JPH05306844A - Heat exchanger for cryogenic refrigerator - Google Patents

Abstract

(57) [Abstract] [Purpose] Heat exchangers for JT refrigerators (13) to (1
In 5), the gas in the low-pressure gas flow path (26) between the inner and outer shells (21) and (22) is blocked by bypassing the fins (23), (23), ... Surrounding the heat transfer tube (24). The gas is satisfactorily applied to the fins (23), (23), ... Without increasing the gap tube to increase the heat exchange efficiency and improve the productivity of the heat exchangers (13)-(15). And to reduce variations in performance. [Structure] The heat transfer tube (24) is composed of a flat tube in which the long axis direction of the cross section is arranged parallel to the axial center line direction of the shells (21), (22). In addition, the fins (2
3), (23), ... Are arranged so as to be inclined in a predetermined direction with respect to a plane passing through the axial center lines of the shells (21), (22), and the gas is axial center lines of the shells (21), (22). Turn around,
The efficiency of the heat exchangers (13) to (15) is further improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cryogenic refrigerator which produces cryogenic levels of refrigeration by adiabatic expansion of compressed refrigerant gas such as helium. The present invention relates to an improvement of a heat exchanger that is cooled by exchanging heat with a low-pressure low-temperature refrigerant gas.

[0002]

2. Description of the Related Art Conventionally, for example, US Pat. No. 422 has been used as a cryogenic refrigerator for cooling a low temperature operating device operated at an extremely low temperature level of about 4K to the same temperature level.
As described in No. 3540, a pre-cooling refrigerator and a J-
A binary circuit refrigerator combined with a T refrigerator is known.

The above-mentioned pre-cooling refrigerator comprises a refrigerator such as a GM cycle (Gifford-McMahon cycle) or an improved Solvay cycle, in which the helium gas (refrigerant gas) compressed by the compressor is adiabatically expanded by an expander. The cold temperature of the gas is generated in the heat station by the temperature drop of the gas.

On the other hand, the JT refrigerator has a precooler for precooling by exchanging heat between the helium gas supplied from the compressor and the heat station of the expander in the precooling refrigerator, and the helium gas is used as a joule gas. Thomson inflates J-
A T-valve and a closed circuit are connected to each other. The helium gas from the compressor is pre-cooled by a pre-cooler, and the pre-cooled helium gas is expanded by Joule-Thomson by the J-T valve to form a gas-liquid mixed state. In addition, the latent heat of vaporization of helium is used to generate cold at a lower level of 4K.

By the way, the JT refrigerator is equipped with a plurality of heat exchangers called JT heat exchangers.
In each of these heat exchangers, heat is exchanged between the helium gases passing through the primary side and the helium gas passing through the secondary side, respectively. That is, as shown in FIG. 4, for example, in the space between the inner and outer cylindrical shells (a) and (b) joined concentrically, a plurality of fins (c1), (c1), ... The heat pipes (c) (high-pressure pipes) are spirally arranged, and the heat transfer pipes (c) are arranged.
The inside is formed in the high-pressure gas flow path (d) (primary side) through which the high-pressure gas supplied from the compressor to the expander flows, while the shell (a) and (b) are surrounded around the heat transfer tube (c). Low pressure gas flow path (e) through which low pressure gas returning from the expander to the compressor flows in the space of
The high temperature gas in the high pressure gas flow path (d) that is formed on the (secondary side) and flows from the compressor to the expander is replaced with the low temperature gas in the low pressure gas flow path (e) that returns from the expander to the compressor. Heat is exchanged between them to cool them. In the figure, (g) is glass wool contained in the inner shell (a).

In the low pressure gas passage (e) between the inner and outer shells (a) and (b), the low pressure gas flows so as to hit the fins (c1), (c1), ... Surrounding the heat transfer tube (c). Is preferable, and the efficiency of the heat exchanger can be increased. However, in reality, the adjacent heat transfer tubes (c), (c)
Between the shells (a) and (b), a large gap is formed between the fins (c1) and (c).
It becomes a wall surface flow that flows along the shell (a) and (b) surfaces while bypassing 1), ..., It is difficult to increase the heat exchange efficiency. Therefore, conventionally, for the purpose of closing the gap,
When the heat transfer tube (c) is spirally wound around the inner shell (a) during assembly of the heat exchanger, the heat transfer tube (c) is placed between the fins (c1) and (c1) of the adjacent heat transfer tubes (c) and (c). A gap tube (f) such as Teflon (registered trademark) is wound, and the fin (c) of the heat transfer tube (c) is used to pass gas through the tube (f).
1) It is designed to be directed to the side.

[0007]

However, winding the tube (f) in this way requires a great deal of work and makes the productivity extremely poor. In addition, it is unavoidable that the winding method requires skill and varies, and when the winding method is not good, there is a problem that a bypass flow of gas is caused and the performance is deteriorated.

The present invention has been made in view of the above problems, and an object thereof is to improve the heat transfer tube itself so that the gas can satisfactorily hit the fins and the heat exchange efficiency can be increased while eliminating the gap tube. In this way, the productivity of the heat exchanger is improved and the variation in its performance is reduced.

[0009]

In order to achieve the above object, in the invention of claim 1, the heat transfer tube itself is constituted by a flat tube.

More specifically, according to the present invention, as shown in FIG. 1, a compressor for compressing a refrigerant gas and a high-pressure refrigerant gas discharged from the compressor are expanded to generate cryogenic cold. The heat exchanger attached to the cryogenic refrigerator provided with the machine (12) is a prerequisite. This heat exchanger comprises inner and outer shells (21), (22) and both shells (21),
(22) spirally arranged, and fins (2
3), (23), ... Standingly provided, a heat transfer tube (24), and a high pressure gas in which the high pressure refrigerant gas supplied from the compressor to the expander (12) flows inside the heat transfer tube (24). While the flow path (25) is formed, around the heat transfer tube (24),
A low pressure gas flow path (26) for flowing low pressure gas returning from the expander (12) to the compressor is formed, and a high pressure gas flow path (2
The high temperature gas in 5) is cooled by exchanging heat with the low temperature gas in the low pressure gas channel (26).

The heat transfer tube (24) is constituted by a flat tube whose cross-section has a major axis extending parallel to the axial direction of the shells (21), (22), and at least the heat transfer tube (24). The fins (23), (23), ... Are erected on the outer periphery of the inner and outer shells (21), (22).

In the invention of claim 2, the fin (2
3), (23), ... Are tilted in a predetermined direction with respect to a plane passing through the axes of the shells (21), (22).

[0013]

With the above construction, in the invention of claim 1, the heat transfer tube (24) in the heat exchanger is a flat tube, and the longitudinal direction of its cross section is the axis of the shells (21), (22). Fins (23), which are arranged parallel to the direction, and which are arranged on the outer periphery of at least the inner and outer shells (21), (22) of the heat transfer tube (24).
Since (23), ... Are erected, the tips of the fins (23), (23), ... On the outer circumference of the heat transfer tube (24) are straight and the shells (21), (22) extend over a long range. It is placed parallel to the surface. Therefore, the shells (21), (22)
The refrigerant gas flowing in the low-pressure gas flow path (26) between them comes into contact with the fins (23), (23), ... In a large range, and the fins (2) of the adjacent heat transfer tubes (24), (24).
3) and (23) and the shells (21) and (22), even if the gap tubes do not close the gaps between the gas and the fins (2).
It is possible to improve the efficiency of the heat exchanger by favorably exchanging heat with 3), (23), ....

Further, since the gap tube is not required as described above, the labor is not required, the productivity of the heat exchanger can be improved, and the variation in the performance is reduced, so that the stable effect can be obtained. ..

According to the second aspect of the invention, the fins (23),
The heat transfer pipes (2) are arranged so that the (23), ...
4) Since it is erected on the outer circumference, the low pressure gas flow path (26)
The gas can be swirled around the axes of the shells (21) and (22), and the efficiency of the heat exchanger can be further improved.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, as shown in FIG. 2, the refrigerator (R) is composed of a dual circuit refrigerator in which a pre-cooling refrigerator (1) and a JT refrigerator (11) are combined.

The precooling refrigerator (1) is composed of a G-M (Gifford-McMahon) cycle refrigerator and is used to precool the helium gas (refrigerant gas) in the JT refrigerator (11). Helium gas is compressed and expanded. This refrigerator (1) is composed of a pre-cooling compressor (not shown) and an expander (2) attached to a cryostat (C) connected in a closed circuit. The expander (2) includes a closed cylindrical case (3) arranged outside the cryostat (C), and a cylinder (4) having a large and small two-stage structure connected to a lower portion of the case (3). Have. The case (3) has a high-pressure gas inlet (5) connected to the discharge side of the pre-cooling compressor and a low-pressure gas outlet (6) connected to the suction side. On the other hand, the cylinder (4) penetrates the upper wall of the cryostat (C) and extends to the inside thereof, and the lower end of the large diameter portion (4a) thereof is cooled and maintained at a predetermined temperature level by the first heat station ( 7) and the lower end of the small diameter portion (4b) is formed in the second heat station (8) which is cooled and maintained at a temperature level lower than that of the first heat station (7).

That is, although not shown here, in the cylinder (4), the heat stations (7),
A free displacer (replacement device) partitioning and forming an expansion space is reciprocally fitted in a position corresponding to (8). On the other hand, in the case (3), a rotary valve that opens and closes each time it rotates and a valve motor that drives the rotary valve are housed. The rotary valve supplies the helium gas flowing from the high-pressure gas inlet (5) to each expansion space in the cylinder (4) or discharges the helium gas expanded in each expansion space from the low-pressure gas outlet (6). To switch to. Then, by opening and closing this rotary valve, the high-pressure helium gas is expanded by Simon in each expansion space in the cylinder (4), and a cryogenic level of cold is generated due to the temperature drop accompanying the expansion.
The cold is applied to the first and second heat stations (7),
Hold at (8). That is, in the pre-cooling refrigerator (1),
The high-pressure helium gas discharged from the compressor is supplied to the expander (2), and the temperature of the heat stations (7) and (8) is lowered by adiabatic expansion in the expander (2), and the J-T A precooler (1) described later in the refrigerator (11)
6) and 17) are pre-cooled, and the expanded low-pressure helium gas is returned to the compressor and re-compressed. The first heat station (7) of the cylinder (4) supports a radiation shield (S) having a substantially closed cylindrical shape arranged in the cryostat (C) so that heat can be transferred.

On the other hand, the JT refrigerator (11) has about 4
A refrigerator for compressing and expanding helium gas in order to generate K level cold, and a JT compressor (not shown) for compressing helium gas, and the compressed helium gas for Joule Thomson Expander to expand (12)
It has and. The expander (12) includes first to third J-T heat exchangers (13) to (15) located inside the radiation shield (S) of the cryostat (C). Each of the JT heat exchangers (13) to (15) has a high pressure gas flow path (2) in the primary side (heat transfer tube (24) described later).
5)) and the helium gas passing through the secondary side (the same low-pressure gas flow path (26)) are exchanged with each other, and the primary side of the first JT heat exchanger (13) is a JT. It is connected to the discharge side of the compressor. Also, the first and second J
The primary side of each of the -T heat exchangers (13) and (14) is an adsorber (20a) for removing contamination, and the first heat station (of the expander (2) in the precooling refrigerator (1) ( 7) It is connected via a first precooler (16) arranged on the outer circumference. Similarly, the primary side of each of the second and third J-T heat exchangers (14) and (15) is connected to the adsorber (20).
b) and a second precooler (17) arranged on the outer circumference of the second heat station (8) of the expander (2). Further, the third J-T heat exchanger (15)
Is connected to a cooler (19) through an adsorber (20c) and a JT valve (18) that expands high-pressure helium gas by Joule-Thomson. (Not shown) is connected so that heat can be transferred. The opening of the JT valve (18) is adjusted from the outside of the cryostat (C) by the operation rod (18a). The cooler (19) is the third and second J-T heat exchangers (1
5) and (14) are connected to the secondary side of the first J-T heat exchanger (13) via the secondary sides thereof, and the secondary side of the first J-T heat exchanger (13) is connected to the above-mentioned J- It is connected to the suction side of the T compressor.

Therefore, in the J-T refrigerator (11), the J-
The helium gas is compressed to a high pressure by the T compressor and supplied to the expander (12), which is supplied to the first to third JT heat exchangers (13) to (15) of the expander (12). , Heat exchange with low-temperature low-pressure helium gas returning to the compressor side, and at the first and second precoolers (16) and (17), the first and second heat stations (7) of the expander (2), After cooling in (8), the JT valve (18) expanded Joule-Thomson to make helium in a gas-liquid mixed state of about 4K at 1 atm in a cooler (19), and cooled by the latent heat of vaporization of this helium. Set the vessel (19) to a cryogenic level (about 4
Cool to K). After that, the helium gas, which has been reduced in pressure by the expansion, is applied to the third to first J-T heat exchangers (15).
(13) through the secondary side, the JT compressor is made to suck and recompress.

The above-mentioned first to third J-T heat exchangers (13)-
(15) has the same configuration, and as shown in FIG. 1, the inner and outer cylindrical shells (21) joined concentrically,
A large number of fins (23), (2
3), ... Heat transfer tube (24) (high pressure tube) with outer circumference attached
Is housed in a spiral form. The internal space of the heat transfer tube (24) is located between the compressor and the expander (13).
-It is formed in the high pressure gas flow path (25) (primary side) through which the high pressure helium gas supplied to the T valve (18) or the cooler (19) flows, while the inner and outer shells () are formed around the heat transfer tube (24). The space between 21) and (22) is formed in the low pressure gas flow path (26) (secondary side) through which the low pressure gas returning from the JT valve (18) or the cooler (19) to the compressor flows. .. Then, from the compressor to the JT valve (18) or cooler (19)
Between the high temperature gas in the high pressure gas passage (25) flowing toward the compressor and the low temperature gas in the low pressure gas passage (26) returning from the JT valve (18) or the cooler (19) to the compressor. Allow to heat exchange and cool. Specifically, in the first J-T heat exchanger (13), high pressure helium gas is supplied from room temperature to 50 K, for example.
The second J-T heat exchanger (14) cools the helium gas from 50K to 15K, and the third J-T heat exchanger (15) cools the helium gas from 15K to about 5K. (27) is glass wool contained in the inner shell (21).

The feature of the present invention resides in the structure of the heat transfer tube (24). That is, the heat transfer tube (24) is a flat tube obtained by flattening an ordinary tube having a circular cross section, and the major axis direction of the cross section is parallel to the axial center lines of the inner and outer shells (21), (22). And are wound around the inner shell (21). Of the outer circumference of the heat transfer tube (24), a large number of fins (23), (23), ... Are transferred to the inner surface side facing the inner shell (21) and the outer surface side facing the outer shell (22), respectively. They are erected at regular intervals in the length direction of the heat pipe. The inner and outer fins (23),
(23), ... Are arranged substantially parallel to a plane passing through the axial center lines of the shells (21), (22).

Next, the operation of the above embodiment will be described. When the refrigerator (R) is in a steady operation state, in the precooling refrigerator (1), the high-pressure helium gas supplied from the precooling compressor expands in each expansion space of the expander (2), and the expansion of this gas occurs. The first heat station (7) of the cylinder (4) is cooled to a predetermined temperature level and the second heat station (8) is cooled to a temperature level lower than that of the first heat station (7) due to the temperature drop accompanying the above. With the cooling of the first heat station (7), the temperature of the radiation shield (S) in contact with the heat station (7) in a heat transfer manner drops to the same temperature level as that of the first heat station (7). As a result, the central portion of the cryostat (C) is shielded from the outside.

On the other hand, at the same time, the JT refrigerator (1
In 1), the high-pressure helium gas discharged from the compressor enters the primary side of the first JT heat exchanger (13) and is heat-exchanged with the low-pressure helium gas on the secondary side returning to the compressor side there. It is cooled from room temperature 300K to about 50K, and then enters the first precooler (16) around the first heat station (7) of the expander (2) and is further cooled. The cooled gas enters the primary side of the second J-T heat exchanger (14) and is cooled to about 15K by heat exchange with the low pressure helium gas on the secondary side, and then expanded (2 ) The second precooler (17) around the second heat station (8) is further cooled. After this, the gas enters the primary side of the third J-T heat exchanger (15) and is cooled to about 5 K by heat exchange with the low-pressure helium gas on the secondary side, and then J-
To the T valve (18). In this JT valve (18), the high-pressure helium gas is throttled and expanded by Joule-Thomson to become helium in a gas-liquid mixed state of 1 atm and about 4 K, and is supplied to the cooler (19). Then, in this cooler (19), a cryogenic level of 4K is obtained by the latent heat of vaporization of the liquid portion in the helium in the gas-liquid mixed state, and the cooling target connected to the cooler (19) is cooled.

In the case of this embodiment, the above-mentioned first to third J-T
The heat transfer tubes (24) for partitioning the high pressure and low pressure gas flow paths (25) and (26) in the heat exchangers (13) to (15) are
The cross-section is constituted by flat tubes arranged parallel to the axial direction of the shells (21) and (22), and the outer circumference of the heat transfer tube (24) on the inner and outer shell (21) and (22) sides. Since the fins (23), (23), ... Are erected on the respective surfaces, the tips of the inner and outer fins (23), (23) ,.
(22) It can be arranged parallel to the surface. As a result, the refrigerant gas flowing through the low pressure gas flow path (26) between the shells (21) and (22) has a large range of fins (23), (23), ...
Without contacting the heat transfer tubes (24), (24), and without using a clearance tube for closing the clearance between the fins (23), (23), ... And the shells (21), (22). , The heat exchange between the gas and the fins (23), (23), can be favorably performed, and the efficiency of the heat exchangers (13) to (15) can be improved.

Moreover, since the gap tube is not required, it is not necessary to wind the tube, and the productivity of the heat exchangers (13) to (15) can be improved. Further, variations in the performance of the heat exchangers (13) to (15) are reduced, and a stable effect can be obtained.

In the above embodiment, the fins (23), (23), which are erected on the inner and outer surfaces of the heat transfer tube (24), respectively.
, Are arranged substantially parallel to the plane passing through the axis of the shells (21), (22), but instead of this, as shown in FIG. 3, the fins (23), (23), ... (In the figure, only the outer fins (23), (23), ... Are shown), and each of the shells (21), (22) is a plane (P) passing through the axial center lines of the shells (21), (22).
It may be arranged to incline in a predetermined direction by an angle (θ). By doing this, the low pressure gas flow path (2
The gas of 6) can be swirled around the axes of the shells (21) and (22) by the guide of the inclined fins (23), (23), ... ) ~
It is possible to further improve the efficiency of (15).

[0028]

As described above, according to the first aspect of the present invention, the heat transfer tube of the heat exchanger in the cryogenic refrigerator has a flat tube whose cross-section has the major axis direction extending parallel to the axial direction of the shell. With this configuration, the heat exchange between the gas and the fins can be favorably performed, the efficiency of the heat exchanger can be improved, and the conventional gap tube for closing the gap where the gas bypasses the fins. Is unnecessary, the productivity of the heat exchanger can be improved, the variation in the performance can be reduced, and stable heat exchange performance can be obtained.

According to the second aspect of the present invention, the fins are erected on the outer circumference of the heat transfer tube so as to be inclined in a predetermined direction with respect to the plane passing through the axis of the shell, so that the gas in the low-pressure gas passage can be guided. It is possible to further improve the efficiency of the heat exchanger by swiveling around the axis line of.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view showing a part of a heat exchanger according to a first embodiment of the present invention.

FIG. 2 is a refrigerant circuit diagram showing the overall configuration of a cryogenic refrigerator.

FIG. 3 is a front view partially showing the arrangement of fins on the outer circumference of the heat transfer tube in the second embodiment.

FIG. 4 is a view corresponding to FIG. 1 showing a conventional example.

[Explanation of symbols]

 (R) Cryogenic refrigerator (1) Precooling refrigerator (11) JT refrigerator (12) Expander (13) to (15) JT heat exchanger (21), (22) Shell (24) Heat transfer tube (25) High pressure gas flow path (26) Low pressure gas flow path

Claims (2)

[Claims] 1. A cryogenic refrigerator provided with a compressor for compressing a refrigerant gas and an expander (12) for expanding a high-pressure refrigerant gas discharged from the compressor to generate a cryogenic level of refrigeration. And is arranged spirally between the inner and outer shells (21), (22) and the shells (21), (22), and fins (23), (23), ... Heat transfer tube (24)
And a high pressure gas flow path (25) through which the high pressure refrigerant gas supplied from the compressor to the expander (12) flows, is formed inside the heat transfer tube (24), while surrounding the heat transfer tube (24). Is formed with a low pressure gas flow path (26) through which low pressure gas returning from the expander (12) to the compressor is formed. In a heat exchanger configured to exchange heat with a low temperature gas for cooling, the heat transfer tube (24) has a shell (2
1) and (22), which are flat tubes extending in parallel with the axial direction of the heat transfer tube (24), at least the inner and outer shells (2)
The fins (23), (2) are provided on the outer periphery on the side of (1), (22).
3), ... are provided upright, a heat exchanger for a cryogenic refrigerator. 2. The heat exchanger for a cryogenic refrigerator according to claim 1, wherein the fins (23), (23), ... Are shells (21),
A heat exchanger for a cryogenic refrigerator, which is inclined in a predetermined direction with respect to a plane passing through an axis line of (22).