JP2006349233A - Cooling storage - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To seal a mixed liquid of refrigerants with different boiling points in a high temperature side secondary refrigerant circulation circuit dissipating heat generated by a Sterling refrigerating machine, and to automatically change a mixing ratio of the refrigerants at operation and at stoppage. <P>SOLUTION: The Sterling refrigerating machine 1 is provided with a warm head 2 and a cold head 3, an interior of the cooling storage is cooled by cold of the cold head 3. Heat of the warm head 2 is dissipated by a first high temperature side secondary refrigerant circulation circuit 10 and a second high temperature side secondary refrigerant circulation circuit 30. A mixed liquid of ethyl alcohol and water is sealed as a secondary refrigerant in the high temperature side refrigerant circulation circuits. An isolation tank 40 taking in vaporized/condensed ethyl alcohol before water and isolating it from a secondary refrigerant circulation flow is arranged in the first high temperature side secondary refrigerant circulation circuit 10. When operation of the Sterling refrigerating machine 1 stops, an electromagnetic control valve 51 in a return circuit 50 connected to the isolation tank 40 is opened by a control part 60, and the ethyl alcohol is returned to the first high temperature side secondary refrigerant circulation circuit 10. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a refrigerator that cools the inside of the refrigerator with the cold generated in the heat absorption part of the Stirling refrigerator. “Refrigerator” is a concept that refers to all devices for lowering the temperature of food and other articles, and may be named as a product such as “refrigerator”, “freezer”, “freezer refrigerator”, and “showcase”.

  Specific chlorofluorocarbons (CFC: chlorofluorocarbon) and alternative chlorofluorocarbons (HCFC: hydrochlorofluorocarbon, HFC: hydrofluorocarbon) are used as refrigerants in the refrigeration cycle of the refrigerator. Among these refrigerants, CFCs and HCFCs are subject to international regulations for their production and use because they are, to some extent, lead to the destruction of the ozone layer. Another problem is that HFCs that do not destroy the ozone layer also have a significant contribution to global warming.

  Therefore, Stirling refrigerators that do not use ozone-depleting substances as a refrigerant are in the spotlight. The Stirling refrigerator uses an inert gas such as helium as the working medium, and the piston and displacer are operated by external power to repeatedly compress and expand the working medium to increase the temperature of the heat dissipating part (worm head) and the heat absorbing part ( Reduce the temperature of the cold head. Then, the heat radiating part radiates heat to the surrounding environment, and the heat absorbing part radiates heat from the interior.

  When performing heat dissipation and heat absorption with a Stirling refrigerator, a secondary refrigerant is often used. That is, a high temperature side evaporator is attached to the heat radiating section, and the secondary refrigerant therein is evaporated by warm heat. The evaporated secondary refrigerant is sent to the high temperature side condenser, where it liquefies and returns to the high temperature side evaporator. A low-temperature side condenser is attached to the heat absorption part, and the secondary refrigerant therein is condensed with cold heat. The condensed secondary refrigerant is sent to the low temperature side evaporator, where it is vaporized and returns to the low temperature side condenser.

Patent Documents 1 to 3 show examples of a refrigerator that circulates the secondary refrigerant as described above and transmits the heat and cold of the Stirling refrigerator. Patent Document 2 discloses a configuration in which the heat of the heat radiating portion is transmitted to the opening of the cooling chamber through the refrigerant pipe to prevent condensation at this location. Patent Document 3 discloses a configuration in which the heat of the heat radiating part is used not only for preventing condensation but also for promoting evaporation of drain and defrosting the heat exchanger for cooling inside the cabinet. A mixed liquid of two or more kinds of refrigerants having different boiling points may be used as the secondary refrigerant. An example of this type of cooling medium is disclosed in Patent Document 4.
Japanese Patent Application Laid-Open No. 2002-221384 (pages 4-5, FIGS. 1-2) JP 2004-101050 A (pages 4 to 6, FIGS. 1 to 6) Japanese Patent Laying-Open No. 2004-20056 (pages 5 to 12, FIGS. 1 to 7) JP-A-5-326773 (2nd page to 3rd page, FIG. 1)

  When using a mixed liquid of two or more kinds of refrigerants having different boiling points, for example, a mixed liquid containing ethyl alcohol as a low-boiling point refrigerant and water as a high-boiling point refrigerant as a secondary refrigerant for radiating heat, In consideration of storage, it is better to increase the ratio of ethyl alcohol to lower the freezing point of the secondary refrigerant. However, since the heat dissipation capability due to latent heat is superior to water, it is better to increase the water ratio if you want to increase the heat dissipation capability. As described above, in the secondary refrigerant in which the low-boiling refrigerant and the high-boiling refrigerant are mixed, the antifreezing and the heat radiation ability are in a trade-off relationship.

  The present invention has been made in view of the above points, and in a refrigerator equipped with a secondary refrigerant circulation circuit that radiates the heat of the heat radiating portion of the Stirling refrigerator by the latent heat of the secondary refrigerant, two or more types having different boiling points from each other The refrigerant mixture is used as the secondary refrigerant, and the mixing ratio of the secondary refrigerant is automatically changed during operation and when stopped, so that heat dissipation performance is improved during operation and anti-freezing performance is improved during stoppage. It is a thing.

  (1) In order to achieve the above-mentioned object, the present invention is a refrigerator that cools the inside of the refrigerator by the cooling heat of the heat absorbing portion of the Stirling refrigerator, and the heat of the heat radiating portion of the Stirling refrigerator is changed to the latent heat of the secondary refrigerant. A secondary refrigerant circulation circuit that dissipates heat by the secondary refrigerant circulation circuit. In the secondary refrigerant circulation circuit, a secondary refrigerant circulation circuit includes a mixture of two or more types of refrigerants having different boiling points as a secondary refrigerant. An isolation tank that takes in and isolates a low-boiling refrigerant that evaporates and condenses prior to a high-boiling refrigerant at the beginning of operation of the Stirling refrigerator, and returns the low-boiling refrigerant accumulated in the isolation tank to the secondary refrigerant circulation circuit A feedback circuit is provided, and control means is provided for returning the low-boiling point refrigerant accumulated in the isolation tank to the secondary refrigerant circulation circuit when the operation of the Stirling refrigerator is stopped.

  According to this configuration, at the beginning of the start of the Stirling refrigerator, the low boiling point refrigerant is evaporated and condensed prior to the high boiling point refrigerant, so that the low boiling point refrigerant is taken into the isolation tank and is isolated from the circulation flow of the secondary refrigerant. Therefore, the remaining secondary refrigerant has a high ratio of high boiling point refrigerant and excellent heat dissipation capability. Thereby, the Stirling refrigerator can be operated with high efficiency. After the Stirling refrigerator has stopped operating, the low-boiling point refrigerant in the isolation tank is returned to the secondary refrigerant circulation circuit, so that the secondary refrigerant has a high ratio of low-boiling point refrigerant and is difficult to freeze.

  (2) Further, in the refrigerator having the above-described configuration, the secondary refrigerant circulation circuit may be provided between a high temperature side evaporator thermally connected to a heat radiating portion of the Stirling refrigerator and a high temperature side condenser for heat dissipation. The second secondary refrigerant circulation circuit for forcibly circulating the secondary refrigerant between the first secondary refrigerant circulation circuit for naturally circulating the secondary refrigerant at the high temperature side evaporator and the heating target portion of the refrigerator. And the isolation tank is connected to the first secondary refrigerant circulation circuit.

  According to this configuration, the low-boiling point refrigerant that has been deprived of heat by the high-temperature side condenser is quickly taken into the isolation tank, and the concentration of the low-boiling point refrigerant in the mixed solution is quickly reduced, so that the Stirling refrigerator can be operated efficiently. Can be promoted.

  (3) Further, according to the present invention, in the cooler configured as described above, a circulation pump for circulating the secondary refrigerant is provided in the second secondary refrigerant circulation circuit, and the control means is predetermined after the Stirling refrigerator is stopped. The circulating pump is operated for a time.

  According to this configuration, after the operation of the Stirling refrigerator is stopped and the low boiling point refrigerant in the isolation tank is returned to the secondary refrigerant circulation circuit, the low boiling point refrigerant and the high boiling point refrigerant are stirred by the operation of the circulation pump. Thus, the uneven density of the low boiling point refrigerant is eliminated, and the secondary refrigerant existing in any part of the secondary refrigerant circulation circuit can be made difficult to freeze.

  (4) Further, according to the present invention, in the refrigerator having the above-described configuration, an isolation valve is provided at the inlet of the isolation tank, and the isolation valve is closed when a predetermined amount of secondary refrigerant is accumulated in the isolation tank. It is characterized by.

  According to this configuration, even the high boiling point refrigerant is accumulated in the isolation tank, and it is possible to prevent a situation where the increase in the concentration of the high boiling point refrigerant in the secondary refrigerant circulating flow is stepped on.

  (5) Further, according to the present invention, in the cooler configured as described above, the isolation valve is a float valve floating on a liquid surface in the isolation tank.

  According to this configuration, the high boiling point refrigerant can be prevented from flowing into the isolation tank by a simple mechanism.

  The feedback circuit may be provided with a control valve for returning the low boiling point refrigerant to the secondary refrigerant circulation circuit.

  According to this configuration, a predetermined amount of the low boiling point refrigerant accumulated in the isolation tank can be discharged to the secondary refrigerant circulation circuit, and the proportion of the low boiling point refrigerant in the secondary refrigerant can be accurately controlled.

  In addition, the isolation valve can be constituted by an electromagnetic control valve, and the control unit can control the opening and closing of the electromagnetic control valve according to the amount of liquid in the isolation tank.

  According to this configuration, since the intake of the low boiling point refrigerant into the isolation tank is stopped after the predetermined amount of low boiling point refrigerant is accumulated in the isolation tank, the ratio of the low boiling point refrigerant in the remaining secondary refrigerant Can be controlled accurately.

  According to the present invention, at the beginning of operation of the Stirling refrigerator, the low-boiling point refrigerant is taken into the isolation tank by utilizing the evaporation and condensation of the low-boiling point refrigerant prior to the high-boiling point refrigerant, and is left in the secondary refrigerant circulation circuit. The Stirling refrigerator can be operated with high efficiency by increasing the ratio of the high boiling point refrigerant and increasing the heat dissipation capacity. After the Stirling refrigerator stops operation, the low-boiling point refrigerant in the isolation tank is returned to the secondary refrigerant circulation circuit to increase the ratio of the low-boiling point refrigerant in the secondary refrigerant, thereby making the secondary refrigerant difficult to freeze. can do.

  Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1 is a schematic configuration diagram of a cooling cycle including a Stirling refrigerator, FIG. 2 is an enlarged cross-sectional view of the isolation tank, FIG. 3 is an enlarged cross-sectional view of the isolation tank in a state different from FIG. 2, and FIG. FIG. 5 is a table showing the relationship between ethyl alcohol concentration and heat dissipation efficiency.

  FIG. 1 shows a cooling cycle used in a refrigerator which is an example of a refrigerator. The Stirling refrigerator 1 generates heat and cold by a reverse Stirling cycle. The heat is taken out from the worm head 2 that is a heat radiating portion, and the cold heat is taken out from the cold head 3 that is a heat absorbing portion.

  A first high temperature side secondary refrigerant circulation circuit 10 is thermally connected to the worm head 2. The first high-temperature side secondary refrigerant circulation circuit 10 is a thermosiphon circulation circuit, and a high-temperature side evaporator 11 mounted in a state where heat is exchanged between the warm heads 2, that is, in a thermally connected state. The high temperature side condenser 12 arrange | positioned on the Stirling refrigerator 1 and the piping 13 which connects the high temperature side evaporator 11 and the high temperature side condenser 12 are included. The first high temperature side secondary refrigerant circuit 10 is sealed with a mixed liquid of ethyl alcohol (low boiling point refrigerant) and water (high boiling point refrigerant) as a secondary refrigerant.

  The high-temperature side condenser 12 has a structure in which a large number of radiating fins made of a metal material having a good heat conductivity are pressure-bonded to a metal tube made of a metal material having a good heat conductivity such as copper or a copper alloy. A cooling fan 14 is combined with the high-temperature side condenser 12.

The cold head 3 is thermally connected to the low temperature side secondary refrigerant circulation circuit 20. The low-temperature side secondary refrigerant circulation circuit 20 is installed in a state in which heat is transferred between the cold heads 3, that is, in a state of being thermally connected, and in a heat-insulating housing of the refrigerator. The low-temperature side evaporator 22, the low-temperature side condenser 21 and the low-temperature side evaporator 22 are connected to each other. The low temperature side secondary refrigerant circulation circuit 20 is filled with a natural refrigerant such as carbon dioxide (CO ₂ ) as a secondary refrigerant.

  Similarly to the high-temperature side condenser 12, the low-temperature side evaporator 22 has a structure in which a number of heat-absorbing fins made of a metal material having a good heat conductivity are press-bonded to a metal tube made of a metal material having a good heat conductivity such as copper or copper alloy. .

  The warm heat of the worm head 2 is also used to prevent condensation at the opening of the refrigerator. For this purpose, the second high temperature side secondary refrigerant circulation circuit 30 is thermally connected to the worm head 2. The second high-temperature side secondary refrigerant circulation circuit 30 is connected to the high-temperature side evaporator 11, the high-temperature side evaporator 11, a pipe 31 that is routed to a heating target location in the heat insulating housing of the refrigerator, and the secondary The circulation pump 32 is configured to forcibly circulate the refrigerant.

  When the Stirling refrigerator 1 is operated, an extremely low temperature cold of −30 ° C. or less is generated in the cold head 3. Due to this cold heat, the gaseous secondary refrigerant in the low-temperature side condenser 21 releases latent heat and is condensed and liquefied. The liquefied secondary refrigerant flows to the low-temperature side evaporator 22 through the pipe 23, vaporizes in the low-temperature side evaporator 22 and takes heat, and absorbs heat at a very low temperature (−30 ° C. or lower). Thereby, the inside of the refrigerator is sufficiently cooled. The vaporized secondary refrigerant returns to the low-temperature side condenser 21, releases latent heat, and is liquefied again. A circulation pump that forcibly circulates the secondary refrigerant may be disposed in the low temperature side secondary refrigerant circulation circuit 20.

  On the other hand, warm heat is radiated from the warm head 2 as waste heat. Due to the warm heat, the liquid secondary refrigerant in the high temperature side evaporator 11 is vaporized and rises to the high temperature side condenser 12. Since the blower 14 air-cools the high temperature side condenser 12, the vaporized secondary refrigerant releases latent heat to liquefy and flow down to the high temperature side evaporator 11. The liquid secondary refrigerant returned to the high temperature side evaporator 11 takes the warm heat of the warm head 2, vaporizes again, and rises to the high temperature side condenser 12. Thus, the first high-temperature side secondary refrigerant circulation circuit 10 performs natural circulation of the secondary refrigerant.

  In the second high temperature side secondary refrigerant circulation circuit 30, the secondary refrigerant is forcedly circulated. The liquid secondary refrigerant that has received the heat from the worm head 2 by the high-temperature side evaporator 11 is drawn into the pipe 31 by the circulation pump 32, and the heat is transmitted to the location where condensation is to be prevented in the refrigerator. Returned to the evaporator 11.

  The first high temperature side secondary refrigerant circulation circuit 10 and the second high temperature side refrigerant circulation circuit 30 share the secondary refrigerant with the high temperature side evaporator 11 as an intermediate, and the secondary refrigerant is ethyl as described above. It is a mixture of alcohol and water. The freezing temperature of the mixture of ethyl alcohol and water decreases as the concentration of ethyl alcohol increases as seen in the table of FIG. That is, the higher the ratio of ethyl alcohol in the mixture, the more difficult it is to freeze.

  On the other hand, the heat radiation efficiency of the mixture of ethyl alcohol and water tends to decrease as the concentration of ethyl alcohol increases, as seen in the table of FIG. That is, the higher the ratio of water in the mixed solution, the better the heat dissipation efficiency.

  As described above, the secondary refrigerant of the first high temperature side secondary refrigerant circulation circuit 10 and the second high temperature side refrigerant circulation circuit 30 is ethylated depending on whether it is intended to prevent freezing or to improve heat dissipation efficiency. The concentration of alcohol is different. In other words, it is desirable that the concentration of ethyl alcohol be suitable for the phase where emphasis is placed on freezing prevention, and the concentration of ethyl alcohol be suitable for the phase where emphasis is placed on improving heat dissipation efficiency. The present invention has been made in response to such a request, and the measures will be described below.

  An isolation tank 40 is disposed in the first high temperature side secondary refrigerant circulation circuit 10. The arrangement place is immediately after the pipe 13 comes out of the high temperature side condenser 12. As shown in FIG. 2, the pipe 13 and the isolation tank 40 are adjacent to each other with the pipe 13 up and the isolation tank 40 down. The inside of the pipe 13 and the inside of the isolation tank 40 are communicated with each other through a communication port 15 formed in the pipe 13. That is, the communication port 15 becomes the entrance of the isolation tank 40.

  An isolation valve 41 is disposed in the isolation tank 40. The isolation valve 41 is a float valve, floats on the liquid in the isolation tank 40, and closes the communication port 15 when the liquid level reaches a certain height.

  One end of a feedback circuit 50 is connected to the bottom of the isolation tank 40. This connection location is the outlet of the isolation tank 40. The other end of the feedback circuit 50 is connected to a position downstream of the connection portion of the isolation tank 40 in the first high temperature side secondary refrigerant circulation circuit 10. The feedback circuit 50 is provided with a control valve for returning the liquid (low boiling point refrigerant) accumulated in the isolation tank 40 to the first high temperature side secondary refrigerant circulation circuit 10. The control valve of the embodiment is an electromagnetic control valve 51 that is controlled to open and close by a control unit 60 that functions as a control unit of the refrigerator.

  The isolation tank 40 functions as follows. At the beginning of the operation of the Stirling refrigerator 1, the temperature of the worm head 2 rises, the liquid secondary refrigerant inside the high-temperature side evaporator 11 is heated, and when the ethyl alcohol evaporation temperature is reached, ethyl, which is a low boiling point refrigerant. Alcohol vaporizes prior to water, which is a high boiling point refrigerant. The vaporized ethyl alcohol rises to the high temperature side condenser 12, where heat is taken away by the cooling air, latent heat is released, condenses, and liquefies again.

  The ethyl alcohol that has become liquid tries to return from the high-temperature side condenser 12 to the high-temperature side evaporator 11, but is taken into the isolation tank 40 through the communication port 15 in the middle. At this time, the electromagnetic control valve 51 is closed. The ethyl alcohol taken into the isolation tank 40 is isolated from the circulating flow of the secondary refrigerant. As the amount of ethyl alcohol in the isolation tank 40 increases, the secondary refrigerant in the first high temperature side secondary refrigerant circulation circuit 10 and the second high temperature side refrigerant circulation circuit 30 has a ratio of water that is a high boiling point refrigerant. Rise. As a result, the amount of latent heat released from the high-temperature side condenser 12 is increased and the heat dissipation efficiency is improved, so that the Stirling refrigerator 1 can be operated with high efficiency.

  The isolation valve 41 rises in proportion to the amount of ethyl alcohol in the isolation tank 40 and approaches the communication port 15. Finally, as shown in FIG. 3, the isolation valve 41 closes the communication port 15 and the secondary refrigerant does not enter the isolation tank 40 from the pipe 13 any more. As a result, even water that is a high-boiling point refrigerant is accumulated in the isolation tank 40, and a situation in which the increase in the concentration of water in the secondary refrigerant circulation flow is prevented is prevented.

  In the steady operation state in which the intake of ethyl alcohol into the isolation tank 40 is stopped, the ethyl alcohol concentration of the secondary refrigerant in the high temperature side evaporator 11 is maintained at the azeotropic concentration (4 to 5%).

  When the operation of the Stirling refrigerator 1 is stopped, the control unit 60 opens the electromagnetic control valve 51 based on the operation. Then, the ethyl alcohol in the isolation tank 40 returns to the first high temperature side secondary refrigerant circulation circuit 10 through the feedback circuit 50 and further returns to the high temperature side evaporator 11. As a result, the secondary refrigerant again has an increased ratio of ethyl alcohol and is difficult to freeze.

  Since the outflow of ethyl alcohol accumulated in the isolation tank 40 is controlled by the electromagnetic control valve 51, a predetermined amount of ethyl alcohol can flow out to the first high temperature side secondary refrigerant circulation circuit 10. The proportion of ethyl alcohol can be accurately controlled.

  The control unit 60 operates the circulation pump 32 of the second high temperature side secondary refrigerant circulation circuit 30 for a predetermined time after the operation of the Stirling refrigerator 1 is stopped. As a result, ethyl alcohol and water are agitated, so that the uneven concentration of ethyl alcohol is eliminated, and the secondary refrigerant existing in any part of the second high-temperature side secondary refrigerant circulation circuit 30 can be made difficult to freeze.

  A second embodiment of the present invention is shown in FIG. FIG. 6 is a schematic configuration diagram of a cooling cycle including a Stirling refrigerator as a component.

  In the first embodiment, the pipe 13 and the isolation tank 40 of the first high-temperature side secondary refrigerant circulation circuit 10 communicate with each other through the communication port 15, and ethyl alcohol in the pipe 13 communicates with the pipe 13. It was configured to freely flow into the isolation tank 40 from the mouth 15. In the second embodiment, the inlet of the isolation tank 40 is connected to the pipe 13 via the inflow pipe 52. An isolation valve 53 is provided in the inflow pipe 52. The isolation valve 53 is an electromagnetic control valve that is controlled to open and close by the control unit 60.

  At the beginning of operation of the Stirling refrigerator 1, the control unit 60 opens the isolation valve 53. For this reason, ethyl alcohol flows into the isolation tank 40 through the inflow pipe 52. The controller 60 closes the isolation valve 53 after observing that a predetermined amount of ethyl alcohol has accumulated in the isolation tank 40 and stops the intake of ethyl alcohol into the isolation tank 40. For this reason, the proportion of ethyl alcohol in the remaining secondary refrigerant can be accurately controlled.

  The determination that a predetermined amount of ethyl alcohol has accumulated in the isolation tank 40 is made after the temperature of the secondary refrigerant in the high temperature side evaporator 11 reaches the ethyl alcohol evaporation temperature and then the secondary refrigerant in the high temperature side evaporator 11. This can be done by predicting the time at which the concentration of ethyl alcohol becomes a predetermined value.

  The time when the ethyl alcohol concentration of the secondary refrigerant in the high temperature side evaporator 11 is a predetermined value can be known as follows. That is, a temperature sensor (not shown) is provided in the worm head 2, and the time after the worm head 2 reaches a predetermined high temperature is measured by the count circuit in the control unit 60. If it is determined through experiments how much ethyl alcohol evaporates per unit time in the high-temperature side evaporator 11 and how much it condenses in the high-temperature side condenser 12 at a predetermined temperature, The amount of ethyl alcohol accumulated can be calculated from the elapsed time after reaching a high temperature. The temperature sensor may be provided in the high temperature side evaporator 11 instead of the worm head 2.

  Instead of estimating the liquid volume using time as a parameter, the liquid volume may be measured directly. That is, a liquid amount sensor is provided in the isolation tank 40, and the amount of ethyl alcohol accumulated is directly measured. As long as there is no danger of igniting ethyl alcohol, any type of liquid level sensor may be used.

    As mentioned above, although each embodiment of the present invention was described, the scope of the present invention is not limited to this, and various modifications can be made without departing from the spirit of the invention.

    The present invention is widely applicable to a refrigerator for home use or business use.

Schematic configuration diagram of a cooling cycle including a Stirling refrigerator Enlarged sectional view of the isolation tank Enlarged sectional view of the isolation tank in a state different from FIG. Table showing the relationship between ethyl alcohol concentration and freezing temperature Table showing the relationship between ethyl alcohol concentration and heat dissipation efficiency Schematic configuration diagram of a cooling cycle according to the second embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stirling refrigerator 2 Warm head 3 Cold head 10 1st high temperature side secondary refrigerant circulation circuit 11 High temperature side evaporator 12 High temperature side condenser 13 Piping 14 Blower 15 Communication port 20 Low temperature side secondary refrigerant circulation circuit 21 Low temperature side condensation Unit 22 Low temperature side evaporator 23 Pipe 30 Second high temperature side secondary refrigerant circulation circuit 31 Pipe 32 Circulation pump 40 Isolation tank 41 Isolation valve 50 Feedback circuit 51 Electromagnetic control valve 52 Inflow pipe 53 Isolation valve 60 Control unit (control means)

Claims (5)

A cooler that cools the interior by the cold heat of the heat absorption part of the Stirling refrigerator, and includes a secondary refrigerant circulation circuit that dissipates the heat of the heat radiation part of the Stirling refrigerator by the latent heat of the secondary refrigerant, In a cooling circuit in which a mixed liquid of two or more kinds of refrigerants having different boiling points is enclosed as a secondary refrigerant in the refrigerant circuit,
In the secondary refrigerant circulation circuit, an isolation tank that takes in and isolates a low-boiling-point refrigerant that evaporates and condenses prior to the high-boiling-point refrigerant at the beginning of operation of the Stirling refrigerator, and a low-boiling-point refrigerant accumulated in the isolation tank Including a feedback circuit that returns the secondary refrigerant to the secondary refrigerant circulation circuit.
A refrigerator having control means for returning a low-boiling point refrigerant accumulated in the isolation tank to a secondary refrigerant circulation circuit based on the stoppage of the Stirling refrigerator.   The secondary refrigerant circulation circuit is a first secondary refrigerant circulation that naturally circulates the secondary refrigerant between a high temperature side evaporator thermally connected to a heat radiating portion of the Stirling refrigerator and a high temperature side condenser for heat radiation. A second secondary refrigerant circulation circuit that forcibly circulates the secondary refrigerant between the circuit, the high-temperature side evaporator, and the location to be heated in the refrigerator, and the isolation to the first secondary refrigerant circulation circuit The refrigerator according to claim 1, wherein a tank is connected.   3. A circulation pump for circulating a secondary refrigerant is provided in the second secondary refrigerant circulation circuit, and the control unit operates the circulation pump for a predetermined time after the Stirling refrigerator is stopped. The refrigerator as described in.   4. The isolation valve according to claim 1, wherein an isolation valve is provided at an inlet of the isolation tank, and the isolation valve is closed when a predetermined amount of secondary refrigerant is accumulated in the isolation tank. 5. Refrigerator.   The refrigerator according to claim 4, wherein the isolation valve is a float valve floating on a liquid surface in the isolation tank.

Images