JPS6357712B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal switch used as a heat transfer element for cooling and heating low temperature equipment such as a helium liquefier cryostat.

FIGS. 1a and 1b are cross-sectional views showing the structure of a conventional thermal switch, with FIG. 1a showing the state during heat cutoff and FIG. 1b showing the state during heat transfer. In both figures 1a and 1b, 1
2 is a first heat transfer body (assumed to be a high temperature side), 2 is a second heat transfer body, and 3 is a bellows that can be expanded and contracted in the axial direction.

A first flange 41 is provided at one end of the bellows 3. This first flange 41 seals one end of the bellows 3 and is provided so as to face the first heat transfer target 1 from the outer surface. A second flange 42 is also provided at the other end of the bellows 3.

This second flange 42 seals the other end of the bellows 3, the other end is fixed to the second heat transfer target body 2, and the second flange 42 seals the other end of the bellows 3.
The flange 41, the second flange 42, and the bellows 3 form a closed container. Further, heat transfer fins 52 are implanted in the second flange 42 and are oriented toward the first flange 41 within the bellows 2 . Similarly, heat transfer fins 51 are also implanted in the first flange 41. This heat transfer fin 5
1 faces toward the second flange 42 .

A certain amount of refrigerant gas 6 is sealed inside the bellows 3, and this refrigerant gas 6 includes, for example,
Hydrogen gas is used.

Thus, the bellows 3, the first flange 41, the second flange 42, the heat transfer fins 51, 52, and the refrigerant gas 6 constitute the thermal switch 7.

FIG. 2 is a cross-sectional view showing a structure in which the thermal switch 7 thus structured is applied to a cryostat. In Fig. 2, the same parts as in Figs. As mentioned above.

Further, 8 is an outer tank that forms an adiabatic vacuum space. Inside this outer tank 8, a first heat transfer target 1, a second heat transfer target 2, and a thermal switch 7 are housed. A superconducting magnet 12 is housed within this second heat transfer target body 2, and this superconducting magnet 12 is immersed in liquid helium 11.

A shield cooling pipe 10 is provided on the outer peripheral surface of the first heat transfer target 1 . This shield cooling pipe 10
is supplied with liquid nitrogen from a liquid nitrogen tank 9, and by supplying this liquid nitrogen, the shield cooling pipe 10 cools the first heat transfer object 1 to about 80K. It's summery.

The liquid nitrogen tank 9 is disposed within the outer tank 8 and above the first heat transfer target.

In order to reduce the amount of liquid helium 11 consumed, the cryostat configured in this way uses liquid nitrogen to cool the superconducting magnet 12 to about 80K.
After cooling to
Cool down to 4.2K.

That is, the cold is transferred from the first heat transfer target 1 cooled to about 80K with liquid nitrogen to the liquid helium tank, that is, the second heat transfer target 2 and the superconducting magnet 12 via the thermal switch 7. , cooled to a predetermined temperature.

In this case, the refrigerant gas 6 sealed in the thermal switch 7 is heated up to 80K from the first heat transfer target 1 to the first flange 41 - heat transfer fin 51 - refrigerant gas 6
-The second heat transfer target 2 is cooled through the heat transfer fins 52 and the second flange 42.

Next, when the fluid helium 11 is injected into the second heat transfer target 2, the heat transfer fin 52 is cooled via the second flange 42, and the refrigerant gas 6 in contact with it is lowered to a predetermined temperature T _C or lower. Then, due to the pressure drop, the bellows 3 contracts and loses contact with the first heat transfer target 1 (FIG. 1a), cutting off heat transfer.

The operating temperature of the thermal switch 7 configured as described above depends on the material and dimensions of the bellows 3 and the refrigerant gas 6.
A desired temperature can be set by appropriately designing the type and pressure, the gap between the first heat transfer target 1 and the second heat transfer target 2, etc.

However, in the conventional thermal switch 7 configured as described above, the pressure of the enclosed refrigerant gas 6 decreases due to a decrease in its operating temperature, so that the contact surface between the first heat transfer object and the first flange 41 decreases. This causes a gradual increase in the contact thermal resistance, which is accompanied by a decrease in the surface pressure of

Furthermore, when a large number of these devices are arranged in parallel under the same temperature conditions, it becomes very difficult to align the “connection” and “disconnection” operations of each device.

This invention was made in order to eliminate the above-mentioned conventional drawbacks, and in particular, it provides a thermal switch that improves heat conductivity in the low-temperature operating range and can reliably connect and disconnect the switch. The purpose is to

Embodiments of the thermal switch of the present invention will be described below with reference to the drawings. FIG. 3 is a sectional view showing the configuration of one embodiment. In FIG. 3, the same parts as in FIG. 1a, FIG. 1b, and FIG.
We will mainly discuss the parts that are different from those in Figures 2 and 2.

In this FIG. 3, the first heat transfer target 1, the second
The heat transfer body 2 and the thermal switch 7 are the same as the conventional one, and in particular, the main body and main structure of the thermal switch 7 are the same as the conventional one, but the structure of the second flange 42 is different.

That is, the second flange 42 of the thermal switch 7 is provided with a ventilation hole 13. This vent hole 13 is provided so as to penetrate from the side wall of the second flange 42 to the bellows 3 and into the airtight container, and one end of a refrigerant pipe line 14 is connected to this vent hole 13.

The refrigerant pipe 14 is provided to supply the refrigerant gas 6 into the bellows 3 and to exhaust it from the bellows 3. A shutoff valve 15 is provided on the refrigerant gas supply side, and a shutoff valve 15 is provided on the refrigerant gas supply side. A shutoff valve 16 is also provided on the discharge side.

In the thermal switch 7 configured in this way, when the shut-off valve 16 is closed and the shut-off valve 15 is opened to guide the refrigerant gas 6 into the bellows 3 and maintained at a constant pressure, the first flange 41 The outer surface of is pressed against the first heat transfer target 1 to transfer heat.

In addition, by closing the shutoff valve 15 and opening the shutoff valve 16 to release the refrigerant gas 6 in the bellows 3 and reduce the pressure, the bellows 3 contracts and the first flange 4
The contact with the first heat transfer target 1 can be removed.

The "on" and "off" states can be artificially controlled by operating the shutoff valves 15 and 16 to supply and release the refrigerant gas 6, regardless of the operating temperature.

FIG. 4 is a sectional view showing an example of a case where the thermal switch 7 according to the present invention is arranged in parallel with a cryostat. In FIG. 4, refrigerant pipes 14 of a plurality of thermal switches 7 are shown.
are connected in parallel, and the shutoff valves 15 and 16 are connected to the tube ends of the refrigerant pipe line 14 that are gathered together in the same way as in the above case, and a plurality of thermal switches 7 are simultaneously connected and disconnected. ” can be controlled.

In this way, multiple thermal switches 7
Since both can be driven by the refrigerant gas 6 under the same conditions, it is possible to eliminate irregularities in operation compared to conventional independent systems. Note that in FIG. 4, the same reference numerals as in FIG. 2 indicate the same parts, and the explanation thereof will be omitted here.

FIG. 5 is a sectional view showing another embodiment of the thermal switch of the present invention. In this Figure 5,
The first heat transfer object 1, the second heat transfer object 2, the bellows 3, the first flange 41, and the second flange 42 are
Although similar to the figure, a new heat transfer member 8 is provided within the bellows 3 between the first flange 41 and the second flange 42.

That is, the heat transfer member 8 is made of a flexible and highly heat-conductive braided copper wire, and both ends thereof are metallurgically joined to the first flange 41 and the second flange 42. , has a meandering shape within the bellows 3.

With this configuration, heat transfer between the first flange 41 and the second flange 42 is performed via the heat transfer member 8 having a lower thermal resistance than the refrigerant gas 6.

FIG. 6 is a sectional view showing the structure of still another embodiment of the thermal switch of the present invention. In the case of this FIG. 6, instead of the braided copper wire forming the heat transfer member 8 in the embodiment of FIG. They are fitted, and one end of the piston-shaped heat transfer body 81 is fixed to the first flange 41 . Further, one end of the cylindrical heat transfer portion 82 is fixed to the second flange 42 .

Furthermore, the cylindrical heat transfer body 82 has ventilation holes 83.
is formed, and the refrigerant gas 6 in the bellows 3 is injected into the cylindrical heat transfer body 82 through this vent hole 83. As a result, the piston-shaped heat transfer body 81 within the cylindrical heat transfer body 82 is pushed up or lowered.

In addition, in a conventional thermal switch, the heat transfer surface on the low temperature side is in principle always fixed, but when implementing this invention, this restriction is not imposed, and the heat transfer surface on the low temperature side is "contacted". Since it is possible to "break", by making the high temperature side the fixed end, the low temperature side,
That is, it becomes possible to reduce the thermal load on the second heat transfer target 2 side during steady state.

In the above embodiment, a case where the present invention is applied to a cryostat has been described, but the present invention is not limited to this example, and it goes without saying that the present invention can be applied to low-temperature equipment such as a helium liquefier or a container.

As detailed above, according to the thermal switch of the present invention, both open ends of the expandable bellows are hermetically sealed with flanges made of a heat transfer material, and the inside of the bellows is inserted from the side of either flange. A vent hole that opens is provided, a refrigerant pipe is connected to this vent hole, the refrigerant pipe is branched into two, a shut-off valve is provided at each end of the pipe, and the bellows is closed by artificially switching the shut-off valve. Supply and exhaust refrigerant gas into the interior, and then turn the thermal switch on and off.
Therefore, when in contact with the heat transfer target, regardless of the operating temperature, a constant contact surface can be maintained and heat can be transferred without reducing thermal conductance.

In addition, by stopping the supply of cooling gas and exhausting the refrigerant gas in the bellows container, you can remove the contact with the heat transfer object, so you can connect and disconnect at the desired temperature regardless of the operating temperature. can be done easily.

Furthermore, when using multiple thermal switches arranged in parallel, the refrigerant pipes of each thermal switch can be connected to each other, and all can be operated simultaneously by operating one set of valves. Even with an eye balance of

[Brief explanation of drawings]

Figure 1a is a cross-sectional view of a conventional thermal switch when heat is cut off from the heat transfer target, and Figure 1b is a cross-sectional view of a conventional thermal switch when heat transfer is cut off from the heat transfer target. 2 is a cross-sectional view showing a state in which a conventional thermal switch is applied to a cryostat, FIG. 3 is a cross-sectional view showing the configuration of an embodiment of the thermal switch of the present invention, and FIG. FIGS. 5 and 6 are cross-sectional views showing the structure of other embodiments of the thermal switch of the present invention, respectively. 1... First heat transfer target, 2... Second heat transfer target, 3... Bellows, 41... First flange, 4
2... Second flange, 51, 52... Heat transfer fin, 6... Refrigerant gas, 7... Thermal switch,
8... Heat transfer member, 81... Piston-shaped heat transfer body, 8
2... Cylindrical heat transfer body, 13, 83... Ventilation hole, 14... Refrigerant pipe line, 15, 16... Shutoff valve.
Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1 A bellows, first and second flanges that respectively seal both open ends of the bellows and form an airtight container that can expand and contract in the axial direction together with the bellows, and a refrigerant pipe connected to the airtight container through a vent hole penetrating into the airtight container from either side of the flange and for sending refrigerant gas into the airtight container; a first shut-off valve that supplies the refrigerant gas; and a second shut-off valve that is provided in the refrigerant pipe and discharges the refrigerant gas in the airtight container through the refrigerant pipe; When the outer surfaces of the two flanges are arranged to face each other between the first heat transfer target body and the second heat transfer target body, and heat transfer between the first and second heat transfer target bodies is carried out, A refrigerant gas is supplied into the airtight container by a first shutoff valve, and the first and second flanges are brought into contact with the first and second heat transfer objects to form a heat transfer path, and no heat transfer occurs. The method is characterized in that the refrigerant gas in the airtight container is exhausted by the operation of the second shutoff valve to cut off heat transfer between the first or second flange and the first or second heat transfer target body. Thermal switch. 2. The thermal switch according to claim 1, wherein the first and second flanges are provided with an expandable heat transfer member that connects the first and second flanges in a heat transferable manner. 3 Multiple units are arranged in parallel, their refrigerant pipes are connected to each other, and a set of shut-off valves for refrigerant gas supply and exhaust are controlled so that they can be operated simultaneously. A thermal switch according to claim 1 or 2, characterized in that: