Experimental investigation of pump-assisted capillary phase change loop

• A pump-assisted capillary phase change loop is presented.
• Both mechanical pump and capillary force are used for driving the working fluid.
• Test results show that no obvious temperature oscillation is observed.
• The loop can operate 17.7 W/cm2 × 1850 mm at the heater surface temperature below 80 °C.
• Initial distribution of working fluid has impact on the operation characteristics.

This paper presents an overview of a novel two-phase loop called “pump-assisted capillary phase change loop” designed to address the drawbacks of temperature oscillation and limited heat transfer distance in loop heat pipes. The proposed loop is a combination of active and passive systems. It is equipped with an evaporator designed in the type of flat-disk, and a biporous wick that provides the capillary force. In addition, methanol is chosen as the working fluid. During the heat-transfer process, the working fluid is transferred by both the capillary force and the driving force of the mechanical pumping. Both the sensitive and the latent heat of the working fluid are utilized to transfer heat. The liquid circulation through the compensation chamber takes away heat leak from the evaporator to the compensation chamber. Test results indicate that the system shows a very fast response to variable heat loads with no obvious temperature oscillation being detected. The maximum heat load the system could transfer increases up to 180 W (heat flux = 17.7 W/cm2) with transport distance of 1850 mm at the heater surface temperature below 80 °C, when the power input of the mechanical pump is 2 W. The evaporator thermal resistance varies between 0.298 K/W and 0.196 K/W at the heat sink temperature of −10 °C.