JPH0370914B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a superconducting cooling device that uses supercritical pressure helium as a refrigerant and forcibly circulates this refrigerant for cooling. This invention relates to a cryogenic cooling device that controls gas.

[Background of the invention]

Compared to immersion cooling, cooling superconducting magnets using a forced flow of helium requires cooling equipment and special conductors, so its development has been somewhat delayed. However, as cooling technology has improved in recent years, it has become possible to consider the application of superconducting magnets to large items such as large fusion magnets and magnets for accelerators, as well as items with special shapes, and development is being carried out in various fields. Ta.

In general, the advantages of forced cooling using supercritical helium are: (1) As shown in Figure 1 a and b, the conductor itself becomes the coolant passage, eliminating the need for a cooling channel and increasing mechanical strength. .

(2) The coil can be easily insulated.

(3) Electrical insulation 1 becomes easy and coils with complex shapes can be made.

(4) The cryostat housing the superconducting coil 2 may simply be a vacuum container.

(5) Heat generated by AC loss can be removed by forced flow.

etc.

FIG. 2 is a schematic diagram showing an example of a forced cooling system in which supercritical pressure helium is used as a refrigerant and liquid helium is supplied from outside to a liquid helium tank.

In the figure, helium gas, which serves as a refrigerant, is compressed by a circulation compressor 4 and led to a cold box 5, where it exchanges heat with return gas in a heat exchanger 6 to lower its temperature. into which it is cooled.

The cooled gas is transferred to the transfer tube 8a.
The superconducting coil in the cryostat 9 is cooled through the transfer tube 8, and the return gas is transferred to the transfer tube 8.
B, enters the cold box 5, expands JT at the Joel-Thomson (JT) valve 11, becomes liquid, and accumulates in a liquid helium tank. The gas evaporated here returns to the circulation compressor 4 via the return pipe 12 and the heat exchanger 6, and is cooled while repeating this process.

Although the conventional forced cooling system has these advantages, it also has the following drawbacks.

First, as shown in FIG. 2, the return gas from the superconducting coil 10 in the cryostat 9 is returned to the cold box via the transfer tube 8b, but during operation, often Thermal vibrations occur in the piping, including the superconducting coil, in the cryostat, causing the refrigerant temperature measured by the superconducting coil to rise rapidly, causing the superconducting coil to transition to normal conductivity.

Another drawback is that the return gas enters the cold box 5 via the transfer tube 8b and is expanded by the JT valve 11 before entering the liquid helium storage tank 7. Since the structure is such that even the return gas of the liquid helium enters the liquid helium storage tank, if high temperature gas enters, the liquid helium will evaporate, increasing the amount of liquid helium consumed. In addition, 3 in the figure is a metal pipe,
3' is a refrigerant passage, 13 is a liquid helium pipe, 1
4 is transfer tube, 15 is JT valve, 16
is a stabilized power supply.

[Purpose of the invention]

An object of the present invention is to provide a high-performance cryogenic cooling device that controls return gas from an object to be cooled, has no thermal vibrations, and consumes little liquid helium.

[Summary of the invention]

The present invention is a superconducting cooling device that uses supercritical helium as a refrigerant and forcibly circulates it through a superconducting coil made of a forced cooling conductor to cool the superconducting coil. A stop valve is provided, the return gas piping from this superconducting coil is branched inside the cold box, a temperature sensor is installed at this branch point, and multiple valves that are activated by detecting the temperature of the return gas are connected downstream of the branch point. It is to be established in

[Embodiments of the invention]

An apparatus for carrying out the invention will be explained with reference to FIG.

The difference from FIG. 2 is that a check valve 19 made of a Teflon bulb 17, as shown enlarged in FIG. is branched into three directions, a temperature sensor 21 is installed at the branch point 20, and a liquid helium storage tank inlet pipe 22 downstream from the branch point,
The return pipe 22' to the heat exchanger and the heat exchanger bypass pipe 23 are activated by sensing the temperature at the branch point. Joel Thomson valve 11' and automatic valve 2
5,26 was installed.

In operation, first, the inside of the cold box 5 and the cryostat 9 are evacuated, and the inside of the system piping is purged. Next, the respective liquids are injected into the liquid nitrogen tank 6' and the liquid helium tank 7, the circulation compressor 4 is started, and the discharge valve 24 is slowly opened to forcefully circulate the compressed helium gas.

The temperature detector at the branch point was set so that the Joel-Thomson valve 11' and the automatic valves 25 and 26 could be opened or closed as desired depending on the temperature of the return gas.

Example 1 First, in order to see the effect of the check valve, the detector settings were removed in the same way as the conventional method, the Joel-Thomson valve 11' was fully opened, and the other two automatic Valves 25 and 26 were closed, and the circulating gas was allowed to flow at a pressure of 5 kg/cm ² G and a flow rate of 3 g/s to 5 g/s.

As a result, when there is no check valve, when the temperature at the cryostat outlet falls below 10〓, the swing width is 20〓.
Some degree of thermal oscillation occurred and it was not possible to obtain a temperature below 6〓, but in this example, no thermal oscillation occurred and the temperature at the cryostat outlet could be stably lowered to 47〓.

Example 2 Next, while leaving the check valve in place, the temperature detector at the branch point was set as follows.

The settings were such that when the temperature of the return gas was between 4.3° and 7°, the Joel-Thomson valve was opened by about 30%, and at this time automatic valves 25 and 26 were closed.

Also, when the temperature exceeds 7〓 and reaches 30〓, the Joel-Thomson valve 11' and the automatic valve 26 are closed, and the other one is closed.
Two automatic valves 25 are opened.

Also, when the temperature exceeds 30°, the Joel-Thompson valve 11' and the automatic valve 25 are closed, and the automatic valve 26 is closed.
I set it to open.

The operation was carried out in the same manner as in Example 1, at a circulating gas pressure of 5 kg/cm ² G and a flow rate of 5 g/s.

As a result, when the return gas temperature is high, it flows to the automatic valve and does not enter the liquid helium tank, and when the temperature is low, it flows to the automatic valve.
The liquefaction was carried out by JT expansion, and the consumption in the liquid helium tank was 25/h, about 50% less than when using the conventional method without a detector.

In the above embodiments, the settings of the temperature sensor are limited, but it goes without saying that these settings can be changed arbitrarily, and the optimum value can be selected depending on the experimental load.

Also, although a Teflon bulb was used for the check valve this time, it is not limited to this.

〔Effect of the invention〕

According to the present invention, since a check valve is used, there is no thermal vibration and it is possible to stably cool the gas to an extremely low temperature.Since the temperature of the return gas is detected and the valve is automatically opened and closed, the liquid Low helium consumption and extremely efficient cooling management.

[Brief explanation of drawings]

Figures 1a and 1b are cross-sectional views of a forcedly cooled superconducting conductor;
FIG. 2 is a system diagram of a conventional forced cooling system, and FIG. 3 is a system diagram of a forced cooling system according to an embodiment of the present invention.
FIG. 4 is an enlarged view of the check valve of FIG. 3. 20... Branch point, 21... Temperature detector, 22,2
2', 23...Piping, 25...Automatic valve, 26...Automatic valve.

Claims (1)

[Scope of Claims] 1. In a cryogenic cooling device including a superconducting coil using supercritical pressure helium as a refrigerant and cooled by forcibly circulating the refrigerant, a return in a cryostat in which the superconducting coil is housed is provided. A check valve is provided in the gas pipe, the return gas pipe is branched within the cold box, a temperature detector is installed at this branch point, and a valve that is activated by detecting the temperature of the return gas is provided downstream of the branch point. A cryogenic cooling device featuring: