JPH07117310B2 - Cryogenic refrigerator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a cryogenic refrigeration system, and particularly to a cryogenic system suitable for a system having a plurality of objects to be cooled each of which needs to select an independent operation mode. The present invention relates to a refrigeration system.

[Conventional technology]

There are superconducting magnets, cryopumps, etc. as objects to be cooled in a cryogenic refrigerator, for example, a helium refrigerator, but the operating state of the objects to be cooled is liquefied helium by cooling from room temperature to liquefied helium temperature (-268 ° C). There are a pre-cooling operation for storing the liquid up to a set value, a steady operation after the liquid storage, and a warming operation for heating up to room temperature.

On the other hand, during the helium gas handling state of the whole system during this period, as shown in FIG. 3, first, most of the gas is held in the medium pressure tank in the stopped state where the whole system is at room temperature. When the helium refrigerator and the liquefied helium container are started and the pre-cooling progresses, the amount of gas held in the medium-pressure tank decreases, and when the helium refrigerator produces liquefied helium, the liquid storage in the liquefied helium container proceeds. In the case of helium, liquefied helium 1 corresponds to 700 liters of helium gas at room temperature and atmospheric pressure.

Precooling of the cooled object is generally started by first precooling to about 80K gas helium from the helium refrigerator, cooling the cooled object to about 100K, and then using liquefied helium generated in the helium refrigerator. Switch to cooling of the cooled object about 20K
Pre-cooling to about 20K, increasing the amount of liquefied helium delivered from the liquefied helium container to cool the object to be cooled to the liquefied helium temperature and store liquid up to a predetermined value.

During this period, the amount of gas held in the medium-pressure tank (represented by the pressure) is maximum when the apparatus is stopped, and is the minimum before the start of increasing the flow rate of liquefied helium from the liquefied helium container to the cooled object. The amount of liquid held in the liquefied helium container (represented by the liquid surface) becomes maximum before the liquid helium precooling of the cooled object is started, and becomes minimum when the liquid storage in the cooled object is completed.

As described above, in the cryogenic refrigeration system, it is necessary to operate the gas handling state of the entire system while paying close attention to the operating state.

Examples of devices related to this type include, for example, JP-A-58-195756 and JP-A-61-22159.

[Problems to be solved by the invention]

The medium-pressure tank serves to collect helium in the system when the system is stopped, and also has a role of a buffer tank for controlling the suction pressure and the discharge pressure of the compressor. Therefore, unless the pressure of the medium pressure tank is maintained within an appropriate range, the suction pressure and the discharge pressure of the compressor cannot be controlled.

On the other hand, if the amount of liquid helium held in the liquid helium container is not appropriate when the liquid helium is started to be fed to the object to be cooled, liquefied helium in the liquid helium container will be exhausted when liquid helium is fed and stored. Become.

In this way, the cryogenic refrigeration system requires comprehensive operation management of the gas handling of the entire system, and the conventional pre-cooling time is not stable because it depends on the experience of the operator. There was a problem that it was necessary to increase the capacity of the liquefied helium container to give a margin. or,
There is a problem that operation becomes extremely difficult in an apparatus in which there are a plurality of objects to be cooled and it is necessary to select an independent operation state for each.

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a cryogenic refrigeration system capable of stable operation control with a device having a minimum required capacity.

[Means for Solving Problems] In the cryogenic refrigerator, the above-mentioned object is to provide a heating means (for example, a heater) for controlling the upper limit liquid level of the cryogenic liquefied gas container in the cryogenic liquefied gas container, and A supply valve that controls the lower limit liquid level of the cryogenic liquefied gas container by adjusting the amount of the cryogenic liquefied gas is provided in the pipe for sending the cryogenic liquefied gas from the cryogenic liquefied gas container to the object to be cooled. This is achieved by providing a control means for controlling the heating means and the supply valve so that the liquid level in the cryogenic liquefied gas container is within a predetermined range when the cooling state is observed.

[Action]

The control means corresponds to the operating state of the object to be cooled, the pressure of the medium-pressure tank is kept within an appropriate range, and the liquefied gas necessary for precooling the object to be cooled is held so that the heating means and the supply valve Set the control settings. According to the control set value, the upper limit liquid level of the cryogenic liquefied gas container is controlled by the heating means,
The lower limit liquid level is controlled by the supply valve. As a result, the equipment in the apparatus may be the minimum required, and stable and smooth operation control can be performed.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 shows a cryogenic refrigerator, in this case a helium refrigerator. In FIG. 1, 1 is a compressor, 2 is a helium refrigerator, 3 is a liquefied helium container which is a cryogenic liquefied gas container, 4a to 4n are objects to be cooled, 5 is a medium pressure tank, 6 is a high pressure control valve, Reference numeral 7 is a low pressure control valve, 8, 9 and 10 are cryogenic refrigerant transfer pipes having a vacuum heat insulation structure, 11 is a helium refrigerator 2
A helium gas supply line for sending a cooling gas from the cooled objects 4a to 4n, 12, 13a to 13n are superconducting level gauges, 20 is a heating means heater, 21 is a heater controller, 22 is a supply valve,
Reference numeral 23 is a supply valve controller, and 24 is a state controller. In this case, the control means is composed of the heater controller 21, the supply valve controller 23 and the state controller 24.

Next, the operation of the cryogenic refrigeration system of the present invention configured as described above will be described. The high-pressure helium gas compressed by the compressor 1 is sent to the helium refrigerator 2 and a part thereof becomes liquefied helium, which is sent to the liquefied helium container 3 through the cryogenic refrigerant transfer pipe 8. The liquefied helium in the liquefied helium container 3 is sent to the objects to be cooled 4a to 4n through the cryogenic refrigerant transfer pipe 9, where it is subjected to a heat load to be evaporated and the cryogenic refrigerant transfer pipe 10
Return to helium refrigerator 2. In addition, helium gas not liquefied in the helium refrigerator 2 and liquefied helium container 3
Helium gas evaporated by the heater 20 inside and the object to be cooled
The helium gas returned from 4a to 4n returns to the suction side of the compressor 1. Helium gas in the medium-pressure tank 5 goes in and out via a high-pressure pressure control valve 6 that controls the discharge pressure of the compressor 1 and a low-pressure pressure control valve 7 that controls the suction pressure according to the operating state of the entire system.

The above is the operation in the steady state. Next, the operation after the start of operation will be sequentially described. Most of the system helium gas is held in the medium pressure tank 5 because the entire system is at room temperature at the start of operation, but as the operation continues, the medium pressure tank 5 gradually supplies helium gas and the pressure drops. Go. Cooled object 4a
The initial precooling of ~ 4n is performed with about 80 K of helium gas supplied from the helium gas supply line 11. The object to be cooled 4
The control of a to 4n helium gas and liquefied helium is independently controlled by a control valve (not shown) included in each cooled object.

At the start of operation, all of the objects to be cooled 4a to 4n require pre-cooling, so the state controller 24 sets the control set value of the heater controller 21 to the upper limit, and also the set value of the supply valve controller 23 of the supply valve 22. Set to the maximum limit. That is, the heater 20 is not included in the initial stage,
The supply valve 22 is closed.

When the pre-cooling of the helium refrigerator 2 and the liquefied helium container 3 progresses and the liquefied helium can be produced, the pressure in the medium pressure tank 5 starts to decrease rapidly and the liquid level of the liquefied helium container 3 starts to rise. When the instruction of the liquid level gauge 12 exceeds the set value of the supply valve controller 23, the supply valve 22 starts to open and precooling of the objects to be cooled 4a to 4n with liquefied helium is started. When the indication of the liquid level gauge 12 further rises and reaches the set value of the heater controller 21, the heater 20 is turned on and the upper limit of the held liquefied helium in the liquefied helium container is controlled so that the pressure in the medium pressure tank 5 does not abnormally decrease.

When the pre-cooling of the cooled objects 4a to 4n progresses and reaches a steady state where the pre-cooling of one cooled object is completed, the state controller 24 sets the control set values of the heater controller 21 and the supply valve controller 23, respectively. Reduce by a predetermined amount. That is, for example, when the precooling of the cooled object 4a is completed and the steady state is reached, the liquid level gauge 13a detects the completion of the liquid storage and sends a signal to the state controller 24. As a result, the state controller 24 sets the preset relationship between the number of cooled objects in the steady state and the set liquid level as shown in FIG. 2, and sets the heater controller 21 and the supply valve controller 23. Indicate the amount. Hereinafter, the state controller 24 sequentially controls appropriate gas handling of the entire system in accordance with the operating state of the cooled object.

As described above, the liquefied helium container 3 and the cooled object 4a-
The amount of helium gas held by 4n is abnormally increased, the pressure of the intermediate pressure tank 5 is abnormally lowered, and the low pressure control valve 7 is prevented from being uncontrollable, and is also used for precooling the cooled objects 4a to 4n. Control is performed so that the required liquefied helium is held in the liquefied helium container 3.

Note that FIG. 2 shows an example of the relationship between the control set values of the heater controller 21 and the supply valve controller 23 set by the state controller 24 and the operating state of the cooled object.

As described above, according to the present embodiment, the gas handling control of the complicated whole system can be appropriately and automatically performed.
This has the effect of minimizing the number of equipment components and the effect of stable and smooth operation control. Furthermore, there is an economic effect such as not requiring a skilled operator.

In the above one embodiment, the state controller, the heater controller, and the supply valve controller have been described as independent instruments, but various configurations are applicable for specific applications such as performing all of these controls in the computer. It is clear that this is possible.

〔The invention's effect〕

According to the present invention, the number of devices such as a medium-pressure tank in the device may be the minimum required, and stable and smooth operation control can be achieved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a cryogenic refrigeration system which is an embodiment of the present invention, FIG. 2 is a conceptual diagram showing an example of control set values in FIG. 1,
FIG. 3 is a diagram showing the relationship of the refrigerant gas amount in the cryogenic refrigerator. 1 ... Compressor, 2 ... Helium refrigerator, 3 ... Liquefied helium container, 4a-4n ... Cooled object, 5 ... Medium pressure tank, 6
... High pressure control valve, 7 ... Low pressure control valve, 8,9,10 ...
… Cryogenic refrigerant transfer pipe, 11 …… Helium gas supply line, 12,13a to 13n …… Level gauge, 20 …… Heater, 21 ……
Heater controller, 22 …… Supply valve, 23 …… Supply valve controller,
24 …… State controller

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 61-22159 (JP, A) JP 63-6354 (JP, A)

Claims (2)

[Claims] 1. A compressor for compressing a refrigerant gas, a cryogenic refrigerator for introducing a high-pressure refrigerant gas compressed by the compressor to produce a cryogenic liquefied gas, and a cryogenic temperature for the cryogenic refrigerator. A cryogenic liquefied gas container that stores a liquefied gas, a cooled object that is cooled by the cryogenic liquefied gas, and an intermediate pressure tank that stores the refrigerant gas. A heating means is provided inside, and a supply valve for adjusting the amount of cryogenic liquefied gas is provided in the pipe for sending the cryogenic liquefied gas from the cryogenic liquefied gas container to the object to be cooled, and the cooling state of the object to be cooled is provided. The cryogenic refrigerating apparatus is provided with control means for controlling the heating means and the supply valve so that the liquid level in the cryogenic liquefied gas container is within a predetermined range. 2. The control means performs the lower limit liquid level control and the control set value of the heating means for performing the upper limit liquid level control of the cryogenic liquefied gas container in accordance with the operating state of the object to be cooled. The cryogenic refrigerator according to claim 1, wherein the control set value of the supply valve is automatically changed.