Forced Boiling of Nonazeotropic Immiscible Mixture in a Supercapillary Microchannel Array for Ultra-High Heat Flux Removal with Chip Junction Temperature below 85°C

In this study, a structure-optimized two-phase microchannel heat sink with sintered submicron nucleation sites was developed and tested. The copper-based microchannels had a rectangular cross-section with an equivalent hydraulic diameter of 222 µm. The subcooled flow boiling characteristics were comprehensively compared between pure HFE-7100 and a non-azeotropic, immiscible binary mixture of HFE-7100 and water, considering heating areas of 1 and 5 cm2. The total heating power input to the test section were 100–1500 and 250–3000 W for a 1 and 5 cm2 heat source, respectively, with a flow rate ranging from 50 to 150 L/h. Compared to pure HFE-7100, the non-azeotropic immiscible binary mixture of HFE-7100/water in the sintered porous microchannels exhibited a much higher overall heat transfer coefficient and lower power consumption. To maintain the junction temperature of a high power electronic chip below 85°C, the proposed supercapillary microchannel heat sink could effectively dissipate the heat flux of 1275 W/cm2 over 1 cm2 heat source and 500 W/cm2 over 5 cm2 heat source. In addition, the volume ratio of the binary mixture strongly influence the two-phase flow heat transfer characteristics. An optimal volume ratio exist in terms of the thermal resistance-pumping power minimization (HFE-7100:water=2:8 is recommended in this study). The findings of this investigation on the flow boiling properties of non-azeotropic immiscible mixtures help fill a gap in the related field.