Temperature variation on the heated base of a solid substrate cooled with different type of heat sinks
Three-dimensional numerical studies were carried out to investigate forced convection heat transfer and fluid flow in a solid substrate cooled using different types of micro heat sinks. The objective of this study is to investigate which heat sink type gives the lowest temperature variation on the heated base of the solid substrate which is being cooled. A low temperature variation indicates a low temperature gradient which, in practical application, improves the reliability of the electronic device. The different heat sinks considered are single microchannels, two-layer microchannels with parallel and counter-flow of fluid, single microchannels inserted with circularshaped micro pin fins and two-layer microchannels inserted with circular-shaped pin fins. All the heat sinks are geometrically optimised using a computational fluid dynamics code with a goal driven optimisation algorithm subject to global constraints. The thermal performance of the heat sinks considered in this study is based on two objectives namely, the minimisation of the peak temperature which results in maximisation of the thermal conductance and the lowest temperature variation on the heated base. The heat sink with the largest value of thermal conductance and lowest temperature variation on the heated base for the range of pressure drop considered is chosen as the best heat sink design. Numerical results of thermal performance for fixed axial length of the solid showed that cooling the solid substrate with the two-layer microchannel with counter-flow of fluid gave the lowest temperature difference at base of the solid substrate and also performed best in maximising thermal conductance at pressure drops of 20 and 30kPa.