JPH0689958B2 - Helium refrigerator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement of a helium refrigerator in which precooled helium gas is subjected to Joule-Thomson expansion (isoenthalpy expansion) to generate cryogenic temperature. is there.

(Prior Art) The present applicant has previously proposed, as this type of helium refrigerator, the one disclosed in JP-A-62-116869. This is a multi-stage refrigerator such as a GM type or an improved Solvay type that constitutes a pre-cooling refrigerator, in which a high pressure helium gas precooled to a low temperature by an expander incorporated therein is expanded by Joule-Thomson to obtain a pole. It is designed to generate a low temperature. That is, the specific configuration is GM
Type and improved solve type multi-stage refrigerators, the high-pressure helium gas supplied from the high-stage compressor is expanded by an expander with a built-in regenerator, and many helium gases are returned to the high-stage compressor again. This expansion action causes each heat station to generate a low temperature to be pre-cooled, and a part of the low-temperature high-pressure helium gas derived from the lowest temperature part of the expander is squeezed by the JT valve to be expanded by Joule-Thomson. After that, it is guided to a cooler to cool the object to be cooled by its latent heat of vaporization, and thereafter, a countercurrent type heat exchanger and a heat exchanger for recovering cold heat are applied from the cooler to the front of the JT valve. The helium gas is cooled or preheated in the heat station of the expander, guided to the suction side of the low-stage compressor, and returned to the suction side of the high-stage compressor again.

(Problems to be solved by the invention) By the way, in the helium refrigerator as described above, passage and blocking of passage of the helium gas flowing into the expander are alternately performed by an opening / closing operation according to the rotating operation of the rotary valve. The gas is adiabatically expanded, but due to the opening / closing operation associated with the rotary operation of the rotary valve, the pressure of the helium gas derived from the lowest temperature part of the expander (that is, the gas pressure before the JT valve). ) Fluctuates and negative pressure is generated. Therefore, in the gas outlet part of the lower end of the expander,
A check valve is installed to prevent backflow to the expander side.
A buffer tank is provided to reduce the pressure pulsation of high-pressure helium gas.

However, when the capacity of the buffer tank is small, it is not possible to effectively suppress the fluctuation of the JT valve front pressure of the helium gas, and as a result, the temperature of the cooler also fluctuates and the suction of the low-stage compressor. The gas pressure on the side (J-T return pressure) may also fluctuate significantly, leading to a decrease in reliability of the low-stage compressor.

On the other hand, if the capacity of the buffer tank is increased, the size of the cryogenic portion is increased in size together with the need for the check valve, and the circuit configuration becomes complicated.

The present invention has been made in view of these points, and an object thereof is to reduce the gas pressure on the suction side of a high-stage compressor (that is, the pressure of helium gas derived from the lowest temperature part of the expander) and the low-stage compression. Installation of check valves and buffer tanks by effectively suppressing the pressure fluctuation of helium gas derived from the lowest temperature part of the expander by utilizing the pressure difference with the gas pressure on the suction side of the machine. Helium gas J-
The pressure before the T valve is stabilized at a high pressure to suppress temperature fluctuations in the cooler to a small extent, and also effectively suppress fluctuations in the gas pressure on the suction side of the low-stage compressor to improve the reliability of the low-stage compressor. And the size of the cryogenic part is reduced to simplify the circuit configuration.

(Means for Solving Problems) In order to achieve the above object, the solving means of the present invention is
As shown in the drawings and FIG. 2, the high-pressure helium gas supplied from the high-stage compressor (2) is supplied to the rotary valve (6) of the expander (4) containing the regenerators (8) and (9). Each heat station (1) is expanded while being expanded according to the rotating operation and returning a large amount of the helium gas to the high-stage compressor (2).
A multi-stage refrigerator (3) such as a GM type or an improved Solvay type that generates a low temperature is provided in 0) and (11). A part of the helium gas at low temperature and high pressure is led out from the lowest temperature part of the expander (4) in the multistage refrigerator (3), and the derived helium gas is expanded by Joule-Thomson J-
The T-valve (18), a cooler (19) for cooling an object to be cooled with helium expanded by the J-T valve (18), and helium gas from the cooler (19) are supplied to the J-T A JT heat exchanger (17) for exchanging heat with the helium gas before being expanded by the valve (18) is provided. Further, heat exchangers (20) to (23) are attached to the heat stations (10) and (11) and / or the cylinder parts (5a) and (5b) of the expander (4),
The heat exchangers (20) to (23) are configured to recover the cold heat of the low-pressure helium gas from the heat exchanger (17) and compress the low-pressure helium gas heated to room temperature. The low-stage compressor (1) introduced again to the suction side of the high-stage compressor (2) is provided. Further, a gas return passage (14) for returning a large amount of helium gas expanded in the expander (4) to the suction side of the high-stage compressor (2), and the heat exchangers (20) to (23) for recovering cold heat. ) From the gas return passage (24) for returning the helium gas from the) to the low-stage compressor (1),
The configuration is such that the bypass passage (26) having the throttle mechanism (27) communicates with each other.

(Operation) With the above configuration, in the present invention, the high-pressure helium gas supplied from the high-stage compressor (2) is expanded by the expander (4) of the multi-stage refrigerator (3), and most of it is gas again. While returning to the high-stage compressor (2) via the return passage (14), the heat stations (10), (11) of the expander (4) are cooled by the cold heat generated by this expansion action, and an extremely low temperature is generated. To do. Then, a part of the high-pressure helium gas whose temperature has become low in the expander (4) of the multistage refrigerator (3) is led out of the expander (4) from the lowest temperature part thereof, and the JT heat exchanger. After flowing into (17) and being cooled by the heat exchanger (17), the JT valve (1
8). In the JT valve (18), the gas expands by Joule-Thomson into helium in a gas-liquid mixed state of about 4.2K,
The helium in the gas-liquid mixed state is supplied to the cooler (19) to evaporate the liquid component and the latent heat of evaporation cools the object to be cooled. The low-pressure low-temperature helium gas discharged from the cooler (19) flows into the secondary side of the JT heat exchanger (17) to
The helium gas on the secondary side is cooled, and the expander (4) is further installed.
Heat exchanger (2) attached to the heat station (10), (11) and / or the cylinder part (5a), (5b) of
Cold heat is recovered by (0) to (23) and returns to normal temperature. Then, the low-pressure gas at room temperature returns to the suction side of the low-stage compressor (1) through the gas return passage (24), and the low-stage compressor (1).
And is returned to the system of the multi-stage refrigerator (3), sucked into the high-stage compressor (2), compressed again, and supplied to the expander (4).

In that case, in the expander (4), although a pressure fluctuation occurs in the helium gas of the expander (4) as the rotary operation of the rotary valve (6) is repeated, a lot of the helium gas (high-stage compressor ( Part of the helium gas returning to 2) passes through the gas return passageway (14) through the bypass passageway (26), is throttled by the throttling mechanism (27) and is depressurized to the suction side of the low-stage compressor (1). Because it flows, the pressure fluctuation is effectively suppressed,
The helium gas pressure (JT valve front pressure) derived from the lowest temperature part of the expander (4) is in a pressure state where the pressure fluctuation is extremely small. As a result, the temperature fluctuation in the cooler (19) becomes extremely small and stable. Moreover, because of the presence of the bypass passage (26), most of the helium gas discharged from the low-stage compressor (1) circulates through the bypass passage (26), so that the suction gas pressure is stable and low. The reliability of the stage compressor (1) is improved. Moreover,
Since the fluctuation of the gas pressure can be effectively suppressed only by providing the bypass passage (26) having the throttle mechanism (27), the check valve and the buffer tank are unnecessary, and the circuit configuration can be simplified.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 shows the overall circuit configuration of a helium refrigerator in an embodiment of the present invention, (1) is a low-stage compressor that compresses low-pressure helium gas to a predetermined pressure (for example, 1 atm to 10 atm),
(2) is a high-stage compressor that is connected to the discharge side of the low-stage compressor (1) and compresses the high-pressure helium gas discharged from the low-stage compressor (1) to a higher pressure (for example, 24 atm). There
The high-pressure helium gas discharged from the high-stage compressor (2) was attached to the cryostat (C) (low temperature tank) G-
It is supplied to the expander (4) of the multi-stage refrigerator (3) such as M type and improved solvee type. The expander (4) has two stages of cylinder parts (5a) and (5b) as shown in enlarged detail in FIG. 2, and has a high pressure side inlet (5c) and a low pressure side outlet (5d) of helium gas. A casing (5) with an opening, and a helium gas that is provided in the casing (5) and opens at every rotation to allow the helium gas that has flowed in from the high pressure side inlet (5c) of the casing (5) to pass through and adiabatically expand Rotating valve (6)
And a valve motor (7) for driving and rotating the valve (6), and first and second regenerators (8) for respectively storing cold heat generated by adiabatic expansion of helium gas according to the rotation of the rotary valve (6). ) And (9).
Further, the high pressure side inlet side (5c) and the low pressure side outlet (5d) of the casing (5) are connected to the high pressure compressor (2) by a gas supply passage (13) and a gas return, respectively, as shown in FIG. Gas is circulated through the passage (14),
Most of the helium gas expanded in the expander (4) is returned to the suction side of the high-stage compressor (2) through the gas return passage (14), and the cold heat generated by adiabatic expansion is stored in the first and second cold storage. It is stored in the vessels (8) and (9).

Further, at the lower ends of the cylinder parts (5a), (5b) of the casing (5), the first and second regenerators (8),
First and second heat stations (10) and (11) for receiving cold heat from (9) are provided, and the cold heat stored in the first and second regenerators (8) and (9) causes 1
And the second heat stations (10), (11). In addition, (5e) and (5f) are radiation shield parts integrally provided at the lower ends of the heat stations (10) and (11), respectively, and are a cryostat (C).
When the expander (4) is attached to the heat exchanger, heat is prevented from entering the cryostat (C) through the attachment portion.

In the second heat station (11) of the casing (5) of the expander (4), a gas lead-out portion for leading out a part of the helium gas from the lowest temperature portion of the expander (4) to the outside of the casing (5). (12) is provided, and the gas outlet (12)
A JT valve (18) is connected to the JT valve (18) via a primary side (17a) of a JT heat exchanger (17), which is an ordinary countercurrent type heat exchanger such as Collins type and laminated type. , And the JT valve (18)
A cooler (19) is connected to the JT valve (18) via the JT heat exchanger (17) to introduce the helium gas from the lowest temperature part of the expander (4) to the JT valve (18). -Joule Thomson expansion (isoenthalpic expansion) with T valve (18), 1 atmosphere, 4.2
The helium in the gas-liquid mixed state of K is supplied, and the helium in the gas-liquid mixed state is supplied to the cooler (19), and the temperature level of 4.2 K is maintained by the latent heat of vaporization of the liquid component of helium to keep the temperature inside the cryostat (C). Is configured to cool the object to be cooled.

Further, the cooler (19) is the JT heat exchanger (17).
Is connected to the secondary side (17b) of the JT heat exchanger (1
In 7), the low temperature and low pressure helium gas from the cooler (19) is heat-exchanged with the helium gas passing through the primary side (17a) before being expanded by the JT valve (18) to cool the gas. Has been done.

Further, in the casing (5) of the expander (4), first and second heat exchange cylinders are formed by winding, for example, gas pipes around the outer peripheries of the cylinders (5a), (5b) and soldering. The first and second heat exchangers (20) and (21) and the first and second heat stations (10) and (11) have the same structure as the cylinder heat exchangers (20) and (21), respectively. Second heat station heat exchanger (2
2) and (23) are attached, the both cylinder part heat exchangers (20) and (21) are connected in series via the first heat station heat exchanger (22), and the second heat exchanger The inflow side of the heat station heat exchanger (23) is connected to the secondary side (17b) of the JT heat exchanger (17), while the outflow side of the first cylinder heat exchanger (20). Is connected to the suction side of the low-stage compressor (1) through the gas return passage (24), and has a low pressure after passing through the secondary side (17b) of the JT heat exchanger (17). Helium gas is supplied in order to the second heat station heat exchanger (23), the second cylinder part heat exchanger (21), the first heat station heat exchanger (22), and the first cylinder part heat exchanger (20). ) To recover the cold heat of the low-pressure helium gas, and to cool the final first cylinder heat exchanger (2 0) leaked from about 1
Helium gas at atmospheric pressure is sucked into the low-stage compressor (1), compressed, and supplied to the high-stage compressor (2). Therefore, the helium gas derived from the expander (4) of the multi-stage refrigerator (3) is cooled by the JT heat exchanger (17) and then expanded by Joule-Thomson by the JT valve (18) to cool the cooler ( 19), and then from the cooler (19) through the heat exchangers (20) to (23) to the heat exchangers (20) to (2).
The temperature is raised to room temperature by 3), the low-pressure helium gas at room temperature is sent to the low-stage compressor (1), and the compressor (1) returns it to the high-stage compressor (2) of the multistage refrigerator (3) again. The JT circuit (25) thus configured is configured.

A gas return passage (14) for returning the helium gas discharged from the low-pressure side outlet (5d) of the expander (4) to the suction side of the high-stage compressor (2), and a heat exchanger for cold heat recovery ( 20) ~ (21)
First heat exchanger (20) located on the downstream side of the cylinder
From the low-stage compressor (1) to the gas return passage (24) for returning the helium gas to the suction side of the low-stage compressor (1) by a bypass passage (26), and in the middle of the bypass passage (26), A capillary tube (27) as a throttle mechanism is provided.

Therefore, in the above embodiment, the high stage and the low stage
When the compressors (1) and (2) of the stage are started and the refrigerator is in a steady operation, the gas supply passage (13) from the high-stage compressor (2)
High-pressure helium gas supplied via the expander is expanded in the expander (4) of the multistage refrigerator (3), and the cold heat generated by the expansion of this gas is stored in the regenerators (8) and (9). Further, the expander (4) is driven by the low-temperature low-pressure helium gas that returns to the low-stage compressor (1) via the heat exchangers (20) to (23) attached to the outer periphery of the casing (5) of the expander (4). After being cooled, these cooling effects keep the first heat station (10) of the expander (4) at a temperature level of about 77K and the second heat station (11) at a temperature level of about 15K. Be done. Therefore, the helium gas expanded by the expander (4) is mostly (90 to 99%) from the regenerators (8) and (9) due to the characteristics of the GM or the solve cycle, and the gas return passage (14 ) To the suction side of the high-stage compressor (2), re-compressed by the compressor (2) and supplied to the expander (4).

Then, due to the expansion in the expander (4), the minimum temperature (about
The rest of the low-temperature high-pressure helium gas (15K) (1-10
%) Is the gas outlet (1) of the second heat station (11)
2), which is discharged from the JT heat exchanger (1
It enters into the primary side (17a) of 7) and is heat-exchanged with the return helium gas passing through its secondary side (17b) to be cooled. The high-pressure helium gas that has passed through the JT heat exchanger (17) is throttled by the JT valve (18) and expanded by Joule-Thomson to 1
It becomes helium in a gas-liquid mixed state of atmospheric pressure and 4.2K, and reaches the cooler (19), where the liquid component in helium is evaporated and its latent heat is the object to be cooled in the cryostat (C). Used for cooling.

After that, the low-pressure saturated helium gas discharged from the cooler (19) enters the secondary side (17b) of the JT heat exchanger (17) to cool the high-pressure helium gas on the primary side (17a). To do. Next, the gas is the second heat station heat exchanger (23) attached to the casing (5) of the expander (4), the second cylinder part heat exchanger (21), and the first heat station heat exchanger. (22) and the first cylinder part heat exchanger (20) in order, and those heat exchangers (20) to (23)
After the cold heat is recovered by the low-pressure compressor (1) via the gas return passage (24), the low-temperature compressor (1) compresses the cold heat to a predetermined pressure, and the high-pressure gas is expanded by the expander. The helium gas returned from (4) via the gas return passageway (14) is further compressed to a higher pressure by the high-stage compressor (2) and then supplied to the expander (4). After that, the same cycle as described above is repeated to perform continuous operation.

At this time, in the expander (4), the pressure of the expanded helium gas fluctuates as the rotary valve (6) that adiabatically expands the helium gas repeatedly rotates (opens and closes). In a process in which a higher pressure is returned to the high-stage compressor (2), most of the gas passes through the gas return passageway (14) through the bypass passageway (26), and then the capillary tube (27) in the bypass passageway (26). While reaching the gas return passageway (24) while being reduced in pressure by the
Since it returns to the suction side of the low-stage compressor (1) from 4), the pressure fluctuation is effectively suppressed. As a result, the pressure (J-T) of the low-temperature high-pressure helium gas that enters the primary side (17a) of the JT heat exchanger (17) from the gas outlet (12) of the expander (4).
The pre-valve pressure) is in a state where the pressure fluctuation is sufficiently suppressed, and the temperature in the cooler (19) is also stabilized as the pressure fluctuation is suppressed. Moreover, due to the presence of the bypass passage (26), most of the helium gas discharged from the low-stage compressor (1) circulates through the bypass passage (26), so that the gas pressure in the gas return passage (24) is reduced. Stable,
The gas suction pressure of the low-stage compressor (1) is effectively stabilized, and the reliability of the low-stage compressor (1) is improved. Also,
Capillary tube (27) for the fluctuation of the JT valve front pressure
Since it is effectively suppressed by the bypass passage (26) that has the structure, it is not necessary to install a check valve or a buffer tank in the cryogenic area around the JT heat exchanger (17), and the circuit configuration is simplified accordingly. You can

Further, the heat exchangers (20) to (23) are attached to the outer periphery of the casing (5) of the expander (4) in the multistage refrigerator (3) to recover the cold heat of the low pressure helium gas after Joule-Thomson expansion. Since it is used for cooling the helium gas in the expander (4), it is possible to reduce the required number of countercurrent type JT heat exchangers, making the helium refrigerator extremely compact and low cost. can do. As described above, the heat exchanger (20) to the expander (4) of the multi-stage refrigerator (3)
Since (23) is attached, the efficiency of the heat exchanger tends to decrease slightly. However, on the other hand, the invasion heat due to heat conduction loss, shuttle loss, pumping loss, etc. through the wall surface can be reduced, which results in compensating for the decrease in efficiency of the heat exchanger. From the above, for example, for infrared sensors, Josephson elements, etc., the ratio of heat entering from the room temperature is relatively large and the load at the 4.2K temperature level is small (about 0.5W).
This is advantageous when cooling an object to be cooled.

Furthermore, since the JT circuit (25) is integrated into the multi-stage refrigerator (3) to make the device structure compact,
When mounted on the cryostat (C), the area of the radiation shield parts (5e), (5f) of the casing (5) of the expander (4) can be smaller than that of the conventional one, and the radiation shield performance is improved accordingly. Can be made.

In the above embodiment, the bypass tube (26) is provided with the capillary tube (27) as a throttle mechanism.
Of course, the throttle mechanism may be configured by a flow control valve.

Moreover, in the said Example, both the cylinder part heat exchangers (20) and (21) and the heat station heat exchangers (22) and (23)) were attached to the outer periphery of the casing (5) of the expander (4). However, any one of the heat exchangers (20), (21) and (22), (23) may be omitted.

(Effects of the Invention) As described above, according to the helium refrigerator of the present invention, the helium gas after expansion accompanying the opening / closing operation of the rotary valve in the expander in a multistage refrigerator such as a GM type or an improved Solvay type. Since the pressure fluctuation of the pressure was effectively suppressed by the bypass circuit with the throttling mechanism that connects the intake sides of the low-stage compressor and the high-stage compressor to each other, the J
-It is possible to stabilize the temperature inside the cooler by effectively suppressing the fluctuation of the pressure before the T valve, and stabilize the gas pressure on the suction side of the low-stage compressor to improve the reliability of the low-stage compressor. Can be achieved. Moreover, since the bypass passage with the throttling mechanism suppresses fluctuations in the JT valve front pressure, a check valve and a buffer tank installed in a cryogenic portion can be eliminated, and the circuit structure can be simplified. You can

[Brief description of drawings]

The drawings show an embodiment of the present invention, FIG. 1 is an overall configuration diagram of a helium refrigerator, and FIG. 2 is a vertical sectional view of an expander in a multistage refrigerator. (1) …… Low-stage compressor, (2) …… High-stage compressor, (3)
…… Multi-stage refrigerator, (4) …… Expander, (5a), (5b)…
… Cylinder, (6) …… Rotary valve, (8), (9)
…… Regenerator, (10), (11) …… Heat station,
(17) …… JT heat exchanger, (18) …… JT valve, (1
9) …… Cooler, (20), (21) …… Cylinder heat exchanger, (22), (23) …… Heat station heat exchanger,
(25) …… JT circuit, (26) …… Bypass passage, (2
7) …… Capillary tube.

Claims (1)

[Claims] 1. A high-pressure helium gas supplied from a high-stage compressor (2) is expanded by a expander (4) containing regenerators (8), (9) according to a rotary operation of a rotary valve (6). A multi-stage refrigerator such as a GM type or an improved solvee type that expands and returns a large amount of the helium gas to the high-stage compressor (2) while generating low temperatures in the heat stations (10) and (11). J- which comprises (3) and expands the remaining low-temperature high-pressure helium gas derived from the lowest temperature part of the expander (4) in the multistage refrigerator (3) by Joule-Thomson expansion
The T-valve (18), a cooler (19) for cooling an object to be cooled with helium expanded by the J-T valve (18), and helium gas from the cooler (19) are supplied to the J-T A JT heat exchanger (17) for exchanging heat with the helium gas before expansion with the valve (18), and a heat station (1 for the expander (4).
0), (11) and / or cylinder part (5a), (5b)
Attached to the heat exchanger (20) for recovering the cold heat of the low-pressure helium gas from the JT heat exchanger (17).
(23) and a low-stage compressor (1) for compressing the low-pressure helium gas heated to room temperature and introducing the gas into the suction side of the high-stage compressor (2) again. ), A large amount of helium gas expanded in the high-stage compressor (2) is returned to the suction side of the high-pressure compressor (2), and the helium gas from the heat exchangers (20) to (23) for cold heat recovery is reduced. A helium refrigerator characterized in that a bypass passage (26) having a throttle mechanism (27) communicates with the gas return passage (24) returning to the stage compressor (1).