Variable View Factor Two-Phase Radiator

Variable View Factor Two-Phase Radiator

Variable view factor radiators are needed for manned missions and satellites to maintain a target temperature band of the cooled media or environment over widely varying power and heat sink conditions. Under a NASA SBIR program, Advanced Cooling Technologies is developing a vapor-pressure-driven variable-view-factor radiator that is deployable, operates with variable geometry and offers high turndown ratio of its thermal resistance to the sink. The proposed device, utilizes two-phase heat transfer and novel geometric features that adaptively (and elastically) adjust the view factor in response to internal (vapor) pressure and, implicitly, temperature. The radiator folds into a teardrop shape to minimize view factor when cold, and opens to maximize view factor when heated. This is facilitated by dynamic feedback between pressure inside the hollow curved panels of the radiator and the radiator structure itself, which permits a change of shape within the elastic limit of the material – thereby resulting in a reversible, deployable and variable view factor radiator that works via a two-phase heat rejection mechanism. The paper will discuss the proof-of-concept development that includes lab-scale experimental results, structural studies describing opening sensitivity including design optimization for environmental conditions, and overall TCS performance when utilizing the variable view factor radiator. Initially, a baseline design of the radiator was modeled, fabricated, and tested in a laboratory environment. Subsequently, structural studies were performed to understand how opening sensitivity is effected by geometric parameters including wall thickness, gap space, major radius, and other features. Design optimization seeks to maximize the opening sensitivity thus lowering the temperature difference between heat source and sink across the range of shapes between closed and fully open. Geometric features that increase opening sensitivity will be presented as well as their impact on TCS performance.

Work performed under NASA (SBIR) contract 80NSSC18P2187.