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Legitimacy of the local thermal equilibrium hypothesis in porous media: A comprehensive review

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journal contribution
posted on 2022-06-28, 03:54 authored by Gazy F Al-Sumaily, Amged Al Ezzi, Hayder A Dhahad, Mark C Thompson, Talal YusafTalal Yusaf

Local thermal equilibrium (LTE) is a frequently-employed hypothesis when analysing convection heat transfer in porous media. However, investigation of the non-equilibrium phenomenon exhibits that such hypothesis is typically not true for many circumstances such as rapid cooling or heating, and in industrial applications involving immediate transient thermal response, leading to a lack of local thermal equilibrium (LTE). Therefore, for the sake of appropriately conduct the technological process, it has become necessary to examine the validity of the LTE assumption before deciding which energy model should be used. Indeed, the legitimacy of the LTE hypothesis has been widely investigated in different applications and different modes of heat transfer, and many criteria have been developed. This paper summarises the studies that investigated this hypothesis in forced, free, and mixed convection, and presents the appropriate circumstances that can make the LTE hypothesis to be valid. For example, in forced convection, the literature shows that this hypothesis is valid for lower Darcy number, lower Reynolds number, lower Prandtl number, and/or lower solid phase thermal conductivity; however, it becomes invalid for higher effective fluid thermal conductivity and/or lower interstitial heat transfer coefficient.

History

Volume

14

Issue

23

Start Page

1

End Page

47

Number of Pages

47

eISSN

1996-1073

Publisher

MDPI

Additional Rights

CC BY 4.0

Language

en

Peer Reviewed

  • Yes

Open Access

  • Yes

Acceptance Date

2021-11-26

External Author Affiliations

University of Technology, Iraq

Era Eligible

  • Yes

Medium

Electronic

Journal

Energies

Article Number

8114