JPS61250482A - Method of preventing heat intrusion of he liquefying refrigerator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to extremely low temperatures such as the cryogenic environment part of the H'e liquefaction refrigeration system and the cryogenic refrigerant transfer pipe, so it is easy to apply to many people. The present invention relates to a method for preventing heat intrusion at a site without incurring equipment costs and running costs as much as possible.

In He liquefaction refrigerators, there is a large temperature difference between the cryogenic part and the room temperature part, so there is an unavoidable problem in the structure in which helium enters the cryogenic part from the room temperature part by radiation or conduction. Therefore, by providing a heat shield section between the room temperature section and the extremely low temperature section and supplying cold to the heat shield section, heat intrusion into the extremely low temperature section is prevented as much as possible. For example, in terms of radiation heat transfer, the temperature of the heat shield part is loo'K.
It is known that the amount of radiant heat input to the extremely low temperature section can be reduced to about 1/Zoo of the amount of radiation from the room temperature section. By the way, as a method of supplying cold to the heat shield section, the following methods have been proposed or implemented.

(Method of Supplying Liquid Nitrogen) A He refrigerator, which is a typical example of a cryogenic device that applies the thermodynamic principles of the Claude cycle or Brighton cycle, is illustrated as follows. Figure 3 shows the He refrigerator. In the schematic explanatory diagram illustrating, the He refrigeration system M1 is composed of heat exchangers 5a to 5e, expanders 7a and 7b, a Joule-Thompson (hereinafter referred to as JT) valve 6, etc., and a vacuum insulation container 4 containing these. a He liquefaction refrigerator 2, a compressor connected to the population side of the refrigerator 2; It is mainly composed of a cryogenic environment m10 connected to the outlet side of the refrigerator a2.

After the He gas is pressurized by Li1 machine 3,
The expander 7 is lowered through the fifth heat exchangers 5a to 5e (hereinafter, this descending flow path is referred to as the "high pressure side flow path") and receives heat exchange.
It is cooled by the cold generated in a and 7b, and further JTTe
After being partially liquefied by isenthalpic expansion to nearly 3 atmospheric pressure and becoming a gas-liquid mixture of He, that is, He mist, the cryogenic refrigerant is sent from the cryogenic refrigerant transfer pipe 8 into the cryogenic environment IO, and the The object to be cooled 9 placed in the section 10 is cooled to an extremely low temperature. A typical example of a specific use of the cryogenic environment section 10 is, for example, cooling of a superconducting coil using the TFL conduction phenomenon at a cryogenic temperature.

Now, the He mist that has been vaporized by absorbing the heat of the object to be cooled 9 existing in the cryogenic environment section 10 turns into He gas and rises through the heat exchangers 5a to 5e of the liquefaction refrigerator 2 in the opposite direction (hereinafter referred to as He mist). )°This L! A, the flow path is referred to as a "low pressure side flow path"), and after cooling the He gas flowing through the counterflow high pressure side flow path, it becomes He gas at approximately normal temperature and normal pressure and returns to compression fi3. By circulating the He gas through this wave path, the object to be cooled 9 in the cryogenic environment section IO is continuously kept at a cryogenic temperature.

In such a He liquefaction refrigeration system, the cryogenic environment section 10
In addition, the cryogenic refrigerant transfer pipe 8 is not housed in the vacuum insulation container 4, and since the cryogenic refrigerant is stored or flows, the temperature difference between the cryogenic refrigerant transfer pipe 8 and the room temperature part is large. Ability is wasted.

Therefore, for the purpose of preventing heat intrusion, it is considered necessary to provide a mechanism for shielding radiant heat in the cryogenic refrigerant transfer section 8a and the cryogenic environment section IO, respectively. As shown in FIG.
It is possible to use a method of providing heat shielding by disposing a lb. lb and supplying a refrigerant such as liquefied N2 thereto.

However, the method shown in Figure 4.5 requires the installation of liquid N2 supply equipment and supply amount control equipment, which has the disadvantage of high equipment costs. If there is no supply, the required capacity cannot be demonstrated, so there is a problem that the degree of freedom in operation is low, and a large amount of running cost is required because liquid N2 is consumed.
As shown in the figure, it is possible to use the cooling of the evaporated gas of cryogenic liquid, but this method cannot work effectively unless the container has a small mouth and a long length, such as a dewar bottle. Therefore, it is difficult to apply it to general cryogenic environment parts with large diameters.

[Problems to be Solved by the Invention] The present invention has been made with attention to these circumstances, and aims to prevent heat intrusion into the cryogenic chilled tofu transfer pipe and the cryogenic environment while suppressing equipment costs and running costs. This is intended to provide a method that can be used.

[Means for Solving the Problems] The present invention, which has achieved objective L1, provides a heat shield section around the cryogenic environment section and the cryogenic refrigerant transfer pipe, and connects it to the exhaust pipe or high pressure of any expander. The gist is that the cooling gas flowing through the side flow path is supplied to the heat shield section.

[Function] As described above, by supplying a cold temperature of about 100' to the mature shield part, the heat intrusion can be reduced to 1/100, and the heat intrusion becomes almost no problem. Therefore, in the present invention, as a rough guide, we select a part in the He liquefaction refrigerator where a refrigerant of about 100' flows, and supply the cold gas extracted from there to the cryogenic refrigerant transfer pipe and the heat shield part of the cryogenic environment part. I decided to do so. In other words, since the refrigerant gas produced by the He liquefied refrigerator itself is supplied to the heat shield part, there is no need to provide a liquid N2 storage tank or a liquid N2 supply line outside the system, which reduces equipment costs, and also reduces the amount of gas supplied. After passing through the heat shield, the refrigerant gas is returned to the low-pressure side flow path of the He liquefaction refrigerator, so the refrigerant gas is not consumed. In other words, the refrigerant gas is not used like when using a separately prepared refrigerant such as liquid N2. Since there is no need to dissipate the refrigerant gas into the air, there is no need for refrigerant costs, and running costs can be significantly reduced.

Although it is preferable to use the exhaust pipe of the high-temperature side expander or the high-pressure side flow path through which the high-pressure gas cooled by the refrigeration generated by the high-temperature side expander flows as the outlet for the cooling gas supplied to the heat shield, the cooling gas temperature Since there is no problem even if the temperature is lower than the above (approximately 100'), the cooling gas may be taken out from the exhaust pipe of another expander or the high-pressure side passage through which the cooling gas at a lower temperature flows.

[Example] Fig. 1 is a flow diagram #J showing an embodiment of the method of the present invention, in which cryogenic refrigerant transfer pipe 8. Heat shield parts 11, lla, llb,
LLC and lid are installed. Then, the cooling gas extraction pipe 20 is branched from the exhaust part of the expander 7a on the high temperature side, and a flow path is connected so that the cooling gas flows in the order of the heat shield parts 11, 11a-1id, and then passes through these heat shield parts. The cooled gas is returned to the flow path 11 through which the cooling gas from the high-temperature side expander 7a is introduced into the low-pressure side flow path. Note that a throttle 12 is interposed in the flow path 11 to adjust the flow rate of the cooling gas flowing to the heat shield portion 11 and the like.

In the embodiment described above, the cryogenic refrigerant transfer pipe 8 and the cryogenic environment section 1O are thermally protected by the heat shield sections 11a to 11lid, so that heat intrusion from the room temperature section is prevented. Also, since the inside of the vacuum insulated container 4 is cooled by the heat shield part 11, the heat exchanger, especially the low temperature side heat exchanger 5e, 5d
This prevents heat from entering. In addition, liquid N is used to prevent heat intrusion.
2. Since no supply equipment is required, the equipment cost is small.
Since the cooling gas that has passed through is returned to the low-pressure side flow path via the flow path 21, the refrigerant gas is not lost, and heat intrusion can be economically prevented. FIG. 2 is a flow explanatory diagram showing another embodiment, in which the apparatus is roughly the same as that in FIG. 1, and in particular, the mature shield section 11. lla to 1lcl are provided at the same locations as above. However, these mature shield parts 11
, lla to lid is drawn out from the high pressure side passage H between the heat exchangers 5b and 50. Further, the gas that has passed through the heat shield portions 11, 1la-11cf is returned to the low-pressure side flow path between the heat exchangers 5c and 5b via the pressure reducing valve 19.

In this embodiment, the same effects as described above can be obtained.

[Effects of the Invention] The present invention is configured as described above, and can prevent heat intrusion while significantly reducing equipment costs and running costs.

[Brief explanation of the drawing]

FIGS. 1 and 2 are flow explanatory diagrams showing embodiments of the present invention, and FIGS. 3 to 6 are schematic diagrams for explaining a conventional heat intrusion prevention method. l...He liquefaction refrigerator 2...He liquefaction refrigerator 3
...Compressor 4...Vacuum insulation container 5a~
5e heat exchanger 6...JT valve? a, 7b...
Expander 8... Cryogenic refrigerant transfer pipe lO... Cryogenic environment section

Claims (1)

[Claims] The high-pressure He gas obtained by the compressor is precooled in stages by heat exchange using the cold obtained by multiple expanders, and then passed through a Joule-Thomson valve to generate liquid He. A method for preventing heat intrusion in a He liquefaction refrigeration system that is supplied to a low-temperature environment section, in which a heat shield section is provided around the cryogenic environment section and the cryogenic refrigerant transfer pipe, and the exhaust pipe of any expander or high pressure The cooling gas flowing through the side flow path is supplied to the heat shield part, and the cooling gas that has passed through the heat shield part is returned to the low pressure side flow path.
Method for preventing heat intrusion into e-liquefaction refrigeration equipment.