JPH0349024B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention relates to a cryogenic refrigerator, and particularly to a cryogenic refrigerator that does not require various load conditions and requires long-term continuous operation. [Background of the Invention] Cryogenic refrigerators such as helium refrigerators require a long time to precool from room temperature, and therefore special measures are taken for transient operation control. Additionally, mechanisms have been devised to perform control in accordance with the load on the object to be cooled during steady operation. Hereinafter, a conventional cryogenic refrigerator will be explained with reference to FIG. 1, taking a helium refrigerator as an example of the cryogenic refrigerator. In FIG. 1, a helium refrigerator 10 mainly includes a cold storage tank 11 that is evacuated, heat exchangers 12a to 12e, and expanders 13a and 13b. In the cold storage tank 11, heat exchangers 12a to 12e are sequentially arranged from the top to the bottom in FIG.
4 is provided to communicate each high pressure flow path of the heat exchangers 12a to 12e, and a low pressure line 15 is provided to communicate with each high pressure flow path of the heat exchangers 12a to 12e.
~12e are provided in communication with each of the low pressure channels. An expander line 16 is branched from the high pressure line 14 between the heat exchanger 12a and the heat exchanger 12b, and the branched end is connected to the low pressure line between the heat exchangers 12d and 12e via the medium pressure flow path of the heat exchanger 12c. 15
is connected to. A bypass line 17 branches from the high pressure line 14 between the heat exchangers 12d and 12e, and the branched end of the bypass line 17 is connected to the heat exchanger 12.
e Connected to the low pressure line 15 on the upstream side. An expander inlet valve 18 is provided on the upstream side of the heat exchanger 12c in the expander line 16, and an expander 13a is provided in the expander line 16 between the expander inlet valve 18 and the heat exchanger 12c. There is. An expander 13b is provided in the expander line 16 on the downstream side of the heat exchanger 12c. The bypass line 17 includes a pre-cooling valve 1.
9, and a Jul-Thomson expansion valve (hereinafter abbreviated as JT valve) 20 is provided at the refrigerant outlet end (lower end in FIG. 1) of the high pressure line 14.
The compressor 30 is arranged outside the cold storage tank 11, and its discharge end is connected to one end of a pipe 31, and its suction end is connected to one end of a pipe 32. The other end of the pipe 31 is the refrigerant inlet end of the high pressure line 14 (in FIG.
The other end of the pipe 32 is connected to the refrigerant outlet end (the upper end in FIG. 1) of the low pressure line 15. Further, a medium pressure tank 40 is arranged outside the cold storage tank 11, and the medium pressure tank 40 and the pipes 31, 3
2 are connected by pipes 41 and 42, respectively, and pressure regulating valves 43a and 43b are provided in the pipes 41 and 42, respectively. A cryostat inner tank (hereinafter abbreviated as cryo inner tank) 51 of the cryostat 50 which is in vacuum communication with the cold storage tank 11 has a cooled body 52 built therein. At the outlet end of the JT valve 20,
One end of the refrigerant supply line 21 is connected, and the other end is communicated with the cryo inner tank 51. The refrigerant inlet end (lower end in FIG. 1) of the low pressure line 15 is connected to the cryo inner tank 51 in communication with the gas layer. In FIG. 1, high-pressure beryum gas (hereinafter abbreviated as high-pressure GHe) compressed and pressurized by a compressor 30 is introduced into a high-pressure line 14 through a pipe 31, and is supplied to a high-pressure flow path of a heat exchanger 12a. While flowing through this high-pressure flow path, the high-pressure GHe is cooled by exchanging heat with low-pressure helium gas (hereinafter abbreviated as low-pressure GHe) flowing through the low-pressure flow path of the heat exchanger 12a. It is discharged from the flow path. A portion of this discharged high pressure GHe is flowed into the expander line 16. The divided high-pressure GHe passes through the expander inlet valve 18 and performs adiabatic expansion work in the expander 13a to generate cold, and then exchanges heat with the low-pressure GHe flowing through the low-pressure flow path in the heat exchanger 12c, and then, The expander 13b performs adiabatic expansion work again to generate cold, which is merged with low-pressure GHe flowing through the low-pressure line 15 between the heat exchangers 12d and 12e. On the other hand, the remaining high-pressure GHe is transferred to the low-pressure GHe in the heat exchangers 12a to 12e.
After being sequentially cooled by heat exchange with JT valve 20, it is expanded and liquefied. Liquefied helium gas (hereinafter abbreviated as LHe) is supplied to the cryo tank 51 via the refrigerant supply line 21.
The object to be cooled 52 is immersed in LHe. LHe in the cryo inner tank 51 partially evaporates into low pressure GHe due to absorption of the refrigeration load including the cooled body 52 of the cryostat 50, and this low pressure GHe is transferred to the heat exchanger 1.
The cold is recovered by heat exchange with high-pressure GHe in 2e to 12a, and then returned to the compressor 30. Next, the basic functions of each valve will be explained. (1) Expansion inlet valve 18 The first function is a load control function of the expanders 13a and 13b. The expanders 13a and 13b include
A control device (not shown) is attached to absorb the work of adiabatic expansion of helium gas (hereinafter abbreviated as GHe), but its control range is not wide. On the other hand, the load due to adiabatic expansion work increases in proportion to the inlet GHe temperature if the expansion ratio remains the same. Therefore, when starting up the helium refrigerator 10, a load that cannot be controlled by the control device may be applied. Therefore, when starting the helium refrigerator 10, the expander inlet valve 18
It is necessary to control the load by reducing the expansion ratio in the expanders 13a and 13b. The second function is to control the operation of the helium refrigerator 10 in accordance with the load conditions of the cryostat 50 during steady operation. That is, the flow rate ratio of high-pressure GHe to be diverted to the expander line 16 differs greatly between when the load condition of the cryostat 50 is only a refrigeration load and when it is other, for example, a liquefaction load.
The expander inlet valve 18 is used to control the operation of the helium refrigerator 10 in response to such load conditions. (2) JT valve 20 The JT valve 20 is basically used to adjust the capacity of the helium refrigerator 10. (3) Precooling valve 19 The precooling valve 19 is used for bypass during precooling operation of the helium refrigerator 10. That is, since the heat exchanger 12e has high performance and the JT valve 20 is designed to suit the usage conditions during steady operation, only a small amount of GHe can flow during precooling operation, and precooling takes a long time. . Therefore, in order to shorten this precooling operation time, the heat exchanger 12e can be bypassed by the precooling valve 19 during the precooling operation. (4) Pressure adjustment valves 43a, 43b Pressure adjustment valves 43a, 43b are intermediate pressure tank 40
High pressure GHe and low pressure GHe as a buffer
Performs pressure control. In such cryogenic refrigerators, the expander inlet valve,
Using expensive cryogenic valves such as JT valves and pre-cooling valves,
In addition, this made the cryogenic piping inside the cold storage tank complicated, resulting in an increase in cost. Another disadvantage was that the reliability of the cryogenic valve was relatively low, thereby reducing the reliability of the cryogenic refrigerator. In addition, because the operation part of the cryogenic valve needs to be placed outside the cold storage tank, heat leaks from the operation part into the cold storage tank, which has the disadvantage of reducing the performance of the cryogenic refrigerator. Ta. Another drawback was that it became difficult to operate the cryogenic refrigerator due to the large number of operation parts during operation. [Object of the Invention] An object of the present invention is to provide a cryogenic refrigerator that can reduce the cost by eliminating the need for an expensive cryogenic valve. [Summary of the Invention] The present invention provides a heat exchanger system in which a plurality of heat exchangers are arranged in a cold storage tank that is evacuated, and a high-pressure line that communicates with a high-pressure flow path of the heat exchanger branches within the cold storage tank. An expander is installed in the expander line that merges with the low pressure line that communicates with the low pressure flow path of It is characterized by the provision of a pressure regulating means, which eliminates the need for an expensive cryogenic valve. [Embodiment of the Invention] The basic functions of cryogenic valves used in conventional cryogenic refrigerators are as described above. In a cryogenic refrigerator, each cryogenic valve has its own meaning and effect. However, the main operation is, for example, refrigeration operation,
For cryogenic refrigerators that do not require diverse load conditions and require long-term continuous operation, a fundamental reconsideration is possible. Therefore, as a result of intensive study on such cryogenic refrigerators, we found that among the cryogenic valves, the expander inlet valve controls the load of the expander during precooling by adjusting the pressure of the high-pressure refrigerant gas introduced into the high-pressure line. The knowledge that this can be done by changing the flow rate of the refrigerant gas divided into the expander line is eliminated, as the expansion machine can be designed in accordance with the main operating conditions for the steady-state operation mode. and also
It was found that the JT valve only needs to be a fixed throttle means, and that the refrigerating capacity can be easily adjusted by adjusting the pressure of the high-pressure refrigerant gas introduced into the high-pressure line. Note that the purpose of the precooling valve is to shorten the precooling time, and in such a cryogenic refrigerator, the precooling time is not a big problem and can be omitted. An embodiment of the present invention will be described below with reference to FIGS. 2 to 4. In this case, the cryogenic refrigerator is a helium refrigerator. In FIG. 2, the refrigerant outlet end (second
At the lower end in the figure, a fixed throttle means, for example, an orifice-type fixed throttle means 60 as shown in FIG. 3, is provided in place of the conventional JT valve. The fixed throttle means 60 includes a flange 61 provided on the high pressure line 14 and a flange 62 provided on the refrigerant supply line 21.
It has a structure in which the orifice 63 is fixed with. In this case, no special refrigerant pressure adjustment means is provided, and the pressure length component 4 is provided on the refrigerant inlet end side of the high pressure line 14 and outside the cold storage tank 11.
32 is commonly used as pressure adjustment means. Also,
Bypass line shown in Figure 1, expander inlet valve,
Each pre-cooling valve passage has been removed. In addition, the second
In the figure, other devices, parts, etc. that are the same as those in FIG. In FIG. 2, the refrigerating capacity of the helium refrigerator 10 during steady operation is controlled by adjusting the pressure of high-pressure GHe introduced into the high-pressure line 14.
That is, the set value of the pressure regulating valve 43a is adjusted according to the refrigeration load. When the helium refrigerator 10 is a helium refrigerator that does not require various load conditions and requires long-term continuous operation, there is a difference between the pressure P of the high pressure GHe introduced into the high pressure line 14 and the refrigeration capacity Q.
As shown in FIG. 4, an almost linear relationship holds true. Thereby, the refrigerating capacity of the helium refrigerator 10 during steady operation can be easily controlled by adjusting the pressure of the high-pressure GHe introduced into the high-pressure line 14 using the pressure regulating valve 43a. In addition, the pressure P of the high pressure GHe introduced into the high pressure line 14 in FIG.
is expressed by equation (1), and refrigeration capacity Q is expressed by equation (2). P = High pressure line inlet pressure / Compressor discharge pressure x 100 (
%)...(1) Q = Actual refrigeration capacity/Design refrigeration capacity x 100 (%)...
...(2) Next, to control the braking load of the expanders 13a and 13b during pre-cooling operation, the pressure of the high-pressure GHe introduced into the high-pressure line 14 is adjusted to This can be done by adjusting with the regulating valve 43a. With the refrigerator as in this embodiment, the following effects can be obtained. (1) An expensive cryogenic valve is not required, and the cryogenic piping inside the cold storage tank can be simplified, so the price of the helium refrigerator can be reduced. (2) Since a cryogenic valve, which is relatively unreliable, is not required, the reliability of the helium refrigerator can be improved. (3) There is no need for a cryogenic valve, which also eliminates the need for an operating section, which prevents heat from entering the cold storage tank.
This can prevent performance deterioration of the helium refrigerator. (4) The number of operating parts during operation can be greatly reduced, making the operation of the helium refrigerator extremely simple. In addition to this embodiment, pressure means such as a pressure regulating valve may be installed on the piping that is located on the refrigerant inlet end side of the high pressure line and outside the cold storage tank and connects the discharge end of the compressor and the inlet end of the high pressure line. The pressure adjusting means may be provided to adjust the pressure of the high pressure GHe introduced into the high pressure line, or the compressor itself may be equipped with the function of a pressure adjusting means to directly adjust the pressure. good. Alternatively, the pressure of the high-pressure GHe introduced into the high-pressure line may be directly adjusted by adjusting the flow rate of the high-pressure GHe introduced into the high-pressure line. In addition, in this embodiment, a fixed throttle means is installed in the cold storage tank in place of the JT valve, but if it is at the refrigerant outlet end of the high-pressure line, it can also be installed inside the cryostat. If the cryostat and the cryostat are connected by a cryotransfer pipe, it may be provided in the middle of the cryotransfer pipe. As a fixed throttle means to replace the JT valve,
In addition to this embodiment, any device whose opening degree cannot be changed during operation, such as a bench lily type fixed throttle means, can be applied without any problem. [Effects of the Invention] The present invention provides a heat exchanger system in which a plurality of heat exchangers are arranged in a cold storage tank that is evacuated, and a high pressure line that communicates with a high pressure flow path of the heat exchanger branches out from a high pressure line that communicates with a high pressure flow path of the heat exchanger. An expander is installed in the expander line that joins the low pressure line that communicates with the low pressure flow path of By providing a pressure adjustment means, there is no need for an expensive cryogenic valve, and this also simplifies the cryogenic piping inside the cold storage tank.
This has the effect of reducing the cost of cryogenic refrigerators.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a conventional helium refrigerator, FIG. 2 is a block diagram showing an example of the configuration of a helium refrigerator according to the present invention, and FIG. 3 is a block diagram showing the configuration of a helium refrigerator according to the present invention. Enlarged longitudinal sectional view of the means, 4th
The figure is a diagram showing the relationship between the pressure of high-pressure GHe introduced into the high-pressure line and the refrigerating capacity. 11... Cold storage tank, 12a to 12e... Heat exchanger, 13a, 13b... Expander, 14... High pressure line, 15... Low pressure line, 43a... Pressure regulating valve, 60... Fixed throttle means.

Claims (1)

[Claims] 1 A plurality of heat exchangers are arranged in a cold storage tank that is evacuated, and a high pressure line that is connected to a high pressure flow path of the heat exchanger branches within the cold storage tank and connects to a low pressure flow path of the heat exchanger. An expander is provided in an expander line that merges with the communicating low-pressure line, a fixed throttle means is provided at the refrigerant outlet end of the high-pressure line, and a refrigerant pressure adjustment device is provided at the refrigerant inlet end of the high-pressure line and outside the cold storage tank. A cryogenic refrigerator characterized by being provided with means.