AN EXPERIMENTAL STUDY ON POOL BOILING OF SATURATED FC-72 IN HIGHLY POROUS ALUMINUM METAL FOAMS

摘要

An experimental study of pool boiling of FC-72 in highly porous metal foam heat sinks is reported. A heat generating electronic chip is simulated by placing an array of electrical resistances on an aluminum block. A metal foam block attached to this aluminum block serves as the heat sink. Experiments were conducted with samples of porosities and pore sizes in the range of 90-98% and 5-40 pores per inch (PPI) respectively. The effects of these parameters on the temperature overshoot at the onset of nucleate boiling, the critical heat flux and the heat transfer performance of the heat sinks are discussed. The experimental results obtained are compared with those for boiling over a flat plate and also with previous studies of pool boiling in media of porosity lower than media 75%. Our results indicate that the temperature excursion usually observed for fluorinert fluids at the onset of nucleate boiling is not present. There is also an increase in the overall heat transfer performance and the critical heat flux values compared to those for boiling over a flat plate. For the same pore size, the low porosity samples exhibit a significantly higher heat transfer in the low heat flux regimes. For similar porosity, increased heat transfer is observed with an increase in PPI. Finally, a correlation of the data obtained in the nucleate boiling regime is constructed to show the dependence of the heat transfer performance on the surface overheat and the metal foam geometry.