Entropy 2005, 7[4], 234-252
Entropy
ISSN 1099-4300
http://www.mdpi.org/entropy/

Numerical Prediction of Entropy Generation in Separated Flows

Eiyad Abu-Nada

Department of Mechanical Engineering, Hashemite University, Zarqa, 13115, Jordan,
Tel. 00962 5 3903333 Fax: 009622 5 3826613,
E-mail: eiyad@hu.edu.jo

Received: 17 July 2005 / Accepted: 5 September 2005 / Published: 6 October 2005

Abstract: The present research investigates second law analysis of laminar flow over a backward facing step (BFS). Entropy generation due to separation, reattachment, recirculation and heat transfer is studied numerically. Local entropy generation distributions were obtained by solving momentum, energy, and entropy generation equations. The effect of dimensionless temperature difference number (τ) and Brinkman number (Br) on the total entropy generation number (Ns) was investigated. Moreover, the effect of Reynolds number (Re) on the value of Ns was reported. It was found that as Re increased the value of Ns increased. Also, as Br increased the value of Ns increased. However, it was found that as τ increased the value of Ns decreased. For the bottom wall of the channel, the maximum value of Ns occurs inside the recirculation zone and reduces to a minimum value at the point of reattachment point. Also, for Re ≥ 500, a second peak of entropy generation appears after the reattachment point. For the top wall of the channel, the value of Ns has a maximum value directly above the step and its value reduced downstream the step. The contribution of the top wall to Ns downstream the point of reattachment was relatively small.

Keywords: entropy generation; backward facing step; separated flow; heat transfer.


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