Thermo-hydraulic characteristics and structural optimization of supercritical CO2-cooled microchannel heat sink

Supercritical carbon dioxide (sCO2) serves as an efficient working fluid in microchannel heat sinks (MCHS), effectively mitigating heat dissipation challenges in high heat flux microelectronic devices. Nonetheless, the issue of flow acceleration affecting micro-scale heat transfer, especially in channels with diameters <0.2 mm, warrants additional investigation. Flow acceleration exacerbates temperature non-uniformity, consequently diminishing heat transfer efficiency. Numerical simulations were conducted to examine the thermo-hydraulic characteristics of sCO2 in microchannels featuring complex structures including ribs and cavities. The channel had a diameter of 0.133 mm, with heat flux to mass flow rate (q/G) ranging from 0.1 to 0.5 kJ/kg. Three-dimensional entropy production rate (Sg) maps and corresponding heat maps were utilized to establish boundary conditions and evaluate heat transfer optimization. Additionally, structural optimizations were performed to rectify temperature non-uniformity in sCO2 within MCHS. The results indicate that the entropy production rate (Sg) of sCO2 initially decreased and then increased with the increase in q/G and dimensionless enthalpy (h*). The optimized MCHS demonstrated enhanced temperature uniformity, with a maximum temperature difference of 1.8 K, notably lower than that of the non-optimized MCHS (5.3 K). This study offers a theoretical basis for the design and implementation of sCO2 in micro-scale MCHS.