JPH04335959A - Cryogenic refrigerating machine - Google Patents

Abstract

PURPOSE:To make the refrigerating capacity per unit circulation quantity at a third heat stage fully effective by adjustment corresponding to the temperature at a second heat stage. CONSTITUTION:In a cryogenic refrigerating machine which is equipped with a compression unit 200 having Joule-Thomson heat exchangers 1,2,3 on a Joule-Thomson side, with a precooler 10 having a first heat stage 11 and a second heat stage 12, with a Joule-Thomson valve 6, and with a third (final) heat stage 13, there are provided a high-pressure control valve 208 and a temperature detector 7, the high-pressure control valve 208 being designed to control the highpressure-side pressure in said Joule-Thomson-side compression unit 200 and the temperature detector 7 being designed to detect the temperature at said second heat stage 12 and output the result. In a system with this setup, a pressure regulator 8 for controlling said high-pressure control valve 208 is provided and the value of the high-pressure-side pressure that brings the refrigerating capacity to the peak is stored in memory for a given temperature at said second heat stage 12 so that, on the basis of the temperature detected by said temperature detector 7, the high-pressure-side pressure in the compression unit 200 is controlled in such a manner as to bring it to the value preliminarily set as a target and stored 10 memory as above. Thus a maximum can be achieved in the refrigerating capacity per unit circulation quantity at the third heat stage 13.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cryogenic refrigerator that obtains cryogenic temperatures at an absolute temperature of 4K level.

0002

[Prior Art] Conventionally, this type of cryogenic refrigerator was
This is already known as disclosed in Japanese Patent No.-235650. As shown in Fig. 3, this conventional cryogenic refrigerator has Joule-Thomson heat exchangers A, B, and C connected in three stages inside a vacuum container D, and two Joule-Thomson heat exchangers connected in the preceding stages. A precooler E having a first heat stage A Joule-Thompson valve V and a final third heat stage Z are respectively provided, and the high-pressure inlet side and low-pressure outlet side of the pre-stage heat exchanger A are connected to the Joule-Thompson side compressor. In addition, the precooler E is connected to the precooling side compression unit G, and by operating these compression units F and G together, a low temperature of 40 to 50K is obtained in the first heat stage X, and the second heat stage Obtain a low temperature of 12-20K on stage Y,
Furthermore, the third heat stage Z has a cryogenic temperature of 4K level,
It is used to cool superconducting magnets, etc. Although not disclosed in the above-mentioned Japanese Patent Application Laid-open No. 61-235650, the high-pressure gas pipe of the compression unit F is provided with a high-pressure control system that controls the high pressure on the high-pressure side of the pre-stage heat exchanger A in two stages. During cool-down operation, the high-pressure control valve is switched to the fully closed side to maximize the high-pressure pressure, and during steady operation, the high-pressure control valve is switched to the constant opening side to control the high-pressure side of the pre-stage heat exchanger A. The high pressure is always controlled to be a constant pressure.

0003

However, with the above configuration, the high pressure on the high pressure side of the Joule-Thompson side compression unit during steady operation is high pressure regardless of the temperature at each of the heat stages X, Y, and Z. Since the pressure is always controlled to be constant by the control valve, there is a problem in that the refrigerating capacity per unit circulation amount in the third heat stage Z cannot be sufficiently exhibited. That is, since the high pressure is controlled to a constant pressure as described above, if the temperature of the second heat stage Y changes as shown in Figure 2, the heat exchange efficiency in the final stage Joule-Thompson heat exchanger C will deteriorate. Become,
This results in the third heat stage Z not being able to fully demonstrate its refrigerating capacity per unit circulation amount.

The present invention focuses on the fact that when the high pressure is controlled to a constant pressure, the refrigerating capacity per unit circulation amount in the third heat stage depends on the temperature of the second heat stage Y. By finding the high pressure at which the refrigeration capacity peaks in accordance with the temperature of the second heat stage, and by controlling this high pressure, it is possible to improve the heat exchange efficiency in the final stage Joule-Thompson heat exchanger, and to fully utilize the refrigeration capacity. It was invented with a focus on the following:
The purpose is to make it possible to fully utilize the refrigerating capacity in the third heat stage, and another purpose is to improve the refrigerating capacity by controlling the high pressure during steady operation, while at the time of cool-down, the cool-down time is The point is that it can be shortened.

[0005]

[Means for Solving the Problems] Therefore, in order to achieve the above object, the present invention provides Joule-Thomson heat exchangers 1, 2, and 3 connected in multiple stages, and a Joule-Thomson heat exchanger 1 on the previous stage side. , a precooler 10 having a first heat stage 11 and a second heat stage 12 for precooling the refrigerant flowing out from the high pressure outlet side of 2, and the high pressure outlet side and the low pressure inlet side of the final stage Joule-Thompson heat exchanger 3. In a cryogenic refrigerator equipped with a Joule-Thompson valve 6 and a final third heat stage 13 connected between them, a high pressure control valve 208 is provided to control the high pressure on the high pressure inlet side of the first stage heat exchanger 1. In addition, the second heat stage 12
A temperature detector 7 is provided to detect and output the temperature of
A high pressure at which the refrigerating capacity reaches a peak with respect to the temperature in the second heat stage 12 is memorized, and the high pressure control valve 2 is operated based on the temperature detected by the temperature detector 7.
08 and operates the high pressure control valve 208 to control the high pressure to a previously stored target high pressure.

The pressure regulator 8 is also provided with a cool-down control means 9 that stops the output to the high-pressure control valve 208 during the cool-down operation until the temperature in the second heat stage 12 reaches the target temperature. is preferable.

[0007]

[Operation] The temperature of the second heat stage 12 is constantly detected by the temperature detector 7, and the detected value is output to the pressure regulator 8. Since the high pressure at which the refrigerating capacity reaches its peak is stored in advance, the high pressure control valve 2 is controlled by the pressure regulator 8 based on the temperature detected by the temperature detector 7.
08, a command signal is output, the high pressure control valve 208 is operated, and the high pressure becomes the pre-stored target high pressure,
That is, the temperature at the second heat stage 12 is
The refrigerating capacity of the heat stage 13 is controlled to a high pressure at which it reaches its peak, and therefore the third heat stage 1
The refrigeration capacity in 3 can be fully demonstrated.

Further, the pressure regulator 8 is provided with a high pressure control valve 2 until the temperature at the second heat stage 12 reaches the target temperature.
By providing a cool-down control means 9 that stops output to 08, during cool-down operation, the high pressure is increased and the gas circulation amount is increased, regardless of the temperature in the second heat stage 12, to achieve rapid cooling. Since it is possible to down, the high pressure can be controlled during steady operation, and the cool-down time can be shortened while improving the refrigerating capacity as described above.

[0009]

[Embodiment] The cryogenic refrigerator shown in FIG. 1 includes a cryostat 100 in which first to third Joule-Thompson heat exchangers 1, 2, and 3 are built in a stainless steel vacuum container 20 that supports a precooler 10. A Joule-Thomson side compression unit 200 comprising low-stage and high-stage compressors 201 and 202, compressing helium gas and supplying it to each of the Joule-Thomson heat exchangers 1, 2, and 3, and a pre-cooling compressor 301. , a pre-cooling side compression unit 300 that compresses helium gas for pre-cooling and supplies it to the pre-cooling machine 10.

[0010] Each of the Joule-Thompson heat exchangers 1 and 2
, 3 are connected in multiple stages via first and second high-pressure connecting pipes 30 and 31 and first and second low-pressure connecting pipes 32 and 33, and the first Joule-Thompson heat exchanger in the previous stage The high-pressure inlet of the first Joule-Thompson heat exchanger 1 and the discharge port of the high-stage compressor 202 are connected by a high-pressure gas pipe 203, and the low-pressure outlet of the first Joule-Thompson heat exchanger 1 is connected to the discharge port of the high-stage compressor 202.
01 is connected through a low pressure gas pipe 204. In addition, first and second coolers 4 and 5 are provided in the middle of the first and second high-pressure connecting pipes 30 and 31, and a third cooler in the latter stage is provided.
A Joule-Thomson valve 6 and an absorber 35 for removing impurities from the helium gas flowing into the Joule-Thomson valve 6 are provided between the high-pressure outlet and the low-pressure inlet of the Joule-Thomson heat exchanger 3.

[0011] The precooler 10 also includes a first cooling unit on the front stage side.
The refrigerant flowing out from the high pressure outlet side of the second Joule-Thompson heat exchangers 1 and 2 is transferred to the first and second coolers 4 and 5.
A third heat stage 13 is provided on the outlet side of the Joule-Thompson valve 6 in the communication pipe 34.

The Joule-Thomson side compression unit 200 also includes the low-stage compressor 201 with a large capacity for compressing helium gas into 1 to 5 atoms, and the low-stage compressor 201.
The high-stage compressor 202 has a small capacity and compresses helium gas compressed into 6 to 19 atoms, and the high-stage compressor 20
The high-pressure gas pipe 203 is equipped with an oil separator 205 and an adsorber 206 installed in the high-pressure gas pipe 203 of No. 2, and discharges high-pressure helium gas from the high-stage compressor 202 to the high-pressure gas pipe 203 to remove the heat on the cryostat 100 side. In addition to supplying the helium gas to the exchangers 1, 2, and 3, low-pressure helium gas is returned to the low-stage compressor 201 from the low-pressure gas pipe 204. Further, the high pressure gas pipe 203 is provided with a branch pipe 207 communicating with the discharge side line of the low stage compression 201, and the branch pipe 207 is connected to the high pressure on the high pressure side of the first Joule-Thompson heat exchanger 1. A high pressure control valve 208 for controlling pressure, a gas replenishment ballast tank 209 for replenishing gas to the discharge line of the low stage compressor 201, and an intermediate pressure control valve 210 are interposed.

The precooling side compression unit 300 also connects the precooling compressor 301 and the precooler 10 via a high pressure gas pipe 302 and a low pressure gas pipe 303, and connects the high pressure gas pipe 302 to an oil separation A surge bottle 306 is provided in the low pressure gas pipe 303, high pressure helium gas is supplied from the precooling compressor 301 to the precooler 10, and the low pressure helium gas after being expanded in the precooler 10 is provided. is returned to the pre-cooling compressor 301.

In each compression unit 200, 300, reference numerals 211, 307 are cooling water coils, and the cooling water coil 211 cools the discharge gas coils 212, 213 and the injection oil coils 214, 215.
In addition, the cooling water coil 307 causes the discharge gas coil 308 to
And the injection oil coil 309 is cooled.

[0015] Thus, the compression units 200, 30
0, the high pressure gas pipe 203 is connected to the first to
The high-pressure helium gas flowing into the third Joule-Thomson heat exchangers 1, 2, and 3 is cooled by the low-pressure helium gas on each return side of each heat exchanger 1, 2, and 3, and
from the high pressure outlet of the first Joule-Thompson heat exchanger 1 to the first
The high-pressure helium gas flowing out into the cooler 4 is cooled to a temperature of 40 to 50 K by the first heat stage 11, and the high-pressure helium gas flowing out into the second cooler 5 from the high-pressure outlet of the second Joule-Thompson heat exchanger 2 The helium gas is cooled to a temperature of 12 to 18 K by the second heat stage 12, and the high-pressure helium gas flowing out from the high-pressure outlet of the third Joule-Thomson heat exchanger 3 is expanded by the Joule-Thomson valve 6, and then It is cooled to an extremely low temperature of 4.2K by the third heat stage 3.

In the embodiment shown in FIG. 1, the refrigerator configured as described above is provided with a temperature detector 7 for detecting the temperature of the second heat stage 12, and the high pressure control valve 208 is While the high pressure can be adjusted by controlling the opening, a valve opening signal is output to the high pressure control valve 208 based on the temperature detected by the temperature detector 7, and the high pressure is adjusted to a predetermined level. A pressure regulator 8 is provided to control the pressure.

That is, the refrigerating capacity QP per unit circulation amount G in the third heat stage 13 is as shown in FIG.
The lower the temperature of the heat stage 12, the higher the temperature can be.However, at the same temperature, the heat exchange efficiency of the third Joule-Thomson heat exchanger 3 depends on the high pressure in the Joule-Thomson side compression unit 200, and the predetermined high pressure The refrigerating capacity per unit circulation amount reaches its peak at the pressure. In other words, the high pressure at which the refrigerating capacity per unit circulation amount in the third heat stage 13 is maximum is:
This will largely depend on the temperature of the second heat stage 12. Note that the value indicated by point M in FIG. 2 is the peak value, and even if the high pressure at that time is further increased, the refrigerating capacity will decrease without increasing any further.

Therefore, the high pressure at which the refrigerating capacity is maximized with respect to the temperature in the second heat stage 12 is determined, and this value is stored in the memory section provided in the pressure regulator 8, and The high pressure value stored in advance is read out based on the temperature detected by the high pressure control valve 208, and a valve opening signal corresponding to this pressure is output to the high pressure control valve 208, so that the high pressure pressure is stored in advance. The high pressure of the Joule-Thompson side compression unit 200 is adjusted to a pre-stored target high pressure.

In the embodiment shown in FIG. 1, the high pressure control valve 208 is provided with a pressure detector 36, and the output side of the pressure detector 36 is connected to the input side of the pressure regulator 8 to provide feedback. A circuit is formed to improve the accuracy of adjusting the high pressure by the pressure regulator 8.

The pressure detector 36 may be provided in the branch pipe 207 instead of being provided in the high pressure gas pipe 203.

[0021]Also, the adjustment of the high pressure by the pressure regulator 8 is preferably controlled linearly with respect to the temperature change of the second heat stage 12. The adjustment of the high pressure may be controlled in stages. In this case, it is preferable to use a differential of, for example, plus or minus 0.5K.

Furthermore, although the valve opening degree control of the high pressure control valve 208 by the pressure regulator 8 may be carried out all the time from the start of operation to the end of operation of the refrigerator, the second If the temperature of the heat stage 12 is high, even if the high pressure of the Joule-Thompson side compression unit 200 is controlled, the refrigerating capacity of the third heat stage 13 cannot be expected to improve, and on the contrary, the cool-down time will become longer. , the pressure regulator 8 is configured to stop the output from the pressure regulator 8 to the high pressure control valve 208 during a cool-down operation, that is, during a cool-down operation until the temperature of the second heat stage 12 reaches, for example, 18K. Preferably, a cool-down control means 9 is provided. By doing this, during cool-down operation, the second heat stage 1
Regardless of the temperature of the compressor 2, the high pressure increases, the amount of helium gas circulated in the Joule-Thompson compression unit 200 increases, and the cool-down time is shortened.

The present invention is constructed as described above, and when the refrigerator starts operating, during cool-down operation until the temperature at the second heat stage 12 reaches, for example, 18K,
The cool-down control means 9 of the pressure regulator 8 outputs a command signal to stop the output from the pressure regulator 8 to the high pressure control valve 208, so the high pressure control valve 208 is fully closed.
Since the entire amount of high-pressure helium gas discharged from the high-stage compressor 202 to the high-pressure gas pipe 203 is supplied to each Joule-Thompson heat exchanger 1, 2, and 3, cooling can be performed quickly. It can save time.

After the temperature of the second heat stage 12 falls below 18 K by this cool-down operation, the temperature of the second heat stage 12 is determined based on the temperature of the second heat stage 12 detected by the temperature detector 7. A command signal is output from the pressure regulator 8 to the high pressure control valve 208, and the valve opening degree of the high pressure control valve 208 is controlled, so that the high pressure in the high pressure gas pipe 203 corresponds to the temperature of the second heat stage 12. It linearly adjusts to the target high pressure.

[0025] Therefore, when the high pressure in the high pressure gas pipe 203 is lower than the target high pressure stored in advance in the pressure regulator 8 for a certain temperature in the second heat stage 12, the pressure regulator 8 to high pressure control valve 208
The high-pressure control valve 208 is controlled to reduce its valve opening by the command signal output to The pressure is controlled to the memorized target high pressure. Therefore, during steady operation, the temperature of the third heat stage 13 is always higher than that of the second heat stage 12.
Since the refrigerating capacity can be controlled to a high pressure that reaches its peak,
The temperature at the second heat stage 12 is, for example, 18 to 1
Even if the temperature varies within the range of 2K, the heat exchange efficiency in the third Joule-Thompson heat exchanger 3 can be improved, and the third heat stage 13 can always fully demonstrate its refrigerating capacity.

In the embodiment described above, the refrigerator is equipped with two Joule-Thompson heat exchangers 1 and 2 on the front stage side, but the Joule-Thompson heat exchangers 1 and 2 on the front stage side are equipped with three Joule-Thompson heat exchangers 1 and 2. It may be more than one.

Further, the temperature detector 7 may be attached to the second heat stage 12 instead of being attached to the second cooler 5 as shown in FIG.

[0028]

Effects of the Invention As described above, the present invention has the following advantages: Joule-Thompson heat exchangers 1, 2, 3 connected in multiple stages The first heat stage 11 and the second heat stage 11 pre-cool the
A precooler 10 having a heat stage 12, a Joule-Thompson valve 6 connected between the high-pressure outlet side and the low-pressure inlet side of the final stage Joule-Thompson heat exchanger 3, and a final third Joule-Thompson heat exchanger 3.
In a cryogenic refrigerator equipped with a heat stage 13,
A high pressure control valve 208 is provided to control the high pressure on the high pressure inlet side of the pre-stage heat exchanger 1, and a temperature detector 7 detects and outputs the temperature of the second heat stage 12.
while storing the high pressure at which the refrigerating capacity peaks with respect to the temperature in the second heat stage 12, and outputting it to the high pressure control valve 208 based on the temperature detected by the temperature detector 7, Since the pressure regulator 8 is provided to control the high pressure to a pre-stored target high pressure by operating the high pressure control valve 208, the high pressure on the Joule-Thomson side can be circulated in unit cycles with respect to the temperature of the second heat stage 12. Since the refrigerating capacity per volume can be controlled to a high pressure that peaks, even if the temperature of the second heat stage 12 fluctuates, the heat exchange efficiency in the third Joule-Thompson heat exchanger 3 can be improved, and the third The heat stage 13 can always fully demonstrate its refrigerating capacity.

Furthermore, by providing the pressure regulator 8 with a cool-down control means 9 that stops the output to the high-pressure control valve 208 during the cool-down operation until the temperature in the second heat stage 12 reaches the target temperature. Regardless of the temperature at the second heat stage 12, the high pressure can be raised to a high range to increase the amount of gas circulation and allow rapid cooldown, so the high pressure can be controlled during steady operation, and the high pressure can be controlled as described above. Not only can it improve the freezing ability, but it can also shorten the cooldown time.

[Brief explanation of drawings]

FIG. 1 is a piping system diagram showing an embodiment of the refrigerator of the present invention.

FIG. 2 is a characteristic diagram showing the relationship between the refrigerating capacity per unit circulation amount in the third heat stage and the high pressure in the Joule-Thompson side compression unit.

FIG. 3 is a piping system diagram of a conventional refrigerator.

[Explanation of symbols]

1, 2, 3 Joule-Thomson heat exchanger 6
joule thomson valve 7
Temperature detector 8 Pressure regulator 9 Cool down control means 10
Precooler 11 First heat stage 12
2nd heat stage 13 3rd
Heat stage 208 High pressure control valve

Claims (2)

[Claims] [Claim 1] Joule-Thomson heat exchangers 1, 2, and 3 connected in multiple stages, and a first refrigerant that precools refrigerant flowing out from the high-pressure outlet side of the Joule-Thomson heat exchangers 1 and 2 on the previous stage side.
A precooler 10 having a heat stage 11 and a second heat stage 12, and a Joule-Thomson heat exchanger 3 connected between the high-pressure outlet side and the low-pressure inlet side of the final stage Joule-Thomson heat exchanger 3.
In a cryogenic refrigerator equipped with a Thomson valve 6 and a final third heat stage 13, a high pressure control valve 208 is provided to control the high pressure on the high pressure inlet side of the first stage heat exchanger 1, and the second heat stage A temperature detector 7 is provided that detects and outputs the temperature of 12, and also stores a high pressure at which the refrigerating capacity reaches a peak with respect to the temperature in the second heat stage 12, and also stores the temperature detected by the temperature detector 7. Cryogenic refrigeration characterized by being provided with a pressure regulator 8 which outputs an output to the high pressure control valve 208 based on the above, and operates the high pressure control valve 208 to control the high pressure to a pre-stored target high pressure. Machine. [Claim 2] During the cool-down operation, the pressure regulator 8 operates until the temperature at the second heat stage 12 reaches the target temperature.
The cryogenic refrigerator according to claim 1, further comprising a cool-down control means (9) for stopping the output to the high-pressure control valve (208).