POOL BOILING HEAT TRANSFER FROM PLAIN AND MICROPOROUS, SQUARE PIN FINNED SURFACES IN SATURATED FC-72

摘要

The present research is an experimental study of "doubleenhancement" behavior in pool boiling from heater surfaces simulatingmicroelectronic devices immersed in saturated FC-72 at atmosphericpressure. The term "double enhancement" refers to the combination of twodifferent enhancement techniques: a large-scale area enhancement (squarepin fm array) and a small-scale surface enhancement (microporous coating).Fin lengths were varied from 0 (flat surface) to 8 mm. Effects of this doubleenhancement technique on critical heat flux (CHF) and nucleate boiling heattransfer in the horizontal orientation (fins are vertical) are investigated.Results showed significant increases in nucleate boiling heat transfercoefficients with the application of the microporous coating to the heatersurfaces. CHF was found to be relatively insensitive to surfacemicrostructure for the finned surfaces except in the case of the surface with 8mm long fins. The nucleate boiling and CFIF behavior has been found to bethe result of multiple, counteracting mechanisms; surface area enhancement,fm efficiency, surface microstructure (active nucleation site density), vaporbubble departure resistance, and re-wetting liquid flow resistance.