Numerical study of TPMS-based microchannel heat sinks using supercritical CO2: Effects of structure type and volume fraction

The development of additive manufacturing has enabled the fabrication of complex microchannel heat sinks (MCHSs) based on triply periodic minimal surface (TPMS) structures. Meanwhile, supercritical CO₂ (sCO2) has emerged as a promising coolant due to its favorable thermophysical properties. This study integrates these two advances by investigating the thermohydraulic performance of six TPMS-based MCHSs using sCO2, including sheet- and solid-network variants of Gyroid, Diamond, and IWP structures. The influence of volume fraction and the effectiveness of a graded distribution strategy are systematically examined. Results show that sheet-network structures offer superior cooling performance but higher pressure drops than solid-network ones. The performance ranking, based on a performance index, consistently follows Gyroid $>$ Diamond $>$ IWP. Increasing the volume fraction enhances cooling but also increases pressure drop. A graded volume fraction, with a higher value near the heated surface and a lower one farther from it, effectively reduces pressure drop with only a moderate compromise in cooling. Overall, the Gyroid-Sheet structure with a high volume fraction and an optional graded design is recommended for high heat flux cooling applications. This study provides practical guidance for designing TPMS-based MCHSs with sCO2, advancing the application of additive manufacturing and the use of sCO2 in next-generation thermal management systems.