Combined pressure and subcooling effects on pool boiling from a PPGA chip package

This study presents a detailed experimental investigation of the combined effects of pressure and subcooling on nucleate pool boiling and critical heat flux (CHF) for degassed fluorocarbon FC-72 boiling on a plastic-pin-grid-array (PPGA) chip package. In these experiments, pressure was varied between 101.3 and 303.9 kPa, and the subcooling ranged from 0 to 65°C. As expected, lower wall superheats resulted from increases in pressure, while subcooling had a minimal effect on fully-developed pool boiling. However, the superheat reductions and CHF enhancements were found to be smaller than those predicted by existing models. The saturation CHF increased by nearly 17% for an increase in pressure from 101.3 to 202.7 kPa. In experiments with both FC-72 and FC-87, further increases in pressure did not produce any significant increase in CHF. At a pressure of 101.3 kPa, a subcooling of 30°C increased CHF on horizontal, upward-facing chips by approximately 50% as compared to 70% on vertically oriented packages. The enhancement in CHF due to subcooling decreased rapidly with increasing pressure and the data showed that the influence of pressure and subcooling on CHF is not additive. A correlation to predict pool boiling CHF under the combined effects of pressure and subcooling is proposed