JPH06268267A - Cryogenic refrigerator - Google Patents

Abstract

PURPOSE:To enhance a cryogenic refrigerator in evaporated coolant gas recovering capacity keeping it at a certain level in refrigerating capacity when a superconducting magnet is excited or demagnetized. CONSTITUTION:A piping system which connects compressors 1, which feed coolant gas of normal temperature and high pressure to a refrigerator 2, together in series and another piping system which connects the compressors 1 together in parallel are provided, the compressors 1 are connected in series when the refrigerator 2 is kept in a normal operation and connected in parallel by switching valves when a superconducting magnet is excited or demagnetized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cryogenic refrigerator for cooling superconducting magnets and the like.

[0002]

2. Description of the Related Art FIG. 2 is a schematic circuit diagram of a conventional cryogenic refrigeration system, in which 1 is a compressor, 2 is a refrigerator, 3 is a buffer tank, 4 is a JT valve, 5 is a liquid refrigerant tank, 6a,
6b is a solenoid valve, and 8 is a pressure regulating valve. In the conventional cryogenic refrigeration system, the solenoid valve 6a is used during normal liquefaction and freezing operation.
With 6b closed, the room temperature and high pressure refrigerant gas discharged from the compressor 1 is pre-cooled to below the reversing temperature of the refrigerant gas by heat exchange with the refrigerant gas in the low pressure pipe and the refrigerator cold head in the refrigerator. , JT valve 4 is further liquefied and cooled by the Joule-Thomson expansion. When a heat load higher than usual is applied to the liquid refrigerant tank due to the demagnetization of the superconducting magnet, the liquid refrigerant evaporates, and the amount of refrigerant gas in the circulation circuit increases. In this case, close the solenoid valve 6a,
Open 6b to switch the circuit. That is, by filling the buffer tank 3 with the refrigerant gas that has been flowing from the high pressure side of the compressor to the refrigerator 2 during normal operation, the increased refrigerant gas in the circulation circuit is temporarily taken out of the circulation circuit to obtain a cryogenic temperature. It has the effect of suppressing the pressure rise in the container and the temperature rise that occurs at the same time. When the heat load returns to normal and the liquefaction progresses and the refrigerant gas in the circulation circuit becomes insufficient, this time, the refrigerant gas is replenished from the buffer tank 3 through the pressure regulating valve 8 and reliquefied.

[0003]

In the conventional cryogenic refrigeration system, the compressor only recovers the evaporated refrigerant gas when an overheat load is applied to the liquid refrigerant tank, such as during demagnetization. Since the high-pressure refrigerant gas is not supplied to the refrigerator, the refrigerating capacity is temporarily lost and the cold air contained in the evaporated refrigerant gas in the low-pressure pipe cannot be effectively used. In addition, since the processing capacity of the compressor is basically the same as that during normal operation, if the amount of generated refrigerant gas exceeds the processing capacity of the compressor, there may be situations in which even recovery may not be possible. was there. The present invention has been made to solve the above-mentioned problems, and provides a cryogenic refrigeration system having an improved recovery capability of evaporated refrigerant gas while maintaining the refrigeration capability to some extent even during demagnetization of the superconducting magnet. With the goal.

[0004]

The cryogenic refrigeration system of the present invention has a piping system for connecting in series a plurality of compressors for supplying a refrigerant gas at room temperature and high pressure to the refrigerator and a piping system for connecting them in parallel. However, connect the compressors in series during normal operation,
This device has a structure in which the compressors can be connected in parallel by switching the valve when the superconducting magnet is demagnetized.

[0005]

According to the present invention, in a cryogenic refrigeration system including a refrigerator and a plurality of compressors for supplying high-pressure refrigerant gas to the refrigerator, the plurality of compressors are used in series during normal operation and the superconducting magnet A pipe that can be used in parallel by switching the valve during demagnetization was provided. For this reason, the processing capacity of the compressor is increased at the time of excitation / demagnetization, etc., and it is possible to prevent the pressure in the liquid refrigerant tank from rising. Further, it becomes possible to send the refrigerant gas to the refrigerator as much as the processing capacity of the compressor has been spared, and the cold air of the generated refrigerant gas can be effectively used.

[0006]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic circuit diagram of a cryogenic refrigerator according to the present invention. 1 is a compressor, 2 is a refrigerator, 3 is a buffer tank, 4 is a JT valve, 5 is a liquid refrigerant tank, 6a, 6b, 6c.
, 6d and 6e are solenoid valves, 7a and 7b are check valves, and 8 is a pressure regulating valve. During normal operation of the refrigeration system, the solenoid valve 6a
Is open, solenoid valve 6b is closed, solenoid valve 6c is closed, solenoid valve 6d is open, solenoid valve 6e is closed, and compressor 1 is connected in series. The refrigerant gas is compressed by the compressor 1 and is pre-cooled to a temperature not higher than the inversion temperature of the refrigerant gas by heat exchange with the refrigerant gas in the low-pressure pipe or the refrigerator cold head in the refrigerator, and the JT valve 4
It is further cooled or liquefied by expanding Joule Thomson. The refrigerant gas evaporated in the liquid refrigerant tank and the refrigerant gas that has not been liquefied are heat-exchanged with the high-pressure refrigerant gas in the refrigerator and then introduced into the compressor. When the heat load increases due to the demagnetization of the superconducting magnet and the amount of the refrigerant gas evaporated in the liquid refrigerant tank increases, the solenoid valve 6a is opened, the solenoid valve 6b is opened, the solenoid valve 6c is opened, the solenoid valve 6d is closed, and the solenoid valve 6d is closed. The valve 6e is opened and the two compressors 1 are connected in parallel. At this time, the check valve 7a is prevented so that the high pressure refrigerant gas does not flow back to the low pressure side of the compressor.
, 7b act. The pressure of the refrigerant gas discharged by the parallel connection of the compressor 1 decreases, but the recovery capacity of the evaporated refrigerant gas doubles. Therefore, the ability to collect the refrigerant gas that has evaporated in the liquid refrigerant tank is improved, such as during demagnetization
Even when the heat load in the liquid refrigerant tank is large, it is possible to sufficiently prevent the internal pressure of the liquid refrigerant tank from rising. Moreover, since the processing capacity of the compressor has a margin, it becomes possible to fill the buffer tank 3 with the refrigerant gas from the solenoid valve 6b and at the same time to send the refrigerant gas to the refrigerator. Since the refrigerant gas pressure is lowered, the JT effect is lowered, but there is an advantage that the cold air possessed by the low-pressure refrigerant gas can be effectively used. When there is a large amount of evaporated refrigerant gas and there is not enough processing capacity even when the compressors are connected in parallel, the electromagnetic valve 6a may be closed to concentrate the recovery of the refrigerant gas. When the heat load returns to normal and liquefaction progresses and the refrigerant gas in the circulation circuit becomes insufficient, the refrigerant gas is replenished through the pressure adjusting valve 8 and reliquefied as in the conventional cryogenic refrigeration system. .

[0007]

As described above, according to the present invention, the refrigerating capacity can be improved by connecting the compressors of the cryogenic refrigeration system in series during the normal operation, and the circulation can be performed during the demagnetization of the superconducting magnet. Since the amount of refrigerant gas in the circuit increases, it is possible to prevent the rise of pressure and temperature in the liquid refrigerant tank by improving the recovery capacity of the evaporated refrigerant gas by connecting them in parallel while maintaining some refrigeration capacity. There is an effect that can be done. As a result, it becomes possible to operate the compressor optimally depending on the situation, and it is also possible to send the refrigerant gas to the refrigerator as much as there is room in the processing capacity of the evaporated refrigerant gas of the compressor. The cold air of the refrigerant gas can be effectively used.

[Brief description of drawings]

FIG. 1 is a schematic circuit diagram of a cryogenic refrigerator according to an embodiment of the present invention.

FIG. 2 is a schematic circuit diagram of a conventional cryogenic refrigerator.

[Explanation of symbols]

 1 Compressor 2 Refrigerator 3 Buffer tank 4 JT valve 5 Liquid refrigerant tank 6a, 6b, 6c, 6d, 6e Solenoid valve 7a, 7b Check valve 8 Pressure adjustment valve

Claims (1)

[Claims] 1. A cryogenic refrigerating apparatus using a JT valve, a plurality of compressors, a piping system connecting the compressors in series and a piping system connecting them in parallel, a solenoid valve provided in the piping, and a reverse valve. A cryogenic refrigeration system having a stop valve and having a structure capable of switching the compressor from series connection to parallel connection or from parallel connection to series connection by a solenoid valve and a check valve in the pipe.