Browsing by Author "Foley, Lauren"
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Item Mitigation of Orion Ammonia Boiler Outlet Coolant Thermal Stratification(48th International Conference on Environmental Systems, 2018-07-08) Ungar, Eugene K.; Foley, LaurenPart of NASA’s Orion Multi-Purpose Crew Vehicle (MPCV) active thermal control system is the Ammonia Boiler Heat Exchanger (ABHX). The ABHX is used as a topper when the Orion radiators cannot provide sufficient cooling and is the sole method of cooling the spacecraft after the command module/service module separation prior to reentry. Ammonia and propylene glycol water (PGW) flow through the heat exchanger in a counter-flow fashion, allowing the evaporating ammonia to cool the PGW. After exiting the heat exchanger , the PGW travels through a 0.5-inch diameter tube with three bends and enters temperature sensor block containing two thermistors. Development testing showed that the floe at the sensor block was not well mixed - the two PGW temperature sensors registered temperature differences of up to 5°C. A gravity fed water test stand was constructed of 1 inch clear PVC pipe to investigate the stratification. The test stand contained a long lead in section to allow the flow to fully develop. The bend area was geometrically scaled and the water flow rate was set to match the PGW Reynolds number of approximately 1000. Dye injection was used to visually assess the flow and mixing. Baseline testing clearly showed that the flow was poorly mixed at the thermistor location. Turbulators of different types and lengths were added to mix the flow. In the end, a turbulator configuration was chosen that resulted in well mixed flow while adding minimal pressure drop. In the present work, the Orion stratification issue is described, the test stand configuration and scaling is detailed, and the test is discussed. The chosen turbulator configuration is explained and its effect on the performance of the Orion ABHX is described.Item Performance Testing and Modeling of a Scaled Fusible Heat Sink Test Article for Exploration Vehicles(2020 International Conference on Environmental Systems, 2020-07-31) Hillstrom, Alexander; Massina, Christopher; Foley, Lauren; Abraham, Brittany; Andish, KambizA water based fusible heat sink is envisioned for use in several future human space vehicles ranging from a deep space habitable airlock to lunar rovers. This radiator concept has the potential to enable active thermal control systems with a single benign working fluid (such as propylene glycol water) as dynamic loading is buffered by the heat capacity of the integrated water layer. This paper presents the results of evaluations of a scaled test article which includes integrated coolant tubes through the radiator’s water reservoir. This testing was completed to validate analysis results and provide insight into freeze direction and control given the enclosure volume’s unique geometry and internal features. The coolant flows through the radiator in two tube bank layers. The first layer is contained within the water volume near the heat rejection interface, i.e. the radiating surface, and the second layer is submerged within the entrained water volume. The inlet temperature and flow rates of each layer can be controlled independently to better match the thermal performance expected in the full scale radiator. Results indicate that a predictable freeze direction can be obtained repeatedly and the associated water ice spike formation can be tolerated by a flexible enclosure. Implications for the next iteration of full scale hardware design are also discussed.