JP2024030044A - Refrigerant discharge method - Google Patents

Abstract

The present invention suppresses solidification of refrigerant in a refrigerant circulation system when discharging the refrigerant from the refrigerant circulation system. A refrigerant discharge method according to an embodiment includes the steps of: adding an additive to the refrigerant circulation system to reduce the pressure at the triple point of the refrigerant after addition; and discharging the refrigerant to which the additive has been added to the outside of the refrigerant circulation system. [Selection diagram] Figure 1

Description

The present disclosure relates to a refrigerant discharge method.

For example, there is a known refrigeration cycle device that uses CO ₂ as a refrigerant and is configured so that the CO ₂ refrigerant can be discharged to the outside during maintenance or equipment removal (for example, see Patent Document 1). ).

JP2009-299981A

In the above-mentioned refrigeration cycle device, if an attempt is made to discharge the CO ₂ refrigerant from the refrigerant circulation system during maintenance, there is a risk that the CO ₂ refrigerant will solidify within the refrigerant circulation system. In relatively large equipment, if the CO ₂ refrigerant solidifies in the refrigerant circulation system, maintenance of the refrigerant circulation system may be hindered, or work must be stopped until the solidified CO ₂ refrigerant is dissolved or vaporized. As a result, it may take a long time to discharge.

In view of the above-mentioned circumstances, at least one embodiment of the present disclosure aims to suppress solidification of the refrigerant within the refrigerant circulation system when the refrigerant is discharged from the refrigerant circulation system.

(1) A refrigerant discharge method according to at least one embodiment of the present disclosure includes:
adding into the refrigerant circulation system an additive that reduces the triple point pressure of the refrigerant after addition by adding it to the refrigerant in the refrigerant circulation system;
discharging the refrigerant to which the additive has been added to the outside of the refrigerant circulation system;
Equipped with

According to at least one embodiment of the present disclosure, solidification of the refrigerant within the refrigerant circulation system can be suppressed when the refrigerant is discharged from the refrigerant circulation system.

1 is an overall configuration diagram of a soil freezing device as an example of a refrigeration cycle device to which a refrigerant discharge method according to some embodiments is applied. 5 is a flowchart showing the flow of processing performed in the control device 50 when implementing the refrigerant discharge method according to some embodiments. 5 is a flowchart showing the flow of processing performed in the control device 50 when implementing the refrigerant discharge method according to some embodiments.

Hereinafter, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present disclosure, and are merely illustrative examples. do not have.
For example, expressions expressing relative or absolute positioning such as "in a certain direction,""along a certain direction,""parallel,""orthogonal,""centered,""concentric," or "coaxial" are strictly In addition to representing such an arrangement, it also represents a state in which they are relatively displaced with a tolerance or an angle or distance that allows the same function to be obtained.
For example, expressions such as "same,""equal," and "homogeneous" that indicate that things are in an equal state do not only mean that things are exactly equal, but also have tolerances or differences in the degree to which the same function can be obtained. It also represents the existing state.
For example, expressions expressing shapes such as squares and cylinders do not only refer to shapes such as squares and cylinders in a strict geometric sense, but also include uneven parts and chamfers to the extent that the same effect can be obtained. Shapes including parts, etc. shall also be expressed.
On the other hand, the expressions "comprising,""comprising,""comprising,""containing," or "having" one component are not exclusive expressions that exclude the presence of other components.

FIG. 1 is an overall configuration diagram of a soil freezing device as an example of a refrigeration cycle device to which a refrigerant discharge method according to some embodiments is applied.
A soil freezing device 1 according to some embodiments includes a refrigerator 5 having a primary refrigerant circulation system 3 and a secondary refrigerant circulation system 10 connected to the primary refrigerant circulation system 3 via a heat exchanger 7. ing.

The secondary refrigerant circulation system 10 according to some embodiments includes a receiver tank 11 that can receive the refrigerant from the heat exchanger 7 and a refrigerant in the receiver tank 11 in the refrigerant circuit 21 of the secondary refrigerant circulation system 10 . A pump 13 for circulating the refrigerant in a secondary refrigerant circulation system and a plurality of freezing pipes 15 buried in the soil for freezing the soil 30 are provided. The secondary refrigerant circulation system 10 according to some embodiments includes a liquid header 17 for distributing liquid-phase refrigerant to a plurality of freezing pipes 15 in a refrigerant circulation path 21, and a liquid header 17 for distributing liquid-phase refrigerant to a plurality of freezing pipes 15, and a liquid header 17 for distributing liquid-phase refrigerant to a plurality of freezing pipes 15. A gas header 19 is provided for collecting the refrigerant.
In the secondary refrigerant circulation system 10 according to some embodiments, the refrigerant (secondary refrigerant) is, for example, a CO ₂ refrigerant.

In the secondary refrigerant circulation system 10 according to some embodiments, a purge flow path 25 is connected to a refrigerant flow path 23 that connects the gas header 19 and the receiver tank 11. A purge valve 33 is provided in the purge flow path 25 . The purge valve 33 is, for example, a solenoid valve controlled by a control device 50, which will be described later.
A silencer 27 may be provided at the outlet of the purge flow path 25 for muffling noise when the secondary refrigerant is discharged to the outside of the secondary refrigerant circulation system 10, as described later.

The secondary refrigerant circulation system 10 according to some embodiments includes an additive cylinder 41 for adding an additive Ad to the secondary refrigerant circulation system 10 to reduce the pressure at the triple point of the secondary refrigerant, as described later. Configured to be connectable. For example, in the secondary refrigerant circulation system 10 according to some embodiments, the additive supply channel 29 for supplying the additive Ad from the additive cylinder 41 to the secondary refrigerant circulation system 10 is connected to the receiver tank 11. ing. The additive supply channel 29 is provided with a charge pump 31 and a charge valve 35 for adding the additive Ad into the secondary refrigerant circulation system 10 (receiver tank 11). The charge pump 31 and the charge valve 35 are controlled, for example, by a control device 50, which will be described later.
Further, the secondary refrigerant circulation system 10 according to some embodiments includes a weight sensor 67 that can measure the weight of the additive cylinder 41.

In the secondary refrigerant circulation system 10 according to some embodiments, the additive supply channel 29 is connected to a service valve 37 for injecting the secondary refrigerant into the receiver tank 11, for example, as shown in FIG. It may be directly connected to the receiver tank 11. For example, when adding the additive supply channel 29 to the existing secondary refrigerant circulation system 10, the additive supply channel 29 can be easily added by connecting to the existing service valve 37.

The secondary refrigerant circulation system 10 according to some embodiments includes a pressure sensor 61 for detecting the pressure in the receiver tank 11 and a level for detecting the liquid level of the secondary refrigerant in the receiver tank 11. A sensor 62 and a temperature sensor 64 for detecting the temperature of the secondary refrigerant in the receiver tank 11 are provided.

The soil freezing device 1 according to some embodiments includes a control device 50 for controlling each part of the soil freezing device 1.
The control device 50 according to some embodiments includes a processor 51 that executes various calculation processes, and a memory 53 that non-temporarily or temporarily stores various data processed by the processor 51. The processor 51 is realized by a CPU, GPU, MPU, DSP, various other arithmetic devices, or a combination thereof. The memory 53 is realized by ROM, RAM, flash memory, or a combination thereof.
In the following description, the control contents of the control device 50 will be mainly described with respect to the discharge of the secondary refrigerant in the secondary refrigerant circulation system 10. Note that the control contents of the control device 50 will be described in detail later.

In the soil freezing device 1 configured as described above, the secondary refrigerant cooled by the refrigerator 5 via the heat exchanger 7 is supplied to the liquid header 17 by the pump 13, and from the liquid header 17 to the plurality of freezing pipes 15. supplied to
The secondary refrigerant supplied to the plurality of freezing tubes 15 takes heat from the soil around the plurality of freezing tubes 15 when evaporating within the plurality of freezing tubes 15 . As a result, the soil around the plurality of freezing pipes 15 is frozen.

The gas phase secondary refrigerant evaporated within the plurality of freezing tubes 15 is collected by the gas header 19 and returned to the receiver tank 11.
The gas phase secondary refrigerant in the receiver tank is cooled and liquefied by the heat exchanger 7, and returns to the receiver tank 11 as a liquid phase secondary refrigerant.

In the soil freezing device 1 configured as described above, for example, when performing maintenance on the secondary refrigerant circulation system 10 or when removing the freezing pipe 15, the secondary refrigerant in the secondary refrigerant circulation system 10 is It is necessary to discharge the refrigerant from within the secondary refrigerant circulation system 10 to the outside.
However, when the secondary refrigerant is discharged, if the pressure within the secondary refrigerant circulation system 10 decreases to a pressure below the triple point (CO ₂ refrigerant: 0.417 MPa), the secondary refrigerant solidifies within the secondary refrigerant circulation system 10. There is a risk of
If the secondary refrigerant solidifies in the secondary refrigerant circulation system 10, maintenance such as replacing the strainer (not shown) or removing the frozen pipe cannot be performed until the solidified secondary refrigerant vaporizes or liquefies. Furthermore, if the secondary refrigerant solidifies within the secondary refrigerant circulation system 10, the pump 13 cannot be operated until the solidified secondary refrigerant vaporizes or liquefies.

Therefore, in the refrigerant discharge method according to some embodiments, an additive Ad is added to the secondary refrigerant circulation system 10 to reduce the pressure at the triple point of the added secondary refrigerant by adding it to the secondary refrigerant. After reducing the pressure at the triple point of the added secondary refrigerant, the secondary refrigerant in the secondary refrigerant circulation system 10 is discharged to the outside of the secondary refrigerant circulation system 10.
That is, the refrigerant discharge method according to some embodiments includes adding into the refrigerant circulation system an additive Ad that reduces the pressure at the triple point of the added refrigerant by adding it to the refrigerant in the refrigerant circulation system, which will be described later. and a step of discharging the refrigerant to which the additive Ad has been added outside the refrigerant circulation system (discharging step S300), which will be described later.
As a result, the additive Ad is added to the refrigerant in the refrigerant circulation system to reduce the pressure at the triple point of the refrigerant after addition, so when the refrigerant is discharged from the refrigerant circulation system, the refrigerant is recirculated. Solidification of refrigerant within the system can be suppressed.

Here, the additive Ad that can be added to the secondary refrigerant to reduce the pressure at the triple point of the secondary refrigerant after addition is different from the refrigerant (CO ₂ refrigerant) used as the secondary refrigerant. It is a refrigerant, such as ethane, R1234yf, R1336mzz (E), R1234ze (z), etc.

FIGS. 2A and 2B are flowcharts showing the flow of processing performed in the control device 50 when implementing the refrigerant discharge method according to some embodiments. A program for executing the processes shown in the flowcharts of FIGS. 2A and 2B is read from the memory 53 and executed by the processor 51 when the processor 51 receives a start signal for the secondary refrigerant discharge process.

The refrigerant discharge method according to some embodiments includes a step S100 of discharging a part of the refrigerant to which the additive Ad is not added, a step S200 of adding the refrigerant, and a step S300 of discharging the refrigerant.
In the refrigerant discharge method according to some embodiments, Step S100 of discharging a part of the refrigerant to which the additive Ad is not added includes Step S1, Step S3, and Step S5, which will be described later, and Step S200 of adding includes steps S7, S9, S11, S13, and S15, which will be described later, and step S300, which will be discharged, includes steps S17 and S19, which will be described later.

As shown in FIG. 2A, in step S1, the processor 51 outputs control signals for starting the operation of the refrigerator 5, starting the operation of the pump 13, and opening the purge valve 33.
Thereby, circulation of the secondary refrigerant cooled by the refrigerator 5 in the secondary refrigerant circulation system 10 is started. That is, by pressurizing (pressurizing) the inside of the secondary refrigerant circulation system 10 by the pump 13, the inside of the secondary refrigerant circulation system 10 is pressurized (pressurizing) regardless of heating.
Further, by performing step S1, a part of the secondary refrigerant circulating within the secondary refrigerant circulation system 10 is discharged to the outside of the secondary refrigerant circulation system 10 via the purge flow path 25.
Note that at the time when step S1 is performed, the charge valve 35 is closed and the charge pump 31 is stopped.

In this way, in the refrigerant discharge method according to some embodiments, before performing the adding step S200 described later, a part of the secondary refrigerant to which no additives have been added is removed from the outside of the secondary refrigerant circulation system 10. discharge.
In the secondary refrigerant circulation system 10 shown in FIG. step S100) of discharging a part of the.
Thereby, the total amount of additive Ad added into the secondary refrigerant circulation system 10 in addition step S200 described later can be suppressed.

In the refrigerant discharge method according to some embodiments, in Step S100 of discharging a part of the refrigerant to which no additive Ad has been added, the inside of the secondary refrigerant circulation system 10 is pressurized by the pump 13. The secondary refrigerant is discharged to the outside of the secondary refrigerant circulation system 10.
This makes it possible to suppress the pressure drop within the secondary refrigerant circulation system 10 during the process of discharging the secondary refrigerant within the secondary refrigerant circulation system 10 to the outside of the secondary refrigerant circulation system 10. In this case, solidification of the secondary refrigerant to which the additive Ad is not added can be suppressed.

In step S3, the processor 51 waits until the pressure Pr in the receiver tank 11 detected by the pressure sensor 61 becomes equal to or lower than the specified pressure P1. When the processor 51 determines that the pressure Pr in the receiver tank 11 has become equal to or lower than the specified pressure P1, the process proceeds to step S5, and the liquid level Lr of the secondary refrigerant in the receiver tank 11 detected by the level sensor 62 has reached the lower limit L1. Wait until the following. When the processor 51 determines that the liquid level of the secondary refrigerant in the receiver tank 11 has become equal to or lower than the lower limit L1, the processor 51 proceeds to step S7 and issues a control signal to stop the pump 13 and a closing operation of the purge valve 33. Outputs a control signal to As a result, the pump 13 is stopped and the purge valve 33 is closed.
Further, in step S7, the processor 51 outputs a control signal for opening the charge valve 35 and a control signal for starting the operation of the charge pump 31. As a result, the charge valve 35 opens, the charge pump 31 starts operating, and the addition of the additive Ad to the receiver tank 11 is started.
Here, the specified pressure P1 is an arbitrary pressure until the secondary refrigerant does not reach the triple point, and the lower limit L1 of the liquid level Lr is such that the suction head of the pump 13 is secured and proper operation can be continued. Any liquid level.

In step S7 (adding step S200), at least a portion of the additive Ad is added into the receiver tank 11 (liquid phase portion of the receiver tank 11) with the purge valve 33 closed.
As a result, the secondary refrigerant containing the additive Ad is not discharged to the outside of the secondary refrigerant circulation system 10 when adding the additive Ad. It is easy to understand the amount of additive Ad present. Therefore, the mixing ratio Rt of the secondary refrigerant and the additive Ad becomes easier to manage.

In step S7 (adding step S200), at least a portion of the additive Ad may be added into the receiver tank 11 while the operation of the pump 13 is stopped and the purge valve 33 is closed.
This makes it easier to manage the mixing ratio of the secondary refrigerant and additive Ad in the receiver tank 11.

In step S9, the processor 51 waits until the amount of additive Ad added to the receiver tank 11 becomes equal to or greater than a specified amount.
Specifically, the processor 51 calculates the amount of the additive Ad added to the receiver tank 11 from the amount of change in the weight of the additive cylinder 41 detected by the weight sensor 67. The processor 51 then adjusts the secondary refrigerant and additive Ad in the receiver tank 11 based on the amount of the secondary refrigerant in the receiver tank 11 corresponding to the lower limit L1 of the liquid level Lr and the added amount of the additive Ad. Calculate the mixing ratio Rt.
Then, the processor 51 waits until the mixture ratio Rt of the secondary refrigerant and the additive Ad in the receiver tank 11 reaches a predetermined mixture ratio Rt1.
Note that the predetermined mixing ratio Rt1 is such that, for example, the secondary refrigerant to which the additive Ad is added does not solidify even under atmospheric pressure.

Furthermore, if the relationship between the mixing ratio Rt of the additive Ad and the saturation pressure of the secondary refrigerant to which the additive Ad has been added is known, it can be determined from the saturation pressure and temperature of the secondary refrigerant after the addition of the additive Ad. The mixing ratio Rt of the additive Ad can be determined.
Therefore, in step S9, the processor 51 determines the temperature of the pressure inside the receiver tank 11 based on the pressure Pr inside the receiver tank 11 detected by the pressure sensor 61 and the temperature Tr inside the receiver tank 11 detected by the temperature sensor 64. The mixing ratio Rt of the secondary refrigerant and the additive Ad may be calculated.

If it is determined in step S9 that the amount of additive Ad added to the receiver tank 11 is equal to or greater than the specified amount, the process proceeds to step S11, where the processor 51 outputs a control signal to start the operation of the pump 13. . As a result, the operation of the pump 13 is started, and the pressure at the triple point is below the desired pressure (for example, the pressure at the triple point at which the secondary refrigerant does not solidify even under atmospheric pressure as described above). Since the secondary refrigerant liquid can be sent from the receiver tank 11 to the secondary refrigerant circulation system 10, the secondary refrigerant liquid in the secondary refrigerant circulation system 10 whose triple point pressure is below the desired pressure The time required to replace can be shortened.

Note that when step S11 is executed, the charge valve 35 is open and the charge pump 31 is operating, so the addition of the additive Ad to the receiver tank 11 continues.
By starting the operation of the pump 13, the secondary refrigerant to which the additive Ad has not been added will return to the receiver tank 11. However, by continuing to add the additive Ad, the contents in the receiver tank 11 will be A decrease in the mixing ratio Rt of the additive Ad in the secondary refrigerant can be suppressed.

After performing step S11, in step S13 shown in FIG. 2B, the processor 51 waits until the specified time T1 has elapsed.
Here, the specified time T1 is, for example, when the secondary refrigerant containing the additive Ad in the receiver tank 11 is sent by the pump 13, circulates within the secondary refrigerant circulation system 10, and returns to the receiver tank 11 again. This is the time it takes to arrive.

After waiting until the specified time T1 has elapsed in step S13, the process proceeds to step S15, and the processor 51 waits until the pressure Pr in the receiver tank 11 detected by the pressure sensor 61 becomes equal to or higher than the specified pressure P2.
Here, the specified pressure P2 is a saturation pressure corresponding to a mixing ratio Rt at which the secondary refrigerant to which the additive Ad is added does not solidify even under atmospheric pressure.

When the processor 51 determines that the pressure Pr in the receiver tank 11 has become equal to or higher than the specified pressure P2, the processor 51 proceeds to step S17 and issues a control signal for closing the charge valve 35 and stops the operation of the charge pump 31. Outputs control signals for As a result, the charge valve 35 is closed, the charge pump 31 is stopped, and the addition of the additive Ad to the receiver tank 11 is stopped.
Further, in step S17, the processor 51 outputs a control signal for stopping the pump 13 and a control signal for opening the purge valve 33. As a result, the pump 13 is stopped and the purge valve 33 is opened.
As a result, the secondary refrigerant to which the additive Ad has been added is discharged from the purge valve 33 to the outside of the secondary refrigerant circulation system 10.

After performing step S17, in step S19, the processor 51 waits until the pressure P in the secondary refrigerant circulation system 10 becomes equal to or lower than the atmospheric pressure Pp.
Note that the processor 51 may make the above judgment by regarding the pressure Pr in the receiver tank 11 detected by the pressure sensor 61 as the pressure P in the secondary refrigerant circulation system 10. The above judgment may be made based on the pressure detected by another pressure sensor (not shown) for detecting the pressure P of .
When the processor 51 determines that the pressure P within the secondary refrigerant circulation system 10 has become equal to or lower than the atmospheric pressure Pp, the processor 51 ends the processing by this program.

In this way, the refrigerant discharging method according to some embodiments includes step S200 of adding and step S300 of discharging.
As a result, the additive Ad, which is added to the refrigerant (secondary refrigerant) in the refrigerant circulation system (secondary refrigerant circulation system 10) to reduce the pressure at the triple point of the added refrigerant (secondary refrigerant), is circulated in the refrigerant. Since it is added into the refrigerant circulation system (secondary refrigerant circulation system 10), when the refrigerant (secondary refrigerant) is discharged from the refrigerant circulation system (secondary refrigerant circulation system 10), the Solidification of the refrigerant (secondary refrigerant) can be suppressed.

In the refrigerant discharging method according to some embodiments, in the adding step S200, the additive Ad may be added to a storage section capable of storing the secondary refrigerant liquid, such as the receiver tank 11.
In addition, in the above description, the receiver tank 11 was mentioned as an example of a storage part that is included in the refrigerant circulation system and is capable of storing refrigerant liquid. Ad may also be added. As a storage section other than the receiver tank 11, for example, in the example shown in FIG. 1, the liquid header 17 can be mentioned.

As described above, in order to understand the triple point of the refrigerant after adding the additive Ad, it is necessary to know the mixing ratio of the refrigerant and the additive Ad.
According to the refrigerant discharge method according to some embodiments, by adding the additive Ad to the storage part (receiver tank 11), the refrigerant liquid (secondary refrigerant circulating liquid) in the storage part (receiver tank 11) and The mixing ratio with the additive Ad becomes easier to control. Moreover, according to the refrigerant discharge method according to some embodiments, the refrigerant liquid (secondary refrigerant circulation) and the additive Ad in the storage section (receiver tank 11) are easily mixed, and the mixing ratio, i.e. This makes it easier to suppress local variations in the concentration of the additive Ad.

In the refrigerant discharge method according to some embodiments, in the adding step S200 (step S9 and step S15), the pressure (pressure Pr) and temperature (temperature Tr) of the refrigerant (secondary refrigerant) in the storage section (receiver tank 11) are ), it is preferable to judge the progress of addition of the additive Ad.
As mentioned above, if the relationship between the mixing ratio Rt of the additive Ad and the saturation pressure of the refrigerant to which the additive Ad is added is known, the addition can be determined based on the saturation pressure and temperature of the refrigerant after adding the additive Ad. The mixture ratio Rt of the substances Ad can be grasped.
Therefore, since the mixing ratio Rt of the additive Ad can be determined from the pressure and temperature of the refrigerant (secondary refrigerant) in the storage section (receiver tank 11), it becomes easier to judge the progress of addition of the additive Ad.

In the refrigerant discharge method according to some embodiments, in the adding step S200 (step S15), the refrigerant is added based on the pressure (pressure Pr) and temperature (temperature Tr) of the refrigerant (secondary refrigerant) in the storage section (receiver tank 11). It is recommended to determine when to end the addition of the additive Ad. In the discharging step S300, after the addition of the additive Ad is completed in the adding step S200 (step S15), the refrigerant to which the additive Ad has been added (secondary It is recommended to drain the refrigerant).
As a result, the mixing ratio Rt of the additive Ad can be determined from the pressure (pressure Pr) and temperature (temperature Tr) of the refrigerant (secondary refrigerant) in the storage section (receiver tank 11), so when the addition of the additive Ad ends, That is, it becomes easier to judge whether the refrigerant to which the additive Ad has been added is no longer solidified even under atmospheric pressure.
Further, according to the refrigerant discharge method according to some embodiments, the refrigerant (secondary refrigerant) that does not solidify even under atmospheric pressure can be discharged to the outside of the refrigerant circulation system (secondary refrigerant circulation system 10), so the refrigerant circulation system Solidification of the refrigerant (secondary refrigerant) within the refrigerant circulation system (secondary refrigerant circulation system 10) can be suppressed when the refrigerant (secondary refrigerant) is discharged from the (secondary refrigerant circulation system 10).

In the refrigerant discharge method according to some embodiments, the refrigerant to which the additive Ad is added may be a secondary refrigerant, and the refrigerant circulation system to which the additive Ad is added is the secondary refrigerant circulation system 10. There may be.
Thereby, when the secondary refrigerant in the secondary refrigerant circulation system 10 is discharged to the outside of the secondary refrigerant circulation system 10, solidification of the secondary refrigerant in the secondary refrigerant circulation system 10 can be suppressed.

In the refrigerant discharge method according to some embodiments, the secondary refrigerant circulation system 10 may be connected to the primary refrigerant circulation system 3 via the heat exchanger 7. In the adding step S200, the additive Ad is preferably added to the receiver tank 11 provided in the secondary refrigerant circulation system 10, which can receive the refrigerant from the heat exchanger 7.
This makes it easier to manage the mixing ratio Rt between the secondary refrigerant liquid and the additive Ad in the receiver tank 11. Moreover, according to the refrigerant discharge method according to some embodiments, the secondary refrigerant liquid and the additive Ad in the receiver tank 11 are easily mixed, and the mixing ratio RT, that is, the concentration of the additive Ad is This makes it easier to suppress existing variations.

In the refrigerant discharge method according to some embodiments, in the adding step S200, the additive Ad may be added to the refrigerant flow path 28 on the suction side of the pump 13 instead of to the receiver tank 11.
This allows the additive Ad to be added to a relatively low pressure area in the secondary refrigerant circulation system 10, making it relatively easy to add the additive.
Furthermore, since the secondary refrigerant liquid and the additive Ad are mixed together when passing through the pump 13, local variations in the mixing ratio Rt, that is, the additive concentration can be suppressed.

In the refrigerant discharge method according to some embodiments, in the adding step S200, the additive Ad may be added to the refrigerant flow path 28 on the suction side of the pump 13 instead of the receiver tank 11 while driving the pump 13.
As a result, by driving the pump 13, the pressure in the refrigerant flow path 28 on the suction side is reduced, making it relatively easy to add the additive Ad. Since mixing with the additive Ad is promoted, local variations in the mixing ratio Rt, that is, the concentration of the additive Ad can be suppressed.

In the refrigerant discharge method according to some embodiments, in the adding step S200, the additive Ad may be added to the gas phase portion 45 instead of the liquid phase portion 47 of the refrigerant circulation system (secondary refrigerant circulation system 10). .
In addition, in the case of the secondary refrigerant circulation system 10 shown in FIG. 1, the gas phase section 45 serving as the addition site for the additive Ad may be, for example, the gas header 19, the refrigerant channel 23 connecting the gas header 19 and the receiver tank 11, Examples include the gas phase portion of the receiver tank 11.
Thereby, the additive Ad can be added to the gas phase portion 45 of the refrigerant circulation system (secondary refrigerant circulation system 10).

In the refrigerant discharge method according to some embodiments, the refrigerant to be discharged may be a CO ₂ refrigerant.
As a result, when the secondary refrigerant in the secondary refrigerant circulation system 10 is discharged to the outside of the secondary refrigerant circulation system 10, the CO ₂ refrigerant is relatively likely to solidify the secondary refrigerant in the secondary refrigerant circulation system 10. Even in this case, solidification of the CO ₂ refrigerant in the secondary refrigerant circulation system 10 can be suppressed.

The present disclosure is not limited to the embodiments described above, and also includes forms in which modifications are added to the embodiments described above, and forms in which these forms are appropriately combined.
For example, the refrigerant discharge method according to some embodiments may be applied to a direct expansion type refrigeration apparatus.
Moreover, in the refrigerant discharge method according to some embodiments, a worker may perform at least some of the steps from step S1 to step S19 in the flowcharts of FIGS. 2A and 2B described above.

The contents described in each of the above embodiments can be understood as follows, for example.
(1) A refrigerant discharge method according to at least one embodiment of the present disclosure includes adding the refrigerant (secondary refrigerant) in the refrigerant circulation system (secondary refrigerant circulation system 10) to the refrigerant (secondary refrigerant) after addition. Step S200 of adding an additive Ad to the refrigerant circulation system (secondary refrigerant circulation system 10) to reduce the pressure at the triple point of and step S300 for discharging the refrigerant (secondary refrigerant).

According to the method (1) above, by adding the refrigerant (secondary refrigerant) in the refrigerant circulation system (secondary refrigerant circulation system 10), the pressure at the triple point of the refrigerant (secondary refrigerant) after addition is reduced. Since the additive Ad is added into the refrigerant circulation system (secondary refrigerant circulation system 10), when the refrigerant (secondary refrigerant) is discharged from the refrigerant circulation system (secondary refrigerant circulation system 10), the refrigerant circulation system (secondary Solidification of the refrigerant (secondary refrigerant) in the refrigerant circulation system 10) can be suppressed.

(2) In some embodiments, in the method of (1) above, in the adding step S200, the refrigerant circulation system (secondary refrigerant circulation system 10) is equipped with a refrigerant liquid (secondary refrigerant liquid) that can be stored. It is preferable to add the additive Ad to the storage section (receiver tank 11).

In order to understand the triple point of the refrigerant after adding the additive Ad, it is necessary to understand the mixing ratio of the refrigerant and the additive.
According to the method (2) above, the mixing ratio Rt between the refrigerant liquid (secondary refrigerant liquid) and the additive Ad in the storage section (receiver tank 11) can be easily managed. Further, according to the method (2) above, the refrigerant liquid (secondary refrigerant liquid) and the additive Ad in the storage section (receiver tank 11) are easily mixed, and the mixing ratio Rt, that is, the additive Ad is This makes it easier to suppress local variations in additive concentration.

(3) In some embodiments, in the method (2) above, the amount of stored refrigerant liquid (secondary refrigerant liquid) stored in the storage section (receiver tank 11) before performing the adding step S200. (step S100 of discharging a part of the refrigerant to which the additive Ad is not added).

According to the method (3) above, the total amount of additive Ad added into the refrigerant circulation system (secondary refrigerant circulation system 10) can be suppressed.

(4) In some embodiments, in the method (3) above, in the adding step S200, the refrigerant circulation system (secondary refrigerant circulation system 10) is At least a portion of the additive Ad may be added to the storage section (receiver tank 11) while the purge valve 33 for discharging the refrigerant (secondary refrigerant) to the outside is closed.

According to the method (4) above, when adding the additive Ad, the refrigerant containing the additive Ad (secondary refrigerant) is not discharged to the outside of the refrigerant circulation system (secondary refrigerant circulation system 10). When adding the additive Ad, it is easy to grasp the amount of the additive Ad present in the refrigerant circulation system (secondary refrigerant circulation system 10). This makes it easier to manage the mixing ratio Rt of the refrigerant (secondary refrigerant) and the additive Ad.

(5) In some embodiments, in the method of (4) above, in step S200 of adding the refrigerant (secondary refrigerant) to the cooling load (freezing pipe 15) in the refrigerant circulation system (secondary refrigerant circulation system 10). At least a portion of the additive Ad may be added to the storage section (receiver tank 11) while the operation of the pump 13 for supplying the additive Ad is stopped and the purge valve 33 is closed.

According to the method (5) above, the mixing ratio Rt of the refrigerant (secondary refrigerant) and the additive Ad in the storage section (receiver tank 11) can be easily managed.

(6) In some embodiments, in the method of (5) above, in the adding step S200, when it is determined that the amount of the additive added to the reservoir is equal to or more than the specified amount, the pump is operated. It is a good idea to start.

According to the method (6) above, the refrigerant liquid whose triple point pressure is lower than the desired pressure is sent from the storage section (receiver tank 11) to the refrigerant circulation system (secondary refrigerant circulation system 10). Since it is possible to replace the refrigerant liquid (secondary refrigerant) in the refrigerant circulation system (secondary refrigerant circulation system 10) with the refrigerant liquid (secondary refrigerant) whose triple point pressure is below the desired pressure, The time required can be shortened.

(7) In some embodiments, in the method of (6) above, in the adding step S200, the addition of the additive Ad may be continued even after the operation of the pump 13 is started.

According to the method (7) above, by starting the operation of the pump 13, the refrigerant (secondary refrigerant) to which the additive Ad is not added returns to the storage section (receiver tank 11). By continuing to add the additive Ad, it is possible to suppress a decrease in the mixture ratio Rt of the additive Ad in the refrigerant liquid (secondary refrigerant liquid) in the storage section (receiver tank 11).

(8) In some embodiments, in any of the methods (2) to (7) above, in the adding step S200, the pressure (pressure Pr ) and temperature (temperature Tr) to judge the progress of addition of the additive Ad.

According to the method (8) above, since the mixing ratio of the additive can be determined from the pressure (pressure Pr) and temperature (temperature Tr) of the refrigerant in the storage section, it becomes easier to judge the progress of addition of the additive.

(9) In some embodiments, in the method of (8) above, in the adding step, the end time of addition of the additive is determined based on the pressure (pressure Pr) and temperature (temperature Tr) of the refrigerant in the storage section. It is good to judge. In the discharging step, the refrigerant to which the additive has been added may be discharged to the outside of the refrigerant circulation system after the addition of the additive is completed in the adding step.

According to the method (9) above, since the mixing ratio Rt of the additive Ad can be determined from the pressure (pressure Pr) and temperature (temperature Tr) of the refrigerant (secondary refrigerant) in the storage section (receiver tank 11), the additive Ad It becomes easier to judge when the addition of Ad has ended, that is, whether the refrigerant (secondary refrigerant) to which the additive Ad has been added has stopped solidifying even under atmospheric pressure.
Furthermore, according to the method (9) above, the refrigerant (secondary refrigerant) that does not solidify even under atmospheric pressure can be discharged to the outside of the refrigerant circulation system (secondary refrigerant circulation system 10). When the refrigerant (secondary refrigerant) is discharged from the circulation system 10), solidification of the refrigerant (secondary refrigerant) in the refrigerant circulation system (secondary refrigerant circulation system 10) can be suppressed.

(10) In some embodiments, in any of the methods (1) to (9) above, the refrigerant may be a secondary refrigerant, and the refrigerant circulation system may be the secondary refrigerant circulation system 10. It's okay.

According to the method (10) above, when discharging the secondary refrigerant in the secondary refrigerant circulation system 10 to the outside of the secondary refrigerant circulation system 10, solidification of the secondary refrigerant in the secondary refrigerant circulation system 10 is prevented. It can be suppressed.

(11) In some embodiments, in the method (10) above, the secondary refrigerant circulation system 10 may be connected to the primary refrigerant circulation system 3 via the heat exchanger 7. In the adding step S200, the additive Ad is preferably added to the receiver tank 11 provided in the secondary refrigerant circulation system 10, which can receive the refrigerant (secondary refrigerant) from the heat exchanger 7.

According to the method (11) above, the mixing ratio Rt of the secondary refrigerant liquid and the additive Ad in the receiver tank 11 can be easily managed. Further, according to the method (11) above, the secondary refrigerant liquid and the additive Ad in the receiver tank 11 are easily mixed, and local variations in the mixing ratio Rt, that is, the concentration of the additive Ad becomes easier to suppress.

(12) In some embodiments, in the method of (1) above, in the adding step S200, the refrigerant (secondary refrigerant) is added to the cooling load (freezing pipe 15) in the refrigerant circulation system (secondary refrigerant circulation system 10). The additive Ad may be added to the refrigerant flow path 28 on the suction side of the pump 13 for supplying.

According to the method (12) above, the additive Ad can be added to a relatively low pressure area in the refrigerant circulation system (secondary refrigerant circulation system 10), so it is relatively easy to add the additive Ad.
Further, according to the method (12) above, since the mixing of the refrigerant liquid (secondary refrigerant liquid) and the additive Ad is promoted when passing through the pump 13, the mixing ratio Rt, that is, the addition of the additive Ad Local variations in concentration can be suppressed.

(13) In some embodiments, in the method (12) above, in the adding step S200, the additive Ad may be added to the refrigerant flow path 28 on the suction side while driving the pump 13.

According to the method (13) above, the pressure in the refrigerant flow path 28 on the suction side is reduced by driving the pump 13, so it is relatively easy to add the additive Ad.
Further, according to the method (13) above, since the mixing of the refrigerant liquid (secondary refrigerant liquid) and the additive Ad is promoted when passing through the pump 13, the mixing ratio Rt, that is, the addition of the additive Ad Local variations in concentration can be suppressed.

(14) In some embodiments, in the method of (1) above, in the adding step S200, the additive Ad may be added to the gas phase section 45 of the refrigerant circulation system (secondary refrigerant circulation system 10). .

According to the method (14) above, the additive Ad can be added to the gas phase portion 45 of the refrigerant circulation system (secondary refrigerant circulation system 10).

(15) In some embodiments, in any of the methods (1) to (14) above, before performing the adding step S200, the addition is performed outside the refrigerant circulation system (secondary refrigerant circulation system 10). It is preferable to include step S100 of discharging a part of the refrigerant (secondary refrigerant) to which the substance Ad is not added.

According to the method (15) above, the total amount of additive Ad added to the refrigerant circulation system (secondary refrigerant circulation system 10) can be suppressed.

(16) In some embodiments, in the method (15) above, in step S100 of discharging a part of the refrigerant to which the additive Ad is not added, cooling is performed in the refrigerant circulation system (secondary refrigerant circulation system 10). While pressurizing the inside of the refrigerant circulation system (secondary refrigerant circulation system 10) by the pump 13 for supplying refrigerant (secondary refrigerant) to the load (freeze pipe 15), the refrigerant (secondary refrigerant) to which no additive Ad has been added is ) is preferably discharged to the outside of the refrigerant circulation system (secondary refrigerant circulation system 10).

According to the method (16) above, the refrigerant is circulated in the process of discharging the refrigerant (secondary refrigerant) in the refrigerant circulation system (secondary refrigerant circulation system 10) to the outside of the refrigerant circulation system (secondary refrigerant circulation system 10). Since the pressure drop in the system (secondary refrigerant circulation system 10) can be suppressed, solidification of the refrigerant (secondary refrigerant) to which no additives are added can be suppressed in the refrigerant circulation system (secondary refrigerant circulation system 10). .

(17) In some embodiments, in any of the methods (1) to (16) above, the refrigerant may be a CO ₂ refrigerant.

According to the method (17) above, when discharging the refrigerant (secondary refrigerant) in the refrigerant circulation system (secondary refrigerant circulation system 10) to the outside of the refrigerant circulation system (secondary refrigerant circulation system 10), the refrigerant Even if the refrigerant (secondary refrigerant) in the circulation system (secondary refrigerant circulation system 10) is a CO ₂ refrigerant that is relatively likely to solidify, the CO ₂ refrigerant in the refrigerant circulation system (secondary refrigerant circulation system 10) Can suppress solidification.

1 Soil freezing device 3 Primary refrigerant circulation system 5 Refrigerator 7 Heat exchanger 10 Secondary refrigerant circulation system 11 Receiver tank 13 Pump 15 Freezing tube 17 Liquid header 28 Refrigerant passage 31 Charge pump 35 Charge valve 45 Gas phase section

Claims (17)

adding into the refrigerant circulation system an additive that reduces the pressure at the triple point of the refrigerant after addition by adding it to the refrigerant in the refrigerant circulation system;
discharging the refrigerant to which the additive has been added to the outside of the refrigerant circulation system;
Equipped with
Refrigerant discharge method. In the adding step, the additive is added to a storage part that is provided in the refrigerant circulation system and is capable of storing refrigerant liquid.
The refrigerant discharge method according to claim 1. before implementing the adding step, reducing the amount of the refrigerant liquid stored in the storage section;
Equipped with
The refrigerant discharge method according to claim 2. In the adding step, at least a portion of the additive is added to the storage section with a purge valve provided in the refrigerant circulation system for discharging the refrigerant to the outside of the refrigerant circulation system closed.
The refrigerant discharge method according to claim 3. In the adding step, operation of a pump for supplying the refrigerant to a cooling load in the refrigerant circulation system is stopped, and at least a part of the additive is added to the storage section with the purge valve closed. Added,
The refrigerant discharge method according to claim 4. In the adding step, when it is determined that the amount of the additive added to the storage section is equal to or more than a specified amount, operation of the pump is started.
The refrigerant discharge method according to claim 5. In the adding step, the addition of the additive is continued even after the operation of the pump is started.
The refrigerant discharge method according to claim 6. In the adding step, the progress of adding the additive is determined based on the pressure and temperature of the refrigerant in the storage section.
The refrigerant discharge method according to any one of claims 2 to 7. In the adding step, determining the end time of adding the additive based on the pressure and temperature of the refrigerant in the storage section,
9. The refrigerant discharging method according to claim 8, wherein in the discharging step, the refrigerant to which the additive has been added is discharged to the outside of the refrigerant circulation system after the addition of the additive is finished in the adding step. The refrigerant is a secondary refrigerant,
The refrigerant circulation system is a secondary refrigerant circulation system,
The refrigerant discharge method according to any one of claims 1 to 7. The secondary refrigerant circulation system is connected to the primary refrigerant circulation system via a heat exchanger,
In the adding step, the additive is added to a receiver tank provided in the secondary refrigerant circulation system that can receive the refrigerant from the heat exchanger.
The refrigerant discharge method according to claim 10. In the adding step, the additive is added to a refrigerant flow path on the suction side of a pump for supplying the refrigerant to a cooling load in the refrigerant circulation system.
The refrigerant discharge method according to claim 1. In the adding step, the additive is added to the refrigerant flow path on the suction side while driving the pump.
The refrigerant discharge method according to claim 12. In the adding step, the additive is added to a gas phase part of the refrigerant circulation system.
The refrigerant discharge method according to claim 1. Before carrying out the adding step, discharging a part of the refrigerant to which the additive is not added to the outside of the refrigerant circulation system;
Equipped with
The refrigerant discharge method according to any one of claims 1 to 7, 12 to 14. In the step of discharging a part of the refrigerant to which the additive is not added, the additive is added while pressurizing the inside of the refrigerant circulation system by a pump for supplying the refrigerant to a cooling load in the refrigerant circulation system. discharging the unused refrigerant to the outside of the refrigerant circulation system;
The refrigerant discharge method according to claim 15. the refrigerant is a _CO2 refrigerant;
A refrigerant discharge method according to any one of claims 1 to 7 and 12 to 14.

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