Effect of surface modification and substrate material on flow and heat transfer characteristics in microchannel heat sink

The conjugate effect is significant when the area of substrate perpendicular to the coolant flow direction is comparable to channel cross-sectional area. The effects of conjugate heat transfer have been studied for different materials and various bottom substrate thicknesses. Three-dimensional rectangular microchannel with waviness at selective location has been studied numerically. The working fluid is water, and the study has been conducted for the range of Re, 100 ≤ Re ≤ 1000. The significance of wall thickness and materials with different thermal conductivity while applying constant heat flux boundary condition has been analyzed. The bottom wall thickness is varied from 0.5 to 2 H ch for each material while side wall thickness is maintained constant. The effect of surface modification on the flow characteristics is carefully studied by allowing fully developed flow at the channel entry. ICEM CFD tool is used for generating non-uniform mesh. Three-dimensional numerical simulations are carried out using finite volume method-based solver ANSYS Fluent 19 and the conservation equations are solved using second-order upwind scheme. Present numerical results of base case with plane wall are validated using published experimental results. The larger convective area and Dean vortices help the heat transfer enhancement. The conjugate heat transfer effect is analyzed through conduction thermal resistance and overall thermal resistance variation. The copper substrate material with 0.5 H ch thickness maintains uniform temperature distribution in the bottom wall. The average heat transfer coefficient values decrease when the substrate wall thickness increases except at very low Reynolds number.