Thermal and hydrodynamic performances of MHD ferrofluid flow inside a porous channel

Abstract

MHD mixed convection heat transfer inside a rectangular porous channel under the effects of constant and alternating magnetic fields has been experimentally investigated. Deionized water containing magnetite particles flows through the channel filled with copper foam as a porous media. A constant heat flux condition is imposed on the top and bottom plates of the channel, while the side walls are adiabatic. Experiments were carried out at Gr=7.31×106 and 373≤Re≤1186. Influence of porous media, volume fraction of ferrofluid (ϕ=0.5%, 1%, 1.5%), Reynolds number and magnetic field intensities and frequencies (B=250, 450G and f=5, 10Hz) on the characteristics of heat transfer and hydrodynamic are studied. The experimental results revealed that the copper foam has a significant effect on the thermal and hydrodynamic performances of the channel due to heat spreading through the copper matrix, better mixing of the fluid and extending the heat transfer area. It was observed that employing ferrofluid with different volume fractions increases both heat transfer rate and pressure drop because of thermal conductivity and viscosity increment, respectively. Applying constant magnetic field causes aggregation of nanoparticles in the area where the magnetic field is applied and consequently, heat transfer and pressure drop increase. Moreover employing alternating magnetic field further increased the heat transfer rate due to more intensified disturbance of the thermal boundary layer and improvement of the nanoparticles migrations. The alternating magnetic field reduced pressure drop because of the periodic magnetic forces, leading to enhanced overall performance of the channel.