Two-phase microgap cooling of a thermally-simulated microprocessor chip

Forced flow of refrigerants and dielectric liquids, undergoing phase change in a microgap channel above an active chip is a promising candidate for the thermal management of advanced semiconductor devices. This paper presents two-phase heat transfer and pressure drop results for a chip-scale, uniformly heated, microgap channel using HFE-7100 and FC-87 as the working fluids. Results for two channel configurations are presented: a chip-size, short channel, representative of a product configuration and a longer channel, representing a laboratory prototype. Each microgap channel was tested with three nominal gap heights: 100, 200, and 500 micrometer. An inverse computation technique is used to determine the heat flow into the wetted surface of the microgap channel, and subsequently, the local heat transfer coefficients on the surface. A detailed analysis of the microgap heat transfer data for two-phase flow of HFE-7100 and FC-87, sorted by the Taitel and Dukler flow regime mapping methodology, is performed. Sections of the characteristic M-shaped heat transfer coefficient variation with quality (or superficial velocity) for the flow of dielectric liquids in miniature channels are identified. The inflection point in this inverse parabolic curve is seen to equate approximately with flow regime transition from Intermittent to Annular. The predictive accuracy of Chen (1966) and Shah (1976) classical two-phase heat transfer correlations for miniature channel flow is examined for both average and local heat transfer coefficients.