JP3278973B2 - Cryogenic refrigerator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cryogenic refrigerator in which a refrigerant gas such as helium compressed by a compressor is adiabatically expanded to generate cryogenic cooling.

[0002]

2. Description of the Related Art Conventionally, a cryogenic refrigerator used for cooling a low-temperature operating device operated at a cryogenic level of about 4K to the same temperature level is described in, for example, US Pat. No. 4,223,540. Thus, a pre-cooling refrigeration means comprising a refrigeration circuit such as a GM (Gifford McMahon) cycle for pre-cooling the high-pressure helium gas discharged from the compressor, and the high-pressure gas pre-cooled by the pre-cooling refrigeration means is supplied by Joule Thomson J- with J-T valve to expand
A refrigerator having a combination with a T (Jule-Thomson) refrigerator is known. In this type of cryogenic refrigerator, J-
A cooler is provided on the low pressure side of the T-valve so that the cooler generates 4K-level cold. At this time, there is a closed cycle type in which the helium gas supplied from the JT valve to the cooler is returned to the compressor as it is. In this closed cycle type, in order to maintain the safety of the liquefied gas, Separately, a large container for storing the evaporative gas is required in the room temperature section.

On the other hand, there is an open-cycle type which can eliminate the need for such a large storage container at a room temperature. The open cycle type is provided with a refrigerant container for storing liquid helium.
Helium that has been expanded into a gas-liquid state by T expansion is stored in a refrigerant container, while evaporative gas in the refrigerant container is recovered to the JT refrigeration means side and can be maintained in a high-pressure state at room temperature. .

[0004]

However, in the conventional open cycle type, the conventional open cycle type has
Since the gas discharged from the J-T valve flows into the refrigerant container and stirs the gas, the heat entering the liquid helium from the upper wall portion of the container, which has a relatively high temperature, tends to increase. Further, when returning the evaporative gas in the refrigerant container to the compressor side, the superheated gas in the recovered refrigerant container is introduced to the JT refrigeration means side, and the gas temperature in front of the JT valve tends to increase. For these reasons, there is a problem that the actual refrigeration capacity is reduced.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to maintain the advantage of the open cycle type in which the evaporative gas can be recovered on the JT refrigeration means side while maintaining the advantage of the infiltration heat during the steady operation. And to prevent the introduction of superheated gas effectively.

[0006]

In order to achieve the above-mentioned object, according to the first aspect of the present invention, a condensing heat exchanger is provided in a refrigerant container to provide a closed cycle type, while a JT refrigeration means is provided. In this case, the position corresponding to the superheat temperature of the low pressure pipe and the refrigerant container are communicated with each other.

Specifically, in the present invention, as shown in FIG. 1, a pre-cooling refrigeration means (A) for pre-cooling the high-pressure refrigerant gas discharged from the compressor (1) and a pre-cooling refrigeration means (A) A cryogenic refrigerator including a JT refrigeration means (B) for expanding the pre-cooled high-pressure refrigerant gas by Joule-Thomson by a JT valve (3) and a refrigerant container (8) for storing a refrigerant liquid. It is a premise.

The refrigerant gas disposed in the refrigerant container (8) and evaporated in the refrigerant container (8) is supplied to the JT
A condensing heat exchanger (9) for condensing with the low-pressure refrigerant gas expanded by Joule-Thomson in the refrigeration means (B), and a position corresponding to the superheat temperature in the low-pressure pipe of the JT refrigeration means (B) and the refrigerant container (8) ) Are communicated with each other, and the evaporated refrigerant gas in the refrigerant container (8) is cooled by the JT refrigeration means (B).
A communication pipe (10) is provided on the side.

According to a second aspect of the present invention, in the first aspect of the present invention, the JT refrigeration means (B) sucks the high-pressure refrigerant gas discharged from the compressor (1) into the compressor (1). It has JT heat exchange means (2) for exchanging heat with low-temperature low-pressure refrigerant gas. Then, J-
The communication pipe (10) is connected to a position corresponding to the superheat temperature in the low pressure pipe of the T heat exchange means (2).

According to the third aspect of the present invention, the first or second aspect is provided.
In the invention of the above, the condensing heat exchanger (9) and the communication pipe (1)
0) can be removed from the refrigerant container (8).

[0011]

According to the above construction, according to the first aspect of the present invention, during normal operation, the high-pressure refrigerant gas discharged from the compressor (1) and precooled by the precooling refrigeration means (A) is supplied to the JT refrigeration means ( The JT valve (3) of B) expands into a low-pressure refrigerant gas by Joule-Thomson expansion, and is guided to the condensing heat exchanger (9) in the refrigerant container (8). In the condensing heat exchanger (9), the refrigerant gas evaporated in the refrigerant container (8) is cooled and condensed by the low-pressure refrigerant gas. At this time,
The low-pressure refrigerant gas passes through the inside of the condensing heat exchanger (9) and is returned to the low-temperature pipe of the JT refrigeration means (B), so that the refrigerant in the refrigerant container (8) is not stirred, and Does not cause an increase in infiltration heat. On the other hand, the evaporated refrigerant gas in the refrigerant container (8) is recovered to the JT refrigeration means (B) via the communication pipe (10). During the steady operation, the communication pipe (10) communicates with a position corresponding to the superheat temperature in the low pressure pipe of the JT refrigeration means (B), so that the refrigerant gas and the refrigerant at the position corresponding to the superheat temperature in the low pressure pipe are provided. The superheated gas in the vessel (8) is balanced at both ends of the communication pipe (10), whereby the superheated gas in the refrigerant vessel (8) is suppressed from flowing into the low-pressure pipe. Thereby, JT
Superheated gas is not introduced into the low pressure pipe of the refrigeration means (B),
Therefore, it is possible to prevent the gas temperature before the JT valve (3) of the JT refrigeration means (B) from increasing.

According to the second aspect of the present invention, the communication pipe (10) is
JT heat exchange means (2) of JT refrigeration means (B)
The heat exchange between the refrigerant gas passing through the high-pressure pipe of the JT heat exchange means (2) and the low-temperature refrigerant gas passing through the low-pressure pipe by communicating with the position corresponding to the superheat temperature in the low-pressure pipe. In addition, it is possible to prevent the superheated gas in the refrigerant container (8) from being introduced into the low-pressure pipe and to reduce the cooling capacity for the refrigerant gas on the high-pressure pipe side.
It is possible to prevent the gas temperature before the JT valve (3) of the refrigerating means (B) from increasing.

According to the third aspect of the present invention, the condensing heat exchanger (9)
In addition, since the communication pipe (10) can be removed from the refrigerant container (8), maintenance and inspection of the refrigerator can be easily performed.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the overall configuration of a cryogenic refrigerator according to this embodiment.
An M refrigeration circuit (A) is combined with a JT refrigeration circuit (B) as JT refrigeration means.

The JT refrigeration circuit (B) is a refrigeration circuit for compressing and expanding helium gas as a refrigerant to generate about 4K-level cold, and compresses and discharges helium gas. J-T heat exchange means for exchanging heat between the compressor unit (1) and the low-pressure low-pressure helium gas sucked into the compressor unit (1) by the high-pressure helium gas discharged from the compressor unit (1) J-
A T heat exchanger (2) and a JT valve (3) for expanding the high-pressure helium gas precooled by the GM refrigeration circuit (A) into Joule-Thomson gas are provided. The ph diagram showing the relationship between the pressure (p) of the helium gas and the enthalpy (h) in this JT refrigeration cycle is shown by a solid line in FIG.

The compressor unit (1) includes a low-stage compressor (1a) for compressing helium gas to a predetermined pressure and a high-pressure helium gas discharged from the low-stage compressor (1a) to a higher pressure. And a high-stage compressor (1b). This high-stage compressor (1b) also serves as the compressor of the GM refrigeration circuit (A).

The GM refrigeration circuit (A) comprises the high-stage compressor (1b) and the expander (4) connected in a closed circuit,
The expander (4) includes a cylinder (5) having a large and small two-stage structure, and a switching unit (6) connected to the cylinder (5). The switching unit (6) includes the high-stage compressor (1).
The high-pressure pipe extending from the discharge side and the low-pressure pipe extending from the suction side in b) are connected to each other, and the high-pressure pipe and the low-pressure pipe are alternately connected to the cylinder (5). On the other hand, although not shown, a free displacer having a large and small two-stage structure is fitted in the cylinder (5) so as to be able to reciprocate.
The respective expansion spaces are formed so as to be defined on the distal end side of the large diameter portion and the distal end side of the small diameter portion. The large-diameter end of the cylinder (5) is cooled and held at a predetermined temperature level in the first heat station (5a), and the small-diameter end is cooled and held at a lower temperature level than the first heat station (5a). And a second heat station (5b). The free displacer reciprocates in the cylinder (5) by alternately communicating the high-pressure gas pipe and the low-pressure gas pipe in the cylinder (5). The ph diagram in this GM refrigeration cycle is shown by a dashed line in FIG.

The JT heat exchanger (2) exchanges heat between the helium gas passing through the high-pressure pipe and the low-pressure pipe, respectively. The first to third three-stage JT heat exchangers are used. (2a) to (2c) are connected in series. First
The high-pressure pipe of the JT heat exchanger (2a) is connected to the discharge side of the high-stage compressor (1b). The high-pressure pipes of the first and second JT heat exchangers (2a) and (2b) are arranged on the outer periphery of the first heat station (5a) in the expander (2) of the GM refrigeration circuit (A). The first precooler (7
a) and also through the second and third heat exchangers (2b),
Both high-pressure pipes of (2c) are connected to each other via a second precooler (7b) arranged on the outer periphery of the second heat station (5b) of the expander (2). Further, the high pressure pipe of the third JT heat exchanger (2c) is a JT valve (3).
On the low pressure side of the JT valve (3), a dewar (8) as a refrigerant container for storing liquid helium and cooling an object to be cooled is connected. In the dewar (8), a condensing heat exchanger (9) for condensing the evaporated helium gas in the dewar (8).
Are arranged.

As shown in FIG. 3, the condensing heat exchanger (9) has an inner and outer double cylindrical shell (9) concentrically joined.
a) and (9b). A JT valve (3) is connected to the proximal end of the inner shell (9a), and the outer shell (9a) is connected.
The third J-T heat exchanger (2c) is connected to the base end of b) through a low-pressure pipe. The outer shell (9b)
Is closed with a bottom, and a number of disk-shaped fins (9c) are integrally mounted on the outer periphery thereof at predetermined pitch intervals in the axial direction. The condensing heat exchanger (9) is configured to be removable from the outside in the horizontal direction with respect to the heat exchanger mounting hole (8a) formed in the side wall of the dewar (8), and as shown in FIG. A seal (9d) is provided around the outer periphery of the base of the heat exchanger (9), and the condensing heat exchanger (9) is attached to the heat exchanger mounting hole (8a) of the dewar (8). The space between the mounting hole (8a) and the mounting hole (8a) is sealed by a seal portion (9d).
The outer diameter of the seal portion (9d) is the same as that of each fin (9d).
c) so that each fin (9c) does not interfere with the dewar (8) when the condensing heat exchanger (9) is removed from the dewar (8). It has become.

Further, the Dewar (8) and the third JT
A communication pipe (10) is provided between the dewar (8) and the position corresponding to the superheat temperature in the low-pressure pipe of the third JT heat exchanger (2c), between the heat exchanger (2c) and the heat exchanger (2c). Has been established. An end of the communication pipe (10) on the dewar (8) side is opened at a position corresponding to a superheat temperature in the dewar (8). Also, this communication pipe (10) can be removed from the outside in the horizontal direction with respect to the communication pipe mounting hole (8b) formed in the dewar (8), and like the condensation heat exchanger (9). A seal portion (10a) is provided around the outer periphery of the base portion of the portion inserted into the dewar (8) to seal the space between the communication pipe mounting hole (8b).

Therefore, according to this embodiment, during normal operation, the helium gas compressed to a high pressure by the compressor unit (1) is supplied to the first to third JT heat exchangers (2a).
To (2c), and heat-exchanged with the low-temperature and low-pressure helium gas returning to the compressor unit (1) side to be cooled. The first and second precoolers (7a) and (7b) respectively perform G-cooling. After being cooled by the first and second heat stations (5a) and (5b) of the M refrigeration circuit (A), it is expanded by Joule-Thomson by the JT valve (3) to be in a gas-liquid mixed state of about 4K, The helium gas stored in the dewar (8) is condensed around the condensing heat exchanger (9) as shown in FIG.
It becomes liquid helium of about 4K.

At this time, the helium gas discharged from the JT valve (3) is returned to the low temperature pipe of the third JT heat exchanger (2c) through the condensing heat exchanger (9). The helium gas in 8) is not agitated, so that the heat entering the liquid helium from the upper wall portion of the Dewar (8), which is at a relatively high temperature, can be suppressed from increasing. Helium gas in the refrigerant container (8) is recovered to the JT refrigeration means (B) through the communication pipe (10). At the time of steady operation, since the communication pipe (10) is connected to a position corresponding to the superheat temperature in the low-pressure pipe of the third JT heat exchanger (2c), helium gas is supplied at both ends of the communication pipe (10). Pressure and temperature will be balanced. In particular, since the stirring in the dewar (8) by the helium gas from the JT valve (3) does not occur, the equilibrium state is stably maintained. Therefore, the superheated gas in the dewar (8) is prevented from flowing into the low-pressure pipe, so that the superheated gas is prevented from being introduced and the pre-cooling capacity of the high-pressure pipe against helium gas can be prevented from being reduced. The gas temperature before the T valve (3) can be prevented from increasing.

Further, the condensing heat exchanger (9) and the communication pipe (10) can be removed from the heat exchanger mounting hole (8a) and the communication pipe mounting hole (8b) of the dewar (8), respectively. Therefore, there is an advantage that maintenance and inspection of the refrigerator are easy.

In the above embodiment, the JT heat exchanger (2) is divided into three stages of first to third heat exchangers (2a) to (2c), and a third heat exchanger (2c) is provided. A communication pipe (10) communicates with a substantially central portion of the low-pressure pipe described above, and the communication position of the communication pipe to the JT heat exchange means is, for example, between the second heat exchanger and the third heat exchanger. It may be. In addition, depending on the position corresponding to the superheat temperature during the steady operation, the communication pipe can communicate with the low-pressure pipe other than the JT heat exchanger.

[0025]

As described above, according to the first aspect of the present invention, the refrigerant gas evaporated in the refrigerant container for storing the refrigerant liquid is expanded by Joule-Thomson by the JT valve of the JT refrigeration means. A condensing heat exchanger for condensing with the low-pressure refrigerant gas is provided, and a communication pipe for recovering the evaporated refrigerant gas in the refrigerant container to the JT refrigeration means side is connected to a position corresponding to the superheat temperature in the low-pressure pipe of the JT refrigeration means. By doing so, the gas discharged from the JT valve can be returned to the low-temperature pipe of the JT refrigeration means via the condensation heat exchanger, preventing the refrigerant in the refrigerant container from being stirred and preventing the intrusion heat. In addition to suppressing the increase, the state of the refrigerant gas at both ends of the communication pipe is balanced with each other during the steady operation, thereby preventing the superheated gas in the refrigerant container from being introduced into the JT refrigeration means through the communication pipe. Can do , By these, it is possible to suppress a reduction in refrigerating capacity of the J-T refrigeration unit.

According to the second aspect of the present invention, since the communication pipe is connected to a position corresponding to the superheat temperature in the low-pressure pipe of the JT heat exchange means of the JT refrigeration means, the JT heat exchange means can be operated during a steady operation. The superheated gas in the refrigerant container can be prevented from being introduced into the low-pressure pipe of the means through the communication pipe, and the cooling capacity of the JT heat exchange means with respect to the refrigerant gas on the high-pressure pipe side is prevented from being reduced, so that the JT can be prevented. A decrease in the refrigerating capacity of the refrigerating means can be suppressed.

According to the third aspect of the present invention, since the condensing heat exchanger and the communication pipe are configured to be detachable from the refrigerant container, the refrigerator is operated by removing the condensing heat exchanger and the communication pipe from the refrigerant container. Maintenance work can be facilitated.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing a cryogenic refrigerator according to an embodiment of the present invention.

FIG. 2 is a ph diagram of the cryogenic refrigerator.

FIG. 3 is a schematic view showing a main part of the embodiment.

FIG. 4 is a perspective view showing a dewar side end of a condensing heat exchanger and a communication pipe.

[Description of Signs] (1) Compressor unit (compressor) (2) JT heat exchanger (JT heat exchange means) (3) JT valve (8) Dewar (refrigerant container) (9) Condensing heat exchanger (10) Communication pipe (A) GM refrigeration circuit (precooling refrigeration means) (B) JT refrigeration circuit (JT refrigeration means)

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F25B 9/00 395 F25B 9/00 F25B 9/02

Claims (3)

(57) [Claims] A pre-cooling refrigeration means (A) for pre-cooling a high-pressure refrigerant gas discharged from a compressor (1), and a high-pressure refrigerant gas pre-cooled by the pre-cooling refrigeration means (A) is supplied to a J-T valve (3). ), A cryogenic refrigerator comprising a JT refrigeration means (B) for expanding Joule Thomson by means of a refrigerant and a refrigerant container (8) for storing a refrigerant liquid, wherein the refrigerant is disposed in the refrigerant container (8). A condensing heat exchanger (9) for condensing the refrigerant gas evaporated in the vessel (8) with the low-pressure refrigerant gas expanded by Joule-Thomson in the JT refrigeration means (B); and the JT refrigeration means (B) And a communication pipe (10) for communicating the superheat temperature equivalent position in the low pressure pipe with the refrigerant container (8) and recovering the evaporated refrigerant gas in the refrigerant container (8) to the JT refrigeration means (B) side. A cryogenic refrigerator comprising: 2. The cryogenic refrigerator according to claim 1, wherein the JT refrigeration means (B) is configured to cool the high-pressure refrigerant gas discharged from the compressor (1) into a low-temperature refrigerant sucked into the compressor (1). JT heat exchange means (2) for exchanging heat with the low-pressure refrigerant gas is provided, and a communication pipe (10) is communicated with a position corresponding to the superheat temperature in the low-pressure pipe of the JT heat exchange means (2). A cryogenic refrigerator. 3. The cryogenic refrigerator according to claim 1, wherein the condensing heat exchanger (9) and the communication pipe (10) are each configured to be able to be removed from the refrigerant container (8). Characterized cryogenic refrigerator.