permeable tubing and infrared laser absorption spectroscopy. Water Resour. Res., 49, 1-9.

Multicomponent Droplet Evaporation on Chemical Micro-Patterned Surfaces

PubMed Central

He, Minghao; Liao, Dong; Qiu, Huihe

2017-01-01

The evaporation and dynamics of a multicomponent droplet on a heated chemical patterned surface were presented. Comparing to the evaporation process of a multicomponent droplet on a homogenous surface, it is found that the chemical patterned surface can not only enhance evaporation by elongating the contact line, but also change the evaporation process from three regimes for the homogenous surface including constant contact line (CCL) regime, constant contact angle (CCA) regime and mix mode (MM) to two regimes, i.e. constant contact line (CCL) and moving contact line (MCL) regimes. The mechanism of contact line stepwise movement in MCL regimes in the microscopic range is investigated in detail. In addition, an improved local force model on the contact line was employed for analyzing the critical receding contact angles on homogenous and patterned surfaces. The analysis results agree well for both surfaces, and confirm that the transition from CCL to MCL regimes indicated droplet composition changes from multicomponent to monocomponent, providing an important metric to predict and control the dynamic behavior and composition of a multicomponent droplet using a patterned surface. PMID:28157229

Experimental results and a self-consistent model of evaporation and high heat flux extraction by evaporating flow in a micro-grooved blade

NASA Astrophysics Data System (ADS)

Monazami, Reza; Saadat, Mehdi; Zhu, Jianzhong; Haj-Hariri, Hossein

2015-11-01

The problem of evaporation from a vertical micro-grooved blade heated from above is investigated. The required superheat to handle the incoming flux is calculated using the results of the study by Monazami and Haj-Hariri (2012). The relation between the applied heat flux, dry-out length and the maximum equilibrium temperature for several geometries and working fluids are studied. Furthermore, a computational study of the evaporating meniscus is conducted to evaluate the evaporation rates and dissipated heat flux at the liquid-vapor interface. The computational study accounts for the flow and heat transfer in both liquid and vapor phases. The results of this study indicate that the micro-grooved structure can dissipate heat fluxes as high as 10MW/m2 for superheats as low as 5 degrees Kelvin. Experiments are conducted to verify the computational and analytical results. The findings of this work are applicable to the design of thermal management systems for high heat flux applications. Partially supported by the MAXNET Energy Partnership (Max Planck Institute and UVA).

The interaction of Dirac particles with a Hawking charged radiating black hole

NASA Astrophysics Data System (ADS)

Kubik, Erik

2007-08-01

The interaction of spin 1/2 fields with a charged, evaporating black hole (EBH) is investigated. Using the Vaidya metric to model the Hawking evaporating black hole, the wave equation for a massless spinor field is obtained. The resulting field equation is solved utilizing techniques developed by Brill and Wheeler. Unlike previous efforts, a charged, evaporating black hole has never been used as a background to investigate spin 1/2 quantum field propagation, e.g., Brill and Wheeler considered massless spin 1/2 interactions in a static, Schwarzschild background. Using the WKB approximation, the wave equation is solved for the case of an EBH with constant luminosity. Analysis of the effective potential at different stages of evaporation is made including the dependence on the parameters of the system such as the total angular momentum, energy of the incident field, and luminosity of the evaporating black hole. Utilizing techniques of Mukhopad-hey, the transmission and reflection coefficients for the massless spinors are computed and compared to Schwarzschild result for both the high energy and hard scattering cases. The effect of the time dependence of the space-time metric has an important effect on the behavior of quantum fields over the lifetime of the evaporating black hole and may provide a signature for the detection of such objects.

Water potential changes in faecal matter and Escherichia coli survival.

PubMed

Garfield, L M; Walker, M J

2008-10-01

This study investigated the influence of a range of evaporation rates (2.0, 5.3 and 7.4 mm day(-1)) on degradation of E. coli (ATCC Strain 25922) inoculated in canine faeces. Experiments were carried out in an environmental chamber and a first order exponential decay function (Chick's Law) was used to estimate degradation rates. We estimated die-off coefficients using linear regression. Die-off rates were -0.07, -0.22 and -0.23 h(-1), respectively, for evaporation rates of 2.0, 5.3 and 7.4 mm day(-1) (P = 0.000+, for each model). Nearly complete die-off was found within 15-60 h (7.4-2.0 mm day(-1) evaporation rates), which corresponds with a water potential of approximately -22.4 MPa. This study indicates that canine faeces need not be desiccated to achieve complete loss of indicator organisms. Water potential, which is a combination of osmotic and matric potential, is a key stress that increases as evaporation removes water from the faecal matrix and increases concentration of the remaining faecal solution. Evaporation may remove populations of indicator organisms in faeces relatively quickly, even though faeces are not completely dehydrated. This research may be used as the foundation for studies more closely resembling real-world evaporation conditions including diurnal fluctuations, rewetting and freezing.

Estimation of Transpiration and Water Use Efficiency Using Satellite and Field Observations

NASA Technical Reports Server (NTRS)

Choudhury, Bhaskar J.; Quick, B. E.

2003-01-01

Structure and function of terrestrial plant communities bring about intimate relations between water, energy, and carbon exchange between land surface and atmosphere. Total evaporation, which is the sum of transpiration, soil evaporation and evaporation of intercepted water, couples water and energy balance equations. The rate of transpiration, which is the major fraction of total evaporation over most of the terrestrial land surface, is linked to the rate of carbon accumulation because functioning of stomata is optimized by both of these processes. Thus, quantifying the spatial and temporal variations of the transpiration efficiency (which is defined as the ratio of the rate of carbon accumulation and transpiration), and water use efficiency (defined as the ratio of the rate of carbon accumulation and total evaporation), and evaluation of modeling results against observations, are of significant importance in developing a better understanding of land surface processes. An approach has been developed for quantifying spatial and temporal variations of transpiration, and water-use efficiency based on biophysical process-based models, satellite and field observations. Calculations have been done using concurrent meteorological data derived from satellite observations and four dimensional data assimilation for four consecutive years (1987-1990) over an agricultural area in the Northern Great Plains of the US, and compared with field observations within and outside the study area. The paper provides substantive new information about interannual variation, particularly the effect of drought, on the efficiency values at a regional scale.

Where do forests influence rainfall?

NASA Astrophysics Data System (ADS)

Wang-Erlandsson, Lan; van der Ent, Ruud; Fetzer, Ingo; Keys, Patrick; Savenije, Hubert; Gordon, Line

2017-04-01

Forests play a major role in hydrology. Not only by immediate control of soil moisture and streamflow, but also by regulating climate through evaporation (i.e., transpiration, interception, and soil evaporation). The process of evaporation travelling through the atmosphere and returning as precipitation on land is known as moisture recycling. Whether evaporation is recycled depends on wind direction and geography. Moisture recycling and forest change studies have primarily focused on either one region (e.g. the Amazon), or one biome type (e.g. tropical humid forests). We will advance this via a systematic global inter-comparison of forest change impacts on precipitation depending on both biome type and geographic location. The rainfall effects are studied for three contemporary forest changes: afforestation, deforestation, and replacement of mature forest by forest plantations. Furthermore, as there are indications in the literature that moisture recycling in some places intensifies during dry years, we will also compare the rainfall impacts of forest change between wet and dry years. We model forest change effects on evaporation using the global hydrological model STEAM and trace precipitation changes using the atmospheric moisture tracking scheme WAM-2layers. This research elucidates the role of geographical location of forest change driven modifications on rainfall as a function of the type of forest change and climatic conditions. These knowledge gains are important at a time of both rapid forest and climate change. Our conclusions nuance our understanding of how forests regulate climate and pinpoint hotspot regions for forest-rainfall coupling.

Nuclear level densities of 64 , 66 Zn from neutron evaporation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramirez, A. P. D.; Voinov, A. V.; Grimes, S. M.

Double differential cross sections of neutrons from d+ 63,65Cu reactions have been measured at deuteron energies of 6 and 7.5 MeV. The cross sections measured at backward angles have been compared to theoretical calculations in the framework of the statistical Hauser-Feshbach model. Three different level density models were tested: the Fermi-gas model, the Gilbert-Cameron model, and the microscopic approach through the Hartree-Fock-Bogoliubov method (HFBM). The calculations using the Gilbert-Cameron model are in best agreement with our experimental data. Level densities of the residual nuclei 64Zn and 66Zn have been obtained from statistical neutron evaporation spectra. In conclusion, the angle-integrated crossmore » sections have been analyzed with the exciton model of nuclear reaction.« less

Nuclear level densities of 64 , 66 Zn from neutron evaporation

DOE PAGES

Ramirez, A. P. D.; Voinov, A. V.; Grimes, S. M.; ...

2013-12-26

Double differential cross sections of neutrons from d+ 63,65Cu reactions have been measured at deuteron energies of 6 and 7.5 MeV. The cross sections measured at backward angles have been compared to theoretical calculations in the framework of the statistical Hauser-Feshbach model. Three different level density models were tested: the Fermi-gas model, the Gilbert-Cameron model, and the microscopic approach through the Hartree-Fock-Bogoliubov method (HFBM). The calculations using the Gilbert-Cameron model are in best agreement with our experimental data. Level densities of the residual nuclei 64Zn and 66Zn have been obtained from statistical neutron evaporation spectra. In conclusion, the angle-integrated crossmore » sections have been analyzed with the exciton model of nuclear reaction.« less

Numerical analysis of natural convection in liquid droplets by phase change

NASA Astrophysics Data System (ADS)

Duh, J. C.; Yang, Wen-Jei

1989-09-01

A numerical analysis is performed on thermocapillary buoyancy convection induced by phase change in a liquid droplet. A finite-difference code is developed using an alternating-direction implicit (ADI) scheme. The intercoupling relation between thermocapillary force, buoyancy force, fluid property, heat transfer, and phase change, along with their effects on the induced flow patterns, are disclosed. The flow is classified into three types: thermocapillary, buoyancy, and combined convection. Among the three mechanisms, the combined convection simulates the experimental observations quite well, and the basic mechanism of the observed convection inside evaporating sessile drops is thus identified. It is disclosed that evaporation initiates unstable convection, while condensation always brings about a stable density distribution which eventually damps out all fluid disturbances. Another numerical model is presented to study the effect of boundary recession due to evaporation, and the 'peeling-off' effect (the removal of the surface layer of fluid by evaporation) is shown to be relevant.

Interaction of evaporating and condensing particles in the free-molecular regime

NASA Astrophysics Data System (ADS)

Kogan, M. N.; Bobrov, I. N.; Cercignani, C.; Frezzotti, A.

1995-07-01

In a previous paper it was shown that repulsive/attractive forces arise between evaporating/ condensing particles in the free-molecular regime. Here we obtain explicit expressions for these forces in the case of spherical particles with equal temperatures. The temperature of the surrounding vapor is, generally speaking, different from that of the particles. Numerical results are obtained for different values of the ratios between particle and vapor temperatures and pressures, of the particles radii and of the evaporation coefficients. In the case when the evaporation coefficient equals unity, an exact expression is obtained for the force between particles of different radii. A simple model describing coagulation processes and taking the above-mentioned forces into account is proposed. It is shown that for large values of the vapor supersaturation, the influence of these forces on the coagulation rate may be very pronounced.

Numerical analysis of natural convection in liquid droplets by phase change

NASA Technical Reports Server (NTRS)

Duh, J. C.; Yang, Wen-Jei

1989-01-01

A numerical analysis is performed on thermocapillary buoyancy convection induced by phase change in a liquid droplet. A finite-difference code is developed using an alternating-direction implicit (ADI) scheme. The intercoupling relation between thermocapillary force, buoyancy force, fluid property, heat transfer, and phase change, along with their effects on the induced flow patterns, are disclosed. The flow is classified into three types: thermocapillary, buoyancy, and combined convection. Among the three mechanisms, the combined convection simulates the experimental observations quite well, and the basic mechanism of the observed convection inside evaporating sessile drops is thus identified. It is disclosed that evaporation initiates unstable convection, while condensation always brings about a stable density distribution which eventually damps out all fluid disturbances. Another numerical model is presented to study the effect of boundary recession due to evaporation, and the 'peeling-off' effect (the removal of the surface layer of fluid by evaporation) is shown to be relevant.

The evolution of 17O-excess in surface water of the arid environment during recharge and evaporation.

PubMed

Surma, J; Assonov, S; Herwartz, D; Voigt, C; Staubwasser, M

2018-03-21

This study demonstrates the potential of triple O-isotopes to quantify evaporation with recharge on a salt lake from the Atacama Desert, Chile. An evaporative gradient was found in shallow ponds along a subsurface flow-path from a groundwater source. Total dissolved solids (TDS) increased by 177 g/l along with an increase in δ 18 O by 16.2‰ and in δD by 65‰. 17 O-excess decreased by 79 per meg, d-excess by 55‰. Relative humidity (h), evaporation over inflow (E/I), the isotopic composition of vapor ( * R V ) and of inflowing water ( * R WI ) determine the isotope distribution in 17 O-excess over δ 18 O along a well-defined evaporation curve as the classic Craig-Gordon model predicts. A complementary on-site simple (pan) evaporation experiment over a change in TDS, δ 18 O, and 17 O-excess by 392 g/l, 25.0‰, and -130 per meg, respectively, was used to determine the effects of sluggish brine evaporation and of wind turbulence. These effects translate to uncertainty in E/I rather than h. The local composition of * R V relative to * R WI pre-determines the general ability to resolve changes in h. The triple O-isotope system is useful for quantitative hydrological balancing of lakes and for paleo-humidity reconstruction, particularly if complemented by D/H analysis.

Effect of material flexibility on the thermodynamics and kinetics of hydrophobically induced evaporation of water.

PubMed

Altabet, Y Elia; Haji-Akbari, Amir; Debenedetti, Pablo G

2017-03-28

The evaporation of water induced by confinement between hydrophobic surfaces has received much attention due to its suggested functional role in numerous biophysical phenomena and its importance as a general mechanism of hydrophobic self-assembly. Although much progress has been made in understanding the basic physics of hydrophobically induced evaporation, a comprehensive understanding of the substrate material features (e.g., geometry, chemistry, and mechanical properties) that promote or inhibit such transitions remains lacking. In particular, comparatively little research has explored the relationship between water's phase behavior in hydrophobic confinement and the mechanical properties of the confining material. Here, we report the results of extensive molecular simulations characterizing the rates, free energy barriers, and mechanism of water evaporation when confined between model hydrophobic materials with tunable flexibility. A single-order-of-magnitude reduction in the material's modulus results in up to a nine-orders-of-magnitude increase in the evaporation rate, with the corresponding characteristic time decreasing from tens of seconds to tens of nanoseconds. Such a modulus reduction results in a 24-orders-of-magnitude decrease in the reverse rate of condensation, with time scales increasing from nanoseconds to tens of millions of years. Free energy calculations provide the barriers to evaporation and confirm our previous theoretical predictions that making the material more flexible stabilizes the confined vapor with respect to liquid. The mechanism of evaporation involves surface bubbles growing/coalescing to form a subcritical gap-spanning tube, which then must grow to cross the barrier.

Evaporation Kinetics of Polyol Droplets: Determination of Evaporation Coefficients and Diffusion Constants

NASA Astrophysics Data System (ADS)

Su, Yong-Yang; Marsh, Aleksandra; Haddrell, Allen E.; Li, Zhi-Ming; Reid, Jonathan P.

2017-11-01

In order to quantify the kinetics of mass transfer between the gas and condensed phases in aerosol, physicochemical properties of the gas and condensed phases and kinetic parameters (mass/thermal accommodation coefficients) are crucial for estimating mass fluxes over a wide size range from the free molecule to continuum regimes. In this study, we report measurements of the evaporation kinetics of droplets of 1-butanol, ethylene glycol (EG), diethylene glycol (DEG), and glycerol under well-controlled conditions (gas flow rates and temperature) using the previously developed cylindrical electrode electrodynamic balance technique. Measurements are compared with a model that captures the heat and mass transfer occurring at the evaporating droplet surface. The aim of these measurements is to clarify the discrepancy in the reported values of mass accommodation coefficient (αM, equals to evaporation coefficient based on microscopic reversibility) for 1-butanol, EG, and DEG and improve the accuracy of the value of the diffusion coefficient for glycerol in gaseous nitrogen. The uncertainties in the thermophysical and experimental parameters are carefully assessed, the literature values of the vapor pressures of these components are evaluated, and the plausible ranges of the evaporation coefficients for 1-butanol, EG, and DEG as well as uncertainty in diffusion coefficient for glycerol are reported. Results show that αM should be greater than 0.4, 0.2, and 0.4 for EG, DEG, and 1-butanol, respectively. The refined values are helpful for accurate prediction of the evaporation/condensation rates.

Evaluation of land-surface interaction in ECMWF and NCEP/NCAR reanalysis models over grassland (FIFE) and boreal forest (BOREAS)

NASA Astrophysics Data System (ADS)

Betts, Alan K.; Viterbo, Pedro; Beljaars, Anton; Pan, Hua-Lu; Hong, Song-You; Goulden, Mike; Wofsy, Steve

1998-09-01

The National Center for Environmental Prediction and National Center for Atmospheric Research (NCEP/NCAR) and European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis models are compared with First ISLSCP (International Satellite Land Surface Climatology Project) Field Experiment (FIFE) grassland data from Kansas in 1987 and Boreal Ecosystem-Atmosphere Study (BOREAS) data from an old black spruce site in 1996 near Thompson, Manitoba. Some aspects of the comparison are similar for the two ecosystems. Over grassland and after snowmelt in the boreal forest, both models represent the seasonal cycle of near-surface temperature well. The two models have quite different soil hydrology components. The ECMWF model includes soil water nudging based on low level humidity errors. While this works quite well for the FIFE grassland, it appears to give too high evaporation over the boreal forest. The NCEP/NCAR model constrains long-term drifts by nudging deep soil water toward climatology. Over the FIFE site, this seems to give too low evaporation in midsummer, while at the BOREAS site, evaporation in this model is high. Both models have some difficulty representing the surface diurnal cycle of humidity. In the NCEP/NCAR reanalysis this leads to errors primarily in June, when the surface boundary layer stays saturated and too much precipitation occurs. In the ECMWF reanalysis there is a morning peak of mixing ratio, which an earlier work showed resulted from too shallow a boundary layer in the morning. Over the northern boreal forest there are important physical processes, which are not represented in either reanalysis model. In particular very high model albedos in spring, when there is snow under the forest canopy, lead to a very low daytime net radiation. This in turn leads to a large underestimate of the daytime surface fluxes, particularly the sensible heat flux, and to daytime model surface temperatures that are as much as 15 K low. In addition, the models do not account for the reduction in evaporation associated with frozen soil, and they generally have too large evapotranspiration in June and July, probably because they do not model the tight stomatal control of the coniferous forest.

A cloudy planetary boundary layer oscillation arising from the coupling of turbulence with precipitation in climate simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, X.; Klein, S. A.; Ma, H. -Y.

The Community Atmosphere Model (CAM) adopts Cloud Layers Unified By Binormals (CLUBB) scheme and an updated microphysics (MG2) scheme for a more unified treatment of cloud processes. This makes interactions between parameterizations tighter and more explicit. In this study, a cloudy planetary boundary layer (PBL) oscillation related to interaction between CLUBB and MG2 is identified in CAM. This highlights the need for consistency between the coupled subgrid processes in climate model development. This oscillation occurs most often in the marine cumulus cloud regime. The oscillation occurs only if the modeled PBL is strongly decoupled and precipitation evaporates below the cloud.more » Two aspects of the parameterized coupling assumptions between CLUBB and MG2 schemes cause the oscillation: (1) a parameterized relationship between rain evaporation and CLUBB's subgrid spatial variance of moisture and heat that induces an extra cooling in the lower PBL and (2) rain evaporation which happens at a too low an altitude because of the precipitation fraction parameterization in MG2. Either one of these two conditions can overly stabilize the PBL and reduce the upward moisture transport to the cloud layer so that the PBL collapses. Global simulations prove that turning off the evaporation-variance coupling and improving the precipitation fraction parameterization effectively reduces the cloudy PBL oscillation in marine cumulus clouds. By evaluating the causes of the oscillation in CAM, we have identified the PBL processes that should be examined in models having similar oscillations. This study may draw the attention of the modeling and observational communities to the issue of coupling between parameterized physical processes.« less

A cloudy planetary boundary layer oscillation arising from the coupling of turbulence with precipitation in climate simulations

DOE PAGES

Zheng, X.; Klein, S. A.; Ma, H. -Y.; ...

2017-08-24

The Community Atmosphere Model (CAM) adopts Cloud Layers Unified By Binormals (CLUBB) scheme and an updated microphysics (MG2) scheme for a more unified treatment of cloud processes. This makes interactions between parameterizations tighter and more explicit. In this study, a cloudy planetary boundary layer (PBL) oscillation related to interaction between CLUBB and MG2 is identified in CAM. This highlights the need for consistency between the coupled subgrid processes in climate model development. This oscillation occurs most often in the marine cumulus cloud regime. The oscillation occurs only if the modeled PBL is strongly decoupled and precipitation evaporates below the cloud.more » Two aspects of the parameterized coupling assumptions between CLUBB and MG2 schemes cause the oscillation: (1) a parameterized relationship between rain evaporation and CLUBB's subgrid spatial variance of moisture and heat that induces an extra cooling in the lower PBL and (2) rain evaporation which happens at a too low an altitude because of the precipitation fraction parameterization in MG2. Either one of these two conditions can overly stabilize the PBL and reduce the upward moisture transport to the cloud layer so that the PBL collapses. Global simulations prove that turning off the evaporation-variance coupling and improving the precipitation fraction parameterization effectively reduces the cloudy PBL oscillation in marine cumulus clouds. By evaluating the causes of the oscillation in CAM, we have identified the PBL processes that should be examined in models having similar oscillations. This study may draw the attention of the modeling and observational communities to the issue of coupling between parameterized physical processes.« less

Alternative refrigerants and refrigeration cycles for domestic refrigerators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sand, J.R.; Rice, C.L.; Vineyard, E.A.

1992-12-01

This project initially focused on using nonazeotropic refrigerant mixtures (NARMs) in a two-evaporator refrigerator-freezer design using two stages of liquid refrigerant subcooling. This concept was proposed and tested in 1975. The work suggested that the concept was 20% more efficient than the conventional one-evaporator refrigerator-freezer (RF) design. After considerable planning and system modeling based on using a NARM in a Lorenz-Meutzner (L-M) RF, the program scope was broadened to include investigation of a ``dual-loop`` concept where energy savings result from exploiting the less stringent operating conditions needed to satisfy cooling, of the fresh food section. A steady-state computer model (CYCLE-Z)more » capable of simulating conventional, dual loop, and L-M refrigeration cycles was developed. This model was used to rank the performance of 20 ozone-safe NARMs in the L-M refrigeration cycle while key system parameters were systematically varied. The results indicated that the steady-state efficiency of the L-M design was up to 25% greater than that of a conventional cycle. This model was also used to calculate the performance of other pure refrigerants relative to that of dichlorodifluoromethane, R-12, in conventional and dual-loop RF designs. Projected efficiency gains for these cycles were more modest, ranging from 0 to 10%. Individual compressor calorimeter tests of nine combinations of evaporator and condenser temperatures usually used to map RF compressor performance were carried out with R-12 and two candidate L-M NARMs in several compressors. Several models of a commercially produced two-evaporator RF were obtained as test units. Two dual-loop RF designs were built and tested as part of this project.« less

Effect of spatial resolution on remote sensing estimation of total evaporation in the uMngeni catchment, South Africa

NASA Astrophysics Data System (ADS)

Shoko, Cletah; Clark, David; Mengistu, Michael; Dube, Timothy; Bulcock, Hartley

2015-01-01

This study evaluated the effect of two readily available multispectral sensors: the newly launched 30 m spatial resolution Landsat 8 and the long-serving 1000 m moderate resolution imaging spectroradiometer (MODIS) datasets in the spatial representation of total evaporation in the heterogeneous uMngeni catchment, South Africa, using the surface energy balance system model. The results showed that sensor spatial resolution plays a critical role in the accurate estimation of energy fluxes and total evaporation across a heterogeneous catchment. Landsat 8 estimates showed better spatial representation of the biophysical parameters and total evaporation for different land cover types, due to the relatively higher spatial resolution compared to the coarse spatial resolution MODIS sensor. Moreover, MODIS failed to capture the spatial variations of total evaporation estimates across the catchment. Analysis of variance (ANOVA) results showed that MODIS-based total evaporation estimates did not show any significant differences across different land cover types (one-way ANOVA; F1.924=1.412, p=0.186). However, Landsat 8 images yielded significantly different estimates between different land cover types (one-way ANOVA; F1.993=5.185, p<0.001). The validation results showed that Landsat 8 estimates were more comparable to eddy covariance (EC) measurements than the MODIS-based total evaporation estimates. EC measurement on May 23, 2013, was 3.8 mm/day, whereas the Landsat 8 estimate on the same day was 3.6 mm/day, with MODIS showing significantly lower estimates of 2.3 mm/day. The findings of this study underscore the importance of spatial resolution in estimating spatial variations of total evaporation at the catchment scale, thus, they provide critical information on the relevance of the readily available remote sensing products in water resources management in data-scarce environments.

Control of stain geometry by drop evaporation of surfactant containing dispersions.

PubMed

Erbil, H Yildirim

2015-08-01

Control of stain geometry by drop evaporation of surfactant containing dispersions is an important topic of interest because it plays a crucial role in many applications such as forming templates on solid surfaces, in ink-jet printing, spraying of pesticides, micro/nano material fabrication, thin film coatings, biochemical assays, deposition of DNA/RNA micro-arrays, and manufacture of novel optical and electronic materials. This paper presents a review of the published articles on the diffusive drop evaporation of pure liquids (water), the surfactant stains obtained from evaporating drops that do not contain dispersed particles and deposits obtained from drops containing polymer colloids and carbon based particles such as carbon nanotubes, graphite and fullerenes. Experimental results of specific systems and modeling attempts are discussed. This review also has some special subtopics such as suppression of coffee-rings by surfactant addition and "stick-slip" behavior of evaporating nanosuspension drops. In general, the drop evaporation process of a surfactant/particle/substrate system is very complex since dissolved surfactants adsorb on both the insoluble organic/inorganic micro/nanoparticles in the drop, on the air/solution interface and on the substrate surface in different extends. Meanwhile, surfactant adsorbed particles interact with the substrate giving a specific contact angle, and free surfactants create a solutal Marangoni flow in the drop which controls the location of the particle deposition together with the rate of evaporation. In some cases, the presence of a surfactant monolayer at the air/solution interface alters the rate of evaporation. At present, the magnitude of each effect cannot be predicted adequately in advance and consequently they should be carefully studied for any system in order to control the shape and size of the final deposit. Copyright © 2014 Elsevier B.V. All rights reserved.

Terrestrial Water Balances in the Face of Variable Climate over 49 years in Southern Michigan

NASA Astrophysics Data System (ADS)

Hamilton, S. K.; Hussain, M. Z.

2014-12-01

The difference between precipitation and stream discharge over annual periods provides an indication of the total water loss to evaporation and evapotranspiration. The response of evaporative water loss to climate variability and change affects groundwater recharge, stream flow, and lake levels, and is a topic of ongoing debate in the upper Midwest US region and elsewhere. This study examined the watershed water balance for Augusta Creek, which drains a 95-km2 glacial landscape in southwestern Michigan covered by cropland, grassland, forest, and wetlands. The climate is humid and temperate; between 1964-2012 the water-year precipitation averaged 947 mm and ranged from 695-1386 mm. Comparison of precipitation on the upland watershed to baseflow discharge (USGS data; baseflow estimation by WHAT model) across the 49-year record shows that total evaporative water loss averaged 562 +/- 104 mm and ranged from 385-897 mm, with no apparent trend over the record. The evaporative water loss accounts for a mean (s.d.) of 59 +/- 6% of precipitation (range, 48-70%). Evaporative water loss was positively related to total precipitation (r2 = 0.73), but the percentage of precipitation lost to evaporation was only weakly (r2 = 0.12) related to total precipitation. This water balance approach to infer evaporative water loss compares well with direct measurements in the same watershed since 2009 using eddy covariance (grasslands and crops) and soil moisture monitoring by time-domain reflectometry (grasslands, crops, and forest). Thus the evaporative water loss, which is predominantly by evapotranspiration, is linearly related to total precipitation, leaving a relatively consistent proportion for groundwater recharge and streamflow.

Evaporating Atmospheres Around Close-in Exoplanets.

NASA Astrophysics Data System (ADS)

Owen, J.; Jackson, A.; Wu, Y.; Adams, F.

2014-12-01

The majority of currently observed exoplanets appear exceeding close to the central star (<0.1 AU) and as such are subject to intense high energy radiation from UV & X-ray photons. We will discuss that in such environments the atmospheres these planets are heated sufficiently that they can escape the planet's gravitational field in a hydrodynamic trans-sonic wind. We will show that this hydrodynamic mass-loss occurs for the majority of exoplanets at short periods, and for low-mass planets (<50 Mearth) is vigorous enough to significantly alter the planet's evolution. In some cases we will argue that an originally gas rich exoplanet can be completely evaporated leaving behind a bare rock core. In addition, we will present new multi-dimensional simulations of evaporation that include realistic treatment of the radiative transfer. These new simulations show that evaporation from 'hot' Jupiters is likely to be magnetically controlled, where mass-loss can only occur along open filed lines, where the interaction between the stellar and planetary magnetic field strongly controls the geometry of the evaporative flow. We will indicate how these new multi-dimensional radiation-magneto-hydrodynamic calculations can be used to study the time-dependence of the outflow and link the small but growing number of observations of exoplanet evaporation to the theoretical models. Finally, we will indicate that asymmetric evaporative flows can lead to orbital evolution of planets at close separations. Figure Caption: "Flow structure from an evaporating Hot Jupiter with a magnetic field strength of 0.3 Gauss. Top panels show density and magnetic field configuration and bottom panel shows plasma beta and velocity structure; left panels show simulation domain, right panels show a zoom in on the planet."

On The Validity of the Assumed PDF Method for Modeling Binary Mixing/Reaction of Evaporated Vapor in GAS/Liquid-Droplet Turbulent Shear Flow

NASA Technical Reports Server (NTRS)

Miller, R. S.; Bellan, J.

1997-01-01

An Investigation of the statistical description of binary mixing and/or reaction between a carrier gas and an evaporated vapor species in two-phase gas-liquid turbulent flows is perfomed through both theroetical analysis and comparisons with results from direct numerical simulations (DNS) of a two-phase mixing layer.

Delineating sources of groundwater recharge in an arsenic-affected Holocene aquifer in Cambodia using stable isotope-based mixing models

NASA Astrophysics Data System (ADS)

Richards, Laura A.; Magnone, Daniel; Boyce, Adrian J.; Casanueva-Marenco, Maria J.; van Dongen, Bart E.; Ballentine, Christopher J.; Polya, David A.

2018-02-01

Chronic exposure to arsenic (As) through the consumption of contaminated groundwaters is a major threat to public health in South and Southeast Asia. The source of As-affected groundwaters is important to the fundamental understanding of the controls on As mobilization and subsequent transport throughout shallow aquifers. Using the stable isotopes of hydrogen and oxygen, the source of groundwater and the interactions between various water bodies were investigated in Cambodia's Kandal Province, an area which is heavily affected by As and typical of many circum-Himalayan shallow aquifers. Two-point mixing models based on δD and δ18O allowed the relative extent of evaporation of groundwater sources to be estimated and allowed various water bodies to be broadly distinguished within the aquifer system. Model limitations are discussed, including the spatial and temporal variation in end member compositions. The conservative tracer Cl/Br is used to further discriminate between groundwater bodies. The stable isotopic signatures of groundwaters containing high As and/or high dissolved organic carbon plot both near the local meteoric water line and near more evaporative lines. The varying degrees of evaporation of high As groundwater sources are indicative of differing recharge contributions (and thus indirectly inferred associated organic matter contributions). The presence of high As groundwaters with recharge derived from both local precipitation and relatively evaporated surface water sources, such as ponds or flooded wetlands, are consistent with (but do not provide direct evidence for) models of a potential dual role of surface-derived and sedimentary organic matter in As mobilization.

Evaporation estimation of rift valley lakes: comparison of models.

PubMed

Melesse, Assefa M; Abtew, Wossenu; Dessalegne, Tibebe

2009-01-01

Evapotranspiration (ET) accounts for a substantial amount of the water flux in the arid and semi-arid regions of the World. Accurate estimation of ET has been a challenge for hydrologists, mainly because of the spatiotemporal variability of the environmental and physical parameters governing the latent heat flux. In addition, most available ET models depend on intensive meteorological information for ET estimation. Such data are not available at the desired spatial and temporal scales in less developed and remote parts of the world. This limitation has necessitated the development of simple models that are less data intensive and provide ET estimates with acceptable level of accuracy. Remote sensing approach can also be applied to large areas where meteorological data are not available and field scale data collection is costly, time consuming and difficult. In areas like the Rift Valley regions of Ethiopia, the applicability of the Simple Method (Abtew Method) of lake evaporation estimation and surface energy balance approach using remote sensing was studied. The Simple Method and a remote sensing-based lake evaporation estimates were compared to the Penman, Energy balance, Pan, Radiation and Complementary Relationship Lake Evaporation (CRLE) methods applied in the region. Results indicate a good correspondence of the models outputs to that of the above methods. Comparison of the 1986 and 2000 monthly lake ET from the Landsat images to the Simple and Penman Methods show that the remote sensing and surface energy balance approach is promising for large scale applications to understand the spatial variation of the latent heat flux.

Vapor shielding models and the energy absorbed by divertor targets during transient events

DOE Office of Scientific and Technical Information (OSTI.GOV)

Skovorodin, D. I., E-mail: dskovorodin@gmail.com; Arakcheev, A. S.; Pshenov, A. A.

2016-02-15

The erosion of divertor targets caused by high heat fluxes during transients is a serious threat to ITER operation, as it is going to be the main factor determining the divertor lifetime. Under the influence of extreme heat fluxes, the surface temperature of plasma facing components can reach some certain threshold, leading to an onset of intense material evaporation. The latter results in formation of cold dense vapor and secondary plasma cloud. This layer effectively absorbs the energy of the incident plasma flow, turning it into its own kinetic and internal energy and radiating it. This so called vapor shieldingmore » is a phenomenon that may help mitigating the erosion during transient events. In particular, the vapor shielding results in saturation of energy (per unit surface area) accumulated by the target during single pulse of heat load at some level E{sub max}. Matching this value is one of the possible tests to verify complicated numerical codes, developed to calculate the erosion rate during abnormal events in tokamaks. The paper presents three very different models of vapor shielding, demonstrating that E{sub max} depends strongly on the heat pulse duration, thermodynamic properties, and evaporation energy of the irradiated target material. While its dependence on the other shielding details such as radiation capabilities of material and dynamics of the vapor cloud is logarithmically weak. The reason for this is a strong (exponential) dependence of the target material evaporation rate, and therefore the “strength” of vapor shield on the target surface temperature. As a result, the influence of the vapor shielding phenomena details, such as radiation transport in the vapor cloud and evaporated material dynamics, on the E{sub max} is virtually completely masked by the strong dependence of the evaporation rate on the target surface temperature. However, the very same details define the amount of evaporated particles, needed to provide an effective shielding to the target, and, therefore, strongly influence resulting erosion rate. Thus, E{sub max} cannot be used for validation of shielding models and codes, aimed at the target material erosion calculations.« less

Estimation of groundwater recharge to chalk and sandstone aquifers using simple soil models

NASA Astrophysics Data System (ADS)

Ragab, R.; Finch, J.; Harding, R.

1997-03-01

On the assumption that the water draining below the root zone is potentially available for groundwater recharge, two current UK methods for estimating annual groundwater recharge have been compared with a new soil model using data from four sites under permanent grass in the UK: two sites representative of the Chalk aquifer at Bridgest Farm (Hampshire) and Fleam Dyke (Cambridgeshire), and two sites on the Triassic sandstone at Bicton College (Devon) and Bacon Hall (Shropshire). A Four Root Layers Model (FRLM), the Penman-Grindley model and the UK Meteorological Office Rainfall and Evaporation Calculation System (MORECS) were used. The new soil model was run with potential evaporation as input both from the MORECS and from the Penman-Monteith equation. The models were run for the Chalk sites both with and without a bypass flow of 15% of rainfall. Bypass was not considered for the sandstone sites. The performance of the models was tested against neutron probes measurements of soil moisture deficits. In addition, the annual groundwater recharge estimated from the models was compared with the published values obtained from the 'zero flux plane' method. Generally, the Penman-Grindley model was more successful in predicting the time for soil to return to its field capacity than in predicting the magnitude of the soil moisture deficit. The annual groundwater recharge was predicted with reasonable accuracy. The MORECS relatively tended to overestimate the soil moisture deficits and to delay the time at which the soil returns to its field capacity. The consequences were underestimates of annual groundwater recharge, owing either to the higher values of potential evaporation calculated from the MORECS or tothe high available water capacity values associated with the soils under consideration. The new soil model (FRLM) predicts the soil moisture deficits successfully and hence is reliable in estimating the annual groundwater recharge. The model is capable of doing this with potential evaporation input calculated either from the MORECS or from the Penman-Monteith equation. The model also demonstrated that the inclusion of 15% of rainfall as bypass flow is viable for Chalk sites.

The water cycle in the general circulation model of the martian atmosphere

NASA Astrophysics Data System (ADS)

Shaposhnikov, D. S.; Rodin, A. V.; Medvedev, A. S.

2016-03-01

Within the numerical general-circulation model of the Martian atmosphere MAOAM (Martian Atmosphere: Observation and Modeling), we have developed the water cycle block, which is an essential component of modern general circulation models of the Martian atmosphere. The MAOAM model has a spectral dynamic core and successfully predicts the temperature regime on Mars through the use of physical parameterizations typical of both terrestrial and Martian models. We have achieved stable computation for three Martian years, while maintaining a conservative advection scheme taking into account the water-ice phase transitions, water exchange between the atmosphere and surface, and corrections for the vertical velocities of ice particles due to sedimentation. The studies show a strong dependence of the amount of water that is actively involved in the water cycle on the initial data, model temperatures, and the mechanism of water exchange between the atmosphere and the surface. The general pattern and seasonal asymmetry of the water cycle depends on the size of ice particles, the albedo, and the thermal inertia of the planet's surface. One of the modeling tasks, which results from a comparison of the model data with those of the TES experiment on board Mars Global Surveyor, is the increase in the total mass of water vapor in the model in the aphelion season and decrease in the mass of water ice clouds at the poles. The surface evaporation scheme, which takes into account the turbulent rise of water vapor, on the one hand, leads to the most complete evaporation of ice from the surface in the summer season in the northern hemisphere and, on the other hand, supersaturates the atmosphere with ice due to the vigorous evaporation, which leads to worse consistency between the amount of the precipitated atmospheric ice and the experimental data. The full evaporation of ice from the surface increases the model sensitivity to the size of the polar cap; therefore, the increase in the latter leads to better results. The use of a more accurate dust scenario changes the model temperatures, which also strongly affects the water cycle.

The Interplay Between Transpiration and Runoff Formulations in Land Surface Schemes Used with Atmospheric Models

NASA Technical Reports Server (NTRS)

Koster, Rindal D.; Milly, P. C. D.

1997-01-01

The Project for Intercomparison of Land-surface Parameterization Schemes (PILPS) has shown that different land surface models (LSMS) driven by the same meteorological forcing can produce markedly different surface energy and water budgets, even when certain critical aspects of the LSMs (vegetation cover, albedo, turbulent drag coefficient, and snow cover) are carefully controlled. To help explain these differences, the authors devised a monthly water balance model that successfully reproduces the annual and seasonal water balances of the different PILPS schemes. Analysis of this model leads to the identification of two quantities that characterize an LSM's formulation of soil water balance dynamics: (1) the efficiency of the soil's evaporation sink integrated over the active soil moisture range, and (2) the fraction of this range over which runoff is generated. Regardless of the LSM's complexity, the combination of these two derived parameters with rates of interception loss, potential evaporation, and precipitation provides a reasonable estimate for the LSM's simulated annual water balance. The two derived parameters shed light on how evaporation and runoff formulations interact in an LSM, and the analysis as a whole underscores the need for compatibility in these formulations.

The interplay between transpiration and Runoff formulations in land surface schemes used with atmospheric models

USGS Publications Warehouse

Koster, R.D.; Milly, P.C.D.

1997-01-01

The Project for Intercomparison of Land-surface Parameterization Schemes (PILPS) has shown that different land surface models (LSMs) driven by the same meteorological forcing can produce markedly different surface energy and water budgets, even when certain critical aspects of the LSMs (vegetation cover, albedo, turbulent drag coefficient, and snowcover) are carefully controlled. To help explain these differences, the authors devised a monthly water balance model that successfully reproduces the annual and seasonal water balances of the different PILPS schemes. Analysis of this model leads to the identification of two quantities that characterize an LSM's formulation of soil water balance dynamics: 1) the efficiency of the soil's evaporation sink integrated over the active soil moisture range, and 2) the fraction of this range over which runoff is generated. Regardless of the LSM's complexity, the combination of these two derived parameters with rates of interception loss, potential evaporation, and precipitation provides a reasonable estimate for the LSM's simulated annual water balance. The two derived parameters shed light on how evaporation and runoff formulations interact in an LSM, and the analysis as a whole underscores the need for compatibility in these formulations.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hagos, Samson M.; Feng, Zhe; Burleyson, Casey D.

Regional cloud permitting model simulations of cloud populations observed during the 2011 ARM Madden Julian Oscillation Investigation Experiment/ Dynamics of Madden-Julian Experiment (AMIE/DYNAMO) field campaign are evaluated against radar and ship-based measurements. Sensitivity of model simulated surface rain rate statistics to parameters and parameterization of hydrometeor sizes in five commonly used WRF microphysics schemes are examined. It is shown that at 2 km grid spacing, the model generally overestimates rain rate from large and deep convective cores. Sensitivity runs involving variation of parameters that affect rain drop or ice particle size distribution (more aggressive break-up process etc) generally reduce themore » bias in rain-rate and boundary layer temperature statistics as the smaller particles become more vulnerable to evaporation. Furthermore significant improvement in the convective rain-rate statistics is observed when the horizontal grid-spacing is reduced to 1 km and 0.5 km, while it is worsened when run at 4 km grid spacing as increased turbulence enhances evaporation. The results suggest modulation of evaporation processes, through parameterization of turbulent mixing and break-up of hydrometeors may provide a potential avenue for correcting cloud statistics and associated boundary layer temperature biases in regional and global cloud permitting model simulations.« less

Is it Becoming Warmer and Wetter in the Antarctic? A Look at Evaporation from the Southern Ocean

NASA Astrophysics Data System (ADS)

Boisvert, L.; Shie, C. L.

2017-12-01

The process of evaporation provides water vapor from the surface to the atmosphere, where it becomes the most radiatively important and abundant greenhouse gas altering the Earth's energy balance. Hence evaporation plays an essential role in a wide variety of atmospheric and oceanic problems. Evaporation is a key component of both the water cycle and the surface energy balance and thus information on this process is crucial in understanding the interaction between the atmosphere and oceans, global energy and water cycle variability, and in improving model simulations of climate variations. Although evaporation is an important term in climate model physics it is often poorly captured because surface in-situ measurements of evaporation are scarce in both space and time, especially over the Polar Regions, because evaporation is not easily measured directly. The Antarctic sea ice acts as a barrier between the ocean and atmosphere inhibiting the exchange of heat, momentum, and moisture. However, variations in the sea ice cover could lead to changes in the amount of moisture supplied to the atmosphere. Variations in the sea ice coverage could potentially allow for larger vertical moisture fluxes that affect surface energy budgets, larger occurrences of low-level clouds, and higher near-surface humidity and temperatures. These changes to the local atmosphere could then potentially impact nearby atmospheric conditions over the Antarctic ice sheet, which could be particularly important in regions that are susceptible to collapse like the West Antarctic Ice Sheet. NASA's Atmospheric Infrared Sounder (AIRS) has been used in multiple studies to study sea-ice atmosphere interactions in the Arctic Ocean with great success, specifically in evaporation (i.e. the moisture flux). However, little research has been done looking at the moisture flux from the Antarctic sea ice pack and nearby areas of the Southern Ocean. This work will use data from AIRS and the moisture flux scheme from Boisvert et al., 2013, which utilizes the Monin-Obukhov Similarity Theory. Changes have been made to the boundary layer parameterizations specifically for sea ice in order to produce a 2003-2016 moisture flux product for the Antarctic sea ice. Regional and seasonal differences will be addressed along with any trends and interannual variability.

Advancing representation of hydrologic processes in the Soil and Water Assessment Tool (SWAT) through integration of the TOPographic MODEL (TOPMODEL) features

USGS Publications Warehouse

Chen, J.; Wu, Y.

2012-01-01

This paper presents a study of the integration of the Soil and Water Assessment Tool (SWAT) model and the TOPographic MODEL (TOPMODEL) features for enhancing the physical representation of hydrologic processes. In SWAT, four hydrologic processes, which are surface runoff, baseflow, groundwater re-evaporation and deep aquifer percolation, are modeled by using a group of empirical equations. The empirical equations usually constrain the simulation capability of relevant processes. To replace these equations and to model the influences of topography and water table variation on streamflow generation, the TOPMODEL features are integrated into SWAT, and a new model, the so-called SWAT-TOP, is developed. In the new model, the process of deep aquifer percolation is removed, the concept of groundwater re-evaporation is refined, and the processes of surface runoff and baseflow are remodeled. Consequently, three parameters in SWAT are discarded, and two new parameters to reflect the TOPMODEL features are introduced. SWAT-TOP and SWAT are applied to the East River basin in South China, and the results reveal that, compared with SWAT, the new model can provide a more reasonable simulation of the hydrologic processes of surface runoff, groundwater re-evaporation, and baseflow. This study evidences that an established hydrologic model can be further improved by integrating the features of another model, which is a possible way to enhance our understanding of the workings of catchments.

Structure and optical properties of evaporated films of the Cr- and V-group metals

NASA Technical Reports Server (NTRS)

Nestell, J. E., Jr.; Christy, R. W.; Cohen, M. H.; Ruben, G. C.

1980-01-01

Thin films of Cr, Mo, and W rapidly evaporated in high vacuum (5 x 10 to the -7th torr) onto room-temperature substrates show anomalously low reflectance (compared to bulk samples). From electron and X-ray diffraction and electron microscopy, the normal bcc crystal structure is found, but with very fine grains. Columnar grains about 100 A in diameter were separated by a less dense grain-boundary network about 10-A wide. The measured optical conductivity agrees with an inhomogeneous-medium model that assumes the normal crystalline conductivity for the grain interiors, with model parameters that correlate to the observed columnar grain size. In contrast, V and Nb films rapidly evaporated onto room-temperature substrates have the reflectance of bulk crystalline material. On liquid-nitrogen temperature substrates, however, V and Nb have normal bcc crystal structure but with small flat-plate grains, and the same model, with appropriate parameters, accounts for the optical conductivity. The difference between these two groups apparently depends on residual gases segregated at the grain boundaries in the Cr-group films.

Constrained variability of modeled T:ET ratio across biomes

NASA Astrophysics Data System (ADS)

Fatichi, Simone; Pappas, Christoforos

2017-07-01

A large variability (35-90%) in the ratio of transpiration to total evapotranspiration (referred here as T:ET) across biomes or even at the global scale has been documented by a number of studies carried out with different methodologies. Previous empirical results also suggest that T:ET does not covary with mean precipitation and has a positive dependence on leaf area index (LAI). Here we use a mechanistic ecohydrological model, with a refined process-based description of evaporation from the soil surface, to investigate the variability of T:ET across biomes. Numerical results reveal a more constrained range and higher mean of T:ET (70 ± 9%, mean ± standard deviation) when compared to observation-based estimates. T:ET is confirmed to be independent from mean precipitation, while it is found to be correlated with LAI seasonally but uncorrelated across multiple sites. Larger LAI increases evaporation from interception but diminishes ground evaporation with the two effects largely compensating each other. These results offer mechanistic model-based evidence to the ongoing research about the patterns of T:ET and the factors influencing its magnitude across biomes.

Evaporation of Accretion Disks around Black Holes: The Disk-Corona Transition and the Connection to the Advection-dominated Accretion Flow.

PubMed

Liu; Yuan; Meyer; Meyer-Hofmeister; Xie

1999-12-10

We apply the disk-corona evaporation model (Meyer & Meyer-Hofmeister) originally derived for dwarf novae to black hole systems. This model describes the transition of a thin cool outer disk to a hot coronal flow. The mass accretion rate determines the location of this transition. For a number of well-studied black hole binaries, we take the mass flow rates derived from a fit of the advection-dominated accretion flow (ADAF) model to the observed spectra (for a review, see Narayan, Mahadevan, & Quataert) and determine where the transition of accretion via a cool disk to a coronal flow/ADAF would be located for these rates. We compare this with the observed location of the inner disk edge, as estimated from the maximum velocity of the Halpha emission line. We find that the transition caused by evaporation agrees with this determination in stellar disks. We also show that the ADAF and the "thin outer disk + corona" are compatible in terms of the physics in the transition region.

Modeling of thin film GaAs growth

NASA Technical Reports Server (NTRS)

Heinbockel, J. H.

1982-01-01

A potential scaling Monte Carlo model of crystal growth is developed. The model is a modification of the solid-on-solid method for studying crystal growth in that potentials at surface sites are continuously updated on a time scale reflecting the surface events of migration, incorporation and evaporation. The model allows for B on A type of crystal growth and lattice disregistry by the assignment of potential values at various surface sites. The surface adatoms are periodically assigned a random energy from a Boltzmann distribution and this energy determines whether the adatoms evaporate, migrate or remain stationary during the sampling interval. For each addition or migration of an adatom, the surface potentials are adjusted to reflect the adsorption, migration or desorption potential changes.

Tear film dynamics with evaporation, wetting, and time-dependent flux boundary condition on an eye-shaped domain

PubMed Central

Li, Longfei; Braun, R. J.; Maki, K. L.; Henshaw, W. D.; King-Smith, P. E.

2014-01-01

We study tear film dynamics with evaporation on a wettable eye-shaped ocular surface using a lubrication model. The mathematical model has a time-dependent flux boundary condition that models the cycles of tear fluid supply and drainage; it mimics blinks on a stationary eye-shaped domain. We generate computational grids and solve the nonlinear governing equations using the OVERTURE computational framework. In vivo experimental results using fluorescent imaging are used to visualize the influx and redistribution of tears for an open eye. Results from the numerical simulations are compared with the experiment. The model captures the flow around the meniscus and other dynamic features of human tear film observed in vivo. PMID:24926191

Vegetation root zone storage and rooting depth, derived from local calibration of a global hydrological model

NASA Astrophysics Data System (ADS)

van der Ent, R.; Van Beek, R.; Sutanudjaja, E.; Wang-Erlandsson, L.; Hessels, T.; Bastiaanssen, W.; Bierkens, M. F.

2017-12-01

The storage and dynamics of water in the root zone control many important hydrological processes such as saturation excess overland flow, interflow, recharge, capillary rise, soil evaporation and transpiration. These processes are parameterized in hydrological models or land-surface schemes and the effect on runoff prediction can be large. Root zone parameters in global hydrological models are very uncertain as they cannot be measured directly at the scale on which these models operate. In this paper we calibrate the global hydrological model PCR-GLOBWB using a state-of-the-art ensemble of evaporation fields derived by solving the energy balance for satellite observations. We focus our calibration on the root zone parameters of PCR-GLOBWB and derive spatial patterns of maximum root zone storage. We find these patterns to correspond well with previous research. The parameterization of our model allows for the conversion of maximum root zone storage to root zone depth and we find that these correspond quite well to the point observations where available. We conclude that climate and soil type should be taken into account when regionalizing measured root depth for a certain vegetation type. We equally find that using evaporation rather than discharge better allows for local adjustment of root zone parameters within a basin and thus provides orthogonal data to diagnose and optimize hydrological models and land surface schemes.

Vegetation root zone storage and rooting depth, derived from local calibration of a global hydrological model

NASA Astrophysics Data System (ADS)

van der Ent, Ruud; van Beek, Rens; Sutanudjaja, Edwin; Wang-Erlandsson, Lan; Hessels, Tim; Bastiaanssen, Wim; Bierkens, Marc

2017-04-01

The storage and dynamics of water in the root zone control many important hydrological processes such as saturation excess overland flow, interflow, recharge, capillary rise, soil evaporation and transpiration. These processes are parameterized in hydrological models or land-surface schemes and the effect on runoff prediction can be large. For root zone parameters in global hydrological models are very uncertain as they cannot be measured directly at the scale on which these models operate. In this paper we calibrate the global hydrological model PCR-GLOBWB using a state-of-the-art ensemble of evaporation fields derived by solving the energy balance for satellite observations. We focus our calibration on the root zone parameters of PCR-GLOBWB and derive spatial patterns of maximum root zone storage. We find these patterns to correspond well with previous research. The parameterization of our model allows for the conversion of maximum root zone storage to root zone depth and we find that these correspond quite well to the point observations where available. We conclude that climate and soil type should be taken into account when regionalizing measured root depth for a certain vegetation type. We equally find that using evaporation rather than discharge better allows for local adjustment of root zone parameters within a basin and thus provides orthogonal data to diagnose and optimize hydrological models and land surface schemes.

A transient analysis of frost formation on a parallel plate evaporator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martinez-Frias, J.; Aceves, S.M.; Hernandez-Guerrero, A.

1996-12-31

This paper presents the development of a transient model for evaluating frost formation on a parallel plate evaporator for heat pump applications. The model treats the frost layer as a porous substance, and applies the equations of conservation of mass, momentum and energy to calculate the growth and densification of the frost layer. Empirical correlations for thermal conductivity and tortuosity as a function of density are incorporated from previous studies. Frost growth is calculated as a function of time, Reynolds number, longitudinal location, plate temperature, and ambient air temperature and humidity. The main assumptions are: ideal gas behavior for airmore » and water vapor, uniform frost density and thermal conductivity across the thickness of the frost layer; and quasi-steady conditions during the whole process. The mathematical model is validated by comparing the predicted values of frost thickness and frost density with results obtained in recent experimental studies. A good agreement was obtained in the comparison. The frost formation model calculates pressure drop and heat transfer resistance that result from the existence of the frost layer, and it can therefore be incorporated into a heat pump model to evaluate performance losses due to frosting as a function of weather conditions and time of operation since the last evaporator defrost.« less

Study on water evaporation rate from indoor swimming pools

NASA Astrophysics Data System (ADS)

Rzeźnik, Ilona

2017-11-01

The air relative humidity in closed spaces of indoor swimming pools influences significantly on users thermal comfort and the stability of the building structure, so its preservation on suitable level is very important. For this purpose, buildings are equipped with HVAC systems which provide adequate level of humidity. The selection of devices and their technical parameters is made using the mathematical models of water evaporation rate in the unoccupied and occupied indoor swimming pool. In the literature, there are many papers describing this phenomena but the results differ from each other. The aim of the study was the experimental verification of published models of evaporation rate in the pool. The tests carried out on a laboratory scale, using model of indoor swimming pool, measuring 99cm/68cm/22cm. The model was equipped with water spray installation with six nozzles to simulate conditions during the use of the swimming pool. The measurements were made for conditions of sports pools (water temperature 24°C) and recreational swimming pool (water temperature 34°C). According to the recommendations the air temperature was about 2°C higher than water temperature, and the relative humidity ranged from 40% to 55%. Models Shah and Biasin & Krumm were characterized by the best fit to the results of measurements on a laboratory scale.

Model of convection mass transfer in titanium alloy at low energy high current electron beam action

NASA Astrophysics Data System (ADS)

Sarychev, V. D.; Granovskii, A. Yu; Nevskii, S. A.; Konovalov, S. V.; Gromov, V. E.

2017-01-01

The convection mixing model is proposed for low-energy high-current electron beam treatment of titanium alloys, pre-processed by heterogeneous plasma flows generated via explosion of carbon tape and powder TiB2. The model is based on the assumption vortices in the molten layer are formed due to the treatment by concentrated energy flows. These vortices evolve as the result of thermocapillary convection, arising because of the temperature gradient. The calculation of temperature gradient and penetration depth required solution of the heat problem with taking into account the surface evaporation. However, instead of the direct heat source the boundary conditions in phase transitions were changed in the thermal conductivity equation, assuming the evaporated material takes part in the heat exchange. The data on the penetration depth and temperature distribution are used for the thermocapillary model. The thermocapillary model embraces Navier-Stocks and convection heat transfer equations, as well as the boundary conditions with the outflow of evaporated material included. The solution of these equations by finite elements methods pointed at formation of a multi-vortices structure when electron-beam treatment and its expansion over new zones of material. As the result, strengthening particles are found at the depth exceeding manifold their penetration depth in terms of the diffusion mechanism.

A sensor-based energy balance method for the distributed estimation of evaporation over the North American Great Lakes

NASA Astrophysics Data System (ADS)

Fries, K. J.; Kerkez, B.; Gronewold, A.; Lenters, J. D.

2014-12-01

We introduce a novel energy balance method to estimate evaporation across large lakes using real-time data from moored buoys and mobile, satellite-tracked drifters. Our work is motivated by the need to improve our understanding of the water balance of the Laurentian Great Lakes basin, a complex hydrologic system that comprises 90% of the United States' and 20% of the world's fresh surface water. Recently, the lakes experienced record-setting water level drops despite above-average precipitation, and given that lake surface area comprises nearly one third of the entire basin, evaporation is suspected to be the primary driver behind the decrease in water levels. There has historically been a need to measure evaporation over the Great Lakes, and recent hydrological phenomena (including not only record low levels, but also extreme changes in ice cover and surface water temperatures) underscore the urgency of addressing that need. Our method tracks the energy fluxes of the lake system - namely net radiation, heat storage and advection, and Bowen ratio. By measuring each of these energy budget terms and combining the results with mass-transfer based estimates, we can calculate real-time evaporation rates on sub-hourly timescales. To mitigate the cost prohibitive nature of large-scale, distributed energy flux measurements, we present a novel approach in which we leverage existing investments in seasonal buoys (which, while providing intensive, high quality data, are costly and sparsely distributed across the surface of the Great Lakes) and then integrate data from less costly satellite-tracked drifter data. The result is an unprecedented, hierarchical sensor and modeling architecture that can be used to derive estimates of evaporation in real-time through cloud-based computing. We discuss recent deployments of sensor-equipped buoys and drifters, which are beginning to provide us with some of the first in situ measurements of overlake evaporation from Earth's largest lake system, opening up the potential for improved and integrated monitoring and modeling of the Great Lakes water budget.

Duplex Tear Film Evaporation Analysis.

PubMed

Stapf, M R; Braun, R J; King-Smith, P E

2017-12-01

Tear film thinning, hyperosmolarity, and breakup can cause irritation and damage to the human eye, and these form an area of active investigation for dry eye syndrome research. Recent research demonstrates that deficiencies in the lipid layer may cause locally increased evaporation, inducing conditions for breakup. In this paper, we explore the conditions for tear film breakup by considering a model for tear film dynamics with two mobile fluid layers, the aqueous and lipid layers. In addition, we include the effects of osmosis, evaporation as modified by the lipid, and the polar portion of the lipid layer. We solve the system numerically for reasonable parameter values and initial conditions and analyze how shifts in these cause changes to the system's dynamics.

The Competition between Liquid and Vapor Transport in Transpiring Leaves1[W][OPEN

PubMed Central

Rockwell, Fulton Ewing; Holbrook, N. Michele; Stroock, Abraham Duncan

2014-01-01

In leaves, the transpirational flux of water exits the veins as liquid and travels toward the stomata in both the vapor and liquid phases before exiting the leaf as vapor. Yet, whether most of the evaporation occurs from the vascular bundles (perivascular), from the photosynthetic mesophyll cells, or within the vicinity of the stomatal pore (peristomatal) remains in dispute. Here, a one-dimensional model of the competition between liquid and vapor transport is developed from the perspective of nonisothermal coupled heat and water molecule transport in a composite medium of airspace and cells. An analytical solution to the model is found in terms of the energy and transpirational fluxes from the leaf surfaces and the absorbed solar energy load, leading to mathematical expressions for the proportions of evaporation accounted for by the vascular, mesophyll, and epidermal regions. The distribution of evaporation in a given leaf is predicted to be variable, changing with the local environment, and to range from dominantly perivascular to dominantly peristomatal depending on internal leaf architecture, with mesophyll evaporation a subordinate component. Using mature red oak (Quercus rubra) trees, we show that the model can be solved for a specific instance of a transpiring leaf by combining gas-exchange data, anatomical measurements, and hydraulic experiments. We also investigate the effect of radiation load on the control of transpiration, the potential for condensation on the inside of an epidermis, and the impact of vapor transport on the hydraulic efficiency of leaf tissue outside the xylem. PMID:24572172

Effects of carbonyl bond, metal cluster dissociation, and evaporation rates on predictions of nanotube production in high-pressure carbon monoxide

NASA Technical Reports Server (NTRS)

Scott, Carl D.; Smalley, Richard E.

2003-01-01

The high-pressure carbon monoxide (HiPco) process for producing single-wall carbon nanotubes (SWNTs) uses iron pentacarbonyl as the source of iron for catalyzing the Boudouard reaction. Attempts using nickel tetracarbonyl led to no production of SWNTs. This paper discusses simulations at a constant condition of 1300 K and 30 atm in which the chemical rate equations are solved for different reaction schemes. A lumped cluster model is developed to limit the number of species in the models, yet it includes fairly large clusters. Reaction rate coefficients in these schemes are based on bond energies of iron and nickel species and on estimates of chemical rates for formation of SWNTs. SWNT growth is measured by the conformation of CO2. It is shown that the production of CO2 is significantly greater for FeCO because of its lower bond energy as compared with that of NiCO. It is also shown that the dissociation and evaporation rates of atoms from small metal clusters have a significant effect on CO2 production. A high rate of evaporation leads to a smaller number of metal clusters available to catalyze the Boudouard reaction. This suggests that if CO reacts with metal clusters and removes atoms from them by forming MeCO, this has the effect of enhancing the evaporation rate and reducing SWNT production. The study also investigates some other reactions in the model that have a less dramatic influence.

Effects of Carbonyl Bond and Metal Cluster Dissociation and Evaporation Rates on Predictions of Nanotube Production in HiPco

NASA Technical Reports Server (NTRS)

Scott, Carl D.; Smalley, Richard E.

2002-01-01

The high-pressure carbon monoxide (HiPco) process for producing single-wall carbon nanotubes (SWNT) uses iron pentacarbonyl as the source of iron for catalyzing the Boudouard reaction. Attempts using nickel tetracarbonyl led to no production of SWNTs. This paper discusses simulations at a constant condition of 1300 K and 30 atm in which the chemical rate equations are solved for different reaction schemes. A lumped cluster model is developed to limit the number of species in the models, yet it includes fairly large clusters. Reaction rate coefficients in these schemes are based on bond energies of iron and nickel species and on estimates of chemical rates for formation of SWNTs. SWNT growth is measured by the co-formation of CO2. It is shown that the production of CO2 is significantly greater for FeCO due to its lower bond energy as compared with that ofNiCO. It is also shown that the dissociation and evaporation rates of atoms from small metal clusters have a significant effect on CO2 production. A high rate of evaporation leads to a smaller number of metal clusters available to catalyze the Boudouard reaction. This suggests that if CO reacts with metal clusters and removes atoms from them by forming MeCO, this has the effect of enhancing the evaporation rate and reducing SWNT production. The study also investigates some other reactions in the model that have a less dramatic influence.

The competition between liquid and vapor transport in transpiring leaves.

PubMed

Rockwell, Fulton Ewing; Holbrook, N Michele; Stroock, Abraham Duncan

2014-04-01

In leaves, the transpirational flux of water exits the veins as liquid and travels toward the stomata in both the vapor and liquid phases before exiting the leaf as vapor. Yet, whether most of the evaporation occurs from the vascular bundles (perivascular), from the photosynthetic mesophyll cells, or within the vicinity of the stomatal pore (peristomatal) remains in dispute. Here, a one-dimensional model of the competition between liquid and vapor transport is developed from the perspective of nonisothermal coupled heat and water molecule transport in a composite medium of airspace and cells. An analytical solution to the model is found in terms of the energy and transpirational fluxes from the leaf surfaces and the absorbed solar energy load, leading to mathematical expressions for the proportions of evaporation accounted for by the vascular, mesophyll, and epidermal regions. The distribution of evaporation in a given leaf is predicted to be variable, changing with the local environment, and to range from dominantly perivascular to dominantly peristomatal depending on internal leaf architecture, with mesophyll evaporation a subordinate component. Using mature red oak (Quercus rubra) trees, we show that the model can be solved for a specific instance of a transpiring leaf by combining gas-exchange data, anatomical measurements, and hydraulic experiments. We also investigate the effect of radiation load on the control of transpiration, the potential for condensation on the inside of an epidermis, and the impact of vapor transport on the hydraulic efficiency of leaf tissue outside the xylem.

Quest for consistent modelling of statistical decay of the compound nucleus

NASA Astrophysics Data System (ADS)

Banerjee, Tathagata; Nath, S.; Pal, Santanu

2018-01-01

A statistical model description of heavy ion induced fusion-fission reactions is presented where shell effects, collective enhancement of level density, tilting away effect of compound nuclear spin and dissipation are included. It is shown that the inclusion of all these effects provides a consistent picture of fission where fission hindrance is required to explain the experimental values of both pre-scission neutron multiplicities and evaporation residue cross-sections in contrast to some of the earlier works where a fission hindrance is required for pre-scission neutrons but a fission enhancement for evaporation residue cross-sections.