Fabrication and Experimental Testing of Variable-View Factor Two-Phase Radiators

Radiators for manned spacecraft, satellites, planetary rovers and unmanned spacecraft are sized for the highest power at the hottest sink conditions, so they are oversized and prone to freezing at low sink temperatures. In order to address the need for light-weight, deployable and efficient radiators capable of passive thermal control and a significant heat rejection turndown ratio, Advanced Cooling Technologies, Inc. (ACT) has developed a novel vapor-pressure-driven variable-view-factor and deployable radiator that passively operates with variable geometry (i.e., view factor). The device utilizes two-phase heat transfer and novel geometric features that passively (and reversibly) adjust the view factor in response to the internal vapor pressure in the radiator. The variable-view-factor two-phase radiator (VVFTPR) consists of hollow curved and straight panels, filled with a two-phase fluid. An increase in internal vapor-pressure, due to an increase in fluid temperature, results in elastic bending of the curved panel and an increase in view-factor. In addition, since the radiator is a two-phase device, its efficiency will approach unity.

ACT and the Edison Welding Institute (EWI) have successfully manufactured and tested VVFTPR panel prototypes from aluminum 7075 via ultrasonic welding. Two radiator prototypes will be presented. The first prototype was made of several separate channels containing a two-phase working fluid. The second prototype utilized a continuous channel design that allowed the working fluid to flow continuously through the prototype and could function as a radiator for loop heat pipes. This paper discusses the manufacturing process and experimental testing of the prototypes.