Microchannel heat sink on one hand enjoys benefits of intensified several folds heat transfer performance but on the other hand has to suffer aggravated form of trifling limitations associated with imperfect hydrodynamics and heat transfer behavior. Flow maldistribution is one of such limitation that exaggerates temperature nonuniformity across parallel microchannels leading to increase in maximum base temperature. Recently, variable width channels approach had been proposed by the current authors to mitigate the flow maldistribution in parallel microchannels heat sinks (MCHS), and in the current numerical study, variable height approach is opted for flow maldistribution mitigation. It is found that variable height microchannels heat sinks (VHMCHS) approach mitigates flow maldistribution rapidly in comparison to variable width microchannels heat sinks (VWMCHS) approach, almost 50% computational time can be saved by VHMCHS approach. Average fluid–solid interface temperature fluctuation across parallel microchannels reduces 3.3 °C by VHMCHS in comparison to VWMCHS approach. The maximum and average temperatures of the base of the heat sink are further reduced by 5.1 °C and 2.7 °C, respectively, for the VHMCHS. It is found that overall heat transfer performance of the heat sink improves further by 3.8% and 5.1% for the VWMCHS and VHMCHS, respectively. The pressure drop penalty of the VHMCHS is found to be 7.2% higher than VWMCHS.

Flow rate non-uniformities (termed maldistribution) among a stack of microchannels connected with each other through the inlet/outlet plenums of a microchannel heat sink (MCHS) is one of the major hindrances associated with effective and efficient operations. It induces many undesirable effects, including accentuation of lateral and flow-direction non-uniformities in surface temperatures (for uniform heat-flux loads). This can lead to feedback induced lateral heat-flow in the electronics underneath the MCHS, which is to be avoided. For the reported numerical study of single-phase liquid cooling, a new flow maldistribution mitigation technique – involving splitting of the single inlet port to the inlet manifold (conventional) into two separate inlet ports – is proposed and results are compared with the conventional method. Proposed scheme helps in reducing the flow maldistribution (its measure defined in the paper) problem. For the case of two ports in the front of the inlet manifold, the reduction is about 26.2% and for the case of one suitably placed port on each side of the inlet manifold, the flow rate maldistribution is reduced by about 68.5% and, in addition, MCHS efficiency (defined as heat carrying capacity per unit pumping power) is improved by 7.7%.