Miao Jianyin

Development and Test Results of a Dual Compensation Chamber Loop Heat Pipe

A dual compensation chamber loop heat pipe is developed to solve the problem of the relative orientation limit between the evaporator and the compensation chambers. The construction of the evaporator and the compensation chambers is presented. The concurrent design method of the working fluid charge mass and the compensation chamber volumes, that can realize the objectives where, within a certain temperature range, the dual compensation chamber loop heat pipe cannot only start up and operate normally at any orientation, but can also avoid the most difficult startup situation, is introduced. The operation and the thermal control characteristics of the dual compensation chamber loop heat pipe are investigated. Test results indicate that in some heat load regions, the operating temperatures vary with the relative orientation between the evaporator and the compensation chambers. This is explained by the thermal equilibrium of the compensation chamber and the usage efficiency of the return liquid subcooling. The test results and discussion of the dual compensation chamber loop heat pipe suggest that part of the return liquid subcooling that cools the liquid to be locally subcooled must be considered in the mathematical modeling of the loop heat pipe.

Investigation of Effects of Auxiliary Measures for Startup of Loop Heat Pipes

Experiments have been conducted to investigate the feasibility of two active measures, namely, local heating on the evaporator and cooling the compensation chamber, with a thermoelectric cooler. A new passive auxiliary measure, which utilizes the latent heat of phase change material to maintain the compensation chamber temperature at the melting point to help estimate the required superheat, has been presented for the first time. The effects of the three auxiliary measures on startups and the steady-state operation have been investigated. Test results indicate that the three auxiliary measures are helpful in establishing the required liquid superheat and reducing the evaporator temperature overshoot, as well as in lessening the startup time. Local heating on the evaporator near the evaporator outlet will not affect the steady-state operation, whereas local heating on the evaporator near the compensation chamber will lead to either sustaining operating temperature rises or higher operating temperatures. The continued operation of the thermoelectric cooler will decrease the operating temperatures at low heat loads and the typical V operating temperature curve will be changed to a nearly linear one. At too low heat loads, the phase change material can only delay the evaporator temperature rise and gain time for the loop heat pipe to wait for the arrival of a higher heat load, which is more favorable for startups.

Ground test method and results of closed two-phase thermosyphons for the moon exploration spacecraft Chang’E-3

Closed two-phase thermosyphons were developed for the thermal control system in the Chinese moon exploration spacecraft ChangE-3. This is the first space application for the thermosyphon. The biggest challenge of the thermal control system was to maintain the equipment temperature levels to help the lander and the rover survive the 14-earth day cold night without power supply. Closed two-phase thermosyphons were designed to transfer the RHU heat to the equipments at lunar night. The thermal control system could require no power supply and less weight to survive the explorer at lunar night. The ground test method was established to verify the heat transfer capability of the loops that will operate on the moon surface by sextupling the cross section area of the reservoir and decreasing the height difference between the reservoir and the reservoir to be a sixth of the real difference. The thermal vacuum test results of the two-phase loop designed for the lunar rover will be presented.