Effect Of Evaporation Research Articles

Numerical investigation on droplet lateral movement in post-dryout region

This paper presents a numerical study of droplet lateral movement and droplet deposition behaviors in the post-dryout region using the Discrete Particle Model (DPM) in ANSYS FLUENT. The investigation focuses on the analysis of droplet lateral movement, including single droplet trajectory, the statistic distribution and average value of droplets radial velocity, and droplet transverse between central and near wall regions. The single droplet trajectory shows the droplet dynamic behavior in the near wall region vividly. The droplet radial velocities are plotted as histogram to display the droplets statistic characteristics. The average value of droplets radial velocities toward the wall are plotted along the radial distance. In addition, to quantitatively display the size and evaporation effect on droplet deposition, three new parameters presenting overall movement behavior, i.e. droplet deposition mass flux, droplet deposition velocity as well as droplet entrainment velocity are introduced and derived from the CFD results. The comparison of results with varying initial droplet size indicates that droplets with smaller sizes exhibit higher average velocities toward the wall. A smaller initial droplet size leads to a higher deposition velocity, lower entrainment velocity, and thus a higher droplet deposition mass flux. The histogram of droplet radial velocities reveals that the droplet evaporation significantly reduces the number of droplets with small radial velocities toward the wall, resulting in a decrease in overall droplet deposition mass flux. Furthermore, through the comparison of overall movement behavior parameters, evaporation not only inhibits droplet motion toward the wall but also noticeably enhances droplet movement away from the wall. This inhibition effect on droplet deposition and enhancement effect on droplet entrainment become more pronounced with increasing evaporation intensity.

Large eddy simulation of spray combustion in a model swirl burner using the two-phase spray flamelet model

Strong turbulence-chemistry interactions in turbulent spray combustion need to be closed by accurate combustion models in the framework of large eddy simulation (LES). The two-phase spray flamelet/ progress variable (TSFPV) model has exhibited good predictions in spray combustion simulation since it takes into account droplet evaporation effects during flamelet modelling. In our previous studies, the TSFPV model was validated on simple configurations of non-swirling jet spray flames. In this research, the model is further applied to the LES of the complicated configuration of the Cambridge model swirl burner. The M-shaped flame structure is well reproduced according to the comparisons of the simulation results with experimental images. The simulation results agree well with the experimental data in terms of quantitative statistics of droplet diameter and velocity. The complicated flame structures, especially for the inner flame brush in the two-phase spray combustion regime, are further analysed. Strong droplets/ flame interactions occur where some droplets penetrate the flame region, emphasising the influence of the evaporation source terms on the flame structure. The heat release rate in the inner flame region is greater than that in the outer flame region, which is consistent with the experiments. The droplet dynamics are analysed based on the scatter plots of droplet axial velocity and the results show that the behaviour of droplets of different sizes varies. The spray flame analyses promote the understanding of the complex spray flame structure in the complicated swirling flame configuration.

Quantitative impacts of climate change and human activities on grassland growth in Xinjiang, China

Grassland is an important vegetation type in Xinjiang, China, playing a crucial role in the terrestrial carbon cycle. Previous studies have shown that both climate change and human activities significantly impact grassland growth. However, research quantifying the contributions of these two factors to grassland changes is still not thorough enough. This study utilized remote sensing data, i.e., Normalized Difference Vegetation Index (NDVI), to analyze the spatial trends of grassland changes from 1982 to 2015, and the correlation between NDVI and climate factors. Then, relative contributions of climate change and human activities to grassland changes were explored across Xinjiang. The results indicated that there was a significant spatial heterogeneity in the interannual variations of NDVI in the study area, showing an overall increasing trend (covering 62.5% of the study area). This was mainly attributed to the warming and humidifying trend of Xinjiang’s climate in recent decades, where increased precipitation and rising temperatures promoted grassland growth. The main regions with increased NDVI included the western part of Changji Hui Autonomous Prefecture, the southern part of Tacheng Prefecture, and the northwestern part of the Tarim Basin; while the areas with decreased NDVI were mainly located in the western part of the study area, e.g., the Ili River basin, and the Tekes River basin. Compared to precipitation, NDVI showed a stronger correlation with temperature, which was related to temperature promoting organic matter decomposition and enhancing vegetation nutrient utilization efficiency. NDVI was negatively correlated with VPD, mainly due to the effects of transpiration and surface evaporation. In terms of grassland growth, climate change (52%) contributed as much as human activity (48%). For the grassland reduction, human activities played a larger role. Overall, in mountainous and flat areas, human activities contributed more (64.29%) than climate change (35.71%), including activities such as grazing and urbanization.

Moisture-Electric Generators Working in Subzero Environments Based on Laser-Engraved Hygroscopic Hydrogel Arrays.

Moisture-electric generators (MEGs) generate power by adsorbing water from the air. However, their performance at low temperatures is hindered due to icing. In the present work, MEG arrays are developed by laser engraving techniques and a modulated low-temperature hydrogel as the absorbent material. LTH effectively captures moisture and maintains ion dissociation and migration even at subzero temperatures. Based on the double electric layer pseudocapacitance model, the oscillating circuit theory is introduced to explain the effects of moisture absorption, evaporation, and ion migration on the output current of the MEG, and the circuit calculations are matched with the experimental results. Molecular dynamics simulations indicate that LTH's low-temperature stability results from preferential hydrogen bonding between glycerol molecules and H2O, which disrupts H2O-H2O hydrogen bonds and slows water crystallization. A single MEG unit (0.25 cm2) can produce up to ∼0.8 V and ∼21.2 μW/cm2 at room temperature, and at -35 °C with 16% RH, it generates ∼0.58 V and ∼14.35 μA. MEG realizes the following applications: MEG successfully drives electronic devices in snow; arrays of 16 MEGs can power portable electronics, and 384 MEGs can achieve up to 210 V; MEG absorbs moisture in water and drives LEDs by blowing up; MEG has a flexible wearable nature; MEG is used for respiratory monitoring and photoelectric sensors.

A new procedure for volcanic glass hydrogen isotope studies of tuffaceous sediments and its application in the North American Cordillera

Hydrated volcanic glass δD (δDg) values of pure tuffs have been used to reconstruct paleoprecipitation δD in paleoelevation and paleoclimate studies. These hydrated glasses in tuffaceous sediments hold the potential for providing extended and continuous paleoprecipitation δDw records due to their abundance in the geologic record. However, glasses in such materials may be recycled and subjected to surface alteration, and the δDw values of the water that hydrated the glasses can vary across different depositional environments. Here we first develop a method to reduce the influence of recycled glass and surface alteration, then apply the method to the Eocene−Oligocene tuffaceous sediments in the Sage Creek basin, southwestern Montana, USA, to examine the variation of δDg in different depositional environments and test a previous interpretation of early Oligocene surface uplift in southwestern Montana. Our integration of microscopic observations of glass morphology and lab experiments of hydrofluoric acid (HF) abrasion of glasses for various durations (30 s to 30 min) shows that 10% HF abrasion for at least 5 min removes most of the recycled glass in tuffaceous sediments and does not change the δDg values and hydration water contents. Our data also show that pumice and cuspate glasses have higher δDg and water content than blocky glasses, which explains some of the δDg variations. The extended HF abrasion method was applied to 91 tuffaceous sandstone samples from floodplain and alluvial/fluvial channel facies in the Renova Formation in the Sage Creek basin. The results show that the δDg values exhibit greater variations in trunk and avulsion channels and floodplain facies than in paleosols. These variations are likely due to the mixing of waters derived from diverse elevations and sources, with differing evaporation degrees and glass types. This study underscores the significant potential of utilizing hydrated volcanic glass δDg from tuffaceous sediments for paleoclimate and paleoelevation studies. Nonetheless, it is important to assess the influence of depositional environment when interpreting such data. Paleosols are more suitable than other facies for reconstructing basinal precipitation δDw, but it is crucial to evaluate the effect of evaporation on paleosol δDg before interpretation. Additionally, the study reveals an absence of the anticipated early Oligocene negative δDg shift, calling for further investigation of this hypothesis.

Below-cloud evaporation effect on stable isotopes on precipitation on the Gannan Plateau region based on Stewart model

Below-cloud evaporation effect on stable isotopes on precipitation on the Gannan Plateau region based on Stewart model

Analysis of Groundwater Hydrochemical Variation and Its Source During the Low Water Level Period in the Southern Oasis Area of Gaochang District, Turpan City

To explore the changes in groundwater hydrochemistry and its source influence in the low water level period of the southern oasis area of Gaochang District, Turpan City before and after the management of groundwater overexploitation, based on 12 groups of water samples in 2016 （three groups of unconfined water, nine groups of confined water） and 18 groups of water samples in 2023 （five groups of unconfined water, thirteen groups of confined water）, mathematical statistics, hydrochemical diagraph, hydrogen and oxygen isotope means, and an absolute principle component-multiple linear regression （APCS-MLR） model were used to analyze the changes and sources of groundwater hydrochemistry. The results showed that due to the dynamic conditions of groundwater, the dominant cation changed from Na+ to Ca2+, and the anion changed from HCO3- to SO42-. The dominant cation of confined water changed from Ca2+ to Na+, and the dominant anion remained unchanged as SO42-. The main supply source of both unconfined water and confined water was atmospheric precipitation, which was affected by evaporation, and the effect of evaporation of unconfined water was greater than that of confined water. The chemical composition of groundwater was mainly controlled by rock weathering and cation exchange. Na+, Ca2+, and Mg2+ were mainly derived from the dissolution of evaporative salt rock and silicate salt rock. NO3- was mainly derived from agricultural fertilizers, human and animal manure, and domestic sewage. Leaching and enrichment （F1）, agricultural activity and primary geological activity （F2）, and industrial activity （F3） were the main factors affecting groundwater chemistry in the study area, and the contribution rates were 58.41%, 18.12%, and 9.12%, respectively.

Microscale Electrical Resistivity Measurements to Investigate Particle Distribution.

The functional performance of a particulate thin film depends greatly on the particle distribution that forms during drying. In situ methods for monitoring the impact of different processing parameters on the distribution of particles currently require expensive and specialized equipment. This work addresses this gap by miniaturizing a geophysical prospecting method to thin-film applications. In this method, four-electrode resistivity measurements at variable probe spacing detect changes in the vertical particle concentration profile. A heuristic colloidal drying model describes the particle distribution during drying in terms of the relative effects of Brownian diffusion, sedimentation, and evaporation. For sedimentation- and evaporation-dominated drying, the film is modeled as two stratified layers of different concentrations. Solving this model simultaneously alongside Laplace's equation for electrostatic resistance identifies the parameters necessary to distinguish between diffusion-, sedimentation-, and evaporation-dominated drying. For resistive particles in a conductive solvent, simulations predict that the normalized thickness of the top layer, δt/H0, must exceed a critical value to distinguish between different drying regimes. The heuristic model results are validated theoretically by comparison to a physics-based drying model. Model predictions are experimentally validated by fabricating a custom microlithography four-line probe device and measuring the transient resistance of systems for which the drying mechanism is known. This work offers a low-cost and in situ method to identify drying mechanisms and extract physical parameters that better characterize the processing-structure-function relationships for many coatings.

Impact of Heat Exchanger Fouling in Bioethanol Plants

Bioethanol plays a major role in improving the sustainability of a carbon-intensive sector such as transportation. With a pressing need in the industry to reduce carbon intensity of the ethanol production itself, it is of paramount importance ensuring that thermal systems are as efficient as possible. One of the biggest challenges that leads to significant operational issues, extra energy and water consumption, unplanned plant shutdowns and unnecessary CO2 emissions is fouling, the progressive deposition of low thermal conductivity material on thermal surfaces. This unwanted deposition reduces the thermal efficiency of key equipment, including heat exchangers and evaporators and increases pressure drops. In this paper, a mathematical model for the most energy-intensive section of a typical 50 MGY dry-grind ethanol plant is developed to assess the economic and environmental impact of fouling. The model includes double effect evaporators integrated with the beer column and two reboilers and allows quantifying the Key Performance Indicators under different combinations of fouling rates, operating conditions and cleaning effectiveness. Results show that even if regular cleaning cycles are performed, following current industry standards, the impact of fouling is still significant, with emissions of 15,435 ton CO2/year (81.67g CO2/l), additional energy of 70,809 MWh/year (0.38 kWh/l), additional water use of 106,738 m3/year (0.56l/l), and additional costs of 3.53 MM$ per year (0.02 $/l). Moreover, by optimising the selection of cleaning agents, costs can be reduced up to 65-70% while water consumption, energy use and emission release can be curbed by 70 to 80%. Other strategies to mitigate fouling (e.g. increasing steam pressure) were also identified and discussed.

Effects of Evaporation and Body Thermal Plume on Cough Droplet Dispersion and Exposure Risk for Queuing People.

The transmission of virus-containing droplets among multiple people in an outdoor environment is seldom evaluated. In this study, an Euler-Lagrange computational fluid dynamics approach was used to investigate the effects of evaporation and the body thermal plume on the dispersion of coughed droplets under various wind conditions, and the infection risk was evaluated for various arrangements of individuals queuing outdoors using virtual manikin models. The evaporation time was longer for larger droplets and in a more humid environment. Transient evaporation strongly affected the motion of droplets ranging in diameter from 60 to 150 μm. The body thermal plume affected airflow and particle dispersion under weak wind conditions, but its effect was negligible at wind speeds greater than 0.8 m/s. Droplets smaller than 100 μm could reach the head of a susceptible person, suggesting a high exposure risk. The exposure fraction and body deposition were highest in an all-male queue sequence and lowest for a male-female-male-female-male queue sequence.

The Evapotranspiration Characteristics and Evaporative Cooling Effects of Different Vegetation Types on an Intensive Green Roof: Dynamic Performance Under Different Weather Conditions

Previous research has demonstrated that the multiple environmental benefits of green roofs are primarily associated with their evaporative cooling effect. However, current studies on green roof evapotranspiration (ET) mainly focus on extensive green roofs, and the evaporative cooling effect of intensive green roofs is still unclear. Using the intensive green roof of AQUA City in Nanjing as a case study, this research employs the three-temperature (3T) model combined with high-resolution thermal infrared imagery obtained via an unmanned aerial vehicle (UAV) to estimate the ET of different vegetation types. The study aims to explore the spatiotemporal variations in surface temperature, evapotranspiration (ET) rate, and evaporative cooling rate for various vegetation types under typical seasonal (summer and winter) and weather conditions (sunny, cloudy, and rainy before and after rainy days). The results showed that: (1) the ET rates and evaporative cooling effects of different types of vegetation differed significantly, with shrubs having the fastest ET rates, followed by arbors, and grasslands having relatively low ET rates. (2) Solar radiation and air temperature are the most crucial meteorological parameters for inducing ET on green roofs. In this study, the evaporative cooling performance showed the patterns of summer > winter and sunny > cloudy > rainy days. (3) In the spatial distribution of tree and irrigation plant groups, some low-temperature diffusion phenomena to the adjacent small microenvironments were evident, while the diffusion effect in winter is smaller and mainly shows the opposite warming characteristics. This study offers a valuable reference for quantifying the ET and evaporative cooling effects of various vegetation types on intensive green roofs, facilitating the optimization of vegetation configuration and supporting sustainable urban development.

The effects of evaporation and precipitation on droughts under global change

Drought can be defined as a kind of natural disaster, with a series of effects in different aspects of human life, including environment, economic, ecosystem and agriculture. Previous studies has delved more deeply into the impact of drought, examining it through a range of drought indices, including PEI, SPEI, PDSI, and others. Our study is aims to analyze and research the effects of evaporation and precipitation on droughts under global climate change. Through the temperature changing data research the global climate change feature, analyzing the development of droughts using a drought assessment index (P-E) and making use of bucket model to analyze the relationship between precipitation rate and soil moisture. Research found that the average land temperature is increasing. On the context of this change, the change of evaporation and precipitation causes dry regions to become drier and wet regions wetter. Furthermore, the 20% decrease of precipitation leads to about a one-fifth decline in soil water content, and a lower precipitation rate would speed up the drought states. Meanwhile, soil moisture can also lead to an increase in precipitation. A coupling phenomenon between precipitation rate and soil moisture is exist. This study provides a new point for predicting future droughts conditions.

Effect of Evaporation and Condensation Temperature on Performance of Organic Rankine System Using R134a, R417A, R422D, R245fa

Organic Rankine Cycles (ORCs) are identified as one of the most promising technologies for generating electricity from low-grade heat sources. Unlike conventional Rankine cycles, ORCs operate at lower temperatures and pressures. This allows them to utilize organic fluids or refrigerants as the working fluid instead of water, which is better suited for high-pressure and high-temperature applications. The performance and design of an ORC system are heavily dependent on the chosen working fluid. Therefore, selecting the right working fluid is crucial for a specific application, such as solar thermal, geothermal, or waste heat recovery. This study analyzed the performance of ORCs using four different working fluids: R-134a, R-245fa, R417A, and R422D. The researchers investigated how variations in condensation and evaporation temperatures affect thermal efficiency, mass flow rate, pump power, and turbine pressure ratio. The Engineering Equation Solver (EES) program was used for analyses. The results demonstrated that condensation and evaporation temperatures significantly influence system performance. The study found that ORC systems using R417A and R422D exhibited higher efficiencies compared to the other working fluids analyzed. Additionally, these fluids required lower mass flow rates per unit of power generation compared to the other fluids.

Vapor shielding effect and selective evaporation analysis of paired unary and binary mixture droplets using surface plasmon resonance imaging and CFD predictions

Vapor shielding effect and selective evaporation analysis of paired unary and binary mixture droplets using surface plasmon resonance imaging and CFD predictions

A computational workflow for end-to-end simulation of percutaneous absorption.

Presented is the development of a workflow for end-to-end (e2e) in silico modelling of percutaneous absorption under a range of test conditions, integrating multiple calculation and analysis steps for in-silico simulation of dermal absorption. The aim is to achieve a digital twin that can be used by non-modelling experts to simulate transdermal permeation. A KNIME-based toolbox is used to create the workflow for the E2E in-silico model. The workflow first combines physicochemical property informatics (ChemAxon), molecular dynamics (MD) modelling, and quantitative structure-property relations (QSPRs) to calculate the diffusion and partition properties of permeants in heterogeneous skin layers and complex formulation vehicles. These are then set as input parameters to physiologically based pharmacokinetics (PBPK) model to simulate percutaneous absorption under complex in vitro testing or in vivo exposure conditions set by the end user. Integrated into the PBPK model is the evaporation of volatile permeants and solvents for in vitro unoccluded conditions. The workflow generates a report of the results and records the tested formulation in a database. The workflow has been tested against several sets of published in vitro permeation test (IVPT) results of percutaneous absorption involving different formulation vehicles. The model predictions of formulation and evaporation effects on percutaneous absorption agreed well with experimental data. By automating multiple calculation steps from permeant property, diffusion-partition skin layers and formulation vehicles, to PBPK modelling of dermal absorption, the workflow provides a user-friendly means for non-modelling experts to conduct in-silico simulations of transdermal absorption under various conditions. The workflow is robust to simulate the impact of complex formulation and exposure conditions including evaporation of volatile permeants and solvents on the delivery into the skin.

Influence of liquid–vapor phase change on the self-propelled motion of droplets on wettability gradient surfaces

Self-propelled motion of sessile droplets on gradient surfaces is key to the advancement of microfluidic, nanofluidic, and surface fluidic technologies. Precise control over droplet dynamics, which often involves liquid–vapor phase transitions, is crucial for a variety of applications, including thermal management, self-cleaning surfaces, biochemical assays, and microreactors. Understanding how specific phase changes like condensation and evaporation affect droplet motion is essential for enhancing droplet manipulation and improving transport efficiency. We use the thermal Navier–Stokes–Korteweg equations to investigate the effects of condensation and evaporation on the motion and internal dynamics of droplets migrating across a surface with a linear surface energy profile. The study focuses on the early dynamics of self-propelled motion of a phase changing droplet at sub-micron scale before viscous forces are comparable with the gradient forces. Our results demonstrate that phase change significantly affects the self-propelled motion of droplets by reshaping interfacial mass flux distributions and internal flow dynamics. Condensation increases droplet volume and promotes extensive spreading toward regions of higher wettability, while evaporation reduces both volume and spreading. These changes in droplet shape and size directly affect the driving forces of motion, augmenting self-propulsion through condensation and suppressing it during evaporation. Additionally, each phase change type generates distinct internal flow patterns within the droplet, with condensation and evaporation exhibiting unique circulatory movements driven by localized phase changes near the contact lines.

Effects of droplet evaporation on turbulence characteristics in a supersonic mixing layer

Effects of droplet evaporation on turbulence characteristics in a supersonic mixing layer

High-salt-resistance aerogels composed of chitosan and anode powder for effective solar interfacial evaporation

Solar interfacial evaporation technology is widely utilized for seawater desalination and wastewater treatment, which are currently areas of significant research interest. The primary factors to consider when transitioning the evaporator from laboratory settings to practical applications are its mechanical stability and resistance to salt. In the present study, composite aerogels consisting of an anode powder (AP), polypyrrole (Ppy), and chitosan (CS) were produced by a conventional technique involving physical cross-linking and in situ growth. The resulting aerogel has a compact pore structure that enhances the scattering of light on its surface and increases the area available for evaporation. As a result, the material exhibits exceptional photothermal capabilities, with water evaporation rates and photothermal conversion efficiencies of 1.865 kg m−2 h−1 and 85.96%, respectively, when exposed to 1 sun illumination. Simultaneously, the aerogel exhibits exceptional efficacy in water purification and resistance to salt when employed for the treatment of heavy-metal wastewater, seawater, and highly concentrated saline solutions. Furthermore, the utilization of AP as a light-absorbing substance aligns with the principles of green chemistry by promoting the recycling and repurposing of waste materials. These results provide novel insights into the potential applications of lithium battery waste and the optimization of solar-interfacial-evaporator design.

Molecular-level analysis of alkyl chain dependent voltage-induced microfluidic alcohol droplet actuation on Teflon/Pt/glass substrate: Revealing the unconventional directional movement

Current study investigates the voltage-induced actuation of alcohol droplets on a Teflon/Pt/Glass substrate, emphasizing the influence of alkyl chain length on microfluidic droplet behavior. The wetting and electrowetting properties of different alcohols with increasing carbon chain length, namely, methanol, ethanol, 1-propanol, and 1-butanol, are examined by using both experimental techniques and the simulations of classical molecular dynamics (MD). An increase in the wetting nature of these alcohol droplets is observed with the increase in carbon chain length. A greater penetration into the Teflon surface is observed for alcohols with longer alkyl chain lengths from MD simulations. The evaporative nature of alcohol droplets and the consequent effect of evaporation on wetting are also examined. Voltage-modified change in contact angle, droplet displacement or spreading, and voltage-induced work of spreading, are investigated to study the actuation of such alcohol droplets. A unique, voltage-triggered directional displacement/spreading of the droplets towards ground electrode is observed, in contrast to the conventional electrowetting behavior. These insights underscore the influence of molecular interactions in voltage-actuated droplet dynamics, having significant implications as a design parameter in the development of digital microfluidics-based lab-on-a-chip devices.

Water-salt transport modeling and sulfate erosion mechanisms in cultural heritage under microclimate

The microclimate of the environment influences the characteristics of salt erosion in historical cultural heritage, determining the pattern of salt weathering and the mechanism of salt-action. The study focuses on the influence of cultural heritage microclimate on salt weathering, and the study aims to understand the weathering mechanism by combining the theory of crystalline weathering with temperature and humidity variation. The study comprised immersing sandstone from the Yungang Grottoes, a World Heritage Site, in a sulfate salt solution and simulation of salt deterioration under on-site cyclic variable temperature and humidity conditions. The article designs the accumulation of salt crystallization at the sandstone surface under the effect of salt evaporation and visualizes the water-salt migration and crystallization process by ion chromatography (IC), microelectrode, and hyperspectral techniques. The corresponding types of sulfate deterioration under different weathering simulation conditions are investigated to probe the mechanism behind different weathering patterns. In the first part, we construct a water-salt migration test, combining hyperspectral techniques and microelectrodes to visualize the weathering patterns, compositional characteristics, and spatial and temporal changes of water-salt transport based on Fick's law to establish a mathematical model and simulate it in COMSOL multi-physics field simulation software. Subsequently, tests were carried out on sandstone with sulfate solution at variable temperatures and humidity levels to simulate the process of salt weathering. The results demonstrated that different salt solutions, such as Na2SO4 and MgSO4, lead to the dissolution of clay minerals. At the same time, crystallization disrupts the sandstone structure, causing degradation of its physico-mechanical properties after several weathering cycles, and there are significant differences in the salt crystallization patterns at different temperatures and after cycling at different humidities.