JPH0611199A - Supercritical helium generating device - Google Patents

Abstract

PURPOSE:To provide a supercritical helium generating device, capable of generating cryogenic supercritical helium efficiently and stably by a simple constitution for the device. CONSTITUTION:Helium gas in a low-pressure side liquid helium reserving tank 32 is sucked by an ejector 40 to bring the inside of the reserving tank 32 into a condition of low pressure. The driving fluid of the ejector 40 is cooled by heat exchangers 33, 34 in liquid helium reserving tanks 31, 32 to supercritical helium and is introduced into a high-pressure side liquid helium reserving tank through the ejector 40. The liquid helium of the low-pressure side liquid helium tank 32 is supplied while expanding high-pressure and low-temperature helium, deprived by cooling through the first heat exchanger 33 in the high-pressure side liquid helium reserving tank 31, through, a JT value 42.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a supercritical helium generator, and more particularly to a device for efficiently generating supercritical helium for cooling a superconducting magnet or the like to an extremely low temperature.

[0002]

2. Description of the Related Art Supercritical helium has heretofore been used as a means for cooling the above superconducting magnet and the like to an extremely low temperature of several K. As a means for generating this supercritical helium, a heat exchanger is installed in a storage tank that stores liquid helium having an appropriate saturation temperature in accordance with the supply temperature of supercritical helium, and the supercritical helium is flown through the heat exchanger. A device for cooling to a desired temperature is used.

That is, as shown in FIG. 4, a heat exchanger 2 is provided in a liquid helium storage tank 1 which stores low temperature liquid helium LHe.
Is provided, and the heat exchanger 2 is provided with a compressor 10, a heat exchanger group 4,
It is supplied through a pipe 3 from a helium refrigerator composed of an appropriate number of expansion turbines and pipes connecting them, and returns to a heat exchanger group 4 to exchange heat with helium to obtain a high pressure. Helium is flowed to generate supercritical helium at a desired temperature.

The above-mentioned supercritical helium is supplied via a tube 5 to a cooled object such as a superconducting magnet, and is supplied to a cooling path 6 for cooling it. After cooling the object to be cooled, the helium reaches the JT valve 8 through the pipe 7, expands and becomes a multiphase flow of liquid helium and helium gas, and flushes into the liquid helium storage tank 1.

The helium gas generated in the liquid helium storage tank 1 is led out to the pipe 9 as return helium, and after the high pressure helium supplied is cooled by the heat exchanger 4, it is sucked into the compressor 10 and Circulate the path.

In the apparatus having such a structure, the pressure in the liquid helium storage tank 1 must be set to the atmospheric pressure or lower depending on the temperature of the supercritical helium required to sufficiently cool the object to be cooled. When the inside of the liquid helium storage tank 1 becomes atmospheric pressure or less, the helium sucked into the compressor 10 through the pipe 9 also becomes atmospheric pressure or less, and therefore the compressor 10
The suction pressure of becomes negative pressure. When the suction pressure of the compressor 10 becomes the atmospheric pressure or the negative pressure as described above, the volume flow rate increases, the compressor 10 becomes large-sized, and the compression ratio increases and the efficiency decreases.

For this reason, as shown in FIG. 5, two high-pressure and low-pressure liquid helium storage tanks 11a and 11b are provided, and heat exchangers 12a and 12b are respectively installed,
By cooling the helium in two stages, the load on the low-pressure side liquid helium storage tank 11b is reduced, and the recovery amount of helium below atmospheric pressure from the low-pressure side liquid helium storage tank 11b is reduced.

The above liquid helium storage tanks 11a, 11
The high pressure and the low pressure in b mean the relative high and low pressures of both, and are different from the general concept of high-pressure gas.

In the apparatus shown in FIG. 5, high-pressure helium supplied from a helium refrigerator (not shown) through the pipe 13 is cooled by the heat exchanger group 14 and the heat exchangers 12a and 12b, and the pipe 15 cools the object to be cooled. Is supplied to the cooling path 16 for cooling the. Helium led out from the cooling passage 16 to the pipe 17 is
The JT valve 18 expands to form a gas-liquid mixed phase flow, which flashes into the liquid helium storage tank 11a on the high pressure side.

From the liquid helium storage tank 11a on the high pressure side, a helium gas is discharged through a pipe 19, and
Liquid helium is supplied to the low-pressure side liquid helium storage tank 11b from the bottom through the flow rate control valve 20. Further, low-pressure helium gas is led out from the low-pressure liquid helium storage tank 11b by a pipe 21.

The helium gas in the pipe 19 is sucked into the compressor of the helium refrigerator in the same manner as described above, and the low-pressure helium gas in the pipe 21 is separated from the helium gas in the pipe 19 by a separately provided low-pressure compressor or the like. After raising the pressure to the same level, it is sucked into the compressor of the helium refrigerator.

[0012]

As described above, since the liquid helium storage tank has two stages, the processing flow rate of the compressor having a low suction pressure can be reduced, and the efficient problem of the compressor is solved to some extent. However, since there are two systems of return helium, there is a problem that the number of flow paths of the heat exchanger group for heat exchange between the return helium and the supplied high-pressure helium increases, and the device becomes complicated. there were.

Therefore, an object of the present invention is to provide a supercritical helium generator capable of efficiently and stably generating cryogenic supercritical helium with a simple device structure.

[0014]

In order to achieve the above object, the supercritical helium generator of the present invention has, as a first configuration, a compressor for compressing helium, and heat exchange between return helium and compressed helium. Heat exchanger, expansion turbine for adiabatic expansion of compressed helium, low temperature compressed helium JT
In a supercritical helium generator equipped with a JT valve for expansion, a liquid helium storage tank with a built-in cooling heat exchanger,
Two liquid helium storage tanks having different saturation pressures, heat exchangers respectively provided in the liquid helium storage tanks, high-pressure low-temperature helium heat exchangers in the high-pressure side liquid helium storage tanks, low-pressure side liquid helium storage tanks After being sequentially introduced into a heat exchanger inside and cooled, a means for supplying the cooled object and a high-pressure helium after cooling the cooled object are used as a drive source to suck the helium gas in the low-pressure liquid helium storage tank. An ejector, a means for introducing the helium after the ejector is introduced into the high-pressure side liquid helium storage tank, and a part of the high-pressure low-temperature helium derived from the heat exchanger in the high-pressure side liquid helium storage tank are branched and expanded. And a means for introducing the liquid helium into the liquid helium storage tank on the low pressure side.

According to a second aspect of the present invention, the drive source of the ejector is part of the high-pressure low-temperature helium in place of the high-pressure helium after cooling the object to be cooled, and the high-pressure helium after cooling the object to be cooled is used. After expanding the high-pressure helium, a means for introducing the high-pressure helium into the high-pressure side liquid helium storage tank is provided.

[0016]

[Operation] According to the first configuration, the high-pressure low-temperature helium supplied from the helium refrigerator is cooled by both heat exchangers to cool the cooled object, and then expanded by the ejector to expand the liquid on the high-pressure side. Introduced into the helium storage tank. At this time, since the low-pressure liquid helium gas in the low-pressure side liquid helium tank is sucked by the ejector, the low-pressure side liquid helium tank can be set in a desired low-pressure state, and the low-pressure helium gas is also sucked by the ejector and is high Since it is introduced into the liquid helium storage tank on the side and returned from the storage tank as helium to the compressor of the helium refrigerator, it is not necessary to increase the return helium flow path of the heat exchanger group of the helium refrigerator.

Liquid helium is supplied to the low-pressure side liquid helium storage tank from a helium refrigerator, and is cooled by a heat exchanger in the high-pressure side liquid helium storage tank and discharged to obtain high-pressure low-temperature supercritical helium. The flash loss can be reduced because it is expanded. Further, since the flash loss is small, the amount of low-pressure helium gas to be sucked by the ejector can be reduced.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail below based on the embodiments shown in the drawings. First, FIG. 1 shows the first of the present invention.
An example is shown. This supercritical helium generator includes two liquid helium storage tanks 31 and 32 on the high pressure side and the low pressure side having different saturation pressures, and the liquid helium storage tanks 31 and 3.
First and second heat exchangers 3 respectively provided in 2
3, 34 and the high-pressure low-temperature helium supplied from the pipe 36 through the heat exchanger group 35 of the helium refrigerator having the same configuration as described above, the first heat exchange provided in the high-pressure side liquid helium storage tank 31. Vessel 33 and low-pressure side liquid helium storage tank 3
2 is introduced into the second heat exchanger 34 in order and cooled to make supercritical helium, and then a pipe 38 is supplied to a cooling path 37 for cooling the object to be cooled; Using high pressure helium in the supercritical state after cooling the body,
An ejector 40 for sucking the helium gas in the low-pressure liquid helium storage tank 32 through a pipe 39, and a pipe 41 for introducing helium into a gas-liquid multiphase flow after the ejector 40 is introduced into the high-pressure liquid helium storage tank 31. And a part of the high-pressure low-temperature helium in the supercritical state derived from the first heat exchanger 33 in the high-pressure side liquid helium storage tank 31 is branched,
A pipe 43 for introducing into the low pressure side liquid helium storage tank 32 after being expanded by the T valve 42, and a high pressure side liquid helium storage tank 31.
Helium gas in the heat exchanger group 35 of the helium refrigerator
And a pipe 44 for returning to the compressor via the.

Since the helium refrigerator including the heat exchanger group 35 can be constructed in the same manner as the conventional one, detailed illustration and description thereof will be omitted.

In the supercritical helium generator configured as described above, the circulating helium compressed by the compressor of the above-mentioned helium refrigerator is cooled by the heat exchanger group 35 and the expansion turbine by being cooled, and After passing through the final-stage heat exchanger of the exchanger group 35, a supercritical state or a state close to a supercritical state is established. For example, low-temperature helium gas supplied from a pipe 36 at a pressure of 14 kg / cm ² G and a temperature of 6 K is used for the first heat exchange The vessel 33 and the second heat exchanger 34 are sequentially cooled to generate, for example, supercritical helium having a temperature of about 4.2 K, and the tube 3
8 to supply to a cooling path 37 for cooling a cooled object such as a superconducting magnet.

At this time, in order to cool the supplied supercritical helium to 4.2K, the liquid helium in the low pressure side liquid helium storage tank 32 is 4.2K or less, for example, 4.2K.
It is necessary to set the pressure to 15K, but the corresponding pressure is 0.
It will be 93 atm.

Therefore, in the above-mentioned conventional apparatus, the suction pressure of the compressor becomes a negative pressure and the compression ratio of the compressor is increased, so that the efficiency is significantly lowered, and the flow paths of the heat exchanger group are increased, so that the apparatus configuration is increased. However, by sucking the helium gas in the low-pressure side liquid helium storage tank 32 by the ejector 40 as described above, the low-pressure side liquid helium storage tank 32 can be used without using a low-pressure compressor or a vacuum pump. Within 0.
It can be maintained at a pressure of 93 atm.

Further, since the high pressure helium after the cooling passage 37 of the cooled object is led out is used as the drive source of the ejector 40, the energy at the time of expansion which has been conventionally expanded by the JT valve is converted into the low pressure helium gas. It can be effectively used as inhalation energy.

Further, the low-pressure helium gas is stored in the high-pressure side liquid helium storage tank 31 together with the expanded high-pressure helium gas.
Since it is introduced into the storage tank 31, the saturation pressure in the storage tank 31, for example, 1.28 atm. Therefore, the gas returned to the compressor is only the helium gas having the pressure in the high-pressure side liquid helium storage tank 31, the suction pressure of the compressor does not become a negative pressure, and the number of flow paths of the heat exchanger group 35 does not change. Need not be increased.

Liquid helium is supplied to the low pressure side liquid helium storage tank 32 from the helium refrigerator, and the first heat exchanger 33 in the high pressure side liquid helium storage tank 31 is supplied.
Since a part of the high-pressure and low-temperature helium in the supercritical state cooled in step 2 is branched and JT-expanded, the flash loss can be reduced. Further, since the flash loss is small, the amount of helium gas generated in the low-pressure side liquid helium storage tank 32 is also reduced, and thus the amount of low-pressure helium gas to be sucked by the ejector can be reduced,
It becomes possible to generate supercritical helium at a lower temperature by making the pressure inside the storage tank 31 lower.

Next, FIG. 2 shows a second embodiment of the present invention. In the following description, the same elements as those in the first embodiment will be designated by the same reference numerals and detailed description thereof will be omitted.

In this embodiment, a part of the high-pressure low-temperature helium supplied from the pipe 36 through the heat exchanger group 35 of the helium refrigerator is used as the drive source of the ejector 40. That is, the pipe 50 is branched from the pipe 36, and the pipe 50
Ejector 40 is installed in the low pressure side liquid helium storage tank 3
2 is configured to suck the helium gas inside, and the helium after cooling the cooling path 37 of the cooled object is
The JT valve 51 expands and flushes into the high-pressure side liquid helium storage tank 31.

With this configuration, even if the temperature of helium after cooling the cooling passage 37 of the object to be cooled 37 is high and the liquid helium required in the high-pressure side liquid helium storage tank 31 is not sufficiently obtained. Stable operation can be performed.

FIG. 3 shows a third embodiment of the present invention, in which the suction efficiency of the low pressure helium gas in the ejector 40 is improved, and a control system is added to the device having the configuration shown in FIG. It is a thing.

First, in the apparatus of the present embodiment, a heat exchanger 61 for exchanging heat with the liquid helium in the high-pressure side liquid helium storage tank 31 is provided in the middle of the pipe 39 for discharging the helium gas from the low-pressure side liquid helium storage tank 32. After the low-pressure helium gas is cooled by the heat exchanger 61, the low-pressure helium gas is sucked by the ejector 40.

As a result, the temperature of the gas sucked by the ejector 40 can be lowered, and the suction efficiency can be improved.

In the apparatus of this embodiment, a liquid level gauge L and a pressure gauge P are provided in the low pressure side liquid helium storage tank 32 so that the liquid amount and the pressure in the low pressure side liquid helium storage tank 32 are kept constant. .

That is, the liquid level gauge L detects the liquid level height in the low-pressure side liquid helium storage tank 32, and J according to the detected value.
The opening degree of the T valve 42 is adjusted, and thereby the liquid amount is adjusted. Further, the pressure gauge P detects the pressure in the low pressure side liquid helium storage tank 32 and adjusts the opening degree of the pressure control valve 62 according to the detected value, whereby the low pressure side liquid helium storage tank 32 is obtained.
Adjust the pressure inside.

As a result, the low-pressure side liquid helium storage tank 32
The amount and pressure of the liquid inside can be automatically kept constant, and stable operation can be performed.

[0035]

As described above, in the supercritical helium generator of the present invention, a low pressure liquid helium storage tank can be obtained very easily by sucking the helium gas in the storage tank with an ejector. It is possible to supply supercritical helium at an extremely low temperature. Moreover, since the efficiency of the compressor of the helium refrigerator is not reduced and the flow path of the heat exchanger group is not increased, the device configuration can be simplified and the manufacturing cost and the operating cost can be reduced. .

Further, liquid helium to be supplied to the low-pressure side storage tank is supplied from a helium refrigerator, cooled by a heat exchanger in the high-pressure side liquid helium storage tank, and expanded to expand the supercritical high-pressure low-temperature helium. Since the flash loss can be reduced and the amount of low-pressure helium gas to be sucked by the ejector can be reduced, supercritical helium at a lower temperature can be supplied.

[Brief description of drawings]

FIG. 1 is a system diagram showing a first embodiment of a supercritical helium generator of the present invention.

FIG. 2 is a system diagram showing a second embodiment of the same.

FIG. 3 is a system diagram of a third embodiment of the same.

FIG. 4 is a system diagram showing an example of a conventional supercritical helium generator.

FIG. 5 is a system diagram showing another example of the same.

[Explanation of symbols]

31 ... High-pressure side liquid helium storage tank 32 ... Low-pressure side liquid helium storage tank 33 ... First heat exchanger 34 ... Second heat exchanger 35 ...
Heat exchanger group 37 ... Cooling path 40 ... Ejector 42 ... JT valve L ... Liquid level gauge P ... Pressure gauge

Claims (2)

[Claims] 1. A compressor for compressing helium, a heat exchanger for exchanging heat between return helium and compressed helium, an expansion turbine for adiabatically expanding compressed helium, a JT valve for JT expanding low temperature compressed helium, and a heat exchanger for cooling. In a supercritical helium generator including a liquid helium storage tank and the like containing therein, two liquid helium storage tanks having different saturation pressures, and heat exchangers respectively provided in the liquid helium storage tanks,
High-pressure low-temperature helium is introduced into the heat exchanger in the high-pressure side liquid helium storage tank and the heat exchanger in the low-pressure side liquid helium storage tank in order, and after cooling, means for supplying to the cooled object, and cooling the cooled object After using the high-pressure helium as a drive source, an ejector for sucking the helium gas in the low-pressure side liquid helium storage tank, a means for introducing the helium after ejecting the ejector into the high-pressure side liquid helium storage tank, and the high-pressure side Supercritical helium generation, characterized in that a part of the high-pressure low-temperature helium derived from the heat exchanger in the liquid helium storage tank is branched, expanded, and then introduced into the low-pressure side liquid helium storage tank. apparatus. 2. A drive source of the ejector is a part of the high-pressure low-temperature helium in place of the high-pressure helium after cooling the object to be cooled, and the high-pressure helium after cooling the object to be cooled is expanded. The supercritical helium generator according to claim 1, further comprising means for introducing the liquid helium storage tank on the high pressure side.