Long-term space missions require minimized boil-off from liquid hydrogen and oxygen tanks to increase the payload mass fraction at launch. Vapor-cooled shielding technologies can use liquid hydrogen boil-off vapors to refrigerate and potentially eliminate boil-off from liquid oxygen tanks. Statistical thermodynamic calculations estimate that the amount of refrigeration provided by hydrogen for a liquid oxygen tank can be increased up to 50% through catalysis of parahydrogen–orthohydrogen conversion. Based on this prediction, a cryocatalysis hydrogen experiment facility was developed as a proof of concept. Hydrogen is liquefied in a noncatalytic condenser and vapor venting controlled via a proportional-integral-derivative controller. The effective heat capacity of the effluent is measured directly through a change in temperature of the known mass flow and applied heater power. The change in parahydrogen–orthohydrogen composition is validated independently with a thermal conductivity probe calibrated in situ. A maximum increase in the effective heat capacity of 35% was observed for hydrogen flow through activated ferric-oxide catalyst at a mass flow rate of . This result indicates that significant reductions to in-space venting of hydrogen and oxygen are possible through vapor-cooled shielding technologies that catalyze parahydrogen–orthohydrogen conversion.
Parahydrogen–Orthohydrogen Conversion for Enhanced Vapor-Cooled Shielding of Liquid Oxygen Tanks
Journal of Thermophysics and Heat Transfer ; 28 , 4 ; 717-723
2014-07-15
7 pages
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch
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