LBM simulation of thermo-hydrodynamic and irreversibility characteristics of a nanofluid in microchannel heat sink under affecting a magnetic field

Abstract

ABSTRACT Understanding thermo-hydrodynamic characteristics of microchannels is of importance to fabricate efficient heat sinks, due to wide applications of cooling modules in microscales. In this work, water-alumina nanofluid heat transfer and laminar flow field of a microchannel under imposing a magnetic field is studied. The microchannel is partially heated by a constant heat flux. The effects of various values of Hartmann number, varying between 0 and 40, Reynolds number, increased from 10 to 500, and volume fraction of nanoparticles, which falls between 0 and 0.06, on the problem physics are investigated. Lattice-Boltzmann numerical method is applied to simulate the hydrodynamic and thermal field. Further, the energy loss due to thermal, frictional and magnetic mechanisms is also computed. It is shown that heat transfer is intensified by strengthening magnetic force, Reynolds number or concentration of nanoparticles. This is such that increasing Hartmann number from 0 to 40 or volume fraction of the nanofluid from 0 to 0.06 makes 150% increment in Nusselt number. Intensifying Reynolds number from 100 to 500 causes 200% rising in Nusselt number, as well. It is found that the thermal response of the microchannel to variation of pertinent parameters is nonlinear. Comparing the various sources of entropy generation shows that the thermal mechanism is most influential by the value of one order of magnitude larger than the other sources.