Mixed convection and thermodynamic irreversibilities in MHD nanofluid stagnation-point flows over a cylinder embedded in porous media

Alizadeh, R., Karimi, N. , Arjmandzadeh, R. and Mehdizadeh, A. (2019) Mixed convection and thermodynamic irreversibilities in MHD nanofluid stagnation-point flows over a cylinder embedded in porous media. Journal of Thermal Analysis and Calorimetry, 135(1), pp. 489-506. (doi:10.1007/s10973-018-7071-8)

Alizadeh, R., Karimi, N. , Arjmandzadeh, R. and Mehdizadeh, A. (2019) Mixed convection and thermodynamic irreversibilities in MHD nanofluid stagnation-point flows over a cylinder embedded in porous media. Journal of Thermal Analysis and Calorimetry, 135(1), pp. 489-506. (doi:10.1007/s10973-018-7071-8)

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Abstract

The impingement of CuO-water nanofluid flows upon a cylinder subject to a uniform magnetic field with constant surface temperature and embedded in porous media is investigated for the first time in literature. The surface of the cylinder can feature uniform or non-uniform mass transpiration and is hotter than the incoming nanofluid flow. The gravitational effects are taken into account and the three-dimensional governing equations of mixed convection in curved porous media, under magnetohydrodynamic effects, are reduced to those solvable by a finite difference scheme. Through varying a mixed convection parameter, the situations dominated by forced, mixed and free convection are examined systematically. The numerical solutions of these equations reveal the flow velocity and temperature fields as well as the Nusselt number and induced shear stress. These are then used to calculate the rate of entropy generation within the system by viscous and heat transfer irreversibilities. The results show that Nusselt number increases with increasing the concentration of nanoparticles, while it slightly deceases through intensifying the magnetic parameter. Non-uniform transpiration is shown to strongly affect the average rate of heat transfer. Importantly, it is demonstrated that the specific mode of heat convection can majorly influence the intensity of entropy generation and that the irreversibilities are much larger under natural convection compared to those in mixed and forced convection. Calculation of Bejan number shows that this is due to more pronounced relative contribution of viscous irreversibilities when free convection effects dominate the mixed convection process.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Karimi, Dr Nader
Authors: Alizadeh, R., Karimi, N., Arjmandzadeh, R., and Mehdizadeh, A.
College/School:College of Science and Engineering > School of Engineering > Systems Power and Energy
Journal Name:Journal of Thermal Analysis and Calorimetry
Publisher:Springer
ISSN:1388-6150
ISSN (Online):1572-8943
Published Online:27 February 2018
Copyright Holders:Copyright © 2018 The Authors
First Published:First published in Journal of Thermal Analysis and Calorimetry 135(1): 489-506
Publisher Policy:Reproduced under a Creative Commons License

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