Characterisation Of A Novel Pulsating Heat Pipe Cooler For Power Electronics At Extreme Ambient Temperatures

A compact and low cost pulsating heat pipe cooler (PHP) based on automotive technology is presented. This technology uses numerous aluminium MultiPort Extruded (MPE) tubes with capillary sized channels disposed in parallel to achieve the desired compactness. The sub-channels of the MPEs are connected in a serpentine manner by means of fluid distribution elements integrated in the evaporator and condenser manifolds. This configuration enables the oscillation of liquid slugs and elongated bubbles between the evaporator and the condenser areas.In the present paper the experimental results of an open loop type PHP with refrigerants fluids R134a and R245fa are presented. Tests have been carried out for air temperatures ranging between -60 and 60 degrees C at a fixed air flow rate of 480 m(3)/h and heat loads from 3 to 13 W/cm(2). The experimental results show the different thermo-physical properties effect of the two tested fluids on the cooler performances: R134a is more adapted to low saturation temperature than R245fa and the contrary has been observed at high saturation temperatures. This is due to the fact that R245fa reaches its viscous limit at low temperatures while at high temperatures R134a reaches its critical temperature.