Surface Evaporation Rate Research Articles

Cooling potential of cement concrete pavements based on their thermophysical properties

Impermeable paving surfaces constitute one of the main causes of the aggravation of the urban heat island phenomenon. The replacement of such surfaces with cool pavements represents an innovative and promising approach to mitigate this phenomenon. In this study, the investigated cool pavements allow to restrict the rise in the surface temperature by facilitating the evaporation of water through capillary pores. This process occurs from the water-supplied base to the surface exposed to solar radiation. The pavement's cooling potential is quantified by its surface temperature, influenced by various factors, including prevailing weather conditions, thermophysical properties of the pavement, and its initial temperature and saturation state. Within the scope of this research, the pavement’s qualification for its cooling potential is carried out based on the results of an experimental thermophysical characterization. The main objective is to identify the thermophysical properties governing the surface temperature of the pavement under external climatic conditions.To achieve this objective, 21 cement concrete pavements with different formulations are initially identified. These pavements are categorized into two series: the first (denoted as BS) comprises 8 pavements made from recycled sand and containing hydrophilic materials, while the second (denoted as BI) includes 13 pavements made from structural insulating concrete. The methods employed for pavement characterization are outlined, and the corresponding results, encompassing thermophysical properties measurements and surface temperature values, are presented. Analysis of these results reveals new correlations between thermophysical properties and surface temperature. These correlations highlight the coupling between pavement properties, that dictate surface temperature under real summer conditions, contingent on whether the pavement is draining or non-draining. Furthermore, a robust negative linear correlation (R2= 0.92) is identified between surface temperature and evaporation rate under controlled conditions. This underscores the pivotal role of evaporation in substantially regulating the surface temperature of both types of pavements.

Effects of increased rainfall on heat and mass transfer and deformation of sulfate saline soil: An experimental investigation

To study the effect of increased rainfall on the heat and mass transfer and deformation characteristics of sulfate saline soil, a geometric similarity ratio model (1:6) of the natural site was created inside the self-developed indoor baseplate-atmospheric dual-temperature control model box. For the first time, combined with the characteristics of the surface energy change, the characteristics of water-heat-salt-mechanical coupling changes within sulfate saline soil under normal rainfall and twice the increase in rainfall were studied. The results show that the increased rainfall leads to a more significant decrease in upward shortwave radiation and downward longwave radiation, as well as a more significant increase in the surface net radiation and surface evaporation rate. Additionally, the increase in rainfall leads to an obvious cooling trend in the surface temperature. Compared with normal rainfall, an increase in rainfall leads to a significant increase in soil water content and conductivity, while soil heat flux and temperature significantly decrease. The increased rainfall caused a temperature drop of 1.6 °C at 5 cm of saline soil. Moreover, the increased rainfall leads to an increase in the heat release time of sulfate saline soil. Meanwhile, the impact of increased rainfall on the soil water content, conductivity, and temperature gradually weakens with increasing depth. The increased rainfall can exacerbate thawing settlement deformation and alleviate salt frost heave deformation. Compared with normal rainfall, twice the increase in rainfall results in a 0.9 mm increase in thawing settlement deformation and a 2.5 mm decrease in salt frost heave deformation.

Theoretical Analysis of Landfill Gas Migration in Capillary Barrier Covers Considering Effects of Waste Temperature

The high-temperature and high-humidity conditions arising from the biochemical degradation of landfill waste result in significant temperature gradients within the landfill cover. The effects of waste temperature on landfill gas transport and microbial aerobic methane oxidation are not fully understood. In this study, a fully coupled theoretical model was developed to simulate the interactions of moisture, heat, and gas transport within a capillary barrier cover. A series of parametric studies were carried out to investigate the influence of the combined effects of temperature gradient, initial soil moisture content, and landfill gas generation rate on methane transport, oxidation, and emissions. The simulated results indicated that increasing waste temperature intensified the temperature gradient, leading to higher surface evaporation rates and variations in methane oxidation efficiencies. Additionally, variations in initial soil moisture content and landfill gas generation rates were found to significantly impact gas migration and methane oxidation in the cover. This study demonstrates the critical role of waste temperature in landfill gas migration within landfill cover systems, providing technical methodologies for the optimized design of soil cover systems.

Numerical study on the evaporation rate of an electronic cigarette atomizer

This work establishes an evaporation model for the electronic cigarette atomizer based on convective mass transfer theory, which is implemented through Fluent user-defined functions (UDFS). By adding the convection–diffusion equation and considering the energy loss caused by evaporation and the temperature variation over the atomizer body, the evaporation rate of the e-liquid from the atomizer is more accurately calculated, compared to the previous evaporation model based on the assumption of constant temperature over the atomizer body. The effects of external airflow velocity, atomizer porosity, heating power, atomizer shape, heating method, and groove width on the average surface temperature and evaporation rate of the atomizer are examined. The results show that compared with other factors, the external air flow velocity has relatively insignificant influence on the evaporation rate of the atomizer. Within a certain range, as the porosity of the atomizer decreases or the heating power increases, the evaporation rate of the atomizer increases. The cylindrical atomizer has better evaporation performance than the cuboid and grooved atomizer, if all atomizer surfaces are heated, however, when the heating area of the grooved atomizer is optimized, i.e., only the surfaces with large evaporation rates are heated, the evaporation rate of a grooved atomizer can be higher than that of a cylindrical atomizer. The evaporation rate increases with increasing groove width, in the parameter range studied.

Experimental and analytical examinations of a single-glazed solar still desalination with a spray-feeding water system with an artificial neural network

Using solar stills to desalinate salt water effectively provides clean water in remote areas at affordable prices. It is well-established that a crucial factor in enhancing the efficiency of solar desalination systems is increasing brackish water's surface evaporation rate by minimizing surface tension and boosting thermal energy. However, recent studies and proposed ideas indicate a limited and insufficient focus on this aspect. As a response, this research introduces a novel approach to raising the temperature of saline water. This is achieved through a system that involves simultaneous saline water spraying and circulation, affecting all factors and effectively reducing the surface evaporation rate. This approach impacts factors influencing surface evaporation rates and offers advantages such as low thermal inertia, reduced surface tension, and enhanced thermal energy within the desalination system. Therefore, the main goal of this study will be to improve the performance of the solar desalination system through circulating preheated salt water spray and using artificial neural networks and machine learning algorithms to obtain the function of predicting the amount of fresh water produced. The results of this study show that the evaporative heat transfer coefficient of the introduced system is significantly larger than that of the conventional solar still unit, with an average difference of about 43.98%. Also, the results of daily water output in both systems show a significant increase and superiority of 28.75% in freshwater production for the modified system. Also, the efficiency of the improved system is 65.18% higher than that of the passive solar distillation system, and the cost per liter was 0.059 ($/L/m2). The results of this study highlight the effectiveness of the saltwater spraying technique in enhancing the performance of solar desalination systems, making it a valuable prospect for future industrial applications in desalination systems and into energy systems for smart cities as a sagacious strategy towards clean and sustainable process.

Salt-resistant solar water desalination system via surface modification and configuration engineering

Floating solar water desalination systems have received a lot of attention since they are portable, low cost, environmentally friendly, and highly efficient. However, salt accumulation on the evaporation surface and water transfer channels is one of the main obstacle to the development of these systems. In this work, two strategies of surface modification and configuration engineering are focused on to make the devices salt-resistant. First, the system becomes salt-resistant by formation of a hydration layer on the water manager and light absorber surface through cross-linking of polyethylene glycol diacrylate. Remarkably, the surface-modified device shows a water evaporation rate of 1.34 kg.m−2.h−1 and a conversion efficiency of 91.75 % in artificial seawater. There is no salt accumulation on the evaporation surface of surface-modified devices after desalination in the simulated seawater. In the second strategy, the water transferring to the evaporation surface and water evaporation rate are balanced by tuning the number of water transport channels and location. The engineered device shows an evaporation rate of 0.98 kg.m−2.h−1 and an efficiency of 75.5 % in a high saline solution (20 wt% NaCl). Simultaneous surface modification and configuration engineering improve the salt resistivity, showing that the configuration should be engineered according to the water salinity.

Evaporation and wetting behavior of water on the laser-textured silicon substrate

It is important to elucidate the impact of surface micromorphology on the evaporation mechanism and behavior to design rational micromorphologies for enhancing/regulating evaporation. In this study, we investigated the wetting and evaporation behaviors of water droplets on monocrystalline silicon surfaces with concentric circular textures etched using a laser engraving system at varying spacing intervals. Only when the texture spacing overlapped did it exhibit a significantly increased apparent surface energy and evaporation rate. The droplet volume decreased consistently at a constant evaporation rate at different temperatures, and the process involved two stages: constant contact radius (CCR) and constant contact angle (CCA). Laser etching increases the thickness of the oxide film from 10 to 377 nm, resulting in enhanced hydrophilicity. For millimeter-sized droplets, microscopic capillary phenomena in the vicinity of the triple line dominated the evaporation behavior rather than liquid/gas interface evaporation.

Liquid-Vapor Interface of Aqueous Ethylene Glycol Solutions: A Molecular Dynamics Study.

While the organic constituent in an aqueous binary solution enriches its liquid-vapor (l-v) interface, the extent of enrichment can depend nonlinearly on its mole fraction. A microscopic quantification and rationalization of this behavior are crucial to understand the dependence of properties such as surface tension and evaporation rate of the solution on its composition. Extensive all-atom molecular dynamics simulations of aqueous ethylene glycol (EG) solutions show that the composition of the solution at the l-v interface deviates the most from that in the bulk solution at an EG mole fraction of 0.3. The population of EG molecules with their central C-C dihedral in the gauche conformation was found to be higher at the l-v interface than that in the bulk solution to facilitate the orientation of its hydrophobic methyl groups toward the vapor phase. Free energy calculations reveal that in dilute EG solutions, an EG molecule is most stable at the l-v interface. The behavior of vapor pressure in aqueous EG solutions is ideal and follows Raoult's law, while in contrast, the aqueous solution of dimethyl sulfoxide does not. A rationale for the same is provided through the orientational distribution of interfacial water molecules in the respective solutions.

Surface tension and evaporation behavior of liquid fuel droplets at transcritical conditions: Towards bridging the gap between molecular dynamics and continuum simulations

The phase transition from subcritical to supercritical conditions, referred to as transcritical behavior, significantly impacts the evaporation and fuel–air mixing in high-pressure liquid-fuel propulsion systems. Transcritical behavior is characterized as a transition from classical two-phase evaporation to a single-phase gas-like diffusion regime as surface tension and latent heat of vaporization reduce. However, the interfacial behavior represented by the surface tension coefficient and evaporation rate during this transition which are crucial inputs for Computational Fluid Dynamics (CFD) simulations of practical transcritical fuel spray is still missing. This study aims at developing new evaporation rate and surface tension models for transcritical n-dodecane droplets using molecular dynamics (MD) simulations irrespective of the droplet size. As MD simulations are primarily limited to the nanoscale, the new models can bridge the gap between MD and continuum simulations and enable the direct application of these findings to microscopic droplets. A new characteristic timescale, i.e., “undroplet time,” is defined which marks the transition from classical two-phase evaporation to single-phase gas-like diffusion behavior. The undroplet time indicates the onset of droplet core disintegration and penetration of nitrogen molecules into the droplet, which occurs after the vanishment of the surface tension. By normalizing the time with respect to the undroplet time, the rate of surface tension decay, evaporation rate, and the rate of droplet mass depletion become independent of the droplet size. Calculation of pairwise correlation coefficients for the entire MD results shows that both surface tension coefficient and evaporation rate are strongly correlated with the background temperature, while pressure and droplet size play a less significant role past the critical point. Therefore, new models for surface tension coefficient and evaporation rate spanning from sub- to supercritical conditions are developed as a function of background pressure and temperature, which can be used in continuum simulations. The identified phase change behavior based on the undroplet time shows a good agreement with the phase change regime maps obtained using microscale experiments and nanoscale MD predictions.

Numerical simulation and optimization of surface evaporation in a 3D solar still for improved performance

This article focuses on the numerical simulation of the surface evaporation process within a 3D solar still. Inside the solar still chamber, water is maintained at a specific level and undergoes evaporation due to solar heat. The numerical simulation utilizes computational fluid dynamics (CFD) techniques. The primary objective of this study is to enhance the performance of the solar still system by increasing the rate of surface evaporation. The study optimized the system using design of experiments (DOE) and the response surface method (RSM). It investigated three input parameters – chamber height, water depth, and glass wall temperature – within defined ranges, measuring their impact on the target parameter. Optimal design conditions were determined, where the system exhibited peak performance with a chamber height of 1 m, a water depth of 0.2 m, and a glass wall temperature of 333.15 K. Under these conditions, the surface evaporation rate reached a maximum value of 0.00733960 kg/m³·K. Compared to baseline conditions, the optimal configuration yielded a significant 215.6 % increase in system performance. These findings underscore the substantial impact of these parameters on the efficiency of the solar still system.

A Moist Potential Vorticity Model for Midlatitude Long-Lived Mesoscale Convective Systems over Land

Abstract Mesoscale convective systems (MCSs) bring large amounts of rainfall and strong wind gusts to the midlatitude land regions, with significant impacts on local weather and hydrologic cycle. However, weather and climate models face a huge challenge in accurately modeling the MCS life cycle and the associated precipitation, highlighting an urgent need for a better understanding of the underlying mechanisms of MCS initiation and propagation. From a theoretical perspective, a suitable model to capture the realistic properties of MCSs and isolate the bare-bones mechanisms for their initiation, intensification, and eastward propagation is still lacking. To simulate midlatitude MCSs over land, we develop a simple moist potential vorticity (PV) model that readily describes the interactions among PV perturbations, air moisture, and soil moisture. Multiple experiments with or without various environmental factors and external forcing are used to investigate their impacts on MCS dynamics and mesoscale circulation vertical structures. The result shows that mechanical forcing can induce lower-level updraft and cooling, providing favorable conditions for MCS initiation. A positive feedback among surface winds, evaporation rate, and air moisture similar to the wind-induced surface heat exchange over tropical ocean is found to support MCS intensification. Both background surface westerlies and vertical westerly wind shear are shown to provide favorable conditions for the eastward propagation of MCSs. Last, our result highlights the crucial role of stratiform heating in shaping mesoscale circulation response. The model should serve as a useful tool for understanding the fundamental mechanisms of MCS dynamics.

Solar-powered and antibacterial water purification via Cu-BTC-embedded reduced graphene oxide nanocomposite aerogels

Advancements in the design of porous active materials for interfacial solar evaporation have shown promise in the development of next-generation solar evaporation active materials that can present a wide range of water-purification properties. In this study, a new class of metal–organic nanoparticles-embedded reduced graphene oxide (rGO) nanocomposite aerogels is developed, with both solar steam generation behavior and antibacterial properties. The self-assembly process is used to introduce Cu-BTC nanoparticles (Cu-BTC NPs) into the structure of rGO aerogels to fabricate Cu-BTC/rGO nanocomposite aerogels. By varying the content of Cu-BTC NPs in the self-assembly precursor solution, the surface area, pore texture, and evaporation rate of samples are altered to reach both high energy conversion efficiency and antibacterial properties. An evaporation rate of 1.13 kg/m2h and an efficiency of 81.8% are achieved when the highest content of Cu-BTC NPs (1 mg/ml) is introduced to the precursor solution. This evaporation efficiency is 32% and 59% higher than that of the rGO aerogel and pure water, respectively. This behavior is related to the surface area and pore size of the nanocomposite aerogels, which increase and decrease with the content of Cu-BTC NPs, respectively. Additionally, the Cu-BTC/rGO aerogel presents antibacterial activity against S. aureus and E. coli. As a result, Cu-BTC/rGO nanocomposite aerogels have great potential as active materials for the design of next-generation solar steam generation systems for the treatment of wastewater contaminated with pathogenic bacteria.

Effect of Solvent on Convectively Driven Silica Particle Assembly: Decoupling Surface Tension, Viscosity, and Evaporation Rate

The process of convectively self-assembling particles in films suffers from low reproducibility due to its high dependency on particle concentration, as well as a variety of interactions and physical parameters. Inhomogeneities in flow rates and instabilities at the air-liquid interface are mostly responsible for reproducibility issues. These problems are aggravated by adding multiple components to the dispersion, such as binary solvent mixtures or surfactant/polymer additives, both common approaches to control stick-slip behavior. When an additive is used, not only does it change the surface tension, but also the viscosity and the evaporation rate. Worse yet, gradients in these three properties can form, which then lead to Marangoni currents. Here, we use a series of alcohols to study the role of viscosity independently of other solvent properties, to show its impact on stick-slip behavior and interband distances. We show that mixtures of glycerol and alcohol or poly(acrylic acid) and alcohol lead to more complex patterning. Marangoni currents are not always observed in co-solvent systems, being dependent on the rate of solvent evaporation. To produce homogeneous particle assemblies and control stick-slip behavior, gradients must be avoided, and the surface tension and viscosity need both be carefully controlled.

Lattice Boltzmann simulation of surface evaporation in porous media

In this study, the phase-change lattice Boltzmann method was used to simulate the evaporation phenomenon on the surface of a porous medium. A new wetting boundary scheme was proposed to consider the surface wettability. The effect of surface wettability on the evaporation in the porous medium was studied. It is found that when the porous medium is hydrophilic, the surface evaporation rate can be increased by reducing the contact angle of the porous media skeleton. However, as the contact angle of the skeleton decreases, the benefit of decreasing the contact angle to improve the evaporation rate decreases.

Hydrology of Acidic Mine Pit Lake: A Case Study of ex-Copper mine Pit Lake, Mamut, Sabah Malaysia.

Hydrological study of pit lake was carried out in ex-Mamut Copper Mine (MCM), Ranau Sabah. Gauging stations were established to measure surface inflows and outflows of the pit lake. Each station was equipped with a continuous water level recorder to record water level data at 10–minutes intervals. Rainfall and evaporation were measured respectively using storage gauge and evaporation pan. Over the entire study period, surface inflow accounted for 32.11% of the water entering the lake, the rest being provided by direct precipitation on the lake surface. Surface outflow discharges 53.13% of the water from the lake. Evaporation from the lake contributed 30.10% of water loss to the atmosphere. Changes of storage ranged from 61.09 mm to 241.56 mm per month. Simple linear regression analysis showed that, changes in lake level can be explained through rainfall and resulting tributary inflows, rate of surface outflow and evaporation, which would allow projections of possible future levels to be made by analysis of these components.

Numerical and Analytical Investigation of the Surface Evaporation Rate of the Different Nanofluids and Optimization Results by Using the RSM Method

Numerical and Analytical Investigation of the Surface Evaporation Rate of the Different Nanofluids and Optimization Results by Using the RSM Method

Synthesis and Performances of Shrinkage-Reducing Polycarboxylate Superplasticizer in Cement-Based Materials.

Reducing or eliminating cracks caused by shrinkage of cementitious materials remains a daunting challenge for construction engineers. Drying shrinkage and autogenous shrinkage are the main shrinkage types in the service process of cement-based materials, which have a great impact on engineering applications. If cracks in concrete generate by drying or autogenous shrinkage, the mechanical properties, water resistance and durability of concrete will be also affected. It is an effective method to use chemical admixtures to inhibit the shrinkage of cement-based materials. Polycarboxylate plasticizer (PCE) is an important chemical admixture in cement-based materials and is widely used in practical engineering. It can bring great value by reducing the shrinkage effect through molecular design. Through our innovative design, a series of shrinkage-reducing polycarboxylate superplasticizers (SRPs) were synthesized, their molecular structures were confirmed by Fourier transform infrared spectroscopy (FTIR) and their molecular properties were determined by gel permeation chromatography (GPC). Furthermore, the shrinkage performances at different ages of the mortars containing the synthesized SRPs with different structures were systematically evaluated. The results showed that compared with the blank sample, the dry shrinkage rate and free shrinkage rate of the mortars containing SRP decreased by over 20% and 15%, respectively. Additionally, the shrinkage rates of the mortars containing SRP were significantly lower than that of the mortar containing conventional PCE, and moreover, the water-reducing performance was improved compared to conventional PCE. Based on the experimental results of surface tension and evaporation rate of different SRP solutions, the mechanism of the shrinkage-reducing effect was probed, as expected to provide guidance for the design and development of new shrinkage-reducing admixtures.

Evaporation of ultra-thin water film on hot spot with nanopillar array

For the ultra-thin film evaporation, a hot spot was formed by a local dry out, resulting in the heat transfer deterioration. In this work, the stable evaporation of ultra-thin water film on hot spot with designed nanopillar structure was studied based on the non-equilibrium molecular dynamics (MD) simulation. The variation of molecular motion trajectories, evaporation rate and number of migrating water molecules in different regions were recorded over time in the simulation. The results show that the nanopillar array on the hot spot can attract the surrounding liquid to wet the overheated region due to the strong solid-liquid interaction, both the evaporation stability and heat transfer performance can be improved. By comparing three surfaces with different nanopillar arrays on hot spot, it shows that the evaporation rate is one important factor affecting the amount of liquid replenishment: with the increasing number of nanopillars, both the evaporation performance and liquid replenishment capacity are improved. Moreover, the effect of two designed nanostructure configurations on the evaporation performance was investigated. Compared to the configuration of only nanopillar array on the hot spot, the configuration of nanopillar array on the whole surface has a lower temperature for the nanopillars and delays the occurrence of dry out, while the averaged evaporation rate may be reduced as well. Therefore, there is a trade-off between the surface temperature reduction and evaporation rate enhancement. The findings in this study can provide a guidance for the thermal design for the hot spot in the chip cooling technique under the high heat flux application.

Fabric-based all-weather-available photo-electro-thermal steam generator with high evaporation rate and salt resistance

Solar-driven steam generation is a practical strategy to harness solar energy for desalination and production of clean water with a minimized carbon footprint. However, this strategy suffers from a low evaporation rate under weak illumination on cloudy days or at night. Herein, we present a fabric-based all-weather-available photo-electrothermal steam generator (P/ET-SG) capable of regulating the surface temperature and evaporation rate by the coupling effect of photo-thermal and electro-thermal heating depending on the light conditions. An unprecedented high surface temperature of 52°C in the wet state and an evaporation rate of 2.61 kg m−2 h−1 were achieved by the P/ET-SG under 1 sun with only 1 V input voltage owing to the uniform heat distribution and the coupled electro-thermal source. The oneway fluidic design of the P/ET-SG effectively prevented salt precipitation during continuous desalination in 24 h and was able to remove salt granules from the evaporation surface. Furthermore, the P/ET-SG demonstrated a high evaporation rate of 2.58 kg m−2 h−1 in the purification of concentrated saline water and dye-contaminated water with high efficiency (>99.9%). This study offers new thoughts for the design of all-weather-available solar steam generators with high efficiency and makes a step forward towards fast purification of concentrated saline water and wastewater.

Identifying Reservoirs and Estimating Evaporation Losses in a Large Arid Inland Basin in Northwestern China

Reservoirs play a vital role in agricultural irrigation, food security, and ecological protection in arid and semi–arid areas where water resources are scarce. In the Tarim Basin (TB) in northwestern China, a large number of reservoirs have been built or are being built, resulting in significant evaporation losses. However, information about the distribution, area and evaporation rate of the reservoirs in TB is limited. To contribute, we present an inventory of reservoirs and calculate their monthly surface area and evaporation rate during the study period of 1990–2019, using the TerraClimate dataset, Google Earth Engine (GEE) platform, Landtrendr algorithm, Penman method, and Landsat images. The results suggest: (1) The inventory of 167 reservoirs in TB consists of 142 existing reservoirs (built before 1990), 5 new reservoirs (mountain reservoirs, built during 1990–2019), and 20 dried–up reservoirs (plain reservoirs that went extinct during 1990–2019). (2) The reservoir types in TB are mainly plain reservoirs with an altitude of less than 1500 m and an area of less than 10 km2, accounting for about 88% of the total number of reservoirs. (3) The surface area of the reservoirs increased at a significant rate (p < 0.05) of 12.45 km2/y from 401 km2 in 1990 to 766 km2 in 2019. (4) The evaporation rate of the reservoirs increased at a slight trend of 0.004 mm/d/a and varied from 2.57 mm/d in 1990 to 2.39 mm/d in 2019. Lastly, (5) The evaporation losses of reservoirs in TB significantly increased (p < 0.05) from 4.72 × 108 m3 to 4.92 × 108 m3 due to the significant increase in reservoir surface area (p < 0.05) and the slight increase in evaporation rate from 1990 to 2019. This study provides essentials of the reservoir inventory, surface area, and evaporation rate with considerable baseline inferences for TB that may be beneficial for long–term investigations and assist in local water resources decision support and sustainable management in arid regions.