JPH01123954A - Cryogenic expansion machine - Google Patents

Abstract

PURPOSE: To make the passage resistance of a refrigerant flowing in a heat accumulator uniform and improve a heat exchanging efficiency by making the void ratio of the buffer space side of the heat accumulator higher than that of an expansion space and sequentially combining materials high in their specific heat and thermal conductivity in respective temperature zones. CONSTITUTION: A heat storage material 15 is formed with a nickel wire gauze 18 and a copper wire gauze 20 in its buffer space 11 side in the order of high specific heat. The expansion space 12 side thereof is formed with a tungsten wire gauze 19. The number of meshes of the wire gauze of the buffer space 11 side is smaller than that of the expansion space 12 side to enlarge clearances. The heat storage material 15 for precooling working refrigerant for cooling a load heat exchanger 17 to cryogenic temperature serves to make the passage resistance of the working refrigerant uniform even when the temperature of working refrigerant flowing in a displacer 10 becomes low from the buffer space 11 side to the expansion space 12 side and the specific volume thereof is reduced. Thus, uniform heat exchanging efficiency is obtained in respective passages.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to an improvement in a cryogenic expander using a gas cycle such as a Gifford-McMahon cycle or a Solvay cycle.

(B) Prior Art A conventional cryogenic expander is constructed as shown in, for example, Japanese Patent Publication No. 45-4787. Here, a conventional example will be explained with reference to this publication. In Figure 3, 5
0 is a compressor, and 51 and 52 are an intake pipe and an exhaust pipe, each having an intake valve 53 or an exhaust valve 54, and communicating the compressor 50 and the heat storage device 55. Reference numeral 56 denotes a cylinder having a displacer 58 driven by a crank mechanism 57. Movement of this displacer forms an expansion space 59, and this expansion space communicates with the heat storage device 55 through a vibro 0. In addition, displacer 58
The crank mechanism 57 that drives the intake valve 53 and the exhaust valve 5
4, and the supply valve 53 is connected to the displacer 58.
It opens when it reaches bottom dead center and closes just before it reaches top dead center. The exhaust valve 54 opens when the displacer 58 reaches the top dead center and closes when the displacer 58 reaches the bottom dead center. 61 is a load heat exchanger, and this heat exchanger is attached to the vibro 0 to cool the object to be cooled.

In the cryogenic expander with this structure, the refrigerant compressed by the compressor 50 is guided from the inlet valve 53 to the heat storage device 55, and the refrigerant pre-cooled in the heat storage device is adiabatically expanded in the expansion space 59 and cooled by itself. When the exhaust valve 54 is opened, the load heat exchanger 61 is cooled by the refrigerant flowing from the expansion space 59 to the heat storage device 55, so that the object to be cooled is cooled to an extremely low temperature.

(C) Problems to be Solved by the Invention However, since the conventional heat storage device 55 is made of wire mesh made of the same material and has the same number of meshes, when the porosity is adjusted to the compressor 55 side, the expansion space 59 side Although the pressure loss is reduced, the heat exchange efficiency deteriorates.Also, if the porosity is adjusted to the expansion space 59 side, the pressure loss on the compressor 50 side increases, reducing the cooling temperature in the expansion space 59. There were some problems, such as not being able to do anything.

This invention solves the above-mentioned problems, and aims to increase the pressure loss in the heat storage device by 41 degrees and increase the heat storage capacity.

(d) Means for solving the problem This invention makes the buffer space side of the heat storage device have a larger porosity than the expansion space side, and sequentially combines materials that have higher specific heat and thermal conductivity in each temperature range. It is something that

(E) Effect By having the above structure, this invention makes the passage resistance of the refrigerant flowing through the heat storage unit uniform, increases the heat capacity stored by heat exchange, and increases the temperature of the refrigerant that expands adiabatically in the expansion space. is made so that it is low.

(f) Examples The present invention will be explained below based on the examples shown in FIGS. 1 and 2.

Reference numeral 1 denotes a compressor, and an inlet vibrator 3 having an inlet valve 2 and an exhaust vibrator 5 having an exhaust valve 4 are connected to this compressor. The intake and exhaust vibes are assembled together and connected to an intake/exhaust port 8 provided on the upper wall 7 of the cylinder 6. Inside the cylinder 6 is a display that reciprocates up and down by a shaft 9 connected to a drive device (not shown). -10 is accommodated, and a buffer space 11 and an expansion space 12 of variable volume are defined by this displacer. Also, displacer
Seal rings 13, 14 are attached to the outer periphery of 10. The buffer space 1 and the expansion space 12 are communicated with each other via a heat storage material 15 filled in the displacer 10. A load heat exchanger 17 is attached to the bottom wall 16 of the cylinder 6 to cool the object to be cooled.

The heat storage material 15 has a temperature of 300°K to 22°C on the buffer space 11 side.
A nickel wire mesh 18 with a high specific heat in the range of 0 degrees, a tungsten wire mesh 19 with a high specific heat in the range of 140"K to 70" on the expansion space 12 side, and a tungsten wire mesh 19 with a high specific heat in the range of 140"K to 70" in the middle,
It is formed with a copper wire mesh 20 having a large specific heat in the range of 40 degrees, and the number of meshes of the wire mesh is smaller on the buffer space 11 side than on the expansion space 12 side, so that the gap is larger.

In the cryogenic expander configured as described above, the working refrigerant pressurized by the compressor 1 is supplied when the displacer 10 is at the lowest position (top dead center) on the expansion space 12 side in the cylinder 6. The inlet valve 2 is opened, the exhaust valve 4 is closed, and the air flows from the inlet vibe 3 into the buffer space 11. Then, the displacer 10 is inserted into the buffer space 1 from the expansion space 12 side.
In the process of moving to the first side, the working refrigerant in the buffer space 11 flows into the expansion space 12 while being precooled by the heat storage material 15 inside the displacer 10.

After that, when the displacer 10 reaches the highest position (bottom dead center) on the side of the buffer space 11 in the cylinder 6, the supply valve 2 is closed, the exhaust valve 4 is opened, and the working refrigerant expands in the expansion space 12. and cools itself. Again, in the process of the displacer 10 moving from the buffer space 11 side to the expansion space 12 side, the working refrigerant in the expansion space 12 passes through the buffer space 11 while further cooling the heat storage material 5 inside the displacer 10, and the exhaust vibrator 4 Then return to compressor 1. Thereafter, the load heat exchanger 17 on the bottom wall 16 of the cylinder 6 is repeatedly cooled to a cryogenic temperature.

The heat storage material 15 that pre-cools the working refrigerant that cools the load heat exchanger 17 to an extremely low temperature can be displaced by increasing the number of meshes of the wire gauze and narrowing the gap from the buffer space 11 side to the expansion space 12 side. The working refrigerant flowing inside the chamber 10 becomes lower in temperature from the buffer space 11 side toward the expansion space 12 side, so that even if the specific volume decreases, the passage resistance becomes uniform, and the heat exchange efficiency in each passage part is improved. I try to make it even.

Further, the heat storage material 15 is made of a wire mesh made of a material having a large heat capacity for each temperature zone, so that the heat exchange efficiency can be improved.

(g) Effects of the Invention The cryogenic expansion machine of this invention has a larger porosity on the bulge space side of the heat storage material than on the expansion space side, and also combines materials that have higher specific heat and thermal conductivity at each temperature reached. Therefore, by changing the passage area and porosity of the working refrigerant whose specific volume changes with temperature, the resistance of each passage can be made uniform and the heat exchange efficiency in the heat storage device can be improved. .

[Brief explanation of the drawing]

Figures 1 and 2 illustrate this invention, with Figure 1 being a schematic sectional view of a cryogenic expander, Figure 2 being a schematic diagram of a heat storage device, and Figure 3 being a schematic sectional view of a cryogenic expander.
The figure is a schematic diagram of a conventional cryogenic expander. 6...Cylinder, 10...Displacer-1
11... Buffer space, 12... Expansion space, 1
5... Heat storage material.

Claims (1)

[Claims] 1. A cylinder, a displacer that slides back and forth within the cylinder, and a buffer space and an expansion space defined inside the cylinder by the displacer;
In a cryogenic expander equipped with a heat storage device disposed in a gas flow path communicating between the buffer space and the expansion space, the heat storage device has a larger porosity on the buffer space side than on the expansion space side, and , a cryogenic expansion machine characterized by a sequential combination of materials that have high specific heat and thermal conductivity in each temperature range.