Experimental Comparison on Thermal Performance of Pulsating Heat Pipe and Embedded Heat Pipe Heat Spreaders

Two passive heat spreaders: one based on Embedded conventional Heat Pipes (EHP), and one based on internal capillary channel Pulsating Heat Pipes (PHP) were fabricated and tested for electronics cooling. The outer diameter of the heat pipes in the EHP was 5 mm, while the capillary channel diameter in the PHP was 1.6 mm. The PHP was charged with propylene up to 50% by volume. Experiments were performed at operating heat sink temperatures of -10 °C, 20 °C, and 40 °C with a stop condition of either dry-out or maximum heat spreader temperature of 70 °C. At low heat sink temperatures, the thermal conductance of the PHP was comparable to the EHP. At higher heat sink temperatures of 20 °C and 40 °C, the thermal conductance of EHP was found to be significantly higher than the PHP. In the case of the PHP, dry-out was around 57.3 W/cm
²
at a low heat sink temperature of -10 °C, while no dry-out was observed in the PHP. When the heat sink temperature was 20 °C and 40 °C, dry-out occurred in the PHP at a heat flux of 47.3 W/cm
²
and 27.1 W/cm
²
, respectively. EHP, on the other hand, did not show signs of dry-out at these heat sink temperatures. From experiments, it was determined that the thermal performance of the PHP was better than EHP at low to moderate heat flux until 38 W/cm
²
at a low heat sink temperature. At higher heat fluxes and heat sink temperatures, EHP showed higher thermal conductance than the PHP heat spreader at almost all heat fluxes.