Design and Performance of a Two-Phase Thermal Storage Unit at 120 Kelvin

A cryogenic thermal storage unit useful in the 120 Kelvin (K) temperature regime has been designed, developed, and tested to meet the Air Forces' requirement for 1500 joules of storage in ten minutes. The Brilliant Eyes Thermal Storage Unit (BETSU) is composed of a hydrocarbon Phase Change Material (PCM) enclosed in a canister with internal conductance fins. The PCM has a melting point of 120 K and absorbs energy when solid PCM melts to liquid. The PCM would then be re-frozen using a cryogenic cooler before the next heat load application. The BETSU utilizes 2-methylpentane as the 120 K PCM working fluid and will be flown on board the Shuttle (STS-62) in early March 1994 as part of the CRYOTP II (Cryogenic Test Platform II) experiment package. The BETSU program objectives were to design and fabricate a Cryogenic Thermal Storage Unit (TSU) for space applications, to verify flight performance and to correlate the flight and ground test results. There has been very limited experience with the space flight of cryogenic phase change materials and the micro-gravity effects on a TSUs' performance.