Title: Local exergy loss rate in convective heat transfer

Authors: Chuanshan Dai; Haojie Cheng; Haiyan Lei; Yakun Xu

Addresses: Key Laboratory of Efficient Utilization of Low and Medium Grade Energy, MOE, School of Mechanical Engineering, Tianjin University, Tianjin 300072, China ' Mechanical Engineering of Tianjin University, Tianjin 30072, China ' Key Laboratory of Efficient Utilization of Low and Medium Grade Energy, MOE, School of Mechanical Engineering, Tianjin University, Tianjin 300072, China ' Qingdao Institute of Measurement Technology, Qingdao, Shandong Province 266000, China

Abstract: The equation of local exergy loss rate in forced convective heat transfer has been derived in present work. The obtained exergy loss equation involves exergy loss due to heat transfer and pressure drop as well as exergy generation on account of viscous heat dissipation. The dimensionless form of local exergy loss rate and entropy generation different from the previous can also be obtained. Moreover, the calculation results of two convective heat transfer problems about local exergy loss and local entropy generation proposed by Bejan are given. The effect of temperature difference, Prandtl number and Eckert number on exergy loss and entropy generation has been analysed and the comparison between exergy loss and entropy generation under various conditions has been made. Results shows that for Poiseuille flow the local exergy loss greatly differs from the entropy generation due to the presence of pressure drop. However, viscous dissipation takes an important role in exergy loss for Couette flow on account of no pressure drop.

Keywords: local exergy loss; convective heat transfer; local entropy generation.

DOI: 10.1504/IJEX.2017.087644

International Journal of Exergy, 2017 Vol.24 No.2/3/4, pp.133 - 150

Received: 24 Nov 2016
Accepted: 01 Mar 2017

Published online: 22 Oct 2017 *

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