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Free convection heat transfer and entropy generation analysis of water-Fe3O4/CNT hybrid nanofluid in a concentric annulus

Amin Shahsavar (Department of Mechanical Engineering, Kermanshah University of Technology, Kermanshah, Iran)
Pouyan Talebizadeh Sardari (Department of Mechanical and Aeronautical Engineering, University of Nottingham, Nottingham, UK)
D. Toghraie (Department of Mechanical Engineering, Islamik Azad University, Khomeinishahr Branch, Isfahan, Iran)

International Journal of Numerical Methods for Heat & Fluid Flow

ISSN: 0961-5539

Article publication date: 30 November 2018

Issue publication date: 22 February 2019

453

Abstract

Purpose

This paper aims to numerically investigate the heat transfer and entropy generation characteristics of water-based hybrid nanofluid in natural convection flow inside a concentric horizontal annulus.

Design/methodology/approach

The hybrid nanofluid is prepared by suspending tetramethylammonium hydroxide-coated Fe3O4 (magnetite) nanoparticles and gum arabic (GA)-coated carbon nanotubes (CNTs) in water. The effects of nanoparticle volume concentration and Rayleigh number on the streamlines, isotherms, average Nusselt number and the thermal, frictional and total entropy generation rates are investigated comprehensively.

Findings

Results show the advantageous effect of hybrid nanofluid on the average Nusselt number. Furthermore, the study of entropy generation shows the increment of both frictional and thermal entropy generation rates by increasing Fe3O4 and CNT concentrations at various Rayleigh numbers. Increasing Rayleigh number from 103 to 105, at Fe3O4 concentration of 0.9 per cent and CNT concentration of 1.35 per cent, increases the average Nusselt number, thermal entropy generation rate and frictional entropy generation rate by 224.95, 224.65 and 155.25 per cent, respectively. Moreover, increasing the Fe3O4 concentration from 0.5 to 0.9 per cent, at Rayleigh number of 105 and CNT concentration of 1.35 per cent, intensifies the average Nusselt number, thermal entropy generation rate and frictional entropy generation rate by 18.36, 22.78 and 72.7 per cent, respectively.

Originality/value

To the best knowledge of the authors, there are not any archival publications considering the detailed behaviour of the natural convective heat transfer and entropy generation of hybrid nanofluid in a concentric annulus.

Keywords

Citation

Shahsavar, A., Talebizadeh Sardari, P. and Toghraie, D. (2019), "Free convection heat transfer and entropy generation analysis of water-Fe3O4/CNT hybrid nanofluid in a concentric annulus", International Journal of Numerical Methods for Heat & Fluid Flow, Vol. 29 No. 3, pp. 915-934. https://doi.org/10.1108/HFF-08-2018-0424

Publisher

:

Emerald Publishing Limited

Copyright © 2018, Emerald Publishing Limited

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