Two-stage pulse tube refrigeration with helium and hydrogen mixture.

Based on the previous studies, a further experimental investigation on two-component helium and hydrogen mixtures in a two-stage pulse tube refrigerator was carried out. The experimental results using helium and hydrogen mixtures, with 7, 20, 34, 45 and 60% hydrogen, compared to pure helium in 20 K temperature range are presented and showed that both COP and refrigeration power are better than that of using pure helium. The maximum gains in cooling power of 25% and COP of 31% at hydrogen molar fraction 60% have been obtained near 20 K in the experiment. During the cooling process of pulse tube refrigeration with the mixtures, the phenomena of phase transforms and a near stable temperature platform with 0.9 W heat load, which is independent on fraction around the triple phase point of hydrogen (13.95 K), was observed.