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This paper is related to the theoretical investigation of a space radiator with integrated multiple variable conductance heat pipes. Such a radiator is desirable to keep temperature variations of sensitive amplifiers in communication satellites within a few degrees, independent on their heat dissipation. For the purpose of dynamic studies of this kind of cooling system three aluminum/acetone heat pipes controlled by argon gas are thermally coupled in the evaporator and condenser area. A finite difference analysis is applied to study the system's response in case of failure of one of the heat pipes. The effects of change of spacing between the heat pipes and slitting of the radiator are mentioned.

Circumferentially grooved heat pipe evaporators have been proposed as an alternative solution to obtain high capillary pressure and large liquid cross sections to reduce the viscous pressure losses in the liquid flow. Such evaporators have been employed in a capillary pumped two-phase loop and first results have been reported for loop operation in the mechanical pump assisted mode. Additional tests have been carried out in order to determine the performance of the loop also in the capillary pumped mode. Using freon 11 as the working fluid, heat fluxes up to 12 kW/m2 have been measured. For ammonia, the corresponding value is estimated to be about 78 kW/m2. A theoretical analysis is also presented in order to understand differing performances of the individual capillary pumps.