Modeling of Complex Oxygen Compression Heating Scenarios for the Exploration Extravehicular Mobility Unit Umbilical



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49th International Conference on Environmental Systems


Following an Extravehicular Activity (EVA), the primary oxygen tank located in the Portable Life Support System (PLSS) of the Exploration Extravehicular Mobility Unit (xEMU) must be refilled before the suit can be used again. The oxygen filling operation requires the Service and Cooling Connector (SCC) component of the Exploration Service and Cooling Umbilical (ESCU) to be connected to its counterpart on the Display and Control Unit (DCU) located on the front of the suit. Charging the ESCU with high pressure oxygen gas results in compression heating in the ESCU oxygen lines and therefore has the potential to auto ignite non-metallic components in the SCC. To mitigate the potential ignition hazard, an orifice upstream of the umbilical must be sized such that the umbilical supplies oxygen at a minimum flow rate of 6 lbm per hour, but also prevents ignition of the downstream soft components. Techniques used to model this scenario employ both AutoCAD Thermal Desktop with SINDA/FLUINT package, to describe the heat transfer in fluid pipes with regular, consistent, cross sectional shapes, and ANSYS CFD (Computational Fluid Dynamic) software, to capture the heat transfer profile of the complex geometry located within the SCC. The mass flow rate (specific to the orifice open area) just upstream of the SCC acts as the input into the ANSYS Fluent model through which the temperature of the soft components can be obtained. The ANSYS model additionally provides the necessary information to solve for the unknown heat transfer coefficients within the irregular SCC geometry, thus allowing for an accurate but simplified representation of the SCC fluid lines to be added to the Thermal Desktop model. When working in conjunction, the two software optimize the speed and accuracy of modeling compression heating in complex oxygen systems.


Margot Steely, Jacobs Engineering, USA
Thomas Paul, Jacobs Engineering, USA
ICES402: Extravehicular Activity: PLSS Systems
The 49th International Conference on Environmental Systems as held in Boston, Massachusetts, USA on 07 July 2019 through 11 July 2019.


Computational fluid dynamics, ANSYS, AutoCAD Thermal Desktop, Exploration mobility unit, Compression heating, service and cooling connector, display and control unit, umbilical, oxygen