The impacts of non-uniform magnetic field on free convection heat transfer of a magnetizable micropolar nanofluid

Abstract

Purpose

The purpose of this study is to numerically study the heat transfer of free convection of a magnetizable micropolar nanofluid inside a semicircular enclosure.

Design/methodology/approach

The flow domain is under simultaneous influences of two non-uniform magnetic fields generated by current carrying wires. The directions of the currents are the same. Although the geometry is symmetric, it is physically asymmetric. The impacts of key parameters, including Rayleigh number Ra = 10³-10⁶, Hartman number Ha = 0-50, vortex viscosity parameter Δ = 0-4, nanoparticles volume fraction φ = 0-0.04 and magnetic number Mn_f = 0-1000, on the macro- and micro-scales flows, temperature and heat transfer rate are studied.

Finding

The outcomes show that dispersing of the nanoparticles in the host fluid increases the strength of macro- and micro-scale flows. When Mn_f = 0, the increment of the vortex viscosity parameter increases the strength of the particles micro-rotations, while this characteristic is decreased by growing Δ for Mn_f ≠ 0. The increment of Δ and Ha decreases the rate of heat transfer. The increment of Ha decreases the enhancement percentage of heat transfer rate because of dispersing nanoparticles, known as En parameter. In addition, the value of Δ has no effect on En. Moreover, the average Nusselt number Nu_avg and En remain constant by increasing the magnetic number Mn_f for different volume fraction values.

Originality/value

The authors believe that all of the results, both numerical and asymptotic, are original and have not been published elsewhere yet.

Citation

Namazian, Z. and Mehryan, S.A.M. (2019), "The impacts of non-uniform magnetic field on free convection heat transfer of a magnetizable micropolar nanofluid", International Journal of Numerical Methods for Heat & Fluid Flow, Vol. 29 No. 10, pp. 3685-3706. https://doi.org/10.1108/HFF-10-2018-0551