JPS61223455A - Cryogenic refrigerator and operation method thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of the Invention] A wood furnace relates to cryogenic refrigeration* that requires a cooling temperature below the atmospheric pressure saturation temperature and its operating method.

In particular, the present invention relates to a cryogenic refrigeration system suitable for objects to be cooled using ultra-ffi dynamic helium, and a method of operating the same.

[Background of the invention]

When considering a superconducting magnet as an object to be cooled in a cryogenic refrigerator, one of the cooling methods is to use superfluid helium. Liquid helium at about 1.8K (
Superfluid helium is obtained by cooling to a saturation pressure of about 10 tons), exhibiting unique properties such as low viscosity and extremely high heat transfer rate of 575r. On the other hand, one of the characteristics of the superconducting wire used in the electromotive conducting magnet, which is the body to be cooled, is that the lower the cooling temperature, the higher the current density. In other words, by using superfluid lithium, a turbulent magnetic field can be obtained with a compact superconducting magnet, making it one of the most effective cooling methods. Hereinafter, the case of liquid helium as the cryogenic liquefied refrigerant will be explained as an example.

FIG. 1g2 is a block diagram showing an example of the configuration of a conventional superfluid helium system 2. As shown in FIG. In Fig. 2, 1 is a compressor, 2
3a to 3f are cryogenic refrigerators, 3a to 3f are heat exchangers, 4 is an expansion valve, 5 is a Joule-Thomson expansion valve (hereinafter referred to as JT valve), 6a and 6b are expanders, 7 is a liquid nitrogen supply pipe,
11 is a cryogenic refrigerant supply pipe, 12 is a cryogenic refrigerator pipe, 13
1 is an extremely low wet pressure reduced refrigerant return pipe; 2 is a cryostat; 21 is a gas-liquid separator;

Next, a conventional superfluid helium 1 configured as described above is used.
The operation of 118 will be explained. Compression W! The helium gas compressed to high pressure in step 1 is introduced into cryogenic refrigerator 2,
The first heat exchanger 3a exchanges heat with the low-pressure return gas and liquid nitrogen introduced from the liquid nitrogen supply pipe 7, and the second heat exchanger 3b cools the gas, which is then branched into an expander line and a JT line. do. The high-pressure helium branched into the expander line passes through the expander valve 4, performs adiabatic expansion work in the first expander 6a, lowers its temperature, and enters the fourth heat exchanger 3d. After cooling, the second expander 6b performs adiabatic expansion work again to lower the temperature and join the low pressure line. On the other hand, the high-pressure helium branched to the JT line is in the 3rd to m! 6
The gas is sequentially cooled in the heat exchangers 3C to 3f, and adiabatically expanded to near atmospheric pressure in the JT valve 5, whereby a part of the gas liquefies and becomes a gas-liquid mixed phase state. The cryogenic refrigerant in a gas-liquid mixed phase state is supplied to the cryostat (9) through the cryogenic refrigerant supply pipe 11.

Gas and liquid are separated by a gas-liquid separator 4. The separated gas passes through the cryocooler refrigerating section and returns to the cryocooler 2.
The first heat exchanger 3f to 3a recovers the cooled liquid, returns it to the ambient temperature, and returns it to the suction side of the compressor 171a.Meanwhile, the fresh liquid separator 71a separates the liquid at a temperature of approximately 4.4K (approximately 1.2 atm). The liquid helium of ) is reduced in pressure to about 10 Torr with a pressure reducing valve (1) and supplied to a liquid helium tank (2), which becomes superfluid helium with a pressure of about 1.8 Torr and cools the superconducting magnet. The cryogenic reduced pressure gas that has been gasified by cooling the superconducting Magratos passes through the modified wet reduced pressure refrigerant return pipe 13 and is heated to ambient temperature by a heater (supply), and then is sucked into the compressor 1 by the vacuum pump 31. The pressure is increased to the maximum pressure and returned to the suction side of the compressor 1.

Conventional superfluid helium equipment with the above configuration and operation does not effectively recover the cryogenic temperature of the cryogenic decompression refrigerant (hereinafter referred to as return refrigerant) that cools the superconducting magnet and gasifies it, resulting in a reduction in efficiency. It was a bad 'iNM.

Incidentally, related devices of this type include, for example, Japanese Patent Application Laid-Open No. 151850/1983.

[Purpose of the invention]

An object of the present invention is to provide a "cryogenic refrigerator" that can efficiently cool objects to be cooled that require cooling 8112 below the atmospheric pressure saturation temperature by effectively recovering the cold of the return refrigerant, and a method for operating the same. There is a particular thing.

[Summary of the invention]

In the conventional superfluid helium system, the return coolant from the object to be cooled was not recovered by cooling. This is because in order to recover the cold, it is necessary to introduce the returned refrigerant into a cryogenic refrigerator and exchange heat with a heat exchanger, but in the case of superfluid helium, the pressure is extremely low at approximately 10 Torr, so there is no pressure loss. This was because it had to be made smaller and required a very large heat exchanger. In order to solve the above-mentioned problems, focusing on the fact that pressure loss is approximately proportional to gas pressure, the return refrigerant at a pressure of 10 Torr is increased by 50 to 10 Torr using pressure boosting means.
By increasing the pressure to an intermediate pressure of 0 Torr, the heat exchanger can be sized to a practical size. On the other hand, when the pressure of the return refrigerant is increased by the pressure increasing means, the temperature of the return refrigerant increases. In general, the evaluation of cooling is proportional to the reciprocal of the absolute temperature (α1/T), and the pressure loss is roughly proportional to the 1.25th power of the absolute temperature. It is not systemically efficient to increase the pressure by other means.

The most effective system can be realized by recovering the returned refrigerant in a cold state using a part of the heat exchanger in the cryogenic section, raising the pressure to an intermediate pressure using a pressure booster, and recovering the coolant again in the heat exchanger.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the m1 diagram. In FIG. 1, in order to avoid duplication, the same parts as in FIG. 2 are given the same reference numerals and their explanations are omitted, and the parts that are different in FIG. 2 will be mainly described.

Figure 1 shows #1 of one implementation of the ultra-low refrigeration product of the present invention.
FIG. 2 is a block diagram showing the configuration. ! l! In Figure 1.

7 is a cryogenic refrigerator capable of cold recovery of the return stroke low-temperature decompression refrigerant from the object to be cooled; 38' to 3 d' and 3 f' are heat exchangers in which channels through which the return refrigerant flows are formed; 9 31' is a pressure reducing pump for raising the pressure from the intermediate pressure raised by the lowering vacuum pump 9 to the suction pressure of the compressor 1.Other parts 1.1 It is similar to FIG.

The operation of the refrigeration system of the present invention constructed as described above will be explained below.

The return refrigerant that has been gasified by cooling the superconducting magnet U, which is a liquid cooling body, passes through the cryocooler tube 13, is introduced into the cryocooler 2', and is recovered by the sixth heat exchanger 3f'. After that, the cryogenic vacuum pump 9 is used to generate a
The pressure is increased to an intermediate pressure of n, and then the fourth to first heat exchangers 3
It is cooled and recovered by heat exchange between d' and 3a', and the pressure is increased to the suction pressure of the compressor 1 by the pressure reducing pump 31', and it joins the low pressure line and returns to the suction side of the compressed filter.

As described in detail above, in order to perform cryogenic recovery of the return coolant, it is possible to realize a system that can efficiently cool a superconducting magnet, and to raise the pressure to an intermediate pressure using a cryogenic vacuum pump. Can be made into a compact device. Furthermore, after recovering the cold refrigerant in some heat exchangers, it is introduced into the cryogenic vacuum pump, which improves the efficiency of cold recovery. #It has the effect of keeping the temperature of the low-temperature vacuum pump at a stable condition.

〔Effect of the invention〕

As explained above, the present invention can effectively recover the cold of the return refrigerant, so it has the effect of efficiently cooling objects to be cooled that require a cooling temperature below the atmospheric pressure saturation temperature.

[Brief explanation of drawings]

FIG. 1 is a Brolik diagram showing the configuration of an embodiment of the cryogenic refrigeration system according to the X invention, and FIG. 2 is a block diagram showing the configuration of a conventional super-submerged helium cavern δ. 1...Compressor, 2...Cryogenic refrigerator,
3 a' to 3d, 3f... Heat exchanger, 9.
...Cryogenic vacuum pump, 24...Superconducting magnet vl' Agent: Patent attorney Katsuo Ogawa,'°

Claims (1)

[Scope of Claims] 1. A polar system consisting of a compressor that compresses and circulates refrigerant gas, a cryogenic refrigerator that produces cryogenic liquefied refrigerant, and a cooled body that is cooled to a temperature below atmospheric pressure saturation temperature. In a low temperature refrigeration system, a flow path through which the return refrigerant from the object to be cooled flows is formed in a heat exchanger of the cryogenic refrigerator, and the pressure of the return refrigerant is increased to an intermediate pressure between the heat exchangers. A cryogenic freezing device characterized by being provided with means. 2. In a cryogenic refrigeration system comprising a compressor that compresses and circulates refrigerant gas, a cryogenic refrigerator that generates a polarization temperature liquefied refrigerant, and a cooled object that is cooled to a temperature below the atmospheric pressure saturation temperature, the above-mentioned The method includes a step of increasing the pressure of the return refrigerant from the object to be cooled to an intermediate pressure, and a step of cooling the refrigerant gas that becomes the cryogenic liquefied refrigerant with the return refrigerant and recovering the cold of the return refrigerant. Features: How to operate cryogenic refrigeration equipment.