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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Solar-driven interfacial evaporation

As a ubiquitous solar-thermal energy conversion process, solar-driven evaporation has attracted tremendous research attention owing to its high conversion efficiency of solar energy and transformative industrial potential. In recent years, solar-driven interfacial evaporation by localization of solar-thermal energy conversion to the air/liquid interface has been proposed as a promising alternative to conventional bulk heating-based evaporation, potentially reducing thermal losses and improving energy conversion efficiency. In this Review, we discuss the development of the key components for achieving high-performance evaporation, including solar absorbers, evaporation structures, thermal insulators and thermal concentrators, and discuss how they improve the performance of the solar-driven interfacial evaporation system. We describe the possibilities for applying this efficient solar-driven interfacial evaporation process for energy conversion applications. The exciting opportunities and challenges in both fundamental research and practical implementation of the solar-driven interfacial evaporation process are also discussed.

charge transport↗
DOE OSTI2015

CHROMOSPHERIC EVAPORATION IN AN X1.0 FLARE ON 2014 MARCH 29 OBSERVED WITH IRIS AND EIS

Chromospheric evaporation refers to dynamic mass motions in flare loops as a result of rapid energy deposition in the chromosphere. These motions have been observed as blueshifts in X-ray and extreme-ultraviolet (EUV) spectral lines corresponding to upward motions at a few tens to a few hundreds of km s{sup −1}. Past spectroscopic observations have also revealed a dominant stationary component, in addition to the blueshifted component, in emission lines formed at high temperatures (∼10 MK). This is contradictory to evaporation models predicting predominant blueshifts in hot lines. The recently launched Interface Region Imaging Spectrograph (IRIS) provides high-resolution imaging and spectroscopic observations that focus on the chromosphere and transition region in the UV passband. Using the new IRIS observations, combined with coordinated observations from the EUV Imaging Spectrometer, we study the chromospheric evaporation process from the upper chromosphere to the corona during an X1.0 flare on 2014 March 29. We find evident evaporation signatures, characterized by Doppler shifts and line broadening, at two flare ribbons that are separating from each other, suggesting that chromospheric evaporation takes place in successively formed flaring loops throughout the flare. More importantly, we detect dominant blueshifts in the high-temperature Fe xxi line (∼10 MK), in agreement with theoretical predictions. We also find that, in this flare, gentle evaporation occurs at some locations in the rise phase of the flare, while explosive evaporation is detected at some other locations near the peak of the flare. There is a conversion from gentle to explosive evaporation as the flare evolves.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Thermal evaporation sources for wide-area deposition

A thermal evaporation source includes: a crucible configured to contain a volume of evaporant and a vapor space above the evaporant; a manifold body having within it a hollow expansion chamber that is flowably connected to the vapor space via one or more restriction orifices; one or more effusion nozzles flowably connected to the expansion chamber and exiting an outer surface of the thermal evaporation source, the nozzle(s) oriented to direct an evaporant vapor flow out of the source vertically downward, in one or more horizontal directions, or in one or more directions intermediate between horizontal and vertically downward; and a heater capable of heating some or all of the thermal evaporation source to a temperature sufficient to produce the one or more evaporant vapor flows when a vacuum is applied to the thermal evaporation source.

Birkmire, Robert W.↗
DOE OSTI2024

Impact of Floating PV (FPV) System on Water Evaporation: Case Study of an Open Loop Reservoir in North Carolina

Fresh water scarcity is becoming one of the important concerns worldwide. This situation of water scarcity is further exacerbated by the increase in water evaporation due to climate change. This manuscript will address this concern by considering the impact of floating photovoltaics (FPVs) systems on water evaporation. The installation of PV modules on the water bodies can help reduce the water evaporation rate from reservoirs by reducing the evaporating area of the water surface. This work evaluates the effect of FPV on water evaporation rates in the TuckerTown reservoir located in North Carolina state of United States. Meteorological data, such as mean temperature and dew-point, are used to calculate the rate of the water evaporation by Linacre method. The simulation results for the TuckerTown case study showed that the aggregated avoided evaporated volume for one year is 9 million gallons.

14 SOLAR ENERGY↗
DOE OSTI2018

Cementitious Waste Form Development for Treatment of EMF Evaporator Bottoms - 18611

Direct Feed Low-Activity Waste operations at the Hanford Site (Washington State, USA) involve concentrating the Hanford low-activity waste (LAW) melter off-gas condensate waste stream by evaporation at the Effluent Management Facility (EMF) followed by recycle back to the melter feed. The EMF evaporator bottoms waste stream is expected to contain variable, high levels of halides and sulfate that could strain LAW melter performance and co-mingled radionuclides, technetium-99 ({sup 99}Tc) and iodine-129 ({sup 129}I), that readily volatilize in the LAW melter and are expected to accumulate during recycle. To this end, there is a need for alternative disposition paths for the EMF evaporator bottoms waste stream that bypass recycling to the LAW melter. One such alternative is solidification in low-temperature cementitious waste forms (CWFs) that meet disposal facility acceptance criteria. The work herein addresses recent waste form development and testing performed to identify CWF candidates that meet off-site disposal acceptance criteria and/or on-site Hanford Integrated Disposal Facility waste acceptance criteria. Phase one testing activities included the production and evaporation of simulated EMF evaporator feed from the Hanford Waste Treatment and Immobilization Plant melter offgas effluent liquid secondary waste stream, which was then analyzed to demonstrate the behavior and fate of contaminants of concern (COCs). Based on analyses from these preliminary tests, a simulant for the EMF evaporator bottoms waste stream was formulated and used to evaluate several dry material compositions proposed for CWF development and testing. In particular, dry ingredient recipes used in early testing efforts contained a combination of ordinary Portland cement (OPC), Class F fly ash (FA), blast furnace slag (BFS), Aquaset{sup R} II-H, and/or Aquaset{sup R} II-GH to generate CWFs at various water-to-dry material ratios. CWFs were then tested according to the Toxicity Characteristic Leaching Procedure (TCLP) for COCs, such as Cr, Zn, As, and Se, to determine which specimens comply with land disposal restrictions (40 CFR 268). The results of TCLP testing showed that chromium leaching was a persistent challenge, except when using the original Cast Stone dry ingredient recipe (8% OPC, 47% BFS, 45% FA) to immobilize the EMF evaporator bottoms simulant. Improving Cr immobilization and evaluating leaching behavior for COC Hg were identified as objectives for the second phase of testing. During second phase testing efforts, a screening test was performed to determine whether the bulk EMF waste composition is a factor in producing an acceptable solidified waste form. A series of eight simulants with varying concentrations of major salts of boron, chloride, nitrite, and sulfate were prepared and immobilized using three dry ingredient recipes. Each dry ingredient recipe contained two to three of the following: BFS, OPC, FA, and Aquaset{sup R} II-GH. All eight simulants were spiked with Zn, Cr, As, Se, and Hg prior to production of the CWFs, similar to previous tests, and used to test for residual free liquids and TCLP analysis. The TCLP results indicate that all phase two formulated CWFs meet land disposal requirements when compared to Universal Treatment Standards (40 CFR 268) for hazardous wastes, regardless of simulant composition. Furthermore, re-absorption of residual free liquids is most quickly achieved for nearly all simulant compositions using the original Cast Stone recipe; however, replicas analysis is required to corroborate these findings. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2019

Impact of ethanol blending into gasoline on aromatic compound evaporation and particle emissions from a gasoline direct injection engine

This study examined the interactions of ethanol with aromatic compounds on aromatic species evolution during gasoline evaporation and the consequent impacts on particle emissions from a single-cylinder, gasoline direct injection engine. From a chemical kinetic standpoint, the dilution of the aromatic species in gasoline by ethanol blending should reduce particle emissions because aromatics are the primary species that form particles during gasoline combustion. However, increased evaporative cooling from the ethanol and ethanol's effect on when aromatics in the fuel droplet (or surface film or pool) evaporate can drive an increase in particle emissions. The objective of this study was to quantify these competing effects. The results show that a combination of ethanol's increased evaporative cooling and impact on aromatic compound vapor-liquid equilibrium can extend droplet lifetime and cause aromatics to evaporate later in the droplet evaporation process than would be the case without ethanol. When fuels were burned in a direct-injection single-cylinder engine at high speed (2500 rpm) and relatively high load, ethanol blending caused an increase in particle emissions for fuels containing a low vapor pressure aromatic. At a lower speed (1500 rpm), no statistically significant increase in particle emissions was observed, likely because more time was available for evaporation and mixing to occur. In contrast, particle emissions from a fuel blended with a high vapor pressure aromatic were either insensitive to or reduced by ethanol blending, likewise to engine operating conditions. Current models for predicting particle emissions from gasoline engines, such as particulate matter index (PMI), generally lack variables for non-linear interactions between ethanol and gasoline hydrocarbons. To identify nonlinear interactions between predictor variables that might better explain the observed particle emissions, the least absolute shrinkage and selection operator (LASSO) regularized regression approach was employed. Among the predictor variables evaluated was the Yield Sooting Index (YSI) which is as an improved measure to quantify the aromatic's chemical tendency to generate particle emissions. Following this analysis, two variables were selected based on their frequent appearance. The first was ethanol mole percent multiplied by aromatic mole percent divided by aromatic vapor pressure [(EtOH * Aro%)/Aro VP@443 K]. The second was aromatic mole percent multiplied by aromatic YSI divided by aromatic molecular weight [(Aro% * Aro YSI)/Aro MW]. The results of linear regression including only these two combined explanatory variables achieved an r 2 = 0.959, substantially improved over the PMI model (r 2 = 0.688) and provides insight into how the PMI formalism might be modified to account for non-linear oxygenate-hydrocarbon coupling.

09 BIOMASS FUELS↗
DOE OSTI2024

Evaporation from thin porous Coatings: Pore size effects and predictive equation for homogeneous coatings

Evaporation of small water droplets on solids is hindered because surface tension pulls the droplet into a spherical cap that has a small perimeter. Our solution is to coat a solid with a very thin, porous layer into which the droplet flows to create a large-area disk with concomitant high rate of evaporation. We investigate evaporation by varying factors that have not been previously considered: pore size and distribution, contact angle, temperature, and relative humidity (RH). A larger pore size resulted in faster evaporation, which we explain through faster transport within the coating. Even faster evaporation occurred for a bilayer structure with small particles on the air side and larger particles on the solid side. Further, the water advancing contact angle had an insignificant effect in the range from < 10° through to 60°. Our results for different pore sizes, temperature, humidity, and contact angle all collapse onto a single curve when appropriately normalized. This validates an equation that can be used for the evaporation from a homogeneous coating that depends only one empirical factor and the droplet volume. Since the volume is often user-controlled, we envisage that this equation can be used to predict evaporation and guide design of fast-drying coatings.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

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

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

36 MATERIALS SCIENCE↗
DOE OSTI2015

OPTIMAL ELECTRON ENERGIES FOR DRIVING CHROMOSPHERIC EVAPORATION IN SOLAR FLARES

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

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Production and characterization of thin film group IIIB, IVB and rare earth hydrides by reactive evaporation

A recent short history of reactive evaporation by D. M. Mattox [History Corner—A Short History of Reactive Evaporation, SVC Bulletin (Society of Vacuum Coaters, Spring 2014), p. 50–51] describes various methods for producing oxides, nitrides, carbides, and some compounds, but hydrides were not mentioned. A study was performed in the mid-1970s at the General Electric Company Neutron Devices Department in Largo, FL, by the author to study preparation of thin film hydrides using reactive evaporation and to determine their unique characteristics and properties. Films were produced of scandium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), and the rare earth praseodymium (Pr), neodymium (Nd), gadolinium (Gd), dysprosium (Dy), and erbium (Er) hydrides by hot crucible filament and electron beam evaporation in atmospheres of deuterium and tritium gases. All-metal vacuum systems were used and those used with tritium were dedicated for this processing. Thin film test samples 1000 nm thick were prepared on 1.27 cm diameter molybdenum disk substrates for each occluder (i.e., an element that can react with hydrogen to form a hydride) material. Loading characteristics as determined by gas-to-metal atomic ratios, oxidation characteristics as determined by argon–sputter Auger analysis, film structure as determined by scanning electron microscope analysis, and film stress properties as determined by a double resonator technique were used to define properties of interest. Results showed hydrogen-to-metal atomic ratios varied from 1.5 to 2.0 with near maximum loading for all but Pr and Nd occluders which correlated with the oxidation levels observed, with all occluder oxidation levels being variable due to vacuum system internal processing conditions and the materials used. Surface oxide levels varied from ∼80 Å to over 1000 Å. For most films studied, results showed that a maximum loading ratio of near 2.0 and a minimum surface oxide level of ∼80 Å could be obtained with a bulk film oxygen level of ∼0.54 oxygen as determined by microprobe analysis when an evaporation rate of ∼0.313 mg/cm{sup 2} min was used in an atmosphere of D{sub 2} or T{sub 2} gas at a system deposition pressure of 1 × 10{sup −3 }Torr (1.33 × 10{sup −1 }Pa) in an evaporation time of ∼2 min. Platelet type (i.e., a film microstructure showing an overlay of flat plates with large grain sizes) film structures were observed for most films with some film mechanical properties determined (i.e., grain size and Vickers μ-hardness), and reduced stress levels were seen with initial normalized differential (tensile) stress levels being (1.0–4.0) × 10{sup 8 }dyne/cm{sup 2} for tritium loaded samples and (1.5 ± 0.5) × 10{sup 9 }dyne/cm{sup 2} for deuterium loaded samples. Also, stress aging characteristics were determined for some hydride films prepared in a radioactive tritium gas atmosphere. Tritium loading, however, had the undesirable characteristic of having to dispose of the internal processing system fixtures, which can be minimized, but the reactive evaporation technique produced desirable thin films.

36 MATERIALS SCIENCE↗
DOE OSTI2013

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

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

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2013

Analysis Of 2H-Evaporator Scale Pot Bottom Sample [HTF-13-11-28H]

Savannah River Remediation (SRR) is planning to remove a buildup of sodium aluminosilicate scale from the 2H-evaporator pot by loading and soaking the pot with heated 1.5 M nitric acid solution. Sampling and analysis of the scale material from the 2H evaporator has been performed so that the evaporator can be chemically cleaned beginning July of 2013. Historically, since the operation of the Defense Waste Processing Facility (DWPF), silicon in the DWPF recycle stream combines with aluminum in the typical tank farm supernate to form sodium aluminosilicate scale mineral deposits in the 2H-evaporator pot and gravity drain line. The 2H-evaporator scale samples analyzed by Savannah River National Laboratory (SRNL) came from the bottom cone sections of the 2H-evaporator pot. The sample holder from the 2H-evaporator wall was virtually empty and was not included in the analysis.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

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

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

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Experimental investigation of elemental and isotopic evaporation processes by laser heating in an aerodynamic levitation furnace

In this report we carried out evaporation experiments on a B-type calcium–aluminium-rich inclusion (CAI) melt in a gas-mixing aerodynamic levitation laser furnace, at 1873 K and an oxygen partial pressure of 10 -9.1 atm, for durations ranging from 60 to 600 s. Evaporation of SiO 2 and MgO follow the same trend as those observed in vacuum furnace experiments at the same temperature and starting composition, showing that their evaporation relative to one another from the melt is independent of pressure, oxygen fugacity, and hydrodynamical regime specific to the furnace. Isotopic ratios of Mg and Si in evaporation residues are used to derive fractionation factors of α 26/24 Mg vap-liq = 0.9906± 0.0004 and α 30/28 Si vap-lip = 0.9943±0.0003, which are both significantly closer to unity than those found for evaporation in a vacuum, which translates to less isotope fractionation. The residues are also less isotopically fractionated than expected for cases in which transport of the gas species away from the melt is diffusion-controlled at 1-atm. By analysing the flow regimes in our furnace, we find that advection by the levitating gas is the primary mode of mass transport away from the melt surface, as opposed to diffusion-limited transport in a vacuum or 1-atm tube furnace. A modified Hertz–Knudsen–Langmuir formulation accounts for this process, and shows that isotopic fractionation of both Si and Mg reflect a saturation factor (ratio of the pressure of the evaporating species to vapour saturation pressure) equal to 0.75. This is in perfect accord with recent measurements of Cu isotopic fractionation using a similar furnace. The fact that three elements (Mg, Si, Cu) with varying equilibrium vapour pressures, activity coefficients in the liquid, and diffusion coefficients in the gas have the same scaling behaviour to saturation pressure is a strong indication that the mechanism controlling evaporation is driven by the hydrodynamical regime imposed in the furnace. Therefore, this class of experiments can be used to constrain processes in which advection dominates over diffusion, such as (but not limited to) planetary ejecta, tektites, giant impacts, nebular condensation in a turbulent flow, or nuclear fallout material. Finally, the possibility to reach high temperatures (in excess of 3500 K) in this furnace allows it to be used to evaluate the activity coefficients of melt components in extreme conditions relevant to molten planetary interiors (i.e., magma oceans), with a specific focus on refractory elements.

58 GEOSCIENCES↗
DOE OSTI2013

A Rinsing Effluent Evaporator for Dismantling Operations - 13271

Between 1958 and 1997, the UP1 plant at Marcoule - located in the south of France - reprocessed and recycled nearly 20,000 MT of used fuel from special defense applications reactors, as well as fuel from the first generation of electricity generating reactors in France (natural uranium fuel, CO{sub 2}-cooled, graphite-moderated). Decommissioning and Dismantling of the UP1 plant and its associated units started in 1998. Since 2005, the UP1 facility has been operated by AREVA as the Marcoule Management and Operation contractor for French Atomic Energy Commission (CEA). An important part of this decommissioning program deals with the vitrification facility of Marcoule. This facility includes 20 tanks devoted to interim storage of highly active solutions, prior to vitrification. In 2006, a rinsing program was defined as part of the tank cleanup strategy. The main objective of the rinsing phases was to decrease activity in order to limit the volume of 'long-life active' waste produced during the decommissioning operations, so the tanks can be dismantled without the need of remote operations. To enable this rinsing program, and anticipating large volumes of generated effluent, the construction of an evaporation unit proved to be essential. The main objective of this unit was to concentrate the effluent produced during tank rinsing operations by a factor of approximately 10, prior to it being treated by vitrification. The evaporator design phase was launched in September 2006. The main challenge for the Project team was the installation of this new unit within a nuclear facility still in operation and in existing compartments not initially designed for this purpose. Cold operating tests were completed in 2008, and in May 2009, the final connections to the process were activated to start the hot test phase. During the first hot test operations performed on the first batches of clean-up effluent, the evaporator had a major operating problem. Extremely large quantities of foam were produced, affecting the evaporator operation, and creating the risk of a reduction in its capacity and throughput performance. A task force of AREVA process, operations, and safety experts from Marcoule and the La Hague reprocessing complex was assembled. New operating parameters were defined and tested to improve the process. Since then, the evaporator has performed very satisfactorily. The foam buildup phenomenon has been brought under complete control. All the different types of effluents produced during cleanup operations have been concentrated, and the results obtained in terms of quality and throughput, have ensured a consistent supply to the vitrification unit. The evaporator was operated until the end of April 2012, and enabled the production of 500 cubic meters of very high activity effluent, concentrating the fission products rinsed from the storage tanks. The evaporator will now be deactivated and decommissioned, with the first rinsing and cleanup operations scheduled to begin in 2014. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2024

Ensemble modeling of global lake evaporation under climate change

Global projections of lake evaporation are typically based on simulations using single mechanistic models. However, because of its complex interactions with various lake physical properties, environmental and anthropogenic drivers, lake evaporation is highly variable and sensitive to the choice of model used. In this study, we present a multi-model analysis to investigate differences across global simulations of lake evaporation during the warm-season using three different lake models driven by outputs from four general circulation models (GCM) (i.e. 12 model combinations in total) for historic and future scenarios. Our results suggest substantial differences among lake-climate model simulations of lake evaporation. These differences varied throughout the 20th and 21st century, with model driver data explaining 74% of the variance in future projections of warm- season lake evaporation. Our projections indicate that, by the end of the 21st century (2070–2099), global annual lake evaporation rates will increase by 10–27% under Representative Concentration Pathways (RCPs) 2.6–8.5. Finally, we highlight the importance of using a multi-model approach for the prediction of future global lake evaporation responses to climate change.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

How Much Water Is Evaporated Across California? A Multiyear Assessment Using a Biophysical Model Forced With Satellite Remote Sensing Data

Abstract California is expected to experience great spatial/temporal variations evaporation. These variations arise from strong north‐south, east‐west gradients in rainfall and vegetation, strong interannual variability in rainfall (±30%) and strong seasonal variability in the supply and demand for moisture. We used the Breathing Earth System Simulator to evaluate the rates and sums of evaporation across California, over the 2001–2017 period. Breathing Earth System Simulator is a bottom‐up, biophysical model that couples subroutines that calculate the surface energy balance, photosynthesis, and stomatal conductance. The model is forced with high‐resolution remote sensing data (1 km).The questions we address are as follows: How much water is evaporated across the natural and managed ecosystems of California? How much does evaporation vary during the booms and busts in annual rainfall? and Is evaporation increasing with time due to a warming climate? Mean annual evaporation, averaged over the 2001–2017 period, was relatively steady (393 ± 21 mm/year) given the high interannual variation in precipitation (519 ± 140 mm/year). No significant trend in evaporation at the statewide level was detected over this time period, despite a background of a warming climate. Irrigated agricultural crops and orchards, at 1‐km scale, use less water than inferred estimates for individual fields. This leaves the potential for sharing water, a scarce resource, more equitably among competing stakeholders, for example, farms, fish, people, and ecosystems.

Baldocchi, Dennis↗
DOE OSTI2019

Study of Evaporation of Laser-Heated Iron–Carbon Nanoparticles Using Analysis of Thermal Radiation

Evaporation of iron nanoparticles in carbon shells under pulsed laser irradiation is analyzed. Iron–carbon nanoparticles are synthesized in a shock tube reactor with the aid of pyrolysis of the 0.25% Fe(CO){sub 5} + 0.25% C{sub 6}H{sub 6} mixture in argon. Laser radiation is used for additional heating to temperatures that exceed the evaporation threshold of the iron core of nanoparticles. Time profiles of the thermal radiation of laser-heated nanoparticles are measured. The two-color pyrometry is used to determine the evaporation temperature of nanoparticles, and the laser extinction makes it possible to monitor the loss of volume fraction of the condensed phase upon evaporation. Approximation of experimental signals of laser-heated nanoparticles using model curves is employed to determine effective enthalpy of evaporation of iron–carbon nanoparticles. It is shown that the iron core of nanoparticles is evaporated through the carbon shell and the energy spent by such a process is approximately twice greater than the evaporation enthalpy of bulk iron with free surface.

77 NANOSCIENCE AND NANOTECHNOLOGY↗