Effect of Tapered Gap Angle and Height on the Thermal Performance of a Two-Phase Cold Plate for High Heat Dissipation

The rapid growth of GPU integration for AI workloads in modern data centers has intensified power consumption and thermal management challenges. Although single-phase cooling methods such as jet impingement and microchannel systems have been widely explored, their high pumping power demand limits overall energy efficiency. Two-phase cooling, by exploiting phase change, offers superior heat transfer performance; however, reliable operation requires enhancement of the Critical Heat Flux (CHF). Existing approaches largely rely on boiling-enhanced surfaces involving complex fabrication, whereas tapered gap structures provide a simpler alternative. In this study, a pool-boiling-based cooling plate with tapered gap structures was developed to cool high-power chips with reduced pumping power. Experimental investigations revealed that CHF in non-inclined structures increased with gap height, while tapered structures exhibited an optimal gap height. The configuration with H/W = 1 and a 20° inclination achieved the lowest thermal resistance (0.061 K/W), the highest heat transfer coefficient (20,185 W/m²⋅K), and a junction temperature of 191.1°C. Compared with an unstructured case, CHF improved by up to 78% (105 W/cm²). These results demonstrate that tapered gap structures can be effectively optimized in two-phase cold plate designs, providing enhanced thermal performance and design flexibility for next-generation high-power electronic devices.