Combined heat and mass transfer analyses in catalytic microreactors partially filled with porous material - The influences of nanofluid and different porous-fluid interface models

Abstract

This paper reports a theoretical analysis of heat and mass transfer in the microchannels partially filled with porous materials and used in thermos-chemical microreactors. A first order catalytic chemical reaction is considered on the internal surfaces of a parallel-plates microchannel. The local thermal non-equilibrium approach along with two well-established porous-fluid interface models is employed to investigate the heat transfer within the porous section of the microreactor. The analysis further accounts for the finite thickness of the surrounding solid walls of the microchannel. The dispersion equations in both porous and clear sections of the microchannel are coupled with the fluid temperature through considering the thermal diffusion of mass. In addition, to enhance heat transfer in the partially-filled microchannel, the base fluid is replaced by a nanofluid. The results show that inclusion of the finite thickness of the walls in the thermal analysis can majorly affect the temperature fields and Nusselt number (Nu). In particular, the optimal thickness of the porous insert for achieving the maximum Nu is found to be strongly influenced by the wall thickness. It is also shown that the specific porous-fluid interface model, thicknesses of the porous section and that of the walls, and the volumetric concentration of the nanoparticles can all impart significant effects upon the concentration of chemical species and their distribution across the microchannel. More specifically, the concentration field within the porous region is found to be considerably dependent on the implemented porous-fluid interface model.