EXPERIMENTAL CHARACTERIZATION OF A DOUBLE BACK TO BACK PULSATING HEAT PIPE FOR POWER ELECTRONICS

Experimental characterization of a 104-turn pulsating heat pipe (PHP) cooler using R245fa and based on the automotive heat exchanger technology for power electronics thermal management is presented. The effects of fluid filling ratio, orientation, and heat load up to 5.75 kW per PHP were investigated. Thermal resistances as low as 8.5 K/kW were measured at 2000 m3/h air flow. However, a thermal resistance increase of 19% and 25% was measured in horizontal and inverted orientations, respectively. Periodic pressure peaks were measured, but with different amplitudes depending on the orientation. The condenser was found to be subcooled at all fillings and all orientations while the evaporator was very close to the saturation temperature. There was superheating measured at the evaporator manifold only at very low fluid fillings. There was a minimum in thermal resistance located between 40% and 50% fluid filling, for all orientations and heat loads tested. The maximal thermal resistance depended very little on the heat load. For a given set of operating conditions, a high frequency combined with low amplitude pressure peaks yielded better cooling performances.