Testing of the Multi-Fluid Evaporator Prototype

Hamilton Sundstrand has developed a scalable evaporative heat rejection system called the Multi-Fluid Evaporator (MFE). It was designed to support the Orion Crew Module and to support future Constellation missions. The MFE would be used from Earth sea level conditions to the vacuum of space. This system combines the functions of the Space Shuttle flash evaporator and ammonia boiler into a single compact package with improved freeze-up protection. The heat exchanger core is designed so that radial flow of the evaporant provides increasing surface area to keep the back pressure low. The multiple layer construction of the core allows for efficient scale up to the desired heat rejection rate. A full-scale unit uses multiple core sections that, combined with a novel control scheme, manage the risk of freezing the heat exchanger cores.

A four-core MFE prototype was built in 2007. The prototype underwent check-out testing before being installed into NASA's Advanced Thermal Technology Integrated Test. The integrated test ran the MFE through fourteen test conditions, which used a 50/50 mix of propylene glycol and water as the heat transport fluid and deionized water as the evaporant. These tests revealed how the MFE performs with propylene glycol as the coolant instead of water and point toward design changes that can be made to improve the evaporator's performance. This paper discusses the results of the Multi-Fluid Evaporator prototype testing and concludes with the status of present work.