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The precise design of heat exchangers in automobile air conditioning systems for more sustainable electric vehicles requires an enhanced assessment of CFD mechanistic models for the subcooled boiling flow of pure eco-friendly refrigerant. Computational Multiphase Flow Dynamics (CMFDs) relies on two-phase closure models to accurately depict the complex physical phenomena involved in flow boiling. This paper thoroughly examines two-phase CMFD flow boiling, incorporating sensitivity analyses of critical parameters such as boiling closures, momentum closures, and population balance models. Three datasets from the DEBORA experiment, involving vertical pipes with subcooled boiling flow of refrigerant at three different pressures and varying levels of inlet liquid subcooling, are used for comparison with CFD simulations. This study integrates nucleate site density and bubble departure diameter models to enhance wall boiling model accuracy. It aims to investigate various interfacial forces and examines the S-Gamma and Adaptive Multiple Size-Group (A-MuSiG) size distribution methods for their roles in bubble break up and coalescence. These proposed approaches demonstrate their efficacy, contributing to a deeper understanding of flow boiling phenomena and the development of more accurate models. This investigation offers valuable insights into selecting the most appropriate sub-closure models for both boiling closure and momentum closure in simulating boiling flows. [ABSTRACT FROM AUTHOR]

Cement-based materials encompass a broad spectrum of construction materials that utilize cement as the primary binding agent. Among these materials, concrete stands out as the most commonly employed. The cement, which is the principal constituent of these materials, undergoes a hydration reaction with water, playing a crucial role in the formation of the hardened composite. However, the exothermic nature of this reaction leads to significant temperature rise within the concrete elements, particularly during the early stages of hardening and in structures of substantial thickness. This temperature rise underscores the critical importance of predictive modeling in this domain. This paper presents a review of modeling approaches designed to predict temperature and accompanying moisture fields during concrete hardening, examining different levels of modeling accuracy and essential input parameters. While modern commercial finite element method (FEM) software programs are available for simulating thermal and moisture fields in concrete, they are accompanied by inherent limitations that engineers must know. The authors further evaluate effective commercial software tools tailored for predicting these effects, intending to provide construction engineers and stakeholders with guidance on managing temperature and moisture impacts in early-age concrete. [ABSTRACT FROM AUTHOR]

Based on air-, water-, and ground-source heat pump systems, a novel type of heat pump system, named the heat-source tower heat pump system (HSTHPS), has recently been developed in the southern area of China. The HSTHPS overcomes the evaporator frosting problems of the air-source heat pump system (ASHPS) when the ambient temperature is lower, and it avoids the geological condition constraints of the water- and ground-source heat pump systems. However, studies on the HSTHPS are insufficient, thereby limiting its development and applications. Thus, the present review provides a detailed literature review on the advancements of HSTHPSs in China, including the HSTHPS operation principle, heat-source tower (HST) structure, heat and mass transfer characteristics, HSTHPS performance, antifreeze solution use, and antifreeze solution regeneration. Studies on the heat and mass transfer characteristics of HSTs are sufficient for guiding the application. Regarding open systems, the solution drifting to the air needs to resolved, and future studies need to focus on structure optimization for heat exchangers in closed systems. Moreover, advanced defrosting technology should be applied to closed-type HSTs, and a suitable operation strategy for HSTHPSs should be developed. Future priorities should involve integrating HSTHPSs with additional renewable energy in order to achieve continuous, stable, and efficient heating in winter based on the characteristics of local climate and renewable energy. [ABSTRACT FROM AUTHOR]

Treatment methods for high-salt wastewater mainly consist of physical methods, chemical methods and biological methods. However, there are some problems, such as slow treatment speed, high investment costs and low treatment efficiency. To address NaCl solutions, in this study, a circulatory flash system was designed based on gas–liquid equilibrium, mass conservation equation and energy conservation equation. A circulatory flash evaporation simulation and a static flash evaporation experiment were conducted on NaCl solutions under various operating conditions to investigate the effects of heating temperature, flash pressure and initial NaCl concentration on the circulatory flash evaporation system. The significance of each factor's influence on the evaporation fraction and energy consumption was examined through static flash experiments. The simulation results demonstrated that increasing the heating temperature, decreasing the flash pressure and having a higher initial NaCl concentration could enhance the treatment capacity of high-salt wastewater. The flow rate of vapor outlets increased with higher heating temperature but decreased as the flash pressure rose. The experimental results demonstrated that flash evaporation pressure was the primary factor influencing both the evaporation fraction and the energy consumption per unit mass of vapor produced. It was observed that with an increase in heating temperature, the flash pressure decreased and there was a corresponding decrease in energy consumption per unit mass of vapor produced. The optimal experimental conditions were achieved at a heating temperature of 99 °C, a flash pressure of 15 kPa, and an initial NaCl concentration of 20%. [ABSTRACT FROM AUTHOR]

The humidifier plays a key role in a humidification–dehumidification (HDH) desalination system; it directly affects both the freshwater production efficiency and energy consumption ratio of the system. In this study, for a humidifier in an HDH system, a heat–mass coupled differential equation model of spray water and air on the surface of the packing material was established, and the effects of parameters such as the spray water temperature (tw), mass flow rate of spray water (mw), air temperature (ta), and air mass flow rate (ma) on the humidification performance of humidifiers composed of eight different types of packing materials were investigated. The results show the following: (1) Under the same inlet spray water and air conditions, the humidification performance of different packing materials from good to bad is as follows: cellulose paper, polypropylene, hackettes, saddles, snowflakes, wooden slats, polyvinyl chloride, gunny bag cloth. (2) Increasing the tw can significantly improve the humidification performance. To achieve higher humidification energy efficiency, it is recommended to increase the tw to above 80 °C. (3) With the increase in the mw, although the humidification efficiency (εhum) decreases slightly, the humidification rate (mhum) increases, and the specific humidification energy ratio (ηhum) decreases accordingly. To maintain a high mhum and a low ηhum, it is advisable to control the mw at not less than 0.5 kg/s. (4) Increasing the humidifier inlet ta can improve the mhum, εhum, and ηhum, although not as effectively as increasing tw. (5) Increasing the ma can improve mhum and εhum. However, it simultaneously increases the ηhum. The results of this study can provide theoretical guidance for the selection of efficient packing materials and the optimization of humidifier operating conditions in HDH desalination systems. [ABSTRACT FROM AUTHOR]

As ice-like crystals and non-stoichiometric compounds comprising gas and water, natural gas hydrates have drawn significant attention as a potential alternative energy source. This work focuses on holistically reviewing theoretical modeling and numerical studies conducted on the production of gas from natural gas hydrates. Firstly, fundamental models for the dissociation of a hydrate in a porous sediment are summarized in terms of the phase equilibrium and dissociation kinetics. The main features of different models and improvements for them are identified by clarifying crucial driving mechanisms and kinetic parameters. Subsequently, various numerical works addressing the dissociation of a hydrate in a porous sediment and the flow characteristics in a wellbore are reviewed, including aspects such as the theoretical background, computational scheme, and the physics involved. In general, profiting from a significant capacity to solve nonlinear differential equations, numerical simulations have contributed to great progress in fundamentally understanding the mechanism driving gas production and in developing effective exploitation methods. Owing to the substantial fundamental physics involved in the exploitation of natural gas hydrates, existing challenges, alternative strategies, and future directions are provided correspondingly from a practical application perspective. [ABSTRACT FROM AUTHOR]

Natural gas is one of the most common forms of energy in our daily life, and it is composed of multicomponent hydrocarbon gas mixtures (mainly of methane, ethane and propane). It is of great significant to reveal the condensation mechanism of multicomponent mixtures for the development and utilization of natural gas. A numerical model was adopted to analyze the heat and mass transfer characteristics of propane condensation in binary and ternary gas mixtures on a vertical cold plate. Multicomponent diffusion equations and the volume of fluid method (VOF) are used to describe the in-phase and inter-phase transportation. The conditions of different wall sub-cooled temperatures (temperature difference between the wall and saturated gas mixture) and the inlet molar fraction of methane/ethane are discussed. The numerical results show that ethane gas is more likely to accumulate near the wall compared with the lighter methane gas. The thermal resistance in the gas boundary layer is one hundred times higher than that of the liquid film, revealing the importance of diffusion resistance. The heat transfer coefficients increased about 11% (at ΔT = 10 K) and 7% (at ΔT = 40 K), as the molar fraction of ethane increased from 0 to 40%. Meanwhile, the condensation heat transfer coefficient decreased by 53~56% as the wall sub-cooled temperature increased from 10 K to 40 K. [ABSTRACT FROM AUTHOR]

In this study, a novel experimental model was proposed, built, and tested to present an efficient and simple method for cooling protective helmets. The system was based on an evaporative cooling technique in which water is used as a coolant sprayed over a canvas covering the outer helmet's surface. A solar fan was provided to enhance the evaporation rate. The experimental results were used with the main laws of heat and mass to evaluate evaporation and heat transfer rates. The proposed system was compared by other two cases, the uncovered dry helmet and the wet-covered one without using the fan. The inner and outer surface temperatures reached were characterized by a good level of stability and by being compatible with human comfort conditions. The addition of the wet cover led to a temperature drop in both the outer and inner surfaces of the helmet by about 9 degrees, and the addition of the fan led to an additional drop of about 5 degrees. There were increases in the cooling rate by 63.3% by adding the wet cover and by 131.7% after adding the fan. The system is characterized by free power consumption and simplicity in implementation. [ABSTRACT FROM AUTHOR]

Structure parameters have an important influence on the refrigeration performance of pulse tube refrigerators. In this paper, a method combining the Kriging metamodel and Non-Dominated Sorting Genetic Algorithm II (NSGA II) is proposed to optimize the structure of regenerators and pulse tubes to obtain better cooling capacity. Firstly, the Kriging metamodel of the original pulse tube refrigerator CFD model is established to improve the iterative solution efficiency. On this basis, NSGA II was applied to the optimization iteration process to obtain the optimal and worst Pareto front solutions for cooling performance, the heat and mass transfer characteristics of which were further analyzed comparatively to reveal the influence mechanism of the structural parameters. The results show that the Kriging metamodel presents a prediction error of about 2.5%. A 31.24% drop in the minimum cooling temperature and a 31.7% increase in cooling capacity at 120 K are achieved after optimization, and the pressure drop loss at the regenerator and the vortex in the pulse tube caused by the structure parameter changes are the main factors influencing the whole cooling performance of the pulse tube refrigerators. The current study provides a scientific and efficient design method for miniature cryogenic refrigerators. [ABSTRACT FROM AUTHOR]

The present article investigates viscous fluid flow's heat and mass transfers over a stretching/shrinking sheet using the single and multi-wall carbon nanotube models. The analysis considers the effects of thermal radiation, induced slip, mass transpiration, and inclined magnetic force. The effect of the carbon nanotube model on fluid flow has not been considered in previous studies. By exploiting the similarity variable, the governing nonlinear partial differential equations are converted into nonlinear ordinary differential equation. The derived equations are solved analytically, and we obtained an exact solution for the velocity and energy conservation equation. The physical parameters of interest such as induced slip parameter, suction/injection, magnetic field, thermal radiation, and shear stress are analyzed and presented graphically. In particular, we show that the fluid flow in a single wall carbon nanotube transfers more energy than the multivalued nanotubes. [ABSTRACT FROM AUTHOR]

This particular study focuses on investigating the heat and mass transport characteristics of a liquid flow across the conical gap (CG) of a cone-disk apparatus (CDA). The cone and disk may be taken as stationary or rotating at varying angular velocities. Consideration is given to heat transport affected by solar radiation. The Rosseland approximation is used for heat radiation calculations in the current work. To observe the mass deposition variation on the surface, the effect of thermophoresis is taken into account. Appropriate similarity transformations are used to convert the three-dimensional boundary-layer governing partial differential equations (PDEs) into a nonlinear ordinary differential equations (ODEs) system. Particularly for the flow, thermal and concentration profiles, plots are provided and examined. Results reveal that the flow field upsurges significantly with upward values of Reynolds numbers for both cone and disk rotations. The increase in values of the radiation parameter improves heat transport. Moreover, it is detected that the stationary cone and rotating disk model shows improved heat transport for an increase in the values of the radiation parameter. [ABSTRACT FROM AUTHOR]

Ammonia (NH3) is regarded as a promising medium of hydrogen storage, due to its large hydrogen storage density, decent performance on safety and moderate storage conditions. On the user side, NH3 is generally required to decompose into hydrogen for utilization in fuel cells, and therefore it is vital for the NH3-based hydrogen storage technology development to study NH3 decomposition processes and improve the decomposition efficiency. Numerical simulation has become a powerful tool for analyzing the NH3 decomposition processes since it can provide a revealing insight into the heat and mass transfer phenomena and substantial guidance on further improving the decomposition efficiency. This paper reviews the numerical simulations of NH3 decomposition in various application scenarios, including NH3 decomposition in microreactors, coupled combustion chemical reactors, solid oxide fuel cells, and membrane reactors. The models of NH3 decomposition reactions in various scenarios and the heat and mass transport in the reactor are elaborated. The effects of reactor structure and operating conditions on the performance of NH3 decomposition reactor are analyzed. It can be found that NH3 decomposition in microchannel reactors is not limited by heat and mass transfer, and NH3 conversion can be improved by using membrane reactors under the same conditions. Finally, research prospects and opportunities are proposed in terms of model development and reactor performance improvement for NH3 decomposition. [ABSTRACT FROM AUTHOR]

Surface tension is a meaningful parameter influencing boiling and condensation in macroscopic scale, in confined spaces, or for nanofluids; it further affects boiling with surfactants. Surface, or interfacial, tension is an important property in the research into increasing heat transfer, enhancing efficiency of photovoltaic systems, improving engine operation, or forming drugs or polymers. It is often determined using axisymmetric drop shape analysis based on the differential equations system formulated by Bashforth and Adams. The closed-form expression of the interface shape states the radii defining the bubbles are the negative numbers, which causes the temperature profile drops along the heat transfer direction, e.g., in the Wiśniewski formulas for the temperature in the vapor bubbles; moreover, the drop, or bubble, possesses only one main radius of curvature, which may reduce the number of the unknowns and equations in the Bashforth and Adams algorithm. An alternative method applying the closed-form expression for the droplet shape is validated for the water (denser) drop flowing down in octane (the lighter liquid); its spare equation is used for verifying the outcomes. [ABSTRACT FROM AUTHOR]

Drying is a complex process of simultaneous heat, mass, and momentum transport phenomena with continuous phase changes. Numerical modelling is one of the most effective tools to mechanistically express the different physics of drying processes for accurately predicting the drying kinetics and understanding the morphological changes during drying. However, the mathematical modelling of drying processes is complex and computationally very expensive due to multiphysics and the multiscale nature of heat and mass transfer during drying. Physics-informed machine learning (PIML)-based modelling has the potential to overcome these drawbacks and could be an exciting new addition to drying research for describing drying processes by embedding fundamental transport laws and constraints in machine learning models. To develop such a novel PIML-based model for drying applications, it is necessary to have a fundamental understanding of heat, mass, and momentum transfer processes and their mathematical formulation of drying processes, in addition to data-driven modelling knowledge. Based on a comprehensive literature review, this paper presents two types of information: fundamental physics-based information about drying processes and data-driven modelling strategies to develop PIML-based models for drying applications. The current status of physics-based models and PIML-based models and their limitations are discussed. A sample PIML-based modelling framework for drying application is presented. Finally, the challenges of addressing simultaneous heat, mass, and momentum transport phenomena in PIML modelling for optimizing the drying process are presented at the end of this paper. It is expected that the information in this manuscript will be beneficial for further advancing the field. [ABSTRACT FROM AUTHOR]

A deep understanding of the dissociation and transportation mechanism of natural gas hydrate (NGH), taking into account the effects of geo-stress, contributes to optimizing the development strategy and increases the exploitation efficiency of NGH. In this paper, the mathematical model, coupled with fluid heat and mass transfer, multiphase flow mechanics, and reaction kinetics with phase change in the process of hydrate decomposition was established. An axisymmetric two-dimensional model was developed to simulate the depressurization decomposition process of natural gas hydrate in the Berea sandstones. FLUENT software was used to solve the fundamental governing equations of the multi-phase flow, and UDF programming was employed to program the hydrate decomposition model and the modified permeability model in the dissociation and transportation of NGH. The simulation results were then validated by Masuda's experimental data. The effects of gas saturation, outlet pressure, temperature, absolute permeability and geo-stress on the decomposition of natural gas hydrate were studied. The results indicated that a higher absolute permeability, higher initial gas saturation, lower outlet pressure, and higher initial temperature advance the decomposition rate of hydrate. Thus, an optimized production plan is essential to promote the extraction efficiency of the NGH. The geo-stress causes a decrease in the porosity and permeability of the porous rock, which restricts the efficiency of the heat and mass transfer by the fluid flow, leading to a slower dissociation and transportation rate of the NGH. Thus, it is important to take geo-stress into consideration and balance the extracting efficiency and the well pressure, especially when the NGH is developed by depressurization. [ABSTRACT FROM AUTHOR]

In this study, the impact of hydrogen concentration on deflagration to detonation transition (DDT) and detonation diffraction mechanisms was investigated. The combustion chamber was an ENACCEF facility, with nine obstacles at a blockage ratio of 0.63 and three mixtures with hydrogen concentrations of 13%, 20%, and 30%. Detonation diffraction mechanisms were numerically investigated by a density-based solver of OpenFOAM CFD toolbox named ddtFoam. In this simulation, for the low Mach numbers, the pddtFoam solver was applied, and for high speeds, the pddtFoam solver switched to the ddtFoam solver to simulate flame propagation without resolving all microscopic details in the flow in the CFD grid, and to provide a basis for simulating flame acceleration (FA) and the onset of detonation in large three-dimensional geometries. The results showed that, for the lean H2–air mixture with 13% hydrogen concentration, intense interaction between propagating flame and turbulent flow led to a rapid transition from slow to fast deflagration. However, the onset of detonation did not occur inside the tube. For the H2–air mixture with 20% hydrogen concentration, the detonation initiation appeared in the acceleration tube. It was also found that following the diffraction of detonation, the collision of transverse waves with the wall of the tube and the reflection of transverse waves were the most essential and effective parameters in the re-initiation of the detonation. For the H2–air mixture with 30% hydrogen concentration, the detonation initiation occurred while passing through the obstacles. Subsequently, at detonation diffraction, the direct initiation mechanism was observed. [ABSTRACT FROM AUTHOR]

Due to a large amount of particulate matter in industrial flue gas, the formation of particulate deposits on the flue wall will increase the instability of equipment operation, which needs to be solved urgently. In this paper, a numerical investigation on the characteristics of particulate deposition and removal in the furnace flue was carried out for waste heat and energy recovery. This research adopted a comprehensive fouling model combined with the discrete phase model (DPM) which was performed by the CFD framework and extended by user-defined functions (UDFs). Firstly, the particulate deposition and removal algorithms were proposed to develop the judgment criterion of particle fouling based on the Grant and Tabakoff particle–wall rebound model and the Johnson–Kendall–Roberts (JKR) theory. This model not only considered the particles transport, sticking, rebound, and removal behaviors, but also analyzed the deposition occurring through the multiple impactions of particles with the flue wall. Then, the influence of furnace gas velocity, particle concentration, and inflection angle α of the tee section on the particulate fouling were predicted. The results show that the furnace gas velocity, particle concentration, and flue structure have significant effects on particle fouling and distribution, and the particle fouling mainly occurs in the blind elbow section and the tee sections of the flue. In addition, the fouling mass of particles decreases with an increasing furnace gas velocity and the decrease in particle concentration. Lastly, the fouling mass of particles decreases with the increase in the inflection angle α of the tee section, and the location of particle fouling gradually transfers from the blind elbow section to the tee section. [ABSTRACT FROM AUTHOR]

To accurately study the drying characteristics of tobacco strips in the process of redrying, a discrete heaped physical model of tobacco strips is built. Based on this model, a convective drying multiphase porous media model of the heaped tobacco strips is established, which considers the binary diffusion and transport of vapor inside and outside the tobacco leaf. The model is solved using COMSOL Multiphysics, and the accuracy of the model is verified by experiments. The changes in hot air velocity, vapor and moisture content, and evaporation rate in heaped tobacco strips with different thicknesses are analyzed. The results show that: it is feasible to study the drying characteristics of tobacco strips in redrying using a discrete heaped model; there were significant differences in water content, evaporation rate, and temperature in different regions of heaped tobacco strips; the increase in heaping thickness will significantly reduce the uniformity of heat and mass transfer of tobacco strips in the process of convection drying. This model can provide a reference for the study of heat and mass transfer in porous media, such as tobacco strips in the heaping state. [ABSTRACT FROM AUTHOR]

To investigate the influence of thermal effects on the hydrogen desorption performance of the metal hydride hydrogen storage system, a two-dimensional numerical model was established based on a small metal hydride hydrogen storage tank, and its accuracy was verified by the temperature variations in the reaction zone of the hydrogen storage tank during hydrogen desorption. In addition, the influence of the heat transfer medium on the heat and mass transfer performance of the hydrogen desorption reaction was analyzed. An external heat transfer bath was added to simulate the thermal effect of the model during the hydrogen desorption reaction. The temperature and type of heat transfer medium in the heat transfer bath were modified, and the temperature and reaction fraction variations in each zone of the hydrogen storage model were analyzed. The results showed that under heat transfer water flow, the reaction rate in the center region of the hydrogen storage tank was gradually lower than that in the wall region. The higher the temperature of water flow, the shorter the total time required for the hydrogen desorption reaction and the shortening amplitude is reduced. The variations in the temperature and hydrogen storage capacity during hydrogen desorption were similar, with water and oil as the heat transfer medium, under the same flow rate and heat transfer temperature, however, the heat transfer time and hydrogen desorption time of water were about 10% and 5% shorter than that of oil, respectively. When the air was used as the heat transfer medium, the heat transfer rate of the air convection in the channel was lower than the heat transfer rate of the tank wall, reducing the temperature difference between the air and alloy on both sides of the wall, decreasing heat transfer efficiency, and significantly prolonging the time required for hydrogen desorption. [ABSTRACT FROM AUTHOR]

China is a large agricultural country that is leading worldwide in the annual number of agricultural products and exports. However, the growth and harvest of fruits and vegetables are greatly affected by geographical conditions, climate and other factors, which will lead to their rotting in peak season and shortages in the off-season. Therefore, it is necessary to vigorously promote the development of drying technology. The explosion puffing technology at low temperature and high pressure is a kind of compound drying technology which can enable the puffed product to obtain the advantages of honeycomb, good rehydration, a short running time, etc. With the guidance of the theory of heat and mass transfer and relevant thermodynamics laws, this study has established high-pressure extruding technology in low-temperature heating; expanded the two-phase theoretical model, using mass conservation and the law of the conservation of energy to analyze the coupled heat and mass transfer process and influencing factors; and researched the influence of the operation temperature, pressure and time on the properties of dried fruit. [ABSTRACT FROM AUTHOR]

In recent years, growing energy demands and environmental pollution caused by the extensive use of fossil fuels have inspired considerable research interest in adsorptive heat transformation (AHT). This technology offers effective utilization of low-grade solar or waste thermal energy for cooling and heating with low environmental impact. Increasing the AHT power is a keystone for further development and dissemination of this emerging technology. The AHT power is mainly determined by ad/desorption dynamics, which is significantly hindered by slow heat transfer between the adsorbent and heat exchanger. Shaping the adsorbent bed as a coating on the heat exchanger surface is considered an effective route to enhance heat transfer and increase the AHT power. In this review, the technology of adsorbent coating for AHT is comprehensively surveyed, including coating synthesis, adsorption dynamics, and use in real AHT devices. The advantages of the coated bed configuration are considered, and its challenges are outlined. Finally, recommendations for better organization of the coating's structure for rational control of the relative contributions of heat and mass transfer are considered. [ABSTRACT FROM AUTHOR]

A brief review of the development of ideas on extremal principles in the theory of heat and mass transfer processes (including those in reacting media) is given. The extremal principles of non-equilibrium thermodynamics are critically examined. Examples are shown in which the mechanical use of entropy production-based principles turns out to be inefficient and even contradictory. The main problem of extremal principles in the theory of irreversible processes is the impossibility of their generalization, often even within the framework of a class of problems. Alternative extremal formulations are considered: variational principles for heat and mass transfer equations and other dissipative systems. Several extremal principles are singled out, which make it possible to simplify the numerical solution of the initial equations. Criteria are proposed that allow one to classify extremal principles according to their areas of applicability. Possible directions for further research in the search for extremal principles in the theory of irreversible processes are given. [ABSTRACT FROM AUTHOR]

This paper presents a modelling of nanofluid flow using Caputo fractional derivatives through conservative equations of mass and momentum, and provides an exact solution on un-steady convective flow over a vertical plate with the mass diffusion effect, in association with an energy equation. H2O is the base liquid with clay nanoparticles floating in it in a uniform way. Boussinessq's approach is used in the momentum equation for pressure gradient. The non-dimensional fluid temperature, species concentration and fluid transport are derived together with Jacob Fourier sine and Laplace transform techniques in terms of exponential decay function, and the inverse is computed further in terms of the Mittag-Leffler function. The impact of various physical quantities is interpreted with the fractional order of the Caputo derivatives. The obtained temperature, transport and species concentration profiles show behaviors for 0 < α < 1, where α is the fractional parameter. The rate of heat and mass transfer coefficients for the significance of physical quantities of interest are also obtained and presented through graphs. The impact of the nanoparticle volume fraction on the flow field is observed. At larger values of the fractional parameter, the velocity, temperature, and concentration distributions grow more quickly. In addition to that, it is found the concentration profiles behave in the opposite way for the volume fraction of nanofluids. [ABSTRACT FROM AUTHOR]

This paper presents the modelling of heat and moisture transfer in a clothes-conditioning unit with the aim of improving the moisture content distribution to the clothes. A multicomponent, non-reacting, two-phase Eulerian–Eulerian model was utilised to solve the computational model. The clothes inside the conditioning unit were modeled as retangular towels (porous medium) of uniform thickness. Mass flow distribution of air and steam through the clothes was studied by systematically varying the steam nozzle angle (30° to 75°) and air inflow grill angle (45° to 105°). The simulation results were studied to identify the impact of design parameters on the mass flow distribution inside the clothes-conditioning unit. The mass flow of steam and the air–steam mixture were calculated through each towel in the forward and reverse direction. Response surface analysis was conducted to correlate the total mass flow rate and steam mass flow rate through each towel with the design variables. Moreover, a multiobjective genetic algorithm was employed to optimise the mass flow through the clothes and ascertain the optimal design configuration. The geometric configuration with a steam nozzle angle of 45° and air grill angle of 105° resulted in optimal steam and mixture distribution. [ABSTRACT FROM AUTHOR]

A modified class of temporal discretization schemes for partial differential equations (PDEs) is proposed, explicit and second to fifth-order accurate in time. In time, the stability region of the proposed modified second-order scheme is larger than the standard second-order Adams–Bashforth method constructed on two time levels. A modification made for the Du Fort–Frankel method was also implemented in the proposed second-order scheme, which permits the little larger stability region, but the scheme becomes first-order accurate. Since the Du Fort–Frankel method cannot be employed without a modification of averaging in time levels, the proposed second-order scheme can be used without any modification. The proposed modified scheme with different orders in space and second orders in time was implemented for heat and mass transfer of chemically reactive fluid flow in a rectangular duct. The flow is generated due to applying different pressure gradients. The contour plots of velocity, temperature, and concentration profiles are portrayed at different pressure gradients; Péclet number in heat transfer, Péclet number in mass transfer, reaction parameter, and at different times. In addition, stability and convergence conditions for the considered system of linear and non-linear PDEs consisting of non-dimensional momentum, energy, and concentration equations were found for two cases. The displayed graphs depict the transfer of heat in the fluid, which rises due to heated boundaries, and the transfer of mass in the fluid at various moments. Classical models can be solved using the proposed method, which has a faster convergence rate than the standard or classical approach. This approach is illustrated through computer simulations that demonstrate its key computational features. It is believed that the data presented in this study will serve as a useful source for future fluid flow investigations to be conducted in an industrial setting within an enclosed area. [ABSTRACT FROM AUTHOR]

A mechanically pumped two-phase loop (MPTL) system used for the accurate and stable thermal control of orbital heat sources can show excellent characteristics. In order to study the dynamic behaviors of heat and mass transfer of MPTL systems, particularly in response to heat load variations, a transient numerical model was developed by using the time-dependent Navier-Stokes equations. A comparison between the simulation and test results indicated that the errors of mass flow rate were at around ±10%, of which the validity and accuracy were verified. The model was used to study the operating state, and flow and heat characteristics on the basis of the analyses of variations in mass flow rate, temperature, and quality under different operating conditions. Above all, the complex transient behaviors in response to heat load variations in an MPTL system were studied in this model, such as the mass transfer between the accumulator and loop. Results indicate that the phenomenon of mass exchange occurs between the main loop and the accumulator when the heating power increased or decreased. Variations in temperature and pressure in the accumulator were different for the cases of increasing and decreasing power. The slope of the exchange rate curve and the maximal value of the flow rate decreased with the increase in filling amount. The model could be used to guide the design of MPTL systems and to predict the behavior before a system is built. [ABSTRACT FROM AUTHOR]

Utilizing biological processes for hydrogen production via gasification is a promising alternative method to coal gasification. The present study proposes a dynamic simulation model that uses a one-dimensional heat-transfer analysis method to simulate a biohydrogen production system. The proposed model is based on an existing experimental design setup. It is used to simulate a biohydrogen production system driven by the waste heat from an integrated gasification combined cycle (IGCC) power plant equipped with carbon capture and storage technologies. The data from the simulated results are compared with the experimental measurement data to validate the developed model's reliability. The results show good agreement between the experimental data and the developed model. The relative root-mean-square error for the heat storage, feed-mixing, and bioreactor tanks is 1.26%, 3.59%, and 1.78%, respectively. After the developed model's reliability is confirmed, it is used to simulate and optimize the biohydrogen production system inside the IGCC power plant. The bioreactor tank's time constant can be improved when reducing the operating volume of the feed-mixing tank by the scale factors of 0.75 and 0.50, leading to a 15.76% and 31.54% faster time constant, respectively, when compared with the existing design. [ABSTRACT FROM AUTHOR]

A 2-D numerical simulation model was established based on a small-sized metal hydride storage tank, and the model was validated by the existing experiments. An external cooling bath was equipped to simulate the heating effects of hydrogen absorption reactions. Furthermore, both the type and the flow rate of the cooling fluids in the cooling bath were altered, so that changes in temperature and hydrogen storage capacity in the hydrogen storage model could be analyzed. It is demonstrated that the reaction rate in the center of the hydrogen storage tank gradually becomes lower than that at the wall surface. When the flow rate of the fluid is small, significant differences can be found in the cooling liquid temperature at the inlet and the outlet cooling bath. In areas adjacent to its inlet, the reaction rate is higher than that at the outlet, and a better cooling effect is produced by water. As the flow rate increases, the total time consumed by hydrogen adsorption reaction is gradually reduced to a constant value. At the same flow rate, the wall surface of the tank shows a reaction rate insignificantly different from that in its center, provided that cooling water or oil coolant is replaced with air. [ABSTRACT FROM AUTHOR]

A hybrid air conditioning system, which is composed of a novel gravity-assisted heat pipe (GAHP)-based indirect evaporative cooler (IEC) and direct expansion (DX) cooling coil, is proposed and investigated here. After developing a mathematical model to describe the performance of the GAHP-based IEC, the hybrid system is evaluated during the cooling design day for providing thermal comfort for an office building in Poland. The results are obtained and compared with the combination of a rotary heat exchanger (RHE) and DX cooling coil as the conventional hybrid system. The comparison is performed by analyzing cooling capacity, electricity consumption, and coefficient of performance profiles, which describe the technical, energy, and efficiency aspects, respectively. The results show that the GAHP-based IEC hybrid system is able to enhance the energy performance significantly compared to the conventional one. The proposed hybrid HVAC system improves COP by 39.2% and reduces electricity consumption by 45.0%, according to the design-day of 24 August and the outdoor temperature of 30 °C. As a result, the total operating cost for the assumed cooling season is reduced by 51.7%. [ABSTRACT FROM AUTHOR]

In this paper, a plate counter-flow dew-point evaporative cooling system was designed with a nanoporous membrane covered on the surface of the wet channel for enhancement of heat and mass transfer. First, the operating principle of this device and theoretical analysis of nanoporous membrane evaporation were discussed in detail. Then, the impacts of several operating parameters on cooling performance, mainly including inlet air temperature, humidity, velocity, and the effect of utilizing the membrane, were investigated in trials. It was found that the cooling performance can be improved by using membrane significantly. In the dry channel, the maximum temperature decrease can reach 12.5 °C. At a high inlet air temperature, the product air can be dropped to a lower temperature, contributing to a more significant heat transfer process. Lower humidity, on the other hand, resulted in a reduced product air temperature and a lower cooling efficiency. Under the condition of 50% humidity, the wet-bulb efficiency and dew-point efficiency were 1.09 and 0.79, respectively. With the inlet air velocity increasing from 1.5 m/s to 2 m/s, the outlet air temperature would rise, and the wet-bulb efficiency and dew-point efficiency would decrease. To achieve better cooling performance, inlet air velocity ought to be limited to a low speed. [ABSTRACT FROM AUTHOR]

In this paper, the 3-D squeezing flow of viscous incompressible fluid between two parallel plates rotating at the same rate is investigated. The flow is observed under the influence of the varying magnetic field. The flow phenomena are modeled by utilizing the basic governing equations, i.e., equation of continuity, coupled Navier Stokes, and Magnetic Field equations. Using appropriate similarity transformations, the resultant partial differential equations are then transformed into a system of ordinary differential equations. The computational technique is developed via the Homotopy Analysis Method (HAM) to obtain the solution of transformed systems of ordinary differential equations. The influence of several engineering fluid parameters, such as squeeze Reynolds number, magnetic field strength parameter, and magnetic Reynolds number, on velocity and magnetic field components, are observed from different graphs. It has been investigated that by increasing the squeeze Reynolds number, fluid velocity in the y and z directions will be increased as well. On the magnetic field component along the y-axis, an increasing influence of squeezing Reynolds number is also noticed. Similarly, raising the magnetic Reynolds number increases the velocity along the y-axis, whereas the inverse relationship is found for magnetic field components. Furthermore, for each flow phenomenon, an error analysis is also presented. [ABSTRACT FROM AUTHOR]

Maintaining the performance of a fuel cell stack requires appropriate management of water in the membrane electrode. One solution is to apply an external humidifier to the supply gases. However, the operating conditions change continuously, which significantly affects the humidifier performance and supply gas characteristics. A straightforward humidifier module is needed for integration with the fuel cell system model. In this study, a lumped-mass model was used to simulate a hollow-fiber membrane humidifier and investigate the effects of various input conditions on the humidifier performance. The lumped-mass model can account for heat transfer and vapor transport in the membrane bundle without losing simplicity. The humidifier module was divided into three parts: a heat and mass exchanger in the middle and two manifolds at the ends of the exchanger. These components were modeled separately and linked to each other according to the flow characteristics. Simulations were performed to determine the humidifier response under both steady-state and transient conditions, and water saturation was observed in the outlet manifold that may affect the humidifier performance. The findings on the effects of the operating conditions and humidifier dimensions on the cathode gas can be used to improve humidifier design and control. [ABSTRACT FROM AUTHOR]

We investigated the effect of electrolyte thickness and operating temperature on the heat and mass transfer characteristics of solid oxide fuel cells. We conducted extensive numerical simulations to analyze single cell performance of a planar solid oxide fuel cell (SOFC) with electrolyte thicknesses from 80 to 100 µm and operating temperatures between 700 °C and 800 °C. The commercial computational fluid dynamics (CFD) code was utilized to simulate the transport behavior and electrochemical reactions. As expected, the maximum power density increased with decreasing electrolyte thickness, and the difference became significant when the current density increased among different electrolyte thicknesses at a fixed temperature. Thinner electrolytes are beneficial for volumetric power density due to lower ohmic loss. Moreover, the SOFC performance enhanced with increasing operating temperature, which substantially changed the reaction rate along the channel direction. This study can be used to help design SOFC stacks to achieve enhanced heat and mass transfer during operation. [ABSTRACT FROM AUTHOR]

In this work, the problem of hydrodynamic, heat and mass transfer and stability in a salt gradient solar pond has been numerically studied by means of computational fluid dynamics in transient regime. The body of the simulated pond is an enclosure of height H and length L wherein an artificial salinity gradient is created in order to suppress convective motions induced by solar radiation absorption and to stabilize the solar pond during the period of operation. Here we show the distribution of velocity, temperature and salt concentration fields during energy collection and storage in a solar pond filled with water and constituted by three different salinity zones. The bottom of the pond is blackened and the free-surface is subjected to heat losses by convection, evaporation and radiation while the vertical walls are adiabatic and impermeable. The governing equations of continuity, momentum, thermal energy and mass transfer are discretized by finite-volume method in transient regime. Velocity vector fields show the presence of thin convective cells in the upper convective zone (UCZ) and large convective cells in the lower convective zone (LCZ). This study shows the importance of buoyancy ratio in the decrease of temperature in the UCZ and in the preservation of high temperature in the LCZ. It shows also the importance of the thickness of Non-Convective Zone (NCZ) in the reduction of the upwards heat losses. [ABSTRACT FROM AUTHOR]

In the face of increasing demands with regard to the share of renewable energy sources in the energy mix, adsorption chillers are becoming a potentially important part of the energy transition. A key component of this type of equipment is the heat exchanger in the adsorption bed, the design of which affects both heat and mass transfer. This study includes an analysis of the geometry and materials used to manufacture such heat exchangers. The geometry analysis is mainly based on the evaluation of the impact of the different dimensions of the exchanger components on heat and mass transfer in the bed. The second part of the study focuses on material-related issues where the main emphasis is on the analysis of the thermal inertia of the exchanger. The paper analyses the latest research on the design of exchangers in adsorption beds, mainly from 2015–2021. Currently, the commonly used SCP and COP coefficients and various test conditions do not provide sufficient information for comparative analysis of adsorption bed heat exchangers, so the authors propose to introduce a new index for the evaluation of heat exchangers in terms of the effect of the design parameters on the energy efficiency of an adsorption chiller. [ABSTRACT FROM AUTHOR]

Hydrogen purification is an important part of hydrogen energy utilization. This study aimed to perform hydrogen purification of multi-component gas (H2/CO2/CH4/CO/N2 = 0.79/0.17/0.021/0.012/0.007) by one-column vacuum pressure swing adsorption (VPSA) and pressure swing adsorption (PSA). AC5-KS was selected as the adsorbent for hydrogen purification due to its greater adsorption capacity compared to R2030. Furthermore, VPSA and PSA 10-step cycle models were established to simulate the hydrogen purification process using the Aspen Adsorption platform. The simulation results showed that the hydrogen purification performance of VPSA is better than that of PSA on AC5-KS adsorbent. The effects of feeding time and purging time on hydrogen purity and recovery were also discussed. Results showed that feeding time has a negative effect on hydrogen purity and a positive effect on hydrogen recovery, while purging time has a positive effect on hydrogen purity and a negative effect on hydrogen recovery. By using an artificial neural network (ANN), the relationship between the inputs (feeding time and purging time) and outputs (hydrogen purity and recovery) was established. Based on the ANN, the interior point method was applied to optimize hydrogen purification performance. Considering two optimization cases, the optimized feeding time and purging time were obtained. The optimization results showed that the maximum hydrogen recovery reached 88.65% when the feeding time was 223 s and the purging time was 96 s. The maximum hydrogen purity reached 99.33% when the feeding time was 100 s and the purging time was 45 s. [ABSTRACT FROM AUTHOR]

A theoretical model was developed to investigate a falling-film absorber on horizontal tubes with an aqueous alkaline nitrate solution as working fluid. The absorbent, composed of an aqueous solution of nitrates (Li, K, Na) in salt mass percentages of 53%, 28%, and 19% respectively, offers favourable thermal stability, corrosiveness, and heat and mass transfer conditions which can be appropriate for absorption cooling cycles driven by high-temperature heat sources. The mathematical model developed characterises the heat and mass transfer processes and the flow regime effect (droplet-formation, droplet-fall, and falling-film) on the falling-film absorber. The results show the importance of the falling-film and droplet-formation flow regimes in the absorption process. The solution temperature and concentration profiles inside the absorber were established together with their values at the exit. The results obtained by the theoretical model were well in agreement with the experimental data obtained by the authors in a previous study. Deviations in predicting the solution and cooling water temperatures at the absorber exit were around 1 °C and for the concentration of the solution leaving the absorber, around 0.49%. The mathematical model also predicts the absorption rate at 4.7 g·m−2·s−1 for the absorber design and operating conditions used in the present work. This value is 22% higher than the experimental value obtained by the authors in their previous experimental work. The deviation is attributed to approximations incorporated into the model, especially as regards surface wettability and calculation of the mass transfer coefficients for each flow regime. [ABSTRACT FROM AUTHOR]

Solar photovoltaic (PV) applications are gaining a great interest worldwide and dominating the renewable energy sector. However, the solar PV panels' performance is reduced significantly with the increase in their operating temperature, resulting in a substantial loss of energy production and poor economic scenarios. This research contributes to overcoming the PV performance degradation due to the temperature rise. This work involves experimental and theoretical studies on cooling of PV panels using the evaporative cooling (EC) principle. A new EC design to cool the bottom surface of a PV panel was proposed, fabricated, tested, and modeled. A series of experimentation readings under real conditions showed the effectiveness of the method. A steady state heat and mass transfer model was implemented and compared with the experimental data. Fair agreement between the results of the modelling and experimental work was observed. It was found that the temperature of the PV panel can be decreased by 10 °C and the power improvement achieved was 5%. Moreover, the EC helps to stabilize the panels' temperature fluctuation, which results in a better regulation of electrical power output and reduces the uncertainty associated with solar PV systems. [ABSTRACT FROM AUTHOR]

The aircraft ice protection system that can guarantee flight safety consumes a part of the energy of the aircraft, which is necessary to be optimized. A study for the mechanism of the heat load reduction in the thermal anti-icing system under the evaporative mode was presented. Based on the relationship between the anti-icing heat load and the heating power distribution, an optimization method involved in the genetic algorithm was adopted to optimize the anti-icing heat load and obtain the optimal heating power distribution. An experiment carried out in an icing wind tunnel was conducted to validate the optimized results. The mechanism of the anti-icing heat load reduction was revealed by analyzing the influences of the key factors, such as the heating range, the surface temperature and the convective heat transfer coefficient. The results show that the reduction in the anti-icing heat load is actually the decrease in the convective heat load. In the evaporative mode, decreasing the heating range outside the water droplet impinging limit can reduce the convective heat load. Evaporating the runback water in the high-temperature region can lead to the less convective heat load. For the airfoil, the heating power distribution that has an opposite trend with the convective heat transfer coefficient can reduce the convective heat load. Thus, the optimal heating power distribution has such a trend that is low at the leading edge, high at the water droplet impinging limit and zero at the end of the protected area. [ABSTRACT FROM AUTHOR]

A study was conducted on the double diffusion by natural convection because of the effects of heat and pollutant sources placed at one third of the closed cavity's height. The heat and pollution sources were analyzed separately and simultaneously. The study was considered for the Rayleigh number interval 10 4   ≤   R a   ≤   10 10 . Three case studies were analyzed: (1) differentially heated closed cavity with only heat sources; (2) differentially heated closed cavity with only pollutant sources; and (3) differentially heated closed cavity with heat and pollutant sources. The governing equations of the system were solved through the finite volume technique. The turbulence solution was done with the k-ε model. The dominant influence of the buoyancy forces was found due to the pollutant diffusion on the flow pattern, and an internal temperature increase was observed with the simple diffusion. The most critical case was obtained through the double diffusive convection with an average temperature value of 32.57 °C. Finally, the Nusselt number increased as the Rayleigh number increased; however, the Sherwood number either increased or decreased when the Rayleigh number increased. The highest mean concentration recorded was 2808 ppm; this was found with the value R a = 10 6 . [ABSTRACT FROM AUTHOR]

In this numerical study, a direct contact membrane distillation (DCMD) system has been modeled considering various angles for the membrane unit and the Reynolds number range of 500 to 2000. A two-dimensional model developed based on the Navier–Stokes, energy, and species transport equations were used. The governing equations were solved using the finite volume method (FVM). The results showed that with an increase in the Reynolds number of up to 1500, the heat transfer coefficient for all membrane angles increases, except for the inclination angle of 60°. Also, an increase in the membrane angle up to 90° causes the exit influence to diminish and the heat transfer to be augmented. Such findings revealed that the membrane inclination angle of 90° (referred to as the vertical membrane) with Reynolds number 2000 could potentially have the lowest temperature difference. Likewise, within the Reynolds numbers of 1000 and 2000, by changing the inclination angle of the membrane, temperature difference remains constant, however, for Reynolds numbers up to 500, the temperature difference reduces intensively. [ABSTRACT FROM AUTHOR]

Optimal performance parameters must be found in order to organize efficient heat and mass transfer and effective flue gas cooling using a wet scrubber. Mathematical models are widely used for system optimization. However, a significant number of the available models have application limitations. This study presents a universal model for heat and mass transfer simulation in a scrubber called a fog unit, which has been developed and validated. Validation was performed by comparing the experimental and calculated results. Good agreement was achieved among the data, with differences between results not exceeding 10%. The model facilitates an investigation of the effects of gas flow, droplet size, and sprayed water on heat recovery from flue gas. An experimental matrix for fog unit capacity which included five main variables was designed and analyzed. The boundaries of the parameters are set considering the results of the experiments. The optimization method used is the path of the steepest ascent. The obtained results show the parameter change steps to achieve higher capacity of the condenser. In the studied unit, the maximum condenser capacity is limited by a flue gas flow value of 0.01 Nm3/s. The condenser optimization study that was conducted is viewed as a basis for further studies. [ABSTRACT FROM AUTHOR]

The investigation and improvement of the cooling process of lithium-ion batteries (LIBs) used in battery electric vehicles (BEVs) and hybrid electric vehicles (HEVs) are required in order to achieve better performance and longer lifespan. In this manuscript, the temperature and velocity profiles of cooling plates used to cool down the large prismatic Graphite/LiFePO4 battery are presented using both laboratory testing and modeling techniques. Computed tomography (CT) scanning was utilized for the cooling plate, Detroit Engineering Products (DEP) MeshWorks 8.0 was used for meshing of the cooling plate, and STAR CCM+ was used for simulation. The numerical investigation was conducted for higher C-rates of 3C and 4C with different ambient temperatures. For the experimental work, three heat flux sensors were attached to the battery surface. Water was used as a coolant inside the cooling plate to cool down the battery. The mass flow rate at each channel was 0.000277677 kg/s. The k-ε model was then utilized to simulate the turbulent behaviour of the fluid in the cooling plate, and the thermal behaviour under constant current (CC) discharge was studied and validated with the experimental data. This study provides insight into thermal and flow characteristics of the coolant inside a cooing plate, which can be used for designing more efficient cooling plates. [ABSTRACT FROM AUTHOR]

To simulate aircraft thermal anti-icing systems and solve the conjugate heat transfer of air-droplet flow and solid skin, the heat and mass transfer model of the runback water on the anti-icing surface was combined with the heat conduction equation of the skin by loosely coupled methods. According to the boundary conditions used for the runback water conservation equations, two loose-coupling methods for the heat exchange between the runback water and the solid skin were developed based on surface heat flow and surface temperature, respectively. The anti-icing and ice accretion results of a NACA 0012 electro-thermal anti-icing system were obtained by the two loose-coupling methods. The heat flow-based method directly solves the thermodynamic model of the runback water without any extra assumptions, but the convergence rate is relatively slow. On the other hand, the temperature-based method achieves higher calculation speed, but the freezing point is extended to an artificial temperature range between water and ice phases. When the value of the artificial temperature range is small, the results obtained by the temperature-based method are consistent with those of the heat flow-based method, indicating that the effect of freezing point extension can be ignored for thermal anti-icing simulation. Furthermore, the solutions of the two methods are in acceptable and comparable agreement with the experimental and simulative results in the literature, confirming their feasibility and effectiveness. In addition, it is found that the ice thicknesses and ice shapes rise obviously near the runback water limits as a result of the transverse heat conduction of the solid skin. [ABSTRACT FROM AUTHOR]

Current disquisition is presented to excogitate heat and mass transfer features of second grade fluid flow generated by an inclined cylinder under the appliance of diffusion, radiative heat flux, convective and Joule heating effects. Mathematical modelling containing constitutive expressions by obliging fundamental conservation laws are constructed in the form of partial differential equations. Afterwards, transformations are implemented to convert the attained partial differential system into ordinary differential equations. An implicit finite difference method known as the Keller Box was chosen to extract the solution. The impact of the flow-controlling variables on velocity, temperature and concentration profiles are evaluated through graphical visualizations. Variations in skin friction, heat transfer and mass flux coefficients against primitive variables are manipulated through numerical data. It is inferred from the analysis that velocity of fluid increases for incrementing magnitude of viscoelastic parameter and curvature parameter whereas it reduces for Darcy parameter whereas skin friction coefficient decreases against curvature parameter. Assurance of present work is manifested by constructing comparison with previous published literature. [ABSTRACT FROM AUTHOR]

In the present work, the effects of different operating parameters on the performance of a gravity-assisted heat pipe-based indirect evaporative cooler (GAHP-based IEC) were investigated. The aim of the theoretical study is to evaluate accurately the cooling performance indicators, such as the coefficient of performance (COP), wet bulb effectiveness, and cooling capacity. To predict the effectiveness of the air cooler under a variety of conditions, the comprehensive calculation method was adopted. A mathematical model was developed to simulate numerically the heat and mass transfer processes. The mathematical model was validated adequately using experimental data from the literature. Based on the conducted numerical simulations, the most favorable ranges of operating conditions for the GAHP-based IEC were established. Moreover, the conducted studies could contribute to the further development of novel evaporative cooling systems employing gravity-assisted heat pipes as efficient equipment for transferring heat. [ABSTRACT FROM AUTHOR]

Spray cooling is widely used in relieving heat stress in dairy cows during summer, in which the cooling effect is highly correlated to the diameter of water droplet. To optimize the average diameter of spraying droplet (ADSD) in the process of heat transfer, a theoretical analysis was performed based on the enthalpy difference theory in this study. A platform was built to simulate the processes of spray cooling and its heat stress alleviation to dairy cows in field, and a field experiment was applied to verify the diameter of water droplets suitable for spray cooling. Heat exchange was calculated for eighteen different ADSD in three different environment conditions in the laboratory. The spraying droplets with eighteen diameters were formed by using six different nozzles under the combinations of three pressures and two wind speeds conditions, which were controlled by heaters. The relationship between the ADSD and heat exchange was established with the purpose to determine the appropriate diameter for practical production. In the field test, body temperature, rectal temperature, and respiratory rate of dairy cows were monitored, and the heat exchange was analyzed to verify the optimal diameter spraying cooling in summer. Results showed that the heat exchange generally increased as ADSD increased, and maximum heat exchanges were reached when the ADSD was averaged at 0.914 mm and 0.995 mm, under which the models of the corresponding nozzles were 9080 and 9010, respectively. After that, the heat exchange decreased as the ADSD continued to increase. Field experiment indicated that the best cooling effect could be achieved with the ADSD of 0.947 mm, and the water consumption for spray cooling was reduced by 22.8% under the scenario. [ABSTRACT FROM AUTHOR]

This paper presents a comparative study of the cross-flow regenerative heat and mass exchanger (HMX) and the conventional cross-flow HMX for indirect evaporative cooling (IEC) with numerical methods. The objective of this study is mainly to clarify the applicability of the two HMXs. The numerical model was built and validated by existing experimental data. The difference in heat and mass transfer between the two HMXs was revealed by analyzing the change of the temperature and moisture content of the air, and the influence of the main operating parameters on the cooling performance of the HMXs was analyzed. In the typical operating conditions, when the HMXs are used alone, the cooling performance of the regenerative HMX is better than that of the conventional HMX under low supply air flow rate. When the HMXs are used in the multistage evaporative cooling systems with high supply air flow rate, the conventional HMX is more suitable as the first stage of the system to pre-cool the supply air, while the regenerative HMX is more suitable as the second stage to re-cool the supply air. [ABSTRACT FROM AUTHOR]

This Editorial provides an introduction to and an overview of the special issue "Electric Fields in Energy and Process Engineering". [ABSTRACT FROM AUTHOR]

Heat and mass transfer as well as chemical reactions in technical processes can be enhanced by using electric fields. This paper provides an overview of current fundamental and applied research as well as potential technical applications of electric fields in energy and process engineering. This includes electrosprays, technical combustors as well as electrochemical reforming and plasma gasification of waste or biomass. Other emerging fields are plasma technologies for treatment of water, surfaces and gases including flue gases. In particle or aerosol-laden flows, plasmas are used to promote particle nucleation and surface growth for controlled nanomaterial synthesis. Furthermore, non-invasive diagnostics based on electromagnetic fields and electric fluid properties are relevant techniques for online control and optimization of technical processes. Finally, an overview of laser-based techniques is provided for studying electro-hydrodynamic effects, temperature, and species concentrations in plasma and electric-field enhanced processes. [ABSTRACT FROM AUTHOR]