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Paragon Space Development Corporation is developing a single-loop, non-toxic, active pumped thermal control design for robust, reliable operation near stagnation regimes as experienced in low power/cold environments. This research uses a safe fluid named Galden® HT170, manufactured by Solvay Solexis that has lower temperature stalling characteristics over typical space-based radiator fluids such as propylene glycol/water (PGW). A test bed and stagnation test article were designed, built and then modeled using Thermal Desktop® software to explore tube stagnation using Galden. Tube stagnation was sequentially controlled in each tube in a predictable manner, while collecting data to validate models. The data compared well to the modeling results. Fluid-compatibility results also showed no degradation to the fluid or to the aluminum tubing and weld materials and structures

Radiator stagnation is being explored to design single loop thermal control systems using Galden HT170 for heat rejection systems requiring large turn-down ratios. A previous Small Business Innovation Research (SBIR) Phase 1 studied sequential stagnation in a system of different length tubing. As part of a follow-on Phase 2, tests were performed to study the effects of adding a facesheet in a manner consistent with typical spacecraft radiator effectiveness. Onset of stagnation for different tubes was demonstrated for a given inlet temperature by lowering mass flow rate. Temperature and/or mass flow rate were increased to investigate stagnation recovery. A Thermal Desktop® model was built to simulate the test. Test results and modeling comparisons are presented.