NATURAL CONVECTION IN MAGNETIC NANOFLUIDS

Abstract

In the forced convection heat transfer, the magnetic nanofluids have been proved efficient, theoretically and experimentally. But, a conflict exists between the theoretical and experimental studies on the natural convection heat transfer in magnetic nanofluids. The theoretical investigations evidenced an enhancement in the heat transfer capabilities of magnetic nanofluids in natural convection. In contrast, a deterioration was reported in the experimental findings, which are very few in number and based on the Rayleigh Bénard convection model. The above conflict between the theoretical and experimental studies on natural convection and to provide more information on the open cavity natural convection is the inspiration of the current study. A cubic cavity, heated from the bottom and open from the top to a controlled environment, is filled by the water-based Fe3O4-water magnetic nanofluids. First, the analysis is done on the water as the working fluid to validate the test section as well as provide more information on the thermal boundary layer properties and temperature fluctuation in the open cavity, followed by the Fe3O4-water magnetic nanofluids of different particle concentrations. The particle concentrations of 0.01 and 0.1 vol.%, and the presence of externally applied magnetic field intensity from 0 to 730 Gauss are selected to investigate their effects on the heat transfer. In addition to the concentrations and magnetic field, the heat flux at the bottom plate is the other parameter, which is examined in the present study.