JPH08254365A - Double inlet type pulse pipe freezer and its operating method - Google Patents

Abstract

PURPOSE: To provide a double inlet type pulse freezer and its operating method in which a stable freezing temperature can be attained even if the freezer is operated for a long period of time. CONSTITUTION: A temperature sensor 13 for measuring a freezing temperature is fixed to a low temperature end of a pulse pipe 4 of a conventional type double inlet type pulse pipe freezer, resulting in making a double inlet type pulse pipe freezer 10 in which a pressure changing-over valve 2 is controlled by a controller 14 to which its temperature signal is inputted and an intermittent operation can be performed. The freezing temperature is kept stable for a long period of time by keeping it within a desired temperature range and by performing the intermittent operation.

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, and more particularly to a double inlet type pulse tube refrigerator that provides a stable refrigeration temperature and a method of operating the same.

[0002]

2. Description of the Related Art Equipment and devices used in environments where maintenance is impossible, such as infrared detectors mounted on artificial satellites, magnetic resonance imaging diagnostic equipment (MRI), and SQU.
High reliability is required for a cooling refrigerator attached to medical equipment such as an ID brain (magnetocardiography) measuring device or equipment such as a superconducting computer which is assumed to be continuously used for a long time. A pulse tube refrigerator having no moving parts in the low temperature part is most suitable for this type of cooling refrigerator.

Typical examples of the pulse tube refrigerator are an orifice type and a double inlet type, and there is also a type called a basic type. FIG. 2 is a piping system diagram of a double-inlet type pulse tube refrigerator 20 as a conventional example. The working fluid (for example, helium gas) compressor 1 includes a pressure switching valve 2 in which a high pressure valve 2a and a low pressure valve 2b are alternately opened and closed.
Room temperature end 3h of the regenerator 3 filled with wire mesh etc. via
The low temperature end 3c of the hollow pulse tube 4 is connected to the low temperature end 4c of the hollow pulse tube 4. The room temperature end 4h of the pulse tube 4 is connected to the buffer container 6 via the orifice 5 as a narrow opening. Further, a short-circuit passage 11 that does not pass through the regenerator 3 and the pulse tube 4 is provided together with the flow rate adjusting mechanism 12. Further, a cooling water pipe 9 is attached in contact with the room temperature end 4h of the pulse pipe 4. The heat exchange between the wall of the pulse tube 4 and the working fluid is minute. Incidentally, the short-circuit flow path 1 including the flow rate adjusting mechanism 12 described above.
An orifice type pulse tube refrigerator does not have 1 and further, a basic type pulse tube refrigerator has neither the orifice 5 nor the buffer container 6 together with the above-mentioned short circuit passage 11.

Referring to FIG. 2, the case where the flow rate adjusting mechanism 12 is completely closed (corresponding to an orifice type pulse tube refrigerator) will be described. When the high pressure valve 2a is opened and the low pressure valve 2b is closed in the pressure switching valve 2 to switch to the high pressure side, the high pressure working fluid compressed in the compressor 1 causes the regenerator 3 to move from the room temperature end 3h to the low temperature end 3c. As the temperature of the pulse tube 4 decreases, the temperature of the pulse tube 4 decreases from the low temperature end 4c of the pulse tube 4
Flows in. The working fluid that has been present in the pulse tube 4 before that is pushed by the inflowing working fluid and is compressed and moves toward the room temperature end 4h of the pulse tube 4. As a result, the pressure in the pulse tube 4 becomes higher than the pressure in the buffer container 6, and the working fluid in the pulse tube 4 passes through the orifice 5 and flows into the buffer container 6.

Subsequently, in the pressure switching valve 2, the low pressure valve 2b
Is opened and the high pressure valve 2a is closed and switched to the low pressure side, the working fluid in the pulse tube 4 causes the regenerator 3 to move to the low temperature end 3 thereof.
The temperature rises by passing from c to the room temperature end 3h, and flows toward the suction port of the compressor 1 via the low pressure valve 2b. At this time, the pressure in the pulse tube 4 becomes lower than the pressure in the buffer container 6, so that the working fluid in the buffer container 6 flows into the pulse tube 4 through the orifice 5.

Now, assuming that there is no working fluid passing through the orifice 5 and the heat exchange between the working fluid and the wall of the pulse tube 4 is negligible, the working fluid in the pulse tube 4 is It merely repeats adiabatic compression and expansion, and the phase of pressure fluctuation and the phase of displacement of the working fluid always match. However, in reality, since the working fluid passing through the orifice 5 exists, the phase of the pressure fluctuation and the displacement of the working fluid generally do not match, and a component having a phase difference of 90 degrees is generated. Due to this component, an enthalpy flow is generated in the pulse tube 4, and the expansion work of the working fluid at the low temperature end 4c of the pulse tube 4 is transmitted to the room temperature end 4h of the pulse tube 4 and converted into heat at the orifice 5 for cooling. The water in the water pipe 9 is carried out of the pulse pipe 4. As described above, refrigeration due to the expansion of the working fluid occurs at the low temperature end 4c of the pulse tube 4, and by repeating this, the function as the refrigerator is maintained. That is, the object to be cooled is thermally connected to the low temperature end 4c of the pulse tube 4 to be cooled.

Next, a case where the flow rate adjusting mechanism 12 is opened so that the working fluid flows at a predetermined flow rate through the short circuit passage 11 will be described. When the pressure switching valve 2 is switched to the high pressure side, the working fluid compressed by the compressor 1, passing through the regenerator 3 and cooled flows into the pulse tube 4 from the low temperature end 4c of the pulse tube 4, at the same time, the short-circuit passage is formed. The working fluid at room temperature flows into the pulse tube 4 from the room temperature end 4h of the pulse tube 4 via 11.

When the pressure switching valve 2 is switched to the low pressure side, the working fluid in the pulse tube 4 expands and flows toward the suction port of the compressor 1 via the regenerator 3, and at the same time, a part of the working fluid is pulsed. Returning from the room temperature end 4h of the pipe 4 to the compressor 1 via the short-circuit passage 11 and the low pressure valve 2b.

Since the flow rate adjusting mechanism 12 of the short circuit passage 11 is opened as described above, the working fluid cooled in the regenerator 3 flows into the pulse tube 4 from the low temperature end 4c, and at the same time,
The working fluid at room temperature flows in from the room temperature end 4h, but since the working fluid at room temperature has the same volume and a smaller mass than the cooled working fluid at low temperature, when the flow rate adjusting mechanism 12 of the short-circuit passage 11 is closed. In comparison, the amount of working fluid flowing into the pulse tube 4 is small. Accordingly, the compression ratio of the compressor 1 can be increased and the performance of the refrigerator can be improved. Further, since the working fluid is caused to flow into the pulse tube 4 from the short-circuit flow path 11, the movement (displacement) of the working fluid passing through the regenerator 3 at the low temperature end 4c of the pulse tube 4 is reduced accordingly. Accordingly, the loss (shuttle loss) due to heat carried from the room temperature side to the low temperature side by the working fluid is also reduced.

As described above, the double inlet type pulse tube refrigerator 20 has another type of pulse tube refrigerator including the orifice type pulse tube refrigerator due to the short-circuit passage 11 and the flow rate adjusting mechanism 12 provided therein. It has better freezing performance than the machine.

However, when the double-inlet type pulse tube refrigerator 20 is continuously operated for a long time, as shown in FIG.
It was found that, as shown in, the freezing temperature rises significantly and the freezing temperature fluctuates greatly. In FIG. 3, the horizontal axis represents operating time and the vertical axis represents freezing temperature.

As described above, in the double-inlet type pulse tube refrigerator 20, the working fluid in the pulse tube 4 flows from the low temperature end 4c to the room temperature end 4h and the room temperature end 4h by switching the pressure switching valve 2. From the low temperature end 4c to the low temperature end 4c of the pulse tube 4
The principle of refrigeration is to pump heat from room temperature to room temperature edge 4h.

However, as is common to all pulse tube refrigerators including the double inlet type, it is known that a direct current component independent of time exists in the pulse tube 4 in addition to the oscillating flow. .

The reason why the refrigerating temperature greatly changes after continuous operation for a long time in the double inlet type pulse tube refrigerator 20 is considered as follows. That is, the direct-current component of the flow of the working fluid in the pulse tube 4 remains in the pulse tube 4 in the orifice type or basic type pulse tube refrigerator without the short-circuit flow path 11 and affects the performance of the refrigerator. On the other hand, in the double-inlet type pulse tube refrigerator 20 having the short-circuit passage 11, an annular passage having the short-circuit passage 11, the regenerator 3, and the pulse tube 4 as passages is formed, while not having a great influence. Therefore, the DC component of the flow of the working fluid does not remain in the pulse tube 4 but becomes a circulating flow in the annular flow path. Then, the driving force that generates this circulating flow is very small, so that the circulating flow grows over a long period of time. In this way, the freezing temperature of the double-inlet type pulse tube refrigerator 20 may become unstable and fluctuate after a long continuous operation.

[0015]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a double inlet refrigerator having a stable refrigerating temperature even when it is operated for a long time, and an operating method thereof. .

[0016]

The above object is to provide a flow path from a working fluid compressor to a buffer container via a pressure switching valve, a regenerator, a pulse tube, and an orifice or a throttle valve, and the pressure switching valve. A double inlet type pulse tube comprising a flow path connecting the regenerator and the regenerator, a short circuit flow path connecting the pulse tube and a flow path connecting the orifice or the throttle valve, and a flow rate adjusting mechanism provided in the short circuit flow path. In the refrigerator,
A detection system for detecting the freezing temperature at the low temperature end of the pulse tube, and a control system for controlling the start and stop of the operation of the double inlet type pulse tube refrigerator according to the detected freezing temperature are provided. And a double-inlet type pulse tube refrigerator.

Further, the above object is to provide a flow path from a working fluid compressor to a buffer container via a pressure switching valve, a regenerator, a pulse tube, and an orifice or a throttle valve, the pressure switching valve and the regenerator. For a double inlet type pulse tube refrigerator consisting of a short-circuit flow passage connecting the flow passage connecting the pulse pipe and the orifice or throttle valve and a flow rate adjusting mechanism provided in the short-circuit flow passage, A double inlet provided with a detection system for detecting the freezing temperature at the low temperature end of the pulse tube, and a control system for controlling the start and stop of the operation of the double inlet type pulse tube refrigerator according to the detected freezing temperature. Type pulse tube refrigerator, when the freezing temperature is higher than a predetermined temperature range, the double inlet type pulse tube refrigerator is started to operate, and the freezing temperature is lower than the predetermined temperature range. How the operation of the double inlet type pulse tube refrigerator, characterized in that stops the operation of the double inlet type pulse tube refrigerator if the is accomplished by.

[0018]

In the double-inlet type pulse tube refrigerator of claim 1, a detection system for detecting the freezing temperature at the low temperature end of the pulse tube, and controlling the start and stop of the operation of the refrigerator according to the detected freezing temperature. The control system enables the intermittent operation depending on the freezing temperature.

In the method for operating the double-inlet type pulse tube refrigerator of claim 2, the operation of the refrigerator is started when the freezing temperature is higher than a predetermined temperature range, and when the freezing temperature is lower than the predetermined temperature range. Since the refrigerator is intermittently operated so as to be stopped, the refrigeration temperature is maintained within a predetermined temperature range, and the refrigerator temperature does not fluctuate even when the refrigerator is operated for a long time.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A double inlet type pulse tube refrigerator and an operating method thereof according to embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a piping system diagram of a double inlet type pulse tube refrigerator 10 of the embodiment. Basically, the double-inlet type pulse tube refrigerator 20 of the conventional example is configured similarly to the conventional example. Therefore, different points between the two will be described below, and common constituent elements will be denoted by the same reference numerals, and The description is omitted.

That is, in the double inlet type pulse tube refrigerator 10 of this embodiment, a temperature sensor 13 for measuring the refrigeration temperature is attached to the low temperature end 4c of the pulse tube 4, and the signal from the temperature sensor 13 is the controller. The controller 14 can stop or start the switching of the high pressure valve 2a and the low pressure valve 2b in the pressure switching valve 2 according to the refrigerating temperature. Stopping the switching stops the pressure fluctuation in the pulse tube 4, and consequently stops the operation of the double inlet type pulse tube refrigerator 10. Conversely, the start of switching is the start of operation. That is, the start and stop of the operation of the double inlet type pulse tube refrigerator 10 can be controlled according to the freezing temperature.

When the refrigerating temperature measured by the temperature sensor 13 becomes higher than a predetermined temperature range using the double inlet type pulse tube refrigerator 10, the controller 1
4, the operation of the refrigerator 10 is started, and when the freezing temperature by the temperature sensor 13 becomes lower than a predetermined temperature range, the operation of the refrigerator 10 is stopped by the controller 14 and the intermittent operation is performed. Due to this intermittent operation, the freezing temperature at the low temperature end 4c of the pulse tube 4 is maintained within a predetermined temperature range, and the freezing temperature is stabilized even after a long time has passed, as seen in the conventional double inlet type pulse tube refrigerator 20. Temperature fluctuations do not occur.

This is because during the period in which the operation of the double-inlet type pulse tube refrigerator 10 of the present embodiment is stopped by intermittent operation, the working fluid is supplied to the annular channel consisting of the short-circuit passage 11, the regenerator 3, and the pulse tube 4. It is thought that the driving force for generating the circulating flow disappears and the existing circulating flow decays and disappears with time.

The embodiments of the present invention have been described above. Of course, the present invention is not limited to these, and various modifications can be made based on the technical idea of the present invention.

For example, in the present embodiment, the operation of the double-inlet type pulse tube refrigerator 10 was started and stopped by controlling the switching of the pressure switching valve 2 from the controller 14. It may be configured to control the driving and stopping of the.

In the present embodiment, the cooling water pipe 9 is provided in contact with the room temperature end 4h of the pulse tube 4, but the cooling water pipe 9 may be omitted.

Further, in this embodiment, an orifice 5 as a narrow opening is provided between the pulse tube 4 and the buffer container 6.
However, instead of this, a throttle valve whose opening degree can be adjusted may be provided.

Further, in the present embodiment, the high temperature side with respect to the low temperature end 3c of the regenerator 3 is a room temperature end 3h, and the high temperature side with respect to the low temperature end 4c of the pulse tube 4 is a room temperature end 4h. Although the case where the high temperature side is placed in an atmosphere at room temperature has been described, these high temperature sides may be placed in an atmosphere having a temperature higher than room temperature, and, of course, may be placed in an atmosphere having a temperature lower than room temperature.

[0030]

As described above, according to the double inlet type pulse tube refrigerator according to claim 1 of the present invention, the refrigerating temperature is maintained within a predetermined temperature range by the intermittent operation of the refrigerator, and the refrigerating temperature is maintained for a long period of time. It can be stabilized over.

According to the method of operating the double-inlet type pulse tube refrigerator according to the second aspect, the refrigerating temperature is maintained within a predetermined temperature range and is stabilized for a long time.
Then, the reliability of the double-inlet type pulse tube refrigerator is enhanced by this, which greatly contributes to the expansion of the application field.

[Brief description of drawings]

FIG. 1 is a piping system diagram of a double inlet type pulse tube refrigerator of an embodiment.

FIG. 2 is a piping system diagram of a conventional double-inlet type pulse tube refrigerator.

FIG. 3 is a diagram showing the relationship between operating time and freezing temperature in a conventional double-inlet type pulse tube refrigerator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Compressor 2 Switching valve 3 Regenerator 4 Pulse tube 4c Low temperature end of pulse tube 5 Orifice 6 Buffer container 9 Cooling water piping 10 Double-inlet type pulse tube refrigerator 11 of an example 11 Short-circuit flow path 12 Flow control mechanism 13 Temperature sensor 14 controller

Claims (2)

[Claims] 1. A flow path from a compressor for working fluid to a buffer container through a pressure switching valve, a regenerator, a pulse tube, and an orifice or a throttle valve, and a flow path connecting the pressure switching valve and the regenerator. In a double-inlet type pulse tube refrigerator comprising a short-circuit passage connecting the pulse tube and a passage connecting the orifice or the throttle valve and a flow rate adjusting mechanism provided in the short-circuit passage, a low temperature end of the pulse tube And a control system for controlling the start and stop of the operation of the double-inlet type pulse tube refrigerator in accordance with the detected refrigerating temperature. Type pulse tube refrigerator. 2. A flow path from a compressor for working fluid to a buffer container via a pressure switching valve, a regenerator, a pulse tube, and an orifice or a throttle valve, and a flow path connecting the pressure switching valve and the regenerator. For a double inlet type pulse tube refrigerator consisting of a short-circuit passage connecting the pulse tube and a passage connecting the orifice or the throttle valve and a flow rate adjusting mechanism provided in the short-circuit passage, the low temperature of the pulse tube Double inlet type pulse tube refrigerator provided with a detection system for detecting the freezing temperature at the end and a control system for controlling the start and stop of the operation of the double inlet type pulse tube refrigerator according to the detected freezing temperature In the above, when the freezing temperature becomes higher than a predetermined temperature range, the operation of the double inlet type pulse tube refrigerator is started, and when the freezing temperature becomes lower than the predetermined temperature range, the dub A method for operating a double-inlet type pulse tube refrigerator, which is characterized in that the operation of a double-inlet type pulse tube refrigerator is stopped.