JPH11182958A - Pulse pipe refrigerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the length of a resonance tube for a heat driving type compressor to miniaturize and compact the same by a method wherein a mixed gas, in which helium and the other rare gas are mixed so that the acoustic velocity of the same becomes smaller than that of helium, is sealed into the resonance tube. SOLUTION: Upon operation, a mixed gas 27 of helium(He) and xenon(Xe) is sealed into a resonance tube. The molecular weight of the mixed gas 27 is increased by four times or more and the acoustic velocity of the same is reduced to the half or less, compared with conventional helium, whereby the length of the resonance tube 21 can be shortened to the half or less of a conventional resonance tube. Further, the Prandtl number of the mixed gas 27 is reduced to one by three (1/3) of helium whereby the thickness of temperature boundary layer of the mixed gas 27 is increased whereby the heat transfer characteristics of a stack 22 and the mixed gas 27 are improved. According to this method, the performance of heat driving type compressor 100 is improved and a miniaturized and compacted pulse pipe refrigerator can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse tube refrigerator having a heat driven compressor used for liquefying liquid hydrogen or the like.

[0002]

2. Description of the Related Art FIG. 3 shows a pulse tube refrigerator using a heat driven compressor utilizing self-excited vibration of gas in a resonance tube as a compressor of a pulse tube refrigerator used for liquefying liquid hydrogen. One example of the related art is shown.

In FIG. 3, reference numeral 1 denotes a cylindrical insulated vacuum container having a bottom for reducing heat intrusion from the outside, and 2 denotes a flange portion for covering an upper portion of the insulated vacuum container 1. Reference numeral 3 denotes a liquid nitrogen tank housed inside the heat-insulating vacuum vessel 1 for shielding radiant heat from room temperature, and reference numeral 4 denotes liquid nitrogen housed in the liquid nitrogen tank 3. Reference numeral 5 denotes a first-stage pulse tube, 7 denotes a first-stage regenerator, and 13 denotes a second-stage regenerator. The high-temperature end of the first-stage pulse tube 5 is connected to the flange portion 2 of the heat-insulated vacuum vessel 1.
And the low-temperature end is connected to the low-temperature end of the first-stage regenerator 7 by a conduit 6.

8a is a first stage bypass pipe connecting the high temperature end of the first stage regenerator 7 and the high temperature end of the first stage pulse tube 5, and 8 is a bypass valve for opening and closing the bypass line 8a. It is. Reference numeral 11 denotes a second-stage pulse tube.
The high-temperature end is thermally coupled to the flange portion 2 and the low-temperature end is connected to a low-temperature end of the second-stage regenerator 13 by a conduit 12.

Reference numeral 14a denotes a second-stage bypass pipe connecting the high-temperature end of the second-stage regenerator 13 and the high-temperature end of the second-stage pulse tube 11, and 14 denotes a bypass valve for opening and closing the bypass pipe 14a. is there. 10 is a bypass pipe 8a for the first stage.
1 is connected to the first stage buffer, 9 is the same buffer 10
And a first-stage orifice valve provided in the connection conduit to the first stage. Reference numeral 16 denotes a second-stage buffer connected to the second-stage bypass pipe 14a, and reference numeral 15 denotes a second-stage orifice valve provided in a connection line to the buffer 16.

The bypass valves 8 and 14 and the orifice valves 9 and 15 control the phase difference between the pressure oscillation and the velocity amplitude fluctuation of the gas in the first pulse tube 5 and the second pulse tube 11. Performs the function of the mechanism. The regenerator 7,
As a material of No. 13, Er ₃ Ni or the like which is a magnetic regenerator material is used.

[0007] Reference numeral 17 denotes a cryogenic fluid such as liquid hydrogen having a boiling point of 4 or less of the above-mentioned liquid nitrogen, which is sealed in a closed container 18. Reference numeral 19 denotes a heat exchanger installed at the low-temperature end of the second-stage regenerator 13.
Is liquefied on the surface of the fins 20 of the heat exchanger 19 so as to become liquid again.

Reference numeral 21 denotes a resonance tube containing a helium gas 25 therein. The resonance tube 21 is provided with a high-temperature side heat exchanger 23, a low-temperature side heat exchanger 24, and a stack 22.
The stack 22 is formed, for example, by stacking stainless steel plates having a thickness of about 0.5 mm at intervals of about 1 mm. 2
Reference numeral 6 denotes a conduit connecting the resonance tube 21 and the first-stage regenerator 7.

The high-temperature side heat exchanger 23 is
When the low-temperature side heat exchanger 24 is kept at room temperature while being heated to about ℃, self-excited vibration is generated in the helium gas 25 penetrating into the stack 22, and a standing wave of pressure vibration is generated in the resonance tube 21. By doing so, the heat driven compressor 100 in which pressure amplitude is constantly generated is configured. The pressure amplitude in the heat driven compressor 100 is transmitted to the first and second pulse tubes 5 and 11 and the regenerators 7 and 13 via the conduit 26.

During operation of the pulse tube refrigerator configured as described above, when a high-pressure gas with a pressure amplitude is introduced from the heat-driven compressor 100 through the conduit 26, the cold storage The gas in the vessels 7, 13 and the first and second stage pulse tubes 6, 11 is pushed by the high pressure gas. The gas having no place to go is generated at the high-temperature ends of the first-stage and second-stage pulse tubes 5 and 11, and the heat is exhausted to the flange portion 2 of the insulated vacuum vessel 1. Next, when low-pressure gas is sent from the heat-driven compressor 100, the regenerators 7, 13
The gas in the first-stage and second-stage pulse tubes 6 and 11 expands while applying cold to the regenerators 7 and 13.

[0011]

However, the bypass pipe refrigerator having the above-mentioned conventional heat driven compressor 100 has the following problems. That is, in the pulse tube refrigerator, as described above, the helium gas 25 sealed in the resonance tube 21 of the heat driven compressor 100 is used as the working gas. However, the same helium gas 2
5 has a very high sound speed, the heat-driven compressor 100
When the resonance frequency is set to several tens Hz which is equal to the operation frequency of the pulse tube refrigerator, the length of the resonance tube 21 becomes longer, and the pulse tube refrigerator including the heat driven compressor 100 becomes larger.

SUMMARY OF THE INVENTION An object of the present invention is to provide a compact and compact pulse tube refrigerator by shortening the length of a resonance tube of a heat driven compressor.

[0013]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a first means of the present invention is to provide a working gas filled in a resonance tube by heating and cooling the working gas. Equipped with a heat driven compressor that generates self-excited vibration,
A pulse tube refrigerator for cooling and liquefying a fluid in a container such as hydrogen by applying a pressure amplitude of a working gas from the heat-driven compressor to a pulse tube and a regenerator of the refrigerator body. A pulse tube refrigerator is characterized in that a mixed gas of helium gas and another rare gas is used as a working gas sealed in the tube, and a mixed gas having a higher sound speed than helium gas is used.

In the first means, it is preferable that the mixed gas is a mixture of helium (He) and xenon (Xe).

According to the above-mentioned means, a mixed gas in which helium is mixed with another rare gas so that the sound speed of the gas is lower than that of helium is sealed in the resonance tube. Even when helium gas is used, the sound speed is reduced by a considerable amount as compared with the use of helium gas.

In particular, when a mixed gas of helium (He) and xenon (Xe) is used as the mixed gas and the molar ratio of both is set to about He = 89% and Xe = 11%, the case where the molecular weight is helium is obtained. The sound speed becomes four times or more, the sound speed becomes half or less, and the length of the resonance tube can be reduced to half or less. In addition, the mixed gas also has a Prandtl number of 1/3 or less of helium, increases the thickness of the temperature boundary layer of the mixed gas in the heat driven compressor, and improves the heat transfer characteristics between the stack and the mixed gas. The performance of the heat driven compressor is improved.

Further, the second means is that the mixed gas on the heat driven compressor side and the working gas on the refrigerator main body side are connected to a conduit connecting the heat driven compressor and the refrigerator main body. A shut-off mechanism such as a bellows with a piston, which shuts off to prevent mixing of both gases and enables transmission of the pressure amplitude on the heat driven compressor side to the refrigerator main body side, is provided.

According to the second means, the xenon (Xe) in the mixed gas is condensed and liquefied at the low temperature end of the regenerator whose temperature is the lowest when the cryogenic fluid is generated. The blocking mechanism provided between the refrigerator and the refrigerator body prevented mixing of the mixed gas in the resonance tube with the working gas on the refrigerator body, so that xenon condensation occurred.
Liquefaction is avoided.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIGS. FIG. 1 is a configuration diagram of a pulse tube refrigerator provided with a heat driven compressor 100 according to an embodiment of the present invention, and FIG. 2 is a table showing an example of chemical and physical properties of a working gas.

In FIG. 1, reference numeral 1 denotes a cylindrical insulated vacuum vessel having a bottom for reducing heat intrusion from the outside, and 2 denotes a flange portion for covering the upper part of the insulated vacuum vessel 1. Reference numeral 3 denotes a liquid nitrogen tank housed inside the heat-insulating vacuum vessel 1 for shielding radiant heat from room temperature, and reference numeral 4 denotes liquid nitrogen housed in the liquid nitrogen tank 3. 5 is a first-stage pulse tube, 7 is a first-stage regenerator, and 13 is a second-stage regenerator.
As a material of No. 13, Er ₃ Ni, which is a magnetic regenerator, is used. The high-temperature end of the first-stage pulse tube 5 is thermally coupled to the flange portion 2 of the heat-insulated vacuum vessel 1, and the low-temperature end is connected to the low-temperature end of the first-stage regenerator 7 by a conduit 6. I have.

Reference numeral 8a denotes a first-stage bypass pipe connecting the high-temperature end of the first-stage regenerator 7 to the high-temperature end of the first-stage pulse tube 5, and 8 denotes a bypass valve for opening and closing the bypass line 8a. It is. Reference numeral 11 denotes a second-stage pulse tube.
The high-temperature end is thermally coupled to the flange portion 2 and the low-temperature end is connected to a low-temperature end of the second-stage regenerator 13 by a conduit 12.

Reference numeral 14a denotes a second-stage bypass pipe connecting the high-temperature end of the second-stage regenerator 13 and the high-temperature end of the second-stage pulse tube 11, and 14 denotes a bypass valve for opening and closing the bypass pipe 14a. is there. 10 is a bypass pipe 8a for the first stage.
1 is connected to the first stage buffer, 9 is the same buffer 10
And a first-stage orifice valve provided in the connection conduit to the first stage.

Reference numeral 16 denotes the bypass pipe 1 for the second stage.
A second-stage buffer connected to 4a, 15 is a second-stage orifice valve provided in a connection line to the buffer 16.

Reference numeral 17 denotes a cryogenic fluid such as liquid hydrogen having a boiling point of 4 or less of the above-mentioned liquid nitrogen, which is sealed in a closed container 18. Reference numeral 19 denotes a heat exchanger installed at the low-temperature end of the second-stage regenerator 13 and has fins 20 provided above the cryogenic fluid 17 in the vessel 18. The configuration of the pulse tube refrigerator described above is the same as that of the prior art shown in FIG.

In the embodiment of the present invention, the heat driven compressor 100 is improved. That is, in FIG.
Is a resonance tube of the heat driven compressor 100,
A mixed gas 27 composed of helium gas and a rare gas other than helium gas is sealed therein. As an example of the mixed gas 27, as shown in FIG. 2, there is one having a molar ratio of helium (He) and xenon (Xe) of 89% / 11%.
FIG. 2 shows the chemical and physical properties of the helium gas and the mixed gas applied to this embodiment.

The resonance tube 21 is provided with a high-temperature side heat exchanger 23, a low-temperature side heat exchanger 24 and a stack 22. The stack 22 is formed, for example, by stacking stainless steel plates having a thickness of about 0.5 mm at intervals of about 1 mm. A conduit 26 connects the resonance tube 21 and the first-stage regenerator 7.

Reference numeral 28 denotes a container provided in the conduit 26. A plate 29 also serving as a piston and a partition plate and a bellows 30 for supporting the plate 29 on the container 28 are provided in the container 28, and the plate 29 and the bellows 30 serve as a heat-driven compressor 100 side and a refrigerator main body. The gas with the 200 side is shut off.

During operation of the pulse tube refrigerator having the above configuration, the high temperature side heat exchanger 23 of the heat driven compressor 100 is heated to about 400 ° C. and the low temperature side heat exchanger 24 is maintained at room temperature. The self-excited vibration is generated in the mixed gas 27 entering the stack 22, and the standing wave of the pressure vibration is generated in the resonance tube 21, so that the pressure amplitude is constantly generated. The pressure amplitude acts on the plate 29 and the bellows 30 in the container 28 via the conduit 26, and the plate 29 and the bellows 30 expand and contract, and the first stage on the refrigerator main body 200 side via the conduit 26. Are transmitted to the second-stage pulse tubes 5 and 11 and the regenerators 7 and 13.

7, 13 and first and second stage pulse tubes 6,
The gas in 11 is pushed by the mixed gas with the above pressure amplitude. And the gas with no place to go is the first stage,
Heat is generated at the high-temperature ends of the second-stage pulse tubes 5 and 11, and the heat is discharged to the flange portion 2 of the heat-insulated vacuum vessel 1. Next, when a low-pressure gas is sent from the heat-driven compressor 100,
The gas in the regenerators 7 and 13 and the first and second stage pulse tubes 6 and 11 expands while applying cold to the regenerators 7 and 13. In the container 18, the cryogenic fluid 1
7, the fluid liquefies on the surface of the fins 20 of the heat exchanger 19 provided in the container 18, becomes a liquid again, and is stored at the bottom of the container 18.

The bypass valves 8 and 14 and the orifice valves 9 and 15 are connected to the first-stage pulse tube 5 and the second
It controls the phase difference between pressure oscillations and velocity amplitude variations of the gas in the stepped pulse tube 11.

In this operation, the resonance tube 21
Helium (He) and Xenon (Xe) as shown in FIG.
The mixed gas 27 has a molecular weight that is four times or more as compared with that of the conventional helium 25 and the sound speed is reduced to less than half, so that the length of the resonance tube 21 is also less than half. Is shortened to Further, since the Prandtl number of the mixed gas 27 is also reduced to 1/3 or less of the helium 25, the temperature boundary layer thickness of the mixed gas 27 is increased, and the heat transfer characteristic between the stack 22 and the mixed gas 27 is improved. . Thereby, the performance of the heat driven compressor 100 is also improved.

Further, using the mixed gas 27 of helium (He) and xenon (Xe) according to the embodiment of the present invention,
It is most preferable that the mixed gas 27 be passed directly to the regenerators 7 and 13 as the working gas of the refrigerator main body 200 to liquefy the hydrogen in the container 18 to generate the cryogenic fluid (liquid hydrogen) 17. Second-stage regenerator 13 whose temperature drops
At the low temperature end, xenon (Xe) in the mixed gas 27 is condensed and liquefied. In the embodiment of the present invention, the vessel 26 is connected to the conduit 26 connecting the heat driven compressor 100 and the refrigerator main body 200. Since the mixed gas 27 in the resonance tube 21 and the working gas on the side of the refrigerator main body 200 are cut off by providing the plate 29 and the bellows 30 supported in the piston 28, the condensation and liquefaction of xenon are prevented. , The refrigerator operates smoothly.

[0033]

The present invention is configured as described above.
According to the present invention, since a mixed gas in which helium and another noble gas are mixed in the resonance tube so that the sound speed of the gas is lower than that of helium is sealed, the required length of the resonance tube is reduced due to the decrease in the sound speed. The sound speed is reduced by a considerable amount compared to the time of use. As a result, the length of the heat driven compressor is shortened, and a compact and compact pulse tube refrigerator can be obtained.

If a mixed gas of helium and xenon is used as the mixed gas, the Prandtl number of the mixed gas is reduced to 1/3 or less of that of helium. And the heat transfer characteristics between the stack and the mixed gas are improved, and the performance of the heat driven compressor is improved.

Further, according to the third and fourth aspects of the present invention, the gas mixture in the resonance tube and the operation of the refrigerator main body side are controlled by a shut-off mechanism provided between the heat driven compressor and the refrigerator main body. Since the mixing with the gas is prevented, the condensation and liquefaction of xenon at the low-temperature end of the regenerator are prevented, so that the operation of the pulse tube refrigerator due to such a phenomenon can be prevented.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a pulse tube refrigerator according to an embodiment of the present invention.

FIG. 2 is a table showing chemical and physical properties of the working gas for a refrigerator.

FIG. 3 is a diagram showing a conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 heat-driven compressor 200 refrigerator main unit 1 adiabatic vacuum vessel 2 flange 3 liquid nitrogen tank 4 liquid nitrogen 5 first stage pulse tube 6,12 conduit 7 regenerator (first stage) 8,14 bypass valve 8a, 14a Bypass pipe 9,15 orifice valve 10,16 buffer 11 second stage pulse tube 13 regenerator (second stage) 17 cryogenic fluid 18 container 19 heat exchanger 20 fin 21 resonance tube 22 stack 23 high temperature side heat exchanger 24 low temperature Side heat exchanger 26 Conduit 27 Mixed gas 28 Container 29 Plate 30 Bellows

Claims (4)

[Claims] A working gas sealed in a resonance tube is heated and
A heat driven compressor that generates self-excited vibration in the working gas by cooling is provided, and the pressure amplitude of the working gas from the heat driven compressor is applied to the pulse tube and regenerator of the refrigerator main body. In a pulse tube refrigerator for cooling and liquefying a fluid in a container such as hydrogen, a mixed gas of helium gas and another rare gas having a sound velocity higher than that of helium gas is mixed with the working gas sealed in the resonance tube. A pulse tube refrigerator characterized by using gas. 2. The pulse tube refrigerator according to claim 1, wherein the mixed gas is a mixture of helium (He) and xenon (Xe). 3. A method of heating working gas sealed in a resonance tube.
A heat driven compressor that generates self-excited vibration in the working gas by cooling is provided, and the pressure amplitude of the working gas from the heat driven compressor is applied to the pulse tube and regenerator of the refrigerator main body. In a pulse tube refrigerator for cooling and liquefying a fluid in a container such as hydrogen, the mixed gas and the refrigerator on the side of the thermally driven compressor are connected to a conduit connecting the thermally driven compressor and the refrigerator main body. A shut-off mechanism, such as a bellows with a piston, that shuts off the working gas on the main body side to prevent mixing of both gases, and enables transmission of the pressure amplitude of the heat driven compressor to the refrigerator main body side. Tube refrigerator provided with 4. A pipe line for connecting the heat driven compressor and the refrigerator main body, wherein the mixed gas on the heat driven compressor side and the working gas on the refrigerator main body side are cut off and both gases are shut off. The pulse according to claim 1 or 2, further comprising a shut-off mechanism such as a bellows with a piston for preventing the mixing of the heat-driven compressor and transmitting the pressure amplitude of the heat-driven compressor to the refrigerator main body. Tube refrigerator.