Immersion cooling of high heat flux microelectronics with dielectric liquids

This paper explores the use of direct liquid cooling, by immersion of the components in inert, non-toxic, high dielectric strength perfluorocarbon liquids. Boiling heat transfer with the candidate liquids provides heat transfer coefficients that are as much as two orders of magnitude higher than achievable with forced convection of air. Unfortunately, the highly effective nucleate boiling domain terminates at the so-called Critical Heat Flux, approximately in the range of 20 W/cm² at atmospheric conditions and saturation temperature. Consequently, if immersion cooling is to be used for next generation chips, ways must be found to increase the pool boiling CHF of these dielectric liquids. Use of a pool boiling CHF correlation, developed in this laboratory, points to the possibility of reaching a CHF of nearly 60 W/cm², using elevated pressure and subcooling, along with a dilute mixture of a high boiling point fluorocarbon, and applying a microporous coating to the surface of the chip