Numerical investigation of the thermohydraulic characteristics of microchannel heat sinks using supercritical CO₂ as a coolant

For compact electronic devices, high-pressure drops that characterize microchannel heat sinks (MCHS) is an issue that needs to be resolved to reduce the size of heat-removing systems. In this regard, supercritical carbon dioxide (sCO₂) can be of great value due to its favorable thermophysical properties near the critical point. Thus, the potential of the proposed coolant (sCO₂) for microchannel heat sinks (MCHS) is numerically investigated and compared with the conventional liquid coolant. Moreover, a header geometry with minimum flow maldistribution is designed for both coolants. Finally, the impact of various operating conditions on the thermal and hydraulic performance of the proposed sCO₂-cooled MCHS is investigated to evaluate its optimal operating conditions. To accomplish this, a 3D Reynolds Averaged Navier–Stokes (RANS) model is developed to analyze the thermal and hydraulic performance of both coolants. Thermophysical properties of sCO₂ are implemented through a high-resolution real gas property (RGP) file to capture abrupt variations in its properties and ensure the model's precision. Results suggest that replacing water with sCO₂ can enhance the thermal performance of microchannel heat sinks by up to 32% at higher flow rates of the coolant, while pressure losses can be reduced by up to 7 times compared to water-cooled MCHS. Moreover, it is found that sCO₂-cooled MCHS can maintain a steady base temperature, even during overload conditions. The proposed coolant can be used to design highly efficient and compact cooling systems with the capability of enhancing the MCHS overall performance by up to 2.2 times.