JPH04186B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a helium refrigeration system, and particularly to a helium refrigeration system suitable for a cryostat equipped with a condenser to cool the condenser.

[Background of the invention]

Conventional helium refrigeration equipment, for example,
As described in Japanese Patent No. 126168, a condensing heat exchanger was attached to the nozzle of a cryostat, and the heat exchanger was cooled by a refrigerator via a helium transfer tube.

Conventional devices do not take into consideration the fact that the condensing heat exchanger is detachably provided. That is,
When using a condensing heat exchanger attached to the nozzle of a general cryostat, which supplies liquid helium from the nozzle and then supplies it again from the nozzle when the liquid helium inside becomes low, it is possible to re-condense the evaporated gas inside the cryostat. Even if it is liquefied, there is a problem with airtightness and the liquid helium inside gradually decreases, so it is necessary to remove the condensing heat exchanger and supply liquid helium. Therefore, it is necessary to easily attach and detach the condensing heat exchanger.

[Purpose of the invention]

An object of the present invention is to install a refrigerator that cools a condenser and a cryostat separately, and to connect the condenser and refrigerator attached to the cryostat with a transfer tube. An object of the present invention is to provide a helium refrigeration system in which a condenser can be easily attached and detached.

[Summary of the invention]

In the present invention, a high-temperature condenser is cooled by a high-pressure helium gas pipe in an intermediate temperature range, and a low-temperature condenser is cooled by a pipe behind the Joel-Thomson valve, and the condenser is passed through the transfer tube. By making the piping smaller and making it more flexible,
Even in a helium refrigeration system in which a refrigerator that cools the condenser and a cryostat are placed separately and a transfer tube is used to connect the condenser attached to the cryostat and the refrigerator, the condenser attached to the cryostat is It is designed to be easily attached and detached.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG.

A portion of the high-pressure helium gas compressed by the first-stage compressor 1 and the second-stage compressor 2 is supplied to the expander 3, where it is adiabatically expanded in the first-stage expander 4 and second-stage expander 5. This generates refrigeration, which returns to medium-pressure helium gas between the first-stage compressor 1 and the second-stage compressor 2.

The remaining high-pressure helium gas enters the first heat exchanger 6, where it is cooled by counter-flowing low-pressure helium gas. The cooled high-pressure helium gas enters the condensing coil 8 via the pipe 7. In the process of passing through the condensing coil 8, the evaporated gas from the liquid nitrogen tank 25 for the radiation shield of the cryostat 24 is reliquefied in the condenser 18. The high pressure helium gas leaving the condensing coil 8 passes through a pipe 9 and enters the first cooling coil 10, where it is further cooled by the first stage expander 4. Thereafter, it enters the second heat exchanger 11 and is cooled by low-pressure helium gas flowing oppositely.

After exiting the second heat exchanger 11, the second cooling coil 1
2, where it is further cooled by the second stage expander 5 and enters the third heat exchanger 13. Even in the third heat exchanger 13, the first heat exchanger 6, the second heat exchanger 11
As in the case of , it is cooled by the low-pressure helium gas flowing oppositely, and finally enters the Joel-Thompson valve 14 as high-pressure helium gas of 10K or less. High pressure in the process of passing through the Joel-Thomson valve 14,
Low-temperature helium gas expands adiabatically and some of the gas liquefies due to the Joel-Thomson effect. The low-pressure, low-temperature gas containing liquefied gas enters another condensing coil 16 via a pipe 15. Other condensing coils 16
During the process, the vaporized gas from the liquid helium tank 26 in the cryostat 24 is reliquefied in another condenser 19. The low-pressure, low-temperature helium gas coming out of the other condensing coil 16 passes through the pipe 17 to the third
Returning to the heat exchanger 13, hereafter, the second heat exchanger 11,
It returns to the suction side of the first stage compressor 1 via the first heat exchanger 6.

The expander, heat exchanger, etc. are housed in a vacuum cold storage tank 22, and a radiation shield is placed around the second stage expander 5, which is at a relatively low temperature, the second heat exchanger 11, and the third heat exchanger 13. A board 21 is arranged.

Pipes 7, 9, 15, 17 connecting between the vacuum cold storage tank 22 and the condensers 18, 19 are housed in a flexible transfer tube 20,
All spaces between the two are vacuumed to minimize heat intrusion from the outside.

The tips 23 and 32 of the condensers 18 and 19 are inserted into an evaporation tube 27 that is an inlet for injecting liquid nitrogen into the liquid nitrogen tank 5 and an evaporation tube 29 that is an inlet for injecting liquid helium into a liquid helium tank 26, respectively. has been done.

The evaporator tubes 27, 29 are made long to reduce the amount of heat that enters therethrough, and their support tubes 28, 3
0.31 is also longer.

Further, the inside of the cryostat 24 is also generally vacuum insulated to reduce heat intrusion into the liquid helium tank 26 and liquid nitrogen tank 25.

According to this embodiment, the high-pressure helium gas after the first heat exchanger cools the condenser attached to the liquid nitrogen tank, and the low-temperature gas exiting the Joel-Thompson valve cools the condenser attached to the liquid helium tank. Since the system is cooled, pipes with a small diameter can be used for transferring high-pressure helium gas with little pressure loss, and pipes with a small diameter can also be used for transferring low-temperature gas because the amount transferred is small. As a result, the piping that passes through the transfer tube can be made smaller and has better flexibility, which has the effect that the condenser attached to the cryostat can be easily attached and detached.

FIG. 2 shows another embodiment of the condensers 18 and 19 attached to the cryostat 24 of FIG.
The outer casings 33, 33' have an airtight structure, and the space between them is insulated with vacuum layers 34, 34'.

According to this embodiment, there is an effect that heat intrusion into the condensers 19 and 18 is reduced, and heat loss and refrigerator capacity can be reduced.

FIG. 3 shows yet another embodiment of a condenser, in which a liquid receiving tray 36 for returning the liquefied gas condensed in the condensing coils 16, 8 to the liquid helium tank 26 or the liquid nitrogen tank 25, and one end of the liquid receiving plate 36 are shown. It is composed of a conduit 35 connected to the dish 36 and opened at the other end to the liquid helium tank 26 or the liquid nitrogen tank 25. 37 indicates a sealing cover. According to the configuration of this embodiment, evaporated gas does not leak to the outside, and the evaporative gas is connected to the tips 32, 23 of the condensers 19, 18 and the conduit 3.
5 and rises through the condenser coil 1
It is cooled and reliquefied at steps 6 and 8. The re-liquefied liquefied gas becomes droplets and falls onto the liquid receiving pan 36 and is collected in a low central area, and passes through the conduit 35 to the liquid helium tank 26 or the liquid nitrogen tank 25.
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According to this embodiment, since the flow paths for the evaporated gas and the recondensed liquefied gas are separate, the descent of the liquefied gas is inhibited by the rise of the evaporated gas (affected by the so-called vapor lock phenomenon). It has the effect of eliminating things.

FIG. 4 shows another embodiment of the evaporator tubes 27 and 29 of FIG. 1, and as shown in FIG.
If the sealing cover 37 is airtightly covered between the tips 32 and 23 of the evaporators 6 and 8 and the evaporation tubes 29 and 27, liquid helium may leak out for some reason (for example, if the vacuum of the cryostat 24 suddenly deteriorates). or when the amount of evaporated gas from liquid nitrogen increases abnormally, the condenser coil 1
There is a risk that the condensing capacity of the tanks 6 and 8 will be exceeded, and the internal pressures of the liquid helium tank 26 and the liquid nitrogen tank 25 will rise abnormally.

Therefore, as shown in FIG. 4, by arranging an air release line in the normal temperature part of the evaporation tubes 29 and 27, and providing a break safety valve 38 and a throttle 39 at the tip of the line,
Eliminated the danger. That is, according to this embodiment, under normal conditions, the internal pressures of the liquid helium tank 26 and the liquid nitrogen tank 25 are maintained at approximately atmospheric pressure while releasing a very small amount of the evaporated gas through the throttle 39, thereby preventing abnormalities in the internal pressures. When ascending, the liquid helium tank 26 and liquid nitrogen tank 25 can be prevented from being damaged by being released from the safety valve 38.

Although the embodiment shown in Fig. 1 shows a refrigerator configured with a regenerator-type reciprocating type expander, the same effect can be obtained by using a refrigerator configured with a rotary expansion turbine. That is clear.

〔Effect of the invention〕

According to the present invention, a refrigerator for cooling a condenser and a cryostat are arranged separately, and a transfer tube connects the condenser and the refrigerator attached to the cryostat. This has the effect of making it easier to attach and detach the condenser.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing the overall configuration of a helium refrigeration system that is an embodiment of the present invention, Fig. 2 is a partial sectional view showing another embodiment of the condenser shown in Fig. 1, and Fig. 3 is a condenser. FIG. 4 is a partial sectional view showing another embodiment of the evaporation tube portion of the cryostat shown in FIG. 1...First stage compressor, 2...Second stage compressor, 3
... Expander, 6... First heat exchanger, 7,15...
Piping, 8...Condensing coil, 11...Second heat exchanger, 13...Third heat exchanger, 14...Joule-Thomson valve, 16...Other condensing coil, 18...Condenser, 19... ...other condensers, 23, 32... tip, 24... cryostat, 25... liquid nitrogen tank, 26... liquid helium tank.

Claims (1)

[Claims] 1. A compressor that compresses helium gas to high pressure, an expander that adiabatically expands the compressed high-pressure helium gas to generate cold air, and high-pressure helium gas and low-pressure return helium gas. a heat exchanger group that cools high-pressure helium gas by exchanging heat with the heat exchanger, a Joel-Thomson valve that adiabatically expands the high-pressure and low-temperature helium gas that exits the final stage heat exchanger, and a cold generation section of the expander; A vacuum cold storage tank housing the heat exchanger group and the Joel-Thompson valve, first and second condensers provided at the respective injection ports of the liquid nitrogen tank and the liquid helium tank in the cryostat, and the vacuum a transfer tube connecting the cold storage tank and the first and second condensers, and a pipe for flowing high-pressure helium gas in an intermediate temperature range of the heat exchanger group is connected inside the transfer tube to the first and second condensers; The low-temperature helium gas containing the liquefied gas that has exited the Joule-Thomson valve is returned by reciprocating through the condenser of No. A helium refrigeration system characterized in that a pipe for circulating the is reciprocated through the transfer tube and returned through the second condenser, and is connected to a low-pressure return helium gas line at the final stage of the heat exchanger group. Device.