Refrigerant discharge method

Abstract

To suppress solidification of refrigerant in a refrigerant circulation system, when the refrigerant is discharged from the refrigerant circulation system.SOLUTION: A refrigerant discharge method according to one embodiment, includes the steps of: compressing the inside of a refrigerant circulation system; and discharging refrigerant within the refrigerant circulation system to the outside of the refrigerant circulation system while compressing the inside of the refrigerant circulation system in the step of compressing.SELECTED DRAWING: Figure 2A

Description

[Technical field]

[0001] The present disclosure relates to a refrigerant evacuation method. [Background technology]

[0002] For example, CO is used as a refrigerant. 2 In refrigeration cycle equipment using 2 2. Description of the Related Art There is known a refrigeration cycle device that is configured so that a refrigerant can be discharged to the outside (see, for example, Patent Document 1). In such a refrigeration cycle device, CO is released from the refrigerant circulation system during maintenance. 2 When trying to discharge the refrigerant, CO 2 In relatively large equipment, CO may be released into the refrigerant circulation system. 2 If the refrigerant solidifies, it may cause problems in maintaining the refrigerant circulation system, and the solidified CO 2 There is a risk that work will have to be stopped until the refrigerant dissolves or vaporizes, which may result in a long time being required for discharge.

[0003] So, CO 2 In order to prevent the refrigerant from solidifying when it is discharged to the outside, an auxiliary heat exchanger is used to separate the refrigerant from the outside air and CO 2 CO while exchanging heat with the refrigerant 2 There is a refrigeration cycle device that is configured to discharge a refrigerant to the outside (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2009-299981 A [Patent Document 2] Patent No. 5693247 Summary of the Invention [Problem to be solved by the invention]

[0005] However, for example, in the refrigeration cycle device described in Patent Document 2, in an environment where the outside air temperature is low, such as in winter, the auxiliary heat exchanger 2 There is insufficient heat exchange with the refrigerant, and CO 2 When the refrigerant is discharged to the outside, 2 There is a risk of the refrigerant solidifying.

[0006] In view of the above circumstances, at least one embodiment of the present disclosure has an object to suppress solidification of a refrigerant in a refrigerant circulation system when the refrigerant is discharged from the refrigerant circulation system. [Means for solving the problem]

[0007] (1) A refrigerant discharging method according to at least one embodiment of the present disclosure, Pressurizing a refrigerant circulation system; discharging the refrigerant in the refrigerant circulation system to the outside of the refrigerant circulation system while pressurizing the refrigerant in the pressurizing step; Equipped with. Effect of the Invention

[0008] According to at least one embodiment of the present disclosure, solidification of the refrigerant in the refrigerant circulation system can be suppressed when the refrigerant is discharged from the refrigerant circulation system. [Brief description of the drawings]

[0009] [Figure 1A] 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; [Figure 1B] FIG. 1 is an overall configuration diagram of a soil freezing device as another example of a refrigeration cycle device to which a refrigerant discharge method according to some embodiments is applied. [Figure 2A] 5 is a flowchart showing a process performed in a control device when performing a refrigerant discharging method according to some embodiments. [Figure 2B]5 is a flowchart showing a process performed in a control device when performing a refrigerant discharging method according to some embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] 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 components described as the embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present disclosure. For example, expressions expressing relative or absolute configuration, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," not only strictly express such a configuration, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions indicating that things are in an equal state, such as "identical," "equal," and "homogeneous," not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained. For example, expressions describing shapes such as a rectangular shape or a cylindrical shape do not only refer to rectangular shapes, cylindrical shapes, etc. in the strict geometric sense, but also refer to shapes that include uneven portions, chamfered portions, etc., to the extent that the same effect is obtained. On the other hand, the expressions "comprise," "include," "have," "includes," or "have" of one element are not exclusive expressions excluding the presence of other elements.

[0011] FIG. 1A is an overall configuration diagram of a soil freezing device as an example of a refrigeration cycle device to which a refrigerant discharging method according to some embodiments is applied. FIG. 1B is an overall configuration diagram of a soil freezing device as another example of a refrigeration cycle device to which a refrigerant discharging method according to some embodiments is applied. A soil freezing device 1 in 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.

[0012] In the secondary refrigerant circulation system 10 according to some embodiments, a receiver tank 11 capable of receiving the refrigerant from the heat exchanger 7, a pump 13 for circulating the refrigerant in the receiver tank 11 through the secondary refrigerant circulation system, and a plurality of freezing pipes 15 buried in the soil for freezing the soil 30 are provided in a refrigerant circulation path 21 of the secondary refrigerant circulation system 10. In the secondary refrigerant circulation system 10 according to some embodiments, a liquid header 17 for distributing liquid phase refrigerant to the plurality of freezing pipes 15 and a gas header 19 for collecting gas phase refrigerant from the plurality of freezing pipes 15 are provided in the refrigerant circulation path 21. In some embodiments of the secondary refrigerant circulation system 10, the refrigerant (secondary refrigerant) is, for example, CO 2 It is a refrigerant.

[0013] In the secondary refrigerant circulation system 10 according to some embodiments, a solenoid valve 31 controlled by a control device 50 described later is provided in the refrigerant flow path 23 connecting the gas header 19 and the receiver tank 11. A purge flow path 25 is connected to the refrigerant flow path 23 between the gas header 19 and a solenoid valve 31. 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 described later. A silencer 27 may be provided at the outlet of the purge passage 25 to muffle noise when the secondary refrigerant is discharged outside the secondary refrigerant circulation system 10, as described below.

[0014] 1A is configured to be connectable to a nitrogen cylinder 41 as a gas supply source (nitrogen source) for supplying gas (nitrogen) to the secondary refrigerant circulation system 10, as described below. That is, in the secondary refrigerant circulation system 10 shown in FIG 1A, a supply flow path 29 for supplying nitrogen gas from the nitrogen cylinder 41 to the secondary refrigerant circulation system 10 is connected between the solenoid valve 31 and the receiver tank 11 in the refrigerant flow path 23. 1B is connected to an air compressor 43 as a gas supply source (compressed air source) for supplying gas (compressed air) to the secondary refrigerant circulation system 10, as described below, and an air dryer 45 for dehumidifying the compressed air from the air compressor 43. That is, in the secondary refrigerant circulation system 10 shown in FIG 1B, a supply flow path 29 for supplying compressed air from the air compressor 43 to the secondary refrigerant circulation system 10 is connected between the solenoid valve 31 and the receiver tank 11 in the refrigerant flow path 23. In the secondary refrigerant circulation system 10 shown in FIG. 1B, the air compressor 43 may be replaced with a PSA (Pressure Swing Adsorption) or membrane type nitrogen gas generator. A supply valve 35 is provided in the supply flow path 29. The supply valve 35 is, for example, a solenoid valve controlled by a control device 50 described later.

[0015] The secondary refrigerant circulation system 10 shown in FIG. 1A has the advantages that a gas at a relatively high pressure can be easily obtained, a power source for supplying the gas is not required, and the device configuration can be simplified. The secondary refrigerant circulation system 10 shown in FIG. 1B has the advantages of eliminating the need for a cylinder for supplying gas, eliminating the need to replace the cylinder, and reducing costs compared to purging with gas in a cylinder when the purge flow rate becomes high. In addition, in the secondary refrigerant circulation system 10 shown in FIG. 1A, the nitrogen cylinder 41 may be prepared only when the secondary refrigerant in the secondary refrigerant circulation system 10 is discharged from the secondary refrigerant circulation system 10 to the outside. In addition, in the secondary refrigerant circulation system 10 shown in FIG. 1B, the air compressor 43 and the air dryer 45 may be provided only when the secondary refrigerant in the secondary refrigerant circulation system 10 is discharged from the secondary refrigerant circulation system 10 to the outside.

[0016] In some embodiments, the secondary refrigerant circulation system 10 is provided with a pressure sensor 61 for detecting the pressure in the receiver tank 11 and a level sensor 62 for detecting the liquid level of the secondary refrigerant in the receiver tank 11. The secondary refrigerant circulation system 10 according to some embodiments is provided with a pressure sensor 65 and a concentration sensor 66 for detecting the pressure upstream of the purge valve 33 in the purge passage 25 and the concentration of the secondary refrigerant. The concentration sensor 66 may be provided downstream of the purge valve 33. The concentration sensor 66 may be a permanently installed sensor or a simple (handy) sensor. In some embodiments, the secondary refrigerant circulation system 10 is provided with a pressure sensor 67 for detecting the supply pressure of the gas in the supply passage 29.

[0017] The soil freezing apparatus 1 according to some embodiments includes a control device 50 for controlling each part of the soil freezing apparatus 1. A control device 50 according to some embodiments includes a processor 51 that executes various arithmetic 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, a GPU, an MPU, a DSP, various other arithmetic devices, or a combination of these. The memory 53 is realized by a ROM, a RAM, a flash memory, or a combination of these. 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. The control contents of the control device 50 will be described in detail later.

[0018] In the soil freezing device 1 configured in this manner, 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 then supplied from the liquid header 17 to multiple freezing pipes 15. The secondary refrigerant supplied to the freezing pipes 15 absorbs heat from the soil around the freezing pipes 15 when evaporating in the freezing pipes 15. As a result, the soil around the freezing pipes 15 freezes.

[0019] The secondary refrigerant in the gas phase that has evaporated within the multiple freezing pipes 15 is collected in the gas header 19 and returned to the receiver tank 11. The gas-phase secondary refrigerant in the receiver tank is cooled and liquefied in the heat exchanger 7, and returns to the receiver tank 11 as a liquid-phase secondary refrigerant.

[0020] In a soil freezing device 1 configured in this manner, for example, when performing maintenance on the secondary refrigerant circulation system 10 or removing the freezing pipe 15, it is necessary to discharge the secondary refrigerant in the secondary refrigerant circulation system 10 from the secondary refrigerant circulation system 10 to the outside. However, when the secondary refrigerant is discharged, the pressure in the secondary refrigerant circulation system 10 reaches the triple point (CO 2 If the pressure of the refrigerant drops to or below 0.417 MPa, the secondary refrigerant may solidify in the secondary refrigerant circulation system 10. If the secondary refrigerant solidifies in the secondary refrigerant circulation system 10, maintenance such as replacing a strainer (not shown) or removing a frozen pipe cannot be performed until the solidified secondary refrigerant vaporizes or liquefies. In addition, if the secondary refrigerant solidifies in the secondary refrigerant circulation system 10, the pump 13 cannot be operated until the solidified secondary refrigerant vaporizes or liquefies. In order to prevent the secondary refrigerant in the secondary refrigerant circulation system 10 from solidifying when it is discharged to the outside of the secondary refrigerant circulation system 10, a method of heating the secondary refrigerant in the secondary refrigerant circulation system 10 with, for example, a heater may be considered. However, this method requires a relatively large amount of heat to prevent the secondary refrigerant from solidifying, and the heating by the heater cannot keep up with the discharge of the secondary refrigerant, which may result in the secondary refrigerant solidifying. In addition, there are technical issues, such as the difficulty of detecting a sudden rise in the pressure of the secondary refrigerant caused by heating by the heater.

[0021] Therefore, in some embodiments of the refrigerant discharging method, the secondary refrigerant in the secondary refrigerant circulation system 10 is discharged to the outside of the secondary refrigerant circulation system 10 while pressurizing the secondary refrigerant circulation system 10. That is, the refrigerant discharging method according to some embodiments includes a step S100 of pressurizing the secondary refrigerant circulation system 10, which will be described later, and a step S200 of discharging the secondary refrigerant in the secondary refrigerant circulation system 10 to the outside of the secondary refrigerant circulation system 10 while pressurizing the secondary refrigerant circulation system 10 in the pressurizing step S100, which will be described later. This makes it possible to suppress a 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, thereby suppressing solidification of the secondary refrigerant within the secondary refrigerant circulation system 10.

[0022] In some embodiments of the refrigerant discharge method, in the pressurizing step S100, the secondary refrigerant circulation system 10 is pressurized so that the pressure in the secondary refrigerant circulation system 10 is kept at or above the triple point of the secondary refrigerant, as described below. This makes it possible to prevent the secondary refrigerant in the secondary refrigerant circulation system 10 from solidifying by maintaining the pressure in the secondary refrigerant circulation system 10 at or above the triple point of the secondary refrigerant.

[0023] 2A and 2B are flowcharts showing the flow of processes performed in the control device 50 when carrying out a refrigerant discharging method according to some embodiments. When the processor 51 receives a signal to start a secondary refrigerant discharging process, the processor 51 reads and executes a program for executing the processes shown in the flowcharts of Fig. 2A and 2B from the memory 53.

[0024] The method for discharging a refrigerant according to some embodiments includes a pressurizing step S100 and a discharging step S200. In the refrigerant discharging method according to some embodiments, the pressurizing step S100 includes steps S1, S3, S5, S15, and S17, which will be described later. In the following description, unless otherwise specified, the description applies to both the secondary refrigerant circulation system 10 shown in FIG. 1A and the secondary refrigerant circulation system 10 shown in FIG. 1B.

[0025] 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. This starts the circulation of the secondary refrigerant cooled by the refrigerator 5 in the secondary refrigerant circulation system 10. That is, the inside of the secondary refrigerant circulation system 10 is pressurized (increased in pressure) by the pump 13, so that the inside of the secondary refrigerant circulation system 10 is pressurized (increased in pressure) without being heated. Furthermore, by performing step S1, a portion of the secondary refrigerant circulating in the secondary refrigerant circulation system 10 is discharged to the outside of the secondary refrigerant circulation system 10 via the purge flow path 25. At the time when step S1 is performed, the solenoid valve 31 is open, and the supply valve 35 is closed. At the time when step S1 is performed, in the secondary refrigerant circulation system 10 shown in Fig. 1B, the air compressor 43 and the air dryer 45 are stopped, but may be operating.

[0026] 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 becomes equal to or lower than the specified pressure P1, the processor 51 proceeds to step S5 and waits until the liquid level Lr of the secondary refrigerant in the receiver tank 11 detected by the level sensor 62 becomes equal to or lower than the lower limit L1. When the processor 51 determines that the liquid level of the secondary refrigerant in the receiver tank 11 becomes equal to or lower than the lower limit L1, the processor 51 proceeds to step S7 and outputs a control signal to stop the pump 13. This stops the pump 13. Here, the specified pressure P1 is any pressure at which the secondary refrigerant does not reach the triple point, and the lower limit L1 of the liquid level Lr is any liquid level at which the suction head of the pump 13 is ensured and proper operation can be continued.

[0027] In step S9, the processor 51 waits until the pressure Pp upstream of the purge valve 33 in the purge passage 25 detected by the pressure sensor 65 becomes 0.5 MPa or less. When the processor 51 determines that the pressure Pp upstream of the purge valve 33 in the purge passage 25 becomes 0.5 MPa or less, the process proceeds to step S11, where it outputs a control signal for closing the solenoid valve 31. This closes the solenoid valve 31. By closing the solenoid valve 31, it is possible to prevent nitrogen gas or compressed air from flowing into the purge passage 25 via the solenoid valve 31 when nitrogen gas is supplied from the nitrogen cylinder 41 or compressed air is supplied from the air compressor 43 in step S15 to be performed later.

[0028] 2B, in step S13, the processor 51 waits until the pressure Pp upstream of the purge valve 33 in the purge passage 25 detected by the pressure sensor 65 becomes 0.5 MPa or less. When the processor 51 determines that the pressure Pp upstream of the purge valve 33 in the purge passage 25 becomes 0.5 MPa or less, the processor 51 proceeds to step S15 and outputs a control signal for opening the supply valve 35. In the secondary refrigerant circulation system 10 shown in FIG. 1B, the processor 51 may output a control signal to the air compressor 43 and the air dryer 45 to start the operation of the air compressor 43 and the air dryer 45 at step S15 or before reaching step S15. As a result, the supply valve 35 is opened and nitrogen gas or compressed air is supplied into the secondary refrigerant circulation system 10, thereby pressurizing (increasing the pressure) inside the secondary refrigerant circulation system 10 without heating.

[0029] In step S17, the processor 51 waits until the pressure Pp upstream of the purge valve 33 in the purge passage 25 detected by the pressure sensor 65 becomes 0.55 MPa or more. When the processor 51 determines that the pressure Pp upstream of the purge valve 33 in the purge passage 25 becomes 0.55 MPa or more, the processor 51 proceeds to step S19 and outputs a control signal for closing the supply valve 35. This closes the supply valve 35, and stops the supply of nitrogen gas or compressed air into the secondary refrigerant circulation system 10. Note that in the secondary refrigerant circulation system 10 shown in FIG. 1B, in step S19, the processor 51 may output a control signal for stopping the air compressor 43 and the air dryer 45 to the air compressor 43 and the air dryer 45.

[0030] In step S21, the processor 51 detects the concentration Cp of the secondary refrigerant discharged from the purge passage 25 by the concentration sensor 66, and determines whether the concentration Cp is equal to or lower than a reference value C1. In step S21, if the processor 51 determines that the concentration Cp exceeds the reference value C1, the process returns to step S13. In step S21, if the processor 52 determines that the concentration Cp is equal to or less than the reference value C1, the process proceeds to step S23. The reference value C1 is set, for example, when the secondary refrigerant is CO 2 If it is a refrigerant, the concentration Cp is the CO concentration in the surroundings before the purging operation is performed. 2 It is also acceptable to use a value that can be regarded as equivalent to the concentration of According to the above, the secondary refrigerant in the secondary refrigerant circulation system 10 is completely discharged and replaced with nitrogen gas or air, i.e., CO 2 It can be easily determined that there is no risk of solidification.

[0031] In step S23, the processor 51 waits until the pressure Pr in the receiver tank 11 detected by the pressure sensor 61 and the pressure Pp upstream of the purge valve 33 in the purge passage 25 detected by the pressure sensor 65 become atmospheric pressure Pa or lower. When the processor 51 determines that the pressures Pr and Pp are equal to or lower than the atmospheric pressure Pa, it ends the processing of this program.

[0032] As described above, in some embodiments of the refrigerant discharging method, in the pressurizing step S100, in the first period Per1 of the discharging step S200, the secondary refrigerant circulation system 10 may be pressurized by the pump 13. In the pressurizing step S100, in the second period Per2 of the discharging step S200 that is after the first period Per1, the secondary refrigerant circulation system 10 may be pressurized by supplying nitrogen gas or compressed air from outside the secondary refrigerant circulation system 10 into the secondary refrigerant circulation system 10.

[0033] As a result, by pressurizing the secondary refrigerant circulation system 10 using the pump 13 during the first period Per1 when the amount of secondary refrigerant in the secondary refrigerant circulation system 10 is relatively large, the amount of nitrogen gas or compressed air supplied (the amount of nitrogen gas consumed or the amount of power consumed by the air compressor 43) can be reduced compared to the case where the secondary refrigerant circulation system 10 is pressurized by supplying nitrogen gas or compressed air from outside the secondary refrigerant circulation system 10 into the secondary refrigerant circulation system 10 during the first period Per1 and the second period Per2. In addition, according to the refrigerant discharge method of some embodiments, even if the amount of liquid-phase secondary refrigerant decreases during the second period Per2 when the amount of secondary refrigerant in the secondary refrigerant circulation system 10 is relatively small, making it difficult for the pump 13 to pressurize the secondary refrigerant circulation system 10, the secondary refrigerant circulation system 10 can be pressurized by nitrogen gas or compressed air.

[0034] In the refrigerant discharging method according to some embodiments, the first period Per1 may be a period during which the amount of the secondary refrigerant in liquid phase in the receiver tank 11 is greater than a specified amount, i.e., the liquid level Lr is equal to or greater than the lower limit L1. The second period Per2 may be a period during which the amount of the secondary refrigerant in liquid phase is equal to or less than a specified amount, i.e., the liquid level Lr is equal to or less than the lower limit L1. Thus, by appropriately setting the specified amount, i.e., the lower limit L1, the supply amount of nitrogen gas or compressed air can be effectively suppressed. Also, according to the refrigerant discharging method according to some embodiments, by appropriately setting the specified amount, cavitation caused by the pump 13 sucking the gas phase secondary refrigerant can be suppressed, and damage to the pump 13 can be prevented.

[0035] In some embodiments of the refrigerant discharge method, in the pressurizing step S100, during the first period Per1, the secondary refrigerant circulation system 10 may be pressurized by the pump 13 while the refrigerator 5 equipped with the primary refrigerant circulation system 3 is operating. As a result, by operating the refrigerator 5, the gas-phase secondary refrigerant in the receiver tank 11 can be changed to a liquid-phase secondary refrigerant, and the first period Per1 can be lengthened. That is, by operating the refrigerator 5, the amount of secondary refrigerant discharged to the outside of the secondary refrigerant circulation system 10 while pressurizing the inside of the secondary refrigerant circulation system 10 by the pump 13 can be increased. This makes it possible to reduce the consumption of nitrogen gas or compressed air.

[0036] In some embodiments of the refrigerant discharging method, the refrigerant to be discharged may be a secondary refrigerant, and the refrigerant circulation system to which the refrigerant discharging method of some embodiments is applied may be a secondary refrigerant circulation system 10. 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, solidification of the secondary refrigerant in the secondary refrigerant circulation system 10 can be suppressed.

[0037] In the refrigerant discharge method according to some of the embodiments described above, in the pressurizing step S100, both of the following steps are performed: pressurizing the secondary refrigerant circulation system 10 by the pump 13, and pressurizing the secondary refrigerant circulation system 10 by supplying gas (nitrogen gas or compressed air) from outside the secondary refrigerant circulation system 10 into the secondary refrigerant circulation system 10. However, in some embodiments of the refrigerant discharge method, in the pressurizing step S100, only one of pressurizing the secondary refrigerant circulation system 10 by pump 13 or pressurizing the secondary refrigerant circulation system 10 by supplying gas into the secondary refrigerant circulation system 10 from outside the secondary refrigerant circulation system 10 may be performed. That is, in the pressurizing step S100, it is preferable to pressurize the secondary refrigerant circulation system 10 by at least one of pressurizing the secondary refrigerant circulation system 10 using the pump 13, or pressurizing the secondary refrigerant circulation system 10 by supplying gas into the secondary refrigerant circulation system 10 from outside the secondary refrigerant circulation system 10. This makes it relatively easy to prevent the secondary refrigerant from solidifying in the secondary refrigerant circulation system 10 when the secondary refrigerant in the secondary refrigerant circulation system 10 is discharged to the outside of the secondary refrigerant circulation system 10.

[0038] In some embodiments of the refrigerant discharging method, the refrigerant to be discharged is CO 2 It may be a 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 secondary refrigerant in the secondary refrigerant circulation system 10 is relatively likely to solidify, and thus the secondary refrigerant in the secondary refrigerant circulation system 10 is relatively likely to solidify. 2 Even if the refrigerant is a secondary refrigerant, the CO 2 Solidification of the refrigerant can be suppressed.

[0039] The present disclosure is not limited to the above-described embodiments, and includes modifications to the above-described embodiments and appropriate combinations of these modifications. For example, the refrigerant discharge method according to some embodiments may be applied to a direct expansion type refrigeration device. In addition, in the refrigerant discharging method according to some embodiments, at least some of the steps from step S1 to step S27 in the flowcharts of FIGS. 2A and 2B described above may be performed by an operator.

[0040] The contents described in each of the above embodiments can be understood, for example, as follows. (1) A refrigerant discharging method according to at least one embodiment of the present disclosure includes a step S100 of pressurizing a refrigerant circulation system (secondary refrigerant circulation system 10), and a step S200 of discharging the refrigerant in the refrigerant circulation system (secondary refrigerant circulation system 10) to the outside of the refrigerant circulation system (secondary refrigerant circulation system 10) while pressurizing the refrigerant circulation system (secondary refrigerant circulation system 10) in the pressurizing step S100.

[0041] According to the above method (1), the pressure drop in the refrigerant circulation system (secondary refrigerant circulation system 10) can be suppressed 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), so solidification of the refrigerant in the refrigerant circulation system (secondary refrigerant circulation system 10) can be suppressed.

[0042] (2) In some embodiments, in the method (1) above, in the pressurizing step S100, the refrigerant circulation system (secondary refrigerant circulation system 10) may be pressurized so that the pressure in the refrigerant circulation system (secondary refrigerant circulation system 10) is kept at or above the triple point of the refrigerant (secondary refrigerant).

[0043] According to the above method (2), the pressure in the refrigerant circulation system (secondary refrigerant circulation system 10) is kept at a pressure equal to or higher than the triple point of the refrigerant (secondary refrigerant), thereby preventing solidification of the refrigerant (secondary refrigerant) in the refrigerant circulation system (secondary refrigerant circulation system 10).

[0044] (3) In some embodiments, in the method of (1) or (2) above, the refrigerant may be a secondary refrigerant, and the refrigerant circulation system may be a secondary refrigerant circulation system 10.

[0045] According to the above method (3), when the 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.

[0046] (4) In some embodiments, in the method of (3) above, in the pressurizing step S100, the secondary refrigerant circulation system 10 may be pressurized by at least one of pressurizing the secondary refrigerant circulation system 10 using a pump 13 for circulating the refrigerant within the secondary refrigerant circulation system 10, or pressurizing the secondary refrigerant circulation system 10 by supplying a gas (nitrogen gas or compressed air) from outside the secondary refrigerant circulation system 10 into the secondary refrigerant circulation system 10.

[0047] According to the above method (4), solidification of the secondary refrigerant in the secondary refrigerant circulation system 10 when the secondary refrigerant in the secondary refrigerant circulation system 10 is discharged to the outside of the secondary refrigerant circulation system 10 can be relatively easily suppressed.

[0048] (5) In some embodiments, in the method of (4) above, in the pressurizing step S100, in a first period Per1 of the discharging step S200, the secondary refrigerant circulation system 10 may be pressurized by the pump 13. In the pressurizing step S100, in a second period Per2 of the discharging step S200 that is after the first period Per1, the secondary refrigerant circulation system 10 may be pressurized by supplying gas (nitrogen gas or compressed air) from outside the secondary refrigerant circulation system 10 into the secondary refrigerant circulation system 10.

[0049] According to the above method (5), by pressurizing the secondary refrigerant circulation system 10 by the pump 13 during the first period Per1 when the amount of secondary refrigerant in the secondary refrigerant circulation system 10 is relatively large, the amount of gas supplied (amount of gas consumed) can be reduced compared to the case where the secondary refrigerant circulation system 10 is pressurized by supplying gas (nitrogen gas or compressed air) from outside the secondary refrigerant circulation system 10 into the secondary refrigerant circulation system 10 during the first period Per1 and the second period Per2. In addition, even if the amount of secondary refrigerant in the secondary refrigerant circulation system 10 becomes difficult to pressurize by the pump 13 due to the decrease in the liquid phase secondary refrigerant in the second period Per2 when the amount of secondary refrigerant in the secondary refrigerant circulation system 10 is relatively small, the secondary refrigerant can be pressurized by supplying gas (nitrogen gas or compressed air) into the secondary refrigerant circulation system 10.

[0050] (6) In some embodiments, in the method of (5) above, the secondary refrigerant circulation system 10 may be connected to the primary refrigerant circulation system 3 via a heat exchanger 7. The first period Per1 may be a period during which the amount of liquid-phase secondary refrigerant in a receiver tank 11 provided in the secondary refrigerant circulation system 10, which can receive the secondary refrigerant from the heat exchanger 7, is greater than a specified amount. The second period Per2 may be a period during which the amount of liquid-phase secondary refrigerant is equal to or less than a specified amount.

[0051] According to the method (6) above, by appropriately setting the specified amount, the supply amount of gas (nitrogen gas or compressed air) can be effectively suppressed. Also, according to the method (6) above, by appropriately setting the specified amount, cavitation caused by the pump 13 sucking the gas phase secondary refrigerant can be suppressed, and damage to the pump 13 can be prevented.

[0052] (7) In some embodiments, in the method of (6) above, in the pressurizing step S100, during the first period Per1, the secondary refrigerant circulation system 10 may be pressurized by the pump 13 while operating the refrigerator 5 equipped with the primary refrigerant circulation system 3.

[0053] According to the method (7) above, by operating the refrigerator 5, the gas-phase secondary refrigerant in the receiver tank 11 can be changed to a liquid-phase secondary refrigerant, and the first period Per1 can be lengthened. That is, by operating the refrigerator 5, the amount of secondary refrigerant discharged to the outside of the secondary refrigerant circulation system 10 while pressurizing the inside of the secondary refrigerant circulation system 10 by the pump 13 can be increased. This makes it possible to suppress the consumption of gas (nitrogen gas or compressed air).

[0054] (8) In some embodiments, in any of the methods (1) to (7) above, the refrigerant (secondary refrigerant) is CO 2 It may be a refrigerant.

[0055] According to the above method (8), 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), CO, which is relatively prone to solidification of the refrigerant (secondary refrigerant) in the refrigerant circulation system (secondary refrigerant circulation system 10), is discharged. 2 Even if the refrigerant is a secondary refrigerant, the CO 2 Solidification of the refrigerant can be suppressed. [Explanation of symbols]

[0056] 1 Soil freezing device 3 Primary refrigerant circulation system 5. Refrigeration Machine 7 Heat exchanger 10 Secondary refrigerant circulation system 11 Receiver tank 13. Pump

Claims

1. Pressurizing a refrigerant circulation system; discharging the refrigerant in the refrigerant circulation system to the outside of the refrigerant circulation system while pressurizing the refrigerant in the pressurizing step; Equipped with Refrigerant discharge method.

2. In the pressurizing step, the pressure in the refrigerant circulation system is increased so that the pressure in the refrigerant circulation system is maintained at a pressure equal to or higher than the triple point of the refrigerant. The refrigerant discharging method according to claim 1.

3. The refrigerant is a secondary refrigerant, The refrigerant circulation system is a secondary refrigerant circulation system. The refrigerant discharging method according to claim 1 or 2.

4. In the pressurizing step, the secondary refrigerant circulation system is pressurized by performing at least one of pressurizing the secondary refrigerant circulation system with a pump for circulating the refrigerant in the secondary refrigerant circulation system, or pressurizing the secondary refrigerant circulation system by supplying a gas from outside the secondary refrigerant circulation system into the secondary refrigerant circulation system. The refrigerant discharging method according to claim 3.

5. In the pressurizing step, In a first period of the step of discharging, the pump is used to pressurize the secondary refrigerant circulation system; In a second period of the discharging step that is after the first period, a gas is supplied from outside the secondary refrigerant circulation system into the secondary refrigerant circulation system to pressurize the secondary refrigerant circulation system. The refrigerant discharging method according to claim 4.

6. The secondary refrigerant circulation system is connected to the primary refrigerant circulation system via a heat exchanger, the first period is a period during which an amount of the refrigerant in a liquid phase in a receiver tank provided in the secondary refrigerant circulation system that can receive the refrigerant from the heat exchanger is equal to or greater than a specified amount, The second period is a period during which the amount of the refrigerant in the liquid phase is less than the specified amount. The refrigerant discharging method according to claim 5.

7. In the pressurizing step, during the first period, the inside of the secondary refrigerant circulation system is pressurized by the pump while operating a refrigerator including the primary refrigerant circulation system. The refrigerant discharging method according to claim 6.

8. The refrigerant is CO ２ The refrigerant is The refrigerant discharging method according to claim 1 or 2.

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