Experimental study of a Capillary Pumped Loop assisted with a mechanical pump placed at the evaporator inlet

Abstract

The heat transfer performances of capillary-driven evaporators are still improving while their pumping capacity remains drastically limited by the porous wick structure. The pump assistance allows this capillary limit to be overcome and more largely, gives the opportunity of an important enhancement of capillary two-phase loops operating range. An experimental device made of a Capillary Pumped Loop coupled with a controlled centrifugal pump located at the inlet of the evaporator was proposed. We have shown that the hybrid system acts as it would in a simple capillary-driven regime with an operating loop pressure drop far beyond the capillary limit (more than 60kPa i.e. more than 6 times the evaporator capillary limit with methanol) while preserving the evaporator thermal efficiency due to vaporisation. Moreover, we have found that the pump assistance significantly increases the system robustness during large amplitude heat load step and startup by influencing the liquid subcooling and flow rate at the evaporator inlet.