Numerical Investigation of Entropy Generation in Stratified Thermal Stores

This paper investigates the nature of entropy generation in stratified sensible thermal energy stores (SSTES) during charging using a dimensionless axisymmetric numerical model of an SSTES. Time-varying dimensionless entropy generation rates and the cumulative entropy generation in SSTES were determined from finite volume computations. The aspect ratios (AR), Peclet numbers (PeD), and Richardson numbers (Ri), for the stores considered were within the ranges 1≤AR≤4, 5×103≤PeD≤100×103, and 10≤Ri≤104, respectively. Using the Bejan number (Be), the total entropy generation was shown to be almost entirely due to thermal effects in the SSTES. The Be is practically unity for most of the SSTES' charging duration. The contributions of radial thermal gradients to the thermal entropy generation were further shown to be largely negligible in comparison to the contributions of axial thermal gradients, except at low Ri. Entropy generation numbers, Ns, in the SSTES were also computed and found to increase with decreasing AR and PeD and with increasing Ri. PeD was found to have the most significant influence on Ns. Based on this axisymmetric analyses of time-varying entropy generation in SSTES, estimates have been obtained of (1) the relative significance of radial effects on entropy generation within SSTES and (2) the relative significance of viscous shear entropy generation mechanisms within SSTES.

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Effects of circular corners and aspect-ratio on entropy generation due to natural convection of nanofluid flows in rectangular cavities

Thermal Science ◽

10.2298/tsci130201034s ◽

2015 ◽

Vol 19 (5) ◽

pp. 1621-1632 ◽

Cited By ~ 7

Author(s):

Mahmoud Salari ◽

Ali Mohammadtabar ◽

Mohammad Mohammadtabar

Keyword(s):

Natural Convection ◽

Rayleigh Number ◽

Aspect Ratio ◽

Entropy Generation ◽

Volume Fraction ◽

Solid Volume Fraction ◽

Bejan Number ◽

Total Entropy ◽

Aspect Ratios ◽

Corner Radius

In this paper, entropy generation induced by natural convection of cu-water nanofluid in rectangular cavities with different circular corners and different aspect-ratios were numerically investigated. The governing equations were solved using a finite volume approach and the SIMPLE algorithm was used to couple the pressure and velocity fields. The results showed that the total entropy generation increased with the increase of Rayleigh number, irreversibility coefficient, aspect ratio or solid volume fraction while it decreased with the increase of the corner radius. It should be noted that the best way for minimizing entropy generation is decreasing Rayleigh number. This is the first priority for minimizing entropy generation. The other parameters such as radius, volume fraction, etc are placed on the second priority. However, Bejan number had an inverse trend compared with total entropy generation. As an exception, Bejan number and total entropy number had the same trend whenever solid volume fraction increased. Moreover, Nusselt number increased as Rayleigh number, solid volume fraction or aspect ratio increased whereas it decreases with the increase of corner radius.

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Effect of Buoyancy Driven Stream Loop Numbers on Heat Transfer and Entropy Generation

Volume 9: Heat Transfer, Fluid Flows, and Thermal Systems, Parts A, B and C ◽

10.1115/imece2009-12805 ◽

2009 ◽

Author(s):

H. Heidary ◽

M. Davoudi ◽

M. J. Kermani

Keyword(s):

Heat Transfer ◽

Porous Medium ◽

Aspect Ratio ◽

Free Convection ◽

Entropy Generation ◽

Saturated Porous Medium ◽

Numerical Procedure ◽

Bottom Wall ◽

Bejan Number ◽

Aspect Ratios

Free convection in a cavity filled with a fluid-saturated porous medium is from prime importance in many technological applications. Transient free convection in a rectangular cavity filled with a porous medium is numerically studied in this paper. Uniformly and non-uniformly sinusoidal heated bottom wall and adiabatic side walls maintaining constant temperature of cold top wall has been performed. Investigation of problems with this boundary condition is very complicated, as there are a limited number of studies available in the literature dealing with this problem. The finite volume numerical method is used to solve the non-dimensional governing equations. The numerical procedure has been done over a range of Rayleigh number, Ra, 10 ≤ Ra ≤ 103 and Prandtl number, Pr, 0.71 and Aspect ratio, AR, 0.25≤ AR ≤8 and effect of them is investigated on heat transfer and entropy generation. For uniform heating of the bottom wall, the heat transfer rate or Nub is high at the edges of the bottom wall due to the discontinuities present in the temperature boundary conditions at the edges and reduces towards the center of the bottom wall with the minimum value at the center. Effect of streamline loop numbers on heat transfer is shown for various aspect ratios in this study. The present paper analyzes entropy generation induced by free convection and effect of different parameters on entropy generation is studied. Relation of Nusselt number and Bejan number with aspect ratio is given that is due to effect of stream loops number. In lower Ra, because of weak stream, entropy generation is more due to heat transfer irreversibility (HHI).

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Slip flow of Jeffrey nanofluid with activation energy and entropy generation applications

Advances in Mechanical Engineering ◽

10.1177/16878140211006578 ◽

2021 ◽

Vol 13 (3) ◽

pp. 168781402110065

Author(s):

Hu Ge-JiLe ◽

Sumaira Qayyum ◽

Faisal Shah ◽

M Ijaz Khan ◽

Sami Ullah Khan

Keyword(s):

Activation Energy ◽

Entropy Generation ◽

Slip Flow ◽

Graphical Analysis ◽

Thermal Engineering ◽

Bejan Number ◽

Nano Technology ◽

Flow Equations ◽

Jeffrey Nanofluid ◽

Buongiorno Model

The growing development in the thermal engineering and nano-technology, much attention has been paid on the thermal properties of nanoparticles which convey many applications in industrial, technological and medical era of sciences. The noteworthy applications of nano-materials included heat transfer enhancement, thermal energy, solar systems, cooling of electronics, controlling the heat mechanisms etc. Beside this, entropy generation is an optimized scheme which reflects significances in thermodynamics systems to control the higher energy efficiency. On this end, present work presents the slip flow of Jeffrey nanofluid over a stretching sheet with applications of activation energy and viscous dissipation. The entropy generation features along with Bejan number significance is also addressed in present analysis. Buongiorno model of nanofluid is used to discuss the heat and mass transfer. The formulated flow equations are attained into non-dimensional form. An appropriate ND MATHEMATICA built-in scheme is used to find the solution. The solution confirmation is verified by performing the error analysis. For developed flow model and impacted parameters, a comprehensive graphical analysis is performed. It is observed that slip phenomenon is used to decays the velocity profile. Temperature and concentration are in direct relation with Brownian motion parameter and activation energy respectively. Entropy and Bejan number have same results for greater diffusion parameter.

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Entropy generation analysis for MHD flow of water past an accelerated plate

Scientific Reports ◽

10.1038/s41598-021-89744-w ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Tarek N. Abdelhameed

Keyword(s):

Magnetic Field ◽

Entropy Generation ◽

Transfer Problem ◽

Finite Difference Methods ◽

Mhd Flow ◽

Bejan Number ◽

Physical Conditions ◽

Flow Parameters ◽

The Laplace Transform ◽

Constant Heating

AbstractThis article examines the entropy generation in the magnetohydrodynamics (MHD) flow of Newtonian fluid (water) under the effect of applied magnetic in the absence of an induced magnetic field. More precisely, the flow of water is considered past an accelerated plate such that the fluid is receiving constant heating from the initial plate. The fluid disturbance away from the plate is negligible, therefore, the domain of flow is considered as semi-infinite. The flow and heat transfer problem is considered in terms of differential equations with physical conditions and then the corresponding equations for entropy generation and Bejan number are developed. The problem is solved for exact solutions using the Laplace transform and finite difference methods. Results are displayed in graphs and tables and discussed for embedded flow parameters. Results showed that the magnetic field has a strong influence on water flow, entropy generation, and Bejan number.

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Second Law Analysis of Laminar Flow in a Circular Pipe Immersed in an Isothermal Fluid

Journal of Thermodynamics ◽

10.1155/2013/234264 ◽

2013 ◽

Vol 2013 ◽

pp. 1-10 ◽

Cited By ~ 3

Author(s):

Vishal Anand ◽

Krishna Nelanti

Keyword(s):

Laminar Flow ◽

Entropy Generation ◽

Circular Tube ◽

Dimensionless Temperature ◽

Bejan Number ◽

Uniform Wall Temperature ◽

Thermal Boundary Conditions ◽

Fluid Properties ◽

Isothermal Fluid ◽

Uniform Wall

Entropy generation and pumping power to heat transfer ratio (PPR) of a laminar flow, for a circular tube immersed in an isothermal fluid, are studied analytically in this paper. Two different fluids, namely, water and ethylene glycol, are chosen to study the influence of fluid properties on entropy generation and PPR. The expressions for dimensionless entropy generation, Bejan number and PPR are derived in a detailed way and their variations with Reynolds number, external Biot number, and the dimensionless temperature difference are illustrated. The results of the analysis are compared with those for a laminar flow in a circular tube with uniform wall temperature boundary condition. Finally, a criterion is established to determine which type of thermal boundary conditions is more suitable for a particular fluid, with respect to its influence on entropy generation.

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Conjugate Free Convection Heat Transfer and Thermodynamic Analysis of Infrared Suppression Device with Cylindrical Funnels

Journal of Heat Transfer ◽

10.1115/1.4053455 ◽

2022 ◽

Author(s):

Vikrant Chandrakar ◽

Arnab Mukherjee ◽

Jnana Ranjan Senapati ◽

Ashok Kumar Barik

Keyword(s):

Heat Transfer ◽

Entropy Generation ◽

Convection Heat Transfer ◽

Navier Stokes ◽

Bejan Number ◽

Navier Stokes Equation ◽

Ansys Fluent ◽

Geometric Ratio ◽

Flow Rate Increase ◽

Free Convection Heat

Abstract A convection system can be designed as an energy-efficient one by making a considerable reduction in exergy losses. In this context, entropy generation analysis is performed on the infrared suppression system numerically. In addition, results due to heat transfer are also shown. The numerical solution of the Navier-stokes equation, energy equation, and turbulence equation is executed using ANSYS Fluent 15.0. To perform the numerical analysis, different parameters such as the number of funnels, Rayleigh number (Ra), inner surface temperature, and geometric ratio are varied in the practical range. Results are shown in terms of heat transfer, entropy generation, irreversibility (due to heat transfer and fluid friction), and Bejan number with some relevant parameters. Streamlines and temperature contours are also provided for better visualization of temperature and flow field around the device. Results show that heat transfer and mass flow rate increase with the increase in Ra. Entropy generation and the irreversibility rise with an increase in the number of funnels and geometric ratio. Also, the Bejan number decreases with an increase in Ra and the number of funnels. A cooling time is also obtained using the lumped capacitance method.

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Heat Transfer and Entropy Generation Characteristics of a Non-Newtonian Fluid Squeezed and Extruded Between Two Parallel Plates

Journal of Heat Transfer ◽

10.1115/1.4034898 ◽

2016 ◽

Vol 139 (2) ◽

Cited By ~ 9

Author(s):

P Kaushik ◽

Pranab Kumar Mondal ◽

Sukumar Pati ◽

Suman Chakraborty

Keyword(s):

Heat Transfer ◽

Newtonian Fluid ◽

Entropy Generation ◽

Bejan Number ◽

Engineering Systems ◽

Power Law Model ◽

Parallel Plates ◽

Unsteady Heat Transfer ◽

Thermodynamic Performance ◽

Fluid Rheology

This study investigates the unsteady heat transfer and entropy generation characteristics of a non-Newtonian fluid, squeezed and extruded between two parallel plates. In an effort to capture the underlying thermo-hydrodynamics, the power-law model is used here to describe the constitutive behavior of the non-Newtonian fluid. The results obtained from the present analysis reveal the intricate interplay between the fluid rheology and the squeezing dynamics, toward altering the Nusselt number and Bejan number characteristics. Findings from this study may be utilized to design optimal process parameters for enhanced thermodynamic performance of engineering systems handling complex fluids undergoing simultaneous extrusion and squeezing.

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Entropy Analysis on a Three-Dimensional Wavy Flow of Eyring–Powell Nanofluid: A Comparative Study

Mathematical Problems in Engineering ◽

10.1155/2021/6672158 ◽

2021 ◽

Vol 2021 ◽

pp. 1-14

Author(s):

Arshad Riaz ◽

Ahmed Zeeshan ◽

M. M. Bhatti

Keyword(s):

Viscous Dissipation ◽

Newtonian Fluid ◽

Entropy Generation ◽

Pressure Rise ◽

Software Tool ◽

Bejan Number ◽

Mathematical Treatment ◽

Cylindrical Domain ◽

Special Cases ◽

The Impact

The thermal management of a system needs an accurate and efficient measurement of exergy. For optimal performance, entropy should be minimized. This study explores the enhancement of the thermal exchange and entropy in the stream of Eyring–Powell fluid comprising nanoparticles saturating the vertical oriented dual cylindrical domain with uniform thermal conductivity and viscous dissipation effects. A symmetrical sine wave over the walls is used to induce the flow. The mathematical treatment for the conservation laws are described by a set of PDEs, which are, later on, converted to ordinary differential equations by homotopy deformations and then evaluated on the Mathematica software tool. The expression of the pressure rise term has been handled numerically by using numerical integration by Mathematica through the algorithm of the Newton–Cotes formula. The impact of the various factors on velocity, heat, entropy profile, and the Bejan number are elaborated pictorially and tabularly. The entropy generation is enhanced with the variation of viscous dissipation but reduced in the case of the concentration parameter, but viscous dissipation reveals opposite findings for the Newtonian fluid. From the abovementioned detailed discussion, it can be concluded that Eyring–Powell shows the difference in behavior in the entropy generation and in the presence of nanoparticles due to the significant dissipation effects, and also, it travels faster than the viscous fluid. A comparison between the Eyring-Powell and Newtonian fluid are also made for each pertinent parameter through special cases. This study may be applicable for cancer therapy in biomedicine by nanofluid characteristics in various drugs considered as a non-Newtonian fluid.

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Entropy Generation of MHD Poiseuille Flow with Hall and Joule Heating Effects

International Journal of Mechanics ◽

10.46300/9104.2020.14.4 ◽

2020 ◽

Vol 14 ◽

Keyword(s):

Entropy Generation ◽

Joule Heating ◽

Poiseuille Flow ◽

Hall Current ◽

Coupled System ◽

Bejan Number ◽

Electrically Conducting ◽

Heating Effects ◽

Adomian Decomposition ◽

Ion Slip

In this article investigation has been conducted on the effects of Hall parameter, rotation parameter and Joule heating on the entropy generation of fully developed electrically conducting Poiseuille flow. The coupled system of ordinary differential equations for the flow are obtained, non-dimensionalised and solutions are constructed by Adomian decomposition technique. The effects of Hall current, Ion-slip, Joule heating and magnetic parameters on the velocity, temperature, entropy generation and Bejan number are explained and shown graphically. The results indicate that fluid entropy generation is induced by increase in Hall current, rotation and Joule heating parameters. Furthermore Bejan number is accelerated by Hall current, rotation, Magnetic and Joule heating parameters which signifies that heat transfer irreversibility dominates entropy generation.

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Entropy Optimization of Third-Grade Nanofluid Slip Flow Embedded in a Porous Sheet With Zero Mass Flux and a Non-Fourier Heat Flux Model

Frontiers in Physics ◽

10.3389/fphy.2020.00250 ◽

2020 ◽

Vol 8 ◽

Author(s):

K. Loganathan ◽

G. Muhiuddin ◽

A. M. Alanazi ◽

Fehaid S. Alshammari ◽

Bader M. Alqurashi ◽

...

Keyword(s):

Heat Flux ◽

Entropy Generation ◽

Mass Flux ◽

Slip Flow ◽

Porous Plate ◽

Bejan Number ◽

Surface Boundary ◽

Nanoparticle Concentration ◽

Zero Mass ◽

Analysis Scheme

The prime objective of this article is to explore the entropy analysis of third-order nanofluid fluid slip flow caused by a stretchable sheet implanted in a porous plate along with thermal radiation, convective surface boundary, non-Fourier heat flux applications, and nanoparticle concentration on zero mass flux conditions. The governing physical systems are modified into non-linear ordinary systems with the aid of similarity variables, and the outcomes are solved by a homotopy analysis scheme. The impression of certain governing flow parameters on the nanoparticle concentration, temperature, and velocity is illustrated through graphs, while the alteration of many valuable engineering parameters viz. the Nusselt number and Sherwood number are depicted in graphs. Entropy generation with various parameters is obtained and discussed in detail. The estimation of entropy generation using the Bejan number find robust application in power engineering and aeronautical propulsion to forecast the smartness of entire system.

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