# Entropy Generation Through Heat And Fluid Flow Pdf Wiley

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Published: 29.04.2021

- Entropy generation through heat and fluid flow
- Hall Current and Joule Heating Effects on Flow of Couple Stress Fluid with Entropy Generation
- A modified entropy generation number for heat exchangers

This paper demonstrates the difference between the entropy generation number method proposed by Bejan and the method of entropy generation per unit amount of heat transferred in analyzing the thermodynamic performance of heat exchangers, points out the reason for leading to the above difference. A modified entropy generation number for evaluating the irreversibility of heat exchangers is proposed which is in consistent with the entropy generation per unit amount of heat transferred in entropy generation analysis. The entropy generated by friction is also investigated.

## Entropy generation through heat and fluid flow

The present study examines the entropy generation on Couette flow of a viscous fluid in parallel plates filled with deformable porous medium. The fluid is injected into the porous channel perpendicular to the lower wall with a constant velocity and is sucked out of the upper wall with same velocity. The coupled phenomenon of the fluid flow and solid deformation in the porous medium is taken in to consideration. The exact expressions for the velocity of fluid, solid displacement and temperature distribution are found analytically. The effect of pertinent parameters on the fluid velocity, solid displacement and temperature profiles are discussed in detail. The results obtained for the present flow characteristic reveal several interesting behaviors that warrant further study on the deformable porous media.

Gamal M. Chemical entropy generation and magnetohydrodynamic effects on the unsteady heat and fluid flow through a porous medium have been numerically investigated. The entropy generation due to the use of a magnetic field and porous medium effects on heat transfer, fluid friction, and mass transfer have been analyzed numerically. Using a similarity transformation, the governing equations of continuity, momentum, and energy and concentration equations, of nonlinear system, were reduced to a set of ordinary differential equations and solved numerically. Industries developing technology related to heat transfer are more concerned with the design of new thermal systems; thus research is in progress to investigate the hydrodynamic and heat transfer behavior of new forms of heat transfer fluid. Recently, entropy generation or production has been used to gauge the significance of irreversibility related to heat transfer, friction, and other nonideal processes within thermal system by Bejan [ 1 ]. Entropy generation and its minimization have been considered as an effective tool to improve the performance of any heat transfer process.

## Hall Current and Joule Heating Effects on Flow of Couple Stress Fluid with Entropy Generation

Entropy generation in hydromagnetic and thermal boundary layer flow due to radial stretching sheet with Newtonian heating. The entropy generation during hydromagnetic boundary layer flow of a viscous incompressible electrically conducting fluid due to radial stretching sheet with Newtonian heating in the presence of a transverse magnetic field and the thermal radiation has been analyzed. The governing equations are then solved numerically by using the fourth order Runge-Kutta method with shooting technique. The effects of the pertinent parameters on the fluid velocity, temperature, entropy generation number, Bejan number, as well as the shear stress at the surface of the sheet are discussed graphically and quantitatively. It is examined that because the presence of a magnetic field, the entropy generation in a thermal system can be controlled and reduced.

Non-Newtonian fluid flow in a pipe system is considered and a third grade non-Newtonian fluid is employed in the analysis. The velocity and temperature distributions across the pipe are presented. Entropy generation number due to heat transfer and fluid friction is formulated. The influences of non-Newtonian parameter and Brinkman number on entropy generation number are examined. It is found that increasing the non-Newtonian parameter reduces the fluid friction in the region close to the pipe wall.

Optimal paths for minimizing lost available work during heat transfer processes with a generalized heat transfer law. The optimal heating and cooling configurations for minimizing lost available work are derived for the fixed initial and final temperatures of the working fluid of the system low-temperature side. Optimal paths are compared with the common strategies of constant heat flux, constant source reservoir temperature and the minimum entropy generation operation by numerical examples. The obtained results are more general and can provide some theoretical guidelines for the designs and operations of practical heat exchangers. Keywords: Finite time thermodynamics; Lost available work; Optimal control; Heat transfer process; Heat transfer law.

## A modified entropy generation number for heat exchangers

The present study is related to entropy analysis during magnetohydrodynamic MHD boundary layer flow of a viscous incompressible electrically conducting fluid past a stretching cylinder with convective heating in the presence of a transverse magnetic field. The governing boundary layer equations in cylindrical form are simplified by means of appropriate similarity transformations. Numerical solutions with high precision are obtained using Runge-Kutta fourth order scheme with eminent shooting technique. The effects of the pertinent parameters on the fluid velocity, temperature, entropy generation number, Bejan number as well as the shear stress at the surface of the cylinder are discussed graphically and quantitatively.

*In this work, an analytical study of the effects of Hall current and Joule heating on the entropy generation rate of couple stress fluid is performed. It is assumed that the applied pressure gradient induces fluid motion.*

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