Operational Characteristics of Loop Heat Pipe in Microgravity and Normal Gravity Environments

The loop heat pipe(LHP) is an advanced,efficient two-phase heat transfer unit,whose operational performance may be affected by microgravity conditions in contrast to ground-based applications.The performance of on-orbit temperature data and ground test of a copper-propylene LHP with a condenser temperature range of 243.15 K to 303.15 K were employed to compared and analyzed.The LHP has successfully started up for more than 193 times with a good heat transfer performance and a stable start-up stabilization on-orbit under a complex orbital heating environment for more than eight months.With a small heat load(10.0W),the average start-up time is 110.0 s while the start-up temperature ranges from 5.71 K-12.78 K.The start-up time at large temperature differences in the high temperature zone will be higher than the time required for start-up at smaller temperature differences in the low one.When the condenser temperature is 250.0 K,the stable temperature difference on orbit is 3.83 K,which is generally consistent in heat transfer compared to 2.20 K in the ground test.In this paper,we can conclude that the on-orbit flight data up to now can provide a reference to the design of subsequent LHP space applications.