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• The v shape pressure reflects interaction relations among 3 thermodynamic mechanisms. • FFC reflect the intensity and rate of progress of flash at unique start stage. • The factors influencing flash rate and intensity are analyzed. • FFC rises with initial temperature and valve opening degree at unique start stage. • Expanders with larger outlet area or higher working temperature have larger flash intensity. Our experiments showed that a V shape pressure drop appeared at start stage of non-equilibrium flash. V shape pressure drop firstly denoted the generating of superheat degree, which should be the starting force driving the non-equilibrium flash. Then evaporated vapor made up the pressure drop. Finally, a dynamic equilibrium was reached between the flash rate and the outflow rate, and the pressure behaved decreasing gradually. However, few published references focus on this start stage of the non-equilibrium flash. In this paper, experiments of the flash were conducted to investigate the heat and mass characteristics during V shape start stage. Dimensionless flash conversion coefficient (FCC) was proposed to normalize the flash with different initial liquid mass at start stage. The effects of initial temperature and the valve opening degree on the heat and mass characteristics of flash during the V drop start stage were studied. The results showed that the pressure of the working fluid changed dramatically during the V drop start stage. The peak of instant liquid superheat was proportional to the opening degree of the valve, which controlled the outflow rate. The flash rate increased with increasing initial temperature and valve opening degree, which had an approximately linear relationship with the flash time. FCC increased with valve opening degree. It could be deduced that flash intensity or flash rate would be higher for an expander with larger outlet area or higher working temperature. [ABSTRACT FROM AUTHOR]

This paper discusses the effect of temperature polarization in Vacuum Membrane Distillation (VMD). The main motivation for using VMD in this work is that this module configuration is much simpler and more suitable for this kind of investigation than the other MD configurations such as Direct Contact Membrane Distillation (DCMD). The coupling between heat and mass transfer mechanisms at the feed-membrane interface is presented from a theoretical point of view. In addition, a new simple graphical method and a mathematical model for determining VMD flux are presented. The two methods used in evaluating the extent of temperature polarization effect on water vapor flux (flux sensitivity factors and temperature polarization coefficient (TPC)) are also analyzed and compared. The effect of integrating a heat recovery system in a large scale module on the TPC coefficient has also been studied and presented in this paper. [ABSTRACT FROM AUTHOR]

Water huff-n-puff technology is an effective method of enhancing oil recovery in ultra-low permeability reservoirs. However, due to the different temperatures between injection water and the reservoir, the water huff-n-puff inevitably causes the change in reservoir temperature, further affecting oil production. Based on the modified embedded discrete fracture model method, this paper proposes a coupled solution framework of temperature field and flow field considering the complex mass transfer and heat transfer mechanism. Compared with the traditional EDFM method, this method has higher calculation accuracy and more complex coupling mechanisms. The influence degree of five thermal influence mechanisms on oil production is quantified and analyzed, including thermal viscosity reduction, thermal expansion, stress sensitivity considering thermal stress, fracture width change, and change of relative permeability curve with temperature. When the injection temperature is lower than the reservoir temperature, the three mechanisms of thermal viscosity reduction, thermal expansion, and the change of relative permeability curve with temperature have significant adverse effects on oil production. The mechanism simplification strategy of the numerical simulation of the actual model is given, which improves the simulation efficiency. The proposed simulation framework and simplification method have reasonable practicability. This work provides a valuable reference for water huff-n-puff. • An modified EDFM method is proposed considering complex thermal mechanisms. • Quantify the influence degree of different injection temperature effects. • A simplified approach to complex mechanisms to accelerate simulation. [ABSTRACT FROM AUTHOR]

Abstract: This paper aims at developing an analytical model for the coupled heat and mass transfer processes in a counterflow Reversibly Used Cooling Tower (RUCT) based on operating conditions, which is more realistic than most conventionally adopted Merkel approximations. Temperature and moisture content differences are chosen as the driving forces of heat and mass transfer correspondingly and a system of specific difference equations is developed to solve the model more efficiently. The model is investigated by using an iterative algorithm, which is validated with the experimental data reported. The analytical model also accommodates the direct and quick calculation of air and water temperature profiles, moisture content of air and the water mass flow rate change along the vertical length of the RUCT. With the aid of the developed model, the thermal behavior of the counterflow RUCT under various operating and environmental conditions is also studied in this paper. The results reveal that the proposed model can provide a theoretical foundation for practical design and performance evaluation of counterflow RUCT. [Copyright &y& Elsevier]

Abstract: This paper presents a new analytical solution of heat and mass transfer processes in a packed bed liquid desiccant dehumidifier based on the equilibrium humidity on the interface is assumed to be constant. In order to maintain the partial pressure difference on the interface, a high liquid desiccant flow rate is often applied in the practical absorber. Therefore, for a narrow range of operating conditions for practical dehumidification process, we can assume that the equilibrium humidity ratio on the interface is constant. The assumption of constant humidity ratio is applied in this paper for derivation of the analytical solution. The model and the analytical solution predictions were compared against a reliable set of experimental data available in the literature, with very good agreement. According to the Lewis definition in this present study, the Lewis number obtains 0.9. The effects of variables such as air and liquid desiccant flow rate, air temperature and humidity, desiccant temperature and concentration have been investigated on the condensation rate. The results present that design variables such as desiccant concentration, desiccant temperature, air flow rate, and air humidity ratio have the greatest impact on the performance of the dehumidifier. The liquid flow rate and the air temperature have not a significant effect. Furthermore, the effects of air and liquid desiccant flow rate have been reported on the humidity effectiveness of the column. [Copyright &y& Elsevier]

This paper presents experimental tests and theoretical analysis on coupled heat and mass transfer characteristic of a compressed air drying system using liquid desiccant proposed in our previous work. The minimum possible humidity ratio of the processed compressed air can reach 0.11 g/kg under 0.80 MPa, which can satisfy demand of various industrial applications. Effects of operation parameters of the packed dryer on heat and mass transfer coefficients are obtained based on the experimental data and mathematical model. It is found that heat and mass transfer coefficients between compressed air and solution could be remarkably enhanced by increasing the air pressure, compressed air velocity and solution concentration while the influence of solution temperature is negative linearly. Reliable heat and mass transfer coefficients are provided for optimum design of pressurized air dryers, which is also meaningful to understand the heat and mass transfer behavior between compressed air and liquid desiccant. [ABSTRACT FROM AUTHOR]

The combined heat and mass transfer mechanisms owing to the temperature and humidity ratio differences and their influence on the efficiency of different exponential type porous fin configurations are analyzed in this paper. The closed-form temperature solutions for an exponential impermeable dry fin as obtained in an earlier publication (Turkyilmazoglu, 2012) are extended here to the case where the surface of the fin is fully wet and porous. A comparison with the traditional straight porous fins proves that the fin tip temperature and efficiency of the exponential porous wet fins are much better than those of corresponding to the straight porous wet fins. [ABSTRACT FROM AUTHOR]

In this paper we report the extension of an earlier reported DNS method (Deen et al., 2012; Deen and Kuipers, 2013) based on a novel Immersed Boundary Method (IBM) which incorporates the fluid-solid coupling at the level of the discrete field equations. The extended method is used to study coupled mass and heat transport in dense fluid-particle systems where the coupling arises as a consequence of an exothermal chemical reaction proceeding at the exterior surface of the particles. Following a detailed verification (using an independent numerical technique) and validation (using established empirical correlations) we apply our DNS technique to study coupled mass and heat transfer in a dense fluid-particle system. In addition a comparison is made with results obtained from a simple one-dimensional (1D) heterogeneous reactor model which uses empirical closures for the fluid-particle mass and heat transfer coefficients. The main features of the complex transient temperature profiles obtained from our DNS agree quite well with the corresponding profiles obtained from the 1D heterogeneous reactor model. [ABSTRACT FROM AUTHOR]

Abstract: An increased interest in absorption chillers has been observed [1] because these systems can utilize solar, geothermal and biomass energy sources, but also because they are quiet, vibration-free, require little maintenance and are ecological [2]. Instead of a compressor system, which uses electricity, an absorption cooling system, using renewable energy and kinds of waste heat energy, may be used for cooling. This paper presents the simulation of a single stage solar absorption chiller operating with an ammonia–water mixture under steady state conditions. This simulation is based on heat and mass balances for each component. The heat and mass transfers in the absorber, the condensation of binary vapor of ammonia–water in the condenser and a thermosyphon desorber placed under the purification column were modeled. The numerical model was compared and validated with experimental data obtained with a solar absorption chiller. The calculated results agree well with experimental data. Simulations based on experimental data were used to predict the temperature and concentration profiles in each heat exchanger. A parametric study was conducted to investigate the effect of evaporator and desorber temperature on the absorption chiller's performance. The COP decreases by 25% with a decrease of 10 °C in evaporator temperature and the COP increases by 4% with an increase of 10 °C in desorber temperature. [Copyright &y& Elsevier]

Abstract: An understanding of the complex phenomena involved in droplet combustion, such as two-phase flows and heat/mass transfer, is a necessary step towards improving combustion efficiency and reducing pollutant emissions. This paper is focused on an analysis of the droplet temperature evolution across the flame front in two-phase flow systems. In this experiment, the flame was stabilized on a rod at atmospheric pressure and the fuel was liquid at injection, which implies the presence of fuel droplets close to the flame front. However the flame was partially premixed because part of the fuel vaporized quickly and contributed to the stabilization of the flame. The configuration was two-dimensional and so called “V-shape” flame. Two different flow conditions were investigated: a pseudo-laminar flow as the reference case (R) and a low-turbulence level flow (LT). The evolution of the mean fuel droplet temperature across the flame brush was quantified. The shape of the fuel droplet temperatures histogram became clearly bimodal for high values of the mean progress variable , indicating the presence of droplets in the measurement volume that were heated up by the burnt gases and the flame. The temperature evolution and the statistics across the flame front can be used to compare the numerical and the physical models applied to two-phase combustion. [Copyright &y& Elsevier]

Abstract: The objectives of this paper is to report the development and validation of a computational fluid dynamics (CFD) modeling approach to predict heat transfers in arbitrary randomly packed tubular reactors. The capacity of the packed beds to supply or remove heat from the core to the tube walls is indeed critical for the performance of reactors involved in various chemical applications of catalytic reactions. The understanding of the physical mechanisms and the modeling of turbulent heat and mass transfer is thus essential for the design, optimization and scale-up of fixed-bed reactors. For this objective, the heterogeneous catalyst bed can be represented by a macroscopic or homogeneous one where turbulence does exist at the small scales. In this study, an up-scaling approach is considered where the volume averaging procedure is used to derive the macroscopic equations. The flow and turbulent variables are decomposed according to the double decomposition concept within the framework of the volume averaging method. In particular, the dispersive kinetic energy is considered for the modeling of the thermal dispersion term appearing in the macroscopic temperature equation with a k–ε approach. The model is extended for the prediction of the channeling effects near the tube walls. The closure approximations are validated with microscopic simulations performed at the scale of representative elementary volume and comparisons with macroscopic simulations. Several packed bed configurations are considered, and the model predictions for the core heat transfer and the wall heat transfer are also compared to usual correlations when available. The microscopic simulations performed for various particle shapes are also confirming the predominant contribution of the mechanical dispersion to the convective heat transfer. This study is demonstrating the feasibility to predict the global heat transfer inside arbitrary tubular reactors with simple macroscopic simulations as an alternative to complex and computationally expensive microscopic simulations, out of the range of usual engineering tasks. [Copyright &y& Elsevier]

Abstract: In this paper we investigate the flow and heat transfer of a Jeffrey fluid near the stagnation point on a stretching/shrinking sheet with a parallel external flow. The main concern is to analytically investigate the structure of the solutions which might be unique or multiple. It is shown that structure of the solutions strongly depends on a parameter measuring the ratio of strength of the external flow to surface stretching/shrinking, we name it as stretching strength parameter. When this parameter is set to zero, the solutions evolve into the multiple/triple solutions already given in Turkyilmazoglu (2011) [1,2]. For other values, closed-form formulae for the boundary layer equations of the flow are presented for the Jeffrey fluid. Heat transfer analysis is also carried out for a boundary heating process taking into consideration both a uniform wall temperature and a linearly increasing wall temperature. The flow field is found to be influenced by the presence of physical parameters, stretching/shrinking strength, Deborah number and suction/injection parameters, whereas the temperature field is additionally affected by Prandtl number. The velocity/temperature profiles and skin friction coefficient/Nusselt number are easy to conceive from the exact formulas presented, which also provide benchmark for testing other numerical schemes. [Copyright &y& Elsevier]

Abstract: The present paper proposes a sub-model for two-layer zone models to describe heat and mass transfer across the interface between the upper and lower layers as a result of the temperature difference between the two layers. The sub-model is integrated into a two-layer zone fire growth and smoke movement model, which now can predict both pre- and post-flashover fires. The comparison of the numerical predictions of the improved model and experimental data shows that the improved model produces better temperature and heat release rate predictions for both pre- and post-flashover fires than the previous model. Compared with hybrid models consisting of a two-layer zone model and a single-layer zone model, the improved model has no transitional difficulties in switching from the pre- to the post-flashover state and it produces more reasonable temperature gradients for post-flashover fires. [Copyright &y& Elsevier]

Abstract: This paper describes a dynamic model of transient heat and mass transfer across a green roof component. The thermal behavior of the green roof layers is modeled and coupled to the water balance in the substrate that is determined accounting for evapotranspiration. The water balance variations over time directly impact the physical properties of the substrate and the evapotranspiration intensity. This thermal and hydric model incorporates wind speed effects within the foliage through a new calculation of the resistance to heat and mass transfer within the leaf canopy. The developed model is validated with experimental data from a one-tenth-scale green roof located at the University of La Rochelle. A comparison between the numerical and the experimental results demonstrates the accuracy of the model for predicting the substrate temperature and water content variations. The heat and mass transfer mechanisms through green roofs are analyzed and explained using the modeled energy balances, and parametric studies of green roof behavior are presented. A surface temperature difference of up to 25°C was found among green roofs with a dry growing medium or a saturated growing medium. Furthermore, the thermal inertia effects, which are usually simplified or neglected, are taken into account and shown to affect the temperature and flux results. This study highlights the importance of a coupled evapotranspiration process model for the accurate assessment of the passive cooling effect of green roofs. [Copyright &y& Elsevier]

Abstract: The simple clay-pot refrigerator is ideally suited for preserving vegetarian foods in hot and dry climates. The refrigerator works on the evaporative cooling principle. In this paper, steady-state performance of the refrigerator is analysed using Reynolds flow model of convective heat/mass transfer. For the assumed respiratory cooling load, the preservation temperature is predicted under a variety of ambient temperatures and relative humidities. [Copyright &y& Elsevier]

Abstract: This paper reports our efforts to engineer a robust, user-friendly, and broadly tunable helium droplet nozzle, and to quantitatively measure its thermal and mass transport performance. In addition to describing the physical design in detail, we report helium throughput measurements for a 6.4μm diameter nozzle over stagnation conditions ranging from 5 to 50K and 10 to 100bar. The measured flow rates were in excellent agreement with those predicted by a simple effusive flow model for nozzle temperatures above 20K, but were systematically lower for both sub-critical and super-critical jets as the temperature was lowered. The helium flow through a 500μm skimmer was also measured, and the skimmed fraction was found to vary by two orders of magnitude over the range of stagnation conditions investigated. These results indicate a substantial narrowing of the total jet angle spread from ∼90° to 5° at temperatures below 10K. Efforts to image the low temperature jet with Schlieren and shadowgraph techniques were unsuccessful. These details combined with previously reported theory and experiments on the droplet size distributions provide the necessary foundation to predict cluster production rates and to customize nozzle/pump designs for specific applications. [Copyright &y& Elsevier]

Abstract: Enhancement of heat or mass transport from a spherical drop of a dielectric fluid translating in another dielectric fluid in the presence of steady and time periodic electric fields (both uniform and non-uniform) is investigated in this paper. The external problem or the limit of the majority of the transport resistance being in the continuous phase is considered. Using a finite volume formulation, the transient energy (species) conservation equation is solved for Peclet numbers (Pe) varying from 10 to 1000 and dimensionless electric field frequency (ω ∗) from 10 to 50,000 using a fully implicit method. To map the infinite domain in the radial direction, an exponential transformation is employed that provides a fine grid spacing near the drop surface where sharp variations are expected and a coarser grid in the far field where low gradients prevail. The transient temperature distribution and the local and the average Nusselt numbers are obtained and the heat/mass transfer enhancement due to the application of electric field is determined. The effect of electric field is expressed in terms of L, the ratio of the maximum electric-field-induced surface velocity to the translation-induced surface velocity. For the steady and time-periodic electric fields, the heat transfer enhancement increases monotonically with Pe and with L. Also, the heat transport rate is higher when the continuous phase is more viscous compared to the dispersed phase. The steady uniform electric field gives the highest average Nusselt number for heat transfer from the drop surface to the continuous phase, followed by the non-uniform time periodic electric field and then the time periodic uniform electric field. The enhancement relative to pure translation exhibits a non-monotonic dependence on electric field frequency but the highest value is obtained at ω ∗ =0. Earlier studies have shown that there is significant enhancement in the heat/mass transfer in the drop interior with a time periodic electric field compared to a steady uniform electric field when the majority of the transport resistance is in the drop. The results presented here show that an opposite behavior is obtained in the drop exterior , i.e. a steady electric field provides higher heat/mass transfer enhancement compared to a time periodic electric field, when the bulk of the transport resistance is in the continuous phase. Therefore whether the steady or the time periodic electric field provides the most enhancement of heat/mass transfer for a conjugate problem will depend on the relative transport resistance in the two phases. [Copyright &y& Elsevier]

Abstract: Axially rotating heat pipes are devices used to dissipate heat flux through the latent heat of phase change of a fluid at saturation state. In these systems, centrifugal forces due to heat pipe rotation allow the liquid to flow. The present study focuses on cylindrical heat pipes due to the simplicity and cost of the manufacturing of theses devices. This paper presents a steady-state model of heat and mass transfers along the rotating heat pipe. An optimization procedure, which permits to work at a given saturation temperature and so allows to study the parameters influence for given thermophysical properties, has been developed to perform the calculations. The hypotheses of the model are also discussed and examined. Finally, a parametric study has been carried out, using water as a working fluid, to highlight the influence of parameters such as rotational speed, temperature difference between the evaporator wall and the vapour, or the mass of fluid, on the heat transfers. Finally, the operating conditions conducive to maximal performance have been described. [Copyright &y& Elsevier]

Abstract: We study a steady laminar 2-D MHD viscous incompressible flow over a permeable flat plate with thermal convective boundary condition and radiation effects. The viscosity and thermal conductivity of fluid are assumed to vary linearly with temperature. Similarity representation of the governing partial differential equations is obtained via group method. Similarity equations are then solved numerically by implicit finite difference technique. Effects of convective heat transfer parameter (b), radiation parameter (R,) magnetic field parameter (M), the thermal conductivity parameter (S), suction parameter (fw), Prandtl number (Pr) and Schmidt number (Sc) on the dimensionless axial velocity, temperature, concentration, wall temperature, the rate of heat transfer and the rate of mass transfer are investigated. Good agreement is found between the numerical results of the present paper with published result for special case. [Copyright &y& Elsevier]

Abstract: In this paper we investigate the magnetohydrodynamic slip flow of an electrically conducting, viscoelastic fluid past a stretching surface. The main concern is to analytically investigate the structure of the solutions and determine the thresholds beyond which multiple solutions exist or the physical pure exponential type solution ceases to exist. In the case of the presence of multiple solutions, closed-form formulae for the boundary layer equations of the flow are presented for two classes of viscoelastic fluid, namely, the second-grade and Walter’s liquid B fluids. Heat transfer analysis is also carried out for two general types of boundary heating processes, either by a prescribed quadratic power-law surface temperature or by a prescribed quadratic power-law surface heat flux. The flow field is affected by the presence of physical parameters, such as slip, viscoelasticity, magnetic and suction/injection parameters, whereas the temperature field is additionally affected by thermal radiation, heat source/sink, Prandtl and Eckert numbers. The regions of existence or non-existence of unique/multiple solutions sketched by the combination of these parameters are initially worked out by providing critical values and then velocity/temperature profiles and skin friction coefficient/Nusselt number are examined and discussed. [Copyright &y& Elsevier]

Abstract: Prefabricated, lightweight building elements are widely used in the building construction sector. Such elements consist of fibrous thermal insulation encapsulated between two metal sheets. Under various circumstances, moisture can appear in the insulation matrix. Since the temperature of the boundary metal sheets changes dynamically with meteorological conditions, heat and mass transfer between boundaries appear in this case. This paper presents a transient model of the heat and mass transfer, including the sorption and condensation processes. A numerical model considers the dynamical changing of the boundary temperatures. A parametric study considering different amplitudes of temperature change, different moisture masses and different thicknesses of the insulation matrix was made. It was found that a relatively small mass of water in the insulation matrix can result in a significantly increased average heat flux during a periodic cycle. The numerical code was verified with experiments, which showed good agreement with the numerics. [Copyright &y& Elsevier]

Abstract: In the present work a three-dimensional analysis is used to study the heat transfer characteristics of a double-tube helical heat exchangers using nanofluids under laminar flow conditions. CuO and TiO2 nanoparticles with diameters of 24nm dispersed in water with volume concentrations of 0.5–3vol.% are used as the working fluid. The mass flow rate of the nanofluid from the inner tube was kept and the mass flow rate of the water from the annulus was set at either half, full, or double the value. The variations of the nanofluids and water temperatures, heat transfer rates and heat transfer coefficients along inner and outer tubes are shown in the paper. Effects of nanoparticles concentration level and of the Dean number on the heat transfer rates and heat transfer coefficients are presented. The results show that for 2% CuO nanoparticles in water and same mass flow rate in inner tube and annulus, the heat transfer rate of the nanofluid was approximately 14% greater than of pure water and the heat transfer rate of water from annulus than through the inner tube flowing nanofluids was approximately 19% greater than for the case which through the inner and outer tubes flow water. The results also show that the convective heat transfer coefficients of the nanofluids and water increased with increasing of the mass flow rate and with the Dean number. The results have been validated by comparison of simulations with the data computed by empirical equations. [Copyright &y& Elsevier]

Abstract: In Tarzia, Int. Comm. in Heat and Mass Transfer, 25 (1998), 139–147, explicit formulas for the simultaneous determination of unknown thermal coefficients of a semi-infinite material through a phase-change process with temperature-dependent thermal conductivity were obtained. Moreover, ten different cases were studied: four cases of free boundary problems (i.e. Stefan-like problems) and six cases of moving boundary problems (i.e. inverse Stefan-like problems). The goal of this paper is to obtain a numerical sensitivity analysis of the mentioned ten cases for the simultaneous determination of unknown thermal coefficients and to determine the coefficients which are more sensitive with respect to the given parameters. We show numerical result for the aluminum. [Copyright &y& Elsevier]

Abstract: In this paper, the shortage effect of neglecting heat and mass transfer phenomena in mathematical descriptions of pressure drop through venturi scrubbers is studied. For this purpose, a descriptive model is presented with particular emphasis on the mass and energy equations. There is a correction factor introduced, for the first time, and correlated to improve the model predictions in the divergent section. The results indicate that pressure drop prediction is greatly affected by the simplified assumptions of the existing models. In fact, the occurrence of heat and mass transfer phenomena between two phases decreases the pressure drop intensively. Therefore, neglecting the undeniable effects of these phenomena will lead to some large errors. These errors are enhanced in higher gas temperatures, liquid, and gas flow rates, but the gas humidity has a negligible effect. [Copyright &y& Elsevier]

Abstract: This paper deals with the heat and mass transfer characteristics of humid air-flow under frosting conditions. A slit fin bundle was used for the simulation of fins of a heat exchanger. The effects of the cooling block temperature, air humidity and air velocity on the frosting characteristics were experimentally investigated. The frosted mass was affected considerably by the cooling block temperature and air humidity. However, the effect of air velocity on it was not so large. The pressure drop was affected remarkably by all experimental parameters in this study. Local heat flux distribution and frost thickness distribution on each fin were predicted from the measured fin temperatures and the mass and energy conservation equations on the frost surface and inside the frost layer. [Copyright &y& Elsevier]

Abstract: Analytical solutions for evaluating the thermal performances of both chilled water wet cooling coils and direct expansion (DX) wet cooling coils, respectively, under both unit and non-unit Lewis Factors are developed and reported in this paper. The analytical solution was validated by comparing its predictions with those from numerically solving the fundamental governing equations of heat and mass transfer taking place in a wet cooling coil. With the analytical solutions, the distributions of air temperature and humidity ratio along air flow direction in a wet cooling coil can be predicted, and the differences in the thermal performances of the cooling coils under both unit and non-unit Lewis Factors can be identified. The analytical solutions, on one hand, can be a low-cost replacement to numerically solving the fundamental heat and mass transfer governing equations, and on the other hand, is able to deal with evaluating thermal performance for wet air cooling coils operated under both unit and non-unit Lewis Factors. [Copyright &y& Elsevier]

Abstract: In this paper, a numerical investigation of two-dimensional coupled heat and mass transfer during desorption of hydrogen in a cylindrical metal hydride reactor containing MmNi6.4Al0.4 is presented. By considering the variation in heat transfer fluid temperature along the axial direction (variable wall temperature boundary condition), the changes in hydride bed temperature at different axial locations are presented. The effect of variable wall temperature boundary condition on hydrogen desorption rate for different hot fluid temperatures and hydride bed thicknesses is investigated. The rate of hydrogen desorption at different hot fluid temperatures showed good agreement with the experimental data reported in the literature. As the desorption progresses, the change in heat transfer fluid temperature along the axial direction is found to decrease with time and becomes unchanged at the end of the process. The effect of variable wall temperature boundary condition on desorption time is found to be significant for the hydride bed thicknesses of about 7.5mm and more. For a given bed thickness of 17.5mm, the maximum difference in desorption time between variable wall and constant wall temperature convective boundary conditions is about 375s at 303K. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we investigate the effects of thermophoresis on the forced convective laminar flow of a viscous incompressible fluid due to a rapidly rotating disk whose surface temperature is lower than the temperature of its surrounding fluid. The governing equations of continuity, momentum, energy and concentration are transformed using similarity analysis, and the solutions are obtained through numerical techniques. The results show that if the thermophoretic coefficient increases, thermophoretic velocity increases and it intensifies significantly when the relative temperature difference parameter increases. The results also show that axial particle deposition velocity increases as the thermophoretic coefficient as well as Schmidt number increases. [Copyright &y& Elsevier]

Abstract: The prediction of heat and mass transfer in fuel sprays is a key issue in the design of combustors where the fuel is injected in a liquid form. The development and validation of new physical models requires reliable experimental data. This paper reports on an experimental study to characterize the Nusselt and Sherwood numbers of monodisperse droplets made of fuels having different volatilities and evaporating into flowing hot air. Simultaneous measurements of the droplet size and mean temperature allowed evaluating the heat fluxes that take part in the evaporation. The experimental Nusselt and Sherwood numbers are then compared to the case of an isolated droplet. It appears that these numbers are particularly dependent on the interactions between the droplets in a way that depends on the fuel nature. [Copyright &y& Elsevier]

Abstract: This paper discusses the performance investigations of a single-stage metal hydride heat pump (SS-MHHP) working with five different alloy pairs, namely, MmNi4.6Al0.4/MmNi4.6Fe0.4, LaNi4.61Mn0.26Al0.13/La0.6Y0.4Ni4.8Mn0.2, LmNi4.91Sn0.15/Ti0.99Zr0.01V0.43Fe0.09Cr0.05Mn1.5, LaNi4.6Al0.4/MmNi4.15Fe0.85 and Zr0.9Ti0.1Cr0.9Fe1.1/Zr0.9Ti0.1Cr0.6Fe1.4. The performance of the system is predicted by solving the unsteady, two-dimensional coupled heat and mass transfer processes in metal hydride bed of cylindrical configuration using a fully implicit finite volume method. The influences of operating temperatures such as heat source (T H), heat sink (T M) and refrigeration (T C) temperatures on the coefficient of performance (COP) and specific cooling power (SCP) of the system are presented. The predicted hydride bed temperature profiles are compared with the experimental data reported in the literature and a reasonably good agreement is observed between them. The optimum operating temperature ranges of each pair of alloys are suggested. For the selected operating temperatures, a maximum COP of 0.66 is predicted for Zr0.9Ti0.1Cr0.9Fe1.1/Zr0.9Ti0.1Cr0.6Fe1.4 hydride pair, while LmNi4.91Sn0.15/Ti0.99Zr0.01V0.43Fe0.09Cr0.05Mn1.5 hydride pair produces the highest SCP of 53.25W/kg of total mass of the system. [Copyright &y& Elsevier]

Abstract: In this paper, heat and mass transfers in a high-pressure water–gas system with a clear water–gas interface are modeled, and the concept of a pseudo-deformable heat structure is described. The model of the pseudo-deformable heat structure and water vapor bulk condensation under nearly saturated conditions has two distinguishing features. First, the heat structure contacting a deformable fluid volume is modeled as if it deforms along with the deformable fluid; due to this feature, the exact average temperature of the heat structure can be predicted. Second, the rate of change of water vapor mass in the gas dome under nearly saturated conditions is determined by a differential equation derived from the Gibbs free energy function. Then, the rate of bulk condensation is determined from the water vapor mass conservation in the gas dome. The proposed model was partially validated by comparison with the results of the MARS3.1 accumulator model at low temperature conditions. [Copyright &y& Elsevier]

Abstract: The terminology Novel Process Window unites different methods to improve existing processes by applying unconventional and harsh process conditions like: process routes at much elevated pressure, much elevated temperature, or processing in a thermal runaway regime to achieve a significant impact on process performance. This paper is a review of parts of IMM’s works in particular the applicability of above mentioned Novel Process Windows on selected chemical reactions. First, general characteristics of microreactors are discussed like excellent mass and heat transfer and improved mixing quality. Different types of reactions are presented in which the use of microstructured devices led to an increased process performance by applying Novel Process Windows. These examples were chosen to demonstrate how chemical reactions can benefit from the use of milli- and microstructured devices and how existing protocols can be changed toward process conditions hitherto not applicable in standard laboratory equipment. The used milli- and microstructured reactors can also offer advantages in other areas, for example, high-throughput screening of catalysts and better control of size distribution in a particle synthesis process by improved mixing, etc. The chemical industry is under continuous improvement. So, a lot of research is being done to synthesize high value chemicals, to optimize existing processes in view of process safety and energy consumption and to search for new routes to produce such chemicals. Leitmotifs of such undertakings are often sustainable development and Green Chemistry. [Copyright &y& Elsevier]

Abstract: This paper presents an improvement of the scroll compressors model previously published by . This improved model allows the calculation of refrigerant mass flow rate, power consumption and heat flow rate that would be released at the condenser of a heat pump equipped with the compressor, from the knowledge of operating conditions and parameters. Both basic and improved models have been tested on scroll compressors using different refrigerants. This study has been limited to compressors with a maximum electrical power of 14 kW and for evaporation temperatures ranging from −40 to 15 °C and condensation temperatures from 10 to 75 °C. The average discrepancies on mass flow rate, power consumption and heat flow rate are respectively 0.50%, 0.93% and 3.49%. Using a global parameter determination (based on several refrigerants data), this model can predict the behavior of a compressor with another fluid for which no manufacturer data are available. [Copyright &y& Elsevier]

Abstract: The numerical modeling of the conjugate heat transfer and fluid flow through the micro-tube was presented in the paper. Three different fluids with temperature dependent fluid properties are considered: water and two dielectric fluids, HFE-7600 and FC-70. The diameter ratio of the micro-tube was D i/D o =0.1/03mm with a tube length L =70mm, geometry used in [D. Lelea, Nishio S., Takano K., The experimental research on microtube heat transfer and fluid flow of distilled water, International Journal of Heat and Mass Transfer 47 (2004) 2817–2830]. The laminar fluid flow regime is analyzed. Two different heat transfer conditions are considered: heating and cooling. The influence of the temperature dependent thermal conductivity on Nu number is analyzed for these two cases and compared with k =const. [Copyright &y& Elsevier]

Abstract: This paper presents a heat and mass transfer simulation of an adsorber, taking into consideration the geometry of the heat exchanger and the diffusion in the adsorbent medium. In this model, an increment in the direction of heating/cooling fluid containing one (or more) fin pitch was considered. In the domain of this increment, the distribution of the adsorbent temperature was evaluated in the radial and axial directions. The model is validated by experimental data of different adsorbents, volume flows and temperatures. All data were collected in an adsorber test-bench at Fraunhofer ISE. As a result it was found a coefficient of multiple determination of around 0.94 and an error of 20% during the transient. Finally, the model was run on typical operation for cooling application and compared with data from literature. A numerical energy balance was also evaluated. In summary, the results obtained by a independent group shows the same range of confidence of the model developed here, in terms of the tendency of the curves and even the absolute values. [Copyright &y& Elsevier]

Abstract: Falling liquid film is commonly employed in variety of industrial systems, such as LiBr/H2O absorption heat pump or chiller. In this paper, the falling film absorption in aqueous lithium bromide solution was investigated numerically using CFD software package-Fluent. The practical convective boundary condition at the cooling water side was considered. The heat transfer coefficient is assumed constant, and the coolant temperature changes linearly along its flow path. The numerical results indicate that the profile of temperature is exponential and their gradients are high due to the distinct heat effect associated with the absorption at the interface and the cooling effect of coolant at the wall at small downstream distance. As the downstream distance increases, the profile of temperature is nearly linear. The absorption heat and mass fluxes reach a maximum at the inlet region and decrease at the outside of the inlet region. Specially, the effect of variable physical properties on the absorption process was considered and discussed. The prediction of the total absorption mass transfer rate is about 6.5% higher when assuming constant properties. [Copyright &y& Elsevier]

Abstract: The paper continues theoretical studying the heat and mass transfer in the biporous material with the coupled phase transformations. The fine-pored part of the medium is saturated by electrolytic solution and has osmotic and electroosmotic properties. Ice is contained in coarse pores. At the low solution concentration the electric polarization of the medium induced by the temperature gradient may be up to 1V/K. [Copyright &y& Elsevier]

Abstract: An analysis was carried out to study the performance of spine fins of different configurations when subjected to simultaneous heat and mass transfer mechanisms. The temperature and humidity ratio differences are the driving forces for the heat and mass transfer, respectively. Analytical solutions are obtained for the efficiency and temperature distribution over the spine surface when the surface condition is fully wet. A correction chart is developed to correct the value of the dry fin parameter if the fin surface condition is fully wet. The effect of atmospheric pressure on the spine efficiency was also studied as well as the spine optimum geometries were obtained such that a maximum amount of heat transfer rate occurs. It is shown that the closed-form solution for a dry spine case discussed in text books is a special case for the solutions presented in this paper. [Copyright &y& Elsevier]

Abstract: This paper presents a finite element solution of the problem of heat and mass transfer in a hydromagnetic flow of a micropolar fluid past a stretching sheet. The transformed equations for the flow regime are solved numerically by using finite element method. The effect of important parameters namely magnetic field parameter, material parameter, Eckert number and Schmidt number over velocity, microrotation, temperature and concentration functions has been studied. It has been observed that the magnetic field parameter has the effect of reducing the velocity and increasing the microrotation, temperature and concentration while the micropolar parameter has the opposite effect on these functions except temperature function. Temperature increases with the increase in Eckert number and concentration decreases with the increase in Schmidt number. [Copyright &y& Elsevier]

Abstract: The airside heat, mass and momentum transfer characteristics of seven wavy fin-and-tube heat exchangers with hydrophilic coating under dehumidifying conditions were experimented. The test inlet air dry bulb temperatures were 20, 27 and 35 oC, the inlet relative humidity were 50%, 60%, 70% and 80%, and the air velocity were 0.5, 1.0, 2.0, 3.0 and 4.0ms−1. The test results indicate that both the Colburn j m factor and the Colburn j h factor decrease with the increase of fin pitch, and this phenomenon becomes more and more pronounced as Reynolds number decreases. The friction factor is very sensitive to the change of fin pitch, and the friction factor shows a cross-over phenomenon as fin pitch changes. The Colburn j h factor decreases and the Colburn j m factor increases when the number of tube rows increases, while the friction performance is insensitive to the change of the number of tube rows. The effects of inlet relative humidity on the heat transfer and friction performance can be omitted, but the Colburn j m factor decreases with the increase of the inlet relative humidity. The predictive ability of the available state-of-the-art heat transfer and pressure drop correlations was evaluated with the experiment data of the present study. The new heat, mass and momentum transfer correlations were proposed to describe the present test results according to the multiple linear regression technique. The mean deviations of the proposed j h, j m and f correlations are 6.3%, 8.9% and 7.9%, respectively. Comparing to published data reduction method, the process line on psychrometric chart of fin-and-tube heat exchanger for partially wet conditions and more accurate overall heat transfer coefficient equation are put forward in this paper. [Copyright &y& Elsevier]