JPH0350950B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a cryogenic refrigeration method and apparatus.

[Background of the invention]

In a cryogenic refrigeration system, when a superconducting magnet is considered as an object to be cooled, helium is used as a cryogenic refrigerant. Hereinafter, the case of liquid helium as the cryogenic liquefied gas will be explained as an example.

In helium refrigeration systems, it is common practice to provide a heat shield plate at the liquid nitrogen temperature level in order to reduce the heat load on the liquid helium temperature level (-269°C). Furthermore, an intermediate heat shield plate may be provided between the liquid nitrogen temperature level and the liquid helium temperature level to reduce the heat load on the liquid helium temperature level.

Methods for cooling the intermediate heat shield plate in conventional cryogenic refrigeration equipment include a method of providing a cryogenic refrigerator to cool the intermediate heat shield plate, a refrigerant supply pipe at the intermediate heat shield plate temperature level, and a refrigerant return pipe. A cooling method using vaporized cryogenic helium gas and returning it to the suction side of the compressor at room temperature was used, but both methods were expensive and complicated the system. There are problems such as problems such as failure to improve the efficiency of the system.

In addition, related devices of this type include:
For example, Japanese Patent Publication No. 54-30139 can be mentioned.

[Purpose of the invention]

An object of the present invention is to provide a cryogenic freezing method and apparatus that can effectively recover the cold contained in the gas evaporated in the cryogenic container, facilitate pre-cooling in the cryostat, and improve the efficiency of the system. be.

[Summary of the invention]

The present invention provides a cryogenic freezing method in which cryogenic liquefied gas produced by a cryogenic refrigerator is stored in a cryogenic container in a cryostat, and the gas evaporated in the cryogenic container is transferred to a cryogenic refrigerator. At the same time, it is returned to the middle of the low pressure line of the cryocooler through a heat shield plate installed inside the cryostat surrounding the cryocontainer, and is collected.When precooling the cryostat, Most of the gas evaporated in the cryogenic container is recovered through the heat shield plate, and the cryogenic refrigeration equipment is used to compress and circulate the gas, cool the compressed gas, and adiabatically expand it to liquefy it at a cryogenic temperature. The cryostat is equipped with a cryogenic refrigerator that generates gas, and a cryostat that is equipped with a cryogenic container that stores the cryogenic liquefied gas transferred from the cryogenic refrigerator. A first line is installed between the cryostat and the cryostat to return the gas evaporated in the cryostat to the low pressure line of the cryocooler, and a line is installed in the cryostat surrounding the cryostat to transport the gas evaporated in the cryostat. A second line that returns to the middle of the low pressure line of the cryocooler via a heat shield plate is provided, and valves are provided in these lines so that the valve of the first line is throttled and the second line is
By creating a device that can transfer most of the evaporated gas to the cryogenic container, the cold contained in the evaporated gas in the cryogenic container can be effectively recovered, and
This makes pre-cooling inside the cryostat easier and improves system efficiency.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

In the drawing, 1 is a compressor, 2 is a cold box,
3a to 3f are heat exchangers, 4 is an expander inlet valve, 5a
and 5b is an expander, 6 is a Joel Thorson valve (hereinafter referred to as JT valve), 8 is a liquid nitrogen supply pipe, 9 is a liquid nitrogen supply valve, 10 is a refrigerant supply pipe, 11 is a refrigerant return pipe, 20 is a cryostat, and 21 is a 22 is a cryogenic container, 22 is an object to be cooled, such as a superconducting magnet, 23 is a heat shield plate, 24 is a liquid nitrogen supply pipe for heat shield, 25 is a liquid nitrogen outlet pipe for heat shield, and 26 is a liquid nitrogen supply valve for heat shield. , 30 is an intermediate heat shield valve, 31 is a second refrigerant return pipe, 3
2 is a shield refrigerant adjustment valve, and 33 is a return refrigerant adjustment valve. In this case, the cryogenic refrigerator consists of a compressor 1 and a cold box 2.

Next, the operation of the cryogenic refrigeration apparatus configured as above will be explained. Gas compressed by the compressor 1, for example, helium gas, is introduced into the cold box 2, cooled by the first heat exchanger 3a and the second heat exchanger 3b, and then transferred to the expander line and the liquefaction line. Branched out. The high-pressure helium in the expander line passes through the expander inlet valve 4 and performs adiabatic expansion work in the first expander 5a, resulting in a temperature drop, is cooled in the fourth heat exchanger 3d, and is then transferred to the second expander 5b. It performs adiabatic expansion work again, lowers its temperature, and joins the low-pressure line. On the other hand, the high-pressure helium branched into the liquefaction line is cooled to the inversion temperature in the third to sixth heat exchangers 3c to 3f, adiabatically expanded in the JT valve 6, becomes partially liquid helium, and passes through the refrigerant supply pipe 10. It is sent to the cryogenic container 21 within the cryostat 20. The liquid helium sent to the cryogenic container 21 cools the superconducting magnet 22, absorbs heat entering from the normal temperature part, and is gasified. A part of this gas passes through the refrigerant return pipe 11 to the cold box 2.
The refrigerant returns to the compressor 1 after passing through the return refrigerant regulating valve 33 and being cooled and recovered by the sixth to first heat exchangers 3f to 3a. The remaining gas in the cryogenic container 21 cools the intermediate heat shield plate 30, returns to the cold box 2 through the second refrigerant return pipe 31, passes through the shielding refrigerant regulating valve 32, and is transferred to the second heat exchanger 3b. It joins the intermediate low pressure line of the third heat exchanger 3c. The refrigerant for cooling the intermediate heat shield plate 30 is adjusted by the shield refrigerant adjustment valve 32, and the temperature of the intermediate heat shield plate 30 is adjusted between the heat shield plate 23 and the cryogenic container 2.
It is held at a predetermined value between 1 and 1. The return refrigerant adjustment valve 33 is an adjustment valve for bypassing most of the refrigerant supplied by the refrigerant supply valve 10 and cooling the superconducting magnet 22 to the cooling line of the intermediate heat shield plate 30 when the superconducting magnet 22 is precooled. It is a valve. Liquid nitrogen, which is an auxiliary refrigerant, is supplied to the cold box 2 via a liquid nitrogen supply pipe 8 and a liquid nitrogen supply valve 9, and to the cryostat 20, a liquid nitrogen supply pipe 24 for heat shielding and a liquid nitrogen supply pipe for heat shielding are supplied to the cryostat 20. It is supplied through the valve 26, cools the heat shield plate 23 to liquid nitrogen temperature, and exits through the heat shield liquid nitrogen outlet pipe 25.

As described above, according to this embodiment, the cold contained in the helium gas evaporated from liquid helium in the cryogenic container is used to cool the intermediate heat shield plate and pre-cool the helium gas introduced into the cold box of the cryogenic refrigerator. By adjusting the return refrigerant regulating valve of the refrigerant return pipe during precooling of the superconducting magnet, in other words, by adjusting it in the direction of narrowing down, most of the refrigerant that has become high in temperature can be cooled by cooling the intermediate heat shield plate. It can be bypassed to the line and returned to the cold box, making it easier and more efficient to form a cryogenic refrigerator system.
This has the effect of improving system efficiency.

〔Effect of the invention〕

According to the present invention, the cold contained in the gas evaporated in the cryogenic container can be effectively recovered, and the cryostat can be easily precooled, thereby improving the efficiency of the system.

[Brief explanation of drawings]

The drawing is a block diagram showing an example of a cryogenic refrigeration system embodying the present invention. 1...Compressor, 2...Cold box, 21
... Cryogenic container, 30 ... Intermediate heat shield plate, 3
1...Second refrigerant return pipe.

Claims (1)

[Scope of Claims] 1. A step of storing cryogenic liquefied gas produced by a cryogenic refrigerator in a cryogenic container in a cryostat, and storing the gas evaporated in the cryogenic container in the cryogenic refrigerator. a step of recovering the cryostat by returning it to the low pressure line of the cryocooler and returning it to the middle of the low pressure line of the cryocooler via a heat shield plate surrounding the cryostat and provided in the cryostat; A cryogenic freezing method characterized by comprising the step of recovering most of the gas evaporated in the cryogenic container through the heat shield plate side when precooling the tatsuto. 2 Compress and circulate gas and cool and cool the compressed gas.
It is equipped with a cryogenic refrigerator that generates cryogenic liquefied gas through adiabatic expansion, and a cryostat equipped with a cryogenic container that stores the cryogenic liquefied gas transferred from the cryogenic refrigerator, Between the cryostat and the cryocooler, there is a first line for returning the gas evaporated in the cryocontainer to the low pressure line of the cryocooler; a second line that surrounds the cryogenic container and returns to the middle of the low pressure line of the cryogenic refrigerator via a heat shield plate provided in the cryostat, and a valve is provided in these lines; A cryogenic refrigeration system characterized in that, during precooling of the cryostat, a valve in the first line is throttled so that most of the evaporated gas can be transferred to the second line.