Passive Thermal Control Valves for Loop Heat Pipes and Pumped Systems

Advanced Cooling Technologies, Inc. (ACT) will develop Thermal Control Valves (TCVs) for the following applications: 1. Loop Heat Pipes (LHPs) (On/Off), 2. Single Phase Pumped Loops (Proportional), and 3. Pumped Two Phase (P2P) Loops (Backpressure regulators).nbsp; There is a clear need for advanced thermal control solutions that can support extended-duration science payloads on the lunar surface. Since the primary power source for near term Lunar surface science missions is a combination of solar photovoltaic arrays amp; batteries (note that each watt of power required through the lunar night requires ~5 kg of batteries), a thermal control system that rejects daytime heat efficiently amp; conserves energy through the night is essential to keep the payloads, batteries and other critical components at suitable temperatures.nbsp; This proposed program will develop passive Thermal Control Valves, and test them with a low-cost, 3D-printed Loop Heat Pipe (LHP).nbsp;nbsp;nbsp; Conventional LHPs provide very efficient heat transfer between electronics and spacecraft radiators when necessary but require 2-3 W of power continuously to shut down and minimize heat transfer (e.g. through the night), which can increase battery mass substantially if applied for the entire lunar night. The TCV requires no electrical power, passively shutting down the LHP and minimizing power needs and heat losses at nightBy using 3D printing, ACT will develop TCVs integrated with the LHP evaporator (3D printed) and Compensation Chamber.nbsp; The body of the TCV will be printed separately, probably in two sections.nbsp; The TCV will then be welded to the tube through the evaporator end, and the rest of the compensation chamber will be fabricated around it.nbsp;In the Phase II program, ACT will develop TCVs for pumped single- and/or two-phase systems.nbsp; 3D printing of the valve bodies will be examined, to both develop lower mass solutions, and integrate the valves with the cold plates.