Heat Transfer Parameters Research Articles

Augmentation of Convective Heat Transfer through various practices: A Review

In case of various heat transfer applications, there is a necessity for proper utilization of energy sources. In the previous decades, various practices have been taken into consideration for the enhancement of heat transfer. We can categorize these practices in three types – active, passive and compound practices. All or any individual of these techniques have been applied in many heat exchanger application such as in thermal power plants, automobile sector, process industries, air-conditioning apparatus and chemical industries. This paper is an overview of several methods for the augmentation of heat transfer process and parameters. In most of the methods, the work was focused on increasing the surface area of the heat exchanger or on increasing turbulence using some inserts within the heat exchanger. The later part of this manuscript also depicts heat transfer augmentation using Nano-fluids.

The Effect of Carbon Emission Trend on Urban Thermal Environment from the Perspective of Transportation Energy Consumption

Figuring out the action mechanism of carbon emission trend on the influencing factors of urban thermal environment from the perspective of transportation energy consumption is of great significance for transforming citizens’ means of transportation and promoting sustainable development of urban environment. However, existing studies on urban thermal environment generally focus on the quantification of urban landscape forms, the correlation analysis, or the analysis of relative importance, few of them have concerned about the action mechanism of fluid flow, heat transfer, pollutant diffusion and other process parameters on the Urban Heat Island (UHI) effect with both transportation energy consumption and carbon emission trend taken into consideration. For this reason, this paper gave the spatial structure of urban thermal environment, constructed fluid flow control equation, heat transfer control equation, pollutant diffusion control equation, and turbulence model for the urban thermal environment; then, it quantitatively analyzed the UHI intensity and air pollutant concentration, aiming to alleviate the UHI effect under the influence of transportation energy consumption and carbon emission trend. At last, this paper used experimental results to verify the effectiveness of the constructed model and gave the analysis results of thermal environment in the target city.

DETERMINATION OF THE HEAT TRANSFER COEFFICIENT OF A ROTARY EVAPORATOR WITH HEATING FILM-FORMING ELEMENT

In the article, a model of a rotary-film evaporator with a film-forming element, which has a heated reflective surface, was investigated. Such a solution was proposed to stabilize the hydraulic movement of the cut off wave flow due to the reflective surface of a certain geometric shape for the forced direction of the cut raw material to the heating surface. Autonomous heating of the reflecting surface additionally provides a temperature effect in the conditions of movement of raw material particles after cutting. As a result of the analysis of the experimental and theoretical parameters of heat transfer, the criterion equation for the heat transfer coefficient of the evaporator with the proposed film-forming element, which has a reflective heated surface for calculating the heat transfer coefficient from the working surface to the raw material, is substantiated. The resulting equation takes into account the influence of the vertical component of the motion of the raw material film, the centrifugal movement during the rotation of the film-forming element, the mixing of the boiling film of the raw material with steam bubbles, the geometric characteristics of the film-forming blade on the hydrodynamic flow of the raw material. Calculation of a rotary-film evaporator using a criterion equation and a useful heat exchange surface of 0,75 m2 was obtained. The specific metal content in a rotary-film evaporator with a film-forming element having a reflective surface is 57 kg/m2 compared to the vacuum evaporator traditionally used in canning industries 410 kg/m2, which is 7,1 times less. Also, the duration of the temperature effect on the raw material is reduced: a rotary-film evaporator - 200 s and 3600 s in a traditional apparatus. The obtained data will be useful for designing rotary-film apparatuses of various geometrical parameters using hinged blades with a reflective plate.

The role of shadowed droplets in condensation heat transfer

Dropwise condensation (DWC) is a phenomenon of common occurrence and significant utility in nature and technology. In energy applications, sustenance of DWC and avoidance of transition to film formation is directly related to efficient heat removal, ensuring high performance of related devices and processes. The efficiency of heat transfer in DWC depends on the heat transfer rates of individual droplets and the droplet size distribution. While the former can be summarily captured in engineering analysis through thermal resistance modeling, the theoretical analysis of the droplet size distribution involves assumptions often oversimplifying the complexity of droplet interactions, especially in the important sub–10 μm regime. Here, a modeling framework based on the thermal resistance approach is coupled with a dynamic model of droplet interactions: Droplet growth, coalescence, jumping, and removal of condensate due to gravity are all present during the unfolding of the phenomenon to accurately predict the droplet size distribution. The motivation is condensation experiments on superhydrophobic surfaces, namely rough aluminum substrates with a hydrophobic coating. Through the “interaction” of computations with measurements, the experimental findings are explained and critical parameters for condensation heat transfer on superhydrophobic surfaces are illuminated. Although larger droplets can be easily observed in experiments, it is shown that large droplets do not significantly affect heat transfer after reaching such state of growth. Instead, it is the small (with radius < 10 μm) and what we term “shadowed” droplets, i.e., the droplets grown in the shadow of the vertical projection area of the larger droplets, that play an important role in the heat transfer process. Due to the growth of these droplets and their concomitant shadowed coalescence and ensuing re-nucleation, the shift in the droplet size distribution towards smaller sizes is significant-enough to render the heat transfer rate rather insensitive to the presence of large droplets. In this regime, the effect of contact angle hysteresis on heat transfer is not crucial. Through the comparison with measurements, the dominant role of the density of nucleation sites on heat transfer is revealed and an estimation of the density of sites (∼105 mm−2) as a function of subcooling is extracted. Finally, the distribution of sites is found critical for heat transfer; an ordered distribution of sites outperforms random and clustered distributions.

Forced convection heat transfer of nanofluids in turbulent flow in a flat tube of an automobile radiator

Nanofluids are fluids that can be applied in devices to obtain better performances (i.e. energy, heat transfer and others). Latest up to date literatures on nanofluids show that they can be used in engine cooling systems, solar water heating, cooling of electronics, to improving diesel generator efficiency, to improve heat transfer efficiency of chillers, in nuclear reactor and defense and space.This paper focuses on the numerical study of the performance of two nanofluids (Al2O3-water and TiO2-water) in heat transfer by forced convection in a flat tube of an automobile radiator In the computational simulations it was considered that the nanofluids have a constant velocity and a temperature of 363.15 K at the entrance of the tube. The tube wall is at a constant temperature of 303.15 K. This study is restricted to turbulent flows with Reynolds numbers equal to 5000, 10000, 15000 and 20000. The 3D computer simulations were performed using the Fluent software. The characteristic parameters of heat transfer from nanofluids subjected to forced convection were obtained for nanoparticle concentrations up to 10% and were compared with the base fluid (water). The numerical results were validated, comparing the friction coefficient and the Nusselt number with empirical correlations for the turbulent regime, available in the literature. The results for the heat transfer coefficient and the heat flux along the tube, for the studied conditions, are presented. Average values of some parameters associated with heat transfer and fluid flow were also determined, such as heat transfer coefficient, heat flux, Nusselt number, Prandtl number, wall shear stress, pressure drop, density, viscosity, thermal conductivity and specific heat, all of which were found to increase with the concentration of nanoparticles. The heat transfer enhancement with the nanoparticles concentrations up to 10% was also investigated. Furthermore, both nanofluids show the same behavior, for instance, for Re = 5000 the heat transfer enhancement rise 32.7% whereas for Re = 20000 the growth drops slightly to 31.3% with the concentration of Al2O3.

Role of obstructing block on enhanced heat transfer in a concentric annulus

The scope of this work is to investigate the influence of an obstruction size and its location on the buoyancy-driven convection in a concentric annulus. The inner cylinder of an annulus is maintained at higher temperature than the outer cylinder. An obstructing adiabatic block is placed in the space between the annulus. To explore the impact of the obstruction on the thermo-fluid flow structure, the block size and its position are varied. The annular region between the cylinders is assumed to be filled with air. The governing differential equations are solved numerically via the finite volume technique-based solver. The simulations are carried out for a controlling range of Rayleigh numbers (Ra = 103–105). The effect of the block size ( = 0–0.8) and its positions (°) on the heat transfer features are extensively examined. It is observed that the heat transfer is maximum for a particular Rayleigh number, block size, and its position. There exist a critical Rayleigh number (Racr) for the enhanced heat transfer. Depending on the block size and its position and Racr, the flow structure exhibits multi-cellular formation, which dictates the heat transfer markedly. The average heat transfer rate improves markedly up to a certain block size and convection regime, after which thermal behavior deteriorates. The local heat transfer attains a peak value near the location, where multi-cells are formed. The heat transfer enhancement parameter is approximately equal to 10% for the optimum block size. The findings of this study will be very helpful for the designing of the thermal system pertaining to efficient heat exchanging devices and other technological applications. Highlights The influence of location and size of an obstructing adiabatic block on buoyant convection in an annulus of the differentially heated concentric cylinder is investigated. Thermo-fluid flow behavior is markedly influenced by the obstructing block size and its position. The optimum block size and position are determined for the maximum heat transfer in an annulus for various Rayleigh numbers. The critical Rayleigh number for the optimum heat transfer is evaluated. The heat transfer parameter is approximately 10% for the optimum block size.

DIFFERENTIAL METHOD OF QUALITY CONTROL OF PHYSICO-MECHANICAL CHARACTERISTICS OF KNITTED FABRIC FOR BATHING SUIT

The actuality of the introduction of textile materials with the content of nanopowders based on oxides of divalent and trivalent iron has been proven. The main directions of implementation of such materials into real practical results are shown. The algorithm for the synthesis of magnetic nanomaterials was developed. Adhesion properties of magnetic nanopowders to textile fibers are determined. It is shown that exposure for 5 – 7 days ensures almost absolute adhesive resistance and provides a combination of textile properties with magnetic nanopowders. Bacteriostatic properties of nanomagnetic textile materials were determined. For this purpose, the growth dynamics of mold fungi was determined. It is shown that the content of nanomagnetite significantly suppresses the growth of mold infections. The magnetic properties of textile materials are described, the possibilities of their introduction into elements of smart clothing, medical and protective materials are determined. Magnetic technologies in medicine, compression elements of clothing can be provided with the help of magnetic textile materials. The magnetic effects of such materials make it possible to create elements of clothing with a change in geometry. This determines the possibility of using such materials for smart clothes with new effects. The possibilities of creating magnetic nanomaterials with given structural characteristics have been proven. The addition of nanopowders reduces the size dispersion of structural elements, reduces their size, and increases density. This effect allows ensuring the specified transfer characteristics of textile materials, which provide the necessary parameters of heat transfer and mass transfer. The possibilities of using magnetic textile materials against electromagnetic radiation are shown. The structure of directions for the use of magnetic textile materials for medical and protective products, as well as for promising elements of smart clothing, has been developed.

Analysis of MHD Williamson micropolar fluid flow in non-Darcian porous media with variable thermal conductivity

The purpose of this research is to investigate the MHD flow of Williamson fluid through a non-Darcy porous medium with micro-rotation. The governing equations are first converted into a coupled system of ODEs with initial and boundary conditions. The shooting procedure with the Runge-Kutta method is used to solve the ODEs, and determine the impact of various parameters for heat and momentum transfer of boundary layer flow. Finally, all findings are graphed and compared with earlier results to ensure that the current outputs are perfectly valid. Furthermore, it can be seen from the characteristic graph that the system parameters, magnetic field M and non-Darcy F tend to reduce the fluid velocity. Also, a comparison between the two fluid models, Williamson fluid and micropolar fluid have been obtained via the effects of various parameters on skin friction and Nusselt number.

Experimental investigation of the natural convection heat transfer characteristics of cylinder walls with a DBD actuator as the heat source

Conventional electric heating methods applied when evaluating the natural convection heat transfer parameters at the outer walls of cylinders produce uneven heat flows and large measurement errors. The present work addresses these issues by developing a new heating method using a dielectric barrier discharge (DBD) actuator as the heat source. An experimental system is constructed, where the thermal power output of the DBD actuator is first measured by calorimetry, and the natural convection heat transfer characteristics of a representative cylinder are analyzed with an explicit accounting of the temperature distribution at the outer wall of the cylinder. The results demonstrate that the DBD actuator can provide more uniform heat flow than conventional electric heaters. The temperature difference between the top and the bottom of the cylinder wall initially increases with increasing thermal power, decreases to a minimum at a thermal power of about 400 W, and subsequently increases with increasing thermal power. In addition, and the feasibility of the DBD actuator as a heat source is demonstrated according to the high degree of conformation between the calculated values and empirically established correlations between Nusselt number, which generally deviate by less than 10%.

Development of a Nondestructive Monitoring Technique for Vial Freeze-Drying Process using Microwave Resonance Spectroscopy

In this study, we developed a nondestructive monitoring technique for the drying progress of products in vials during the freeze-drying process using microwave resonance spectroscopy. An aqueous mannitol solution, commonly used as an excipient for injectable drugs, was used as the model material. The drying progress was determined using a mathematical model (i.e., Rp−Kv model), in which the parameters of mass and heat transfer were experimentally determined while considering the variation of the drying progress and position of the product on the drying shelf. A strong correlation was found between the extent of drying and changes in the microwave resonance spectrum. The simulation results were regressed against the changes in the resonance peak frequency and resonance intensity. Using this regression equation, the extent of drying could be predicted from the acquired spectral data. In this way, we were able to estimate the design space (the relationship between the operating conditions, internal temperature of the product, and sublimation rate), which changed with the extent of drying from the spectrum obtained inline, showing that it is possible to set the appropriate operating conditions based on the spectra.

Humidifying solar collector for improving the performance of direct solar desalination systems: A theoretical approach

In this paper, a new type of solar collector named humidifying solar collector, that is, a solar collector with air humidification function, is proposed. The particularity of this system compared to previous systems in the literature is that the quantity of liquid water present in the collector at each instant is equal to the quantity that will evaporate within the following unit time, no longer greater. This minimizes the quantity of liquid water present in the collector at each instant, and consequently allows to reach desired evaporation temperatures in shorter times and even under low solar irradiances, and minimizes the thermal resistance between evaporation surface and absorber caused by water depth. Then, a theoretical and comparative study by simulation using Engineering Equation Solver software between the performance of the humidifying solar collector-based solar still (proposed system) and that of the solar air heater-based humidification dehumidification solar desalination system (conventional system) is conducted. The performance parameters assessed are energy and exergy efficiencies, dry air mass flow rate required and the maximum water mass flow rate that can evaporate in that air. The results reveal that, in general case, the proposed system is fundamentally more efficient than the conventional system. For instance, for the sizes and heat transfer parameters chosen in this study, the performance of the proposed system is 1.3–32.2 times higher than that of the conventional system; its freshwater productivity under incident solar irradiance of 900 W/m2 can reach 2.923 kg/h, and can be further improved by optimizing the design of the humidifying solar collector.

LTNE Effects on Triple-Diffusive Convection in Nanofluids

Abstract Triple-diffusive convection for nanofluids in which differences in density are derived because of triple diffusion process, i.e., with three diffusing components: nanoparticles, solute, and heat, using more realistic two temperature model with separate thermal energy equations for the two phases of the considered nanofluid has been investigated by making use of the method of superposition and one term Galerkin technique. A complex system with local thermal non-equilibrium (LTNE) effects along with the Brownian motions and thermophoresis to account for nanoparticles has been considered. The problem is solved for top-heavy arrangement of nanoparticles leading to stationary mode of convection and numerical computations are carried out by using Mathematica software. An additional solute concentration equation supplements the conservation equations due to the existence of solute, which introduces two additional nondimensional parameters, whereas three additional parameters came into existence due to the consideration of LTNE effects. The critical Rayleigh number remains constant for smaller values of interphase heat transfer parameter, whereas it diminishes for the intermediate range and approaches to constant value for higher ranges of the parameters. What all this means is that only the intermediate range of Nield parameter shows stabilizing/destabilizing effects. Interestingly, the additional parameters Lewis number and solute Rayleigh number enhance the effect of destabilization of considered nanofluid layer.

(Digital Presentation) The Role of Heat Transfer in Mitigation of Cascading Thermal Runaway

As the energy density of systems of lithium-ion batteries increases, and as they are employed in larger-scale energy storage systems, greater attention must be paid to the safety of these systems. Failure of a single cell can trigger thermal runaway processes that cascade through the system, endangering first responders and nearby structures. This cascading failure is driven by heat transfer through the system to vulnerable cells and other combustible materials. To understand how to mitigate thermal runaway, the most important heat transfer pathways must be characterized in terms of their magnitude and time scale.Heat must be removed from cells that have gone into thermal runaway without leading vulnerable cells into thermal runaway. The onset of thermal runaway typically occurs around 200oC and depends on the heating time (i.e. cells heated slowly in an oven will begin thermal runaway around 150oC). The objective then becomes avoiding these thermal runaway temperatures for surrounding cells while dissipating any heat released from an initial thermal runaway event.While there are many individual parameters that describe the cells and system, in this work it will be seen that the thermal analysis can be reduced to a collection of non-dimensional parameters. These parameters describe heat conduction within the cell, heat capacity of a cell, total heat released by a cell in thermal runaway, conductive heat transfer to adjacent cells and surroundings, and convective heat transfer to surrounding gases. Figure 1 depicts a notional module of cells packed together where cascading thermal runaway has begun propagating through the cells. Heat is dissipated by conduction away from the thermal runaway front through adjacent cells and to the surroundings through convection. The relative time scales of these rates determine the propagation speed and ultimately the point at which cascading thermal runaway is mitigated.Figure 1 Caption: Heat transfer pathways in a module of tightly packed cells.A simple cell-to-cell propagation scenario is constructed to separately investigate the heat transfer parameter space. In this model scenario, an “initiating” cell is assumed to have just completed thermal runaway and exhausted all its reactants. This heats that cell to a high temperature that depends on the cell chemistry and state of charge. Adjacent to this “initiating” cell is the “target” cell. We use canonical heat transfer problems to identify a set of parameters that determine the temperature of the “target” cell. The parameters consider the thermal resistance between cells and the heat capacity of the involved materials as well as convective heat losses to the ambient surroundings.The thermal parameter space is interrogated by solving the transient heat transfer problem with a combination of analytical techniques and the finite volume software LIM1TR. The maximum temperature reached by the edge of the target cell is recorded and used as the criteria for the boundary between propagation and mitigation. The scaling relationships developed through this analysis can provide thermal engineers and system designers with a framework for predicting the safety of battery pack designs in the context of cascading thermal runaway. Acknowledgment: Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525. This paper describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the U.S. Department of Energy or the United States Government.SAND2021-15938 A Figure 1

Receiving heat from a PCM tank by using natural convection of water and NEPCM: A simulation for LHTES application

Latent heat thermal energy storage (LHTES) systems are widely used due to their ability to store a lot of heat energy as latent, and few studies have directly or indirectly investigated on the heat exchange methods with LHTES systems. In the present study, the free convection of a mixture of water and Nano-encapsulated phase change material (NEPCM) with a porous medium was used to exchange heat energy between a cold-water stream and a hot tank filled phase change material (PCM). NEPCM are nanostructures consisted of a solid shell and a PCM core, and the addition of these nanostructures to water has remarkable effects on the heat transfer parameters. In this research, a number of cases were simulated using computational fluid dynamic (CFD) to observe the impacts of injecting NEPCM to water, the porosity of the porous media and the location of the phase change zone on the average heat flux of the PCM tank. The results showed that increment of porosity number from 0.85 to 0.95 decreased the average heat flux of the PCM tank by 13.8%. Moreover, adding 3% NEPCM to water enhanced the average heat flux of the PCM tank by 22.2% and 18.4% when porosity numbers were 0.85 and 0.95, respectively.

Analytical Solutions to Temperature Field in Various Relative-Scale Media Subjected to a Reciprocating Motion Point Heat Source

To reveal the temperature rise evolution mechanism of isotropic media subjected to reciprocating motion constant-strength point heat source, various forms of analytical solutions are derived on the basis of differentiated relative scales, and non-dimensionalized parameters are designed to characterize the thermal distribution regularities by utilizing numerical calculations. Temperature rise curves of media subjected to a reciprocating motion point heat source allow similar quasi-steady-state characteristics to appear, which finally achieve a stable state, so that the values of surplus temperature oscillate around the constant time-average quantity. The time to reach quasi-steady state, the time-averaged quantity and the fluctuation amplitude of surplus temperature are comprehensively impacted by the dimensionless distance parameter γ, the convective heat transfer parameter ω and the velocity and travel parameter β. This work discusses influence rules of temperature evolution in various relative-scale media and further enriches the moving heat source theory.

Peculiarities of the analytical calculation of heat transfer parameters through a multi-layer enclosing structure in non-stationary mode

A system of algebraic equations is proposed for calculating the parameters of non-stationary complex heat exchange between the premises of the building and the environment (taking into account the thermal effect of insolation on the surface of the enclosing structure), which allows you to solve the following tasks: calculate the temperature field in complex, structurally, multilayered structures, for example, when the location discrete layers; when measuring the temperature at characteristic points (at the joints of layers and surfaces of the structure), the model allows you to determine the thermophysical characteristics of the materials from which the structure consists of layers; when conducting laboratory tests, it allows to significantly reduce their duration; when solving the inverse problem, directly determine the heat transfer resistance of the entire multilayer structure and its individual layers. The level of modern computer technology and special software allows you to quickly and accurately solve the problem of heat transfer through the OC, based on the entire set of climatic factors, without introducing any assumptions and simplifications. In particular, it is quite accurate to take into account the influence of insolation thanks to the information contained in meteorological handbooks. The developed mathematical model allows solving the following tasks: to assess the thermophysical condition of structures designed for different modes of operation and, as a result, to rationally design them for a specific mode or their range; calculate the temperature field in structurally complex multi-layer structures, for example, when the arrangement of layers is discrete. On the basis of the developed mathematical model, the possibility of calculating and optimizing the main thermal parameters of multi-layer enclosing structures, etc. is considered.

Arrhenius energy on asymmetric flow and heat transfer of micropolar fluids with variable properties: A sensitivity approach

Micropolar fluid flow in a channel with variable viscosity, variable thermal conductivity and activation energy is examined numerically using the Runge–Kutta Fehlberg method in this article. Two different boundary conditions are postulated in this study namely Prescribed Surface Temperature (PST) and Newtonian Heating (NH). The numerical outcomes are compared to check the precision of the suggested problem. Significant metrics like Reynolds number, Peclet number for heat and mass transfer, Schmidt number, Activation energy and chemical reaction parameter are graphically described. The influence of the parameters like spin gradient viscosity, vortex viscosity, micro-inertia density on the flow fields are discussed and shown. According to the graphic data, the velocity increases as the viscosity parameter increases whereas the temperature decays for larger values of variable thermal conductivity and also, activation energy enhances the concentration profile. The variation in viscosity parameter shows a significant effect on thermal distribution. The viscosity variation parameter enhances the shear stress and the couple stress. The Peclet number for heat transmission displays a changing effect for high and low Biot numbers regardless of the effect of variable thermal conductivity. This analysis tabulates the link between Nusselt number and Sherwood number over a Peclet number for heat and mass transfer. The skin friction coefficient increases with the viscosity parameter ∊ whereas enhancement in the thermal conductivity parameter decreases the Nusselt number. Furthermore, sensitivity analysis is carried here by developing RSM in order to identify the variations in the input values for the parameters Peh,Pem and N1. The response surface equation is created by using the software package MINITAB-16 by design of experiments. The regression model’s quality of fit is assessed by using the Analysis of Variance.

Drying of porous media: an algorithm to determine effective parameters

The drying process plays an important role in various industries such as chemical engineering, food, agriculture, and construction. The drying process is a complex one due to the phenomena of heat and mass transfer, which take place simultaneously. In principle, these transport processes can be modelling using continuous and discrete approaches. Following the continuous approach, porous media was simulated as continuous, and effective parameters for heat and mass transfer were employed. In this continuous model, the effective diffusivity and effective thermal conductivity parameters had strong effects on the results. The purpose of this research was to develop an algorithm to determine the effective parameters of the drying of porous media by using a continuous model.

Thermal radiation effects on heat transfer in slender packed-bed reactors: Particle-resolved CFD simulations and 2D modeling

Radial heat management is crucial for a safe and stable operation of fixed-bed reactors with small tube-to-particle diameter ratios (N). Under high temperature conditions, thermal radiation can contribute substantially to the overall heat transfer. In the present work, the influence of radiation is studied with particle resolved computational fluid dynamics (PRCFD) in a fixed-bed reactor consisting of 1000 spheres and rings with N = 5.1 over 300 < Rep< 2000 and for three different temperature levels (300–800 ∘C). Two heat transfer parameters, i.e., the wall Nusselt number Nuw and the effective radial thermal conductivity of the bed keff, r, are derived directly from PRCFD. While the radiation effect is minor in keff, r, it is substantial for Nuw, which is not captured adequately in the current correlations presented in literature. Depending on the temperature level and flow conditions, thermal radiation between the hot wall and the packed bed intensifies the radial heat transfer represented by an increase of up to 170 % in Nuw and 65% in keff, r. A 2D axisymmetric pseudo-homogeneous model including the derived heat transfer parameters can predict the radial temperature profile of the PRCFD with reasonable accuracy also with radiation except for the near-wall region.

Analysis of Heat and Mass Transfer of Fractionalized MHD Second-Grade Fluid over Nonlinearly Moving Porous Plate

This study investigates the heat and mass transfer in the MHD flow of fractionalized second-grade fluid induced by impulsively moved bottom porous plate with nonlinear velocity of the magnitude KTD. To acquire the fractionalized nondimensional set of flow administering differential equations, fractional calculus and dimensionless variables are considered. The solution process utilizes Laplace transform and results in the acquired outputs in terms of generalized functions. The exact solutions for concentration, temperature, velocity, and the shear stress are then reduced by certain limits into fractional/traditional second-grade and Newtonian fluids as per the special cases within and out of the magnetic and porous effects. It is observed that these special cases occur in the previous published literature which verify the results of this study. The results are pictorially visualized to perform the analysis for impacts of diverse physical parameters and dimensionless quantities on concentration, temperature, and velocity fields. It is learned from the analysis that magnitude of viscoelastic parameter is directly proportional to velocity whereas the porous and magmatic effects are inversely proportional. Increasing fractional parameter values reduce flow fields of velocity and temperature. Effects of dimensionless parameters for heat and mass transfer are analysed in detail.