JP2001289521A - Pulse-tube refrigerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance a refrigeration capacity of the pulse-tube refrigerator by improving performance of a cold-storage device of the pulse tube refrigerator having a pulse tube. SOLUTION: A meshed cold-storage medium (1) which is formed by braiding wires (1a) of 20-30 μm diameter with a mesh of 15,000-20,000/m is filled in the cold-storage device (2). The internal diameter D of the cold-storage device (2) to the internal diameter d of the pulse tube (3) is in the range of D/d=2.3±0.35. Thus, the surface area of the cold-storage medium (1) becomes larger than it is conventionally is, and the heat exchange efficiency with a working gas is improved. Further, the flow path of the working gas in the cold-storage device (2) is secured to make the device (2) appropriate to the pulse-tube refrigerator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse tube refrigerator using a pulse tube, and more particularly to a regenerator material used for the regenerator.

[0002]

2. Description of the Related Art Conventionally, a Stirling refrigerator in which a displacer is disposed in a cylinder as a lightweight and compact regenerative refrigerator that generates cryogenic-level cold is disclosed in, for example, JP-A-5-133630. To
A pulse tube refrigerator in which the end of a pulse tube is connected to a regenerator has been proposed.

The principle of the above-mentioned pulse tube refrigerator will be described in detail with reference to FIG. 1. A working gas supplied in a compression process of a compressor (C) is connected to a connecting pipe (4), a regenerator (2), and a communication pipe. And enters the pulse tube (3). The working gas supplied by the compressor (C) reaches the communicating portion while being cooled by the regenerator material of the regenerator (2).
A low-pressure working gas is initially contained in the pulse tube (3), but is supplied from the compressor (C) to the regenerator (2).
The working gas in the pulse tube (3) is also compressed by the working gas coming in through. Due to the unidirectional compression effect of the working gas, a temperature gradient is generated in the pulse tube (3).
Then, the generated heat of compression is transmitted to the wall of the pulse tube (3). Since this temperature gradient is positive with respect to the direction of the compression flow, most of the heat of compression is generated at the high temperature end of the pulse tube (3).

On the other hand, when the working gas is recovered by the compressor (C) during the expansion process of the compressor (C), the working gas in the pulse tube (3) expands. The flow direction of this working gas is opposite to that during the compression process, and the pulse tube (3)
There is a temperature gradient in the inside that is negative with respect to the direction of the working gas flow. However, since the heat removal of the hot end is performed before the expansion starts, the average temperature of the entire working gas is lower than that during compression, and as a result, the working gas is supplied to the pulse tube (3).
Receive heat from the wall. The low temperature end of the pulse tube (3) becomes the lowest temperature portion due to this temperature gradient, and cold occurs in this portion. The working gas moves toward the compressor (C) while storing the obtained cold heat in the cold storage material.
By the way, as the cold storage material in the cold storage device (2), a mesh cold storage material made of a metal mesh of copper or stainless steel is used. Usually, the mesh cold storage material of the displacer type Stirling refrigerator is used as the mesh cold storage material. The same one is used.

[0005]

However, the above-described displacer type Stirling refrigerator and pulse tube refrigerator have different structures. In the Stirling refrigerator, the displacer disposed in the cylinder is changed with respect to the change of the working gas pressure in the cylinder. In contrast to the cold head generated by reciprocating with a constant phase difference, the pulse tube refrigerator has no equivalent to the displacer in a Stirling refrigerator, and is operated by an inertance tube connected to the pulse tube. By controlling the phase of the gas pressure and forming a virtual piston in the pulse tube, the cold head is generated at a cryogenic level. In other words, the amount of movement of the working gas in the two refrigerators is greatly different, and the load (heat exchange amount) on the working gas of the regenerator is different. As a result, the refrigerating capacity of the pulse tube refrigerator is filled with the same mesh regenerative material as that of the Stirling refrigerator, thereby causing a problem that the refrigerating capacity is reduced.

[0006] Further, in the pulse tube refrigerator, there is also a problem caused by the inner diameter of the regenerator. That is, as described above, since the heat exchange amounts of the regenerators are different between the two refrigerators, when the regenerator of the Stirling refrigerator having the same refrigerating capacity is used for the pulse tube refrigerator, the inner diameter of the regenerator is too small. Therefore, there is a problem that the performance is insufficient.

The present invention has been made in view of the above points, and an object thereof is to provide a pulse tube refrigerator with a structure of a mesh regenerator used for a regenerator and a size of the regenerator. It is an object of the present invention to improve the performance of a regenerator so as to correspond to a pulse tube refrigerator and improve the refrigerating capacity of the pulse tube refrigerator by adding a device.

[0008]

In order to achieve the above object, according to the present invention, the structure of a mesh regenerator used for a regenerator of a pulse tube refrigerator and the inner diameter of the regenerator are set as follows. I made it.

More specifically, according to the first aspect of the present invention, the compressor (C) for compressing the working gas at a predetermined cycle and the one end of the pulse tube (3) having the internal space are connected to the compressor (C). A buffer (7) connected by a regenerator (2) for exchanging heat with working gas supplied to and discharged from the pulse tube (3), and having the other end of the pulse tube (3) and an internal space of a predetermined volume. And a pulse tube refrigerator connected by a pipe (6),
In the regenerator (2), a wire rod (1
The mesh cold storage material (1) obtained by knitting a) with a mesh roughness of 15,000 to 20,000 lines / m is filled, and the inner diameter D of the regenerator (2) is smaller than the inner diameter d of the pulse tube (3). D / d = 2.3 ± 0.35.

The coarseness of the wire (1a) is 1500
If it is less than 0 / m, a sufficient heat exchange surface area between the mesh cold storage material (1) and the working gas cannot be obtained, while 2
If it exceeds 0000 / m, the pressure loss of the working gas passing through the mesh cold storage material (1) becomes large.
It is set in the range of 000 to 20,000 lines / m. When D / d is less than 1.95, the performance of the regenerator (2) is insufficient with respect to the volume of the pulse tube (3), while D / d is insufficient.
If d exceeds 2.65, the stack height of the mesh regenerator material (1) of the regenerator (2) decreases, and heat is transferred from the low-temperature end to the high-temperature end of the regenerator (2). For this reason, D
/ D is set in the above range of 2.3 ± 0.35.

According to the invention, a wire rod (1a) having a smaller diameter and a finer mesh than the mesh cold storage material (1) used in a conventional Stirling refrigerator or the like.
Is used as the cold storage material (1) of the cold storage device (2), and the heat exchange surface area between the cold storage material (1) and the working gas is further increased. For this reason, a higher heat exchange efficiency than before can be obtained, and the regenerator (2) can be constituted by the mesh regenerator material (1) suitable for the pulse tube refrigerator.

In addition, by setting D / d = 2.3 ± 0.35, the volume of the regenerator (2) becomes larger than before, and the pressure loss is reduced while the flow area of the working gas is sufficiently maintained. At the same time, the amount of the mesh regenerator material (1) filled in the regenerator (2) is increased to improve the heat exchange efficiency between the regenerator (2) and the working gas. Therefore, the regenerative efficiency of the regenerator (2) can be improved, and the refrigerating capacity of the refrigerator can be improved. In addition, the value of 0.35 of D / d is 2.
3 ± 15%. The mesh cold storage material (1) formed by knitting the wire (1a) with a mesh roughness of 15,000 to 20,000 lines / m is a wire (1a) per inch.
Corresponds to approximately 400 to 500 lines. In addition, the conventional wire rod (1
The roughness of the mesh in a) was, for example, 10,000 lines / m, and the value of D / d was 2.0 or less.

According to the second aspect of the present invention, in the pulse tube refrigerator described above, the refrigeration temperature is in a range of 40 to 150K,
In addition, the stacking height of the cold storage material (1) stacked and filled in the cold storage device (2) is 60 to 75 mm.

When the stacking height of the regenerator material (1) is less than 60 mm, heat is transferred from the low-temperature end to the high-temperature end side of the regenerator (2), while when it exceeds 75 mm, the working gas is transferred to the regenerator (2). Since the pressure loss occurs when moving the cold storage material, the stack height of the cold storage material (1) is set to the above-mentioned 60 to 75 mm.

According to the present invention, when a pulse tube refrigerator is used in the above-mentioned refrigeration temperature range, a regenerator (2) suitable for the pulse tube refrigerator can be obtained, and its refrigerating ability can be improved. .

[0016]

FIG. 1 shows a pulse tube refrigerator (R) of the present embodiment. In FIG. 1, (C) is a compressor, in which a reciprocating piston (C1) is inserted and inserted, and the piston (C1) is drivingly connected to a linear motor (not shown). . The piston (C1) reciprocates by the operation of the linear motor, and when a pressure is applied to a working gas such as helium in the compression process, the working gas is generated in each compression space provided in the pulse tube refrigerator (R). Compression causes an increase in temperature. On the other hand, in the expansion process of the compressor (C), when the working gas expands in each space, a temperature drop occurs. Thus, the reciprocating motion of the piston (C1) of the compressor (C) causes a change in pressure and a change in volume of the working gas. The compressor (C) communicates with a high-temperature end of the regenerator (2) via a connection pipe (4).

The regenerator (2) (regenerative heat exchanger)
A mesh cold storage material (1) described later is stored. The high-temperature end of the regenerator (2) on the compressor (C) side receives compression heat of the working gas during the compression process of the compressor (C), and this heat is radiated to the outside. Further, the regenerator (2) is connected to one end of the low-temperature end opposite to the compressor (C), and the connection between the regenerator (2) and the pulse tube (3) generates cryogenic cooling. It is covered by a cold head (5). A communication portion is formed at a connection portion of the regenerator (2) to the pulse tube (3) side, and the pulse tube (3) is connected to the regenerator (2) in the length direction through the communication portion. Are connected, the pulse tube (3) is arranged substantially parallel to the regenerator (2). In the present embodiment, the relationship between the inner diameter D of the regenerator (2) and the inner diameter d of the pulse tube (3) is set to, for example, D / d = 2.3.

A buffer (7) has a space (not shown) therein. The space in the buffer (7) is connected to a high-temperature end of the pulse tube (3) via an inertance tube (6). The working gas extruded from the pulse tube (3) is further cooled by adiabatic expansion in the inertance tube (6), flows into the buffer (7), and flows in the closed space in the buffer (7). I try to control the flow. That is, the working gas supplied from the compressor (C) passes through the connection pipe (4), the regenerator (2), the cold head (5), the pulse pipe (3), and the inertance pipe (6) to pass through the buffer section ( 7) is introduced.

FIG. 2 is an overall view showing the appearance of the mesh cold storage material (1). This mesh cold storage material (1) is made of a wire (1a) having a diameter of 25 μm and having a coarseness of 150, for example.
It shall be knitted to 00 pieces / m. And each wire (1
a) are bundled, and these wires (1a) are combined without being crushed as shown in FIG. 3 to secure a flow path of the working gas. At this time, L shown in FIG.
m. Further, the wire (1a) is made of a cold storage material having a large volume specific heat in the freezing temperature range of 40 to 150K. The mesh regenerator material (1) is laminated in a cylindrical regenerator (2) of the pulse tube refrigerator (R) shown in FIG. In the present embodiment, the stack height of the mesh cold storage material (1) is, for example, 70 mm.

Next, the pulse tube refrigerator (R) of this embodiment
1 will be described with reference to FIG. In the compression process of the compressor (C), the working gas is cooled by performing heat exchange with the mesh cold storage material (1) to release the heat compressed by the regenerator (2). Thereafter, the working gas flows into the pulse tube (3) through the communication part, compresses the working gas in the pulse tube (3), and releases the heat of compression through the wall of the pulse tube (3). I do. Further, the working gas flows into the buffer (7) through the inertance pipe (6). When the working gas is sucked in the expansion process of the compressor (C), the working gas attempts to return from the buffer (7) toward the compressor (C) and moves from the buffer (7) to the inertance pipe. After passing through (6), adiabatic expansion occurs in the pulse tube (3) to further lower the temperature. The cooled working gas reaches the regenerator (2) after cooling the cold head (5), and the mesh regenerator material (1) filled in the regenerator (2) receives the cold heat received from the working gas. accumulate. When the compression and expansion process of the working gas as described above is repeated, heat is removed at the high-temperature end of the regenerator (2) and the pulse tube (3) before the expansion process of the compressor (C). In the expansion process, the working gas receives heat from the wall of the pulse tube (3), so that a cryogenic level of cold can be obtained in the cold head (5).

In this case, during the operation of the refrigerator (R), the working gas such as helium moves in the regenerator (2) during the compression and expansion of the compressor (C). At this time, since the mesh cold storage material (1) used in the present embodiment uses a wire (1a) having a small diameter and a fine mesh, the heat exchange surface area between the cold storage material (1) and the working gas is further improved. And the heat exchange efficiency is higher than in the past, and the refrigerating capacity of the refrigerator (R) can be improved by using the mesh cold storage material (1) suitable for the pulse tube refrigerator (R). In the present embodiment, the inner diameter D of the regenerator (2) and the pulse tube (3)
Since the relationship with the inner diameter d is set to D / d = 2.3, the capacity of the regenerator (2) in comparison with the capacity of the pulse tube (3) is ensured to be larger than before, and the mesh regenerator according to the present invention is used. Even when the material (1) is used, the regenerator (2) has an appropriate volume and a flow area of the working gas with respect to the pulse tube (3). Therefore, during operation of the refrigerator (R), the pulse tube refrigerator is improved by improving the cold storage efficiency of the cold storage (2) such as reducing the pressure loss when the working gas passes through the cold storage (2). The refrigerating capacity of (R) can be improved. The inner diameter D of the regenerator (2) is, as shown in FIG. 4, a cylindrical body (2) made of a phenol resin or the like.
A portion D of the inner diameter excluding a) is shown.

The refrigerating temperature of the pulse tube refrigerator (R) of the present embodiment is in the range of 40 to 150 K. At this time, the lamination of the regenerator material (1) which is laminated and filled in the regenerator (2) When the height is 70 mm, when the pulse tube refrigerator (R) is used in the freezing temperature range, the lamination height of the mesh cold storage material (1) is ensured, and the low temperature of the cold storage (2) is maintained. Edge (eg, cryogenic 80
K) to the high-temperature end (for example, 300K which is room temperature). On the other hand, if the stacking height of the cold storage material (1) is too long, a pressure loss is likely to occur due to the relationship between the flow width of the working gas and the packing density of the cold storage material (1). By setting the stacking height of the cold storage material (1) to the above value, the pressure loss when the working gas moves through the cold storage (2) can be reduced, and a good cold storage (2) can be obtained. As a result, in the present embodiment, the refrigerating capacity of the pulse tube refrigerator (R) can be improved.

In this embodiment, the pulse tube refrigerator (R)
A phase control unit using an inertance pipe (6) as the pipe (6) is used, but other pipes (6) such as a pulse tube refrigerator (R) having an orifice (8) as shown in FIG. And a phase control unit using a pipe (6) such as a double in red type having two orifices (8) and (9) as shown in FIG. .

[0024]

[Experimental Example] (Experimental Example 1) Next, an experimental example implemented using a pulse tube refrigerator will be specifically described. The relationship between the shape of the mesh regenerator and the refrigerating capacity shown in Table 1 and the results obtained by changing the relationship D / d between the inner diameter D of the regenerator and the inner diameter d of the pulse tube will be described.

[0025]

[Table 1]

Table 1 shows that, using a pulse tube refrigerator having a refrigerating capacity of 3 W, the inner diameter D of the regenerator is set to the inner diameter d of the pulse tube.
/D=2.0, 2.3, and 2.6, and changes in the refrigerating capacity (unit: W) of the pulse tube refrigerator when using the regenerative material in Inventive Example 1, Comparative Example 1, and Comparative Example 2. Is shown. Then, the shape of the mesh regenerator material wire was evaluated, and the relationship between the inner diameter D of the regenerator of the pulse tube refrigerator and the inner diameter d of the pulse tube was evaluated.

As shown in Table 1, in Comparative Example 1, a wire rod having a diameter of 35 μm in a regenerator had a roughness of 10,000 lines / m.
And filled with a mesh cold storage material. Then, the refrigerating capacity at each of the D / d values was measured.

In Comparative Example 2, the diameter of the regenerator was 30 mm.
A mesh cold regenerative material obtained by knitting a 1 μm wire with a mesh roughness of 13000 / m, and in Invention Example 1, a 25 μm diameter wire is knitted with a 15000 mesh / m in the regenerator. Mesh regenerator material.

As shown in Table 1, when the shape of the mesh regenerative material of Inventive Example 1 was used and the relation D / d between the inner diameter D of the regenerator and the inner diameter d of the pulse tube was 2.3, the refrigerating capacity was increased. The maximum value is 3W. From this, it can be said that the mesh regenerative material of Inventive Example 1 is more effective than the conventionally used regenerative material and is suitable for a pulse tube refrigerator.

On the other hand, in Comparative Example 1, the refrigeration capacity hardly improved even when the D / d value was changed. It is considered that the reason for this is that the heat storage material has a short heat exchange surface area with the working gas. In Comparative Example 2, the surface area of the mesh regenerator material was made larger than that of Comparative Example 1 to improve the heat exchange efficiency with the working gas. However, compared to Invention Example 1, the optimum refrigerating capacity was obtained. Did not.

From the above, according to Invention Example 1 in which a wire having a smaller diameter and a finer mesh than the conventional mesh regenerator material is used as the regenerator material of the regenerator, the heat of the regenerator material and the working gas is reduced. It can be seen that the exchange surface area is large and a greater heat exchange efficiency than before can be obtained, and that the regenerator can be constituted by a mesh regenerator material suitable for a pulse tube refrigerator.

Table 2 shows an experiment similar to the above in which the refrigerating capacity was 1 W.
It is the result when it performed using the pulse tube refrigerator of No. Similar evaluations can be made in Table 2.

[0033]

[Table 2]

(Experimental Example 2) Next, the relationship between the stacking height of the regenerator material stacked and filled in the regenerator and the refrigerating capacity of the pulse tube refrigerator is described by the inner diameter D of the regenerator and the inner diameter d of the pulse tube. Is shown in Table 3 according to the change of the relationship D / d. In addition, a mesh regenerative material formed by knitting a wire having a diameter of 25 μm with a mesh roughness of 15,000 lines / m was used as the regenerator material to be filled in the regenerator in this experimental example. Generally, when the stacking height of the regenerator material of the pulse tube refrigerator is too short, heat is transmitted from the low temperature end to the high temperature end side of the regenerator, while when the stacking height of the regenerator material is too long, the working gas Pressure loss of the working gas flow is likely to occur due to the relationship between the flow path width and the packing density of the cold storage material. In this experimental example, the refrigerating capacity of the pulse refrigerator was evaluated by changing the heat exchange surface area of the mesh regenerator filled in the regenerator by changing the inner diameter of the pulse tube and the stacking height of the regenerator.

[0035]

[Table 3]

In Table 3, when the relationship D / d between the inner diameter D of the regenerator and the inner diameter d of the pulse tube was changed to 2.0, 2.3, and 2.6, the stacking height of the regenerator material and the refrigerating capacity. The relationship was shown.

As can be seen from the table, when D / d is 2.0, the capacity of the regenerator is not sufficient with respect to the capacity of the pulse tube, and the flow volume of the working gas in the regenerator cannot be secured. It is considered that the refrigeration capacity has decreased. In addition, when D / d is 2.6, the refrigerating capacity is optimal because the heat storage efficiency of the regenerator is reduced because the stacking height of the regenerator material in the regenerator is not sufficient. It is not considered to be. From the table, D / d is 2.3 and the stacking height is 65 mm.
It can be seen that the refrigerating capacity is maximized when. Here, the heat transfer cross-sectional area in Table 3 means the heat exchange surface area of the mesh cold storage material with the working gas when D / d at which the refrigeration capacity is the maximum is 2.3 and the stacking height of the cold storage material is 65 mm. 1 shows the ratio of the heat exchange surface area under each condition when 1 is set to 1. When the D / d is 2.3, the refrigerating capacity shows a good value. In particular, the refrigerating capacity becomes maximum when the stacking height of the regenerator material is 65 mm, and the refrigerating capacity is good even when the stacking height is 75 mm or 85 mm. showed that.

As described above, by setting the stacking height of the regenerator material to a predetermined value in accordance with the relationship between the inner diameter D of the regenerator and the inner diameter d of the pulse tube, the pressure loss when the working gas moves through the regenerator. In addition, it is possible to obtain a regenerator suitable for a pulse tube refrigerator by reducing heat dissipation and maintaining good heat conduction of the regenerator, thereby improving the refrigerating capacity of the pulse tube refrigerator.

[0039]

As described above, according to the first aspect of the present invention, in the pulse tube refrigerator, the diameter of the regenerator is 2 mm.
A wire rod of 0 to 30 μm has an eye roughness of 15,000 to 2,000.
The mesh regenerator material knitted at 0 / m is filled, and the inner diameter D of the regenerator is D / d with respect to the inner diameter d of the pulse tube.
= 2.3 ± 0.35, compared to the mesh cold storage material used in conventional Stirling refrigerators, etc.
The heat exchange surface area of the cold storage material with the working gas becomes larger.
For this reason, greater heat exchange efficiency can be obtained, and the regenerator can be constituted by a mesh regenerator material suitable for a pulse tube refrigerator.

Further, by setting the above D / d, the regenerator has an appropriate volume and a flow area of the working gas with respect to the pulse tube. Therefore, the regenerative efficiency of the regenerator can be improved, and the refrigerating capacity of the refrigerator can be improved.

According to the second aspect of the present invention, in the pulse tube refrigerator, the refrigerating temperature is in a range of 40 to 150 K, and the stacking height of the cold storage material stacked and filled in the regenerator is 60 to 75 mm. Accordingly, the transfer of heat from the low-temperature end to the high-temperature end of the regenerator is suppressed. Further, a good regenerator can be obtained by reducing the pressure loss when the working gas moves through the regenerator, and the refrigerating capacity of the pulse tube refrigerator can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic side view of a pulse tube refrigerator.

FIG. 2 is an overall view showing the appearance of the mesh cold storage material of the present invention.

FIG. 3 is a schematic view showing an enlarged appearance of a mesh cold storage material of the present invention.

FIG. 4 is a sectional view of a regenerator.

FIG. 5 is a schematic side view of an orifice type pulse tube refrigerator.

FIG. 6 is a schematic side view of a double in red type pulse tube refrigerator.

[Explanation of symbols]

 (1) Cold storage material (2) Cold storage (3) Pulse tube (4) Communication part (5) Cold head (7) Buffer (8) Orifice (C) Compressor (R) Pulse tube refrigerator

Claims (2)

[Claims] 1. A compressor (C) for compressing a working gas at a predetermined cycle, and one end of a pulse tube (3) having an internal space are supplied and discharged from the compressor (C) to the pulse tube (3). The other end of the pulse tube (3) and a buffer (7) having a predetermined volume of internal space are connected by a pipe (6). In the pulse tube refrigerator, a wire rod (1) having a diameter of 20 to 30 μm is placed in the regenerator (2).
a) Mesh regenerator material (1) knitted at a mesh roughness of 15,000 to 20,000 lines / m is filled, and the inner diameter D of the regenerator (2) is smaller than the inner diameter d of the pulse tube (3). A pulse tube refrigerator characterized in that D / d = 2.3 ± 0.35. 2. The pulse tube refrigerator according to claim 1, wherein the refrigerating temperature is in a range of 40 to 150 K, and the height of the cold storage material (1) stacked and filled in the cold storage (2) is reduced. A pulse tube refrigerator having a size of 60 to 75 mm.