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1

Evaporation rate of water in hydrophobic confinement  

PubMed Central

The drying of hydrophobic cavities is believed to play an important role in biophysical phenomena such as the folding of globular proteins, the opening and closing of ligand-gated ion channels, and ligand binding to hydrophobic pockets. We use forward flux sampling, a molecular simulation technique, to compute the rate of capillary evaporation of water confined between two hydrophobic surfaces separated by nanoscopic gaps, as a function of gap, surface size, and temperature. Over the range of conditions investigated (gaps between 9 and 14 ? and surface areas between 1 and 9 nm2), the free energy barrier to evaporation scales linearly with the gap between hydrophobic surfaces, suggesting that line tension makes the predominant contribution to the free energy barrier. The exponential dependence of the evaporation rate on the gap between confining surfaces causes a 10 order-of-magnitude decrease in the rate when the gap increases from 9 to 14 ?. The computed free energy barriers are of the order of 50kT and are predominantly enthalpic. Evaporation rates per unit area are found to be two orders of magnitude faster in confinement by the larger (9 nm2) than by the smaller (1 nm2) surfaces considered here, at otherwise identical conditions. We show that this rate enhancement is a consequence of the dependence of hydrophobic hydration on the size of solvated objects. For sufficiently large surfaces, the critical nucleus for the evaporation process is a gap-spanning vapor tube. PMID:22392972

Sharma, Sumit; Debenedetti, Pablo G.

2012-01-01

2

Instructions for measuring the rate of evaporation from water surfaces  

USGS Publications Warehouse

The ·rate of evaporation from water surfaces varies with the temperature of the water, the velocity of the wind at the water surface, and the dryness of the air. Consequently, the rate of evaporation from rivers, lakes, canals, or reservoirs varies widely in different localities and for the same locality in different seasons.

U.S. Geological Survey

1898-01-01

3

Rate of Water Evaporation in Texas.  

E-print Network

.163 . Precipitation, inches 1 39 -49 .79 .84 1.73 2.82 2.84 3.20 2.39 1.72 1.05 .79 21.57 Mean max. temp. Mean min. temp. Mean mean temp. Av. rel. humidity Wind run, miles Big Spring: Evaporation, inches Precipitation, inches Mean max. temB. Mean min. temp....379 16.420 8.047 7.320 7.06818.580 6.178 6.890 6.864 7.167 5.643 4.816 7.780 6.688 7.859 8.773 7.807 7.123 8.184 7.573 8.500 7.200 6.260 7.403 4.746 6.775 5.664 6.477 6.855 7.000 8.494 6.400 6.144 6.017 6.907 8.586 6...

Karper, R. E. (Robert Earl)

1933-01-01

4

The rates at which terrestrial animals lose water through evaporation across the skin and respiratory surfaces  

E-print Network

and respiratory surfaces have important consequences for their water balance, thermoregulation and survivalThe rates at which terrestrial animals lose water through evaporation across the skin required the minimization of evaporative water losses. In response to these demands, animals have evolved

Wolf, Blair O.

5

Evaporation Rate on Tungsten  

E-print Network

Cesium Evaporation Rate on Tungsten Photocathodes Ameerah Jabr-Hamdan Introduction Motivation Research Objective Experiments Results Conclusions Cesium Evaporation Rate on Tungsten Photocathodes supported by IREAP, with funding from NSF and ONR #12;Cesium Evaporation Rate on Tungsten Photocathodes

Anlage, Steven

6

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

PubMed

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. PMID:22049757

Starke, P; Göbel, P; Coldewey, W G

2011-01-01

7

Estimating steady-state evaporation rates from bare soils under conditions of high water table  

USGS Publications Warehouse

A procedure that combines meteorological and soil equations of water transfer makes it possible to estimate approximately the steady-state evaporation from bare soils under conditions of high water table. Field data required include soil-water retention curves, water table depth and a record of air temperature, air humidity and wind velocity at one elevation. The procedure takes into account the relevant atmospheric factors and the soil's capability to conduct 'water in liquid and vapor forms. It neglects the effects of thermal transfer (except in the vapor case) and of salt accumulation. Homogeneous as well as layered soils can be treated. Results obtained with the method demonstrate how the soil evaporation rates·depend on potential evaporation, water table depth, vapor transfer and certain soil parameters.

Ripple, C.D.; Rubin, J.; Van Hylckama, T. E. A.

1970-01-01

8

Evaporation Rates for Liquid Water and Ice Under Current Martian Conditions  

NASA Technical Reports Server (NTRS)

A number of studies have been concerned with the evaporation rates under martian conditions in order to place limits on the possible survival time of both liquid water and ice exposed on the surface of Mars. Such studies also aid in assessing the efficacy of an overlying layer of dust or loose regolith material in providing a barrier to free evaporation and thus prolong the lifetime of water in locations where its availability to putative living organisms would be significant. A better quantitative understanding of the effects of phase changes of water in the near surface environment would also aid the evaluation of the possible role of water in the formation of currently observed features, such as gullies in cliff walls and relatively short-term changes in the albedo of small surface areas ('dark stains'). Laboratory measurements aimed at refinement of our knowledge of these values are described here. The establishment of accurate values for evaporation rates and their dependence on the physical conditions of temperature, pressure and energy input, is an important benchmark for the further investigation of the efficacy of barriers to free evaporation in providing a prolonged period of survival of the water, particularly as a liquid.

Sears, D. W. G.; Moore, S. R.; Meier, A.; Chittenden, J.; Kareev, M.; Farmer, C. B.

2004-01-01

9

Accurate evaporation rates of pure and doped water clusters in vacuum: A statistico-dynamical approach  

NASA Astrophysics Data System (ADS)

Unimolecular evaporation of selected pure (H2O)n and heterogeneous (H2O)n-1X+ water clusters containing a single hydronium or ammonium impurity is investigated in the framework of phase space theory (PST) in its orbiting transition state version. Using the many-body polarizable Kozack-Jordan potential and its extensions for X+=H3O+ and NH4+, the thermal evaporation of clusters containing 21 and 50 molecules is simulated at several total energies. Numerous molecular dynamics (MD) trajectories at high internal energies provide estimates of the decay rate constant, as well as the kinetic energy and angular momentum released upon dissociation. Additional Monte Carlo simulations are carried out to determine the anharmonic densities of vibrational states, which combined with suitable forms for the rotational densities of states provide expressions for the energy-resolved differential rates. Successful comparison between the MD results and the independent predictions of PST for the distributions of kinetic energy and angular momentum released shows that the latter statistical approach is quantitative. Using MD data as a reference, the absolute evaporation rates are calculated from PST over broad energy and temperature ranges. Based on these results, the presence of an ionic impurity is generally found to decrease the rate, however the effect is much more significant in the 21-molecule clusters. Our calculations also suggest that due to backbendings in the microcanonical densities of states the variations of the evaporation rates may not be strictly increasing with energy or temperature.

Calvo, F.; Douady, J.; Spiegelman, F.

2010-01-01

10

Maximum Evaporation Rates of Water Droplets Approaching Obstacles in the Atmosphere Under Icing Conditions  

NASA Technical Reports Server (NTRS)

When a closed body or a duct envelope moves through the atmosphere, air pressure and temperature rises occur ahead of the body or, under ram conditions, within the duct. If cloud water droplets are encountered, droplet evaporation will result because of the air-temperature rise and the relative velocity between the droplet and stagnating air. It is shown that the solution of the steady-state psychrometric equation provides evaporation rates which are the maximum possible when droplets are entrained in air moving along stagnation lines under such conditions. Calculations are made for a wide variety of water droplet diameters, ambient conditions, and flight Mach numbers. Droplet diameter, body size, and Mach number effects are found to predominate, whereas wide variation in ambient conditions are of relatively small significance in the determination of evaporation rates. The results are essentially exact for the case of movement of droplets having diameters smaller than about 30 microns along relatively long ducts (length at least several feet) or toward large obstacles (wings), since disequilibrium effects are then of little significance. Mass losses in the case of movement within ducts will often be significant fractions (one-fifth to one-half) of original droplet masses, while very small droplets within ducts will often disappear even though the entraining air is not fully stagnated. Wing-approach evaporation losses will usually be of the order of several percent of original droplet masses. Two numerical examples are given of the determination of local evaporation rates and total mass losses in cases involving cloud droplets approaching circular cylinders along stagnation lines. The cylinders chosen were of 3.95-inch (10.0+ cm) diameter and 39.5-inch 100+ cm) diameter. The smaller is representative of icing-rate measurement cylinders, while with the larger will be associated an air-flow field similar to that ahead of an airfoil having a leading-edge radius comparable with that of the cylinder. It is found that the losses are less than 5 percent. It is concluded that such losses are, in general, very small (less than 1 percent) in the case of smaller obstacles (of icing-rate measurement- cylinder size); the motional dynamics are such, however, that exceptions will occur by reason of failure of very small droplets (moving along stagnation lines) to impinge upon obstacle surfaces. In such cases, the droplets will evaporate completely.

Lowell, H. H.

1953-01-01

11

Waking to drink: rates of evaporative water loss determine arousal frequency in hibernating bats.  

PubMed

Bats hibernate to cope with low ambient temperatures (T(a)) and low food availability during winter. However, hibernation is frequently interrupted by arousals, when bats increase body temperature (T(b)) and metabolic rate (MR) to normothermic levels. Arousals account for more than 85% of a bat's winter energy expenditure. This has been associated with variation in T(b), T(a) or both, leading to a single testable prediction, i.e. that torpor bout length (TBL) is negatively correlated with T(a) and T(b). T(a) and T(b) were both found to be correlated with TBL, but correlations alone cannot establish a causal link between arousal and T(b) or T(a). Because hydration state has also been implicated in arousals from hibernation, we hypothesized that water loss during hibernation creates the need in bats to arouse to drink. We measured TBL of bats (Pipistrellus kuhlii) at the same T(a) but under different conditions of humidity, and found an inverse relationship between TBL and total evaporative water loss, independent of metabolic rate, which directly supports the hypothesis that hydration state is a cue to arousal in bats. PMID:23364570

Ben-Hamo, Miriam; Muñoz-Garcia, Agustí; Williams, Joseph B; Korine, Carmi; Pinshow, Berry

2013-02-15

12

Metabolic rate and evaporative water loss in the silky starling (Sturnus sericeus).  

PubMed

To better understand the physiological characteristics of the silky starling (Sturnus sericeus), its body temperature (Tb), basal metabolic rate (BMR), evaporative water loss (EWL) and thermal conductance (C) elicited by different ambient temperatures (Ta) (5-30 ?) were determined in the present study. Our results showed that they have a high Tb (41.6 ± 0.1 ?), a wide thermal neutral zone (TNZ) (20-27.5?) and a relatively low BMR within the TNZ (3.37 ± 0.17 mL O?/g·h). The EWL was nearly stable below the TNZ (0.91 ± 0.07 mg H?O/g·h) but increased remarkably within and above the TNZ. The C was constant below the TNZ, with a minimum value of 0.14 ± 0.01 mL O?/g·h·?. These findings indicate that the BMR, Tb and EWL of the silky starling were all affected by Ta, especially when Ta was below 20 ? and the EWL plays an important role in thermal regulation. PMID:25017746

Bao, Huan-Huan; Liang, Qing-Jian; Zhu, Hong-Lei; Zhou, Xiao-Qiu; Zheng, Wei-Hong; Liu, Jin-Song

2014-07-01

13

Water Membrane Evaporator  

NASA Technical Reports Server (NTRS)

A water membrane evaporator (WME) has been conceived and tested as an alternative to the contamination-sensitive and corrosion-prone evaporators currently used for dissipating heat from space vehicles. The WME consists mainly of the following components: An outer stainless-steel screen that provides structural support for the components mentioned next; Inside and in contact with the stainless-steel screen, a hydrophobic membrane that is permeable to water vapor; Inside and in contact with the hydrophobic membrane, a hydrophilic membrane that transports the liquid feedwater to the inner surface of the hydrophobic membrane; Inside and in contact with the hydrophilic membrane, an annular array of tubes through which flows the spacecraft coolant carrying the heat to be dissipated; and An inner exclusion tube that limits the volume of feedwater in the WME. In operation, a pressurized feedwater reservoir is connected to the volume between the exclusion tube and the coolant tubes. Feedwater fills the volume, saturates the hydrophilic membrane, and is retained by the hydrophobic membrane. The outside of the WME is exposed to space vacuum. Heat from the spacecraft coolant is conducted through the tube walls and the water-saturated hydrophilic membrane to the liquid/vapor interface at the hydrophobic membrane, causing water to evaporate to space. Makeup water flows into the hydrophilic membrane through gaps between the coolant tubes.

Ungar, Eugene K.; Almlie, Jay C.

2010-01-01

14

Characteristics of Evaporation Rate of Water in Superheated Steam and Air  

NASA Astrophysics Data System (ADS)

Superheated steam drying and highly humid air drying have been applied in many industrial drying fields, such as drying of by-products of food industry. The most significant reason for this wide range of applications of superheated steam is that more water evaporates in this steam or highly humid air than in dry air above the inversion point temperature. As compared with these wide practical applications, fundamental research for determining controlled operating conditions or optimum design conditions for a superheated steam drying system have not been sufficiently performed. From this viewpoint, in experimenting for drying water in the closed circuit dryer, by changing drying variables, such as the mass velocity of heat transfer of the steam,the existance of the inversion point temperature was confirmed and the locus of the temperature were found. The behavior of the locus enables one to specify the drying variables for a controlled drying system. The difference of the evaporation phenomenon between superheated steam drying and conventional air drying was examined from the heat convection standpoint. The reliability of the data obtained from the experiment was too checked by comparing the data with another reported data.

Nomura, Tomihiro; Nishimura, Nobuya; Hyodo, Tsutomu; Kashiwagi, Takao

15

Field-measured, hourly soil water evaporation stages in relation to reference evapotranspiration rate and soil air temperature ratio  

Technology Transfer Automated Retrieval System (TEKTRAN)

Soil water evaporation takes critical water supplies away from crops, especially in areas where both rainfall and irrigation water are limited. This study measured bare soil water evaporation from clay loam, silt loam, sandy loam, and fine sand soils. It found that on average almost half of the ir...

16

Biology of Myotis thysanodes and M. lucifugus (Chiroptera: Vespertilionidae)—III. Metabolism, heart rate, breathing rate, evaporative water loss and general energetics  

Microsoft Academic Search

Oxygen consumption (OC), weight specific oxygen consumption (VO). heart rate (HR). breathing rate (RR) and evaporative water loss (EWL) differ in adult female Mrotis th.wrnodes and M. ~uc~~uficgus and are significantly related to thermoregulatory performance (regulating or conforming) and to reproductive condition but not to body composttion. spleen or adrenal weights or age class. 2. Multiple regression equation models of

EUGENE H. STUDIER

1976-01-01

17

Sheet Membrane Spacesuit Water Membrane Evaporator  

NASA Technical Reports Server (NTRS)

A document describes a sheet membrane spacesuit water membrane evaporator (SWME), which allows for the use of one common water tank that can supply cooling water to the astronaut and to the evaporator. Test data showed that heat rejection performance dropped only 6 percent after being subjected to highly contaminated water. It also exhibited robustness with respect to freezing and Martian atmospheric simulation testing. Water was allowed to freeze in the water channels during testing that simulated a water loop failure and vapor backpressure valve failure. Upon closing the backpressure valve and energizing the pump, the ice eventually thawed and water began to flow with no apparent damage to the sheet membrane. The membrane evaporator also serves to de-gas the water loop from entrained gases, thereby eliminating the need for special degassing equipment such as is needed by the current spacesuit system. As water flows through the three annular water channels, water evaporates with the vapor flowing across the hydrophobic, porous sheet membrane to the vacuum side of the membrane. The rate at which water evaporates, and therefore, the rate at which the flowing water is cooled, is a function of the difference between the water saturation pressure on the water side of the membrane, and the pressure on the vacuum side of the membrane. The primary theory is that the hydrophobic sheet membrane retains water, but permits vapor pass-through when the vapor side pressure is less than the water saturation pressure. This results in evaporative cooling of the remaining water.

Bue, Grant; Trevino, Luis; Zapata, Felipe; Dillion, Paul; Castillo, Juan; Vonau, Walter; Wilkes, Robert; Vogel, Matthew; Frodge, Curtis

2013-01-01

18

Tear Water Evaporation and Eye Surface Diseases  

Microsoft Academic Search

The water evaporation rate from the tear film of eyes with anterior surface pathology (corneal and\\/or conjunctival scars, meibomitis) was tested by means of the ‘Rolando-Refojo tear evaporimeter’, which allows noninvasive and reproducible test conditions. These eyes show a statistically significant increase in tear evaporation rate compared to normal eyes. The clinical implications of this finding are discussed.

Maurizio Rolando; Miguel F. Refojo; Kenneth R. Kenyon

1985-01-01

19

Evaporation  

NSDL National Science Digital Library

This three-part activity consists of an activity that groups of learners develop themselves, a given procedure, and an optional demonstration. First, learners discuss examples of evaporation and then design and conduct their own test to find out whether heating water has an effect on the rate of evaporation. While waiting for their results, learners conduct another evaporation activity using single drops of water on 2 paper towels, one of which is heated. The optional demonstration compares the rate of evaporation of hot and cold water using a sensitive scale or balance. In each of these experiences with evaporation, learners will identify variables, consider how to best control them, and use their observations to conclude that heating water increases the rate of evaporation.

James H. Kessler

2007-01-01

20

Computation of hypersonic flows with finite rate condensation and evaporation of water  

NASA Technical Reports Server (NTRS)

A computer program for modelling 2D hypersonic flows of gases containing water vapor and liquid water droplets is presented. The effects of interphase mass, momentum and energy transfer are studied. Computations are compared with existing quasi-1D calculations on the nozzle of the NASA Langley Eight Foot High Temperature Tunnel, a hypersonic wind tunnel driven by combustion of natural gas in oxygen enriched air.

Perrell, Eric R.; Candler, Graham V.; Erickson, Wayne D.; Wieting, Alan R.

1993-01-01

21

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

ERIC Educational Resources Information Center

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…

Canpolat, Nurtac

2006-01-01

22

Evaporation  

NSDL National Science Digital Library

The representation is an animation of the water cycle. It shows water evaporating from a large body of water with a descriptive text describing the water cycle process including evaporation, condensation and precipitation. An additional diagram on transport is included.

23

Thermoelectric integrated membrane evaporation water recovery technology  

NASA Technical Reports Server (NTRS)

The recently developed Thermoelectric Integrated Membrane Evaporation Subsystem (TIMES) offers a highly competitive approach to water recovery from waste fluids for future on-orbit stations such as the Space Operations Center. Low power, compactness and gravity insensitive operation are featured in this vacuum distillation subsystem that combines a hollow fiber membrane evaporator with a thermoelectric heat pump. The hollow fiber elements provide positive liquid/gas phase control with no moving parts other than pumps and an accumulator, thus solving problems inherent in other reclamation subsystem designs. In an extensive test program, over 850 hours of operation were accumulated during which time high quality product water was recovered from both urine and wash water at an average steady state production rate of 2.2 pounds per hour.

Roebelen, G. J., Jr.; Winkler, H. E.; Dehner, G. F.

1982-01-01

24

Condensation and evaporation of water vapor in mixed aerosols of liquid droplets and ice: numerical comparison of growth rate expressions  

Microsoft Academic Search

We compare four different H2O mass flux descriptions in simulations of the evolution of mixed water\\/ice aerosol populations undergoing condensational growth. It is shown that the Maxwellian description, ignoring condensation heat release, overestimates the growth rates severely when compared with an exact numerical description. The well-known Mason equation predicts the growth rates somewhat better, but still in an inadequate manner

Jukka Hienola; Markku Kulmala; Ari Laaksonen

2001-01-01

25

Water Purification by Evaporation and Condensation  

NSDL National Science Digital Library

This demonstration illustrates how the water cycle helps to purify water. Students are introduced to the key terms, which are evaporation and condensation. They discover that evaporation is defined as the process through which a liquid becomes a vapor, while condensation is simply the reverse. Students also learn that in the case of water, the main mechanisms for evaporation and condensation are heating and cooling, respectively.

26

Evaporative cooling of speleothem drip water  

PubMed Central

This study describes the first use of concurrent high-precision temperature and drip rate monitoring to explore what controls the temperature of speleothem forming drip water. Two contrasting sites, one with fast transient and one with slow constant dripping, in a temperate semi-arid location (Wellington, NSW, Australia), exhibit drip water temperatures which deviate significantly from the cave air temperature. We confirm the hypothesis that evaporative cooling is the dominant, but so far unattributed, control causing significant disequilibrium between drip water and host rock/air temperatures. The amount of cooling is dependent on the drip rate, relative humidity and ventilation. Our results have implications for the interpretation of temperature-sensitive, speleothem climate proxies such as ?18O, cave microecology and the use of heat as a tracer in karst. Understanding the processes controlling the temperature of speleothem-forming cave drip waters is vital for assessing the reliability of such deposits as archives of climate change. PMID:24895139

Cuthbert, M. O.; Rau, G. C.; Andersen, M. S.; Roshan, H.; Rutlidge, H.; Marjo, C. E.; Markowska, M.; Jex, C. N.; Graham, P. W.; Mariethoz, G.; Acworth, R. I.; Baker, A.

2014-01-01

27

Experimental study on water evaporation from sand using environmental chamber  

E-print Network

and various drying durations were imposed on the soil sample. Atmospheric parameters (air flow rate, relative. The results show that the air and soil temperatures depend on the evaporation process and atmospheric Fontainebleau, succion a` la surface du sol. Introduction Soil water evaporation at the air­soil interface

Paris-Sud XI, Université de

28

Spatially Resolved Evaporative Patterns from Water  

E-print Network

Unexpectedly distinct patterns in evaporation were observed over heated water. Although the patterns had chaotic aspects, they often showed geometric patterns. These patterns bore strong resemblance to the infrared emission patterns observable with a mid-infrared camera focused on the water surface. This similarity puts constraints on the mechanism of evaporation, and leads to a general hypothesis as to the nature of the evaporative process.

Ienna, Federico; Pollack, Gerald H

2011-01-01

29

Evaporation and transport of water isotopologues from Greenland lakes  

NASA Astrophysics Data System (ADS)

Water isotopes are a vital tracer for determining the evaporative source of precipitated water. However, estimates of the isotopic composition of evaporated moisture remain poorly constrained. Our goals were to show that isotopic profiles from a single lake source are observable, simulate these profiles with a simple mass conservation model, better constrain estimates of turbulent diffusion and evaporation using isotopes, and determine if a previously developed model can predict the observed isotopic flux of evaporated moisture accurately under our study conditions. Using an LGR water vapor isotope analyzer, we recorded vertical and horizontal vapor gradients over Greenland lakes 150 m to 5.5 km across under steady-state dominated conditions. We compared model simulations with field observations of humidity and isotopic profiles to determine the best-fit value for the model's turbulent diffusion parameter, allowing us to calculate evaporation rates. The model produced plausible profiles of vapor concentrations above 0.5 m, but overestimated humidity near the water surface. Our calculated evaporation rate decreased as fetch increased contrary to previous studies that show relatively constant evaporation with distance. Part of this discrepancy might have been caused by model simplifications such as assuming horizontally uniform wind speed. Our results also showed that, during gusts, wind speed and vapor concentrations are positively correlated indicating that concentration increase caused by greater turbulence transport outweighed the concentration decrease caused by shorter transit time of advection. Incorporating isotopic data reduced statistical error in evaporation estimates by a factor of two. Estimated evaporation rates, although lower than expected, are within error of rates estimated using an empirical model based on previous Arctic lake studies. We also showed that a model for predicting isotopic ratios of the evaporative flux over ocean produced inaccurate results when applied to lakes due to their smaller fetch. The methods used in our study present a more adequate alternative in lake studies.

Lauder, Alex

30

Water evaporation: a transition path sampling study.  

PubMed

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. PMID:23294322

Varilly, Patrick; Chandler, David

2013-02-01

31

Water Evaporation: A Transition Path Sampling Study  

E-print Network

We use transition path sampling to study evaporation in the SPC/E model of liquid water. Based on 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.

Patrick Varilly; David Chandler

2012-12-12

32

Analysis of defrosted water evaporation from three water trays in refrigerators  

Microsoft Academic Search

The evaporation of defrosted water from vapour compression domestic refrigerators can be a real problem in tropical countries with hot and humid ambient conditions. This poses a challenge to the refrigerator manufacturers to design a water tray with minimal additional cost but with significantly improved evaporation rates. This paper, therefore, analyses the performance of three types of water trays that

G. Xie; P. K. Bansal

2000-01-01

33

Evaporation rate of emulsion and oil-base emulsion pheromones  

Technology Transfer Automated Retrieval System (TEKTRAN)

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...

34

Water Management for Evaporatively Cooled Condensers  

E-print Network

Water Management for Evaporatively Cooled Condensers Theresa Pistochini May 23rd, 2012 ResearchAirCapacity,tons Gallons of Water Continuous Test - Outdoor Air 110-115 Deg F Cyclic Test - Outdoor Air 110-115 Deg F #12 AverageWaterHardness(ppm) Cooling Degree Days (60°F Reference) 20% Population 70% Population 10

California at Davis, University of

35

Prediction of evaporation of defrosted water in refrigerator water trays  

Microsoft Academic Search

The main concern of the present paper is to simulate the evaporation of defrosted water in domestic refrigerator water trays. The tray is assumed to be located above in vicinity to the compressor head, and part of the heat used to evaporate the water is heat from the compressor. The mathematical model is based on that of Bansal and Xie.

Somchai Wongwises; Boonanan Anansauwapak

2005-01-01

36

Evaporation kinetics of acetic acid-water solutions  

NASA Astrophysics Data System (ADS)

The transport of water molecules across vapor-liquid interfaces in the atmosphere is a crucial step in the formation and evolution of cloud droplets. Despite decades of study, the effects of solutes on the mechanism and rate of evaporation and condensation remain poorly characterized. The present work aims to determine the effect of atmospherically-relevant solutes on the evaporation rate of water. In our experiments, we create a train of micron-sized droplets and measure their temperature via Raman thermometry as they undergo evaporation without condensation. Analysis of the cooling rate yields the evaporation coefficient (?). Previous work has shown that inorganic salts have little effect on ?, with surface-adsorbing anions causing a slight reduction in the coefficient from that measured for pure water. Organic acids are ubiquitous in aqueous aerosol and have been shown to disrupt the surface structure of water. Here we describe measurements of the evaporation rate of acetic acid solutions, showing that acetic acid reduces ? to a larger extent than inorganic ions, and that ? decreases with increasing acetic acid concentration.

Duffey, K.; Wong, N.; Saykally, R.; Cohen, R. C.

2012-12-01

37

On the Effect of the Atmosphere on the Evaporation of Sessile Droplets of Water  

E-print Network

On the Effect of the Atmosphere on the Evaporation of Sessile Droplets of Water K. Sefiane1 , S. K into the effect of the atmosphere on the evaporation of pinned sessile droplets of water is described. The experimental work investigated the evaporation rates of sessile droplets in atmospheres of three different

Mottram, Nigel

38

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

PubMed

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. PMID:24506092

Dehaeck, Sam; Rednikov, Alexey; Colinet, Pierre

2014-03-01

39

Development of a Water Cluster Evaporation Model using Molecular Dynamics  

NASA Astrophysics Data System (ADS)

A Monte Carlo simulation using the SPC potential model has been used to determine the potential energy and constant volume heat capacity of water dimers and trimers. It was found that the potential energy almost follows a linear trend versus temperature. The heat capacity fluctuates around 10 cal/mol/K and reaches a maximum around 220 K for the dimer and 240 K for the trimer. The Molecular Dynamics simulation has been used to evaporate water dimers and trimers. The cumulative evaporation probabilities were calculated for temperatures ranging from 240 K to 300 K. The cluster evaporation rates were calculated using Weerashinge's equation, and they were compared with the UDT rates. Both values were found to be in good agreement. Finally, vibrational frequencies were computed.

Borner, Arnaud; Li, Zheng; Levin, Deborah A.

2011-05-01

40

EVAPORATIVE RECOVERY OF CHROMIUM PLATING RINSE WATERS  

EPA Science Inventory

This demonstration project documents the practicality of a new evaporative approach for recovering chromic acid from metal finishing rinse waste waters, as well as the economics of the system under actual operating conditions. The six-month study of chrome plating operations was ...

41

Soil water evaporation and crop residues  

Technology Transfer Automated Retrieval System (TEKTRAN)

Crop residues have value when left in the field and also when removed from the field and sold as a commodity. Reducing soil water evaporation (E) is one of the benefits of leaving crop residues in place. E was measured beneath a corn canopy at the soil suface with nearly full coverage by corn stover...

42

Evaporation rate and vapor pressure of selected polymeric lubricating oils.  

NASA Technical Reports Server (NTRS)

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.

Gardos, M. N.

1973-01-01

43

Isotope Fractionation of Water During Evaporation WithoutCondensation  

SciTech Connect

The microscopic events engendering liquid water evaporation have received much attention over the last century, but remain incompletely understood. We present measurements of isotope fractionation occurring during free molecular evaporation from liquid microjets and show that the isotope ratios of evaporating molecules exhibit dramatic differences from equilibrium vapor values, strong variations with the solution deuterium mole fraction, and a clear temperature dependence. These results indicate the existence of an energetic barrier to evaporation and that the evaporation coefficient of water is less than unity. These new insights into water evaporation promise to advance our understanding of the processes that control the formation and lifetime of clouds in the atmosphere.

Cappa, Christopher D.; Drisdell, Walter S.; Smith, Jared D.; Saykally, Richard J.; Cohen, Ronald C.

2005-10-19

44

Physiological adjustments of sand gazelles (Gazella subgutturosa) to a boom-or-bust economy: standard fasting metabolic rate, total evaporative water loss, and changes in the sizes of organs during food and water restriction.  

PubMed

To test the hypothesis that desert ungulates adjust their physiology in response to long-term food and water restriction, we established three groups of sand gazelles (Gazella subgutturosa): one that was provided food and water (n = 6; CTRL) ad lib. for 4 mo, one that received ad lib. food and water for the same period but was deprived of food and water for the last 4.5 d (n = 6; EXPT(1)), and one that was exposed to 4 mo of progressive food and water restriction, an experimental regime designed to mimic conditions in a natural desert setting (n = 6; EXPT(2)). At the end of the 4-mo experiment, we measured standard fasting metabolic rate (SFMR) and total evaporative water loss (TEWL) of all sand gazelles and determined lean dry mass of organs of gazelles in CTRL and EXPT(2). Gazelles in CTRL had a mean SFMR of 2,524 +/- 194 kJ d(-1), whereas gazelles in EXPT(1) and EXPT(2) had SFMRs of 2,101+/- 232 and 1,365 +/- 182 kJ d(-1), respectively, values that differed significantly when we controlled for differences in body mass. Gazelles had TEWLs of 151.1 +/- 18.2, 138.5 +/- 17.53, and 98.4 +/- 27.2 g H(2)O d(-1) in CTRL, EXPT(1), and EXPT(2), respectively. For the latter group, mass-independent TEWL was 27.1% of the value for CTRL. We found that normally hydrated sand gazelles had a low mass-adjusted TEWL compared with other arid-zone ungulates: 13.6 g H(2)O kg(-0.898) d(-1), only 17.1% of allometric predictions, the lowest ever measured in an arid-zone ungulate. After 4 mo of progressive food and water restriction, dry lean mass of liver, heart, and muscle of gazelles in EXPT(2) was significantly less than that of these same organs in CTRL, even when we controlled for body mass decrease. Decreases in the dry lean mass of liver explained 70.4% of the variance of SFMR in food- and water-restricted gazelles. As oxygen demands decreased because of reduced organ sizes, gazelles lost less evaporative water, probably because of a decreased respiratory water loss. PMID:16826507

Ostrowski, Stephane; Mesochina, Pascal; Williams, Joseph B

2006-01-01

45

Evaporative system for water and beverage refrigeration in hot countries  

E-print Network

Evaporative system for water and beverage refrigeration in hot countries A Saleh1 and MA Al-Nimr2 1 Abstract: The present study proposes an evaporative refrigerating system used to keep water or other are found to be consistent with the available literature data. Keywords: evaporative refrigeration, heat

46

Hollow-Fiber Spacesuit Water Membrane Evaporator  

NASA Technical Reports Server (NTRS)

The hollow-fiber spacesuit water membrane evaporator (HoFi SWME) is being developed to perform the thermal control function for advanced spacesuits and spacecraft to take advantage of recent advances in micropore membrane technology in providing a robust, heat-rejection device that is less sensitive to contamination than is the sublimator. After recent contamination tests, a commercial-off-the-shelf (COTS) micro porous hollow-fiber membrane was selected for prototype development as the most suitable candidate among commercial hollow-fiber evaporator alternatives. An innovative design that grouped the fiber layers into stacks, which were separated by small spaces and packaged into a cylindrical shape, was developed into a full-scale prototype for the spacesuit application. Vacuum chamber testing has been performed to characterize heat rejection as a function of inlet water temperature and water vapor back-pressure, and to show contamination resistance to the constituents expected to be found in potable water produced by the wastewater reclamation distillation processes. Other tests showed tolerance to freezing and suitability to reject heat in a Mars pressure environment. In summary, HoFi SWME is a lightweight, compact evaporator for heat rejection in the spacesuit that is robust, contamination- insensitive, freeze-tolerant, and able to reject the required heat of spacewalks in microgravity, lunar, and Martian environments. The HoFi is packaged to reject 810 W of heat through 800 hours of use in a vacuum environment, and 370 W in a Mars environment. The device also eliminates free gas and dissolved gas from the coolant loop.

Bue, Grant; Trevino, Luis; Tsioulos, Gus; Mitchell, Keith; Settles, Joseph

2013-01-01

47

Evaporation rates of pasture-mesquite vegetation in central Mexico  

NASA Astrophysics Data System (ADS)

The semiarid highlands of Queretaro, in central Mexico, are characterized by booming urban and industrial developments with increasing demand for water. Agriculture takes place in the valleys and the surrounding hills have different types of xeric to subtropical rangeland. Hills are unfit for agriculture and usually are managed for cattle production and fuelwood. However, recent studies suggest that some hill areas are important for groundwater recharge and if they are not protected, important water shortages are envisioned. A critical question involves the effects of land management practices on rangeland hydrologic processes. Evaporation (E), which includes plant and soil evaporation is the largest water loss from rangelands and few data are available for central Mexico. The objective of this study was to estimate E from a mesquite (Prosopis sp.) dominated vegetation using the eddy correlation and the Pennman-Monteith models. Measurements were made during 24 summer days of 2004 at a piedmont site at Amascala, Queretaro (1919 m, 20° 41' N, 100° 16' W). Long term annual rainfall is 568 ± 137 mm. Shrub density was 770 plants per hectare and mean height was 1.8 m. The understory was composed by a mixture of annual and perennial grasses but their biomass was negligible. Agroforestry was the current land use of the site. Shrubs were pruned every 2 or 3 years to maintain its height and promote leafty regrowth. Goats usually browsed the mesquite canopy, but during the time of the study they were excluded from the area.The rainy season started on 15 May and measurements initiated on 1 June, five days after a severe hail storm. Although the mesquite canopy had a full developed canopy with leaf area index of 3.2 by this time, they lost approximately 70% of leaf area. May and June rainfall was 146 mm and 46 mm occurred during the measuring period. Throughout the measurement period E was coupled to global radiation and total evaporation was 73.8 mm. On cloudy days E ranged from 1.1 to 2.0 mm d-1, maximum E was 4.3 mm d-1 on sunny days and the average E was 3.1 mm d-1. Average daily E increased during the measuring period at a rate of 0.05 mm d-1 (r2=0.2, p<0.05). Data suggest that evaporation from a pasture-mesquite vegetation is an important component in the water balance considering the limited rainfall occurring.

Sosa, E. G.; Escobar, A. G.

2004-12-01

48

Is the evaporation water loss of Knot Calidris canutus higher in tropical than in temperate climates?  

Microsoft Academic Search

To test whether Knot Calidris canutus wintering in the tropics suffer higher rates of water loss through evaporation than do Knot wintering at temperate latitudes, we tried to develop a physically realistic model to predict evaporative heat loss from air temperature, wind and humidity. In separate experiments, involving respirometry and double-labelled water, we tried to estimate relevant parameters, In both

N. Verboven; T. Piersma

1995-01-01

49

Sheet Membrane Spacesuit Water Membrane Evaporator Thermal Test  

NASA Technical Reports Server (NTRS)

For future lunar extravehicular activities (EVA), one method under consideration for rejecting crew and electronics heat involves evaporating water through a hydrophobic, porous Teflon(Registered Trademark) membrane. A Spacesuit Water Membrane Evaporator (SWME) prototype using this membrane was successfully tested by Ungar and Thomas (2001) with predicted performance matching test data well. The above referenced work laid the foundation for the design of a compact sheet membrane SWME development unit for use in the Constellation System Spacesuit Element Portable Life Support System (Vogel and et. al., ICES 2008). Major design objectives included minimizing mass, volume, and manufacturing complexity while rejecting a minimum of 810 watts of heat from water flowing through the SWME at 91 kg/hr with an inlet temperature of 291K. The design meeting these objectives consisted of three concentric cylindrical water channels interlaced with four water vapor channels. Two units were manufactured for the purpose of investigating manufacturing techniques and performing thermal testing. The extensive thermal test measured SWME heat rejection as a function of water inlet temperatures, water flow-rates, water absolute pressures, water impurities, and water vapor back-pressures. This paper presents the test results and subsequent analysis, which includes a comparison of SWME heat rejection measurements to pretest predictions. In addition, test measurements were taken such that an analysis of the commercial-off-the-shelf vapor pressure control valve could be performed.

Trevino, Luis A.; Bue, Grant C.

2009-01-01

50

Evaporation rates of alkanes and alkanols from acoustically levitated drops  

Microsoft Academic Search

Evaporation constants of acoustically levitated drops from the homologue series of n-alkanes and 1-alkanols in ambient air have been evaluated by size and temperature measurements. The size of the pure liquid drops, within a diameter range of 0.1 to 2.5 mm, was monitored using a CCD camera, while temperature measurements were carried out by IR thermography. During drop evaporation, water

Rudolf Tuckermann; Sigurd Bauerecker; Bernd Neidhart

2002-01-01

51

Sensible heat observations reveal soil-water evaporation dynamics  

Technology Transfer Automated Retrieval System (TEKTRAN)

Soil water evaporation is important at scales ranging from microbial ecology to large-scale climate. Yet, routine measurments are unable to capture rapidly shifting near-surface soil heat and water processes involved in soil-water evaporation. The objective of this study was to determine the depth a...

52

Investigating the Water Cycle: Using Plants to Study Evaporation  

NSDL National Science Digital Library

In this science activity, students investigate the water cycle by testing the water evaporated from leaves (transpiration) in a field experience. Students use elements of this information to track the water cycle through it's various stages.

53

Study of water evaporation and condensation in a domestic refrigerator loaded by wet product  

Microsoft Academic Search

This study was carried out to gain a better insight into evaporation and condensation phenomena due to natural convection in a domestic refrigerator. An experiment was undertaken in a refrigerator loaded with 40humid plaster cylinders (50mm diameter). The weight variation of the cylinders was followed over 12days and the rate of water evaporation (or condensation for some cylinders) was calculated.

O. Laguerre; S. Benamara; D. Flick

2010-01-01

54

Exploring Evaporation  

NSDL National Science Digital Library

Students learn what evaporation is and how various factors--time, heat, surface area, and wind--affect it. They also discover that water does not always evaporate at the same rate and saltwater leaves something behind when it evaporates. Finally, students a

John Eichinger

2009-05-15

55

Long Duration Testing of a Spacesuit Water Membrane Evaporator Prototype  

NASA Technical Reports Server (NTRS)

The Spacesuit Water Membrane Evaporator (SWME) is a heat-rejection device that is being developed to perform thermal control for advanced spacesuits. Cooling is achieved by circulating water from the liquid cooling garment (LCG) through hollow fibers (HoFi s), which are small hydrophobic tubes. Liquid water remains within the hydrophobic tubes, but water vapor is exhausted to space, thereby removing heat. A SWME test article was tested over the course of a year, for a total of 600 cumulative hours. In order to evaluate SWME tolerance to contamination due to constituents caused by distillation processes, these constituents were allowed to accumulate in the water as evaporation occurred. A test article was tested over the course of a year for a total of 600 cumulative hours. The heat rejection performance of the SWME degraded significantly--below 700 W, attributable to the accumulation of rust in the circulating loop and biofilm growth. Bubble elimination capability, a feature that was previously proven with SWME, was compromised during the test, most likely due to loss of hydrophobic properties of the hollow fibers. The utilization of water for heat rejection was shown not to be dependent on test article, life cycle, heat rejection rate, or freezing of the membranes.

Bue, Grant C.; Makinen, Janice; Cox, Marlon; Watts, Carly; Campbell, Colin; Vogel, Matthew; Colunga, Aaron; Conger, Bruce

2012-01-01

56

Long Duration Testing of a Spacesuit Water Membrane Evaporator Prototype  

NASA Technical Reports Server (NTRS)

The Spacesuit Water Membrane Evaporator (SWME) is a heat-rejection device that is being developed to perform thermal control for advanced spacesuits. Cooling is achieved by circulating water from the liquid cooling garment (LCG) through hollow fibers (HoFi?s), which are small hydrophobic tubes. Liquid water remains within the hydrophobic tubes, but water vapor is exhausted to space, thereby removing heat. A SWME test article was tested over the course of a year, for a total of 1200 cumulative hours. In order to evaluate SWME tolerance to contamination due to constituents caused by distillation processes, these constituents were allowed to accumulate in the water as evaporation occurred. A test article was tested over the course of a year for a total of 1200 cumulative hours. The heat rejection performance of the SWME degraded significantly--below 700 W, attributable to the accumulation of rust in the circulating loop and biofilm growth. Bubble elimination capability, a feature that was previously proven with SWME, was compromised during the test, most likely due to loss of hydrophobic properties of the hollow fibers. The utilization of water for heat rejection was shown not to be dependent on test article, life cycle, heat rejection rate, or freezing of the membranes.

Bue, Grant C.; Makinen, Janice; Cox, Marlon; Watts, Carly; Campbell, Colin; Vogel, Matthew; Colunga, Aaron

2011-01-01

57

Evaporation from a shallow water table: Diurnal dynamics of water and heat at the surface of drying sand  

NASA Astrophysics Data System (ADS)

Accurate estimates of water losses by evaporation from shallow water tables are important for hydrological, agricultural, and climatic purposes. An experiment was conducted in a weighing lysimeter to characterize the diurnal dynamics of evaporation under natural conditions. Sampling revealed a completely dry surface sand layer after 5 days of evaporation. Its thickness was <1 cm early in the morning, increasing to reach 4-5 cm in the evening. This evidence points out fundamental limitations of the approaches that assume hydraulic connectivity from the water table up to the surface, as well as those that suppose monotonic drying when unsteady conditions prevail. The computed vapor phase diffusion rates from the apparent drying front based on Fick's law failed to reproduce the measured cumulative evaporation during the sampling day. We propose that two processes rule natural evaporation resulting from daily fluctuations of climatic variables: (i) evaporation of water, stored during nighttime due to redistribution and vapor condensation, directly into the atmosphere from the soil surface during the early morning hours, that could be simulated using a mass transfer approach and (ii) subsurface evaporation limited by Fickian diffusion, afterward. For the conditions prevailing during the sampling day, the amount of water stored at the vicinity of the soil surface was 0.3 mm and was depleted before 11:00. Combining evaporation from the surface before 11:00 and subsurface evaporation limited by Fickian diffusion after that time, the agreement between the estimated and measured cumulative evaporation was significantly improved.

Assouline, S.; Tyler, S. W.; Selker, J. S.; Lunati, I.; Higgins, C. W.; Parlange, M. B.

2013-07-01

58

Data Mining Approach for Estimation Evaporation from Free Water Surface  

NASA Astrophysics Data System (ADS)

Evaporation is a fundamental parameter in the cycle of hydrology. In the present study, data mining method is used to developed evaporation models. Before modeling, air temperature, water temperature, solar radiation and relative humidity parameters are selected as parameters affecting evaporation. Decision Table, KStar, M5P, Pace Regression, M5`Rules, Neural Network, Regression, Simple Linear Regression and SMO Regression algorithms are used for modeling. Finally, the developed models are compared with measured daily pan evaporation values and Penman method. The comparisons show that there is a good agreement between results of M5P model and measured daily pan evaporation values.

Terzi, Ozlem

59

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

PubMed

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. PMID:1897061

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

1991-01-01

60

Regional rates of sweat evaporation during leg and arm cycling.  

PubMed Central

The rate of sweat evaporation from the arm, chest, back and thigh, aural temperature, skin temperature (arm, chest, back and thigh), heat production (derived from measurements of respiratory gas exchange) and heart rate were measured in 7 men during 15 minutes of leg or arm cycling at 32% of predicted maximum oxygen uptake (VO2 max). The regional sweat evaporation rates and changes in body temperature were similar during both forms of exercise. The peak rates of sweat evaporation from the arm, chest, back and thigh were 15.7 +/- 19.8, 25.0 +/- 21.6, 28.7 +/- 22.7 and 21.0 +/- 18.2 mg.cm-2 hr-1 during leg cycling and 13.2 +/- 11.6, 22.2 +/- 14.4, 27.6 +/- 14.7 and 19.2 +/- 13.3 (SD) mg.cm-2 hr-1 respectively during arm cycling. The sweat evaporation rates from the different body regions were not significantly different from one another. PMID:3697601

Ayling, J H

1986-01-01

61

Quantification of soil water evaporation using TDR-microlysimetry  

Technology Transfer Automated Retrieval System (TEKTRAN)

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...

62

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

NASA Astrophysics Data System (ADS)

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.

Oroud, Ibrahim M.

2011-12-01

63

17Oexcess in evaporated desert waters and vapor from evaporation experiments  

NASA Astrophysics Data System (ADS)

Oxygen and hydrogen isotopes are classical proxies for the investigation of climatic effects in hydrological processes. The combination of the isotopic ratios 17O/16O and 18O/16O in water allowed the determination of mass dependent processes and enabled differentiation between equilibrium and kinetic fractionation (Barkan and Luz, 2007). In analogy to d-excess, deviation in ?17O from the global average trend of meteoric water is defined as: 17Oexcess = ?'17O - 0.528 × ?'18O 17Oexcess depends on the impact of diffusive evaporation into air and thus reflects relative humidity conditions. The isotope ratios of water ?17O and ?18O were determined by isotope ratio gas mass spectrometry in dual inlet mode on a ThermoFinnigan MAT 253. The oxygen was extracted by water fluorination with CoF3. Our average measurement precision for ?17O is ×0.03 ‰, for ?18O ×0.05 ‰ and for 17Oexcess approximately ×7 per meg (1?). We compared 17Oexcess in natural waters from the highly arid deserts of Sistan (East Iran) and Atacama (Chile) with data obtained from evaporation experiments. In these experiments, water was evaporated into a stream of dry nitrogen and vapor collected cryogenically. The data show a systematic depletion of 17Oexcess in water with increasing degree of evaporation in the residual water body. Most negative 17Oexcess were determined for samples from ponds (Sistan) and salars (Atacama). These strongly evaporated samples indicate an evaporation development, following a fractionation trend (?) of approximately 0.523. The evaporation experiment shows a ? of 0.525 and is in agreement with water data from an experiment by Barkan and Luz (2007). The difference between natural and experimental evaporation suggests either different evaporation kinetics in the natural environment, variable proportion of kinetic and equilibrium fractionation, or additional diffusive processes during ground water seepage. References: Barkan, E. and Luz, L. (2007). Diffusivity fractionations of H216O/H217O and H216O/H218O in air and their implications for isotope hydrology. Rapid Commun. Mass Spectrom., Vol. 21, pp. 2999-3005.

Surma, J.; Assonov, S.; Staubwasser, M.

2013-12-01

64

Analysis of evaporative water loss in the Skylab astronauts  

NASA Technical Reports Server (NTRS)

Daily evaporative water losses (EWL) during the three Skylab missions were measured using the indirect mass and water balance techniques. A mean inflight EWL of 860 ml/day-m 2 was obtained for nine men who averaged one hour of daily exercise. Although it was expected the EWL would increase in the hypobaric environment of Skylab (1/3 atmosphere), an average decrease from preflight sea level conditions of 11 percent was measured. The results suggest that weightlessness may have been a factor in modifying EWL primarily by decreasing sweat losses during exercise and possibly by reducing insensible skin losses as well. The weightless environment apparently promotes the formation of a sweat film on the skin surface both directly, by reducing heat and mass convective flow and sweat drippage, and perhaps indirectly by inducing measurable biochemical changes resulting in high initial sweating rates. It is proposed that these high levels of skin wettedness favor sweat suppression by a previously described mechanism.

Leonard, J. I.

1977-01-01

65

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

NASA Technical Reports Server (NTRS)

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.

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

2014-01-01

66

Temperature dependence of the vapor pressure and evaporation coefficient of supercooled water  

NASA Astrophysics Data System (ADS)

We report measurements of the vapor pressure of water over the supercooled temperature range 248 to 273 K derived from evaporation kinetics measurements of single water droplets. Accurate measurements of the relative humidity of the surrounding gas phase are derived from comparative and sequential measurements of the evaporation kinetics of droplets containing sodium chloride. The temperature dependence of the vapor pressure of supercooled water is shown to conform closely to the parameterization provided by Murphy and Koop (2005) once the uncertainties in experimental and thermophysical parameters are accounted for by ensuring an accurate representation of evaporation rates at temperatures above 273 K. Further, from a sensitivity analysis of all of the data over the full temperature range from 248 to 293 K, we can conclude that the evaporation coefficient of water, and thus the mass accommodation coefficient, is greater than, or equal to, 0.5.

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

2014-09-01

67

Influence of solvent evaporation rate and formulation factors on solid dispersion physical stability.  

PubMed

New chemical entities (NCEs) often show poor water solubility necessitating solid dispersion formulation. The aim of the current study is to employ design of experiments in investigating the influence of one critical process factor (solvent evaporation rate) and two formulation factors (PVP:piroxicam ratio (PVP:PRX) and PVP molecular weight (P(MW))) on the physical stability of PRX solid dispersion prepared by the solvent evaporation method. The results showed the rank order of an increase in factors contributing to a decrease in the extent of PRX nucleation being evaporation rate>PVP:PRX>P(MW). The same rank order was found for the decrease in the extent of PRX crystal growth in PVP matrices from day 0 up to day 12. However, after 12days the rank became PVP:PRX>evaporation rate>P(MW). The effects of an increase in evaporation rate and PVP:PRX ratio in stabilizing PRX were of the same order of magnitude, while the effect from P(MW) was much smaller. The findings were confirmed by XRPD. FT-IR showed that PRX recrystallization in the PVP matrix followed Ostwald's step rule, and an increase in the three factors all led to increased hydrogen bonding interaction between PRX and PVP. The present study showed the applicability of the Quality by Design approach in solid dispersion research, and highlights the need for multifactorial analysis. PMID:22024381

Wu, Jian X; Yang, Mingshi; Berg, Frans van den; Pajander, Jari; Rades, Thomas; Rantanen, Jukka

2011-12-18

68

Mechanisms of solvent evaporation encapsulation processes: prediction of solvent evaporation rate.  

PubMed

The mechanism of organic solvent evaporation during microencapsulation and its role during microsphere hardening has been investigated. Evaporation and encapsulation studies were carried out in a jacketed beaker, filled with aqueous hardening solution, which was maintained at constant temperature and constant stirring rate in the turbulent regime. Evaporation of dissolved methylene chloride (MC), ethyl acetate (EA), and acetonitrile (ACN) was examined by the decline in organic solvent concentration in the hardening bath, which was monitored by gas chromatography. The evaporation from the bath followed first-order kinetics under dilute conditions (e.g., MC < 3 mg/mL), yielding an overall permeability coefficient, P. The value of P was theoretically related to the Kolmogorov length-scale of turbulence under conditions that favor liquid-side transport control. According to theory, factors that favored liquid-phase control (as opposed to gas-phase control) were those that favored a high Henry's law constant [i.e., elevated temperature near the normal boiling point (bp) of the organic solvent] and properties of the dissolved organic solvent (i.e., low normal bp and low aqueous solubility). These theoretical hypotheses were confirmed by (1) correlating the experimentally determined P with process variables raised to the appropriate power according to theory, r(2) = 0.95 (i.e., P approximately rotational speed, omega(3/4), impeller diameter, d (5/4), volume of hardening bath, V(-1/4), and the product of kinematic viscosity and diffusion coefficient, nu(-5/12)D (2/3)), and (2) illustrating that at constant temperature, the tendency of the evaporation system to obey liquid-side transport control follows the same order of increasing Henry's law constant (i.e., MC > EA > ACN). To establish the relationship of evaporation with microsphere hardening, the decline in MC concentration was determined in both the continuous and dispersed polymer phases during microencapsulation. By applying a mass balance with respect to MC in the hardening bath, the cumulative hardening profile of the microspheres was accurately predicted from the interpolating functions of the kinetics of MC loss from the bath with and without polymer added. These results have potential use for microsphere formulation, design of encapsulation apparatus, and scale up of microsphere production. PMID:10514360

Wang, J; Schwendeman, S P

1999-10-01

69

Evaporation rate from square capillaries limited by corner flow viscous losses  

NASA Astrophysics Data System (ADS)

High evaporation rates from soil surfaces are sustained by capillary flows drawing water from the receding drying front along liquid pathways in crevices of the pore space. With increasing depth of the drying front viscous losses add to growing gravitational head and at a certain depth overcome capillary drive and disrupt liquid pathways. Viscous losses are significant in fine textured media resulting in earlier capillary failure than predicted by gravity-capillary force balance. To reproduce limitations of viscous corner flow on evaporation rates from angular pores (capillaries) we imaged drying dynamics from a square shaped glass capillary using a high speed camera, to provide for detailed record on receding menisci and thickness of liquid corner films including detachment dynamics at the top of the capillary. Additionally, deposition patterns of dye delineated regions of high rates of phase change (evaporation) showing a decrease in drying rate with recession of menisci and films into the capillary due to increasing diffusive path and reduced gradients. Effects of viscous losses on evaporation dynamics were systematically evaluated by varying ratio of viscous, gravity and capillary forces using different liquids (water, ethanol and octane), capillary geometry (0.5 and 1.0 mm width), and flow rate and direction with respect to gravity (horizontal and vertical arrangement). Experimental results were compared with analytical solutions for corner flow considering viscous losses. Preliminary results indicate that the maximum (main) meniscus depth supporting corner flow is not only dependent on the effective conductivity behind the interfaces, but also on interfacial processes taking place at the very top of the capillary. The pore scale findings will be incorporated into macroscopic models for determining viscous losses from soils and for estimating elapsed times for transition from high capillary-sustained evaporation rates to diffusion limited rates.

Hoogland, F.; Lehmann, P.; Yiotis, A.; Or, D.

2012-04-01

70

A simulation model for evaporation of defrosted water in household refrigerators  

Microsoft Academic Search

This paper presents a simple dynamic simulation model for predicting the evaporation rates of defrosted water from water trays in domestic refrigerators. The model was successfully tested for one domestic refrigerator. The model was used to investigate the effect of different variables (ambient temperature, relative humidity, air velocity, compressor heat, auxiliary condenser) by comparing eight different arrangements with each other

P. K. Bansal; G. Xie

1999-01-01

71

Tillage effects on soil water redistribution and bare soil evaporation throughout a season  

Technology Transfer Automated Retrieval System (TEKTRAN)

Tillage-induced changes in soil properties are difficult to predict, yet can influence how water is redistributed within the profile after precipitation and subsequent evaporation rates. We evaluated the effects of sweep tillage (ST) on near surface soil water dynamics as compared with an untilled (...

72

The desorptivity model of bulk soil-water evaporation  

NASA Technical Reports Server (NTRS)

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.

Clapp, R. B.

1983-01-01

73

Selective Adsorption of Ions to Aqueous Interfaces and its Effects on Evaporation Rates  

NASA Astrophysics Data System (ADS)

By exploiting the strong UV charge-transfer-to-solvent (CTTS) resonances of selected anions in aqueous electrolytes, their interfacial adsorption properties are measured by UV-SHG spectroscopy. Temperature and concentration dependences are determined, with the goal of establishing a molecular description of selective ion adsorption. A study of prototypical chaotrope thiocyanate reveals that its strong adsorption is driven by enthalpic forces and impeded by entropy. A study of nitrite indicates even stronger adsorption as an ion pair with sodium. Evaporation rates are measured by combining liquid microjet technology and Raman thermometry. The relationship between surface propensities of ions and evaporation rates is investigated. A detailed molecular mechanism for aqueous evaporation is sought. W. S. Drisdell, R. J. Saykally, R. C. Cohen Effect of Surface Active Ions on the Rate of Water Evaporation, J. Phys. Chem. C 114, 11880-11885 (2010). D.E. Otten, R. Onorato, R. Michaels, J. Goodknight, R. J. Saykally "Strong Surface Adsorption of Aqueous Sodium Nitrite as an Ion Pair," Chem. Phys. Lett. 519-520, 45-48 (2012). D.E. Otten, P. Shaffer, P. Geissler, R.J. Saykally "Elucidating the Mechanism of Selective Ion Adsorption to the Liguid Water Surface," PNAS 109 (3), 701-705 (2012).

Saykally, Richard J.

2012-06-01

74

Studying biofuel aerosol evaporation rates with single particle manipulation  

NASA Astrophysics Data System (ADS)

The significant increase in the air pollution, and the impact on climate change due to the burning of fossil fuel has led to the research of alternative energies. Bio-ethanol obtained from a variety of feedstocks can provide a feasible solution. Mixing bio-ethanol with gasoline leads to a reduction in CO emission and in NOx emissions compared with the use of gasoline alone. However, adding ethanol leads to a change in the fuel evaporation. Here we present a preliminary investigation of evaporation times of single ethanol-gasoline droplets. In particular, we investigated the different evaporation rate of the droplets depending on the variation in the percentage of ethanol inside them. Two different techniques have been used to trap the droplets. One makes use of a 532nm optical tweezers set up, the other of an electrodynamics balance (EDB). The droplets decreasing size was measured using video analysis and elastic light scattering respectively. In the first case measurements were conducted at 293.15 K and ambient humidity. In the second case at 280.5 K and a controlled environment has been preserved by flowing nitrogen into the chamber. Binary phase droplets with a higher percentage of ethanol resulted in longer droplet lifetimes. Our work also highlights the advantages and disadvantages of each technique for such studies. In particular it is challenging to trap droplets with low ethanol content (such as pure gasoline) by the use of EDB. Conversely such droplets are trivial to trap using optical tweezers.

Corsetti, S.; Miles, R. E. H.; Reid, J. P.; Kiefer, J.; McGloin, D.

2014-09-01

75

Soil, Water and Atmospheric Processes 2h Tutorial Evaporation Simulation of Evaporation.  

E-print Network

form to Ohm's Law ­ for a given potential difference (voltage), current will flow at a rate determined transfer processes. You will use a simulation model of the evaporation process (essentially the PenmanKeating. Activities Log on to the university network and use the FireFox browser to navigate to one of the pages

Moncrieff, John B.

76

Evaporative chemical evolution of natural waters at Yucca Mountain, Nevada  

Microsoft Academic Search

The authors report results from experiments on the evaporative chemical evolution of the two major types of natural waters present at Yucca Mountain, Nevada. The first is represented by J13 well water, a dilute Na–HCO3–CO3 water similar to saturated horizons in volcanic tuffs across the western United States. The second is represented by Ca–C1–SO4-rich pore water that has a higher

N. D Rosenberg; G. E Gdowski; K. G Knauss

2001-01-01

77

Water sources, mixing and evaporation in the Akyatan lagoon, Turkey  

NASA Astrophysics Data System (ADS)

Akyatan lagoon, located southeast of Turkey along the Mediterranean coast, is a choked and hypersaline lagoon, and hosts a large and specific biodiversity including endangered sea turtles and migrating birds. Physicochemical properties of this lagoon were investigated by measuring temperature, salinity, and hydrogen and oxygen isotope ratios of its waters at a seasonal scale during years 2006 and 2007. Winter and spring seasons were dominated by mixing processes between freshwaters and Mediterranean seawater. The majority of spring season waters are formed by evapoconcentration of brackish water at moderate temperatures of 22 ± 2 °C. During summer, hypersaline waters result from evaporation of seawater and brackish waters formed during spring. Evaporation over the Akyatan lagoon reaches up to 76 wt% based on salinity measurements and operated with a dry (relative humidity of 0.15-0.20) and hot (44 ± 6 °C) air. These residual waters were characterized by the maximal seasonal isotopic enrichment in both deuterium and 18O relative to VSMOW. During autumn, most lagoonal waters became hypersaline and were formed by evaporation of waters that had isotopic compositions and salinities close to that of seawater. These autumnal hypersaline waters result from an air humidity close to 0.45 and an atmospheric temperature of evaporation of 35 ± 5 °C, which are responsible for up to 71 wt% of evaporation, with restricted isotopic enrichments relative to VSMOW. During the warm seasons, the combination of air humidity, wind velocity and temperature were responsible for a large kinetic component in the total isotopic fractionation between water liquid and water vapour.

Lécuyer, C.; Bodergat, A.-M.; Martineau, F.; Fourel, F.; Gürbüz, K.; Nazik, A.

2012-12-01

78

Numerical simulation of water evaporation inside vertical circular tubes  

NASA Astrophysics Data System (ADS)

In this paper the results of simplified numerical analysis of water evaporation in vertical circular tubes are presented. The heat transfer in fluid domain (water or wet steam) and solid domain (tube wall) is analyzed. For the fluid domain the temperature field is calculated solving energy equation using the Control Volume Method and for the solid domain using the Finite Element Method. The heat transfer between fluid and solid domains is conjugated using the value of heat transfer coefficient from evaporating liquid to the tube wall. It is determined using the analytical Steiner-Taborek correlation. The pressure changes in fluid are computed using Friedel model.

Oc?o?, Pawe?; Nowak, Marzena; Majewski, Karol

2013-10-01

79

Black Hole Evaporation Rates without Spacetime Samuel L. Braunstein and Manas K. Patra  

E-print Network

Black Hole Evaporation Rates without Spacetime Samuel L. Braunstein and Manas K. Patra Computer tentative step in such a program, we derive the evaporation rate (or radiation spectrum) from black hole hole evaporation, symmetries therein which follow from the inherent high dimensionality of black holes

Braunstein, Samuel L.

80

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

NASA Technical Reports Server (NTRS)

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.

Auer, S.

1976-01-01

81

Evaporator analysis for application to water-source and ice-maker heat pumps  

SciTech Connect

Water-source and ice-maker heat pumps share many characteristics. However, each presents different technical difficulties that have prevented them from being used more widely. In a water-source heat pump a very important consideration is to reduce water consumption, while in an ice-maker heat pump a major concern is to reduce the number of deicing cycles while keeping a high performance. Previous research by this author has indicated that the use of the flow reversal method (reversing periodically the water flow direction in the evaporator) has the effect of partly deicing the evaporator, reducing pressure drop and enhancing heat transfer. This thesis shows the development and application of analytical and numerical models to study the effect of different evaporator parameters on heat pump efficiency, as well as the possible advantages of using the flow reversal method in a water-source or ice-maker heat pump. The conclusion reached from these studies is that periodic water flow reversals inside an evaporator with freezing help improve the performance of a heat pump system in two different ways. First, periodic water flow direction reversals serve to enhance heat transfer in the evaporator. Second, reversing the water flow direction also delays ice blockage in the evaporator, or totally prevents blockage from happening. Delaying ice blockage represents a substantial improvement for ice-maker heat pumps, since these may then operate for a longer time without deicing. Preventing ice blockage represents a substantial improvement for water-source heat pumps, since these may then operate at lower water flow rates.

Aceves-Saborio, S.M.

1989-01-01

82

Physiological responses of a rodent to heliox reveal constancy of evaporative water loss under perturbing environmental conditions.  

PubMed

Total evaporative water loss of endotherms is assumed to be determined essentially by biophysics, at least at temperatures below thermoneutrality, with evaporative water loss determined by the water vapor deficit between the animal and the ambient air. We present here evidence, based on the first measurements of evaporative water loss for a small mammal in heliox, that mammals may have a previously unappreciated ability to maintain acute constancy of total evaporative water loss under perturbing environmental conditions. Thermoregulatory responses of ash-grey mice (Pseudomys albocinereus) to heliox were as expected, with changes in metabolic rate, conductance, and respiratory ventilation consistent with maintaining constancy of body temperature under conditions of enhanced heat loss. However, evaporative water loss did not increase in heliox. This is despite our confirmation of the physical effect that heliox augments evaporation from nonliving surfaces, which should increase cutaneous water loss, and increases minute volume of live ash-grey mice in heliox to accommodate their elevated metabolic rate, which should increase respiratory water loss. Therefore, mice had not only a thermoregulatory but also a hygroregulatory response to heliox. We interpret these results as evidence that ash-grey mice can acutely control their evaporative water loss under perturbing environmental conditions and suggest that hygroregulation at and below thermoneutrality is an important aspect of the physiology of at least some small mammals. PMID:25163919

Cooper, Christine Elizabeth; Withers, Philip Carew

2014-10-15

83

bbThermodynamic quantities and Urmia Sea water evaporation.  

PubMed

The relation between climatic parameters (relative air humidity) and the water activity of the Urmia Sea water determines the possible maximum evaporation of the lake. Using the Pitzer thermodynamic approach, the activity of the Urmia Lake water during evaporation was calculated and compared to the present relative air humidity above the water. Present climatic conditions allow the Urmia Sea water to evaporate down to water with activity of 0.55, corresponding to the lowest air humidity measured over the lake. This water activity falls in the range of halite precipitation, while carnalite precipitation starts at somewhat lower (a H2O = 0.499) point. Our dynamic model predicts that for air humidity as low as 55% (reflecting present climate conditions), the Urmia Sea level may drop to as low as 1270 m (i. e., 1270 m above mean sea level). At that point, the lake water volume will have a volume of 11 km3. For the sake of comparison, at the beginning of 1990, the level of the lake was 1275 m, its volume was 25 km3, and its surface area was 5145 km2. PMID:20356384

Heidari, Nosrat; Roudgar, Mina; Ebrahimpour, Neda

2010-01-01

84

49. LOOKING NORTH AT EVAPORATIVE WASTE WATER TREATMENT COOLING TOWERS, ...  

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

49. LOOKING NORTH AT EVAPORATIVE WASTE WATER TREATMENT COOLING TOWERS, WITH BLOW ENGINE HOUSE No. 3 ON RIGHT, AND FILTER CAKE HOUSE IN FOREGROUND. (Jet Lowe) - U.S. Steel Duquesne Works, Blast Furnace Plant, Along Monongahela River, Duquesne, Allegheny County, PA

85

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

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

86

Cold-hardiness and evaporative water loss in hatchling turtles.  

PubMed

North American turtles hatch in late summer and spend their first winter either on land or underwater. Adaptations for terrestrial overwintering of hatchlings in northern regions, where winter thermal and hydric regimes are harsh, have not been systematically investigated in many species. We measured intrinsic supercooling capacity, resistance to inoculative freezing, and desiccation resistance in hatchlings of terrestrial and aquatic turtles collected from northern (Terrapene ornata, Chrysemys picta bellii, Kinosternon flavescens, Chelydra serpentina) and southern (Chrysemys picta dorsalis, Trachemys scripta, Sternotherus odoratus, Sternotherus carinatus) locales. Supercooling capacity was estimated from the crystallization temperature of turtles cooled in the absence of external ice nuclei. Mean values ranged from -8.1 degrees to -15.5 degrees C and tended to be lower in terrestrial hibernators. Inoculation resistance was estimated from the crystallization temperature of turtles cooled in a matrix of frozen soil. These values (range of means: -0.8 degrees to -13.6 degrees C) also tended to be lower in the terrestrial hibernators, especially C. picta bellii. Mean rates of evaporative water loss varied markedly among the species (0.9-11.4 mg g(-1) d(-1)) and were lowest in the terrestrial hibernators. Most species tolerated the loss of a modest amount of body water, although half of the sample of S. carinatus died from desiccation. In general, turtles did not regain lost body water from wet soil, and immersion in free water was required for rehydration. Therefore, desiccation resistance may be an important adaptation to terrestrial hibernation. Resistances to inoculative freezing and desiccation were directly correlated, perhaps because they are governed by the same morphological characteristics. PMID:11436135

Costanzo, J P; Litzgus, J D; Iverson, J B; Lee, R E

2001-01-01

87

Soil Water Retention Curves and Their Impact on Evaporation  

NASA Astrophysics Data System (ADS)

An accurate description of soil moisture dynamics in both the liquid and vapor phases is crucial to properly estimate soil evaporation. Soil moisture dynamics are largely dependent on the soil water retention. In the most commonly used models the water retention curve diverges at residual water content, the value below which liquid connectivity is lost and liquid flow stops. Not only this is physically unrealistic but results in incorrect evaporation modeling near dry conditions since the water vapor role is limited. We consider two of the main parametrizations that allow vapor flux below residual water content (modified models): one consists in a re-fit of the standard retention curve with zero residual water content, the other, supported by some laboratory measurements, considers a linear extension (on a semi-log plot) of the standard retention curve in the dry region. For a medium-textured sand and a loam we numerically investigate the effects of both the modified and the standard Van Genuchten models on the liquid and vapor transport during the simulated drying process, with and without surface radiative forcing. In the isothermal case, we show how all the models almost identically describe the capillary-dominated evaporative regime whereas when vapor diffusion is the dominant evaporative mechanism the modified models yield larger and longer sustained vapor fluxes, significantly increasing soil water removal. In the presence of diurnal radiative forcing at the soil surface, we focus on the effects of temperature fluctuations on soil water retention. The impact on liquid and vapor fluxes is analyzed in order to assess whether temperature-dependent and dry-extended retention curves may 'fill the gap' or not between theory and some still debated field experimental evidences (e.g. the midday moisture content rise) without the need of introducing any questionable and ad-hoc empirical terms such as vapor enhancement and/or liquid gain factors.

Ciocca, F.; Lunati, I.; Parlange, M. B.

2013-12-01

88

Water table draw down during drainage with evaporation\\/evapotranspiration  

Microsoft Academic Search

Groundwater table behavior in drained lands in addition to tile flow depends upon several other factors. Evaporation\\/evapotranspiration (E\\/ET) from the shallow water table is one of them. The Boussinesq equation for non-steady state groundwater flow with variable drainable porosity was suitably modified by incorporating a non-linear function simulating E\\/ET from the shallow water table. The modified equation was solved numerically

R. S. Pandey; A. K. Bhattacharya; O. P. Singh; S. K. Gupta

1997-01-01

89

Water evaporation particularities in the process of forest fire extinguishing  

NASA Astrophysics Data System (ADS)

Numerical simulation of water massif motion through the high temperature gases corresponding to the typical conditions of forest fires was carried out. Maximal values of part by volume of liquid evaporating from water massif under its motion through the flaming burning area were determined when solving the heat and mass transfer problem under the conditions of endothermic phase transformations. Influence of liquid phase transition heat on the heat and mass transfer conditions on the track of water massif was determined. The expediency of polydisperse interspaced in time and space atomization of water massifs under the large-scale (especially, forest fires) fire extinguishing was proved.

Strizhak, Pavel A.; Volkov, Roman S.; Vysokomornaya, Olga V.; Voytkov, Ivan S.

2015-01-01

90

Evaporating behaviors of water droplet on superhydrophobic surface  

NASA Astrophysics Data System (ADS)

We investigated the dynamic evaporating behaviors of water droplet on superhydrophobic surfaces with micropillars. Our experimental data showed that receding contact angles of the water droplet increased with the decreasing of the scale of the micropillars during evaporation, even though the solid area fractions of the microstructured substrates remained constant. We also experimentally found that the critical contact diameters of the transition between the Cassie-Baxter and Wenzel states are affected not only by the geometrical parameters of the microstructures, but also by the initial volume of the water droplet. The measured critical pressure is consistent with the theoretical model, which validated the pressure-induced impalement mechanism for the wetting state transition.

Hao, PengFei; Lv, CunJing; He, Feng

2012-12-01

91

Temperature measurement of single evaporating water droplets in a nitrogen flow using spontaneous Raman scattering.  

PubMed

The evaporation dynamics of stationary water droplets held within an electrodynamic trap are investigated in a nitrogen flow of variable velocity. In particular, the influence of the nitrogen gas flow on the temperature of the evaporating water droplets is studied. By applying a contact free measurement technique, based on spontaneous Raman scattering, time averaged and time resolved measurements of temperature in the droplet volume are compared. This technique determines the temperature from an intensity ratio in the OH stretching band of the Stokes-Raman scattering after calibration. The measured trends in temperature over the first 5 s of evaporation are found to be in agreement with theoretical calculations of the heat and mass transfer rates. PMID:19851549

Heinisch, Christian; Wills, Jon B; Reid, Jonathan P; Tschudi, Theo; Tropea, Cameron

2009-11-14

92

Evaporation Correction Methods for Microwave Retrievals of Surface Precipitation Rate  

Microsoft Academic Search

Active and passive microwave remote sensing esti- mates of surface precipitation based on signals from hydrometeors aloft require correction for evaporated precipitation that would otherwise reach the ground. This paper develops and compares two near-surface evaporation correction methods using two years of data from 509 globally distributed rain gauges and three passive millimeter-wave Advanced Microwave Sounding Units (AMSUs) aboard National

Chinnawat Surussavadee; David H. Staelin

2011-01-01

93

Evaporation Rates of Oxides from Undoped and Sb-Doped Si Melts under Atmospheres of Pure Ne, Ar, and Kr  

NASA Astrophysics Data System (ADS)

The effect of gaseous Ne, Ar, and Kr on the evaporation rates of oxides from undoped and Sb-doped Si melts was investigated. By measuring the weight loss of a melt using a thermogravimetric method, we determined the evaporation rate of different species from the melts. The measurements were done at a melt temperature of 1442° C and a background gas pressure of 1.02 atm. Because Ar is predominantly used as the background gas in the semiconductor industry, we report evaporation rates relative to the rates under an atmosphere of pure Ar. For the evaporation of SiO from an undoped Si melt, Ne enhanced the evaporation rate by 37% and Kr suppressed the evaporation rate by 13%. For the evaporation of antimony from an Sb-doped Si melt, Ne enhanced the evaporation rate by 18% and Kr suppressed the evaporation rate by 24%. For the evaporation of antimony oxide from an Sb-doped melt, Ne enhanced the evaporation rate by 4% and Kr suppressed the evaporation rate by 63%. We therefore conclude that, compared with Ar, Ne enhances and Kr suppresses the evaporation of oxides from undoped and Sb-doped Si melts. We show that the background gas affects evaporation through gas-phase diffusion; the diffusion coefficient of the evaporating species is the highest in Ne and the lowest in Kr. In addition, we show that the transport of the evaporating species in the melt to the surface also influences the overall evaporation rates.

Huang, Xinming; Terashima, Kazutaka; Tokizaki, Eiji; Kimura, Shigeyuki; Whitby, Evan

1994-07-01

94

Impact of groundwater levels on evaporation and water-vapor fluxes in highly saline soils  

NASA Astrophysics Data System (ADS)

In aquifers of arid and hyper-arid zones, such as those occurring in the Chilean Andes high plateau, it is important to determine both the quantity and location of water discharges at the temporal scales of interest to close the basin's water budget and thus, to manage the water resource properly. In zones where shallow aquifers are the main source of water, overexploitation of the water resource changes the dynamics of water, heat and solute transport in the vadose zone. As aquifers are exploited, fluctuations in depth to groundwater are exacerbated. These fluctuations modify both soil structure and evaporation from the ground, which is typically the most important discharge from the water budget and is very difficult to estimate. Therefore, a correct quantification of evaporation from these soils is essential to improve the accuracy of the water balance estimation. The objective of this study was to investigate the evaporation processes and water-vapor fluxes in a soil column filled with a saline soil from the Salar del Huasco basin, Chile. Water content, electrical conductivity and temperature at different depths in the soil profile were monitored to determine the liquid and vapor fluxes within the soil column. The results showed that evaporation is negligible when the groundwater table is deeper than 1 m. For shallower groundwater levels, evaporation increases in an exponential fashion reaching a value of 3 mm/day when the groundwater table is near the surface of the ground. These evaporation rates are on the same order of magnitude than the field measurements, but slightly lower due to the controlled conditions maintained in the laboratory. Isothermal fluid fluxes were predominant over the non-isothermal fluid and water vapor fluxes. The net flux for all the phreatic levels tested in the laboratory showed different behaviors, with ascending or descending flows as a consequence of changes in water content and temperature distribution within the soil. It was found that evaporation from bare soils occurs as a consequence of vapor transport due to the thermal gradients. This vapor transport was also influences by the salinity of the soil.

Munoz, J. F.; Hernández, M. F.; Braud, I.; Gironas, J. A.; Suarez, F. I.

2012-12-01

95

Spacesuit Water Membrane Evaporator Development for Lunar Missions  

NASA Technical Reports Server (NTRS)

For future lunar extra-vehicular activities (EVA), one method under consideration for rejecting crew and electronics heat involves evaporating water through a hydrophobic, porous Teflon membrane. A Spacesuit Water Membrane Evaporator (SWME) prototype using the Teflon membrane was tested successfully by Ungar and Thomas (2001) with predicted performance matching test data well. The above referenced work laid the foundation for the design of the SWME development unit, which is being considered for service in the Constellation System Spacesuit Element (CSSE) Portable Life Support System (PLSS). Multiple PLSS SWME configurations were considered on the basis of thermal performance, mass, volume, and performance and manufacturing risk. All configurations were a variation of an alternating concentric water and vapor channel configuration or a stack of alternating rectangular water and vapor channels. Supporting thermal performance trades mapped maximum SWME heat rejection as a function of water channel thickness, vapor channel thickness, channel length, number of water channels, porosity of the membrane structural support, and backpressure valve throat area. Preliminary designs of each configuration were developed to determine total mass and volume as well as to understand manufacturing issues. Review of configurations led to the selection of a concentric annulus configuration that meets the requirements of 800 watts (W) of heat rejection. Detailed design of the SWME development unit will be followed by fabrication of a prototype test unit, with thermal testing expected to start in 2008.

Vogel, Matt R.; Peterson, Keith; Zapata, Felipe, III; Dillon, Paul; Trevino, Luis A.

2008-01-01

96

Physiological state influences evaporative water loss and microclimate preference in the snake Vipera aspis.  

PubMed

Animals typically respond to environmental variation by adjusting their physiology, behavior, or both. Ectothermic animals are particularly sensitive to microclimatic conditions and behaviorally thermoregulate to optimize physiological performance. Yet, thermoregulation can be costly and may obligate a physiological tradeoff with water loss. Presumably, this tradeoff intensifies when animals undergo necessary life-history events (e.g., pregnancy or digestion) that impose significant behavioral and physiological changes, including shifts in behavioral thermoregulation and increased metabolic rate. Thus, behavioral responses, such as modified microclimatic preferences, may help mitigate the physiological tradeoff between thermoregulation and water loss. Herein, we examined the influence of major physiological states (specifically, pregnancy, ecdysis, and digestion) on evaporative water loss and on behavioral adjustments in a viviparous snake, Vipera aspis. First, we used open-flow respirometry to measure the effects of physiological states and microclimatic conditions (temperature and humidity) on the rate of total evaporative water loss (TEWL) and metabolic rate (rate of O2 consumption, V?O2). Then, we experimentally tested the influence of physiological state on microclimate selection. We found that energy-demanding physiological states were associated with i) an increased rate of TEWL and V?O2 compared to control states and ii) a slight preference (statistically marginal) for both warm and humid conditions compared to controls, suggesting a state-specificity in behavioral response. Overall our results underline the impact of physiological state on water loss and demonstrate the potential for behavior to mitigate the physiological tradeoff between thermoregulation and water balance. PMID:25725119

Dupoué, Andréaz; Stahlschmidt, Zachary R; Michaud, Bruno; Lourdais, Olivier

2015-05-15

97

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

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

98

A comparison of methods for estimating open-water evaporation in small wetlands  

USGS Publications Warehouse

We compared evaporation measurements from a floating pan, land pan, chamber, and the Priestley-Taylor (PT) equation. Floating pan, land pan, and meteorological data were collected from June 6 to July 21, 2005, at a small wetland in the Canadian River alluvium in central Oklahoma, USA. Evaporation measured with the floating pan compared favorably to 12 h chamber measurements. Differences between chamber and floating pan rates ranged from ?0.2 to 0.3 mm, mean of 0.1 mm. The difference between chamber and land pan rates ranged from 0.8 to 2.0 mm, mean of 1.5 mm. The mean chamber-to-floating pan ratio was 0.97 and the mean chamber-to-land pan ratio was 0.73. The chamber-to-floating pan ratio of 0.97 indicates the use of a floating pan to measure evaporation in small limited-fetch water bodies is an appropriate and accurate method for the site investigated. One-sided Paired t-Tests indicate daily floating pan rates were significantly less than land pan and PT rates. A two-sided Paired t-Test indicated there was no significant difference between land pan and PT values. The PT equation tends to overestimate evaporation during times when the air is of low drying power and tends to underestimate as drying power increases.

Masoner, Jason R.; Stannard, David I.

2010-01-01

99

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

E-print Network

The evaporation of a tiny amount of water on the solid surface with different wettability has been studied by molecular dynamics simulations. We found that, as the surface changed from hydrophobicity to hydrophility, the evaporation speed did not show a monotonically decrease from intuition, but increased first, and then decreased after reached a maximum value. The competition between the number of the 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. A theoretical model based on those two factors can fit the simulation data very well. This finding is helpful in understanding the evaporation on the biological surfaces, designing artificial surface of ultra fast water evaporating or preserving water in soil.

Shen Wang; Yusong Tu; Rongzheng Wan; Haiping Fang

2012-03-08

100

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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...

101

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

USGS Publications Warehouse

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.

Hostetler, S.W.

1991-01-01

102

Respiratory evaporative water loss during hovering and forward flight in hummingbirds.  

PubMed

Hummingbirds represent an end point for small body size and water flux in vertebrates. We explored the role evaporative water loss (EWL) plays in management of their large water pool and its use in dissipating metabolic heat. We measured respiratory evaporative water loss (REWL) in hovering hummingbirds in the field (6 species) and over a range of speeds in a wind tunnel (1 species) using an open-circuit mask respirometry system. Hovering REWL during the active period was positively correlated with operative temperature (T(e)) likely due to some combination of an increase in the vapor-pressure deficit, increase in lung ventilation rate, and reduced importance of dry heat transfer at higher T(e). In rufous hummingbirds (Selasphorus rufus; 3.3g) REWL during forward flight at 6 and 10 m/s was less than half the value for hovering. The proportion of total dissipated heat (TDH) accounted for by REWL during hovering at T(e)> 40°C was <40% in most species. During forward flight in S. rufus the proportion of TDH accounted for by REWL was ~35% less than for hovering. REWL in hummingbirds is a relatively small component of the water budget compared with other bird species (<20%) so cutaneous evaporative water loss and dry heat transfer must contribute significantly to thermal balance in hummingbirds. PMID:22123217

Powers, Donald R; Getsinger, Philip W; Tobalske, Bret W; Wethington, Susan M; Powers, Sean D; Warrick, Douglas R

2012-02-01

103

Cumulative soil water evaporation as a function of depth and time  

Technology Transfer Automated Retrieval System (TEKTRAN)

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...

104

Measured and simulated soil water evaporation from four Great Plains soils  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

105

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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...

106

Trade Study for 9 kW Water Membrane Evaporator  

NASA Technical Reports Server (NTRS)

Sublimators have been proposed and used in spacecraft for heat rejection. Sublimators are desirable heat rejection devices for short duration use because they can transfer large amounts of heat using little mass and are self-regulating devices. Sublimators reject heat into space by freezing water inside a porous substrate, allowing it to sublimate into vapor, and finally venting it into space. The state of the art thermal control system in orbiting spacecraft is a two loop, two fluid system. The external coolant loop typically uses a toxic single phase fluid that acquires heat from the spacecraft and rejects most of it via a radiator. The sublimator functions as a transient topper for orbiting spacecraft during day pass periods when radiator efficiency decreases. The sublimator interfaces with the internal loop through a built in heat exchanger. The internal loop fluid is non-toxic and is typically a propylene glycol and water solution with inhibitors to prevent corrosion with aluminum fins of the heat exchangers. Feedwater is supplied from a separate line to the sublimator to maintain temperature control of the cabin and vehicle hardware. Water membrane evaporators have been developed for spacecraft and spacesuits. They function similar to a sublimator but require a backpressure valve which could be actuated for this application with a simple fully open or fully closed modes. This technology would be applied to orbital thermal control (lunar or planetary). This paper details a trade study showing that evaporators would greatly reduce the consumable that is used, effectively wasted, by sublimators during start up and shut down during the topping phases of each orbit. State of the art for 9 kW sublimators reject about 870 W per kilogram of mass and 1150 W per liter of volume. If water with corrosion inhibitors is used the evaporators would be about 80% of the mass and volume of the equivalent system. The size and mass increases to about 110% if the internal fluid is 50% propylene glycol/50% water. The true benefit comes from the backpressure valve, that prevents the cyclical shutdown/startup loss of the sublimator and amounts to as much as 0.85 kg per orbit.

Bue, Grant C.; Ungar, Gene; Stephan, Ryan

2010-01-01

107

Effect of top soil wettability on water evaporation and plant growth.  

PubMed

In general, agricultural soil surfaces being hydrophilic in nature get easily wetted by water. The water beneath the soil moves through capillary effect and comes to the surface of the soil and thereafter evaporates into the surrounding air due to atmospheric conditions such as sunlight, wind current, temperature and relative humidity. To lower the water loss from soil, an experiment was designed in which a layer of hydrophobic soil was laid on the surface of ordinary hydrophilic soil. This technique strikingly decreased loss of water from the soil. The results indicated that the evaporation rate significantly decreased and 90% of water was retained in the soil in 83h by the hydrophobic layer of 2cm thickness. A theoretical calculation based on diffusion of water vapour (gas phase) through hydrophobic capillaries provide a meaningful explanation of experimental results. A greater retention of water in the soil by this approach can promote the growth of plants, which was confirmed by growing chick pea (Cicer arietinum) plants and it was found that the length of roots, height of shoot, number of branches, number of leaves, number of secondary roots, biomass etc. were significantly increased upon covering the surface with hydrophobic soil in comparison to uncovered ordinary hydrophilic soil of identical depth. Such approach can also decrease the water consumption by the plants particularly grown indoors in residential premises, green houses and poly-houses etc. and also can be very useful to prevent water loss and enhance growth of vegetation in semi-arid regions. PMID:25801650

Gupta, Bharat; Shah, D O; Mishra, Brijesh; Joshi, P A; Gandhi, Vimal G; Fougat, R S

2015-07-01

108

Evaporation Rate Study and NDMA Formation from UDMH/NO2 Reaction Products  

NASA Technical Reports Server (NTRS)

Laboratory samples of uns-dimethylhydrazine (UDMH) fuel/oxidizer (nitrogen dioxide) non-combustion reaction products (UFORP) were prepared using a unique permeation tube technology. Also, a synthetic UFORP was prepared from UDMH, N-nitrosodimethylamine (NDMA), dimethylammonium nitrate, sodium nitrite and purified water. The evaporation rate of UFORP and synthetic UFORP was determined under space vacuum (approx 10(exp -3) Torr) at -40 ?C and 0 ?C. The material remaining was analyzed and showed that the UFORP weight and NDMA concentration decreased over time; however, NDMA had not completely evaporated. Over 85% of the weight was removed by subjecting the UFORP to 10(-3) Torr for 7 hours at -40 ?C and 4 hours at 0 ?C. A mixture of dimethylammonium nitrate and sodium nitrite formed NDMA at a rapid rate in a moist air environment. A sample of UFORP residue was analyzed for formation of NDMA under various conditions. It was found that NDMA was not formed unless nitrite was added.

Buchanan, Vanessa D.; Dee, Louis A.; Baker, David L.

2003-01-01

109

Comparing the mechanism of water condensation and evaporation in glassy aerosol  

PubMed Central

Atmospheric models generally assume that aerosol particles are in equilibrium with the surrounding gas phase. However, recent observations that secondary organic aerosols can exist in a glassy state have highlighted the need to more fully understand the kinetic limitations that may control water partitioning in ambient particles. Here, we explore the influence of slow water diffusion in the condensed aerosol phase on the rates of both condensation and evaporation, demonstrating that significant inhibition in mass transfer occurs for ultraviscous aerosol, not just for glassy aerosol. Using coarse mode (3–4 um radius) ternary sucrose/sodium chloride/aqueous droplets as a proxy for multicomponent ambient aerosol, we demonstrate that the timescale for particle equilibration correlates with bulk viscosity and can be ?103 s. Extrapolation of these timescales to particle sizes in the accumulation mode (e.g., approximately 100 nm) by applying the Stokes-Einstein equation suggests that the kinetic limitations imposed on mass transfer of water by slow bulk phase diffusion must be more fully investigated for atmospheric aerosol. Measurements have been made on particles covering a range in dynamic viscosity from < 0.1 to > 1013 Pa s. We also retrieve the radial inhomogeneities apparent in particle composition during condensation and evaporation and contrast the dynamics of slow dissolution of a viscous core into a labile shell during condensation with the slow percolation of water during evaporation through a more homogeneous viscous particle bulk. PMID:22753520

Bones, David L.; Reid, Jonathan P.; Lienhard, Daniel M.; Krieger, Ulrich K.

2012-01-01

110

Role of transpiration suppression by evaporation of intercepted water in improving irrigation efficiency  

Microsoft Academic Search

Sprinkler irrigation efficiency declines when applied water intercepted by the crop foliage, or gross interception (Igross), as well as airborne droplets and ponded water at the soil surface evaporate before use by the crop. However, evaporation of applied water can also supply some of the atmospheric demands usually met by plant transpiration. Any suppression of crop transpiration from the irrigated

J. A. Tolk; T. A. Howell; J. L. Steiner; D. R. Krieg; A. D. Schneider

1995-01-01

111

Inundation and groundwater dynamics for quantification of evaporative water loss in tropical wetlands  

NASA Astrophysics Data System (ADS)

Characterizing hydrological processes within tropical wetlands is challenging due to their remoteness, complexity and heterogeneity. In particular, estimates of evaporative water loss are inherently uncertain. In view of the large influence on the local and regional climate, the quantification of evaporation is essential for the determination of the water balance of permanent and intermittent water bodies. Data for tropical wetlands are scarce where their remoteness impedes direct evaporation measurements. Seasonal inundation dynamics affect evaporation processes in tropical wetlands, which can be analysed in two stages: the first stage during the wet season and the second stage during the dry season. As yet no adequate method exists for determining second-stage evaporation in a data-scarce environment that additionally allows for a transfer of simulated actual evaporation (AET) to other locations. Our study aimed at developing a process-based model to simulate first- and second-stage evaporation in tropical wetlands. We selected a set of empirical potential evaporation (PET) models of varying complexity, each based on different assumptions and available data sets, and evaluated the models with pan evaporation observations in the Pantanal of South America, one of the largest tropical wetlands in the world. We used high-resolution measurements of surface and groundwater levels at different locations to determine the water available for evaporation. AET was derived by constraining simulated PET based on available water. The model of best fit was applied to different types of water bodies with varying hydroperiods to capture first- and second-stage evaporation across a range of wetland types. With our new model we could quantify evaporative water loss in the dry and the wet season for different locations in the Pantanal. This new spatially explicit approach represents an improvement in our understanding of the role of evaporation in the water balance of the Pantanal. We recommend the application of this model in other remote tropical wetlands, since only a minimum of input data is necessary.

Schwerdtfeger, J.; Johnson, M. S.; Couto, E. G.; Amorim, R. S. S.; Sanches, L.; Campelo, J. H., Jr.; Weiler, M.

2014-11-01

112

Inundation and groundwater dynamics for quantification of evaporative water loss in tropical wetlands  

NASA Astrophysics Data System (ADS)

The remoteness, complexity and heterogeneity of tropical wetlands make the characterisation of their hydrological processes challenging. In particular estimates of evaporative water loss are inherently uncertain. In view of the large influence on the local and regional climate, the quantification of evaporation is essential for the determination of the water balance of permanent and intermittent water bodies. Data for tropical wetlands are scarce where their remoteness impedes direct evaporation measurements. Seasonal inundation dynamics affect evaporation processes in tropical wetlands, which can be analysed in two stages: the first stage during the wet season and the second stage during the dry season. As yet no adequate method exists for determining second stage evaporation without soil moisture data, which are usually unavailable for the remote tropical wetlands. Our study aimed at developing a process-based model to simulate first and second stage evaporation in tropical wetlands. We selected a set of empirical potential evaporation (PET) models of varying complexity, each based on different assumptions and available datasets, and evaluated the models with pan evaporation observations in the Pantanal of South America, one of the largest tropical wetlands in the world. We used high-resolution measurements of surface and groundwater levels at different locations to determine the water available for evaporation. Actual evaporation (AET) was derived by constraining simulated PET based on available water. The model of best fit was applied to different types of water bodies with varying inundation durations and captured first and second stage evaporation. With our new model we could quantify evaporative water loss in the dry and the wet season for different locations in the Pantanal. This new spatially-explicit approach represents an improvement in our understanding of the role of evaporation in the water balance of the Pantanal. We recommend the application of this model in other remote tropical wetlands, since only a minimum of input data is necessary.

Schwerdtfeger, J.; Johnson, M. S.; Couto, E. G.; Amorim, R. S. S.; Sanches, L.; Campelo Júnior, J. H.; Weiler, M.

2014-04-01

113

Evaporation Loss of Light Elements as a Function of Cooling Rate: Logarithmic Law  

NASA Technical Reports Server (NTRS)

Knowledge about the evaporation loss of light elements is important to our understanding of chondrule formation processes. The evaporative loss of light elements (such as B and Li) as a function of cooling rate is of special interest because recent investigations of the distribution of Li, Be and B in meteoritic chondrules have revealed that Li varies by 25 times, and B and Be varies by about 10 times. Therefore, if we can extrapolate and interpolate with confidence the evaporation loss of B and Li (and other light elements such as K, Na) at a wide range of cooling rates of interest based upon limited experimental data, we would be able to assess the full range of scenarios relating to chondrule formation processes. Here, we propose that evaporation loss of light elements as a function of cooling rate should obey the logarithmic law.

Xiong, Yong-Liang; Hewins, Roger H.

2003-01-01

114

Milagro limits and HAWC sensitivity for the rate-density of evaporating Primordial Black Holes  

NASA Astrophysics Data System (ADS)

Primordial Black Holes (PBHs) are gravitationally collapsed objects that may have been created by density fluctuations in the early universe and could have arbitrarily small masses down to the Planck scale. Hawking showed that due to quantum effects, a black hole has a temperature inversely proportional to its mass and will emit all species of fundamental particles thermally. PBHs with initial masses of ?5.0 × 1014 g should be expiring in the present epoch with bursts of high-energy particles, including gamma radiation in the GeV-TeV energy range. The Milagro high energy observatory, which operated from 2000 to 2008, is sensitive to the high end of the PBH evaporation gamma-ray spectrum. Due to its large field-of-view, more than 90% duty cycle and sensitivity up to 100 TeV gamma rays, the Milagro observatory is well suited to perform a search for PBH bursts. Based on a search on the Milagro data, we report new PBH burst rate density upper limits over a range of PBH observation times. In addition, we report the sensitivity of the Milagro successor, the High Altitude Water Cherenkov (HAWC) observatory, to PBH evaporation events.

Abdo, A. A.; Abeysekara, A. U.; Alfaro, R.; Allen, B. T.; Alvarez, C.; Álvarez, J. D.; Arceo, R.; Arteaga-Velázquez, J. C.; Aune, T.; Ayala Solares, H. A.; Barber, A. S.; Baughman, B. M.; Bautista-Elivar, N.; Becerra Gonzalez, J.; Belmont, E.; BenZvi, S. Y.; Berley, D.; Bonilla Rosales, M.; Braun, J.; Caballero-Lopez, R. A.; Caballero-Mora, K. S.; Carramiñana, A.; Castillo, M.; Christopher, G. E.; Cotti, U.; Cotzomi, J.; de la Fuente, E.; De León, C.; DeYoung, T.; Diaz Hernandez, R.; Diaz-Cruz, L.; Díaz-Vélez, J. C.; Dingus, B. L.; DuVernois, M. A.; Ellsworth, R. W.; Fiorino, D. W.; Fraija, N.; Galindo, A.; Garfias, F.; González, M. M.; Goodman, J. A.; Grabski, V.; Gussert, M.; Hampel-Arias, Z.; Harding, J. P.; Hays, E.; Hoffman, C. M.; Hui, C. M.; Hüntemeyer, P.; Imran, A.; Iriarte, A.; Karn, P.; Kieda, D.; Kolterman, B. E.; Kunde, G. J.; Lara, A.; Lauer, R. J.; Lee, W. H.; Lennarz, D.; León Vargas, H.; Linares, E. C.; Linnemann, J. T.; Longo, M.; Luna-GarcIa, R.; MacGibbon, J. H.; Marinelli, A.; Marinelli, S. S.; Martinez, H.; Martinez, O.; Martínez-Castro, J.; Matthews, J. A. J.; McEnery, J.; Mendoza Torres, E.; Mincer, A. I.; Miranda-Romagnoli, P.; Moreno, E.; Morgan, T.; Mostafá, M.; Nellen, L.; Nemethy, P.; Newbold, M.; Noriega-Papaqui, R.; Oceguera-Becerra, T.; Patricelli, B.; Pelayo, R.; Pérez-Pérez, E. G.; Pretz, J.; Rivière, C.; Rosa-González, D.; Ruiz-Velasco, E.; Ryan, J.; Salazar, H.; Salesa, F.; Sandoval, A.; Saz Parkinson, P. M.; Schneider, M.; Silich, S.; Sinnis, G.; Smith, A. J.; Stump, D.; Sparks Woodle, K.; Springer, R. W.; Taboada, I.; Toale, P. A.; Tollefson, K.; Torres, I.; Ukwatta, T. N.; Vasileiou, V.; Villaseñor, L.; Weisgarber, T.; Westerhoff, S.; Williams, D. A.; Wisher, I. G.; Wood, J.; Yodh, G. B.; Younk, P. W.; Zaborov, D.; Zepeda, A.; Zhou, H.

2015-04-01

115

Nanoparticle enhanced evaporation of liquids: A case study of silicone oil and water  

E-print Network

Evaporation is a fundamental physical phenomenon, of which many challenging questions remain unanswered. Enhanced evaporation of liquids in some occasions is of enormous practical significance. Here we report the enhanced evaporation of the nearly permanently stable silicone oil by dispersing with nanopariticles including CaTiO3, anatase and rutile TiO2. The results can inspire the research of atomistic mechanism for nanoparticle enhanced evaporation and exploration of evaporation control techniques for treatment of oil pollution and restoration of dirty water.

Wenbin Zhang; Rong Shen; Kunquan Lu; Ailing Ji; Zexian Cao

2012-10-23

116

Influence of surface wettability on transport mechanisms governing water droplet evaporation.  

PubMed

Prediction and manipulation of the evaporation of small droplets is a fundamental problem with importance in a variety of microfluidic, microfabrication, and biomedical applications. A vapor-diffusion-based model has been widely employed to predict the interfacial evaporation rate; however, its scope of applicability is limited due to incorporation of a number of simplifying assumptions of the physical behavior. Two key transport mechanisms besides vapor diffusion-evaporative cooling and natural convection in the surrounding gas-are investigated here as a function of the substrate wettability using an augmented droplet evaporation model. Three regimes are distinguished by the instantaneous contact angle (CA). In Regime I (CA ? 60°), the flat droplet shape results in a small thermal resistance between the liquid-vapor interface and substrate, which mitigates the effect of evaporative cooling; upward gas-phase natural convection enhances evaporation. In Regime II (60 ? CA ? 90°), evaporative cooling at the interface suppresses evaporation with increasing contact angle and counterbalances the gas-phase convection enhancement. Because effects of the evaporative cooling and gas-phase convection mechanisms largely neutralize each other, the vapor-diffusion-based model can predict the overall evaporation rates in this regime. In Regime III (CA ? 90°), evaporative cooling suppresses the evaporation rate significantly and reverses entirely the direction of natural convection induced by vapor concentration gradients in the gas phase. Delineation of these counteracting mechanisms reconciles previous debate (founded on single-surface experiments or models that consider only a subset of the governing transport mechanisms) regarding the applicability of the classic vapor-diffusion model. The vapor diffusion-based model cannot predict the local evaporation flux along the interface for high contact angle (CA ? 90°) when evaporative cooling is strong and the temperature gradient along the interface determines the peak local evaporation flux. PMID:25105726

Pan, Zhenhai; Weibel, Justin A; Garimella, Suresh V

2014-08-19

117

Huddling reduces evaporative water loss in torpid Natterer's bats, Myotis nattereri.  

PubMed

Periodic arousals during hibernation consume most of the winter energy budget for hibernating mammals. Evaporative water loss (EWL) is thought to affect the frequency of arousals and thus energy balance, and might have dramatic implications for over-winter survival and fitness. We hypothesized that huddling affects EWL and energy expenditure in torpid mammals. We tested this hypothesis using bats as a model and predicted that, during torpor, EWL and energy expenditure of huddling individuals would be lower than in individuals that are not in a huddle. We measured EWL and metabolic rate of torpid Myotis nattereri (Kuhl, 1817) huddling in groups or roosting individually. Evaporative water loss in huddling individual bats was almost 30% lower than in solitary animals (P=0.03), even after correcting for the effects of metabolic rate. Our results suggest that conservation of water is a substantial benefit underlying huddling by bats during hibernation. Ultimately, huddling could reduce the total cost of hibernation by reducing the number of expensive periodic arousals from torpor caused by the need to supplement water. PMID:25289993

Boraty?ski, Jan S; Willis, Craig K R; Jefimow, Ma?gorzata; Wojciechowski, Micha? S

2015-01-01

118

The use of thermogravimetry to follow the rate of evaporation of an ingredient used in perfumes  

Microsoft Academic Search

Ingredients used in the manufacture of perfumes can be investigated by thermogravimetry. In this study the evaporation of\\u000a methyl benzoate was investigated using a simultaneous TG-DTA unit. A rising temperature method of thermal analysis was used\\u000a for the study. The rate of evaporation of the ingredient was calculated from a simple plot of percentage mass lossvs. time. A derivative plot

P. Aggarwal; D. Dollimore; K. Alexander

1997-01-01

119

Soil-water evaporation dynamics determined with measurement of sensible heat transfer  

Technology Transfer Automated Retrieval System (TEKTRAN)

Soil-water evaporation is important in both the hydrologic cycle and the surface energy balance. Yet, routine measurements are unable to capture rapidly shifting near-surface soil heat and water processes involved in evaporation. Recent improvements for fine-scale measurement of soil thermal propert...

120

Sensible Heat Measurements Indicating Depth and Magnitude of Subsurface Soil Water Evaporation  

Technology Transfer Automated Retrieval System (TEKTRAN)

Soil water evaporation is typically determined by techniques that assume the latent heat flux originates from the soil surface. Here, we describe a new technique for determining in situ soil water evaporation dynamics from fine-scale measurements of soil temperature and thermal properties with heat ...

121

O of water vapour, evapotranspiration and the sites of leaf water evaporation in a soybean canopy  

E-print Network

in a predictable way to environmental conditions. Isotopic mass balance dictates that at the time scale of days and temperature associated with canopy structure must be addressed in canopy-scale leaf water models. Finally, we explored this data set for direct evidence of the Péclet effect. Key-words: canopy scale; dew; evaporative

Lee, Xuhui

122

Bioheat model evaluations of laser effects on tissues: role of water evaporation and diffusion  

NASA Astrophysics Data System (ADS)

A two-dimensional, time-dependent bioheat model is applied to evaluate changes in temperature and water content in tissues subjected to laser irradiation. Our approach takes account of liquid-to-vapor phase changes and a simple diffusive flow of water within the biotissue. An energy balance equation considers blood perfusion, metabolic heat generation, laser absorption, and water evaporation. The model also accounts for the water dependence of tissue properties (both thermal and optical), and variations in blood perfusion rates based on local tissue injury. Our calculations show that water diffusion would reduce the local temperature increases and hot spots in comparison to simple models that ignore the role of water in the overall thermal and mass transport. Also, the reduced suppression of perfusion rates due to tissue heating and damage with water diffusion affect the necrotic depth. Two-dimensional results for the dynamic temperature, water content, and damage distributions will be presented for skin simulations. It is argued that reduction in temperature gradients due to water diffusion would mitigate local refractive index variations, and hence influence the phenomenon of thermal lensing. Finally, simple quantitative evaluations of pressure increases within the tissue due to laser absorption are presented.

Nagulapally, Deepthi; Joshi, Ravi P.; Thomas, Robert J.

2011-03-01

123

Partitioning of evaporative water loss into respiratory and cutaneous pathways in Wahlberg's epauletted fruit bats (Epomophorus wahlbergi).  

PubMed

The relative contributions of respiratory and cutaneous evaporation to total evaporative water loss (TEWL) and how the partitioning of these two avenues varies with environmental temperature has received little attention in bats. We trained Wahlberg's epauletted fruit bats (Epomophorus wahlbergi) captured in Pretoria, South Africa, to wear latex masks while hanging in respirometry chambers, and we measured respiratory evaporative water loss (REWL) and cutaneous evaporative water loss (CEWL) over air temperatures (Ta) from 10° to 40°C. The bats' normothermic body temperature (Tb) was approximately 36°C, which increased at higher Ta to 40.5° ± 1.0°C at Ta ? 40°C. Both TEWL and resting metabolic rate (RMR) increased sharply at Ta >35°C, with a mean TEWL at 40°C equivalent to 411% of that at 30°C. The increase in TEWL was driven by large increases in both CEWL and REWL. CEWL comprised more than 50% of TEWL over the entire Ta range, with the exception of Ta ? 40°C, where REWL accounted for 58% of evaporative water loss. Surface area-specific CEWL increased approximately sixfold with increasing Ta. Thermoregulation at Ta approaching or exceeding Tb involved a considerable energetic cost, with RMR at Ta ? 40°C exceeding by 24% that measured at Ta ? 10°C. Our data do not support recent arguments that respiratory gas exchange across the wing membranes represents 5%-10% of the total in E. wahlbergi. PMID:24769711

Minnaar, Ingrid A; Bennett, Nigel C; Chimimba, Christian T; McKechnie, Andrew E

2014-01-01

124

Residual Patterns of Alkyl Polyoxyethylene Surfactant Droplets after Water Evaporation  

Technology Transfer Automated Retrieval System (TEKTRAN)

Using a nonionic, alkyl polyoxyethylene surfactant (X-77®) in aqueous solutions, sessile droplet spreading, pinning, evaporation, contraction, and post-evaporation deposits are characterized. X-77® is widely used in the agricultural field as a spreader/adherent, intended to optimize pathenogenic ag...

125

High rate deposition of transparent conducting oxide thin films by vacuum arc plasma evaporation  

Microsoft Academic Search

Transparent conducting oxide (TCO) thin films have been deposited at a high rate above 370 nm\\/min by vacuum arc plasma evaporation (VAPE) using sintered oxide fragments as the source material. It was found that the deposition rate of TCO films was strongly dependent on the deposition pressure, whereas the obtained electrical properties were relatively independent of the pressure. Resistivities of

Tadatsugu Minami; Satoshi Ida; Toshihiro Miyata

2002-01-01

126

The evaporative requirement for heat balance determines whole-body sweat rate during exercise under conditions permitting full evaporation.  

PubMed

Although the requirements for heat dissipation during exercise are determined by the necessity for heat balance, few studies have considered them when examining sweat production and its potential modulators. Rather, the majority of studies have used an experimental protocol based on a fixed percentage of maximum oxygen uptake (% ). Using multiple regression analysis, we examined the independent contribution of the evaporative requirement for heat balance (Ereq) and % to whole-body sweat rate (WBSR) during exercise. We hypothesised that WBSR would be determined by Ereq and not by % . A total of 23 males performed two separate experiments during which they exercised for 90 min at different rates of metabolic heat production (200, 350, 500 W) at a fixed air temperature (30°C, n = 8), or at a fixed rate of metabolic heat production (290 W) at different air temperatures (30, 35, 40°C, n = 15 and 45°C, n = 7). Whole-body evaporative heat loss was measured by direct calorimetry and used to calculate absolute WBSR in grams per minute. The conditions employed resulted in a wide range of Ereq (131-487 W) and % (15-55%). The individual variation in non-steady-state (0-30 min) and steady-state (30-90 min) WBSR correlated significantly with Ereq (P < 0.001). In contrast, % correlated negatively with the residual variation in WBSR not explained by Ereq, and marginally increased (?2%) the amount of total variability in WBSR described by Ereq alone (non-steady state: R(2) = 0.885; steady state: R(2) = 0.930). These data provide clear evidence that absolute WBSR during exercise is determined by Ereq, not by % . Future studies should therefore use an experimental protocol which ensures a fixed Ereq when examining absolute WBSR between individuals, irrespective of potential differences in relative exercise intensity. PMID:23459754

Gagnon, Daniel; Jay, Ollie; Kenny, Glen P

2013-06-01

127

Spacesuit Water Membrane Evaporator Integration with the ISS Extravehicular Mobility  

NASA Technical Reports Server (NTRS)

NASA has developed a Solid Water Membrane Evaporation (SWME) to provide cooling for the next generation spacesuit. One approach to increasing the TRL of the system is to incorporate this hardware with the existing EMU. Several integration issues were addressed to support a potential demonstration of the SWME with the existing EMU. Systems analysis was performed to assess the capability of the SWME to maintain crewmember cooling and comfort as a replacement for sublimation. The materials of the SWME were reviewed to address compatibility with the EMU. Conceptual system placement and integration with the EMU via an EVA umbilical system to ensure crew mobility and Airlock egress were performed. A concept of operation for EVA use was identified that is compatible with the existing system. This concept is extensible as a means to provide cooling for the existing EMU. The cooling system of one of the EMUs on orbit has degraded, with the root cause undetermined. Should there be a common cause resident on ISS, this integration could provide a means to recover cooling capability for EMUs on orbit.

Margiott, Victoria; Boyle, Robert

2014-01-01

128

A Novel Absorption Cycle for Combined Water Heating, Dehumidification, and Evaporative Cooling  

SciTech Connect

In this study, development of a novel system for combined water heating, dehumidification, and space evaporative cooling is discussed. Ambient water vapor is used as a working fluid in an open system. First, water vapor is absorbed from an air stream into an absorbent solution. The latent heat of absorption is transferred into the process water that cools the absorber. The solution is then regenerated in the desorber, where it is heated by a heating fluid. The water vapor generated in the desorber is condensed and its heat of phase change is transferred to the process water in the condenser. The condensed water can then be used in an evaporative cooling process to cool the dehumidified air exiting the absorber, or it can be drained if primarily dehumidification is desired. Essentially, this open absorption cycle collects space heat and transfers it to process water. This technology is enabled by a membrane-based absorption/desorption process in which the absorbent is constrained by hydrophobic vapor-permeable membranes. Constraining the absorbent film has enabled fabrication of the absorber and desorber in a plate-and-frame configuration. An air stream can flow against the membrane at high speed without entraining the absorbent, which is a challenge in conventional dehumidifiers. Furthermore, the absorption and desorption rates of an absorbent constrained by a membrane are greatly enhanced. Isfahani and Moghaddam (Int. J. Heat Mass Transfer, 2013) demonstrated absorption rates of up to 0.008 kg/m2s in a membrane-based absorber and Isfahani et al. (Int. J. Multiphase Flow, 2013) have reported a desorption rate of 0.01 kg/m2s in a membrane-based desorber. The membrane-based architecture also enables economical small-scale systems, novel cycle configurations, and high efficiencies. The absorber, solution heat exchanger, and desorber are fabricated on a single metal sheet. In addition to the open arrangement and membrane-based architecture, another novel feature of the cycle is recovery of the solution heat energy exiting the desorber by process water (a process-solution heat exchanger ) rather than the absorber exiting solution (the conventional solution heat exchanger ). This approach has enabled heating the process water from an inlet temperature of 15 C to 57 C (conforming to the DOE water heater test standard) and interfacing the process water with absorbent on the opposite side of a single metal sheet encompassing the absorber, process-solution heat exchanger, and desorber. The system under development has a 3.2 kW water heating capacity and a target thermal coefficient of performance (COP) of 1.6.

CHUGH, Devesh [University of Florida, Gainesville; Gluesenkamp, Kyle R [ORNL; Abdelaziz, Omar [ORNL; Moghaddam, Saeed [University of Florida, Gainesville

2014-01-01

129

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

NASA Technical Reports Server (NTRS)

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

Salvucci, Guido D.

2000-01-01

130

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

NASA Technical Reports Server (NTRS)

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

Salvucci, Guido D.

1997-01-01

131

Changing Demands from Riparian Evapotranspiration and Free-Water Evaporation in the Lower Colorado River Basin Under Different Climate Scenarios  

NASA Astrophysics Data System (ADS)

Observed and projected trends in riparian evapotranspiration (ET) and free-water evaporation are examined to improve water demand forecasting for use in modeling of lower Colorado River system reservoir operations. While most previous research has focused on the impacts of climate change and climate variability on water supply, the impacts on water demand under changing climate conditions have not been adequately addressed (NRC, 2007 and Reclamation, 2009). Increases in temperatures and changes in precipitation and wind patterns are expected to increase evaporative demands (Bates and others, 2008), potentially increasing free-water evaporation and ET from riparian vegetation; increasing infiltration rates; altering cropping patterns; and changing the temporal and spatial distribution of water deliveries. This study uses observations and projections under changing climate scenarios of hydroclimatic variables, such as temperature, wind, and precipitation, to analyze their impacts on riparian ET and free-water evaporation in the lower Colorado River mainstream downstream of Lake Mead and Hoover Dam. The projected changes in evaporative demands were assessed to determine their impacts on water supply and reservoir operations in the Colorado River basin under changing climate conditions. Based on analysis of observed and projected hydroclimatic data from the Variable Infiltration Capacity (VIC) hydrologic model, mean annual daily temperature in the lower Colorado River mainstream reach has increased by 0.8° Celsius (C) from the 30-year period ending in 1980 to period ending in 2010 and is projected to increase by an additional 1.7° C by 30-year period ending in 2060. Analysis of riparian ET derived from the ASCE Penman-Monteith method (Allen et al., 2005, from Monteith, 1965 and 1981) and Westenburg et al. (2006) and free-water evaporation derived from the Penman combination model in Dingman (2008) indicates that combined evaporative demand in the lower Colorado River mainstream increased by 14,800 acre-feet, or 1.8 percent, during the 30-year period ending in 2010, and may increase by an additional 16,600 acre-feet, or 2.0 percent, during the 30-year period ending in 2060, when compared to the period from 1951 to 1980. With this projected increase in evaporative demands, the combined storage of Lake Powell and Lake Mead are projected to decrease by a cumulative volume of 75,400 acre-feet, or 0.15 percent of total conservation capacity, based on 10-year running averages ending in years 2020 to 2060. In addition, average annual shortage volumes in the lower Colorado River basin are projected to increase by 40,000 acre-feet, or 0.30 percent, from 2013 to 2060.

Bunk, D. A.; Piechota, T. C.

2012-12-01

132

Single-droplet evaporation kinetics and particle formation in an acoustic levitator. Part 1: evaporation of water microdroplets assessed using boundary-layer and acoustic levitation theories.  

PubMed

The suitability of a single droplet drying acoustic levitator as a model for the spray drying of aqueous, pharmaceutically-relevant solutes used to produce protein-loaded particles has been examined. The acoustic levitator was initially evaluated by measuring the drying rates of droplets of pure water in dependence of drying-air temperature and flow rate. The measured drying rates were higher than those predicted by boundary layer theory because of the effects of primary acoustic streaming. Sherwood numbers of 2.6, 3.6, and 4.4 at drying-air temperatures of 25 degrees C, 40 degrees C, and 60 degrees C were determined, respectively. Acoustic levitation theory could predict the measured drying rates and Sherwood numbers only when a forced-convection drying-air stream was used to neuralize the retarding effect of secondary acoustic streaming on evaporation rate. At still higher drying-air flow rates, the Ranz-Marshall correlation accurately predicts Sherwood number, provided a stable droplet position in the standing acoustic wave is maintained. The measured Sherwood numbers and droplet Reynolds numbers show that experiments performed in the levitator in still air are taking place effectively under conditions of substantial forced convection. The similitude of these values to those occurring in spray dryers is fortuitous for the suitability of the acoustic levitator as a droplet evaporation model for spray drying. PMID:17582811

Schiffter, Heiko; Lee, Geoffrey

2007-09-01

133

Measurements of the evaporation coefficient of water based on molecular gas dynamics  

NASA Astrophysics Data System (ADS)

We propose a novel method for measuring the evaporation coefficient of water using a sound-resonaiice experiment based on the theory of molecular gas dynamics. The evaporation coefficient is one of the parameters contained in the kinetic boundary condition. The evaporation coefficient of water is determined according to the pressure amplitude of the resonant sound wave in a cylindrical space bounded by a sound source and a vapor-liquid interface. The use of the sound wave enables us to conduct the experiment in a weak nonequilibrium state. By comparing the pressure amplitude with the results from a linear acoustic theory, including the effect of the evaporation coefficient on the amplitude variation, we demonstrate that the evaporation coefficient of water is approximately 1.0 near 300 K.

Nakamura, Shigeto; Yano, Takeru

2014-12-01

134

Evaporation of water from pesticide formulations and adjuvant solutions: Modeling and analysis of temperature dependence  

Microsoft Academic Search

The influence of ambient air temperature on the evaporation of water from some pesticide formulations and adjuvant solutions vas measured using a gravimetric method. The degree of hydration was estimated as the difference between the empirically observed and theoretically calculated percentages of non?volatile components in each mixture. Mathematical models were developed to describe the time and temperature dependence of evaporation.

Richard A. Fleming; Alam Sundaram

1989-01-01

135

Reduction of water evaporation in polymerase chain reaction microfluidic devices based on oscillating-flow  

E-print Network

Reduction of water evaporation in polymerase chain reaction microfluidic devices based-chip applications including polymerase chain reaction PCR . We study sample evaporation in poly- meric and hybrid,2 Thenceforth, several microfluidic devices for polymerase chain reaction PCR have been produced as miniaturized

136

Influence of a wick lining on the evaporation rate of lithium from a charge exchange canal  

NASA Astrophysics Data System (ADS)

A wick lining is used with a lithium charge exchange canal for reducing the consumption of lithium. The wick helps to condense the lithium vapour more effectively and to make it flow back to the main oven. For its efficient functioning, the temperature gradient along the wick has to be properly maintained. The present studies were carried out to assess the extent of reduction in lithium loss when using the wick and to determine the optimum temperature settings. The evaporation rate of lithium vapour from a charge exchange canal (General Ionex Model-712) has been investigated in the temperature range from 470 to 575° C. The measurements were carried out with and without a stainless steel wire mesh wick lining, inside the canal. A quartz crystal oscillator type rate meter was used for monitoring the evaporation rate. The results indicate that, when the wick lining is inserted, the reduction in evaporation rate of lithium is only 20%. This differs much from the result of Greenway [Report 85/11, Oxford University, Nuclear Physics Laboratory (1985)] who reported a reduction by a factor of 8. The evaporation rate is also found to depend on the canal end heater temperature, maintained high enough to keep the condensing vapour in liquid state. The optimum temperature settings for the end heaters have been found to be 300 ° C. The experimental arrangements and results are presented in this paper.

Thampi, N. S.; Berger, S.; Dworschak, F.

1992-02-01

137

Reduction of water evaporation in polymerase chain reaction microfluidic devices based on oscillating-flow  

PubMed Central

Producing polymeric or hybrid microfluidic devices operating at high temperatures with reduced or no water evaporation is a challenge for many on-chip applications including polymerase chain reaction (PCR). We study sample evaporation in polymeric and hybrid devices, realized by glass microchannels for avoiding water diffusion toward the elastomer used for chip fabrication. The method dramatically reduces water evaporation in PCR devices that are found to exhibit optimal stability and effective operation under oscillating-flow. This approach maintains the flexibility, ease of fabrication, and low cost of disposable chips, and can be extended to other high-temperature microfluidic biochemical reactors. PMID:20877657

Polini, Alessandro; Mele, Elisa; Sciancalepore, Anna Giovanna; Girardo, Salvatore; Biasco, Adriana; Camposeo, Andrea; Cingolani, Roberto; Weitz, David A.; Pisignano, Dario

2010-01-01

138

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

PubMed

Increased cutaneous resistance to evaporative water loss (Rc) in tree frogs results in decreased water loss rate and increased body temperature. We examined sensitivity of Rc to water vapor density (WVD) in Hyla cinerea by exposing individual frogs and agar models to four different WVD environments and measuring cutaneous evaporative water loss rate and body temperature simultaneously using a gravimetric wind tunnel measuring system. We found that water loss rate varied inversely and body temperature directly with WVD but that models were affected to a greater extent than were animals. Mean Rc was significantly different between the highest WVD environment and each of the three drier environments but did not differ among the drier environments, indicating that Rc initially increases and then reaches a plateau in response to decreasing WVD. Rc was equivalent when calculated using either WVD difference or WVD deficit as the driving force for evaporation. We also directly observed secretions from cutaneous glands while measuring body temperature and tested secretions and skin samples for the presence of lipids. We found that irregular transient body temperature depressions observed during wind tunnel trials occur due to evaporative cooling from intermittent skin secretions containing lipids, although we were unable to identify lipid-secreting glands. PMID:23995486

Wygoda, Mark L; Kersten, Constance A

2013-01-01

139

Emergent relation between surface vapor conductance and relative humidity profiles yields evaporation rates from weather data.  

PubMed

The ability to predict terrestrial evapotranspiration (E) is limited by the complexity of rate-limiting pathways as water moves through the soil, vegetation (roots, xylem, stomata), canopy air space, and the atmospheric boundary layer. The impossibility of specifying the numerous parameters required to model this process in full spatial detail has necessitated spatially upscaled models that depend on effective parameters such as the surface vapor conductance (C(surf)). C(surf) accounts for the biophysical and hydrological effects on diffusion through the soil and vegetation substrate. This approach, however, requires either site-specific calibration of C(surf) to measured E, or further parameterization based on metrics such as leaf area, senescence state, stomatal conductance, soil texture, soil moisture, and water table depth. Here, we show that this key, rate-limiting, parameter can be estimated from an emergent relationship between the diurnal cycle of the relative humidity profile and E. The relation is that the vertical variance of the relative humidity profile is less than would occur for increased or decreased evaporation rates, suggesting that land-atmosphere feedback processes minimize this variance. It is found to hold over a wide range of climate conditions (arid-humid) and limiting factors (soil moisture, leaf area, energy). With this relation, estimates of E and C(surf) can be obtained globally from widely available meteorological measurements, many of which have been archived since the early 1900s. In conjunction with precipitation and stream flow, long-term E estimates provide insights and empirical constraints on projected accelerations of the hydrologic cycle. PMID:23576717

Salvucci, Guido D; Gentine, Pierre

2013-04-16

140

Emergent relation between surface vapor conductance and relative humidity profiles yields evaporation rates from weather data  

PubMed Central

The ability to predict terrestrial evapotranspiration (E) is limited by the complexity of rate-limiting pathways as water moves through the soil, vegetation (roots, xylem, stomata), canopy air space, and the atmospheric boundary layer. The impossibility of specifying the numerous parameters required to model this process in full spatial detail has necessitated spatially upscaled models that depend on effective parameters such as the surface vapor conductance (Csurf). Csurf accounts for the biophysical and hydrological effects on diffusion through the soil and vegetation substrate. This approach, however, requires either site-specific calibration of Csurf to measured E, or further parameterization based on metrics such as leaf area, senescence state, stomatal conductance, soil texture, soil moisture, and water table depth. Here, we show that this key, rate-limiting, parameter can be estimated from an emergent relationship between the diurnal cycle of the relative humidity profile and E. The relation is that the vertical variance of the relative humidity profile is less than would occur for increased or decreased evaporation rates, suggesting that land–atmosphere feedback processes minimize this variance. It is found to hold over a wide range of climate conditions (arid–humid) and limiting factors (soil moisture, leaf area, energy). With this relation, estimates of E and Csurf can be obtained globally from widely available meteorological measurements, many of which have been archived since the early 1900s. In conjunction with precipitation and stream flow, long-term E estimates provide insights and empirical constraints on projected accelerations of the hydrologic cycle. PMID:23576717

Salvucci, Guido D.; Gentine, Pierre

2013-01-01

141

The daily evaporation characteristics of deeply buried phreatic water in an extremely arid region  

NASA Astrophysics Data System (ADS)

Measurements of the daily evaporation characteristics of deeply buried phreatic water in an extremely arid area are reported. The results are used to analyze the mechanism responsible for water movement in the groundwater-soil-plant-atmosphere continuum. A closed PVC greenhouse was set up on Gobi land at the top of the Mogao Grottoes where phreatic water is more than 200 m deep. An air-conditioning unit and an automatic weighing scale were placed inside the greenhouse to condense and monitor phreatic evaporation and soil water changes in this extremely arid region. Soil temperature and humidity at various depths (0-40 cm) and other meteorological factors were also recorded on a sub-hourly basis. The relationship between evaporated water and soil water movement was analyzed by observing changes in soil weight, the condensate from the air-conditioning unit, and air moisture. The results show that phreatic water evaporation occurs from this deeply buried source in this extremely arid zone. The daily characteristics are consistent with the variation in the Sun’s radiation intensity (i.e. both show a sinusoidal behavior). In the daytime, most of the soil water does not evaporate but moves to cooler sub-layers. In the afternoon, the shallow soil layer absorbs moisture as the temperature decreases. At night, an abundance of water vapor moves upwards from the sub-layers and supplements the evaporated and downward-moving moisture of the superstratum in the daytime, but there is no evaporation. The stable, upwardly migrating vapor and film water is supported by geothermy and comes from phreatic water, the daily evaporation characteristics of which changes according to soil temperature when it reaches the ground.

Li, Hongshou; Wang, Wanfu; Liu, Benli

2014-06-01

142

Evaporation from seven reservoirs in the Denver water-supply system, central Colorado  

USGS Publications Warehouse

Seven reservoirs in central Colorado, operated by the Denver Board of Water Commissioners, were studied during 1967-73 to determine evaporation losses. These reservoirs, Elevenmile Canyon, Dillon, Gross, Antero, Cheesman, Williams Fork, and Ralston, are located on both sides of the Continental Divide. Methods for computing evaporation include energy-budget, mass-transfer, and pan relationships. Three reservoirs, Elevenmile Canyon, Dillon, and Gross, had mass-transfer coefficients calibrated by energy-budget studies. At the remaining reservoirs, an empirical technique was used to estimate the mass-transfer coefficient. The enery-budget-calibrated methods give the most accurate evaporation values; the empirical coefficients give only a best estimate of evaporation. All reservoirs should be calibrated by energy-budget studies. The pan method of computing evaporation is the least reliable method because of problems of advected energy through the sides of the pan, representative pan exposure , and the irregularity of ratios of reservoir to pan evaporation. (Woodard-USGS)

Ficke, John F.; Adams, D. Briane; Danielson, T.W.

1977-01-01

143

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

NASA Technical Reports Server (NTRS)

Development of the Advanced Extravehicular Mobility Unit (AEMU) portable life support subsystem (PLSS) is currently under way at NASA Johnson Space Center. The AEMU PLSS features a new evaporative cooling system, the Generation 4 Spacesuit Water Membrane Evaporator (Gen4 SWME). The SWME offers several advantages when compared with prior crewmember cooling technologies, including the ability to reject heat at increased atmospheric pressures, reduced loop infrastructure, and higher tolerance to fouling. Like its predecessors, Gen4 SWME provides nominal crew member and electronics cooling by flowing water through porous hollow fibers. Water vapor escapes through the hollow fiber pores, thereby cooling the liquid water that remains inside of the fibers. This cooled water is then recirculated to remove heat from the crew member and PLSS electronics. Test results from the backup cooling system which is based on a similar design and the subject of a companion paper, suggested that further volume reductions could be achieved through fiber density optimization. Testing was performed with four fiber bundle configurations ranging from 35,850 fibers to 41,180 fibers. The optimal configuration reduced the Gen4 SWME envelope volume by 15% from that of Gen3 while dramatically increasing the performance margin of the system. A rectangular block design was chosen over the Gen3 cylindrical design, for packaging configurations within the AEMU PLSS envelope. Several important innovations were made in the redesign of the backpressure valve which is used to control evaporation. A twin-port pivot concept was selected from among three low profile valve designs for superior robustness, control and packaging. The backpressure valve motor, the thermal control valve, delta pressure sensors and temperature sensors were incorporated into the manifold endcaps, also for packaging considerations. Flight-like materials including a titanium housing were used for all components. Performance testing of the Gen4 SWME is underway.

Bue, Grant C.; Makinen, Janice V.; Miller, Sean; Campbell, Colin; Lynch, Bill; Vogel, Matt; Craft, Jesse; Wilkes, Robert; Kuehnel, Eric

2014-01-01

144

PREDICTING EVAPORATION RATES AND TIMES FOR SPILLS OF CHEMICAL MIXTURES: JOURNAL ARTICLE  

EPA Science Inventory

NRMRL-CIN-0988 Smith*, R.L. Predicting Evaporation Rates and Times for Spills of Chemical Mixtures. The Annals of Occupational Hygiene (Ogden, T. (Ed.), Elsevier) 45 (6):437-445 (2001). EPA/600/J-00/125. 03/16/2000 Spreadsheet and short-cut methods have been developed for p...

145

The temperature variance method: a powerful tool in the estimation of actual evaporation rates  

Microsoft Academic Search

The usefulness of the temperature variance technique for the estimation of actual evaporation rates under humid tropical conditions was tested with a set of micrometerolo gical data collected above a 6- year-old pine plantation in Viti Levu, Fiji. Values for the sensible and latent heat fluxes obtained from the standard deviations of fast responding dry and wet bulb thermocouples during

H. F. VUGTS; M. J. WATERLOO; F. J. BEEKMAN; K. F. A. FRUMAU; L. A. BRUUNZEEL

1993-01-01

146

EFFECT OF HEATING RATE ON EVAPORATIVE HEAT LOSS IN THE MICROWAVE-EXPOSED MOUSE  

EPA Science Inventory

Male CBA/J mice were administered heat loads of 0-28 J. per g at specific absorption rates (SARs) of either 47 or 93 W. per kg by exposure to 2,450-MHz microwave radiation at an ambient temperature of 30 C while evaporative heat loss (EHL) was continuously monitored with dew-poin...

147

RECYCLING NICKEL ELECTROPLATING RINSE WATERS BY LOW TEMPERATURE EVAPORATION AND REVERSE OSMOSIS  

EPA Science Inventory

Low temperature evaporation and reverse osmosis systems were each evaluated (on a pilot scale) on their respective ability to process rinse water collected from a nickel electroplating operation. Each system offered advantages under specific operating conditions. The low temperat...

148

RECYCLING NICKEL ELECTROPLATING RINSE WATERS BY LOW TEMPERATURE EVAPORATION AND REVERSE OSMOSIS  

EPA Science Inventory

Low temperature evaporation and reverse osmosis systems were each evaluated (on a pilot scale) on their respective ability to process rinse water collected from a nickel electroplating operation. ach system offered advantages under specific operating conditions. he low temperatur...

149

A Study of Mechanisms and Supression of Evaporation of Water from Soils  

E-print Network

, polysaccharide-gum mixtures, oil-latex mixtures, fatty alcohols, and reflectance materials. Of these compounds, only crude oil and crude oil-cationic mixtures were effective in suppressing soil water evaporation significantly when applied to smooth Olton loam wet...

Wendt, C. W.

150

Insight into the molecular mechanism of water evaporation via the finite temperature string method  

E-print Network

The process of water's evaporation at its liquid/air interface has proven challenging to study experimentally and, because it constitutes a rare event on molecular time scales, presents a challenge for computer simulations ...

Musolino, Nicholas

151

Use of Air2Air Technology to Recover Fresh-Water from the Normal Evaporative Cooling Loss at Coal-Based Thermoelectric Power Plants  

SciTech Connect

This program was undertaken to build and operate the first Air2Air{trademark} Water Conservation Cooling Tower at a power plant, giving a validated basis and capability for water conservation by this method. Air2Air{trademark} water conservation technology recovers a portion of the traditional cooling tower evaporate. The Condensing Module provides an air-to-air heat exchanger above the wet fill media, extracting the heat from the hot saturated moist air leaving in the cooling tower and condensing water. The rate of evaporate water recovery is typically 10%-25% annually, depending on the cooling tower location (climate).

Ken Mortensen

2009-06-30

152

Evaporative assembly of MEH-PPV rings using mixed solvents at the air/water interface.  

PubMed

Controlling the morphology of conjugated polymers has recently attracted considerable attention because of their applications in photovoltaic (PV) devices and organic light-emitting diodes (OLEDs). Here, we describe the self-assembly of a common conjugated polymer, poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), into ringlike structures via solvent evaporation on an air/water interface. The films are monitored using Brewster angle microscopy (BAM) and transferred onto a solid substrate by either the Langmuir-Blodgett (LB) or the Langmuir-Schaefer (LS) method and further characterized by atomic force microscopy (AFM). The morphology of the MEH-PPV thin film at the air/water interface can be controlled by the spreading solvent. By mixing solvents of varying spreading coefficients and evaporation rates, such as chloroform and chlorobenzene, MEH-PPV can be assembled into micrometer-sized ring structures. The optical properties of these MEH-PPV ring structures are also characterized. Lastly, MEH-PPV can be used as a soft template to organize microscale structures of nanoparticles. PMID:24684587

Chao, Kung-Po; Biswal, Sibani L

2014-04-22

153

Effects of Surface Dipole Lengths on Evaporation of Tiny Water Aggregation  

NASA Astrophysics Data System (ADS)

Using molecular dynamics simulation, we compared evaporation behavior of a tiny amount of water molecules adsorbed on solid surfaces with different dipole lengths, including surface dipole lengths of 1 fold, 2 folds, 4 folds, 6 folds and 8 folds of 0.14 nm and different charges from 0.1e to 0.9e. Surfaces with short dipole lengths (1-fold system) can always maintain hydrophobic character and the evaporation speeds are not influenced, whether the surface charges are enhanced or weakened; but when surface dipole lengths get to 8 folds, surfaces become more hydrophilic as the surface charge increases, and the evaporation speeds increase gradually and monotonically. By tuning dipole lengths from 1-fold to 8-fold systems, we confirmed non-monotonic variation of the evaporation flux (first increases, then decreases) in 4 fold system with charges (0.1e-0.7e), reported in our previous paper [S. Wang, et al., J. Phys. Chem. B 116 (2012) 13863], and also show the process from the enhancement of this unexpected non-monotonic variation to its vanishment with surface dipole lengths increasing. Herein, we demonstrated two key factors to influence the evaporation flux of a tiny amount of water molecules adsorbed on solid surfaces: the exposed surficial area of water aggregation from where the water molecules can evaporate directly and the attraction potential from the substrate hindering the evaporation. In addition, more interestingly, we showed extra steric effect of surface dipoles on further increase of evaporation flux for 2-folds, 4-folds, 6-folds and 8-folds systems with charges around larger than 0.7e. (The steric effect is first reported by parts of our authors [C. Wang, et al., Sci. Rep. 2 (2012) 358]). This study presents a complete physical picture of the influence of surface dipole lengths on the evaporation behavior of the adsorbed tiny amount of water.

Wang, Shen; Tu, Yu-Song; Wan, Rong-Zheng; Fang, Hai-Ping

2013-05-01

154

Impact of Reservoir Evaporation and Evaporation Suppression on Water Supply Capabilities  

E-print Network

(cal/cm2 day mph?C), u = wind speed (mph), eo = saturation vapor pressure at To, and ea = water vapor pressure in the air. Qh, energy conducted from the body of water as sensible heat, can be expanded to represent a heat-transfer equation as...: ( ) where K = an empirical constant obtained during pretreatment calibration (cal/cm2 day mph?C), u = wind speed (mph), To? = observed water surface temperature with film (?C), and To = water surface without film (?C). After making substitutions...

Ayala, Rolando A

2013-04-01

155

Monitoring near surface soil water and associated dynamics of infiltration and evaporation fluxes  

Technology Transfer Automated Retrieval System (TEKTRAN)

In-situ monitoring of soil water has the advantage of integrating the precipitation, evaporation history, and gradual changes in hydraulic properties on the aggregate response of the system, which is manifested as soil water storage. Near-surface soil water and temperature dynamics were monitored th...

156

Evaporative water losses of exercising sheep in neutral and hot climates  

E-print Network

, Australia Hot climates require an accelerated water loss to allowed for thermoregulation (Rai et al, 1979Evaporative water losses of exercising sheep in neutral and hot climates T Othman KG Johnson, DW, Trop Anim Hlth Prod, 11, 51-56). The water losses associated with locomotion should be greater

Paris-Sud XI, Université de

157

Hydroclimatology of Illinois: A comparison of monthly evaporation estimates based on atmospheric water balance and soil water balance  

Microsoft Academic Search

Here we describe the regional-scale hydrological cycle of Illinois, including both the land and atmospheric branches, using a data set on most of the hydrological variables, i.e., precipitation, streamflow, soil water content, snow depth, groundwater level, and atmospheric flux of water vapor. Since direct observations of evaporation are not available, two different approaches, soil water balance and atmospheric water balance,

Pat Jen-Feng Yeh; Michelle Irizarry; Elfatih A. B. Eltahir

1998-01-01

158

Performance of Water Recirculation Loop Maintenance Components for the Advanced Spacesuit Water Membrane Evaporator  

NASA Technical Reports Server (NTRS)

Water loop maintenance components to maintain the water quality of the Advanced Spacesuit Water Membrane Evaporation (SWME) water recirculation loop have undergone a comparative performance evaluation with a recirculating control loop which had no water quality maintenance. Results show that periodic water maintenance can improve performance of the SWME. The SWME is a heat rejection device under development at the NASA Johnson Space Center to perform thermal control for advanced spacesuits. One advantage of this technology is the potential for a significantly greater degree of tolerance to contamination when compared to the existing sublimator technology. The driver for the evaluation of water recirculation maintenance components was to enhance the robustness of the SWME through the leveraging of fluid loop management lessons learned from the International Space Station (ISS). A patented bed design that was developed for a United Technologies Aerospace System military application provided a low pressure drop means for water maintenance in the SWME recirculation loop. The bed design is coupled with high capacity ion exchange resins, organic adsorbents, and a cyclic methodology developed for the Extravehicular Mobility Unit (EMU) Transport Water loop. The maintenance cycle included the use of a biocide delivery component developed for the ISS to introduce a biocide in a microgravity compatible manner for the Internal Active Thermal Control System (IATCS). The leveraging of these water maintenance technologies to the SWME recirculation loop is a unique demonstration of applying the valuable lessons learned on the ISS to the next generation of manned spaceflight Environmental Control and Life Support System (ECLSS) hardware.

Rector, Tony; Peyton, Barbara M.; Steele, John W.; Makinen, Janice; Bue, Grant C.; Campbell, Colin

2014-01-01

159

Evaporation Investigation  

NSDL National Science Digital Library

This is a hands-on lab activity about evaporation. Learners will conduct experiments to observe the process of evaporation. They will then describe the process of evaporation, and the general water cycle, through discussion and pictures. Background information, common preconceptions, a glossary and more is included. This activity is part of the Aquarius Hands-on Laboratory Activities.

2012-08-03

160

Evaporative Evolution of Carbonate-Rich Brines from Synthetic Topopah Spring Tuff Pore Water, Yucca Mountain  

SciTech Connect

The evaporation of a range of synthetic pore water solutions representative of the potential high-level-nuclear-waste repository at Yucca Mountain, NV is being investigated. The motivation of this work is to understand and predict the range of brine compositions that may contact the waste containers from evaporation of pore waters, because these brines could form corrosive thin films on the containers and impact their long-term integrity. A relatively complex synthetic Topopah Spring Tuff pore water was progressively concentrated by evaporation in a closed vessel, heated to 95 C in a series of sequential experiments. Periodic samples of the evaporating solution were taken to determine the evolving water chemistry. According to chemical divide theory at 25 C and 95 C our starting solution should evolve towards a high pH carbonate brine. Results at 95 C show that this solution evolves towards a complex brine that contains about 99 mol% Na{sup +} for the cations, and 71 mol% Cl{sup -}, 18 mol% {Sigma}CO{sub 2}(aq), 9 mol%SO{sub 4}{sup 2-} for the anions. Initial modeling of the evaporating solution indicates precipitation of aragonite, halite, silica, sulfate and fluoride phases. The experiments have been used to benchmark the use of the EQ3/6 geochemical code in predicting the evolution of carbonate-rich brines during evaporation.

Sutton, M; Alai, M; Carroll, S A

2004-04-14

161

Effects of the water retention curve on evaporation from arid soils  

NASA Astrophysics Data System (ADS)

Water retention curves approaching infinitely negative matric potentials at residual water content are widely employed to model soil moisture dynamics. When used in numerical simulations, these retention curves fail to satisfactorily describe evaporation from arid soil (moisture-limited regime) because they do not allow the soil to dry below residual water content. We show that simple modifications can be introduced to prevent unrealistic water retention at residual water content and predict more physically sound moisture dynamics. Modified retention models that allow drying below residual predict a moisture-limited regime characterized by a thin subsurface evaporation zone and produce vapor fluxes up to 3 times larger than classical retention models. This might reduce the need to introduce empirical enhancement factors and improve the capability of modeling evaporation into the atmosphere and runoff in arid regions.

Ciocca, Francesco; Lunati, Ivan; Parlange, Marc B.

2014-05-01

162

Rates of Water Loss and Estimates of Survival Time under Varying Humidity in Juvenile Snapping Turtles ( Chelydra serpentina )  

Microsoft Academic Search

Juvenile snapping turtles may be highly susceptible to dehydration during over- land movement because of their aquatic nature and large surface area to volume ratio. The present study examined the influence of body size and relative humidity on rates of evaporative water loss and estimates of survival time. Larger hatchlings had higher rates of evaporative water loss but longer survival

Michael S. Finkler

2001-01-01

163

Mechanical tuning of the evaporation rate of liquid on crossed fibers.  

PubMed

We investigate experimentally the drying of a small volume of perfectly wetting liquid on two crossed fibers. We characterize the drying dynamics for the three liquid morphologies that are encountered in this geometry: drop, column, and a mixed morphology, in which a drop and a column coexist. For each morphology, we rationalize our findings with theoretical models that capture the drying kinetics. We find that the evaporation rate significantly depends upon the liquid morphology and that the drying of the liquid column is faster than the evaporation of the drop and the mixed morphology for a given liquid volume. Finally, we illustrate that shearing a network of fibers reduces the angle between them, changes the morphology toward the column state, and therefore, enhances the drying rate of a volatile liquid deposited on it. PMID:25716158

Boulogne, François; Sauret, Alban; Soh, Beatrice; Dressaire, Emilie; Stone, Howard A

2015-03-17

164

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

NASA Technical Reports Server (NTRS)

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.

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

1986-01-01

165

Influence of organic films on the evaporation and condensation of water in aerosol.  

PubMed

Uncertainties in quantifying the kinetics of evaporation and condensation of water from atmospheric aerosol are a significant contributor to the uncertainty in predicting cloud droplet number and the indirect effect of aerosols on climate. The influence of aerosol particle surface composition, particularly the impact of surface active organic films, on the condensation and evaporation coefficients remains ambiguous. Here, we report measurements of the influence of organic films on the evaporation and condensation of water from aerosol particles. Significant reductions in the evaporation coefficient are shown to result when condensed films are formed by monolayers of long-chain alcohols [C(n)H(2n+1)OH], with the value decreasing from 2.4 × 10(-3) to 1.7 × 10(-5) as n increases from 12 to 17. Temperature-dependent measurements confirm that a condensed film of long-range order must be formed to suppress the evaporation coefficient below 0.05. The condensation of water on a droplet coated in a condensed film is shown to be fast, with strong coherence of the long-chain alcohol molecules leading to islanding as the water droplet grows, opening up broad areas of uncoated surface on which water can condense rapidly. We conclude that multicomponent composition of organic films on the surface of atmospheric aerosol particles is likely to preclude the formation of condensed films and that the kinetics of water condensation during the activation of aerosol to form cloud droplets is likely to remain rapid. PMID:23674675

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

2013-05-28

166

Influence of organic films on the evaporation and condensation of water in aerosol  

PubMed Central

Uncertainties in quantifying the kinetics of evaporation and condensation of water from atmospheric aerosol are a significant contributor to the uncertainty in predicting cloud droplet number and the indirect effect of aerosols on climate. The influence of aerosol particle surface composition, particularly the impact of surface active organic films, on the condensation and evaporation coefficients remains ambiguous. Here, we report measurements of the influence of organic films on the evaporation and condensation of water from aerosol particles. Significant reductions in the evaporation coefficient are shown to result when condensed films are formed by monolayers of long-chain alcohols [CnH(2n+1)OH], with the value decreasing from 2.4 × 10?3 to 1.7 × 10?5 as n increases from 12 to 17. Temperature-dependent measurements confirm that a condensed film of long-range order must be formed to suppress the evaporation coefficient below 0.05. The condensation of water on a droplet coated in a condensed film is shown to be fast, with strong coherence of the long-chain alcohol molecules leading to islanding as the water droplet grows, opening up broad areas of uncoated surface on which water can condense rapidly. We conclude that multicomponent composition of organic films on the surface of atmospheric aerosol particles is likely to preclude the formation of condensed films and that the kinetics of water condensation during the activation of aerosol to form cloud droplets is likely to remain rapid. PMID:23674675

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

2013-01-01

167

Epiphyte Water Retention and Evaporation in Native and Invaded Tropical Montane Cloud Forests in Hawaii  

NASA Astrophysics Data System (ADS)

Epiphyte water retention was quantified at two montane cloud forest sites in Hawai'i Volcanoes National Park, one native and the other invaded by an alien tree species. Water storage elements measured included all epiphytic mosses, leafy liverworts, and filmy ferns. Tree surface area was estimated and a careful survey was taken to account for all epiphytes in the sample area of the forest. Samples were collected and analyzed in the lab for epiphyte water retention capacity (WRC). Based on the volume of the different kinds of epiphytes and their corresponding WRC, forest stand water retention capacity for each survey area was estimated. Evaporation from the epiphyte mass was quantified using artificial reference samples attached to trees that were weighed at intervals to determine changes in stored water on days without significant rain or fog. In addition, a soil moisture sensor was wrapped in an epiphyte sample and left in the forest for a 6-day period. Epiphyte biomass at the Native Site and Invaded Site were estimated to be 2.89 t ha-1 and 1.05 t ha-1, respectively. Average WRC at the Native Site and Invaded Site were estimated at 1.45 mm and 0.68 mm, respectively. The difference is likely due to the presence of the invasive Psidium cattleianum at the Invaded Site because its smooth stem surface is unable to support a significant epiphytic layer. The evaporation rate from the epiphyte mass near WSC for the forest stand at the Native Site was measured at 0.38 mm day-1, which represented 10.6 % of the total ET from the forest canopy at the Native Site during the period. The above research has been recently complemented by a thorough investigation of the WSC of all water storage elements (tree stems, tree leaves, shrubs, grasses, litter, fallen branches, and epiphytes) at six forested sites at different elevations within, above, and below the zone of frequent cloud-cover. The goal of this study was to create an inexpensive and efficient methodology for acquiring estimates of above-ground water retention in different types of forests by means of minimally-destructive sampling and surveying. The results of this work serve as baseline data providing a range of possible values of the water retention of specific forest elements and the entire above-ground total where no values have been previously recorded.

Mudd, R. G.; Giambelluca, T. W.

2006-12-01

168

Importance of rain evaporation and continental convection in the tropical water cycle.  

PubMed

Atmospheric moisture cycling is an important aspect of the Earth's climate system, yet the processes determining atmospheric humidity are poorly understood. For example, direct evaporation of rain contributes significantly to the heat and moisture budgets of clouds, but few observations of these processes are available. Similarly, the relative contributions to atmospheric moisture over land from local evaporation and humidity from oceanic sources are uncertain. Lighter isotopes of water vapour preferentially evaporate whereas heavier isotopes preferentially condense and the isotopic composition of ocean water is known. Here we use this information combined with global measurements of the isotopic composition of tropospheric water vapour from the Tropospheric Emission Spectrometer (TES) aboard the Aura spacecraft, to investigate aspects of the atmospheric hydrological cycle that are not well constrained by observations of precipitation or atmospheric vapour content. Our measurements of the isotopic composition of water vapour near tropical clouds suggest that rainfall evaporation contributes significantly to lower troposphere humidity, with typically 20% and up to 50% of rainfall evaporating near convective clouds. Over the tropical continents the isotopic signature of tropospheric water vapour differs significantly from that of precipitation, suggesting that convection of vapour from both oceanic sources and evapotranspiration are the dominant moisture sources. Our measurements allow an assessment of the intensity of the present hydrological cycle and will help identify any future changes as they occur. PMID:17268467

Worden, John; Noone, David; Bowman, Kevin

2007-02-01

169

Importance of Rain Evaporation and Continental Convection in the Tropical Water Cycle  

NASA Technical Reports Server (NTRS)

Atmospheric moisture cycling is an important aspect of the Earth's climate system, yet the processes determining atmospheric humidity are poorly understood. For example, direct evaporation of rain contributes significantly to the heat and moisture budgets of clouds, but few observations of these processes are available. Similarly, the relative contributions to atmospheric moisture over land from local evaporation and humidity from oceanic sources are uncertain. Lighter isotopes of water vapour preferentially evaporate whereas heavier isotopes preferentially condense and the isotopic composition of ocean water is known. Here we use this information combined with global measurements of the isotopic composition of tropospheric water vapour from the Tropospheric Emission Spectrometer (TES) aboard the Aura spacecraft, to investigate aspects of the atmospheric hydrological cycle that are not well constrained by observations of precipitation or atmospheric vapour content. Our measurements of the isotopic composition of water vapour near tropical clouds suggest that rainfall evaporation contributes significantly to lower troposphere humidity, with typically 20% and up to 50% of rainfall evaporating near convective clouds. Over the tropical continents the isotopic signature of tropospheric water vapour differs significantly from that of precipitation, suggesting that convection of vapour from both oceanic sources and evapotranspiration are the dominant moisture sources. Our measurements allow an assessment of the intensity of the present hydrological cycle and will help identify any future changes as they occur.

Worden, John; Noone, David; Bowman, Kevin; Beer, R.; Eldering, A.; Fisher, B.; Gunson, M.; Goldman, Aaron; Kulawik, S. S.; Lampel, Michael; Osterman, Gregory; Rinsland, Curtis P.; Rogders, Clive; Sander, Stanley; Shepard, Mark; Webster, Christopher R.; Worden, H. M.

2007-01-01

170

Effects of solvent evaporation on water sorption/solubility and nanoleakage of adhesive systems  

PubMed Central

Objective To evaluate the influence of solvent evaporation in the kinetics of water diffusion (water sorption-WS, solubility-SL, and net water uptake) and nanoleakage of adhesive systems. Material and Methods Disk-shaped specimens (5.0 mm in diameter x 0.8 mm in thickness) were produced (N=48) using the adhesives: Clearfil S3 Bond (CS3)/Kuraray, Clearfil SE Bond - control group (CSE)/Kuraray, Optibond Solo Plus (OS)/Kerr and Scotchbond Universal Adhesive (SBU)/3M ESPE. The solvents were either evaporated for 30 s or not evaporated (N=24/per group), and then photoactivated for 80 s (550 mW/cm2). After desiccation, the specimens were weighed and stored in distilled water (N=12) or mineral oil (N=12) to evaluate the water diffusion over a 7-day period. Net water uptake (%) was also calculated as the sum of WS and SL. Data were submitted to 3-way ANOVA/Tukey's test (?=5%). The nanoleakage expression in three additional specimens per group was also evaluated after ammoniacal silver impregnation after 7 days of water storage under SEM. Results Statistical analysis revealed that only the factor "adhesive" was significant (p<0.05). Solvent evaporation had no influence in the WS and SL of the adhesives. CSE (control) presented significantly lower net uptake (5.4%). The nanoleakage was enhanced by the presence of solvent in the adhesives. Conclusions Although the evaporation has no effect in the kinetics of water diffusion, the nanoleakage expression of the adhesives tested increases when the solvents are not evaporated. PMID:25141201

CHIMELI, Talita Baumgratz Cachapuz; D'ALPINO, Paulo Henrique Perlatti; PEREIRA, Patrícia Nóbrega; HILGERT, Leandro Augusto; DI HIPÓLITO, Vinicius; GARCIA, Fernanda Cristina Pimentel

2014-01-01

171

Poorly water-soluble drug nanoparticles via solvent evaporation in water-soluble porous polymers.  

PubMed

A generic method is described to form poorly water-soluble drug nanoparticles within water-soluble porous polymer by solvent evaporation. The simple dissolution of porous polymer with drug nanoparticles results in stable aqueous drug nanoparticle suspension under the optimized conditions. The porous polymers were prepared by freeze-drying aqueous solutions of polyvinyl alcohol, polyethylene glycol, and a surfactant. They were then used as scaffolds for the formation of nanoparticles by initially soaking them in an organic drug solution, followed with removing the solvent via evaporation under ambient conditions. This process was optimized for an antifungal drug griseofulvin, before being translated to anticonvulsant carbamazepine and antineoplastic paclitaxel via a similar procedure, with an aim to improve the loading of drug nanoparticles. By varying certain process parameters a degree of control over the particle size and surface charge could be attained, as well as the drug to stabilizer ratio (drug payload). Noticeably, aqueous paclitaxel nanoparticles (500 nm) were prepared which used the equivalent of 46% less stabilizer than the formulation Taxol. PMID:23499755

Roberts, Aled D; Zhang, Haifei

2013-04-15

172

Development of a preprototype thermoelectric integrated membrane evaporation subsystem for water recovery  

Microsoft Academic Search

A three-man urine water recovery preprototype subsystem using a new concept to provide efficient potable water recovery from waste fluids on extended duration space flights has been designed, fabricated, and tested. Low power, compactness, and gravity insensitive operation are featured in this vacuum distillation subsystem that combines a hollow fiber polysulfone membrane evaporator with a thermoelectric heat pump. Application and

H. E. Winkler; G. J. Jr. Roebelen

1980-01-01

173

Revisiting the parameterization of potential evaporation as a driver of long-term water balance trends  

E-print Network

trends Michael T. Hobbins,1 Aiguo Dai,2 Michael L. Roderick,1 and Graham D. Farquhar1 Received 4 March, evaporative flux and runoff simulated by the water balance model underlying the Palmer Drought Severity Index is the water balance model underlying calculations of the Palmer Drought Severity Index (PDSI) [Palmer, 1965

Dai, Aiguo

174

Tillage effects on soil water redistribution and bare soil evaporation throughout a season  

Technology Transfer Automated Retrieval System (TEKTRAN)

Tillage-induced changes in soil properties are difficult to predict, yet can influence evaporation, infiltration, and how water is redistributed within the profile after precipitation. We evaluated the effects of sweep tillage (ST) on near surface soil water dynamics as compared with an untilled (UT...

175

Detailed modeling of the evaporation and thermal decomposition of urea-water-solution in SCR systems  

E-print Network

droplets (composed of water and zirconium acetate) axially injected into plasma. As water evaporates, the concentration of solute augments which leads to the formation of a precipitate shell. They studied the effects of droplet size, shell porosity and thickness and they shown different behaviors of droplet for different

Boyer, Edmond

176

Performance of Water Recirculation Loop Maintentance Components for the Advanced Spacesuit Water Membrane Evaporator  

NASA Technical Reports Server (NTRS)

Water loop maintenance components to maintain the water quality of the Advanced Spacesuit Water Membrane Evaporation (SWME) water recirculation loop have undergone a comparative performance evaluation with a second SWME water recirculation loop with no water quality maintenance. Results show the benefits of periodic water maintenance. The SWME is a heat rejection device under development at the NASA Johnson Space Center to perform thermal control for advanced spacesuits. One advantage to this technology is the potential for a significantly greater degree of tolerance to contamination when compared to the existing Sublimator technology. The driver for the evaluation of water recirculation maintenance components was to further enhance this advantage through the leveraging of fluid loop management lessonslearned from the International Space Station (ISS). A bed design that was developed for a UTAS military application, and considered for a potential ISS application with the Urine Processor Assembly, provided a low pressure drop means for water maintenance in a recirculation loop. The bed design is coupled with high capacity ion exchange resins, organic adsorbents, and a cyclic methodology developed for the Extravehicular Mobility Unit (EMU) Transport Water loop. The maintenance cycle included the use of a biocide delivery component developed for ISS to introduce a biocide in a microgravity-compatible manner for the Internal Active Thermal Control System (IATCS). The leveraging of these water maintenance technologies to the SWME recirculation loop is a unique demonstration of applying the valuable lessons learned on the ISS to the next generation of manned spaceflight Environmental Control and Life Support System (ECLSS) hardware.

Rector, Tony; Peyton, Barbara; Steele, John W.; Bue, Grant C.; Campbell, Colin; Makinen, Janice

2014-01-01

177

Performance of Water Recirculation Loop Maintenance Components for the Advanced Spacesuit Water Membrane Evaporator  

NASA Technical Reports Server (NTRS)

Water loop maintenance components to maintain the water quality of the Advanced Spacesuit Water Membrane Evaporation (SWME) water recirculation loop have undergone a comparative performance evaluation with a second SWME water recirculation loop with no water quality maintenance. Results show the benefits of periodic water maintenance. The SWME is a heat rejection device under development at the NASA Johnson Space Center to perform thermal control for advanced spacesuits. One advantage to this technology is the potential for a significantly greater degree of tolerance to contamination when compared to the existing Sublimator technology. The driver for the evaluation of water recirculation maintenance components was to further enhance this advantage through the leveraging of fluid loop management lessons learned from the International Space Station (ISS). A bed design that was developed for a UTAS military application, and considered for a potential ISS application with the Urine Processor Assembly, provided a low pressure drop means for water maintenance in a recirculation loop. The bed design is coupled with high capacity ion exchange resins, organic adsorbents, and a cyclic methodology developed for the Extravehicular Mobility Unit (EMU) Transport Water loop. The maintenance cycle included the use of a biocide delivery component developed for ISS to introduce a biocide in a microgravity compatible manner for the Internal Active Thermal Control System (IATCS). The leveraging of these water maintenance technologies to the SWME recirculation loop is a unique demonstration of applying the valuable lessons learned on the ISS to the next generation of manned spaceflight Environmental Control and Life Support System (ECLSS) hardware.

Rector, Tony; Peyton, Barbara M.; Steele, John W.; Makinen, Janice; Bue, Grant C.; Campbell, Colin

2014-01-01

178

Metabolic rate, thermoregulation and water balance in Lagidium viscacia inhabiting the arid Andean plateau  

Microsoft Academic Search

Lagidium viscacia inhabits where water and food availability is low. We hypothesize that this rodent should minimize metabolic rate and water loss in order to cope with such extreme environments. We observed that Lagidium viscacia has (1) a comparatively lower basal metabolic rate (67%) and thermal conductance (78%) of predicted; (2) a higher pulmocutaneous evaporation rate which is 36% (mesic)

Carlos Tirado; Arturo Cortés; Francisco Bozinovic

2007-01-01

179

Evaporation from porous media in the presence of a water table  

NASA Astrophysics Data System (ADS)

Improved understanding of soil evaporation in presence of a water table is important in many hydrological processes such as analysis of water and energy balance at land surface, and soil salinization. During evaporation, liquid water is transported from water table toward the surface by capillary forces opposed by the downward gravity and viscous forces. In presence of a shallow water table, the capillary forces may be strong enough to maintain liquid continuity extending from water table to the surface where the liquid vaporization occurs. However, when the water table depth is deep, capillary forces may not be able to overcome the resistive forces resulting in interruption of the liquid continuity. In such cases, using hydraulic conductivity and Richard’s equation across the entire soil profile to estimate the evaporative flux causes overlooking the physical mechanisms governing the process, though good agreements might be obtained by applying some fitting parameters in unsaturated hydraulic conductivity to match the prediction with the experimental data. The main objective of the present study is to enhance the awareness of limitation of rather automatic assumption of hydraulic continuity through unsaturated zone across large distances above the water table. We used the concept of evaporation characteristic lengths to predict the maximum height of liquid continuity above the water table. When the depth of water table exceeds this characteristic length deduced from the pore size distribution, the hydraulic connection with surface is interrupted resulting in considerable suppression of evaporation due to the evolution of vaporization plane from the surface to a level below the surface defined by the maximum height of the liquid continuity above the water table. To test this model, laboratory evaporation experiments were conducted using Plexiglas columns (600 mm in height and 70 mm in diameter) packed with sand initially saturated with water exposed to evaporation from top boundary. For water supply, Mariotte bottles mounted on digital balances were connected to the bottom of the columns. We used three types of sand differing in particle size distribution. To maintain constant levels of water table, Mariotte bottles were fixed at different depths below the sand surface. The mass loss from the columns and relative humidity and temperature above the columns were recorded digitally each five minutes for nearly 500 hours. Our results confirmed the critical role of liquid continuity above the water table on the evaporative water losses from porous media. The predicted maximum water table depths marking the transition from atmospheric-limited fluxes to the much lower fluxes limited by the transport properties of the porous medium were in good agreement with the experimental results. In addition to the detailed analysis of the relation between water table depths and evaporative water losses, our results provide new insights regarding solute transports and deposition patterns affected by the depth of water table during evaporation.

Shokri, N.; Salvucci, G.

2010-12-01

180

Spatial changes of the evaporation/inflow ratio of lake water deduced from surface water isotopes in Bangongcuo, western Tibet  

NASA Astrophysics Data System (ADS)

Oxygen isotope analysis provides a practical approach to understand the regional hydrologic cycle and to reconstruct the paleoclimate and paleoenvironment from lacustrine sediment. The large number of inland lakes on the northern part of the Tibetan Plateau provides the opportunity for this work, and an understanding of the isotope variation of the lake water in the water cycle is vital for this purpose. A water isotope sampling network was set up in the Banggongcuo Lake basin in western Tibet in 2009 that measured precipitation, lake water, and river water. Two years of collecting isotope data, together with AWS observations at the Ngari station in the basin, allowed for a study of lake water isotope variations in the water cycle in narrow Banggongcuo Lake. Observations showed much higher water ?18O in the closed lake due to the strong evaporation fractionation process when compared with local precipitation. An obvious spatial change of lake water ?18O was also found, varying from about -4.9‰ in the east to about +0.9‰ in the west. This spatial change is largely due to the fact that the main river water input to the lake is on the eastern part of the lake, while the lake water evaporates out gradually westward. This phenomenon also matches the spatial change of lake water chemical components. We simulate the gradual evaporation of the lake water using an isotope evaporation fractionation model, in an effort to quantitatively estimate the E/I ratio (evaporation to total lake water inflow) in different parts of the lake. From the observation lake water ?18O, we estimate that the E/I ratio is about 42~60% in the eastern part of the lake and increases to 76~87% in the western part.

Wen, R.; Tian, L.; Weng, Y.; Qu, D.

2013-12-01

181

Non-isothermal soil water transport and evaporation  

Microsoft Academic Search

A detailed model was formulated to describe the non-isothermal transport of water in the unsaturated soil zone. The model consists of the coupled equations of mass conservation for the liquid phase, gas phase and water vapor and the energy conservation equation. The water transport mechanisms considered are convection in the liquid phase, and convection, diffusion and dispersion of vapor in

Jordi Grifoll; Josep Ma. Gastoa; Yoram Cohen

2005-01-01

182

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

183

Reduced Volume Prototype Spacesuit Water Membrane Evaporator; A Next-Generation Evaporative Cooling System for the Advanced Extravehicular Mobility Unit Portable Life Support System  

NASA Technical Reports Server (NTRS)

Development of the Advanced Extravehicular Mobility Unit (AEMU) portable life support subsystem (PLSS) is currently under way at NASA Johnson Space Center. The AEMU PLSS features a new evaporative cooling system, the reduced volume prototype (RVP) spacesuit water membrane evaporator (SWME). The RVP SWME is the third generation of hollow fiber SWME hardware. Like its predecessors, RVP SWME provides nominal crew member and electronics cooling by flowing water through porous hollow fibers. Water vapor escapes through the hollow fiber pores, thereby cooling the liquid water that remains inside of the fibers. This cooled water is then recirculated to remove heat from the crew member and PLSS electronics. Major design improvements, including a 36% reduction in volume, reduced weight, and a more flight-like backpressure valve, facilitate the packaging of RVP SWME in the AEMU PLSS envelope. The development of these evaporative cooling systems will contribute to a more robust and comprehensive AEMU PLSS.

Makinen, Janice V.; Anchondo, Ian; Bue, Grant C.; Campbell, Colin; Colunga, Aaron

2013-01-01

184

The design and evaluation of a water delivery system for evaporative cooling of a proton exchange membrane fuel cell  

E-print Network

An investigation was performed to demonstrate system design for the delivery of water required for evaporative cooling of a proton exchange membrane fuel cell (PEMFC). The water delivery system uses spray nozzles capable of injecting water directly...

Al-Asad, Dawood Khaled Abdullah

2009-06-02

185

The impact of evaporation to the isotope composition of DIC in calcite precipitating water films in equilibrium and kinetic fractionation models  

NASA Astrophysics Data System (ADS)

To understand the effects of processes that influence the stable carbon and oxygen isotope ratios of DIC in a small planar water film, two model approaches have been developed in the past, a classical Rayleigh-approach and a kinetic model approach. Here we compare the effect of evaporation on the stable carbon and oxygen isotope ratios 13/12 and 18/16 of DIC, based on calculation with the two model approaches. For the Rayleigh-model, the isotope ratio increases, with increasing evaporation rate. For the kinetic-model the evolution of the isotope ratio, depends, in addition to the evaporation rate, on a fractionation parameter ? ? 1, which results from different equilibrium concentrations with respect to calcite for the heavy and light isotopes in the DIC. In dependence on the evaporation rate, the isotope ratio increases faster, with increasing evaporation rate and reaches a maximum. After the maximum is reached it converges to an equilibrium isotope ratio, which is determined by ?. Both models results indicate, that the effect of evaporation on the stable carbon and oxygen isotope composition can be neglected for relative humidities greater than 85% and wind velocities smaller than 0.2 m/s. Close to ventilated cave sites, however, where humidity can be low and high wind speeds are possible significant changes of the isotope signal may arise.

Dreybrodt, Wolfgang; Deininger, Michael

2014-01-01

186

Temperature dependence of the evaporation lengthscale for water confined between two hydrophobic plates.  

PubMed

Liquid water in a hydrophobic confinement is the object of high interest in physicochemical sciences. Confined between two macroscopic hydrophobic surfaces, liquid water transforms into vapor if the distance between surfaces is smaller than a critical separation, referred to as the evaporation lengthscale. To investigate the temperature dependence of the evaporation lengthscale of water confined between two hydrophobic parallel plates, we use the combination of the density functional theory (DFT) with the probabilistic hydrogen bond (PHB) model for water-water hydrogen bonding. The PHB model provides an analytic expression for the average number of hydrogen bonds per water molecule as a function of its distance to a hydrophobic surface and its curvature. Knowing this expression, one can implement the effect of hydrogen bonding between water molecules on their interaction with the hydrophobe into DFT, which is then employed to determine the distribution of water molecules between two macroscopic hydrophobic plates at various interplate distances and various temperatures. For water confined between hydrophobic plates, our results suggest the evaporation lengthscale to be of the order of several nanometers and a linearly increasing function of temperature from T=293K to T=333K, qualitatively consistent with previous results. PMID:25708521

Djikaev, Yuri S; Ruckenstein, Eli

2015-07-01

187

Finite-mass correction to 2D black-hole evaporation rate  

NASA Astrophysics Data System (ADS)

We numerically analyze the evolution of a two-dimensional dilatonic black hole, within the Callan-Giddings-Harvey-Strominger model. We focus our attention on the finite-mass corrections to the universal evaporation rate which applies at the large-mass limit. Our numerical results confirm a previous theoretical prediction for the first-order (?1/M) correction. In addition, our results strongly suggest that the next-order (?1/M2) term vanishes and provide a rough estimate for the third-order term.

Dori, Liora; Ori, Amos

2012-06-01

188

Urban Signatures: Evaporation (WMS)  

NSDL National Science Digital Library

Big cities influence the environment around them. For example, urban areas are typically warmer than their surroundings. Cities are strikingly visible in computer models that simulate the Earths land surface. This visualization shows evaporation rates predicted by the Land Information System (LIS) for a day in June 2001. Evaporation is lower in the cities because water tends to run off pavement and into drains, rather than being absorbed by soil and plants from which it later evaporates. Only part of the global computation is shown, focusing on the highly urbanized northeast corridor in the United States, including the cities of Boston, New York, Philadelphia, Baltimore, and Washington.

Jeff DeLaBeaujardiere

2005-05-27

189

Arsenic Speciation and Accumulation In Evapoconcentrating Waters Of Agricultural Evaporation Basins  

Technology Transfer Automated Retrieval System (TEKTRAN)

To sustain agricultural productivity, evaporation basins (or ponds) have been widely used for the disposal of agricultural drainage in areas requiring subsurface drainage in the San Joaquin Valley of California, USA. The drainage water contains elevated concentration of trace elements including sele...

190

Transformation Of Arsenic In Agricultural Drainage Water Disposed Into An Evaporation Basin In California, USA.  

Technology Transfer Automated Retrieval System (TEKTRAN)

Evaporation basins have been widely used for the disposal of agricultural drainage in areas requiring subsurface drainage in the San Joaquin Valley of California, a high agricultural production area in USA. The irrigation drainage water contains elevated concentrations of trace elements, including S...

191

Gas exchange in terrestrial environments comes at the cost of evaporative water loss from respiratory surfaces.  

E-print Network

3477 Gas exchange in terrestrial environments comes at the cost of evaporative water loss from of gas exchange, both within and among species (Lighton, 1998; Shelton and Appel, 2001; Chown, 2002). The classical pattern is that of discontinuous gas exchange, or discontinuous gas-exchange cycles (DGC; Lighton

Franz, Nico M.

192

A phylogenetic analysis of basal metabolism, total evaporative water loss, and life-history among foxes from desert and mesic regions  

Microsoft Academic Search

We measured basal metabolic rate (BMR) and total evaporative water loss (TEWL) of species of foxes that exist on the Arabian Peninsula, Blanford’s fox ( Vulpes cana) and two subspecies of Red fox ( Vulpes vulpes). Combining these data with that on other canids from the literature, we searched for specialization of physiological traits among desert foxes using both conventional

J. B. Williams; A. Muñoz-Garcia; S. Ostrowski; B. I. Tieleman

2004-01-01

193

Experimental study of evaporation of horizontal films of water-salt solutions  

NASA Astrophysics Data System (ADS)

The present studies were carried out for the horizontal films (thin layers) of water and water solutions of NaCl, CaCl2, LiCl, and LiBr with different solubility characteristics, as well as with specific features of formation and decay of water hydrates. Required volume of solution Vo of given weight concentration ?o, preliminary heated to the working surface temperature, was put in one step on the horizontal bottom of the bowl, heated to working temperature tCT, by means of volume batchers Thermo Scientific. After evaporation completion, the final mass of solution and form of their residue were registered. At the final stage of evaporation formation of NaCl crystals and water hydrates of CaCl2 · 2H2O, LiCl · H2O, and LiBr · 2H2O occurred.

Elistratov, S. L.; Morozov, V. S.

2015-01-01

194

Insight into the molecular mechanism of water evaporation via the finite temperature string method  

PubMed Central

The process of water's evaporation at its liquid/air interface has proven challenging to study experimentally and, because it constitutes a rare event on molecular time scales, presents a challenge for computer simulations as well. In this work, we simulated water's evaporation using the classical extended simple point charge model water model, and identified a minimum free energy path for this process in terms of 10 descriptive order parameters. The measured free energy change was 7.4 kcal/mol at 298 K, in reasonable agreement with the experimental value of 6.3 kcal/mol, and the mean first-passage time was 1375 ns for a single molecule, corresponding to an evaporation coefficient of 0.25. In the observed minimum free energy process, the water molecule diffuses to the surface, and tends to rotate so that its dipole and one O–H bond are oriented outward as it crosses the Gibbs dividing surface. As the water molecule moves further outward through the interfacial region, its local density is higher than the time-averaged density, indicating a local solvation shell that protrudes from the interface. The water molecule loses donor and acceptor hydrogen bonds, and then, with its dipole nearly normal to the interface, stops donating its remaining hydrogen bond. At that point, when the final, accepted hydrogen bond is broken, the water molecule is free. We also analyzed which order parameters are most important in the process and in reactive trajectories, and found that the relative orientation of water molecules near the evaporating molecule, and the number of accepted hydrogen bonds, were important variables in reactive trajectories and in kinetic descriptions of the process. PMID:23574252

Musolino, Nicholas; Trout, Bernhardt L.

2013-01-01

195

Complementary relationship of evaporation and the mean annual water-energy balance  

Microsoft Academic Search

By combining the complementary relationship of evaporation with the coupled long-term water-energy balance of Porporato et al. (2004) in a Budyko-type framework, one can, from atmospheric measurements alone, derive important ecosystem characteristics, such as the mean effective relative soil moisture and the maximum soil water storage, as well as predict changes in the rooting depth of vegetation as a response

Jozsef Szilagyi; Janos Jozsa

2009-01-01

196

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

PubMed

The Craig-Gordon model (C-G model) [H. Craig, L.I. Gordon. Deuterium and oxygen 18 variations in the ocean and the marine atmosphere. In Stable Isotopes in Oceanographic Studies and Paleotemperatures, E. Tongiorgi (Ed.), pp. 9-130, Laboratorio di Geologia Nucleare, Pisa (1965).] has been synonymous with the isotope effects associated with the evaporation of water from surface waters, soils, and vegetations, which in turn constitutes a critical component of the global water cycle. On the occasion of the four decades of its successful applications to isotope geochemistry and hydrology, an attempt is made to: (a) examine its physical background within the framework of modern evaporation models, (b) evaluate our current knowledge of the environmental parameters of the C-G model, and (c) comment on a general strategy for the use of these parameters in field applications. Despite its simplistic representation of evaporation processes at the water-air interface, the C-G model appears to be adequate to provide the isotopic composition of the evaporation flux. This is largely due to its nature for representing isotopic compositions (a ratio of two fluxes of different isotopic water molecules) under the same environmental conditions. Among many environmental parameters that are included in the C-G model, accurate description and calculations are still problematic of the kinetic isotope effects that occur in a diffusion-dominated thin layer of air next to the water-air interface. In field applications, it is of importance to accurately evaluate several environmental parameters, particularly the relative humidity and isotopic compositions of the 'free-atmosphere', for a system under investigation over a given time-scale of interest (e.g., hourly to daily to seasonally). With a growing interest in the studies of water cycles of different spatial and temporal scales, including paleoclimate and water resource studies, the importance and utility of the C-G model is also likely to grow in the future. PMID:18320426

Horita, Juske; Rozanski, Kazimierz; Cohen, Shabtai

2008-03-01

197

Effect of temperature and humidity on evaporative water loss in Anna's hummingbird ( Calypte anna )  

Microsoft Academic Search

Evaporative water loss (EWL), oxygen concumption \\u000a$$\\\\dot V_{O_2 } $$\\u000a, and body temperature (Tb) of Anna's Hummingbirds (Calypte anna; ca. 4.5g) were measured at combinations of ambient temperature (Ta) and water vapor density (?va) ranging from 20 to 37 °C and 2 to 27 g·m-3, respectively. The EWL decreased linearly with increasing ?va at all temperatures. The slopes of

Donald R. Powers

1992-01-01

198

Evaporation and wetting dynamics of sessile water droplets on submicron-scale patterned silicon hydrophobic surfaces  

SciTech Connect

The evaporation characteristics of 1 l sessile water droplets on hydrophobic surfaces are experimentally examined. The proposed hydrophobic surfaces are composed of submicron diameter and 4.2- m-height silicon post arrays. A digital image analysis algorithm was developed to obtain time-dependent contact angles, contact diameters, and center heights for both non-patterned polydimethylsiloxane (PDMS) surfaces and patterned post array surfaces, which have the same hydrophobic contact angles. While the contact angles exhibit three distinct stages during evaporation in the non-patterned surface case, those in the patterned silicon post array surface case decrease linearly. In the case of post array hydrophobic surfaces, the initial contact diameter remains unchanged until the portion of the droplet above the posts completely dries out. The edge shrinking velocity of the droplet shows nonlinear characteristics, and the velocity magnitude increases rapidly near the last stage of evaporation.

Choi, Chang Kyoung [Michigan Technological University; Shin, Dong Hwan [Chung-Ang University; Lee, Seong Hyuk [Chung-Ang University; Retterer, Scott T [ORNL

2010-01-01

199

Sex differences in the thermoregulation and evaporative water loss of a heterothermic bat, Lasiurus cinereus, during its spring migration.  

PubMed

This study quantifies sex differences in thermoregulation and water loss of a small (20-35 g) insectivorous heterothermic mammal, the hoary bat Lasiurus cinereus, during its spring migration. We measured body temperature, metabolic rate and evaporative water loss, and calculated wet thermal conductance, for bats exposed to air temperatures ranging from 0 to 40 degrees C for periods of 2-5 h. Pregnant females maintained normothermic body temperatures (35.7+/-0.7 degrees C; mean +/- S.E.M.) independent of air temperature. In contrast, males became torpid during the majority (68%) of exposures to air temperatures <25 degrees C. The thermal neutral zone (TNZ) ranged between approximately 30 degrees C and 34 degrees C in both sexes and, within the TNZ, females had lower mass-specific metabolic rates (6.1+/-0.2 mW g(-1)) than males (9.0+/-0.9 mW g(-1)). Wet thermal conductance values in torpid bats (0.7+/-0.5 mW g(-1) deg.(-1)) were lower than those of normothermic individuals (1.1+/-0.3 mW g(-1) deg.(-1)). Mass-specific rates of evaporative water loss in males were consistently higher than in females at most air temperatures and rates of water loss in torpid bats were 63+/-6% of normothermic values. These results suggest that male and pregnant female L. cinereus employ different thermoregulatory strategies during their spring migration. Females defend normothermic body temperatures, presumably to expedite embryonic growth, while males use torpor, presumably to minimize energy and water deficits. These variable thermoregulatory strategies may reflect continental differences in the summer distribution of the sexes. PMID:12939370

Cryan, Paul M; Wolf, Blair O

2003-10-01

200

Evaporative isotope enrichment as a constraint on reach water balance along a dryland river.  

PubMed

Deuterium and oxygen-18 enrichment in river water during its transit across dryland region is found to occur systematically along evaporation lines with slopes of close to 4 in (2)H-(18)O space, largely consistent with trends predicted by the Craig-Gordon model for an open-water dominated evaporating system. This, in combination with reach balance assessments and derived runoff ratios, strongly suggests that the enrichment signal and its variability in the Barwon-Darling river, Southeastern Australia is acquired during the process of evaporation from the river channel itself, as enhanced by the presence of abundant weirs, dams and other storages, rather than reflecting inherited enrichment signals from soil water evaporation in the watershed. Using a steady-state isotope mass balance analysis based on monthly (18)O and (2)H, we use the isotopic evolution of river water to re-construct a perspective of net exchange between the river and its contributing area along eight reaches of the river during a drought period from July 2002 to December 2003, including the duration of a minor flow event. The resulting scenario, which uses a combination of climatological averages and available real-time meteorological data, should be viewed as a preliminary test of the application rather than as a definitive inventory of reach water balance. As expected for a flood-driven dryland system, considerable temporal variability in exchange is predicted. While requiring additional real-time isotopic data for operational use, the method demonstrates potential as a non-invasive tool for detecting and quantifying water diversions, one that can be easily incorporated within existing water quality monitoring activities. PMID:18320430

Gibson, John J; Sadek, Mostafa A; Stone, D J M; Hughes, Catherine E; Hankin, S; Cendon, Dioni I; Hollins, Suzanne E

2008-03-01

201

Effects of crop residue on soil and plant water evaporation in a dryland cotton system  

NASA Astrophysics Data System (ADS)

Dryland agricultural cropping systems emphasize sustaining crop yields with limited use of fertilizer while conserving both rain water and the soil. Conservation of these resources may be achieved with management systems that retain residues at the soil surface simultaneously modifying both its energy and water balance. A conservation practice used with cotton grown on erodible soils of the Texas High Plains is to plant cotton into chemically terminated wheat residues. In this study, the partitioning of daily and seasonal evapotranspiration ( E t) into soil and plant water evaporation was compared for a conventional and a terminated-wheat cotton crop using the numerical model ENWATBAL. The model was configured to account for the effects of residue on the radiative fluxes and by introducing an additional resistance to latent and sensible heat fluxes derived from measurements of wind speed and vapor conductance from a soil covered with wheat-stubble. Our results showed that seasonal E t was similar in both systems and that cumulative soil water evaporation was 50% of E t in conventional cotton and 31% of E t in the wheat-stubble cotton. Calculated values of E t were in agreement with measured values. The main benefit of the wheat residues was to suppress soil water evaporation by intercepting irradiance early in the growing season when the crop leaf area index (LAI) was low. In semiarid regions LAI of dryland cotton seldom exceeds 2 and residues can improve water conservation. Measured soil temperatures showed that early in the season residues reduced temperature at 0.1 m depth by as much as 5°C and that differences between systems diminished with depth and over time. Residues increased lint yield per unit of E t while not modifying seasonal E t and reducing cumulative soil water evaporation.

Lascano, R. J.; Baumhardt, R. L.

1996-03-01

202

Study of environmental isotope distribution in the Aswan High Dam Lake (Egypt) for estimation of evaporation of lake water and its recharge to adjacent groundwater.  

PubMed

Oxygen-18 ((18)0) and deuterium isotopes were used to estimate the evaporation from the Aswan High Dam Lake and to investigate the inter-relation between the lake water and adjacent groundwater.According to stable isotopic analysis of samples taken in 1988 and 1989, the lake can be divided into two sections. In the first section extending between Abu Simbel and a point between EI-Alaki and Krosko, a remarkable vertical gradient of (18)0 and deuterium isotopic composition was observed. The second northern sector extending to the High Dam is characterised by a lower vertical isotopic gradient. In this sector in general, higher values of (18)O and deuterium contents were found at the top and lower values at the bottom. Also a strong horizontal increase of the heavy isotope content was observed. Thus, in the northern section evaporation is of dominating influence on the isotopic composition of the lake water.With the help of an evaporation pan experiment it was possible to calibrate the evaporative isotope enrichment in the lake and to facilitate a preliminary estimate of evaporative losses of lake water. The evaporation from the lake was estimated to be about 19% of the input water flow rate.The groundwater around the lake was investigated and samples from production wells and piezometers were subjected to isotopic analysis. The results indicate that recent recharge to the groundwater aquifer is limited to wells near to the lake and up to a maximum distance of about 10 km. The contribution of recent Nile water to the groundwater in these wells was estimated to range between 23 and 70%. Beyond this distance, palaeowater was observed with highly depleted deuterium and (18)0 contents, which was also confirmed by 14c dating. The age of palaeo groundwater in this area can reach values of more than 26,000 years.Recommendations are given for efficient water management of the lake water. PMID:24198080

Aly, A I; Froehlich, K; Nada, A; Awad, M; Hamza, M; Salem, W M

1993-03-01

203

Adaptation of metabolism and evaporative water loss along an aridity gradient.  

PubMed Central

Broad-scale comparisons of birds indicate the possibility of adaptive modification of basal metabolic rate (BMR) and total evaporative water loss (TEWL) in species from desert environments, but these might be confounded by phylogeny or phenotypic plasticity. This study relates variation in avian BMR and TEWL to a continuously varying measure of environment, aridity. We test the hypotheses that BMR and TEWL are reduced along an aridity gradient within the lark family (Alaudidae), and investigate the role of phylogenetic inertia. For 12 species of lark, BMR and TEWL decreased along a gradient of increasing aridity, a finding consistent with our proposals. We constructed a phylogeny for 22 species of lark based on sequences of two mitochondrial genes, and investigated whether phylogenetic affinity played a part in the correlation of phenotype and environment. A test for serial independence of the data for mass-corrected TEWL and aridity showed no influence of phylogeny on our findings. However, we did discover a significant phylogenetic effect in mass-corrected data for BMR, a result attributable to common phylogenetic history or to common ecological factors. A test of the relationship between BMR and aridity using phylogenetic independent constrasts was consistent with our previous analysis: BMR decreased with increasing aridity. PMID:12590762

Tieleman, B Irene; Williams, Joseph B; Bloomer, Paulette

2003-01-01

204

Tropical Ocean Evaporation/SST Sensitivity and It's Link to Water and Energy Budget Variations During ENSO  

NASA Technical Reports Server (NTRS)

The continuing debate over feedback mechanisms governing tropical sea surface temperatures (SSTs) and tropical climate in general has highlighted the diversity of potential checks and balances within the climate system. Competing feedbacks due to changes in surface evaporation, water vapor, and cloud long- and shortwave radiative properties each may serve critical roles in stabilizing or destabilizing the climate system. It is also intriguing that even those climate variations having origins internal to the climate system - changes in ocean heat transport for example, apparently require complementary equilibrating effects by changes in atmospheric energy fluxes. Perhaps the best observational evidence of this is the relatively invariant nature of tropically averaged net radiation exiting the top-of-atmosphere (TOA) as measured by broadband satellite sensors over the past two decades. Thus, analyzing how these feedback mechanisms are operating within the context of current interannual variability may offer considerable insight for anticipating future climate change. In this paper we focus primarily on interannual variations of ocean evaporative fluxes and their significance for coupled water and energy cycles within the tropical climate system. In particular, we use both the da Silva estimates of surface fluxes (based on the Comprehensive Ocean Atmosphere Data Set, COADS) and numerical simulations from several global climate models to examine evaporation sensitivity to perturbations in SST associated with warm and cold ENSO events. The specific questions we address are as follows: (1) What recurring patterns of surface wind and humidity anomalies are present during ENSO and how do they combine to yield systematic evaporation anomalies?, (2) What is the resulting tropical ocean mean evaporation-SST sensitivity associated with this climate perturbation?, and (3) What role does this evaporation play in tropical heat and water balance over tropical oceanic regions? We use the da Silva ocean flux data to identify composite structure of departures of latent heat flux from climatology. We also show how these patterns arise out of associated wind and humidity anomaly distributions. Our preliminary work shows that evaporation sensitivity estimates from the da Silva / COADS data, computed for the tropical oceans (30 degrees N/S) are in the neighborhood of 5 to 6 W/square m K. Model estimates are also quite close to this figure. This rate is only slightly less than a rate corresponding to constant relative humidity; however, substantial regional departures from constant relative humidity are present. These patterns are robust and we relate the associated wind and humidity fluctuations noted in previous investigations to the derived evaporation anomalies. Finally, these results are interpreted with other data from the Earth radiation Budget Experiment (ERBE), Global Precipitation Climatology Project (GPCP) and NASA's Surface Radiation Budget (SRB) data set to characterize the tropical energetics of ENSO-related climate variability.

Robertson, Franklin R.; Marshall, Susan; Oglesby, Robert; Roads, John; Sohn, Byung-Ju; Arnold, James E. (Technical Monitor)

2001-01-01

205

A hydraulic model is compatible with rapid changes in leaf elongation under fluctuating evaporative demand and soil water status.  

PubMed

Plants are constantly facing rapid changes in evaporative demand and soil water content, which affect their water status and growth. In apparent contradiction to a hydraulic hypothesis, leaf elongation rate (LER) declined in the morning and recovered upon soil rehydration considerably quicker than transpiration rate and leaf water potential (typical half-times of 30 min versus 1-2 h). The morning decline of LER began at very low light and transpiration and closely followed the stomatal opening of leaves receiving direct light, which represent a small fraction of leaf area. A simulation model in maize (Zea mays) suggests that these findings are still compatible with a hydraulic hypothesis. The small water flux linked to stomatal aperture would be sufficient to decrease water potentials of the xylem and growing tissues, thereby causing a rapid decline of simulated LER, while the simulated water potential of mature tissues declines more slowly due to a high hydraulic capacitance. The model also captured growth patterns in the evening or upon soil rehydration. Changes in plant hydraulic conductance partly counteracted those of transpiration. Root hydraulic conductivity increased continuously in the morning, consistent with the transcript abundance of Zea maize Plasma Membrane Intrinsic Protein aquaporins. Transgenic lines underproducing abscisic acid, with lower hydraulic conductivity and higher stomatal conductance, had a LER declining more rapidly than wild-type plants. Whole-genome transcriptome and phosphoproteome analyses suggested that the hydraulic processes proposed here might be associated with other rapidly occurring mechanisms. Overall, the mechanisms and model presented here may be an essential component of drought tolerance in naturally fluctuating evaporative demand and soil moisture. PMID:24420931

Caldeira, Cecilio F; Bosio, Mickael; Parent, Boris; Jeanguenin, Linda; Chaumont, François; Tardieu, François

2014-04-01

206

Improvement to Air2Air Technology to Reduce Fresh-Water Evaporative Cooling Loss at Coal-Based Thermoelectric Power Plants  

SciTech Connect

This program was undertaken to enhance the manufacturability, constructability, and cost of the Air2Air{TM} Water Conservation and Plume Abatement Cooling Tower, giving a validated cost basis and capability. Air2Air{TM} water conservation technology recovers a portion of the traditional cooling tower evaporate. The Condensing Module provides an air-to-air heat exchanger above the wet fill media, extracting the heat from the hot saturated moist air leaving in the cooling tower and condensing water. The rate of evaporate water recovery is typically 10% - 25% annually, depending on the cooling tower location (climate). This program improved the efficiency and cost of the Air2Air{TM} Water Conservation Cooling Tower capability, and led to the first commercial sale of the product, as described.

Ken Mortensen

2011-12-31

207

Sensitivity of Hollow Fiber Spacesuit Water Membrane Evaporator Systems to Potable Water Constituents, Contaminants and Air Bubbles  

NASA Technical Reports Server (NTRS)

The Spacesuit Water Membrane Evaporator (SWME) is the baseline heat rejection technology selected for development for the Constellation lunar suit. The first SWME prototype, designed, built, and tested at Johnson Space Center in 1999 used a Teflon hydrophobic porous membrane sheet shaped into an annulus to provide cooling to the coolant loop through water evaporation to the vacuum of space. This present study describes the test methodology and planning and compares the test performance of three commercially available hollow fiber materials as alternatives to the sheet membrane prototype for SWME, in particular, a porous hydrophobic polypropylene, and two variants that employ ion exchange through non-porous hydrophilic modified Nafion. Contamination tests will be performed to probe for sensitivities of the candidate SWME elements to ordinary constituents that are expected to be found in the potable water provided by the vehicle, the target feedwater source. Some of the impurities in potable water are volatile, such as the organics, while others, such as the metals and inorganic ions are nonvolatile. The non-volatile constituents will concentrate in the SWME as evaporated water from the loop is replaced by the feedwater. At some point in the SWME mission lifecycle as the concentrations of the non-volatiles increase, the solubility limits of one or more of the constituents may be reached. The resulting presence of precipitate in the coolant water may begin to plug pores and tube channels and affect the SWME performance. Sensitivity to macroparticles, lunar dust simulant, and air bubbles will also be investigated.

Bue, Grant C.; Trevino, Luis A.; Fritts, Sharon; Tsioulos, Gus

2008-01-01

208

An improved film evaporation correlation for saline water at sub-atmospheric pressures  

NASA Astrophysics Data System (ADS)

This paper presents an investigation of heat transfer correlation in a falling-film evaporator working with saline water at sub-atmospheric pressures. The experiments are conducted at different salinity levels ranging from 15000 to 90000 ppm, and the pressures were maintained between 0.92 to 2.81 kPa (corresponds to saturation temperatures of 5.9 - 23 0C). The effect of salinity, saturation pressures and chilled water temperatures on the heat transfer coefficient are accounted in the modified film evaporation correlations. The results are fitted to the Han & Fletcher's and Chun & Seban's falling-film correlations which are used in desalination industry. We modify the said correlations by adding salinity and saturation temperature corrections with respective indices to give a better agreement to our measured data.

Shahzada, Muhammad Wakil; Ng, Kim Choon; Thu, Kyaw; Myat, Aung; Gee, Chun Won

2012-06-01

209

Physiological regulation of evaporative water loss in endotherms: is the little red kaluta (Dasykaluta rosamondae) an exception or the rule?  

PubMed

It is a central paradigm of comparative physiology that the effect of humidity on evaporative water loss (EWL) is determined for most mammals and birds, in and below thermoneutrality, essentially by physics and is not under physiological regulation. Fick's law predicts that EWL should be inversely proportional to ambient relative humidity (RH) and linearly proportional to the water vapour pressure deficit (?wvp) between animal and air. However, we show here for a small dasyurid marsupial, the little kaluta (Dasykaluta rosamondae), that EWL is essentially independent of RH (and ?wvp) at low RH (as are metabolic rate and thermal conductance). These results suggest regulation of a constant EWL independent of RH, a hitherto unappreciated capacity of endothermic vertebrates. Independence of EWL from RH conserves water and heat at low RH, and avoids physiological adjustments to changes in evaporative heat loss such as thermoregulation. Re-evaluation of previously published data for mammals and birds suggests that a lesser dependence of EWL on RH is observed more commonly than previously thought, suggesting that physiological independence of EWL of RH is not just an unusual capacity of a few species, such as the little kaluta, but a more general capability of many mammals and birds. PMID:24741015

Withers, Philip C; Cooper, Christine E

2014-06-01

210

Burned and unburned peat water repellency: Implications for peatland evaporation following wildfire  

NASA Astrophysics Data System (ADS)

Water repellency alters soil hydrology after periods of wildfire, potentially modifying the ecosystem recovery to such disturbance. Despite this potential importance, the extent and severity of water repellency within burned peatlands and its importance in regulating peatland recovery to wildfire disturbance remains poorly understood. We characterised the water repellency of peat in a burned (one year post-fire) and unburned peatland in the Western Boreal Plain utilising the water drop penetration time and ethanol droplet molarity tests. Burned Sphagnum moss and feather moss sites had a more severe degree of water repellency than unburned sites, with differences being more pronounced between burned and unburned feather moss sites. Burned feather moss exhibited the most extreme water repellency, followed by unburned feather moss, and burned Sphagnum. The severity of water repellency varied with depth through the near surface of the moss/peat profile. This was most evident within the burned feathermoss where more extreme water repellency was observed at the near-surface compared to the surface, with the most extreme water repellency found at 1 and 5 cm depths. Unburned Sphagnum was completely hydrophilic at all depths. We suggest that the extreme water repellency in near-surface feather moss peat acts as a barrier that impedes the supply of water to the surface that replaces that lost via evaporation. This leads to drying of the near-surface vadose zone within feather moss areas and a concomitantly large decrease in peatland evaporation within feather moss dominated peatlands. This negative feedback mechanism likely enhances the resilience of such peatland to wildfire disturbance, maintaining a high water table position, thereby limiting peat decomposition. In comparison, such a feedback is not observed strongly within Sphagnum, leaving Sphagnum dominated peatlands potentially vulnerable to low water table positions post disturbance.

Kettridge, N.; Humphrey, R. E.; Smith, J. E.; Lukenbach, M. C.; Devito, K. J.; Petrone, R. M.; Waddington, J. M.

2014-05-01

211

Rate Setting for Small Water Systems  

E-print Network

Knowing how to set the proper rate for water service is a challenge for small water systems. They must generate enough revenue to remain solvent, but offer affordable service. This publication describes the various types of rates and explains...

Dozier, Monty; Theodori, Gene L.; Jensen, Ricard

2007-03-28

212

Regional water balance trends and evaporation-transpiration partitioning from a stable isotope survey of lakes in northern Canada  

Microsoft Academic Search

Regional variations in evaporation losses and water budget are interpreted from systematic isotopic patterns in surface waters across a 275,000 km2 region of northern Canada. Differential heavy isotope enrichment in a set of >255 nonheadwater lakes sampled by floatplane during 1993 and 1994 is strongly correlated to varying hydroclimatic conditions across the region. Calculated catchment-weighted evaporation losses typically range from

J. J. Gibson; T. W. D. Edwards

2002-01-01

213

Effects of viscosity, surface tension, and evaporation rate of solvent on dry colloidal structures: A lattice Boltzmann study  

NASA Astrophysics Data System (ADS)

Understanding the mechanisms of how colloidal solution properties and drying processes result in dry colloidal structures is essential for industrial applications such as paint, ceramics, and electrodes. In this study, we develop a computational method to simulate the drying process of colloidal suspensions containing solid particles and polymers. The method consists of a solvent evaporation model, a fluid particle dynamics method, and a two-phase lattice Boltzmann method. We determine that a high-viscosity solvent, small surface tension, and a high evaporation rate of the solvent lead to a structure with dispersed particles and interconnected pores. When these conditions are not present, the particles agglomerate and the pores are disconnected.

Munekata, Toshihisa; Suzuki, Takahisa; Yamakawa, Shunsuke; Asahi, Ryoji

2013-11-01

214

Hollow Fiber Space Suit Water Membrane Evaporator Development for Lunar Missions  

NASA Technical Reports Server (NTRS)

The Space Suit Water Membrane Evaporator (SWME) is the baseline heat rejection technology selected for development for the Constellation lunar suit. The Hollow Fiber (HoFi) SWME is being considered for service in the Constellation Space Suit Element (CSSE) Portable Life Support Subsystem (PLSS) to provide cooling to the thermal loop through water evaporation to the vacuum of space. Previous work described the test methodology and planning to compare the test performance of three commercially available hollow fiber materials as alternatives to the sheet membrane prototype for SWME: 1) porous hydrophobic polypropylene, 2) porous hydrophobic polysulfone, and 3) ion exchange through nonporous hydrophilic modified Nafion. Contamination tests were performed to probe for sensitivities of the candidate SWME elements to organics and non-volative inorganics expected to be found in the target feedwater source, i.e., potable water provided by the vehicle. The resulting presence of precipitate in the coolant water could plug pores and tube channels and affect the SWME performance. From this prior work, a commercial porous hydrophobic hollow fiber was selected to satisfy both the sensitivity question and the need to provide 800 W of heat rejection. This paper describes the trade studies, the design methodology, and the hollow fiber test data used to design a full

Bue, Grant C.; Trevino, Luis A.; Hanford, Anthony J.; Mitchell, Keith

2009-01-01

215

Evaporation of water at the level of bronchial and alveolar structures  

SciTech Connect

The authors' goal in this paper is to investigate the role of the bronchi and alveoli in the evaporation of water by the lungs. The authors sought to determine whether the most distal segments of the respiratory tract, the alveoli, are involved in the mass exchange of water. In order to determine the quantity of water evaporated by the lungs, the exhaled air was cooled to 0/sup 0/C. The amount of condensate was determined gravimetrically during a 15-minute interval. Added to the perfusate was 1 cm/sup 3/ tritiated water of 4 x 10/sup 6/ Bq total activity; as a result of dilution, the activity of the perfusate comprised 0.5 x 10/sup 4/ Bq/cm/sup 3/. The radioactivity of the perfusate and condensate was determined by liquid scintillation radiometry on an RZhB-3-01 apparatus. The lungs were ventilated with atmospheric air or a dry gas mixture of 80% nitrogen and 20% oxygen.

Belyakov, N.A.; Serikov, V.B.; Gevirts, V.B.

1986-03-01

216

Coupled water and heat flow in laboratory evaporation experiments and its effects on soil hydraulic properties estimated by the simplified evaporation method  

NASA Astrophysics Data System (ADS)

The prediction of water fluxes in the field requires an accurate determination of soil hydraulic parameters which define the soil water retention and hydraulic conductivity function. The evaporation method has become a standard tool to quickly and reliably determine soil hydraulic properties in the wet to medium pressure head range. Recently, the method has profited from a significant improvement of soil sensors and data evaluation methods. In most cases, the data obtained from a transient evaporation experiment are evaluated using simplifying assumptions, like the ones implicit to Schindler's or Wind's methods. In the past, the effect of these simplifications on the identification of hydraulic properties has been investigated and found to be relatively minor. These studies were based on the evaluation of computer-generated data which were created by numerical modeling of the evaporation process with the Richards equation, i.e. by assuming isothermal liquid flow. Since evaporation from bare soil will always lead to loss of energy, the assumption of constant temperature is questionable. In addition, the effects of thermal and vapor fluxes on simplified evaluation methods have so far hardly been investigated. In this contribution we analyze the effects of (1) coupled heat and water flow and (2) temperature effects on physical parameters. We firstly generated data by a numerical model which solves the coupled heat and water flow problem first derived by Philip and de Vries, and then used these data as source for the estimation of hydraulic properties with the evaluation methods of Schindler and Wind. The virtual realities covered different atmospheric forcings like changing wind speed and varying incoming shortwave radiation. The objective of this study was to identify under which atmospheric conditions, for which soil textures, and in which pressure head range the simplified evaluation methods lead to unbiased estimates of the soil hydraulic properties.

Iden, Sascha C.; Blöcher, Johanna; Diamantopoulos, Efstathios; Durner, Wolfgang

2014-05-01

217

Effects of heating method and conditions on the evaporation rate and quality attributes of black mulberry (Morus nigra) juice concentrate.  

PubMed

Black mulberry juice was concentrated by different heating methods, including conventional heating and microwave heating, at different operational pressures (7.3, 38.5 and 100 kPa). The effects of each method on evaporation rate, quality attributes of concentrated juice were investigated. The final juice concentration of 42° Brix was achieved in 140, 120, and 95 min at 100, 38.5, and 7.3 kPa respectively by using a rotary evaporator. Applying microwave energy decreased required times to 115, 95, and 60 min. The changes in color, anthocyanin content during the concentration processes were investigated. Hunter parameters (L, a, and b) were measured to estimate the intensity of color loss. All Hunter color parameters decreased with time. Results showed that the degradation of color and consequently anthocyanins, was more pronounced in rotary evaporation compared to microwave heating method. PMID:24425885

Fazaeli, Mahboubeh; Hojjatpanah, Ghazale; Emam-Djomeh, Zahra

2013-02-01

218

A comparison of two techniques for measuring the relative rates of moisture evaporation from limited areas of the skin of Holstein, Jersey and Jersey-Brahman cattle  

E-print Network

gusbgf, groe4, age end 4ato of last salving of test aahaals ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 18 Average evaporation, respiration end pulse rates, rental aad skin tosperscuresl and aoeuaaalatlon of chlorides of breed-age groups fran Nsy 31... ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 31 gffesc of the lengths of tine antuals e?aice4 tesCing for evaporation rates . . . . . . . . . . . . . , . . . . . 34 sveraga races of evaporation in the three breo4 groups during periods ?hen neon daily tenpors- turos Nolo 'bole?snd above 80 9...

Motasem, Mohamed M

1964-01-01

219

Water evaporation versus condensation in a hygroscopic soil A.L. Lozano, F. Cherblanc, J.-C. Benet  

E-print Network

such as water resources management or hazardous waste re- moval, the liquid/vapour phase change is a central phenomenon. It controls the liquid water avail- ability for agriculture in arid regions and rulesWater evaporation versus condensation in a hygroscopic soil A.L. Lozano, F. Cherblanc, J.-C. B

Paris-Sud XI, Université de

220

Effects of Carbonyl Bond and Metal Cluster Dissociation and Evaporation Rates on Predictions of Nanotube Production in HiPco  

NASA Technical Reports Server (NTRS)

The high-pressure carbon monoxide (HiPco) process for producing single-wall carbon nanotubes (SWNT) uses iron pentacarbonyl as the source of iron for catalyzing the Boudouard reaction. Attempts using nickel tetracarbonyl led to no production of SWNTs. This paper discusses simulations at a constant condition of 1300 K and 30 atm in which the chemical rate equations are solved for different reaction schemes. A lumped cluster model is developed to limit the number of species in the models, yet it includes fairly large clusters. Reaction rate coefficients in these schemes are based on bond energies of iron and nickel species and on estimates of chemical rates for formation of SWNTs. SWNT growth is measured by the co-formation of CO2. It is shown that the production of CO2 is significantly greater for FeCO due to its lower bond energy as compared with that ofNiCO. It is also shown that the dissociation and evaporation rates of atoms from small metal clusters have a significant effect on CO2 production. A high rate of evaporation leads to a smaller number of metal clusters available to catalyze the Boudouard reaction. This suggests that if CO reacts with metal clusters and removes atoms from them by forming MeCO, this has the effect of enhancing the evaporation rate and reducing SWNT production. The study also investigates some other reactions in the model that have a less dramatic influence.

Scott, Carl D.; Smalley, Richard E.

2002-01-01

221

Testing of Commercial Hollow Fiber Membranes for Space Suit Water Membrane Evaporator  

NASA Technical Reports Server (NTRS)

Three commercial-off-the-shelf (COTS) hollow fiber (HoFi) membrane evaporators, modified for low pressure, were tested in a vacuum chamber at pressures below 33 pascals as potential space suit water membrane evaporator (SWME) heat rejection technologies. Water quality was controlled in a series of 25 tests, first simulating potable water reclaimed from waste water and then changing periodically to simulate the ever concentrating make-up of the circulating coolant over that is predicted over the course of 100 EVAs. Two of the systems, comprised of non-porous tubes with hydrophilic molecular channels as the water vapor transport mechanism, were severely impacted by the increasing concentrations of cations in the water. One of the systems, based on hydrophobic porous polypropylene tubes was not affected by the degrading water quality, or the presence of microbes. The polypropylene system, called SWME 1, was selected for further testing. An inverse flow configuration was also tested with SWME 1, with vacuum exposure on the inside of the tubes, provided only 20% of the performance of the standard configuration. SWME 1 was also modified to block 50% and 90% of the central tube layers, and tested to investigate performance efficiency. Performance curves were also developed in back-pressure regulation tests, and revealed important design considerations arising from the fully closed valve. SWME 1 was shown to be insensitive to air bubbles injected into the coolant loop. Development and testing of a full-scale prototype based on this technology and these test results is in progress.

Bue, Grant C.; Trevino, Luis; Tsioulos, Gus; Hanford, Anthony

2009-01-01

222

Characteristic of Local Boiling Heat Transfer of Ammonia / Water Binary Mixture on the Plate Type Evaporator  

NASA Astrophysics Data System (ADS)

Ocean thermal energy conversion (OTEC) and discharged thermal energy conversion (DTEC) are expected to be the next generation energy production systems. Both systems use a plate type evaporator, and ammonia or ammonia/water mixture as a working fluid. It is important to clarify heat transfer characteristic for designing efficient power generation systems. Measurements of local boiling heat transfer coefficients and visualization were performed for ammonia /water mixture (z = 0.9) on a vertical flat plate heat exchanger in a range of mass flux (7.5 - 15 kg/m2s), heat flux (15 - 23 kW/m2), and pressure (0.7 - 0.9 MPa). The result shows that in the case of ammonia /water mixture, the local heat transfer coefficients increase with an increase of vapor quality and mass flux, and decrease with an increase of heat flux, and the influence of the flow pattern on the local heat transfer coefficient is observed.

Okamoto, Akio; Arima, Hirofumi; Kim, Jeong-Hun; Akiyama, Hirokuni; Ikegami, Yasuyuki; Monde, Masanori

223

Development of a preprototype thermoelectric integrated membrane evaporation subsystem for water recovery  

NASA Technical Reports Server (NTRS)

A three-man urine water recovery preprototype subsystem using a new concept to provide efficient potable water recovery from waste fluids on extended duration space flights has been designed, fabricated, and tested. Low power, compactness, and gravity insensitive operation are featured in this vacuum distillation subsystem that combines a hollow fiber polysulfone membrane evaporator with a thermoelectric heat pump. Application and integration of these key elements have solved problems inherent in previous reclamation subsystem designs. The hollow fiber elements provide positive liquid/gas phase control with no moving parts other than a waste liquid recirculation pump and a product water withdrawal pump. Tubular membranes provide structural integrity, improving on previous flat sheet membrane designs. A thermoelectric heat pump provides latent energy recovery.

Winkler, H. E.; Roebelen, G. J., Jr.

1980-01-01

224

Comparison of Experimental and Model Data for the Evaporation of a Synthetic Topopah Spring Tuff Pore Water, Yucca Mountain, NV  

SciTech Connect

The evaporation of a range of synthetic pore water solutions representative of the potential high-level-nuclear-waste repository at Yucca Mountain, NV is being investigated. The motivation of this work is to understand and predict the range of brine compositions that may contact the waste containers from evaporation of pore waters, because these brines could form corrosive thin films on the containers and impact their long-term integrity. A relatively complex synthetic Topopah Spring Tuff pore water was progressively concentrated by evaporation in a closed vessel, heated to 95 C in a series of sequential experiments. Periodic samples of the evaporating solution were taken to determine the evolving water chemistry. According to chemical divide theory at 25 C and 95 C our starting solution should evolve towards a high pH carbonate brine. Results at 95 C show that this solution evolves towards a complex brine that contains about 99 mol% Na{sup +} for the cations, and 71 mol% Cl{sup -}, 18 mol% {Sigma}CO{sub 2}(aq), 9 mol% SO{sub 4}{sup 2-} for the anions. Initial modeling of the evaporating solution indicates precipitation of aragonite, halite, silica, sulfate and fluoride phases. The experiments have been used to benchmark the use of the EQ3/6 geochemical code in predicting the evolution of carbonate-rich brines during evaporation.

Alai, M; Sutton, M; Carroll, S

2003-10-14

225

A New Approach to Measure Contact Angle and Evaporation Rate with Flow Visualization in a Sessile Drop  

NASA Technical Reports Server (NTRS)

The contact angle and the spreading process of sessile droplet are very crucial in many technological processes, such as painting and coating, material processing, film-cooling applications, lubrication, and boiling. Additionally, as it is well known that the surface free energy of polymers cannot be directly, measured for their elastic and viscous restraints. The measurements of liquid contact angle on the polymer surfaces become extremely important to evaluate the surface free energy of polymers through indirect methods linked with the contact angle data. Due to the occurrence of liquid evaporation is inevitable, the effects of evaporation on the contact angle and the spreading become very important for more complete understanding of these processes. It is of interest to note that evaporation can induce Marangoni-Benard convection in sessile drops. However, the impacts of the inside convection on the wetting and spreading processes are not clear. The experimental methods used by previous investigators cannot simultaneously measure the spreading process and visualize the convection inside. Based on the laser shadowgraphic system used by the present author, a very simple optical procedure has been developed to measure the contact angle, the spreading speed, the evaporation rate, and to visualize inside convection of a sessile drop simultaneously. Two CCD cameras were used to synchronously record the real-time diameter of the sessile drop, which is essential for determination of both spreading speed and evaporation rate, and the shadowgraphic image magnified by the sessile drop acting as a thin plano-convex lens. From the shadowgraph, the inside convection of the drop can be observed if any and the image outer diameter, which linked to the drop profile, can be measured. Simple equations have been derived to calculate the drop profile, including the instantaneous contact angle, height, and volume of the sessile drop, as well as the evaporation rate. The influence of the inside convection on the wetting and spreading processes can be figured out through comparison of the drop profiles with and without inside convection when the sessile drop is placed at different evaporation conditions.

Zhang, Nengli; Chao, David F.

1999-01-01

226

Estimating increased evaporation losses caused by irrigated agriculture as part of the water balance of the Orari Catchment, Canterbury, New Zealand  

E-print Network

1 Estimating increased evaporation losses caused by irrigated agriculture as part of the water: Irrigated-agriculture, evaporation, water cycle, agriticulture-intensification #12;3 Introduction Water, and that there will be growing demands for water for irrigated agriculture (Doak, 2005; MAF, 2004; Parliamentary Commissioner

Kienzle, Stefan W.

227

Water accounting and vulnerability evaluation (WAVE): considering atmospheric evaporation recycling and the risk of freshwater depletion in water footprinting.  

PubMed

Aiming to enhance the analysis of water consumption and resulting consequences along the supply chain of products, the water accounting and vulnerability evaluation (WAVE) model is introduced. On the accounting level, atmospheric evaporation recycling within drainage basins is considered for the first time, which can reduce water consumption volumes by up to 32%. Rather than predicting impacts, WAVE analyzes the vulnerability of basins to freshwater depletion. Based on local blue water scarcity, the water depletion index (WDI) denotes the risk that water consumption can lead to depletion of freshwater resources. Water scarcity is determined by relating annual water consumption to availability in more than 11,000 basins. Additionally, WDI accounts for the presence of lakes and aquifers which have been neglected in water scarcity assessments so far. By setting WDI to the highest value in (semi)arid basins, absolute freshwater shortage is taken into account in addition to relative scarcity. This avoids mathematical artifacts of previous indicators which turn zero in deserts if consumption is zero. As illustrated in a case study of biofuels, WAVE can help to interpret volumetric water footprint figures and, thus, promotes a sustainable use of global freshwater resources. PMID:24660893

Berger, Markus; van der Ent, Ruud; Eisner, Stephanie; Bach, Vanessa; Finkbeiner, Matthias

2014-04-15

228

Inhibiting ventilatory evaporation produces an adaptive increase in cutaneous evaporation in mourning doves Zenaida macroura.  

PubMed

We tested the hypothesis that birds can rapidly change the conductance of water vapor at the skin surface in response to a changing need for evaporative heat loss. Mourning doves (Zenaida macroura) were placed in a two-compartment chamber separating the head from the rest of the body. The rate of cutaneous evaporation was measured in response to dry ventilatory inflow at three ambient temperatures and in response to vapor-saturated ventilatory inflow at two ambient temperatures. At 35 degrees C, cutaneous evaporation increased by 72 % when evaporative water loss from the mouth was prevented, but no increase was observed at 45 degrees C. For both dry and vapor-saturated treatments, cutaneous evaporation increased significantly with increased ambient temperature. Changes in skin temperature made only a minor contribution to any observed increase in cutaneous evaporation. This indicates that Z. macroura can effect rapid adjustment of evaporative conductance at the skin in response to acute change in thermoregulatory demand. PMID:10518483

Hoffman; Walsberg

1999-01-01

229

Mixed evaporative and meteoric water dolomitization: isotope study of the Zechstein Limestone (Upper Permian), southwestern Poland  

NASA Astrophysics Data System (ADS)

Dolomites of the Zechstein Limestone in western Poland have high 13C values, characteristic of the Zechstein carbonates, and there is some variation in 18O profiles. Dolomites are mostly stoichiometric and well ordered and are characterized by variable crystal textures. The area studied underwent constant burial since the Late Permian and the isotopic curves, despite their complexity, show distinct regularities and signals of meteoric water input that in most cases could occur only during the Permian. Moldic porosity, interpreted as originated shortly after dolomitization, commonly occurs. Stratigraphic patterns and facies analyses suggest that dolomitization phases occurred at the top of each (eustatically controlled) subcycle of the Zechstein Limestone in association to subaerial exposures. Most of the dolomites, therefore, originated during the Permian. A significant proportion of the dolomites originated via meteoric—marine mixing during deposition of the Zechstein Limestone. The mixing mechanism was closely related to sea-level falls. Conventionally, evaporite-related dolomites are believed to have originated in a sabkha environment and/or by the reflux mechanism. The Zechstein Limestone case suggests that the mixing of evaporative and meteoric water may be responsible for dolomitization of other evaporate-related carbonates.

Magaritz, Mordeckai; Tadeusz Marek, Peryt

1994-09-01

230

Modeling Equity for Alternative Water Rate Structures  

NASA Astrophysics Data System (ADS)

The rising popularity of increasing block rates for urban water runs counter to mainstream economic recommendations, yet decision makers in rate design forums are attracted to the notion of higher prices for larger users. Among economists, it is widely appreciated that uniform rates have stronger efficiency properties than increasing block rates, especially when volumetric prices incorporate intrinsic water value. Yet, except for regions where water market purchases have forced urban authorities to include water value in water rates, economic arguments have weakly penetrated policy. In this presentation, recent evidence will be reviewed regarding long term trends in urban rate structures while observing economic principles pertaining to these choices. The main objective is to investigate the equity of increasing block rates as contrasted to uniform rates for a representative city. Using data from four Texas cities, household water demand is established as a function of marginal price, income, weather, number of residents, and property characteristics. Two alternative rate proposals are designed on the basis of recent experiences for both water and wastewater rates. After specifying a reasonable number (~200) of diverse households populating the city and parameterizing each household's characteristics, every household's consumption selections are simulated for twelve months. This procedure is repeated for both rate systems. Monthly water and wastewater bills are also computed for each household. Most importantly, while balancing the budget of the city utility we compute the effect of switching rate structures on the welfares of households of differing types. Some of the empirical findings are as follows. Under conditions of absent water scarcity, households of opposing characters such as low versus high income do not have strong preferences regarding rate structure selection. This changes as water scarcity rises and as water's opportunity costs are allowed to influence uniform rates. The welfare results of these exercises indicate that popular conceptions about increasing block rates may be incorrect insofar as the scarcity-endogenous uniform rate favors low-income households. That is, under scarcity conditions a switch from increasing block rates to full price uniform rates redistributes welfare so as to place more of the welfare burden of conservation on high-income households. Similarly, any household characteristic that tends to accompany low water use (e.g. low property value) generates a the same rate structure preference. These results are an intriguing addition to existing knowledge pertaining to the properties of increasing block rates and uniform rates with respect to criteria such as efficiency, simplicity, effectiveness, and (now) equity.

Griffin, R.; Mjelde, J.

2011-12-01

231

Hollow Fiber Space Water Membrane Evaporator Flight Prototype Design and Testing  

NASA Technical Reports Server (NTRS)

The spacesuit water membrane evaporator (SWME) is being developed to perform thermal control for advanced spacesuits and to take advantage of recent advances in micropore membrane technology. This results in a robust heat-rejection device that is potentially less sensitive to contamination than is the sublimator. The current design was based on a previous design that grouped the fiber layers into stacks, which were separated by small spaces and packaged into a cylindrical shape. This was developed into a full-scale prototype consisting of 14,300 tube bundled into 30 stacks, each of which is formed into a chevron shape and separated by spacers and organized into three sectors of 10 nested stacks. The new design replaced metal components with plastic ones, eliminated the spacers, and has a custom built flight like backpressure valve mounted on the side of the SWME housing to reduce backpressure when fully open. A number of tests were performed in order to improve the strength of the polyurethane header that holds the fibers in place while the system is pressurized. Vacuum chamber testing showed similar heat rejection as a function of inlet water temperature and water vapor backpressure was similar to the previous design. Other tests pushed the limits of tolerance to freezing and showed suitability to reject heat in a Mars pressure environment with and without a sweep gas. Tolerance to contamination by constituents expected to be found in potable water produced by distillation processes was tested in a conventional way by allowing constituents to accumulate in the coolant as evaporation occurs. For this purpose, the SWME cartridge has endured an equivalent of 30 EVAs exposure and demonstrated acceptable performance decline.

Bue, Grant C.; Makinen, Janice; Vogel, Mtthew; Honas, Matt; Dillon, Paul; Colunga, Aaron; Truong, Lily; Porwitz, Darwin; Tsioulos, Gus

2011-01-01

232

Hollow Fiber Flight Prototype Spacesuit Water Membrane Evaporator Design and Testing  

NASA Technical Reports Server (NTRS)

The spacesuit water membrane evaporator (SWME) is being developed to perform thermal control for advanced spacesuits and to take advantage of recent advances in micropore membrane technology. This results in a robust heat-rejection device that is potentially less sensitive to contamination than is the sublimator. The Membrana Celgard X50-215 microporous hollow-fiber (HoFi) membrane was selected after recent extensive testing as the most suitable candidate among commercial alternatives for continued SWME prototype development. The current design was based on a previous design that grouped the fiber layers into stacks, which were separated by small spaces and packaged into a cylindrical shape. This was developed into a full-scale prototype consisting of 14,300 tube bundled into 30 stacks, each of which is formed into a chevron shape and separated by spacers and organized into three sectors of 10 nested stacks. The new design replaced metal components with plastic ones, and has a custom built flight like backpressure valve mounted on the side of the SWME housing to reduce backpressure when fully open. The spacers that provided separation of the chevron fiber stacks were eliminated. Vacuum chamber testing showed improved heat rejection as a function of inlet water temperature and water vapor backpressure compared with the previous design. Other tests pushed the limits of tolerance to freezing and showed suitability to reject heat in a Mars pressure environment with and without a sweep gas. Tolerance to contamination by constituents expected to be found in potable water produced by distillation processes was tested in a conventional way by allowing constituents to accumulate in the coolant as evaporation occurs. For this purpose, the SWME cartridge has endured an equivalent of 30 EVAs exposure and demonstrated minimal performance decline.

Bue, Grant; Vogel, Matt; Makinen, Janice; Tsioulos, Gus

2010-01-01

233

Preliminary evaluation of the performance, water use, and current application trends of evaporative coolers in California climates  

SciTech Connect

This paper describes the latest results of an ongoing analysis investigating the potential for evaporative cooling as an energy-efficient alternative to standard air-conditioning in California residences. In particular, the study uses detailed numerical models of evaporative coolers linked with the DOE-2 building energy simulation program to study the issues of indoor comfort, energy and peak demand savings with and without supplemental air-conditioning and consumptive water use. In addition, limited surveys are used to assess the current market availability of evaporative cooling in California, typical contractor practices and costs, and general acceptance of the technology among engineers, contractors, and manufacturers. The results show that evaporative coolers can provide significant energy and peak demand savings in California residences, but the impact of the increased indoor humidity on human comfort remains an unanswered question that requires further research and clarification. Evaluated against ASHRAE comfort standards developed primarily for air-conditioning both direct and two-stage evaporative coolers would not maintain comfort at peak cooling conditions due to excessive humidity. However, using bioclimatic charts that place human comfort at the 80% relative humidity line, the study suggests that direct evaporative coolers will work in mild coastal climates, while two-stage models should provide adequate comfort in Title 24 houses throughout California, except in the Imperial Valley. The study also shows that evaporative coolers will increase household water consumption by less than 6% on an annual basis, and as much as 23% during peak cooling months, and that the increases in water cost are minimal compared to the electricity savings. Lastly, a survey of engineers and contractors revealed generally positive experiences with evaporative coolers, with operational cost savings, improved comfort, unproved air quality as the primary benefits in their use.

Huang, Y.J.; Hanford, J.W.; Wu, H.F.

1992-09-01

234

The dependence of bulk evaporation coefficients on air-water interfacial conditions as determined by the isotopic method  

Microsoft Academic Search

The analysis of the natural distribution of deuterium and oxygen 18 in moisture inside the turbulent boundary layer developed above a water surface makes possible the investigation of the mechanism of evaporation. The distribution of isotopes in water vapor allows the calculation of the relative contributions of molecular and turbulent transfer to the total mass transport (Merlivat and Coantic, 1975).

Liliane Merlivat

1978-01-01

235

Cutaneous water evaporation--II. Survival of birds under extreme thermal stress.  

PubMed

Two birds, the pigeon (Columba livia) and the partridge (Alectoris chukar), differing in their habits and flight ability were compared with regard to their ability to survive extreme high air temperatures (Ta's). During 270 min survival tests birds were exposed to Ta's between 45 and 60 degrees C and low relative humidities. The pigeon was observed to be unique in its ability to survive 270 min of exposure to 60 degrees C while regulating Tb at 43.8 degrees C. The partridge could not survive 270 min of exposure at Ta's exceeding 48 degrees C. The pigeons were found to be exceptional in their capacity for cutaneous evaporation. Values as high as 20.9 mg H2O/cm-2/hr were measured at 52 degrees C Ta compared to 2.4 mg H2O/cm-2/hr in the partridge. Total evaporation of the pigeon exposed to 56 degrees C Ta was about 20% higher than that in the partridge. Maximum evaporation of the pigeon exposed to 60 degrees C Ta was 34.4 mg H2O/g/hr. The significance of cutaneous water loss for survival during extreme high Ta's is discussed. It is concluded that birds as a class may be divided into two groups with regard to their physiological capacity to withstand heat stress: (1) the majority of studied species employ regular physiological mechanisms and are limited in their cooling capacity to withstand ambient temperatures 48 degrees C; (2) a few avian species, which may be of wide ecological distribution, are equipped with major physiological preadaptations to severe heat stress. PMID:6136379

Marder, J

1983-01-01

236

Performance of a Water Recirculation Loop Maintenance Device and Process for the Advanced Spacesuit Water Membrane Evaporator  

NASA Technical Reports Server (NTRS)

A water loop maintenance device and process to maintain the water quality of the Advanced Spacesuit Water Membrane Evaporation (SWME) water recirculation loop has been undergoing a performance evaluation. The SWME is a heat rejection device under development at the NASA Johnson Space Center to perform thermal control for advanced spacesuits. One advantage to this technology is the potential for a significantly greater degree of tolerance to contamination when compared to the existing Sublimator technology. The driver for the water recirculation maintenance device and process is to further enhance this advantage through the leveraging of fluid loop management lessons-learned from the International Space Station (ISS). A bed design that was developed for a Hamilton Sundstrand military application, and considered for a potential ISS application with the Urine Processor Assembly, provides a low pressure drop means for water maintenance in a recirculation loop. The bed design is coupled with high capacity ion exchange resins, organic adsorbents, and a cyclic methodology developed for the Extravehicular Mobility Unit (EMU) Transport Water loop. The maintenance process further leverages a sorbent developed for ISS that introduces a biocide in a microgravity-compatible manner for the Internal Active Thermal Control System (IATCS). The leveraging of these water maintenance technologies to the SWME recirculation loop is a unique demonstration of applying the valuable lessons learned on the ISS to the next generation of manned spaceflight Environmental Control and Life Support System (ECLSS) hardware. This

Rector, Tony; Steele, John W.; Bue, Grant C.; Campbell, Colin; Makinen, Janice

2012-01-01

237

Correlation between shape, evaporation mode and mobility of small water droplets on nanorough fibres.  

PubMed

The dynamic wetting behaviour and the mobility of droplets on fibres is a very important factor in coating processes, textile fabrication, in self-cleaning processes and in the filtration of fluids. In principal, filter regeneration depends on the mobility of the droplets on the fibre surface. Mobile droplets tend to coalesce which greatly simplifies their removal from the filter. In this contribution mobility analyses of water droplets on monofilaments in air are performed. Studies of droplet evaporation on pure PET fibres and on nanorough fibres coated with SiO2 nanoparticles of diameters between 6 nm and 50 nm in a hydrophilic binder system were done. We show that the mobility of water droplets correlates with the droplet conformation which in turn is determined by the droplet-fibre interface. We demonstrate that fibre coatings can be used to tailor the conformation and mobility of water droplets. The smaller the nanoparticle diameters in the coating are, the smaller are the contact angles between water droplets and fibre and the better is the mobility of the droplets on the fibre. Our results allow a fast optimization of the fibre surface properties which are directly influencing the contact angle, the mobility and the coalescence of water droplets and thus filter regeneration. PMID:24407674

Funk, C S; Winzer, B; Peukert, W

2014-03-01

238

Stable isotope fingerprint of open-water evaporation losses and effective drainage area fluctuations in a subarctic shield watershed  

NASA Astrophysics Data System (ADS)

SummaryStable isotopes of water, oxygen-18 and deuterium, were measured at biweekly to monthly intervals during the open-water season in a small, headwater lake (Pocket Lake, 4.8 ha) near Yellowknife Northwest Territories, and concurrently in a nearby string-of-lakes watershed (Baker Creek, 137 km 2) situated in the subarctic Precambrian Shield region. As measured in water samples collected over a 12 year period (1997-2008), the levels of evaporative isotopic enrichment in both lake and watershed outflow were differentially offset, and seasonal variations were found in both to be driven by variations in open-water evaporation. Systematic differences measured in the magnitude of the offset between the lake and watershed outflow are interpreted as being caused by changes in the effective drainage area contributing to runoff. Based on the observed and extremely consistent relationship between isotopic compositions of lake water and watershed outflow ( r2 = 0.849, p < 0.001) we extend the analysis of open-water evaporation losses and effective drainage areas back to 1991 when less-frequent water sampling at the sites commenced. This 18-year record serves to demonstrate for the first time the expected variability in the evaporation and transpiration partitioning, upper limits on the effective drainage area, and isotopic signals transferred downstream in a typical shield drainage system within the Mackenzie Basin.

Gibson, J. J.; Reid, R.

2010-02-01

239

Full-Scale Hollow Fiber Spacesuit Water Membrane Evaporator Prototype Development and Testing for Advanced Spacesuits  

NASA Technical Reports Server (NTRS)

The spacesuit water membrane evaporator (SWME) is being developed to perform the thermal control function for advanced spacesuits to take advantage of recent advances in micropore membrane technology in providing a robust heat-rejection device that is potentially less sensitive to contamination than is the sublimator. Principles of a sheet membrane SWME design were demonstrated using a prototypic test article that was tested in a vacuum chamber at JSC in July 1999. The Membrana Celgard X50-215 microporous hollow fiber (HoFi) membrane was selected after recent contamination tests as the superior candidate among commercial alternatives for HoFi SWME prototype development. Although a number of design variants were considered, one that grouped the fiber layers into stacks, which were separated by small spaces and packaged into a cylindrical shape, was deemed best for further development. An analysis of test data showed that eight layer stacks of the HoFi sheets that had good exposure on each side of the stack would evaporate water with high efficiency. A design that has 15,000 tubes, with 18 cm of exposed tubes between headers has been built and tested that meets the size, weight, and performance requirements of the SWME. This full-scale prototype consists of 30 stacks, each of which are formed into a chevron shape and separated by spacers and organized into three sectors of ten nested stacks. Testing has been performed to show contamination resistance to the constituents expected to be found in potable water produced by the distillation processes. Other tests showed the sensitivity to surfactants.

Bue, Grant; Trevino, Luis; Tsioulos, Gus; Mitchell, Keith; Dillon, Paul; Weaver, Gregg

2009-01-01

240

Evaporative Concentration of 100x J13 Ground Water at 60% Relative Humidity and 90C  

SciTech Connect

In these experiments we studied the behavior of a synthetic concentrated J13 solution as it comes in contact with a Ni-Cr-Mo-alloy selected for waste canisters in the designated high-level nuclear-waste repository at Yucca Mountain, Nevada. Concentrated synthetic J13 solution was allowed to drip slowly onto heated test specimens (90 C, 60% relative humidity) where the water moved down the surface of the specimens, evaporated and minerals precipitated. Mineral separation or zoning along the evaporation path was not observed. We infer from solid analyses and geochemical modeling, that the most corrosive components (Ca, Mg, and F) are limited by mineral precipitation. Minerals identified by x-ray diffraction include thermonatrite, natrite, and trona, all sodium carbonate minerals, as well as kogarkoite (Na{sub 3}SO{sub 4}F), halite (NaCl), and niter (KNO{sub 3}). Calcite and a magnesium silicate precipitation are based on chemical analyses of the solids and geochemical modeling. The most significant finding of this study is that sulfate and fluoride concentrations are controlled by the solubility of kogarkoite. Kogarkoite thermodynamic data are needed in the Yucca Mountain Project database to predict the corrosiveness of carbonate brines and to establish the extent to which fluoride is removed from the brines as a solid.

Staggs, K; Maureen Alai,; Hailey, P; Carroll, S A; Sutton, M; Nguyen, Q A

2003-12-04

241

Magnetic resonance imaging of slow water flow during infiltration and evaporation by tracer motion  

NASA Astrophysics Data System (ADS)

Water fluxes in soils control many processes in the environment like plant nutrition, solute and pollutant transport. In the last two decades non-invasive visualization methods have been adapted to monitor flux processes on the small scale. Magnetic resonance imaging (MRI), also well known from medical diagnostics, is one of the most versatile ones. It mostly probes directly the substance of interest: water, and it offers many opportunities to manipulate the observed signals for creating different contrasts and thus probing different properties of the porous medium and the embedded fluids. For example, one can make the signal sensitive to the total proton density, i. e. water content, to spatial distributions of relaxation times which reflect pore sizes, to spatial distributions of transport coefficients, and to concentration of contrast agents by using strongly T1 weighted MRI pulse sequences. In this presentation we use GdDTPA2- for monitoring flux processes in soil columns in an ultra-wide bore MRI scanner. It offers the opportunity for monitoring slow water fluxes mainly occurring in soil systems which are not monitorable with direct MRI flow imaging. This contrast agent is most convenient since it behaves conservatively, i.e. it does not sorb at different soil materials and it is chemically stable. Firstly, we show that its mode of action in natural porous media is identical to that known from medical applications as proved by the identical relaxivity parameters [1]. Secondly, the tracer is applied for the visualization of flux processes during evaporation-driven flow. Theoretical considerations by forward simulation predicted a lateral redistribution of solutes during evaporative upward fluxes from highly conductive fine material to neighbouring domains with low water content and conductivity. Here we could prove that such near-surface redistribution really takes place [2]. Thirdly, this tracer is applied for the investigation of water uptake by root systems. Depending on the transpiration conditions slow uptake in the dark is present, where the tracer moves directly into the xylem. When fully illuminated, the tracer uptake is limited by the Caspari band, and it is enriched strongly in the roots cortex. The results so far show that this tracer offers a new window for monitoring slow water fluxes in bare and grown soil columns. [1] Haber-Pohlmeier S, Bechtold M, Stapf, S, Pohlmeier, A. (2010) Vadose Zone Journal 9, 835-845 [2] Bechtold M, Haber-Pohlmeier S, Vanderborght J, Pohlmeier A, Ferré T, Vereecken H. (2011) Geophysical Research Letters 38, L17404

Pohlmeier, A.; Haber-Pohlmeier, S.; Bechtold, M.; Vanderborght, J.; Vereecken, H.

2012-04-01

242

On the evaporation of ammonium sulfate solution  

PubMed Central

Aqueous evaporation and condensation kinetics are poorly understood, and uncertainties in their rates affect predictions of cloud behavior and therefore climate. We measured the cooling rate of 3 M ammonium sulfate droplets undergoing free evaporation via Raman thermometry. Analysis of the measurements yields a value of 0.58 ± 0.05 for the evaporation coefficient, identical to that previously determined for pure water. These results imply that subsaturated aqueous ammonium sulfate, which is the most abundant inorganic component of atmospheric aerosol, does not affect the vapor–liquid exchange mechanism for cloud droplets, despite reducing the saturation vapor pressure of water significantly. PMID:19861551

Drisdell, Walter S.; Saykally, Richard J.; Cohen, Ronald C.

2009-01-01

243

On the evaporation of ammonium sulfate solution  

SciTech Connect

Aqueous evaporation and condensation kinetics are poorly understood, and uncertainties in their rates affect predictions of cloud behavior and therefore climate. We measured the cooling rate of 3 M ammonium sulfate droplets undergoing free evaporation via Raman thermometry. Analysis of the measurements yields a value of 0.58 {+-} 0.05 for the evaporation coefficient, identical to that previously determined for pure water. These results imply that subsaturated aqueous ammonium sulfate, which is the most abundant inorganic component of atmospheric aerosol, does not affect the vapor-liquid exchange mechanism for cloud droplets, despite reducing the saturation vapor pressure of water significantly.

Drisdell, Walter S.; Saykally, Richard J.; Cohen, Ronald C.

2009-07-16

244

Analysis of Water Recovery Rate from the Heat Melt Compactor  

NASA Technical Reports Server (NTRS)

Human space missions generate trash with a substantial amount of plastic (20% or greater by mass). The trash also contains water trapped in food residue and paper products and other trash items. The Heat Melt Compactor (HMC) under development by NASA Ames Research Center (ARC) compresses the waste, dries it to recover water and melts the plastic to encapsulate the compressed trash. The resulting waste disk or puck represents an approximately ten-fold reduction in the volume of the initial trash loaded into the HMC. In the current design concept being pursued, the trash is compressed by a piston after it is loaded into the trash chamber. The piston face, the side walls of the waste processing chamber and the end surface in contact with the waste can be heated to evaporate the water and to melt the plastic. Water is recovered by the HMC in two phases. The first is a pre-process compaction without heat or with the heaters initially turned on but before the waste heats up. Tests have shown that during this step some liquid water may be expelled from the chamber. This water is believed to be free water (i.e., not bound with or absorbed in other waste constituents) that is present in the trash. This phase is herein termed Phase A of the water recovery process. During HMC operations, it is desired that liquid water recovery in Phase A be eliminated or minimized so that water-vapor processing equipment (e.g., condensers) downstream of the HMC are not fouled by liquid water and its constituents (i.e., suspended or dissolved matter) exiting the HMC. The primary water recovery process takes place next where the trash is further compacted while the heated surfaces reach their set temperatures for this step. This step will be referred to herein as Phase B of the water recovery process. During this step the waste chamber may be exposed to different selected pressures such as ambient, low pressure (e.g., 0.2 atm), or vacuum. The objective for this step is to remove both bound and any remaining free water in the trash by evaporation. The temperature settings of the heated surfaces are usually kept above the saturation temperature of water but below the melting temperature of the plastic in the waste during this step to avoid any encapsulation of wet trash which would reduce the amount of recovered water by blocking the vapor escape. In this paper, we analyze the water recovery rate during Phase B where the trash is heated and water leaves the waste chamber as vapor, for operation of the HMC in reduced gravity. We pursue a quasi-one-dimensional model with and without sidewall heating to determine the water recovery rate and the trash drying time. The influences of the trash thermal properties, the amount of water loading, and the distribution of the water in the trash on the water recovery rates are determined.

Balasubramaniam, R.; Hegde, U.; Gokoglu, S.

2013-01-01

245

Design and Evaluation of a Water Recirculation Loop Maintenance Device for the Advanced Spacesuit Water Membrane Evaporator  

NASA Technical Reports Server (NTRS)

A dual-bed device to maintain the water quality of the Advanced Spacesuit Water Membrane Evaporation (SWME) water recirculation loop has been designed and is undergoing testing. The SWME is a heat rejection device under development at the NASA Johnson Space Center to perform thermal control for advanced spacesuits. One advantage to this technology is the potential for a significantly greater degree of tolerance to contamination when compared to the existing Sublimator technology. The driver for the development of a water recirculation maintenance device is to further enhance this advantage through the leveraging of fluid loop management lessons-learned from the International Space Station (ISS). A bed design that was developed for a Hamilton Sundstrand military application, and considered for a potential ISS application with the Urine Processor Assembly, provides a low pressure drop means for water maintenance in a recirculation loop. The bed design is coupled with high capacity ion exchange resins, organic adsorbents, and a cyclic methodology developed for the Extravehicular Mobility Unit (EMU) Transport Water loop. The bed design further leverages a sorbent developed for ISS that introduces a biocide in a microgravity-compatible manner for the Internal Active Thermal Control System (IATCS). The leveraging of these water maintenance technologies to the SWME recirculation loop is a clear demonstration of applying the valuable lessons learned on the ISS to the next generation of manned spaceflight Environmental Control and Life Support System (ECLSS) hardware.

Steele, John W.; Rector, Tony; Bue, Grant C.; Campbell, Colin; Makinen, Janice

2011-01-01

246

Effects of viscosity, surface tension, and evaporation rate of solvent on dry colloidal structures: a lattice Boltzmann study.  

PubMed

Understanding the mechanisms of how colloidal solution properties and drying processes result in dry colloidal structures is essential for industrial applications such as paint, ceramics, and electrodes. In this study, we develop a computational method to simulate the drying process of colloidal suspensions containing solid particles and polymers. The method consists of a solvent evaporation model, a fluid particle dynamics method, and a two-phase lattice Boltzmann method. We determine that a high-viscosity solvent, small surface tension, and a high evaporation rate of the solvent lead to a structure with dispersed particles and interconnected pores. When these conditions are not present, the particles agglomerate and the pores are disconnected. PMID:24329271

Munekata, Toshihisa; Suzuki, Takahisa; Yamakawa, Shunsuke; Asahi, Ryoji

2013-11-01

247

Hollow Fiber Spacesuit Water Membrane Evaporator Development and Testing for Advanced Spacesuits  

NASA Technical Reports Server (NTRS)

The spacesuit water membrane evaporator (SWME) is being developed to perform the thermal control function for advanced spacesuits to take advantage of recent advances in micropore membrane technology in providing a robust heat-rejection device that is potentially less sensitive to contamination than is the sublimator. Principles of a sheet membrane SWME design were demonstrated using a prototypic test article that was tested in a vacuum chamber at JSC in July 1999. The Membrana Celgard X50-215 microporous hollow fiber (HoFi) membrane was selected after recent contamination tests as the most suitable candidate among commercial alternatives for HoFi SWME prototype development. A design that grouped the fiber layers into stacks, which were separated by small spaces and packaged into a cylindrical shape, was developed into a full-scale prototype consisting 14,300 tube bundled into 30 stacks, each of which are formed into a chevron shape and separated by spacers and organized into three sectors of ten nested stacks. Vacuum chamber testing has been performed characterize heat rejection as a function of inlet water temperature and water vapor backpressure and to show contamination resistance to the constituents expected to be found in potable water produced by the distillation processes. Other tests showed the tolerance to freezing and suitability to reject heat in a Mars pressure environment.

Bue, Grant C.; Trevino, Luis A.; Tsioulos, Gus; Settles, Joseph; Colunga, Aaron; Vogel, Matthew; Vonau, Walt

2010-01-01

248

Evaporative tunnel cooling of dairy cows in the southeast. I: effect on body temperature and respiration rate.  

PubMed

The techniques used to mitigate the effects of heat stress on lactating dairy cows are often overwhelmed in the southeastern United States, where elevated heat and humidity often persist for extended periods. A model free-stall barn located at the North Mississippi Branch Experiment Station in Holly Springs was used to evaluate the potential of tunnel ventilation with evaporative cooling to alleviate heat stress in lactating dairy cows. Two studies were conducted using 2 groups of 10 lactating Holsteins housed in the tunnel barn (inside) and 2 groups of matched herdmates housed in an adjacent covered free-stall barn (outside), which was cooled by fans and sprinklers during 2001 or by shade and fans alone in 2003. Peak daytime temperatures inside were 5.2 +/- 0.18 degrees C below that outside in 2001 and 3.1 +/- 0.20 degrees C lower in 2003. Although evaporative cooling increased humidity by 22%, cows housed in the tunnel barn received 84% less exposure to moderate heat stress (temperature-humidity index > 80) in both years. Cooling cows with evaporative tunnel ventilation reduced respiration rates by 15.5 +/- 0.56 breaths/min and rectal temperatures by 0.6 +/- 0.02 degrees C compared with shade and fans alone in 2003. Cooling cows with evaporative tunnel ventilation reduced respiration rates by 13.1 +/- 0.78 breaths/min and rectal temperatures by 0.4 +/- 0.03 degrees C compared with fans and sprinklers in 2001. Thus, tunnel ventilation cooling dramatically reduced the exposure to heat stress and improved the comfort of lactating dairy cows when compared with traditional cooling technologies under the conditions present in the southeastern United States. PMID:16960066

Smith, T R; Chapa, A; Willard, S; Herndon, C; Williams, R J; Crouch, J; Riley, T; Pogue, D

2006-10-01

249

Evaluation of a Remotely Sensed Evaporative Stress Index for Monitoring Patterns of Anomalous Water Use  

NASA Astrophysics Data System (ADS)

Drought assessment is a complex endeavor, requiring monitoring of deficiencies in multiple components of the hydrologic budget. Precipitation anomalies reflect variability in water supply to the land surface, while soil moisture (SM), ground and surface water anomalies reflect deficiencies in moisture storage. In contrast, evapotranspiration (ET) anomalies provide unique yet complementary information, reflecting variations in actual water use by crops and direct evaporation from the soil. For example, precipitation- and ET-based anomalies may differ significantly in regions of intensive irrigation, shallow water table, or deep rooting depth - areas where plants may be more resilient to soil moisture deficiencies inferred from rainfall patterns. In addition, an ET-based index can better capture impacts of hot, windy conditions leading to "flash droughts", where anomalously high water use precipitates rapid decay in soil moisture and crop condition. Here we describe a remotely sensed Evaporative Stress Index (ESI) based on anomalies in actual-to-reference ET ratio, and compare with patterns in precipitation-based drought indicators. Actual ET is derived from thermal remote sensing, using the morning land-surface temperature (LST) rise observed with geostationary satellites. In comparison with vegetation indices, LST is a fast-response variable, with the potential for providing early warning of crop stress reflected in increasing canopy temperatures. Spatiotemporal patterns in ESI reasonably match those in precipitation-based indices (such as SPI and modeled SM) and patterns in the U.S. Drought Monitor. However, because ESI does not use precipitation as an input, it provides an independent assessment of evolving drought conditions, and is more portable to data-sparse parts of the world lacking dense rain-gauge and Doppler radar networks. Integrating LST information from polar orbiting systems, the ESI has unique potential for sensing moisture stress at field scale, benefiting yield estimation and loss compensation efforts. Techniques for identifying flash drought events will be demonstrated, as well as ESI performance over the heat-induced drought events of 2012. The ESI is routinely produced over the continental U.S. using data from GOES, with expansion to North and South America underway. In addition drought monitoring applications are being developed over Africa and Europe using Meteosat land-surface products.

Anderson, M. C.; Hain, C.; Otkin, J.; Zhan, X.

2012-12-01

250

Characterization and morphological analysis of a cholecystokinin derivative peptide-loaded poly(lactide-co-glycolide) microspheres prepared by a water-in-oil-in-water emulsion solvent evaporation method  

Microsoft Academic Search

The water soluble peptide, pBC 264, derived from cholecystokinin and composed of seven aminoacids was encapsulated in poly(lactide-co-glycolide) (PLG) microspheres prepared by a multiple emulsion [(W1\\/O)W2] solvent evaporation method. The encapsulation efficiency of pBC 264 was very low when the inner emulsion contained no stabilizing agent. However, the encapsulation rate was improved by the addition of ovalbumin (OVA) used as

Mar??a J Blanco-Pr??eto; Elias Fattal; Annette Gulik; Jean C Dedieu; Bernard P Roques; Patrick Couvreur

1997-01-01

251

Tried and True: Evaporating is cool  

NSDL National Science Digital Library

Many students hold misconceptions about evaporation. In this short exercise, students will apply the kinetic molecular theory to explain how cold water can evaporate and to observe the cooling effect of evaporation, and develop their own evaporation experiments.

Richard Hand

2006-03-01

252

Influence of pH, salinity, and selenium on the growth of Aeromonas veronii in evaporation agricultural drainage water  

Microsoft Academic Search

Aeromonas veronii was isolated from seleniferous agricultural drainage water and characterized in terms of growth kinetics under changing environmental parameters [i.e. pH, selenium (Se) and salinity (electrical conductivity, EC)] that simulated evaporation. Aeromonas veronii metabolized peptone and was active in volatilizing Se, principally as dimethyl selenide (DMSe). Other volatile products produced included dimethyl disulfide, methyl selenol, dimethyl selenosulfide and dimethyl

R. M. Rael; W. T. Frankenberger

1996-01-01

253

Cutaneous water evaporation--I. Its significance in heat-stressed birds.  

PubMed

In a comparative study on avian cutaneous evaporation, two species of Phasianidae, Japanese quail Coturnix coturnix japonica and chukar partridge Alectoris chukar, and three species of Columbidae, palm dove Streptopelia senegalensis, collared turtle dove Streptopelia decaocto and rock pigeon Columbia livia, were investigated. The skin resistance to vapor diffusion (rs) and cutaneous water loss (CWL) were studied in these birds exposed to air temperatures (Ta) between 20 and 52 degrees C. The skin resistance was measured with Lambda instrument diffusive resistance meter. Skin resistance within the thermo-neutral zone varied between a minimum of 62 sec/cm in the palm dove exposed to 20 degrees C and a maximum of 309.1 sec/cm in the partridge exposed to 36 degrees C. The CWL values were 2.5 mg H2O/cm2.hr and 0.51 mg H2O/cm2.hr respectively. Maximum CWL of the quail and partridge was 1.9-2.1 mg H2O/cm2.hr, equivalent to a cooling capacity of about 17% of metabolic heat production at 45 degrees C Ta. In the palm dove, collared dove and pigeon CWL reached 6.8, 13.1 and 20.9 mg H2O/cm2.hr and rs values reached 31.2, 16.2 and 9.4 sec/cm respectively. The cooling capacity amounted to 51.5, 86.1 and 96.5% of metabolic heat during heat stress (52 degrees C). The significance of skin evaporation in body temperature regulation of heat-stressed birds is discussed. PMID:6136378

Marder, J; Ben-Asher, J

1983-01-01

254

Condensation and evaporation behaviors of micro-water droplets on SUS304 steel observed using the ac noncontact mode of AFM  

Microsoft Academic Search

The condensation and evaporation behaviors of micro-water droplets on SUS304 steel were ex-situ and in-situ observed in ambient air with the ac noncontact mode of atomic force microscope. The change of water volumes and surface areas were introduced to characterize the condensation and evaporation processes.

Rongguang Wang; Mitsuo Kido

2003-01-01

255

Column-scale unsaturated hydraulic conductivity estimates in coarse-textured homogeneous and layered soils derived under steady-state evaporation from a water table  

NASA Astrophysics Data System (ADS)

Steady-state evaporation from a water table has been extensively studied for both homogeneous and layered porous media. For layered media it is of interest to find an equivalent homogeneous medium and define “effective” hydraulic properties. In this paper a new solution for steady-state evaporation from coarse-textured porous media is presented. Based on this solution, the evaporation rate represents a macroscopic (column-scale) measure of unsaturated hydraulic conductivity at the pressure head equal to the maximum extent of the hydraulically connected region above the water table. The presented approach offers an alternative method for determination of unsaturated hydraulic conductivity of homogeneous coarse-textured soils and a new solution for prediction of the effective unsaturated hydraulic conductivity of layered coarse-textured soils. The solution was evaluated with both experimental data and numerical simulations. Comparison with experimental data and numerical results for hypothetically layered soil profiles demonstrate the applicability of the proposed approach for coarse-textured soils.

Sadeghi, Morteza; Tuller, Markus; Gohardoust, Mohammad R.; Jones, Scott B.

2014-11-01

256

Stable isotope estimates of evaporation: inflow and water residence time for lakes across the United States as a tool for national lake water quality assessments  

EPA Science Inventory

Stable isotope ratios of water (delta18O and delta2H) can be very useful in large-scale monitoring programs because water samples are easy to collect and isotope ratios integrate information about basic hydrologic processes such as evaporation as a percentage of inflow (E/I) and ...

257

Separating soil evaporation and crop transpiration to improve crop water use efficiency  

NASA Astrophysics Data System (ADS)

A network of a FAO/IAEA Coordinated Research Project (CRP) on "Managing Irrigation Water to Enhance Crop Productivity under Water-Limiting Conditions: A Role for Isotopic Techniques", involving seven countries was implemented from 2007 to 2012, to identify approaches to improve crop water productivity (production per unit of water input) under water-limiting conditions using isotopic and related techniques. This paper presents findings from the two of the studied sites, one in China and another in Morocco, in using both isotopic and conventional techniques to separate soil evaporation (E) and crop transpiration (T) from total water losses in evapotranspiration (ET) for winter wheat grown under different climatic conditions and methods of irrigation management practices. In the North China Plain (NCP), the estimated E/ET of winter wheat by the isotopic method (Keeling plot using delta oxygen-18 (?18O)) was in agreement with that obtained by conventional methods (eddy covariance and micro-lysimeter). The high correlation between these methods (R2=0.85, n=27) showed that the E from wheat-growing field contributes an average of 30% of water losses for the whole growing season (Nov-June), with higher E percentage (68%) can be expected before elongation stage due to incomplete canopy cover. The results also showed that through deficit irrigation and improved irrigation scheduling, soil E losses could be reduced by 10-30% of the total water loss compared with full irrigation. In Morocco, field Keeling plot isotopic E and T separation study was carried out for two days in spring of 2012 at Sidi Rahal. The percentage contribution of T to total ET was approximately 73%. The experimental results obtained from both China and Moroccan sites were used to validate FAO's AquaCrop model for E and T, and for improving irrigation scheduling and agronomic practices. Good correlation (R2=0.83) was obtained between measured (isotopic) and AquaCrop simulated ET from NCP. The measured and simulated E and T results from Morocco also compared well; the difference in E between the two approaches was only 5-12% over the two-day study.

Heng, Lee; Nguyen, Long; Gong, Daozhi; Mei, Xurong; Amenzou, Noureddine

2014-05-01

258

NEG (non evaporable getter) pumps for organic compounds and water removal in EUVL tools  

NASA Astrophysics Data System (ADS)

One of present EUVL challenges is to reduce as much as possible the organic compounds and water partial pressures during the lithographic process. These gases can in fact interact with sensitive surfaces and, in the presence of EUV radiation, decompose to generate carbon-based films and oxides, which are detrimental to the optics, reducing its performance, lifetime and significantly increasing the equipment total cost of ownership. With this respect, use of Non Evaporable Getter (NEG) pumps seems particularly attractive. Getter pumps are very clean, vibration-free, compact, able to deliver large pumping speed for all active gases, including water and hydrogen. In the present paper, we report for the first time the results of specific tests aimed at measuring the pumping speed for some selected organic compounds, namely toluene and decane (n-decane). The study shows that getter pumps can effectively sorb these large organic molecules with high speed and capacity. Speed and capacity increases when operating the getter cartridge at moderate temperature (e.g. 150-200°C), however remarkable sorption is achieved, even at room temperature, without any power applied. When coupled with turbo-molecular pumps NEG pumps have therefore the potential to improve the ultimate vacuum and mitigate the carbon/oxygen contamination in a UHV lithographic system.

Conte, A.; Manini, P.; Raimondi, S.

2008-03-01

259

Open water evaporation estimation for a small shallow reservoir in winter using surface renewal  

NASA Astrophysics Data System (ADS)

SummaryEvaporation is one of the main components of the energy and water balance of reservoir water behind dams and is a major component of water loss. Measurements in winter of sensible heat ( H) for the small and shallow reservoir of Midmar Dam, KwaZulu-Natal, South Africa were made using the surface renewal (SR) method, a renewal model method that uses the average cubic air temperature structure function and eddy covariance (EC). The small magnitude of H during winter makes it difficult to test the reliability of the H estimates obtained using instruments and sensors mounted above the water surface using the SR, renewal model and EC methods. Latent energy flux was estimated as a residual of the energy balance using additional measurements of net irradiance R n above the water surface and the water-stored heat flux. The SR sensible heat flux ( HSR) was estimated for heights of 1.0, 1.3, 1.9 and 2.5 m above the water surface using two air temperature time lags r of 0.4 and 0.8 s of the 10-Hz measurements. The SR method depends on a weighting factor ? which represents the capability of the atmospheric turbulence to mix the scalar, within the air parcel to be renewed. The factor ? was determined for each measurement height and time lag from the slope of a linear regression relationship forced through the origin of measured EC sensible heat flux ( HEC) values on the y-axis vs.HSR or renewal model H on the x-axis. All ? values obtained using the renewal model method were not statistically different from that obtained using the SR method for z = 1.0 m for both time lags. Using a calibration dataset, an average ? value for the 1.0- and 1.3-m heights of 0.198 for r = 0.4 s and 0.245 for r = 0.8 s for the SR and renewal model methods was obtained. The 30-min HSR, renewal model and HEC estimates were often the smallest component of the energy balance (generally -40 to 40 W m -2) and compared reasonably well for the validation dataset. The heat storage flux G was larger in magnitude (0-200 W m -2) compared to the sensible heat flux. The SR, renewal model and EC latent energy fluxes, each calculated as residuals of the energy balance, were almost the same in magnitude as the available energy flux R n - G due to the relatively small magnitude of the sensible heat flux during the winter measurement period. The daily evaporation ranged between 1.0 and 3.9 mm.

Mengistu, M. G.; Savage, M. J.

2010-01-01

260

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

USGS Publications Warehouse

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.

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

2003-01-01

261

Flow Visualization in Evaporating Liquid Drops and Measurement of Dynamic Contact Angles and Spreading Rate  

NASA Technical Reports Server (NTRS)

A new hybrid optical system, consisting of reflection-refracted shadowgraphy and top-view photography, is used to visualize flow phenomena and simultaneously measure the spreading and instant dynamic contact angle in a volatile-liquid drop on a nontransparent substrate. Thermocapillary convection in the drop, induced by evaporation, and the drop real-time profile data are synchronously recorded by video recording systems. Experimental results obtained from this unique technique clearly reveal that thermocapillary convection strongly affects the spreading process and the characteristics of dynamic contact angle of the drop. Comprehensive information of a sessile drop, including the local contact angle along the periphery, the instability of the three-phase contact line, and the deformation of the drop shape is obtained and analyzed.

Zhang, Neng-Li; Chao, David F.

2001-01-01

262

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

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.

Harwell, Glenn R.

2012-01-01

263

Importance of rain evaporation and continental convection in the tropical water cycle  

Microsoft Academic Search

Atmospheric moisture cycling is an important aspect of the Earth's climate system, yet the processes determining atmospheric humidity are poorly understood. For example, direct evaporation of rain contributes significantly to the heat and moisture budgets of clouds, but few observations of these processes are available. Similarly, the relative contributions to atmospheric moisture over land from local evaporation and humidity from

John Worden; David Noone; Kevin Bowman; Reinhard Beer; Annmarie Eldering; Brendan Fisher; Michael Gunson; Aaron Goldman; Robert Herman; Susan S. Kulawik; Michael Lampel; Gregory Osterman; Curtis Rinsland; Clive Rodgers; Stanley Sander; Mark Shephard; Christopher R. Webster; Helen Worden

2007-01-01

264

TDR water content inverse profiling in layered soils during infiltration and evaporation  

NASA Astrophysics Data System (ADS)

During the last three decades, time domain reflectometry (TDR) has become one of the most commonly used tools for soil water content measurements either in laboratory or in the field. Indeed, TDR provides easy and cheap water content estimations with relatively small disturbance to the investigated soil. TDR measurements of soil water content are based on the strong correlation between relative dielectric permittivity of wet soil and its volumetric water content. Several expressions of the relationship between relative dielectric permittivity and volumetric water content have been proposed, empirically stated (Topp et al., 1980) as well as based on semi-analytical approach to dielectric mixing models (Roth et al., 1990; Whalley, 1993). So far, TDR field applications suffered the limitation due to the capability of the technique of estimating only the mean water content in the volume investigated by the probe. Whereas the knowledge of non homogeneous vertical water content profiles was needed, it was necessary to install either several vertical probes of different length or several horizontal probes placed in the soil at different depths, in both cases strongly increasing soil disturbance as well as the complexity of the measurements. Several studies have been recently dedicated to the development of inversion methods aimed to extract more information from TDR waveforms, in order to estimate non homogeneous moisture profiles along the axis of the metallic probe used for TDR measurements. A common feature of all these methods is that electromagnetic transient through the wet soil along the probe is mathematically modelled, assuming that the unknown soil water content distribution corresponds to the best agreement between simulated and measured waveforms. In some cases the soil is modelled as a series of small layers with different dielectric properties, and the waveform is obtained as the result of the superposition of multiple reflections arising from impedance discontinuities between the layers (Nguyen et al., 1997; Todoroff et al., 1998; Heimovaara, 2001; Moret et al., 2006). Other methods consider the dielectric properties of the soil as smoothly variable along probe axis (Greco, 1999; Oswald et al., 2003; Greco, 2006). Aim of the study is testing the applicability to layered soils of the inverse method for the estimation of water content profiles along vertical TDR waveguides, originally applied in laboratory to homogeneous soil samples with monotonic moisture distributions (Greco, 2006), and recently extended to field measurements with more general water content profiles (Greco and Guida, 2008). Influence of soil electrical conductivity, uniqueness of solution, choices of parametrization, parameters identifiabilty, sensitivity of the method to chosen parameters variations are discussed. Finally, the results of the application of the inverse method to a series of infiltration and evaporation experiments carried out in a flume filled with three soil layers of different physical characteristics are presented. ACKNOWLEDGEMENTS The research was co-financed by the Italian Ministry of University, by means of the PRIN 2006 PRIN program, within the research project entitled ‘Definition of critical rainfall thresholds for destructive landslides for civil protection purposes'. REFERENCES Greco, R., 1999. Measurement of water content profiles by single TDR experiments. In: Feyen, J., Wiyo, K. (Eds.), Modelling of Transport Processes in Soils. Wageningen Pers, Wageningen, the Netherlands, pp. 276-283. Greco, R., 2006. Soil water content inverse profiling from single TDR waveforms. J. Hydrol. 317, 325-339. Greco R., Guida A., 2008. Field measurements of topsoil moisture profiles by vertical TDR probes. J. Hydrol. 348, 442- 451. Heimovaara, T.J., 2001. Frequency domain modelling of TDR waveforms in order to obtain frequency dependent dielectric properties of soil samples: a theoretical approach. In: TDR 2001 - Second International Symposium on Time Domain Reflectometry for Innovative Geotechnical Applications. Northwestern Univer

Greco, R.; Guida, A.

2009-04-01

265

Eddy covariance measurements of surface energy budget and evaporation in a cool season over southern open water in Mississippi  

NASA Astrophysics Data System (ADS)

Eddy covariance measurements of sensible (H) and latent (LE) heat fluxes were made over a large southern open water surface of Ross Barnett Reservoir (the Reservoir hereafter) in Mississippi during the cool season with frequent incursions of cold fronts from 1 September 2007 to 31 January 2008. The eddy covariance tower was located in the middle of the main body of the Reservoir with the tower fetches exceeding 2.0 km in all directions. The Reservoir was ice-free in winter and the water temperatures always decreased with depth. Over the entire cool season, the averaged water surface temperatures were 1.8°C higher than the overlying air (i.e., positive temperature gradients that led to thermally convective conditions) and the averaged vapor pressure near the water surface was 0.8 kPa greater than the overlying air (i.e., positive vapor pressure gradients), though occasionally negative gradients for temperature and vapor pressure were also observed for short periods. On average, the wind speeds were considerably large (3.9 m s-1) to maintain adequate turbulent mixing mechanically. As a consequence of the combined effect of thermally and mechanically generated turbulent mixing, consistently positive H (with a mean H of 20.0 W m-2) and LE (with a mean LE of 80.0 W m-2) occurred during the entire season. These continuous energy losses via H and LE resulted in release of a large amount of energy stored in the water to the atmosphere. The mean Bowen ratio was low for this open water surface (i.e., 0.3), suggesting that most of the energy released from the water fueled evaporation rather than sensible heating of the atmosphere. Nighttime evaporative water losses were substantial, contributing to 45% of the total evaporative water loss in this cool season. Frequent incursions of cold fronts with windy, cold, and dry air masses significantly promoted turbulent exchanges of sensible and latent heat through enhanced turbulent mixing thermally and mechanically, leading to large H and LE events. Daily H and LE (i.e., evaporation) during the passages of cold fronts were on average 2.7 and 7.3 times those in nonevent days, respectively. Given the fact that large H and LE events occurred 26% of the time for our site, these cold front events caused an increase in the seasonal H by 42% and LE by 157%. Therefore changes in frequency, intensity, and duration of synoptic weather events, particularly the incursions of cold fronts, have significant impacts on the surface energy budget and evaporation over water at this site.

Liu, Heping; Zhang, Yu; Liu, Shuhua; Jiang, Haimei; Sheng, Li; Williams, Quinton L.

2009-02-01

266

Spacesuit Water Membrane Evaporator Integration with the ISS Extravehicular Mobility Unit  

NASA Technical Reports Server (NTRS)

NASA has developed a Solid Water Membrane Evaporation (SWME) to provide cooling for the next generation spacesuit. The current spacesuit team has looked at this technology from the standpoint of using the ISS EMU to demonstrate the SWME technology while EVA, and from the standpoint of augmenting EMU cooling in the case of a fouled EMU cooling system. One approach to increasing the TRL of the system is to incorporate this hardware with the existing EMU. Several integration issues were addressed to support a potential demonstration of the SWME with the existing EMU. Systems analysis was performed to assess the capability of the SWME to maintain crewmember cooling and comfort as a replacement for sublimation. The materials of the SWME were reviewed to address compatibility with the EMU. Conceptual system placement and integration with the EMU via an EVA umbilical system to ensure crew mobility and Airlock egress were performed. A concept of operation for EVA use was identified that is compatible with the existing system. This concept is extensible as a means to provide cooling for the existing EMU. The cooling system of one of the EMUs on orbit has degraded, with the root cause undetermined. Should there be a common cause resident on ISS, this integration could provide a means to recover cooling capability for EMUs on orbit.

Margiott, Victoria; Boyle, Robert

2014-01-01

267

Water holding capacity and evaporative loss from organic bedding materials used in livestock facilities  

Technology Transfer Automated Retrieval System (TEKTRAN)

Physical and chemical characteristics of organic bedding materials determine how well they will absorb and retain moisture and may influence the environment in livestock facilities where bedding is used. The objective of this study was to determine water holding capacity (WHC) and rate of evaporativ...

268

Evaporation Anisotropy of Forsterite  

NASA Astrophysics Data System (ADS)

Evaporation anisotropy of a synthetic single crystal of forsterite was investigated by high temperature vacuum experiments. The (001), (010), and (001) surfaces show microstructures characteristic for each surface. Obtained overall linear evaporation rates for the (001), (010), and (001) surfaces are ~17, ~7, and ~22 mm/hour, and the intrinsic evaporation rates, obtained by the change in surface microstructures, are ~10, ~4.5, and ~35 mm/hour, respectively. The difference between the intrinsic evaporation rates and overall rates can be regarded as contribution of dislocation, which is notable for the (100) and (010) surfaces and insignificant for the (001) surface. This is consistent with observed surface microstructures.

Ozawa, K.; Nagahara, H.; Morioka, M.

1996-03-01

269

[Effect of shifting sand burial on evaporation reduction and salt restraint under saline water irrigation in extremely arid region].  

PubMed

The Taklimakan Desert Highway Shelterbelt is drip-irrigated with high saline groundwater (2.58-29.70 g x L(-1)), and shifting sand burial and water-salt stress are most common and serious problems in this region. So it is of great importance to study the effect of shifting sand burial on soil moisture evaporation, salt accumulation and their distribution for water saving, salinity restraint, and suitable utilization of local land and water resources. In this study, Micro-Lysimeters (MLS) were used to investigate dynamics of soil moisture and salt under different thicknesses of sand burial (1, 2, 3, 4, and 5 cm), and field control experiments of drip-irrigation were also carried out to investigate soil moisture and salt distribution under different thicknesses of shifting sand burial (5, 10, 15, 20, 25, 30, 35, and 40 cm). The soil daily and cumulative evaporation decreased with the increase of sand burial thickness in MLS, cumulative evaporation decreased by 2.5%-13.7% compared with control. And evaporative inhibiting efficiency increased with sand burial thickness, evaporative inhibiting efficiency of 1-5 cm sand burial was 16.7%-79.0%. Final soil moisture content beneath the interface of sand burial increased with sand burial thickness, and it increased by 2.5%-13.7% than control. The topsoil EC of shifting sand in MLS decreased by 1.19-6.00 mS x cm(-1) with the increasing sand burial thickness, whereas soil salt content beneath the interface in MLS increased and amplitude of the topsoil salt content was higher than that of the subsoil. Under drip-irrigation with saline groundwater, average soil moisture beneath the interface of shifting sand burial increased by 0.4% -2.0% compare with control, and the highest value of EC was 7.77 mS x cm(-1) when the sand burial thickness was 10 cm. The trend of salt accumulation content at shifting sand surface increased firstly, and then decreased with the increasing sand burial thickness. Soil salt contents beneath the interface of shifting sand burial were much lower than that of shifting sand surface. 35 cm was the critical sand burial thickness for water-saving and salt restraint. In summary, sand burial had obvious inhibition effects on soil evaporation and salt accumulation, so maybe it could be used to save water and reduce salt accumulation in arid shifting desert areas. PMID:25129944

Zhang, Jian-Guo; Zhao, Ying; Xu, Xin-Wen; Lei, Jia-Qiang; Li, Sheng-Yu; Wang, Yong-Dong

2014-05-01

270

A Hydraulic Model Is Compatible with Rapid Changes in Leaf Elongation under Fluctuating Evaporative Demand and Soil Water Status1[C][W][OPEN  

PubMed Central

Plants are constantly facing rapid changes in evaporative demand and soil water content, which affect their water status and growth. In apparent contradiction to a hydraulic hypothesis, leaf elongation rate (LER) declined in the morning and recovered upon soil rehydration considerably quicker than transpiration rate and leaf water potential (typical half-times of 30 min versus 1–2 h). The morning decline of LER began at very low light and transpiration and closely followed the stomatal opening of leaves receiving direct light, which represent a small fraction of leaf area. A simulation model in maize (Zea mays) suggests that these findings are still compatible with a hydraulic hypothesis. The small water flux linked to stomatal aperture would be sufficient to decrease water potentials of the xylem and growing tissues, thereby causing a rapid decline of simulated LER, while the simulated water potential of mature tissues declines more slowly due to a high hydraulic capacitance. The model also captured growth patterns in the evening or upon soil rehydration. Changes in plant hydraulic conductance partly counteracted those of transpiration. Root hydraulic conductivity increased continuously in the morning, consistent with the transcript abundance of Zea maize Plasma Membrane Intrinsic Protein aquaporins. Transgenic lines underproducing abscisic acid, with lower hydraulic conductivity and higher stomatal conductance, had a LER declining more rapidly than wild-type plants. Whole-genome transcriptome and phosphoproteome analyses suggested that the hydraulic processes proposed here might be associated with other rapidly occurring mechanisms. Overall, the mechanisms and model presented here may be an essential component of drought tolerance in naturally fluctuating evaporative demand and soil moisture. PMID:24420931

Caldeira, Cecilio F.; Bosio, Mickael; Parent, Boris; Jeanguenin, Linda; Chaumont, François; Tardieu, François

2014-01-01

271

Numerical Investigation of Physicochemical Processes Occurring During Water Evaporation in the Surface Layer Pores of a Forest Combustible Material  

NASA Astrophysics Data System (ADS)

A numerical investigation of the physicochemical processes occurring during water evaporation from the pores of the surface layer of a forest combustible material has been carried out. The characteristic features of the suppression of the thermal decomposition reaction of a combustible material with water filling fullyits pores and formation of a water fi lm over its surface have been determined. The characteristic times of suppression of thermal decomposition reactions under various environmental conditions and the thickness and kinds of forest combustible material (birch leaves, pine and spruce needles, etc.) have been established.

Zhdanova, A. O.; Kuznetsov, G. V.; Strizhak, P. A.

2014-07-01

272

A simple, time-dependent formula for estimating evaporation rates in Texas  

E-print Network

), and the independent varIable, ambient air temperature (T, ). . . . . . . . . . . . . . . . The mean monthly probability of dry atmos- phere conditions (precipitable water & 1. 00 in) over San Antonio, Texas, after Haker $1969) . 41 44 47 15. The irtercept...

Trenchard, Michael Howard

1976-01-01

273

Characteristic lengths for evaporation suppression from patchy porous surfaces  

NASA Astrophysics Data System (ADS)

For non-uniformly wet porous surfaces, evaporation rates vary nonlinearly with mean surface water content and with the areal fraction of wet patches. The nonlinearity stems from the complex vapor field forming over individual pores and patches that could enhance vapor fluxes from pores surrounded by dry area (relative to fluxes from the same area of free water surface). The resulting evaporation rates from such a surface are similar to free water surface evaporation despite considerably lower evaporating area (low surface water content). Theoretically, such flux compensation could be suppressed by lumping isolated pores into clusters with equal mean water content. The resulting arrangement in wet patches ensures nearly 1D conditions within the patch and some flux enhancement at the periphery. The interplay between patch water content, patch size, and mean surface water content within a prescribed air flow boundary layer was modeled analytically using single pore diffusion as a building block. Results show existence of a characteristic cluster size that yields the largest evaporation suppression for a given boundary layer thickness and spacing between patches. For patches larger than this size, the relative evaporation rate from patchy surface (relative to free water surface evaporation) reaches a predictable rate equal to the fractional area of clusters. Model predictions for the relation between pore cluster size and evaporation suppression were evaluated numerically and in a series of wind tunnel experiments using porous surfaces with different pore clusters. The findings could be used for the design of optimal porous covers for suppressing evaporation losses from water reservoirs, or for controlling evaporative drying from engineered porous surfaces.

Lehmann, Peter; Or, Dani

2014-05-01

274

Dynamic evaporating evolution of profiles for micro droplets on flat surfaces with hydrophilic and hydrophobic treatments  

Microsoft Academic Search

We report the experimental and analysis results of evaporation rates for micro droplets deposited onto flat surfaces that exhibit various hydrophobic and hydrophilic properties. These droplets are pure water regularly used as solvents of evaporative liquid solutions, in which different solid solutes can form versatile microstructures for patterning after dried. Evaporation tests have demonstrated that these micro droplets show significantly

Kun-Ze Tu; Chin-Tai Chen

2011-01-01

275

An automated tunnel evaporation measurement system for confined spaces  

NASA Astrophysics Data System (ADS)

An automated tunnel evaporation-rate measurement system (TEMS) has been designed to measure automatically the evaporation from a cylinder 0·30 m in diameter and 0·10 m tall. This cylinder continuously maintains a constant height of water, with losses to evaporation replenished from a stilling cylinder connected to a water reservoir. The evaporation rate is measured by a transducer located at the bottom of the stilling well. The TEMS was tested over a period of 3 months in an underground research facility with relatively strong wind effects, changing temperature, and changing humidity. During this period, the TEMS continued to function uninterrupted, automatically measuring the evaporation amounts along a tunnel and an enclosed niche. These observations suggest that this tool can be useful for investigations of evaporation processes both in enclosed and ventilated environments. Published in 2002 by John Wiley & Sons, Ltd.

Salve, Rohit

2002-04-01

276

Effect of Water Spray Evaporative Cooling at the Inlet of Regeneration Air Stream on the Performance of an Adsorption Desiccant Cooling Process  

NASA Astrophysics Data System (ADS)

This paper shows an influence of evaporative cooler at the inlet of regeneration air stream of an adsorptive desiccant cooling process on the cooling/dehumidifying performance. This evaporative cooling was expected to cause humidity increase in regeneration air reducing the dehumidifying performance of the honeycomb absorber, while the evaporative cooling plays an important role to produce a lower temperature in supply air. Two different airs to be used for the regeneration of the desiccant wheel were considered. One was fresh outside air (OA mode) and the other was air ventilated from the room (RA mode). Experimental results showed that the amount of dehumidified water obtained at the process without water spray evaporative cooler was actually larger than that of process with water spray evaporative cooler. This behavior was mainly due to increase of humidity or relative humidity in the regeneration air as expected. However, temperature of supply air produced by the process with the evaporator was rather lower than that of the other because of the cooled return air, resulting higher CE value. Regarding the operating mode, the evaporative cooler at the OA-mode was no longer useful at higher ambient humidity because of the difficulty of the evaporation of the water in such high humidity. It was also found that its dehumidifying performance was remarkably decreased at higher ambient humidity and lower regeneration temperature since the effective adsorption capacity at the resulting high relative humidity of the regeneration air decreased.

Ando, Kosuke; Kodama, Akio; Hirose, Tsutomu; Goto, Motonobu; Okano, Hiroshi

277

Improved rate control for electron-beam evaporation and evaluation of optical performance improvements.  

PubMed

A new deposition-rate-control and electron-beam-gun (e-gun) strategy was developed that significantly reduces the growth-rate variations for e-beam-deposited SiO2 coatings. The resulting improvements in optical performance are evaluated for multilayer bandpass filters. The adverse effect of uneven silica-source depletion on coating spectral performances during long deposition runs is discussed. PMID:16539249

Gevelber, Michael; Xu, Bing; Smith, Douglas

2006-03-01

278

Diagnostic Estimates of Terrestrial Water Storage Changes and Evaporation Using the ECMWF Reanalysis ERA-Interim and Hydrometeorological Measurements  

NASA Astrophysics Data System (ADS)

In a global perspective, little is known about terrestrial water storage and evaporation. However, these two variables of the hydrological cycle play a key role not only for agriculture and the estimation of current and future water availability, but also for improvements in seasonal forecasting and climate modeling. Using the atmospheric water balance, accurate estimates of terrestrial water storage variations and evaporation for large river basins can be obtained. Here, we present diagnostic estimates derived with this approach using the recent ECMWF reanalysis ERA-Interim, together with measured runoff for the estimated terrestrial water storage changes, and precipitation for the evapotranspiration estimates. Comparisons with ERA-40-based estimates from the Basin-Scale Water-Balance (BSWB) dataset (Seneviratne et al. 2004, Hirschi et al. 2006a,b; www.iacweb.ethz.ch/data/water_balance/) are performed for several basins. In this analysis, we focus on differences in the annual cycles as well as in the long-term drifts of the derived terrestrial water storage changes. Moreover, we compare the diagnosed ERA-Interim-based terrestrial water storage changes with in-situ soil moisture and snow measurements, as well as satellite retrievals from the Gravity Recovery and Climate Experiment (GRACE). References: Hirschi, M., Seneviratne, S.I., Schär, C. (2006a). Seasonal variations in terrestrial water storage for major midlatitude river basins. J. Hydrometeorol., 7(1):39-60. Hirschi, M., Viterbo, P. and Seneviratne, S.I. (2006b). Basin-scale water-balance estimates of terrestrial water storage variations from ECMWF operational forecast analysis. Geophys. Res. Lett., 33, doi:10.1029/2006GL027659 Seneviratne, S.I., Viterbo, P., Lüthi, D. and Schär, C. (2004). Inferring changes in terrestrial water storage using ERA-40 reanalysis data: The Mississippi river basin. J. Clim., 17, 2039-2057.

Mueller, B.; Hirschi, M.; Seneviratne, S. I.

2009-04-01

279

Hydrogen capacity and absorption rate of the SAES St707 non-evaporable getter at various temperatures.  

SciTech Connect

A prototype of a tritium thermoelectric generator (TTG) is currently being developed at Sandia. In the TTG, a vacuum jacket reduces the amount of heat lost from the high temperature source via convection. However, outgassing presents challenges to maintaining a vacuum for many years. Getters are chemically active substances that scavenge residual gases in a vacuum system. In order to maintain the vacuum jacket at approximately 1.0 x 10{sup -4} torr for decades, nonevaporable getters that can operate from -55 C to 60 C are going to be used. This paper focuses on the hydrogen capacity and absorption rate of the St707{trademark} non-evaporable getter by SAES. Using a getter testing manifold, we have carried out experiments to test these characteristics of the getter over the temperature range of -77 C to 60 C. The results from this study can be used to size the getter appropriately.

Hsu, Irving; Mills, Bernice E.

2010-08-01

280

Combined Evaporation and Salt Precipitation in Porous Media  

NASA Astrophysics Data System (ADS)

The vadose zone pore water contains dissolved salts and minerals; therefore, evaporation results in high rates of salt accumulation that may change the physical and chemical properties of the porous media. Here, a series of experiments, together with a mathematical model, are presented to shed new light on these processes. Experiments included: (1) long-term column evaporation experiments to quantify changes in evaporation rates due to salt precipitation; (2) CT scans of evaporated porous media samples saturated with salt solutions, to observe salt precipitation from micro to macro scales; and (3) Infrared thermography analysis to quantify evaporation rates from porous media surfaces for homogeneous and heterogeneous conditions and constant water table, in the presence of salt precipitation. As expected, the majority of salt crystallization occurs in the upper parts of the matrix, near the evaporation front. For heterogeneous porous matrices, salt precipitation will occur mainly in the fine pore regions as preferential evaporation takes place in these locations. In addition, it was found that the precipitated NaCl salt crust diffusion coefficient for water vapor is one to two orders of magnitude lower than the vapor diffusion coefficient in free air, depending on environmental conditions and salt crystallization rates. Three new stages of evaporation were defined for saline solutions: SS1, SS2 and SS3. SS1 exhibits a low and gradual decrease in the evaporation rate due to osmotic pressure. During SS2, the evaporation rate falls progressively due to salt precipitation; SS3 is characterized by a constant low evaporation rate and determined by the diffusion rate of water vapor through the precipitated salt layer. Even though phenomenologically similar to the classical evaporation stages of pure water, these stages correspond to different mechanisms and the transition between stages can occur regardless the hydraulic conditions. As well, it was shown that matrix heterogeneity lessens the salt effect on evaporation as coarse pore regions are relatively free of salt crystals, facilitating vapor transport towards the atmosphere. This was verified by the thermography analysis that enabled independent quantification of evaporation rates from coarse and fine sections of the media during salt precipitation. This is in contrast to homogeneous conditions, where the salt is distributed homogeneously in the matrix's upper parts, resulting in an increase in matrix resistivity to vapor flow. This research sheds new light on the dynamics of the evaporation process of a saline solution and the importance of considering that natural pore solutions typically include electrolytes.

Weisbrod, N.; Dragila, M. I.; Nachshon, U.; Or, D.; Shaharani, E.; Grader, A.

2012-12-01

281

[Optimal irrigation index for cotton drip irrigation under film mulching based on the evaporation from pan with constant water level].  

PubMed

A field experiment with two irrigation cycles and two irrigating water quotas at squaring stage and blossoming-boll forming stage was conducted in Urumqi of Xinjiang Autonomous Region, Northwest China in 2008-2009, aimed to explore the high-efficient irrigation index of cotton drip irrigation under film mulching. The effects of different water treatments on the seed yield, water consumption, and water use efficiency (WUE) of cotton were analyzed. In all treatments, there was a high correlation between the cotton water use and the evaporation from pan installed above the plant canopy. In high-yield cotton field (including the treatment T4 which had 10 days and 7 days of irrigation cycle with 30.0 mm and 37.5 mm of irrigating water quota at squaring stage and blossoming-boll forming stage, respectively in 2008, and the treatment T1 having 7 days of irrigation cycle with 22.5 mm and 37.5 mm of irrigating water quota at squaring stage and blossoming-boll forming stage, respectively in 2009), the pan-crop coefficient (Kp) at seedling stage, squaring stage, blossoming-boll forming stage, and boll opening stage was 0.29-0.30, 0.52-0.53, 0.74-0.88, and 0.19-0.20, respectively. As compared with the other treatments, T4 had the highest seed cotton yield (5060 kg x hm(-2)) and the highest WUE (1.00 kg x m(-3)) in 2008, whereas T1 had the highest seed cotton yield (4467 kg x hm(-2)) and the highest WUE (0.99 kg x m(-3)) in 2009. The averaged cumulative pan evaporation in 7 days and 10 days at squaring stage was 40-50 mm and 60-70 mm, respectively, and that in 7 days at blossoming-boll forming stage was 40-50 mm. It was suggested that in Xinjiang cotton area, irrigating 45 mm water for seedling emergence, no irrigation both at seedling stage and at boll opening stage, and irrigation was started when the pan evaporation reached 45-65 mm and 45 mm at squaring stage and blossoming-boll stage, respectively, the irrigating water quota could be determined by multiplying cumulative pan evaporation with Kp (the Ko was taken as 0.5, 0.75, 0.85, and 0.75 at squaring stage, early blossoming, full-blossoming, and late blossoming stage, respectively), which could be the high efficient irrigation index to obtain high yield and WUE in drip irrigation cotton field and to save irrigation water resources. PMID:24564144

Shen, Xiao-Jun; Zhang, Ji-Yang; Sun, Jing-Sheng; Gao, Yang; Li, Ming-Si; Liu, Hao; Yang, Gui-Sen

2013-11-01

282

The Case of the Disappearing Water  

NSDL National Science Digital Library

In this experiment, students investigate the evaporation of water as part of a solution to a simulated mystery. They will compare rates of evaporation under different conditions, demonstrate knowledge of the concepts of evaporation, and be able to explain evaporation in the context of the water cycle.

283

Evaporation, Condensation, and Precipitation  

NSDL National Science Digital Library

After completion of this project students should have an understanding of evaporation, condensation, and precipitation in the water cycle. Use the websites provided to answer the questions. Record your answers on the spreadsheet provided. Do you understand how the water cycle works? Begin by watching this short video about the water cycle.water cycle video Use the website to define condensation, precipitation, and evaporation?water cycle List the different types of precipitation from the site.types of precipitation Follow the directions to the experiment on this website to get a better understanding of how evaporation takes ...

Miss Brown

2009-10-21

284

Preferential Evaporation From Heterogeneous Porous Media With Vertical Textural Contrasts  

Microsoft Academic Search

High evaporative drying rates of porous media are typically sustained by capillary water flow to vaporization plane from wet zones below (stage-1 evaporation). The extent of the hydraulically connected region depends on width of the pore size distribution and the interplay between capillarity, gravity and viscous forces. In heterogeneous soils the effective range of hydraulically-connected pore sizes may be enhanced

D. Or; P. Lehmann; N. Shokri; E. Shahraeeni

2008-01-01

285

Cooling rate, heating rate and aging effects in glassy water  

E-print Network

We report a molecular dynamics simulation study of the properties of the potential energy landscape sampled by a system of water molecules during the process of generating a glass by cooling, and during the process of regenerating the equilibrium liquid by heating the glass. We study the dependence of these processes on the cooling/heating rates as well as on the role of aging (the time elapsed in the glass state). We compare the properties of the potential energy landscape sampled during these processes with the corresponding properties sampled in the liquid equilibrium state to elucidate under which conditions glass configurations can be associated with equilibrium liquid configurations.

Nicolas Giovambattista; H. Eugene Stanley; Francesco Sciortino

2004-03-03

286

Reservoir evaporation in central Colorado  

USGS Publications Warehouse

Evaporation losses from seven reservoirs operated by the Denver Water Department in central Colorado were determined during various periods from 1974 to 1980. The reservoirs studies were Ralston, Cheesman, Antero, Williams Fork, Elevenmile Canyon, Dillon, and Gross. Energy-budget and mass-transfer methods were used to determine evaporation. Class-A pan data also were collected at each reservoir. The energy-budget method was the most accurate of the methods used to determine evaporation. At Ralston, Cheesman, Antero, and Williams Fork Reservoirs the energy-budget method was used to calibrate the mass-transfer coefficients. Calibrated coefficients already were available for Elevenmile Canyon, Dillon, and Gross Reservoirs. Using the calibrated coefficients, long-term mass-transfer evaporation rates were determined. Annual evaporation values were not determined because the instrumentation was not operated for the entire open-water season. Class-A pan data were used to determine pan coefficients for each season at each reservoir. The coefficients varied from season to season and between reservoirs, and the seasonal values ranged from 0.29 to 1.05. (USGS)

Spahr, N.E.; Ruddy, B.C.

1983-01-01

287

Formation of Nitrogen- and Sulfur-Containing Light-Absorbing Compounds Accelerated by Evaporation of Water from Secondary Organic Aerosols  

SciTech Connect

Aqueous extracts of secondary organic aerosols (SOA) generated from the ozonolysis of dlimonene were subjected to dissolution, evaporation, and re-dissolution in the presence and absence of ammonium sulfate (AS). Evaporation with AS at pH 4-9 produced chromophores that were stable with respect to hydrolysis and had a distinctive absorption band at 500 nm. Evaporation accelerated the rate of chromophore formation by at least three orders of magnitude compared to the reaction in aqueous solution, which produced similar compounds. Absorption spectroscopy and high-resolution nanospray desorption electrospray ionization (nano-DESI) mass spectrometry experiments suggested that the molar fraction of the chromophores was small (< 2%), and that they contained nitrogen atoms. Although the colored products represented only a small fraction of SOA, their large extinction coefficients (>10{sup 5} L mol{sup -1} cm{sup -1} at 500 nm) increased the effective mass absorption coefficient of the residual organics in excess of 10{sup 3} cm{sup 2} g{sup -1} - a dramatic effect on the optical properties from minor constituents. Evaporation of SOA extracts in the absence of AS resulted in the production of colored compounds only when the SOA extract was acidified to pH {approx} 2 with sulfuric acid. These chromophores were produced by acid-catalyzed aldol condensation, followed by a conversion into organosulfates. The presence of organosulfates was confirmed by high resolution mass spectrometry experiments. Results of this study suggest that evaporation of cloud or fog droplets containing dissolved organics leads to significant modification of the molecular composition and serves as a potentially important source of light-absorbing compounds.

Nguyen, Tran B.; Lee, Paula B.; Updyke, Katelyn M.; Bones, David L.; Laskin, Julia; Laskin, Alexander; Nizkorodov, Sergey

2012-01-14

288

Formation of nitrogen- and sulfur-containing light-absorbing compounds accelerated by evaporation of water from secondary organic aerosols  

NASA Astrophysics Data System (ADS)

Aqueous extracts of secondary organic aerosols (SOA) generated from the ozonolysis of d-limonene were subjected to dissolution, evaporation, and re-dissolution in the presence and absence of ammonium sulfate (AS). Evaporation with AS at pH 4-9 produced chromophores that were stable with respect to hydrolysis and had a distinctive absorption band at 500 nm. Evaporation accelerated the rate of chromophore formation by at least three orders of magnitude compared to the reaction in aqueous solution, which produced similar compounds. Absorption spectroscopy and high-resolution nanospray desorption electrospray ionization (nano-DESI) mass spectrometry experiments suggested that the molar fraction of the chromophores was small (<2%), and that they contained nitrogen atoms. Although the colored products represented only a small fraction of SOA, their large extinction coefficients (>105 L mol-1 cm-1 at 500 nm) increased the effective mass absorption coefficient of the residual organics in excess of 103 cm2 g-1 - a dramatic effect on the optical properties from minor constituents. Evaporation of SOA extracts in the absence of AS resulted in the production of colored compounds only when the SOA extract was acidified to pH ˜ 2 with sulfuric acid. These chromophores were produced by acid-catalyzed aldol condensation, followed by a conversion into organosulfates. The presence of organosulfates was confirmed by high resolution mass spectrometry experiments. Results of this study suggest that evaporation of cloud or fog droplets containing dissolved organics leads to significant modification of the molecular composition and serves as a potentially important source of light-absorbing compounds.

Nguyen, Tran B.; Lee, Paula B.; Updyke, Katelyn M.; Bones, David L.; Laskin, Julia; Laskin, Alexander; Nizkorodov, Sergey A.

2012-01-01

289

Enteric Bacterial Growth Rates in River Water  

PubMed Central

Enteric bacteria, including stocked strains of pathogenic species and organisms naturally present in the stream, were capable of growth in a chemostat with autoclaved river water taken 750 m below a sewage outfall. Maximal specific growth rates for all organisms occurred at 30 C, whereas culture generation times ranged between 33.3 and 116 hr. Of the six laboratory strains of enteric species used, Escherichia coli and Enterobacter aerogenes grew at generation times of 34.5 and 33.3 hr, respectively, while the remaining Proteus, Arizona, Salmonella, and Shigella spp. reproduced at a rate two to three times slower than the coliforms. Little or no growth occurred in the water at incubation temperatures of 20 and 5 C, and death was observed for Salmonella senftenberg at 20 and 5 C and for E. aerogenes and Proteus rettgeri at 5 C. When enteric bacteria naturally present in the river water were employed in similar experiments, coliform bacteria demonstrated a generation time of approximately 116 hr, whereas fecal coliforms failed to grow. Growth of the bacteria from the river demonstrated a periodicity of approximately 100 hr, which suggests that much of the growth of these organisms in the chemostat may be on the glass surfaces. This phenomenon, however, was not observed with any of the stocked enteric species. Neither the stock cultures nor the aquatic strains were capable of growth in autoclaved river water taken above the sewage outfall at the three temperatures tested. PMID:4561100

Hendricks, Charles W.

1972-01-01

290

Heat capacities of freely evaporating charged water clusters A. E. K. Sundn,1  

E-print Network

clusters are studied in the laboratory. Although it is possible to thermalize cluster postproduction, most- tions that the clusters have evaporated a molecule at least once after production and entry into vacuum be inverted to give the heat capacity. II. EXPERIMENTAL SETUP AND PROCEDURE The experiment was carried out

Hansen, Klavs

291

Effect of nitrogen flow rate on the properties of TiN film deposited by e beam evaporation technique  

NASA Astrophysics Data System (ADS)

In this work, titanium nitride (TiN) films have been deposited by e beam evaporation technique on Si/SiO2 (1 0 0) substrates at room temperature. The influence of nitrogen flow rate (N2 = 0, 4, 6, 8 and 10 sccm (standard cubic centimeter per minute)) on the structural, morphological and electrical properties of the TiN films has been studied. The deposited TiN films have been characterized using X-ray diffraction (XRD), XPS (X-ray photoelectron spectroscopy), FESEM (Field emission scanning electron microscopy) and four-point probe resistivity measurement techniques. XRD patterns reveal FCC symmetry of the film with (1 1 1) preferred orientations for Ti film (N2 = 0 sccm) and (2 0 0) preferred orientations for TiN film (N2 = 4, 6, 8 and 10 sccm), respectively. The lattice parameters for TiN films are found to increase from 4.237 Å to 4.239 Å with the increase in nitrogen flow rate. The presence of different phases such as TiN, TiON and TiO2 were confirmed by XPS analysis. The FESEM images of the TiN films showed a smooth morphology with columnar grain structures. The grain size of the TiN films was found to increase as the nitrogen flow rate was increased from 4 to 10 sccm. The electrical resistivity measurement showed that the resistivity of the film decreased from 333 ?? cm to 111 ?? cm on increasing nitrogen flow rate from 4 to10 sccm.

Arshi, Nishat; Lu, Junqing; Koo, Bon Heun; Lee, Chan Gyu; Ahmed, Faheem

2012-09-01

292

Soil water content and evaporation determined by thermal parameters obtained from ground-based and remote measurements  

NASA Technical Reports Server (NTRS)

Soil water contents from both smooth and rough bare soil were estimated from remotely sensed surface soil and air temperatures. An inverse relationship between two thermal parameters and gravimetric soil water content was found for Avondale loam when its water content was between air-dry and field capacity. These parameters, daily maximum minus minimum surface soil temperature and daily maximum soil minus air temperature, appear to describe the relationship reasonably well. These two parameters also describe relative soil water evaporation (actual/potential). Surface soil temperatures showed good agreement among three measurement techniques: in situ thermocouples, a ground-based infrared radiation thermometer, and the thermal infrared band of an airborne multispectral scanner.

Reginato, R. J.; Idso, S. B.; Jackson, R. D.; Vedder, J. F.; Blanchard, M. B.; Goettelman, R.

1976-01-01

293

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

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

294

Evaporation from the shallow Lake Massaciuccoli (Tuscany, Italy) studied using stable isotopes and evaporation pan data  

NASA Astrophysics Data System (ADS)

Oxygen and hydrogen isotope variations monitored in Lake Massaciuccoli (7 km2, 2 m deep, seasonally variable water level) during summer 2008, were compared with those observed in a Class A evaporation pan (diameter 120.6 cm, depth 25.4 cm) placed on the lake eastern shore. Air temperature, pressure, relative humidity, wind speed and direction, solar radiation, water temperature in the lake and the pan were also measured. The pluviometer indicated that no precipitation occurred during the study period. The pan was initially filled with groundwater up to the level of 19.2 cm (219 L), depleted in heavy isotopes with respect to tha lake water. Sodium chloride was added up to the concentration of 1 g×L-1, which is assumed do not affect significantly the evaporation rate till the water volume is reduced to less than 10 %. The Cl- concentration was used to provide an estimation of the evaporated water fraction, in addition to the micrometer measuring the water level variations. The pan water was sampled every 2-3 days and Cl- and stable isotopes determined. The set of stable isotope and evaporation data enabled us to compute the parameters governing the evaporation process and the isotopic exchanges with the atmospheric moisture, according to the procedure proposed by Gonfiantini (1986). The values were applied to test three working hypotheses of water balance of Lake Massaciuccoli: (i) surface inflow and outflow of liquid water are negligible and only evaporation is important; (ii) the inflow is negligible and outflow and evaporation are both significant; (iii) the three terms of balance are all important but the losses by evaporation and outflow exceed inflow (as the lake water level was decreasing). Water exchanges with groundwater are considered negligible. The best agreement between lake and pan data was obtained with the second hypothesis, for which the fraction of water removed by evaporation was estimated to be about 40 % ot he total water losses. This residual 60 % of losses consists essentially of water pumped from the lake for irrigation, in rough agreement with independent estimations. In the final stages of pan water evaporation, the well known hook trend of heavy isotope delta values versus residual water fraction was observed. The data elaboration is being continued and refined. Correction factors for the so called pan effect will also be applied. Collection of atmospheric vapour samples has been started. R. Gonfiantini, 1986. Isotopes in lake studies, in Handbook of Environmental Isotope Geochemistry (P. Fritz and J-Ch. Fontes, Eds.), Vol. 2, pp.113-168.

Baneschi, I.; Gonfiantini, R.; Guidi, M.

2009-04-01

295

The impact of humidity on evaporative cooling in small desert birds exposed to high air temperatures.  

PubMed

Environmental temperatures that exceed body temperature (Tb) force endothermic animals to rely solely on evaporative cooling to dissipate heat. However, evaporative heat dissipation can be drastically reduced by environmental humidity, imposing a thermoregulatory challenge. The goal of this study was to investigate the effects of humidity on the thermoregulation of desert birds and to compare the sensitivity of cutaneous and respiratory evaporation to reduced vapor density gradients. Rates of evaporative water loss, metabolic rate, and Tb were measured in birds exposed to humidities ranging from ?2 to 30 g H2O m(-3) (0%-100% relative humidity at 30°C) at air temperatures between 44° and 56°C. In sociable weavers, a species that dissipates heat primarily through panting, rates of evaporative water loss were inhibited by as much as 36% by high humidity at 48°C, and these birds showed a high degree of hyperthermia. At lower temperatures (40°-44°C), evaporative water loss was largely unaffected by humidity in this species. In Namaqua doves, which primarily use cutaneous evaporation, increasing humidity reduced rates of evaporative water loss, but overall rates of water loss were lower than those observed in sociable weavers. Our data suggest that cutaneous evaporation is more efficient than panting, requiring less water to maintain Tb at a given temperature, but panting appears less sensitive to humidity over the air temperature range investigated here. PMID:25461643

Gerson, Alexander R; Smith, Eric Krabbe; Smit, Ben; McKechnie, Andrew E; Wolf, Blair O

2014-01-01

296

Mixed feed evaporator  

DOEpatents

In the preparation of the gaseous reactant feed to undergo a chemical reaction requiring the presence of steam, the efficiency of overall power utilization is improved by premixing the gaseous reactant feed with water and then heating to evaporate the water in the presence of the gaseous reactant feed, the heating fluid utilized being at a temperature below the boiling point of water at the pressure in the volume where the evaporation occurs.

Vakil, Himanshu B. (Schenectady, NY); Kosky, Philip G. (Ballston Lake, NY)

1982-01-01

297

New explicit equations for the accurate calculation of the growth and evaporation of hydrometeors by the diffusion of water vapor  

NASA Technical Reports Server (NTRS)

The traditional explicit growth equation has been widely used to calculate the growth and evaporation of hydrometeors by the diffusion of water vapor. This paper reexamines the assumptions underlying the traditional equation and shows that large errors (10-30 percent in some cases) result if it is used carelessly. More accurate explicit equations are derived by approximating the saturation vapor-density difference as a quadratic rather than a linear function of the temperature difference between the particle and ambient air. These new equations, which reduce the error to less than a few percent, merit inclusion in a broad range of atmospheric models.

Srivastava, R. C.; Coen, J. L.

1992-01-01

298

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

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

299

Characteristic of local boiling heat transfer of ammonia and ammonia / water binary mixture on the plate type evaporator  

NASA Astrophysics Data System (ADS)

Power generation using small temperature difference such as ocean thermal energy conversion (OTEC) and discharged thermal energy conversion (DTEC) is expected to be the countermeasures against global warming problem. As ammonia and ammonia/water are used in evaporators for OTEC and DTEC as working fluids, the research of their local boiling heat transfer is important for improvement of the power generation efficiency. Measurements of local boiling heat transfer coefficients were performed for ammonia /water mixture ( z = 0.9-1) on a vertical flat plate heat exchanger in a range of mass flux (7.5-15 kg/m2 s), heat flux (15-23 kW/m2), and pressure (0.7-0.9 MPa). The result shows that in the case of ammonia /water mixture, the local heat transfer coefficients increase with an increase of mass flux and composition of ammonia, and decrease with an increase of heat flux.

Okamoto, Akio; Arima, Hirofumi; Ikegami, Yasuyuki

2011-08-01

300

Evaluation of the freeze-thaw/evaporation process for the treatment of produced waters. Final report, August 1992--August 1996  

SciTech Connect

The use of freeze-crystallization is becoming increasingly acknowledged as a low-cost, energy-efficient method for purifying contaminated water. The natural freezing process can be coupled with natural evaporative processes to treat oil and gas produced waters year round in regions where subfreezing temperatures seasonally occur. The climates typical of Colorado`s San Juan Basin and eastern slope, as well as the oil and gas producing regions of Wyoming, are well suited for application of these processes in combination. Specifically, the objectives of this research are related to the development of a commercially-economic FTE (freeze-thaw/evaporation) process for the treatment and purification of water produced in conjunction with oil and natural gas. The research required for development of this process consists of three tasks: (1) a literature survey and process modeling and economic analysis; (2) laboratory-scale process evaluation; and (3) field demonstration of the process. Results of research conducted for the completion of these three tasks indicate that produced water treatment and disposal costs for commercial application of the process, would be in the range of $0.20 to $0.30/bbl in the Rocky Mountain region. FTE field demonstration results from northwestern New Mexico during the winter of 1995--96 indicate significant and simultaneous removal of salts, metals, and organics from produced water. Despite the unusually warm winter, process yields demonstrate disposal volume reductions on the order of 80% and confirm the potential for economic production of water suitable for various beneficial uses. The total dissolved solids concentrations of the FTE demonstration streams were 11,600 mg/L (feed), 56,900 mg/L (brine), and 940 mg/L (ice melt).

Boysen, J.E.; Walker, K.L.; Mefford, J.L.; Kirsch, J.R. [Resource Technology Corp., Laramie, WY (United States); Harju, J.A. [North Dakota Univ., Grand Forks, ND (United States). Energy and Environmental Research Center

1996-06-01

301

Evaporation, transpiration, and ecosystem water use efficiency in a multi-annual sugarcane production system in Hawai'i, USA  

NASA Astrophysics Data System (ADS)

Food and biofuel production will require practices that increase water use efficiency in order to have future sustainability in a water-constrained environment. One possible practice is the use of food and energy crops with multi-annual growing periods, which could reduce bare soil evaporation. We integrated field water budgets, micrometeorology, and plant sampling to observe plant growth and evapotranspiration (ET) in two sugarcane (Saccharum officinarum L.) fields in Hawai'i, USA in contrasting environments with unusually long (18-24 month) growing periods. We partitioned observed ET into evaporation and transpiration using a flux partitioning model and calculated ecosystem water use efficiency (EWUE=Net Ecosystem Productivity/ET) and harvest WUE (HWUE=Aboveground Net Ecosystem Productivity/ET) to assess sugarcane water use efficiency. After the start of the mid-period, our higher elevation, less windy field ('Lee') had a slightly higher mean EWUE (31.5 kg C ha-1 mm-1) than our lower elevation, windier ('Windy') field (mean EWUE of 30.7 kg C ha-1 mm-1). HWUE was also very high (HWUE >27 kg C ha-1 mm-1) in both fields due to aboveground biomass composing >87% of total biomass. Transpiration, as a fraction of total ET, increased rapidly with canopy cover in both fields; during the mid-period, transpiration was an average of 84% of total ET in Windy and 80% in Lee, with Lee showing greater variation than Windy. As expected, daily EWUE increased with canopy cover during the initial growing stages; more significantly, EWUE showed no substantial decrease during the 2nd year with an aging crop. The results illustrate the potential for longer-rotation crop cycles for increasing water use efficiency, particularly in tropical regions.

Anderson, R. G.; Tirado-corbala, R.; Wang, D.; Ayars, J. E.

2013-12-01

302

A new method using evaporation for high-resolution measurements of soil thermal conductivity at changing water contents  

NASA Astrophysics Data System (ADS)

The thermal conductivity of soils is a key parameter to know if their use as heat source or sink is planned. It is required to calculate the efficiency of ground-source heat pump systems in combination with soil heat exchangers. Apart from geothermal energy, soil thermal conductivity is essential to estimate the ampacity for buried power cables. The effective thermal conductivity of saturated and unsaturated soils, as a function of water transport, water vapour transport and heat conduction, mainly depends on the soil water content, its bulk density and texture. The major objectives of this study are (i) to describe the thermal conductivity of soil samples with a non-steady state measurement at changing water contents and for different bulk densities. Based on that it is (ii) tested if available soil thermal conductivity models are able to describe the measured data for the whole range of water contents. The new method allows a continuous measurement of thermal conductivity for soil from full water saturation to air-dryness. Thermal conductivity is measured with a thermal needle probe in predefined time intervals while the change of water content is controlled by evaporation. To relate the measured thermal conductivity to the current volumetric water content, the decrease in weight of the sample, due to evaporation, is logged with a lab scale. Soil texture of the 11 soil substrates tested in this study range between coarse sand and silty clay. To evaluate the impact of the bulk density on heat transport processes, thermal conductivity at 20°C was measured at 1.5g/cm3; 1.7g/cm3 and 1.9g/cm3 for each soil substrate. The results correspond well to literature values used to describe heat transport in soils. Due to the high-resolution and non-destructive measurements, the specific effects of the soil texture and bulk density on thermal conductivity could be proved. Decreasing water contents resulted in a non-linear decline of the thermal conductivity for all samples. Especially for coarse textured soils a rapid decrease of the thermal conductivity was observed, when the volumetric water content drops under a critical level. Higher bulk densities increased the heat transport parameters for soil samples with the same texture. This effect becomes significant at high water saturations. The method used in this study allows easy to use non-steady state measurements of the soil thermal conductivity with a high data resolution and for continuously decreasing water contents. In further studies these measured data will be used to enhance existing pedotransfer functions and models and improve the prediction of soil thermal properties for application-oriented requirements.

Markert, A.; Trinks, S.; Facklam, M.; Wessolek, G.

2012-04-01

303

7-58 A commercial refrigerator with R-134a as the working fluid is considered. The evaporator inlet and exit states are specified. The mass flow rate of the refrigerant and the rate of heat rejected are to be  

E-print Network

7-22 7-58 A commercial refrigerator with R-134a as the working fluid is considered. The evaporator inlet and exit states are specified. The mass flow rate of the refrigerant and the rate of heat rejected are to be determined. Assumptions 1 The refrigerator operates steadily. 2 The kinetic and potential energy changes

Bahrami, Majid

304

Effects of carbonyl bond, metal cluster dissociation, and evaporation rates on predictions of nanotube production in high-pressure carbon monoxide  

NASA Technical Reports Server (NTRS)

The high-pressure carbon monoxide (HiPco) process for producing single-wall carbon nanotubes (SWNTs) uses iron pentacarbonyl as the source of iron for catalyzing the Boudouard reaction. Attempts using nickel tetracarbonyl led to no production of SWNTs. This paper discusses simulations at a constant condition of 1300 K and 30 atm in which the chemical rate equations are solved for different reaction schemes. A lumped cluster model is developed to limit the number of species in the models, yet it includes fairly large clusters. Reaction rate coefficients in these schemes are based on bond energies of iron and nickel species and on estimates of chemical rates for formation of SWNTs. SWNT growth is measured by the conformation of CO2. It is shown that the production of CO2 is significantly greater for FeCO because of its lower bond energy as compared with that of NiCO. It is also shown that the dissociation and evaporation rates of atoms from small metal clusters have a significant effect on CO2 production. A high rate of evaporation leads to a smaller number of metal clusters available to catalyze the Boudouard reaction. This suggests that if CO reacts with metal clusters and removes atoms from them by forming MeCO, this has the effect of enhancing the evaporation rate and reducing SWNT production. The study also investigates some other reactions in the model that have a less dramatic influence.

Scott, Carl D.; Smalley, Richard E.

2003-01-01

305

Water-quality and sediment-chemistry data of drain water and evaporation ponds from Tulare Lake Drainage District, Kings County, California March 1985 to March 1986  

USGS Publications Warehouse

Trace element and major ion concentrations were measured in water samples collected monthly between March 1985 and March 1986 at the MD-1 pumping station at the Tulare Lake Drainage District evaporation ponds, Kings County, California. Samples were analyzed for selected pesticides several times during the year. Salinity, as measured by specific conductance, ranged from 11,500 to 37,600 microsiemens/centimeter; total recoverable boron ranged from 4,000 to 16,000 micrg/L; and total recoverable molybdenum ranged from 630 to 2,600 microg/L. Median concentrations of total arsenic and total selenium were 97 and 2 microg/L. Atrazine, prometone, propazine, and simazine were the only pesticides detected in water samples collected at the MD-1 pumping station. Major ions, trace elements, and selected pesticides also were analyzed in water and bottom-sediment samples from five of the southern evaporation ponds at Tulare Lake Drainage District. Water enters the ponds from the MD-1 pumping station at pond 1 and flows through the system terminating at pond 10. The water samples increased in specific conductance (21,700 to 90,200 microsiemens/centimeter) and concentrations of total arsenic (110 to 420 microg/L), total recoverable boron (12,000 to 80,000 microg/L) and total recoverable molybdenum (1,200 to 5,500 microg/L) going from pond 1 to pond 10, respectively. Pesticides were not detected in water from any of the ponds sampled. Median concentrations of total arsenic and total selenium in the bottom sediments were 4.0 and 0.9 microg/g, respectively. The only pesticides detected in bottom sediment samples from the evaporation ponds were DDD and DDE, with maximum concentration of 0.8 microg/kilogram. (Author 's abstract)

Fujii, Roger

1988-01-01

306

Influence of evaporation, ground water, and uncertainty in the hydrologic budget of Lake Lucerne, a seepage lake in Polk County, Florida  

USGS Publications Warehouse

A detailed hydrologic budget was constructed of a seepage lake of sinkhole origin in the karst terrain of central Florida. During the drought period studied, lake evaporation computed by the energy-budget and mass-transfer methods was the largest component in the budget, followed by rainfall. Ground-water inflow contributed about one-third of the total inflow. Lake leakage was about one-fourth of the evaporative losses and was increased substantially by pumping from the Upper Floridan aquifer.

Lee, Terrie Mackin; Swancar, Amy

1997-01-01

307

Experimental investigations of water fluxes within the soil-vegetation-atmosphere system: Stable isotope mass-balance approach to partition evaporation and transpiration  

NASA Astrophysics Data System (ADS)

Irrigated agriculture is the largest user of freshwater worldwide and the scale of irrigated agriculture can be so large that it can have dramatic effects on the water cycle and even alter regional climates. Therefore, it is vital to improve the water use efficiency of irrigated lands in order to address the sustainable use of water resources, the growing need for agricultural products, and the health of ecosystems. Environmental isotopes have unique attributes that make them particularly suitable for tracing hydrological pathways and quantifying hydrological fluxes within the soil-vegetation-atmosphere system. The stable isotopic composition of soil water is mainly controlled by precipitation or irrigation inputs and evaporative losses. Because transpiration does not fractionate soil water isotopes, it is possible to estimate the relative proportions of evaporation and transpiration using isotopic mass balance calculations. In this study experimental investigations, combining classical hydrometric measurements, tracer hydrological methods and a soil water model were applied to laboratory lysimeters to study the transpiration processes of Teff ( Eragrostis tea (Zucc.) Trotter). Teff is an annual bunch cereal and an important aliment in Ethiopia and Eritrea and it is also gaining popularity in other countries. To determine the soil water contents, sensors using a capacitance/frequency domain technology were installed at different depths and soil water samples for the isotope analysis were taken using pore water samplers. Water contents in different depths and water fluxes, such as percolation and evaporation were modeled using the HYDRUS-1D software package. By using an isotope mass balance model the total evaporation and the fractions between soil evaporation and transpiration could be determined. The water losses which were estimated using the isotope mass-balance approach are in good agreement with the measured values using classical hydrometric measurements. The proportion of water lost by transpiration (T/ET) during the study period was about 0.7 for the Teff covered laboratory set-up.

Wenninger, Jochen; Beza, Desta Tadesse; Uhlenbrook, Stefan

308

CAPSULE REPORT: EVAPORATION PROCESS  

EPA Science Inventory

Evaporation has been an established technology in the metal finishing industry for many years. In this process, wastewaters containing reusable materials, such as copper, nickel, or chromium compounds are heated, producing a water vapor that is continuously removed and condensed....

309

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

Microsoft Academic Search

The existence of ice covered rivers on Mars is considered. It is noted that 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. It is determined that even with a mean Martian insolation rate above the ice of approximately

D. Wallace; C. Sagan

1979-01-01

310

A simple breathing rate-sensing method exploiting a temporarily condensed water layer formed on an oxidized surface  

NASA Astrophysics Data System (ADS)

We describe a very simple breathing rate-sensing method that detects a significant electric current change between two metal electrodes on an oxidized surface. The current change is caused by the formation of a water layer from exhaled breath. We discovered that breathing onto the oxidized surface causes instant water condensation, and it generates 20 times increased current than that measured in the inhalation period. The condensed water quickly evaporates, enabling us to detect dynamic human breathing in real time. We also investigated the breathing rate sensor by varying the relative humidity, temperature, and breathing frequency and confirmed its potential for practical applications.

Seo, Min-Ho; Yang, Hyun-Ho; Choi, Kwang-Wook; Lee, Jae-Shin; Yoon, Jun-Bo

2015-02-01

311

Evaporation and canopy characteristics of coniferous forests and grasslands  

Microsoft Academic Search

Canopy-scale evaporation rate (E) and derived surface and aerodynamic conductances for the transfer of water vapour (gs and ga, respectively) are reviewed for coniferous forests and grasslands. Despite the extremes of canopy structure, the two vegetation types have similar maximum hourly evaporation rates (Emax) and maximum surface conductances (gsmax) (medians = 0.46 mm h-1 and 22 mm s-1). However, on

F. M. Kelliher; R. Leuning; E. D. Schulze

1993-01-01

312

Concentration of saline produced water from coalbed methane gas wells in a multiple-effect evaporator using waste heat from the gas compressor and compressor drive engine  

Microsoft Academic Search

The use of heat of compression from the gas compressor and waste heat from the diesel compressor drive engine in a triple-effect feed forward evaporator was studied as a means of concentrating saline produced water to facilitate its disposal. The saline water, trapped in deeply buried coal seems, must be continuously pumped from coalbed natural gas wells so that the

Leon Y. Sadler; Oommen George

1995-01-01

313

A regime shift in Lake Superior ice cover, evaporation, and water temperature following the warm El Nin~o winter of 19971998  

E-print Network

A regime shift in Lake Superior ice cover, evaporation, and water temperature following the warm El Arbor, Michigan 3 National Oceanic and Atmospheric Administration Great Lakes Environmental Research Laboratory, Ann Arbor, Michigan Abstract Significant trends in Lake Superior water temperature and ice cover

314

Determination of evaporation rates and vapor pressures of very low volatility compounds: a study of the C4-C10 diacarboxylic acids  

NASA Astrophysics Data System (ADS)

A new method for the measurement of evaporation rates and vapor pressures of low volatility compounds was developed and was applied to the homologous C4-C10 dicarboxylic acids. Proton-transfer chemical ionization mass spectrometry was used to directly measure the temperature dependent evaporation rates of aerosol samples collected on a cold plate that could be heated at a known rate. The vapor pressures of the deposited compounds were derived from the observed evaporation rates through application of the Hertz-Knudsen equation. Temperature programmed desorption allows for quantification of the enthalpy (?Hvap) and entropy (?Svap) of vaporization of the diacids and will be described. A strong odd-even effect with respect to the total carbon number is observed in the derived diacid vapor pressures, consistent with previous measurements. However, the vapor pressures from this method tend to be lower than previous measurements. Though seen in the vapor pressure, no odd-even carbon chain length effect is discernible in the measured values of ?Hvap and ?Svap. Perhaps most importantly, these experimental results also suggest that residual solvent molecules (from the aerosol generation process) trapped in the diacid samples can have a considerable influence on the measured thermodynamic parameters and, if not properly accounted for, may give extraneous results.

Cappa, C. D.; Lovejoy, E. R.; Ravishankara, A. R.

2006-12-01

315

Temperature field beneath evaporating surface resolved by infrared thermography  

NASA Astrophysics Data System (ADS)

Land-atmosphere mass exchange is intimately linked with radiation and energy balance of terrestrial surfaces. Surface evaporation is a key hydrologic flux affected by interplay between water supply from below, surface energy input, and exchange across air boundary layer. The thermal signature depression of an evaporating surface is proportional to the magnitude of the flux which makes remote monitoring of fluxes from heterogeneous surface feasible using advanced Infrared thermography (IRT). Inversion of IRT data to evaporation fluxes relies on knowledge of thickness of thermal depression beneath evaporation zone. We develop a mathematical model for 3D temperature field induced by evaporation from a patchy evaporative surface and compare the results with direct IRT measurements of cross section beneath an evaporating surface. Results yield a universal description of evaporative temperature depression that could serve for predicting spatial and temporal evaporation rates distributions based on IRT data. The thickness of thermo-evaporative zone is typically in the range of 10-40 mm for a wide range of soil properties and fluxes.

Shahraeeni, Ebrahim; Or, Dani

2010-05-01

316

Evaporation Dynamics of Moss and Bare Soil in Boreal Forests  

NASA Astrophysics Data System (ADS)

Evaporation dynamics of mosses is a critical process in boreal and arctic systems and represents a key uncertainty in hydrology and climate models. At this point, moss evaporation is not well quantified at the plot or landscape scale. Relative to bare soil or litter evaporation, moss evaporation can be challenging to predict because the water flux is not isolated to the moss surface. Evaporation can originate from nearly 10 cm below the surface. Some mosses can wick moisture from even deeper than 10 cm, which subsequently evaporates. The goal of this study was to use field measurements to quantify the moss evaporation dynamics in a coniferous forest relative to bare ground or litter evaporation dynamics in a deciduous forest in Interior Alaska. Measurements were made in two ecosystem types within the boreal forest of Interior Alaska: a deciduous forest devoid of moss and a coniferous forest with a thick moss layer. A small clear chamber was attached to a LiCor 840 infrared gas analyzer in a closed loop system with a low flow rate. Water fluxes were measured for ~ 90 seconds on each plot in dry and wet soil and moss conditions. Additional measurements included: soil temperature, soil moisture, air temperature, barometric pressure, dew point, relative humidity, and wind speed. Thermal infrared images were also captured in congruence with water flux measurements to determine skin temperature. We found that the moss evaporation rate was over 100% greater than the soil evaporation rate (0.057 g/min vs. 0.024 g/min), and evaporation rates in both systems were most strongly driven by relative humidity and surface temperature. Surface temperature was lower at the birch site than the black spruce site because trees shade the surface beneath the birch. High fluxes associated with high water content were sustained for a longer period of time over the mosses compared to the bare soil. The thermal IR data showed that skin temperature lagged the evaporation flux, such that the evaporation would peak immediately following wetting of the surface but the skin temperatures responded by decreasing 20 minutes later. This study shows the evaporation dynamics of moss and bare ground, which will be incorporated into a hydrology model evaluating freshwater generation from the boreal forest.

Dempster, S.; Young, J. M.; Barron, C. G.; Bolton, W. R.

2013-12-01

317

Export Rates of North Atlantic Deep Water  

Microsoft Academic Search

The concept from Bolin and Rhode (1973) of transit time distributions (TTDs)newline for reservoirs is applied to North Atlantic Deep Water (NADW) in the subpolar North Atlantic. The reservoirs are the different density classes of NADW, i.e. Upper Labrador Sea Water (ULSW), Labrador Sea Water (LSW), Gibbs Fracture Zone Water(GFZW) and Denmark Strait Overflow Water (DSOW). The TTDs for these

R. Steinfeldt; M. Rhein

2009-01-01

318

Efficiency of methods for Karl Fischer determination of water in oils based on oven evaporation and azeotropic distillation.  

PubMed

The efficiency of azeotropic distillation and oven evaporation techniques for trace determination of water in oils has recently been questioned by the National Institute of Standards and Technology (NIST), on the basis of measurements of the residual water found after the extraction step. The results were obtained by volumetric Karl Fischer (KF) titration in a medium containing a large excess of chloroform (> or = 65%), a proposed prerequisite to ensure complete release of water from the oil matrix. In this work, the extent of this residual water was studied by means of a direct zero-current potentiometric technique using a KF medium containing more than 80% chloroform, which is well above the concentration recommended by NIST. A procedure is described that makes it possible to correct the results for dilution errors as well as for chemical interference effects caused by the oil matrix. The corrected values were found to be in the range of 0.6-1.5 ppm, which should be compared with the 12-34 ppm (uncorrected values) reported by NIST for the same oils. From this, it is concluded that the volumetric KF method used by NIST gives results that are much too high. PMID:12659179

Larsson, William; Jalbert, Jocelyn; Gilbert, Roland; Cedergren, Anders

2003-03-15

319

Streamer Evaporation  

NASA Technical Reports Server (NTRS)

Evaporation is the consequence of slow plasma heating near the tops of streamers where the plasma is only weakly contained by the magnetic field. The form it takes is the slow opening of field lines at the top of the streamer and transient formation of new solar wind. It was discovered in polytropic model calculations, where due to the absence of other energy loss mechanisms in magnetostatic streamers, its ultimate endpoint is the complete evaporation of the streamer. This takes, for plausible heating rates, weeks to months in these models. Of course streamers do not behave this way, for more than one reason. One is that there are losses due to thermal conduction to the base of the streamer and radiation from the transition region. Another is that streamer heating must have a characteristic time constant and depend on the ambient physical conditions. We use our global Magnetohydrodynamics (MHD) model with thermal conduction to examine a few examples of the effect of changing the heating scale height and of making ad hoc choices for how the heating depends on ambient conditions. At the same time, we apply and extend the analytic model of streamers, which showed that streamers will be unable to contain plasma for temperatures near the cusp greater than about 2xl0(exp 6) K. Slow solar wind is observed to come from streamers through transient releases. A scenario for this that is consistent with the above physical process is that heating increases the near-cusp temperature until field lines there are forced open. The subsequent evacuation of the flux tubes by the newly forming slow wind decreases the temperature and heating until the flux tubes are able to reclose. Then, over a longer time scale, heating begins to again refill the flux tubes with plasma and increase the temperature until the cycle repeats itself. The calculations we report here are first steps towards quantitative evaluation of this scenario.

Suess, Steven T.; Wang, A. H.; Wu, Shi T.; Nerney, S.

1998-01-01

320

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

USGS Publications Warehouse

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.

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

2008-01-01

321

Effects of crop residue on soil and plant water evaporation in a dryland cotton system  

Microsoft Academic Search

Dryland agricultural cropping systems emphasize sustaining crop yields with limited use of fertilizer while conserving both rain water and the soil. Conservation of these resources may be achieved with management systems that retain residues at the soil surface simultaneously modifying both its energy and water balance. A conservation practice used with cotton grown on erodible soils of the Texas High

R. J. Lascano; R. L. Baumhardt

1996-01-01

322

Flash evaporator systems test  

NASA Technical Reports Server (NTRS)

A flash evaporator heat rejection system representative of that proposed for the space shuttle orbiter underwent extensive system testing at the NASA Johnson Space Center (JSC) to determine its operational suitability and to establish system performance/operational characteristics for use in the shuttle system. During the tests the evaporator system demonstrated its suitability to meet the shuttle requirements by: (1) efficient operation with 90 to 95% water evaporation efficiency, (2) control of outlet temperature to 40 + or - 2 F for partial heat load operation, (3) stability of control system for rapid changes in Freon inlet temperature, and (4) repeated dormant-to-active device operation without any startup procedures.

Dietz, J. B.

1976-01-01

323

ENSO and multi-decadal 'trends' in continental evaporation  

NASA Astrophysics Data System (ADS)

While the hydrological cycle is expected to intensify in response to global warming, little unequivocal evidence of such an acceleration has yet been found on a global scale. This holds in particular for terrestrial evaporation, the crucial return flow of water from continents to atmosphere. Counterintuitively, the few studies that have applied satellite and in situ observations to evaluate multi-decadal trends have uncovered prolonged declines in global average continental evaporation. A priori, these reductions contradict the expectations of an intensifying water cycle. Up to date, the question of whether these declines in evaporation reflect a more permanent feature of global warming or they result from internal climate variability, has been left unanswered. Here, we attempt to answer that question by analyzing global satellite-based datasets of evaporative fluxes, soil moisture and NDVI. Our findings reveal that the reported recent declines in global continental evaporation are not a consequence of a persistent reorganization of the water cycle, but a consequence of internal climate variability. During El Niño, limitations in the supply of moisture in central Australia, southern Africa and eastern South America cause vegetation water-stress and reduced terrestrial evaporation. These regional terrestrial evaporation declines are so pronounced that that determine the total annual volumes of water vapour from continental land surfaces into the atmosphere. Meanwhile, in northern latitudes (where the effects of ENSO are weaker) continental evaporation has raised since the '80s at rates that are consistent with the expectations calculated from air temperature trends. Future changes in continental evaporation will be determined by the response of ENSO to changes in global radiative forcing, which still remains highly uncertain. Opportunely, the increasing timespan of satellite observation records will enable a more significant assessment of the trends in global evaporation in coming years.

Miralles, Diego; Teuling, Ryan; van den Berg, Martinus; Gash, John; Parinussa, Robert; De Jeu, Richard; Beck, Hylke; Holmes, Thomas; Jiménez, Carlos; Verhoest, Niko; Dorigo, Wouter; Dolman, Han

2014-05-01

324

Representative shuttle evaporative heat sink  

NASA Technical Reports Server (NTRS)

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.

Hixon, C. W.

1978-01-01

325

Hot air drum evaporator  

DOEpatents

An evaporation system for aqueous radioactive waste uses standard 30 and 55 gallon drums. Waste solutions form cascading water sprays as they pass over a number of trays arranged in a vertical stack within a drum. Hot dry air is circulated radially of the drum through the water sprays thereby removing water vapor. The system is encased in concrete to prevent exposure to radioactivity. The use of standard 30 and 55 gallon drums permits an inexpensive compact modular design that is readily disposable, thus eliminating maintenance and radiation build-up problems encountered with conventional evaporation systems.

Black, Roger L. (Idaho Falls, ID)

1981-01-01

326

THE USE OF DI WATER TO MITIGATE DUSTING FOR ADDITION OF DWPF FRIT TO THE SLURRY MIX EVAPORATOR  

SciTech Connect

The Defense Waste Processing Facility (DPWF) presently is in the process to determine means to reduce water utilization in the Slurry Mix Evaporator (SME) process, thus reducing effluent and processing times. The frit slurry addition system mixes the dry frit with water, yielding approximately a 50 weight percent slurry containing frit and the other fraction water. This slurry is discharged into the SME and excess water is removed via boiling. To reduce this water load to the SME, DWPF has proposed using a pneumatic system in conveying the frit to the SME, in essence a dry delivery system. The problem associated with utilizing a dry delivery system with the existing frit is the generation of dust when discharged into the SME. The use of water has been shown to be effective in the mining industry as well in the DOE complex to mitigate dusting. The method employed by SRNL to determine the quantity of water to mitigate dusting in dry powders was effective, between a lab and bench scale tests. In those tests, it was shown that as high as five weight percent (wt%) of water addition was required to mitigate dust from batches of glass forming minerals used by the Waste Treatment Plant at Hanford, Washington. The same method used to determine the quantity of water to mitigate dusting was used in this task to determine the quantity of water to mitigate this dusting using as-received frit. The ability for water to mitigate dusting is due to its adhesive properties as shown in Figure 1-1. Wetting the frit particles allows for the smaller frit particles (including dust) to adhere to the larger frit particles or to agglomerate into large particles. Fluids other than water can also be used, but their adhesive properties are different than water and the quantity required to mitigate dusting is different, as was observed in reference 1. Excessive water, a few weight percentages greater than that required to mitigate dusting can cause the resulting material not to flow. The primary objective of this task is to perform bench scale testing on various frits that have been used at DWPF or in test programs at SRNL to determine the quantity of de-ionized (DI) water required to mitigate dusting per mass basis of frit. The quantity of DI water required was determined visually by observing the effluent port of the mixer, and DI water addition was made to the point where no visible dust was observed leaving the effluent port. A total of eight different frits were selected for testing. Secondary objectives in this task include the following: (1) Video taping of the de-dusting procedure, (2) Particle size distribution analyses of the dry and wetted frits at the weight fraction of water required for de-dusting, (3) Plate flow tests to determine angle of flow and quantity of material remaining on plate at 90 degrees, (4) Microscopy of dry and wetted frit, and (5) Effect of excess water for selected frits on plate flow. The above analyses were performed within one hour of water addition, to minimize the effect of evaporative water losses. To better understand the size of dust particles, perform settling tests on selected frits and capture the fines. Analyze the fines for particle size distribution. Finally, it is expected that the surface area of frit is an important parameter in the quantity of water required for dust mitigation. An analysis of particle size distribution (PSD) data of as-received frit analyzed by SRNL over the past two to three years will be performed to determine the variation in the distribution of as-received frit. The following objectives were stated in the Technical Task Request4 as objectives that given adequate time would provide insight in helping DWPF in assessing equipment or processes for de-dusting and processing of dry frit. Due to time constraints, commercial methods for dedusting are provided. These results are detailed in section 3.7. Obtain design information from Hanford with respective to equipment used for dedusting. Suggestions on enhanced design features, such as flush water, pipe air purges, humidified compresse

Hansen, E.

2010-07-21

327

Enzyme Reaction Rates at Limited Water Activities  

Microsoft Academic Search

A well-mixed powder consisting of dry urea and urease exposed to air containing discrete amounts of water vapor showed a release of carbon-14 dioxide above 60-percent relative humidity. The relative activity of urease followed the water-vapor adsorption isotherm of urease. The minimum amount of water required for the reaction observed was 1.3 moles per mole of side-chain polar groups of

J. J. Skujins; A. D. McLaren

1967-01-01

328

Experimental evaluation of a breadboard heat and product-water removal system for a space-power fuel cell designed with static water removal and evaporative cooling  

NASA Technical Reports Server (NTRS)

A test program was conducted to evaluate the design of a heat and product-water removal system to be used with fuel cell having static water removal and evaporative cooling. The program, which was conducted on a breadboard version of the system, provided a general assessment of the design in terms of operational integrity and transient stability. This assessment showed that, on the whole, the concept appears to be inherently sound but that in refining this design, several facets will require additional study. These involve interactions between pressure regulators in the pumping loop that occur when they are not correctly matched and the question of whether an ejector is necessary in the system.

Hagedorn, N. H.; Prokipius, P. R.

1977-01-01

329

Vertical counterflow evaporative cooler  

DOEpatents

An evaporative heat exchanger having parallel plates that define alternating dry and wet passages. A water reservoir is located below the plates and is connected to a water distribution system. Water from the water distribution system flows through the wet passages and wets the surfaces of the plates that form the wet passages. Air flows through the dry passages, mixes with air below the plates, and flows into the wet passages before exiting through the top of the wet passages.

Bourne, Richard C.; Lee, Brian Eric; Callaway, Duncan

2005-01-25

330

Measured soil water evaporation as a function of the square root of time and reference ET  

Technology Transfer Automated Retrieval System (TEKTRAN)

Sunflower (Helianthus annuus L.) is a drought-adapted crop with a short growing season that reduces irrigation requirements and makes it ideal for regions with limited irrigation water supplies. Our objectives were a) to evaluate the yield potential of sunflower under deficit irrigation and b) det...

331

Determining the virtual surface in the thermal evaporation process of magnesium fluoride from a tungsten boat for different deposition rates, to be used in precision optical components  

NASA Astrophysics Data System (ADS)

Vacuum thermal evaporation has, for some time now, been the principal method for the deposition of thin films, given, among other aspects, its simplicity, flexibility, and relatively low cost. Therefore, the development of models attempting to predict the deposition patterns of given thin film materials in different locations of a vacuum evaporation chamber are arguably important. With this in mind, we have designed one of such models for the thermal evaporation process of magnesium fluoride (MgF2), a common material used in optical thin films, originating from a tungsten boat source. For this we took several deposition samples in glass slide substrates at different locations in the vacuum chamber, considering as independent variables the mean deposition rate, and the axial and vertical distances of the source to the substrate. After a careful analysis by matrix method from the spectral transmittance data of the samples, while providing as output data the spectral transmittance, as well as the physical thickness of the films, both as functions of the aforementioned variables, the virtual surface of the source was determined.

Tejada Esteves, A.; Gálvez de la Puente, G.

2013-11-01

332

Effect of argon gas flow rate on properties of film electrodes prepared by thermal vacuum evaporation from synthesized Cu{sub 2}SnSe{sub 3} source  

SciTech Connect

This work describes a new technique to enhance photoresponse of metal chalcogenide-based semiconductor film electrodes deposited by thermal vacuum evaporation under argon gas flow from synthesized Cu{sub 2}SnSe{sub 3} sources. SnSe formation with Cu-doped was obtained under higher argon gas flow rate (V{sub A} = 25 cm{sup 3}/min). Higher value of photoresponse was observed for films deposited under V{sub A} = 25 cm{sup 3}/min which was 9.1%. This finding indicates that Cu atoms inside the SnSe film were important to increase carrier concentrations that promote higher photoresponse.

Sabli, Nordin; Talib, Zainal Abidin; Yunus, Wan Mahmood Mat [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang (Malaysia); Zainal, Zulkarnain [Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang (Malaysia); Hilal, Hikmat S. [SSERL, Department of Chemistry An-Najah N. University, PO Box 7, Nablus, West Bank (Country Unknown); Fujii, Masatoshi [Department of Molecular Science, School of Medicine, Shimane University, Izumo, Shimane, 693-8501 (Japan)

2014-03-05

333

Metallization: Evaporation  

NSDL National Science Digital Library

This website includes an animation depicting an overview of the metallization evaporation processes. Objective: Identify the process of evaporation. This simulation is from Module 061 of the Process & Equipment II Cluster of the MATEC Module Library (MML). You can find this animation under the section "Process & Equipment II." To view other clusters or for more information about the MML visit http://matec.org/ps/library3/process_I.shtml

334

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

USGS Publications Warehouse

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.

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

2000-01-01

335

EFFECTS OF ADDITION RATE AND ACID MATRIX ON THE DESTRUCTION OF AMMONIUM BY THE SEMI-CONTINUOUS ADDITION OF SODIUM NITRITE DURING EVAPORATION  

SciTech Connect

The destruction of ammonium by the semi-continuous addition of sodium nitrite during acidic evaporation can be achieved with a wide range of waste compositions. The efficiency of nitrite utilization for ammonium destruction was observed to vary from less than 20% to 60% depending on operating conditions. The effects of nitric acid concentration and nitrite addition rate are dominant factors that affect the efficiency of nitrite utilization for ammonium destruction. Reducing the acid concentration by performing acid recovery via steam stripping prior to performing nitrite destruction of ammonium will require more nitrite due to the low destruction efficiency. The scale-up of the baseline rate nitrite addition rate from the 100 mL to the 1600 gallon batch size has significant uncertainty and poses the risk of lower efficiency at the plant scale. Experience with plant scale processing will improve confidence in the application of nitrite destruction of ammonium to different waste streams.

Kyser, E

2007-08-27

336

Cooling rate, heating rate, and aging effects in glassy water Nicolas Giovambattista,1  

E-print Network

Cooling rate, heating rate, and aging effects in glassy water Nicolas Giovambattista,1 H. Eugene on the cooling/heating rates as well as on the role of aging (the time elapsed in the glass state). We compare also study the heating rate and aging effects in the glass. We work in the framework of the potential

Sciortino, Francesco

337

Preparation of amorphous solid dispersions by rotary evaporation and KinetiSol Dispersing: approaches to enhance solubility of a poorly water-soluble gum extract.  

PubMed

Acetyl-11-keto-?-boswellic acid (AKBA), a gum resin extract, possesses poor water-solubility that limits bioavailability and a high melting point making it difficult to successfully process into solid dispersions by fusion methods. The purpose of this study was to investigate solvent and thermal processing techniques for the preparation of amorphous solid dispersions (ASDs) exhibiting enhanced solubility, dissolution rates and bioavailability. Solid dispersions were successfully produced by rotary evaporation (RE) and KinetiSol® Dispersing (KSD). Solid state and chemical characterization revealed that ASD with good potency and purity were produced by both RE and KSD. Results of the RE studies demonstrated that AQOAT®-LF, AQOAT®-MF, Eudragit® L100-55 and Soluplus with the incorporation of dioctyl sulfosuccinate sodium provided substantial solubility enhancement. Non-sink dissolution analysis showed enhanced dissolution properties for KSD-processed solid dispersions in comparison to RE-processed solid dispersions. Variances in release performance were identified when different particle size fractions of KSD samples were analyzed. Selected RE samples varying in particle surface morphologies were placed under storage and exhibited crystalline growth following solid-state stability analysis at 12 months in comparison to stored KSD samples confirming amorphous instability for RE products. In vivo analysis of KSD-processed solid dispersions revealed significantly enhanced AKBA absorption in comparison to the neat, active substance. PMID:24329130

Bennett, Ryan C; Brough, Chris; Miller, Dave A; O'Donnell, Kevin P; Keen, Justin M; Hughey, Justin R; Williams, Robert O; McGinity, James W

2015-03-01

338

Improved Evaporation Measurements from Lake Tahoe, California  

Microsoft Academic Search

Accurate measurements of evaporation are important to management of water storage as well as to understanding turnover and nutrient storage in lakes. Evaporation has been a poorly constrained component of past water budget studies of Lake Tahoe, California and is the last major unknown for effective management of the Truckee River basin under the Truckee River Operating Agreement (TROA). Evaporation

G. L. Dana; J. C. Trask

2001-01-01

339

Parameterizations for sulfuric acid\\/water nucleation rates  

Microsoft Academic Search

We present parametrized equations for calculation of sulfuric acid\\/water critical nucleus compositions and homogeneous nucleation rates. The parameterizations are in agreement with the thermodynamically consistent version of classical binary homogeneous nucleation theory [Wilemski, 1984] incorporating the hydration effect. The new parameterizations produce nucleation rates that differ by several orders of magnitude from the rates predicted by other parameterizations available in

Markku Kulmala; Ari Laaksonen; Liisa Pirjola

1998-01-01

340

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

PubMed

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. PMID:22277832

Erbil, H Yildirim

2012-01-15

341

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

NASA Astrophysics Data System (ADS)

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.

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

2009-12-01

342

Tritiated water for estimating total body water and water turnover rate in birds.  

PubMed

The use of tritiated water (TOH) to estimate total body water (TBW) and total water turnover rate was validated in chukar partridges (Alectoris chukar) and sand partridges (Ammoperdix heyi). For six chukar partridges weighing between 315 to 475 g, TOH equilibration with body fluids was less than 45 min after intramuscular or intravenous injections. Mean TOH space in eight chukar partridges was 99.8% of the mean TBW measured by desiccation with individuals ranging between 97.9 and 103.2%. TOH space best approximated TBW when TBW was calculated by using the mean body mass for a bird weighed at TOH injection and at TOH equilibration. Total water intake as estimated by TOH ranged between 90.7 and 113.3% of measured water intake in three sand and three chukar partridges, birds ranging in mass from 145 to 446 g. We conclude that the TOH method provides accurate estimations of TBW and water turnover rates in birds. For birds of up to 500-g body mass, we recommend 45 min for TOH equilibration with body fluids, and intramuscular injections of 0.05 muCi TOH/g body mass for TBW estimations and 0.1 muCi TOH/g body mass for water turnover estimations. PMID:7298458

Degen, A A; Pinshow, B; Alkon, P U; Arnon, H

1981-11-01

343

Thermal tolerance, evaporative water loss, air-water oxygen consumption and zonation of intertidal prosobranchs: a new synthesis  

Microsoft Academic Search

Duration of emergence increases with tidal height on rocky shores therefore, emergence adaptations in intertidal species such as littorine and other prosobranch gastropods have been considered correlated with zonation patterns; temperature tolerance, desiccation resistance and aerial respiration rate all commonly assumed to increase progressively with increasing zonation level. Such direct correlations are rarely observed in nature. Maximal aerial gas exchange

Robert F. McMahon

1990-01-01

344

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

USGS Publications Warehouse

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.

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

2006-01-01

345

Kinetic multi-layer model of gas-particle interactions in aerosols and clouds (KM-GAP): linking condensation, evaporation and chemical reactions of organics, oxidants and water  

NASA Astrophysics Data System (ADS)

We present a novel kinetic multi-layer model for gas-particle interactions in aerosols and clouds (KM-GAP) that treats explicitly all steps of mass transport and chemical reaction of semi-volatile species partitioning between gas phase, particle surface and particle bulk. KM-GAP is based on the PRA model framework (Pöschl-Rudich-Ammann, 2007), and it includes gas phase diffusion, reversible adsorption, surface reactions, bulk diffusion and reaction, as well as condensation, evaporation and heat transfer. The size change of atmospheric particles and the temporal evolution and spatial profile of the concentration of individual chemical species can be modeled along with gas uptake and accommodation coefficients. Depending on the complexity of the investigated system and the computational constraints, unlimited numbers of semi-volatile species, chemical reactions, and physical processes can be treated, and the model shall help to bridge gaps in the understanding and quantification of multiphase chemistry and microphysics in atmospheric aerosols and clouds. In this study we demonstrate how KM-GAP can be used to analyze, interpret and design experimental investigations of changes in particle size and chemical composition in response to condensation, evaporation, and chemical reaction. For the condensational growth of water droplets, our kinetic model results provide a direct link between laboratory observations and molecular dynamic simulations, confirming that the accommodation coefficient of water at ~270 K is close to unity (Winkler et al., 2006). Literature data on the evaporation of dioctyl phthalate as a function of particle size and time can be reproduced, and the model results suggest that changes in the experimental conditions like aerosol particle concentration and chamber geometry may influence the evaporation kinetics and can be optimized for efficient probing of specific physical effects and parameters. With regard to oxidative aging of organic aerosol particles, we illustrate how the formation and evaporation of volatile reaction products like nonanal can cause a decrease in the size of oleic acid particles exposed to ozone.

Shiraiwa, M.; Pfrang, C.; Koop, T.; Pöschl, U.

2012-03-01

346

Kinetic multi-layer model of gas-particle interactions in aerosols and clouds (KM-GAP): linking condensation, evaporation and chemical reactions of organics, oxidants and water  

NASA Astrophysics Data System (ADS)

We present a novel kinetic multi-layer model for gas-particle interactions in aerosols and clouds (KM-GAP) that treats explicitly all steps of mass transport and chemical reaction of semi-volatile species partitioning between gas phase, particle surface and particle bulk. KM-GAP is based on the PRA model framework (Pöschl-Rudich-Ammann, 2007), and it includes gas phase diffusion, reversible adsorption, surface reactions, bulk diffusion and reaction, as well as condensation, evaporation and heat transfer. The size change of atmospheric particles and the temporal evolution and spatial profile of the concentration of individual chemical species can be modeled along with gas uptake and accommodation coefficients. Depending on the complexity of the investigated system, unlimited numbers of semi-volatile species, chemical reactions, and physical processes can be treated, and the model shall help to bridge gaps in the understanding and quantification of multiphase chemistry and microphysics in atmospheric aerosols and clouds. In this study we demonstrate how KM-GAP can be used to analyze, interpret and design experimental investigations of changes in particle size and chemical composition in response to condensation, evaporation, and chemical reaction. For the condensational growth of water droplets, our kinetic model results provide a direct link between laboratory observations and molecular dynamic simulations, confirming that the accommodation coefficient of water at ~270 K is close to unity. Literature data on the evaporation of dioctyl phthalate as a function of particle size and time can be reproduced, and the model results suggest that changes in the experimental conditions like aerosol particle concentration and chamber geometry may influence the evaporation kinetics and can be optimized for efficient probing of specific physical effects and parameters. With regard to oxidative aging of organic aerosol particles, we illustrate how the formation and evaporation of volatile reaction products like nonanal can cause a decrease in the size of oleic acid particles exposed to ozone.

Shiraiwa, M.; Pfrang, C.; Koop, T.; Pöschl, U.

2011-12-01

347

Effects of evaporative cooling on the regulation of body water and milk production in crossbred Holstein cattle in a tropical environment.  

PubMed

The aim of this study was to determine how evaporative cooling modifies body function with respect to water metabolism and other variables relevant to milk synthesis in crossbred cattle. The study was conducted on two groups of 0.875HF:0.125RS crossbred Holstein cattle (87.5%) housed in an open-sided barn with a tiled roof (non-cooled animals) and in a close-sided barn under an evaporative cooling system (cooled animals). The maximum ambient temperature and relative humidity for the non-cooled group were 33 degrees C and 61%, with the corresponding values for the evaporatively cooled barn being 28 degrees C and 84%, respectively. The temperature humidity index (THI) of under non-cooled conditions was higher (P < 0.05) than that in the cooled barn. Rectal temperatures and respiration rates of non-cooled animals were higher (P < 0.05) than those of cooled animals. Daily dry matter intake (DMI) of cooled animals was higher while water intakes were lower (P < 0.05) than those of non-cooled animals. The mean absolute values of plasma volume, blood volume, and extracellular fluid (ECF) of cooled animals were significantly higher (P < 0.05) than those of non-cooled animals throughout all stages of lactation. Milk yields of cooled animals were higher by 42%, 36% and 79% on average than those of non-cooled animals during early-, mid- and late-lactation, respectively. The decline in milk yields as lactation advances was markedly apparent in late-lactating non-cooled animals, while no significant changes in milk composition at different stages of lactation were observed in either group. Mean arterial plasma concentrations, arteriovenous concentration differences (A-V differences) and the extraction ratio across the mammary gland for acetate, glucose and triglyceride of cooled animals were not significantly different compared with values for non-cooled animals. No differences were seen in plasma hormonal levels for triiodotyronine (T(3)) and insulin-like growth factor-1 (IGF-1), but plasma cortisol and thyroxine (T(4)) levels tended to be lower in non-cooled animals. This study suggests that low cooling temperature accompanied by high humidity influences a galactopoietic effect, in part through increases in ECF, blood volume and plasma volume in association with an increase in DMI, which partitions the distribution of nutrients to the mammary gland for milk synthesis. Cooled animals were unable to maintain high milk yield as lactation advances even though a high level of body fluids was maintained during long-term cooled exposure. The decline in milk yield, coinciding with a decrease in net energy for lactation as lactation advances, could be attributed to a local change within the mammary gland. PMID:18427839

Chaiyabutr, N; Chanpongsang, S; Suadsong, S

2008-09-01

348

Root water compensation sustains transpiration rates in an Australian woodland  

NASA Astrophysics Data System (ADS)

We apply a model of root-water uptake to a woodland in Australia to examine the regulation of transpiration by root water compensation (i.e., the ability of roots to regulate root water uptake from different parts of the soil profile depending on local moisture availability). We model soil water movement using the Richards equation and water flow in the xylem with Darcy's equation. These two equations are coupled by a term that governs the exchange of water between soil and root xylem as a function of the difference in water potential between the two. The model is able to reproduce measured diurnal patterns of sap flux and results in leaf water potentials that are consistent with field observations. The model shows that root water compensation is a key process to allow for sustained rates of transpiration across several months. Scenarios with different root depths showed the importance of having a root system deeper than about 2 m to achieve the measured transpiration rates without reducing the leaf water potential to levels inconsistent with field measurements. The model suggests that the presence of more than 5 % of the root system below 0.6 m allows trees to maintain sustained transpiration rates keeping leaf water potential levels within the range observed in the field. According to the model, a large contribution to transpiration in dry periods was provided by the roots below 0.3 m, even though the percentage of roots at these depths was less than 40 % in all scenarios.

Verma, Parikshit; Loheide, Steven P.; Eamus, Derek; Daly, Edoardo

2014-12-01

349

Impact of the Air Flow Pattern and the Thermal Load in a Room on the Heat and Mass Transfer Coefficient across a Person, especially on the Evaporation of Water from the Eyes  

Microsoft Academic Search

The evaporation of water from a small humidified area at head level of a heated dummy is measured. The aim is to find out the influence of the relative humidity and the local mass transfer coefficient on the local evaporation with respect to the behaviour of the tear film in eyes. It is obvious that not only the relative humidity,

KLAUS FITZNER; INGO GORES

350

COMPARING CONSTANT-RATE AND DECLINING-RATE DIRECT FILTRATION OF A SURFACE WATER  

EPA Science Inventory

Pilot-scale constant-rate and declining-rate direct filtration systems were evaluated for treating a high quality surface water, using two flow rates and alum or cationic polymer as the primary coagulant. Turbidity, particle count, and total coliform count were used to compare fi...

351

Evaporation from a small prairie wetland in the Cottonwood Lake Area, North Dakota - An energy-budget study  

USGS Publications Warehouse

Evaporation from Wetland Pl in the Cottonwood Lake area of North Dakota, USA was determined by the energy-budget method for 1982-85 and 1987. Evaporation rates were as high as 0.672 cm day-1. Incoming solar radiation, incoming atmospheric radiation, and long-wave radiation emitted from the water body are the largest energy fluxes to and from the wetland. Because of the small heat storage of the water body, evaporation rates closely track solar radiation on short time scales. The effect of advected energy related to precipitation is small because the water quickly heats up by solar radiation following precipitation. Advected energy related to ground water is minimal because ground-water fluxes are small and groundwater temperature is only about 7 ??C. Energy flux related to sediment heating and thermal storage in the sediments, which might be expected to be large because the water is clear and shallow, affects evaporation rates by less than 5 percent.

Parkhurst, R.S.; Winter, T.C.; Rosenberry, D.O.; Sturrock, A.M.

1998-01-01

352

Sensitivity of potential evaporation estimates to 100 years of climate variability  

NASA Astrophysics Data System (ADS)

Hydrological modeling frameworks require an accurate representation of evaporation fluxes for appropriate quantification of, e.g., the water balance, soil moisture budget, recharge and groundwater processes. Many frameworks have used the concept of potential evaporation, often estimated for different vegetation classes by multiplying the evaporation from a reference surface ("reference evaporation") by crop-specific scaling factors ("crop factors"). Though this two-step potential evaporation approach undoubtedly has practical advantages, the empirical nature of both reference evaporation methods and crop factors limits its usability in extrapolations under non-stationary climatic conditions. In this paper, rather than simply warning about the dangers of extrapolation, we quantify the sensitivity of potential evaporation estimates for different vegetation classes using the two-step approach when calibrated using a non-stationary climate. We used the past century's time series of observed climate, containing non-stationary signals of multi-decadal atmospheric oscillations, global warming, and global dimming/brightening, to evaluate the sensitivity of potential evaporation estimates to the choice and length of the calibration period. We show that using empirical coefficients outside their calibration range may lead to systematic differences between process-based and empirical reference evaporation methods, and systematic errors in estimated potential evaporation components. Quantification of errors provides a possibility to correct potential evaporation calculations and to rate them for their suitability to model climate conditions that differ significantly from the historical record, so-called no-analog climate conditions.

Bartholomeus, R. P.; Stagge, J. H.; Tallaksen, L. M.; Witte, J. P. M.

2015-02-01

353

Evaporative Cooler  

NSDL National Science Digital Library

Explore the concept of evaporative cooling through a hands-on experiment. Use a wet cloth and fan to model an air-conditioner and use temperature and relative humidity sensors to collect data. Then digitally plot the data using graphs in the activity. In an optional extension, make your own modifications to improve the cooler's efficiency.

2012-07-19

354

Evaporating firewalls  

NASA Astrophysics Data System (ADS)

In this note, we begin by presenting an argument suggesting that large AdS black holes dual to typical high-energy pure states of a single holographic CFT must have some structure at the horizon, i.e. a fuzzball/firewall, unless the procedure to probe physics behind the horizon is state-dependent. By weakly coupling the CFT to an auxiliary system, such a black hole can be made to evaporate. In a case where the auxiliary system is a second identical CFT, it is possible (for specific initial states) that the system evolves to precisely the thermofield double state as the original black hole evaporates. In this case, the dual geometry should include the "late-time" part of the eternal AdS black hole spacetime which includes smooth spacetime behind the horizon of the original black hole. Thus, if a firewall is present initially, it evaporates. This provides a specific realization of the recent ideas of Maldacena and Susskind that the existence of smooth spacetime behind the horizon of an evaporating black hole can be enabled by maximal entanglement with a Hawking radiation system (in our case the second CFT) rather than prevented by it. For initial states which are not finely-tuned to produce the thermofield double state, the question of whether a late-time infalling observer experiences a firewall translates to a question about the gravity dual of a typical high-energy state of a two-CFT system.

Van Raamsdonk, Mark

2014-11-01

355

Evaporation-driven instability of the precorneal tear film.  

PubMed

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. PMID:23842140

Peng, Cheng-Chun; Cerretani, Colin; Braun, Richard J; Radke, C J

2014-04-01

356

An indirect evaporative chiller  

Microsoft Academic Search

A novel indirect evaporative chiller driven by outdoor dry air to produce cold water as the cooling source for air conditioning\\u000a systems is introduced, and the principle and the structure of the chiller is presented. The cold water can be produced almost\\u000a reversibly under ideal working conditions, with its temperature infinitely close to the dew point temperature of the inlet

Xiaoyun Xie; Yi Jiang

2010-01-01

357

Household Responses to Increased Water Rates during the California Drought  

Microsoft Academic Search

This paper explores the use of fixed effects and maximum likelihood techniques to estimate household responses to water price increases during the California drought. Estimates are based on bimonthly meter readings from 599 single-family households in the Alameda County Water District over the period 1982-1992, before and after the introduction of a steeply increasing block rate price structure. I find

Ellen M. Pint

1999-01-01

358

Microdroplet evaporation with a forced pinned contact line.  

PubMed

Experimental and numerical investigations of water microdroplet evaporation on heated, laser patterned polymer substrates are reported. The study is focused on both (i) controlling a droplet's contact line dynamics during evaporation to identifying how the contact line influences evaporative heat transfer and (ii) validating numerical simulations with experimental data. Droplets are formed on the polymer surface using a bottom-up methodology, where a computer-controlled syringe pump feeds water through a 200 ?m diameter fluid channel within the heated polymer substrate. This methodology facilitates precise control of the droplet's growth rate, size, and inlet temperature. In addition to this microchannel supply line, the substrate surfaces are laser patterned with a moatlike trench around the fluid-channel outlet, adding additional control of the droplet's contact line motion, area, and contact angle. In comparison to evaporation on a nonpatterned polymer surface, the laser patterned trench increases contact line pinning time by ?60% of the droplet's lifetime. Numerical simulations of diffusion controlled evaporation are compared the experimental data with a pinned contact line. These diffusion based simulations consistently over predict the droplet's evaporation rate. In efforts to improve this model, a temperature distribution along the droplet's liquid-vapor interface is imposed to account for the concentration distribution of saturated vapor along the interface, which yields improved predictions within 2-4% of the experimental data throughout the droplet's lifetime on heated substrates. PMID:25102248

Gleason, Kevin; Putnam, Shawn A

2014-09-01

359

Properties of water surface discharge at different pulse repetition rates  

NASA Astrophysics Data System (ADS)

The properties of water surface discharge plasma for variety of pulse repetition rates are investigated. A magnetic pulse compression (MPC) pulsed power modulator able to deliver pulse repetition rates up to 1000 Hz, with 0.5 J per pulse energy output at 25 kV, was used as the pulsed power source. Positive pulse with a point-to-plane electrode configuration was used for the experiments. The concentration and production yield of hydrogen peroxide (H2O2) were quantitatively measured and orange II organic dye was treated, to evaluate the chemical properties of the discharge reactor. Experimental results show that the physical and chemical properties of water surface discharge are not influenced by pulse repetition rate, very different from those observed for under water discharge. The production yield of H2O2 and degradation rate per pulse of the dye did not significantly vary at different pulse repetition rates under a constant discharge mode on water surface. In addition, the solution temperature, pH, and conductivity for both water surface and underwater discharge reactors were measured to compare their plasma properties for different pulse repetition rates. The results confirm that surface discharge can be employed at high pulse repetition rates as a reliable and advantageous method for industrial and environmental decontamination applications.

Ruma, Hosseini, S. H. R.; Yoshihara, K.; Akiyama, M.; Sakugawa, T.; Lukeš, P.; Akiyama, H.

2014-09-01

360

Properties of water surface discharge at different pulse repetition rates  

SciTech Connect

The properties of water surface discharge plasma for variety of pulse repetition rates are investigated. A magnetic pulse compression (MPC) pulsed power modulator able to deliver pulse repetition rates up to 1000?Hz, with 0.5?J per pulse energy output at 25?kV, was used as the pulsed power source. Positive pulse with a point-to-plane electrode configuration was used for the experiments. The concentration and production yield of hydrogen peroxide (H{sub 2}O{sub 2}) were quantitatively measured and orange II organic dye was treated, to evaluate the chemical properties of the discharge reactor. Experimental results show that the physical and chemical properties of water surface discharge are not influenced by pulse repetition rate, very different from those observed for under water discharge. The production yield of H{sub 2}O{sub 2} and degradation rate per pulse of the dye did not significantly vary at different pulse repetition rates under a constant discharge mode on water surface. In addition, the solution temperature, pH, and conductivity for both water surface and underwater discharge reactors were measured to compare their plasma properties for different pulse repetition rates. The results confirm that surface discharge can be employed at high pulse repetition rates as a reliable and advantageous method for industrial and environmental decontamination applications.

Ruma,; Yoshihara, K. [Graduate School of Science and Technology, Kumamoto University, Kumamoto 860-8555 (Japan); Hosseini, S. H. R., E-mail: hosseini@kumamoto-u.ac.jp; Sakugawa, T.; Akiyama, H. [Graduate School of Science and Technology, Kumamoto University, Kumamoto 860-8555 (Japan); Institute of Pulsed Power Science, Kumamoto University, Kumamoto 860-8555 (Japan); Akiyama, M. [Department of Electrical and Electronic Engineering, Kagoshima University, Kagoshima 890-0065 (Japan); Lukeš, P. [Institute of Plasma Physics, AS CR, Prague, Prague 18200 (Czech Republic)

2014-09-28

361

Pore scale model for evaporation dynamics from soil surfaces with patchy wetness  

NASA Astrophysics Data System (ADS)

The gradual reduction in drying rates from soil surfaces under high atmospheric demand is often attributed to constraints imposed by internal transport mechanisms limiting capillary flows from soil interior towards vaporization plane at the surface. Experimental evidence for high evaporation rates under non-limiting capillary flow conditions suggests that interactions between pore-scale diffusive fluxes from gradually drying porous surfaces and diffusive resistance across air boundary layer thickness, play a crucial role in shaping evaporation dynamics. Results from evaporation experiments using sand columns subjected to potential drying rates ranging from 2 to 30 mm/day (defined by prescribed air velocities) show that for high evaporative demands (>5 mm/day), evaporation rates decreased gradually until a transition to diffusion-controlled stage-II evaporation. In contrast, under low air velocities, a constant drying rate was established and maintained irrespective of drying of the surface or receding drying front. A pore scale model for surface coupling shows evolution of vapor density field from 1-D stratified pattern for the uniformly wet surface to 3-D vapor shells forming over active pores as the surface dries. Calculations show that per-pore vapor diffusion flux increases with increased pore spacing, reduced pore size, and boundary layer thickness. Consequently, for low evaporative demand and thick boundary layer, the resulting flux from isolated pores may fully compensate for reduced surface water content (evaporating area) resulting in constant evaporation rates. These results also suggest that flux compensation for patchy wetness is likely to be less efficient than for spatially (uniformly) distributed pores and thus results in reduced evaporation rates even for low atmospheric demand. The study will address the additional key parameter of wetness patch size and the patchiness spatial structure in relation to boundary layer thickness and impact on evaporation dynamics from heterogeneous surfaces.

Shahraeeni, E.; Lehmann, P.; Or, D.

2012-04-01

362

Realistic Hot Water Draw Specification for Rating Solar Water Heaters: Preprint  

SciTech Connect

In the United States, annual performance ratings for solar water heaters are simulated, using TMY weather and specified water draw. A more-realistic ratings draw is proposed that eliminates most bias by improving mains inlet temperature and by specifying realistic hot water use. This paper outlines the current and the proposed draws and estimates typical ratings changes from draw specification changes for typical systems in four cities.

Burch, J.

2012-06-01

363

Original article Irrigation, faecal water content and development rate  

E-print Network

Original article Irrigation, faecal water content and development rate of free-living stages of irrigation by flooding the pastures on the ability of the eggs of sheep Tri- chostrongyles to develop irrigation or submerged, at different times and durations. The rates of development of Teladorsagia

Paris-Sud XI, Université de

364

Analysis of the e-beam evaporation of titanium and Ti-6Al-4V  

SciTech Connect

An experimental and finite element analysis was performed for the electron-beam evaporation of Ti and Ti-6Al-4V from a bottom-feed system. The bulk evaporation rate was measured by feed consumption, and the pool elevation was held constant by adjusting the feed rate in a closed-loop control system. The instantaneous titanium and aluminum evaporation rates were determined by laser absorption in the vapor plume. Water temperature rises in cooling water circuits provided heat flows, and post-run cross sections revealed the location of the solidification zone. The MELT finite element code was applied to model the steady-state two-dimensional fluid flow and energy transport in the rod. There was good agreement between model and measured values of the heat flows and solidification boundaries for Ti. Measured bulk evaporation rates were similar for Ti and Ti-6-4 with greater variation observed for the Ti values. The model evaporation rates were higher than the measured values, but a similar linear dependence on e-beam power was observed in all cases. In a Ti-6-4 evaporation experiment with steady process conditions, laser absorption measurements showed much larger fluctuations in the evaporation rate for Al than Ti.

Westerberg, K.W.; Merier, T.C.; McClelland, M.A.; Braun, D.G.; Berzins, L.V.; Anklam, T.M.; Storer, J.

1998-02-11

365

Streamer Evaporation  

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

366

An evaporation model of colloidal suspension droplets  

NASA Astrophysics Data System (ADS)

Colloidal suspensions of polymers in water or other solvents are widely used in the pharmaceutical industry to coat tablets with different agents. These allow controlling the rate at which the drug is delivered, taste or physical appearance. The coating is performed by simultaneously spraying and drying the tablets with the colloidal suspension at moderately high temperatures. The spreading of the coating on the pills surface depends on the droplet Webber and Reynolds numbers, angle of impact, but more importantly on the rheological properties of the drop. We present a model for the evaporation of a colloidal suspension droplet in a hot air environment with temperatures substantially lower than the boiling temperature of the carrier fluid. As the liquid vaporizes from the surface, a compacting front advances into the droplet faster than the liquid surface regresses, forming a shell of a porous medium where the particles reach their maximum packing density. While the surface regresses, the evaporation rate is determined by both the rate at which heat is transported to the droplet surface and the rate at which liquid vapor is diffused away from it. This regime continues until the compacting front reaches the center of the droplet, at which point the evaporation rate is drastically reduced.

Sartori, Silvana; Li\\ Nán, Amable; Lasheras, Juan C.

2009-11-01

367

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

PubMed

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. PMID:25372453

Zhong, Xin; Duan, Fei

2014-11-26

368

Impact of ambient conditions on evaporation from porous media  

NASA Astrophysics Data System (ADS)

The complexity of soil evaporation, depending on the atmospheric conditions, emphasizes the importance of its quantification under potential changes in ambient air temperature, Ta, and relative humidity, RH. Mass loss, soil matric tension, and meteorological measurements, carried out in a climate-controlled laboratory, were used to study the effect of ambient conditions on the drying rates of a porous medium. A set of evaporation experiments from initially saturated sand columns were carried out under constant Ta of 6, 15, 25, and 35°C and related RH (0.66, 0.83, 1.08, and 1.41 kPa, respectively). The results show that the expected increase of the stage 1 (S1) evaporation rate with Ta but also revealed an exponential-like reduction in the duration of S1, which decreased from 29 to 2.3 days (at Ta of 6 and 35°C, respectively). The evaporation rate, e(t), was equal to the potential evaporation, ep(t), under Ta = 6°C, while it was always smaller than ep(t) under higher Ta. The cumulative evaporation during S1 was higher under Ta = 6°C than under the higher temperatures. Evaporation rates during S2 were practically unaffected by ambient conditions. The results were analyzed using a mass transfer formulation linking e(t) with the vapor pressure deficit through a resistance coefficient r. It was shown that rS1 (the resistance during S1) is constant, indicating that the application of such an approach is straightforward during S1. However, for evaporation from a free water surface and S2, the resistances, rBL and rS2, were temperature-dependent, introducing some complexity for these cases.

Ben Neriah, Asaf; Assouline, Shmuel; Shavit, Uri; Weisbrod, Noam

2014-08-01

369

Soil water content and evaporation determined by thermal parameters obtained from ground-based and remote measurements  

NASA Technical Reports Server (NTRS)

A procedure is presented for calculating 24-hour totals of evaporation from wet and drying soils. Its application requires a knowledge of the daily solar radiation, the maximum and minimum, air temperatures, moist surface albedo, and maximum and minimum surface temperatures. Tests of the technique on a bare field of Avondale loam at Phoenix, Arizona showed it to be independent of season.

Reginato, R.; Idso, S.; Vedder, J.; Jackson, R.; Blanchard, M.; Goettelman, R.

1975-01-01

370

The Preparation and Characterization of Poly(lactide-co-glycolide) Microparticles. II. The Entrapment of a Model Protein Using a (Water-in-Oil)inWater Emulsion Solvent Evaporation Technique  

Microsoft Academic Search

Poly(lactide-co-glycolide) (PLG) microparticles with entrapped antigens have recently been investigated as controlled-release vaccines. This paper describes the preparation of PLG microparticles with an entrapped model antigen, ovalbumin (OVA), using a (water-in-oil)-in-water emulsion solvent evaporation technique. In a series of experiments, the effects of process parameters on particle size and OVA entrapment were investigated. It was found that smooth, spherical microparticles

Hayley Jeffery; Stanley S. Davis; Derek T. O'Hagan

1993-01-01

371

Measurement of the rate of water translocation through carbon nanotubes.  

PubMed

We present an approach for measuring the water flow rate through individual ultralong carbon nanotubes (CNTs) using field effect transistors array defined on individual tubes. Our work exhibits a rate enhancement of 882-51 and a slip length of 53-8 nm for CNTs with diameters of 0.81-1.59 nm. We also found that the enhancement factor does not increase monotonically with shrinking tube diameter and there exists a discontinuous region around 0.98-1.10 nm. We believe that these single-tube level results would help understand the intrinsic nanofluidics of water in CNTs. PMID:21462938

Qin, Xingcai; Yuan, Quanzi; Zhao, Yapu; Xie, Shubao; Liu, Zhongfan

2011-05-11

372

Water Exchange Rates and Molecular Mechanism around Aqueous Halide Ions  

SciTech Connect

Molecular dynamics simulations were performed to systematically study the water-exchange mechanism around aqueous chloride, bromide, and iodide ions. Transition state theory, Grote-Hynes theory, and the reactive flux method were employed to compute water exchange rates. We computed the pressure dependence of rate constants and the corresponding activation volumes to investigate the mechanism of the solvent exchange event. The activation volumes obtained using the transition state theory rate constants are negative for all the three anions, thus indicating an associative mechanism. Contrary to the transition state theory results, activation volumes obtained using rate constants from Grote-Hynes theory and the reactive flux method are positive, thus indicating a dissociative mechanism. The Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences (BES), of the U.S. Department of Energy (DOE) funded this work. Battelle operates Pacific Northwest National Laboratory for DOE. The calculations were carried out using computer resources provided by BES.

Annapureddy, Harsha V.; Dang, Liem X.

2014-07-17

373

Photoluminescence and anti-deliquesce of cesium iodide and its sodium-doped films deposited by thermal evaporation at high deposition rates  

NASA Astrophysics Data System (ADS)

Cesium iodide (CsI) and sodium iodide (NaI) are good scintillators due to their high luminescence efficiency. These alkali halides can be excited by ultra-violet or by ionizing radiation. In this study, CsI and its Na-doped films about 8 ?m thick were deposited by thermal evaporation boat without heating substrates at high deposition rates of 30, 50, 70, 90, and 110 nm/sec, respectively. The as-deposited films were sequentially deposited a silicon dioxide film to protect from deliquesce. And, the films were also post-annealed in vacuum at 150, 200, 250, and 300 °C, respectively. We calculated the packing densities of the samples according to the measurements of Fourier transform infrared spectroscopy (FTIR) and observed the luminescence properties by photoluminescence (PL) system. The surfaces and cross sections of the films were investigated by scanning electron microscope (SEM). From the above measurements we can find the optimal deposition rate of 90 nm/sec and post-annealing temperature of 250 °C in vacuum for the asdeposited cesium iodide and its sodium-doped films.

Hsu, Jin-Cherng; Chiang, Yueh-Sheng; Ma, Yu-Sheng

2013-03-01

374

Heteroaggregation and sedimentation rates for nanomaterials in natural waters.  

PubMed

Exposure modeling of engineered nanomaterials requires input parameters such as sedimentation rates and heteroaggregation rates. Here, we estimate these rates using quiescent settling experiments under environmentally relevant conditions. We investigated 4 different nanomaterials (C60, CeO2, SiO2-Ag and PVP-Ag) in 6 different water types ranging from a small stream to seawater. In the presence of natural colloids, sedimentation rates ranged from 0.0001 m d(-1) for SiO2-Ag to 0.14 m d(-1) for C60. The apparent rates of heteroaggregation between nanomaterials and natural colloids were estimated using a novel method that separates heteroaggregation from homoaggregation using a simplified Smoluchowski-based aggregation-settling equation applied to data from unfiltered and filtered waters. The heteroaggregation rates ranged between 0.007 and 0.6 L mg(-1) day(-1), with the highest values observed in seawater. We argue that such system specific parameters are key to the development of dedicated water quality models for ENMs. PMID:24119930

Quik, J T K; Velzeboer, I; Wouterse, M; Koelmans, A A; van de Meent, D

2014-01-01

375

RATES, CONSTANTS, AND KINETICS FORMULATIONS IN SURFACE WATER QUALITY MODELING  

EPA Science Inventory

Recent studies are reviewed to provide a comprehensive volume on state-of-the-art formulations used in surface water quality modeling along with accepted values for rate constants and coefficients. Topics covered include system geometric representation (spatial and temporal), phy...

376

Rain Erosion-Does the Rate of Water Effect Erosion?  

NSDL National Science Digital Library

This activity is a guided inquiry investigation where students gather data on rate of water falling on erosion. Student will interpret their data, and develop a conclusion from the data. The data will lead to further questions, which can be developed by the students.

kyle johnson

377

Evaluation of the freeze-thaw/evaporation process for the treatment of produced waters. Quarterly technical progress report, January 1--March 31, 1994  

SciTech Connect

The use of freeze-crystallization is being increasingly acknowledged as a low-cost, energy-efficient method for purifying contaminated water. Freeze-crystallization has been shown to be effective in removing a wide variety of contaminants from water. Water purification by using natural conditions to promote freezing appears to be an extremely attractive process for the treatment of contaminated water in many areas where natural climatic conditions will seasonally promote freezing. The natural freezing process can be coupled with natural evaporative processes to treat oil and gas produced waters year round in regions where subfreezing temperatures seasonally occur. The objectives of this research are related to development of a commercially-economic natural freeze-thaw/evaporation (FTE) process for the treatment and purification of water produced in conjunction with oil and gas. During the reporting period of 1/1/94 to 3/31/94, project research concentrated on Subtasks 2.0 (Task 2 Project Reporting) and 2.1 (Laboratory-scale FTE Simulations) . The objectives of Task 2 are to conduct laboratory- and bench-scale simulations for optimizing the design of the FTE process. Task 2 requires completion of six subtasks: Subtask 2.0 - Task 2 Project Reporting (initiated 3/1/93), Subtask 2.1 - Laboratory-scale FTE Simulations, Subtask 2.2 Re-evaluation of Process Economics Based on Laboratory-scale Process Simulation Results, Subtask 2.3 - Bench-scale FTE Simulations, Subtask 2.4 - Economic Assessment of Bench-scale Simulations, and Subtask 2.5 - Technical Report of Task 2. The construction, shakedown, and operation of the laboratory-scale process simulations planned were planned for this quarter (Subtask 2.1).

Boysen, J.; Morotti, J.

1994-04-01

378

Multispectral remote sensing contribution to land surface evaporation  

NASA Technical Reports Server (NTRS)

The global water cycle is perhaps the most important of all the biogeochemical cycles and evaporation, which is a significant component of the water cycle, is also linked with the energy and carbon cycles. Long-term evaporation over large areas has generally been computed as the difference of precipitation and river runoff. Analysis of short-term evaporation rate and its spatial pattern, however, is extremely complex, and multispectral remotely sensed data could aid in such analysis. Multispectral data considered here are visible and near-infrared reflectances, infrared surface temperature and the 37 GHz brightness temperatures. These observations are found to be not totally independent of each other. A few of their relationships are established and discussed considering physically-based models.

Choudhury, B. J.

1990-01-01

379

Water Vapor, Cloud Liquid Water Paths, and Rain Rates over the Northern High Latitudes  

NASA Astrophysics Data System (ADS)

Data from the Special Sensor Microwave Imager (years 1987-2006), Advanced Microwave Scanning Radiometer, and a surface-based radiometer at Barrow, Alaska are examined for insights into the behavior of water vapor, cloud liquid water and rainrates over the northern high latitudes. Screening for sea ice is accomplished by combining an independent dataset of monthly-mean sea ice fractions with the water vapor path (WVP), cloud liquid water path (LWP), and rainrate (RR) retrievals. The Wentz water vapor path retrieval shows no sensitivity to a proxy for sub-pixel sea ice presence, while the Wentz liquid water path retrievals are sensitive to sea ice presence during summertime when atmospheric variability is high but otherwise their sea-ice screening appears effective. The rainrate retrieval is highly sensitive to sea ice. The seasonal cycle and 1987-2006 time trends are examined. The WVP annual cycle has an amplitude of 1 cm with a July maximum phasing that is consistent with a continental influence. The springtime LWP increase usually occurs in tandem with the WVP increase and slightly lags the falltime WVP decrease. The maximum lag occurs over the northern Pacific, where the maximum LWP occurs in August, one month later than over the northern Atlantic, and is correlated to an August precipitation maximum. The strongest SSMI-derived trend is an increase in wintertime moisture south and southwest of Greenland, consistent with continental air outflow over warmer waters. An interesting feature is an autumnal increase in WVP and LWP north of the Bering Strait from 1989 to 2001 with a subsequent decrease in recent years. This cannot be explained by surface evaporation off of increased areas of open water and instead appears linked to recent decreases in cyclone activity. Winter and spring increases in LWP are noted in the surface-based dataset from Barrow, Alaska.

Zuidema, P.; Joyce, R.

2007-12-01

380

Numerical study of evaporation-induced salt accumulation and precipitation in bare saline soils: Mechanism and feedback  

NASA Astrophysics Data System (ADS)

Evaporation from bare saline soils in coastal wetlands causes salt precipitation in the form of efflorescence and subflorescence. However, it is not clear how much the precipitated salt in turn affects the water transport in the soil and hence the evaporation rate. We hypothesized that efflorescence exerts a mulching resistance to evaporation, while subflorescence reduces the pore space for water vapor to move through the soil. A numerical model is developed to simulate the transport of water, solute, and heat in the soil, and resulting evaporation and salt precipitation with the hypothesized feedback mechanism incorporated. The model was applied to simulate four evaporation experiments in soil columns with and without a fixed shallow water table, and was found to replicate well the experimental observations. The simulated results indicated that as long as the hydraulic connection between the near surface soil layer and the water source in the interior soil layer exists, vaporization occurs near the surface, and salt precipitates exclusively as efflorescence. When such hydraulic connection is absent, the vaporization plane develops downward and salt precipitates as subflorescence. Being more substantial in quantity, efflorescent affects more significantly evaporation than subflorescence during the soil-drying process. Different evaporation stages based on the location of the vaporization plane and the state of salt accumulation can be identified for characterizing the process of evaporation from bare saline soils with or without a fixed shallow water table.

Zhang, Chenming; Li, Ling; Lockington, David

2014-10-01

381

Homogeneous nucleation rate measurements in supersaturated water vapor.  

PubMed

The rate of homogeneous nucleation in supersaturated vapors of water was studied experimentally using a thermal diffusion cloud chamber. Helium was used as a carrier gas. Our study covers a range of nucleation rates from 3x10(-1) to 3x10(2) cm(-3) s(-1) at four isotherms: 290, 300, 310, and 320 K. The molecular content of critical clusters was estimated from the slopes of experimental data. The measured isothermal dependencies of nucleation rate of water on saturation ratio were compared with the prediction of the classical theory of homogeneous nucleation, the empirical prediction of Wolk et al. [J. Chem. Phys. 117, 10 (2002)], the scaled model of Hale [Phys. Rev. A 33, 4156 (1986)], and the former nucleation onset data. PMID:19045352

Brus, David; Zdímal, Vladimír; Smolík, Jirí

2008-11-01

382

Effect of soil type patterns on the variability of bare soil evaporation within a field: comparison of eddy covariance measurements with potential and actual evaporation calculations  

NASA Astrophysics Data System (ADS)

Bare soil evaporation was measured with the eddy-covariance method at the Selhausen field site. The site has a distinct gradient in soil texture with a considerably higher stone content at the upper part of the field. Because of this gradient, a spatial variation in evaporation fluxes in the field is expected. Because of the higher stone content at the upper part of the field, it is expected that the water that is stored in the soil surface layer and can be evaporated at a maximal evaporation rate, which is determined by the energy that is available for evaporation, is considerable smaller in the upper than in the lower part of the field. We investigated whether this hypothesis is supported by eddy covariance (EC) measurements of the evaporation fluxes at the field site. The EC measurements were combined with a footprint model that predicts the location of the soil surface that contributes to the measured evaporation flux. In this way, evaporation measurements of the two parts of the field site could be distinguished. However, since only one EC station was available, simultaneous evaporation measurements for the two field parts were not available. As a consequence, the datasets of measurements had to be interpreted and put into context of the meteorological and soil hydrological conditions. The potential evapotranspiration was calculated using the FAO method (Allen et al., 1998) to represent the meteorological conditions whereas a simple soil evaporation model (Boesten and Stroosnijder, 1986) was used to represent the influence of the precipitation and soil hydrological conditions on the actual evaporation rate. Since different soil parameters were required to describe the evaporation measurements for the upper and lower part of the plot, our starting hypothesis that more water is evaporated in the lower part of the field could be confirmed. Allen, R. G., L. S. Pereira, D. Raes, and M. Smith (1998), Crop evapotranspiration: Guidelines for computing crop water requirements, FAO, Rome (Italy). Boesten, J., and L. Stroosnijder (1986), Simple model for daily evaporation from fallow tilled soil under spring conditions in a temperate climate, Neth. J. Agric. Sci., 34(1), 75-90.

Vanderborght, J.; Graf, A.; Steenpass, C.; Scharnagl, B.; Prolingheuer, N.; Herbst, M.; Vereecken, H.

2009-12-01

383

Observed and modeled multi-year evaporation from three field-scale experiments using water balance and Penman-Monteith methods: Profound effect of material type and wind exposure  

NASA Astrophysics Data System (ADS)

Three instrumented experimental waste-rock piles at the Cu-Zn-Mo Antamina Mine in Peru are composed of distinct types of waste rock but are otherwise almost identical in size and geometry and experience the same atmospheric conditions with the exception of wind exposure. Evaporation from the piles was calculated using the water balance method over three- and four-year periods to determine the effect of material type and meteorological variability on evaporation. Annual changes in water storage were low or negligible except as a result of unusually high annual precipitation. Observed evaporation was high (44% - 75% of precipitation) and was extremely variable annually in the coarsest-grained waste-rock pile 1, most likely as a result of greater wind exposure and air circulation in that pile. Observed evaporation was moderate (36% - 48% of precipitation) with moderate annual variability in the finer-grained, relatively homogeneous waste-rock pile 2. Observed evaporation was low (24% - 32% of precipitation) with low annual variability in the finer-grained, relatively heterogeneous waste-rock pile 3, most likely as a result of low air circulation coupled with complex flow regimes that include high-velocity preferential flow paths. Slightly higher evaporation was observed on the slopes than on the crowns of Pile 2, while much lower evaporation was observed on the slopes than on the crowns of Piles 1 and 3. Evidence suggests that Piles 1 and 3 slope water-balance evaporation estimates are skewed by non-vertical flow and that, in general, evaporation is higher on the slopes than on the crowns of the piles. Evaporation was also estimated using the Food and Agriculture Organization of the United Nations modified Penman-Monteith method (FAO-PM; Allen et al., 1998) using base-case laboratory- and software- derived parameters. The base-case method underestimated observed evaporation calculated by the water balance method for Pile 1, overestimated observed evaporation for Pile 2, and greatly overestimated observed evaporation for Pile 3. The depth of the soil layer which is susceptible to evaporation, Ze, was calibrated from the base-case value of Ze= 0.10 m to values of Ze= 0.27 m (Pile 1), Ze= 0.05 m (Pile 2), and Ze= 0.02 m (Pile 3) to provide a good fit with observed evaporation. It is hypothesized that the Pile 3 calibration of Ze = 0.02 m is less physically realistic than accounting for preferential flow directly. A possible approach would be to modify the FAO-PM formulation by including a coefficient of preferential flow, KPF, on days that exceed a specified threshold daily precipitation, Pi,TH. The results highlight the profound effect of material type on evaporation from waste rock. Fine-grained, relatively homogeneous materials tend to follow traditional evaporation patterns both on the crowns and slopes of waste rock piles. Coarser-grained and more heterogeneous waste rock can have higher or lower evaporation than expected.

Peterson, H. E.; Fretz, N.; Bay, D.; Mayer, K. U.; Smith, L.; Beckie, R. D.

2013-12-01

384

Development of novel zein-sodium caseinate nanoparticle (ZP)-stabilized emulsion films for improved water barrier properties via emulsion/solvent evaporation.  

PubMed

This work attempted to develop novel high barrier zein/SC nanoparticle (ZP)-stabilized emulsion films through microfluidic emulsification (ZPE films) or in combination with solvent (ethyl acetate) evaporation techniques (ZPE-EA films). Some physical properties, including tensile and optical properties, water vapor permeability (WVP), and surface hydrophobicity, as well as the microstructure of ZP-stabilized emulsion films were evaluated and compared with SC emulsion (SCE) films. The emulsion/solvent evaporation approach reduced lipid droplets of ZP-stabilized emulsions, and lipid droplets of ZP-stabilized emulsions were similar to or slightly lower than that of SC emulsions. However, ZP- and SC-stabilized emulsion films exhibited a completely different microstructure, nanoscalar lipid droplets were homogeneously distributed in the ZPE film matrix and interpenetrating protein-oil complex networks occurred within ZPE-EA films, whereas SCE films presented a heterogeneous microstructure. The different stabilization mechanisms against creaming or coalescence during film formation accounted for the preceding discrepancy of the microstructures between ZP-and SC-stabilized emulsion films. Interestingly, ZP-stabilized emulsion films exhibited a better water barrier efficiency, and the WVP values were only 40-50% of SCE films. A schematic representation for the formation of ZP-stabilized emulsion films was proposed to relate the physical performance of the films with their microstructure and to elucidate the possible forming mechanism of the films. PMID:24175664

Wang, Li-Juan; Yin, Ye-Chong; Yin, Shou-Wei; Yang, Xiao-Quan; Shi, Wei-Jian; Tang, Chuan-He; Wang, Jin-Mei

2013-11-20

385

Prediction of corrosion rates of water distribution pipelines according to aggressive corrosive water in Korea.  

PubMed

The drinking water network serving Korea has been used for almost 100 years. Therefore, pipelines have suffered various degrees of deterioration due to aggressive environments. The pipe breaks were caused by in-external corrosion, water hammer, surface loading, etc. In this paper, we focused on describing corrosion status in water distribution pipes in Korea and reviewing some methods to predict corrosion rates. Results indicate that corrosive water of lakes was more aggressive than river water and the winter was more aggressive compared to other seasons. The roughness growth rates of Dongbok lake showed 0.23 mm/year. The high variation of corrosion rates is controlled by the aging pipes and smaller diameter. Also the phenolphthalein test on a cementitious core of cement mortar lined ductile cast iron pipe indicated the pipes over 15 years old had lost 50-100% of their lime active cross sectional area. PMID:14982159

Chung, W S; Yu, M J; Lee, H D

2004-01-01

386

Marangoni Convection and Deviations from Maxwells' Evaporation Model  

NASA Technical Reports Server (NTRS)

We investigate the convective dynamics of evaporating pools of volatile liquids using an ultra-sensitive thermal imaging camera. During evaporation, there are significant convective flows inside the liquid due to Marangoni forces. We find that Marangoni convection during evaporation can dramatically affect the evaporation rates of volatile liquids. A simple heat balance model connects the convective velocities and temperature gradients to the evaporation rates.

Segre, P. N.; Snell, E. H.; Adamek, D. H.

2003-01-01

387

Oxygen consumption, heart rate, rating of perceived exertion, and systolic blood pressure with water treadmill walking.  

PubMed

The purpose of this study was to examine the cardiovascular responses to water treadmill walking at 2.0 mph (3.2 km/hr), 2.5 mph (4.0 km/hr), and 3.0 mph (4.8 km/hr) in older adults. Responses to water treadmill walking in 92 degrees F (33 degrees C) water were compared with responses to land treadmill walking at 70 degrees F (21 degrees C) ambient temperature. After an accommodation period, participants performed 5-min bouts of walking at each speed on 2 occasions. Oxygen consumption (VO2), heart rate (HR), systolic blood pressure (SBP), and rating of perceived exertion (RPE) were significantly higher during therapeutic water treadmill walking than during land treadmill walking. Furthermore, VO2, HR, and RPE measures significantly increased with each speed increase during both land and water treadmill walking. SBP significantly increased with each speed during water treadmill walking but not land treadmill walking. Thus, it is imperative to monitor HR and blood pressure for safety during this mode of activity for older adults. PMID:18212391

Dolbow, David R; Farley, Richard S; Kim, Jwa K; Caputo, Jennifer L

2008-01-01

388

A phylogenetic analysis of basal metabolism, total evaporative water loss, and life-history among foxes from desert and mesic regions.  

PubMed

We measured basal metabolic rate (BMR) and total evaporative water loss (TEWL) of species of foxes that exist on the Arabian Peninsula, Blanford's fox (Vulpes cana) and two subspecies of Red fox (Vulpes vulpes). Combining these data with that on other canids from the literature, we searched for specialization of physiological traits among desert foxes using both conventional least squares regression and regressions based on phylogenetic independent contrasts. Further, we explored the consequences of reduced body size of foxes on life history parameters such as litter size and neonate mass. For Blanford's foxes, Red foxes from the central desert of Arabia, and Red foxes from the more mesic Asir mountains, body mass averaged 1,285 +/- 52 g, 1,967 +/- 289 g, and 3,060 +/- 482 g, respectively, whereas mean BMR, during summer, was 304.5 +/- 32.3 kJ/day, 418.0 +/- 32.4 kJ/day, and 724.1 +/- 120.2 kJ/day (+/- SD). An analysis of covariance with body mass as a covariate showed no statistical differences in BMR among foxes. Analysis of covariance indicated that Red fox from the Asir mountains had a higher TEWL than Red foxes from central Arabia or than Blanford's foxes also from the mountains. Comparisons of all species of desert and mesic foxes showed no significant differences in BMR, nor did desert foxes have a significantly lower BMR than other carnivores. TEWL of desert foxes was lower than other more mesic carnivores; deviations in TEWL ranged from -17.7% for the Fennec fox (Fennecus zerda) to -57.4% for the Kit fox (Vulpes velox). Although desert foxes have a BMR comparable to other more mesic species, it appears that desert foxes do have a smaller body mass, lowering overall energy requirements. We attribute this reduction in body size to the "resource limitation hypothesis" whereby natural selection favors smaller individuals in a resource-limited environment, especially during periods of severe food shortage. However, until common garden experiments are performed, developmental plasticity and acclimation cannot be ruled out as contributors to this pattern. PMID:14564467

Williams, J B; Muñoz-Garcia, A; Ostrowski, S; Tieleman, B I

2004-01-01

389

Safety review of the DCS (Distributed Control System) controlled full scale SRAT/SME (Sludge Receipt Adjustment Tank/Slurry Mix Evaporator) for water runs  

SciTech Connect

This memorandum addresses safety concerns of the Full Scale Sludge Receipt Adjustment Tank/Slurry Mix Evaporator (SRAT/SME) resulting from the installation of the new Distributed Control System (DCS). The present configuration of the SRAT/SME with DCS has been determined to be safe for operational testing with water. Another memorandum will be written after experience has been gained during water runs for actual operation. Previous safety evaluations and process hazard reviews for this facility have addressed normal industrial safety hazards and hazards associated with formic acid handling and operation with organics in the feed. Process operation with the new DCS controls will be very similar to the earlier operation controlled by the Modicon programmable logic controller (PLC). The interlocks for the SRAT/SME that were in the PLC have been programmed into the new DCS and will be reviewed here. 6 refs.

Hacker, B.A.

1988-01-29

390

Formation rates of Subantarctic mode water and Antarctic intermediate water within the South Pacific  

Microsoft Academic Search

The formation of Subantarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW) significantly contributes to the total uptake and storage of anthropogenic gases, such as CO2 and chlorofluorocarbons (CFCs), within the world's oceans. SAMW and AAIW formation rates in the South Pacific are quantified based on CFC-12 inventories using hydrographic data from WOCE, CLIVAR, and data collected in the austral

Corinne A. Hartin; Rana A. Fine; Bernadette M. Sloyan; Lynne D. Talley; Teresa K. Chereskin; James Happell

2011-01-01

391

Performance rating method of thermosyphon solar water heaters  

Microsoft Academic Search

A rating method for the thermal performance of thermosyphon solar water heaters was developed. Except that the outdoor test procedure still follows the Taiwan Standard CNS B7277, a system characteristic efficiency [eta][sub s]* which is defined as the [alpha][sub o], value corrected at M\\/A[sub c]= 75 kg\\/m[sup 2], was derived so that [eta][sub s]* is independent of the M\\/A, ratio.

B HUANG

1993-01-01

392

Heart rate variability in exercising humans: effect of water immersion  

Microsoft Academic Search

Power spectrum analysis of heart-rate variability was made in seven men [mean age 22 (SEM 1) years] in head-out water immersion\\u000a (W) and in air (A, control) at rest and during steady-state cycling to maximal intensity (maximum oxygen uptake, V?O2max). At rest W resulted in a trebled increase in the total power (P?

Renza Perini; Stefania Milesi; Luca Biancardi; David R. Pendergast; Arsenio Veicsteinas

1998-01-01

393

The rate of oxygen isotope exchange between nitrate and water  

NASA Astrophysics Data System (ADS)

The oxygen isotope exchange rate between nitrate and water was measured at a temperature of 50-80 °C and pH -0.6 to 1.1. Oxygen isotope exchange is a first-order reaction, with the exchange rate being strongly affected by both reaction temperature and pH, with increased rates of isotope exchange at higher temperatures and lower pH values. The rate of oxygen isotope exchange under natural conditions is extremely slow, with an estimated half-life for isotope exchange of 5.5 × 109 years at 25 °C and pH 7. The extremely slow rate of oxygen isotope exchange between nitrate and water under typical environmental conditions illustrates that nitrate-?18O signatures (and also nitrate ?17O and ?17O signatures) associated with various nitrate sources, as well as isotope compositions produced by biogeochemical processes, will be preserved. Hence, it is valid to use the value of nitrate-?18O to investigate the sources and biogeochemical behavior of nitrate, in a similar manner to the use of sulfate-?18O signatures to study the sources and biogeochemical behavior of sulfate. Equilibrium oxygen isotope fractionation factors have been determined, although quantification of the nitrate-water equilibrium fractionation factor is not possible due to the presence of nitrate as both protonated (i.e. HNO3) and unprotonated forms (i.e. NO3-) under the experimental conditions, and the difficulty in accurately calculating nitrate speciation in low pH, high ionic strength solutions.

Kaneko, Masanori; Poulson, Simon R.

2013-10-01

394

Simulations of water transport through carbon nanotubes: How different water models influence the conduction rate  

NASA Astrophysics Data System (ADS)

The conduction rate of water through (8,8) and (9,9) carbon nanotubes at 300 K and a pressure difference of 220 MPa is investigated using molecular dynamics simulations. The TIP3P, SPC/E, and TIP4P/2005 water models are considered. The pressure-driven flow rate is found to be strongly model dependent for both nanotubes. The fastest model (TIP3P) has a flow rate that is approximately five times faster than the slowest (TIP4P/2005). It is shown that the flow rate is significantly influenced by the structure taken on by the water molecules confined in the nanotube channels. The slower models, TIP4P/2005 and SPC/E, tend to favor stacked ring arrangements, with the molecules of a ring moving together through the nanotube, in what we term a "cluster-by-cluster" conduction mode. Confined TIP3P water has a much weaker tendency to form ring structures, and those that do form are fragile and break apart under flow conditions. This creates a much faster "diffusive" conduction mode where the water molecules main