Thermal Performance of a Pump-Assisted Capillary Loop Cooler

Abstract

The heat transfer and hydraulic performance of a flat evaporator, pump-assisted capillary loop cooler is evaluated for a 1cm2 heat source. The cooler consists of a copper manifold that houses a compensation chamber that feeds liquid to a sintered, flat evaporator wick below via a micro-tube array. Liquid evaporates from the copper wick as it is attached to the heater through a copper base plate. The custom cooler design offers separate flow routes for liquid and vapor phases during steady operation and thereby maintaining the pressure balance of the flow loop. The cooler performance is evaluated using de-ionized water as the coolant with an inlet volumetric flowrate of 322ml/min. The cooler achieves a steady convective heat transfer coefficient of >95kW/m2K with <2kPa pressure drop, tested up to a maximum heater temperature of 175 °C. An electronic valve installed on the cooler outlet controls the compensation chamber pressure and extends peak heat transfer performance. This control scheme has been experimentally verified to extend the range of peak heat transfer from [356,>537] to [356,>610]W/cm2 within the same temperature range. Such a cooler shows promise for systems of variable thermal load where system pressure is a key consideration.