Convective Heat Transfer of Al2O3 Nanofluids in Porous Media

Abstract

In this study, the performance of a heat sink embedded with a porous medium and nanofluids as coolants is analyzed experimentally. The nanofluid is a mixture of de-ionized water and nanoscale Al2O3 particles with three different volumetric concentrations: ζ = 0.41%, 0.58%, and 0.83%. The experimental test section is a rectangular minichannel filled with metal foam, which is electrically heated to provide a constant heat flux. The porous medium is assumed to be homogeneous and the flow regime is laminar. The result of heat transfer enhancement by slurry of Al2O3 nanofluid in porous media is studied under various flow velocities, heat flux, porous media structure, and particle concentration of nanofluid. The effect of particles volume fraction on heat transfer coefficient is also studied. This experimental study discovers and/or confirms the following hypotheses: (1) nanoparticle slurry in conjunction with metal foam has a significant effect on heat transfer rate; (2) there is an optimum permeability for the foam resulting in maximal heat transfer rate; (3) for a fixed particle concentration, smaller particles are more effective in enhancing heat transfer; and (4) increasing particle concentration results in some gains, but this trend weakens after a threshold.