Thermal analysis of international space station freeze-tolerant early external active thermal control system radiators

Abstract

In the early stages of International Space Station assembly, the photovoltaic (PV) radiators are utilized to dissipate the station’s waste heat. To prevent radiator flow blockage that may occur by freezing of the radiator working fluid during certain cold orbits and low heat load conditions, a freeze tolerant radiator design was developed by NASA. The design not only alleviates the chance of radiator freezing, it can also tolerate high internal pressures that develop during local thawing of frozen flow tubes. To predict thermal performance of the PV radiator at freezing conditions SINDA/FLUINT program was used to model the freeze tolerant radiator design at one ORU level. The results of the analysis indicate that the radiator tubes will not freeze at the worst-case cold conditions specified as having a heat load of 4 kW and subjected to two consecutive cold sink orbits followed by two cold dips–one to −90 °C for 0.25 hour and another to −98.3 °C for 0.15 hour.