Conjugate Heat Transfer in Diverging Microchannels

Abstract

A numerical study has been carried out to determine the effects of axial wall conduction during single-phase steady laminar flow of fluid through rectangular diverging (across the length of the channel) cross-sectional microchannel involving conjugate heat transfer. A constant heat flux boundary condition has been applied on the bottom surface of the substrate on which the microchannel is carved, while all other surfaces of the substrate are subjected to adiabatic condition to simulate insulation. The simulations have been carried out by varying wall thickness to channel height ratio (dsf ~1-24), solid substrate conductivity to working fluid conductivity ratio (ksf ~0.17-703) and Reynolds number (Re~100-1000). For the purpose of comparison simulations for uniform cross-sectional area across the microchannel length has also been carried out. Four different geometrical dimensions, eleven substrate materials and three Reynolds numbers have been considered in this study, which would cover the common scope of uses experienced in micro fluids/microscale heat transfer areas and would provide a wide parametric variation for a generalized visualization of the outcome of this study. The results demonstrate that the conductivity ratio is the pivotal parameter in affecting the extent of axial wall conduction. Very low and very high values of ksf would result in decrease of Nussle number. Such a sensation also exists for uniform square and circular cross-sections.