JPH0349019B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a refrigeration system such as Stirling, Gifford-McMahon, etc. that obtains refrigeration below 10K, and is used for cooling superconducting magnets, Josephson elements, or adsorption panels of cryopumps. used as.

[Prior art]

US Pat. No. 3,692,099 discloses a conventional refrigeration system that uses a substance in a gaseous state at room temperature, particularly helium, as a cold storage material for a cold storage device. This is shown in FIG. In FIG. 1, there is a flow path 2 for the working medium of the refrigerator inside the regenerator 1, which in the case of a single-stage expansion type refrigerator leads to an aftercooler at the upper end 3 and to an expansion space at the lower end 4. In the case of a multi-stage expansion type refrigerator, the upper end 3 leads to the expansion space on the high temperature side, and the lower end 4
It leads to the expansion space on the low temperature side. Although the cold storage material 5 is stored inside the cold storage device 1 and is completely separated from the working medium, heat exchange between the cold storage material 5 and the working medium can be performed efficiently. When the working medium flows in the direction of , the cold storage material 5 absorbs heat from the working medium. Conversely, when the working medium flows in the direction of , the cold storage material 5 releases heat to the working medium. The cold storage material 5 is transferred to the external storage tank 12 through the supply pipe 6.
It is supplied to the regenerator 1 from The pressure inside the regenerator 1 is
The pressure gauge 8 indicates this, and the safety valve 7 can prevent abnormal pressure from occurring. The electrical signal generated by the low temperature pressure sensor 9 is passed through a lead wire 10 to an automatic control valve 11 provided in the normal temperature section.
The automatic control valve 11 opens and closes according to the pressure inside the regenerator 1, and the pressure inside the regenerator 1 can be controlled.

[Problems with conventional technology and their analysis]

When the temperature of the regenerator 1 drops from room temperature (approximately 300K) to 20K or less as the refrigerator operates, the regenerator 1 is supplied with the regenerator material 5 from the external storage tank 12 in order to maintain a constant pressure. There must be. As an example, Figure 2 shows the relationship between temperature and density of helium (pressure 10 atm). As can be seen from Figure 2,
At a temperature of 300K, the density is 1.62×10 ^-3 g/cc. At a temperature of 20K, the density is 2.45×10 ^-2 g/cc, and the temperature
This is about 15 times the density of 300K. Therefore, the pressure inside the regenerator 1 is maintained at 10 atm, and the temperature starts from 300K.
When cooling to 20K, the volume of the regenerator 1 does not change, so it is necessary to replenish the regenerator material 5 with a mass 14 times the original mass. Furthermore, at a temperature of 4K, the density
1.53×10 ^-1 g/cc, which is about 6 of the density at a temperature of 20K.
It will be doubled. Therefore, when the pressure inside the regenerator 1 is maintained at 10 atmospheres and the temperature is further cooled from 20K to 4K, it is necessary to replenish the regenerator material 5 with a mass five times that when the temperature is 20K.

Now, in the cooling process of the regenerator 1, the amount of absorbed heat required to cool the newly inflowing regenerator material 5 is calculated. If the amount of absorbed heat required for cooling from 300K to 20K is △Q _1-2 and the amount of absorbed heat required for cooling from 20K to 4K is △Q _2-3 , the following equation holds true.

△Q _1-2 = reg・ρ ₂・(H ₁ − H ₂ )……(Equation 1) △Q _2-3 = reg・ρ ₂・(H ₂ − H ₃ ) +reg・(ρ _{3 −} ρ ₂ )・(H-H)...(2nd formula) Here, reg: Internal volume of regenerator 1 H: Enthalpy ρ: Density subscript 1...300K, 2...20K, 3...4K.

In addition, the first term on the right side of the second equation is the amount of absorbed heat required to cool the cold storage material 5 existing inside the cold storage device 1 to 4K when the temperature is 20K, and the second term is
The term is the amount of absorbed heat required to cool the cold storage material 5 newly flowing in from the external storage tank 12 at a temperature of 300K to 4K.

Assuming that the internal volume of the regenerator 1 is reg=100 c.c., the following physical property values are substituted into the first and second equations.

H ₁ = 1836 (J/g) H ₂ = 112.9 (J/g) H ₃ = 12.95 (J/g) ρ ₂ = 0.0245 (g/cc) ρ ₃ = 0.153 (g/cc) Therefore, △Q _{1 -2} and △Q _2-3 have the following values.

△Q _1-2 = 4220J ... (3rd equation) △Q _2-3 = 23700J ... (4th equation) From equations 3 and 4, the temperature of regenerator 1 is cooled from 20K to 4K. It can be seen that the amount of absorbed heat required for cooling is approximately 5.6 times that required for cooling from 300K to 20K.

In this way, in the conventional refrigeration system shown in FIG. 1, when the regenerator 1 is cooled, the regenerator material newly flowing into the regenerator 1 to maintain the pressure is transferred to external storage at room temperature. It is supplied directly from tank 12. Therefore, the heat load is concentrated particularly in the lowest temperature part of the refrigeration system, and this heat load increases as the temperature gets lower, and the temperature below 10K, at which the regenerator can operate normally, cannot be reached, or even if it does reach it, it is extremely difficult to reach. It was unstable.

[Traditional issues]

Therefore, the technical object of the present invention is to cool the regenerator to a predetermined temperature and operate it stably.

[Technical means]

The technical means taken to achieve the above-mentioned technical problem is to provide the supply pipe 6 in FIG. 1 with a heat exchange section with a section of the refrigeration system having a higher temperature than the regenerator 1.

[Effect of technical means]

The above technical means works as follows. When the regenerator 1 is being cooled, fresh regenerator material 5 flows into the regenerator 1 from the external storage tank 12 through the supply pipe 6 to maintain the pressure. Since there is a heat exchange section in the supply pipe 6 between the normal temperature part and the lowest temperature part of the refrigeration system, the cold storage material flowing into the regenerator 1 is precooled to a temperature slightly higher than that of the regenerator 1.

For example, when the cold storage material 5 is cooled from a temperature of 20K to 4K, it is assumed that the cold storage material 5 newly flowing into the cold storage device 1 is precooled to a temperature of 30K. At this time, the amount of absorbed heat required to cool the regenerator 1: △
If Q' is set to _2-3 , the following equation holds true.

△Q′ _2-3 = reg・ρ ₂ (H ₂ − H ₃ ) +reg・(ρ ₃ −ρ ₂ )・(H ₄ −H ₃ )
...(Formula 5) Here, subscript 4...30K H ₄ ...168.4J/g is shown.

Furthermore, assuming that the internal volume of the regenerator 1 is reg=100 c.c., the calculation will be as follows.

△Q' _2-3 = 2240J ... (Equation 6) This is approximately 10% of the value of the conventional technology, Equation 4, and the concentration of heat load on the lowest temperature part of the refrigeration system is significantly reduced. I know it will happen. For this reason, the temperature at which the regenerator 1 operates normally is 4K, for example.
cooled down to.

[Special effects caused by the invention]

The present invention produces the following unique effects. That is, in the conventional system, it is also possible to cool the regenerator 1 to a predetermined temperature by cooling the regenerator 1 with a cryogen such as liquid helium at the time of startup. However, in this case, once a heat load exceeding the refrigeration capacity of the refrigeration system is applied, the regenerator 1 cannot return to the predetermined temperature even if the heat load stops acting. Furthermore, another problem arises in that it cannot be started without a cryogen. In contrast, in the case of the present invention, the refrigeration system itself pre-cools the cold storage material 5 and cools the cold storage 1 to a predetermined temperature, so even if a heat load exceeding the refrigeration capacity is applied once, the heat load will be reduced. Once it stops working, the regenerator 1 can return to a predetermined temperature. Also, there is no need to prepare cryogen at startup.

[Embodiments of the present invention] With or without an auxiliary refrigerator; () A heat exchanger with a working medium is provided on the higher temperature side than the regenerator, and an external storage tank and a heat exchanger,
The heat exchanger and regenerator are each connected through a regenerator material supply pipe.

() Connect the regenerator material supply pipe to the regenerator by contacting the expansion cylinder.

() Contact the cool storage material supply pipe with the radiation shield and connect it to the cool storage device.

() Supply the cold storage material to the cold storage device by bringing the supply pipe into contact with another cold storage device.

If there is an auxiliary chiller; () The auxiliary chiller is equipped with a heat exchanger with the working fluid, and the external storage tank and heat exchanger, and the heat exchanger and the main chiller's regenerator, are connected to each other using cold storage material supply pipes. contact.

() Connect the cold storage material supply pipe to the main refrigerator's cold storage by contacting the expansion cylinder of the auxiliary refrigerator.

() Connect the cold storage material supply pipe to the main chiller's cold storage by contacting the radiation shield of the auxiliary chiller.

() Connect the supply pipe of the cold storage material to the cold storage device of the auxiliary refrigerator and connect it to the cold storage device of the main refrigerator.

() The auxiliary chiller connects the cold storage material supply pipe to the heat exchanger plate for precooling the main chiller and connects it to the cold storage of the main chiller.

[First Example] Hereinafter, a first example showing a specific example of the above technical means will be described based on FIG. 3.

In FIG. 3, a compression space 17 formed by a compression cylinder 14 and a compression piston 15 passes through a cooler 18, a first regenerator 19, and a first expansion space 24.
is connected to. The first expansion space 24 passes through the second regenerator 25 and communicates with the second expansion space 27 .
The second expansion space 27 passes through the third regenerator 28 and the third
It communicates with the expansion space 30. Third expansion space 30
passes through the fourth regenerator 1 and communicates with the fourth expansion space 32 . In this way, the compression space 17, the cooler 18, the first regenerator 19, the first expansion space 24,
The refrigeration circuit is constituted by passing through the regenerator 25, the second expansion space 27, the third regenerator 28, the third expansion space 30, the fourth regenerator 1, and the fourth expansion space 32. The inside is filled with helium gas. A rod 14 is connected to the compression piston 15, and a seal 16 for gas sealing is provided on a part of the outer circumference of the compression piston 15.
is provided. First expansion space 24, second expansion space 27, third expansion space 30, and fourth expansion space 3
2 is formed by an expansion cylinder 21 and an expansion piston 22, each having a three-stage convex shape.
On the outer periphery of each stage of the expansion piston, first, second,
3 and 4 Seals 23, 26, 29, and 31 for gas sealing in the expansion spaces 24, 27, 30, and 32 are installed. Further, a rod 20 is connected to the expansion piston 22. The rods 13 and 20 are reciprocating drive mechanisms (for example, crank mechanisms) that are not shown.
connected to.

Inside the fourth regenerator 1, there is a flow path 2 for a working medium, and around the flow path 2, a regenerator material 5 is sealed. be. External storage tank 1
2, first heat exchanger 33, second heat exchanger 34, third
The heat exchanger 35 and the fourth regenerator 1 communicate with each other through a supply pipe 6. A safety valve 7, a pressure gauge 8, and an automatic control valve 11 provided in the room temperature section are attached to the supply pipe 6. An electrical signal from the low temperature pressure sensor 9 is transmitted to an automatic control valve 11 via a lead wire 10.

The operation of the embodiment shown in FIG. 3 will be explained.
The working medium in the compression space 17 is compressed by the compression piston 15
After being compressed, it is cooled by the cooler 18 , passes through the first regenerator 19 , is further cooled, and flows into the first expansion space 24 and the first regenerator 25 . The working medium that has entered the first expansion space 24 is transferred to the expansion piston 2
2 and generates refrigeration at a temperature of about 70K. By the way, the working medium that has flowed into the second regenerator 25 is further cooled and flows into the second expansion space 27 and the third regenerator 28 . The working medium that has flowed into the second expansion space 27 is expanded by the expansion piston 22 to generate refrigeration at a temperature of approximately 30K. on the other hand,
The working medium that has flowed into the third regenerator 28 is further cooled and flows into the third expansion space 30 and the fourth regenerator 1 . The working medium that has flowed into the third expansion space 30 is expanded by the expansion piston 22 to approximately 10K
Temperatures of refrigeration occur. Further, the working medium that has flowed into the fourth regenerator 1 is further cooled and flows into the fourth expansion space 32 . The working medium that has entered the fourth expansion space 32 is expanded by the expansion piston 22 to generate refrigeration at a temperature of approximately 4K. The temperature of the regenerator 1 is at room temperature (approximately 300K) when the refrigerator is started, but reaches 10K to 4K in a steady state.
A method for replenishing the cold storage material 5 during the cooling process of the cold storage device 1 will be explained. When the temperature of the regenerator 1 decreases, the internal pressure decreases. This is detected by the low temperature pressure sensor and an electrical signal is sent to the lead wire 10.
The signal is transmitted to the automatic control valve 11 through the automatic control valve 11, and the automatic control valve 11 is opened. At this time, the cold storage material 5 is passed from the storage tank 12 to the first heat exchanger 33 through the supply pipe 6.
flows into. The cold storage material 5 that has flowed into the first heat exchanger 33 exchanges heat with the working medium in the first expansion space 24, is cooled, and flows into the second heat exchanger 34. The cold storage material 5 that has flowed into the second heat exchanger 34 exchanges heat with the working medium in the second expansion space 27 and is cooled.
It flows into the third heat exchanger 35. Third heat exchanger 35
The cold storage material 5 that has flowed into the third expansion space 30 exchanges heat with the working medium in the third expansion space 30, is cooled, and then flows into the fourth cold storage 1. Cold storage material 5 flowing into the fourth cold storage device 1
is cooled in advance to a temperature slightly higher than that of the regenerator 1 in the third heat exchanger 30, so the heat load applied to the regenerator 1 is much smaller than that of the conventional one shown in FIG. . Therefore,
The regenerator 1 can easily reach a predetermined temperature, for example 4K.

Next, the stability of the regenerator 1 of the refrigeration system of the present invention will be discussed. When a heat load exceeding the refrigerating capacity is applied to the fourth expansion space 32, the temperature of the regenerator 1 increases, and as a result, the internal pressure also increases.
This is detected by the low temperature pressure sensor 9, and an electric signal is transmitted to the automatic control valve 11.
can be opened. Then, the cold storage material 5 in the cold storage device 1 flows into the third heat exchanger 35. The cold storage material 5 that has flowed into the third heat exchanger 35 is still at a lower temperature than the working medium in the third expansion space 30, so after cooling the working medium in the third expansion space 30, the cold storage material 5 flows into the second heat exchanger 35. The liquid flows into the vessel 34. The cold storage material 5 that has flowed into the second heat exchanger 34 is transferred to the first expansion space 27
Since the working medium in the second expansion space 27 is still at a lower temperature than the working medium in the second expansion space 27, after cooling the working medium in the second expansion space 27, the first
It flows into the heat exchanger 33. The cold storage material 5 flowing into the first heat exchanger 33 cools the working medium in the first expansion space 24 and is then returned to the storage tank 12 . In this way, the temperature of the regenerator 1 increases, and the regenerator material 5
Since the cold storage material 5 cools the working medium in the third expansion space 20, the second expansion space 30, and the first expansion space 24 when it flows into the storage tank 12, the heat is reduced compared to conventional cooling systems. Very high resistance to load. Therefore, it can be seen that the refrigeration system of the present invention has excellent stability.

[Second Embodiment] Next, a second embodiment showing a specific example of the technical means of the present invention will be described based on FIG. 4. In Fig. 4, the differences from the first embodiment (Fig. 3) are as follows.
The first heat exchanger 33 and the second heat exchanger 3 in FIG.
4, and the supply pipe 6 instead of the third heat exchanger 35
and the contact portions 36, 37, and 38 of the expansion cylinder 21 are provided. Working medium and cold storage material 5
Although the heat exchange efficiency is slightly lower than that shown in Fig. 3, it is easier to manufacture.

[Third Example] A third example showing a specific example of the technical means of the present invention will be described based on FIG. 5. In FIG. 5, the differences from the first embodiment (FIG. 3) are that radiation shields 39 and 40 are provided, and the first heat exchanger 33 and second heat exchanger in FIG. 34,
and that contact portions 41 and 42 between the supply pipe 6 and the radiation shields 39 and 40 are provided in place of the third heat exchanger 35, and that the supply pipe 6 and the expansion cylinder 21 are provided with contact portions 41 and 42.
The reason is that the contact portion 43 is designed as follows. The radiation shields 39 and 40 block radiation heat from the high temperature part to the low temperature part, and the radiation shield 39
The temperature of the first expansion space 24 and the radiation shield 40 are approximately the same as that of the second expansion space 27. Therefore, the cold storage material 5 is precooled at the contact portions 41 and 42 between the supply pipe 6 and the radiation shields 39 and 40, and finally precooled at the contact portion 43 between the supply pipe 6 and the expansion cylinder 21, and then flows into the regenerator 1. Although the heat exchange efficiency between the working medium and the cold storage material 5 is slightly lower than that shown in FIG. 3, it is easier to manufacture.

[Fourth Example] A fourth example showing a specific example of the technical means of the present invention will be described based on FIG. 6. In Fig. 6, the difference from the first embodiment (Fig. 3) is that the third embodiment is different from the first embodiment (Fig. 3).
Instead of the first heat exchanger 33, second heat exchanger 34, and second heat exchanger 35 in the figure, the supply pipe 6 and the first
The contact portions 44, 45, and 46 of the regenerator 19, the second regenerator 25, and the third regenerator 28 are provided. Although the heat exchange efficiency between the working medium and the cold storage material 5 is slightly lower than that shown in FIG. 3, it is easier to manufacture.

[Fifth Example] A fifth example showing a specific example of the technical means of the present invention will be described based on FIG. 7. The names and functions of each part indicated by numbers 13 to 30 are as follows:
Although it is exactly the same as the first embodiment (FIG. 3), the temperature reached in this part (third expansion space) is about 10K, and it acts as an auxiliary refrigerator 64. To obtain the lowest temperature for a refrigeration system, for example 4K,
The main refrigerator 65 is composed of parts numbered 47 to 57, and parts 1, 2, 5, and 9. A compression space 51 formed by the compression cylinder 48 and the compression piston 49 passes through the cooler 52 and the regenerator 1, and communicates with an expansion space 57 formed by the expansion cinder 54 and the expansion piston 55. In this way, a refrigeration circuit is constructed from the compression space 51, the cooler 52, the regenerator 1, and the expansion space 57, and the auxiliary refrigerator 6
It is separate from the refrigeration circuit No. 4. The refrigeration circuit of the main refrigerator 5 is filled with helium as a working medium. A seal 50 for gas sealing in the compressed air 51 is installed on the outer periphery of the compression piston 49, and a seal 50 for sealing gas in the compressed air 51 is installed on the outer periphery of the expansion piston 55.
A seal 56 is installed to seal the gas inside 7. In addition, the compression piston 49 and the expansion piston 5
5 are connected to rods 47 and 53, respectively. The rods 47, 53 are connected to a reciprocating mechanism (for example, a crank mechanism), which is not shown. heat transfer plate 58,
59 and 60 are the first expansion space 24, the second expansion space 27, and the third expansion space of the auxiliary refrigerator 64, respectively.
It is cooled by the expansion space 30. heat transfer plate 58,
59 and 60 cool the compression cylinder 48, cooler 52, and expansion cylinder 54.
The supply pipe 6 of the cold storage material 5 includes heat exchanger plates 58, 59,
and 60 are provided with contact portions 61, 62, and 63.

In the refrigeration system with such a configuration, the cold storage material 5 that newly flows in during the cooling process of the cold storage device 1 is
Since the supply pipe 6, the heat transfer pipes 58, 59, and 60, and the contact parts 61, 62, and 63 are cooled, the regenerator 1 is cooled with almost no heat load on the main refrigerator 65.
can be cooled down to a predetermined temperature, for example 4K.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram of the prior art that is the basis of the present invention, FIG. 2 is an explanatory graph showing the temperature and density of helium, and FIG. 3 is a diagram showing a specific example of the technical means of the present invention. 4 is an explanatory sectional view of the second embodiment, FIG. 5 is an explanatory sectional view of the third embodiment, and FIG. 6 is an explanatory sectional view of the fourth embodiment. An explanatory sectional view, and FIG. 7 is an explanatory sectional view of the fifth embodiment. 1... Cold storage device, 5... Cold storage material, 21, 54...
...expansion cylinder, 39, 40... radiation shield, 65... main refrigerator, 64... auxiliary refrigerator.

Claims (1)

[Scope of Claims] 1. In a single-stage expansion type refrigeration system that uses a substance that is in a gaseous state at room temperature as a cold storage material for one cold storage device, in the middle of a supply pipe leading to the cold storage device, the cold storage material and the working fluid are mixed together. , an expansion cylinder, and a heat exchange portion with at least one in a radiation shield. 2. In a multistage expansion type refrigeration system that uses a substance that is in a gaseous state at room temperature as a cold storage material for a plurality of cold storage devices, the cold storage material is used in the middle of a supply pipe leading to at least one of the plurality of cold storage devices. and a refrigeration system comprising a working fluid, an expansion cylinder, a radiation shield, and a heat exchange portion with at least one of the regenerators on a higher temperature side than the at least one regenerator. 3. In a refrigeration system consisting of an expansion type main refrigerator that uses a substance that is in a gaseous state at room temperature as a cold storage material for at least one regenerator, and an auxiliary refrigerator that precools the main refrigerant, the at least one regenerator In the middle of the supply pipe communicating with the cold storage material, the working fluid of the auxiliary refrigerator, the expansion cylinder of the auxiliary refrigerator, the radiation shield of the auxiliary refrigerator, and the transmission for the auxiliary refrigerator to precool the main refrigerator. A refrigeration device comprising a heat plate and a heat exchange portion with at least one of the regenerators of the auxiliary refrigerator.