The Low-Temperature Adsorption Characteristics of Activated Carbon With 3He and 4He as Sorption Cooler Cryogens

As a commonly used sub-Kelvin refrigeration technology, helium sorption coolers play an important role in space and ground applications. The adsorption characteristics of the porous material inside the sorption cooler at low temperature have a crucial influence on its performance. At present, the analysis and calculation of sorption coolers are mainly based on helium 4 (He-4) as the working gas, and there is a lack of systematic research on the low-temperature adsorption characteristics of helium-3 (He-3) and its coupling effect characteristics of temperature, pressure, and mass distribution in different components. In this paper, a molecular model of activated carbon that is similar to the actual structure was constructed, and the adsorption isobars and isosteric heat of He-3 and He-4 at 0.8-5 K were comparatively studied based on the grand canonical Monte Carlo (GCMC) method. Besides, the influence of adsorption characteristics of He-3 and He-4 on the condensation efficiency, the mass distribution after condensation equilibrium, and the self-cooling loss of the sorption cooler were analyzed. The results show that for the He-3 sorption cooler, the main factor affecting the condensation efficiency is the adsorbed helium in the sorption pump, while for the He-4 sorption cooler, it is the adsorbed helium and the gas in the dead volume. For both He-3 and He-4 sorption coolers, the condensation efficiency increases as the sorption pump temperature increases or the heat sink temperature decreases, while the self-cooling loss decreases as the heat sink temperature decreases or the operating temperature increases.

Automated summary

Helium sorption coolers are a commonly used sub-Kelvin refrigeration technology, with the adsorption characteristics of the porous material having a crucial impact on their performance at low temperatures. This study compared the adsorption characteristics of helium-3 and helium-4, and analyzed their effects on the efficiency and self-cooling loss of the sorption cooler. The results showed that factors such as adsorbed helium in the sorption pump and dead volume gas play a significant role in the condensation efficiency of the sorption coolers.