Thermal Performance Improvement of Cross-Flow Double-Layered Microchannel Heat Sinks through Proper Header Design

Over the past two decades, double-layered microchannel heat sinks (DL-MCHs) have become increasingly popular as they provide effective performance for electronic cooling, particularly in the counterflow configuration. The cross-flow configuration, which requires much simpler headers, has seldom been considered in the scientific literature, probably due to the possible formation of a hotspot near the outlet port. The aim of this study is to show that cross-flow DL-MCHs can provide performance levels that are comparable to those attained by counterflow DL-MCHs by exploiting the nonuniform flow distribution produced by properly designed headers. Numerical simulations are performed using in-house finite element procedures to solve the parabolized Navier–Stokes equations in the microchannels and the energy equation in the entire computational domain. The analysis is carried out both for ideal linear microchannel velocity distributions and for the realistic velocity distributions induced by headers with or without baffles, as proposed by the authors in previous papers. The optimal degree of velocity nonuniformity in the microchannels yielding the best thermal performance was found to depend on the flow rate. For instance, in the case of optimal linear variations of the microchannel velocity distribution, the thermal resistance was reduced by 11.8%, 7.1%, and 4.4% compared to the case with uniform inlet velocities, and it was only 3.4%, 1.8%, and 0.3% higher than that of the counterflow configuration for average microchannel velocities equal to 0.5, 1, and 2 m/s, respectively. The main conclusion is that the cross-flow configuration, with its simple headers and piping, can achieve thermal resistance and temperature uniformity on the heated surface that are very similar to that of the counter-flow configuration through proper header design that ensures a suitable microchannel velocity distribution.