Parametric study of pool boiling from porous graphite foams in dielectric liquids

An experimental investigation of pool boiling on porous graphite foams is presented in this paper. A compact thermosyphon was developed to conduct the experiments using different types of graphite foams as evaporator inserts. Two dielectric liquids viz. FC-12 and HFE-700 were used as phase change coolants to investigate the effects of pore diameter and thermal conductivity of the foams on pool boiling heat transfer. It is found that the boiling heat transfer is affected by phase change coolant types. The difference of thermophysical properties between FC-12 and HFE-7000 resulted in different boiling characteristics on porous graphite foams. The experimental results indicate that thermal conductivity and pore diameter exhibit an interrelated effect on boiling performance. The compromise of these foam properties affects the bubble departure frequency which dominates the boiling heat transfer coefficient. This study demonstrates that the designed air-cooled thermosyphon can maintain the heater surface temperature below 85°C at heat flux of 112 W/cm².