Characteristics of thermo-physical process in 4K pulse tube


The great leader Comrade Kim Il Sung said as follows.

"Efforts should be made to develop cell engineering, gene engineering, superhigh-pressure physics and ultracryogenics, exploit atomic solar and other new sources of energy and study closely lasers and plasma so that these can be used extensively in the national economy."

Nowadays, 4K pulse tube cryocoolers (PTCs) are being widely used in material research at cryogenic temperature, superconductive electronics, aerospace, communication, biology, medicine and so on. However, their cooling performance is still not so good compared with that of 4K GM cryocoolers, the main reason for this is that the characteristics of thermo-physical process in 4K pulse tube has not yet been revealed obviously in detail.

Up to now, compared to numerous experimental studies on 4 K PTCs, there have been still insufficient theoretical analyses on them. Recently CFD study on two or three dimension pulse tube model is increasingly intensified to deepen understanding the refrigeration mechanism in PTCs. However, unfortunately, most of them treated the refrigeration temperature above 40 K where He-4 behaves as ideal gas rather than near 4 K where He-4 behaves as real gas.

Cryogenics research group of faculty of physics of Kim Il Sung University newly revealed the characteristics of thermo-physical process in 4K pulse tube in microscopic viewpoint, studying on 4K GM type two-stage PTC.

4K pulse tube has been simulated by CFD considering the real gas properties of helium to investigate thermodynamic cycle of different gas parcels in the pulse tube.

Results show that helium behaves more likely as real gas from the center to the wall of the pulse tube. The heat transfers from the hot side to the cold side including boundary layer, and there is few difference of its amount in central part and inside the boundary layer.

Besides, the heat transfers mainly from the hot side to the cold side in 4K pulse tube except the cold end, its amount rapidly decreases from the hot end to the middle part and slowly does towards the cold end. On the other hand, the heat transfers from the cold side to the hot side in the boundary layer, its amount linearly increases from the cold end to the hot end.

The detailed contents of our research results can be seen in "CFD study on the thermo-physical process in 4 K pulse tube" of "International Journal of Modern Physics B"(2020). (

The movement of the different gas parcels in pulse tube
Figure. 1 The movement of the different gas parcels in pulse tube

The heat exchange QB
Figure. 2 The heat exchange QB'AB and QBCB' in the pulse tube cold end

The heat exchnage QB
Figure. 3 The heat exchnage QB'AB along the pulse tube

The heat exchnage QBCB
Figure. 4 The heat exchnage QBCB' along the pulse tube