JPH0648123B2 - Helium refrigeration equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to a helium refrigerating apparatus for obtaining a cryogenic temperature.

(Prior Art) In recent years, development of a helium refrigerating device for obtaining a cryogenic temperature has been underway, and for example, a cryogenic refrigerating device described in Japanese Patent Publication No. 58-21186 is proposed. That is, in a Joule-Thomson circuit (hereinafter referred to as a JT circuit), after cooling high-pressure helium gas discharged from one compressor with low-pressure helium gas returning to the compressor and a precooler provided separately, Thomson valve (hereinafter referred to as JT valve)
Then, the pressure is reduced to obtain cryogenic helium (gas-liquid mixed state), and the latent heat of vaporization of helium in the gas-liquid mixed state is used for cryogenic cooling.

(Problems to be Solved by the Invention) Generally, in a helium refrigeration system, immediately after the start of operation (J
The initial cooling process from the helium temperature after the -T valve ≈ 300 K) to the steady-state refrigeration operation (helium temperature before the J-T valve ≈ 5 K), that is, the helium weight circulation amount through the J-T valve during the so-called cooldown operation is Although it is almost the same at any temperature level, the volume circulation rate depends on the helium gas temperature before the JT valve because it depends on the change in the helium gas density. Therefore, the helium volume circulation amount at the start of operation is 60 to 100 times that at steady operation, and if the J-T valve opening is operated at 4.2K level at steady operation, J- due to over-throttlement, As a result of the large pressure loss at the T valve, J-
The T-return pressure is extremely reduced, becomes lower than the set pressure of the reduction switch, and the operation of the low-pressure switch causes the operation to be disabled.

Therefore, in the helium refrigerating apparatus having the configuration shown in the above-mentioned known example, the J-T valve is fully opened at the start of operation, and
-As the helium gas temperature in front of the T valve decreases, J
-It is necessary to frequently perform the operation of reducing the opening degree of the T valve. Therefore, there is a problem that a person has to drive for several hours during the cool-down driving.

The present invention has been made to solve the above-mentioned problems.
The purpose of the present invention is to maintain the opening of the valve at a steady operation level immediately after the start of operation so that the JT valve operation during the cool down operation becomes unnecessary.

(Means for Solving Problems) In the present invention, as means for solving the above problems,
As shown in FIG. 1, a gas ballast tank for adjusting the amount of helium gas flowing through the JT circuit 2 is provided with a JT circuit 2 and a precooling refrigeration circuit 1 for cooling the helium gas flowing through this circuit. In a helium refrigerating apparatus having a flow rate adjusting bypass circuit 39 having a flow control unit 37, a throttle mechanism 46 and a cooler of the refrigerating apparatus are provided between the high pressure refrigerant gas pipe 25 and the low pressure refrigerant gas pipe 26 in the JT circuit 2. A cool-down bypass circuit 45, which is connected in series with an on-off valve 47 that opens only during the down operation, is attached, and the opening of the J-T valve 21 during the cool down operation is reduced to a steady operation level. I am trying to be able to do it.

(Operation) In the present invention, during the cool-down operation, even if the operation is performed with the opening degree of the J-T valve 21 in the J-T circuit 2 reduced to the steady operation level, it is separate from the flow rate adjusting bypass circuit 39. Most of the circulating helium gas in the JT circuit 2 bypasses the bypass circuit 45 by opening the opening / closing valve 47 of the bypass circuit 45 formed in the JT valve 21.
The helium gas passing through becomes the remaining part, and an effect of preventing an extreme decrease in the JT return pressure can be obtained.

(Examples) Hereinafter, preferred examples of the present invention will be described with reference to the accompanying drawings.

This helium refrigeration system is composed of a pre-cooling refrigeration circuit 1 and a JT circuit 2.

The pre-cooling / refrigerating circuit 1 includes a pre-cooling compressor 3 for compressing pre-cooling helium gas, an oil separator 4, an adsorber 5, an expander 6 and a surge bottle 7, which will be described in detail later, in a refrigerant gas pipeline (that is, The high pressure refrigerant gas line 23 and the low pressure refrigerant gas line 24) are connected to each other. Here, the precooling compressor 3, the oil separator 4, the adsorber 5, and the surge bottle 7 form a precooling compressor unit A.

On the other hand, the JT circuit 2 includes a large capacity low-stage compressor 8, an oil separator 9, a small capacity high-stage compressor 10, an oil separator 11, an adsorber 12, and a first Joule-Thomson heat exchanger ( Below, J-
(T heat exchanger) 13, adsorber 14, first precooler 1
5, second J-T heat exchanger 16, adsorber 17, second precooler 18, third J-T heat exchanger 19, adsorber 20, J-T valve 21, cooler 22, the third, second And the first J-T heat exchangers 19, 16 and 13 are sequentially connected to the refrigerant gas pipe (that is,
The high pressure refrigerant gas pipe 25 and the low pressure refrigerant gas pipe 26) are connected to each other. Here, the low-stage and high-stage compressors 8 and 10, the oil separators 9 and 11, the adsorber 12, and the gas ballast tank 37 described below are the JT side compressor unit B.
Are configured.

The pre-cooling compressor 3, low-stage and high-stage compressors 8 and 1
0 is provided with cooling water coils 27, 28 and 29, respectively.
According to the respective discharge gas coils 30, 31, 32
And the oil coils 33, 34, 35 for injection can be cooled.

The oil separated by the oil separators 4, 9 and 11 is injected into the suction sides of the compressors 3, 8 and 10, respectively.

Each of the adsorbers 5, 12, 14, 17, 20 has a function of removing impurities in the helium gas in each state.

The surge bottle 7 has the function of reducing the pulsation of the low-pressure helium gas returned to the pre-cooling compressor 3.

In the JT circuit 2, a high pressure control valve 36, a gas ballast tank 37 and an intermediate pressure control valve are provided between the high pressure refrigerant gas pipe 25 on the outlet side of the adsorber 12 and the suction side of the high pressure compressor 10. A bypass circuit 39 provided with 38 is interposed. The gas ballast tank 37 includes a high pressure control valve 36.
Alternatively, it has an action of adjusting the amount of helium gas circulating in the JT circuit 2 by controlling the opening and closing of the intermediate pressure control valve 38.

The expander 6, the JT heat exchangers 13, 16, 19, the precoolers 15, 18, the JT valve 21, and the cooler 22 are housed in a vacuum container 40 maintained at a high degree of vacuum, and The second and third J-T heat exchangers 16 and 19, the second precooler 18,
The J-T valve 21 and the cooler 22 are surrounded by the wide radiation shield 41 to form a cryostat C. Reference numeral 42 is a thermometer that detects the temperature of the cooler 22. The expander 6 has a high-pressure side inlet 61 connected to the discharge side of the pre-cooling compressor 3 and a low-pressure side outlet 62 connected to the suction side of the pre-cooling compressor 3, and is cooled in the expansion stroke of the high-pressure helium gas inside the expander 6. The helium gas flowing through the JT circuit 2 is precooled in the first and second precoolers 15 and 18 provided on the outer circumferences of the first and second heat stations 70 and 71. .

As a feature of the present invention, in the first embodiment shown in FIG. 1, the high pressure refrigerant gas pipe 25 (specifically, the outlet side of the adsorber 12) and the low pressure refrigerant in the JT side compressor unit B are provided. A bypass circuit 45 including a capillary tube 46 acting as a throttle mechanism and an electromagnetic valve 47 acting as an opening / closing valve in series between the gas pipe 26 (specifically, the suction side of the low-stage compressor 8). Is attached. The solenoid valve 47 is opened only during the cool down operation and closed at the end of the cool down.

Next, the operation of the helium refrigeration system of the first embodiment will be described.

First, the operation during the cool down operation from the start of operation to the steady operation will be described.

Simultaneously with the start of operation, the solenoid valve 47 of the bypass circuit 45 is opened. Then, since the opening of the J-T valve 21 is restricted to the opening of the steady operation level (that is, 4.2K level), most of the helium gas discharged from the high stage compressor 10 at the start of operation is held. Passes through the bypass circuit 45 and the low-stage compressor 8
The helium gas that has been sucked into the JT valve 21 and becomes the remaining part. Therefore, the J-T circuit return pressure (ie,
The suction pressure of the low-stage compressor 8 does not drop extremely, and the operation can be continued.

During the cool-down operation, the high-pressure helium gas discharged from the high-stage compressor 10 has the first and second precoolers 15 and 1 attached to the heat stations 70 and 71 of the expander 6, respectively.
The temperature of the helium gas in front of the J-T heat exchangers 13, 16 and 19 and the J-T valve 21 is gradually lowered. As the helium gas temperature decreases, the density of the helium gas naturally increases, the amount of helium gas passing through the JT valve 21 gradually increases, and conversely the amount of bypassing through the bypass circuit 45 decreases. When the helium temperature after the J-T valve 21 approaches the steady operation level of 4.2K, the solenoid valve 47 of the bypass circuit 45 is closed. Then, the total amount of helium gas discharged from the high-stage compressor 10 is reduced to the JT valve 2
A helium liquefaction temperature of 4.2 K is obtained through 1.

During the cool-down operation, the amount of high-temperature helium gas that passes through the J-T valve 21 is suppressed. Therefore, the amount of liquid helium vaporized when used as a device for recondensing helium by the cooler 22 Can be reduced.

Next, when the steady operation state is reached, the low-stage compressor 8 is started, the JT circuit return helium gas from the cryostat C is sucked and compressed by the low-stage compressor 8, and the cooling water coil 28 cools the helium gas. After cooling to room temperature of 300 K and separating oil by the oil separator 9, the high-stage compressor 10 sucks and compresses.
After that, the cooling water coil 29 cools the room temperature to 300K.
To the adsorber 12 after the oil is separated by the oil separator 11
Then, impurities are adsorbed and clean high-pressure helium gas is supplied to the cryostat C.

The high-pressure helium gas supplied to the cryostat C side enters the primary side of the first J-T heat exchanger 13 and exchanges heat with the low-pressure helium gas on the secondary side returning to the J-T side compressor unit B, from room temperature 300K. Expander 6 cooled to about 70K
Enters the first precooler 15 provided on the outer periphery of the first heat station 70 (50 to 60K), is cooled to about 55K by the expander 6, enters the primary side of the second J-T heat exchanger 16, and J The second pre-cooling provided to the outer periphery of the second heat station 71 (15 to 20K) of the expander 6 by exchanging heat with the low pressure helium gas on the secondary side returning to the -T side compressor unit B to cool to about 20K. It enters the vessel 18 and is cooled to about 15K by the expander 6, and further the third J-T heat exchanger 1
9 enters the primary side, returns to the JT side compressor unit B, and exchanges heat with the low pressure helium gas on the secondary side to be cooled to about 5K, and reaches the JT valve 21. During the above process,
At the outlet side of each J-T heat exchanger 13, 16, 19 adsorbers 14, 17, 20 adsorb impure gases such as nitrogen, oxygen, and hydrogen at a low temperature to produce cleaner helium gas.
The -T valve 21 and the precoolers 15 and 18 are prevented from being clogged.

Then, the high-pressure helium gas is throttled by the J-T valve 21, expanded by Joule-Thomson, and becomes helium in a gas-liquid mixed state of 1 atm and 4.2 K and is supplied to the cooler 22. In the cooler 22, the latent heat of vaporization of the liquid portion of helium is used for liquefying or recondensing another helium gas or for cooling the cooled object.

As a result, the low-pressure helium gas returning from the cooler 22 to the secondary side of the third JT heat exchanger 19 becomes a saturated gas of about 4.2K. And this low pressure helium gas is
In the JT heat exchangers 16 and 13, the high-pressure helium gas on the primary side is cooled, the temperature rises to about 300K, and the JT side compressor unit B is returned to. After that, the same cycle is repeated and the freezing operation is performed.

FIG. 2 shows a second embodiment of the present invention, in which the bypass circuit 45 connects the high-pressure side outlet and the low-pressure side inlet of the first J-T heat exchanger 13 on the cryostat C side. It is attached in between.

Since the operation of this embodiment is the same as that of the first embodiment, its explanation is omitted.

In each of the above-described embodiments, the timing for closing the solenoid valve 47 is selected by detecting the decrease in the helium temperature or the high pressure after the JT valve 21, which indicates that the cooldown has ended.

(Effects of the Invention) As described above, according to the present invention, during the cool down operation, the bypass circuit 39 for adjusting the flow rate is provided between the high pressure refrigerant gas pipe 25 and the low pressure refrigerant gas pipe 26 of the JT circuit 2. By opening the opening / closing valve 47 of the bypass circuit 45 provided separately from the above, most of the high pressure helium gas in the JT circuit 2 is bypassed to the low pressure side through the bypass circuit 45, and at the same time as the end of the cool down, Since the on-off valve 47 is closed to perform the steady operation, there is an excellent effect that the cool-down automatic operation can be performed without operating the opening degree of the JT valve 21.

Also, when using this helium refrigeration system as a recondenser for liquid helium, the JT valve 21 should be operated during the cool-down operation.
Since the amount of helium gas having a high temperature passing therethrough is suppressed, there is also an effect that the evaporation amount of liquid helium can be decreased.

[Brief description of drawings]

FIG. 1 is a system diagram of a helium refrigeration system according to a first embodiment of the present invention, and FIG. 2 is a main part system diagram of a helium refrigeration system according to a second embodiment of the present invention. 1 ... Pre-cooling refrigeration circuit 2 ... Joule-Thomson circuit 13 ... 1st Joule-Thomson heat exchanger 21 ... Joule-Thomson valve 25 ... High-pressure refrigerant gas pipe 26 ... Low-pressure refrigerant gas pipe 45 ... Bypass circuit 46 ... Throttle mechanism 47 …… Open / close valve B …… JT side compressor unit C …… Cryostat

Front page continued (72) Inventor Kazuo Miura 1304 Kanaoka-machi, Sakai City, Osaka Prefecture Daikin Industries, Ltd. Sakai Plant Kanaoka Factory (72) Satoshi Noguchi 1304, Kanaoka-machi, Sakai City, Osaka Prefecture Daikin Industry Co., Ltd. Kanaoka In the factory (56) References JP-A-60-26257 (JP, A)

Claims (3)

[Claims] 1. A gas for adjusting the amount of helium gas flowing through the Joule-Thomson circuit (2), comprising a Joule-Thomson circuit (2) and a pre-cooling refrigeration circuit (1) for cooling the helium gas flowing through the circuit. In a helium refrigeration system provided with a flow rate adjusting bypass circuit (39) having a ballast tank (37), a high pressure refrigerant gas pipe (25) and a low pressure refrigerant gas pipe (26) in the Joule-Thomson circuit (2) A cool-down bypass circuit (45) consisting of a throttle mechanism (46) and an on-off valve (47) that opens only during the cool-down operation of the refrigeration system is connected in series between the cooler and A helium refrigeration system characterized in that the opening of the Joule-Thomson valve (21) during operation can be kept at a steady operation level. 2. The cool-down bypass circuit (45),
The helium refrigeration system according to claim 1, which is attached between the high pressure refrigerant gas pipe (25) and the low pressure refrigerant gas pipe (26) in the compressor unit (B) on the side of the Joule-Thomson circuit. 3. The bypass circuit for cool down (45),
The helium refrigeration system according to claim 1, which is attached between the high-pressure side outlet and the low-pressure side inlet of the first Joule-Thomson heat exchanger (13) in the cryostat (C).