Estimation Of Evaporation Rate Research Articles

Mathematical modelling of evaporation rate and heating of biodiesel blends of a single-component droplets

Biodiesel serve as promising fuel and optimal alternative for mitigating the present issues of fuel scarcity and emission control in compression ignition engines. Several Researches have concluded that engine performance and it’s emission characteristics heavily depends on pa-rameters like fuel droplet spray formation, atomization, evaporation and combustion which in turn depend on thermophysical properties of biodiesel fuel. In this study, the thermophysical properties like normal boiling, critical properties, vapor pressure, latent heat of vaporization, liquid density, liquid viscosity, liquid thermal conductivity, gas diffusion coefficients of two biodiesel fuels sample: Madhuca Indica and Radish oil are determined using standard correla-tion. Accurate mathematical model for estimation of evaporation rate and combustion of sin-gle component biodiesel droplet is framed and validated with single droplet setup experiment result for Jatropa Methyl Ester (JME), Karanjan Methyl Ester (KME), Mahua Methyl Ester (MME), Neem Methyl Ester (NME), Palm Methyl Ester (PME) oil and this model is further extrapolated to predict the evaporation and combustion behaviour of two unexperimented oil, Madhuca and Radish. It is found that Madhuca oil has the higher evaporation constant value of 0.1466 mm2/s and thus lowest lifetime in among the biodiesel fuel studied. This value is attributed to lower mo-lecular weight and higher molecular diffusivity. On the other hand reverse trend is observed in Radish with lower evaporation constant and higher lifetime. This study behaves as compre-hensive methodology for estimating the behaviour of biodiesel based on their composition and chemical structure and also as firm framework for combustion modelling in enhancing engine performance.

Forecasting monthly pan evaporation using hybrid additive regression and data-driven models in a semi-arid environment

Exact estimation of evaporation rates is very important in a proper planning and efficient operation of water resources projects and agricultural activities. Evaporation is affected by many driving forces characterized by nonlinearity, non-stationary, and stochasticity. Such factors clearly hinder setting up rigorous predictive models. This study evaluates the predictability of coupling the additive regression model (AR) with four ensemble machine-learning algorithms—random Subspace (RSS), M5 pruned (M5P), reduced error pruning tree (REPTree), and bagging for estimating pan evaporation rates. Meteorological data encompass maximum temperature, minimum temperature, mean temperature, relative humidity, and wind speed from three different agroclimatic stations in Iraq (i.e., Baghdad, Mosul, and Basrah) were utilized as predictor parameters. The regression model in addition to the sensitivity analysis was employed to identify the best-input combinations for the evaluated methods. It was demonstrated that the AR-M5P estimated the evaporation with higher accuracy than others when combining wind speed, relative humidity, and the minimum and mean temperatures as input parameters. The AR-M5P model provided the best performance indicators, i.e., MAE = 33.82, RMSE = 45.05, RAE = 24.75, RRSE = 28.50, and r = 0.972 for Baghdad; MAE = 25.82, RMSE = 35.95, RAE = 23.75, RRSE = 29.64, and r = 0.956 for Mosul station, respectively. The outcomes of this study proved the superior performance of the hybridized methods in addressing such intricate hydrological relationships and hence could be employed for other environmental problems.

Estimating Inhalation Exposure Resulting from Evaporation of Volatile Multicomponent Mixtures Using Different Modelling Approaches.

In many professional and industrial settings, liquid multicomponent mixtures are used as solvents, additives, coatings, biocidal products, etc. Since, in all of these examples, hazardous liquids can evaporate in the form of vapours, for risk assessments it is important to know the amount of chemicals in the surrounding air. Although several models are available in legal contexts, the current implementations seem to be unable to correctly simulate concentration changes that actually occur in volatile mixtures and in particular in thin films. In this research, the estimation of evaporation rates is based on models that take into account non-ideal behaviour of components in liquids and backpressure effects as well. The corresponding system of differential equations is solved numerically using an extended Euler algorithm that is based on a discretisation of time and space. Regarding air dispersion of volatile components, the model builds upon one-box and two-box mass balance models, because there is some evidence that these models, when selected and applied appropriately, can predict occupational exposures with sufficient precision. That way, numerical solutions for a wide variety of exposure scenarios with instantaneous and continuous/intermittent application, even considering “moving worker situations”, can be obtained. A number of example calculations have been carried out on scenarios where binary aqueous solutions of hydrogen peroxide or glutaraldehyde are applied as a biocidal product to surfaces by wiping. The results reveal that backpressure effects caused by large emission sources as well as deviations from liquid-phase ideality can influence the shape of the concentration time curves significantly. The results also provide some evidence that near-/far-field models should be used to avoid underestimation of exposure in large rooms when small/medium areas are applied. However, the near-field/far-field model should not be used to estimate peak exposure assuming instantaneous application, because then the models tend to overestimate peak exposure significantly. Although the example calculations are restricted to aqueous binary mixtures, the proposed approach is general and can be used for arbitrary liquid multicomponent mixtures, as long as backpressure effects and liquid-phase non-idealities are addressed adequately.

Evaluasi Metode Pendugaan Laju Evapotranspirasi Standar (ETo) Menggunakan Bahasa Pemograman Visual Basic Microsoft Excel di Kabupaten Nagan Raya Aceh

Estimation of evaporation rate is needed in hydrological data, especially in irrigation and drainage planning data. The method for estimating the evapotranspiration rate recommended by FAO is the Penman - Monteith method, however apart from this method there are still several methods that can be used if the data obtained in the field are different. Evaluation of the method of estimating the rate of evapotranspration is expected to help in choosing the right method when different data is obtained, so with this evaluation, we can see the accuracy of the methods. The methods that are closest to accuracy with the Penman - Monteith method are Hargreaves, Makkink, Turc, Blaney-Cridlle and Penman. If ordered based on the ranking of the evaluation results, the method that is closest to the Penman - Monteith method is Hargreaves, because of all the evaluation variabels Hargreaves has the best evaluation value. While the closest model based on the best R2 value is the Jensen-Haise model, but the error value of this model is very high.

Determination of Evaporative Fluxes Using a Bench-Scale Atmosphere Simulator

An accurate determination of evaporative fluxes is critical for efficient water management in semi-arid climates such as in the Canadian Prairies. The main achievements of this research are the design and operation of a bench-scale atmosphere simulator, performance evaluation using selected weather scenarios pertaining to regional atmospheric conditions, validation using established empirical correlations, and estimation of evaporation rates and the amount for a typical local water body. Results indicate that the measured data achieved the target values for the various parameters and the data were found to be stable during the 3-h test duration. The vapour flux was found to have large variation during summer (0.120 g∙s−1∙m−2 during the day and 0.047 g∙s−1∙m−2 at night), low variation during spring (0.116 g∙s−1∙m−2 during the day and 0.062 g∙s−1∙m−2 at night), and negligible change during fall (0.100 g∙s−1∙m−2 during the day and 0.076 g∙s−1∙m−2 at night). The measured vapour flux was generally within one standard deviation of the equality line when compared with that predicted by both the mass-transfer equations and the combination equations. The average evaporation ranged from 4 mm∙d−1 to 8 mm∙d−1 during the day and decreased to 1 mm∙d−1 to 3 mm∙d−1 at night. The 24-h evaporation was found to be 8 ± 1 mm∙d−1 from late April through late October. Likewise, the cumulative annual evaporation was found to be 1781 mm, of which 82% occurs during the day and 18% at night.

Modeling the monthly pan evaporation rates using artificial intelligence methods: a case study in Iraq

In arid areas, the estimation of evaporation rates plays a considerable role on both water resources management and agricultural activities. Hence, it is of utmost importance to determine the best model to predict these rates. This study investigates the applicability of using quantile regression forest in predicting the pan evaporation. The model was configured using data from three different meteorological stations located in arid to semi-arid climates in Iraq. These stations were in the cities of Baghdad, Basrah, and Mosul, which are located in the middle, south, and north of the country, respectively. The performance of quantile regression forests was compared with three kinds of artificial intelligence methods i.e. random forests, support vector machine, and artificial neural network in addition to the conventional multiple linear regression models. The maximum temperature (°C), minimum temperature (°C), relative humidity (%), and wind speed (m/sec) were used as input parameters to the predictive models. The collected data (from 1990 to 2013) was randomly partitioned into two periods; 75% for calibration and 25% for validation. The fivefold cross validation was used during the calibration stage for better model predictability. The results were evaluated using three performance criteria: determination coefficient (R2), root mean square error (RMSE), and Nash and Sutcliff coefficient efficiency (NSE). Results showed that the quantile regression forests model attained the optimum performance among the evaluated methods. The value of R2, RMSE, and NSE during validation was 0.99, 17.96 mm, and 0.99 at Baghdad; 0.98, 23.36 mm, and 0.98 at Basrah; and 0.99, 14.44 mm, and 0.99 at Mosul, respectively. Therefore, this method is the most appropriate one to use for predicting evaporation rates in arid to semi-arid climates.

Estimation of evaporation rate of water droplet group in spray drying process

Spray drying is a fundamental process in several industries. As many factors affect the particulate product property in complex manners, optimal operating conditions have been determined through trial and error. In a spray dryer, numerous sprayed droplets form a tear-shaped droplet aggregate (droplet group), in which each droplet evaporates at a different rate. Owing to the complicated evaporation behavior of a droplet group, a detailed mechanism of dried particle generation has yet to be sufficiently elucidated. The objective of this study is to investigate the effects of the operating conditions of spray drying processes on the evaporation rate of a droplet group. Numerical simulations were performed under various conditions to calculate the evaporation rates of a droplet group in a spray drying process. A method for estimating the evaporation rate of a droplet group based on the operating conditions, using the thermal efficiency and Nusselt number, is proposed.

Estimation of evaporation rates in the north west Arabian gulf based on sea surface temperature and Meteorological data

Bulk aerodynamic formula (Singh's equations) was used to study the evaporation in the north west Arabian gulf. Evaporation was estimated for the region. The annual averages of evaporation in the area are (mm /yr) for two years (2014-2015) 23, 22 respectively. Evaporation is higher in the region during June, July, August, September and October. The correlation between the humidity gradient (ew-ea) and monthly averages of evaporation were high in all regions being approximately 0.8, whereas the correlation between monthly averages of evaporation and wind speed were about 0.6. The main cause of higher evaporation was the humidity gradient (ew-ea), i.e., higher humidity gradient. These variations were related to the changes in humidity and the wind speed at this location.

Estimation of evaporation rates in the north west Arabian gulf based on sea surface temperature and Meteorological data

Estimation of evaporation rates in the north west Arabian gulf based on sea surface temperature and Meteorological data

Estimation of Evaporation Rate from Gold-Silicon Alloy Based on the Nucleation Time and Nanowire Length Distributions

Nanowires are one of the most promising building blocks for various nanoelectronic devices. Nanowires are usually grown via the so-called vapor-liquid-solid mechanism on the surfaces activated by the droplets of a catalyst (e.g., Au). Here we theoretically studied the impact of the evaporation from the droplet on the nucleation statistics. Within the semi-analyticalapproach, we obtain the relation between the nucleation time distributions and the evaporation rate of atoms from the droplet. We analyze the Si NW length-time dependences to estimate theeffective lifetime of a silicon atom in a gold-silicon alloy at 550°C is about 5 s.

Experimental test for the estimation of the evaporation rate in indoor swimming pools: Validation of a new CFD-based simulation methodology

The aim of this work is to present an experimental procedure at laboratory scale that was developed to validate a new CFD-based methodology for the estimation of water evaporation rate in indoor swimming pools, under a wide range of convective flow conditions (36 experiments) and focussing on the most common operation conditions of these facilities: low air mean velocities (0.08–0.24 m/s), and water and air temperatures in the ranges 24-28 °C and 26-30 °C, respectively. One of the main hypotheses of the simulation methodology set a free slip wall condition (no shear stress) at the air-water interface, based on the fact that the dynamic boundary layer depth will be smaller than the thickness of the thermal and humidity boundary layers in this kind of flows. The comparison between simulated and experimental results show that the modelling strategy proposed is a promising tool, with average relative errors of 9% for the typical mixed convection flows in indoor swimming pools.

Experimental estimation of evaporation rates of water droplets in high-temperature gases

Evaporation rates of water droplets in high-temperature gases were experimentally determined using high-speed video recording cameras and low-inertia thermocouples (for heated air flow as an example). The experiments were carried out for droplets of initial size (radius) 1–3 mm at an air temperature of 500–1000 K. Dependences of the evaporation rate of water droplets on time and gas temperature were obtained for various initial droplet sizes.

Evaporation from a shallow, saline lake in the Nebraska Sandhills: Energy balance drivers of seasonal and interannual variability

Despite potential evaporation rates in excess of the local precipitation, dry climates often support saline lakes through groundwater inputs of water and associated solutes. These groundwater-fed lakes are important indicators of environmental change, in part because their shallow water levels and salinity are very sensitive to weather and climatic variability. Some of this sensitivity arises from high rates of open-water evaporation, which is a dominant but poorly quantified process for saline lakes. This study used the Bowen ratio energy budget method to calculate open-water evaporation rates for Alkali Lake, a saline lake in the Nebraska Sandhills region (central United States), where numerous groundwater-fed lakes occupy the landscape. Evaporation rates were measured during the warm season (May – October) over three consecutive years (2007–2009) to gain insights into the climatic and limnological factors driving evaporation, as well as the partitioning of energy balance components at seasonal and interannual time scales. Results show a seasonal peak in evaporation rate in late June of 7.0mmday−1 (on average), with a maximum daily rate of 10.5mmday−1 and a 3-year mean July-September (JAS) rate of 5.1mmday−1, which greatly exceeds the long-term JAS precipitation rate of 1.3mmday−1. Seasonal variability in lake evaporation closely follows that of net radiation and lake surface temperature, with sensible heat flux and heat storage variations being relatively small, except in response to short-term, synoptic events. Interannual changes in the surface energy balance were weak, by comparison, although a 6-fold increase in mean lake level over the three years (0.05–0.30m) led to greater heat storage within the lake, an enhanced JAS lake-air temperature gradient, and greater sensible heat loss. These large variations in water level were also associated with large changes in absolute salinity (from 28 to 118gkg−1), with periods of high salinity characterized by reductions in mass transfer estimates of evaporation rate by up to 20%, depending on atmospheric conditions and absolute salinity. Energy balance estimates of evaporation, on the other hand, were found to be less sensitive to variations in salinity. These results provide regional insights for lakes in the Nebraska Sandhills region and implications for estimation of the energy and water balance of saline lakes in similar arid and semi-arid landscapes.

Estimation of evaporation rate of cesium from hot sodium pool to inert cover gas of typical SFR

Estimation of evaporative release of Cesium-137 (Cs-137) from the hot pool of Sodium cooled Fast Reactor (SFR) under normal operating condition and hypothetical core meltdown accident scenario is important in safety analysis due to the radiological consequences associated with Cs release. A methodology has been developed to estimate the cesium evaporation rate from hot pool to inert cover gas region of typical SFR under fuel pin clad failure scenario based on the temperature and concentration dependent activity coefficient of cesium estimated using the Flory–Huggins solution theory. The predicted equilibrium partition coefficient (KD) values of cesium are validated with theoretical and experimental data available in literature. It has been observed that the KD of cesium is decreasing with increase in Cs concentration. A correlation has been developed for KD as a function of temperature in the infinite dilute solution regime. The present methodology predicted Retention Factor (RF) values of Cs based on the estimated KD values are closer to the experimental results compared to the published results of empirical models in the SFR hot pool temperature range. The methodology has been used for evaluating the evaporative release of cesium along with sodium from hot pool to cover gas region of typical SFR under fuel pin clad failure scenario. These estimations are useful for evaluating the radioactive dose due to Cs transport from SFR sodium pool to its inert argon cover gas region.

Estimates of Evaporation Rates from Wounds for Various Dressing/Support Surface Combinations

The management of exudate is an essential aspect of wound care. The wound bed must remain moist to promote healing, but care must be taken to remove excess fluid to avoid maceration and subsequent breakdown of the periwound site, which could serve as a possible portal to infection. Excess fluid is typically absorbed into and/or evaporates through the wound dressing or may be managed by a powered vacuum-assisted closure device. Although the moisture vapor permeability has been studied for dressings, the rate of evaporation associated with wound's immediate treatment environment, or dressing/treatment surface interface, has not been addressed to date. It is essential for caregivers to have an understanding of how these 2 interventions work together in order to provide optimal care to the wound patient. The purpose of this study was to provide estimates of evaporative withdrawal rates for various wound dressings and therapeutic support surfaces.

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

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

Numerical evaluation of subsurface soil water evaporation derived from sensible heat balance

A recently introduced measurement approach allows in situ determination of subsurface soil water evaporation by means of heat‐pulse probes (HPP). The latent heat component of subsurface evaporation is estimated from the residual of the sensible heat balance. This heat balance method requires measurement of vertical soil temperature and estimates of thermal properties for soil water evaporation determination. Our objective was to employ numerically simulated thermal and hydraulic processes using constant or diurnally cycled surface boundary conditions to evaluate and understand this technique. Three observation grid spacings, namely, 6 mm (tri‐needle HPP), 3 mm (penta‐needle HPP) and 1 mm, along with three soil textures (sand, silt, and silty clay) were used to test the heat balance method. The comparison of heat balance–based evaporation rate estimates with an independent soil profile water balance revealed substantial errors when thermal conductivity was averaged spatially across the evaporation front. Since the conduction component of heat flux is the dominant process at the evaporation front, the estimation of evaporation rate was significantly improved using depth‐dependent instead of a space‐averaged . A near‐surface “undetectable zone” exists, where the heat balance calculation is irreconcilable, resulting in underestimation of total subsurface evaporation. The method performs better for medium‐ and coarse‐textured soils than for fine‐textured soils, where portions of the drying front may be maintained longer within the undetectable zone. Using smaller temperature sensor spacing near the soil surface minimized underestimation from the undetectable zone and improved accuracy of total subsurface evaporation rate estimates.

Measurement of grassland evaporation using a surface-layer scintillometer

A dual-beam surface-layer scintillometer (SLS) was used to estimate sensible heat flux (H) every 2 min for a path length of either 50 or 101 m, for more than 30 months in a mesic grassland in eastern South Africa. The SLS method relies on Monin-Obukhov similarity theory, the correlation between the laser beam signal amplitude variances and the covariance of the logarithm of the beam signal amplitude measured using 2 laser detectors. Procedures for checking SLS data integrity in real-time are highlighted as are the post-data collection rejection procedures. From the H estimates, using SLS and measurements of soil heat flux and net irradiance, evaporation rates were calculated as a residual of the shortened energy balance equation and compared with grass reference evaporation rates (ETo). Inconsistent hourly ETo values occur in the late afternoon due to the incorrect assumption that the soil heat flux is 10% of net irradiance. The SLS estimates of H and the estimates of evaporation rate as a residual compared favourably with those obtained using the Bowen ratio and eddy covariance methods for cloudless days, cloudy days and days with variable cloud. There was no evidence for the eddy covariance measurements of H being underestimated in comparison to the Bowen ratio and SLS measurements. On many days, the diurnal variation in SLS H was asymmetrical, peaking before noon.Keywords: energy balance, Bowen ratio, eddy covariance, grass reference evaporation, rejection criteria

A simple surface conductance model to estimate regional evaporation using MODIS leaf area index and the Penman‐Monteith equation

We introduce a simple biophysical model for surface conductance, Gs, for use with remotely sensed leaf area index (Lai) data and the Penman‐Monteith (PM) equation to calculate daily average evaporation, E, at kilometer spatial resolution. The model for Gs has six parameters that represent canopy physiological processes and soil evaporation: gsx, maximum stomatal conductance; Q50 and D50, the values of solar radiation and atmospheric humidity deficit when the stomatal conductance is half its maximum; kQ and kA, extinction coefficients for visible radiation and available energy; and f, the ratio of soil evaporation to the equilibrium rate corresponding to the energy absorbed at the soil surface. Model parameters were estimated using 2–3 years of data from 15 flux station sites covering a wide range of climate and vegetation types globally. The PM estimates of E are best when all six parameters in the Gs model are optimized at each site, but there is no significant reduction in model performance when Q50, D50, kQ, and kA are held constant across sites and gsx and f are optimized (linear regression of modeled mean daily evaporation versus measurements: slope = 0.83, intercept = 0.22 mm/d, R2 = 0.80, and N = 10623). The average systematic root‐mean‐square error in daytime mean evaporation was 0.27 mm/d (range 0.09–0.50 mm/d) for the 15 sites. The average unsystematic component was 0.48 mm/d (range 0.28–0.71 mm/d). The new model for Gs with two parameters yields better estimates of E than an earlier, simple model Gs = cLLai, where cL is an optimized parameter. Our study confirms that the PM equation provides reliable estimates of evaporation rates from land surfaces at daily time scales and kilometer space scales when remotely sensed leaf area indices are incorporated into a simple biophysical model for surface conductance. Developing remote sensing techniques to measure the temporal and spatial variation in f is expected to enhance the utility of the model proposed in this paper.

Estimation of evaporation rate from soil surface using stable isotopic composition of throughfall and stream water in a tropical seasonal rain forest of Xishuangbanna, Southwest China

Xishuangbanna is located at the northern edge of the distribution of tropical forests in Southeast Asia, and it has a very high frequency of radiation fog, especially during the dry season (November-April). In this study, rainwater, throughfall, intercepted fog water (fog drip) by forest canopy, and stream water were collected in January 2002 and December 2003 for stable isotopic analysis at a tropical seasonal rain forest site in Xishuangbanna, Southwest China. The objective of the study is to estimate the evaporation rate from the forest floor. The stable hydrogen (δD) and oxygen isotope composition (δ 18O) of rainwater, throughfall, fog drip, and stream water was determined using an isotope ratio mass spectrometer. Stream water during the non-storm runoff period was considered to reflect the effect of evaporation from the forest floor. The evaporation rates from the forest floor were estimated using isotope composition values in stream water and the total throughfall was estimated using the Rayleigh distillation equation under equilibrium conditions. The results indicated that the annual weighted means of δD and δ 18O in fog drip were consistently more enriched than those of rainwater and stream water, and the fog drip was thought to contain water that had evaporated and recycled. The weighted means of δD and δ 18O in stream water during the non-storm runoff period were 5.69% and 0.39% more enriched than those of the total throughfall (rain throughfall + fog drip) in 2002, while in 2003 these were 5.05% and 0.28%, respectively. Evapotranspiration in the humid year 2002 and the dry year 2003, computed from the water balance, was 1186 mm and 987 mm, respectively, which was quite low when compared with the values reported in some humid tropical forests. Consequently, the evaporation rate from the forest floor was 5.1% of the evapotranspiration in 2002, and 3.1% in 2003. The lower evaporation rate was thought to be mainly a result of the influence of the high frequency of heavy radiation fog on the rain forest during the night in the dry season (November-April).