Enhanced Pool Boiling With Ethanol at Subatmospheric Pressures for Electronics Cooling

The growing trend in miniaturization of electronics has generated a need for efficient thermal management of these devices. Boiling has the ability to dissipate a high heat flux while maintaining a small temperature difference. A vapor chamber with pool boiling offers an effective way to provide cooling and to maintain temperature uniformity. The objective of the current work is to investigate pool boiling performance of ethanol on enhanced microchannel surfaces. Ethanol is an attractive working fluid due to its better heat transfer performance and higher heat of vaporization compared to refrigerants, and lower normal boiling point compared to water. The saturation temperature of ethanol can be further reduced to temperatures suitable for electronics cooling by lowering the pressure. Experiments were performed at four different absolute pressures, 101.3 kPa, 66.7 kPa, 33.3 kPa, and 16.7 kPa using different microchannel surface configurations. Heat dissipation in excess of 900 kW/m(2) was obtained while maintaining the wall surface below 85 degrees C at 33 kPa. Flammability, toxicity, and temperature overshoot issues need to be addressed before practical implementation of ethanol-based cooling systems can occur.