JPH02298764A - Pulse tube type refrigerator - Google Patents

Abstract

PURPOSE:To improve refrigerating efficiency without loss of merits of light weight, compact structure and high reliability and to efficiently generate low temperature by connecting a buffer tank or a variable volume space via a one-way valve. CONSTITUTION:When a piston 12 is directed toward a top dead point in a pulsating manner, fluid in a compressing space 15 and fluid in a pulse tube 5 are adiabatically compressed, and compression heats are discharged via radiators 16, 6. In this case, the fluid in the space 15 is cooled by a cold accumulator 2, fed to the tube 5, the fluid in the tube 5 is adiabatically compressed to radiate heat by the radiator 6, and fed into a buffer tank 10 via a check valve 9 which is opened when it becomes a certain pressure. Then, when the piston 12 is directed toward a bottom dead point in a pulsating manner, the pressure in the space 15 is abruptly lowered. Accordingly, a check valve 11 is opened, and the fluid in the tank 10 is returned to the space 15. In this case, the phases of the hydraulic pressure in the tank 10 and the space 15 are deviated to obtain a low temperature.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a refrigerator that is characterized by its simple structure, low cost, and high reliability and is used in cooling high-temperature superconductors, vacuum equipment, etc. be.

[Prior art] B/I, X tube type refrigerators were developed in 1963 by W, E,
It was first proposed by rd.

This low-temperature generation method uses the non-equilibrium state characteristics of the working fluid as its operating principle, making it difficult to derive and analyze equations for actual operating conditions.

Furthermore, although many papers have published the principles of low-temperature generation in pulse tube refrigerators, there are many assumptions in the conditions and the theory has not yet been established.

However, it has been demonstrated that low-temperature production is actually possible.

[Problem to be solved by the invention] Existing pulse tube refrigerators have a simple equipment configuration and are characterized by high reliability as refrigerators because there are no moving parts in the low temperature section. However, it has the disadvantage that its efficiency is worse than any other type of refrigerator. For example, to obtain 1 watt of refrigeration output at an absolute temperature of 77, approximately 1 kilowatt of power was required.

In other words, there has been a desire for a pulse tube refrigerator that is highly efficient without sacrificing the advantages of conventional refrigerators.

[Means for Solving the Problems] As described above, the present invention aims to increase the efficiency of a pulse tube refrigerator without impairing the conventional advantages, and does not include any low-temperature movable mechanism such as a piston in the low-temperature part. The present invention proposes a pulse tube refrigerator which is characterized by efficiently generating 100°C or less at an absolute temperature without the need for heat, and by achieving high reliability due to its simple structure.

That is, in contrast to the conventional pulse tube refrigerator, which consists of a regenerator, a heat exchanger, a pulse tube, and a refrigeration section, the heat of the working fluid can be reduced by connecting a buffer tank or variable capacity space through a one-way valve. It is proposed to improve the efficiency of exchange and increase the efficiency of pulse tube refrigerators.

[Function] To achieve the above object, the present invention cools the working fluid from the compressor through a valve or the working fluid from the compression section through a radiator into a regenerator, and further cools the working fluid through a refrigerating section and a pulse generator. After passing through a pipe, etc., the heat is radiated by a heat exchanger located at approximately room temperature, and the heat is transferred mechanically, fluidically, electromagnetically, or After being put into the variable volume space of the back pressure part of the compression piston at approximately room temperature controlled by either, or into a tank with a constant volume, the discharge side check valve and/or fluid regulating valve. The object to be cooled is cooled in the refrigeration section through a pulse tube, warmed in a regenerator, and then returned to the compressor through a valve, or heated in the regenerator and returned to the compression space again to generate low temperature. This is how it was done.

[Example] The present invention will be explained with reference to the drawings.

FIG. 1 is an explanatory diagram of the structure of a conventional pulse tube refrigerator.

Working fluid from a compressor (not shown) (mainly helium,
The fluid (hereinafter referred to as "fluid") enters the regenerator 2, which is made of several hundred layers of 150-mesh wire mesh as a regenerator material, through an inlet valve 1 that is intermittently opened and closed at, for example, 15 atm, its temperature drops, and it exchanges heat with the fluid to cool the part. The remaining fluid is adiabatically compressed inside the hollow pulse tube 5, which is filled with almost nothing, than the refrigeration section 3. At that time, the temperature of the remaining fluid rises, and the heat of compression is transferred to the heat exchanger at almost room temperature. 6 to the atmosphere or heat exchanger 6
The heat is radiated to a cooling fluid (not shown) that comes into contact with the cooling fluid.

At this time, the pulse tube 5 has a temperature of about 320 K in the heat exchanger 6, assuming that the absolute temperature of the freezing section 3 is 77 and the room temperature is 300 K.
Maintain a temperature gradient up to

That is, it is 320-77-243, maintaining a temperature difference of 243 degrees.

Next, when the discharge valve 7, which opens and closes intermittently, opens the fluid remaining inside the heat exchanger 6 and the pulse tube 5, the fluid remaining in the pulse tube 5 and the regenerator material gap inside the regenerator 2 is removed again. The temperature drops while being pushed out, the temperature rises by cooling an object to be cooled (not shown) in the freezing section 3, the temperature is further warmed in the regenerator 2, and the material is returned to the compressor through the discharge valve 7 at about room temperature at a pressure of about 5 atmospheres. This is done continuously to generate low temperature.

Note that the refrigeration obtained in the refrigeration section 3 is achieved by the fact that when the discharge valve 7 opens, the fluid remaining in the regenerator etc. continuously performs the work of pushing the fluid in the pipe that returns to the compressor (not shown). This is achieved by a phase shift between the fluid inside the pulse tube and the fluid returning to the compressor from the vicinity of the discharge valve 7. In addition, theoretically, the amount of refrigeration obtained by subtracting the inefficiency in the regenerator 2 and the adiabatic loss from the heat radiation amount in the heat exchanger 6 is obtained as the amount of refrigeration.

That is, the virtual maximum value of the amount of refrigeration can be taken as the amount of refrigeration equal to the energy radiated to the outside of the refrigerator.

Note that the discharge valve 7 is closed when the suction valve 1 is open.
The open time in one cycle is longer than that of the suction valve 1.

As mentioned above, conventional pulse tube refrigerators have a simple equipment configuration and can generate low temperatures even without a moving mechanism in the low temperature section, and have the features of a highly reliable refrigerator, but they are inefficient. was the only drawback.

FIG. 2 is an explanatory diagram of the basic flow path arrangement and cross-sectional structure of the pulse tube refrigerator of the present invention, which has improved the structure of FIG. 1 to achieve high efficiency. By opening the suction valve 1 momentarily and immediately closing it, the regenerator 2,
The fluid passes through the refrigeration section 3 and the pulse tube 5, is cooled by the radiator 6, and is adiabatically connected to the buffer tank IO having a certain volume through the inflow side check valve (hereinafter referred to as the "through valve") 8 through which fluid flows only in a fixed direction. released. The compression heat at this time is radiated from the outer surface of the radiator 6 and the buffer tank 10 to the atmosphere or to other fluids to be cooled.

Next, when the discharge valve 7 is opened, the fluid in the buffer tank 10 is cooled by the discharge side check valve 11, cools an object to be cooled (not shown) in the radiator 6, pulse tube 5, and refrigeration part 3, and is warmed in the regenerator 2.
It returns to the compressor from the discharge valve 7 at approximately 5 atmospheres. (For example, the operating pressure of the fluid may be 15 and 8 atm, or 20 and 10 atm, but the higher the pressure ratio, the higher the efficiency, but the greater the vibration.) When the suction valve 1 is closed, the fluid inside the refrigerator is After being sealed at approximately 15 atmospheres, when the discharge valve 7 opens, the fluid remaining in the buffer tank 10, the pulse tube 5, the space in the regenerator 2, etc. is simultaneously discharged from the discharge valve 7, and the compressor Due to the work of adiabatically compressing the fluid in the pipe that returns to a low pressure, the fluid especially before and after the refrigeration section 3 expands, and a low temperature is obtained.

In the basic diagram in Figure 2, the basic feature of the equipment configuration is that two check valves and one buffer tank have been added to the prototype in Figure 1. 1 opens and does not open until the internal pressure of the refrigerator reaches a certain pressure (for example,
When the pressure of the fluid inside the refrigerator is 1 atm and valve 7 is closed and valve 1 is opened and fluid at 15 atm enters and enters, the pressure inside the refrigerator increases little by little and when it reaches 15 atm, the check valve 8 opens. This period is called the pressure rise time, and the time from when valve 1 closes and valve 7 opens until the check valve IT opens is called the fall time).During this pressure rise time, the fluid releases heat in the radiator 6. The residence time is longer than in the structure shown in FIG. 1, and the amount of heat dissipated increases accordingly.

Furthermore, when the discharge valve 7 opens and the pressure drops to a certain level, the check valve 11 opens, and during this falling time, the fluid in the buffer tank IO stays and radiates heat. The amount of heat dissipated increases compared to the structure of

In other words, the amount of heat dissipated is considered to be almost equivalent to the amount of refrigeration as explained in Figure 1, so the amount of refrigeration increases at each step.For example, when the input is 1 kilowatt, the refrigeration temperature in '17 is about 1 watt. However, in the structure shown in Figure 2, the power consumption increased to approximately 4 watts.

It is also possible to replace the two valves 1.7 with one electrically or mechanically driven rotary valve.

FIG. 3 shows a main embodiment of the present invention, showing a suction valve 1 and a discharge valve 7.
was removed, and instead of the compressor, although not shown, a piston 12 reciprocated mechanically by a crankshaft, a cam, etc. or by a linear motor was used to compress and expand the fluid in the compression space 15. is a feature.

Note that a working fluid having a pressure of approximately 20 atmospheres is pre-caulked and sealed in this compression space.

The piston 12 is connected and fixed to a rotor part 21 of an induction type or synchronous type linear motor, and is reciprocated by electromagnetic action with a stator 14. Although not shown, this mechanism uses hot transistors and others to detect and control the position of the electromagnetic piston (12 and 21).

Further, the present invention can be implemented with either a synchronous type or an induction type electromagnetic mechanism.

18 is a piston control mechanism using fluid and mechanical springs for positioning the piston and rotor and for smoothly reciprocating the piston 12, and the heat generated by the expansion work is caused by the fluid remaining inside and the materials that come into contact with this mechanism. Heat is radiated to the outside of the refrigerator through heat conduction.

20 is a Biston ring, 19 is a fluid reservoir, 22 is a fluid supply valve, and 1B is a radiator that radiates heat to the atmosphere or other fluid 17 to be cooled. The structure of the equipment up to this point is different from that shown in Figure 2. The low temperature generation mechanism is such that when the piston 12 moves toward the top dead center in a pulsed manner, the fluid in the compression space 15 and the fluid in the pulse tube 5 are adiabatically compressed, and the heat of compression is released by the radiators 1B and 6. At this time, the fluid in the compression space 15 is cooled in the regenerator 2 and enters the pulse tube 5, and the fluid in the pulse tube 5 is adiabatically compressed and radiates heat in the radiator 6, and a check valve opens when a certain pressure is reached. It enters the buffer tank IO through valve 8.

Next, when the piston 12 moves toward the bottom dead center in a pulsed manner, the pressure in the compression space 15 suddenly drops, so the check valve 11 opens and the fluid in the buffer tank 10 returns to the compression space 15.

At this time, the fluid pressures in the buffer tank 10 and the compression space 15 are out of phase, so that a low temperature is obtained. In other words, it does expansion work.

Regarding the amount of heat dissipation, the structure is almost the same as the one shown in Figure 2, but
With this method, the reciprocating motion of the piston 12 can be driven in a sine-like manner or in a square wave manner by using a linear motor, and although it depends on the driving frequency, it is possible to drive the reciprocating movement of the piston 12 in a square wave manner even if the mechanical vibration increases somewhat. When driven to 5 to 6 watts, a freezing amount of 5 to 6 watts can be obtained.

FIG. 4 shows another embodiment of the present invention which is improved based on the basic structure shown in FIG.
-1 and 5-1 and 5-2, which are separated into two pulse tubes 5, are further provided with flow rate regulating valves 23 and 24. A major feature of improved efficiency is that when the compression piston 12 moves toward the top dead center in a pulsed manner, the fluid compressed in a pulsed manner from the compression space 15 and other parts is transferred to the check valve 8, the radiator 6-11, and the flow rate adjustment valve 23. through the buffer space 10-1 of variable volume, but at the same time it does the work of pushing up the compression piston 12, so the power with which the compression piston 12 compresses the fluid is 20 to 3
It is a 0% decrease.

Next, when the compression piston 12 moves toward the bottom dead center, the fluid in the buffer space 10-1 passes through the radiator 6-2, the flow rate adjustment valve 24, the check valve 11, the pulse tube 5-2, and the refrigeration section 3.
It returns to the compression space 15 from the regenerator 2 and the radiator 18.

Furthermore, in changing the strokes of these two fluids, the fluid flow rates can be controlled by the flow rate regulating valves 23 and 24, so that the maximum amount of refrigeration can be obtained at the required refrigeration temperature. In experiments, a maximum of 8 watts was obtained at 77K.

In addition, the valve 25 is connected to the piston control mechanism 18 as well as the fluid reservoir 9.
The piston 12 has a function of automatically adjusting the pressure of the piston 12 and the back pressure of the piston 12 to smoothly reciprocate the piston 12.

That is, by separating and inserting a part of the working fluid that enters the variable space 1O-1 through the valve 25 into the fluid reservoir 19, fluid pressure acts on the lower surface of the rotor lower part 21, further reducing the amount of work of the compression piston. You can.

Also, by sucking and discharging the working fluid into the variable space to-1 and the fluid reservoir 19, the piston 12 and the rotor part 21
A cooling effect can be expected.

FIG. 5 is a structural explanatory diagram of still another embodiment improved based on the structure of FIG. 4, in which one or more central pulse tubes 5-
The main feature is that the regenerator 2-1, which is composed of several hundred layers of metal mesh and other materials, is installed in a concentric circle around axis 3, and the structure is simpler than that shown in Fig. 4. be. The central heat exchanger 8-3 may be connected before or after the check valve 8, but if it is connected after, the fluid heat due to adiabatic compression will heat the valve and accelerate its deterioration.

In addition, the intensive heat exchanger B-3 and the radiator IB-2 can be integrated into an integrated radiator, and the flow rate adjustment valve 23 may be connected before or after the check valve 8. In cases where it is not necessary to change the required refrigeration temperature, the check valve does not need to be installed if the CV value of the check valve is kept constant and the opening/closing pressure can be adjusted accurately.

With this method, a refrigeration output of 8 to 10 watts was easily obtained.

Note that the regenerator and pulse tube of the embodiment of the present invention shown in FIGS.
If the amount of heat radiation in step 2 is sufficient, the heat sink 18゜18-1
．． The structure of the pulse tube refrigerator of the present invention enables low temperature generation even if 18-2 is a simple air-cooled structure or is removed to eliminate fluid pressure loss.

[Effects of the Invention] As described above, the present invention can significantly improve the refrigeration efficiency without sacrificing the advantages of the conventional pulse tube refrigerator, which has a small number of parts, is lightweight, compact, and has high reliability. This enabled efficient low-temperature generation. Therefore, it is possible to make the refrigerator lighter than before, and it is expected that a cheaper refrigerator will be provided.

[Brief explanation of the drawing]

Fig. 1 is a structural explanatory diagram of a conventional pulse tube refrigerator, Fig. 2 is a basic structural diagram of the pulse tube refrigerator of the present invention, and Fig. 3 is a structural explanatory diagram of a conventional pulse tube refrigerator.
4 is a structural explanatory diagram of a main embodiment of the present invention, FIG. 4 is a structural explanatory diagram of another embodiment of the present invention, and FIG. 5 is a structural explanatory diagram of still another embodiment of the present invention. Arrows in the figure indicate the direction of fluid flow. 1... Suction valve, 2... Regenerator, 3... Refrigeration section, 4
...Pulse tube part, 5-1...Inflow side pulse tube, 5
-2... Discharge side pulse tube, 5-3... Central pulse tube, 6... Heat exchanger, 6-1... Inflow side heat exchanger, 6
-2...Discharge side heat exchanger, 8-3...Intensive heat exchanger, 7...Discharge valve, 8...Inflow side check valve, 9...Flow rate control valve (not shown) ), IO... buffer tank, 1
0-1... Variable capacity buffer space, 11... Discharge side check valve, 12... Piston, 13... Rotor of linear motor, 14... Stator-115... Compression space, 18 ...Radiator, 17...Fluid to be cooled, 18
... Spring, 19 ... Fluid reservoir, 20 ... Piston ring, 21 ... Linear hair-goo rotor lower part, 22 ... Fluid supply valve, 23 ... Inflow side flow rate adjustment valve, 24 ...Discharge side flow rate adjustment valve, 25...valve.

Claims (3)

[Claims] (1) In a pulse tube refrigerator consisting of a regenerator, a heat exchanger, a pulse tube, a refrigeration section, etc., the working fluid from the compression space 15 of the compressor built into the pulse tube refrigerator is transferred to the radiator 18. After passing through the refrigeration section 3, pulse tube 5, etc., the heat is radiated by the heat exchanger 6 in the room temperature section, and the inflow side check valve 8 and flow rate adjustment valve are cooled. After flowing into the buffer tank 10 via the discharge check valve 11 and/or the flow rate adjustment valve, the object to be cooled is passed through the pulse tube 5 again through the discharge check valve 11 and/or the flow rate adjustment valve. After cooling and further heating in the regenerator 2, the compressed space 15 is heated via the radiator 18.
A pulse tube refrigerator characterized by the ability to return to (2) The pulse tube refrigerator according to claim 1, wherein the buffer tank is constituted by at least a variable capacity buffer space of the compressor. (3) Claim 2 characterized in that the one or more pulse tubes are arranged so as to be surrounded by a plurality of regenerators.
The pulse tube refrigerator described.