JPS5821186B2 - cryogenic freezing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in cryogenic refrigeration equipment, such as helium refrigeration equipment.

An example of a cryogenic helium refrigeration system that has been commonly used in the past will be explained based on Fig. 1.
Reference numeral 2 indicates a vacuum tank that maintains the interior at a high degree of vacuum, and 2 indicates a liquid helium tank housed within the vacuum tank. Inside the liquid helium tank 2, objects to be cooled such as superconducting coils are housed.

4 is a Joule-Thomson circuit (hereinafter referred to as JT circuit) that cools the liquid helium tank 2, 4a is a gas compressor, and 4b is a
y 4c and 4d are each a countercurrent type first heat exchanger,
The second heat exchanger and the Joule-Thomson heat exchanger (hereinafter referred to as
4e and 4f are the first and second coolers, 4g is a Joule-Doomson expansion valve (hereinafter referred to as JT expansion well), and 4h is a low pressure gas holder.

Further, 41 indicates each heat exchanger 4 from the discharge side of the gas compressor 4a.
4j is a high-pressure refrigerant gas pipe that runs from the JT expansion valve 4g to the secondary side of the liquid helium tank 2 and each of the heat exchangers 4d to 4b through the primary sides of 4b to 4d. This is a low-pressure refrigerant gas pipe line that extends through the gas compressor 4a to the suction side of the gas compressor 4a.

5 is a bypass valve for pre-cooling to reduce the pressure of the low-temperature high-pressure refrigerant gas cooled by the first cooler 4e during initial cooling and lead it to the ram tank 2; via J
A first pre-cooling refrigerator is used to cool the high-pressure refrigerant gas in the T circuit to approximately 70°K, and 7 is a second pre-cooling refrigerator that similarly cools the high-pressure refrigerant gas to approximately 15°K via the second cooler 4f. There is a pre-cooling refrigerator.

Further, 8 is a liquid helium transfer pipe for transferring liquid helium from an external liquid helium container (not shown) to the liquid helium tank 2, and 8a is a stop valve that closes the tip of the transfer pipe.

In the conventional helium refrigeration system described above, when the body 3 to be cooled is cooled to the liquid helium temperature and a steady refrigeration operation is performed, the high-pressure refrigerant gas is supplied from the gas compressor 4a through the high-pressure refrigerant gas pipe 41. High-pressure refrigerant gas is supplied to each heat exchanger 4
As it flows through the primary side of gases b to 4d, it is pre-cooled to an extremely low temperature by coolers, 4e and 4f, and isenthalpically expanded to almost atmospheric pressure in JT expansion valve 4g, liquefying a part of the gas and turning it into a liquid. It is supplied to the helium tank 2.

The object to be cooled 3 housed in the liquid helium tank 2 is cooled and maintained at a constant temperature by the latent heat of vaporization of the liquid helium.

When the refrigerating capacity of the JT circuit 4 and the refrigerating load of the object to be cooled 3 are in balance, the same amount of low-temperature, low-pressure refrigerant gas as the high-pressure refrigerant gas supplied from the gas compressor 4a is supplied from the liquid helium tank 2. Each heat exchanger 4d to 4 passes through a low pressure refrigerant gas pipe 4j.
It returns to the secondary side of B, reaches almost room temperature while exchanging heat with the high-pressure refrigerant gas on the first side of each heat exchanger, is sucked into the gas compressor 4a, and is again boosted to high pressure by the gas compressor 4a. It becomes a refrigerant gas, and the same cycle is repeated thereafter to perform refrigeration operation.

Next, to explain the operation of this helium refrigeration system during the initial cooling process from room temperature to steady refrigeration operation, JT
If the gas compressor 4a of the circuit 4 and the first and second precooling refrigerators 6 and 7 are started simultaneously, each heat exchanger 4b to 4d of the JT circuit 4 will be activated as the temperature decreases due to the precooling refrigerator. cooled down.

However, when operating with a flow line similar to steady refrigeration operation, the cooling effect of the JT expansion valve 4g occurs in the temperature range below about 40° in the case of helium.
In the initial cooling process in which this cooling effect cannot be expected, the low-temperature high-pressure refrigerant gas cooled by the pre-cooling refrigerators 6 and 7 and the high-temperature low-pressure refrigerant gas returning from the liquid helium tank 2 are combined in the final JT heat exchanger 4d. Since the heat exchange results in an equilibrium state with an opposite temperature gradient, the liquid helium tank 2 cannot be cooled.

Therefore, in the conventional helium refrigerator, a bypass valve 5 for pre-cooling is provided, and the low-temperature high-pressure refrigerant gas cooled by the pre-cooling refrigerator is depressurized and guided directly to the liquid helium tank 2 for initial cooling.

In the apparatus shown in FIG.
After that, the bypass valve 5 is closed and liquid helium is injected into the liquid helium tank 2 from the external liquid helium container via the liquid helium transfer pipe 8, and the liquid helium tank 2 is heated to a predetermined temperature. lower it to the required level and store the required amount of helium.

When the transfer of liquid helium is completed, the stop valve 7a is closed and the steady freezing operation as described above is started.

In the conventional helium refrigeration system configured as described above, J
In addition to the T expansion valve 4g, a bypass valve 5 for initial cooling is required, and during the initial cooling process, J
This has the disadvantage that two valves, the T expansion valve 4g and the bypass valve 50, must be operated to control the appropriate flow rate.

In view of these drawbacks, the present invention eliminates the need for providing the above-mentioned bypass valve by cooling the high-pressure refrigerant gas passing through the JT heat exchanger with a pre-cooling refrigerator during initial cooling, and shifts to steady-state refrigeration operation. After that, the high-pressure refrigerant gas and the pre-cooling refrigerator are thermally shut off to prevent the high-pressure refrigerant gas from being heated by the pre-cooling refrigerator. The object of the present invention is to provide a cryogenic refrigeration device that can apparently easily perform initial cooling and steady-state refrigeration operation.

Hereinafter, a second embodiment of the helium refrigeration device according to the present invention will be described.
The diagram will be explained.

In the present invention, the basic components are constructed in the same way as the conventional ρ helium refrigeration system shown in FIG. 1, and the same parts as in FIG. 1 are designated by the same reference numerals.

In this embodiment, heat is transferred between a part of the high-pressure refrigerant gas pipe 4j that communicates the primary side port of the JT heat exchanger 4d and the JT expansion valve 4g and the low temperature end of the first precooling refrigerator 6. They are connected via a controller 9.

The heat transfer controller 9 controls the high-pressure refrigerant gas and the first pre-cooling refrigerant gas when the temperature of the high-pressure refrigerant gas flowing through the high-pressure refrigerant gas pipe 4j is higher than the low temperature end of the first pre-cooling refrigerator 6, such as during initial cooling.
The high-pressure refrigerant gas is cooled by heat exchange with the low-temperature end of the pre-cooling refrigerator 6, while the temperature of the high-pressure refrigerant gas is lower than the low-temperature end of the first pre-cooling refrigerator 6, as in the steady freezing operation. Sometimes, it has the function of thermally insulating both.

FIG. 3 shows an example of the heat transfer controller 9. In FIG. 3, 9a is a light blue metal with low thermal conductivity (for example, light blue stainless steel), and 9b is a seal for the light blue 9a. An upper flange is attached to the low-temperature end of the first pre-cooled frozen rock 6 to transfer heat, 9c is a lower flange that seals the lower end of the light blue 9a, and 9d is a refrigerant gas sealed in the light blue. Here, nitrogen gas is filled.

The high pressure refrigerant gas pipe line 41 is connected to the lower flange 9 of the light blue color 9a.
It is penetrated on the c side, and is connected to the light blue penetration part by brazing or the like to maintain airtightness of the refrigerant gas 9d.

Moreover, 9e is a heat transfer fin provided on the outer periphery of the high-pressure refrigerant gas pipe 41 in order to increase the amount of heat exchanged between the high-pressure refrigerant gas and the sealed refrigerant gas 9d.

The initial cooling process of the helium refrigeration system having the above configuration will be explained.

In this case, as described above, the operating temperatures of the first precooling refrigerator 6 and the precooling refrigerator 7 are set to 70° and 15°, respectively.
In addition, the operating temperature of the heat transfer controller 9, that is, the temperature at which the sealed nitrogen gas condenses, is set to about 78°.

As in the past, if the gas compressor 4a and No. 1 of the JT circuit 4 and the second precooling refrigerators 6 and 7 are started at the same time, each heat of the JT circuit 4 is Exchangers 4b-4d are cooled.

In the conventional device, as mentioned above, the cooling effect of the JT expansion valve 4g cannot be expected in this initial cooling process, so the high-pressure refrigerant gas flowing through the JT heat exchanger 4d is not cooled. In the container 4d, an equilibrium state is reached due to heat exchange between the high pressure refrigerant gas on the primary side and the low pressure refrigerant gas on the secondary side.

However, in this embodiment, the nitrogen in the heat transfer controller 9 is in a gaseous state in a humidity region of 78° or more, and the convection causes a flow between the high-pressure refrigerant gas and the low-temperature end of the first pre-cooling refrigerator 6. Since heat exchange is performed, the high-pressure refrigerant gas flowing through the JT heat exchanger 4d is further cooled via the heat transfer controller 9, thereby making it possible to cool the liquid helium tank 2.

When the liquid helium bath 2 is cooled to about 78°K by this initial cooling, the initial cooling ends.

After this, liquid helium is subsequently injected from the external container through the liquid helium transfer pipe 8 as in the conventional case,
If the temperature is lowered to a predetermined level and the required amount of liquid is stored, steady operation will begin.

At this time, the heat transfer controller 9 cools the high-pressure refrigerant gas at the outlet of the JT heat exchanger 4d to 78 degrees or less by injection cooling with liquid helium, and the nitrogen gas 9d in the heat transfer leg 9 condenses and liquefies. Therefore, heat exchange between the high-pressure refrigerant gas and the first pre-cooling refrigerator 6 is cut off, preventing the high-pressure refrigerant gas from being heated by the first pre-cooling refrigerator 6, and ensuring smooth steady operation. .

Next, another embodiment of the present invention is shown in FIG. , 10,
The high pressure refrigerant gas pipe 41 from the outlet of the JT heat exchanger 4d to the JT expansion valve 4g is connected in series via the heat transfer controller 9 of the first precooling refrigerator 6 and the heat transfer controller 10 of the second precooling refrigerator 7. Connected.

If the second heat transfer controller 10 is provided as in this embodiment, hydrogen gas is sealed inside it, and its operating temperature is set to 20°K, the JT expansion valve 4g can be connected to the liquid helium tank 2 during initial cooling.
Since the low-temperature gas at 20° is supplied, the initial cooling temperature of the object to be cooled 3 can be lowered to a lower temperature
Therefore, the amount of liquid helium injected from the outside can be reduced.

In this case, if the second precooling refrigerator 7 has sufficient refrigerating capacity,
The cooling effect of the JT expansion valve 4g can also be expected, and it is also possible to reach liquid helium humidity without supplying liquid helium from the outside.

Note that the heat transfer controller 10 operates in the same manner as the heat transfer controller 9 attached to the first precooling refrigerator 6 described above, and when the temperature is below 20 degrees, the heat transfer between the second precooling refrigerator 7 and the high-pressure refrigerant gas is reduced. It is possible to cut off the transmission of refrigeration and allow steady refrigeration operation to occur.

Although the above embodiment applies the present invention to a helium refrigeration system, it is not limited to this example, and it goes without saying that it can be similarly applied to other gas refrigeration systems equipped with a JT circuit.

Furthermore, the heat transfer controller shown in Fig. 3 utilizes the difference in thermal conductivity caused by changes in the state of sealed nitrogen or hydrogen. The thermal conductivity may be changed by mechanically contacting and separating the low-humidity end of the

As described above, in the cryogenic refrigeration system of the present invention, a heat transfer controller is interposed between the high-pressure refrigerant gas pipe coming out of the countercurrent heat exchanger and the precooling refrigerator to transfer heat. ,
Since the system is designed to shut off, there is no need for a pre-cooling bypass valve for initial cooling.
This has the effect that reasonable cooling can be performed from initial cooling to steady refrigeration operation by simple operation of only the T-expansion valve.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing a conventional helium refrigeration system, Fig. 2 is a system diagram showing an embodiment of the helium refrigeration system according to the present invention, and Fig. 3 is an enlarged view of the main parts of Fig. 2. The sectional view, FIG. 4, is a system diagram of another embodiment of the present invention. In addition, in the figures, the same reference numerals indicate the same or the same corresponding parts. 4...Joule-Thomson circuit, 4d...
...JT heat exchanger, 41...High pressure refrigerant gas pipeline, 6...First pre-cooling refrigerator, 7...Second
Pre-cooling refrigerator, 9, 10...Heat transfer controller, 9a.
...Light blue, 9b...Top flange, 9C
...Pa.Lower flange 9d...Refrigerant gas.

Claims (1)

[Scope of Claims] 1. In a cryogenic refrigeration system comprising a Joule-Thompson circuit and a pre-cooling refrigerator that cools high-pressure refrigerant gas flowing through this circuit, a counter-current refrigeration system located at the most downstream of the Joule-Thompson circuit The high-pressure refrigerant gas pipe drawn out from the outlet of the heat exchanger and the pre-cooling refrigerator are connected via a heat transfer controller that controls thermal communication and interruption between the two. Cryogenic freezing equipment. 2. The cryogenic refrigeration apparatus according to claim 1, wherein a plurality of the precooling refrigerators and heat transfer controllers are provided, and the control temperatures of the heat transfer controllers are different from each other. 3. The heat transfer controller is composed of a sealed cylinder provided at the low-temperature end of the precooling refrigerator and penetrated by the high-pressure refrigerant gas pipe, and a refrigerant gas sealed inside the sealed cylinder. A cryogenic refrigeration apparatus according to claim 1 or 2, characterized in that: