JPH0689956B2 - Small He liquefaction refrigeration system - Google Patents

Description

TECHNICAL FIELD The present invention relates to a small He liquefaction refrigerating apparatus.

(Prior Art) Currently, cryogenic equipment including small superconducting magnets is cooled by precooling with liquid nitrogen (hereinafter LN ₂ ), discharging LN ₂ and replacing with He gas, and then liquid helium (hereinafter LHe). It is done by pre-cooling at and collecting LHe. After that, long-term cooling is performed by methods such as replenishment of LHe, cooling of the shield plate by a He refrigerator, and recondensation of evaporated He gas.

(Problems to be solved by the invention) Provided is a closed-cycle compact He liquefier refrigeration system capable of precooling, liquefaction, long-term cooling, and gas recovery without using external LN ₂ or LHe for cooling compact superconducting magnets. , It aims to save labor and improve operability by automating it so that even an amateur can easily operate it.

(Solution by the Invention) For supplying He to the liquefying refrigerator A and the refrigerator 21 for precooling
The compressor unit B connected to the He container 8 is connected in a closed circuit, and the He liquefaction refrigerator A has a plurality of stages of heat exchangers 12, 13, 14 for pre-expanding high pressure He and a refrigerator for pre-cooling. Pipes in thermal contact with 21 heat load flanges 10 and 11 and two JT valves 15
And a He liquefaction circuit having a gas pressure driven JT valve 15a and piping, and having a switchable three-way valve 16 and a low temperature valve 28
-T valve 15, three-way valve 16 and J-T circuit equipped with a condenser circuit consisting of a condenser pipe 27, gas pressure driven condensed He supply valve 24, pressure reducing valve 25, check valve 26, and precooling refrigerator 21 Heat load flange
A circuit that has a pipe in thermal contact with 10, 11 and that supplies He for condensation connected to the JT circuit, and flows through these circuits
A precooling refrigerator 21 for precooling He is further provided, and a liquid He container 18 for accommodating an object to be cooled is provided, and the gas pressure drive valves 15a, 16, 16a, 24 and He supply connected to an automatic control device are provided. In order to enable automatic operation by switching the valve 33 etc., the thermometer 29 and liquid for obtaining the operation control signal of the He liquefaction refrigeration system
A He liquid level gauge 30 was provided in the liquid He container.

(Example) The He liquefaction refrigeration system is a He liquefaction refrigerator A and the He liquefaction refrigerator A.
It is composed of a compressor unit B connected to the pipe lines 34, 35, 36. And with one device, pre-cooling of the cooled object, liquid He
The liquid storage, recondensation of evaporated He gas, condensed liquefaction of He gas, and recovery of liquefied He can be performed automatically.

Inside the He liquefier refrigerator A, a precooling refrigerator 21 having heat load flanges 10 and 11, a condenser circuit consisting of a JT valve 15, a three-way valve 16 and a condenser 27, and a JT valve 15 And three-way valve 16 and liquid He
A direct liquefaction circuit consisting of vessel 18 and cryovalve 28 is provided.

Further, in order to supply He gas for condensing and liquefying, the filter 19, the condensed He supply valve 24, the pressure reducing valve 25, the check valve 26 and the condensed He are
A supply system 23 is provided.

A storage tank 6 is provided in the compressor unit B, and the tank 6 is connected to a He container 8.

(Operation and automatic control) High-purity He is supplied to the high-pressure side and low-pressure side in the He gas system before operation.
It is sealed at a pressure of kg / cm ² G. When the operation switch of the control circuit (not shown) is turned on to enter the cooling mode, the condensed He supply valve 24 is closed, and the c-b direction of the three-way valve 16 and the low temperature valve 28.
And the three-way valve 16a opens in the b-a direction for switching operation, and at the same time, the first-stage compressor 1, the second-stage compressor 2 and the pre-cooling refrigerator.
21 starts.

The He compressed in the first-stage compressor 1 in the compressor unit B is further compressed in the second-stage compressor 2 to 20 kg / cm ² G, and passes through the oil separator 3 and the adsorber 4 to become clean He. Pipeline 34
And flow to the He liquefaction refrigerator A.

He flowing into the liquefying refrigerator A was cooled by the precooling refrigerator 21 and J-T.
Break into the circuit. The He flowing into the pre-cooling refrigerator 21 generates a low temperature, and the first stage heat load flange 10 and the second stage heat load flange 11
And is sucked into the two-stage compressor 2 in the compressor unit B via the pipe 35. On the other hand, He of JT circuit is filter 19,
It is cooled by the one-stage heat load flange 10 through the one-stage heat exchanger 12, passes through the two-stage heat exchanger 13, and is further cooled by the two-stage heat load flange 11, and is a three-stage heat exchanger 14 and a JT valve 15. Then, the superconducting coil 17 and the liquid helium container 18 are directly cooled by expanding the pressure to 0.2 kg / cm ² G or less.

This low-pressure He passes through the low-temperature valve 28, the pre-cooling circuit 31, the three-way valve 16a, and the one-stage heat exchanger 12, exchanges heat with the high-pressure inflow He to raise the temperature, and the pipeline 36 to the one-stage compressor 1 of the compressor unit B. Is inhaled through. When the thermometer 29 of the liquid He container 18 reaches 25K in this state, the three-way valve 16a is switched and the pre-cooling circuit 31 is closed, and the three-way valve 16a is opened in the ca direction. Therefore, by exchanging heat in the two-stage heat exchanger 13 and the three-stage heat exchanger 14, J-
The high-pressure He flowing into the T-valve 15 is further cooled, and becomes a lower-temperature He by the Joule-Thomson effect, further cooling the superconducting coil 17 and the liquid He container 18. Eventually, a part of He that has flowed out of the c-b direction of the three-way valve 16 is liquefied, and eventually liquid He is collected in the liquid He container 18 and the liquid surface rises. liquid
When the liquid He in the He container 18 reaches a certain height, the liquid level gauge 30 senses it, and the three-way valve 16 operates to switch to close the c-b direction.
The −a direction opens, and the low temperature valve 28 closes.

Thus, the He refrigerant (mixture of gas and mist) generated by the Joule-Thomson effect in the JT valve 15 flows in the condenser 27. As a result, the He vaporized in the liquid He container 18 is condensed in the condenser 27.
Is re-condensed to become a liquid, and the liquid He in the liquid He container 18 is kept constant.

On the other hand, in this state, the condensed He supply valve 24 is opened, and the pressure is adjusted by the pressure reducing valve 25 so that the pressure of the liquid He container 18 becomes higher than the pressure of the condenser 27 (0.1 to 0.3 kg / cm ² G). When He is supplied through the supply system 23, it is cooled by the first-stage heat load flange 10 and the second-stage heat load flange 11, and finally condensed by the condenser 27 and accumulated as liquid He.

The He required for the above cooling operation is supplied from the He container 8 connected to the compressor unit A through the pipe line 37.

When stopping the cooling operation, use the stop switch of the control circuit.
When turned on, the recovery mode is entered, the pre-cooling refrigerator 21 is stopped, the low temperature valve 28 is opened, the compressor unit B continues the recovery operation, and the vaporized He in the liquid He container 18 is recovered into the He container 8. After that, when the thermometer 29 reaches normal temperature, the compressor unit B is stopped and the state before the operation is restored. After that, the above operation is repeated.

The function of controlling the pressure of the compressor unit B is as follows.
When He exceeds 20 kg / cm ² G or more, the primary pressure regulator 5 operates and holds He in the storage tank 6, and when the suction pressure of the first-stage compressor 1 drops, the secondary pressure regulator 7 operates and the storage He in the tank 6 and the He container 8 is supplied. Further, when the pre-cooling refrigerator 21 is stopped, the differential pressure adjuster 9 operates, so that the high, medium and low pressures of the entire device are automatically adjusted.

Next, a control method of the apparatus shown in FIG. 1 will be described with reference to the second block diagram.

Operation; 1) When the operation switch of the control panel is turned on, the one-stage compressor 1, the two-stage compressor 2, and the refrigerator motor 32 are started, and at the same time, the three-way valve 16 is c-b and the three-way valve 166a is b-a. Open in the direction of. The supply valve 33 is also opened. Then from the compressor unit B
The He gas flows into the pre-cooling refrigerator 21 and the JT circuit of the He liquefying refrigerator A, and the pre-cooling operation of the liquid He container 18 is started. At this time, both J-T valves 15 and 15a are open. In addition, J-T
The valve 15 is normally open and is used as a fixed valve.

2) When the thermometer 29 indicates 25K or less, the JT valve 15a closes,
The flow rate of the JT valve is reduced, and the three-way valve 16a is opened in the ca direction to further cool the inside of the liquid He container 18.

3) When the thermometer 29 falls below 5K, the liquid level gauge 30 is turned on and operates. When the liquid level gauge 30 shows 100%, the LHe liquefaction is completed, so the three-way valve 16 is opened in the direction of ca, and the low temperature valve 28
Close. ... Recondensation and liquefaction state.

4) After that, liquid He is added by power lead and other operations.
When LHe in the container 18 is vaporized and released, the liquid level of LHe decreases. When the liquid level gauge 30 indicates 80% or less, the condensed He supply valve 24 is opened and He is supplied to be condensed and liquefied to increase the LHe liquid level. When the liquid level gauge 30 shows 100% again, the condensed He supply valve 24 is closed. The above operation is repeated.

5) When the cooling operation is completed, LHe in the liquid He container 18 is recovered to prepare for the next operation.

About collection; 6) When the collection switch is turned on to start the collection operation,
The refrigerator motor 32 stops, the low temperature valve 28 opens, and the supply valve
33 closes. LHe is vaporized and collected as He gas in the storage tank 6 of the compressor unit B or the He container 8.

7) When the thermometer 29 reaches 5K or higher, the power of the liquid level gauge 30 is turned off.
And protects the liquid level gauge 30. After that, when the thermometer 29 indicates 265K or higher, the first-stage and second-stage compressors 1 and 2 stop at the same time and the recovery operation ends (in the above description, the set temperature of the thermometer 29 was set to 265K, 25K, and 5K. , 265K, 25K can also be changed. The same applies to the setting of the liquid level gauge 30).

(Effect) It was made possible to automatically perform pre-cooling of the object to be cooled, storage of LHe, recondensation of evaporated He gas, condensation and liquefaction of He gas, and recovery of liquefied He with one device. Because it was done like this,
The operation of a small superconducting magnet does not require the complicated operation of first inserting LN ₂ to cool, then discharging the remaining N ₂ gas through He gas, and inserting LHe, and it can be easily operated even by an amateur. I can do it now.

[Brief description of drawings]

 FIG. 1 is a piping diagram of a small He liquefaction refrigeration system according to the present invention. FIG. 2 is a block diagram of the automatic control of the device. In the figure: 1 ... One-stage compressor, 2 ... Two-stage compressor, 3 ... Oil separator, 4 ... Adsorber, 5 ... Primary pressure regulator, 6 ... Storage tank, 7 ... Secondary pressure regulator , 8 …… He container 9 …… Differential pressure regulator 10 …… One-stage heat load flange 11 …… Two-stage heat load flange 12 …… One-stage heat exchanger, 13 …… Two-stage heat exchanger 14 …… Three-stage heat Exchanger, 15 …… JT valve (1) 15a …… (gas pressure drive) JT valve (2) 16 …… (gas pressure drive) 3-way valve (1) 16a …… (gas pressure drive) 3way Valve (2) 17 …… Superconducting coil, 18 …… Liquid He container 19 …… Filter, 20 …… Shield plate 21 …… Precooling refrigerator, 22 …… Vacuum insulation container 23 …… Condensed He supply system 24 …… (Gas pressure drive) Condensed He supply valve 25 …… Pressure reducing valve, 26 …… Check valve 27 …… Condenser 28 …… (Gas pressure drive) Low temperature valve 29 …… Thermometer, 30 …… Liquid level gauge 31… … Pre-cooling circuit, 32… For refrigerator Motor 33 …… (Gas pressure drive) Supply valve 34,35,36,37 …… Pipeline

Claims (1)

[Claims] 1. He liquefaction refrigerator (A) and precooling refrigerator (21)
And a compressor unit (B) connected to a He container (8) for supplying He to the above in a closed circuit, and the He liquefaction refrigerator (A) has a plurality of stages for free expansion of high pressure He. JT connected in parallel with the pipes that are in thermal contact with the heat load flanges (10, 11) of the heat exchanger (12, 13, 14) and the precooling refrigerator (21)
He liquefaction circuit having a valve (15), a gas pressure driven J-T valve (15a) and a pipe, and having a switchable gas pressure driven three-way valve (16) and a gas pressure driven low temperature valve (28); -T valve (1
5), a three-way valve (16), a JT circuit equipped with a condenser circuit consisting of a condenser pipe (27), and a gas pressure driven condensed He supply valve (2
4), pressure reducing valve (25), check valve (26), and precooling refrigerator (2)
A circuit that has piping that is in thermal contact with the heat load flanges (10, 11) in 1) and that supplies He for condensation that is connected to the JT circuit, and refrigeration for precooling that precools He that flows through these circuits. Machine (21), liquid He container (18) for storing the object to be cooled is provided, and automatic operation is possible by switching the gas pressure drive valve and He supply valve (33) connected to the automatic control device. Therefore, a small He liquefaction refrigeration apparatus, characterized in that a thermometer (29) and a liquid He level gauge (30) for obtaining an operation control signal of the He liquefaction refrigeration apparatus are provided in the liquid He container. .