An experimental study on the heat transfer and pressure drop characteristics of electronics cooling heat sinks with FC-72 flow boiling

An experimental study was performed to measure FC-72(C6F14) flow boiling heat transfer and pressure drop in heat sinks for electronics cooling. The heat sink had cooling cross section area of 38.0 × 37.0 mm with rectangular fins. The height, length and thickness of a fin was 5.0, 24.0 and 1.0 mm, respectively. The width of fluid channels between the fins was 1.0 mm. The heat sink consisted of a heating and cooling section, and a cover. Two types of heat sinks were used in this study. The two heat sinks were different only in the cover, and the machined depth of the cover was 5.0 and 8.0 mm, respectively. Electric heating from 100 to 300 W was supplied by cartridge heaters and it was equivalent to the heat flux from 71.12 to 213.4 kW/m2 based on the cross section area of the cooled surface. The saturation temperatures of the FC-72 were from 59.8 °C to 71.5 °C during the experiment and the mass fluxes were from 24.2 to 230.0 kg/m2s. The trend of heat transfer and pressure drop variation with the change of vapor quality was similar to that of flow boiling in tubes such as the increase of heat transfer and pressure drop with the increase of vapor quality before dryout. Similar heat transfer coefficients and pressure drop values were measured under the same mass flow conditions for both types of heat sinks. In this study, the cooling performance with liquid water was also measured at the same heat sinks. The comparison of experimental data presented that the cooling capacity with FC-72 flow boiling was up to 330 % higher than that with liquid water. However, the FC-72 pressure drop was also significantly higher than water.