Evaporation Calculations Research Articles

Improved model for calculation of evaporation from water pools

Calculation of evaporation is needed for a variety of water pools in many applications under diverse conditions. Many prediction methods have been published including one by the present author. An improved model is presented here that shows good agreement with data that include natural and forced convection, laboratory vessels, indoor and outdoor swimming pools, and spent fuel pools of nuclear power plants. The range of data includes pool area from 0.022 to 525 m2, water temperatures from 7 °C to 94 °C, air temperatures from 6 °C to 51 °C, relative humidity from 16% to 98%, and air velocity up to 1.9 m/s. These data from 24 studies are predicted with a mean absolute deviation of 13.9%. The same data are also compared to a number of other prediction methods; their deviations from data are much larger. In view of its good agreement with such a wide range of data from many sources, the proposed model is recommended for use in design and analysis.

The MaRIUS‐G2G datasets: Grid‐to‐Grid model estimates of flow and soil moisture for Great Britain using observed and climate model driving data

AbstractThe MaRIUS‐G2G datasets were produced for the MaRIUS (Managing the Risks, Impacts and Uncertainties of drought and water Scarcity) project, using the Grid‐to‐Grid (G2G) national‐scale hydrological model for Great Britain. There are six separate datasets, with each of three combinations of meteorological driving data (two observation‐based and one from climate model ensembles) used to produce two types of outputs (daily time‐series of natural river flow for 260 sites, and monthly 1 × 1 km grids of natural flow and soil moisture in the unsaturated zone). The driving data required by G2G are rainfall and potential evaporation (PE). Two of the datasets from observation‐based driving data use rainfall from CEH‐GEAR (CEH‐Gridded Estimates of Areal Rainfall) with PE from MORECS (Met Office Rainfall and Evaporation Calculation System), and cover the period 1960–2015, while the other two use CEH‐GEAR rainfall with PE derived from 5 km temperature data using the Oudin method, and cover 1891–2015. The two datasets based on driving data (rainfall and PE) from the climate model ensembles cover three periods: Historical Baseline (1900–2006), Near‐Future (2020–2049), and Far‐Future (2070–2099). Data for a 30‐year Baseline period (1975–2004), against which the Near‐Future and Far‐Future periods should be compared, are also available directly. There are 100 members in each ensemble, and the future periods use the RCP8.5 emissions scenario. This paper provides details of the G2G model and the different sets of meteorological driving data, as well as the availability and formatting of the output datasets. It also describes some recent and potential applications of the datasets, which have already been used to support historical and future analyses of low flow and drought characteristics across Britain, and provides some guidance on how the climate model‐driven datasets should (and should not) be used.Open PracticesThis article has earned an Open Data badge for making publicly available the digitally‐shareable data necessary to reproduce the reported results. The data is available at DOI 10.5285/5f3c1a02-d5c4-4faa-9353-e8b68ce2ace2. Learn more about the Open Practices badges from the Center for Open Science: https://osf.io/tvyxz/wiki.

Steam generation enabled by a high efficiency solar absorber with thermal concentration

Solar steam generation, a typical solar energy utilization way, has wide applications and attracts many researches, such as the enhancement achieving by numerous nanomaterials and porous membranes. However, some issues need to be solved (e.g., blockage of pore structures and poisoning of film nanoparticles (NPs)), which are critical for developing sustained and efficient evaporation processes. In this sense, we developed herein a novel evaporation method involving a thin water layer and a highly efficient solar absorber for enhanced steam generation. This technology prevented pore blockage and poisoning of NPs by employing a dense surface structure and continuous water flow. A C-Au-TiO2 solar absorber prepared by a sol-gel method with a superior photo-thermal conversion capacity, even for lights with large angles of incidence was the key to enhance the solar steam generation process. By experiments and theoretical calculations for solar evaporation, the steam generation performance and heat change process were investigated. It was found that improving the light absorption of the solar absorber and reducing the thermal loss were effective methods to enhance evaporation rate and efficiency, while reducing the water height could cut down the time needed to reach stable stage. And the C-Au-TiO2 solar absorber achieved a significantly enhanced solar steam generation, which may pave the way for developing new highly efficient solar steam generation paths.

Using deuterium excess, precipitation and runoff data to determine evaporation and transpiration: A case study from the Shawan Test Site, Puding, Guizhou, China

Separating watershed evapotranspiration into its evaporation and transpiration components is important for calculating the carbon that is assimilated by terrestrial vegetation in carbon cycle studies. The key step in this separation is to quantify the evaporation component. The deuterium excess (d-excess) in meteoric water has been shown to be an important indicator of both the original source of the water vapor and the humidity at the vapor source area. It has also shown promise for use in investigating the evaporation losses. While many studies have used the δD/δ18O method to study watershed evaporation, few have discussed the differences between the δD/δ18O (single isotope system) and d-excess (dual isotope system) methods in quantifying watershed evaporation. Given the complexity of natural watersheds, the Shawan Test Site was established at Puding, China, to study the water cycle in five concrete tanks (simulated watersheds) with different land uses over one hydrologic year. There were no plants in two of the tanks (bare rock and bare soil), which allowed verification of evaporation calculations derived from the d-excess and δD/δ18O methods. δD or δ18O values of precipitation in the rainy season, when most of the groundwater recharge occurs, showed great variability. In contrast, the d-excess of the meteoric waters collected during the same rainy season was much more stable than the δD or δ18O values. We quantified the annual evaporative loss of the five watersheds using both methods. Comparison of the results indicated that the d-excess method is more acceptable than the δD/δ18O method due to the stability of d-excess. Calculated ratios of transpiration to evapotranspiration in three tanks planted with vegetation were 56.8% in cultivated land, 70.9% in shrub land, and 85.9% in grassland, demonstrating that in well vegetated watersheds, this component of the cycle is controlled chiefly by plant transpiration. Land use has an important impact on the hydrologic cycle in a watershed, and the d-excess calculations conducted in this study provide new insights for quantifying components of the cycle, especially in the East Asian monsoon region which has rainfall with a large range in δD or δ18O values.

Performance evaluation of oil spill software systems in early fate and trajectory of oil spill: comparison analysis of OILMAP and PISCES 2 in Mersin bay spill.

The aim of this study is to evaluate the performance level of two advanced oil spill software systems in early transport and fate of oil spill through algorithms accepted in oil spill literature. To do this, the performance level of software systems mostly used in real cases have been compared. OILMAP (the oil spill prediction modeling system) and PISCES 2 (potential incident simulation, control and evaluation system) have been used for spill trajectory in the light of four spill scenarios. The findings reveal that the OILMAP has predicted a relatively larger area of spill. In addition, OILMAP has achieved closer results to the calculations of approaches adopted in the literature for evaporation calculations. Besides, OILMAP software has provided highly reliable results in the evaporation rates of oil compared to the calculations of PISCES 2. On the other hand, as for the determination of the risky area, both software systems have yielded results with high reliability values, which could be used in taking precautions against oil spill in such areas.

Magnesium Loss in Nd:YAG Pulsed Laser Welding of Aluminum Alloys

In the current investigation, the loss of magnesium (Mg) in Nd:YAG pulsed laser welding of a number of aluminum (Al) alloys was studied both experimentally and numerically. The experimental results showed that at a fixed average laser power, with the increasing pulse frequency, Mg concentration of the weld metals decreased. A numerical model was developed for the calculation of Mg evaporation from the weld pool. The model predicted a trend in the changes of Mg concentration of the weld pool, working best for alloys containing the higher levels of Mg. The calculations showed that with the increasing pulse frequency from 15 to 40 Hz, due to a decrease in the average temperature of the weld pool, Mg loss in terms of mass per unit area of the weld spot actually decreased from 230 × 10−5 to 120 × 10−5 kg/m2. However, due to a decrease in the weld penetration/volume, the effective Mg loss of the weld metal in terms of concentration increased from 110 × 10−1 to 260 × 10−1 kg/m3. It was shown that due to interactions between Mg and other main alloying elements, the activity coefficient of Mg had to be modified for the model to accurately predict Mg evaporation of the weld pool.

Mathematical modelling for ecohydrological management of an endangered endorheic salt lake in the semiarid Pampean region, Argentina

In this work, we propose a mathematical model within a dynamic optimization framework to address the management of a salt lake in a semiarid region in Argentina (Chasicó Lake). The main objective is to elaborate strategies to control recurrent floods and keep salinity values around the physiological optimum for the high-commercial value fish silverside. The model comprises dynamic mass balances for water and salt, as well as evaporation calculation based on energy and momentum balances on a daily basis. A collection of meteorological and hydraulic data in the basin for several decades and bathymetric information is included. The simulation of different scenarios with historical data provide a deeper insight into the ecohydrological dynamics of Chasicó Lake basin. Model predictions under moderate drought conditions, with rainfall about 70% of the historic average, show a large increase in salinity after three years under that setting. This would induce drastic changes in ecological conditions producing fish mass mortality, what likely occurred repeatedly throughout the lake’s history, since such dry periods occurred repeatedly during the analyzed 1911‐2016 period. The comparison between drought and wet scenarios indicates a differential vulnerability dynamics in which the system shows less resistance to the effects of drought than to those due to floods. The proposed model allows the determination of optimal lake tributary diversion flowrate to prevent flooding of croplands, keeping lake salinity within optimal values for silverside, and providing water for the creation of wetlands for wildlife and an artificial reservoir for alleviation of wet period effects.

Sensitivity of a Simulated Squall Line During Southern China Monsoon Rainfall Experiment to Parameterization of Microphysics

AbstractA squall line on 22 May 2014 during the Southern China Monsoon Rainfall Experiment period is simulated with four bulk microphysical parameterizations (BMPs) using the Weather Research and Forecasting (WRF) model. Although most BMPs are able to capture the basic features of the squall line, the movement, morphology, and especially the length of the simulated squall lines differ significantly among BMPs. Morrison scheme tends to simulate a slower moving squall line with a weaker cold pool and better trailing stratiform cloud and precipitation due to the smaller snow fall speed and faster generation of snow particles than other schemes. Assuming hail or graupel in different schemes could result in different melting profiles of rimed‐ice particles, with hail melted substantially below the 0°C isotherm and contributing to the cold pool production significantly in WRF double‐moment six‐class microphysics scheme because of its use of larger fall speed for hail. Although ice‐phase particles simulated differ significantly among BMPs, it is rain evaporation that dominates the cold pool generation and maintenance of the squall line in this case. Stronger rain evaporation generally contributes to stronger cold pools and thus faster movement and longer simulated squall lines. Failure of the Stony Brook University‐YLin scheme in capturing the squall line was identified to be related to the turnoff of rain evaporation once environmental relative humidity is larger than 90%. With modifications of rain evaporation calculation and saturation adjustment method, the scheme is able to simulate this squall line reasonably well.

Evaporation-induced receding contact lines in partial-wetting regime on a heated substrate

The moving contact line is a nanoscale joint providing critical boundary conditions for the liquid interface in a wetting system. Our understanding about the partial-wetting contact line is highly limited which is especially true when the situation is complicated by phase change that is ubiquitous in nature and technologies. In this work we explored evaporation-induced receding contact lines in partial wetting regime by means of two modes of atomic force microscopy scanning. By means of tapping mode scanning, the intrinsic meniscus profile was found to be linear down to the apparent contact line without bending in profile, which greatly facilitates the modeling about the intrinsic meniscus. The local angle on the contact line systematically varied with the moving speed, which fact is against the widely used constant assumption in hydrodynamic models. Using the tapping mode scanning and also force curve method with either soft or stiff probes, a layer of nano thin film was detected on the substrate beyond the contact line. The nano film thickness slightly decreased with the distance away from the contact line, and finally reached a constant that was the adsorbed i.e. non-evaporating film thickness if the tests were in a vapor chamber. We further investigated advancing contact lines in open air, and still detected the nano thin film in front of the contact line as a precursor. The nano thin film can provide extra evaporation area, which could rationalize the abnormal ultrahigh evaporation flux observed in recent experiments on nanoscale menisci. Guidance is provided for the calculation of partial-wetting contact line evaporation.

Methodological Aspects of the Estimation of Soil Water Evaporation upon Mulching with Vegetative Remains in Arid Regions

The method and scheme of the calculation of soil water evaporation upon mulching in arid regions are presented. A detailed description of the parameters of information support is given. The proposed simplified scheme for the calculation of soil water evaporation upon mulching is based on parametrization of precipitation. Precipitation parametrization simplifies much of the calculation of soil water evaporation with mulching while maintaining acceptable accuracy.

Formation of Superheavy Elements: Study Based on Dynamical Approach

Using multi-dimensional Langevin equations for the probability distribution of the distance between the surfaces of two approaching nuclei, we have studied the formation of superheavy elements via calculation of evaporation and fission cross sections of these elements. Evaporation residue cross sections have been calculated for the 1n, 2n, 3n, 4n, and 5n evaporation channels using one and four dimensional Langevin equations for the 48Ca+226Ra, 232Th, 238U, 237Np, 239,240,242,244Pu, 243Am, 245,248Cm, 249Bk, and 249Cf reactions. Our results show that with increasing dimension of Langevin equations the evaporation residue cross section is increased. Also, obtained results based on fourdimensional Langevin are in better agreement with experimental data in comparison with one-dimensional model.

Measuring and modelling energy partitioning in canopies of varying complexity using MAESPA model

Evapotranspiration and energy partitioning are complex to estimate because they result from the interaction of many different processes, especially in multi-species and multi-strata ecosystems. We used MAESPA model, a mechanistic, 3D model of coupled radiative transfer, photosynthesis, and balances of energy and water, to simulate the partitioning of energy and evapotranspiration in homogeneous tree plantations, as well as in heterogeneous multi-species, multi-strata agroforests with diverse spatial scales and management schemes. The MAESPA model was modified to add (1) calculation of foliage surface water evaporation at the voxel scale; (2) computation of an average within-canopy air temperature and vapour pressure; and (3) use of (1) and (2) in iterative calculations of soil and leaf temperatures to close ecosystem-level energy balances. We tested MAESPA model simulations on a simple monospecific Eucalyptus stand in Brazil, and also in two complex, heterogeneous Coffea agroforests in Costa Rica. MAESPA satisfactorily simulated the daily and seasonal dynamics of net radiation (RMSE = 29.6 and 28.4 W m−2; R2 = 0.99 and 0.99 for Eucalyptus and Coffea sites respectively) and its partitioning between latent-(RMSE = 68.1 and 37.2 W m−2; R2 = 0.87 and 0.85) and sensible-energy (RMSE = 54.6 and 45.8 W m−2; R2 = 0.57 and 0.88) over a one-year simulation at half-hourly time-step. After validation, we use the modified MAESPA to calculate partitioning of evapotranspiration and energy between plants and soil in the above-mentioned agro-ecosystems. In the Eucalyptus plantation, 95% of the outgoing energy was emitted as latent-heat, while the Coffea agroforestry system’s partitioning between sensible and latent-heat fluxes was roughly equal. We conclude that MAESPA process-based model has an appropriate balance of detail, accuracy, and computational speed to be applicable to simple or complex forest ecosystems and at different scales for energy and evapotranspiration partitioning.

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

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

Dead Sea evaporation by eddy covariance measurements vs. aerodynamic, energy budget, Priestley–Taylor, and Penman estimates

Abstract. The Dead Sea is a terminal lake, located in an arid environment. Evaporation is the key component of the Dead Sea water budget and accounts for the main loss of water. So far, lake evaporation has been determined by indirect methods only and not measured directly. Consequently, the governing factors of evaporation are unknown. For the first time, long-term eddy covariance measurements were performed at the western Dead Sea shore for a period of 1 year by implementing a new concept for onshore lake evaporation measurements. To account for lake evaporation during offshore wind conditions, a robust and reliable multiple regression model was developed using the identified governing factors wind velocity and water vapour pressure deficit. An overall regression coefficient of 0.8 is achieved. The measurements show that the diurnal evaporation cycle is governed by three local wind systems: a lake breeze during daytime, strong downslope winds in the evening, and strong northerly along-valley flows during the night. After sunset, the strong winds cause half-hourly evaporation rates which are up to 100 % higher than during daytime. The median daily evaporation is 4.3 mm d−1 in July and 1.1 mm d−1 in December. The annual evaporation of the water surface at the measurement location was 994±88 mm a−1 from March 2014 until March 2015. Furthermore, the performance of indirect evaporation approaches was tested and compared to the measurements. The aerodynamic approach is applicable for sub-daily and multi-day calculations and attains correlation coefficients between 0.85 and 0.99. For the application of the Bowen ratio energy budget method and the Priestley–Taylor method, measurements of the heat storage term are inevitable on timescales up to 1 month. Otherwise strong seasonal biases occur. The Penman equation was adapted to calculate realistic evaporation, by using an empirically gained linear function for the heat storage term, achieving correlation coefficients between 0.92 and 0.97. In summary, this study introduces a new approach to measure lake evaporation with a station located at the shoreline, which is also transferable to other lakes. It provides the first directly measured Dead Sea evaporation rates as well as applicable methods for evaporation calculation. The first one enables us to further close the Dead Sea water budget, and the latter one enables us to facilitate water management in the region.

Calculation of Open Water Evaporation as a Climate Parameter

Calculation of open water evaporation is important for hydrology, industry, agriculture, environment, and other fields. The available methods of calculating evaporation are based on field or laboratory experiments and should not be used for scale-up to open water evaporation for similitude relationships cannot be correctly obtained. The methods are thus unjustified scientifically. In addition, surface evaporation is not a local phenomenon that is a function of independent meteorological parameters. These are in fact dependent parameters, and the solar energy exchanged with the surface of the earth is the only independent variable for open water evaporation. Contrary to the existing methods, meteorological records and measurements are therefore not required. Many parts of the world do not have full or partial records available. For these, the available methods are likely not to be useful. In addition, future meteorological records or measurements cannot be made available for evaporation projection in a warming world. This may well place a limit on using the existing methods. The work presented in this manuscript reveals a new understanding of evaporation as a climate parameter instead and can be calculated as such. Minimal to no meteorological records or measurements may be required. The advantages of the proposed method are scientific justification, simplicity, accuracy, versatility, low to virtually no cost, and can be used to map present and future evaporation in a short period of time.

Life Evaluation of a Lanthanum Hexaboride Hollow Cathode for High-Power Hall Thruster

Lanthanum hexaboride () hollow cathodes have been in development in the United States for electric thruster applications for nearly 15 years. The life of the lanthanum-hexaboride insert in these hollow cathodes is projected to range from 10 kh to over 100 kh based on insert evaporation calculations. A detailed investigation of the life of a 1.5 cm outside-diameter lanthanum-hexaboride hollow cathode has been made. This cathode can provide discharge currents between 5 and 100 A and has an estimated lifetime in excess of 50 kh depending on discharge current and mass flow rate. The insert evaporation rate is determined from a 4000 h discharge wear test of a laboratory model cathode, where insert weight-loss measurements were made at the start, middle, and end of the test. Detailed insert temperature and plasma measurements are used in a one-dimensional disk evaporation model that accommodates the insert temperature profiles found with different discharge currents, flow rates, and cathode orifice diameters, to predict the insert life. The results suggest that insert outgassing is significant early in life, and lanthanum redeposition reduces the net evaporation rate and extends the cathode life.

Fuel Evaporation in an Atmospheric Premixed Burner: Sensitivity Analysis and Spray Vaporization

Calculation of evaporation requires accurate thermophysical properties of the liquid. Such data are well-known for conventional fossil fuels. In contrast, e.g., thermal conductivity or dynamic viscosity of the fuel vapor are rarely available for modern liquid fuels. To overcome this problem, molecular models can be used. Currently, the measurement-based properties of n-heptane and diesel oil are compared with estimated values, using the state-of-the-art molecular models to derive the temperature-dependent material properties. Then their effect on droplet evaporation was evaluated. The critical parameters were liquid density, latent heat of vaporization, boiling temperature, and vapor thermal conductivity where the estimation affected the evaporation time notably. Besides a general sensitivity analysis, evaporation modeling in a practical burner ended up with similar results. By calculating droplet motion, the evaporation number, the evaporation-to-residence time ratio can be derived. An empirical cumulative distribution function is used for the spray of the analyzed burner to evaluate evaporation in the mixing tube. Evaporation number did not exceed 0.4, meaning a full evaporation prior to reaching the burner lip in all cases. As droplet inertia depends upon its size, the residence time has a minimum value due to the phenomenon of overshooting.

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

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

Estimation of open water evaporation using land-based meteorological data

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

Calculation of Steady-State Evaporation for an Arbitrary Matric Potential at Bare Ground Surface

Evaporation from soil columns in the presence of a water table is a long lasting subject that has received great attention for many decades. Available analytical studies on the subject often involve an assumption that the potential evaporation rate is much less than the saturated hydraulic conductivity of the soil. In this study, we develop a new semi-analytical method to estimate the evaporation rate for an arbitrary matric potential head at bare soil surface without assuming that the potential evaporation rate is much less than the saturated hydraulic conductivity of the soil. The results show that the evaporation rates calculated by the new solutions fit well with the HYDRUS-1D simulation. The new solutions also can reproduce the results of potential evaporation rate calculated from previous equations under the special condition of an infinite matric potential head at bare soil surface. The developed new solutions expand our present knowledge of evaporation estimation at bare ground surface to more general field conditions.