Non-Uniform Magnetic Field Effect on Forced Convection Heat Transfer of Flattened Tubes Using Two-Phase Mixture Model

Abstract

The effect of non-uniform magnetic field on forced convection heat transfer of ferrofluids in flattened tubes has been investigated numerically using two-phase mixture model. The equilibrium magnetization for the ferrofluids is considered, and the linear relationship of magnetization with applied magnetic field intensity is assumed to relax. The main goal of the current research is to study the effect of tube flattening under the non-uniform magnetic field and influence of three various positions of current-carrying wires on flow structure and thermal-hydraulic performance of laminar ferrofluids flow in flattened tubes. Numerical results have been presented within the electric current range of 1–5 A. Results demonstrated that the heat transfer coefficient has been varied from 300 to 1800 W/m² K. In addition, the non-uniform magnetic field with a wire affects the flow structure, and creates two major and four minor vortices in the flattened tubes; but, in the presence of two parallel wires, only four major vortices are created. It is also observed that when the two parallel wires are located in the flat parts of the flattened tubes, the average heat transfer has been reached to its maximum (the heat transfer enhancement is about 240%). However, in contrast to this enhancement, the pressure drop also increases about 82%. Finally, the position of two wires in flat parts is appropriate to enhance the heat transfer while flattening the tube.

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Notes on contributors

Elnaz Yousefi

Elnaz Yousefi received her bachelor’s degree in Mechanical Engineering at Imam Khomeini International University, Qazvin, Iran. Her main areas of research interests are computational fluid dynamics, turbulent flow, convection heat transfer, and magneto-hydrodynamics.

Hamid Reza Nazif

Hamid Reza Nazif received his BS and MS in Mechanical Engineering from Sharif University of Technology and Amirkabir University of Technology in 1996 and 1998, respectively. He received his PhD degree in 2011. His main areas of research interests are computational fluid dynamics, turbulent flow, heat transfer, multi-phase flow, heat and mass transfer in porous media, and the kinetic theory of granular flow.

Hasan Najafi Khaboshan

Hasan Najafi Khaboshan gained a master’s degree in Mechanical Engineering at Imam Khomeini International University, Qazvin, Iran (in 2017). He received his bachelor’s degree in Mechanical Engineering in 2015. His main areas of research interests are turbulent flow, convection heat transfer, multi-phase flows, computational fluid dynamics, and fluid flow control in industrial applications.

Amiratabak Azarinia

Amiratabak Azarinia is a master’s student in Mechanical Engineering at the Faculty of Aerospace Engineering, Khaje Nasir Toosi University of Technology, Tehran, Iran. His fields of research interests are fluid dynamics, heat transfer, and thermodynamics.