Effects of magnetic fields and nanoparticle concentration on hydro-thermal performance of a surface enhanced microchannel

Abstract

This article numerically investigates fluid flow and heat transfer in plain wall (PWMC) and oblique fin (OFMC) microchannels under varying magnetic fields using water- Al2O3 nanofluid as a working fluid. Effects of magnetic flux (Hartmann number, Ha = 0–30), fluid velocity (Reynolds number, Re = 100–500), and nanoparticle volume fraction (ϕ = 0%–2%) on the overall thermo-fluid performance are analyzed. Magnetic fields can significantly improve the heat transfer in OFMC in a higher rate compared to the PWMC. Also, there is a less increment on the pressure drop in the OFMC in comparison to PWMC. In addition, individual, as well as combined effect of Joule and viscous heating on the thermo-fluid performance is investigated. Due to the combined effect of Joule and viscous heating, the Performance Evaluation Criterion (PEC) in OFMC can be improved by 21%. However, the PEC in OFMC can be enhanced by 55% without considering the combined effect. The detailed characteristics flow and heat transfer are also studied by analyzing the velocity contours, isotherms, streamlines, friction factors, and Nusselt numbers. The present study concludes the importance of consideration of Joule and viscous heating for an accurate modeling, where the viscous heating plays the dominant role. The present findings can be instrumental in enhancing the performance of micro heat sinks to optimize hydrothermal performance in high powered motors, nuclear fusion reactors etc., where magnetic field is present.