Formation of coffee-stain patterns at the nanoscale: The role of nanoparticle solubility and solvent evaporation rate.

PubMed

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

2017-03-21

When droplets of nanoparticle suspension evaporate from surfaces, they leave behind a deposit of nanoparticles. The mechanism of evaporation-induced pattern formation in the deposit is studied by molecular dynamics simulations for sessile nanodroplets. The influence of the interaction between nanoparticles and liquid molecules and the influence of the evaporation rate on the final deposition pattern are addressed. When the nanoparticle-liquid interaction is weaker than the liquid-liquid interaction, an interaction-driven or evaporation-induced layer of nanoparticles appears at the liquid-vapor interface and eventually collapses onto the solid surface to form a uniform deposit independently of the evaporation rate. When the nanoparticle-liquid and liquid-liquid interactions are comparable, the nanoparticles are dispersed inside the droplet and evaporation takes place with the contact line pinned at a surface defect. In such a case, a pattern with an approximate ring-like shape is found with fast evaporation, while a more uniform distribution is observed with slower evaporation. When the liquid-nanoparticle interaction is stronger than the liquid-liquid interaction, evaporation always occurs with receding contact line. The final deposition pattern changes from volcano-like to pancake-like with decreasing evaporation rate. These findings might help to design nanoscale structures like nanopatterns or nanowires on surface through controlled solvent evaporation.

Formation of coffee-stain patterns at the nanoscale: The role of nanoparticle solubility and solvent evaporation rate

NASA Astrophysics Data System (ADS)

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

2017-03-01

When droplets of nanoparticle suspension evaporate from surfaces, they leave behind a deposit of nanoparticles. The mechanism of evaporation-induced pattern formation in the deposit is studied by molecular dynamics simulations for sessile nanodroplets. The influence of the interaction between nanoparticles and liquid molecules and the influence of the evaporation rate on the final deposition pattern are addressed. When the nanoparticle-liquid interaction is weaker than the liquid-liquid interaction, an interaction-driven or evaporation-induced layer of nanoparticles appears at the liquid-vapor interface and eventually collapses onto the solid surface to form a uniform deposit independently of the evaporation rate. When the nanoparticle-liquid and liquid-liquid interactions are comparable, the nanoparticles are dispersed inside the droplet and evaporation takes place with the contact line pinned at a surface defect. In such a case, a pattern with an approximate ring-like shape is found with fast evaporation, while a more uniform distribution is observed with slower evaporation. When the liquid-nanoparticle interaction is stronger than the liquid-liquid interaction, evaporation always occurs with receding contact line. The final deposition pattern changes from volcano-like to pancake-like with decreasing evaporation rate. These findings might help to design nanoscale structures like nanopatterns or nanowires on surface through controlled solvent evaporation.

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.

Molecular investigation of evaporation of biodroplets containing single-strand DNA on graphene surface.

PubMed

Akbari, Fahimeh; Foroutan, Masumeh

2018-02-14

In this study, the water droplet behaviour of four different types of single-strand DNA with homogeneous base sequence on a graphene substrate during evaporation of the droplet was investigated using molecular dynamics (MD) simulation. The simulation results indicated that the evaporation depended on the DNA sequence. The observed changes can be divided into four parts: (i) vaporization mode, (ii) evaporation flux, (iii) mechanism of single-strand placement on the surface, and (iv) consideration of remaining single strands after evaporation. Our simulation observations indicated different evaporation modes for thymine biodroplets as compared to those for other biodroplets. The evaporation of the thymine biodroplets occurred with an increase in the contact angle, while that of the other biodroplets occur in a constant contact angle mode. Moreover, thymine biodroplets generate the lowest contact line compared to other single strands, and it is always placed far away from the centre of the droplets during evaporation. Investigating variations in the evaporation flux shows that thymine has the highest evaporation flux and guanine has the lowest. Moreover, during initial evaporation, the flux of evaporation increases at the triple point of the biodroplets containing thymine single strands, while it decreases in the other biodroplets. The following observation was obtained from the study of the placement of single strands on the substrate: guanine and thymine interacted slower than other single strands during evaporation with graphene, adenine single strand had a higher folding during evaporation, and guanine single strand showed the lowest end-to-end distance. The investigation of single-strand DNA after evaporation shows that adenine produces the most stable structure at the end of evaporation. In addition, cytosine is the most stretched single-strand DNA due to its lack of internal π-π stacking and hydrogen bonding. Therefore, cytosine single strand is more accessible for use in microarrays to detect target single strands.

Quantifying Evaporation and Evaluating Runoff Estimation Methods in a Permeable Pavement System - abstract

EPA Science Inventory

Studies on quantifying evaporation in permeable pavement systems are limited to few laboratory studies that used a scale to weigh evaporative losses and a field application with a tunnel-evaporation gauge. A primary objective of this research was to quantify evaporation for a la...

Purfication kinetics of beryllium during vacuum induction melting

NASA Technical Reports Server (NTRS)

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

1972-01-01

The kinetics of evaporation in binary alloys were quantitatively treated. The formalism so developed works well for several systems studied. The kinetics of purification of beryllium was studied through evaporation data actually acquired during vacuum induction melting. Normal evaporation equations are shown to be generally valid and useful for understanding the kinetics of beryllium purification. The normal evaporation analysis has been extended to cover cases of limited liquid diffusion. It was shown that under steady-state evaporation, the solute concentration near the surface may be up to six orders of magnitude different from the bulk concentration. Corrections for limited liquid diffusion are definitely needed for the highly evaporative solute elements, such as Zn, Mg, and Na, for which the computed evaporation times are improved by five orders of magnitude. The commonly observed logarithmic relation between evaporation time and final concentration further supports the validity of the normal evaporation equations.

Capillary Limit in a Loop Heat Pipe with Dual Evaporators

NASA Technical Reports Server (NTRS)

Ku, Jentung; Birur, Gajanana; Obenschain, Arthur F. (Technical Monitor)

2002-01-01

This paper describes a study on the capillary limit of a loop heat pipe (LHP) with two evaporators and two condensers. Both theoretical analysis and experimental investigation are conducted. Tests include heat load to one evaporator only, even heat loads to both evaporators and uneven heat load to both evaporators. Results show that after the capillary limit is exceeded, vapor will penetrate through the wick of the weaker evaporator and the compensation chamber (CC) of that evaporator will control the loop operating temperature regardless of which CC has been in control prior to the event Because the evaporator can tolerate vapor bubbles, the loop may continue to work and reach a new steady state at a higher operating temperature. The loop may even function with a modest increase in the heat load past the capillary limit With a heat load to only one evaporator, the capillary limit can be identified by rapid increases in the operating temperature and in the temperature difference between the evaporator and the CC. However, it is more difficult to tell when the capillary limit is exceeded if heat loads are applied to both evaporators. In all cases, the loop can recover by reducing the heat load to the loop.

Linking soil type and rainfall characteristics towards estimation of surface evaporative capacitance

NASA Astrophysics Data System (ADS)

Or, D.; Bickel, S.; Lehmann, P.

2017-12-01

Separation of evapotranspiration (ET) to evaporation (E) and transpiration (T) components for attribution of surface fluxes or for assessment of isotope fractionation in groundwater remains a challenge. Regional estimates of soil evaporation often rely on plant-based (Penman-Monteith) ET estimates where is E is obtained as a residual or a fraction of potential evaporation. We propose a novel method for estimating E from soil-specific properties, regional rainfall characteristics and considering concurrent internal drainage that shelters soil water from evaporation. A soil-dependent evaporative characteristic length defines a depth below which soil water cannot be pulled to the surface by capillarity; this depth determines the maximal soil evaporative capacitance (SEC). The SEC is recharged by rainfall and subsequently emptied by competition between drainage and surface evaporation (considering canopy interception evaporation). We show that E is strongly dependent on rainfall characteristics (mean annual, number of storms) and soil textural type, with up to 50% of rainfall lost to evaporation in loamy soil. The SEC concept applied to different soil types and climatic regions offers direct bounds on regional surface evaporation independent of plant-based parameterization or energy balance calculations.

The continuous similarity model of bulk soil-water evaporation

NASA Technical Reports Server (NTRS)

Clapp, R. B.

1983-01-01

The continuous similarity model of evaporation is described. In it, evaporation is conceptualized as a two stage process. For an initially moist soil, evaporation is first climate limited, but later it becomes soil limited. During the latter stage, the evaporation rate is termed evaporability, and mathematically it is inversely proportional to the evaporation deficit. A functional approximation of the moisture distribution within the soil column is also included in the model. The model was tested using data from four experiments conducted near Phoenix, Arizona; and there was excellent agreement between the simulated and observed evaporation. The model also predicted the time of transition to the soil limited stage reasonably well. For one of the experiments, a third stage of evaporation, when vapor diffusion predominates, was observed. The occurrence of this stage was related to the decrease in moisture at the surface of the soil. The continuous similarity model does not account for vapor flow. The results show that climate, through the potential evaporation rate, has a strong influence on the time of transition to the soil limited stage. After this transition, however, bulk evaporation is independent of climate until the effects of vapor flow within the soil predominate.

Infrared thermography of evaporative fluxes and dynamics of salt deposition on heterogeneous porous surfaces

NASA Astrophysics Data System (ADS)

Nachshon, Uri; Shahraeeni, Ebrahim; Or, Dani; Dragila, Maria; Weisbrod, Noam

2011-12-01

Evaporation of saline solutions from porous media, common in arid areas, involves complex interactions between mass transport, energy exchange and phase transitions. We quantified evaporation of saline solutions from heterogeneous sand columns under constant hydraulic boundary conditions to focus on effects of salt precipitation on evaporation dynamics. Mass loss measurements and infrared thermography were used to quantify evaporation rates. The latter method enables quantification of spatial and temporal variability of salt precipitation to identify its dynamic effects on evaporation. Evaporation from columns filled with texturally-contrasting sand using different salt solutions revealed preferential salt precipitation within the fine textured domains. Salt precipitation reduced evaporation rates from the fine textured regions by nearly an order of magnitude. In contrast, low evaporation rates from coarse-textured regions (due to low capillary drive) exhibited less salt precipitation and consequently less evaporation rate suppression. Experiments provided insights into two new phenomena: (1) a distinct increase in evaporation rate at the onset of evaporation; and (2) a vapor pumping mechanism related to the presence of a salt crust over semidry media. Both phenomena are related to local vapor pressure gradients established between pore water and the surface salt crust. Comparison of two salts: NaCl and NaI, which tend to precipitate above the matrix surface and within matrix pores, respectively, shows a much stronger influence of NaCl on evaporation rate suppression. This disparity reflects the limited effect of NaI precipitation on matrix resistivity for solution and vapor flows.

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.

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.

Evaporation determined by the energy-budget method for Mirror Lake, New Hampshire

USGS Publications Warehouse

Winter, T.C.; Buso, D.C.; Rosenberry, D.O.; Likens, G.E.; Sturrock, A.M.; Mau, D.P.

2003-01-01

Evaporation was determined by the energy-budget method for Mirror Lake during the open water periods of 1982-1987. For all years, evaporation rates were low in spring and fall and highest during the summer. However, the times of highest evaporation rates varied during the 6 yr. Evaporation reached maximum rates in July for three of the years, in June for two of the years, and in August for one of the years. The highest evaporation rate during the 6-yr study was 0.46 cm d-1 during 27 May-4 June 1986 and 15-21 July 1987. Solar radiation and atmospheric radiation input to the lake and long-wave radiation emitted from the lake were by far the largest energy fluxes to and from the lake and had the greatest effect on evaporation rates. Energy advected to and from the lake by precipitation, surface water, and ground water had little effect on evaporation rates. In the energy-budget method, average evaporation rates are determined for energy-budget periods, which are bounded by the dates of thermal surveys of the lake. Our study compared evaporation rates calculated for short periods, usually ???1 week, with evaporation rates calculated for longer periods, usually ???2 weeks. The results indicated that the shorter periods showed more variability in evaporation rates, but seasonal patterns, with few exceptions, were similar.

Variability of Evaporation and Precipitation over the Ocean from Satellite Data

NASA Astrophysics Data System (ADS)

Malinin, V. N.; Gordeeva, S. M.

2017-12-01

HOAPS-3 and PMWC satellite archives for 1988-2008 are used to estimate moisture-exchange components between the ocean and atmosphere (evaporation, precipitation, and the difference between them or effective evaporation). Moisture-exchange components for the entire World Ocean and for the North Atlantic Ocean within 30°-60° N are calculated. A strong overestimation of the global values of effective evaporation by HOAPS data (mainly caused by a decrease in precipitation) is shown. In the interannual variability of effective evaporation, there is clearly an overestimated positive trend, which contradicts the real increase in the Global Sea Level. Large systematic errors in moisture-exchange components are revealed for the North Atlantic water area. According to HOAPS data, there is a significant underestimation of evaporation and effective evaporation. According to PMWC data, the amount of precipitation is significantly overestimated and evaporation is underestimated. As a consequence, effective evaporation becomes negative, which is impossible. Low accuracy in the estimation of moisture-exchange components and the need to improve old estimates and develop new evaporation and precipitation databases based on satellite data are noted.

Differences in evaporation between a floating pan and class a pan on land

USGS Publications Warehouse

Masoner, J.R.; Stannard, D.I.; Christenson, S.C.

2008-01-01

Research was conducted to develop a method for obtaining floating pan evaporation rates in a small (less than 10,000 m2) wetland, lagoon, or pond. Floating pan and land pan evaporation data were collected from March 1 to August 31, 2005, at a small natural wetland located in the alluvium of the Canadian River near Norman, Oklahoma, at the U.S. Geological Survey Norman Landfill Toxic Substances Hydrology Research Site. Floating pan evaporation rates were compared with evaporation rates from a nearby standard Class A evaporation pan on land. Floating pan evaporation rates were significantly less than land pan evaporation rates for the entire period and on a monthly basis. Results indicated that the use of a floating evaporation pan in a small free-water surface better simulates actual physical conditions on the water surface that control evaporation. Floating pan to land pan ratios were 0.82 for March, 0.87 for April, 0.85 for May, 0.85 for June, 0.79 for July, and 0.69 for August. ?? 2008 American Water Resources Association.

Evaporation of Liquid Droplet in Nano and Micro Scales from Statistical Rate Theory.

PubMed

Duan, Fei; He, Bin; Wei, Tao

2015-04-01

The statistical rate theory (SRT) is applied to predict the average evaporation flux of liquid droplet after the approach is validated in the sessile droplet experiments of the water and heavy water. The steady-state experiments show a temperature discontinuity at the evaporating interface. The average evaporation flux is evaluated by individually changing the measurement at a liquid-vapor interface, including the interfacial liquid temperature, the interfacial vapor temperature, the vapor-phase pressure, and the droplet size. The parameter study shows that a higher temperature jump would reduce the average evaporation flux. The average evaporation flux can significantly be influenced by the interfacial liquid temperature and the vapor-phase pressure. The variation can switch the evaporation into condensation. The evaporation flux is found to remain relative constant if the droplet is larger than a micro scale, while the smaller diameters in nano scale can produce a much higher evaporation flux. In addition, a smaller diameter of droplets with the same liquid volume has a larger surface area. It is suggested that the evaporation rate increases dramatically as the droplet shrinks into nano size.

Experimental Measurements of Spreading of Volatile Liquid Droplets

NASA Technical Reports Server (NTRS)

Zhang, Neng-Li; Chao, David F.

2001-01-01

Based on the laser shadowgraphic system used by the first author of the present paper, a simple optical system, which combined the laser shadowgraphy and the direct magnified-photography, has been developed to measure the contact angle, the spreading speed, and the evaporation rate. Additionally, the system can also visualize thermocapillary convection inside of a sessile drop simultaneously. The experimental results show that evaporation/condensation and thermocapillary convection in the sessile drop induced by the evaporation strongly affects the wetting and spreading of the drop. Condensation always promotes the wetting and spreading of the drop. Evaporation may increase or decrease the contact angle of the evaporating sessile drops, depending on the evaporation rate. The thermocapillary convection in the drop induced by the evaporation enhances the effects of evaporation to suppress the spreading.

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.

Ecohydrology of the wetland-forestland interface: hydrophobicity in leaf litter and its potential effect on surface evaporation

NASA Astrophysics Data System (ADS)

Probert, Samantha; Kettridge, Nicholas; Devito, Kevin; Hurley, Alexander

2017-04-01

Riparian wetlands represent an important ecotone at the interface of peatlands and forests within the Western Boreal Plain of Canada. Water storage and negative feedbacks to evaporation in these systems is crucial for the conservation and redistribution of water during dry periods and providing ecosystem resilience to disturbance. Litter cover can alter the relative importance of the physical processes that drive soil evaporation. Negative feedbacks to drying are created as the hydrophysical properties of the litter and soil override atmospheric controls on evaporation in dry conditions, subsequently dampening the effects of external forcings on the wetland moisture balance. In this study, water repellency in leaf litter has been shown to significantly correlate with surface-atmosphere interactions, whereby severely hydrophobic leaf litter is linked to the highest surface resistances to evaporation, and therefore lowest instantaneous evaporation. Decreasing moisture is associated with increasing hydrophobicity, which may reduce the evaporative flux further as the dry hydrophobic litter creates a hydrological disconnect between soil moisture and the atmosphere. In contrast, hydrophilic litter layers exhibited higher litter moistures, which is associated with reduced resistances to evaporation and enhanced evaporative fluxes. Water repellency of the litter layer has a greater control on evaporation than the presence or absence of litter itself. Litter removal had no significant effect on instantaneous evaporation or surface resistance to evaporation except under the highest evaporation conditions, where litter layers produced higher resistance values than bare peat soils. However, litter removal modified the dominant physical controls on evaporation: moisture loss in plots with leaf litter was driven by leaf and soil hydrophysical properties. Contrastingly, bare peat soils following litter removal exhibited cooler, wetter surfaces and were more strongly correlated to atmospheric controls. The interaction between evaporation, hydrophobicity and moisture of the soil surface, or litter, presents a potentially significant negative feedback to drying across wetland-forestland interfaces.

Bio-inspired evaporation through plasmonic film of nanoparticles at the air-water interface.

PubMed

Wang, Zhenhui; Liu, Yanming; Tao, Peng; Shen, Qingchen; Yi, Nan; Zhang, Fangyu; Liu, Quanlong; Song, Chengyi; Zhang, Di; Shang, Wen; Deng, Tao

2014-08-27

Plasmonic gold nanoparticles self-assembled at the air-water interface to produce an evaporative surface with local control inspired by skins and plant leaves. Fast and efficient evaporation is realized due to the instant and localized plasmonic heating at the evaporative surface. The bio-inspired evaporation process provides an alternative promising approach for evaporation, and has potential applications in sterilization, distillation, and heat transfer. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

40 CFR 86.096-35 - Labeling.

Code of Federal Regulations, 2010 CFR

2010-07-01

... indication of which test procedure was used to certify the evaporative family, e.g., “Evaporative Family xx (§ 86.130-96 procedures)” or “Evaporative Family xx (§ 86.130-78 procedures).” (N)(1) For vehicles... which test procedure was used to certify the evaporative family, e.g., “Evaporative Family xx (§ 86.130...

Exploring Ultimate Water Capillary Evaporation in Nanoscale Conduits.

PubMed

Li, Yinxiao; Alibakhshi, Mohammad Amin; Zhao, Yihong; Duan, Chuanhua

2017-08-09

Capillary evaporation in nanoscale conduits is an efficient heat/mass transfer strategy that has been widely utilized by both nature and mankind. Despite its broad impact, the ultimate transport limits of capillary evaporation in nanoscale conduits, governed by the evaporation/condensation kinetics at the liquid-vapor interface, have remained poorly understood. Here we report experimental study of the kinetic limits of water capillary evaporation in two dimensional nanochannels using a novel hybrid channel design. Our results show that the kinetic-limited evaporation fluxes break down the limits predicated by the classical Hertz-Knudsen equation by an order of magnitude, reaching values up to 37.5 mm/s with corresponding heat fluxes up to 8500 W/cm 2 . The measured evaporation flux increases with decreasing channel height and relative humidity but decreases as the channel temperature decreases. Our findings have implications for further understanding evaporation at the nanoscale and developing capillary evaporation-based technologies for both energy- and bio-related applications.

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 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

Evaporation of tiny water aggregation on solid surfaces with different wetting properties.

PubMed

Wang, Shen; Tu, Yusong; Wan, Rongzheng; Fang, Haiping

2012-11-29

The evaporation of a tiny amount of water on the solid surface with different wettabilities has been studied by molecular dynamics simulations. From nonequilibrium MD simulations, we found that, as the surface changed from hydrophobic to hydrophilic, the evaporation speed did not show a monotonic decrease as intuitively expected, but increased first, and then decreased after it reached a maximum value. The analysis of the simulation trajectory and calculation of the surface water interaction illustrate that the competition between the number of water molecules on the water-gas surface from where the water molecules can evaporate and the potential barrier to prevent those water molecules from evaporating results in the unexpected behavior of the evaporation. This finding is helpful in understanding the evaporation on biological surfaces, designing artificial surfaces of ultrafast water evaporating, or preserving water in soil.

A semi-analytical model of disk evaporation by thermal conduction

NASA Astrophysics Data System (ADS)

Dullemond, C. P.

1999-01-01

The conditions for disk evaporation by electron thermal conduction are examined, using a simplified semi-analytical 1-D model. The model is based on the mechanism proposed by Meyer & Meyer-Hofmeister ( te{meyermeyhof:1994}) in which an advection dominated accretion flow evaporates the top layers from the underlying disk by thermal conduction. The evaporation rate is calculated as a function of the density of the advective flow, and an analysis is made of the time scales and length scales of the dynamics of the advective flow. It is shown that evaporation can only completely destroy the disk if the conductive length scale is of the order of the radius. This implies that radial conduction is an essential factor in the evaporation process. The heat required for evaporation is in fact produced at small radii and transported radially towards the evaporation region.

Analysis of the effects of evaporative cooling on the evaporation of liquid droplets using a combined field approach

PubMed Central

Xu, Xuefeng; Ma, Liran

2015-01-01

During liquid evaporation, the equations for the vapor concentration in the atmosphere and for the temperature in the liquid are coupled and must be solved in an iterative manner. In the present paper, a combined field approach which unifies the coupled fields into one single hybrid field and thus makes the iteration unnecessary is proposed. By using this approach, the influences of the evaporative cooling on the evaporation of pinned sessile droplets are investigated, and its predictions are found in good agreement with the previous theoretical and experimental results. A dimensionless number Ec which can evaluate the strength of the evaporative cooling is then introduced, and the results show that both the evaporation flux along the droplet surface and the total evaporation rate of the droplet decrease as the evaporative cooling number Ec increases. For drying droplets, there exists a critical value EcCrit below which the evaporative cooling effect can be neglected and above which the significance of the effect increases dramatically. The present work may also have more general applications to coupled field problems in which all the fields have the same governing equation. PMID:25721987

Simple scaling laws for the evaporation of droplets pinned on pillars: Transfer-rate- and diffusion-limited regimes.

PubMed

Hernandez-Perez, Ruth; García-Cordero, José L; Escobar, Juan V

2017-12-01

The evaporation of droplets can give rise to a wide range of interesting phenomena in which the dynamics of the evaporation are crucial. In this work, we find simple scaling laws for the evaporation dynamics of axisymmetric droplets pinned on millimeter-sized pillars. Different laws are found depending on whether evaporation is limited by the diffusion of vapor molecules or by the transfer rate across the liquid-vapor interface. For the diffusion-limited regime, we find that a mass-loss rate equal to 3/7 of that of a free-standing evaporating droplet brings a good balance between simplicity and physical correctness. We also find a scaling law for the evaporation of multicomponent solutions. The scaling laws found are validated against experiments of the evaporation of droplets of (1) water, (2) blood plasma, and (3) a mixture of water and polyethylene glycol, pinned on acrylic pillars of different diameters. These results shed light on the macroscopic dynamics of evaporation on pillars as a first step towards the understanding of other complex phenomena that may be taking place during the evaporation process, such as particle transport and chemical reactions.

Simple scaling laws for the evaporation of droplets pinned on pillars: Transfer-rate- and diffusion-limited regimes

NASA Astrophysics Data System (ADS)

Hernandez-Perez, Ruth; García-Cordero, José L.; Escobar, Juan V.

2017-12-01

The evaporation of droplets can give rise to a wide range of interesting phenomena in which the dynamics of the evaporation are crucial. In this work, we find simple scaling laws for the evaporation dynamics of axisymmetric droplets pinned on millimeter-sized pillars. Different laws are found depending on whether evaporation is limited by the diffusion of vapor molecules or by the transfer rate across the liquid-vapor interface. For the diffusion-limited regime, we find that a mass-loss rate equal to 3/7 of that of a free-standing evaporating droplet brings a good balance between simplicity and physical correctness. We also find a scaling law for the evaporation of multicomponent solutions. The scaling laws found are validated against experiments of the evaporation of droplets of (1) water, (2) blood plasma, and (3) a mixture of water and polyethylene glycol, pinned on acrylic pillars of different diameters. These results shed light on the macroscopic dynamics of evaporation on pillars as a first step towards the understanding of other complex phenomena that may be taking place during the evaporation process, such as particle transport and chemical reactions.

Experimental research on bypass evaporation tower technology for zero liquid discharge of desulfurization wastewater.

PubMed

Ma, Shuangchen; Chai, Jin; Wu, Kai; Xiang, Yajun; Jia, Shaoguang; Li, Qingsong

2018-03-20

Zero liquid discharge (ZLD) of wastewater has become the trend of environmental governance after the implementation of 'The Action Plan for Prevention and Treatment of Water Pollution' in China, desulfurization wastewater has gained more attention due to its complex composition and heavy metals. However, current technologies for ZLD have some shortcomings such as high cost and insufficient processing capacity, ZLD cannot be achieved actually. This paper proposes a new evaporation drying technology. An independent bypass evaporation tower was built, part of the hot flue gas before the air preheater was introduced into the evaporation tower for desulfurization wastewater evaporation, and the generated dust after evaporation was discharged back to the flue duct before electrostatic precipitator. This paper reports on the performance of desulfurization wastewater evaporation and the characteristics of evaporation products in depth and makes a comprehensive discussion of the impact on the existing equipment based on the self-designed evaporation tower. Research suggests that this technology has high system reliability and little effect on subsequent equipment and provides theoretical and practical data. Due to environmental policies and huge market demand for ZLD of desulfurization wastewater, bypass evaporation tower technology has a great application prospect in the future.

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.

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.

Evaporation components of a boreal forest: variations during the growing season

NASA Astrophysics Data System (ADS)

Grelle, A.; Lundberg, A.; Lindroth, A.; Morén, A.-S.; Cienciala, E.

1997-10-01

To improve the understanding of interactions between the boreal forest and the climate system as a key issue for global climate change, the water budget of a mixed pine and spruce forest in central Sweden was estimated by measurements of the water flux components and the total evaporation flux during the period 16 May-31 October 1995. Total evaporation was measured using eddy correlation and the components were obtained using measurements of precipitation, throughfall, tree transpiration, and forest floor evaporation. On a daily basis, tree transpiration was the dominant evaporation component during the vegetation period. However, it could be efficiently blocked by a wet canopy associated with large interception evaporation. The accumulated total evaporation was 399 mm, transpiration was 243 mm, forest floor evaporation was 56 mm and interception evaporation was 74 mm. The accumulated sum of interception, transpiration, and floor evaporation was 51 mm larger than the actual measured total evaporation. This difference was mainly attributed to the fact that transpiration was measured in a rather dense 50-year-old stand while total evaporation represented the average conditions of older, roughly 100-year-old stands. To compare eddy-correlation measurements with small-scale measurements of evaporation components, a source area analysis was made to select the flux data that give the best representation of the investigated stand. Especially under stable atmospheric conditions the requirements for surface homogeneity were very high and extreme care had to be taken to be aware of the flux source areas. Canopy water storage was determined by two methods: by the water balance of the canopy, which gave a result of 3.3 mm; and by the so-called minimum method based on plots of throughfall versus precipitation, which gave a much lower value of 1.5 mm. Seasonal interception evaporation constituted 30% of the precipitation.

Effects of Evaporation/Condensation on Spreading and Contact Angle of a Volatile Liquid Drop

NASA Technical Reports Server (NTRS)

Zhang, Nengli; Chao, David F.; Singh, Bhim S. (Technical Monitor)

2000-01-01

Effects of evaporation/condensation on spreading and contact angle were experimentally studied. A sessile drop of R-113 was tested at different vapor environments to determine the effects of evaporation/condensation on the evolution of contact diameter and contact angle of the drop. Condensation on the drop surface occurs at both the saturated and a nonsaturated vapor environments and promotes the spreading. When the drop is placed in the saturated vapor environment it tends to completely wetting and spreads rapidly. In a nonsaturated vapor environment, the evolution of the sessile drop is divided three stages: condensation-spreading stage, evaporation-retracting stage and rapid contracting stage. In the first stage the drop behaves as in the saturated environment. In the evaporation -retracting stage, the competition between spreading and evaporation of the drop determines the evolution characteristics of the contact diameter and the contact angle. A lower evaporation rate struggles against the spreading power to turn the drop from spreading to retracting with a continuous increase of the contact angle. The drop placed in open air has a much higher evaporation rate. The strong evaporation suppresses the spreading and accelerates the retraction of the drop with a linear decrease of the contact diameter. The contraction of the evaporating drops is gradually accelerated when the contact diameter decreases to 3 min and less till drying up, though the evaporation rate is gradually slowing down.

On the link between potential evaporation and regional evaporation from a CBL perspective

NASA Astrophysics Data System (ADS)

Lhomme, J. P.; Guilioni, L.

2010-07-01

The relationship between potential evaporation and actual evaporation was first examined by Bouchet (Proc Berkeley Calif Symp IAHS Publ, 62:134-142, 1963) who considered potential evaporation as the consequence of regional evaporation due to atmospheric feedbacks. Using a heuristic approach, he derived a complementary relationship which, despite no real theoretical background, has proven to be very useful in interpreting many experimental data under various climatic conditions. Here, the relationship between actual and potential evaporation is reinterpreted in the context of the development of the convective boundary layer (CBL): first, with a closed-box approach, where the CBL has an impermeable lid; and then with an open system, where air is exchanged between the CBL and its external environment. By applying steady forcing to these systems, it is shown that an equilibrium state is reached, where potential evaporation has a specific equilibrium formulation as a function of two parameters: one representing large-scale advection and the other the feedback effect of regional evaporation on potential evaporation, i.e. a kind of “medium-scale advection”. It is also shown that the original form of Bouchet’s complementary relationship is not verified in the equilibrium state. This analysis leads us to propose a new and more rational approach of the relationship between potential and actual evaporation through the effective surface resistance of the region.

Kinetic Limited Water Evaporation in Hydrophilic Nanofluidic Channels

NASA Astrophysics Data System (ADS)

Li, Yinxiao; Alibakhshi, Mohammad Amin; Xie, Quan; Duan, Chuanhua

2015-11-01

Capillary evaporation is one of the most efficient approaches for heat and mass transfer, but the interfacial resistance in capillary evaporation governed by the kinetic theory has remained poorly understood. Here we report experimental studies of the kinetic-limited water capillary evaporation in 2-D hydrophilic nanochannels. A novel hybrid nanochannel design is employed to guarantee sufficient water supply to the liquid/vapor evaporation interface and to enable precise evaporation rate measurements. We study the effects of confinement (16 ~ 105nm), temperature (20 ~ 40 °C), and relative humidity (0% ~ 60%) on the evaporation rate and the evaporation coefficient. A maximum evaporation flux of 21287 micron/s is obtained in 16-nm nanochannels at 40°C and RH =0%, which corresponds to a heat flux of 4804 W/cm°. The evaporation coefficient is found to be independent on geometrical confinement, but shows a clear dependence on temperature, decreasing from 0.55 at 20°C to 0.5 at 40 °C. These findings have implications for understanding heat and mass transport in nanofluidic devices and porous media, and shed light on further development of evaporation-based technologies for thermal management, membrane purification and lab-on-a-chip devices. The work is supported by the American Chemical Society Petroleum Research Fund (ACS PRF # 54118-DNI7) and the Faculty Startup Fund (Boston University, USA).

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.

The simultaneous mass and energy evaporation (SM2E) model.

PubMed

Choudhary, Rehan; Klauda, Jeffery B

2016-01-01

In this article, the Simultaneous Mass and Energy Evaporation (SM2E) model is presented. The SM2E model is based on theoretical models for mass and energy transfer. The theoretical models systematically under or over predicted at various flow conditions: laminar, transition, and turbulent. These models were harmonized with experimental measurements to eliminate systematic under or over predictions; a total of 113 measured evaporation rates were used. The SM2E model can be used to estimate evaporation rates for pure liquids as well as liquid mixtures at laminar, transition, and turbulent flow conditions. However, due to limited availability of evaporation data, the model has so far only been tested against data for pure liquids and binary mixtures. The model can take evaporative cooling into account and when the temperature of the evaporating liquid or liquid mixture is known (e.g., isothermal evaporation), the SM2E model reduces to a mass transfer-only model.

Water evaporation from substrate tooth surface during dentin treatments.

PubMed

Kusunoki, Mizuho; Itoh, Kazuo; Gokan, Yuka; Nagai, Yoshitaka; Tani, Chihiro; Hisamitsu, Hisashi

2011-01-01

The purpose of this study was to evaluate changes in the quantity of water evaporation from tooth surfaces. The amount of water evaporation was measured using Multi probe adapter MPA5 and Tewameter TM300 (Courage+Khazaka Electric GmbH, Köln, Germany) after acid etching and GM priming of enamel; and after EDTA conditioning and GM priming of dentin. The results indicated that the amount of water evaporation from the enamel surface was significantly less than that from the dentin. Acid etching did not affect the water evaporation from enamel, though GM priming significantly decreased the evaporation (83.48 ± 15.14% of that before priming). The evaporation from dentin was significantly increased by EDTA conditioning (131.38 ± 42.08% of that before conditioning) and significantly reduced by GM priming (80.26 ± 7.43% of that before priming). It was concluded that dentin priming reduced water evaporation from the dentin surface.

Normal evaporation of binary alloys

NASA Technical Reports Server (NTRS)

Li, C. H.

1972-01-01

In the study of normal evaporation, it is assumed that the evaporating alloy is homogeneous, that the vapor is instantly removed, and that the alloy follows Raoult's law. The differential equation of normal evaporation relating the evaporating time to the final solute concentration is given and solved for several important special cases. Uses of the derived equations are exemplified with a Ni-Al alloy and some binary iron alloys. The accuracy of the predicted results are checked by analyses of actual experimental data on Fe-Ni and Ni-Cr alloys evaporated at 1600 C, and also on the vacuum purification of beryllium. These analyses suggest that the normal evaporation equations presented here give satisfactory results that are accurate to within an order of magnitude of the correct values, even for some highly concentrated solutions. Limited diffusion and the resultant surface solute depletion or enrichment appear important in the extension of this normal evaporation approach.

Evaporative lithographic patterning of binary colloidal films.

PubMed

Harris, Daniel J; Conrad, Jacinta C; Lewis, Jennifer A

2009-12-28

Evaporative lithography offers a promising new route for patterning a broad array of soft materials. In this approach, a mask is placed above a drying film to create regions of free and hindered evaporation, which drive fluid convection and entrained particles to regions of highest evaporative flux. We show that binary colloidal films exhibit remarkable pattern formation when subjected to a periodic evaporative landscape during drying.

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.

Estimation of evaporation from open water - A review of selected studies, summary of U.S. Army Corps of Engineers data collection and methods, and evaluation of two methods for estimation of evaporation from five reservoirs in Texas

USGS Publications Warehouse

Harwell, Glenn R.

2012-01-01

Organizations responsible for the management of water resources, such as the U.S. Army Corps of Engineers (USACE), are tasked with estimation of evaporation for water-budgeting and planning purposes. The USACE has historically used Class A pan evaporation data (pan data) to estimate evaporation from reservoirs but many USACE Districts have been experimenting with other techniques for an alternative to collecting pan data. The energy-budget method generally is considered the preferred method for accurate estimation of open-water evaporation from lakes and reservoirs. Complex equations to estimate evaporation, such as the Penman, DeBruin-Keijman, and Priestley-Taylor, perform well when compared with energy-budget method estimates when all of the important energy terms are included in the equations and ideal data are collected. However, sometimes nonideal data are collected and energy terms, such as the change in the amount of stored energy and advected energy, are not included in the equations. When this is done, the corresponding errors in evaporation estimates are not quantifiable. Much simpler methods, such as the Hamon method and a method developed by the U.S. Weather Bureau (USWB) (renamed the National Weather Service in 1970), have been shown to provide reasonable estimates of evaporation when compared to energy-budget method estimates. Data requirements for the Hamon and USWB methods are minimal and sometimes perform well with remotely collected data. The Hamon method requires average daily air temperature, and the USWB method requires daily averages of air temperature, relative humidity, wind speed, and solar radiation. Estimates of annual lake evaporation from pan data are frequently within 20 percent of energy-budget method estimates. Results of evaporation estimates from the Hamon method and the USWB method were compared against historical pan data at five selected reservoirs in Texas (Benbrook Lake, Canyon Lake, Granger Lake, Hords Creek Lake, and Sam Rayburn Lake) to evaluate their performance and to develop coefficients to minimize bias for the purpose of estimating reservoir evaporation with accuracies similar to estimates of evaporation obtained from pan data. The modified Hamon method estimates of reservoir evaporation were similar to estimates of reservoir evaporation from pan data for daily, monthly, and annual time periods. The modified Hamon method estimates of annual reservoir evaporation were always within 20 percent of annual reservoir evaporation from pan data. Unmodified and modified USWB method estimates of annual reservoir evaporation were within 20 percent of annual reservoir evaporation from pan data for about 91 percent of the years compared. Average daily differences between modified USWB method estimates and estimates from pan data as a percentage of the average amount of daily evaporation from pan data were within 20 percent for 98 percent of the months. Without any modification to the USWB method, average daily differences as a percentage of the average amount of daily evaporation from pan data were within 20 percent for 73 percent of the months. Use of the unmodified USWB method is appealing because it means estimates of average daily reservoir evaporation can be made from air temperature, relative humidity, wind speed, and solar radiation data collected from remote weather stations without the need to develop site-specific coefficients from historical pan data. Site-specific coefficients would need to be developed for the modified version of the Hamon method.

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.

Steady Method for the Analysis of Evaporation Dynamics.

PubMed

Günay, A Alperen; Sett, Soumyadip; Oh, Junho; Miljkovic, Nenad

2017-10-31

Droplet evaporation is an important phenomenon governing many man-made and natural processes. Characterizing the rate of evaporation with high accuracy has attracted the attention of numerous scientists over the past century. Traditionally, researchers have studied evaporation by observing the change in the droplet size in a given time interval. However, the transient nature coupled with the significant mass-transfer-governed gas dynamics occurring at the droplet three-phase contact line makes the classical method crude. Furthermore, the intricate balance played by the internal and external flows, evaporation kinetics, thermocapillarity, binary-mixture dynamics, curvature, and moving contact lines makes the decoupling of these processes impossible with classical transient methods. Here, we present a method to measure the rate of evaporation of spatially and temporally steady droplets. By utilizing a piezoelectric dispenser to feed microscale droplets (R ≈ 9 μm) to a larger evaporating droplet at a prescribed frequency, we can both create variable-sized droplets on any surface and study their evaporation rate by modulating the piezoelectric droplet addition frequency. Using our steady technique, we studied water evaporation of droplets having base radii ranging from 20 to 250 μm on surfaces of different functionalities (45° ≤ θ a,app ≤ 162°, where θ a,app is the apparent advancing contact angle). We benchmarked our technique with the classical unsteady method, showing an improvement of 140% in evaporation rate measurement accuracy. Our work not only characterizes the evaporation dynamics on functional surfaces but also provides an experimental platform to finally enable the decoupling of the complex physics governing the ubiquitous droplet evaporation process.

Estimation of bare soil evaporation for different depths of water table in the wind-blown sand area of the Ordos Basin, China

NASA Astrophysics Data System (ADS)

Chen, Li; Wang, Wenke; Zhang, Zaiyong; Wang, Zhoufeng; Wang, Qiangmin; Zhao, Ming; Gong, Chengcheng

2018-04-01

Soil surface evaporation is a significant component of the hydrological cycle, occurring at the interface between the atmosphere and vadose zone, but it is affected by factors such as groundwater level, soil properties, solar radiation and others. In order to understand the soil evaporation characteristics in arid regions, a field experiment was conducted in the Ordos Basin, central China, and high accuracy sensors of soil moisture, moisture potential and temperature were installed in three field soil profiles with water-table depths (WTDs) of about 0.4, 1.4 and 2.2 m. Soil-surface-evaporation values were estimated by observed data combined with Darcy's law. Results showed that: (1) soil-surface-evaporation rate is linked to moisture content and it is also affected by air temperature. When there is sufficient moisture in the soil profile, soil evaporation increases with rising air temperature. For a WTD larger than the height of capillary rise, the soil evaporation is related to soil moisture content, and when air temperature is above 25 °C, the soil moisture content reduces quickly and the evaporation rate lowers; (2) phreatic water contributes to soil surface evaporation under conditions in which the WTD is within the capillary fringe. This indicates that phreatic water would not participate in soil evaporation for a WTD larger than the height of capillary rise. This finding developed further the understanding of phreatic evaporation, and this study provides valuable information on recognized soil evaporation processes in the arid environment.

Low internal pressure in femtoliter water capillary bridges reduces evaporation rates.

PubMed

Cho, Kun; Hwang, In Gyu; Kim, Yeseul; Lim, Su Jin; Lim, Jun; Kim, Joon Heon; Gim, Bopil; Weon, Byung Mook

2016-03-01

Capillary bridges are usually formed by a small liquid volume in a confined space between two solid surfaces. They can have a lower internal pressure than the surrounding pressure for volumes of the order of femtoliters. Femtoliter capillary bridges with relatively rapid evaporation rates are difficult to explore experimentally. To understand in detail the evaporation of femtoliter capillary bridges, we present a feasible experimental method to directly visualize how water bridges evaporate between a microsphere and a flat substrate in still air using transmission X-ray microscopy. Precise measurements of evaporation rates for water bridges show that lower water pressure than surrounding pressure can significantly decrease evaporation through the suppression of vapor diffusion. This finding provides insight into the evaporation of ultrasmall capillary bridges.

Microfabricated valveless devices for thermal bioreactions based on diffusion-limited evaporation.

PubMed

Wang, Fang; Yang, Ming; Burns, Mark A

2008-01-01

Microfluidic devices that reduce evaporative loss during thermal bioreactions such as PCR without microvalves have been developed by relying on the principle of diffusion-limited evaporation. Both theoretical and experimental results demonstrate that the sample evaporative loss can be reduced by more than 20 times using long narrow diffusion channels on both sides of the reaction region. In order to further suppress the evaporation, the driving force for liquid evaporation is reduced by two additional techniques: decreasing the interfacial temperature using thermal isolation and reducing the vapor concentration gradient by replenishing water vapor in the diffusion channels. Both thermal isolation and vapor replenishment techniques can limit the sample evaporative loss to approximately 1% of the reaction content.

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.

[Study on membrane type leaf water evaporation inhibitors for improving effect of preventing diseases and pest controlling of Lycium barbarum].

PubMed

Wang, Dan-Dan; Lv, Zhe; Xu, Chang-Qing; Liu, Sai; Chen, Jun; Peng, Xiao; Wu, Yan

2018-01-01

Through indoor and field comparative experiments, the properties of membrane type leaf evaporation inhibitors and its effects on photosynthesis of Lycium barbarum and compatibility and synergistic of pesticide were studied. The evaporation inhibitors and L. barbarum were chosen to investigate the suppression of water evaporation and the compatibility with pesticides. The effect of evaporation inhibitors on photosynthesis of L. barbarum leaves was determined by the chlorophyll fluorescence imaging system. The results showed that water evaporation of L. barbarum leaves of different leaf age were evidently suppressed after treated with evaporation inhibitor. The inhibitor was well compatible with pesticide and effectively improved the pesticide efficacy，and had no significant effect on chlorophyll fluorescence parameters. It is concluded that the evaporation inhibitor has good compatibility with the pesticide, and has remarkable effect of restraining moisture evaporation, which make it can be used for reducing the dosage and improving the efficacy of the pesticide in the field of L. barbarum. Copyright© by the Chinese Pharmaceutical Association.

Comparison study on the calculation formula of evaporation mass flux through the plane vapour-liquid interface

NASA Astrophysics Data System (ADS)

Zhang, L.; Li, Y. R.; Zhou, L. Q.; Wu, C. M.

2017-11-01

In order to understand the influence of various factors on the evaporation rate on the vapor-liquid interface, the evaporation process of water in pure steam environment was calculated based on the statistical rate theory (SRT), and the results were compared with those from the traditional Hertz-Knudsen equation. It is found that the evaporation rate on the vapor-liquid interface increases with the increase of evaporation temperature and evaporation temperature difference and the decrease of vapor pressure. When the steam is in a superheated state, even if the temperature of the liquid phase is lower than that of the vapor phase, the evaporation may also occur on the vapor-liquid interface; at this time, the absolute value of the critical temperature difference for occurring evaporation decreases with the increase of vapor pressure. When the evaporation temperature difference is smaller, the theoretical calculation results based on the SRT are basically the same as the predicated results from the Hertz-Knudsen equation; but the deviation between them increases with the increase of temperature difference.

Evaporative cooler including one or more rotating cooler louvers

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

Gerlach, David W

An evaporative cooler may include an evaporative cooler housing with a duct extending therethrough, a plurality of cooler louvers with respective porous evaporative cooler pads, and a working fluid source conduit. The cooler louvers are arranged within the duct and rotatably connected to the cooler housing along respective louver axes. The source conduit provides an evaporative cooler working fluid to the cooler pads during at least one mode of operation.

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.

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.

Evaporation From Soil Containers With Irregular Shapes

NASA Astrophysics Data System (ADS)

Assouline, Shmuel; Narkis, Kfir

2017-11-01

Evaporation from bare soils under laboratory conditions is generally studied using containers of regular shapes where the vertical edges are parallel to the flow lines in the drying domain. The main objective of this study was to investigate the impact of irregular container shapes, for which the flow lines either converge or diverge toward the surface. Evaporation from initially saturated sand and sandy loam soils packed in cones and inverted cones was compared to evaporation from corresponding cylindrical columns. The initial evaporation rate was higher in the cones, and close to potential evaporation. At the end of the experiment, the cumulative evaporation depth in the sand cone was equal to that in the column but higher than in the inverted cone, while in the sandy loam, the order was cone > column > inverted cone. By comparison to the column, stage 1 evaporation was longer in the cones, and practically similar in the inverted cones. Stage 2 evaporation rate decreased with the increase of the evaporating surface area. These results were more pronounced in the sandy loam. For the sand column, the transition between stage 1 and stage 2 evaporation occurred when the depth of the saturation front was approximately equal to the characteristic length of the soil. However, for the cone and the inverted cone, it occurred for a shallower depth of the saturation front. It seems therefore that the concept of the characteristic length derived from the soil hydraulic properties is related to drying systems of regular shapes.

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.

Evaporation, precipitation, and associated salinity changes at a humid, subtropical estuary

USGS Publications Warehouse

Sumner, D.M.; Belaineh, G.

2005-01-01

The distilling effect of evaporation and the diluting effect of precipitation on salinity at two estuarine sites in the humid subtropical setting of the Indian River Lagoon, Florida, were evaluated based on daily evaporation computed with an energy-budget method and measured precipitation. Despite the larger magnitude of evaporation (about 1,580 mm yr-1) compared to precipitation (about 1,180 mm yr-1) between February 2002 and January 2004, the variability of monthly precipitation induced salinity changes was more than twice the variability of evaporation induced changes. Use of a constant, mean value of evaporation, along with measured values of daily precipitation, were sufficient to produce simulated salinity changes that contained little monthly (root-mean-square error = 0.33??? mo-1 and 0.52??? mo-1 at the two sites) or cumulative error (<1??? yr-1) compared to simulations that used computed daily values of evaporation. This result indicates that measuring the temporal variability in evaporation may not be critical to simulation of salinity within the lagoon. Comparison of evaporation and precipitation induced salinity changes with measured salinity changes indicates that evaporation and precipitation explained only 4% of the changes in salinity within a flow-through area of the lagoon; surface water and ocean inflows probably accounted for most of the variability in salinity at this site. Evaporation and precipitation induced salinity changes explained 61% of the variability in salinity at a flow-restricted part of the lagoon. ?? 2005 Estuarine Research Federation.

Evaporation of pure liquid sessile and spherical suspended drops: a review.

PubMed

Erbil, H Yildirim

2012-01-15

A sessile drop is an isolated drop which has been deposited on a solid substrate where the wetted area is limited by a contact line and characterized by contact angle, contact radius and drop height. Diffusion-controlled evaporation of a sessile drop in an ambient gas is an important topic of interest because it plays a crucial role in many scientific applications such as controlling the deposition of particles on solid surfaces, in ink-jet printing, spraying of pesticides, micro/nano material fabrication, thin film coatings, biochemical assays, drop wise cooling, deposition of DNA/RNA micro-arrays, and manufacture of novel optical and electronic materials in the last decades. This paper presents a review of the published articles for a period of approximately 120 years related to the evaporation of both sessile drops and nearly spherical droplets suspended from thin fibers. After presenting a brief history of the subject, we discuss the basic theory comprising evaporation of micrometer and millimeter sized spherical drops, self cooling on the drop surface and evaporation rate of sessile drops on solids. The effects of drop cooling, resultant lateral evaporative flux and Marangoni flows on evaporation rate are also discussed. This review also has some special topics such as drop evaporation on superhydrophobic surfaces, determination of the receding contact angle from drop evaporation, substrate thermal conductivity effect on drop evaporation and the rate evaporation of water in liquid marbles. Copyright © 2011 Elsevier B.V. All rights reserved.

Do lipids retard the evaporation of the tear fluid?

PubMed

Rantamäki, Antti H; Javanainen, Matti; Vattulainen, Ilpo; Holopainen, Juha M

2012-09-21

We examined in vitro the potential evaporation-retarding effect of the tear film lipid layer (TFLL). The artificial TFLL compositions used here were based on the present knowledge of TFLL composition. A custom-built system was developed to measure evaporation rates at 35°C. Lipids were applied to an air-water interface, and the evaporation rate through the lipid layer was defined as water loss from the interface. A thick layer of olive oil and a monolayer of long-chain alcohol were used as controls. The artificial TFLLs were composed of 1 to 4 lipid species: polar phosphatidylcholine (PC), nonpolar cholesteryl ester, triglycerides, and wax ester (WE). Brewster angle microscopy (BAM) and interfacial shear rheometry (ISR) were used to assess the lateral structure and shear stress response of the lipid layers, respectively. Olive oil and long-chain alcohol decreased evaporation by 54% and 45%, respectively. The PC monolayer and the four-component mixtures did not retard evaporation. WE was the most important evaporation-retardant TFLL lipid (∼20% decrease). In PC/WE mixtures, an ∼90% proportion of WE was required for evaporation retardation. Based on BAM and ISR, WE resulted in more condensed layers than the non-retardant layers. Highly condensed, solid-like lipid layers, such as those containing high proportions of WEs, are evaporation-retardant. In multi-component lipid layers, the evaporation-retardant interactions between carbon chains decrease and, therefore, these lipid layers do not retard evaporation.

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].

PREDICTING EVAPORATION RATES AND TIMES FOR SPILLS OF CHEMICAL MIXTURES

EPA Science Inventory

Spreadsheet and short-cut methods have been developed for predicting evaporation rates and evaporation times for spills (and constrained baths) of chemical mixtures. Steady-state and time-varying predictions of evaporation rates can be made for six-component mixtures, includ...

Evaporation rate and vapor pressure of selected polymeric lubricating oils.

NASA Technical Reports Server (NTRS)

Gardos, M. N.

1973-01-01

A recently developed ultrahigh-vacuum quartz spring mass sorption microbalance has been utilized to measure the evaporation rates of several low-volatility polymeric lubricating oils at various temperatures. The evaporation rates are used to calculate the vapor pressures by the Langmuir equation. A method is presented to accurately estimate extended temperature range evaporation rate and vapor pressure data for polymeric oils, incorporating appropriate corrections for the increases in molecular weight and the change in volatility of the progressively evaporating polymer fractions. The logarithms of the calculated data appear to follow linear relationships within the test temperature ranges, when plotted versus 1000/T. These functions and the observed effusion characteristics of the fluids on progressive volatilization are useful in estimating evaporation rate and vapor pressure changes on evaporative depletion.

Low internal pressure in femtoliter water capillary bridges reduces evaporation rates

PubMed Central

Cho, Kun; Hwang, In Gyu; Kim, Yeseul; Lim, Su Jin; Lim, Jun; Kim, Joon Heon; Gim, Bopil; Weon, Byung Mook

2016-01-01

Capillary bridges are usually formed by a small liquid volume in a confined space between two solid surfaces. They can have a lower internal pressure than the surrounding pressure for volumes of the order of femtoliters. Femtoliter capillary bridges with relatively rapid evaporation rates are difficult to explore experimentally. To understand in detail the evaporation of femtoliter capillary bridges, we present a feasible experimental method to directly visualize how water bridges evaporate between a microsphere and a flat substrate in still air using transmission X-ray microscopy. Precise measurements of evaporation rates for water bridges show that lower water pressure than surrounding pressure can significantly decrease evaporation through the suppression of vapor diffusion. This finding provides insight into the evaporation of ultrasmall capillary bridges. PMID:26928329

Is evaporative colling important for shallow clouds?

NASA Astrophysics Data System (ADS)

Gentine, P.; Park, S. B.; Davini, P.; D'Andrea, F.

2017-12-01

We here investigate and test using large-eddy simulations the hypothesis that evaporative cooling might not be crucial for shallow clouds. Results from various Shallow convection and stratocumulus LES experiments show that the influence of evaporative cooling is secondary compared to turbulent mixing, which dominates the buoyancy reversal. In shallow cumulus subising shells are not due to evaporative cooling but rather reflect a vortical structure, with a postive buoyancy anomaly in the core due to condensation. Disabling evaporative cooling has negligible impact on this vortical structure and on buoyancy reversal. Similarly in non-precipitating stratocumuli evaporative cooling is negeligible copmared to other factors, especially turbulent mixing and pressure effects. These results emphasize that it may not be critical to icnlude evaporative cooling in parameterizations of shallow clouds and that it does not alter entrainment.

Localised boundary air layer and clothing evaporative resistances for individual body segments.

PubMed

Wang, Faming; del Ferraro, Simona; Lin, Li-Yen; Sotto Mayor, Tiago; Molinaro, Vincenzo; Ribeiro, Miguel; Gao, Chuansi; Kuklane, Kalev; Holmér, Ingvar

2012-01-01

Evaporative resistance is an important parameter to characterise clothing thermal comfort. However, previous work has focused mainly on either total static or dynamic evaporative resistance. There is a lack of investigation of localised clothing evaporative resistance. The objective of this study was to study localised evaporative resistance using sweating thermal manikins. The individual and interaction effects of air and body movements on localised resultant evaporative resistance were examined in a strict protocol. The boundary air layer's localised evaporative resistance was investigated on nude sweating manikins at three different air velocity levels (0.18, 0.48 and 0.78 m/s) and three different walking speeds (0, 0.96 and 1.17 m/s). Similarly, localised clothing evaporative resistance was measured on sweating manikins at three different air velocities (0.13, 0.48 and 0.70 m/s) and three walking speeds (0, 0.96 and 1.17 m/s). Results showed that the wind speed has distinct effects on local body segments. In contrast, walking speed brought much more effect on the limbs, such as thigh and forearm, than on body torso, such as back and waist. In addition, the combined effect of body and air movement on localised evaporative resistance demonstrated that the walking effect has more influence on the extremities than on the torso. Therefore, localised evaporative resistance values should be provided when reporting test results in order to clearly describe clothing local moisture transfer characteristics. Localised boundary air layer and clothing evaporative resistances are essential data for clothing design and assessment of thermal comfort. A comprehensive understanding of the effects of air and body movement on localised evaporative resistance is also necessary by both textile and apparel researchers and industry.

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.

Evaporation in equilibrium, in vacuum, and in hydrogen gas

NASA Technical Reports Server (NTRS)

Nagahara, Hiroko

1993-01-01

Evaporation experiments were conducted for SiO2 in three different conditions: in equilibrium, in vacuum, and in hydrogen gas. Evaporation rate in vacuum is about two orders of magnitude smaller than that in equilibrium, which is consistent with previous works. The rate in hydrogen gas changes depending on hydrogen pressure. The rate at 10 exp -7 bar of hydrogen pressure is as small as that of free evaporation, but at 10 exp -5 bar of hydrogen pressure it is larger than that in equilibrium. In equilibrium and in vacuum, the evaporation rate is limited by decomposition of SiO2 on the crystal surface, but it is limited by a diffusion process for evaporation in hydrogen gas. Therefore, evaporation rate of minerals in the solar nebula can be shown neither by that in equilibrium nor by that in vacuum. The maximum temperature of the solar nebula at the midplane at 2-3 AU where chondrites are believed to have originated is calculated to be as low as 150 K, 1500 K, or in between them. The temperature is, in any case, not high enough for total evaporation of the interstellar materials. Therefore, evaporation of interstellar materials is one of the most important processes for the origin and fractionation of solid materials. The fundamental process of evaporation of minerals has been intensively studied for these several years. Those experiments were carried out either in equilibrium or in vacuum; however, evaporation in the solar nebula is in hydrogen (and much smaller amount of helium) gas. In order to investigate evaporation rate and compositional (including isotopic) fractionation during evaporation, vaporization experiments for various minerals in various conditions are conducted. At first, SiO2 was adopted for a starting material, because thermochemical data and its nature of congruent vaporization are well known. Experiments were carried out in a vacuum furnace system.

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

Spacesuit Water Membrane Evaporator; An Enhanced Evaporative Cooling Systems for the Advanced Extravehicular Mobility Unit Portable Life Support System

NASA Technical Reports Server (NTRS)

Bue, Grant C.; Makinen, Janice V.; Miller, Sean.; Campbell, Colin; Lynch, Bill; Vogel, Matt; Craft, Jesse; Petty, Brian

2014-01-01

Spacesuit Water Membrane Evaporator - Baseline heat rejection technology for the Portable Life Support System of the Advanced EMU center dot Replaces sublimator in the current EMU center dot Contamination insensitive center dot Can work with Lithium Chloride Absorber Radiator in Spacesuit Evaporator Absorber Radiator (SEAR) to reject heat and reuse evaporated water The Spacesuit Water Membrane Evaporator (SWME) is being developed to replace the sublimator for future generation spacesuits. Water in LCVG absorbs body heat while circulating center dot Warm water pumped through SWME center dot SWME evaporates water vapor, while maintaining liquid water - Cools water center dot Cooled water is then recirculated through LCVG. center dot LCVG water lost due to evaporation (cooling) is replaced from feedwater The Independent TCV Manifold reduces design complexity and manufacturing difficulty of the SWME End Cap. center dot The offset motor for the new BPV reduces the volume profile of the SWME by laying the motor flat on the End Cap alongside the TCV.

Vapor-based interferometric measurement of local evaporation rate and interfacial temperature of evaporating droplets.

PubMed

Dehaeck, Sam; Rednikov, Alexey; Colinet, Pierre

2014-03-04

The local evaporation rate and interfacial temperature are two quintessential characteristics for the study of evaporating droplets. Here, it is shown how one can extract these quantities by measuring the vapor concentration field around the droplet with digital holographic interferometry. As a concrete example, an evaporating freely receding pending droplet of 3M Novec HFE-7000 is analyzed at ambient conditions. The measured vapor cloud is shown to deviate significantly from a pure-diffusion regime calculation, but it compares favorably to a new boundary-layer theory accounting for a buoyancy-induced convection in the gas and the influence upon it of a thermal Marangoni flow. By integration of the measured local evaporation rate over the interface, the global evaporation rate is obtained and validated by a side-view measurement of the droplet shape. Advective effects are found to boost the global evaporation rate by a factor of 4 as compared to the diffusion-limited theory.

The impact of surface chemistry on the performance of localized solar-driven evaporation system

PubMed Central

Yu, Shengtao; Zhang, Yao; Duan, Haoze; Liu, Yanming; Quan, Xiaojun; Tao, Peng; Shang, Wen; Wu, Jianbo; Song, Chengyi; Deng, Tao

2015-01-01

This report investigates the influence of surface chemistry (or wettability) on the evaporation performance of free-standing double-layered thin film on the surface of water. Such newly developed evaporation system is composed of top plasmonic light-to-heat conversion layer and bottom porous supporting layer. Under solar light illumination, the induced plasmonic heat will be localized within the film. By modulating the wettability of such evaporation system through the control of surface chemistry, the evaporation rates are differentiated between hydrophilized and hydrophobized anodic aluminum oxide membrane-based double layered thin films. Additionally, this work demonstrated that the evaporation rate mainly depends on the wettability of bottom supporting layer rather than that of top light-to-heat conversion layer. The findings in this study not only elucidate the role of surface chemistry of each layer of such double-layered evaporation system, but also provide additional design guidelines for such localized evaporation system in applications including desalination, distillation and power generation. PMID:26337561

The impact of surface chemistry on the performance of localized solar-driven evaporation system.

PubMed

Yu, Shengtao; Zhang, Yao; Duan, Haoze; Liu, Yanming; Quan, Xiaojun; Tao, Peng; Shang, Wen; Wu, Jianbo; Song, Chengyi; Deng, Tao

2015-09-04

This report investigates the influence of surface chemistry (or wettability) on the evaporation performance of free-standing double-layered thin film on the surface of water. Such newly developed evaporation system is composed of top plasmonic light-to-heat conversion layer and bottom porous supporting layer. Under solar light illumination, the induced plasmonic heat will be localized within the film. By modulating the wettability of such evaporation system through the control of surface chemistry, the evaporation rates are differentiated between hydrophilized and hydrophobized anodic aluminum oxide membrane-based double layered thin films. Additionally, this work demonstrated that the evaporation rate mainly depends on the wettability of bottom supporting layer rather than that of top light-to-heat conversion layer. The findings in this study not only elucidate the role of surface chemistry of each layer of such double-layered evaporation system, but also provide additional design guidelines for such localized evaporation system in applications including desalination, distillation and power generation.

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.

An Ultrathin Nanoporous Membrane Evaporator.

PubMed

Lu, Zhengmao; Wilke, Kyle L; Preston, Daniel J; Kinefuchi, Ikuya; Chang-Davidson, Elizabeth; Wang, Evelyn N

2017-10-11

Evaporation is a ubiquitous phenomenon found in nature and widely used in industry. Yet a fundamental understanding of interfacial transport during evaporation remains limited to date owing to the difficulty of characterizing the heat and mass transfer at the interface, especially at high heat fluxes (>100 W/cm 2 ). In this work, we elucidated evaporation into an air ambient with an ultrathin (≈200 nm thick) nanoporous (≈130 nm pore diameter) membrane. With our evaporator design, we accurately monitored the temperature of the liquid-vapor interface, reduced the thermal-fluidic transport resistance, and mitigated the clogging risk associated with contamination. At a steady state, we demonstrated heat fluxes of ≈500 W/cm 2 across the interface over a total evaporation area of 0.20 mm 2 . In the high flux regime, we showed the importance of convective transport caused by evaporation itself and that Fick's first law of diffusion no longer applies. This work improves our fundamental understanding of evaporation and paves the way for high flux phase-change devices.

Comparison of energy-budget evaporation losses from two morphometrically different Florida seepage lakes

USGS Publications Warehouse

Sacks, L.A.; Lee, T.M.; Radell, M.J.

1994-01-01

Evaporation was computed by the energy-budget method for two north Florida lakes with similar surface areas but different depths, for the period May 1989 to December 1990. Lake Barco, in north-central Florida, is shallow, with an average depth of 3 m; Lake Five-O, in the Florida panhandle, is considerably deeper, with an average depth of 9.5 m. As a result, the thermal regime and seasonal evaporation rates of the lakes are different. Evaporation from the shallower lake was higher than that from the deeper lake in the winter and spring. In the late summer and autumn, however, the situation is reversed. Evaporation from the shallow lake is directly related to the amount of incoming shortwave radiation because of its limited ability to store energy. The lag in evaporation at the deeper lake is a function of the greater amount of heat that it seasonally stores and releases. The difference in annual evaporation between Lake Barco (151 cm year-1) and Lake Five-O (128 cm year-1) is related to differences in regional climatic conditions between the two sites. Additionally, higher than normal evaporation rates at the two lakes are probably related to drought conditions experienced in north Florida during 1990, which resulted in higher temperatures and more incoming radiation. Monthly evaporation at Lake Barco could usually be estimated within 10% of the energy-budget evaporation using a constant pan coefficient. This lake may be representative of other shallow lakes that do not store considerable heat. Monthly evaporation at Lake Five-O, however, could not be estimated accurately by using an annual pan coefficient because of the large seasonal influence of change in stored heat. Monthly mass-transfer evaporation compared well with energy-budget evaporation at Lake Barco, but did not compare well at Lake Five-O. These errors may also be associated with changes in heat storage. Thus, the thermal regime of the lake must be considered to estimate accurately the seasonal evaporation rates from a deep lake. ?? 1994.

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.

Multi-leg heat pipe evaporator

NASA Technical Reports Server (NTRS)

Alario, J. P.; Haslett, R. A. (Inventor)

1986-01-01

A multileg heat pipe evaporator facilitates the use and application of a monogroove heat pipe by providing an evaporation section which is compact in area and structurally more compatible with certain heat exchangers or heat input apparatus. The evaporation section of a monogroove heat pipe is formed by a series of parallel legs having a liquid and a vapor channel and a communicating capillary slot therebetween. The liquid and vapor channels and interconnecting capillary slots of the evaporating section are connected to the condensing section of the heat pipe by a manifold connecting liquid and vapor channels of the parallel evaporation section legs with the corresponding liquid and vapor channels of the condensing section.

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.

Water Evaporation from Acoustically Levitated Aqueous Solution Droplets.

PubMed

Combe, Nicole A; Donaldson, D James

2017-09-28

We present a systematic study of the effect of solutes on the evaporation rate of acoustically levitated aqueous solution droplets by suspending individual droplets in a zero-relative humidity environment and measuring their size as a function of time. The ratios of the early time evaporation rates of six simple salts (NaCl, NaBr, NaNO 3 , KCl, MgCl 2 , CaCl 2 ) and malonic acid to that of water are in excellent agreement with predictions made by modifying the Maxwell equation to include the time-dependent water activity of the evaporating aqueous salt solution droplets. However, the early time evaporation rates of three ammonium salt solutions (NH 4 Cl, NH 4 NO 3 , (NH 4 ) 2 SO 4 ) are not significantly different from the evaporation rate of pure water. This finding is in accord with a previous report that ammonium sulfate does not depress the evaporation rate of its solutions, despite reducing its water vapor pressure, perhaps due to specific surface effects. At longer evaporation times, as the droplets approach crystallization, all but one (MgCl 2 ) of the solution evaporation rates are well described by the modified Maxwell equation.

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.

Multilayer composite material and method for evaporative cooling

NASA Technical Reports Server (NTRS)

Buckley, Theresa M. (Inventor)

2002-01-01

A multilayer composite material and method for evaporative cooling of a person employs an evaporative cooling liquid that changes phase from a liquid to a gaseous state to absorb thermal energy. The evaporative cooling liquid is absorbed into a superabsorbent material enclosed within the multilayer composite material. The multilayer composite material has a high percentage of the evaporative cooling liquid in the matrix. The cooling effect can be sustained for an extended period of time because of the high percentage of phase change liquid that can be absorbed into the superabsorbent. Such a composite can be used for cooling febrile patients by evaporative cooling as the evaporative cooling liquid in the matrix changes from a liquid to a gaseous state to absorb thermal energy. The composite can be made with a perforated barrier material around the outside to regulate the evaporation rate of the phase change liquid. Alternatively, the composite can be made with an imperveous barrier material or semipermeable membrane on one side to prevent the liquid from contacting the person's skin. The evaporative cooling liquid in the matrix can be recharged by soaking the material in the liquid. The multilayer composite material can be fashioned into blankets, garments and other articles.

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.

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.

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.

PROCESS WATER BUILDING, TRA605. FLASH EVAPORATOR, CONDENSER (PROJECT FROM EVAPORATOR), ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

PROCESS WATER BUILDING, TRA-605. FLASH EVAPORATOR, CONDENSER (PROJECT FROM EVAPORATOR), AND STEAM EJECTOR (ALONG REAR WALL). INL NEGATIVE NO. 4377. M.H. Bartz, Photographer, 3/5/1952 - Idaho National Engineering Laboratory, Test Reactor Area, Materials & Engineering Test Reactors, Scoville, Butte County, ID

Heat pulse probe measurements of soil water evaporation in a corn field

USDA-ARS?s Scientific Manuscript database

Latent heat fluxes from cropped fields consist of soil water evaporation and plant transpiration. It is difficult to accurately separate evapotranspiration into evaporation and transpiration. Heat pulse probes have been used to measure bare field subsurface soil water evaporation, however, the appl...

7 CFR 58.913 - Evaporators and vacuum pans.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 7 Agriculture 3 2010-01-01 2010-01-01 false Evaporators and vacuum pans. 58.913 Section 58.913....913 Evaporators and vacuum pans. All equipment used in the removal of moisture from milk or milk... Sanitary Standards for Milk and Milk Products Evaporators and Vacuum Pans. ...

7 CFR 58.913 - Evaporators and vacuum pans.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 7 Agriculture 3 2014-01-01 2014-01-01 false Evaporators and vacuum pans. 58.913 Section 58.913....913 Evaporators and vacuum pans. All equipment used in the removal of moisture from milk or milk... Sanitary Standards for Milk and Milk Products Evaporators and Vacuum Pans. ...

7 CFR 58.913 - Evaporators and vacuum pans.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 7 Agriculture 3 2011-01-01 2011-01-01 false Evaporators and vacuum pans. 58.913 Section 58.913....913 Evaporators and vacuum pans. All equipment used in the removal of moisture from milk or milk... Sanitary Standards for Milk and Milk Products Evaporators and Vacuum Pans. ...

7 CFR 58.913 - Evaporators and vacuum pans.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 7 Agriculture 3 2013-01-01 2013-01-01 false Evaporators and vacuum pans. 58.913 Section 58.913....913 Evaporators and vacuum pans. All equipment used in the removal of moisture from milk or milk... Sanitary Standards for Milk and Milk Products Evaporators and Vacuum Pans. ...

7 CFR 58.913 - Evaporators and vacuum pans.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 7 Agriculture 3 2012-01-01 2012-01-01 false Evaporators and vacuum pans. 58.913 Section 58.913....913 Evaporators and vacuum pans. All equipment used in the removal of moisture from milk or milk... Sanitary Standards for Milk and Milk Products Evaporators and Vacuum Pans. ...

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

Apparatus and method for evaporator defrosting

DOEpatents

Mei, Viung C.; Chen, Fang C.; Domitrovic, Ronald E.

2001-01-01

An apparatus and method for warm-liquid defrosting of the evaporator of a refrigeration system. The apparatus includes a first refrigerant expansion device that selectively expands refrigerant for cooling the evaporator, a second refrigerant expansion device that selectively expands the refrigerant after the refrigerant has passed through the evaporator, and a defrosting control for the first refrigerant expansion device and second refrigerant expansion device to selectively defrost the evaporator by causing warm refrigerant to flow through the evaporator. The apparatus is alternately embodied with a first refrigerant bypass and/or a second refrigerant bypass for selectively directing refrigerant to respectively bypass the first refrigerant expansion device and the second refrigerant expansion device, and with the defrosting control connected to the first refrigerant bypass and/or the second refrigerant bypass to selectively activate and deactivate the bypasses depending upon the current cycle of the refrigeration system. The apparatus alternately includes an accumulator for accumulating liquid and/or gaseous refrigerant that is then pumped either to a refrigerant receiver or the first refrigerant expansion device for enhanced evaporator defrosting capability. The inventive method of defrosting an evaporator in a refrigeration system includes the steps of compressing refrigerant in a compressor and cooling the refrigerant in the condenser such that the refrigerant is substantially in liquid form, passing the refrigerant substantially in liquid form through the evaporator, and expanding the refrigerant with a refrigerant expansion device after the refrigerant substantially passes through the evaporator.

Simulation of Heterogeneous Atom Probe Tip Shapes Evolution during Field Evaporation Using a Level Set Method and Different Evaporation Models

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

Xu, Zhijie; Li, Dongsheng; Xu, Wei

2015-04-01

In atom probe tomography (APT), accurate reconstruction of the spatial positions of field evaporated ions from measured detector patterns depends upon a correct understanding of the dynamic tip shape evolution and evaporation laws of component atoms. Artifacts in APT reconstructions of heterogeneous materials can be attributed to the assumption of homogeneous evaporation of all the elements in the material in addition to the assumption of a steady state hemispherical dynamic tip shape evolution. A level set method based specimen shape evolution model is developed in this study to simulate the evaporation of synthetic layered-structured APT tips. The simulation results ofmore » the shape evolution by the level set model qualitatively agree with the finite element method and the literature data using the finite difference method. The asymmetric evolving shape predicted by the level set model demonstrates the complex evaporation behavior of heterogeneous tip and the interface curvature can potentially lead to the artifacts in the APT reconstruction of such materials. Compared with other APT simulation methods, the new method provides smoother interface representation with the aid of the intrinsic sub-grid accuracy. Two evaporation models (linear and exponential evaporation laws) are implemented in the level set simulations and the effect of evaporation laws on the tip shape evolution is also presented.« less

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

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

Evaporation effect on two-dimensional wicking in porous media.

PubMed

Benner, Eric M; Petsev, Dimiter N

2018-03-15

We analyze the effect of evaporation on expanding capillary flow for losses normal to the plane of a two-dimensional porous medium using the potential flow theory formulation of the Lucas-Washburn method. Evaporation induces a finite steady state liquid flux on capillary flows into fan-shaped domains which is significantly greater than the flux into media of constant cross section. We introduce the evaporation-capillary number, a new dimensionless quantity, which governs the frontal motion when multiplied by the scaled time. This governing product divides the wicking behavior into simple regimes of capillary dominated flow and evaporative steady state, as well as the intermediate regime of evaporation influenced capillary driven motion. We also show flow dimensionality and evaporation reduce the propagation rate of the wet front relative to the Lucas-Washburn law. Copyright © 2017 Elsevier Inc. All rights reserved.

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

[Characteristics of evaporation over broadleaved Korean pine forest in Changbai Mountains, Northeast China during snow cover period in winter].

PubMed

Li, Hui-dong; Guan, De-xin; Wang, An-zhi; Wu, Jia-Bing; Jin, Chang-jie; ShiI, Ting-ting

2013-04-01

Based on the measurement data of water vapor flux by open-path eddy covariance system and of the micrometeorological factors in broad-leaved Korean pine forest in Changbai Mountains during the snow cover period from 2002 to 2005, this paper analyzed the dynamics of snow cover evaporation and the relationships between the evaporation and meteorological factors. The energy balanced ratio during the snow cover period was 79. 9% , and the latent heat flux accounted for 21. 4% of net radiation. The diurnal variation of the evaporation presented a single-peak curve, and the evaporation rate during snow-melting period was higher than that during stable snow cover period. The half-hour evaporation presented liner relationship with net radiation and quadratic relationship with air temperature. The daily evaporation presented quadratic relationship with net radiation and exponential relationship with air temperature. The daily evaporation presented a dynamic trend of decreasing-stable-increasing, with the maximum at increasing stage and the minimum at stable stage. The maximum value of the daily evaporation was 0.73 mm d-1, and the minimum value was 0. 004 mm d-1. During the snow cover periods of 2002-2003, 2003-2004 and 2004-2005, the annual evaporation was 27.6, 25.5, and 22.9 mm, accounting for 37.9% , 19.5% , and 30. 0% of the precipitation in the same periods, respectively. The mean value of the daily evaporation in the three periods was 0. 17, 0. 19, and 0. 17 mm d-1, respectively.

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.

Effects of straw mulching on soil evaporation during the soil thawing period in a cold region in northeastern China

NASA Astrophysics Data System (ADS)

Fu, Qiang; Yan, Peiru; Li, Tianxiao; Cui, Song; Peng, Li

2018-04-01

To study the effect of straw mulching on soil water evaporation, it is necessary to measure soil water evaporation under different conditions of straw mulching during the soil thawing period. A field experiment was conducted in winter, and soil evaporation was measured using a microlysimeter on bare land (LD) and 4500 (GF4500), 9000 (GF9000) and 13500 kg/hm2 (GF13500) straw mulch. The influence of different quantities of straw mulch on soil water evaporation during the thawing period was analyzed using the Mallat algorithm, statistical analysis and information cost function. The results showed that straw mulching could delay the thawing of the surface soil by 3-6 d, decrease the speed at which the surface soil thaws by 0.40-0.80 cm/d, delay the peak soil liquid water content, increase the soil liquid water content, reduce the cumulative evaporation by 2.70-7.40 mm in the thawing period, increase the range of soil evaporation by 0.04-0.10 mm in the early stage of the thawing period, and reduce the range of soil evaporation by 0.25-0.90 mm in the late stage of the thawing period. Straw mulching could reduce the range of and variation in soil evaporation and can reduce the effect of random factors on soil evaporation. When the amount of straw mulch exceeded 9000 kg/hm2, the effect of increasing the amount of straw mulch on daily soil water evaporation was small.

Laboratory simulation of processes of evaporation, condensation, and sputtering taking place on the surface of the moon

NASA Technical Reports Server (NTRS)

Nusinov, M. D.; Kochnev, V. A.; Chernyak, Y. B.; Kuznetsov, A. V.; Kosolapov, A. I.; Yakovlev, O. I.

1974-01-01

Study of evaporation, condensation and sputtering on the moon can provide information on the same processes on other planets, and reveal details of the formation of the lunar regolith. Simulation methods include vacuum evaporation, laser evaporation, and bubbling gas through melts.

Turkish Undergraduates' Misconceptions of Evaporation, Evaporation Rate, and Vapour Pressure

ERIC Educational Resources Information Center

Canpolat, Nurtac

2006-01-01

This study focused on students' misconceptions related to evaporation, evaporation rate, and vapour pressure. Open-ended diagnostic questions were used with 107 undergraduates in the Primary Science Teacher Training Department in a state university in Turkey. In addition, 14 students from that sample were interviewed to clarify their written…

Evaporation rate-based selection of supramolecular chirality.

PubMed

Hattori, Shingo; Vandendriessche, Stefaan; Koeckelberghs, Guy; Verbiest, Thierry; Ishii, Kazuyuki

2017-03-09

We demonstrate the evaporation rate-based selection of supramolecular chirality for the first time. P-type aggregates prepared by fast evaporation, and M-type aggregates prepared by slow evaporation are kinetic and thermodynamic products under dynamic reaction conditions, respectively. These findings provide a novel solution reaction chemistry under the dynamic reaction conditions.

7 CFR 58.217 - Evaporators and/or vacuum pans.

Code of Federal Regulations, 2011 CFR

2011-01-01

....217 Evaporators and/or vacuum pans. Evaporators or vacuum pans or both, with open type condensers shall be equipped with an automatic condenser water level control, barometric leg, or so constructed so... Sanitary Standards for Milk and Milk Products Evaporators and Vacuum Pans. When enclosed type condensers...

Portable brine evaporator unit, process, and system

DOEpatents

Hart, Paul John; Miller, Bruce G.; Wincek, Ronald T.; Decker, Glenn E.; Johnson, David K.

2009-04-07

The present invention discloses a comprehensive, efficient, and cost effective portable evaporator unit, method, and system for the treatment of brine. The evaporator unit, method, and system require a pretreatment process that removes heavy metals, crude oil, and other contaminates in preparation for the evaporator unit. The pretreatment and the evaporator unit, method, and system process metals and brine at the site where they are generated (the well site). Thus, saving significant money to producers who can avoid present and future increases in transportation costs.

Effects of the local structure dependence of evaporation fields on field evaporation behavior

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

Yao, Lan; Marquis, Emmanuelle A., E-mail: emarq@umich.edu; Withrow, Travis

2015-12-14

Accurate three dimensional reconstructions of atomic positions and full quantification of the information contained in atom probe microscopy data rely on understanding the physical processes taking place during field evaporation of atoms from needle-shaped specimens. However, the modeling framework for atom probe microscopy has only limited quantitative justification. Building on the continuum field models previously developed, we introduce a more physical approach with the selection of evaporation events based on density functional theory calculations. This model reproduces key features observed experimentally in terms of sequence of evaporation, evaporation maps, and depth resolution, and provides insights into the physical limit formore » spatial resolution.« less

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.

Universal evaporation dynamics of a confined sessile droplet

NASA Astrophysics Data System (ADS)

Bansal, Lalit; Hatte, Sandeep; Basu, Saptarshi; Chakraborty, Suman

2017-09-01

Droplet evaporation under confinement is ubiquitous to multitude of applications such as microfluidics, surface patterning, and ink-jet printing. However, the rich physics governing the universality in the underlying dynamics remains grossly elusive. Here, we bring out hitherto unexplored universal features of the evaporation dynamics of a sessile droplet entrapped in a 3D confined fluidic environment. We show, through extensive set of experiments and theoretical formulations, that the evaporation timescale for such a droplet can be represented by a unique function of the initial conditions. Moreover, using same theoretical considerations, we are able to trace and universally merge the volume evolution history of the droplets along with evaporation lifetimes, irrespective of the extent of confinement. We also showcase the internal flow transitions caused by spatio-temporal variation of evaporation flux due to confinement. These findings may be of profound importance in designing functionalized droplet evaporation devices for emerging engineering and biomedical applications.

Evaporation of inclined water droplets.

PubMed

Kim, Jin Young; Hwang, In Gyu; Weon, Byung Mook

2017-02-16

When a drop is placed on a flat substrate tilted at an inclined angle, it can be deformed by gravity and its initial contact angle divides into front and rear contact angles by inclination. Here we study on evaporation dynamics of a pure water droplet on a flat solid substrate by controlling substrate inclination and measuring mass and volume changes of an evaporating droplet with time. We find that complete evaporation time of an inclined droplet becomes longer as gravitational influence by inclination becomes stronger. The gravity itself does not change the evaporation dynamics directly, whereas the gravity-induced droplet deformation increases the difference between front and rear angles, which quickens the onset of depinning and consequently reduces the contact radius. This result makes the evaporation rate of an inclined droplet to be slow. This finding would be important to improve understanding on evaporation dynamics of inclined droplets.

Evaporation of inclined water droplets

PubMed Central

Kim, Jin Young; Hwang, In Gyu; Weon, Byung Mook

2017-01-01

When a drop is placed on a flat substrate tilted at an inclined angle, it can be deformed by gravity and its initial contact angle divides into front and rear contact angles by inclination. Here we study on evaporation dynamics of a pure water droplet on a flat solid substrate by controlling substrate inclination and measuring mass and volume changes of an evaporating droplet with time. We find that complete evaporation time of an inclined droplet becomes longer as gravitational influence by inclination becomes stronger. The gravity itself does not change the evaporation dynamics directly, whereas the gravity-induced droplet deformation increases the difference between front and rear angles, which quickens the onset of depinning and consequently reduces the contact radius. This result makes the evaporation rate of an inclined droplet to be slow. This finding would be important to improve understanding on evaporation dynamics of inclined droplets. PMID:28205642

Scaling up nanoscale water-driven energy conversion into evaporation-driven engines and generators

PubMed Central

Chen, Xi; Goodnight, Davis; Gao, Zhenghan; Cavusoglu, Ahmet H.; Sabharwal, Nina; DeLay, Michael; Driks, Adam; Sahin, Ozgur

2015-01-01

Evaporation is a ubiquitous phenomenon in the natural environment and a dominant form of energy transfer in the Earth's climate. Engineered systems rarely, if ever, use evaporation as a source of energy, despite myriad examples of such adaptations in the biological world. Here, we report evaporation-driven engines that can power common tasks like locomotion and electricity generation. These engines start and run autonomously when placed at air–water interfaces. They generate rotary and piston-like linear motion using specially designed, biologically based artificial muscles responsive to moisture fluctuations. Using these engines, we demonstrate an electricity generator that rests on water while harvesting its evaporation to power a light source, and a miniature car (weighing 0.1 kg) that moves forward as the water in the car evaporates. Evaporation-driven engines may find applications in powering robotic systems, sensors, devices and machinery that function in the natural environment. PMID:26079632

Mountain evaporation profiles on the island of Hawai'i

NASA Astrophysics Data System (ADS)

Bean, Christine; Juvik, James O.; Nullet, Dennis

1994-04-01

Evaporation was measured along three altitudinal transects on Mauna Loa, on the island of Hawai'i. Stations lie between 70 and 3400 m a.s.l. and included environments ranging from tropical rainforest with 6 m year -1 annual rainfall to barren, subalpine lava fields in a dry environment above a persistent, subsidence temperature inversion. Average daily evaporation decreased with elevation between sea-level and about 1200 m, and then increased with elevation above that level. Evaporation minima ranged from 1.9 to 2.2 mm day -1. The maximum evaporation rate, 6.1 mm day -1, was at the highest site, Mauna Loa Observatory at 3400 m. Analysis of pan-evaporation data collected at 3400 m showed that standard formulae based on other meteorological variables provided good approximations of measured evaporation. Transect data were also compared with similar measurements from mountains on other Hawaiian islands.

Scaling up nanoscale water-driven energy conversion into evaporation-driven engines and generators

NASA Astrophysics Data System (ADS)

Chen, Xi; Goodnight, Davis; Gao, Zhenghan; Cavusoglu, Ahmet H.; Sabharwal, Nina; Delay, Michael; Driks, Adam; Sahin, Ozgur

2015-06-01

Evaporation is a ubiquitous phenomenon in the natural environment and a dominant form of energy transfer in the Earth's climate. Engineered systems rarely, if ever, use evaporation as a source of energy, despite myriad examples of such adaptations in the biological world. Here, we report evaporation-driven engines that can power common tasks like locomotion and electricity generation. These engines start and run autonomously when placed at air-water interfaces. They generate rotary and piston-like linear motion using specially designed, biologically based artificial muscles responsive to moisture fluctuations. Using these engines, we demonstrate an electricity generator that rests on water while harvesting its evaporation to power a light source, and a miniature car (weighing 0.1 kg) that moves forward as the water in the car evaporates. Evaporation-driven engines may find applications in powering robotic systems, sensors, devices and machinery that function in the natural environment.

Effects of biochar addition on evaporation in the five typical Loess Plateau soils

USDA-ARS?s Scientific Manuscript database

Soil evaporation is the main route of soil moisture loss and often exceeds precipitation in the arid and semi-arid regions of the Loess Plateau. This study was conducted to determine whether biochar addition could reduce soil evaporation in drylands. We measured the evaporative loss in five typical ...

Efficiency of using solid wood fuels in maple syrup evaporators

Treesearch

Lawrence D. Garrett

1981-01-01

A study of commercial, wood-fired evaporators revealed that normal expected thermal efficiencies are between 35 and 50 percent. The moisture content and quality of wood fuels used and the design and method of firing the evaporator are critical in determining evaporator efficiency and the economic implications of using wood.

Influence of GaAs substrate properties on the congruent evaporation temperature

NASA Astrophysics Data System (ADS)

Spirina, A. A.; Nastovjak, A. G.; Shwartz, N. L.

2018-03-01

High-temperature annealing of GaAs(111)A and GaAs(111)B substrates under Langmuir evaporation conditions was studied using Monte Carlo simulation. The maximal value of the congruent evaporation temperature was estimated. The congruent evaporation temperature was demonstrated to be dependent on the surface orientation and concentration of surface defects.

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.

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.

Concentrated Brine Treatment using New Energy in Coal Mine Evaporation Ponds

NASA Astrophysics Data System (ADS)

Li, Ting; Li, Jingfeng

2017-12-01

Recently, more and more coal mine water is being advanced treated and reused in China. The concentrated brine that results from advanced treatment methods can only be evaporated in an evaporation pond. Because of limited treatment capabilities and winter freezing, evaporation ponds often overflow, causing environment contamination. In this paper, based on analysis of brine water quality and economic-technical feasibility, we present a suitable treatment method for brine in evaporation ponds as electrodialysis using solar energy. In addition, we propose a new system to treat brine in coal mine evaporation ponds, which is powered by solar and wind. The operating efficiency of this treatment system proposed in this paper can meet the concentrated brine treatment demands in most coal mines in western mining areas of China and it places the photovoltaic power generation plates on the surface of the evaporation pond on a fixed floating island, which reduces any risk associated with land acquisition. This system can enhance brine treatment efficiency, requires a reduced evaporation pond area, increases the utilization of coal mine water, and minimizes the risk of environment contamination.

Report on Analyses of WAC Samples of Evaporator Overheads - 2004

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

Oji, L

2005-03-18

In November and December of 2004, the Tank Farm submitted annual samples from 2F, 2H and 3H Evaporator Overhead streams for characterization to verify compliance with the new Effluent Treatment Facility (ETF) Waste Acceptance Criteria (WAC) and to look for organic species. With the exception of slightly high ammonia in the 2F evaporator overheads and high radiation control guide number for the 3H and 2F evaporator overhead samples, all the overheads samples were found to be in compliance with the Effluent Treatment Facility WAC. The ammonium concentration in the 2F-evaporator overhead, at 33 mg/L, was above the ETF waste watermore » collection tank (WWCT) limits of 28 mg/L. The RCG Number for the 3H and 2F evaporator samples at, respectively, 1.38E-02 and 8.24E-03 were higher than the WWCT limit of 7.69E-03. The analytical detection limits for americium-241 and radium-226 in the evaporator samples were not consistently met because of low WWCT detection limits and insufficient evaporator samples.« less

Effects on evaporation rates from different water-permeable pavement designs.

PubMed

Starke, P; Göbel, P; Coldewey, W G

2011-01-01

The urban water balance can be attenuated to the natural by water-permeable pavements (WPPs). Furthermore, WPPs have a 16% higher evaporation rate than impermeable pavements, which can lead to a better urban climate. Evaporation rates from pavements are influenced by the pavement surface and by the deeper layers. By a compared evaporation measurement between different WPP designs, the grain size distribution of the sub-base shows no influence on the evaporation rates in a significant way. On the contrary, a sub-base made of a twin-layer decreases the evaporation by 16% compared to a homogeneous sub-base. By a change in the colour of the paving stone, 19% higher evaporation rates could be achieved. A further comparison shows that the transpiration-effect of the grass in grass pavers increases the evaporation rates more than threefold to pervious concrete pavements. These high evapotranspiration rates can not be achieved with a pervious concrete paving stone. In spite of this, the broad field of application of the pervious concrete paving stone increases the importance in regard to the urban climate.

Estimating pothole wetland connectivity to Pipestem Creek ...

EPA Pesticide Factsheets

Understanding hydrologic connectivity between wetlands and perennial streams is critical to understanding how reliant stream flow is on wetlands within their watershed. We used the isotopic evaporation signal in water to examine hydrologic connectivity within Pipestem Creek, North Dakota, with a watershed dominated by prairie potholes. During a decadal period of wet conditions, Pipestem Creek contained evaporated water that had approximately half the isotopic evaporative enrichment signal found in most evaporated permanent wetlands. If evaporation was mainly occurring within the stream, we expected the evaporation signal to increase from the headwaters with distance downstream. However, the signal either remained similar or decreased downstream over the two years of sampling. Groundwater measured at the water table adjacent to Pipestem Creek had isotopic values that indicated recharge from winter precipitation and had no significant evaporation. Using isotopic theory and discharge data, we estimated the surface area of open water necessary to generate the evaporation signal found within Pipestem Creek over time. The range of evaporating surface-area estimates was highly dynamic, spanning from 43 to 2653 ha and varying primarily with discharge. The average value (just over 600 ha) was well above the surface area of Pipestem Creek network (245 ha). This estimate of contributing area indicated that Prairie Pothole wetlands were important sources of stream fl

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.

Development of Apparatus for Microgravity Experiments on Evaporation and Combustion of Palm Methyl Ester Droplet in High-Pressure Environments

NASA Astrophysics Data System (ADS)

Suzuki, Masato; Nomura, Hiroshi; Hashimoto, Nozomu

New apparatus for microgravity experiments was developed in order to obtain fundamental data of single droplet evaporation and combustion of palm methyl ester (PME) for understanding PME spray combustion in internal combustion engines. n-hexadecane droplet combustion and evaporation experiments were also performed to obtain single-component fuel data. Combustion experiments were performed at atmospheric pressure and room temperature. For droplet evaporation experiments, ambient temperature and pressure were varied from 473 to 873 K and 0.10 to 4.0 MPa, respectively. Microgravity conditions were employed for evaporation experiments to prevent natural convection. Droplet diameter history of a burning PME droplet is similar to that of n-hexadecane. Droplet diameter history of an evaporating PME droplet is different from that of n-hexadecane at low ambient temperatures. In the latest stage of PME droplet evaporation, temporal evaporation constant decreases remarkably. At ambient temperatures sufficiently above the boiling temperature of PME components, droplet diameter history of PME and n-hexadecane are similar to each other. Corrected evaporation lifetime τ of PME at 873 K as a function of ambient pressure was obtained at normal and microgravity. At normal gravity, τ monotonically decreases with ambient pressure. On the other hand, at microgravity, τ increases with ambient pressure, and then decreases.

Evaporation from Lake Michie, North Carolina 1961-71

USGS Publications Warehouse

Yonts, W.L.; Giese, G.L.; Hubbard, E.F.

1973-01-01

The Geological Survey, in cooperation with the city of Durham, N. C., collected evaporation data at Lake Michie, Durham's 480-acre water-supply reservoir, for 10 consecutive years from September 1961 to September 1971. Wind speed, air temperature, and water temperature-collected continuously-were used in conjunction with water-budget data to calibrate the semi-empirical mass-transfer equation, E Nu(eo - ea), where E is evaporation; N is the mass-transfer coefficient, which is a constant for a given lake; u is wind speed; eo is the vapor pressure of the saturated air at the water surface; and ea is the vapor pressure of the surrounding air. For evaporation expressed in inches, the mass-transfer coefficient for Lake Michie is 0.0036.During the study period the average annual evaporation from Lake Michie was 37.9 inches. Within-year variation of evaporation from the lake is sinusoidal, with a high during July averaging 4.71 inches and a low during January averaging 1.45 inches.Evaporation from Lake Michie was 0.72 (or about three-quarters) of the evaporation from the National Weather Service evaporation pan at Chapel Hill. This ratio, called a pan coefficient, was not constant throughout the year, ranging from an average of 0.57 for April to 1.09 for December.

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.

Determination of clothing evaporative resistance on a sweating thermal manikin in an isothermal condition: heat loss method or mass loss method?

PubMed

Wang, Faming; Gao, Chuansi; Kuklane, Kalev; Holmér, Ingvar

2011-08-01

This paper addresses selection between two calculation options, i.e heat loss option and mass loss option, for thermal manikin measurements on clothing evaporative resistance conducted in an isothermal condition (T(manikin) = T(a) = T(r)). Five vocational clothing ensembles with a thermal insulation range of 1.05-2.58 clo were selected and measured on a sweating thermal manikin 'Tore'. The reasons why the isothermal heat loss method generates a higher evaporative resistance than that of the mass loss method were thoroughly investigated. In addition, an indirect approach was applied to determine the amount of evaporative heat energy taken from the environment. It was found that clothing evaporative resistance values by the heat loss option were 11.2-37.1% greater than those based on the mass loss option. The percentage of evaporative heat loss taken from the environment (H(e,env)) for all test scenarios ranged from 10.9 to 23.8%. The real evaporative cooling efficiency ranged from 0.762 to 0.891, respectively. Furthermore, it is evident that the evaporative heat loss difference introduced by those two options was equal to the heat energy taken from the environment. In order to eliminate the combined effects of dry heat transfer, condensation, and heat pipe on clothing evaporative resistance, it is suggested that manikin measurements on the determination of clothing evaporative resistance should be performed in an isothermal condition. Moreover, the mass loss method should be applied to calculate clothing evaporative resistance. The isothermal heat loss method would appear to overestimate heat stress and thus should be corrected before use.

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.

Evaporative losses from soils covered by physical and different types of biological soil crusts

USGS Publications Warehouse

Chamizo, S.; Cantón, Y.; Domingo, F.; Belnap, J.

2013-01-01

Evaporation of soil moisture is one of the most important processes affecting water availability in semiarid ecosystems. Biological soil crusts, which are widely distributed ground cover in these ecosystems, play a recognized role on water processes. Where they roughen surfaces, water residence time and thus infiltration can be greatly enhanced, whereas their ability to clog soil pores or cap the soil surface when wetted can greatly decrease infiltration rate, thus affecting evaporative losses. In this work, we compared evaporation in soils covered by physical crusts, biological crusts in different developmental stages and in the soils underlying the different biological crust types. Our results show that during the time of the highest evaporation (Day 1), there was no difference among any of the crust types or the soils underlying them. On Day 2, when soil moisture was moderately low (11%), evaporation was slightly higher in well-developed biological soil crusts than in physical or poorly developed biological soil crusts. However, crust removal did not cause significant changes in evaporation compared with the respective soil crust type. These results suggest that the small differences we observed in evaporation among crust types could be caused by differences in the properties of the soil underneath the biological crusts. At low soil moisture (<6%), there was no difference in evaporation among crust types or the underlying soils. Water loss for the complete evaporative cycle (from saturation to dry soil) was similar in both crusted and scraped soils. Therefore, we conclude that for the specific crust and soil types tested, the presence or the type of biological soil crust did not greatly modify evaporation with respect to physical crusts or scraped soils.

Conjunctival Tear Layer Temperature, Evaporation, Hyperosmolarity, Inflammation, Hyperemia, Tissue Damage, and Symptoms: A Review of an Amplifying Cascade.

PubMed

McMonnies, Charles W

2017-12-01

This review examines the evidence for and significance of pre-conjunctival tear temperature being higher than central pre-corneal temperature with associated more rapid evaporation of warmer pre-conjunctival tears in normal eyes but especially in hyperemic dry eye disease. PubMed searches using the terms "evaporative dry eye," "conjunctival tear evaporation," "tear evaporation," and "dry eye conjunctival hyperemia" indicated 157, 49, 309, and 96 potentially relevant papers, respectively. Selections from these lists were the basis for examining the significance of the evidence relevant to pre-conjunctival tear layer temperature and evaporation. There is evidence supporting an amplifying inflammatory and para-inflammatory hyperemia dry eye cascade, which increases pre-conjunctival tear temperature and the risk of accelerated pre-conjunctival tear evaporation with exacerbated osmolarity elevation and inflammation. Dry eye cascade amplification is consistent with increases in symptoms and inflammatory as well as para-inflammatory hyperemia toward the end of the waking day. Apart from age-related conjunctivochalasis, dry eye-related conjunctival epithelial cell pathology including reduced goblet cell numbers and associated mucin deficiency, squamous metaplasia, and increased separation of cell layers could help to destabilize tears and facilitate evaporation as part of an amplifying cascade. Greater difficulty in assessing conjunctival tear break up may contribute to an underestimation of a role for faster evaporation of pre-conjunctival tears in dry eye disease and help explain any non-correspondence between symptoms and corneal signs of dry eye disease. Success with anti-inflammatory therapies for dry eye disease may be at least partly due to reductions in conjunctival hyperemia and deamplification of evaporative cascades. Conjunctival inflammatory hyperemia in other diseases may contribute to accelerated pre-conjunctival tear evaporation and the risk of tear-deficiency- associated exacerbation of those diseases including impaired responses to therapeutic approaches to them. Similarly, postsurgical conjunctival inflammation and associated acceleration of tear evaporation could contribute to delayed wound healing.

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.

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.

Thermal performance of a multi-evaporator loop heat pipe with thermal masses and thermal electrical coolers

NASA Technical Reports Server (NTRS)

Ku, Jentung; Ottenstein, Laura; Birur, Gajanana

2004-01-01

This paper describes thermal performance of a loop heat pipe (LHP) with two evaporators and two condensers in ambient testing. Each evaporator has an outer diameter of 15mm and a length of 76mm, and has an integral compensation chamber (CC). An aluminum mass of 500 grams is attached to each evaporator to simulate the instrument mass. A thermal electric cooler (TEC) is installed on each CC to provide heating as well as cooling for CC temperature control. A flow regulator is installed in the condenser section to prevent vapor from going back to the evaporators in the event that one of condenser is fully utilized. Ammonia was used ad the working fluid. Tests conducted included start-up, power cycle, heat load sharing, sink temperature cycle, operating temperature control with TECs, and capillary limit tests. Experimental data showed that the loop could start with a heat load of less than 1OW even with added thermal masses. The loop operated stably with even and uneven evaporator heat loads, and even and uneven condenser sink temperatures. The operating temperature could be controlled within +/-0.5K of the set point temperature using either or both TECs, and the required TEC control heater power was less than 2W under most test conditions. Heat load sharing between the two evaporators was also successfully demonstrated. The loop had a heat transport capability of 120W to 140W, and could recover from a dry-out when the heat load was reduced. The 500-gram aluminum mass on each evaporator had a negligible effect on the loop operation. Existing LHPs servicing the orbiting spacecraft have a single evaporator with an outer diameter of about 25mm. Important performance characteristics demonstrated by this LHP included: 1) Operation of an LHP with 15mm diameter evaporators; 2) Robustness and reliability of an LHP with multiple evaporators and multiple condensers under various test conditions; 3) Heat load sharing among LHP evaporators; 4) Effectiveness of TECs in controlling the LHP operating temperature; and 5) Effectiveness of the flow regulator in preventing vapor from going back the evaporators.

Thermal Performance of a Multi-Evaporator Loop Heat Pipe with Thermal Masses and Thermoelectric Coolers

NASA Technical Reports Server (NTRS)

Ku, Jen-Tung; Ottenstein, Laura; Birur, Gajanana

2004-01-01

This paper describes thermal performance of a loop heat pipe (LHP) with two evaporators and two condensers in ambient testing. Each evaporator has an outer diameter of 15mm and a length of 76mm, and has an integral compensation chamber (CC). An aluminum mass of 500 grams is attached to each evaporator to simulate the instrument mass. A thermoelectric cooler (TEC) is installed on each CC to provide heating as well as cooling for CC temperature control. A flow regulator is installed in the condenser section to prevent vapor from going back to the evaporators in the event that one of the condensers is fully utilized. Ammonia was used as the working fluid. Tests conducted included start-up, power cycle, heat load sharing, sink temperature cycle, operating temperature control with TECs, and capillary limit tests. Experimental data showed that the loop could start with a heat load of less than 10W even with added thermal masses. The loop operated stably with even and uneven evaporator heat loads, and even and uneven condenser sink temperatures. The operating temperature could be controlled within +/- 0.5K of the set point temperature using either or both TECs, and the required TEC control heater power was less than 2W under most test conditions. Heat load sharing between the two evaporators was also successfully demonstrated. The loop had a heat transport capability of 120W to 140W, and could recover from a dry-out when the heat load was reduced. The 500-gram aluminum mass on each evaporator had a negligible effect on the loop operation. Existing LHPs servicing orbiting spacecraft have a single evaporator with an outer diameter of about 25mm. Important performance characteristics demonstrated by this LHP included: 1) Operation of an LHP with 15mm diameter evaporators; 2) Robustness and reliability of an LHP with multiple evaporators and multiple condensers under various test conditions; 3) Heat load sharing among LHP evaporators; 4) Effectiveness of TECs in controlling the LHP operating temperature; and 5 ) Effectiveness of the flow regulator in preventing vapor from going back the evaporators.

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.

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.

Iodine retention during evaporative volume reduction

DOEpatents

Godbee, H.W.; Cathers, G.I.; Blanco, R.E.

1975-11-18

An improved method for retaining radioactive iodine in aqueous waste solutions during volume reduction is disclosed. The method applies to evaporative volume reduction processes whereby the decontaminated (evaporated) water can be returned safely to the environment. The method generally comprises isotopically diluting the waste solution with a nonradioactive iodide and maintaining the solution at a high pH during evaporation.

Quantum Evaporation from Liquid 4He by Rotons

NASA Astrophysics Data System (ADS)

Hope, F. R.; Baird, M. J.; Wyatt, A. F. G.

1984-04-01

We have shown that rotons as well as phonons can evaporate 4He atoms in a single-quantum process. Measurements of the time of flight and the angular distribution of the evaporated atoms clearly distinguish between evaporation by phonons and rotons. The results indicate that energy and the parallel component of momentum are conserved at the free liquid surface.

Evaporation from a sphagnum moss surface

Treesearch

D.S. Nichols; J.M. Brown

1980-01-01

Peat cores, 45 cm in diameter, were collected from a sphagnum bog in northern Minnesota, and used to measure the effects of different temperatures and water levels on evaporation from a sphagnum moss surface in a growth chamber. Under all conditions, evaporation from the moss surface was greater than that from a free-water surface. Evaporation from the moss increased...

Low chemical concentrating steam generating cycle

DOEpatents

Mangus, James D.

1983-01-01

A steam cycle for a nuclear power plant having two optional modes of operation. A once-through mode of operation uses direct feed of coolant water to an evaporator avoiding excessive chemical concentration buildup. A recirculation mode of operation uses a recirculation loop to direct a portion of flow from the evaporator back through the evaporator to effectively increase evaporator flow.

Research Status of Evaporative Condenser

NASA Astrophysics Data System (ADS)

Wang, Feifei; Yang, Yongan

2018-02-01

Reducing energy consumption, saving water resources, recycling cool water are main directions of China’s development. Evaporative condenser using latent heat reduces water resources waste, with energy-saving advantages. This paper reviews the research status of evaporative condenser at home and abroad, and introduces the principle, classification, various influencing factors of evaporative condenser, and puts forward the future research direction.

Laboratory prototype flash evaporator

NASA Technical Reports Server (NTRS)

Gaddis, J. L.

1972-01-01

A laboratory prototype flash evaporator that is being developed as a candidate for the space shuttle environmental control system expendable heat sink is described. The single evaporator configuration uses water as an evaporant to accommodate reentry and on-orbit peak heat loads, and Freon 22 for terrestrial flight phases below 120,000 feet altitude. The design features, fabrication techniques used for the prototype unit, redundancy considerations, and the fluid temperature control arrangement are reported in detail. The results of an extensive test program to determine the evaporator operational characteristics under a wide variety of conditions are presented.

Effect of Surface Excess Energy Transport on the Rupture of an Evaporating Film

NASA Astrophysics Data System (ADS)

Luo, Yan; Zhou, Jianqiu; Yang, Xia; Liu, Rong

2018-05-01

In most of existing works on the instabilities of an evaporating film, the energy boundary condition only takes into account contributions of the evaporation latent heat and the heat conduction in the liquid. We use a new generalized energy boundary condition at the evaporating liquid-vapor interface, in which the contribution of the transport of the Gibbs excess energy is included. We have derived the long-wave equations in which the thickness of film and the interfacial temperature are coupled to describe the dynamics of an evaporating thin film. The results of our computation show that the transport of the Gibbs excess internal energy delay the rupture of thin films due to van de Waals force, evaporating effect and vapor recoil.

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

Retrofit device to improve vapor compression cooling system performance by dynamic blower speed modulation

DOEpatents

Roth, Robert Paul; Hahn, David C.; Scaringe, Robert P.

2015-12-08

A device and method are provided to improve performance of a vapor compression system using a retrofittable control board to start up the vapor compression system with the evaporator blower initially set to a high speed. A baseline evaporator operating temperature with the evaporator blower operating at the high speed is recorded, and then the device detects if a predetermined acceptable change in evaporator temperature has occurred. The evaporator blower speed is reduced from the initially set high speed as long as there is only a negligible change in the measured evaporator temperature and therefore a negligible difference in the compressor's power consumption so as to obtain a net increase in the Coefficient of Performance.

Enhancement of Water Evaporation on Solid Surfaces with Nanoscale Hydrophobic-Hydrophilic Patterns.

PubMed

Wan, Rongzheng; Wang, Chunlei; Lei, Xiaoling; Zhou, Guoquan; Fang, Haiping

2015-11-06

Using molecular dynamics simulations, we show that the evaporation of nanoscale water on hydrophobic-hydrophilic patterned surfaces is unexpectedly faster than that on any surfaces with uniform wettability. The key to this phenomenon is that, on the patterned surface, the evaporation rate from the hydrophilic region only slightly decreases due to the correspondingly increased water thickness; meanwhile, a considerable number of water molecules evaporate from the hydrophobic region despite the lack of water film. Most of the evaporated water from the hydrophobic region originates from the hydrophilic region by diffusing across the contact lines. Further analysis shows that the evaporation rate from the hydrophobic region is approximately proportional to the total length of the contact lines.

Real evaporative cooling efficiency of one-layer tight-fitting sportswear in a hot environment.

PubMed

Wang, F; Annaheim, S; Morrissey, M; Rossi, R M

2014-06-01

Real evaporative cooling efficiency, the ratio of real evaporative heat loss to evaporative cooling potential, is an important parameter to characterize the real cooling benefit for the human body. Previous studies on protective clothing showed that the cooling efficiency decreases with increasing distance between the evaporation locations and the human skin. However, it is still unclear how evaporative cooling efficiency decreases as the moisture is transported from the skin to the clothing layer. In this study, we performed experiments with a sweating torso manikin to mimic three different phases of moisture absorption in one-layer tight-fitting sportswear. Clothing materials Coolmax(®) (CM; INVISTA, Wichita, Kansas, USA; 100%, profiled cross-section polyester fiber), merino wool (MW; 100%), sports wool (SW; 50% wool, 50% polyester), and cotton (CO; 100%) were selected for the study. The results demonstrated that, for the sportswear materials tested, the real evaporative cooling efficiency linearly decreases with the increasing ratio of moisture being transported away from skin surface to clothing layer (adjusted R(2) >0.97). In addition, clothing fabric thickness has a negative effect on the real evaporative cooling efficiency. Clothing CM and SW showed a good ability in maintaining evaporative cooling efficiency. In contrast, clothing MW made from thicker fabric had the worst performance in maintaining evaporative cooling efficiency. It is thus suggested that thin fabric materials such as CM and SW should be used to manufacture one-layer tight-fitting sportswear. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Diurnal Course of Evaporation From the Dead Sea in Summer: A Distinct Double Peak Induced by Solar Radiation and Night Sea Breeze

NASA Astrophysics Data System (ADS)

Lensky, N. G.; Lensky, I. M.; Peretz, A.; Gertman, I.; Tanny, J.; Assouline, S.

2018-01-01

Partitioning between the relative effects of the radiative and aerodynamic components of the atmospheric forcing on evaporation is challenging since diurnal distributions of wind speed and solar radiation typically overlap. The Dead Sea is located about a 100 km off the Eastern Mediterranean coast, where and the Mediterranean Sea breeze front reaches it after sunset. Therefore, in the Dead Sea the peaks of solar radiation and wind speed diurnal cycles in the Dead Sea are distinctly separated in time, offering a unique opportunity to distinguish between their relative impacts on evaporation. We present mid-summer eddy covariance and meteorological measurements of evaporation rate and surface energy fluxes over the Dead Sea. The evaporation rate is characterized by a clear diurnal cycle with a daytime peak, few hours after solar radiation peak, and a nighttime peak coincident with wind speed peak. Evaporation rate is minimum during sunrise and sunset. Measurements of evaporation rate from two other water bodies that are closer to the Mediterranean coast, Eshkol Reservoir, and Lake Kinneret, present a single afternoon peak, synchronous with the sea breeze. The inland diurnal evaporation rate cycle varies with the distance from the Mediterranean coast, following the propagation of sea breeze front: near the coast, wind speed, and radiation peaks are close and consequently a single daily evaporation peak appears in the afternoon; at the Dead Sea, about a 100 km inland, the sea breeze front arrives at sunset, resulting in a diurnal evaporation cycle characterized by a distinct double peak.

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.

Evaporation kinetics and phase of laboratory and ambient secondary organic aerosol.

PubMed

Vaden, Timothy D; Imre, Dan; Beránek, Josef; Shrivastava, Manish; Zelenyuk, Alla

2011-02-08

Field measurements of secondary organic aerosol (SOA) find significantly higher mass loads than predicted by models, sparking intense effort focused on finding additional SOA sources but leaving the fundamental assumptions used by models unchallenged. Current air-quality models use absorptive partitioning theory assuming SOA particles are liquid droplets, forming 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 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. We found that even when gas phase organics are removed, it takes ∼24 h for pure α-pinene SOA particles to evaporate 75% of their mass, which is in sharp contrast to the ∼10 min time scale predicted by current kinetic models. Adsorption of "spectator" organic vapors during SOA formation, and aging of these coated SOA particles, dramatically reduced the evaporation rate, and in some cases nearly stopped it. Ambient SOA was found to exhibit evaporation behavior very similar to that of laboratory-generated coated and aged SOA. For all cases studied in this work, SOA evaporation behavior is nearly size-independent and does not follow the evaporation kinetics of liquid droplets, in sharp contrast with model assumptions. The findings about SOA phase, evaporation rates, and the importance of spectator gases and aging all indicate that there is need to reformulate the way SOA formation and evaporation are treated by models.

Evaporative water loss, relative water economy and evaporative partitioning of a heterothermic marsupial, the monito del monte (Dromiciops gliroides).

PubMed

Withers, Philip C; Cooper, Christine E; Nespolo, Roberto F

2012-08-15

We examine here evaporative water loss, economy and partitioning at ambient temperatures from 14 to 33°C for the monito del monte (Dromiciops gliroides), a microbiotheriid marsupial found only in temperate rainforests of Chile. The monito's standard evaporative water loss (2.58 mg g(-1) h(-1) at 30°C) was typical for a marsupial of its body mass and phylogenetic position. Evaporative water loss was independent of air temperature below thermoneutrality, but enhanced evaporative water loss and hyperthermia were the primary thermal responses above the thermoneutral zone. Non-invasive partitioning of total evaporative water loss indicated that respiratory loss accounted for 59-77% of the total, with no change in respiratory loss with ambient temperature, but a small change in cutaneous loss below thermoneutrality and an increase in cutaneous loss in and above thermoneutrality. Relative water economy (metabolic water production/evaporative water loss) increased at low ambient temperatures, with a point of relative water economy of 15.4°C. Thermolability had little effect on relative water economy, but conferred substantial energy savings at low ambient temperatures. Torpor reduced total evaporative water loss to as little as 21% of normothermic values, but relative water economy during torpor was poor even at low ambient temperatures because of the relatively greater reduction in metabolic water production than in evaporative water loss. The poor water economy of the monito during torpor suggests that negative water balance may explain why hibernators periodically arouse to normothermia, to obtain water by drinking or via an improved water economy.

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.

Evaporation kinetics and phase of laboratory and ambient secondary organic aerosol

PubMed Central

Vaden, Timothy D.; Imre, Dan; Beránek, Josef; Shrivastava, Manish; Zelenyuk, Alla

2011-01-01

Field measurements of secondary organic aerosol (SOA) find significantly higher mass loads than predicted by models, sparking intense effort focused on finding additional SOA sources but leaving the fundamental assumptions used by models unchallenged. Current air-quality models use absorptive partitioning theory assuming SOA particles are liquid droplets, forming 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 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. We found that even when gas phase organics are removed, it takes ∼24 h for pure α-pinene SOA particles to evaporate 75% of their mass, which is in sharp contrast to the ∼10 min time scale predicted by current kinetic models. Adsorption of “spectator” organic vapors during SOA formation, and aging of these coated SOA particles, dramatically reduced the evaporation rate, and in some cases nearly stopped it. Ambient SOA was found to exhibit evaporation behavior very similar to that of laboratory-generated coated and aged SOA. For all cases studied in this work, SOA evaporation behavior is nearly size-independent and does not follow the evaporation kinetics of liquid droplets, in sharp contrast with model assumptions. The findings about SOA phase, evaporation rates, and the importance of spectator gases and aging all indicate that there is need to reformulate the way SOA formation and evaporation are treated by models. PMID:21262848

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.

Expressions for the Evaporation and Condensation Coefficients in the Hertz-Knudsen Relation.

PubMed

Persad, Aaron H; Ward, Charles A

2016-07-27

Although the Hertz-Knudsen (HK) relation is often used to correlate evaporation data, the relation contains two empirical parameters (the evaporation and condensation coefficients) that have inexplicably been found to span 3 orders of magnitude. Explicit expressions for these coefficients have yet to be determined. This review will examine sources of error in the HK relation that have led to the coefficients' scatter. Through an examination of theoretical, experimental, and molecular dynamics simulation studies of evaporation, this review will show that the HK relation is incomplete, since it is missing an important physical concept: the coupling between the vapor and liquid phases during evaporation. The review also examines a modified HK relation, obtained from the quantum-mechanically based statistical rate theory (SRT) expression for the evaporation flux and applying a limit to it in which the thermal energy is dominant. Explicit expressions for the evaporation and condensation coefficients are defined in this limit, with the surprising result that the coefficients are not bounded by unity. An examination is made with 127 reported evaporation experiments of water and of ethanol, leading to a new physical interpretation of the coefficients. The review concludes by showing how seemingly small simplifications, such as assuming thermal equilibrium across the liquid-vapor interface during evaporation, can lead to the erroneous predictions from the HK relation that have been reported in the literature.

Evaporation from bare ground with different water-table depths based on an in-situ experiment in Ordos Plateau, China

NASA Astrophysics Data System (ADS)

Zhang, Zaiyong; Wang, Wenke; Wang, Zhoufeng; Chen, Li; Gong, Chengcheng

2018-03-01

The dynamic processes of ground evaporation are complex and are related to a multitude of factors such as meteorological influences, water-table depth, and materials in the unsaturated zone. To investigate ground evaporation from a homogeneous unsaturated zone, an in-situ experiment was conducted in Ordos Plateau of China. Two water-table depths were chosen to explore the water movement in the unsaturated zone and ground evaporation. Based on the experimental and calculated results, it was revealed that (1) bare ground evaporation is an atmospheric-limited stage for the case of water-table depth being close to the capillary height; (2) the bare ground evaporation is a water-storage-limited stage for the case of water-table depth being beyond the capillary height; (3) groundwater has little effect on ground-surface evaporation when the water depth is larger than the capillary height; and (4) ground evaporation is greater at nighttime than that during the daytime; and (5) a liquid-vapor interaction zone at nearly 20 cm depth is found, in which there exists a downward vapor flux on sunny days, leading to an increasing trend of soil moisture between 09:00 to 17:00; the maximum value is reached at midday. The results of this investigation are useful to further understand the dynamic processes of ground evaporation in arid areas.

Increasing the Efficiency of a Thermoelectric Generator Using an Evaporative Cooling System

NASA Astrophysics Data System (ADS)

Boonyasri, M.; Jamradloedluk, J.; Lertsatitthanakorn, C.; Therdyothin, A.; Soponronnarit, S.

2017-05-01

A system for reducing heat from the cold side of a thermoelectric (TE) power generator, based on the principle of evaporative cooling, is presented. An evaporative cooling system could increase the conversion efficiency of a TE generator. To this end, two sets of TE generators were constructed. Both TE generators were composed of five TE power modules. The cold and hot sides of the TE modules were fixed to rectangular fin heat sinks. The hot side heat sinks were inserted in a hot gas duct. The cold side of one set was cooled by the cooling air from a counter flow evaporative cooling system, whereas the other set was cooled by the parallel flow evaporative cooling system. The counter flow pattern had better performance than the parallel flow pattern. A comparison between the TE generator with and without an evaporative cooling system was made. Experimental results show that the power output increased by using the evaporative cooling system. This can significantly increase the TE conversion efficiency. The evaporative cooling system increased the power output of the TE generator from 22.9 W of ambient air flowing through the heat sinks to 28.6 W at the hot gas temperature of 350°C (an increase of about 24.8%). The present study shows the promising potential of using TE generators with evaporative cooling for waste heat recovery.

Pulse thermal energy transport/storage system

DOEpatents

Weislogel, Mark M.

1992-07-07

A pulse-thermal pump having a novel fluid flow wherein heat admitted to a closed system raises the pressure in a closed evaporator chamber while another interconnected evaporator chamber remains open. This creates a large pressure differential, and at a predetermined pressure the closed evaporator is opened and the opened evaporator is closed. This difference in pressure initiates fluid flow in the system.

Enhancing mercury removal across air pollution control devices for coal-fired power plants by desulfurization wastewater evaporation.

PubMed

Bin, Hu; Yang, Yi; Cai, Liang; Yang, Linjun; Roszak, Szczepan

2017-10-09

Desulfurization wastewater evaporation technology is used to enhance the removal of gaseous mercury (Hg) in conventional air pollution control devices (APCDs) for coal-fired power plants. Studies have affirmed that gaseous Hg is oxidized and removed by selective catalytic reduction (SCR), an electrostatic precipitator (ESP) and wet flue gas desulfurization (WFGD) in a coal-fired thermal experiment platform with WFGD wastewater evaporation. Effects of desulfurization wastewater evaporation position, evaporation temperature and chlorine ion concentration on Hg oxidation were studied as well. The Hg 0 oxidation efficiency was increased ranging from 30% to 60%, and the gaseous Hg removal efficiency was 62.16% in APCDs when wastewater evaporated before SCR. However, the Hg 0 oxidation efficiency was 18.99% and the gaseous Hg removal efficiency was 40.19% in APCDs when wastewater evaporated before ESP. The results show that WFGD wastewater evaporation before SCR is beneficial to improve the efficiency of Hg oxidized and removed in APCDs. Because Hg 2+ can be easily removed in ACPDs and WFGD wastewater in power plants is enriched with chlorine ions, this method realizes WFGD wastewater zero discharge and simultaneously enhances Hg removal in APCDs.

Effect of Mg or Ag addition on the evaporation field of Al.

PubMed

Aruga, Yasuhiro; Nako, Hidenori; Tsuneishi, Hidemasa; Hasegawa, Yuki; Tao, Hiroaki; Ichihara, Chikara; Serizawa, Ai

2013-09-01

It is known that the distribution of the charge-states as well as the evaporation field shift to higher values as the specimen temperature is decreased at a constant rate of evaporation. This study has explored the effect of Mg or Ag addition on the evaporation field of Al in terms of the charge state distribution of the field evaporated Al ions. The fractional abundance of Al(2+) ions with respect to the total Al ions in Al-Mg alloy is lower than that in pure Al, whereas it shows higher level in the Al-Ag alloy at lower temperatures. The temperature dependence of the fractional abundance of Al(2+) ions has been also confirmed, suggesting that Al atoms in the Al-Mg alloy need lower evaporation field, while higher field is necessary to evaporate Al atoms in the Al-Ag alloy, compared with pure Al. This tendency is in agreement with that of the evaporation fields estimated theoretically by means of measurements of the work function and calculations of the binding energy of the pure Al, Al-Mg and Al-Ag alloys. Copyright © 2012 Elsevier B.V. All rights reserved.

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

Evaporation heat transfer of carbon dioxide at low temperature inside a horizontal smooth tube

NASA Astrophysics Data System (ADS)

Yoon, Jung-In; Son, Chang-Hyo; Jung, Suk-Ho; Jeon, Min-Ju; Yang, Dong-Il

2017-05-01

In this paper, the evaporation heat transfer coefficient of carbon dioxide at low temperature of -30 to -20 °C in a horizontal smooth tube was investigated experimentally. The test devices consist of mass flowmeter, pre-heater, magnetic gear pump, test section (evaporator), condenser and liquid receiver. Test section is made of cooper tube. Inner and outer diameter of the test section is 8 and 9.52 mm, respectively. The experiment is conducted at mass fluxes from 100 to 300 kg/m2 s, saturation temperature from -30 to -20 °C. The main results are summarized as follows: In case that the mass flux of carbon dioxide is 100 kg/m2 s, the evaporation heat transfer coefficient is almost constant regardless of vapor quality. In case of 200 and 300 kg/m2 s, the evaporation heat transfer coefficient increases steadily with increasing vapor quality. For the same mass flux, the evaporation heat transfer coefficient increases as the evaporation temperature of the refrigerant decreases. In comparison of heat transfer correlations with the experimental result, the evaporation heat transfer correlations do not predict them exactly. Therefore, more accurate heat transfer correlation than the previous one is required.

The desorptivity model of bulk soil-water evaporation

NASA Technical Reports Server (NTRS)

Clapp, R. B.

1983-01-01

Available models of bulk evaporation from a bare-surfaced soil are difficult to apply to field conditions where evaporation is complicated by two main factors: rate-limiting climatic conditions and redistribution of soil moisture following infiltration. Both factors are included in the "desorptivity model', wherein the evaporation rate during the second stage (the soil-limiting stage) of evaporation is related to the desorptivity parameter, A. Analytical approximations for A are presented. The approximations are independent of the surface soil moisture. However, calculations using the approximations indicate that both soil texture and soil moisture content at depth significantly affect A. Because the moisture content at depth decreases in time during redistribution, it follows that the A parameter also changes with time. Consequently, a method to calculate a representative value of A was developed. When applied to field data, the desorptivity model estimated cumulative evaporation well. The model is easy to calculate, but its usefulness is limited because it requires an independent estimate of the time of transition between the first and second stages of evaporation. The model shows that bulk evaporation after the transition to the second stage is largely independent of climatic conditions.

Effects of seawater flow rate and evaporation temperature on performance of Sherbet type ice making machine

NASA Astrophysics Data System (ADS)

Son, C. H.; Yoon, J. I.; Choi, K. H.; Lee, H. K.; Lee, K. S.; Moon, C. G.; Seol, S. H.

2018-01-01

This study analyzes performance of the sherbet type ice making machine using seawater with respect to seawater volumetric flow rate, evaporation temperature, cooling water inlet and seawater inlet temperature as variables. Cooling water inlet and seawater inlet temperature are set considering average temperature of South Korea and the equator regions. Volumetric flow rate of seawater range is 0.75-1.75 LPM in this experiment. The results obtained from the experiment are as follows. As the seawater volumetric flow rate increases, or seawater inlet temperature increases, evaporation capacity tends to increase. At the point of seawater inlet temperature of 27°C and volumetric flow rate of 1.0LPM, evaporation capacity is over 2kW. On the other hand, results of COP change tendency are different from that of evaporation capacity. It appears to increase until volumetric flow rate of 1.0LPM, and decrease gradually from volumetric flow rate of 1.5LPM. This is due to the increase of compressor work to keep the evaporation pressure in accordance with the temperature of heat source. As the evaporation temperature decreases from -8 to -15°C, the evaporation capacity increases, but the COP decreases.

A refinement of the combination equations for evaporation

USGS Publications Warehouse

Milly, P.C.D.

1991-01-01

Most combination equations for evaporation rely on a linear expansion of the saturation vapor-pressure curve around the air temperature. Because the temperature at the surface may differ from this temperature by several degrees, and because the saturation vapor-pressure curve is nonlinear, this approximation leads to a certain degree of error in those evaporation equations. It is possible, however, to introduce higher-order polynomial approximations for the saturation vapor-pressure curve and to derive a family of explicit equations for evaporation, having any desired degree of accuracy. Under the linear approximation, the new family of equations for evaporation reduces, in particular cases, to the combination equations of H. L. Penman (Natural evaporation from open water, bare soil and grass, Proc. R. Soc. London, Ser. A193, 120-145, 1948) and of subsequent workers. Comparison of the linear and quadratic approximations leads to a simple approximate expression for the error associated with the linear case. Equations based on the conventional linear approximation consistently underestimate evaporation, sometimes by a substantial amount. ?? 1991 Kluwer Academic Publishers.

Potential for natural evaporation as a reliable renewable energy resource

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

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

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 in this paper 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. Wemore » 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.« less

Snap evaporation of droplets on smooth topographies.

PubMed

Wells, Gary G; Ruiz-Gutiérrez, Élfego; Le Lirzin, Youen; Nourry, Anthony; Orme, Bethany V; Pradas, Marc; Ledesma-Aguilar, Rodrigo

2018-04-11

Droplet evaporation on solid surfaces is important in many applications including printing, micro-patterning and cooling. While seemingly simple, the configuration of evaporating droplets on solids is difficult to predict and control. This is because evaporation typically proceeds as a "stick-slip" sequence-a combination of pinning and de-pinning events dominated by static friction or "pinning", caused by microscopic surface roughness. Here we show how smooth, pinning-free, solid surfaces of non-planar topography promote a different process called snap evaporation. During snap evaporation a droplet follows a reproducible sequence of configurations, consisting of a quasi-static phase-change controlled by mass diffusion interrupted by out-of-equilibrium snaps. Snaps are triggered by bifurcations of the equilibrium droplet shape mediated by the underlying non-planar solid. Because the evolution of droplets during snap evaporation is controlled by a smooth topography, and not by surface roughness, our ideas can inspire programmable surfaces that manage liquids in heat- and mass-transfer applications.

Method and apparatus for flash evaporation of liquids

DOEpatents

Bharathan, Desikan

1984-01-01

A vertical tube flash evaporator for introducing a superheated liquid into a flash evaporation chamber includes a vertical inlet tube with a flared diffuser portion at its upper outlet end. A plurality of annular screens are positioned in axially spaced-apart relation to each other around the periphery of the vertical tube and below the diffuser portion thereof. The screens are preferably curved upward in a cup-shaped configuration. These flash evaporators are shown in an ocean thermal energy conversion unit designed for generating electric power from differential temperature gradients in ocean water. The method of use of the flash evaporators of this invention includes flowing liquid upwardly through the vertical tube into the diffuser where initial expansion and boiling occurs quite violently and explosively. Unvaporized liquid sheets and drops collide with each other to enhance surface renewal and evaporation properties, and liquid flowing over the outlet end of the diffuser falls onto the curved screens for further surface renewal and evaporation.

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.

Water droplet evaporation from sticky superhydrophobic surfaces

NASA Astrophysics Data System (ADS)

Lee, Moonchan; Kim, Wuseok; Lee, Sanghee; Baek, Seunghyeon; Yong, Kijung; Jeon, Sangmin

2017-07-01

The evaporation dynamics of water from sticky superhydrophobic surfaces was investigated using a quartz crystal microresonator and an optical microscope. Anodic aluminum oxide (AAO) layers with different pore sizes were directly fabricated onto quartz crystal substrates and hydrophobized via chemical modification. The resulting AAO layers exhibited hydrophobic or superhydrophobic characteristics with strong adhesion to water due to the presence of sealed air pockets inside the nanopores. After placing a water droplet on the AAO membranes, variations in the resonance frequency and Q-factor were measured throughout the evaporation process, which were related to changes in mass and viscous damping, respectively. It was found that droplet evaporation from a sticky superhydrophobic surface followed a constant contact radius (CCR) mode in the early stage of evaporation and a combination of CCR and constant contact angle modes without a Cassie-Wenzel transition in the final stage. Furthermore, AAO membranes with larger pore sizes exhibited longer evaporation times, which were attributed to evaporative cooling at the droplet interface.

Scaling up nanoscale water-driven energy conversion into evaporation-driven engines and generators

DOE PAGES

Chen, Xi; Goodnight, Davis; Gao, Zhenghan; ...

2015-06-16

Evaporation is a ubiquitous phenomenon in the natural environment and a dominant form of energy transfer in the Earth’s climate. Engineered systems rarely, if ever, use evaporation as a source of energy, despite myriad examples of such adaptations in the biological world. In this work, we report evaporation-driven engines that can power common tasks like locomotion and electricity generation. These engines start and run autonomously when placed at air–water interfaces. They generate rotary and piston-like linear motion using specially designed, biologically based artificial muscles responsive to moisture fluctuations. Using these engines, we demonstrate an electricity generator that rests on watermore » while harvesting its evaporation to power a light source, and a miniature car (weighing 0.1 kg) that moves forward as the water in the car evaporates. Evaporation-driven engines may find applications in powering robotic systems, sensors, devices and machinery that function in the natural environment.« less

Testing of a Miniature Loop Heat Pipe with Multiple Evaporators and Multiple Condensers for Space Applications

NASA Technical Reports Server (NTRS)

Nagano, Hosei; Ku, Jentung

2006-01-01

Thermal performance of a miniature loop heat pipe (MLHP) with two evaporators and two condensers is described. A comprehensive test program, including start-up, high power, low power, power cycle, and sink temperature cycle tests, has been executed at NASA Goddard Space Flight Center for potential space applications. Experimental data showed that the loop could start with heat loads as low as 2W. The loop operated stably with even and uneven evaporator heat loads, and even and uneven condenser sink temperatures. Heat load sharing between the two evaporators was also successfully demonstrated. The loop had a heat transport capability of l00W to 120W, and could recover from a dry-out by reducing the heat load to evaporators. Low power test results showed the loop could work stably for heat loads as low as 1 W to each evaporator. Excellent adaptability of the MLHP to rapid changes of evaporator power and sink temperature were also demonstrated.

Role of ocean evaporation in California droughts and floods

NASA Astrophysics Data System (ADS)

Wei, Jiangfeng; Jin, Qinjian; Yang, Zong-Liang; Dirmeyer, Paul A.

2016-06-01

Since winter 2011, a record-breaking drought has occurred in California. Studies found that the drought is mainly caused by a persistent high-pressure system off the U.S. West Coast, which is linked to Pacific sea surface temperature anomalies. The water cycles associated with the droughts and floods are still not clearly understood. Here we show that the atmospheric circulation off the West Coast not only controls the atmospheric convergence and formation of precipitation but also largely determines surface wind speed, which further affects the evaporation over the eastern North Pacific, the major evaporative moisture source for California precipitation. Because of this mechanism, the ocean evaporation over the eastern North Pacific has been reduced during the recent drought. However, the ocean evaporation anomalies have little direct influence on California precipitation, especially during dry years, mainly because of their weak amplitudes. The California droughts cannot be readily attributed to the reduced ocean evaporation. The association between increased Pacific evaporation and floods over California is somewhat stronger.

Method and apparatus for flash evaporation of liquids

DOEpatents

Bharathan, D.

1984-01-01

A vertical tube flash evaporator for introducing a super-heated liquid into a flash evaporation chamber includes a vertical inlet tube with a flared diffuser portion at its upper outlet end. A plurality of annular screens are positioned in axially spaced-apart relation to each other around the periphery of the vertical tube and below the diffuser portion thereof. The screens are preferably curved upward in a cup-shaped configuration. These flash evaporators are shown in an ocean thermal energy conversion unit designed for generating electric power from differential temperature gradients in ocean water. The method of use of the flash evaporators of this invention includes flowing liquid upwardly through the vertical tube into the diffuser where initial expansion and boiling occurs quite violently and explosively. Unvaporized liquid sheets and drops collide with each other to enhance surface renewal and evaporation properties, and liquid flowing over the outlet end of the diffuser falls onto the curved screens for further surface renewal and evaporation.

Scaling up nanoscale water-driven energy conversion into evaporation-driven engines and generators

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

Chen, Xi; Goodnight, Davis; Gao, Zhenghan

Evaporation is a ubiquitous phenomenon in the natural environment and a dominant form of energy transfer in the Earth’s climate. Engineered systems rarely, if ever, use evaporation as a source of energy, despite myriad examples of such adaptations in the biological world. In this work, we report evaporation-driven engines that can power common tasks like locomotion and electricity generation. These engines start and run autonomously when placed at air–water interfaces. They generate rotary and piston-like linear motion using specially designed, biologically based artificial muscles responsive to moisture fluctuations. Using these engines, we demonstrate an electricity generator that rests on watermore » while harvesting its evaporation to power a light source, and a miniature car (weighing 0.1 kg) that moves forward as the water in the car evaporates. Evaporation-driven engines may find applications in powering robotic systems, sensors, devices and machinery that function in the natural environment.« less

Molecular dynamics study on the microscopic details of the evaporation of water.

PubMed

Mason, Phillip E

2011-06-16

Molecular dynamics simulations were conducted on a drop of water (containing 4890 TIP3P waters) at 350 K. About 70 evaporation events were found and characterized in enough detail to determine significant patterns relating to the mechanism of evaporation. It was found that in almost all evaporation events that a single, high-energy state immediately preceded the evaporation event. In ∼50% of the cases, this high-energy state involved a short oxygen-oxygen distance, suggesting a van der Waals collision, whereas in the remaining cases, a short hydrogen-hydrogen distance was found, suggesting an electrostatic "collision". Of the high-energy states that led to evaporation, about half occurred when the coordination number of water was 1, and about half, when the coordination number was 2. It was found that the 1-coordinated waters (∼1% of the surface waters) and 2-coordinated waters (6% of the surface waters) were responsible for almost all the evaporation events. © 2011 American Chemical Society

Estimating soil water evaporation using radar measurements

NASA Technical Reports Server (NTRS)

Sadeghi, Ali M.; Scott, H. D.; Waite, W. P.; Asrar, G.

1988-01-01

Field studies were conducted to evaluate the application of radar reflectivity as compared with the shortwave reflectivity (albedo) used in the Idso-Jackson equation for the estimation of daily evaporation under overcast sky and subhumid climatic conditions. Soil water content, water potential, shortwave and radar reflectivity, and soil and air temperatures were monitored during three soil drying cycles. The data from each cycle were used to calculate daily evaporation from the Idso-Jackson equation and from two other standard methods, the modified Penman and plane of zero-flux. All three methods resulted in similar estimates of evaporation under clear sky conditions; however, under overcast sky conditions, evaporation fluxes computed from the Idso-Jackson equation were consistently lower than the other two methods. The shortwave albedo values in the Idso-Jackson equation were then replaced with radar reflectivities and a new set of total daily evaporation fluxes were calculated. This resulted in a significant improvement in computed soil evaporation fluxes from the Idso-Jackson equation, and a better agreement between the three methods under overcast sky conditions.

Urban evaporation rates for water-permeable pavements.

PubMed

Starke, P; Göbel, P; Coldewey, W G

2010-01-01

In urban areas the natural water balance is disturbed. Infiltration and evaporation are reduced, resulting in a high surface runoff and a typical city climate, which can lead to floods and damages. Water-permeable pavements have a high infiltration rate that reduces surface runoff by increasing the groundwater recharge. The high water retention capacity of the street body of up to 51 l/m(2) and its connection via pores to the surface lead to higher evaporation rates than impermeable surfaces. A comparison of these two kinds of pavements shows a 16% increase in evaporation levels of water-permeable pavements. Furthermore, the evaporation from impermeable pavements is linked directly to rain events due to fast-drying surfaces. Water-permeable pavements show a more evenly distributed evaporation after a rain event. Cooling effects by evaporative heat loss can improve the city climate even several days after rain events. On a large scale use, uncomfortable weather like sultriness or dry heat can be prevented and the urban water balance can be attenuated towards the natural.

Enhancing Localized Evaporation through Separated Light Absorbing Centers and Scattering Centers

PubMed Central

Zhao, Dengwu; Duan, Haoze; Yu, Shengtao; Zhang, Yao; He, Jiaqing; Quan, Xiaojun; Tao, Peng; Shang, Wen; Wu, Jianbo; Song, Chengyi; Deng, Tao

2015-01-01

This report investigates the enhancement of localized evaporation via separated light absorbing particles (plasmonic absorbers) and scattering particles (polystyrene nanoparticles). Evaporation has been considered as one of the most important phase-change processes in modern industries. To improve the efficiency of evaporation, one of the most feasible methods is to localize heat at the top water layer rather than heating the bulk water. In this work, the mixture of purely light absorptive plasmonic nanostructures such as gold nanoparticles and purely scattering particles (polystyrene nanoparticles) are employed to confine the incident light at the top of the solution and convert light to heat. Different concentrations of both the light absorbing centers and the light scattering centers were evaluated and the evaporation performance can be largely enhanced with the balance between absorbing centers and scattering centers. The findings in this study not only provide a new way to improve evaporation efficiency in plasmonic particle-based solution, but also shed lights on the design of new solar-driven localized evaporation systems. PMID:26606898

Potential for natural evaporation as a reliable renewable energy resource

DOE PAGES

Cavusoglu, Ahmet-Hamdi; Chen, Xi; Gentine, Pierre; ...

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 in this paper 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. Wemore » 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.« less

Evaporation-Triggered Segregation of Sessile Binary Droplets.

PubMed

Li, Yaxing; Lv, Pengyu; Diddens, Christian; Tan, Huanshu; Wijshoff, Herman; Versluis, Michel; Lohse, Detlef

2018-06-01

Droplet evaporation of multicomponent droplets is essential for various physiochemical applications, e.g., in inkjet printing, spray cooling, and microfabrication. In this work, we observe and study the phase segregation of an evaporating sessile binary droplet, consisting of a miscible mixture of water and a surfactantlike liquid (1,2-hexanediol). The phase segregation (i.e., demixing) leads to a reduced water evaporation rate of the droplet, and eventually the evaporation process ceases due to shielding of the water by the nonvolatile 1,2-hexanediol. Visualizations of the flow field by particle image velocimetry and numerical simulations reveal that the timescale of water evaporation at the droplet rim is faster than that of the Marangoni flow, which originates from the surface tension difference between water and 1,2-hexanediol, eventually leading to segregation.

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.

Effect of two sweating simulation methods on clothing evaporative resistance in a so-called isothermal condition.

PubMed

Lu, Yehu; Wang, Faming; Peng, Hui

2016-07-01

The effect of sweating simulation methods on clothing evaporative resistance was investigated in a so-called isothermal condition (T manikin  = T a  = T r ). Two sweating simulation methods, namely, the pre-wetted fabric "skin" (PW) and the water supplied sweating (WS), were applied to determine clothing evaporative resistance on a "Newton" thermal manikin. Results indicated that the clothing evaporative resistance determined by the WS method was significantly lower than that measured by the PW method. In addition, the evaporative resistances measured by the two methods were correlated and exhibited a linear relationship. Validation experiments demonstrated that the empirical regression equation showed highly acceptable estimations. The study contributes to improving the accuracy of measurements of clothing evaporative resistance by means of a sweating manikin.

Electron beam assisted field evaporation of insulating nanowires/tubes

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

Blanchard, N. P., E-mail: nicholas.blanchard@univ-lyon1.fr; Niguès, A.; Choueib, M.

2015-05-11

We demonstrate field evaporation of insulating materials, specifically BN nanotubes and undoped Si nanowires, assisted by a convergent electron beam. Electron irradiation leads to positive charging at the nano-object's apex and to an important increase of the local electric field thus inducing field evaporation. Experiments performed both in a transmission electron microscope and in a scanning electron microscope are presented. This technique permits the selective evaporation of individual nanowires in complex materials. Electron assisted field evaporation could be an interesting alternative or complementary to laser induced field desorption used in atom probe tomography of insulating materials.

Effect of evaporative surface cooling on thermographic assessment of burn depth

NASA Technical Reports Server (NTRS)

Anselmo, V. J.; Zawacki, B. E.

1977-01-01

Differences in surface temperature between evaporating and nonevaporating, partial- and full-thickness burn injuries were studied in 20 male, white guinea pigs. Evaporative cooling can disguise the temperature differential of the partial-thickness injury and lead to a false full-thickness diagnosis. A full-thickness burn with blister intact may retain enough heat to result in a false partial-thickness diagnosis. By the fourth postburn day, formation of a dry eschar may allow a surface temperature measurement without the complication of differential evaporation. For earlier use of thermographic information, evaporation effects must be accounted for or eliminated.

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.

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.

Modelling sub-daily evaporation from a small reservoir.

NASA Astrophysics Data System (ADS)

McGloin, Ryan; McGowan, Hamish; McJannet, David; Burn, Stewart

2013-04-01

Accurate quantification of evaporation from small water storages is essential for water management and is also required as input in some regional hydrological and meteorological models. Global estimates of the number of small storages or lakes (< 0.1 kilometers) are estimated to be in the order of 300 million (Downing et al., 2006). However, direct evaporation measurements at small reservoirs using the eddy covariance or scintillometry techniques have been limited due to their expensive and complex nature. To correctly represent the effect that small water bodies have on the regional hydrometeorology, reliable estimates of sub-daily evaporation are necessary. However, evaporation modelling studies at small reservoirs have so far been limited to quantifying daily estimates. In order to ascertain suitable methods for accurately modelling hourly evaporation from a small reservoir, this study compares evaporation results measured by the eddy covariance method at a small reservoir in southeast Queensland, Australia, to results from several modelling approaches using both over-water and land-based meteorological measurements. Accurate predictions of hourly evaporation were obtained by a simple theoretical mass transfer model requiring only over-water measurements of wind speed, humidity and water surface temperature. An evaporation model that was recently developed for use in small reservoir environments by Granger and Hedstrom (2011), appeared to overestimate the impact stability had on evaporation. While evaporation predictions made by the 1-dimensional hydrodynamics model, DYRESM (Dynamic Reservoir Simulation Model) (Imberger and Patterson, 1981), showed reasonable agreement with measured values. DYRESM did not show any substantial improvement in evaporation prediction when inflows and out flows were included and only a slighter better correlation was shown when over-water meteorological measurements were used in place of land-based measurements. Downing, J. A., Y. T. Prairie, J. J. Cole, C. M. Duarte, L. J. Tranvik, R. G. Striegl, W. H. McDowell, P. Kortelainen, N. F. Caraco, J. M. Melack and J. J. Middelburg (2006), The global abundance and size distribution of lakes, ponds, and impoundments, Limnology and Oceanography, 51, 2388-2397. Granger, R.J. and N. Hedstrom (2011), Modelling hourly rates of evaporation from small lakes, Hydrological and Earth System Sciences, 15, doi:10.5194/hess-15-267-2011. Imberger, J. and J.C. Patterson (1981), Dynamic Reservoir Simulation Model - DYRESM: 5, In: Transport Models for Inland and Coastal Waters. H.B. Fischer (Ed.). Academic Press, New York, 310-361.

Well logging evaporative thermal protection system

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

Lamers, M.D.; Martelli, V.P.

1981-02-03

An evaporative thermal protection system for use in hostile environment well logging applications, the system including a downhole thermal protection cartridge disposed within a well logging sonde or tool to keep a payload such as sensors and support electronics cool, the cartridge carrying either an active evaporative system for refrigeration or a passive evaporative system, both exhausting to the surface through an armored flexible fluidic communication mechanical cable.

The influence of the surface composition of mixed monolayer films on the evaporation coefficient of water.

PubMed

Miles, Rachael E H; Davies, James F; Reid, Jonathan P

2016-07-20

We explore the dependence of the evaporation coefficient of water from aqueous droplets on the composition of a surface film, considering in particular the influence of monolayer mixed component films on the evaporative mass flux. Measurements with binary component films formed from long chain alcohols, specifically tridecanol (C13H27OH) and pentadecanol (C15H31OH), and tetradecanol (C14H29OH) and hexadecanol (C16H33OH), show that the evaporation coefficient is dependent on the mole fractions of the two components forming the monolayer film. Immediately at the point of film formation and commensurate reduction in droplet evaporation rate, the evaporation coefficient is equal to a mole fraction weighted average of the evaporation coefficients through the equivalent single component films. As a droplet continues to diminish in surface area with continued loss of water, the more-soluble, shorter alkyl chain component preferentially partitions into the droplet bulk with the evaporation coefficient tending towards that through a single component film formed simply from the less-soluble, longer chain alcohol. We also show that the addition of a long chain alcohol to an aqueous-sucrose droplet can facilitate control over the degree of dehydration achieved during evaporation. After undergoing rapid gas-phase diffusion limited water evaporation, binary aqueous-sucrose droplets show a continued slow evaporative flux that is limited by slow diffusional mass transport within the particle bulk due to the rapidly increasing particle viscosity and strong concentration gradients that are established. The addition of a long chain alcohol to the droplet is shown to slow the initial rate of water loss, leading to a droplet composition that remains more homogeneous for a longer period of time. When the sucrose concentration has achieved a sufficiently high value, and the diffusion constant of water has decreased accordingly so that bulk phase diffusion arrest occurs in the monolayer coated particle, the droplet is found to have lost a greater proportion of its initial water content. A greater degree of slowing in the evaporative flux can be achieved by increasing the chain length of the surface active alcohol, leading to a greater degree of dehydration.

Contrasting roles of interception and transpiration in the hydrological cycle - Part 2: Moisture recycling

NASA Astrophysics Data System (ADS)

van der Ent, R. J.; Wang-Erlandsson, L.; Keys, P. W.; Savenije, H. H. G.

2014-12-01

The contribution of land evaporation to local and remote precipitation (i.e. moisture recycling) is of significant importance to sustain water resources and ecosystems. But how important are different evaporation components in sustaining precipitation? This is the first paper to present moisture recycling metrics for partitioned evaporation. In the companion paper Wang-Erlandsson et al. (2014) (hereafter Part 1), evaporation was partitioned into vegetation interception, floor interception, soil moisture evaporation and open-water evaporation (constituting the direct, purely physical fluxes, largely dominated by interception), and transpiration (delayed, biophysical flux). Here, we track these components forward as well as backward in time. We also include age tracers to study the atmospheric residence times of these evaporation components. We present a new image of the global hydrological cycle that includes quantification of partitioned evaporation and moisture recycling as well as the atmospheric residence times of all fluxes. We demonstrate that evaporated interception is more likely to return as precipitation on land than transpired water. On average, direct evaporation (essentially interception) is found to have an atmospheric residence time of 8 days, while transpiration typically resides for 9 days in the atmosphere. The process scale over which evaporation recycles is more local for interception compared to transpiration; thus interception generally precipitates closer to its evaporative source than transpiration, which is particularly pronounced outside the tropics. We conclude that interception mainly works as an intensifier of the local hydrological cycle during wet spells and wet seasons. On the other hand, transpiration remains active during dry spells and dry seasons and is transported over much larger distances downwind, where it can act as a significant source of moisture. Thus, as various land-use types can differ considerably in their partitioning between interception and transpiration, our results stress that land-use changes (e.g. forest-to-cropland conversion) do not only affect the magnitude of moisture recycling, but could also influence the moisture recycling patterns and lead to a redistribution of water resources. As such, this research highlights that land-use changes can have complex effects on the atmospheric branch of the hydrological cycle.

Molecular characterization and volatility evolution of α-pinene ozonolysis SOA during isothermal evaporations

NASA Astrophysics Data System (ADS)

D'Ambro, E.; Schobesberger, S.; Lopez-Hilfiker, F.; Shilling, J. E.; Lee, B. H.; Thornton, J. A.

2017-12-01

α-Pinene (C10H16), the most abundantly emitted monoterpene, is a large contributor to global biogenic secondary organic aerosol (SOA) budgets due to its high SOA yields upon oxidation. We probe the volatility and evaporation behavior upon dilution of α-pinene SOA to further our understanding of the nascent volatility distribution, viscosity, and how these evolve in time absent photochemical oxidation. We present molecular composition measurements of the gas and particle phases of α-pinene ozonolysis SOA formed at 0% and 50% relative humidity (RH), followed by room-temperature evaporation in ultra-high purity N2 humidified to 20-90% RH. Experiments were performed in the Pacific Northwest National Laboratory 10.6 m3 and the University of Washington 0.7 m3 environmental chambers utilizing a Filter Inlet for Gases and AEROsols (FIGAERO) coupled to a high-resolution time of flight chemical ionization mass spectrometer utilizing iodide adduct ionization. We present novel insights into the total mass that evaporates as a function of time from 10 min to 24 hours without heating, the molecular speciation of the evaporate, as well as the effective volatility and composition of the SOA mass remaining. Consistent with previous studies, we find two stages of evaporation: a rapid loss of a large portion of the total signal over the course of ≤3 hours, followed by a stage of much slower evaporation over the proceeding 21 hours. Varying the RH of formation effects evaporation rate on timescales ≤3 hours, however the mass fraction remaining after 24 hours converges to 30-50% under all formation and evaporation RHs. We simulate the evaporation behavior and remaining fractions desorbed via temperature programmed thermal desorption to derive effective saturation vapor concentrations, mass accommodation coefficients, and rates of chemical evolution producing both higher and lower volatility components during the evaporation time period.

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.

Evaluation of tear evaporation from ocular surface by functional infrared thermography.

PubMed

Tan, Jen-Hong; Ng, E Y K; Acharya, U Rajendra

2010-11-01

A novel technique was developed to measure tear evaporation and monitor its variation with respect to time, for the studying of ocular physiology based on dynamic functional infrared thermography and the first law of thermodynamics using the measured ocular surface temperatures (OSTs). This is a noninvasive, noncontact temperature measuring method that is widely applied in the field of biomedicine. A simple method based on the ocular thermal data was proposed to measure the rate of tear evaporation. The OST of 60 normal subjects were recorded in the form of sequential thermal images. For each thermal sequence, the ocular region was selected and warped to a standard form. Thermal data within the regions were processed, on the basis of the first law of thermodynamics to derive the evaporation rate. For elder subjects (aged above 35), the rate was determined to be 55.82 Wm(-2) and for younger subjects, the rate was 58.9 Wm(-2). The corneal rate of evaporation in elder subjects was found statistically (p < 0.11) larger than their younger counterparts. The rate of blinking was observed to be related to the variation of evaporation rate. The authors have measured the evaporation rate on a sequence of thermographic images. A region of interest was selected at first and the same region on all the images were warped into a standard form. Calculations were performed based on the thermal data in those regions to obtain the values of interest. The authors found that the tear evaporation rate for subjects of all age groups was 57.36 +/- 12.73 Wm(-2) and the corneal tear evaporation was higher in elder subjects. The corneal rate of evaporation fluctuated in a larger magnitude in subjects who blinked more than average.

Analysis of the climate variability on Lake Nasser evaporation based on the Bowen ratio energy budget method.

PubMed

Elsawwaf, Mohamed; Willems, Patrick

2012-04-01

Variations in lake evaporation have a significant impact on the energy and water budgets of lakes. Understanding these variations and the role of climate is important for water resources management as well as predicting future changes in lake hydrology as a result of climate change. This study presents a comprehensive, 10-year analysis of seasonal, intraseasonal, and interannual variations in lake evaporation for Lake Nasser in South Egypt. Meteorological and lake temperature measurements were collected from an instrumented platform (Raft floating weather station) at 2 km upstream ofthe Aswan High Dam. In addition to that, radiation measurements at three locations on the lake: Allaqi, Abusembel and Arqeen (respectively at 75, 280 and 350 km upstream of the Aswan High Dam) are used. The data were analyzed over 14-day periods from 1995 to 2004 to provide bi-weekly energy budget estimates of evaporation rate. The mean evaporation rate for lake Nasser over the study period was 5.88 mm day(-1), with a coefficient of variation of 63%. Considerable variability in evaporation rates was found on a wide range of timescales, with seasonal changes having the highest coefficient of variation (32%), followed by the intraseasonal (28%) and interannual timescales (11.6%; for summer means). Intraseasonal changes in evaporation were primarily associated with synoptic weather variations, with high evaporation events tending to occur during incursions of cold, dry air (due, in part, to the thermal lag between air and lake temperatures). Seasonal variations in evaporation were largely driven by temperature and net energy advection, but are out-of-phase with changes in wind speed. On interannual timescales, changes in summer evaporation rates were strongly associated with changes in net energy advection and showed only moderate connections to variations in temperature or humidity.

Assessing the ability of potential evapotranspiration models in capturing dynamics of evaporative demand across various biomes and climatic regimes with ChinaFLUX measurements

NASA Astrophysics Data System (ADS)

Zheng, Han; Yu, Guirui; Wang, Qiufeng; Zhu, Xianjin; Yan, Junhua; Wang, Huimin; Shi, Peili; Zhao, Fenghua; Li, Yingnian; Zhao, Liang; Zhang, Junhui; Wang, Yanfen

2017-08-01

Estimates of atmospheric evaporative demand have been widely required for a variety of hydrological analyses, with potential evapotranspiration (PET) being an important measure representing evaporative demand of actual vegetated surfaces under given metrological conditions. In this study, we assessed the ability of various PET models in capturing long-term (typically 2003-2011) dynamics of evaporative demand at eight ecosystems across various biomes and climatic regimes in China. Prior to assessing PET dynamics, we first examined the reasonability of fourteen PET models in representing the magnitudes of evaporative demand using eddy-covariance actual evapotranspiration (AET) as an indicator. Results showed that the robustness of the fourteen PET models differed somewhat across the sites, and only three PET models could produce reasonable magnitudes of evaporative demand (i.e., PET ≥ AET on average) for all eight sites, including the: (i) Penman; (ii) Priestly-Taylor and (iii) Linacre models. Then, we assessed the ability of these three PET models in capturing dynamics of evaporative demand by comparing the annual and seasonal trends in PET against the equivalent trends in AET and precipitation (P) for particular sites. Results indicated that nearly all the three PET models could faithfully reproduce the dynamics in evaporative demand for the energy-limited conditions at both annual and seasonal scales, while only the Penman and Linacre models could represent dynamics in evaporative demand for the water-limited conditions. However, the Linacre model was unable to reproduce the seasonal switches between water- and energy-limited states for some sites. Our findings demonstrated that the choice of PET models would be essential for the evaporative demand analyses and other related hydrological analyses at different temporal and spatial scales.

Numerical modelling and experimental study of liquid evaporation during gel formation

NASA Astrophysics Data System (ADS)

Pokusaev, B. G.; Khramtsov, D. P.

2017-11-01

Gels are promising materials in biotechnology and medicine as a medium for storing cells for bioprinting applications. Gel is a two-phase system consisting of solid medium and liquid phase. Understanding of a gel structure evolution and gel aging during liquid evaporation is a crucial step in developing new additive bioprinting technologies. A numerical and experimental study of liquid evaporation was performed. In experimental study an evaporation process of an agarose gel layer located on Petri dish was observed and mass difference was detected using electronic scales. Numerical model was based on a smoothed particle hydrodynamics method. Gel in a model was represented as a solid-liquid system and liquid evaporation was modelled due to capillary forces and heat transfer. Comparison of experimental data and numerical results demonstrated that model can adequately represent evaporation process in agarose gel.

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.

Moisture variation associated with water input and evaporation during sewage sludge bio-drying.

PubMed

Cai, Lu; Gao, Ding; Chen, Tong-Bin; Liu, Hong-Tao; Zheng, Guo-Di; Yang, Qi-Wei

2012-08-01

The variation of moisture during sewage sludge bio-drying was investigated. In situ measurements were conducted to monitor the bulk moisture and water vapor, while the moisture content, water generation, water evaporation and aeration water input of the bio-drying bulk were calculated based on the water mass balance. The moisture in the sewage sludge bio-drying material decreased from 66% to 54% in response to control technology for bio-drying. During the temperature increasing and thermophilic phases of sewage sludge bio-drying, the moisture content, water generation and water evaporation of the bulk initially increased and then decreased. The peak water generation and evaporation occurred during the thermophilic phase. During the bio-drying, water evaporation was much greater than water generation, and aeration facilitated the water evaporation. Copyright © 2012. Published by Elsevier Ltd.

Sub- and super-Maxwellian evaporation of simple gases from liquid water

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

Kann, Z. R.; Skinner, J. L., E-mail: skinner@chem.wisc.edu

2016-04-21

Non-Maxwellian evaporation of light atoms and molecules (particles) such as He and H{sub 2} from liquids has been observed experimentally. In this work, we use simulations to study systematically the evaporation of Lennard-Jones particles from liquid water. We find instances of sub- and super-Maxwellian evaporation, depending on the mass of the particle and the particle-water interaction strength. The observed trends are in qualitative agreement with experiment. We interpret these trends in terms of the potential of mean force and the effectiveness and frequency of collisions during the evaporation process. The angular distribution of evaporating particles is also analyzed, and itmore » is shown that trends in the energy from velocity components tangential and normal to the liquid surface must be understood separately in order to interpret properly the angular distributions.« less

A phylogenetic approach to total evaporative water loss in mammals.

PubMed

Van Sant, Matthew J; Oufiero, Christopher E; Muñoz-Garcia, Agustí; Hammond, Kimberly A; Williams, Joseph B

2012-01-01

Maintaining appropriate water balance is a constant challenge for terrestrial mammals, and this problem can be exacerbated in desiccating environments. It has been proposed that natural selection has provided desert-dwelling mammals physiological mechanisms to reduce rates of total evaporative water loss. In this study, we evaluated the relationship between total evaporative water loss and body mass in mammals by using a recent phylogenetic hypothesis. We compared total evaporative water loss in 80 species of arid-zone mammals to that in 56 species that inhabit mesic regions, ranging in size from 4 g to 3,500 kg, to test the hypothesis that mammals from arid environments have lower rates of total evaporative water loss than mammals from mesic environments once phylogeny is taken into account. We found that arid species had lower rates of total evaporative water loss than mesic species when using a dichotomous variable to describe habitat (arid or mesic). We also found that total evaporative water loss was negatively correlated with the average maximum and minimum environmental temperature as well as the maximum vapor pressure deficit of the environment. Annual precipitation and the variable Q (a measure of habitat aridity) were positively correlated with total evaporative water loss. These results support the hypothesis that desert-dwelling mammals have lower rates of total evaporative water loss than mesic species after controlling for body mass and evolutionary relatedness regardless of whether categorical or continuous variables are used to describe habitat.

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.

A sensor architecture for real-time, in situ measurement of overlake evaporation on the Laurentian Great Lakes

NASA Astrophysics Data System (ADS)

Kerkez, B.; Fries, K. J.; Gronewold, A.; Lenters, J. D.

2014-12-01

While overlake evaporation is a major component of the Great Lakes' water balance, our scientific understanding of the climatic drivers of evaporation and its effects on water levels is significantly impeded by limited data. Existing measurement methods, such as eddy covariance, are not easily implemented in offshore applications. As such, there are only a handful of sites making direct, overlake measurements of evaporation on the entire Great Lakes, where the lake surface area comprises nearly one third of the entire basin. Long-term forecasts of water levels are thus very uncertain, particularly relating to climatic forcing, which is known to be a major driver of evaporation. We present a novel sensor architecture which is deployed on buoys, both tethered and drifting, to provide real-time measurements of overlake evaporation across the Great Lakes. Our system is comprised of a hierarchy of low-power, cost-effective sensor nodes, which carry out on-board computations to estimate evaporation in real-time. An ultra-low power microcontroller samples a suite of sensors to compute evaporation based on the Bowen ratio energy budget approach. The readings are then transmitted via satellite modules to a cloud-based server infrastructure for real-time updated scientific analysis and forecasting. Initial assessment of our new satellite drifter platform indicates robust field performance, validating its use in ongoing efforts to deploy a large-scale evaporation observation network across the Great Lakes basin.

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

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.

Continuous shear rheometry of o/w emulsions; control of evaporation in cone/plate geometry.

PubMed

Orafidiya, L O

1989-05-01

Volatile solvents may evaporate during cone/plate viscometry so that false rheograms develop. This surface evaporation was prevented in a cod-liver oil-in-water emulsion stabilized with zanthoxylum gum by layering a film of cod-liver oil on the exposed surface of the emulsion test sample. The oil layer effectively prevented evaporation and did not alter significantly the rheological behaviour of the test material.

Introducing ultrasonic falling film evaporator for moderate temperature evaporation enhancement.

PubMed

Dehbani, Maryam; Rahimi, Masoud

2018-04-01

In the present study, Ultrasonic Falling Film (USFF), as a novel technique has been proposed to increase the evaporation rate of moderate temperature liquid film. It is a proper method for some applications which cannot be performed at high temperature, such as foodstuff industry, due to their sensitivity to high temperatures. Evaporation rate of sodium chloride solution from an USFF on an inclined flat plate compared to that for Falling Film without ultrasonic irradiation (FF) at various temperatures was investigated. The results revealed that produced cavitation bubbles have different effects on evaporation rate at different temperatures. At lower temperatures, size fluctuation and collapse of bubbles and in consequence induced physical effects of cavitation bubbles resulted in more turbulency and evaporation rate enhancement. At higher temperatures, the behavior was different. Numerous created bubbles joined together and cover the plate surface, so not only decreased the ultrasound vibrations but also reduced the evaporation rate in comparison with FF. The highest evaporation rate enhancement of 353% was obtained at 40 °C at the lowest Reynolds number of 250. In addition, the results reveal that at temperature of 40 °C, USFF has the highest efficiency compared to FF. Copyright © 2017 Elsevier B.V. All rights reserved.

Confinement-induced alterations in the evaporation dynamics of sessile droplets.

PubMed

Bansal, Lalit; Chakraborty, Suman; Basu, Saptarshi

2017-02-07

Evaporation of sessile droplets has been a topic of extensive research. However, the effect of confinement on the underlying dynamics has not been well explored. Here, we report the evaporation dynamics of a sessile droplet in a confined fluidic environment. Our findings reveal that an increase in the channel length delays the completion of the evaporation process and leads to unique spatio-temporal evaporation flux and internal flow. The evaporation modes (constant contact angle and constant contact radius) during the droplet lifetime however exhibit global similarity when normalized by appropriate length and timescales. These results are explained in light of an increase in vapor concentration inside the channel due to greater accumulation of water vapor on account of increased channel length. We have formulated a theoretical framework which introduces two key parameters namely an enhanced concentration of the vapor field in the vicinity of the confined droplet and a corresponding accumulation lengthscale over which the accumulated vapor relaxes to the ambient concentration. Using these two parameters and modified diffusion based evaporation we are able to show that confined droplets exhibit a universal behavior in terms of the temporal evolution of each evaporation mode irrespective of the channel length. These results may turn out to be of profound importance in a wide variety of applications, ranging from surface patterning to microfluidic technology.

Estimating pothole wetland connectivity to Pipestem Creek ...

EPA Pesticide Factsheets

Understanding hydrologic connectivity between wetlands and perennial streams is critical to understanding how reliant stream flow is on wetlands within their watershed. We used the isotopic evaporation signal in water to examine wetland-stream hydrologic connectivity within the Pipestem Creek watershed, North Dakota, a watershed dominated by prairie-pothole wetlands. During a wetter-than-normal decade, Pipestem Creek exhibited an evaporated-water signal that had approximately half the isotopic-enrichment signal found in most evaporatively enriched pothole wetlands. If evaporation was mainly occurring within the stream, we expected the evaporation signal to increase from upstream towards downstream. However, the signal either remained similar or decreased downstream over the two years of sampling. Groundwater measured at the water table adjacent to Pipestem Creek had isotopic values that indicated recharge from winter precipitation and had no significant evaporative enrichment. Using isotopic theory and discharge data, we estimated the surface area of open water necessary to generate the evaporation signal found within Pipestem Creek over time. The range of evaporating surface-area estimates was highly dynamic, spanning from 35 to 2380 ha of open water contributing to streamflow over time, and varied primarily with the amount of discharge. The median value (417 ha) was well above the surface area of the Pipestem Creek network (245 ha), and only two periods

Evaporation of sessile droplets affected by graphite nanoparticles and binary base fluids.

PubMed

Zhong, Xin; Duan, Fei

2014-11-26

The effects of ethanol component and nanoparticle concentration on evaporation dynamics of graphite-water nanofluid droplets have been studied experimentally. The results show that the formed deposition patterns vary greatly with an increase in ethanol concentration from 0 to 50 vol %. Nanoparticles have been observed to be carried to the droplet surface and form a large piece of aggregate. The volume evaporation rate on average increases as the ethanol concentration increases from 0 to 50 vol % in the binary mixture nanofluid droplets. The evaporation rate at the initial stage is more rapid than that at the late stage to dry, revealing a deviation from a linear fitting line, standing for a constant evaporation rate. The deviation is more intense with a higher ethanol concentration. The ethanol-induced smaller liquid-vapor surface tension leads to higher wettability of the nanofluid droplets. The graphite nanoparticles in ethanol-water droplets reinforce the pinning effect in the drying process, and the droplets with more ethanol demonstrate the depinning behavior only at the late stage. The addition of graphite nanoparticles in water enhances a droplet baseline spreading at the beginning of evaporation, a pinning effect during evaporation, and the evaporation rate. However, with a relatively high nanoparticle concentration, the enhancement is attenuated.

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.

Floatable, Self-Cleaning, and Carbon-Black-Based Superhydrophobic Gauze for the Solar Evaporation Enhancement at the Air-Water Interface.

PubMed

Liu, Yiming; Chen, Jingwei; Guo, Dawei; Cao, Moyuan; Jiang, Lei

2015-06-24

Efficient solar evaporation plays an indispensable role in nature as well as the industry process. However, the traditional evaporation process depends on the total temperature increase of bulk water. Recently, localized heating at the air-water interface has been demonstrated as a potential strategy for the improvement of solar evaporation. Here, we show that the carbon-black-based superhydrophobic gauze was able to float on the surface of water and selectively heat the surface water under irradiation, resulting in an enhanced evaporation rate. The fabrication process of the superhydrophobic black gauze was low-cost, scalable, and easy-to-prepare. Control experiments were conducted under different light intensities, and the results proved that the floating black gauze achieved an evaporation rate 2-3 times higher than that of the traditional process. A higher temperature of the surface water was observed in the floating gauze group, revealing a main reason for the evaporation enhancement. Furthermore, the self-cleaning ability of the superhydrophobic black gauze enabled a convenient recycling and reusing process toward practical application. The present material may open a new avenue for application of the superhydrophobic substrate and meet extensive requirements in the fields related to solar evaporation.

Evaporation Rate of Water as a Function of a Magnetic Field and Field Gradient

PubMed Central

Guo, Yun-Zhu; Yin, Da-Chuan; Cao, Hui-Ling; Shi, Jian-Yu; Zhang, Chen-Yan; Liu, Yong-Ming; Huang, Huan-Huan; Liu, Yue; Wang, Yan; Guo, Wei-Hong; Qian, Ai-Rong; Shang, Peng

2012-01-01

The effect of magnetic fields on water is still a highly controversial topic despite the vast amount of research devoted to this topic in past decades. Enhanced water evaporation in a magnetic field, however, is less disputed. The underlying mechanism for this phenomenon has been investigated in previous studies. In this paper, we present an investigation of the evaporation of water in a large gradient magnetic field. The evaporation of pure water at simulated gravity positions (0 gravity level (ab. g), 1 g, 1.56 g and 1.96 g) in a superconducting magnet was compared with that in the absence of the magnetic field. The results showed that the evaporation of water was indeed faster in the magnetic field than in the absence of the magnetic field. Furthermore, the amount of water evaporation differed depending on the position of the sample within the magnetic field. In particular, the evaporation at 0 g was clearly faster than that at other positions. The results are discussed from the point of view of the evaporation surface area of the water/air interface and the convection induced by the magnetization force due to the difference in the magnetic susceptibility of water vapor and the surrounding air. PMID:23443127

Interactions of fat globule surface proteins during concentration of whole milk in a pilot-scale multiple-effect evaporator.

PubMed

Ye, Aiqian; Singh, Harjinder; Taylor, Michael W; Anema, Skelte G

2004-11-01

The changes in milk fat globules and fat globule surface proteins during concentration of whole milk using a pilot-scale multiple-effect evaporator were examined. The effects of heat treatment of milk at 95 degrees C for 20 s, prior to evaporation, on fat globule size and the milk fat globule membrane (MFGM) proteins were also determined. In both non-preheated and preheated whole milk, the size of milk fat globules decreased while the amount of total surface proteins at the fat globules increased as the milk passed through each effect of the evaporator. In non-preheated samples, the amount of caseins at the surface of fat globules increased markedly during evaporation with a relatively small increase in whey proteins. In preheated samples, both caseins and whey proteins were observed at the surface of fat globules and the amounts of these proteins increased during subsequent steps of evaporation. The major original MFGM proteins, xanthine oxidase, butyrophilin, PAS 6 and PAS 7, did not change during evaporation, however, PAS 6 and PAS 7 decreased during preheating. These results indicate that the proteins from the skim milk were adsorbed onto the fat globule surface when the milk fat globules were disrupted during evaporation.

Influence of instrument conditions on the evaporation behavior of uranium dioxide with UV laser-assisted atom probe tomography

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

Valderrama, B.; Henderson, H.B.; Gan, J.

2015-04-01

Atom probe tomography (APT) provides the ability to detect subnanometer chemical variations spatially, with high accuracy. However, it is known that compositional accuracy can be affected by experimental conditions. A study of the effect of laser energy, specimen base temperature, and detection rate is performed on the evaporation behavior of uranium dioxide (UO 2). In laser-assisted mode, tip geometry and standing voltage also contribute to the evaporation behavior. In this investigation, it was determined that modifying the detection rate and temperature did not affect the evaporation behavior as significantly as laser energy. It was also determined that three laser evaporationmore » regimes are present in UO 2. Very low laser energy produces a behavior similar to DC-field evaporation, moderate laser energy produces the desired laser-assisted field evaporation characteristic and high laser energy induces thermal effects, negatively altering the evaporation behavior. The need for UO 2 to be analyzed under moderate laser energies to produce accurate stoichiometry distinguishes it from other oxides. The following experimental conditions providing the best combination of mass resolving power, accurate stoichiometry, and uniform evaporation behavior: 50 K, 10 pJ laser energy, a detection rate of 0.003 atoms per pulse, and a 100 kHz repetition rate.« less

Desertification of the peritoneum by thin-film evaporation during laparoscopy.

PubMed

Ott, Douglas E

2003-01-01

To assess the effects of gas flow during insufflation on peritoneal fluid and peritoneal tissue regarding transient thermal behavior and thin-film evaporation. The effects of laparoscopic gas on peritoneal cell desiccation and peritoneal fluid thin-film evaporation were analyzed. Measurment of tissue and peritoneal fluid and analysis of gas flow dynamics during laparoscopy. High-velocity gas interface conditions during laparoscopic gas insufflation result in peritoneal surface temperature and decreases up to 20 degrees C/second due to rapid thin-film evaporation of the peritoneal fluid. Evaporation of the thin film of peritoneal fluid extends quickly to the peritoneal cell membrane, causing peritoneal cell desiccation, internal cytoplasmic stress, and disruption of the cell membrane, resulting in loss of peritoneal surface continuity and integrity. Changing the gas conditions to 35 degrees C and 95% humidity maintains normal peritoneal fluid thin-film characteristics, cellular integrity, and prevents evaporative losses. Cold, dry gas and the characteristics of the laparoscopic gas delivery apparatus cause local peritoneal damaging alterations by high-velocity gas flow with extremely dry gas, creating extreme arid surface conditions, rapid evaporative and hydrological changes, tissue desiccation, and peritoneal fluid alterations that contribute to the process of desertification and thin-film evaporation. Peritoneal desertification is preventable by preconditioning the gas to 35 degrees C and 95% humidity.

ACID EVAPORATION OF ULTIMA GOLD TM AB LIQUID SCINTILLATION COCKTAIL RESIDUE

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

Kyser, E.; Fondeur, F.; Crump, S.

2011-12-21

Prior analyses of samples from the F/H Lab solutions showed the presence of diisopropylnapthalene (DIN), a major component of Ultima Gold{trademark} AB liquid scintillation cocktail (LSC). These solutions are processed through H-Canyon Tank 10.5 and ultimately through the 17.8E evaporator. Similar solutions originated in SRNL streams sent to the same H Canyon tanks. This study examined whether the presence of these organics poses a process-significant hazard for the evaporator. Evaporation and calorimetry testing of surrogate samples containing 2000 ppm of Ultima Gold{trademark} AB LSC in 8 M nitric acid have been completed. These experiments showed that although reactions between nitricmore » acid and the organic components do occur, they do not appear to pose a significant hazard for runaway reactions or generation of energetic compounds in canyon evaporators. The amount of off-gas generated was relatively modest and appeared to be well within the venting capacity of the H-Canyon evaporators. A significant fraction of the organic components likely survives the evaporation process primarily as non-volatile components that are not expected to represent any new process concerns during downstream operations such as neutralization. Laboratory Waste solutions containing minor amounts of DIN can be safely received, stored, transferred, and processed through the canyon waste evaporator.« less

Evaporation rate of water as a function of a magnetic field and field gradient.

PubMed

Guo, Yun-Zhu; Yin, Da-Chuan; Cao, Hui-Ling; Shi, Jian-Yu; Zhang, Chen-Yan; Liu, Yong-Ming; Huang, Huan-Huan; Liu, Yue; Wang, Yan; Guo, Wei-Hong; Qian, Ai-Rong; Shang, Peng

2012-12-11

The effect of magnetic fields on water is still a highly controversial topic despite the vast amount of research devoted to this topic in past decades. Enhanced water evaporation in a magnetic field, however, is less disputed. The underlying mechanism for this phenomenon has been investigated in previous studies. In this paper, we present an investigation of the evaporation of water in a large gradient magnetic field. The evaporation of pure water at simulated gravity positions (0 gravity level (ab. g), 1 g, 1.56 g and 1.96 g) in a superconducting magnet was compared with that in the absence of the magnetic field. The results showed that the evaporation of water was indeed faster in the magnetic field than in the absence of the magnetic field. Furthermore, the amount of water evaporation differed depending on the position of the sample within the magnetic field. In particular, the evaporation at 0 g was clearly faster than that at other positions. The results are discussed from the point of view of the evaporation surface area of the water/air interface and the convection induced by the magnetization force due to the difference in the magnetic susceptibility of water vapor and the surrounding air.

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.

Experimental Investigations of the Internal Energy of Molecules Evaporated via Laser-induced Acoustic Desorption into a Fourier-transform Ion Cyclotron Resonance Mass Spectrometer (LIAD/FT-ICR)

PubMed Central

Shea, Ryan C.; Petzold, Christopher J.; Liu, Ji-ang; Kenttämaa, Hilkka I.

2008-01-01

The internal energy of neutral gas-phase organic and biomolecules, evaporated by means of laser-induced acoustic desorption (LIAD) into a Fourier-transform ion cyclotron resonance mass spectrometer (FT-ICR), was investigated through several experimental approaches. The desorbed molecules were demonstrated not to undergo degradation during the desorption process by collecting LIAD-evaporated molecules and subjecting them to analysis by electrospray ionization/quadrupole ion trap mass spectrometry. Previously established gas-phase basicity (GB) values were remeasured for LIAD-evaporated organic molecules and biomolecules with the use of the bracketing method. No endothermic reactions were observed. The remeasured basicity values are in close agreement with the values reported in the literature. The amount of internal energy deposited during LIAD is concluded to be less than a few kcal/mol. Chemical ionization with a series of proton transfer reagents was employed to obtain a breakdown curve for a protonated dipeptide, val-pro, evaporated by LIAD. Comparison of this breakdown curve with a previously published analogous curve obtained by using substrate-assisted laser desorption (SALD) to evaporate the peptide suggests that the molecules evaporated via LIAD have less internal energy than those evaporated via SALD. PMID:17263513

Real-time direct measurement of liquid (water) evaporation by simple disturbance inhibited interfometry technique

NASA Astrophysics Data System (ADS)

Kim, Yong Gi

2017-11-01

A real-time in-situ interferometry method was proposed to measure water (liquid) evaporation directly over the liquid surface inside the reservoir. The direct evaporation measurement relied on the counting the number of sinusoidal fringes. As the water inside reservoir evaporated, the depth of the water decreases a little thus the optical path length changes. Evaporation signals have been determined as a function of the focusing beam position of the signal beam over the liquid surface. In interferometry technique, the most limiting factors are surface disturbances and vibrations over the liquid surface. This limiting factor was simply inhibited by placing a long cylindrical aluminum tube around the signal beam of the interferometer over the liquid surface. A small diameter cylindrical Al tube diminished vibrations and wind induced surface ripples more effectively than that of the larger one. Water evaporation was successfully measured in real-time with a warm water and cold water even under windy condition with an electric fan. The experimental results demonstrated that the interferometry technique allows determining of liquid evaporation in real-time. Interferometric technique opens up a new possibility of methodology for liquid evaporation measurement even in several environmental disturbances, such as, vibration, surface disturbance, temperature change and windy environments.

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.

Further Evaluation of an Emperical Equation for Annual Total Evaporation

NASA Technical Reports Server (NTRS)

Choudhury, Bhaskar J.

1999-01-01

An empirical equation for annual total evaporation based on annual precipitation and net radiation was found to provide evaporation within 10% of the observed values at seven locations within temperate and tropical regions, but it overestimated evaporation by 90% at one location within the tundra region. A synthesis of observations at two other locations within the tundra region gives overestimates of about 65%. A general analysis of observed precipitation, net radiation, and runoff within the tundra region shows that the empirical equation is generally biased to overestimate annual evaporation within the tundra region. A theoretical analysis is being done to understand the reason behind this bias.

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.

A microscopic description of black hole evaporation via holography

DOE PAGES

Berkowitz, Evan; Hanada, Masanori; Maltz, Jonathan

2016-07-19

Here, we propose a description of how a large, cold black hole (black zero-brane) in type IIA superstring theory evaporates into freely propagating D0-branes, by solving the dual gauge theory quantitatively. The energy spectrum of emitted D0-branes is parametrically close to thermal when the black hole is large. The black hole, while initially cold, gradually becomes an extremely hot and stringy object as it evaporates. As it emits D0-branes, its emission rate speeds up and it evaporates completely without leaving any remnant. Hence this system provides us with a concrete holographic description of black hole evaporation without information loss.

A microscopic description of black hole evaporation via holography

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

Berkowitz, Evan; Hanada, Masanori; Maltz, Jonathan

Here, we propose a description of how a large, cold black hole (black zero-brane) in type IIA superstring theory evaporates into freely propagating D0-branes, by solving the dual gauge theory quantitatively. The energy spectrum of emitted D0-branes is parametrically close to thermal when the black hole is large. The black hole, while initially cold, gradually becomes an extremely hot and stringy object as it evaporates. As it emits D0-branes, its emission rate speeds up and it evaporates completely without leaving any remnant. Hence this system provides us with a concrete holographic description of black hole evaporation without information loss.

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

Jia, Kun; Li, Xiang-Dong, E-mail: lixd@nju.edu.cn

Millisecond pulsars (MSPs) are thought to originate from low-mass X-ray binaries (LMXBs). The discovery of eclipsing radio MSPs, including redbacks and black widows, indicates that evaporation of the donor star by the MSP’s irradiation takes place during the LMXB evolution. In this work, we investigate the effect of donor evaporation on the secular evolution of LMXBs, considering different evaporation efficiencies and related angular momentum loss. We find that for widening LMXBs, the donor star leaves a less massive white dwarf than without evaporation; for contracting systems, evaporation can speed up the evolution, resulting in dynamically unstable mass transfer and possiblymore » the formation of isolated MSPs.« less

Aggregation-Induced Emission Luminogen-Based Direct Visualization of Concentration Gradient Inside an Evaporating Binary Sessile Droplet.

PubMed

Cai, Xin; Xie, Ni; Qiu, Zijie; Yang, Junxian; He, Minghao; Wong, Kam Sing; Tang, Ben Zhong; Qiu, Huihe

2017-08-30

In this study, the concentration gradient inside evaporating binary sessile droplets of 30, 50, and 60 vol % tetrahydrofuran (THF)/water mixtures was investigated. The 5 μL THF/water droplets were evaporated on a transparent hydrophobic substrate. This is the first demonstration of local concentration mapping within an evaporating binary droplet utilizing the aggregation-induced emission material. During the first two evaporation stages of the binary droplet, the local concentration can be directly visualized by the change of fluorescence emission intensity. Time-resolved average and local concentrations can be estimated by using the pre-established function of fluorescence intensity versus water volume fraction.

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...

Experimental investigation of interfacial energy transport in an evaporating sessile droplet for evaporative cooling applications

NASA Astrophysics Data System (ADS)

Mahmud, Md. Almostasim; MacDonald, Brendan D.

2017-01-01

In this paper we experimentally examine evaporation flux distributions and modes of interfacial energy transport for continuously fed evaporating spherical sessile water droplets in a regime that is relevant for applications, particularly for evaporative cooling systems. The contribution of the thermal conduction through the vapor phase was found to be insignificant compared to the thermal conduction through the liquid phase for the conditions we investigated. The local evaporation flux distributions associated with thermal conduction were found to vary along the surface of the droplet. Thermal conduction provided a majority of the energy required for evaporation but did not account for all of the energy transport, contributing 64 ±3 % , 77 ±3 % , and 77 ±4 % of the energy required for the three cases we examined. Based on the temperature profiles measured along the interface we found that thermocapillary flow was predicted to occur in our experiments, and two convection cells were consistent with the temperature distributions for higher substrate temperatures while a single convection cell was consistent with the temperature distributions for a lower substrate temperature.

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

Evaporation of a Volatile Liquid Lens on the Surface of an Immiscible Liquid.

PubMed

Sun, Wei; Yang, Fuqian

2016-06-21

The evaporation behavior of toluene and hexane lenses on the surface of deionized (DI) water is studied. The toluene and hexane lenses during evaporation experience an advancing stage and a receding stage. There exists a significant difference of the evaporation behavior between the toluene lenses and the hexane lenses. The lifetime and largest diameter of both the toluene and hexane lenses increase with increasing the initial volume of the lenses. For the evaporation of the toluene lenses, the lifetime and largest diameter of the lenses decrease with increasing the temperature of DI water. The effect of the residual of the oil molecules on the evaporation of toluene lenses at a temperature of 21 °C is investigated via the evaporation of a series of consecutive toluene lenses being placed on the same position of the surface of DI water. The temporal evolution of the toluene lenses placed after the first toluene lens deviates significantly from that of the first toluene lens. Significant increase of the receding speed occurs at the dimensionless time in a range 0.7-0.8.

Evaporation of a sessile water drop and a drop of aqueous salt solution.

PubMed

Misyura, S Y

2017-11-07

The influence of various factors on the evaporation of drops of water and aqueous salt solution has been experimentally studied. Typically, in the studies of drop evaporation, only the diffusive vapor transfer, radiation and the molecular heat conduction are taken into account. However, vapor-gas convection plays an important role at droplet evaporation. In the absence of droplet boiling, the influence of gas convection turns out to be the prevailing factor. At nucleate boiling, a prevailing role is played by bubbles generation and vapor jet discharge at a bubble collapse. The gas convection behavior for water and aqueous salt solution is substantially different. With a growth of salt concentration over time, the influence of the convective component first increases, reaches an extremum and then significantly decreases. At nucleate boiling in a salt solution it is incorrect to simulate the droplet evaporation and the heat transfer in quasi-stationary approximation. The evaporation at nucleate boiling in a liquid drop is divided into several characteristic time intervals. Each of these intervals is characterized by a noticeable change in both the evaporation rate and the convection role.

Evaporation from groundwater discharge playas, Estancia Basin, central New Mexico

USGS Publications Warehouse

Menking, Kirsten M.; Anderson, Roger Y.; Brunsell, Nathaniel A.; Allen, Bruce D.; Ellwein, Amy L.; Loveland, Thomas A.; Hostetler, Steven W.

2000-01-01

Bowen ratio meteorological stations have been deployed to measure rates of evaporation from groundwater discharge playas and from an adjacent vegetated bench in the Estancia Basin, in central New Mexico. The playas are remnants of late Pleistocene pluvial Lake Estancia and are discharge areas for groundwater originating as precipitation in the adjacent Manzano Mts. They also accumulate water during local precipitation events. Evaporation is calculated from measured values of net radiation, soil heat flux, atmospheric temperature, and relative humidity. Evaporation rates are strongly dependent on the presence or absence of standing water in the playas, with rates increasing more than 600% after individual rainstorms. Evaporation at site E-12, in the southeastern part of the playa Complex, measured 74 cm over a yearlong period from mid-1997 through mid-1998. This value compares favorably to earlier estimates from northern Estancia playas, but is nearly three times greater than evaporation at a similar playa in western Utah. Differences in geographical position, salt crust composition, and physical properties may explain some of the difference in evaporation rates in these two geographic regions.

Effects of climatic seasonality on the isotopic composition of evaporating soil waters

NASA Astrophysics Data System (ADS)

Benettin, Paolo; Volkmann, Till H. M.; von Freyberg, Jana; Frentress, Jay; Penna, Daniele; Dawson, Todd E.; Kirchner, James W.

2018-05-01

Stable water isotopes are widely used in ecohydrology to trace the transport, storage, and mixing of water on its journey through landscapes and ecosystems. Evaporation leaves a characteristic signature on the isotopic composition of the water that is left behind, such that in dual-isotope space, evaporated waters plot below the local meteoric water line (LMWL) that characterizes precipitation. Soil and xylem water samples can often plot below the LMWL as well, suggesting that they have also been influenced by evaporation. These soil and xylem water samples frequently plot along linear trends in dual-isotope space. These trend lines are often termed "evaporation lines" and their intersection with the LMWL is often interpreted as the isotopic composition of the precipitation source water. Here we use numerical experiments based on established isotope fractionation theory to show that these trend lines are often by-products of the seasonality in evaporative fractionation and in the isotopic composition of precipitation. Thus, they are often not true evaporation lines, and, if interpreted as such, can yield highly biased estimates of the isotopic composition of the source water.

Coffee-stain growth dynamics on dry and wet surfaces

NASA Astrophysics Data System (ADS)

Boulogne, François; Ingremeau, François; Stone, Howard A.

2017-02-01

The drying of a drop containing particles often results in the accumulation of the particles at the contact line. In this work, we investigate the drying of an aqueous colloidal drop surrounded by a hydrogel that is also evaporating. We combine theoretical and experimental studies to understand how the surrounding vapor concentration affects the particle deposit during the constant radius evaporation mode. In addition to the common case of evaporation on an otherwise dry surface, we show that in a configuration where liquid is evaporating from a flat surface around the drop, the singularity of the evaporative flux at the contact line is suppressed and the drop evaporation is homogeneous. For both conditions, we derive the velocity field and we establish the temporal evolution of the number of particles accumulated at the contact line. We predict the growth dynamics of the stain and the drying timescales. Thus, dry and wet conditions are compared with experimental results and we highlight that only the dynamics is modified by the evaporation conditions, not the final accumulation at the contact line.

Evaporation mitigation by floating modular devices

NASA Astrophysics Data System (ADS)

Hassan, M. M.; Peirson, W. L.

2016-05-01

Prolonged periods of drought and consequent evaporation from open water bodies in arid parts of Australia continue to be a threat to water availability for agricultural production. Over many parts of Australia, the annual average evaporation exceeds the annual precipitation by more than 5 times. Given its significance, it is surprising that no evaporation mitigation technique has gained widespread adoption to date. High capital and maintenance costs of manufactured products are a significant barrier to implementation. The use of directly recycled clean plastic containers as floating modular devices to mitigate evaporation has been investigated for the first time. A six-month trial at an arid zone site in Australia of this potential cost effective solution has been undertaken. The experiment was performed using clean conventional drinking water bottles as floating modules on the open water surface of 240-L tanks with three varying degrees of covering (nil, 34% and 68%). A systematic reduction in evaporation is demonstrated during the whole study period that is approximately linearly proportional to the covered surface. These results provide a potential foundation for robust evaporation mitigation with the prospect of implementing a cost-optimal design.

Characteristics of the Self-evaporation Behavior of Sprinkled Water near the Triple Point

NASA Astrophysics Data System (ADS)

Aizawa, Kazuo; Hayashi, Kanetoshi; Ogoshi, Hidemasa; Maeyama, Katsuya; Yonezawa, Noriyuki

For the sake of capturing the basic data in concern with the designing of vacuum evaporation apparatus, characteristics of the self-evaporation behavior of sprinkled water near the triple point has been investigated experimentally. The relationship between the amount of the vaporized water and the pressure in the vessel was elucidated quantitatively on the condition that over-heated water was sprinkled from water supplying nozzles of diameter of 4 mm into the center of the steam area in the heat insulation glass evaporation vessel having diameter of 200 mm and height of 1100 mm. Even under the mild water sprinkling conditions such as no small particle formation, small Reynolds number, and small Weber number, the temperature effectiveness of the self-evaporation in the center of the steam was as high as 80%, which clearly shows the effectiveness of this water-sprinkling method. In addition, the basic data for system designing such as water evaporation coefficient from water layer surface and temperature effectiveness of self-evaporation during the f1ight in the steam space were obtained.

Heat Load Sharing in a Capillary Pumped Loop with Multiple Evaporators and Multiple Condensers

NASA Technical Reports Server (NTRS)

Ku, Jentung

2005-01-01

This paper describes the heat load sharing function among multiple parallel evaporators in a capillary pumped loop (CPL). In the normal mode of operation, the evaporators cool the instruments by absorbing the waste heat. When an instruments is turned off, the attached evaporator can keep it warm by receiving heat from other evaporators serving the operating instruments. This is referred to as heat load sharing. A theoretical basis of heat load sharing is given first. The fact that the wicks in the powered evaporators will develop capillary pressure to force the generated vapor to flow to cold locations where the pressure is lower leads to the conclusion that heat load sharing is an inherent function of a CPL with multiple evaporators. Heat load sharing has been verified with many CPLs in ground tests. Experimental results of the Capillary Pumped Loop 3 (CAPL 3) Flight Experiment are presented in this paper. Factors that affect the amount of heat being shared are discussed. Some constraints of heat load sharing are also addressed.

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.

TANK 26 EVAPORATOR FEED PUMP TRANSFER ANALYSIS

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

Tamburello, D; Si Lee, S; Richard Dimenna, R

2008-09-30

The transfer of liquid salt solution from Tank 26 to an evaporator is to be accomplished by activating the evaporator feed pump, located approximately 72 inches above the sludge layer, while simultaneously turning on the downcomer. Previously, activation of the evaporator feed pump was an isolated event without any other components running at the same time. An analysis of the dissolved solution transfer has been performed using computational fluid dynamics methods to determine the amount of entrained sludge solids pumped out of the tank to the evaporator with the downcomer turned on. The analysis results showed that, for the maximummore » and minimum supernate levels in Tank 26 (252.5 and 72 inches above the sludge layer, respectively), the evaporator feed pump will entrain between 0.05 and 0.1 wt% sludge solids weight fraction into the eductor, respectively. Lower tank liquid levels, with respect to the sludge layer, result in higher amounts of sludge entrainment due to the increased velocity of the plunging jets from the downcomer and evaporator feed pump bypass as well as decreased dissipation depth.« less

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.

Effects of Lily Pads on Evaporation

NASA Astrophysics Data System (ADS)

Cooley, Keith R.; Idso, Sherwood B.

1980-06-01

Measurements of evaporation from open water and water partially covered by lily pads have indicated that for the portion of the surface area covered by lily pads, evaporation is reduced to about 84% of that occurring from open water.

Method of making a coating of a microtextured surface

DOEpatents

Affinito, John D [Tucson, AZ; Graff, Gordon L [West Richland, WA; Martin, Peter M [Kennewick, WA; Gross, Mark E [Pasco, WA; Burrows, Paul E [Kennewick, WA; Sapochak, Linda S [Henderson, NV

2004-11-02

A method for conformally coating a microtextured surface. The method includes flash evaporating a polymer precursor forming an evaporate, passing the evaporate to a glow discharge electrode creating a glow discharge polymer precursor plasma from the evaporate, cryocondensing the glow discharge polymer precursor plasma on the microtextured surface and crosslinking the glow discharge polymer precursor plasma thereon, wherein the crosslinking resulting from radicals created in the glow discharge polymer precursor plasma.

Representative shuttle evaporative heat sink

NASA Technical Reports Server (NTRS)

Hixon, C. W.

1978-01-01

The design, fabrication, and testing of a representative shuttle evaporative heat sink (RSEHS) system which vaporizes an expendable fluid to provide cooling for the shuttle heat transport fluid loop is reported. The optimized RSEHS minimum weight design meets or exceeds the shuttle flash evaporator system requirements. A cold trap which cryo-pumps flash evaporator exhaust water from the CSD vacuum chamber test facility to prevent water contamination of the chamber pumping equipment is also described.

/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.

Controlling water evaporation through self-assembly

PubMed Central

Roger, Kevin; Liebi, Marianne; Heimdal, Jimmy; Pham, Quoc Dat; Sparr, Emma

2016-01-01

Water evaporation concerns all land-living organisms, as ambient air is dryer than their corresponding equilibrium humidity. Contrarily to plants, mammals are covered with a skin that not only hinders evaporation but also maintains its rate at a nearly constant value, independently of air humidity. Here, we show that simple amphiphiles/water systems reproduce this behavior, which suggests a common underlying mechanism originating from responding self-assembly structures. The composition and structure gradients arising from the evaporation process were characterized using optical microscopy, infrared microscopy, and small-angle X-ray scattering. We observed a thin and dry outer phase that responds to changes in air humidity by increasing its thickness as the air becomes dryer, which decreases its permeability to water, thus counterbalancing the increase in the evaporation driving force. This thin and dry outer phase therefore shields the systems from humidity variations. Such a feedback loop achieves a homeostatic regulation of water evaporation. PMID:27573848

Evaporative Cooling Membrane Device

NASA Technical Reports Server (NTRS)

Lomax, Curtis (Inventor); Moskito, John (Inventor)

1999-01-01

An evaporative cooling membrane device is disclosed having a flat or pleated plate housing with an enclosed bottom and an exposed top that is covered with at least one sheet of hydrophobic porous material having a thin thickness so as to serve as a membrane. The hydrophobic porous material has pores with predetermined dimensions so as to resist any fluid in its liquid state from passing therethrough but to allow passage of the fluid in its vapor state, thereby, causing the evaporation of the fluid and the cooling of the remaining fluid. The fluid has a predetermined flow rate. The evaporative cooling membrane device has a channel which is sized in cooperation with the predetermined flow rate of the fluid so as to produce laminar flow therein. The evaporative cooling membrane device provides for the convenient control of the evaporation rates of the circulating fluid by adjusting the flow rates of the laminar flowing fluid.

Bio-inspired intelligent evaporation modulation in a thermo-sensitive nanogel colloid solution for self-thermoregulation.

PubMed

Huang, Zhi; Liu, Kang; Feng, Yanhui; Zhou, Jun; Zhang, Xinxin

2017-06-28

Intelligent evaporation and temperature modulation plays an important role in self-regulation of living organisms and many industrial applications. Here we demonstrate that a poly(N-isopropylacrylamide) (PNIPAM) nanogel colloid solution can spontaneously and intelligently modulate its evaporation rate with temperature variation, which has a larger evaporation rate than distilled water at a temperature higher than its lower critical solution temperature (LCST) and a smaller evaporation rate at a temperature lower than its LCST. It performs just like human skin. Theoretical analysis based on the thermodynamic derivation reveals that the evaporation rate transition around the LCST may originate from the saturated vapor pressure transition caused by the status transformation of the PNIPAM additives. An intelligent thermoregulation system based on the PNIPAM colloid solution is also demonstrated, illustrating its potential for intelligent temperature control and acting as an artificial skin.

Cooling system having dual suction port compressor

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

Wu, Guolian

2017-08-29

A cooling system for appliances, air conditioners, and other spaces includes a compressor, and a condenser that receives refrigerant from the compressor. The system also includes an evaporator that receives refrigerant from the condenser. Refrigerant received from the condenser flows through an upstream portion of the evaporator. A first portion of the refrigerant flows to the compressor without passing through a downstream portion of the evaporator, and a second portion of the refrigerant from the upstream portion of the condenser flows through the downstream portion of the evaporator after passing through the upstream portion of the evaporator. The second portionmore » of the refrigerant flows to the compressor after passing through the downstream portion of the evaporator. The refrigeration system may be configured to cool an appliance such as a refrigerator and/or freezer, or it may be utilized in air conditioners for buildings, motor vehicles, or other such spaces.« less

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

Evaporation of nanoscale water on a uniformly complete wetting surface at different temperatures.

PubMed

Guo, Yuwei; Wan, Rongzheng

2018-05-03

The evaporation of nanoscale water films on surfaces affects many processes in nature and industry. Using molecular dynamics (MD) simulations, we show the evaporation of a nanoscale water film on a uniformly complete wetting surface at different temperatures. With the increase in temperature, the growth of the water evaporation rate becomes slow. Analyses show that the hydrogen bond (H-bond) lifetimes and orientational autocorrelation times of the outermost water film decrease slowly with the increase in temperature. Compared to a thicker water film, the H-bond lifetimes and orientational autocorrelation times of a monolayer water film are much slower. This suggests that the lower evaporation rate of the monolayer water film on a uniformly complete wetting surface may be caused by the constriction of the water rotation due to the substrate. This finding may be helpful for controlling nanoscale water evaporation within a certain range of temperatures.

Using evaporation to control capillary instabilities in micro-systems.

PubMed

Ledesma-Aguilar, Rodrigo; Laghezza, Gianluca; Yeomans, Julia M; Vella, Dominic

2017-12-06

The instabilities of fluid interfaces represent both a limitation and an opportunity for the fabrication of small-scale devices. Just as non-uniform capillary pressures can destroy micro-electrical mechanical systems (MEMS), so they can guide the assembly of novel solid and fluid structures. In many such applications the interface appears during an evaporation process and is therefore only present temporarily. It is commonly assumed that this evaporation simply guides the interface through a sequence of equilibrium configurations, and that the rate of evaporation only sets the timescale of this sequence. Here, we use Lattice-Boltzmann simulations and a theoretical analysis to show that, in fact, the rate of evaporation can be a factor in determining the onset and form of dynamical capillary instabilities. Our results shed light on the role of evaporation in previous experiments, and open the possibility of exploiting diffusive mass transfer to directly control capillary flows in MEMS applications.

Evaluating evaporation from field crops using airborne radiometry and ground-based meteorological data

USGS Publications Warehouse

Jackson, R. D.; Moran, M.S.; Gay, L.W.; Raymond, L.H.

1987-01-01

Airborne measurements of reflected solar and emitted thermal radiation were combined with ground-based measurements of incoming solar radiation, air temperature, windspeed, and vapor pressure to calculate instantaneous evaporation (LE) rates using a form of the Penman equation. Estimates of evaporation over cotton, wheat, and alfalfa fields were obtained on 5 days during a one-year period. A Bowen ratio apparatus, employed simultaneously, provided ground-based measurements of evaporation. Comparison of the airborne and ground techniques showed good agreement, with the greatest difference being about 12% for the instantaneous values. Estimates of daily (24 h) evaporation were made from the instantaneous data. On three of the five days, the difference between the two techniques was less than 8%, with the greatest difference being 25%. The results demonstrate that airborne remote sensing techniques can be used to obtain spatially distributed values of evaporation over agricultural fields. ?? 1987 Springer-Verlag.

Radiation-stimulated explosive evaporation and burning of hydrogen droplets in hot aerosol mixtures

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

Osipov, V. V.; Marchenko, M. P.; Khasin, M.

2016-06-13

We present results of analytical and numerical investigation of explosive evaporation and burning scenarios of hydrogen droplets in hydrogen/oxygen aerosols. The following two scenarios have been elucidated. The first scenario, corresponding to sufficiently large droplets, is characterized by three stages: (i) an essentially homogeneous heating of a droplet to a near-critical temperature by IR radiation from the hot gas; (ii) explosive evaporation; and (iii) burning of hydrogen cloud formed by evaporation. The second scenario, corresponding to small droplets, differs in that a droplet is heated mainly by thermal conduction from the hot gas. The heating is accompanied by evaporation whichmore » can become explosive at the final stage of evaporation. The crossover droplet size separating the two scenarios is calculated. Conservative finite-difference numerical analysis is used to explore the predicted scenarios and verify analytical estimates.« less

Refrigeration system having dual suction port compressor

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

Wu, Guolian

A cooling system for appliances, air conditioners, and other spaces includes a compressor, and a condenser that receives refrigerant from the compressor. The system also includes an evaporator that receives refrigerant from the condenser. Refrigerant received from the condenser flows through an upstream portion of the evaporator. A first portion of the refrigerant flows to the compressor without passing through a downstream portion of the evaporator, and a second portion of the refrigerant from the upstream portion of the condenser flows through the downstream portion of the evaporator after passing through the upstream portion of the evaporator. The second portionmore » of the refrigerant flows to the compressor after passing through the downstream portion of the evaporator. The refrigeration system may be configured to cool an appliance such as a refrigerator and/or freezer, or it may be utilized in air conditioners for buildings, motor vehicles, or other such spaces.« less

Controlling water evaporation through self-assembly.

PubMed

Roger, Kevin; Liebi, Marianne; Heimdal, Jimmy; Pham, Quoc Dat; Sparr, Emma

2016-09-13

Water evaporation concerns all land-living organisms, as ambient air is dryer than their corresponding equilibrium humidity. Contrarily to plants, mammals are covered with a skin that not only hinders evaporation but also maintains its rate at a nearly constant value, independently of air humidity. Here, we show that simple amphiphiles/water systems reproduce this behavior, which suggests a common underlying mechanism originating from responding self-assembly structures. The composition and structure gradients arising from the evaporation process were characterized using optical microscopy, infrared microscopy, and small-angle X-ray scattering. We observed a thin and dry outer phase that responds to changes in air humidity by increasing its thickness as the air becomes dryer, which decreases its permeability to water, thus counterbalancing the increase in the evaporation driving force. This thin and dry outer phase therefore shields the systems from humidity variations. Such a feedback loop achieves a homeostatic regulation of water evaporation.

Water evaporation on highly viscoelastic polymer surfaces.

PubMed

Pu, Gang; Severtson, Steven J

2012-07-03

Results are reported for a study on the evaporation of water droplets from a highly viscoelastic acrylic polymer surface. These are contrasted with those collected for the same measurements carried out on polydimethylsiloxane (PDMS). For PDMS, the evaporation process involves the expected multistep process including constant drop area, constant contact angle, and finally a combination of these steps until the liquid is gone. In contrast, water evaporation from the acrylic polymer shows a constant drop area mode throughout. Furthermore, during the evaporation process, the drop area actually expands on the acrylic polymer. The single mode evaporation process is consistent with formation of wetting structures, which cannot be propagated by the capillary forces. Expansion of the drop area is attributed to the influence of the drop capillary pressure. Furthermore, the rate of drop area expansion is shown to be dependent on the thickness of the polymer film.

[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.

Mean-field kinetic theory approach to evaporation of a binary liquid into vacuum

NASA Astrophysics Data System (ADS)

Frezzotti, A.; Gibelli, L.; Lockerby, D. A.; Sprittles, J. E.

2018-05-01

Evaporation of a binary liquid into near-vacuum conditions has been studied using numerical solutions of a system of two coupled Enskog-Vlasov equations. Liquid-vapor coexistence curves have been mapped out for different liquid compositions. The evaporation process has been investigated at a range of liquid temperatures sufficiently lower than the critical one for the vapor not to significantly deviate from the ideal behavior. It is found that the shape of the distribution functions of evaporating atoms is well approximated by an anisotropic Maxwellian distribution with different characteristic temperatures for velocity components normal and parallel to the liquid-vapor interface. The anisotropy reduces as the evaporation temperature decreases. Evaporation coefficients are computed based on the separation temperature and the maximum concentration of the less volatile component close to the liquid-vapor interface. This choice leads to values which are almost constant in the simulation conditions.

Effect of UV irradiation on the evaporation rate of alcohols droplets

NASA Astrophysics Data System (ADS)

Korobko, O. V.; Britan, A. V.; Verbinskaya, G. H.; Gavryushenko, D. A.

2015-06-01

The effect of ultraviolet irradiation with a wavelength of 390 nm on the evaporation of droplets of the homologous series of alcohols ( n-propanol, n-butanol, n-pentanol, n-heptanol, n-octanol, and n-decanol) at 10, 30, 50, 100, and 200 mm Hg in an atmosphere of dry nitrogen is studied. The values of the evaporation rate of alcohols are calculated with and without irradiation. Starting from n-pentanol, the rate of evaporation grows strongly for droplets of higher alcohols under the effect of low-power irradiation not associated with the heating of the evaporating droplets of alcohols. The obtained results are analyzed by comparing them to experimental data on neutron scattering by alcohols. It is shown that free convection must be considered in order to describe the evaporation process. Expressions of different authors for describing this effect are analyzed.

Surface tension of evaporating nanofluid droplets

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

Chen, Ruey-Hung; Phuoc, Tran X.; Martello, Donald

2011-05-01

Measurements of nanofluid surface tension were made using the pendant droplet method. Three different types of nanoparticles were used - laponite, silver and Fe 2O 3 - with de-ionized water (DW) as the base fluid. The reported results focus on the following categories; (1) because some nanoparticles require surfactants to form stable colloids, the individual effects of the surfactant and the particles were investigated; (2) due to evaporation of the pendant droplet, the particle concentration increases, affecting the apparent surface tension; (3) because of the evaporation process, a hysteresis was found where the evaporating droplet can only achieve lower valuesmore » of surface tension than that of nanofluids at the same prepared concentrations: and (4) the Stefan equation relating the apparent surface tension and heat of evaporation was found to be inapplicable for nanofluids investigated. Comparisons with findings for sessile droplets are also discussed, pointing to additional effects of nanoparticles other than the non-equilibrium evaporation process.« less

Evaluation of three energy balance-based evaporation models for estimating monthly evaporation for five lakes using derived heat storage changes from a hysteresis model

NASA Astrophysics Data System (ADS)

Duan, Zheng; Bastiaanssen, W. G. M.

2017-02-01

The heat storage changes (Q t) can be a significant component of the energy balance in lakes, and it is important to account for Q t for reasonable estimation of evaporation at monthly and finer timescales if the energy balance-based evaporation models are used. However, Q t has been often neglected in many studies due to the lack of required water temperature data. A simple hysteresis model (Q t = a*Rn + b + c* dRn/dt) has been demonstrated to reasonably estimate Q t from the readily available net all wave radiation (Rn) and three locally calibrated coefficients (a-c) for lakes and reservoirs. As a follow-up study, we evaluated whether this hysteresis model could enable energy balance-based evaporation models to yield good evaporation estimates. The representative monthly evaporation data were compiled from published literature and used as ground-truth to evaluate three energy balance-based evaporation models for five lakes. The three models in different complexity are De Bruin-Keijman (DK), Penman, and a new model referred to as Duan-Bastiaanssen (DB). All three models require Q t as input. Each model was run in three scenarios differing in the input Q t (S1: measured Q t; S2: modelled Q t from the hysteresis model; S3: neglecting Q t) to evaluate the impact of Q t on the modelled evaporation. Evaluation showed that the modelled Q t agreed well with measured counterparts for all five lakes. It was confirmed that the hysteresis model with locally calibrated coefficients can predict Q t with good accuracy for the same lake. Using modelled Q t as inputs all three evaporation models yielded comparably good monthly evaporation to those using measured Q t as inputs and significantly better than those neglecting Q t for the five lakes. The DK model requiring minimum data generally performed the best, followed by the Penman and DB model. This study demonstrated that once three coefficients are locally calibrated using historical data the simple hysteresis model can offer reasonable Q t to force energy balance-based evaporation models to improve evaporation modelling at monthly timescales for conditions and long-term periods when measured Q t are not available. We call on scientific community to further test and refine the hysteresis model in more lakes in different geographic locations and environments.

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.

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.

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.

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.

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.

4D Imaging of Salt Precipitation during Evaporation from Saline Porous Media Influenced by the Particle Size Distribution

NASA Astrophysics Data System (ADS)

Norouzi Rad, M.; Shokri, N.

2014-12-01

Understanding the physics of water evaporation from saline porous media is important in many processes such as evaporation from porous media, vegetation, plant growth, biodiversity in soil, and durability of building materials. To investigate the effect of particle size distribution on the dynamics of salt precipitation in saline porous media during evaporation, we applied X-ray micro-tomography technique. Six samples of quartz sand with different grain size distributions were used in the present study enabling us to constrain the effects of particle and pore sizes on salt precipitation patterns and dynamics. The pore size distributions were computed using the pore-scale X-ray images. The packed beds were saturated with NaCl solution of 3 Molal and the X-ray imaging was continued for one day with temporal resolution of 30 min resulting in pore scale information about the evaporation and precipitation dynamics. Our results show more precipitation at the early stage of the evaporation in the case of sand with the larger particle size due to the presence of fewer evaporation sites at the surface. The presence of more preferential evaporation sites at the surface of finer sands significantly modified the patterns and thickness of the salt crust deposited on the surface such that a thinner salt crust was formed in the case of sand with smaller particle size covering larger area at the surface as opposed to the thicker patchy crusts in samples with larger particle sizes. Our results provide new insights regarding the physics of salt precipitation in porous media during evaporation.

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.

Morphological Evolution of Block Copolymer Particles: Effect of Solvent Evaporation Rate on Particle Shape and Morphology.

PubMed

Shin, Jae Man; Kim, YongJoo; Yun, Hongseok; Yi, Gi-Ra; Kim, Bumjoon J

2017-02-28

Shape and morphology of polymeric particles are of great importance in controlling their optical properties or self-assembly into unusual superstructures. Confinement of block copolymers (BCPs) in evaporative emulsions affords particles with diverse structures, including prolate ellipsoids, onion-like spheres, oblate ellipsoids, and others. Herein, we report that the evaporation rate of solvent from emulsions encapsulating symmetric polystyrene-b-polybutadiene (PS-b-PB) determines the shape and internal nanostructure of micron-sized BCP particles. A distinct morphological transition from the ellipsoids with striped lamellae to the onion-like spheres was observed with decreasing evaporation rate. Experiments and dissipative particle dynamics (DPD) simulations showed that the evaporation rate affected the organization of BCPs at the particle surface, which determined the final shape and internal nanostructure of the particles. Differences in the solvent diffusion rates in PS and PB at rapid evaporation rates induced alignment of both domains perpendicular to the particle surface, resulting in ellipsoids with axial lamellar stripes. Slower evaporation rates provided sufficient time for BCP organization into onion-like structures with PB as the outermost layer, owing to the preferential interaction of PB with the surroundings. BCP molecular weight was found to influence the critical evaporation rate corresponding to the morphological transition from ellipsoid to onion-like particles, as well as the ellipsoid aspect ratio. DPD simulations produced morphologies similar to those obtained from experiments and thus elucidated the mechanism and driving forces responsible for the evaporation-induced assembly of BCPs into particles with well-defined shapes and morphologies.

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

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.

An Investigation of Graduate Scientists' Understandings of Evaporation and Boiling.

ERIC Educational Resources Information Center

Goodwin, Alan; Orlik, Yuri

2000-01-01

Uses a video presentation of six situations relating to the evaporation and boiling of liquids and the escape of dissolved gases from solution and investigates graduate scientists' understanding of the concepts of boiling and evaporation. (Author/YDS)

Quantifying Evaporation in a Permeable Pavement System

EPA Science Inventory

Studies quantifying evaporation from permeable pavement systems are limited to a few laboratory studies and one field application. This research quantifies evaporation for a larger-scale field application by measuring the water balance from lined permeable pavement sections. Th...

EVAPORATOR FLOOR, CLARIFIERS TO THE LEFT, SCALES TO THE RIGHT, ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

EVAPORATOR FLOOR, CLARIFIERS TO THE LEFT, SCALES TO THE RIGHT, EVAPORATOR CELLS ONE, TWO AND THREE IN THE BACKGROUND. VIEW FROM NORTHWEST FROM LIME VATS - Lihue Plantation Company, Sugar Mill Building, Haleko Road, Lihue, Kauai County, HI

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.

A new investigation on the water isotopes in the Badain Jaran Desert, China, for inferring water origination

NASA Astrophysics Data System (ADS)

Wu, X.; Wang, Y.; Wang, X. S.; Hu, B.

2017-12-01

Stable isotope δ2H, δ18O and d-excess values of water have previously been used to study the hydraulic connection of groundwater between the surrounding areas such as Heihe River Basin, Qilian Mountain and the Badain Jaran desert (BJD), China. We choose to focus on the effects of strong evaporation on the isotopic characteristics of water in the desert to better understand the origin of water in the BJD. A series of evaporation experiments were conducted in the desert to examine how it may change during evaporation and infiltration under local environmental conditions. Evaporation from open water was monitored in two experiments using local groundwater and lake water, respectively. And evaporation of soil water was observed in three pits which were excavated to different depths below a flat ground surface to install the evaporation-infiltration systems. Water samples were also collected from lakes, a spring and local unconfined aquifer for analyses of stable hydrogen and oxygen isotope ratios, and d-excess values in the BJD. The results show that water isotope contents became progressively enriched along an evaporation line, and the d-excess values decreased with the evaporation. The strong relationship of d-excess and δ18O values was observed from both the experiments and the water samples of groundwater and lakes, which is considered to be a signature of strong evaporation. Also, all the values of groundwater and lake water samples fall along with the evaporation line established through the evaporation experiments, indicating that lakes and groundwater in the study area have evolved from meteoric precipitation under modern or similar to modern climatic conditions. Analysis of a few previously published d-excess and δ18O values of groundwater from the BJD, Lake Eyre Basin, Australia, and Jabal Hafit mountain, United Arab Emirates reveals strong relationships between the two, suggesting similar recharge processes as observed in the BJD. This study demonstrated that the characteristic water isotopic patterns resulting from evaporation could be utilized to help resolve ambiguities in the interpretation of water isotope data in terms of recharge sources, especially, in the arid regions, such as the central Australia and the deserts of United Arab Emirates.

Theoretical and testing performance of an innovative indirect evaporative chiller

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

Jiang, Yi; Xie, Xiaoyun

2010-12-15

An indirect evaporative chiller is a device used to produce chilled water at a temperature between the wet bulb temperature and dew point of the outdoor air, which can be used in building HVAC systems. This article presents a theoretical analysis and practical performance of an innovative indirect evaporative chiller. First, the process of the indirect evaporative chiller is introduced; then, the matching characteristics of the process are presented and analyzed. It can be shown that the process that produces cold water by using dry air is a nearly-reversible process, so the ideal produced chilled water temperature of the indirectmore » evaporative chiller can be set close to the dew point temperature of the chiller's inlet air. After the indirect evaporative chiller was designed, simulations were done to analyze the output water temperature, the cooling efficiency relative to the inlet dew point temperature, and the COP that the chiller can performance. The first installation of the indirect evaporative chiller of this kind has been run for 5 years in a building in the city of Shihezi. The tested output water temperature of the chiller is around 14-20 C, which is just in between of the outdoor wet bulb temperature and dew point. The tested COP{sub r,s} of the developed indirect evaporative chiller reaches 9.1. Compared with ordinary air conditioning systems, the indirect evaporative chiller can save more than 40% in energy consumption due to the fact that the only energy consumed is from pumps and fans. An added bonus is that the indirect evaporative chiller uses no CFCs that pollute to the aerosphere. The tested internal parameters, such as the water-air flow rate ratio and heat transfer area for each heat transfer process inside the chiller, were analyzed and compared with designed values. The tested indoor air conditions, with a room temperature of 23-27 C and relative humidity of 50-70%, proved that the developed practical indirect evaporative chiller successfully satisfy the indoor air conditioning load for the demo building. The indirect evaporative chiller has a potentially wide application in dry regions, especially for large scale commercial buildings. Finally, this paper presented the geographic regions suitable for the technology worldwide. (author)« less

From evaporating pans to transpiring plants (John Dalton Medal Lecture)

NASA Astrophysics Data System (ADS)

Roderick, Michael

2013-04-01

The name of the original inventor of irrigated agriculture is lost to antiquity. Nevertheless, one can perhaps imagine an inquisitive desert inhabitant noting the greener vegetation along a watercourse and putting two and two together. Once water was being supplied and food was being produced it would be natural to ask a further question: how much water can we put on? No doubt much experience was gained down through the ages, but again, one can readily imagine someone inverting a rain gauge, filling it with water and measuring how fast the water evaporated. The inverted rain gauge measures the demand for water by the atmosphere. We call it the evaporative demand. I do not know if this is what actually happened but it sure makes an interesting start to a talk. Evaporation pans are basically inverted rain gauges. The rain gauge and evaporation pan measure the supply and demand respectively and these instruments are the workhorses of agricultural meteorology. Rain gauges are well known. Evaporation pans are lesser known but are in widespread use and are a key part of several national standardized meteorological networks. Many more pans are used for things like scheduling irrigation on farms or estimating evaporation from lakes. Analysis of the long records now available from standardized networks has revealed an interesting phenomenon, i.e., pan evaporation has increased in some places and decreased in other but when averaged over large numbers of pans there has been a steady decline. These independent reports from, for example, the US, Russia, China, India, Thailand, are replicated in the southern hemisphere in, for example, Australia, New Zealand and South Africa. One often hears the statement that because the earth is expected to warm with increasing greenhouse gas emissions then it follows that water will evaporate faster. The pan evaporation observations show that this widely held expectation is wrong. When expectations disagree with observations, it is the observations that win. That is the basis of science. In this Dalton Medal lecture we first examine pan evaporation observations and show why pan evaporation has declined. Armed with that knowledge we then investigate the consequences for plant water use and how this is directly coupled to the catchment water balance.

Isotope mass fractionation during evaporation of Mg2SiO4

NASA Technical Reports Server (NTRS)

Davis, Andrew M.; Clayton, Robert N.; Mayeda, Toshiko K.; Hashimoto, Akihiko

1990-01-01

Synthetic forsterite (Mg2SiO4) was partially evaporated in vacuum for various durations and at different temperatures. The residual charges obtained when molten Mg2SiO4 was evaporated to 12 percent of its initial mass were enriched in heavy isotopes by about 20, 30, and 15 per mil/amu for O, Mg, and Si, respectively, whereas solid forsterite evaporated to a similar residual mass fraction showed negligible fractionations. These results imply that calcium and aluminum-rich refractory inclusions in carbonaceous chondrites must have been at least partially molten in the primordial solar nebula if the observed large mass fractionation effects were caused by evaporation processes in the nebula.

Studies on droplet evaporation and combustion in high pressures

NASA Technical Reports Server (NTRS)

Sato, J.

1993-01-01

High pressure droplet evaporation and combustion have been studied up to 15 MPa under normal and microgravity fields. From the evaporation studies, it has been found that in the supercritical environments, the droplet evaporation rate and lifetime take a maximum and a minimum at an ambient pressure over the critical pressure. Its maximum and minimum points move toward the lower ambient pressures if the ambient temperature is increased. It has been found from the combustion studies that the burning life time takes a minimum at an ambient pressure being equal to the critical pressure. It is attributable to both the pressure dependency of the diffusion rate and the droplet evaporation characteristics described above.

Fabrication of Josephson Junction without shadow evaporation

NASA Astrophysics Data System (ADS)

Wu, Xian; Ku, Hsiangsheng; Long, Junling; Pappas, David

We developed a new method of fabricating Josephson Junction (Al/AlOX/Al) without shadow evaporation. Statistics from room temperature junction resistance and measurement of qubits are presented. Unlike the traditional ``Dolan Bridge'' technique, this method requires two individual lithographies and straight evaporations of Al. Argon RF plasma is used to remove native AlOX after the first evaporation, followed by oxidation and second Al evaporation. Junction resistance measured at room temperature shows linear dependence on Pox (oxidation pressure), √{tox} (oxidation time), and inverse proportional to junction area. We have seen 100% yield of qubits made with this method. This method is promising because it eliminates angle dependence during Junction fabrication, facilitates large scale qubits fabrication.

Method of junction formation for CIGS photovoltaic devices

DOEpatents

Delahoy, Alan E.

2006-03-28

Sulfur is used to improve the performance of CIGS devices prepared by the evaporation of a single source ZIS type compound to form a buffer layer on the CIGS. The sulfur may be evaporated, or contained in the ZIS type material, or both. Vacuum evaporation apparatus of many types useful in the practice of the invention are known in the art. Other methods of delivery, such as sputtering, or application of a thiourea solution, may be substituted for evaporation.

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?

The Evaporation and Degradation of N-Nitroso Dimethyl Amine in Aqueous Solutions.

DTIC Science & Technology

The fate of N-Nitroso Dimethyl Amine ( NDMA ) in aqueous solutions and in a 25 percent caustic waste stream which is produced in the manufacture of...degradation of NDMA in an open lagoon. It was found that for basic solutions, the removal was primarily evaporation, whereas, evaporation is low for...that nitrite severely inhibits the photolysis of NDMA in acid and neutral pHs, and an increase in ionic strength slightly increases the evaporation rate

Method of junction formation for CIGS photovoltaic devices

DOEpatents

Delahoy, Alan E.

2010-01-26

Sulfur is used to improve the performance of CIGS devices prepared by the evaporation of a single source ZIS type compound to form a buffer layer on the CIGS. The sulfur may be evaporated, or contained in the ZIS type material, or both. Vacuum evaporation apparatus of many types useful in the practice of the invention are known in the art. Other methods of delivery, such as sputtering, or application of a thiourea solution, may be substituted for evaporation.

The role of ultra-fast solvent evaporation on the directed self-assembly of block polymer thin films

NASA Astrophysics Data System (ADS)

Drapes, Chloe; Nelson, G.; Grant, M.; Wong, J.; Baruth, A.

The directed self-assembly of nano-structures in block polymer thin films viasolvent vapor annealing is complicated by several factors, including evaporation rate. Solvent vapor annealing exposes a disordered film to solvent(s) in the vapor phase, increasing mobility and tuning surface energy, with the intention of producing an ordered structure. Recent theoretical predictions reveal the solvent evaporation affects the resultant nano-structuring. In a competition between phase separation and kinetic trapping during drying, faster solvent removal can enhance the propagation of a given morphology into the bulk of the thin film down to the substrate. Recent construction of a purpose-built, computer controlled solvent vapor annealing chamber provides control over forced solvent evaporation down to 15 ms. This is accomplished using pneumatically actuated nitrogen flow into and out of the chamber. Furthermore, in situ spectral reflectance, with 10 ms temporal resolution, monitors the swelling and evaporation. Presently, cylinder-forming polystyrene-block-polylactide thin films were swollen with 40% (by volume) tetrahydrofuran, followed by immediate evaporation under a variety of designed conditions. This includes various evaporation times, ranging from 15 ms to several seconds, and four unique rate trajectories, including linear, exponential, and combinations. Atomic force microscopy reveals specific surface, free and substrate, morphologies of the resultant films, dependent on specific evaporation conditions. Funded by the Clare Boothe Luce Foundation and Nebraska EPSCoR.

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.

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.

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.

The contribution of evaporative emissions from gasoline vehicles to the volatile organic compound inventory in Mexico City.

PubMed

Schifter, I; Díaz, L; Rodríguez, R; González-Macías, C

2014-06-01

The strategy for decreasing volatile organic compound emissions in Mexico has been focused much more on tailpipe emissions than on evaporative emissions, so there is very little information on the contribution of evaporative emissions to the total volatile organic compound inventory. We examined the magnitudes of exhaust and evaporative volatile organic compound emissions, and the species emitted, in a representative fleet of light-duty gasoline vehicles in the Metropolitan Area of Mexico City. The US "FTP-75" test protocol was used to estimate volatile organic compound emissions associated with diurnal evaporative losses, and when the engine is started and a journey begins. The amount and nature of the volatile organic compounds emitted under these conditions have not previously been accounted in the official inventory of the area. Evaporative emissions from light-duty vehicles in the Metropolitan Area of Mexico City were estimated to be 39 % of the total annual amount of hydrocarbons emitted. Vehicles built before 1992 (16 % of the fleet) were found to be responsible for 43 % of the total hydrocarbon emissions from exhausts and 31 % of the evaporative emissions of organic compounds. The relatively high amounts of volatile organic compounds emitted from older vehicles found in this study show that strong emission controls need to be implemented in order to decrease the contribution of evaporative emissions of this fraction of the fleet.

Influence of forced air volume on water evaporation during sewage sludge bio-drying.

PubMed

Cai, Lu; Chen, Tong-Bin; Gao, Ding; Zheng, Guo-Di; Liu, Hong-Tao; Pan, Tian-Hao

2013-09-01

Mechanical aeration is critical to sewage sludge bio-drying, and the actual water loss caused by aeration can be better understood from investigations of the relationship between aeration and water evaporation from the sewage sludge bio-drying pile based on in situ measurements. This study was conducted to investigate the effects of forced air volume on the evaporation of water from a sewage sludge bio-drying pile. Dewatered sewage sludge was bio-dried using control technology for bio-drying, during which time the temperature, superficial air velocity and water evaporation were measured and calculated. The results indicated that the peak air velocity and water evaporation occurred in the thermophilic phase and second temperature-increasing phase, with the highest values of 0.063 ± 0.027 m s(-1) and 28.9 kg ton(-1) matrix d(-1), respectively, being observed on day 4. Air velocity above the pile during aeration was 43-100% higher than when there was no aeration, and there was a significantly positive correlation between air volume and water evaporation from day 1 to 15. The order of daily means of water evaporation was thermophilic phase > second temperature-increasing phase > temperature-increasing phase > cooling phase. Forced aeration controlled the pile temperature and improved evaporation, making it the key factor influencing water loss during the process of sewage sludge bio-drying. Copyright © 2013 Elsevier Ltd. All rights reserved.

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.

Evaporation estimates from the Dead Sea and their implications on its water balance

NASA Astrophysics Data System (ADS)

Oroud, Ibrahim M.

2011-12-01

The Dead Sea (DS) is a terminal hypersaline water body situated in the deepest part of the Jordan Valley. There is a growing interest in linking the DS to the open seas due to severe water shortages in the area and the serious geological and environmental hazards to its vicinity caused by the rapid level drop of the DS. A key issue in linking the DS with the open seas would be an accurate determination of evaporation rates. There exist large uncertainties of evaporation estimates from the DS due to the complex feedback mechanisms between meteorological forcings and thermophysical properties of hypersaline solutions. Numerous methods have been used to estimate current and historical (pre-1960) evaporation rates, with estimates differing by ˜100%. Evaporation from the DS is usually deduced indirectly using energy, water balance, or pan methods with uncertainty in many parameters. Accumulated errors resulting from these uncertainties are usually pooled into the estimates of evaporation rates. In this paper, a physically based method with minimum empirical parameters is used to evaluate historical and current evaporation estimates from the DS. The more likely figures for historical and current evaporation rates from the DS were 1,500-1,600 and 1,200-1,250 mm per annum, respectively. Results obtained are congruent with field observations and with more elaborate procedures.

Sampling gaseous compounds from essential oils evaporation by solid phase microextraction devices

NASA Astrophysics Data System (ADS)

Cheng, Wen-Hsi; Lai, Chin-Hsing

2014-12-01

Needle trap samplers (NTS) are packed with 80-100 mesh divinylbenzene (DVB) particles to extract indoor volatile organic compounds (VOCs). This study compared extraction efficiency between an NTS and a commercially available 100 μm polydimethylsiloxane-solid phase microextration (PDMS-SPME) fiber sampler used to sample gaseous products in heated tea tree essential oil in different evaporation modes, which were evaporated respectively by free convection inside a glass evaporation dish at 27 °C, by evaporation diffuser at 60 °C, and by thermal ceramic wicks at 100 °C. The experimental results indicated that the NTS performed better than the SPME fiber samplers and that the NTS primarily adsorbed 5.7 ng ethylbenzene, 5.8 ng m/p-xylenes, 11.1 ng 1,2,3-trimethylbenzene, 12.4 ng 1,2,4-trimethylbenzene and 9.99 ng 1,4-diethylbenzene when thermal ceramic wicks were used to evaporate the tea tree essential oil during a 1-hr evaporation period. The experiment also indicated that the temperature used to heat the essential oils should be as low as possible to minimize irritant VOC by-products. If the evaporation temperature does not exceed 100 °C, the concentrations of main by-products trimethylbenzene and diethylbenzene are much lower than the threshold limit values recommended by the National Institute for Occupational Safety and Health (NIOSH).

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.

Contrasting roles of interception and transpiration in the hydrological cycle - Part 2: Moisture recycling

NASA Astrophysics Data System (ADS)

van der Ent, R. J.; Wang-Erlandsson, L.; Keys, P. W.; Savenije, H. H. G.

2014-03-01

The contribution of land evaporation to local and remote precipitation (i.e., moisture recycling) is of significant importance to sustain water resources and ecosystems. But how important are different evaporation components in sustaining precipitation? This is the first paper to present moisture recycling metrics for partitioned evaporation. In the companion paper, Part 1, evaporation was partitioned into vegetation interception, floor interception, soil moisture evaporation and open water evaporation (constituting the direct, purely physical fluxes, largely dominated by interception), and transpiration (delayed, biophysical flux). Here, we track these components forward as well as backward in time. We also include age tracers to study the atmospheric residence times of these evaporation components. As the main result we present a new image of the global hydrological cycle that includes quantification of partitioned evaporation and moisture recycling as well as the atmospheric residence times of all fluxes. We demonstrate that evaporated interception is more likely to return as precipitation on land than transpired water. On average, direct evaporation (essentially interception) is found to have an atmospheric residence time of eight days, while transpiration typically resides nine days in the atmosphere. Interception recycling has a much shorter local length scale than transpiration recycling, thus interception generally precipitates closer to its evaporative source than transpiration, which is particularly pronounced outside the tropics. We conclude that interception mainly works as an intensifier of the local hydrological cycle during wet spells. On the other hand, transpiration remains active during dry spells and is transported over much larger distances downwind where it can act as a significant source of moisture. Thus, as various land-use types can differ considerably in their partitioning between interception and transpiration, our results stress that land-use changes (e.g., forest to cropland conversion) do not only affect the magnitude of moisture recycling, but could also influence the moisture recycling patterns and lead to a redistribution of water resources. As such, this research highlights that land-use changes can have complex effects on the atmospheric branch of the hydrological cycle.

Evaporation rate of emulsion and oil-base emulsion pheromones

USDA-ARS?s Scientific Manuscript database

Knowledge of pheromone evaporation rate is critical to distribute pheromone containers effectively in the forest, orchard and field. There are several factors influencing the pheromone evaporation rate that include wind speed, container size and porosity, release area, temperature, humidity, pherom...

A portable device for the measurement of evaporative water loss.

DOT National Transportation Integrated Search

1967-08-01

A portable device has been developed for the precise measurement of evaporative water loss. Under appropriate conditions the measurement of evaporative water loss may be used as an index of 'emotional stress' in flying personnel. The apparatus incorp...

27 CFR 30.32 - Determination of proof obscuration.

Code of Federal Regulations, 2012 CFR

2012-04-01

... evaporation method may be used only for spirits in the range of 80-100 degrees at gauge proof. (b) Evaporation... evaporation of 25 milliliters 0.125 gram, the amount of solids present in 100 milliliters of the spirits is 0...

27 CFR 30.32 - Determination of proof obscuration.

Code of Federal Regulations, 2011 CFR

2011-04-01

... evaporation method may be used only for spirits in the range of 80-100 degrees at gauge proof. (b) Evaporation... evaporation of 25 milliliters 0.125 gram, the amount of solids present in 100 milliliters of the spirits is 0...

27 CFR 30.32 - Determination of proof obscuration.

Code of Federal Regulations, 2014 CFR

2014-04-01

... evaporation method may be used only for spirits in the range of 80-100 degrees at gauge proof. (b) Evaporation... evaporation of 25 milliliters 0.125 gram, the amount of solids present in 100 milliliters of the spirits is 0...

27 CFR 30.32 - Determination of proof obscuration.

Code of Federal Regulations, 2013 CFR

2013-04-01

... evaporation method may be used only for spirits in the range of 80-100 degrees at gauge proof. (b) Evaporation... evaporation of 25 milliliters 0.125 gram, the amount of solids present in 100 milliliters of the spirits is 0...

Quantification of soil water evaporation using TDR-microlysimetry

USDA-ARS?s Scientific Manuscript database

Soil water evaporation is conventionally measured using microlysimeters by evaluating the daily change in mass. Daily removal is laborious and replacement immediately after irrigation events is impractical because of field wetness which leads to delays and an underestimation of evaporation. Irrigati...

EVALUATION OF HADWACO MVR EVAPORATOR, ETV REPORT& STATEMENT

EPA Science Inventory

Hadwaco US, Inc., manufactures a commercial ready mechanical vapor recompression (MVR) evaporator for use in the metal finishing industry. The evaporator utilizes proven MVR and falling film principles, with the key innovation being the construction material of the heat transfer ...

DWPF Recycle Evaporator Simulant Tests

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

Stone, M

2005-04-05

Testing was performed to determine the feasibility and processing characteristics of an evaporation process to reduce the volume of the recycle stream from the Defense Waste Processing Facility (DWPF). The concentrated recycle would be returned to DWPF while the overhead condensate would be transferred to the Effluent Treatment Plant. Various blends of evaporator feed were tested using simulants developed from characterization of actual recycle streams from DWPF and input from DWPF-Engineering. The simulated feed was evaporated in laboratory scale apparatus to target a 30X volume reduction. Condensate and concentrate samples from each run were analyzed and the process characteristics (foaming,more » scaling, etc) were visually monitored during each run. The following conclusions were made from the testing: Concentration of the ''typical'' recycle stream in DWPF by 30X was feasible. The addition of DWTT recycle streams to the typical recycle stream raises the solids content of the evaporator feed considerably and lowers the amount of concentration that can be achieved. Foaming was noted during all evaporation tests and must be addressed prior to operation of the full-scale evaporator. Tests were conducted that identified Dow Corning 2210 as an antifoam candidate that warrants further evaluation. The condensate has the potential to exceed the ETP WAC for mercury, silicon, and TOC. Controlling the amount of equipment decontamination recycle in the evaporator blend would help meet the TOC limits. The evaporator condensate will be saturated with mercury and elemental mercury will collect in the evaporator condensate collection vessel. No scaling on heating surfaces was noted during the tests, but splatter onto the walls of the evaporation vessels led to a buildup of solids. These solids were difficult to remove with 2M nitric acid. Precipitation of solids was not noted during the testing. Some of the aluminum present in the recycle streams was converted from gibbsite to aluminum oxide during the evaporation process. The following recommendations were made: Recycle from the DWTT should be metered in slowly to the ''typical'' recycle streams to avoid spikes in solids content to allow consistent processing and avoid process upsets. Additional studies should be conducted to determine acceptable volume ratios for the HEME dissolution and decontamination solutions in the evaporator feed. Dow Corning 2210 antifoam should be evaluated for use to control foaming. Additional tests are required to determine the concentration of antifoam required to prevent foaming during startup, the frequency of antifoam additions required to control foaming during steady state processing, and the ability of the antifoam to control foam over a range of potential feed compositions. This evaluation should also include evaluation of the degradation of the antifoam and impact on the silicon and TOC content of the condensate. The caustic HEME dissolution recycle stream should be neutralized to at least pH of 7 prior to blending with the acidic recycle streams. Dow Corning 2210 should be used during the evaporation testing using the radioactive recycle samples received from DWPF. Evaluation of additional antifoam candidates should be conducted as a backup for Dow Corning 2210. A camera and/or foam detection instrument should be included in the evaporator design to allow monitoring of the foaming behavior during operation. The potential for foam formation and high solids content should be considered during the design of the evaporator vessel.« less

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.

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.

[Dynamics of Irreversible Evaporation of a Water-Protein Droplet and a Problem of Structural and Dynamical Experiments with Single Molecules].

PubMed

Shaitan, K V; Armeev, G A; Shaytan, A K

2016-01-01

We discuss the effect of isothermal and adiabatic evaporation of water on the state of a water-protein droplet. The discussed problem is of current importance due to development of techniques to perform single molecule experiments using free electron lasers. In such structure-dynamic experiments the delivery of a sample into the X-ray beam is performed using the microdroplet injector. The time between the injection and delivery is in the order of microseconds. In this paper we developed a specialized variant of all-atom molecular dynamics simulations for the study of irreversible isothermal evaporation of the droplet. Using in silico experiments we determined the parameters of isothermal evaporation of the water-protein droplet with the sodium and chloride ions in the concentration range of 0.3 M at different temperatures. The energy of irreversible evaporation determined from in silico experiments at the initial stages of evaporation virtually coincides with the specific heat of evaporation for water. For the kinetics of irreversible adiabatic evaporation an exact analytical solution was obtained in the limit of high thermal conductivity of the droplet (or up to the droplet size of -100 Å). This analytical solution incorporates parameters that are determined using in silico. experiments on isothermal droplet evaporation. We show that the kinetics of adiabatic evaporation and cooling of the droplet scales with the droplet size. Our estimates of the water-protemi droplet. freezing rate in the adiabatic regime in a vacuum chamber show that additional techniques for stabilizing the temperature inside the droplet should be used in order to study the conformational transitions of the protein in single molecules. Isothermal and quasi-isothermal conditions are most suitable for studying the conformational transitions upon object functioning. However, in this case it is necessary to take into account the effects of dehydration and rapid increase of ionic strength in an aqueous microenvironment surrounding the protein.

Thermal and chemical evolution in the early Solar System as recorded by FUN CAIs: Part II - Laboratory evaporation of potential CMS-1 precursor material

NASA Astrophysics Data System (ADS)

Mendybaev, Ruslan A.; Williams, Curtis D.; Spicuzza, Michael J.; Richter, Frank M.; Valley, John W.; Fedkin, Alexei V.; Wadhwa, Meenakshi

2017-03-01

We present the results of laboratory experiments in which a forsterite-rich melt estimated to be a potential precursor of Allende CMS-1 FUN CAI was evaporated into vacuum for different lengths of time at 1900 °C. The evaporation of this melt resulted in residues that define trajectories in chemical as well as magnesium, silicon and oxygen isotopic composition space and come very close to the measured properties of CMS-1. The isotopic composition of the evaporation residues was also used to determine the kinetic isotopic fractionation factors [α2,1 (vapor-melt) defined as the ratio of isotopes 2 and 1 of a given element in the evaporating gas divided by their ratio in the evaporating source] for evaporation of magnesium (α25,24 for 25Mg/24Mg), silicon (α29,28 for 29Si/28Si) and oxygen (α18,16 for 18O/16O) from the forsterite-rich melt at 1900 °C. The values of α25,24 = 0.98383 ± 0.00033 and α29,28 = 0.99010 ± 0.00038 are essentially independent of change in the melt composition as evaporation proceeds. In contrast, α18,16 changes from 0.9815 ± 0.0016 to ∼0.9911 when the residual melt composition changes from forsteritic to melilitic. Using the determined values of α25,24 and α29,28 and present-day bulk chemical composition of the CMS-1, the composition of the precursor of the inclusion was estimated to be close to the clinopyroxene + spinel + forsterite assemblage condensed from a solar composition gas. The correspondence between the chemical composition and isotopic fractionation of experimental evaporation residues and the present-day bulk chemical and isotopic compositions of CMS-1 is evidence that evaporation played a major role in the chemical evolution of CMS-1.

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.

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.

Evaporative moisture loss from heterogeneous stone: Material-environment interactions during drying

NASA Astrophysics Data System (ADS)

McAllister, Daniel; Warke, Patricia; McCabe, Stephen; Gomez-Heras, M.

2016-11-01

The complexities of evaporation from structurally and mineralogically heterogeneous sandstone (Locharbriggs Sandstone) are investigated through a laboratory-based experiment in which a variety of environmental conditions are simulated. Data reported demonstrate the significance of material-environment interactions on the spatial and temporal variability of evaporative dynamics. Evaporation from porous stone is determined by the interplay between environmental, material and solution properties, which govern the rate and mode by which water is transmitted to, and subsequently removed from, an evaporating surface. Initially, when the stone is saturated, evaporation is characterized by high rates of moisture loss primarily controlled by external atmospheric conditions. However, as drying progresses, eventually the hydraulic continuity between the stone surface and subsurface is disrupted with recession of the drying front and a decrease in evaporation rates which become reliant on the ability of the material to transport water vapour to the block surface. Pore size distribution and connectivity, as well as other material properties, control the timing of each stage of evaporation and the nature of the transition. These experimental data highlight the complexity of evaporation, demonstrating that different regions of the same stone can exhibit varying moisture dynamics during drying and that the rate and nature of evaporative loss differs under different environmental conditions. The results identify the importance of material-environment interactions during drying and that stone micro-environmental conditions cannot be inferred from ambient data alone. These data have significance for understanding the spatial distribution of stone surface weathering-related morphologies in both the natural and built environments where mineralogical and/or structural heterogeneity creates differences in moisture flux and hence variable drying rates. Such differences may provide a clearer explanation for the initiation and subsequent development of complex weathering responses where areas of significant deterioration can be found alongside areas that exhibit little or no evidence of surface breakdown.

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.

Spin distribution of evaporation residues formed in complete and incomplete fusion in 16O+154Sm system

NASA Astrophysics Data System (ADS)

Singh, D.; Linda, Sneha B.; Giri, Pankaj K.; Mahato, Amritraj; Tripathi, R.; Kumar, Harish; Afzal Ansari, M.; Sathik, N. P. M.; Ali, Rahbar; Kumar, Rakesh; Muralithar, S.; Singh, R. P.

2017-11-01

Spin distributions for several evaporation residues populated in the 16O+154Sm system have been measured at projectile energy ≈ 6.2 MeV/A by using the charged particle-γ-coincidence technique. The measured spin distributions of the evaporation residues populated through incomplete fusion associated with 'fast' α and 2α-emission channels are found to be entirely different from fusion-evaporation channels. It is observed that the mean input angular momentum for the evaporation residues formed in incomplete fusion channel is relatively higher than that observed for evaporation residues in complete fusion channels. The feeding intensity profile of evaporation residues populated through complete fusion and incomplete fusion have also been studied. The incomplete fusion channels are found to have narrow range feeding only for high spin states, while complete fusion channels are strongly fed over a broad spin range and widely populated. Comparison of present results with earlier data suggests that the mean input angular momentum values are relatively smaller for spherical target than that of deformed target using the same projectile and incident energy highlighting the role of target deformation in incomplete fusion dynamics.

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.

The relationship between air layers and evaporative resistance of male Chinese ethnic clothing.

PubMed

Wang, Faming; Peng, Hui; Shi, Wen

2016-09-01

In this study, the air layer distribution and evaporative resistances of 39 sets of male Chinese ethnic clothing were investigated using a sweating thermal manikin and the three-dimensional (3D) body scanning technique. Relationships between the evaporative resistance and air layers (i.e., air gap thickness and air volume) were explored. The results demonstrated that the clothing total evaporative resistance increases with the increasing air gap size/air volume, but the rate of increase gradually decreases as the mean air gap size or the total air volume becomes larger. The clothing total evaporative resistance reaches its maximum when the average air gap size and the total air volume are 41.6 mm and 69.9 dm(3), respectively. Similar general trends were also found between local mean air gap size and clothing local evaporative resistance at different body parts. However, different body parts show varied rates of increase and decrease in the local evaporative resistance. The research findings provide a comprehensive database for predicting overall and local human thermal comfort while wearing male Chinese ethnic clothing. Copyright © 2016 Elsevier Ltd. All rights reserved.

Accelerated evaporation of water on graphene oxide.

PubMed

Wan, Rongzheng; Shi, Guosheng

2017-03-29

Using molecular dynamics simulations, we show that the evaporation of nanoscale volumes of water on patterned graphene oxide is faster than that on homogeneous graphene oxide. The evaporation rate of water is insensitive to variation in the oxidation degree of the oxidized regions, so long as the water film is only distributed on the oxidized regions. The evaporation rate drops when the water film spreads onto the unoxidized regions. Further analysis showed that varying the oxidation degree observably changed the interaction between the outmost water molecules and the solid surface, but the total interaction for the outmost water molecules only changed a very limited amount due to the correspondingly regulated water-water interaction when the water film is only distributed on the oxidized regions. When the oxidation degree is too low and some unoxidized regions are also covered by the water film, the thickness of the water film decreases, which extends the lifetime of the hydrogen bonds for the outmost water molecules and lowers the evaporation rate of the water. The insensitivity of water evaporation to the oxidation degree indicates that we only need to control the scale of the unoxidized and oxidized regions for graphene oxide to regulate the evaporation of nanoscale volumes of water.

A Paleoevaporation Proxy Using Compound Specific Stable Isotope Measurements from Peatland Biomarkers

NASA Astrophysics Data System (ADS)

Wang, J.; Nichols, J. E.; Huang, Y.

2009-12-01

It is important to understand how evaporation from wetlands changes with climate. To do this, we have developed a paleoevaporation proxy for use in ombrotrophic peatland sediments. Using compound specific hydrogen isotopic ratios of vascular plant and Sphagnum biomarkers, we can quantitatively reconstruct past changes in evaporation. The contrast in H isotopic ratios of water available to living Sphagnum and water in the acrotelm can be used to estimate “f”—the fraction of water remaining after evaporation. Vascular plant leaf waxes record H isotopic ratios of precipitation which is little affected by evaporation, whereas the Sphagnum biomarker, C23 n-alkane, records H isotopic ratios of the water inside its cells and between its leaves, which is strongly affected by evaporation at the bog surface. Evaporation changes can then be calculated with the H-isotopic ratios of the two types of biomarkers. We calibrated the apparent fractionation of D/H ratios from source water to C23 n-alkane with lab-grown Sphagnum. We also present several reconstructions of paleoevaporation from peatlands throughout eastern North America. By comparison with overall hydrologic balance, we are able to understand the varying role of evaporation in the hydrologic system in both time and space.

Wetting and evaporation of salt-water nanodroplets: A molecular dynamics investigation.

PubMed

Zhang, Jun; Borg, Matthew K; Sefiane, Khellil; Reese, Jason M

2015-11-01

We employ molecular dynamics simulations to study the wetting and evaporation of salt-water nanodroplets on platinum surfaces. Our results show that the contact angle of the droplets increases with the salt concentration. To verify this, a second simulation system of a thin salt-water film on a platinum surface is used to calculate the various surface tensions. We find that both the solid-liquid and liquid-vapor surface tensions increase with salt concentration and as a result these cause an increase in the contact angle. However, the evaporation rate of salt-water droplets decreases as the salt concentration increases, due to the hydration of salt ions. When the water molecules have all evaporated from the droplet, two forms of salt crystals are deposited, clump and ringlike, depending on the solid-liquid interaction strength and the evaporation rate. To form salt crystals in a ring, it is crucial that there is a pinned stage in the evaporation process, during which salt ions can move from the center to the rim of the droplets. With a stronger solid-liquid interaction strength, a slower evaporation rate, and a higher salt concentration, a complete salt crystal ring can be deposited on the surface.

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

Comprehensive study of thin film evaporation from nanoporous membranes for enhanced thermal management

NASA Astrophysics Data System (ADS)

Wilke, Kyle; Barabadi, Banafsheh; Lu, Zhengmao; Zhang, Tiejun; Wang, Evelyn

Performance of emerging electronics is often dictated by the ability to dissipate heat generated in the device. Thin film evaporation from nanopores promises enhanced thermal management by reducing the thermal transport resistance across the liquid film while providing capillary pumping. We present a study of the dependence of evaporation from nanopores on a variety of geometric parameters. Anodic aluminum oxide membranes were used as an experimental template. A biphilic treatment was also used to create a hydrophobic section of the pore to control meniscus location. We demonstrated different heat transfer regimes and observed more than an order of magnitude increase in dissipated heat flux by confining fluid within the nanopore. Pore diameter had little effect on evaporation performance at pore radii of this length scale due to the negligible conduction resistance from the pore wall to the evaporating interface. The dissipated heat flux scaled linearly with porosity as the evaporative area increased. Furthermore, it was demonstrated that moving the meniscus as little as 1 μm into the pore could decrease performance significantly. The results provide a better understanding of evaporation from nanopores and provide guidance in future device design.

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

Does non-ionizing radiant energy affect determination of the evaporation rate by the gradient method?

PubMed

Kjartansson, S; Hammarlund, K; Oberg, P A; Sedin, G

1991-01-01

A study was performed to investigate whether measurements of the evaporation rate from the skin of newborn infants by the gradient method are affected by the presence of non-ionizing radiation from phototherapy equipment or a radiant heater. The evaporation rate was measured experimentally with the measuring sensors either exposed to or protected from non-ionizing radiation. Either blue light (phototherapy) or infrared light (radiant heater) was used; in the former case the evaporation rate was measured from a beaker of water covered with a semipermeable membrane, and in the latter case from the hand of an adult subject, aluminium foil or with the measuring probe in the air. No adverse effect on the determinations of the evaporation rate was found in the presence of blue light. Infrared radiation caused an error of 0.8 g/m2h when the radiant heater was set at its highest effect level or when the ambient humidity was high. At low and moderate levels the observed evaporation rate was not affected. It is concluded that when clinical measurements are made from the skin of newborn infants nursed under a radiant heater, the evaporation rate can appropriately be determined by the gradient method.

Evaporation-induced cavitation in nanofluidic channels

PubMed Central

Duan, Chuanhua; Karnik, Rohit; Lu, Ming-Chang; Majumdar, Arun

2012-01-01

Cavitation, known as the formation of vapor bubbles when liquids are under tension, is of great interest both in condensed matter science as well as in diverse applications such as botany, hydraulic engineering, and medicine. Although widely studied in bulk and microscale-confined liquids, cavitation in the nanoscale is generally believed to be energetically unfavorable and has never been experimentally demonstrated. Here we report evaporation-induced cavitation in water-filled hydrophilic nanochannels under enormous negative pressures up to -7 MPa. As opposed to receding menisci observed in microchannel evaporation, the menisci in nanochannels are pinned at the entrance while vapor bubbles form and expand inside. Evaporation in the channels is found to be aided by advective liquid transport, which leads to an evaporation rate that is an order of magnitude higher than that governed by Fickian vapor diffusion in macro- and microscale evaporation. The vapor bubbles also exhibit unusual motion as well as translational stability and symmetry, which occur because of a balance between two competing mass fluxes driven by thermocapillarity and evaporation. Our studies expand our understanding of cavitation and provide new insights for phase-change phenomena at the nanoscale. PMID:22343530

Desiccation of a pool of blood: from fluid mechanics to forensic investigations

NASA Astrophysics Data System (ADS)

Nicloux, Celine; Brutin, David

2012-11-01

The evaporation of biological fluids (with droplet configuration) has been studied since a few years due 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 evaporation of a pool of blood is studied in order to link the pattern formation and the evaporation dynamics. We intend to transfer the knowledge acquired for drops on pool to improve the forensic investigations. In this study, we focus on both pool of blood and pure water to determine the transition region from drop to pool and then to characterize the evaporation rate in the pool configuration. The spreading of blood which can be seen as a complex fluid is strongly influenced the substrate nature. The initial contact angle of blood on different substrate nature will influence the maximum thickness of the layer and then will influence the evaporation mass flux. The authors gratefully acknowledge the help and the fruitful discussions raised with A. Boccoz.

Direct retrieval of ocean surface evaporation and latent heat flux from the spacebased observations

NASA Technical Reports Server (NTRS)

Liu, W. T.; Tang, W.

2000-01-01

The Tropical Rain Measuring Mission (TRMM) provides the opportunity to improve the spacebased estimation of evaporation. An algorithm for retrieving evaporation directly from the radiances observed by the TRMM Microwave Imager and its validation results are described.

PRODUCTION ENGINEERING AND MARKETING ANALYSIS OF THE ROTATING DISK EVAPORATOR

EPA Science Inventory

Recent EPA-funded research into the onsite, mechanical evaporation of wastewater from single family homes revealed that a rotating disk evaporator (RDE) could function in a nondischarging mode. Such a device has potential use where site limitations preclude conventional methods o...

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

Multileg Heat-Pipe Evaporator

NASA Technical Reports Server (NTRS)

Alario, J. P.; Haslett, R. A.

1986-01-01

Parallel pipes provide high heat flow from small heat exchanger. Six parallel heat pipes extract heat from overlying heat exchanger, forming evaporator. Vapor channel in pipe contains wick that extends into screen tube in liquid channel. Rods in each channel hold wick and screen tube in place. Evaporator compact rather than extended and more compatible with existing heat-exchanger geometries. Prototype six-pipe evaporator only 0.3 m wide and 0.71 m long. With ammonia as working fluid, transports heat to finned condenser at rate of 1,200 W.

Development of a laboratory prototype spraying flash evaporator.

NASA Technical Reports Server (NTRS)

Gaddis, J. L.

1972-01-01

A functional description of the flash evaporator that is being developed as a candidate for the Space Shuttle Environmental Control System thermal control is presented. A single evaporator configuration uses water as an evaporant to accommodate on-orbit peak heat loads and Freon 22 for terrestrial flight phases below 120,000 ft altitude. Development history, test plans, and operational characteristics are described. Detailed information is included to show: design features, fabrication techniques used for a prototype unit, redundancy considerations, and the control arrangement.

Evaporation from cultivated and semi-wild Sudanian Savanna in west Africa

NASA Astrophysics Data System (ADS)

Ceperley, Natalie C.; Mande, Theophile; van de Giesen, Nick; Tyler, Scott; Yacouba, Hamma; Parlange, Marc B.

2017-08-01

Rain-fed farming is the primary livelihood of semi-arid west Africa. Changes in land cover have the potential to affect precipitation, the critical resource for production. Turbulent flux measurements from two eddy-covariance towers and additional observations from a dense network of small, wireless meteorological stations combine to relate land cover (savanna forest and agriculture) to evaporation in a small (3.5 km2) catchment in Burkina Faso, west Africa. We observe larger sensible and latent heat fluxes over the savanna forest in the headwater area relative to the agricultural section of the watershed all year. Higher fluxes above the savanna forest are attributed to the greater number of exposed rocks and trees and the higher productivity of the forest compared to rain-fed, hand-farmed agricultural fields. Vegetation cover and soil moisture are found to be primary controls of the evaporative fraction. Satellite-derived vegetation index (NDVI) and soil moisture are determined to be good predictors of evaporative fraction, as indicators of the physical basis of evaporation. Our measurements provide an estimator that can be used to derive evaporative fraction when only NDVI is available. Such large-scale estimates of evaporative fraction from remotely sensed data are valuable where ground-based measurements are lacking, which is the case across the African continent and many other semi-arid areas. Evaporative fraction estimates can be combined, for example, with sensible heat from measurements of temperature variance, to provide an estimate of evaporation when only minimal meteorological measurements are available in remote regions of the world. These findings reinforce local cultural beliefs of the importance of forest fragments for climate regulation and may provide support to local decision makers and rural farmers in the maintenance of the forest areas.

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.

Isothermal evaporation of ethanol in a dynamic gas atmosphere.

PubMed

Milev, Adriyan S; Wilson, Michael A; Kannangara, G S Kamali; Feng, Hai; Newman, Phillip A

2012-01-12

Optimization of evaporation and pyrolysis conditions for ethanol are important in carbon nanotube (CNT) synthesis. The activation enthalpy (ΔH(‡)), the activation entropy (ΔS(‡)), and the free energy barrier (ΔG(‡)) to evaporation have been determined by measuring the molar coefficient of evaporation, k(evap), at nine different temperatures (30-70 °C) and four gas flow rates (25-200 mL/min) using nitrogen and argon as carrier gases. At 70 °C in argon, the effect of the gas flow rate on k(evap) and ΔG(‡) is small. However, this is not true at temperatures as low as 30 °C, where the increase of the gas flow rate from 25 to 200 mL/min results in a nearly 6 times increase of k(evap) and decrease of ΔG(‡) by ~5 kJ/mol. Therefore, at 30 °C, the effect of the gas flow rate on the ethanol evaporation rate is attributed to interactions of ethanol with argon molecules. This is supported by simultaneous infrared spectroscopic analysis of the evolved vapors, which demonstrates the presence of different amounts of linear and cyclic hydrogen bonded ethanol aggregates. While the amount of these aggregates at 30 °C depends upon the gas flow rate, no such dependence was observed during evaporation at 70 °C. When the evaporation was carried out in nitrogen, ΔG(‡) was almost independent of the evaporation temperature (30-70 °C) and the gas flow rate (25-200 mL/min). Thus the evaporation of ethanol in a dynamic gas atmosphere at different temperatures may go via different mechanisms depending on the nature of the carrier gas.

Hybrid Cu(2)O diode with orientation-controlled C(60) polycrystal.

PubMed

Izaki, Masanobu; Saito, Takamasa; Ohata, Tatsuya; Murata, Kazufumi; Fariza, Binti Mohamad; Sasano, Junji; Shinagawa, Tsutomu; Watase, Seiji

2012-07-25

We report on a hybrid diode composed of a 2.1 eV bandgap p-cupric oxide (Cu2O) semiconductor and fullerene (C60) layer with a face-centered cubic configuration. The hybrid diode has been constructed by electrodeposition of the 500 nm thick Cu2O layer in a basic aqueous solution containing a copper acetate hydrate and lactic acid followed by a vacuum evaporation of the 50 nm thick C60 layer at the evaporation rate from 0.25 to 1.0 Å/s. The C60 layers prepared by the evaporation possessed a face-centered cubic configuration with the lattice constant of 14.19 A, and the preferred orientation changed from random to (111) plane with decrease in the C60 evaporation rate from 1.0 to 0.25 Å/s. The hybrid p-Cu2O/C60 diode showed a rectification feature regardless of the C60 evaporation rate, and both the rectification ratio and forward current density improved with decrease in the C60 evaporation rate. The excellent rectification with the ideality factor of approximately 1 was obtained for the 500 nm thick (111)-Cu2O/50 nm thick (111)-fcc-C60/bathocuproine (BCP) diode at the C60 evaporation rate of 0.25 Å /s. The hybrid Cu2O/C60 diode prepared by stacking the C60 layer at the evaporation rate of 0.25 Å/s revealed the photovoltaic performance of 8.7 × 10(-6)% in conversion efficiency under AM1.5 illumination, and the conversion efficiency changed depending on the C60 evaporation rate.

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.

Experimental Investigation of Heat Pipe Startup Under Reflux Mode

NASA Technical Reports Server (NTRS)

Ku, Jentung

2018-01-01

In the absence of body forces such as gravity, a heat pipe will start as soon as its evaporator temperature reaches the saturation temperature. If the heat pipe operates under a reflux mode in ground testing, the liquid puddle will fill the entire cross sectional area of the evaporator. Under this condition, the heat pipe may not start when the evaporator temperature reaches the saturation temperature. Instead, a superheat is required in order for the liquid to vaporize through nucleate boiling. The amount of superheat depends on several factors such as the roughness of the heat pipe internal surface and the gravity head. This paper describes an experimental investigation of the effect of gravity pressure head on the startup of a heat pipe under reflux mode. In this study, a heat pipe with internal axial grooves was placed in a vertical position with different tilt angles relative to the horizontal plane. Heat was applied to the evaporator at the bottom and cooling was provided to the condenser at the top. The liquid-flooded evaporator was divided into seven segments along the axial direction, and an electrical heater was attached to each evaporator segment. Heat was applied to individual heaters in various combinations and sequences. Other test variables included the condenser sink temperature and tilt angle. Test results show that as long as an individual evaporator segment was flooded with liquid initially, a superheat was required to vaporize the liquid in that segment. The amount of superheat required for liquid vaporization was a function of gravity pressure head imposed on that evaporator segment and the initial temperature of the heat pipe. The most efficient and effective way to start the heat pipe was to apply a heat load with a high heat flux to the lowest segment of the evaporator.

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.

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

Horst Meyer and Quantum Evaporation

NASA Astrophysics Data System (ADS)

Balibar, S.

2016-11-01

With their 1963 article in Cryogenics Horst Meyer and his collaborators triggered intense research activity on the evaporation of superfluid helium. Discussing this subject with him in 1975 was enlightening. Fifty years later, the analogy between the photoelectric effect and the evaporation of superfluid helium in the low temperature limit is not yet clear, although remarkable progress has been made in its observation and its understanding. This special issue of the Journal of Low Temperature Physics is an opportunity to recall the history of quantum evaporation, and to express my gratitude to Horst Meyer. It describes quickly most of the experimental and theoretical works which have been published on quantum evaporation during the last 50 years, but it is not a comprehensive review of this fascinating subject.

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.

Evaporation kinetics in the hanging drop method of 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; these results are applied to 18 different drop and well arrangements commonly encountered in the laboratory, taking into account the chemical nature of the salt, the drop size and shape, the drop concentration, the well size, the well concentration, and the temperature. It is found that the rate of evaporation increases with temperature, drop size, and with the salt concentration difference between the drop and the well. The evaporation possesses no unique half-life. Once the salt in the drop achieves about 80 percent of its final concentration, further evaporation suffers from the law of diminishing returns.

Comparison of evaporation computation methods, Pretty Lake, Lagrange County, northeastern Indiana

USGS Publications Warehouse

Ficke, John F.

1972-01-01

The different methods, although poor, agree that evaporation when there is ice cover is generally small (less than 0.1 cm day" 1 ), but the evaporation rates during the few days just before freezeup or just after ice breakup are significant

Measurement of sub-canopy evaporation in a flooded forest

USDA-ARS?s Scientific Manuscript database

Evapotranspiration is the dominant water efflux in many forested wetlands, but few studies have quantified the contribution of subcanopy evaporation. The goal of this study is to investigate the subcanopy energy balance to more fully understand physical controls over evaporation. We used Bowen ratio...

Evaporative Emissions from In-Use Vehicles: Test Fleet Expansion (CRC E-77-2b) Final Report

EPA Pesticide Factsheets

Report describes the ongoing investigation into the evaporative emission performance of aging light-duty vehicles. The objective was to add additional data to the Coordinating Research Council's (CRC) E-77-2 evaporative emission/permeation test program

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.

Specificity Switching Pathways in Thermal and Mass Evaporation of Multicomponent Hydrocarbon Droplets: A Mesoscopic Observation.

PubMed

Nasiri, Rasoul; Luo, Kai H

2017-07-10

For well over one century, the Hertz-Knudsen equation has established the relationship between thermal - mass transfer coefficients through a liquid - vapour interface and evaporation rate. These coefficients, however, have been often separately estimated for one-component equilibrium systems and their simultaneous influences on evaporation rate of fuel droplets in multicomponent systems have yet to be investigated at the atomic level. Here we first apply atomistic simulation techniques and quantum/statistical mechanics methods to understand how thermal and mass evaporation effects are controlled kinetically/thermodynamically. We then present a new development of a hybrid method of quantum transition state theory/improved kinetic gas theory, for multicomponent hydrocarbon systems to investigate how concerted-distinct conformational changes of hydrocarbons at the interface affect the evaporation rate. The results of this work provide an important physical concept in fundamental understanding of atomistic pathways in topological interface transitions of chain molecules, resolving an open problem in kinetics of fuel droplets evaporation.

Water evaporation in silica colloidal deposits.

PubMed

Peixinho, Jorge; Lefèvre, Grégory; Coudert, François-Xavier; Hurisse, Olivier

2013-10-15

The results of an experimental study on the evaporation and boiling of water confined in the pores of deposits made of mono-dispersed silica colloidal micro-spheres are reported. The deposits are studied using scanning electron microscopy, adsorption of nitrogen, and adsorption of water through attenuated total reflection-infrared spectroscopy. The evaporation is characterized using differential scanning calorimetry and thermal gravimetric analysis. Optical microscopy is used to observe the patterns on the deposits after evaporation. When heating at a constant rate and above boiling temperature, the release of water out of the deposits is a two step process. The first step is due to the evaporation and boiling of the surrounding and bulk water and the second is due to the desorption of water from the pores. Additional experiments on the evaporation of water from membranes having cylindrical pores and of heptane from silica deposits suggest that the second step is due to the morphology of the deposits. Copyright © 2013 Elsevier Inc. All rights reserved.

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.

Role of air sampling in investigation of an outbreak of legionnaires' disease associated with exposure to aerosols from an evaporative condenser.

PubMed

Breiman, R F; Cozen, W; Fields, B S; Mastro, T D; Carr, S J; Spika, J S; Mascola, L

1990-06-01

Epidemiologic studies have suggested that legionnaires' disease can be transmitted to susceptible hosts by contaminated aerosolized water from cooling towers and evaporative condensers; however, epidemic strains of Legionella have not been isolated by air sampling at such sites during epidemiologic investigations. An outbreak of legionnaires' disease occurred at a retirement hotel; Legionella pneumophila serogroup 1 was isolated from an evaporative condenser and from potable water. A case-control study showed that the only significant exposure risk was in area A. L. pneumophila serogroup 1 was isolated during air sampling near the evaporative condenser exhaust site, the air conditioning intake vent, and an air vent in area A, but not in shower stalls. Monoclonal antibody subtype patterns of L. pneumophila serogroup 1 isolates from patients matched those from the evaporative condenser but not from shower water. Air sampling and monoclonal antibody subtyping results support epidemiologic evidence that the evaporative condenser was the source of this outbreak.

Evaporation of ice in planetary atmospheres: Ice-covered rivers on Mars

NASA Technical Reports Server (NTRS)

Wallace, D.; Sagan, C.

1978-01-01

The evaporation rate of water ice on the surface of a planet with an atmosphere involves an equilibrium between solar heating and radiative and evaporative cooling of the ice layer. The thickness of the ice is governed principally by the solar flux which penetrates the ice layer and then is conducted back to the surface. Evaporation from the surface is governed by wind and free convection. In the absence of wind, eddy diffusion is caused by the lower density of water vapor in comparison to the density of the Martian atmosphere. For mean martian insolations, the evaporation rate above the ice is approximately 10 to the minus 8th power gm/sq cm/s. Evaporation rates are calculated for a wide range of frictional velocities, atmospheric pressures, and insolations and it seems clear that at least some subset of observed Martian channels may have formed as ice-chocked rivers. Typical equilibrium thicknesses of such ice covers are approximately 10m to 30 m; typical surface temperatures are 210 to 235 K.

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

Water-evaporation-induced electricity with nanostructured carbon materials.

PubMed

Xue, Guobin; Xu, Ying; Ding, Tianpeng; Li, Jia; Yin, Jun; Fei, Wenwen; Cao, Yuanzhi; Yu, Jin; Yuan, Longyan; Gong, Li; Chen, Jian; Deng, Shaozhi; Zhou, Jun; Guo, Wanlin

2017-05-01

Water evaporation is a ubiquitous natural process that harvests thermal energy from the ambient environment. It has previously been utilized in a number of applications including the synthesis of nanostructures and the creation of energy-harvesting devices. Here, we show that water evaporation from the surface of a variety of nanostructured carbon materials can be used to generate electricity. We find that evaporation from centimetre-sized carbon black sheets can reliably generate sustained voltages of up to 1 V under ambient conditions. The interaction between the water molecules and the carbon layers and moreover evaporation-induced water flow within the porous carbon sheets are thought to be key to the voltage generation. This approach to electricity generation is related to the traditional streaming potential, which relies on driving ionic solutions through narrow gaps, and the recently reported method of moving ionic solutions across graphene surfaces, but as it exploits the natural process of evaporation and uses cheap carbon black it could offer advantages in the development of practical devices.

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.

Characteristics of low-temperature short heat pipes with a nozzle-shaped vapor channel

NASA Astrophysics Data System (ADS)

Seryakov, A. V.

2016-01-01

This paper presents the results of experimental and numerical studies of heat transfer and swirling pulsating flows in short low-temperature heat pipes whose vapor channels have the form of a conical nozzle. It has been found that as the evaporator of the heat pipe is heated, pressure pulsations occur in the vapor channel starting at a certain threshold value of the heat power, which is due to the start of boiling in the evaporator. The frequency of the pulsations has been measured, and their dependence on the superheat of the evaporator has been determined. It has been found that in heat pipes with a conical vapor channel, pulsations occur at lower evaporator superheats and the pulsation frequency is greater than in heat pipes of the same size with a standard cylindrical vapor channel. It has been shown that the curve of the heat-transfer coefficient versus thermal load on the evaporator has an inflection corresponding to the start of boiling in the capillary porous evaporator of the heat pipe.

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.

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.

GLOBAL INSTABILITY OF THE EXO-MOON SYSTEM TRIGGERED BY PHOTO-EVAPORATION

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

Yang, Ming; Xie, Ji-Wei; Zhou, Ji-Lin

2016-12-10

Many exoplanets have been found in orbits close to their host stars and thus they are subject to the effects of photo-evaporation. Previous studies have shown that a large portion of exoplanets detected by the Kepler mission have been significantly eroded by photo-evaporation. In this paper, we numerically study the effects of photo-evaporation on the orbital evolution of a hypothesized moon system around a planet. We find that photo-evaporation is crucial to the stability of the moon system. Photo-evaporation can erode the atmosphere of the planet thus leading to significant mass loss. As the planet loses mass, its Hill radiusmore » shrinks and its moons increase their orbital semimajor axes and eccentricities. When some moons approach their critical semimajor axes, global instability of the moon system would be triggered, which usually ends up with two, one or even zero surviving moons. Some lost moons could escape from the moon system to become a new planet orbiting the star or run away further to become a free-floating object in the Galaxy. Given the destructive role of photo-evaporation, we speculate that exomoons are less common for close-in planets (<0.1 au), especially those around M-type stars, because they are more X-ray luminous and thus enhancing photo-evaporation. The lessons we learn in this study may be helpful for the target selection of on-going/future exomoon searching programs.« less

Increasing the collected energy and reducing the water requirements in salt-gradient solar ponds

NASA Astrophysics Data System (ADS)

Suarez, F. I.; Ruskowitz, J. A.; Tyler, S. W.; Childress, A. E.

2013-12-01

Salt-gradient solar ponds are low-cost, large-scale solar collectors with integrated storage that can be used as an energy source in many thermal systems. For instance, solar ponds have proven to be a promising solution to drive thermal desalination in arid zones. However, in zones with limited water availability, where evaporation constrains the use of solar ponds in areas with the greatest potential for solar energy development, evaporation losses at the surface of the pond constrain their use. Therefore, evaporation represents a significant challenge for development of these low-cost solar systems in arid settings. In this investigation, different transparent floating elements were tested to suppress evaporation: flat discs, hemispheres, and a continuous cover. Flat discs were the most effective evaporation suppression element. Evaporation decreased from 4.8 to 2.5 mm/day when 88% of the pond was covered with the flat discs. In addition, the highest temperature increased from 34 to 43°C and the heat content increased from 179 to 220 MJ (a 22% increase). Reduced evaporative losses at the surface of the pond resulted in lower conductive losses from the storage zone and increased the collected energy. The magnitude of evaporation reduction observed in this work is important as it allows solar pond operation in locations with limited water supply for replenishment. The increase in stored heat allows more energy to be withdrawn from the pond for use in external applications, which significantly improves the thermal efficiencies of solar ponds.

Marangoni Flow Induced Evaporation Enhancement on Binary Sessile Drops.

PubMed

Chen, Pin; Harmand, Souad; Ouenzerfi, Safouene; Schiffler, Jesse

2017-06-15

The evaporation processes of pure water, pure 1-butanol, and 5% 1-butanol aqueous solution drops on heated hydrophobic substrates are investigated to determine the effect of temperature on the drop evaporation behavior. The evolution of the parameters (contact angle, diameter, and volume) during evaporation measured using a drop shape analyzer and the infrared thermal mapping of the drop surface recorded by an infrared camera were used in investigating the evaporation process. The pure 1-butanol drop does not show any thermal instability at different substrate temperatures, while the convection cells created by the thermal Marangoni effect appear on the surface of the pure water drop from 50 °C. Because 1-butanol and water have different surface tensions, the infrared video of the 5% 1-butanol aqueous solution drop shows that the convection cells are generated by the solutal Marangoni effect at any substrate temperature. Furthermore, when the substrate temperature exceeds 50 °C, coexistence of the thermal and solutal Marangoni flows is observed. By analyzing the relation between the ratio of the evaporation rate of pure water and 1-butanol aqueous solution drops and the Marangoni number, a series of empirical equations for predicting the evaporation rates of pure water and 1-butanol aqueous solution drops at the initial time as well as the equations for the evaporation rate of 1-butanol aqueous solution drop before the depletion of alcohol are derived. The results of these equations correspond fairly well to the experimental data.

Drop evaporation on superhydrophobic PTFE surfaces driven by contact line dynamics.

PubMed

Ramos, S M M; Dias, J F; Canut, B

2015-02-15

In the present study, we experimentally study the evaporation modes and kinetics of sessile drops of water on highly hydrophobic surfaces (contact angle ∼160°), heated to temperatures ranging between 40° and 70 °C. These surfaces were initially constructed by means of controlled tailoring of polytetrafluoroethylene (PTFE) substrates. The evaporation of droplets was observed to occur in three distinct phases, which were the same for the different substrate temperatures. The drops started to evaporate in the constant contact radius (CCR) mode, then switched to a more complex mode characterized by a set of stick-slip events accompanied by a decrease in contact angle, and finally shifted to a mixed mode in which the contact radius and contact angle decreased simultaneously until the drops had completely evaporated. It is shown that in the case of superhydrophobic surfaces, the energy barriers (per unit length) associated with the stick-slip motion of a drop ranges in the nJ m(-1) scale. Furthermore, analysis of the evaporation rates, determined from experimental data show that, even in the CCR mode, a linear relationship between V(2/3) and the evaporation time is verified. The values of the evaporation rate constants are found to be higher in the pinned contact line regime (the CCR mode) than in the moving contact line regime. This behavior is attributed to the drop's higher surface to volume ratio in the CCR mode. Copyright © 2014 Elsevier Inc. All rights reserved.

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.

Atom probe tomography evaporation behavior of C-axis GaN nanowires: Crystallographic, stoichiometric, and detection efficiency aspects

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

Diercks, David R., E-mail: ddiercks@mines.edu; Gorman, Brian P.; Kirchhofer, Rita

2013-11-14

The field evaporation behavior of c-axis GaN nanowires was explored in two different laser-pulsed atom probe tomography (APT) instruments. Transmission electron microscopy imaging before and after atom probe tomography analysis was used to assist in reconstructing the data and assess the observed evaporation behavior. It was found that the ionic species exhibited preferential locations for evaporation related to the underlying crystal structure of the GaN and that the species which evaporated from these locations was dependent on the pulsed laser energy. Additionally, the overall stoichiometry measured by APT was significantly correlated with the energy of the laser pulses. At themore » lowest laser energies, the apparent composition was nitrogen-rich, while higher laser energies resulted in measurements of predominantly gallium compositions. The percent of ions detected (detection efficiency) for these specimens was found to be considerably below that shown for other materials, even for laser energies which produced the expected Ga:N ratio. The apparent stoichiometry variation and low detection efficiency appear to be a result of evaporation of Ga ions between laser pulses at the lowest laser energies and evaporation of neutral N{sub 2} species at higher laser energies. All of these behaviors are tied to the formation of nitrogen-nitrogen bonds on the tip surface, which occurred under all analysis conditions. Similar field evaporation behaviors are therefore expected for other materials where the anionic species readily form a strong diatomic bond.« less

Simulated Waste Testing Of Glycolate Impacts On The 2H-Evaporator System

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

Martino, C. J.

2013-08-13

Glycolic acid is being studied as a total or partial replacement for formic acid in the Defense Waste Processing Facility (DWPF) feed preparation process. After implementation, the recycle stream from DWPF back to the high-level waste tank farm will contain soluble sodium glycolate. Most of the potential impacts of glycolate in the tank farm were addressed via a literature review, but several outstanding issues remained. This report documents the non-radioactive simulant tests impacts of glycolate on storage and evaporation of Savannah River Site high-level waste. The testing for which non-radioactive simulants could be used involved the following: the partitioning ofmore » glycolate into the evaporator condensate, the impacts of glycolate on metal solubility, and the impacts of glycolate on the formation and dissolution of sodium aluminosilicate scale within the evaporator. The following are among the conclusions from this work: Evaporator condensate did not contain appreciable amounts of glycolate anion. Of all tests, the highest glycolate concentration in the evaporator condensate was 0.38 mg/L. A significant portion of the tests had glycolate concentration in the condensate at less than the limit of quantification (0.1 mg/L). At ambient conditions, evaporator testing did not show significant effects of glycolate on the soluble components in the evaporator concentrates. Testing with sodalite solids and silicon containing solutions did not show significant effects of glycolate on sodium aluminosilicate formation or dissolution.« less

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.

Nanoparticle agglomeration in an evaporating levitated droplet for different acoustic amplitudes

NASA Astrophysics Data System (ADS)

Tijerino, Erick; Basu, Saptarshi; Kumar, Ranganathan

2013-01-01

Radiatively heated levitated functional droplets with nanosilica suspensions exhibit three distinct stages namely pure evaporation, agglomeration, and finally structure formation. The temporal history of the droplet surface temperature shows two inflection points. One inflection point corresponds to a local maximum and demarcates the end of transient heating of the droplet and domination of vaporization. The second inflection point is a local minimum and indicates slowing down of the evaporation rate due to surface accumulation of nanoparticles. Morphology and final precipitation structures of levitated droplets are due to competing mechanisms of particle agglomeration, evaporation, and shape deformation. In this work, we provide a detailed analysis for each process and propose two important timescales for evaporation and agglomeration that determine the final diameter of the structure formed. It is seen that both agglomeration and evaporation timescales are similar functions of acoustic amplitude (sound pressure level), droplet size, viscosity, and density. However, we show that while the agglomeration timescale decreases with initial particle concentration, the evaporation timescale shows the opposite trend. The final normalized diameter can be shown to be dependent solely on the ratio of agglomeration to evaporation timescales for all concentrations and acoustic amplitudes. The structures also exhibit various aspect ratios (bowls, rings, spheroids) which depend on the ratio of the deformation timescale (tdef) and the agglomeration timescale (tg). For tdef

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.

Tank 26 Evaporator Feed Pump Transfer Analysis

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

Tamburello, David; Dimenna, Richard; Lee, Si

2009-02-11

The transfer of liquid salt solution from Tank 26 to an evaporator is to be accomplished by activating the evaporator feed pump, located approximately 72 inches above the sludge layer, while simultaneously turning on the downcomer. Previously, activation of the evaporator feed pump was an isolated event without any other components running at the same time. An analysis of the dissolved solution transfer has been performed using computational fluid dynamics methods to determine the amount of entrained sludge solids pumped out of the tank to the evaporator with the downcomer turned on. The analysis results showed that, for the maximummore » and minimum supernate levels in Tank 26 (252.5 and 72 inches above the sludge layer, respectively), the evaporator feed pump will entrain between 0.03 and 0.1 wt% sludge undissolved solids weight fraction into the eductor, respectively, and therefore are an order of magnitude less than the 1.0 wt% undissolved solids loading criteria to feed the evaporator. Lower tank liquid levels, with respect to the sludge layer, result in higher amounts of sludge entrainment due to the increased velocity of the plunging jets from the downcomer and evaporator feed pump bypass as well as decreased dissipation depth. Revision 1 clarifies the analysis presented in Revision 0 and corrects a mathematical error in the calculations for Table 4.1 in Revision 0. However, the conclusions and recommendations of the analysis do not change for Revision 1.« less

Effect of Variable Gravity on Evaporation of Binary Fluids in a Capillary Pore Evaporator

NASA Technical Reports Server (NTRS)

Girgis, Morris M.; Matta, Nabil S.; Kolli, Kiran; Brown, Leon; Bain, James, Jr.; McGown, Juantonio

1996-01-01

The research project focuses on experimental investigation of the capillary-pumped evaporative heat transfer phenomenon. The objective is to examine whether the heat transfer and stability of a heated meniscus in a capillary pore can be enhanced by adding trace amounts of a non-volatile solute to a solvent and to understand the changes that occur. The experimental setup consists of a single pore evaporator connected to a reservoir which supplies liquid to the evaporator. In addition to the experiments of capillary-pumped evaporation, a parallel experimental study has been conducted to systematically investigate the effects of gravity as well as the effects of bulk composition on the heat transfer characteristics of evaporating binary thin films near the contact line region along an inclined heated surface. To investigate the buoyancy effects on evaporation along an inclined heated surface, the angle of inclination from a horizontal plane was varied fro 15 C to 90 C. An optimum concentration between 0.5% and 1% decane in pentane/decane solutions has been demonstrated at different angles of inclination. Improved heat transfer was found for the geometry with the smallest angle of inclination of 15 degrees. In addition, flow visualization has revealed that at low inclination angles effective heat transfer takes place primarily due to an extension of the thin film near the contact line. At these low inclination angles, the optimum concentration is associated with enhanced wetting characteristics and reduced thermocapillary stresses along the interface.

40 CFR 721.8775 - Substituted pyridines.

Code of Federal Regulations, 2011 CFR

2011-07-01

... tertiary waste treatment will occur, or treatment in a lined, self-contained solar evaporation pond where...-contained solar evaporation pond where UV light will degrade the substance, the number of kilograms per day... a lined, self-contained solar evaporation pond where UV light will degrade the substance, the number...

Use of a Spacer Vest to Increase Evaporative Cooling Under Military Body Armor

DTIC Science & Technology

2006-07-01

could significantly improve wearer thermal comfort . A study that tested six different configurations (closed, open front, open sides, all with and...thermal and evaporative resistances of the IBA, allowing for increases in predicted human sweat evaporation and overall thermal comfort during exposure

Representational Issues in Students Learning about Evaporation

ERIC Educational Resources Information Center

Tytler, Russell; Prain, Vaughan; Peterson, Suzanne

2007-01-01

This study draws on recent research on the central role of representation in learning. While there has been considerable research on students' understanding of evaporation, the representational issues entailed in this understanding have not been investigated in depth. The study explored students' engagement with evaporation phenomena through…

Droplet Evaporator For High-Capacity Heat Transfer

NASA Technical Reports Server (NTRS)

Valenzuela, Javier A.

1993-01-01

Proposed heat-exchange scheme boosts heat transfer per unit area. Key component is generator that fires uniform size droplets of subcooled liquid at hot plate. On impact, droplets spread out and evaporate almost instantly, removing heat from plate. In practice, many generator nozzles arrayed over evaporator plate.

40 CFR 721.8775 - Substituted pyridines.

Code of Federal Regulations, 2010 CFR

2010-07-01

... tertiary waste treatment will occur, or treatment in a lined, self-contained solar evaporation pond where...-contained solar evaporation pond where UV light will degrade the substance, the number of kilograms per day... a lined, self-contained solar evaporation pond where UV light will degrade the substance, the number...

40 CFR 86.1824-08 - Durability demonstration procedures for evaporative emissions.

Code of Federal Regulations, 2010 CFR

2010-07-01

... deterioration rate and emission level that effectively represents a significant majority of the distribution of... stabilize the permeability of all non-metallic fuel and evaporative system components to the mileage... permeability of evaporative and fuel system components. The manufacturer must also provide information...

40 CFR 86.1824-08 - Durability demonstration procedures for evaporative emissions.

Code of Federal Regulations, 2011 CFR

2011-07-01

... deterioration rate and emission level that effectively represents a significant majority of the distribution of... stabilize the permeability of all non-metallic fuel and evaporative system components to the mileage... permeability of evaporative and fuel system components. The manufacturer must also provide information...

40 CFR 86.1824-08 - Durability demonstration procedures for evaporative emissions.

Code of Federal Regulations, 2013 CFR

2013-07-01

... deterioration rate and emission level that effectively represents a significant majority of the distribution of... stabilize the permeability of all non-metallic fuel and evaporative system components to the mileage... permeability of evaporative and fuel system components. The manufacturer must also provide information...

Analysis of Evaporative On-Board Diagnostic (OBD) Readiness and DTCs Using I/M Data

EPA Science Inventory

Gasoline vehicles are equipped with evaporative emissions control systems that control vapor from the fuel storage system while a vehicle is sitting or driving. When these systems or the vehicle’s gasoline delivery system malfunction, excessive evaporative emissions can be emitte...

Magnitude and variability of land evaporation and its components at the global scale

USDA-ARS?s Scientific Manuscript database

A physics-based methodology is applied to estimate global land-surface evaporation from multi-satellite observations. GLEAM (Global Land-surface Evaporation: the Amsterdam Methodology) combines a wide range of remotely sensed observations within a Priestley and Taylor-based framework. Daily actual e...

An investigation of electrohydrodynamic heat pipes

NASA Technical Reports Server (NTRS)

Loehrke, R. I.

1977-01-01

The principles of electrohydrodynamic heat pip operation are first discussed. Evaporator conductance experiments are then described. A heat pipe was designed in which grooved and ungrooved evaporator surfaces could be interchanged to evaluate the necessity of capillary grooves. Optimum electrode spacing was also studied. Finally, heat convection in evaporating thin films is considered.

The Development of Young Children's Understanding of the Process of Evaporation.

ERIC Educational Resources Information Center

Beveridge, Michael

1985-01-01

This investigation of the development of young children's concept of evaporation examines their intuitive explanations of real world events involving evaporation. A study of the effects of providing evidence contradicting their explanations and of directing their attention to relevant situational features provides insight into the development of…

40 CFR 1042.107 - Evaporative emission standards.

Code of Federal Regulations, 2010 CFR

2010-07-01

... fuels (for example, natural gas). (b) If an engine uses a volatile liquid fuel, such as methanol, the engine's fuel system and the vessel in which the engine is installed must meet the evaporative emission... emissions are controlled. (2) Present test data to show that fuel systems and vessels meet the evaporative...

40 CFR 1042.107 - Evaporative emission standards.

Code of Federal Regulations, 2011 CFR

2011-07-01

... fuels (for example, natural gas). (b) If an engine uses a volatile liquid fuel, such as methanol, the engine's fuel system and the vessel in which the engine is installed must meet the evaporative emission... emissions are controlled. (2) Present test data to show that fuel systems and vessels meet the evaporative...

21 CFR 131.130 - Evaporated milk.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 2 2011-04-01 2011-04-01 false Evaporated milk. 131.130 Section 131.130 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN...) Description. Evaporated milk is the liquid food obtained by partial removal of water only from milk. It...

21 CFR 131.130 - Evaporated milk.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 2 2012-04-01 2012-04-01 false Evaporated milk. 131.130 Section 131.130 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN...) Description. Evaporated milk is the liquid food obtained by partial removal of water only from milk. It...

21 CFR 131.130 - Evaporated milk.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 2 2013-04-01 2013-04-01 false Evaporated milk. 131.130 Section 131.130 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN...) Description. Evaporated milk is the liquid food obtained by partial removal of water only from milk. It...

Cumulative soil water evaporation as a function of depth and time

USDA-ARS?s Scientific Manuscript database

Soil water evaporation is an important component of the surface water balance and the surface energy balance. Accurate and dynamic measurements of soil water evaporation enhance the understanding of water and energy partitioning at the land-atmosphere interface. The objective of this study is to mea...

Sensible heat balance measurements of soil water evaporation beneath a maize canopy

USDA-ARS?s Scientific Manuscript database

Soil water evaporation is an important component of the water budget in a cropped field. Few methods are available for continuous and independent measurement of soil water evaporation. A sensible heat balance (SHB) approach has recently been demonstrated for continuously determining soil water evapo...

40 CFR 86.1824-08 - Durability demonstration procedures for evaporative emissions.

Code of Federal Regulations, 2014 CFR

2014-07-01

... for evaporative emissions. Eligible small-volume manufacturers or small-volume test groups may...-based measurements except the bleed emission test. The standard for bleed emissions applies for the full... manufacturer must conduct at least one evaporative emission test at each of the five different mileage points...

40 CFR 86.098-28 - Compliance with emission standards.

Code of Federal Regulations, 2010 CFR

2010-07-01

... useful life relative to the evaporative emission level at 4,000 miles as follows: (1) Factor = Evaporative emission level at the useful life mileage for that standard minus the evaporative emission level... applicable usefule life relative to the refueling emission level at 4,000 miles as follows: (1) Factor...

40 CFR 86.098-28 - Compliance with emission standards.

Code of Federal Regulations, 2011 CFR

2011-07-01

... useful life relative to the evaporative emission level at 4,000 miles as follows: (1) Factor = Evaporative emission level at the useful life mileage for that standard minus the evaporative emission level... applicable usefule life relative to the refueling emission level at 4,000 miles as follows: (1) Factor...

40 CFR 1039.107 - What evaporative emission standards and requirements apply?

Code of Federal Regulations, 2010 CFR

2010-07-01

... 1048 that apply to spark-ignition engines, as follows: (a) Follow the steps in 40 CFR 1048.245 to show...-IGNITION ENGINES Emission Standards and Related Requirements § 1039.107 What evaporative emission standards and requirements apply? There are no evaporative emission standards for diesel-fueled engines, or...

16 CFR 305.14 - Energy information disclosures for heating and cooling equipment.

Code of Federal Regulations, 2014 CFR

2014-01-01

... accordance with § 305.5. The energy efficiency rating(s) for split-system condenser-evaporator coil combinations shall be either: (A) The energy efficiency rating of the actual condenser-evaporator coil...-evaporator coil combination that is the particular manufacturer's most commonly sold combination for that...

A Simpler Way to Tame Multiple-Effect Evaporators.

ERIC Educational Resources Information Center

Joye, Donald D.; Koko, F. William Jr.

1988-01-01

Presents a new method to teach the subject of evaporators which is both simple enough to use in the classroom and accurate and flexible enough to be used as a design tool in practice. Gives an example using a triple evaporator series. Analyzes the effect of this method. (CW)

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.

Potable water recovery for spacecraft application by electrolytic pretreatment/air evaporation

NASA Technical Reports Server (NTRS)

Wells, G. W.

1975-01-01

A process for the recovery of potable water from urine using electrolytic pretreatment followed by distillation in a closed-cycle air evaporator has been developed and tested. Both the electrolytic pretreatment unit and the air evaporation unit are six-person, flight-concept prototype, automated units. Significantly extended wick lifetimes have been achieved in the air evaporation unit using electrolytically pretreated, as opposed to chemically pretreated, urine feed. Parametric test data are presented on product water quality, wick life, process power, maintenance requirements, and expendable requirements.

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.

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.

Annealing dependence of residual stress and optical properties of TiO2 thin film deposited by different deposition methods.

PubMed

Chen, Hsi-Chao; Lee, Kuan-Shiang; Lee, Cheng-Chung

2008-05-01

Titanium oxide (TiO(2)) thin films were prepared by different deposition methods. The methods were E-gun evaporation with ion-assisted deposition (IAD), radio-frequency (RF) ion-beam sputtering, and direct current (DC) magnetron sputtering. Residual stress was released after annealing the films deposited by RF ion-beam or DC magnetron sputtering but not evaporation, and the extinction coefficient varied significantly. The surface roughness of the evaporated films exceeded that of both sputtered films. At the annealing temperature of 300 degrees C, anatase crystallization occurred in evaporated film but not in the RF ion-beam or DC magnetron-sputtered films. TiO(2) films deposited by sputtering were generally more stable during annealing than those deposited by evaporation.

Hydronic rooftop cooling systems

DOEpatents

Bourne, Richard C [Davis, CA; Lee, Brian Eric [Monterey, CA; Berman, Mark J [Davis, CA

2008-01-29

A roof top cooling unit has an evaporative cooling section that includes at least one evaporative module that pre-cools ventilation air and water; a condenser; a water reservoir and pump that captures and re-circulates water within the evaporative modules; a fan that exhausts air from the building and the evaporative modules and systems that refill and drain the water reservoir. The cooling unit also has a refrigerant section that includes a compressor, an expansion device, evaporator and condenser heat exchangers, and connecting refrigerant piping. Supply air components include a blower, an air filter, a cooling and/or heating coil to condition air for supply to the building, and optional dampers that, in designs that supply less than 100% outdoor air to the building, control the mixture of return and ventilation air.

Building micro-soccer-balls with evaporating colloidal fakir drops

NASA Astrophysics Data System (ADS)

Gelderblom, Hanneke; Marín, Álvaro G.; Susarrey-Arce, Arturo; van Housselt, Arie; Lefferts, Leon; Gardeniers, Han; Lohse, Detlef; Snoeijer, Jacco H.

2013-11-01

Drop evaporation can be used to self-assemble particles into three-dimensional microstructures on a scale where direct manipulation is impossible. We present a unique method to create highly-ordered colloidal microstructures in which we can control the amount of particles and their packing fraction. To this end, we evaporate colloidal dispersion drops from a special type of superhydrophobic microstructured surface, on which the drop remains in Cassie-Baxter state during the entire evaporative process. The remainders of the drop consist of a massive spherical cluster of the microspheres, with diameters ranging from a few tens up to several hundreds of microns. We present scaling arguments to show how the final particle packing fraction of these balls depends on the drop evaporation dynamics, particle size, and number of particles in the system.

Dual manifold heat pipe evaporator

DOEpatents

Adkins, Douglas R.; Rawlinson, K. Scott

1994-01-01

An improved evaporator section for a dual manifold heat pipe. Both the upper and lower manifolds can have surfaces exposed to the heat source which evaporate the working fluid. The tubes in the tube bank between the manifolds have openings in their lower extensions into the lower manifold to provide for the transport of evaporated working fluid from the lower manifold into the tubes and from there on into the upper manifold and on to the condenser portion of the heat pipe. A wick structure lining the inner walls of the evaporator tubes extends into both the upper and lower manifolds. At least some of the tubes also have overflow tubes contained within them to carry condensed working fluid from the upper manifold to pass to the lower without spilling down the inside walls of the tubes.

Apparatus for diffusion-gap thermal desalination

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

Lowenstein, Andrew

A thermal distillation apparatus including evaporation surfaces that are wetted with a solution, and from which at least some of the volatile solvent contained in the solution evaporates, condensers having an external surface in close proximity to, but not touching, a corresponding one of the one or more evaporation surfaces, and on which vapors of the solvent condense, releasing thermal energy that heats a flow of the solution moving upward within the condensers, spacers that prevent contact between the evaporating surfaces and the condensers, wherein spaces between the evaporating surfaces and the condensers are filled with a gaseous mixture composedmore » of solvent vapor and one or more non-condensable gases, and except for diffusion of the solvent vapor relative to the non-condensable gases, the gaseous mixture is stationary.« less

Evaporating Spray in Supersonic Streams Including Turbulence Effects

NASA Technical Reports Server (NTRS)

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

2006-01-01

Evaporating spray plays an important role in spray combustion processes. This paper describes the development of a new finite-conductivity evaporation model, based on the two-temperature film theory, for two-phase numerical simulation using Eulerian-Lagrangian method. The model is a natural extension of the T-blob/T-TAB atomization/spray model which supplies the turbulence characteristics for estimating effective thermal diffusivity within the droplet phase. Both one-way and two-way coupled calculations were performed to investigate the performance of this model. Validation results indicate the superiority of the finite-conductivity model in low speed parallel flow evaporating sprays. High speed cross flow spray results indicate the effectiveness of the T-blob/T-TAB model and point to the needed improvements in high speed evaporating spray modeling.

Study of Evaporation Rate of Water in Hydrophobic Confinement using Forward Flux Sampling

NASA Astrophysics Data System (ADS)

Sharma, Sumit; Debenedetti, Pablo G.

2012-02-01

Drying of hydrophobic cavities is of interest in understanding biological self assembly, protein stability and opening and closing of ion channels. Liquid-to-vapor transition of water in confinement is associated with large kinetic barriers which preclude its study using conventional simulation techniques. Using forward flux sampling to study the kinetics of the transition between two hydrophobic surfaces, we show that a) the free energy barriers to evaporation scale linearly with the distance between the two surfaces, d; b) the evaporation rates increase as the lateral size of the surfaces, L increases, and c) the transition state to evaporation for sufficiently large L is a cylindrical vapor cavity connecting the two hydrophobic surfaces. Finally, we decouple the effects of confinement geometry and surface chemistry on the evaporation rates.

Alternate high capacity heat pipe

NASA Technical Reports Server (NTRS)

Voss, F. E.

1986-01-01

The performance predictions for a fifty foot heat pipe (4 foot evaporator - 46 foot condensor) are discussed. These performance predictions are supported by experimental data for a four foot heat pipe. Both heat pipes have evaporators with axial groove wick structures and condensers with powder metal external artery wick structures. The predicted performance of a rectangular axial groove/external artery heat pipe operating in space is given. Heat transport versus groove width is plotted for 100, 200 and 300 grooves in the evaporator. The curves show that maximum power is achieved for groove widths from 0.040 to 0.053 as the number of grooves varies from 300 to 100. The corresponding range of maximum power is 3150 to 2400 watts. The relationships between groove width and heat pipe evaporate diameter for 100, 200 and 300 grooves in the evaporator are given. A four foot heat pipe having a three foot condenser and one foot evaporator was built and tested. The evaporator wick structure used axial grooves with rectangular cross sections, and the condenser wick structure used powder metal with an external artery configuration. Fabrication drawings are enclosed. The predicted and measured performance for this heat pipe is shown. The agreement between predicted and measured performance is good and therefore substantiates the predicted performance for a fifty foot heat pipe.

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.

Estimation of land-surface evaporation at four forest sites across Japan with the new nonlinear complementary method.

PubMed

Ai, Zhipin; Wang, Qinxue; Yang, Yonghui; Manevski, Kiril; Zhao, Xin; Eer, Deni

2017-12-19

Evaporation from land surfaces is a critical component of the Earth water cycle and of water management strategies. The complementary method originally proposed by Bouchet, which describes a linear relation between actual evaporation (E), potential evaporation (E po ) and apparent potential evaporation (E pa ) based on routinely measured weather data, is one of the various methods for evaporation calculation. This study evaluated the reformulated version of the original method, as proposed by Brutsaert, for forest land cover in Japan. The new complementary method is nonlinear and based on boundary conditions with strictly physical considerations. The only unknown parameter (α e ) was for the first time determined for various forest covers located from north to south across Japan. The values of α e ranged from 0.94 to 1.10, with a mean value of 1.01. Furthermore, the calculated evaporation with the new method showed a good fit with the eddy-covariance measured values, with a determination coefficient of 0.78 and a mean bias of 4%. Evaluation results revealed that the new nonlinear complementary relation performs better than the original linear relation in describing the relationship between E/E pa and E po /E pa , and also in depicting the asymmetry variation between E pa /E po and E/E po .

The influence of gravity on the distribution of the deposit formed onto a substrate by sessile, hanging, and sandwiched hanging drop evaporation.

PubMed

Sandu, Ion; Fleaca, Claudiu Teodor

2011-06-15

The focus of the present article is the study of the influence of gravity on the particle deposition profiles on a solid substrate during the evaporation of sessile, hanging and sandwiched hanging drops of colloidal particle suspensions. For concentrations of nanoparticles in the colloidal solutions in the range 0.0001-1 wt.%, highly diluted suspensions will preferentially form rings while concentrated suspensions will preferentially form spots in both sessile and hanging drop evaporation. For intermediary concentrations, the particle deposition profiles will depend on the nanoparticle aggregation dynamics in the suspension during the evaporation process, gravity and on the detailed evaporation geometry. The evaporation of a drop of toluene/carbon nanoparticle suspension hanging from a pendant water drop will leave on the substrate a circular spot with no visible external ring. By contrast, a clear external ring is formed on the substrate by the sessile evaporation of a similar drop of suspension sandwiched between a water drop and the substrate. From the application viewpoint, these processes can be used to create preferential electrical conductive carbon networks and contacts for arrays of self-assembled nanostructures fabricated on solid substrates as well as on flexible polymeric substrates. Copyright © 2011 Elsevier Inc. All rights reserved.

Evaporation of NaCl solution from porous media with mixed wettability

NASA Astrophysics Data System (ADS)

Bergstad, Mina; Shokri, Nima

2016-05-01

Evaporation of saline water from porous media is ubiquitous in many processes including soil salinization, crop production, and CO2 sequestration in deep saline acquirer. It is controlled by the transport properties of porous media, atmospheric conditions, and properties of the evaporating saline solution. In the present study, the effects of mixed wettability conditions on the general dynamics of water evaporation from porous media saturated with NaCl solution were investigated. To do so, we conducted a comprehensive series of evaporation experiments using sand mixtures containing different fractions of hydrophobic grains saturated with NaCl solutions. Our results showed that increasing fraction of hydrophobic grains in the mixed wettability sand pack had minor impact on the evaporative mass losses due to the presence of salt whose precipitation patterns were significantly influenced by the mixed wettability condition. Through macroscale and microscale investigations, we found formation of patchy efflorescence in the case of mixed wettability sand pack as opposed to crusty efflorescence in the case of completely hydrophilic porous media. Furthermore, the presence of salty water and hydrophobic grains in the sand pack significantly influenced the general dynamics and morphology of the receding drying front. Our results extend the understanding of the saline water evaporation from porous media with direct applications to various hydrological and engineering processes.

TANK 32 EVAPORATOR FEED PUMP TRANSFER ANALYSIS

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

Tamburello, D; Richard Dimenna, R; Si Lee, S

2009-01-27

The transfer of liquid salt solution from Tank 32 to an evaporator is to be accomplished by activating the evaporator feed pump, with the supernate surface at a minimum height of approximately 74.4 inches above the sludge layer, while simultaneously turning on the downcomer with a flow rate of 110 gpm. Previously, activation of the evaporator feed pump was an isolated event without any other components running at the same time. An analysis of the dissolved solution transfer has been performed using computational fluid dynamics (CFD) methods to determine the amount of entrained sludge solids pumped out of the tankmore » toward the evaporator with the downcomer turned on. The analysis results shows that, for the minimum tank liquid level of 105 inches above the tank bottom (which corresponds to a liquid depth of 74.4 inches above the sludge layer), the evaporator feed pump will contain less than 0.1 wt% sludge solids in the discharge stream, which is an order of magnitude less than the 1.0 wt% undissolved solids (UDS) loading criteria to feed the evaporator. Lower liquid levels with respect to the sludge layer will result in higher amounts of sludge entrainment due to the increased plunging jet velocity from the downcomer disturbing the sludge layer.« less

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.

Simultaneous spreading and evaporation: recent developments.

PubMed

Semenov, Sergey; Trybala, Anna; Rubio, Ramon G; Kovalchuk, Nina; Starov, Victor; Velarde, Manuel G

2014-04-01

The recent progress in theoretical and experimental studies of simultaneous spreading and evaporation of liquid droplets on solid substrates is discussed for pure liquids including nanodroplets, nanosuspensions of inorganic particles (nanofluids) and surfactant solutions. Evaporation of both complete wetting and partial wetting liquids into a nonsaturated vapour atmosphere are considered. However, the main attention is paid to the case of partial wetting when the hysteresis of static contact angle takes place. In the case of complete wetting the spreading/evaporation process proceeds in two stages. A theory was suggested for this case and a good agreement with available experimental data was achieved. In the case of partial wetting the spreading/evaporation of a sessile droplet of pure liquid goes through four subsequent stages: (i) the initial stage, spreading, is relatively short (1-2 min) and therefore evaporation can be neglected during this stage; during the initial stage the contact angle reaches the value of advancing contact angle and the radius of the droplet base reaches its maximum value, (ii) the first stage of evaporation is characterised by the constant value of the radius of the droplet base; the value of the contact angle during the first stage decreases from static advancing to static receding contact angle; (iii) during the second stage of evaporation the contact angle remains constant and equal to its receding value, while the radius of the droplet base decreases; and (iv) at the third stage of evaporation both the contact angle and the radius of the droplet base decrease until the drop completely disappears. It has been shown theoretically and confirmed experimentally that during the first and second stages of evaporation the volume of droplet to power 2/3 decreases linearly with time. The universal dependence of the contact angle during the first stage and of the radius of the droplet base during the second stage on the reduced time has been derived theoretically and confirmed experimentally. The theory developed for pure liquids is applicable also to nanofluids, where a good agreement with the available experimental data has been found. However, in the case of evaporation of surfactant solutions the process deviates from the theoretical predictions for pure liquids at concentration below critical wetting concentration and is in agreement with the theoretical predictions at concentrations above it. Crown Copyright © 2013. All rights reserved.

Pore scale investigation of salt precipitation inside drying porous media resolved by 4D X-ray Microscopy Imaging

NASA Astrophysics Data System (ADS)

Norouzi Rad, M.

2016-12-01

Precipitation and deposition of salts in porous media is important in many natural processes as well as industrial and environmental applications since it can modify the structure and transport properties of porous media. In the presence of soluble salt in water during evaporation from porous media, salt is transported by convection induced by capillary liquid flow toward the evaporating surface where it accumulates, whereas diffusion tends to spread the salt and homogenize concentrations in space. Therefore, the competition between the convection and diffusion (characterized by Peclet number) affects the dynamics of salt distribution in porous media. As shown in previous studies (1-3) salt crust thickness and its coverage on the surface are highly influenced by the pore size distribution on the surface and active evaporation spots. In the current study, we focus on the precipitation dynamics and pattern during diffusion-driven evaporation period (the so-called stage-2 of evaporation) when the surface is dried and vaporization plane moves below the surface. Therefore, precipitation occurs inside the porous media during this period. To investigate the details of this process, 4D X-ray Microscopy was utilized. To do so, a packed bed of silica sand was saturated with 4 Molal NaCl solution and X-ray Microscopy was used to image the sample at well-defined time intervals during the evaporation process to provide pore scale information on evaporation and precipitation dynamics. The resulted 3-D pore-scale images were segmented to quantify the evaporative water losses and the dynamics and patterns of salt precipitation inside porous media with particular focus on the characterization of the processes occurring during stage-2 evaporation affecting the precipitation dynamics. [1] Norouzi Rad, M., N. Shokri, A. Keshmiri, P. Withers (2015), Effects of grain and pore size on salt precipitation during evaporation from porous media: A pore-scale investigation, Trans. Porous. Med., 110(2), 281-294. [2] Norouzi Rad, M., N. Shokri (2014), Effects of grain angularity on NaCl precipitation in porous media during evaporation, Water Resour. Res., 50, 9020-9030. [3] Norouzi Rad, M., N. Shokri, M. Sahimi (2013), Pore-Scale Dynamics of Salt Precipitation in Drying Porous Media, Phys. Rev. E, 88, 032404.

Evaluating The Reliability of Point Estimates of Wetland Evaporation

NASA Astrophysics Data System (ADS)

Gavin, H.; Agnew, C. T.

The Penman-Monteith formulation of evaporation has been criticised for its reliance upon point estimates raising concerns that areal estimates of wetland evaporation based upon single weather stations can be misleading. Typically wetlands are composed of a complex mosaic of land cover types each of which can produce different evaporative rates. The need to account for wetland patches when monitoring hydrological fluxes has been noted, while Morton (1983) has long argued for a fundamentally different approach to the calculation of regional evaporation. This paper presents the work carried out at wet grassland in Southern England that was monitored with several automatic weather stations (AWS) and a bowen ratio station to investigate microclimate variations. The significance of fetch was examined using the approach adopted by Gash (1986) based upon surface roughness to estimate the fraction of evaporation sensed from a specific distance upwind of the monitoring station. This theoretical analysis reveals that the fraction of evaporation contributed by the surrounding area steadily increases to a value of 77% at a distance of 224m and thereafter declines rapidly, under stable atmospheric conditions. Thus point climate observations may not reflect surface conditions at greater distances. This result was tested through the deployment offour AWS around the wetland. The data yielded a different response, suggesting that homogeneous conditions prevailed and the central AWS did provide reliable areal estimates of evaporation. The apparent contradiction is a result of not accounting for wind speeds found in wetlands that lead to widespread atmospheric mixing. These findings are typical of moist conditions whereas for example Guo and Scheupp (1994) found that a patchwork of dry fields and wet ditches, characteristic of the study site in summer, could produce differences of up to 50% in evaporation. The paper will also present the initial results of an investigation of the role of dry patches upon wetland evaporation estimates. Morton, F.I. 1983 Operational estimates of evapotranspiration and their significance to the science and practice of hydrology. Journal of Hydrology 66 1:76. Gash, J.H.C. 1986 A note on estimating the effect of limited fetch on micrometeorological evaporation measurements. Boundary Layer Meteorology 35: 409-413. Guo, Y. Schuepp, P.H. 1994a On surface energy balance over the northern wetlands 1. The effects of small-scale temperature and wetness heterogeneity. Journal of Geophysical Research 99 (D1) 1601-1612.

A New Microstructure Device for Efficient Evaporation of Liquids

NASA Astrophysics Data System (ADS)

Brandner, Juergen J.; Maikowske, Stefan; Vittoriosi, Alice

Evaporation of liquids is of major interest for many topics in process engineering. One of these is chemical process engineering, where evaporation of liquids and generation of superheated steam is mandatory for numerous processes. Generally, this is performed by use of classical pool boiling and evaporation process equipment. Another possibility is creating mixtures of gases and liquids, combined with a heating of this haze. Both methods provide relatively limited performance. Due to the advantages of microstructure devices especially in chemical process engineering [1] the interest in microstructure evaporators and steam generators have been increased through the last decade. In this publication several microstructure devices used for evaporation and generation of steam as well as superheating will be described. Here, normally electrically powered devices containing micro channels as well as non-channel microstructures are used due to better controllability of the temperature level. Micro channel heat exchangers have been designed, manufactured and tested at the Institute for Micro Process Engineering of the Karlsruhe Institute of Technology for more than 15 years. Starting with the famous Karlsruhe Cube, a cross-flow micro channel heat exchanger of various dimensions, not only conventional heat transfer between liquids or gases have been theoretically and experimentally examined but also phase transition from liquids to gases (evaporation) and condensation of liquids. However, the results obtained with sealed microstructure devices have often been unsatisfying. Thus, to learn more onto the evaporation process itself, an electrically powered device for optical inspection of the microstructures and the processes inside has been designed and manufactured [2]. This was further optimized and improved for better controllability and reliable experiments [3]. Exchangeable metallic micro channel array foils as well as an optical inspection of the evaporation process by high-speed videography have been integrated into the experimental setup. Fundamental research onto the influences of the geometry and dimensions of the integrated micro channels, the inlet flow distribution system geometry as well as the surface quality and surface coatings of the micro channels have been performed. While evaporation of liquids in crossflow and counterflow or co-current flow micro channel devices is possible, it is, in many cases, not possible to obtain superheated steam due to certain boundary conditions [4]. In most cases, the residence time is not sufficiently long, or the evaporation process itself cannot be stabilized and controlled precisely enough. Thus, a new design was proposed to obtain complete evaporation and steam superheating. This microstructure evaporator consists of a concentric arrangement of semi-circular walls or semi-elliptic walls providing at least two nozzles to release the generated steam. The complete arrangement forms a row of circular blanks. An example of such geometry is shown in Figure 7. A maximum power density of 1400 kW·m-2 has been transferred using similar systems, while liquid could be completely evaporated and the generated steam superheated. This is, compared to liquid heat exchanges, a small value, but it has to be taken in account that the specific heat capacity of vapour is considerably smaller than that of liquids. It could also be shown that the arrangement in circular blanks with semi-elliptic side walls acts as a kind of micro mixer for the remaining liquid and generated steam and, therefore, enhances the evaporation.

Oxygen Isotopic Fractionation During Evaporation of SiO2 in Vacuum and in H Gas

NASA Astrophysics Data System (ADS)

Nagahara, H.; Young, E. D.; Hoering, T. C.; Mysen, B. O.

1993-07-01

Chondritic components, chondrules, CAIs, and some parts of the matrix are believed to have formed and/or thermally processed in the solar nebula. If this scenario is the case, they should be fractionated for major and minor elements and isotopes according to the formation temperature. This is true for major and trace elements, but is not the case for isotopes. Differences in oxygen isotopic composition among meteorite groups are interpreted to be the results of mixing of gas and dust from different oxygen reservoirs, and the effect of isotopic fractionation is negligible for most meteorites except for rare CAIs. Davis et al. [1] studied the isotopic fractionation of SiO2, MgO, and forsterite and showed that oxygen isotopic fractionation from solid materials is very small, but that from liquid is significant. Evaporation in the solar nebula should, however, be in hydrogen gas, which is reactive with silicates. Therefore, the effect of hydrogen gas on the evaporation behaviors of silicates, including mode of evaporation, evaporation rate, and compositional and isotopic fractionation, should be studied. Nagahara [2] studied the evaporation rate of SiO2 in equilibrium, in constant evacuation (free evaporation), and in hydrogen, and showed that the rate in hydrogen gas is orders of magnitude larger than that in vacuum; the mode of evaporation also differs from that in vacuum. Oxygen isotopic fractionation during evaporation of SiO2 in constant evacuation and in hydrogen gas at two different total pressures are studied in the present study. The starting material is a single crystal of natural quartz, which should transform into high cristobalite at experimental conditions. The powdered starting material was kept in a graphite capsule without a cap and set in a vacuum chamber with and without hydrogen gas flow. Experimental temperature was 1600 degrees C. Oxygen isotopic compositions (^18O/^16O) were measured with the CO2laser heating fluorination technique. Oxygen isotope measurements, including ^17O and silicon isotope measurements, are now in progress, and some of the results are shown in this paper. Oxygen isotopic compositions of residues in vacuum and in hydrogen gas of total pressure of 2.6 x 10^-5 bar, which approximates the pressure of the solar nebula at the midplane at 2-3 AU, are shown in comparison with evaporation rate (Figs. 1 and 2). Oxygen isotopic fractionation is remarkable in a constant evacuation, but is negligible in hydrogen gas of 2.6 x 10^-5 bar total pressure. In vacuum, delta ^18O of solid residue increases with increasing degree of evaporation. The curve is best fit to delta ^18O = 0.00094x^2 + 0.00173x + 19.606 (r = 0.997), where x is the degree of evaporation in weight percent. The curve is fit to the Rayleigh fractionation curve with a constant fractionation factor (alpha(sub)vap-sol) of 0.9970. Figures 1 and 2 show that evaporation is significant but oxygen isotopic fractionation is insignificant in hydrogen gas in the approximate solar nebular condition. The high evaporation rate in hydrogen gas is due to the fact that evaporation is a decomposition reaction of an oxide, which should be accelerated in reducing condition. The rate, however, can be explained by an unknown diffusion process that is possible when hydrogen is reactive with silica [2]. In a fairly high hydrogen pressure, isotopic fractionation is suppressed. On the other hand, in vacuum, the evaporation rate is small but the degree of isotopic fractionation is significant. The results suggest that chondrules and CAIs without isotopic mass fractionation could have been formed in the solar nebula, but that mass loss during heating should have been significant. The CAIs with significant mass fractionation such as HAL could have been formed in vacuum. References: [1] Davis A. et al. (1990) Nature, 347, 655-658. [2] Nagahara H. (1993) LPS XXIV, 1045-1046. Fig. 1, which appears here in the hard copy, shows the evaporation rate of SiO2 heated at 1600 degrees C in vacuum and in hydrogen gas of 2.6 x 10^-5 bar as a function of time. Fig. 2, which appears here in the hard copy, shows oxygen isotopic composition (delta ^18O) of evaporation residue of SiO2.

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.

Environmental and Groundwater Controls on Evaporation Rates of A Shallow Saline Lake in the Western Sandhills Nebraska, USA

NASA Astrophysics Data System (ADS)

Peake, C.; Riveros-Iregui, D.; Lenters, J. D.; Zlotnik, V. A.; Ong, J.

2013-12-01

The western Sand Hills of Nebraska exhibit many shallow saline lakes that actively mediate groundwater-lake-atmospheric exchanges. The region is home to the largest stabilized dune field in the western hemisphere. Most of the lakes in the western Sand Hills region are saline and support a wide range of ecosystems. However, they are also highly sensitive to variability in evaporative and groundwater fluxes, which makes them a good laboratory to examine the effects of climate on the water balance of interdunal lakes. Despite being semiarid, little is known about the importance of groundwater-surface water interactions on evaporative rates, or the effects of changes in meteorological and energy forcings on the diel, and seasonal dynamics of evaporative fluxes. Our study is the first to estimate evaporation rates from one of the hundreds of shallow saline lakes that occur in the western Sand Hills region. We applied the energy balance Bowen ratio method at Alkali Lake, a typical saline western Sand Hills lake, over a three-year period (2007-2009) to quantify summer evaporation rates. Daily evaporation rates averaged 5.5 mm/day from July through September and were largely controlled by solar radiation on a seasonal and diel scales. Furthermore, the range of annual variability of evaporation rates was low. Although less pronounced, groundwater level effects on evaporation rates were also observed, especially from August through October when solar radiation was lower. The lake exhibits significant fluctuation in lake levels and combined with a shallow lake bed, large changes in lake surface area are observed. Our findings also show that with the onset of summer conditions, lake surface area can change very rapidly (e.g. 24% of its surface area or ~16.6 hectares were lost in less than ~2 months). In every year summer evaporation exceeded annual rainfall by an average of 28.2% suggesting that groundwater is a significant component of the lake water balance, it is important for sustaining life of surrounding ecosystems, and during the growing season it is transiently stored in the lake before it is rapidly lost to the atmosphere.

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).

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

Molecular dynamics study on condensation/evaporation coefficients of chain molecules at liquid-vapor interface

NASA Astrophysics Data System (ADS)

Nagayama, Gyoko; Takematsu, Masaki; Mizuguchi, Hirotaka; Tsuruta, Takaharu

2015-07-01

The structure and thermodynamic properties of the liquid-vapor interface are of fundamental interest for numerous technological implications. For simple molecules, e.g., argon and water, the molecular condensation/evaporation behavior depends strongly on their translational motion and the system temperature. Existing molecular dynamics (MD) results are consistent with the theoretical predictions based on the assumption that the liquid and vapor states in the vicinity of the liquid-vapor interface are isotropic. Additionally, similar molecular condensation/evaporation characteristics have been found for long-chain molecules, e.g., dodecane. It is unclear, however, whether the isotropic assumption is valid and whether the molecular orientation or the chain length of the molecules affects the condensation/evaporation behavior at the liquid-vapor interface. In this study, MD simulations were performed to study the molecular condensation/evaporation behavior of the straight-chain alkanes, i.e., butane, octane, and dodecane, at the liquid-vapor interface, and the effects of the molecular orientation and chain length were investigated in equilibrium systems. The results showed that the condensation/evaporation behavior of chain molecules primarily depends on the molecular translational energy and the surface temperature and is independent of the molecular chain length. Furthermore, the orientation at the liquid-vapor interface was disordered when the surface temperature was sufficiently higher than the triple point and had no significant effect on the molecular condensation/evaporation behavior. The validity of the isotropic assumption was confirmed, and we conclude that the condensation/evaporation coefficients can be predicted by the liquid-to-vapor translational length ratio, even for chain molecules.

Effect of Nd:YAG laser on the solvent evaporation of adhesive systems.

PubMed

Batista, Graziela Ribeiro; Barcellos, Daphne Câmara; Rocha Gomes Torres, Carlos; Damião, Álvaro José; de Oliveira, Hueder Paulo Moisés; de Paiva Gonçalves, Sérgio Eduardo

2015-01-01

This study evaluated the influence of Nd:YAG laser on the evaporation degree (ED) of the solvent components in total-etch and self-etch adhesives. The ED of Gluma Comfort Bond (Heraeus-Kulzer) one-step self-etch adhesive, and Adper Single Bond 2 (3M ESPE), and XP Bond (Dentsply) total-etch adhesives was determined by weight alterations using two techniques: Control--spontaneous evaporation of the solvent for 5 min; Experimental--Nd:YAG laser irradiation for 1 min, followed by spontaneous evaporation for 4 min. The weight loss due to evaporation of the volatile components was measured at baseline and after 10 s, 20 s, 30 s, 40 s, 50 s, 60 s, 70 s, 80 s, 90 s, 100 s, 110 s, 2 min, 3 min, 4 min, and 5 min. Evaporation of solvent components significantly increased with Nd:YAG laser irradiation for all adhesives investigated. Gluma Comfort Bond showed significantly higher evaporation of solvent components than Adper Single Bond 2 and XP Bond. All the adhesives lost weight quickly during the first min of Nd:YAG laser irradiation. The application of Nd:YAG laser on adhesives before light curing had a significant effect on the evaporation of the solvent components, and the ED of Gluma Comfort Bond one-step self-etch adhesive was significantly higher than with Adper Single Bond 2 and XP Bond total-etch adhesives. The use of the Nd:YAG laser on the uncured adhesive technique can promote a greater ED of solvents, optimizing the longevity of the adhesive restorations.

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.

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.

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.

Mass and heat transfer between evaporation and condensation surfaces: Atomistic simulation and solution of Boltzmann kinetic equation.

PubMed

Zhakhovsky, Vasily V; Kryukov, Alexei P; Levashov, Vladimir Yu; Shishkova, Irina N; Anisimov, Sergey I

2018-04-16

Boundary conditions required for numerical solution of the Boltzmann kinetic equation (BKE) for mass/heat transfer between evaporation and condensation surfaces are analyzed by comparison of BKE results with molecular dynamics (MD) simulations. Lennard-Jones potential with parameters corresponding to solid argon is used to simulate evaporation from the hot side, nonequilibrium vapor flow with a Knudsen number of about 0.02, and condensation on the cold side of the condensed phase. The equilibrium density of vapor obtained in MD simulation of phase coexistence is used in BKE calculations for consistency of BKE results with MD data. The collision cross-section is also adjusted to provide a thermal flux in vapor identical to that in MD. Our MD simulations of evaporation toward a nonreflective absorbing boundary show that the velocity distribution function (VDF) of evaporated atoms has the nearly semi-Maxwellian shape because the binding energy of atoms evaporated from the interphase layer between bulk phase and vapor is much smaller than the cohesive energy in the condensed phase. Indeed, the calculated temperature and density profiles within the interphase layer indicate that the averaged kinetic energy of atoms remains near-constant with decreasing density almost until the interphase edge. Using consistent BKE and MD methods, the profiles of gas density, mass velocity, and temperatures together with VDFs in a gap of many mean free paths between the evaporation and condensation surfaces are obtained and compared. We demonstrate that the best fit of BKE results with MD simulations can be achieved with the evaporation and condensation coefficients both close to unity.

Molecular dynamics study on condensation/evaporation coefficients of chain molecules at liquid–vapor interface

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

Nagayama, Gyoko, E-mail: nagayama@mech.kyutech.ac.jp; Takematsu, Masaki; Mizuguchi, Hirotaka

2015-07-07

The structure and thermodynamic properties of the liquid–vapor interface are of fundamental interest for numerous technological implications. For simple molecules, e.g., argon and water, the molecular condensation/evaporation behavior depends strongly on their translational motion and the system temperature. Existing molecular dynamics (MD) results are consistent with the theoretical predictions based on the assumption that the liquid and vapor states in the vicinity of the liquid–vapor interface are isotropic. Additionally, similar molecular condensation/evaporation characteristics have been found for long-chain molecules, e.g., dodecane. It is unclear, however, whether the isotropic assumption is valid and whether the molecular orientation or the chain lengthmore » of the molecules affects the condensation/evaporation behavior at the liquid–vapor interface. In this study, MD simulations were performed to study the molecular condensation/evaporation behavior of the straight-chain alkanes, i.e., butane, octane, and dodecane, at the liquid–vapor interface, and the effects of the molecular orientation and chain length were investigated in equilibrium systems. The results showed that the condensation/evaporation behavior of chain molecules primarily depends on the molecular translational energy and the surface temperature and is independent of the molecular chain length. Furthermore, the orientation at the liquid–vapor interface was disordered when the surface temperature was sufficiently higher than the triple point and had no significant effect on the molecular condensation/evaporation behavior. The validity of the isotropic assumption was confirmed, and we conclude that the condensation/evaporation coefficients can be predicted by the liquid-to-vapor translational length ratio, even for chain molecules.« less

Molecular dynamics study on condensation/evaporation coefficients of chain molecules at liquid-vapor interface.

PubMed

Nagayama, Gyoko; Takematsu, Masaki; Mizuguchi, Hirotaka; Tsuruta, Takaharu

2015-07-07

The structure and thermodynamic properties of the liquid-vapor interface are of fundamental interest for numerous technological implications. For simple molecules, e.g., argon and water, the molecular condensation/evaporation behavior depends strongly on their translational motion and the system temperature. Existing molecular dynamics (MD) results are consistent with the theoretical predictions based on the assumption that the liquid and vapor states in the vicinity of the liquid-vapor interface are isotropic. Additionally, similar molecular condensation/evaporation characteristics have been found for long-chain molecules, e.g., dodecane. It is unclear, however, whether the isotropic assumption is valid and whether the molecular orientation or the chain length of the molecules affects the condensation/evaporation behavior at the liquid-vapor interface. In this study, MD simulations were performed to study the molecular condensation/evaporation behavior of the straight-chain alkanes, i.e., butane, octane, and dodecane, at the liquid-vapor interface, and the effects of the molecular orientation and chain length were investigated in equilibrium systems. The results showed that the condensation/evaporation behavior of chain molecules primarily depends on the molecular translational energy and the surface temperature and is independent of the molecular chain length. Furthermore, the orientation at the liquid-vapor interface was disordered when the surface temperature was sufficiently higher than the triple point and had no significant effect on the molecular condensation/evaporation behavior. The validity of the isotropic assumption was confirmed, and we conclude that the condensation/evaporation coefficients can be predicted by the liquid-to-vapor translational length ratio, even for chain molecules.

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

Smoothed particle hydrodynamics method for evaporating multiphase flows.

PubMed

Yang, Xiufeng; Kong, Song-Charng

2017-09-01

The smoothed particle hydrodynamics (SPH) method has been increasingly used for simulating fluid flows; however, its ability to simulate evaporating flow requires significant improvements. This paper proposes an SPH method for evaporating multiphase flows. The present SPH method can simulate the heat and mass transfers across the liquid-gas interfaces. The conservation equations of mass, momentum, and energy were reformulated based on SPH, then were used to govern the fluid flow and heat transfer in both the liquid and gas phases. The continuity equation of the vapor species was employed to simulate the vapor mass fraction in the gas phase. The vapor mass fraction at the interface was predicted by the Clausius-Clapeyron correlation. An evaporation rate was derived to predict the mass transfer from the liquid phase to the gas phase at the interface. Because of the mass transfer across the liquid-gas interface, the mass of an SPH particle was allowed to change. Alternative particle splitting and merging techniques were developed to avoid large mass difference between SPH particles of the same phase. The proposed method was tested by simulating three problems, including the Stefan problem, evaporation of a static drop, and evaporation of a drop impacting a hot surface. For the Stefan problem, the SPH results of the evaporation rate at the interface agreed well with the analytical solution. For drop evaporation, the SPH result was compared with the result predicted by a level-set method from the literature. In the case of drop impact on a hot surface, the evolution of the shape of the drop, temperature, and vapor mass fraction were predicted.

DWPF RECYCLE EVAPORATOR FLOWSHEET EVALUATION (U)

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

Stone, M

2005-04-30

The Defense Waste Processing Facility (DWPF) converts the high level waste slurries stored at the Savannah River Site into borosilicate glass for long-term storage. The vitrification process results in the generation of approximately five gallons of dilute recycle streams for each gallon of waste slurry vitrified. This dilute recycle stream is currently transferred to the H-area Tank Farm and amounts to approximately 1,400,000 gallons of effluent per year. Process changes to incorporate salt waste could increase the amount of effluent to approximately 2,900,000 gallons per year. The recycle consists of two major streams and four smaller streams. The first majormore » recycle stream is condensate from the Chemical Process Cell (CPC), and is collected in the Slurry Mix Evaporator Condensate Tank (SMECT). The second major recycle stream is the melter offgas which is collected in the Off Gas Condensate Tank (OGCT). The four smaller streams are the sample flushes, sump flushes, decon solution, and High Efficiency Mist Eliminator (HEME) dissolution solution. These streams are collected in the Decontamination Waste Treatment Tank (DWTT) or the Recycle Collection Tank (RCT). All recycle streams are currently combined in the RCT and treated with sodium nitrite and sodium hydroxide prior to transfer to the tank farm. Tank Farm space limitations and previous outages in the 2H Evaporator system due to deposition of sodium alumino-silicates have led to evaluation of alternative methods of dealing with the DWPF recycle. One option identified for processing the recycle was a dedicated evaporator to concentrate the recycle stream to allow the solids to be recycled to the DWPF Sludge Receipt and Adjustment Tank (SRAT) and the condensate from this evaporation process to be sent and treated in the Effluent Treatment Plant (ETP). In order to meet process objectives, the recycle stream must be concentrated to 1/30th of the feed volume during the evaporation process. The concentrated stream must be pumpable to the DWPF SRAT vessel and should not precipitate solids to avoid fouling the evaporator vessel and heat transfer coils. The evaporation process must not generate excessive foam and must have a high Decontamination Factor (DF) for many species in the evaporator feed to allow the condensate to be transferred to the ETP. An initial scoping study was completed in 2001 to evaluate the feasibility of the evaporator which concluded that the concentration objectives could be met. This initial study was based on initial estimates of recycle concentration and was based solely on OLI modeling of the evaporation process. The Savannah River National Laboratory (SRNL) has completed additional studies using simulated recycle streams and OLI{reg_sign} simulations. Based on this work, the proposed flowsheet for the recycle evaporator was evaluated for feasibility, evaporator design considerations, and impact on the DWPF process. This work was in accordance with guidance from DWPF-E and was performed in accordance with the Technical Task and Quality Assurance Plan.« less

Partitioning evaporation and transpiration in a maize field with heat-pulse sensors used for evaporation

USDA-ARS?s Scientific Manuscript database

Evaporation (E) and transpiration (T) occur simultaneously in many systems with varying levels of importance, yet terms are typically lumped as evapotranspiration (ET) due to difficulty with distinguishing component fluxes. Few studies have measured all three terms (ET, E, and T), and in the few cas...

Deconstructing Learning in Science--Young Children's Responses to a Classroom Sequence on Evaporation.

ERIC Educational Resources Information Center

Tytler, Russell; Peterson, Suzanne

2001-01-01

Tracks five-year-old children's ideas by a range of means during and subsequent to a classroom sequence on evaporation. Explores the relationship between social and individual perspectives on learning, and questions some assumptions underlying conceptual change research. Analyzes the children's explanations of various evaporation phenomena over…

40 CFR 799.1053 - Trichlorobenzenes.

Code of Federal Regulations, 2014 CFR

2014-07-01

... systems that control for evaporation of the test substance, shall be conducted for 1,2,3- and 1,2,4... through systems, and systems that control for evaporation of the test substance shall be conducted for 1,2... systems that control evaporation of the test substance shall be conducted for 1,2,3-trichlorobenzene. A 96...

40 CFR 799.1053 - Trichlorobenzenes.

Code of Federal Regulations, 2013 CFR

2013-07-01

... systems that control for evaporation of the test substance, shall be conducted for 1,2,3- and 1,2,4... through systems, and systems that control for evaporation of the test substance shall be conducted for 1,2... systems that control evaporation of the test substance shall be conducted for 1,2,3-trichlorobenzene. A 96...

40 CFR 799.1053 - Trichlorobenzenes.

Code of Federal Regulations, 2012 CFR

2012-07-01

... systems that control for evaporation of the test substance, shall be conducted for 1,2,3- and 1,2,4... through systems, and systems that control for evaporation of the test substance shall be conducted for 1,2... systems that control evaporation of the test substance shall be conducted for 1,2,3-trichlorobenzene. A 96...

43 CFR 418.36 - Incentives for additional long term conservation.

Code of Federal Regulations, 2014 CFR

2014-10-01

... be reduced by the incremental amount of evaporation which occurs as a result of the increased surface area of the reservoir due to the additional storage. The evaporation rate used will be either the net evaporation measured or the net historical average after precipitation is taken into account. The method of...

43 CFR 418.36 - Incentives for additional long term conservation.

Code of Federal Regulations, 2013 CFR

2013-10-01

... be reduced by the incremental amount of evaporation which occurs as a result of the increased surface area of the reservoir due to the additional storage. The evaporation rate used will be either the net evaporation measured or the net historical average after precipitation is taken into account. The method of...

43 CFR 418.36 - Incentives for additional long term conservation.

Code of Federal Regulations, 2012 CFR

2012-10-01

... be reduced by the incremental amount of evaporation which occurs as a result of the increased surface area of the reservoir due to the additional storage. The evaporation rate used will be either the net evaporation measured or the net historical average after precipitation is taken into account. The method of...

The Boltzmann Constant from a Snifter

ERIC Educational Resources Information Center

Tyukodi, B.; Sarkozi, Zs.; Neda, Z.; Tunyagi, A.; Gyorke, E.

2012-01-01

Evaporation of a small glass of ethylic alcohol is studied both experimentally and through an elementary thermal physics approach. For a cylindrical beaker and no air flow in the room, a simple quadratic relation is found between the evaporation time and the mass of evaporated liquid. This problem and the obtained results offer excellent…

Partitioning evaporation and transpiration in a maize field using heat pulse sensors for evaporation measurement

USDA-ARS?s Scientific Manuscript database

Evapotranspiration (ET) is the sum of soil water evaporation (E) and plant transpiration (T). E and T occur simultaneously in many systems with varying levels of importance, yet it is often very challenging to distinguish these fluxes separately in the field. Few studies have measured all three term...

40 CFR 1045.145 - Are there interim provisions that apply only for a limited time?

Code of Federal Regulations, 2012 CFR

2012-07-01

.... You may sell or install fuel tanks that do not meet the specified permeation standards without...: (1) You may earn an evaporative emission allowance from one fuel tank certified to EPA's evaporative... this evaporative emission allowance by selling one fuel tank that does not meet the specified...

40 CFR 1045.145 - Are there interim provisions that apply only for a limited time?

Code of Federal Regulations, 2014 CFR

2014-07-01

.... You may sell or install fuel tanks that do not meet the specified permeation standards without...: (1) You may earn an evaporative emission allowance from one fuel tank certified to EPA's evaporative... this evaporative emission allowance by selling one fuel tank that does not meet the specified...

40 CFR 1045.145 - Are there interim provisions that apply only for a limited time?

Code of Federal Regulations, 2011 CFR

2011-07-01

.... You may sell or install fuel tanks that do not meet the specified permeation standards without...: (1) You may earn an evaporative emission allowance from one fuel tank certified to EPA's evaporative... this evaporative emission allowance by selling one fuel tank that does not meet the specified...

Evaporation, Boiling and Bubbles

ERIC Educational Resources Information Center

Goodwin, Alan

2012-01-01

Evaporation and boiling are both terms applied to the change of a liquid to the vapour/gaseous state. This article argues that it is the formation of bubbles of vapour within the liquid that most clearly differentiates boiling from evaporation although only a minority of chemistry textbooks seems to mention bubble formation in this context. The…

10 CFR 429.16 - Central air conditioners and heat pumps.

Code of Federal Regulations, 2013 CFR

2013-01-01

...-system, when combined with a selected evaporator coil (indoor unit) or a set of selected indoor units...-evaporator coil combination selected for tests pursuant to paragraph (a)(2)(i) of this section shall include the evaporator coil that is likely to have the largest volume of retail sales with the particular...

10 CFR 429.16 - Central air conditioners and heat pumps.

Code of Federal Regulations, 2012 CFR

2012-01-01

...-system, when combined with a selected evaporator coil (indoor unit) or a set of selected indoor units...-evaporator coil combination selected for tests pursuant to paragraph (a)(2)(i) of this section shall include the evaporator coil that is likely to have the largest volume of retail sales with the particular...

10 CFR 429.16 - Central air conditioners and heat pumps.

Code of Federal Regulations, 2014 CFR

2014-01-01

...-system, when combined with a selected evaporator coil (indoor unit) or a set of selected indoor units...-evaporator coil combination selected for tests pursuant to paragraph (a)(2)(i) of this section shall include the evaporator coil that is likely to have the largest volume of retail sales with the particular...

Application of self-preservation in the diurnal evolution of the surface energy budget to determine daily evaporation

NASA Technical Reports Server (NTRS)

Brutsaert, Wilfried; Sugita, Michiaki

1992-01-01

Evaporation from natural land surfaces often exhibits a strong variation during the course of a day, mostly in response to the daily variation of radiative energy input at the surface. This makes it difficult to derive the total daily evaporation, when only one or a few instantaneous estimates of evaporation are available. It is often possible to resolve this difficulty by assuming self-preservation in the diurnal evolution of the surface energy budget. Thus if the relative partition of total incoming energy flux among the different components remains the same, the ratio of latent heat flux and any other flux component can be taken as constant through the day. This concept of constant flux ratios is tested by means of data obtained during the First ISLSCP Field Experiment; the instantaneous evaporation values were calculated by means of the atmospheric boundary layer bulk similarity approach with radiosonde profiles and radiative surface temperatures. Good results were obtained for evaporative flux ratios with available energy flux, with net radiation, and with incoming shortwave radiation.

Fate of sulfur mustard on soil: Evaporation, degradation, and vapor emission.

PubMed

Jung, Hyunsook; Kah, Dongha; Chan Lim, Kyoung; Lee, Jin Young

2017-01-01

After application of sulfur mustard to the soil surface, its possible fate via evaporation, degradation following absorption, and vapor emission after decontamination was studied. We used a laboratory-sized wind tunnel, thermal desorber, gas chromatograph-mass spectrometry (GC-MS), and 13 C nuclear magnetic resonance ( 13 C NMR) for systematic analysis. When a drop of neat HD was deposited on the soil surface, it evaporated slowly while being absorbed immediately into the matrix. The initial evaporation or drying rates of the HD drop were found to be power-dependent on temperature and initial drop volume. Moreover, drops of neat HD, ranging in size from 1 to 6 μL, applied to soil, evaporated at different rates, with the smaller drops evaporating relatively quicker. HD absorbed into soil remained for a month, degrading eventually to nontoxic thiodiglycol via hydrolysis through the formation of sulfonium ions. Finally, a vapor emission test was performed for HD contaminant after a decontamination process, the results of which suggest potential risk from the release of trace chemical quantities of HD into the environment. Copyright © 2016 Elsevier Ltd. All rights reserved.

Evaporation from Lake Mead, Arizona and Nevada, 1997-99

USGS Publications Warehouse

Westenburg, Craig L.; DeMeo, Guy A.; Tanko, Daron J.

2006-01-01

Lake Mead is one of a series of large Colorado River reservoirs operated and maintained by the Bureau of Reclamation. The Colorado River system of reservoirs and diversions is an important source of water for millions of people in seven Western States and Mexico. The U.S. Geological Survey, in cooperation with the Bureau of Reclamation, conducted a study from 1997 to 1999 to estimate evaporation from Lake Mead. For this study, micrometeorological and hydrologic data were collected continually from instrumented platforms deployed at four locations on the lake, open-water areas of Boulder Basin, Virgin Basin, and Overton Arm and a protected cove in Boulder Basin. Data collected at the platforms were used to estimate Lake Mead evaporation by solving an energy-budget equation. The average annual evaporation rate at open-water stations from January 1998 to December 1999 was 7.5 feet. Because the spatial variation of monthly and annual evaporation rates was minimal for the open-water stations, a single open-water station in Boulder Basin would provide data that are adequate to estimate evaporation from Lake Mead.

Effect of surfactant concentration on the evaporation of droplets on cotton (Gossypium hirsutum L.) leaves.

PubMed

Zhou, Zhaolu; Cao, Chong; Cao, Lidong; Zheng, Li; Xu, Jun; Li, Fengmin; Huang, Qiliang

2018-04-05

The evaporation kinetics of pesticide droplets deposited on a leaf surface can affect their application efficiency. Evaporation of droplets on the hydrophobic leaves has received considerable attention, but little is known about hydrophilic leaf surfaces. In this study, the effect of surfactant concentration on the evaporation of droplets deposited on cotton leaves was investigated. The evaporation time is roughly decreased for concentrations ranging from 0% to 0.01% and increased from 0.01% to 0.10%. Contrary to the widely held belief that pesticide retention on target crops can rapidly be formed only with surfactant concentrations exceeding the CMC (critical micelle concentration), this study demonstrates that, on hydrophilic cotton leaves, fast evaporation of the droplet at surfactant concentrations of 0.01% (CMC) can reduce the volume quickly, lower the loss point and enhance pesticide retention. In addition, the evolution of droplet volume, height and contact angle on the cotton leaf surface were measured to confirm this conclusion. The result presented herein can be used to guide the use of surfactants and pesticides in agriculture. Copyright © 2018 Elsevier B.V. All rights reserved.

Fate of Potential Contaminants Due to Disposal of Olive Mill Wastewaters in Unprotected Evaporation Ponds.

PubMed

Kavvadias, V; Elaiopoulos, K; Theocharopoulos, Sid; Soupios, P

2017-03-01

The disposal of olive mill wastewaters (OMW) in shallow and unprotected evaporation ponds is a common, low-cost management practice, followed in Mediterranean countries. So far, the fate of potential soil pollutants in areas located near evaporation ponds is not adequately documented. This study investigates the extent in which the long-term disposal of OMW in evaporation ponds can affect the soil properties of the area located outside the evaporation pond and assesses the fate of the pollution loads of OMW. Four soil profiles situated outside and around the down slope side of the disposal area were excavated. The results showed considerable changes in concentration of soil phenols at the down-site soil profiles, due to the subsurface transport of the OMW. In addition, excessive concentrations of NH 4 + , PO 4 3- and phenols were recorded in liquid samples taken from inside at the bottom of the soil profiles. It is concluded that unprotected evaporation ponds located in light texture soils pose a serious threat to favour soil and water pollution.

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.

Measuring the Nonuniform Evaporation Dynamics of Sprayed Sessile Microdroplets with Quantitative Phase Imaging.

PubMed

Edwards, Chris; Arbabi, Amir; Bhaduri, Basanta; Wang, Xiaozhen; Ganti, Raman; Yunker, Peter J; Yodh, Arjun G; Popescu, Gabriel; Goddard, Lynford L

2015-10-13

We demonstrate real-time quantitative phase imaging as a new optical approach for measuring the evaporation dynamics of sessile microdroplets. Quantitative phase images of various droplets were captured during evaporation. The images enabled us to generate time-resolved three-dimensional topographic profiles of droplet shape with nanometer accuracy and, without any assumptions about droplet geometry, to directly measure important physical parameters that characterize surface wetting processes. Specifically, the time-dependent variation of the droplet height, volume, contact radius, contact angle distribution along the droplet's perimeter, and mass flux density for two different surface preparations are reported. The studies clearly demonstrate three phases of evaporation reported previously: pinned, depinned, and drying modes; the studies also reveal instances of partial pinning. Finally, the apparatus is employed to investigate the cooperative evaporation of the sprayed droplets. We observe and explain the neighbor-induced reduction in evaporation rate, that is, as compared to predictions for isolated droplets. In the future, the new experimental methods should stimulate the exploration of colloidal particle dynamics on the gas-liquid-solid interface.

Application of the PJ and NPS evaporation duct models over the South China Sea (SCS) in winter

PubMed Central

Yang, Shaobo; Li, Xingfei; Wu, Chao; He, Xin; Zhong, Ying

2017-01-01

The detection of duct height has a significant effect on marine radar or wireless apparatus applications. The paper presents two models to verify the adaptation of evaporation duct models in the SCS in winter. A meteorological gradient instrument used to measure evaporation ducts was fabricated using hydrological and meteorological sensors at different heights. An experiment on the adaptive characteristics of evaporation duct models was carried out over the SCS. The heights of the evaporation ducts were measured by means of log-linear fit, Paulus-Jeske (PJ) and Naval Postgraduate School (NPS) models. The results showed that NPS model offered significant advantages in stability compared with the PJ model. According the collected data computed by the NPS model, the mean deviation (MD) was -1.7 m, and the Standard Deviation (STD) of the MD was 0.8 m compared with the true value. The NPS model may be more suitable for estimating the evaporation duct height in the SCS in winter due to its simpler system characteristics compared with meteorological gradient instruments. PMID:28273113

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.

Formation of Particulate Matter from the Oxidation of Evaporated Wastewater from Hydraulic Fracturing Activity

NASA Astrophysics Data System (ADS)

Hildebrandt Ruiz, L.; Bean, J. K.; Bilotto, A.

2017-12-01

The use of hydraulic fracturing for production of petroleum and natural gas has increased dramatically in the last decade, but the environmental impacts of this technology remain unclear. Experiments were conducted to quantify airborne emissions from twelve samples of hydraulic fracturing flowback wastewater collected in the Permian Basin, as well as the photochemical processing of these emissions leading to the formation of particulate matter. The concentration of total volatile carbon (TVC, hydrocarbons evaporating at room temperature) averaged 29 milligrams of carbon per liter (mgC/L) and the TVC evaporation rate averaged 1357 mgC/L-m2-min. After photochemical oxidation under high NOx conditions the amount of organic particulate matter formed per milliliter of wastewater evaporated averaged 24 micrograms (µg); the amount of ammonium nitrate formed averaged 262 µg. In the state of Texas, the potential formation of PM from evaporated flowback wastewater is similar to the estimated PM emissions from diesel engines used in oil rigs, emphasizing the need to quantify wastewater evaporation and atmospheric processing of these emissions.

Prediction of WBGT-based clothing adjustment values from evaporative resistance

PubMed Central

BERNARD, Thomas E.; ASHLEY, Candi D.; GARZON, Ximena P.; KIM, Jung-Hyun; COCA, Aitor

2017-01-01

Wet bulb globe temperature (WBGT) index is used by many professionals in combination with metabolic rate and clothing adjustments to assess whether a heat stress exposure is sustainable. The progressive heat stress protocol is a systematic method to prescribe a clothing adjustment value (CAV) from human wear trials, and it also provides an estimate of apparent total evaporative resistance (Re,T,a). It is clear that there is a direct relationship between the two descriptors of clothing thermal effects with diminishing increases in CAV at high Re,T,a. There were data to suggest an interaction of CAV and Re,T,a with relative humidity at high evaporative resistance. Because human trials are expensive, manikin data can reduce the cost by considering the static total evaporative resistance (Re,T,s). In fact, as the static evaporative resistance increases, the CAV increases in a similar fashion as Re,T,a. While the results look promising that Re,T,s can predict CAV, some validation remains, especially for high evaporative resistance. The data only supports air velocities near 0.5 m/s. PMID:29033404

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.

Process control plan for 242-A Evaporator Campaign 95-1

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

Le, E.Q.; Guthrie, M.D.

1995-05-18

The wastes from tanks 106-AP, 107-AP, and 106-AW have been selected to be candidate feed wastes for Evaporator Campaign 95-1. The wastes in tank 106-AP and 107-AP are primarily from B-Plant strontium processing and PUREX neutralized cladding removal, respectively. The waste in tank 106-AW originated primarily from the partially concentrated product from 242-A Evaporator Campaign 94-2. Approximately 8.67 million liters of waste from these tanks will be transferred to tank 102-AW during the campaign. Tank 102-AW is the dedicated waste feed tank for the evaporator and currently contains 647,000 liters of processable waste. The purpose of the 242-A Evaporator Campaignmore » 95-1 Process Control Plan (hereafter referred to as PCP) is to certify that the wastes in tanks 106-AP, 107-AP, 102-AW, and 106-AW are acceptable for processing through evaporator and provide a general description of process strategies and activities which will take place during Campaign 95-1. The PCP also summarizes and presents a comprehensive characterization of the wastes in these tanks.« less

Solutal Marangoni flow as the cause of ring stains from drying salty colloidal drops

NASA Astrophysics Data System (ADS)

Marin, Alvaro; Karpitschka, Stefan; Rossi, Massimiliano; Kaehler, Christian J.; Noguera-Marin, Diego; Rodriguez-Valverde, Miguel A.

2017-11-01

Salts can be found in different forms in almost any evaporating droplet in nature, our homes and in laboratories. The transport processes in such apparently simple systems differ strongly from `sweet' evaporating droplets since the liquid flows in the inverse direction due to Marangoni stresses at the surface. Such an effect has crucial consequences to salt crystallization processes and to the evaporation itself. In this work we show measurements that not only confirm clearly the details of the inverted flow patterns, but also permit us to calculate the surface tension gradients responsible for the reversal. Such a reversal does not prevent the coffee-stain effect; on the contrary, particles accumulate and get trapped at the liquid-air interface driven by the surface flow. In order to prove this, we show measurements of the full three-dimensional flow inside the evaporating salty droplet, confocal imaging is used to quantify the growth of the particle deposits for different salt concentrations, and we compare the experimental results with numerical simulations that capture the solvent evaporation, the evaporation-induced liquid flow and the quasi-equilibrium liquid-gas interface.

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.

Gravity Effects in Condensing and Evaporating Films

NASA Technical Reports Server (NTRS)

Hermanson, J. C.; Som, S. M.; Allen, J. S.; Pedersen, P. C.

2004-01-01

A general overview of gravity effects in condensing and evaporating films is presented. The topics include: 1) Research Overview; 2) NASA Recognizes Critical Need for Condensation & Evaporation Research to Enable Human Exploration of Space; 3) Condensation and Evaporation Research in Reduced Gravity is Enabling for AHST Technology Needs; 4) Differing Role of Surface Tension on Condensing/Evaporating Film Stability; 5) Fluid Mechanisms in Condensing and Evaporating Films in Reduced Gravity; 6) Research Plan; 7) Experimental Configurations for Condensing Films; 8) Laboratory Condensation Test Cell; 9) Aircraft Experiment; 10) Condensation Study Current Test Conditions; 11) Diagnostics; 12) Shadowgraph Images of Condensing n- pentane Film in Unstable (-1g) Configuration; 13) Condensing n-Pentane Film in Normal Gravity (-1g) at Constant Pressure; 14) Condensing n-Pentane Film in Normal Gravity (-1g) with Cyclic Pressure; 15) Non-condensing Pumped Film in Normal Gravity (-1g); 16) Heat Transfer Coefficient in Developing, Unstable Condensing Film in Normal Gravity; 17) Heat Transfer for Unsteady Condensing Film (-1g); 18) Ultrasound Measurement of Film Thickness N-pentane Film, Stable (+1g) Configuration; and 19) Ultrasound Measurement of Film Thickness N-pentane Film, Unstable (-1g) Configuration.

Prediction of WBGT-based clothing adjustment values from evaporative resistance.

PubMed

Bernard, Thomas E; Ashley, Candi D; Garzon, Ximena P; Kim, Jung-Hyun; Coca, Aitor

2017-12-07

Wet bulb globe temperature (WBGT) index is used by many professionals in combination with metabolic rate and clothing adjustments to assess whether a heat stress exposure is sustainable. The progressive heat stress protocol is a systematic method to prescribe a clothing adjustment value (CAV) from human wear trials, and it also provides an estimate of apparent total evaporative resistance (R e,T,a ). It is clear that there is a direct relationship between the two descriptors of clothing thermal effects with diminishing increases in CAV at high R e,T,a . There were data to suggest an interaction of CAV and R e,T,a with relative humidity at high evaporative resistance. Because human trials are expensive, manikin data can reduce the cost by considering the static total evaporative resistance (R e,T,s ). In fact, as the static evaporative resistance increases, the CAV increases in a similar fashion as R e,T,a . While the results look promising that R e,T,s can predict CAV, some validation remains, especially for high evaporative resistance. The data only supports air velocities near 0.5 m/s.

[Interlaboratory Study on Evaporation Residue Test for Food Contact Products (Report 1)].

PubMed

Ohno, Hiroyuki; Mutsuga, Motoh; Abe, Tomoyuki; Abe, Yutaka; Amano, Homare; Ishihara, Kinuyo; Ohsaka, Ikue; Ohno, Haruka; Ohno, Yuichiro; Ozaki, Asako; Kakihara, Yoshiteru; Kobayashi, Hisashi; Sakuragi, Hiroshi; Shibata, Hiroshi; Shirono, Katsuhiro; Sekido, Haruko; Takasaka, Noriko; Takenaka, Yu; Tajima, Yoshiyasu; Tanaka, Aoi; Tanaka, Hideyuki; Tonooka, Hiroyuki; Nakanishi, Toru; Nomura, Chie; Haneishi, Nahoko; Hayakawa, Masato; Miura, Toshihiko; Yamaguchi, Miku; Watanabe, Kazunari; Sato, Kyoko

2018-01-01

An interlaboratory study was performed to evaluate the equivalence between an official method and a modified method of evaporation residue test using three food-simulating solvents (water, 4% acetic acid and 20% ethanol), based on the Japanese Food Sanitation Law for food contact products. Twenty-three laboratories participated, and tested the evaporation residues of nine test solutions as blind duplicates. For evaporation, a water bath was used in the official method, and a hot plate in the modified method. In most laboratories, the test solutions were heated until just prior to evaporation to dryness, and then allowed to dry under residual heat. Statistical analysis revealed that there was no significant difference between the two methods, regardless of the heating equipment used. Accordingly, the modified method provides performance equal to the official method, and is available as an alternative method.

The influence of droplet evaporation on fuel-air mixing rate in a burner

NASA Technical Reports Server (NTRS)

Komiyama, K.; Flagan, R. C.; Heywood, J. B.

1977-01-01

Experiments involving combustion of a variety of hydrocarbon fuels in a simple atmospheric pressure burner were used to evaluate the role of droplet evaporation in the fuel/air mixing process in liquid fuel spray flames. Both air-assist atomization and pressure atomization processes were studied; fuel/air mixing rates were determined on the basis of cross-section average oxygen concentrations for stoichiometric overall operation. In general, it is concluded that droplets act as point sources of fuel vapor until evaporation, when the fuel jet length scale may become important in determining nonuniformities of the fuel vapor concentration. In addition, air-assist atomizers are found to have short droplet evaporation times with respect to the duration of the fuel/air mixing process, while for the pressure jet atomizer the characteristic evaporation and mixing times are similar.

Air Evaporation closed cycle water recovery technology - Advanced energy saving designs

NASA Technical Reports Server (NTRS)

Morasko, Gwyndolyn; Putnam, David F.; Bagdigian, Robert

1986-01-01

The Air Evaporation water recovery system is a visible candidate for Space Station application. A four-man Air Evaporation open cycle system has been successfully demonstrated for waste water recovery in manned chamber tests. The design improvements described in this paper greatly enhance the system operation and energy efficiency of the air evaporation process. A state-of-the-art wick feed design which results in reduced logistics requirements is presented. In addition, several design concepts that incorporate regenerative features to minimize the energy input to the system are discussed. These include a recuperative heat exchanger, a heat pump for energy transfer to the air heater, and solar collectors for evaporative heat. The addition of the energy recovery devices will result in an energy reduction of more than 80 percent over the systems used in earlier manned chamber tests.