Testing of the Multi-Fluid Evaporator Engineering Development Unit

Hamilton Sundstrand is under contract with the NASA Johnson Space Center to develop a scalable, evaporative heat rejection system called the Multi-Fluid Evaporator (MFE). It is being designed to support the Orion Crew Module and to support future Constellation missions. A MFE would be used from Earth sea level conditions to the vacuum of space. The current Space Shuttle configuration utilizes an ammonia boiler and flash evaporator system to achieve cooling at all altitudes. With the MFE system, both functions are combined into a single compact package with significant weight reduction and improved freeze-up protection. The heat exchanger core is designed so that radial flow of the evaporant provides increasing cross-sectional area to keep the back pressure low. Its multiple layer construction allows for efficient scale up to the desired heat rejection rate. The full scale MFE prototype will be constructed with four core sections that, combined with a novel control scheme, manage the risk of freezing the heat exchanger cores.

A sub-scale MFE engineering development unit (EDU) has been built, and is identical to one of the four sections of a full scale prototype. The EDU has completed testing, with an overall test objective to determine its thermal performance. Check-out and thermal performance tests simulated how each of the four sections of the prototype would perform by varying the chamber pressure, evaporant flow rate, coolant flow rate and coolant temperature. A second set of thermal verification tests was conducted with an outlet steam header in place to verify that the outlet steam orifices prevent freeze-up in the core while also allowing the desired thermal turn-down ratio. This paper discusses the EDU tests and results.