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Heat transfer enhancement with nanofluid in an open enclosure due to discrete heaters mounted on sidewalls and a heated inner block

Endalkachew Getachew Ushachew (Guru Jambheshwar University of Science and Technology, Hisar, India)
Mukesh Kumar Sharma (Department of Mathematics, Guru Jambheshwer University of Science and Technology, Hisar, India)
Mohammad Mehdi Rashidi (Department of Mechanics, Tongji University, Shanghai, China)

International Journal of Numerical Methods for Heat & Fluid Flow

ISSN: 0961-5539

Article publication date: 10 December 2020

Issue publication date: 6 July 2021

179

Abstract

Purpose

The purpose of this study is to explore the heat transfer enhancement in copper–water nanofluid flowing in a diagonally vented rectangular enclosure with four discrete heaters mounted centrally on the sidewalls and a square-shaped embedded heated block in the influence of a static magnetic field.

Design/methodology/approach

Four discrete heaters are mounted centrally on each sidewall of the rectangular enclosure that embraces a heated square block. A static transverse magnetic field is acting on the vertical walls. The Navier–Stokes equations of motion and the energy equation are modified by incorporating Lorentz force and basic physical properties of nanofluid. The derived momentum and energy equations are tackled numerically using the successive over-relaxation technique associating with the Gauss–Seidel iteration technique. The effects of physical parameters connected to dynamics of flow and heat convection are explored from streamlines and isotherms graphs and discussed numerically in terms of Nusselt number.

Findings

The effect of the embedded heated square block size and its location in the enclosure, nanoparticles volume fraction and the intensity of the magnetic field on flow and heat transfer are computed. Compared with the case when no heated block is embedded in the enclosure, in free convection at Ra = 106, the average local Nusselt number on the wall-mounted heaters is attenuated by 8.25%, 11.24% and 12.75% when the enclosure embraced a heated square block of side length 10% of H, 20% of H and 30% of H, respectively. An increase in Hartmann number suppresses the heat convection.

Research limitations/implications

The enhancement in the convective heat is greater when the buoyancy effect dominates the viscous effects. Placing the embedded heated block near the inlet vent, the lower temperature zone has reduced while the embedded heated block is at the central location of the enclosure, the high-temperature zone has expanded. The external magnetic field can be used as a non-invasive controlling device.

Practical implications

The numerically simulated results for heat convection of water-based copper nanofluid agreed qualitatively with the existing experimental results.

Social implications

The models could be used in designing a target-oriented heat exchanger.

Originality/value

The paper includes a comparative study for three locations of the embedded heated square. The optimal results for the centrally located heated block are also performed for three different sizes of the embedded block. The numerically simulated results are compared with the published numerical and experimental studies.

Keywords

Citation

Getachew Ushachew, E., Sharma, M.K. and Rashidi, M.M. (2021), "Heat transfer enhancement with nanofluid in an open enclosure due to discrete heaters mounted on sidewalls and a heated inner block", International Journal of Numerical Methods for Heat & Fluid Flow, Vol. 31 No. 7, pp. 2172-2196. https://doi.org/10.1108/HFF-09-2020-0605

Publisher

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Emerald Publishing Limited

Copyright © 2020, Emerald Publishing Limited

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