Parametric Inwestigation Into the Effects of Pressure, SubcooIing3 Surface Augmentation and Choice of Coolant on Pool Boiling in the Design of Cooling Systems for High-Power-Density Electronic Chips

A high power electronic chip was simulated experimentally to investigate upper cooling capabilities using a variety of pool boiling enhancement techniques. Parametric effects of system pressure, subcooling, surface augmentation, and choice of coolant on boiling heat transfer from a vertical 12.7'x 12.7 mm flat surface were examined. The two fluorocarbon coolants tested, FC-72 and FC-87, resulted in similar boiling curves, but FC-87 significantly reduced chip surface temperature for a given heat flux. Increasing pressure enhanced boiling performance and critical heat flux slightly. However, the significant increase in chip temperature, and the practical problems associated with packaging electronic hardware in a pressurized environment precluded pressurization as a viable enhancement option. Subcooling was very effective in increasing critical heat flux and significantly reducing bubble size and growth of the bubble boundary layer on the chip surface. Surface augmentation was also effective in enhancing critical heat flux; however, some surface geometries promoted noticeable temperature excursion at incipience.