Abstract: A two-phase capillary pumped loop heat transfer system adapted primarily for use on space vehicles, includes a wickless condenser tube which receives gaseous phase working fluid from the evaporator capillaries, rejects heat from the working fluid to a heat sink (e.g. outer space) and thereby converts the gaseous phase working fluid to its liquid phase, and returns the liquid phase working fluid to the evaporator to complete the thermal cycle. A portion of the condenser tube is supported by a rigid radiator structure external to the spacecraft. At least a portion of the condenser tube is deformable to permit the radiator structure to be deployed from a first predetermined position to a second predetermined position with respect to the spacecraft. The deformable segment of the condenser tube can be formed into a helical coil used as a spring to assist deployment of the radiator panel.

Abstract: A hybrid capillary/mechanical two-phase thermal loop has a sensor connected in parallel with a number of evaporators to regulate the flowrate of a booster pump providing working fluid to the evaporator capillaries. This sensor is made of a coiled, conductive tube connected in parallel with the evaporators, with an inside diameter substantially greater than the inside diameters of the evaporator capillaries. A conductive wire extends within said tube, but is insulated from electrical contact with the tube. The working fluid contained within the tube acts as a dielectric between the tube and wire. The amount of liquid phase working fluid within the tube can be determined by measuring the electrical capacitance between the tube and wire. The flowrate of the booster pump is then regulated as a function of the measured capacitance to maintain a substantially constant amount of liquid phase working fluid within the sensor tube.