The treatment of ammonia nitrogen wastewater(ANW)has garnered significant attention due to the ecology,and even biology is under increasing threat from over discharge ANW.Conventional ANW treatment methods often encou...The treatment of ammonia nitrogen wastewater(ANW)has garnered significant attention due to the ecology,and even biology is under increasing threat from over discharge ANW.Conventional ANW treatment methods often encounter challenges such as complex processes,high costs and secondary pollution.Considerable progress has been made in employing solar-induced evaporators for wastewater treatment.However,there remain notable barriers to transitioning from fundamental research to practical applications,including insufficient evaporation rates and inadequate resistance to biofouling.Herein,we propose a novel evaporator,which comprises a bio-enzyme-treated wood aerogel that serves as water pumping and storage layer,a cost-effective multi-walled carbon nanotubes coated hydrophobic/hydrophilic fibrous nonwoven mat functioning as photothermal evaporation layer,and aggregation-induced emission(AIE)molecules incorporated as anti-biofouling agent.The resultant bioinspired evaporator demonstrates a high evaporation rate of 12.83 kg m^(−2) h^(−1) when treating simulated ANW containing 30 wt%NH4Cl under 1.0 sun of illumination.AIE-doped evaporator exhibits remarkable photodynamic antibacterial activity against mildew and bacteria,ensuring outstanding resistance to biofouling over extended periods of wastewater treatment.When enhanced by natural wind under 1.0 sun irradiation,the evaporator achieves an impressive evaporation rate exceeding 20 kg m^(−2) h^(−1) .This advancement represents a promising and viable approach for the effective removal of ammonia nitrogen wastewater.展开更多
Evaporating bubble column reactor (EBCR) is a kind of aerated reactor in which the reaction heat is removed by the evaporation of volatile reaction mixture. In this paper, a mathematical model that accounts for the ga...Evaporating bubble column reactor (EBCR) is a kind of aerated reactor in which the reaction heat is removed by the evaporation of volatile reaction mixture. In this paper, a mathematical model that accounts for the gas-liquid exothermic reaction and axial dispersions of both gas and liquid phase is employed to study the performance of EBCR for the process of p-xylene(PX) oxidation. The computational results show that there are remarkable concentration and temperature gradients in EBCR for high ratio of height to diameter (H/DT). The temperature is lower at the bottom of column and higher at the top, due to rapid evaporation induced by the feed gas near the bottom. The concentration profiles in the gas phase are more nonuniform than those (except PX) in the liquid phase, which causes more solvent burning consumption at high H/DT ratio. For p-xylene oxidation, theo ptimal H/DT is around 5.展开更多
A new technology for the crystallization of ammonium paratungstate with coarse grain has beenstudied. The factors influencing the physi-chemical properties of ammonium paratungstate crystal, such astemperature, concen...A new technology for the crystallization of ammonium paratungstate with coarse grain has beenstudied. The factors influencing the physi-chemical properties of ammonium paratungstate crystal, such astemperature, concentration, seed crystal, agitation. etc. were examined. It is necessary to keep high temperature and low concentration in the process. and the addition of seed crystal and agitation with air is also in favor of the system. Ammonium paratungstate crystal with particle size of 36-42 μm and apparent density of2. 0-2. 2 g·cm- 3 were obtained by controlling suitable technological parameters.展开更多
Research the evaporating crystalization process of the magnesium sulfate subtypes brine at high temperature from Dalangtan salt lake in Qinghai province.It was revealed that the salt lake is a typical subtype magnesium
The purpose of this study is to investigate the effect of fuel properties on liquid and vapor penetrations in evaporating spray systems. A recently developed model, which can simultaneously account for the finite ther...The purpose of this study is to investigate the effect of fuel properties on liquid and vapor penetrations in evaporating spray systems. A recently developed model, which can simultaneously account for the finite thermal conductivity, finite mass diffusivity and turbulence effects within atomizing multi-component liquid fuel sprays, is utilized for the numerical predictions. Two different multi-component fuels with different boiling temperatures,densities and other thermal properties are implemented in the KIVA-3V computational fluid dynamics(CFD)code to study the evaporation behaviors. A six-component surrogate fuel is used to emulate the relevant volatility property of the real diesel fuel, and a second bi-component fuel is chosen to represent a low boiling-temperature fuel. The numerical results are compared with the experimental data, and the representative results are obtained.For a lower density and lower boiling temperature fuel, the liquid penetration length is shorter. However, the vapor penetration lengths are not affected by the fuel type in terms of fuel volatility. Available experimental data are used for validation and appraisal of the multi-component evaporation model.展开更多
Under Rayleigh equilibrium condition, stable isotopic ratio in residual water increases with the decrease of the residual water proportion f exponentially, and the fractionation rate of stable isotopes is inversely pr...Under Rayleigh equilibrium condition, stable isotopic ratio in residual water increases with the decrease of the residual water proportion f exponentially, and the fractionation rate of stable isotopes is inversely proportional to temperature. However, under kinetic evaporation condition, the fi＇actionation of stable isotopes is not only related to the phase temperature but also influenced by the atmospheric humidity and the mass exchange between liquid and vapor phases. The ratio 6 in residual water will not change with f after undergoing evaporation of a long time for great relative humidity. The rate that the evaporating water body reaches isotopic steady state is mainly dependent on the relative humidity in atmosphere. The analysis shows that the actual mean linear variety rates, about -30.0, of the δ^18O in residual water versus the residual water proportion at Nagqu and Amdo stations are consistent with the simulated process under temperature of 20℃ and relative humidity of 50%. The distillation line simulated under Rayleigh equilibrium condition is analogous to the global meteoric water line （MWL） as the temperature is about 20℃. Under non-equilibrium condition, the slope and constant values of distillation line are directly proportional to temperature and relative humidity. According to the basic data, the simulated distillation line is very consistent with the actual distillation line of Qinghai Lake.展开更多
The variation of stable isotope ratios in natural waters provides valuable information that can be used to trace water movement. Evaporation plays a crucial role in determining the variation of stable isotopes. In thi...The variation of stable isotope ratios in natural waters provides valuable information that can be used to trace water movement. Evaporation plays a crucial role in determining the variation of stable isotopes. In this paper, several evaporation experiments were conducted in order to study the stable isotopic fractionation mechanism of water and analyze the influence of different temperatures on evaporation fractionation. Three group experiments of water evaporation under different temperatures and initial isotopic values were carried out. The results show that fractionation factors of hydrogen and oxygen may increase with temperature, and the average enrichment degree of hydrogen isotope D is 3.432 times that of oxygen isotope 18O. The results also show that the isotopic composition of the initial water has little influence on water evaporation fractionation, which is mainly affected by the state variables in the evaporation process, such as temperature. This research provides experimental data for further understanding the evaporation fractionation mechanism.展开更多
Consideration of stable isotopes in precipitation is valuable for investigating hydrological processes.Therefore,correcting the measured isotopic composition of precipitation under below-cloud evaporation is necessary...Consideration of stable isotopes in precipitation is valuable for investigating hydrological processes.Therefore,correcting the measured isotopic composition of precipitation under below-cloud evaporation is necessary.An accurate description of the underlying processes affecting stable isotopic composition of precipitation could help improve our understanding of the water cycle.The transitivity between monsoonal and arid climates was reflected by the evaporation rate of falling raindrops in precipitation in the Qilian Mountains,a typical transition zone between Tibetan Plateau and arid region of China.Considering 1310 precipitation event-scale samples,based on stable isotope analysis method,the mean below-cloud evaporation rate(f)in the study area was measured as 12.00%during the summer half-year(May-October).The evaporation rate on the northern slopes(12.70%)of the Qilian Mountains in China was significantly higher than that on the southern slopes(9.98%).The transition between monsoonal and arid climates was reflected in the evaporation rate of falling raindrops during precipitation in the Qilian Mountains of China.Below-cloud evaporation contributed to a noticeable enrichment of stable isotopes in the precipitation in the study area.The monthly precipitationδ^(18)O enrichment rate in the Qilian Mountains of China from May to October was 29.18%,23.35%,25.60%,22.99%,31.64%,and 14.72%,respectively.For every 1.00%increase in the evaporation rate of raindrops in Qilian Mountains of China,the changes in the concentration of oxygen isotopes from the bottom of the clouds to the ground increased by 0.92‰;however,with an evaporation rate of<5.00%,for every 1.00%increase in the evaporation rate of raindrops the changes in the concentration of oxygen isotopes from the bottom of the clouds to the ground increased by 1.00‰could also be observed.Furthermore,altitude was an important factor affecting below-cloud evaporation in the study area.展开更多
Classical theories have successfully provided an explanation for convection in a liquid layer heated from below without evaporation. However, these theories are inadequate to account for the convective instabilities i...Classical theories have successfully provided an explanation for convection in a liquid layer heated from below without evaporation. However, these theories are inadequate to account for the convective instabilities in an evaporating liquid layer, especially in the case when it is cooled from below. In the present paper, we study the onset of Marangoni convection in a liquid layer being overlain by a vapor layer. A new two-sided model is put forward instead of the one-sided model in previous studies. Marangoni-Béard instabilities in evaporating liquid thin layers are investigated with a linear instability analysis. We define a new evaporation Blot number, which is different from that in previous studies and discuss the influences of reference evaporating velocity and evaporation Blot number on the vapor-liquid system. At the end, we explain why the instability occurs even when an evaporating liquid layer is cooled from below.展开更多
The main objective of this paper is to develop a simpleand efficient numerical model for estimation of heat and mass transfer between water spray drops and airstreamin horizontal parallel flow which enable us to accur...The main objective of this paper is to develop a simpleand efficient numerical model for estimation of heat and mass transfer between water spray drops and airstreamin horizontal parallel flow which enable us to accurateprediction of evaporative cooling performance.Thephysical process of a droplet evaporating in finite airflowhas been studied.Four basic differential equations havebeen developed with their numerical solutions providedby figures.展开更多
In the framework of the two-continuum approach, using the matched asymptotic expansion method, the equations of a laminar boundary layer in mist flows with evaporating droplets were derived and solved. The similarity ...In the framework of the two-continuum approach, using the matched asymptotic expansion method, the equations of a laminar boundary layer in mist flows with evaporating droplets were derived and solved. The similarity criteria controlling the mist flows were determined. For the flow along a curvilinear surface, the forms of the boundary layer equations differ from the regimes of presence and absence of the droplet inertia deposition. The numerical results were presented for the vapor-droplet boundary layer in the neighborhood of a stagnation point of a hot blunt body. It is demonstrated that, due to evaporation, a droplet-free region develops near the wall inside the boundary layer. On the upper edge of this region, the droplet radius tends to zero and the droplet number density becomes much higher than that in the free stream. The combined effect of the droplet evaporation and accumulation results in a significant enhancement of the heat transfer on the surface even for small mass concentration of the droplets in the free stream.展开更多
Spray experiments of RP-3 jet fuel at non-evaporating and evaporating environments were studied on a constant volume spray chamber,and diffusive back-imaging technique was used to capture the transient spray developme...Spray experiments of RP-3 jet fuel at non-evaporating and evaporating environments were studied on a constant volume spray chamber,and diffusive back-imaging technique was used to capture the transient spray development processes.Spray tip penetration,projected spray area and cone angle of RP-3 jet fuel were derived from the spray development images,and compared to those of diesel fuel.It is observed that non-evaporating sprays of RP-3 jet fuel and diesel fuel do not exhibit significant differences,as their spray penetration distances,projected spray areas and spray cone angles are consistent at most test conditions.The evaporating sprays of RP-3 jet fuel produce shorter liquid-phase penetration distances and lower projected spray areas than those of diesel fuel,and these differences are particularly pronounced at low ambient temperatures.However,fuel effects on the evaporating spray cone angle are insignificant.Further,increased ambient density or ambient temperature shortens the liquid-phase spray penetration distance and reduces the liquid-phase spray area,and these effects are more pronounced for diesel fuel than RP-3 jet fuel.展开更多
Velocity field of evaporating liquid film in a wiped molecular distillator was simulated with a computational fluid dynamics (CFD) software, and two turbulent models treating near-wall flow were compared. Differences ...Velocity field of evaporating liquid film in a wiped molecular distillator was simulated with a computational fluid dynamics (CFD) software, and two turbulent models treating near-wall flow were compared. Differences between wiped and other molecular distillations were intro-duced to explain why turbulent model should be used in this simulation. Three assumptions were made in order to simplify simulating processes. In rotating coordinate system, fixed other settings, the above two turbulent models were used, and the volume of fluid (VOF) multiphase model was also applied to tracking the liquid-gas surface. Both of the simulating results are basically iden-tical with real situation and were compared in several aspects. It was concluded that both of the turbulent models are suitable in this simulation.展开更多
The evaporating momentum force and the shear force acting on the meniscus of an evaporating and elongating bubble in flow boiling in microchannel have been investigated theoretically and numerically.The concept of the...The evaporating momentum force and the shear force acting on the meniscus of an evaporating and elongating bubble in flow boiling in microchannel have been investigated theoretically and numerically.The concept of the effective evaporation region and the theory of the liquid layer supplement between elongated bubble and microchannel are proposed,and the analytical expressions of the evaporating momentum force and shear force have been obtained.The relative importance of both forces has been determined by the method of magnitude analysis and numerical simulation.It has been found that the evaporating momentum force can always be neglected in analyzing the bubble elongation process and the motion law of meniscus of elongated bubble in microchannel flow boiling,but whether the shear force should be considered or not is determined by its relative order of magnitude and the particular conditions such as channel dimension and the operating conditions.展开更多
The evaporating section of the pulsating heat pipe(PHP)is in direct contact with the electronics when it is used for heat dissipation,and thus the evaporating temperature uniformity has an important effect on the safe...The evaporating section of the pulsating heat pipe(PHP)is in direct contact with the electronics when it is used for heat dissipation,and thus the evaporating temperature uniformity has an important effect on the safe and reliable operation of electronic equipment.On the basis of these conditions,an experimental study on the evaporating temperature uniformity of the PHP with surfactant solutions at different concentrations was conducted at the heat fluxes of(1911–19427)W/m^(2).Sodium stearate was utilized for the solute;the surfactant solutions were prepared with the concentrations of 0.001 wt%,0.002 wt%,and 0.004 wt%,respectively,and the filling ratios of the PHP were 0.31,0.44 and 0.57,respectively.The experimental results revealed that under all tested working conditions,the highest temperature always appeared in the intermediate zone of the evaporating section.As the heat flux increased,the temperature differences among different zones rose initially and then reduced due to the change of the flow motion and the flow pattern.The evaporating temperature uniformity of the sodium stearate solutions-PHP was better than that of the deionized water-PHP,which suggested that the evaporating temperature uniformity might be improved through decreasing the surface tension.Furthermore,combined with the effect of surface tension and viscosity,for different filling ratios,the required concentration was different when the best evaporating temperature uniformity was achieved.To be specific,when the filling ratio were 0.31 and 0.44,the best evaporating temperature uniformity was achieved at the concentration of 0.004 wt%,while at the filling ratio of 0.57,the best evaporating temperature uniformity was attained at the concentration of 0.002 wt%.展开更多
By combining the merits of radiative cooling(RC)and evaporation cooling(EC),radiative coupled evaporative cooling(REC)has attracted considerable attention for sub-ambient cooling purposes.However,for outdoor devices,t...By combining the merits of radiative cooling(RC)and evaporation cooling(EC),radiative coupled evaporative cooling(REC)has attracted considerable attention for sub-ambient cooling purposes.However,for outdoor devices,the interior heating power would increase the working temperature and fire risk,which would suppress their above-ambient heat dissipation capabilities and passive water cycle properties.In this work,we introduced a REC design based on an all-in-one photonic hydrogel for above-ambient heat dissipation and flame retardancy.Unlike conventional design RC film for heat dissipation with limited cooling power and fire risk,REC hydrogel can greatly improve the heat dissipation performance in the daytime with a high workload,indicating a 12.0℃lower temperature than the RC film under the same conditions in the outdoor experiment.In the nighttime with a low workload,RC-assisted adsorption can improve atmospheric water harvesting to ensure EC in the daytime.In addition,our REC hydrogel significantly enhanced flame retardancy by absorbing heat without a corresponding temperature rise,thus mitigating fire risks.Thus,our design shows a promising solution for the thermal management of outdoor devices,delivering outstanding performance in both heat dissipation and flame retardancy.展开更多
While desalination is a key solution for global freshwater scarcity,its implementation faces environmental challenges due to concentrated brine byproducts mainly disposed of via coastal discharge systems.Solar interfa...While desalination is a key solution for global freshwater scarcity,its implementation faces environmental challenges due to concentrated brine byproducts mainly disposed of via coastal discharge systems.Solar interfacial evaporation offers sustainable management potential,yet inevitable salt nucleation at evaporation interfaces degrades photothermal conversion and operational stability via light scattering and pathway blockage.Inspired by the mangrove leaf,we propose a photothermal 3D polydopamine and polypyrrole polymerized spacer fabric(PPSF)-based upward hanging model evaporation configuration with a reverse water feeding mechanism.This design enables zero-liquiddischarge(ZLD)desalination through phase-separation crystallization.The interconnected porous architecture and the rough surface of the PPSF enable superior water transport,achieving excellent solar-absorbing efficiency of 97.8%.By adjusting the tilt angle(θ),the evaporator separates the evaporation and salt crystallization zones via controlled capillary-driven brine transport,minimizing heat dissipation from brine discharge.At an optimal tilt angle of 52°,the evaporator reaches an evaporation rate of 2.81 kg m^(−2) h^(−1) with minimal heat loss(0.366 W)under 1-sun illumination while treating a 7 wt%waste brine solution.Furthermore,it sustains an evaporation rate of 2.71 kg m^(−2) h^(−1) over 72 h while ensuring efficient salt recovery.These results highlight a scalable,energy-efficient approach for sustainable ZLD desalination.展开更多
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 decre...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.展开更多
In this paper, evaporation of sessile water droplets containing fluorescent polystyrene （PS） microparticles on polydimethylsiloxane （PDMS） surfaces with different curing ratios was studied experimentally using las...In this paper, evaporation of sessile water droplets containing fluorescent polystyrene （PS） microparticles on polydimethylsiloxane （PDMS） surfaces with different curing ratios was studied experimentally using laser confocal microscopy. At the beginning, there were some microparticles located at the contact line and some microparticles moved towards the line. Due to contact angle hysteresis, at first both the contact line and the microparticles were pinned. With the depinning contact line, the microparticles moved together spontaneously. Using the software Image J, the location of contact lines at different time were acquired and the circle centers and radii of the contact lines were obtained via the least square method. Then the average distance of two neighbor contact lines at a certain time interval was obtained to characterize the motion of the contact line. Fitting the distance-time curve at the depinning contact line stage with polynomials and differentiating the polynomials with time, we obtained the velocity and acceleration of both the contact line and the microparticles located at the line. The velocity and the maximum acceleration were, respectively, of the orders of 1 p.m/s and 20-200 nm/s2, indicating that the motion of the microparticles located at the depinning contact line was quasi-static. Finally, we presented a theoretical model to describe the quasi-static process, which may help in understanding both self-pinning and depinning of microparticles.展开更多
The study of quantum thermal effect of non-static black hole is generalized to the space-time with coordinate (t, r) as variables. Tortoise coordinate equations which are different from not only static space-time but ...The study of quantum thermal effect of non-static black hole is generalized to the space-time with coordinate (t, r) as variables. Tortoise coordinate equations which are different from not only static space-time but also the non-statie space-time described by advanced-Eddington coordinate v have been chosen. Under the condition that the effect of Hawking evaporation is considered, the temperature of black hole and the location of horizon are shown. The results indicate that Hawking radiation temperature can be regarded as a compensating effect under the time-scale transformation.展开更多
基金supported by the National Natural Science Foundation of China(52203226)the Fundamental Research Funds for the Central Universities(2232023G-06).
文摘The treatment of ammonia nitrogen wastewater(ANW)has garnered significant attention due to the ecology,and even biology is under increasing threat from over discharge ANW.Conventional ANW treatment methods often encounter challenges such as complex processes,high costs and secondary pollution.Considerable progress has been made in employing solar-induced evaporators for wastewater treatment.However,there remain notable barriers to transitioning from fundamental research to practical applications,including insufficient evaporation rates and inadequate resistance to biofouling.Herein,we propose a novel evaporator,which comprises a bio-enzyme-treated wood aerogel that serves as water pumping and storage layer,a cost-effective multi-walled carbon nanotubes coated hydrophobic/hydrophilic fibrous nonwoven mat functioning as photothermal evaporation layer,and aggregation-induced emission(AIE)molecules incorporated as anti-biofouling agent.The resultant bioinspired evaporator demonstrates a high evaporation rate of 12.83 kg m^(−2) h^(−1) when treating simulated ANW containing 30 wt%NH4Cl under 1.0 sun of illumination.AIE-doped evaporator exhibits remarkable photodynamic antibacterial activity against mildew and bacteria,ensuring outstanding resistance to biofouling over extended periods of wastewater treatment.When enhanced by natural wind under 1.0 sun irradiation,the evaporator achieves an impressive evaporation rate exceeding 20 kg m^(−2) h^(−1) .This advancement represents a promising and viable approach for the effective removal of ammonia nitrogen wastewater.
基金Supported by the National Natural Science Foundation of China (No. 20076039) and SINOPEC.
文摘Evaporating bubble column reactor (EBCR) is a kind of aerated reactor in which the reaction heat is removed by the evaporation of volatile reaction mixture. In this paper, a mathematical model that accounts for the gas-liquid exothermic reaction and axial dispersions of both gas and liquid phase is employed to study the performance of EBCR for the process of p-xylene(PX) oxidation. The computational results show that there are remarkable concentration and temperature gradients in EBCR for high ratio of height to diameter (H/DT). The temperature is lower at the bottom of column and higher at the top, due to rapid evaporation induced by the feed gas near the bottom. The concentration profiles in the gas phase are more nonuniform than those (except PX) in the liquid phase, which causes more solvent burning consumption at high H/DT ratio. For p-xylene oxidation, theo ptimal H/DT is around 5.
文摘A new technology for the crystallization of ammonium paratungstate with coarse grain has beenstudied. The factors influencing the physi-chemical properties of ammonium paratungstate crystal, such astemperature, concentration, seed crystal, agitation. etc. were examined. It is necessary to keep high temperature and low concentration in the process. and the addition of seed crystal and agitation with air is also in favor of the system. Ammonium paratungstate crystal with particle size of 36-42 μm and apparent density of2. 0-2. 2 g·cm- 3 were obtained by controlling suitable technological parameters.
基金financially supported with General Project of Nat-ural Science Foundation of China (No. 21373252)
文摘Research the evaporating crystalization process of the magnesium sulfate subtypes brine at high temperature from Dalangtan salt lake in Qinghai province.It was revealed that the salt lake is a typical subtype magnesium
基金the Third Round"985 Project"Through the University of Michigan-Shanghai Jiao Tong University Joint Institute(No.TS0321337001)
文摘The purpose of this study is to investigate the effect of fuel properties on liquid and vapor penetrations in evaporating spray systems. A recently developed model, which can simultaneously account for the finite thermal conductivity, finite mass diffusivity and turbulence effects within atomizing multi-component liquid fuel sprays, is utilized for the numerical predictions. Two different multi-component fuels with different boiling temperatures,densities and other thermal properties are implemented in the KIVA-3V computational fluid dynamics(CFD)code to study the evaporation behaviors. A six-component surrogate fuel is used to emulate the relevant volatility property of the real diesel fuel, and a second bi-component fuel is chosen to represent a low boiling-temperature fuel. The numerical results are compared with the experimental data, and the representative results are obtained.For a lower density and lower boiling temperature fuel, the liquid penetration length is shorter. However, the vapor penetration lengths are not affected by the fuel type in terms of fuel volatility. Available experimental data are used for validation and appraisal of the multi-component evaporation model.
基金N ational N atural Science Foundation of China, N o.40271025 the N ational H igh Technology Research andD evelopm ent Program of China (863 Program ), N o.2002A A 135360+1 种基金 the Program of Education D epartm ent ofH unan Province,N o.03C210the CA S Tianshan G laciologicalStation Foundation,N o.TZ2000-02
文摘Under Rayleigh equilibrium condition, stable isotopic ratio in residual water increases with the decrease of the residual water proportion f exponentially, and the fractionation rate of stable isotopes is inversely proportional to temperature. However, under kinetic evaporation condition, the fi＇actionation of stable isotopes is not only related to the phase temperature but also influenced by the atmospheric humidity and the mass exchange between liquid and vapor phases. The ratio 6 in residual water will not change with f after undergoing evaporation of a long time for great relative humidity. The rate that the evaporating water body reaches isotopic steady state is mainly dependent on the relative humidity in atmosphere. The analysis shows that the actual mean linear variety rates, about -30.0, of the δ^18O in residual water versus the residual water proportion at Nagqu and Amdo stations are consistent with the simulated process under temperature of 20℃ and relative humidity of 50%. The distillation line simulated under Rayleigh equilibrium condition is analogous to the global meteoric water line （MWL） as the temperature is about 20℃. Under non-equilibrium condition, the slope and constant values of distillation line are directly proportional to temperature and relative humidity. According to the basic data, the simulated distillation line is very consistent with the actual distillation line of Qinghai Lake.
基金supported by the National Natural Science Foundation of China (Grant No. 50679024)the Innovation Program for College Graduate of Jiangsu Province of 2007 (Grant No. CX07B_130Z)
文摘The variation of stable isotope ratios in natural waters provides valuable information that can be used to trace water movement. Evaporation plays a crucial role in determining the variation of stable isotopes. In this paper, several evaporation experiments were conducted in order to study the stable isotopic fractionation mechanism of water and analyze the influence of different temperatures on evaporation fractionation. Three group experiments of water evaporation under different temperatures and initial isotopic values were carried out. The results show that fractionation factors of hydrogen and oxygen may increase with temperature, and the average enrichment degree of hydrogen isotope D is 3.432 times that of oxygen isotope 18O. The results also show that the isotopic composition of the initial water has little influence on water evaporation fractionation, which is mainly affected by the state variables in the evaporation process, such as temperature. This research provides experimental data for further understanding the evaporation fractionation mechanism.
基金Under the auspices of the Joint Funds of the National Natural Science Foundation of China(No.U22A20592)the National Key Research and Development Program of China(No.2020YFA0607702)+2 种基金the Second Tibetan Plateau Scientific Expedition and Research Program(No.2019QZKK0405)Chinese Academy of Sciences Young Crossover Team Project(No.JCTD-2022-18)Excellent doctoral program in Gansu Province(No.22JR5RA052)。
文摘Consideration of stable isotopes in precipitation is valuable for investigating hydrological processes.Therefore,correcting the measured isotopic composition of precipitation under below-cloud evaporation is necessary.An accurate description of the underlying processes affecting stable isotopic composition of precipitation could help improve our understanding of the water cycle.The transitivity between monsoonal and arid climates was reflected by the evaporation rate of falling raindrops in precipitation in the Qilian Mountains,a typical transition zone between Tibetan Plateau and arid region of China.Considering 1310 precipitation event-scale samples,based on stable isotope analysis method,the mean below-cloud evaporation rate(f)in the study area was measured as 12.00%during the summer half-year(May-October).The evaporation rate on the northern slopes(12.70%)of the Qilian Mountains in China was significantly higher than that on the southern slopes(9.98%).The transition between monsoonal and arid climates was reflected in the evaporation rate of falling raindrops during precipitation in the Qilian Mountains of China.Below-cloud evaporation contributed to a noticeable enrichment of stable isotopes in the precipitation in the study area.The monthly precipitationδ^(18)O enrichment rate in the Qilian Mountains of China from May to October was 29.18%,23.35%,25.60%,22.99%,31.64%,and 14.72%,respectively.For every 1.00%increase in the evaporation rate of raindrops in Qilian Mountains of China,the changes in the concentration of oxygen isotopes from the bottom of the clouds to the ground increased by 0.92‰;however,with an evaporation rate of<5.00%,for every 1.00%increase in the evaporation rate of raindrops the changes in the concentration of oxygen isotopes from the bottom of the clouds to the ground increased by 1.00‰could also be observed.Furthermore,altitude was an important factor affecting below-cloud evaporation in the study area.
基金The project supported by the National Natural Science Foundation of China （10372105） and the Knowledge Innovation Program of Chinese Academy of Sciences （KJCX2-SW-L05 and KGCX-SW-409） The English text was polished by Keren Wang.
文摘Classical theories have successfully provided an explanation for convection in a liquid layer heated from below without evaporation. However, these theories are inadequate to account for the convective instabilities in an evaporating liquid layer, especially in the case when it is cooled from below. In the present paper, we study the onset of Marangoni convection in a liquid layer being overlain by a vapor layer. A new two-sided model is put forward instead of the one-sided model in previous studies. Marangoni-Béard instabilities in evaporating liquid thin layers are investigated with a linear instability analysis. We define a new evaporation Blot number, which is different from that in previous studies and discuss the influences of reference evaporating velocity and evaporation Blot number on the vapor-liquid system. At the end, we explain why the instability occurs even when an evaporating liquid layer is cooled from below.
文摘The main objective of this paper is to develop a simpleand efficient numerical model for estimation of heat and mass transfer between water spray drops and airstreamin horizontal parallel flow which enable us to accurateprediction of evaporative cooling performance.Thephysical process of a droplet evaporating in finite airflowhas been studied.Four basic differential equations havebeen developed with their numerical solutions providedby figures.
文摘In the framework of the two-continuum approach, using the matched asymptotic expansion method, the equations of a laminar boundary layer in mist flows with evaporating droplets were derived and solved. The similarity criteria controlling the mist flows were determined. For the flow along a curvilinear surface, the forms of the boundary layer equations differ from the regimes of presence and absence of the droplet inertia deposition. The numerical results were presented for the vapor-droplet boundary layer in the neighborhood of a stagnation point of a hot blunt body. It is demonstrated that, due to evaporation, a droplet-free region develops near the wall inside the boundary layer. On the upper edge of this region, the droplet radius tends to zero and the droplet number density becomes much higher than that in the free stream. The combined effect of the droplet evaporation and accumulation results in a significant enhancement of the heat transfer on the surface even for small mass concentration of the droplets in the free stream.
基金supported by National Natural Science Foundation of China(Grant Nos.52022058 and 51776124)by Ministry of Education of China(Grant No.6141A020335)。
文摘Spray experiments of RP-3 jet fuel at non-evaporating and evaporating environments were studied on a constant volume spray chamber,and diffusive back-imaging technique was used to capture the transient spray development processes.Spray tip penetration,projected spray area and cone angle of RP-3 jet fuel were derived from the spray development images,and compared to those of diesel fuel.It is observed that non-evaporating sprays of RP-3 jet fuel and diesel fuel do not exhibit significant differences,as their spray penetration distances,projected spray areas and spray cone angles are consistent at most test conditions.The evaporating sprays of RP-3 jet fuel produce shorter liquid-phase penetration distances and lower projected spray areas than those of diesel fuel,and these differences are particularly pronounced at low ambient temperatures.However,fuel effects on the evaporating spray cone angle are insignificant.Further,increased ambient density or ambient temperature shortens the liquid-phase spray penetration distance and reduces the liquid-phase spray area,and these effects are more pronounced for diesel fuel than RP-3 jet fuel.
基金the National Natural Science Foundation of China(Grant No.20176037).
文摘Velocity field of evaporating liquid film in a wiped molecular distillator was simulated with a computational fluid dynamics (CFD) software, and two turbulent models treating near-wall flow were compared. Differences between wiped and other molecular distillations were intro-duced to explain why turbulent model should be used in this simulation. Three assumptions were made in order to simplify simulating processes. In rotating coordinate system, fixed other settings, the above two turbulent models were used, and the volume of fluid (VOF) multiphase model was also applied to tracking the liquid-gas surface. Both of the simulating results are basically iden-tical with real situation and were compared in several aspects. It was concluded that both of the turbulent models are suitable in this simulation.
基金supported by National Natural Science Foundation of China(No.51176008)National Key Technology R&D Program(No.2012BAB12B02)Jiangsu Key Laboratory of Process Enhancement&New Energy Equipment Technology(Nanjing University of Technology)
文摘The evaporating momentum force and the shear force acting on the meniscus of an evaporating and elongating bubble in flow boiling in microchannel have been investigated theoretically and numerically.The concept of the effective evaporation region and the theory of the liquid layer supplement between elongated bubble and microchannel are proposed,and the analytical expressions of the evaporating momentum force and shear force have been obtained.The relative importance of both forces has been determined by the method of magnitude analysis and numerical simulation.It has been found that the evaporating momentum force can always be neglected in analyzing the bubble elongation process and the motion law of meniscus of elongated bubble in microchannel flow boiling,but whether the shear force should be considered or not is determined by its relative order of magnitude and the particular conditions such as channel dimension and the operating conditions.
基金supported by State Key Laboratory of Air-Conditioning Equipment and System Energy Conservation(No.ACSKL2019KT08)Natural Science Foundation of Zhejiang Province(No.LZ19E060001)。
文摘The evaporating section of the pulsating heat pipe(PHP)is in direct contact with the electronics when it is used for heat dissipation,and thus the evaporating temperature uniformity has an important effect on the safe and reliable operation of electronic equipment.On the basis of these conditions,an experimental study on the evaporating temperature uniformity of the PHP with surfactant solutions at different concentrations was conducted at the heat fluxes of(1911–19427)W/m^(2).Sodium stearate was utilized for the solute;the surfactant solutions were prepared with the concentrations of 0.001 wt%,0.002 wt%,and 0.004 wt%,respectively,and the filling ratios of the PHP were 0.31,0.44 and 0.57,respectively.The experimental results revealed that under all tested working conditions,the highest temperature always appeared in the intermediate zone of the evaporating section.As the heat flux increased,the temperature differences among different zones rose initially and then reduced due to the change of the flow motion and the flow pattern.The evaporating temperature uniformity of the sodium stearate solutions-PHP was better than that of the deionized water-PHP,which suggested that the evaporating temperature uniformity might be improved through decreasing the surface tension.Furthermore,combined with the effect of surface tension and viscosity,for different filling ratios,the required concentration was different when the best evaporating temperature uniformity was achieved.To be specific,when the filling ratio were 0.31 and 0.44,the best evaporating temperature uniformity was achieved at the concentration of 0.004 wt%,while at the filling ratio of 0.57,the best evaporating temperature uniformity was attained at the concentration of 0.002 wt%.
基金financially supported by the Science and Technology Innovation Program of Hunan Province(2024RC3003)the Central South University Innovation-Driven Research Programme(2023CXQD012)the Initiative for Sustainable Energy for its financial support。
文摘By combining the merits of radiative cooling(RC)and evaporation cooling(EC),radiative coupled evaporative cooling(REC)has attracted considerable attention for sub-ambient cooling purposes.However,for outdoor devices,the interior heating power would increase the working temperature and fire risk,which would suppress their above-ambient heat dissipation capabilities and passive water cycle properties.In this work,we introduced a REC design based on an all-in-one photonic hydrogel for above-ambient heat dissipation and flame retardancy.Unlike conventional design RC film for heat dissipation with limited cooling power and fire risk,REC hydrogel can greatly improve the heat dissipation performance in the daytime with a high workload,indicating a 12.0℃lower temperature than the RC film under the same conditions in the outdoor experiment.In the nighttime with a low workload,RC-assisted adsorption can improve atmospheric water harvesting to ensure EC in the daytime.In addition,our REC hydrogel significantly enhanced flame retardancy by absorbing heat without a corresponding temperature rise,thus mitigating fire risks.Thus,our design shows a promising solution for the thermal management of outdoor devices,delivering outstanding performance in both heat dissipation and flame retardancy.
基金supported by National Key Research and Development Program of China(2022YFB3804902,2022YFB3804900)the National Natural Science Foundation of China(52203226,52161145406,42376045)the Fundamental Research Funds for the Central Universities(2232024Y-01,2232025D-02).
文摘While desalination is a key solution for global freshwater scarcity,its implementation faces environmental challenges due to concentrated brine byproducts mainly disposed of via coastal discharge systems.Solar interfacial evaporation offers sustainable management potential,yet inevitable salt nucleation at evaporation interfaces degrades photothermal conversion and operational stability via light scattering and pathway blockage.Inspired by the mangrove leaf,we propose a photothermal 3D polydopamine and polypyrrole polymerized spacer fabric(PPSF)-based upward hanging model evaporation configuration with a reverse water feeding mechanism.This design enables zero-liquiddischarge(ZLD)desalination through phase-separation crystallization.The interconnected porous architecture and the rough surface of the PPSF enable superior water transport,achieving excellent solar-absorbing efficiency of 97.8%.By adjusting the tilt angle(θ),the evaporator separates the evaporation and salt crystallization zones via controlled capillary-driven brine transport,minimizing heat dissipation from brine discharge.At an optimal tilt angle of 52°,the evaporator reaches an evaporation rate of 2.81 kg m^(−2) h^(−1) with minimal heat loss(0.366 W)under 1-sun illumination while treating a 7 wt%waste brine solution.Furthermore,it sustains an evaporation rate of 2.71 kg m^(−2) h^(−1) over 72 h while ensuring efficient salt recovery.These results highlight a scalable,energy-efficient approach for sustainable ZLD desalination.
基金supported by the National Natural Science Foundation of China (Grant No. 11072126)
文摘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.
基金supported by the National Natural Science Foundation of China(Grant Nos.11572114,11572335,and U1562105)the Opening Fund of State Key Laboratory of Nonlinear Mechanics(LNM)+1 种基金the CAS Strategic Priority Research Program(Grant No.XDB22040403)and the CAS Key Research Program of Frontier Sciences(Grant No.QYZDJ-SSW-JSC019)
文摘In this paper, evaporation of sessile water droplets containing fluorescent polystyrene （PS） microparticles on polydimethylsiloxane （PDMS） surfaces with different curing ratios was studied experimentally using laser confocal microscopy. At the beginning, there were some microparticles located at the contact line and some microparticles moved towards the line. Due to contact angle hysteresis, at first both the contact line and the microparticles were pinned. With the depinning contact line, the microparticles moved together spontaneously. Using the software Image J, the location of contact lines at different time were acquired and the circle centers and radii of the contact lines were obtained via the least square method. Then the average distance of two neighbor contact lines at a certain time interval was obtained to characterize the motion of the contact line. Fitting the distance-time curve at the depinning contact line stage with polynomials and differentiating the polynomials with time, we obtained the velocity and acceleration of both the contact line and the microparticles located at the line. The velocity and the maximum acceleration were, respectively, of the orders of 1 p.m/s and 20-200 nm/s2, indicating that the motion of the microparticles located at the depinning contact line was quasi-static. Finally, we presented a theoretical model to describe the quasi-static process, which may help in understanding both self-pinning and depinning of microparticles.
基金Project supported by the National Natural Science Foundation of China
文摘The study of quantum thermal effect of non-static black hole is generalized to the space-time with coordinate (t, r) as variables. Tortoise coordinate equations which are different from not only static space-time but also the non-statie space-time described by advanced-Eddington coordinate v have been chosen. Under the condition that the effect of Hawking evaporation is considered, the temperature of black hole and the location of horizon are shown. The results indicate that Hawking radiation temperature can be regarded as a compensating effect under the time-scale transformation.
