LOOP HEAT PIPE FOR SPACECRAFT THERMAL CONTROL: THERMO VACUUM PERFORMANCE TEST RESULTS
A loop heat pipe (LHP) with a heat transport capacity of 500 W
and ammonia as working fluid is developed for spacecraft
thermal management. LHP evaporator utilizes grooved cylindrical sintered nickel as primary wicking structure to generate the capillary forces to drive the working fluid through the loop. LHP condenser is bolted to the thermo vacuum chamber cold plate which is maintained at a constant temperature. As a part of ground qualification program thermo vacuum tests have been conducted on the LHP for heat loads from 50 W to 500 W. Detailed results to determine the thermal performance of the LHP and the system behavior during the tests are presented in this paper. LHP successfully started up from a heat load of 50 W and could be operated up to 500W. The condensation lengths at different heat loads are inferred from the steady sate temperature measurements. Test results indicate that thermal contact conductance needs to be carefully considered. The operating temperature exhibits the classical LHP curve-first decreasing then increasing with heat load. The thermo vacuum test has demonstrated the feasibility of the LHP as a heat transport device for spacecraft thermal control.