Development of an experimental small loop heat pipe with polytetrafluoroethylene wicks

This paper reports the development of an experimental small loop heat pipe with polytetrafluoroethylene (PTFE) wicks. Three kinds of PTFE porous materials were fabricated, and their wick properties were evaluated. It was clarified that the peak pore radii of the PTFE porous materials ranged from 0.8 to 2.2 μm, and their porosities ranged from 27 to 50%. A small loop heat pipe with PTFE wicks was designed using these properties, and an experimental small loop heat pipe, for which the wick in an evaporator is exchangeable, was fabricated. The experimental loop was tested with 1.2 and 2.2 μmPTFE wicks under atmospheric conditions. The test result with a 2.2 μmPTFE wick showed a high operating temperature, possibly due to vapor leak from the evaporator grooves to the compensation chamber. The test results with the 1.2 μm PTFE wick showed a lower operating temperature, lower thermal resistance, and stable operation of the loop heat pipe.