Thermal Vaccuum Testing of a Miniature Propylene Loop Heat Pipe

Abstract

This paper presents the design and thermal vacuum testing of a Miniature Loop Heat Pipe (MLHP) with propylene as working fluid. It is for cooling a prototype lunar power device and so needs to work against lunar gravity. The target operating condition was to convey 20W in the +20C to -30C temperature range. All wetted materials were stainless steel, while an aluminum saddle and radiator panel were used to enhance heat spreading. The outer diameter of the LHP primary wick is 5mm and the length is 55mm. The Bubble test showed a pore radius of 1.2 micrometer. The radiator is 265mm x 270mm. The MLHP was tested at different heat loads, different orientations in the gravity field and two sink temperatures of +20C and -30C. The MLHP thermal performance test included startup and steady state operation. Maximum heat transport limit was found to be 25W and peak conductance 6.6 W/C.