Optimisation of a heat pump for satellite cooling

Satellites are deployed into near earth orbit in order to provide a platform for a wide range of missions, including telecommunications systems, surveillance systems and astronomical systems.

These systems have seen a large increase in electrical component power density. It is currently common practice to use heat pipes to conduct the heat generated by the electrical components to the radiators of the satellite, but tomorrow's electrical components will have heat fluxes high enough to render this system unfeasible. As a result, it is necessary to develop heat pump systems that can operate in low-gravity environments with high reliability and efficiency to cool electrical components in the satellite.

In a recent paper*, I. Bell and V. Lemort, with University of Liège, Belgium, consider a conventional heat pump that uses an oil-free scroll compressor, since oil-refrigerant separation is difficult in low-gravity environment. There are a number of other unique features to this system, including the fact that all the heat rejection occurs through radiative heat transfer and the heat load is fixed (rather than being a function of source and sink temperatures).

The authors conclude that this heat-pump system, using R152A as a refrigerant, can achieve a relatively good coefficient of performance (> 4 for reasonable conditions); they stress that the component temperatures in the evaporator are quite high in the refrigerant dryout region; so, when designing satellite heat pump systems (and electronic cooling systems in general), it is critical to have sufficient factor of safety on the thermal design in the dryout and superheated zones.

*I. Bell, V. Lemort, Optimization of a heat pump for satellite cooling, 15th International Refrigeration and Air Conditioning Conference at Purdue, 2014

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