Results of Experimental and Theoretical Study of Ammonia based Loop Heat Pipe

The next generation of ISRO's high power spacecraft with electrical power generation of 10kW or more will require deployable thermal radiators for handling high heat dissipations of their payloads. These thermal management devices should transfer a large amount of heat from the spacecraft to the deployed radiators. Loop heat pipe (LHP) is the state-of-art for high heat transport flexible couplings between payload and radiator in a deployable thermal radiator system. LHPs are gaining importance as a part of the thermal control system of modern high power spacecraft, terrestrial electronic thermal management, cryogenics, etc. They are two-phase heat transport devices that have a working principle similar to that of heat pipes closed evaporation and condensation cycle being maintained by capillary pumping. A laboratory model ammonia LHP was designed and fabricated at Thermal Systems Group, ISAC to demonstrate the operation and capability of air Ammonia LHP. The developed LHP is capable of transporting at least 400W over a distance of 3m. Data from an in-house developed analytical thermo-hydraulic model of LHPs was correlated with the experimental observations. The analytical model predicts experimental data very well.