Consideration is given to the use of a hydrogen refrigerator to assist in the production of temperatures below those obtained with hydrogen. A hydrogen refrigerator is used to maintain a precooling evaporator at or near 21 °K in a helium gas circuit. The helium circuit may be arranged to produce liquid for external use or to pro¬duce refrigeration between 21 °K and 4. 2 °K in a closed system.nCharts have been developed that show the requirements of the composite helium - hydrogen system and the effect of heat exchanger performance. The relative quantities of refrigeration (hydrogen and helium) at various temperature levels have been determined.
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