Fluid flow and heat transfer in microchannel heat sink based on porous fin design concept

In this work, we propose a new design concept of microchannel heat sink, in which solid fins are replaced by porous fins, to reduce the pressure drop across the heat sink. The Forchheimer-Brinkman-Darcy model is used to investigate the effectiveness of this design. The results show that the pressure drop of the new design is reduced by 43.0% to 47.9% at various coolant flow rates as compared with that of the conventional heat sink, with only about 5% increase in the thermal resistance. The pressure drop reduction is attributed to "slip" of coolant on the channel wall due to the presence of porous fins. The drag reduction efficiency for the new design is also calculated by the slip theory extensively used in ultrahydrophobic surfaces, and the calculated value is very close to our simulation value. The results also show that the drag reduction efficiency strongly depends on the porous fin parameters. A larger "slip" velocity of coolant occurs at a higher permeability, a smaller quadratic drag factor, or a larger width ratio of fin-to-pitch, which corresponds to a larger "slip" length. As a result, the pressure drop becomes lower at these conditions. (C) 2015 Elsevier Ltd. All rights reserved.