An Open Loop Pulsating Heat Pipe for Integrated Electronic Cooling Applications

Abstract

Increasing trends toward integrated power electronic systems demand advancements in novel, efficient thermal management solutions to cope with the increasing the power density. This paper investigates the performance of a novel open loop pulsating heat pipe embedded in an FR4 organic substrate. The heat pipe is comprised of 26 parallel minichannels, 13 turns with an average hydraulic diameter of 1.7 mm and maximum surface roughness of 2.5 μm. The bulk thermal performance of three saturated working fluids—Novec 649, Novec 7200 and Ethanol (99.8%)—is investigated in terms of fill ratio, three angles of orientation, and applied heat fluxes ranging from 0.4 to 2.5 W/cm2 at subambient pressures. Novec 649 achieved quasi-stable pulsations at lower heat fluxes compared to Novec 7200 and Ethanol (99.8%). In addition, the dielectric Novec 649 fluid showed significant potential for integrated heat spreading applications demonstrating heat transfer of up to 176 W and thermal resistances as low as 0.25 °C/W for a filling ratio of 30%—16 times greater than that of a standard dry FR4 substrate