JPH0730965B2 - Superfluid helium generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a superfluid helium generator.

(Prior Art) To cool a superconducting coil to a temperature below the lambda point, superfluid helium is required. There are several methods for producing superfluid helium, and among them, there is a cooling device using a Joule-Thomson heat exchanger (hereinafter abbreviated as JT heat exchanger) as shown in FIG.

In this cooling device, a superfluid helium tank 3 is housed in a normal-flow helium tank 2 containing 4.2K of liquid helium 1. The normal flow helium tank 2 includes an inner tank 4, an outer tank 5, and
It is composed of a vacuum heat insulating layer 6 formed between the outer tanks 4 and 5. The superfluid helium tank 3 also has an inner tank 7, an outer tank 8
It is composed of a vacuum heat insulating layer 9 formed between the outer tanks 7 and 8.

In the superfluid helium tank 3, a superconducting coil 10, which is an object to be cooled, a coil-type heat exchanger 11, and liquid helium 12 pressurized to atmospheric pressure are housed. One end 11a of the heat exchanger 11 penetrates the upper wall of the inner tank 7 to reach the exhaust pipe 13, and the other end 11b penetrates the upper wall of the inner tank 7 to reach the inside of the exhaust pipe 13. It is connected to the discharge port of the placed Joule-Thomson valve (hereinafter abbreviated as JT valve) 14. Exhaust pipe 13
Inside, a tube coil 15 that constitutes a JT heat exchanger K is arranged along the inner surface of the exhaust pipe 13. One end of the pipe coil 15 is connected to the inlet of the JT valve 14, the other end of the pipe coil 15 penetrates the wall of the exhaust pipe 13, and the opening 16 is located in the normal flow helium tank 2. Further, a cylindrical flow passage cross-sectional area setting member 17 that determines the flow passage cross-sectional area is inserted in the pipe coil 15.

In the figure, 18 is a connecting pipe for injecting liquid helium into the superfluid helium tank 3, 19 is a plug, and 20 is a connecting pipe for connecting the inside of the superfluid helium tank 2 with the inside of the superfluid helium tank 3. 21 shows a plug that is inserted into the connecting pipe 20 and functions as a safety valve, 22 shows an operating rod for controlling the JT valve 14 from the outside, and 23 shows a support material for the superconducting coil 10. ing.

Thus, this cooling device cools the liquid helium 12 in the superfluid helium tank 3 to the superfluid temperature as follows. That is, the inside of the exhaust pipe 13 is exhausted by a vacuum pump (not shown). By this exhaust, a part of the liquid helium 1 in the normal flow helium tank 2 is piped from the opening 16
It flows into 15. The liquid helium flowing through the tube coil 15 was expanded by Joule-Thomson with the JT valve 14 and the lambda point (2.1
7) The following gases and liquids flow to the heat exchanger 11.
When flowing through the heat exchanger 11, the liquid component evaporates, whereby the liquid helium 12 in the superfluid helium tank 3 is cooled to the superfluid temperature. Then, the low-temperature helium gas discharged from the heat exchanger 11 flows through the exhaust pipe 13 to the vacuum pump, and precools the liquid helium flowing in the pipe coil 15 in this process.

As can be seen from this operation, the exhaust pipe 13, the pipe coil 15, and the flow passage cross-sectional area setting member 17 constitute the JT heat exchanger K, and cool the liquid helium 12 in the superfluid helium tank 3 to the superfluid temperature. Plays an important role in getting involved.

However, the superfluid helium generator configured as described above has the following problems. That is, the JT heat exchanger K exchanges heat between the high-temperature and high-pressure liquid helium flowing inside the tube coil 15 and the low-pressure and low-temperature helium gas flowing outside the tube coil 15. When the temperature of the liquid helium 12 in the fluid helium tank 3 gradually decreases, the temperature of the liquid helium flowing in the tube coil 15 also changes accordingly. This is because the density of the helium gas discharged from the heat exchanger 11 changes. Therefore, the heat exchange efficiency in the JT heat exchanger K also changes. The JT heat exchanger K incorporated in this type of cooling device is desired to have the highest heat exchange efficiency at all temperatures during cooling. However, the heavy JT heat exchanger K cannot be used with the highest heat exchange efficiency at all temperatures, and as a result, when incorporated in a superfluid helium production cooling device, it cannot be used for cooling. There was a problem that it took a long time.

(Problems to be Solved by the Invention) As described above, the conventional superfluid helium generator cannot be used while maintaining the maximum heat exchange efficiency over the entire temperature range.

Therefore, an object of the present invention is to provide a superfluid helium generator which can be always used with the highest heat exchange efficiency despite having a simple structure.

[Structure of the Invention] (Means for Solving the Problems) The present invention is directed to a helium tank containing normal-flowing liquid helium therein, a liquid helium inside, and immersion in liquid helium in the helium tank. A superfluid helium tank having an adiabatic function housed in the helium tank, a first heat exchanger housed in the superfluid helium tank, and a helium tank in the helium tank A second heat exchanger and a Joule-Thomson valve arranged in a space isolated from the liquid helium in the liquid helium and the liquid helium in the superfluid helium; No. 2 heat exchanger, the Joule-Thomson valve, the first heat exchanger, and the liquid helium in the superfluid helium tank by flowing through a path through the space. A superfluid helium generator comprising: a helium guide means for precooling the normal-flowing liquid helium flowing in the first heat exchanger while being cooled down to the space and flowing in the space; As a heat exchanger of a tube, a tube coil formed by winding a tube in the shape of a conical head cylinder is provided, and a flow path having a conical surface adapted to fit to the inner or outer surface of the tube coil so that the tube coil can be fitted. A cross-sectional area adjusting member is provided, and means for varying the degree of fitting of the flow path cross-sectional area adjusting member with the pipe coil is provided according to the outlet temperature of the helium guiding means.

(Operation) If the degree of fitting with the pipe coil is changed by moving the flow passage cross-sectional area adjusting member, the flow passage cross-sectional area of the low pressure / low temperature fluid flowing outside the pipe coil changes. Therefore, if the flow passage cross-sectional area is changed according to the temperature (density) of the low-pressure / low-temperature fluid, it is possible to prevent changes in heat exchange efficiency due to changes in density, and always use with the highest heat exchange efficiency.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a main part of a superfluid helium generator according to an embodiment of the present invention. The superfluid helium generator according to this embodiment differs from the conventional device mainly in the configuration of the JT heat exchanger Ka. Therefore, the same parts as those in FIG. 2 are denoted by the same reference numerals, and the detailed description of the overlapping parts will be omitted.

The JT heat exchanger Ka incorporated in this device is configured as follows. That is, a tapered portion 31 whose diameter gradually increases from the lower side to the upper side is provided at a midway position of the exhaust pipe 13a, and the pipe coil 15a is arranged in close contact with the inner surface of the portion 31. Therefore, the tube coil 15a
Is shaped like a frusto-conical cylinder whose diameter decreases toward the bottom. Then, attach the lower end of the tube coil 15a to the JT
It is connected to the inlet of the valve 14, and the upper end side is inserted into the liquid helium 1 in the superfluid helium tank through the wall of the exhaust pipe 13a.

On the other hand, in the pipe coil 15a, a flow passage cross-sectional area adjusting member 32 is arranged so as to fit into the pipe coil 15a. The flow path cross-sectional area adjusting member 32 is formed into a frustoconical cylinder shape having an inclination angle equal to the inner surface side inclination angle along the axial direction of the tube coil 15a, and a cylindrical portion 33 arranged with the small diameter side facing downward. , And a closing plate 34 provided so as to close the large diameter side of the cylindrical portion 33. The closing plate 34 is connected to the lower end of the operating cylinder 35, and the upper end side of the operating cylinder 34 is connected to a position adjusting mechanism (not shown) provided outside through the exhaust pipe 13a. The operation rod 22 of the JT valve 14 is guided to the outside through the inside of the operation cylinder 35, and a seal member 35 is mounted between the operation rod 22 and the operation cylinder 35 to allow relative movement therebetween. .

With such a configuration, the helium gas discharged from one end 11a of the heat exchanger arranged in the superfluid helium tank 3 will reach the lower end of the exhaust pipe 13a as indicated by the broken line arrow in the figure. After flowing, the JT valve 14 is cooled and then flows between the tapered portion 31 and the tubular portion 33 of the flow passage cross-sectional area adjusting member 32. In this process, the liquid helium flowing in the tube coil 15a is precooled. Then, it flows above the exhaust pipe 13a.

In this case, when the operation cylinder 35 is moved in the direction indicated by the solid arrow 37 in the figure by the position adjusting mechanism provided outside, the interval between the portion 31 and the cylinder portion 33, that is, the flow passage cross-sectional area can be changed. You can In this way, changing the cross-section area
Since the amount of gas in contact with 15a can be changed, the heat exchange efficiency can be changed. Therefore, the exhaust pipe 13a
By adjusting the cross-sectional area of the flow passage according to the temperature of the gas flowing inside, it is possible to always use with the highest heat exchange efficiency, and as a result, the time required for cooling can be shortened.

The present invention is not limited to the above embodiment. For example, fins may be provided on the surface of the tube coil 15a to further improve the heat exchange efficiency. Further, in the above-described embodiment, the flow passage cross-sectional area adjusting member is fitted inside the pipe coil formed in a conical tubular shape, but it is fitted outside the pipe coil to reduce the flow passage cross-sectional area. It may be variable.

[Advantages of the Invention] As described above, according to the present invention, the superfluid helium generator that can be always used with the highest heat exchange efficiency by adjusting the fitting degree between the flow path cross-sectional area adjusting member and the pipe coil. Can be provided.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a main part of a superfluid helium generator according to an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view of a conventional superfluid helium generator. Ka …… JT heat exchanger, 13a …… Exhaust pipe, 15a …… Tube coil, 31
...... Tapered part, 32 …… Flow path cross-sectional area adjusting member, 33 …… Cylinder part, 34 …… Closing plate, 35 …… Operation cylinder.

Claims (1)

[Claims] 1. A helium tank containing normal liquid helium therein, and a heat insulating function housed in the helium tank in such a form that the liquid helium is contained therein and is immersed in the liquid helium in the helium tank. A superfluid helium tank, a first heat exchanger housed in the superfluid helium tank, an ordinary fluid liquid helium in the helium tank and a liquid helium in the superfluid helium tank. A second heat exchanger and a Joule-Thomson valve disposed in a space isolated from the second heat exchanger, the Joule-Thomson valve, and the first While passing through the heat exchanger and the space to cool the liquid helium in the superfluid helium tank to the superfluid temperature and to flow through the space A superfluid helium generator having a helium guide means for precooling the normal-flowing liquid helium flowing in the first heat exchanger, wherein the second heat exchanger is a tube with a conical head cylinder. And a pipe cross-sectional area adjusting member having a conical surface adapted to the inner or outer surface of the pipe coil so that the pipe coil can be fitted to the pipe coil. A superfluid helium generator comprising means for varying the degree of fitting of the flow path cross-sectional area adjusting member with the tube coil according to the temperature.