Heat Transfer and Entropy Generation Analyses of Forced Convection Through Porous Media Using Pore Scale Modeling

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Mehrdad Torabi ◽  
Mohsen Torabi ◽  
G. P. Peterson
Keyword(s):  
Entropy Generation ◽  
Reynolds Numbers ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Bejan Number ◽  
Current Investigation ◽  
Pore Scale ◽  
Cross Sectional ◽  
Scale Modeling ◽  
Performance Evaluation Criterion

The objective of the current investigation is to investigate the entropy generation inside porous media utilizing a pore scale modeling approach. The current investigation improves the thermodynamics performance of the recent analysis (Int. J. Heat Mass Transfer, 2016, 99, pp. 303–316) by considering different cross-sectional configurations and analyzing the thermal system for various Reynolds numbers, porosities, and a comparison between the previous and current investigation. The Nusselt number, the dimensionless volume-averaged entropy generation rate, Bejan number, and performance evaluation criterion (PEC) are all presented and discussed. The dimensionless volume-averaged entropy generation rate was found to increase with increasing Reynolds number, with the increase being higher for lower porosity medium. A slight variation of the dimensionless volume-averaged entropy generation rate is observed for higher Reynolds numbers which is confirmed for both cross-sectional configurations. Examination of the Bejan number demonstrates heat transfer irreversibility (HTI) dominance for most of the Reynolds number ranges examined. The results indicate that the longitudinal elliptical cross-sectional configuration with porosity equals to 0.53 provides superior performance when applying the performance evaluation criterion utilized.

Numerical Investigation of Local Entropy Generation for Laminar Flow in Rotating-Disk Systems

2010 ◽  
Vol 132 (9) ◽  
Author(s):  
Mohammad Shanbghazani ◽  
Vahid Heidarpoor ◽  
Marc A. Rosen ◽  
Iraj Mirzaee
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Laminar Flow ◽  
Entropy Generation ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Bejan Number ◽  
Local Entropy ◽  
Fluid Friction ◽  
Local Entropy Generation

The entropy generation is investigated numerically in axisymmetric, steady-state, and incompressible laminar flow in a rotating single free disk. The finite-volume method is used for solving the momentum and energy equations needed for the determination of the entropy generation due to heat transfer and fluid friction. The numerical model is validated by comparing it to previously reported analytical and experimental data for momentum and energy. Results are presented in terms of velocity distribution, temperature, local entropy generation rate, Bejan number, and irreversibility ratio distribution for various rotational Reynolds number and physical cases, using dimensionless parameters. It is demonstrated that increasing rotational Reynolds number increases the local entropy generation rate and irreversibility rate, and that the irreversibility is mainly due to heat transfer while the irreversibility associated with fluid friction is minor.

Modeling heat transfer of nanofluid flow in microchannels with electrokinetic and slippery effects using Buongiorno’s model

2019 ◽  
Vol 29 (8) ◽  
pp. 2566-2587 ◽  
Author(s):  
Hang Xu ◽  
Huang Huang ◽  
Xiao-Hang Xu ◽  
Qiang Sun
Keyword(s):  
Heat Transfer ◽  
Entropy Generation ◽  
Slip Length ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Lower Wall ◽  
Volumetric Concentration ◽  
Nanofluid Flow ◽  
Cross Sectional ◽  
Content Type

PurposeThis paper aims to study the heat transfer of nanofluid flow driven by the move of channel walls in a microchannel under the effects of the electrical double layer and slippery properties of channel walls. The distributions of velocity, temperature and nanoparticle volumetric concentration are analyzed under different slip-length. Also, the variation rates of flow velocity, temperature, concentration of nanoparticle, the pressure constant, the local volumetric entropy generation rate and the total cross-sectional entropy generation are analyzed.Design/methodology/approachA recently developed model is chosen which is robust and reasonable from the point of view of physics, as it does not impose nonphysical boundary conditions, for instance, the zero electrical potential in the middle plane of the channel or the artificial pressure constant. The governing equations of flow motion, energy, electrical double layer and stream potential are derived with slip boundary condition presented. The model is non-dimensionalized and solved by using the homotopy analysis method.FindingsSlip-length has significant influences on the velocity, temperature and nanoparticle volumetric concentration of the nanofluid. It also has strong effects on the pressure constant. With the increase of the slip-length, the pressure constant of the nanofluid in the horizontal microchannel decreases. Both the local volumetric entropy generation rate and total cross-sectional entropy generation rate are significantly affected by both the slip-length of the lower wall and the thermal diffusion. The local volumetric entropy generation rate at the upper wall is always higher than that around the lower wall. Also, the larger the slip-length is, the lower the total cross-sectional entropy generation rate is when the thermal diffusion is moderate.Originality/valueThe findings in this work on the heat transfer and flow phenomena of the nanofluid in microchannel are expected to make a contribution to guide the design of micro-electro-mechanical systems.

Thermodynamic Analysis of Magnetohydrodynamic Third Grade Fluid Flow with Variable Properties

2021 ◽  
Vol 55 ◽  
pp. 28-46
Author(s):  
Kgomotshwana Frans Thosago ◽  
Lazarus Rundora ◽  
Samuel Olumide Adesanya
Keyword(s):  
Fluid Flow ◽  
Thermodynamic Analysis ◽  
Entropy Generation ◽  
Generation Rate ◽  
Third Grade ◽  
Entropy Generation Rate ◽  
Bejan Number ◽  
Third Grade Fluid ◽  
Entropy Generation Minimization ◽  
Grade Fluid

This article aims to computationally study entropy generation in a magnetohydrodynamic (MHD) third grade fluid flow in a horizontal channel with impermeable walls. The fluids viscosity and thermal conductivity are assumed to be dependent on temperature. The flow is driven by an applied uniform axial pressure gradient between infinite parallel plates and is considered to be incompressible, steady and fully developed. Adomian decomposition method (ADM) is used to obtain series solutions of the nonlinear governing equations. Thermodynamic analysis is done by computing the entropy generation rate and the irreversibility ratio (Bejan number). The effects of the various pertinent embedded parameters on the velocity field, temperature field, entropy generation rate and Bejan number are analysed through vivid graphical manipulations. The analysis shows that an appropriate combination of thermophysical parameters efficiently achieves entropy generation minimization in the thermomechanical system. The analysis shows that entropy generation minimization is achieved by increasing the magnetic field and the third grade material parameters, and therefore designs and processes incorporating MHD third grade fluid flow systems are far more likely to give optimum and efficient performance.

Entropy generation and thermo-diffusion effects on unsteady chemically reactive slip flow between two rotating disks

2019 ◽  
Vol 29 (10) ◽  
pp. 3795-3821
Author(s):  
Sumaira Qayyum ◽  
Muhammad Ijaz Khan ◽  
Tasawar Hayat ◽  
Ahmed Alsaedi
Keyword(s):  
Magnetic Field ◽  
Entropy Generation ◽  
Stokes Equations ◽  
Tangential Velocity ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Bejan Number ◽  
Thermal Equation ◽  
Content Type ◽  
Flow Variables

Purpose The purpose of this study is to analyze the Entropy generation analysis and heat transport in three-dimensional flow between two stretchable disks. Joule heating and heat generation/absorption are incorporated in the thermal equation. Thermo-diffusion effect is also considered. Flow is conducting for time-dependent applied magnetic field. Induced magnetic field is not taken into consideration. Velocity and thermal slip conditions at both the disks are implemented. The flow problem is modeled by using Navier–Stokes equations with entropy generation rate and Bejan number. Design/methodology/approach Von Karman transformations are used to reduce the nonlinear governing expressions into an ordinary one and then tackled by homotopy analysis method for convergent series solutions. The nonlinear expressions for total entropy generation rate are obtained with appropriate transformations. The impacts of different flow variables on velocity, temperature, entropy generation rate and Bejan number are described graphically. Velocity, temperature and concentration gradients are discussed in the presence of flow variables. Findings Axial, radial and tangential velocity profiles show decreasing trend for larger values of velocity slip parameters. For a larger Brinkman number, the entropy generation increases, while a decreasing trend is noticed for Bejan number. Originality/value To the best of the authors’ knowledge, no such analyses have been reported in the literature.

Entropy generation in radiative flow of Ree-Eyring fluid due to due rotating disks

2019 ◽  
Vol 29 (6) ◽  
pp. 2057-2079 ◽  
Author(s):  
Muhammad Ijaz Khan ◽  
Sohail Ahmad Khan ◽  
Tasawar Hayat ◽  
Muhammad Faisal Javed ◽  
Ahmed Alsaedi
Keyword(s):  
Heat Transfer ◽  
Entropy Generation ◽  
Magnetic Parameter ◽  
Nonlinear Flow ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Bejan Number ◽  
Rotating Disks ◽  
Content Type ◽  
The Impact

Purpose This study aims to examine the flow characteristics of Ree–Eyring fluid between two rotating disks. The characteristics of heat transfer are discussed in presence of viscous dissipation, heat source/sink and nonlinear radiative heat flux. Design/methodology/approach Nonlinear flow expressions lead to ordinary ones through adequate similarity transformations. The ordinary differential system has been tackled through optimal homotopic method. The impact of different flow variables on the velocity field, entropy generation rate and temperature fields is graphically discussed. The surface drag force and heat transfer rate are numerically examined via various pertinent parameters. Findings By minimization of values of stretching parameter and Brinkman number, the entropy generation rate can be controlled. The entropy generation rate enhances for higher values of magnetic parameter, while the Bejan number is decreased via magnetic parameter. Originality/value No such work is yet published in the literature.

scholarly journals Entropy Generation in MHD Eyring–Powell Fluid Flow over an Unsteady Oscillatory Porous Stretching Surface under the Impact of Thermal Radiation and Heat Source/Sink

2018 ◽  
Vol 8 (12) ◽  
pp. 2588 ◽  
Author(s):  
Sayer Alharbi ◽  
Abdullah Dawar ◽  
Zahir Shah ◽  
Waris Khan ◽  
Muhammad Idrees ◽  
...  
Keyword(s):  
Heat Source ◽  
Thermal Radiation ◽  
Entropy Generation ◽  
Stretching Sheet ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Bejan Number ◽  
Temperature Function ◽  
Source Sink ◽  
The Impact

In this article, we have briefly examined the entropy generation in magnetohydrodynamic (MHD) Eyring–Powell fluid over an unsteady oscillating porous stretching sheet. The impact of thermal radiation and heat source/sink are taken in this investigation. The impact of embedded parameters on velocity function, temperature function, entropy generation rate, and Bejan number are deliberated through graphs, and discussed as well. By studying the entropy generation in magnetohydrodynamic Eyring–Powell fluid over an unsteady oscillating porous stretching sheet, the entropy generation rate is reduced with escalation in porosity, thermal radiation, and magnetic parameters, while increased with the escalation in Reynolds number. Also, the Bejan number is increased with the escalation in porosity and magnetic parameter, while increased with the escalation in thermal radiation parameter. The impact of skin fraction coefficient and local Nusselt number are discussed through tables. The partial differential equations are converted to ordinary differential equation with the help of similarity variables. The homotopy analysis method (HAM) is used for the solution of the problem. The results of this investigation agree, satisfactorily, with past studies.

Entropy analysis of Poiseuille nanofluid flow in a porous channel with slip and convective boundary conditions under magnetic field

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
S. Das ◽  
S. Chakraborty ◽  
R. N. Jana
Keyword(s):  
Magnetic Field ◽  
Entropy Generation ◽  
Poiseuille Flow ◽  
Magnetic Parameter ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Convective Heating ◽  
Bejan Number ◽  
Content Type ◽  
Hydrodynamic Slip

Purpose This study aims to expose the flow phenomena and entropy generation during a; magnetohydrodynamic (MHD) Poiseuille flow of water-based nanofluids (NFs) in a porous channel subject to hydrodynamic slip and convective heating boundary conditions. The flow caused by the uniform pressure; gradient between infinite parallel plates is considered steady and fully developed. The nanoparticles; namely, copper, alumina and titanium oxide are taken with pure water as the base fluid. Viscous dissipation and Joule heating impacts are also incorporated in this investigation. Design/methodology/approach The reduced governing equations are solved analytically in closed form. The physical insights of noteworthy parameters on the important flow quantities are demonstrated through graphs and analyzed elaborately. The thermodynamic analysis is performed by calculating entropy generation; rate and Bejan number. A graphical comparison between solutions corresponding to NFs and regular fluid in the channel is also provided. Findings The analysis of the results divulges that entropy generation minimization can be achieved by an appropriate combination of the geometrical and physical parameters of thermomechanical systems. It is reported that ascent in magnetic parameter number declines the velocity profiles, while the inverse pattern is witnessed with augmentation in hydrodynamic slip parameters. The temperature dissemination declines with the growth of Biot numbers. It is perceived that the entropy generation rate lessens with an upgrade in magnetic parameter, whereas the reverse trend of Bejan number is perceived with expansion in magnetic parameter and Biot number. The important contribution of the result is that the entropy generation rate is controlled with an appropriate composition of thermo-physical parameter values. Moreover, in the presence of a magnetic field and suction/injection at the channel walls, the shear stresses at the channel walls are reduced about two times. Practical implications In various industrial applications, minimizing entropy generation plays a significant role. Miniaturization of entropy is the utilization of the energy of thermal devices such as micro heat exchangers, micromixers, micropumps and cooling microelectromechanical devices. Originality/value An attentive review of the literature discloses that quite a few studies have been conducted on entropy generation analysis of a fully developed MHD Poiseuille flow of NFs through a permeable channel subject to the velocity slip and convective heating conditions at the walls.

Entropy Generation Analysis for Microscale Forced Convection in Thermal Entrance Region

2012 ◽  
Vol 28 (1) ◽  
pp. 71-76 ◽  
Author(s):  
V. Vandadi ◽  
A. Vandadi ◽  
H. Niazmand ◽  
C. Aghanajafi
Keyword(s):  
Entropy Generation ◽  
Analytical Study ◽  
Entrance Region ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Bejan Number ◽  
Thermal Entrance Region ◽  
Circular Microchannel ◽  
Thermal Entrance ◽  
Steady Laminar

ABSTRACTAn analytical study on entropy generation considering viscous dissipation effect in the circular microchannel is reported. The fluid flow is steady, laminar, hydrodynamically fully developed and thermally developing. In the first law analysis, appropriate dimensionless variables are applied to solve the energy equation in the thermal entrance region of microchannel. Subsequently the obtained temperature field is used to derive an expression for entropy generation rate. The effect of Knudsen number and Brinkman number on the entropy generation rate and Bejan number in different axial location is presented.

Analysis of entropy generation in an inclined channel flow containing two immiscible micropolar fluids using HAM

2016 ◽  
Vol 26 (3/4) ◽  
pp. 1027-1049 ◽  
Author(s):  
J. Srinivas ◽  
J.V. Ramana Murthy ◽  
Ali J Chamkha
Keyword(s):  
Entropy Generation ◽  
Flow Region ◽  
Flow Equation ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Bejan Number ◽  
Micropolar Fluids ◽  
Content Type ◽  
Inclined Channel ◽  
Homotopy Analysis

Purpose – The purpose of this paper is to examine the flow, heat transfer and entropy generation characteristics for an inclined channel of two immiscible micropolar fluids. Design/methodology/approach – The flow region consists of two zones, the flow of the heavier fluid taking place in the lower zone. The flow is assumed to be governed by Eringen’s micropolar fluid flow equation. The resulting governing equations are then solved using the homotopy analysis method. Findings – The following findings are concluded: first, the entropy generation rate is more near the plates in both the zones as compared to that of the interface. This indicates that the friction due to surface on the fluids increases entropy generation rate. Second, the entropy generation rate is more near the plate in Zone I than that of Zone II. This may be due to the fact that the fluid in Zone I is more viscous. This indicates the more the viscosity of the fluid is, the more the entropy generation. Third, Bejan number is the maximum at the interface of the fluids. This indicates that the amount of exergy (available energy) is maximum and irreversibility is minimized at the interface between the fluids. Fourth, as micropolarity increases, entropy generation rate near the plates decreases and irreversibility decreases. This indicates an important industrial application for micropolar fluids to use them as a good lubricant. Originality/value – The problem is original as no work has been reported on entropy generation in an inclined channel with two immiscible micropolar fluids.

scholarly journals A novel method for estimating the entropy generation rate in a human body

2007 ◽  
Vol 11 (1) ◽  
pp. 75-92 ◽  
Author(s):  
Azizur Rahman
Keyword(s):  
Heat Transfer ◽  
Entropy Generation ◽  
Human Body ◽  
Production Cross ◽  
Internal Heat ◽  
The Body ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Cross Sectional ◽  
Speed Effect

The main objective of this study is to show a method for calculating entropy generation (Sgen) in a human body under various environmental and physiological conditions. The Sgen in a human body is a measure of activeness of motions, reactions, and irreversibility of processes occurring in a body and is a kind of holistic and thermodynamic index, which characterizes a human body as a whole. Human body at healthier and normal condition generates the least amount of Sgen. Heat transfer over a human body, activity (at rest, Sgen = 0.21J/sK or exercise, Sgen=2.19 J/sK or at death, Sgen = 0J/sK), ambient, body and mean radiant temperatures, emissivity and absorbity of human skin, internal heat elimination, body weight and height, and air speed effect much more on the Sgen in a human body compared to the effects of mass exchange into and out of the body, internal heat production, cross-sectional area of human body, clothing, altitude, and relative humidity of the surrounding air. Among these factors entropy production due to heat transfer over a human body plays a significant role in the total entropy generation rate. .

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