Cryo

The cooling effect from the para-ortho hydrogen conversion (POC) combined with a vapor-cooled shield (VCS) and multi-layer insulation (MLI) can effectively extend the storage duration of liquid hydrogen in cryogenic tanks. However, there is currently no effective and straightforward empirical correlation available for predicting the catalytic POC efficiency in VCS pipelines. This study focuses on the development of correlations for the catalytic conversion of para-hydrogen to ortho-hydrogen in pipelines, particularly in the context of cryogenic hydrogen storage systems. A model that incorporates the Langmuir adsorption characteristics of catalysts and introduces the concept of conversion efficiency to quantify the catalytic process’s performance is introduced. Experimental data were obtained in the temperature range of 141.9~229.9 K from a cryogenic hydrogen catalytic conversion facility, where the effects of temperature, pressure, and flow rate on the catalytic conversion efficiency were analyzed. Based on a validation against the experimental data, the proposed model offers a reliable method for predicting the cooling effects and optimizing the catalytic conversion process in VCS pipelines, which may contribute to the improvement of liquid hydrogen storage systems, enhancing both the efficiency and duration of storage.

With the growth in global energy demand and increasing concern over the environmental issues associated with fossil fuels, magnetic confinement fusion (MCF) has gained widespread attention as a clean and sustainable energy solution. The superconducting magnet systems in MCF devices operate under liquid helium temperature of 4.2 K and strong magnetic fields, requiring structural materials to possess exceptional high strength, high toughness, and non-magnetic properties. This paper reviews recent research advances in cryogenic high-strength and high-toughness austenitic stainless steels (ASSs) for MCF devices, focusing on modified grades like 316LN and JK2LB used in the International Thermonuclear Experimental Reactor (ITER) project, as well as China’s CHN01 steel developed for the China Fusion Engineering Test Reactor (CFETR) project. The mechanical properties at 4.2 K (including yield strength (R_p0.2), fracture toughness (K(J)_Ic), and Elongation (e)), microstructural evolutions, weldability, and manufacturing challenges of these materials are systematically analyzed. Finally, the different technical approaches and achievements in material development among Japan, the United States, and China are compared, the current limitations of these materials in terms of weld integrity and manufacturability are discussed, and future research directions are outlined.

As an important component of the Stirling-type pulse tube cryocooler (SPTC), an efficient phase shifter can significantly improve the cooling capacity. This paper combines the advantages of the cold inertance tube and reservoir (ITR) and the active warm displacer (AWD) in an 8 K Stirling-type pulse tube cryocooler. Through numerical simulation methods, the influence of structural parameters of the cold ITR and operating parameters of AWD on acoustic power and impedance was studied. The results indicate that the length and diameter of the inertance tube, as well as the displacement and phase of the AWD, will affect the distribution of PV power inside the middle heat exchanger. The impedance distribution inside the pulse tubes of the higher-temperature section and the lower-temperature section changes in opposite directions. Through experiment, the effectiveness of the cold ITR and the adjustment function of the AWD were verified. A cooling capacity of 74 mW at 8 K can be obtained with the electric power of 177.5 W and a precooling capacity of 9.1 W/70 K. The AWD has a significant adjustment effect on T1 and T2, reaching the lowest no-load temperature at 2.13 mm and 48°, respectively, with a minimum no-load temperature of 5.13 K.