JP2013076511A - Freezing apparatus and defrosting method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a low-cost defrosting means capable of suppressing the consumption of excess electric power by utilizing electric power required for reducing a temperature of a load handling room without adopting a sprinkling system or an electric heater system.SOLUTION: An air cooler 26d or the like is arranged in each of load handling rooms 7A to C and a first liquid receiver 42 for circulating a COsolution is arranged in the air cooler 26d or the like. The first liquid receiver 42 is held at a high pressure of a degree of 4.0 MPa capable of storing the COsolution of 5-10°C. During the defrost operation of the air coolers 26a to c installed in freezing rooms 5A to C, interiors of the load handling rooms 7A to C are cooled and the COsolution collecting the retaining heat of the load handling rooms is supplied to the air coolers 26a to c to perform defrosting.

Description

  The present invention relates to a refrigeration apparatus for a freezer provided with a cargo handling room, and defrosts an air cooler of the freezer using heat recovered by air conditioning in the cargo handling room.

From the viewpoint of global environmental conservation, refrigeration systems using natural refrigerants have been reviewed. Among natural refrigerants, NH ₃ has an ozone depletion coefficient of zero and a global warming coefficient of almost zero, and has excellent performance as a refrigerant. Therefore, the number of refrigeration apparatuses using NH ₃ as a refrigerant is increasing. However, since NH ₃ is toxic, it is relatively safe and many refrigeration apparatuses using a CO ₂ liquid having excellent characteristics as a medium for carrying heat as a secondary refrigerant have been adopted.

FIG. 8 of Patent Document 1 discloses a freezer having a cargo handling chamber and an NH ₃ / CO ₂ refrigeration apparatus. The structure of this freezer will be described with reference to FIG. In FIG. 4, the refrigeration apparatus 100 includes an outdoor unit A and a ceiling-mounted air cooler 118 using CO ₂ brine provided inside a freezer B. In the outdoor unit A, an NH ₃ circulation path (primary refrigerant circuit) 102 is provided with a compressor 104, an evaporative condenser (evaporator) 106, a cascade condenser 108, and an expansion valve 110 to form a refrigeration cycle.

A CO ₂ circulation path (secondary refrigerant circuit) 112 is connected to the cascade capacitor 108. The CO ₂ circulation path 112 is provided with a liquid receiver 114, a liquid pump 116, and the ceiling air cooler 118. In the cascade condenser 108, the CO ₂ brine is cooled by NH ₃ , and the cooled CO ₂ brine cools the air in the freezer B by the ceiling air cooler 118. The CO ₂ brine gasified by cooling the air is cooled and liquefied by NH _{3 in} a brine cooler (cascade condenser) 108. By repeating this cycle, the air in the freezer B is indirectly cooled by NH ₃ circulating in the primary refrigerant circuit 102.

  There is a cargo handling room adjacent to the freezer. Compared to storage-type freezers, logistics-type freezers where goods to be frozen are frequently put in and out respond to frequent loading and unloading operations, HACCP (Food Hazard Analysis / Important Control Point System) measures, product temperature maintenance, etc. Due to the quality measures, a large-sized cargo handling room has been required. Also, the cargo handling room tends to be cold and sealed. In Patent Document 2, a dehumidification chamber provided with a unit cooler is provided between the dock shelter and the opening of the cargo handling chamber that is sealed at a low temperature in order to suppress the occurrence of condensation due to intrusion of outside air into the cargo handling chamber. A configuration is disclosed.

On the other hand, the water vapor contained in the air in the freezer condenses and solidifies on the cooling surface cooled by low-temperature CO ₂ in the air cooler, and accumulates as frost. Since this frost hinders heat transfer and reduces the thermal efficiency of the refrigeration apparatus, it is necessary to defrost regularly. In a refrigeration apparatus using CO ₂ as a secondary refrigerant, water spray type defrost is generally performed in which normal temperature water is sprayed onto a cooling surface. However, sprinkling type defrost is superior in that defrosting is reliably performed, but it is necessary to introduce room temperature water into a freezer in a low temperature atmosphere, and various measures such as prevention of freezing must be taken. In addition, the sprayed room-temperature water promotes the formation of frost and has a surface opposite to defrost.

Therefore, a defrost method that does not perform watering is required. One defrosting method that does not use water is an electric heater type. This method is a method in which an electric heater is incorporated in the air cooler and energized and heated during defrosting to melt frost. As another defrost method, there is a hot gas system that uses the retained heat of the discharge gas of the compressor of the refrigeration apparatus. In Patent Document 3 and Patent Document 4, in the NH ₃ / CO ₂ refrigeration apparatus, a hot gas type defrost that melts frost adhering to the cooling surface by introducing high-temperature CO ₂ gas on the compressor discharge side into the air cooler. Means are disclosed.

Japanese Patent Laid-Open No. 2005-172416 (FIG. 8) Japanese Patent Laid-Open No. 2002-303477 US Pat. No. 5,400,615 International Publication No. WO02 / 066908 (A1)

  Watering type defrost is excellent in that defrosting is performed reliably, but has the above-mentioned problems. In the electric heater method, the electric power used to heat the electric heater becomes power consumption, which consumes extra power, and reverses the low temperature maintenance of the freezer for the amount of heating of the air cooler, reducing the thermal efficiency of the refrigeration equipment There is a problem of doing.

Moreover, the hot gas system using the discharge gas of the compressor has a high pressure around 5.0 MPa at 20 to 30 ° C. when the discharge gas is CO ₂ . For this reason, it is necessary to increase the strength of piping and structures through which high-pressure CO ₂ gas flows, and extra costs are required. In addition, it is necessary to operate the refrigeration apparatus for defrosting, which consumes extra power.

  In view of the problems of the prior art, the present invention uses electric power required for lowering the temperature of the cargo handling room without using a watering type or an electric heater type in a freezer having a sealed and temperature-lowered cargo handling room. Thus, an object of the present invention is to realize a low-cost defrost unit that does not consume extra power.

In order to achieve this object, a defrosting method for a refrigeration apparatus according to the present invention is provided in a freezer having a cargo handling chamber, and is connected to a primary refrigerant circuit that constitutes a refrigeration cycle using NH ₃ as a refrigerant, and the primary refrigerant circuit. In a defrosting method for a refrigeration apparatus comprising a secondary refrigerant circuit in which a CO ₂ liquid cooled by NH ₃ circulates, and a first air cooler provided in the freezer interposed in the secondary refrigerant circuit, CO ₂ fluid between a second air cooler provided in the handling chamber, a first receiver that the CO ₂ fluid is pressure adjusted so as to be stored at room temperature below the temperature exceed 0 ℃ The cargo handling room cooling process for cooling the handling room to a temperature exceeding 0 ° C. and below room temperature, and the heat stored in the handling room is recovered in the handling room cooling process, and the CO ₂ liquid is first received. Circulate from the liquid to the first air cooler, It is made of the defrost step of carrying out the frost.

In the method of the present invention, the pressure of the first receiver is adjusted, and a CO ₂ liquid having a saturation temperature exceeding 0 ° C. and below normal temperature, for example, 5 to 10 ° C. is stored. This CO ₂ liquid is circulated through a second air cooler provided in the handling chamber, and the handling chamber is cooled to a temperature exceeding 0 ° C. and below normal temperature, for example, 10 to 15 ° C. Next, at the time of the defrosting process of the freezer, the CO ₂ liquid having a defrostable temperature recovered from the heat stored in the cargo handling chamber is circulated to the first air cooler to defrost the first air cooler. Thus, since the freezer is defrosted using the heat recovered from the cargo handling chamber, the freezer can be defrosted at low cost without consuming excess power.

In addition, as disclosed in Patent Documents 3 and 4, defrosting is not performed using CO ₂ hot gas but sensible heat of the CO ₂ liquid, so that stable heating is possible. Moreover, since the CO ₂ liquid is used, the pressure does not become high, and the installation of pressure-resistant piping and pressure-resistant equipment becomes unnecessary. Furthermore, unlike the case where CO ₂ hot gas is used, it is not necessary to operate the refrigeration apparatus for defrosting, and only the CO ₂ liquid stored in the first receiver is used, so that extra power is consumed. No need to consume.

In the method of the present invention, the defrost process includes a pre-process for returning the CO ₂ liquid remaining in the first air cooler to the first receiver after the normal freezing operation of the freezer, and a defrost of the first air cooler. And a post-process for returning the CO ₂ liquid remaining in the first air cooler to the first receiver after completion, and the liquid level of the CO ₂ liquid in the first receiver is set to the set value. If exceeded, the CO ₂ liquid of the _first liquid receiver is transferred to the _second liquid receiver provided in the secondary refrigerant circuit, and the CO ₂ liquid level of the _first liquid receiver is controlled below the set value. A CO ₂ liquid level control process to be performed may be further added.

The first liquid receiver that stores the CO ₂ liquid having a saturation temperature of more than 0 ° C. and not more than room temperature is higher in pressure than the second liquid receiver that stores the CO ₂ liquid having the saturation temperature of the freezing temperature of less than 0 ° C. Retained. Therefore, it is difficult to return the CO ₂ liquid once stored in the second receiver to the first receiver, and vice versa. Accordingly, the CO ₂ liquid remaining in the first air cooler at the start and end of the defrost process is always returned to the first liquid receiver, so that the CO ₂ liquid stored in the _first liquid receiver. Keep the amount always high. When the first receiver of pooled CO ₂ liquid liquid level exceeds the set value, maintain proper storage amount of the first receiver sends a CO ₂ liquid to the second liquid receiver . Thereby, the storage amount of the first liquid receiver and the second liquid receiver can be appropriately maintained.

The refrigeration apparatus of the present invention that can be directly used for carrying out the method of the present invention is provided in a freezer having a cargo handling chamber, and a primary refrigerant circuit constituting a refrigeration cycle using NH ₃ as a refrigerant, and connected to the primary refrigerant circuit A refrigerating apparatus comprising a secondary refrigerant circuit in which a CO ₂ liquid cooled by NH ₃ is circulated and a first air cooler provided in the freezer and interposed in the secondary refrigerant circuit. A second air cooler provided in the chamber, a first liquid receiver whose pressure is adjusted so that the CO ₂ liquid can be stored at a temperature higher than 0 ° C. and lower than normal temperature, and a second air cooler, A first CO ₂ circulation path disposed between the first liquid receiver, a cargo handling room cooling section comprising the first CO ₂ circulation path, and a connection between the first liquid receiver and the first air cooler. The second CO ₂ circulation path, and the second air cooling of the CO ₂ liquid in the first receiver during the normal freezing operation. Circulates in the rejector, cools the cargo handling chamber, and circulates the CO ₂ liquid in the first receiver through the second CO ₂ circulation path to the first air cooler during the defrost operation, The defrosting of the air cooler No. 1 is performed.

In the apparatus of the present invention, the pressure of the first liquid receiver is adjusted, and a CO ₂ liquid having a saturation temperature exceeding 0 ° C. and below normal temperature, for example, 5 to 10 ° C. is stored. This CO ₂ liquid is circulated through the second air cooler, and the cargo handling chamber is cooled to a temperature exceeding 0 ° C. and below normal temperature, for example, 10 to 15 ° C. Next, at the time of the defrosting process of the freezer, the CO ₂ liquid having a defrostable temperature recovered from the heat stored in the cargo handling chamber is circulated to the first air cooler to defrost the first air cooler. Thus, since the freezer is defrosted using the heat recovered from the cargo handling chamber, the freezer can be defrosted at low cost without consuming excess power.

In the device of the present invention, a second receiver that is provided in the secondary refrigerant circuit, the internal pressure is maintained at a lower pressure than the first receiver, and the CO ₂ liquid is maintained at the freezing temperature, and the first receiver A communication path connecting between the tank and the _second liquid receiver, a first on-off valve provided in the communication path, and a liquid level of the CO ₂ liquid provided in the _first liquid receiver. A level meter to detect, and when the detected value of the level meter exceeds a set value, the first on-off valve is opened to send the CO ₂ liquid of the first receiver to the second receiver, it may be configured to control the CO ₂ liquid level of the first liquid receiver below the set value.

The first liquid receiver that stores the CO ₂ liquid having a saturation temperature exceeding 0 ° C. and the normal temperature or lower is higher in pressure than the second liquid receiver that stores the CO ₂ liquid having the saturation temperature of the freezing temperature of 0 ° C. or lower. Retained. Therefore, it is difficult to return the CO ₂ liquid once stored in the second receiver to the first receiver. Therefore, normally, the amount of CO ₂ liquid stored in the first receiver is always increased. When the first receiver of pooled CO ₂ liquid liquid level exceeds the set value, maintain proper storage amount of the first receiver sends a CO ₂ liquid to the second liquid receiver . Thereby, the storage amount of the first liquid receiver and the second liquid receiver can be appropriately maintained.

In the device according to the present invention, the second CO ₂ circulation path includes a branch path that is branched upstream of the first air cooler and connected to the gas phase part of the first liquid receiver, and when the defrost operation starts. And at the end of the defrosting operation, the CO ₂ liquid remaining in the first air cooler in the state where the first air cooler and the gas phase part of the first liquid receiver are conducted through the branch path It is good to return to 1 receiver. The branch passage a first air cooler and that were passed to a vapor phase portion of the first receiver through, CO ₂ liquid remaining in the first air cooler, the second CO ₂ It becomes easy to return to the first liquid receiver through the circulation path.

Thus, at the start of the defrost operation and at the end of the defrost operation, the CO ₂ liquid remaining in the first air cooler is returned to the first liquid receiver, so that the amount of CO ₂ liquid in the first liquid receiver under high pressure is restored. Can always be larger than the amount of CO ₂ liquid in the second receiver under low pressure. When the storage volume of the first liquid receiver exceeds the set value, the storage volume of the first liquid receiver and the _second liquid receiver is always appropriate by sending the CO ₂ liquid to the _second liquid receiver. Can be held in value.

In the present invention apparatus is connected to the first receiver, the NH ₃ is provided a second primary refrigerant circuit constituting the refrigeration cycle as a refrigerant to cool the CO ₂ of the first CO ₂ circulation path by NH ₃ It may be configured as follows. When the cooling load of the handling chamber is large and the amount of heat recovered by cooling the handling chamber is greater than the amount of heat used during the defrosting process, a second primary refrigerant circuit using NH ₃ as a refrigerant is provided, Cool the receiver CO ₂ liquid to the required temperature. As a result, the temperature of the CO ₂ liquid in the first receiver can be maintained at a temperature necessary for cooling the cargo handling chamber.

According to the method of the present invention, the CO ₂ liquid is circulated from the _first liquid receiver whose pressure is adjusted so that the CO ₂ liquid can be stored at a temperature higher than 0 ° C. and below the normal temperature to the cargo handling chamber. Since the heat stored in the cargo handling room is recovered, the CO ₂ liquid, which is the defrostable temperature, is circulated from the first receiver to the freezer to defrost the first air cooler. Therefore, energy-saving and low-cost defrosting that does not require extra power can be performed without performing watering type or electric heater type defrosting. In addition, more stable heating than the CO ₂ hot gas system is possible, and since the CO ₂ liquid is used, the pressure is not increased, and the installation of pressure-resistant piping and pressure-resistant equipment becomes unnecessary.

Further, according to the apparatus of the present invention, during the normal freezing operation, the CO ₂ liquid in the first receiver is circulated to the second air cooler via the first CO ₂ circulation path to cool the cargo handling chamber. In addition, during the defrost operation, the CO ₂ liquid of the first liquid receiver is circulated to the first air cooler via the second CO ₂ circulation path so that the first air cooler is defrosted. Therefore, the same effect as the method of the present invention can be obtained.

1 is an overall configuration diagram of a refrigeration apparatus according to a first embodiment of the method and apparatus of the present invention. It is a whole block diagram of the freezing apparatus which concerns on 2nd Embodiment of this invention method and apparatus. It is a whole block diagram of the freezing apparatus which concerns on 3rd Embodiment of this invention method and apparatus. It is an overall configuration diagram showing a conventional _NH 3 / CO ₂ refrigeration system.

  Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this embodiment are not intended to limit the scope of the present invention to that unless otherwise specified.

(Embodiment 1)
A first embodiment of the method and apparatus of the present invention will be described with reference to FIG. In FIG. 1, a three-story F-class freezer 1 is provided above the ground GL, and a semi-basement 3 is provided adjacent to the freezer 1. On each floor of the freezer 1, freezer rooms 5 </ b> A to C and a cargo handling room 7 </ b> A to C adjacent to the freezer 1 are provided. The first floor cargo handling room 7A has a larger area than the cargo handling rooms on the other floors. An elevator is provided between the cargo handling rooms on each floor, and the article to be frozen can be transferred to each floor by this elevator.

  The unloading room 7A on the first floor is provided with a loading / unloading doorway (dock), and the rear portion of the transport vehicle T is inserted into the loading / unloading doorway to carry in / out the frozen product. In the cargo handling room 7A, a dock shelter 9 is provided to cover the entrance / exit door. Air conditioned air in the building escapes to the outside by the dock shelter 9, and outside air, rain wind, moisture, dust, pests, etc. enter the building. Is prevented. The main part of the refrigeration apparatus 10 is provided inside the semi-basement 3. Inside the semi-basement 3, an ammonia refrigerator 12A is provided.

The ammonia refrigerator 12A includes a primary refrigerant circuit 14 through which NH ₃ circulates, a compressor 16 provided in the primary refrigerant circuit 14, an expansion valve 18, a cascade condenser 20, and an evaporative condenser (evaporator) 21. Yes. The evacon 21 is provided on the roof of the semi-basement 3. A CO ₂ circulation path 22 is provided between the cascade capacitor 20 and the second liquid receiver 24. The CO ₂ gas in the second receiver 24 flows into the cascade condenser 20 via the CO ₂ circulation path 22, is cooled by NH ₃ in the cascade condenser 20, is liquefied, and returns to the second receiver 24.

One or more air coolers 26a to 26d are arranged in the freezing rooms 5A to 5C and the handling room 7A, respectively. The handling chambers 7B and 7C are also provided with small air coolers (not shown). The second liquid receiver 24 and the air coolers 26a to 26c provided in the freezer compartments 5A to C are connected by a main CO ₂ circulation path 28 and branch CO ₂ circulation paths 30, 32, and 34. ing. The liquid pump 29 provided in the forward path 28a of the main CO ₂ circulation path 28 sends the CO ₂ liquid in the _second liquid receiver 24 to the air coolers 26a to 26c to cool the air in the freezer compartments 5A to 5C. To do.

The forward path 28 a of the main CO ₂ circulation path 28 is connected to the lower part of the second liquid receiver 24, and the return path 28 b is connected to the upper part of the second liquid receiver 24. The CO ₂ liquid is sent to the air coolers 26a to 26c by the liquid pump 29 provided in the forward path 28a. On-off valves 36a, 36b, 38a, 38b, 40a and 40b are provided in the forward and return paths of the branch CO ₂ circulation paths 30, 32 and 34, respectively.

Inside the semi-basement 3, a first liquid receiver 42 is provided adjacent to the second liquid receiver 24. The first liquid receiver 42 is provided with two sets of CO ₂ circulation paths. One is the CO ₂ circulation path 44 provided between the first liquid receiver 42 and the cargo handling chambers 7A to 7C, and the other is the first liquid receiver 42 and the air coolers 26a to 26c. The forward path is composed of the forward path 46a of the main CO ₂ circulation path 46 and the forward paths 48a, 50a and 52a of the branch CO ₂ circulation path, and the return path is the return path 46b and the branch CO of the main CO ₂ circulation path 46. _It consists of _two circulation paths 48b, 50b and 52b. On-off valves 54a, 54b, 56a, 56b, 58a and 58b are interposed in the forward and return paths of the branch CO ₂ circulation path.

The forward path 44a of the CO ₂ circulation path 44 is provided with a liquid pump 60 for sending the CO ₂ liquid to the air cooler 26d and the like, and the forward path 46a of the main CO ₂ circulation path 46 is fed with the CO ₂ liquid to the air coolers 26a to 26a. A liquid pump 62 for sending to c is provided. The air coolers 26a to 26d are provided with a drain pan 64 that receives condensed water or melted water melted during defrosting operation. Each drain pan 64 is provided with a drainage channel 66, and each drainage channel 66 is connected to a drainage main pipe 68. The condensed water generated in the air coolers 26a to 26d is discharged to the outside of the class F freezer 1 through the main drainage channel 68.

In such a configuration, the CO ₂ gas stored in the second liquid receiver 24 flows into the cascade capacitor 20 and is cooled by NH ₃ circulating in the primary refrigerant circuit 14. The cooled CO ₂ liquid returns to the _second liquid receiver 24. The internal pressure of the _second liquid receiver 24 is maintained at around 1.2 MPa, and the CO ₂ liquid in the _second liquid receiver 24 is maintained at −32 ° C., for example. During the normal refrigeration operation, the on-off valves 36a, 36b, 38a, 38b, 40a and 40b are opened, and the −32 ° C. CO ₂ liquid in the second receiver 24 is transferred to the forward path 28a of the main CO ₂ circulation path 28 and The air is supplied to the air coolers 26a to 26c through the outgoing paths of the branch CO ₂ circulation paths 30, 32, and 34. The on-off valves 54a, 54b, 56a, 56b, 58a and 58b are closed.

The air coolers 26a to 26c are provided with a fan 27 to form an air flow, and the internal air is cooled by the CO ₂ liquid flowing through the heat transfer tubes of the air coolers 26a to 26c. The inside air is kept at -25 ° C. The CO ₂ liquid is partially vaporized by the air coolers 26a to 26c, and the partially vaporized CO ₂ liquid passes through the return path of the branch CO ₂ circulation paths 30, 32 and 34 and the return path 28b of the main CO ₂ circulation path 28. Return to the second receiver 24.

The internal pressure of the first liquid receiver 42 is maintained at around 4.0 MPa, and the CO ₂ liquid in the _first liquid receiver 42 is maintained at 5 to 10 ° C. During the normal freezing operation, the CO ₂ liquid in the _first liquid receiver 42 passes through the forward path 44a of the CO ₂ circulation path 44 and is supplied to the air cooler 26d provided in the cargo handling chambers 7A to 7C. The air cooler 26d or the like is provided with a fan 27, and the air in the cargo handling chambers 7A to 7C is cooled by the air cooler 26d or the like and maintained at 10 to 15 ° C. The air in the cargo handling chambers 7A to C is cooled by the air cooler 26d, etc., and the CO ₂ liquid partially vaporized by absorbing the heat of the air passes through the return path 44b to the first liquid receiver 42. Return.

During the defrost operation, the on-off valves 36a, 36b, 38a, 38b, 40a and 40b are closed, and the on-off valves 54a, 54b, 56a, 56b, 58a and 58b are opened. The CO ₂ liquid at 5 to 10 ° C. from the first liquid receiver 42 passes through the forward path 46a of the main CO ₂ circulation path 46 and the forward paths 48a, 50a and 52a of the branch CO ₂ circulation path, and is sent to the air coolers 26a to 26c. It is done. In the air coolers 26a to 26c, the CO ₂ liquid heats the heat transfer tube from the inside and melts and removes frost attached to the outer surface of the heat transfer tube. The CO ₂ liquid that has melted the frost and released heat returns to the first receiver 42 through the return paths 48b, 50b and 52b of the branch CO ₂ circulation path and the return path 46b of the main CO ₂ circulation path 46. The defrost operation is usually performed once or twice a day.

According to the present embodiment, the CO ₂ liquid sent from the first liquid receiver 42 cools the air in the cargo handling chambers 7A to C, recovers the retained heat of the cargo handling chambers 7A to C, and retains it. Since the defrosting of the air coolers 26a to 26c is performed using heat, it is not necessary to use a watering type defrost, and the defrosting of the air coolers 26a to 26c is possible without consuming extra power. become.

Also, rather than the defrosting using CO ₂ hot gas, since it is defrosting by sensible heat of the CO ₂ fluid, it is possible to stably heated. Also, since the CO ₂ liquid is used, the pressure is not increased, so the main CO ₂ circulation path 46, the forward paths 48a, 50a, 52a and the return paths 48b, 50b and 52b of the branch CO ₂ circulation path, and the air coolers 26a to 26c. There is no need to use pressure-resistant piping or pressure-resistant equipment for the heat transfer section. Further, unlike the case of using CO ₂ hot gas, it is not necessary to operate the refrigeration apparatus for defrosting, and only the CO ₂ liquid stored in the _first liquid receiver 42 is used. Does not have to consume.

(Embodiment 2)
Next, a second embodiment of the method and apparatus of the present invention will be described with reference to FIG. In FIG. 2, a communication path 70 that connects a lower region of the first liquid receiver 42 and a lower region of the second liquid receiver 24 is provided, and an open / close valve 72 is interposed in the communication path 70. Further, the first liquid receiver 42 is provided with a level meter 74 for detecting the liquid level of the CO ₂ liquid. When the liquid level exceeds a set value, the opening / closing valve 72 is controlled by a signal from the level meter 74. It is configured to open. Further, branch paths 76a, 76b, and 76c branch to the downstream paths 48a, 50a, and 52a of the branch CO ₂ circulation path on the downstream side of the on-off valves 54a, 56a, and 58a and connect to the return path 46b of the main CO ₂ circulation path 46. Is provided. On-off valves 78a, 78b and 78c are interposed in these branch paths. Other configurations are the same as those of the first embodiment.

  In the present embodiment, the normal freezing operation of the freezing rooms 5A to 5C and the cargo handling rooms 7A to 7C is performed by the same operation as in the first embodiment. During the normal freezing operation of the freezer compartments 5A to 5C, the on-off valves 36a, 36b, 38a, 38b, 40a and 40b are opened, and the on-off valves 54a, 54b, 56a, 56b, 58a, 58b and 78a-c are closed. . After the normal freezing operation is completed, the on-off valves 36a, 36b, 38a, 38b, 40a and 40b are closed, and the on-off valves 54a, 54b, 56a, 56b, 58a, 58b and the on-off valves 78a to 78c are opened.

At the start of the defrost operation, the CO ₂ liquid remaining in the air coolers 26a to 26c is returned to the first liquid receiver 42 via the return paths 48b, 50b and 52b of the branch CO ₂ circulation path. In this state, defrost operation is continued. At the end of the defrost operation, the open / close valves 54a, 56a and 58a are closed, and the open / close valves 54b, 56b and 58b and the open / close valves 78a to 78c are opened. In this way, the upper part of the air coolers 26a to 26c and the gas phase of the first liquid receiver 42 are connected, so that the CO ₂ liquid in the air coolers 26a to 26c falls into the first liquid receiver 42. It becomes easy to do. Thus, the CO ₂ liquid in the air coolers 26a to 26c can be returned to the first liquid receiver 42 via the return paths 48b, 50b, and 52b.

Thus, at the beginning and end of the defrosting operation, since the back of the CO ₂ liquid remaining in the air cooler 26a~c the first receiver 42, the first receiver 42 CO ₂ The liquid level gradually rises. When the level meter 74 detects that the CO ₂ liquid level of the _first liquid receiver 42 exceeds the set value, the on-off valve 72 is opened, and the CO ₂ liquid in the first liquid receiver 42 is discharged to the second liquid. To the receiver 24.

The main CO ₂ circulation path 28 and the main CO ₂ circulation path 46 are indirectly connected through the air coolers 26a to 26c. Therefore, unless the return amount of the CO ₂ liquid returned to the _first liquid receiver 42 or the second liquid receiver 24 is not controlled, the CO ₂ liquid is unevenly distributed in either one. Since the internal pressure of the first receiver 42 is higher than the internal pressure of the second liquid receiver 24, if the CO ₂ fluid is unevenly distributed in the second liquid receiver 24, the first receiving the CO ₂ liquid It becomes difficult to return to the liquid container 42. According to the present embodiment, in addition to the operational effects obtained in the first embodiment, the CO ₂ storage amount of the first liquid receiver 42 and the second liquid receiver 24 can be appropriately maintained.

Further, at the start and end of the defrost operation, the on-off valves 78a to 78c are opened, and the air coolers 26a to 26c and the gas phase part of the first liquid receiver 42 are made conductive through the branch paths 76a to 76c. As a result, the CO ₂ liquid remaining in the air coolers 26 a to 26 c can be easily returned to the first liquid receiver 42. Accordingly, the residual CO ₂ liquid can be quickly returned to the first liquid receiver 42 via the return paths 48 b, 50 b, 52 b of the branch CO ₂ circulation path and the return path 46 b of the main CO ₂ circulation path 46.

(Embodiment 3)
Next, a third embodiment of the method and apparatus of the present invention will be described with reference to FIG. The present embodiment is an example in which an ammonia refrigerator 12B is additionally installed in the semi-basement 3. In the ammonia refrigerator 12B, a primary refrigerant circuit 14 in which NH 3 circulates is provided with a compressor 16, an expansion valve 18, a cascade condenser 20, and an evaporator 21 arranged on the roof of the semi-basement 3. Further, a CO ₂ circulation path 80 that connects the cascade capacitor 20 and the first liquid receiver 42 is provided. Other configurations are the same as those of the second embodiment.

When the cooling load such as the air cooler 26d provided in the handling chambers 7A to C is large, the handling chambers 7A to 7C cannot be cooled only by the cold heat obtained during the defrost operation of the air coolers 26a to 26c. Therefore, the ammonia refrigerator 12B is provided as in this embodiment. With ammonia refrigerator 12B, by cooling the first liquid receiver 42 CO ₂ liquid stored in, it can be held at a temperature which is set to CO ₂ liquid in the first liquid receiver 42.

  According to the present invention, in the refrigeration apparatus provided in the freezer having the cargo handling chamber, the amount of heat obtained by cooling the cargo handling chamber is used for the defrosting process, so that excess power is not consumed and stable. And low-cost defrost operation.

DESCRIPTION OF SYMBOLS 1 F class freezer 3 Semi-basement 5A-C Freezing room 7A-C Handling room 9 Dock shelter 10,100 Refrigeration equipment 12A Ammonia refrigerator 12B Ammonia refrigerator (2nd primary refrigerant circuit)
14,102 Primary refrigerant circuit 16,104 Compressor 18,110 Expansion valve 20,108 Cascade condenser 21,106 Evaporative condenser (Evacon)
22, 80, 112 CO ₂ circulation path 24 Second receiver 26a-c Air cooler (first air cooler)
27d Air cooler (second air cooler)
27 Fan 28 Main CO ₂ circuit 29, 60, 62, 116 Liquid pump 30, 32, 34 Branch CO ₂ circuit 42 First receiver 44 CO ₂ circuit (first CO ₂ circuit)
46 Main CO ₂ circuit (second CO ₂ circuit)
48b, 50b, 52b Return path 54b, 56b, 58b, 72, 78a-c On-off valve 64 Drain pan 66 Drainage path 68 Main drainage path 70 Communication path 72 On-off valve 76a-c Branching path 114 Receiving device 118 Ceiling suspended air cooler A Outdoor unit B Freezer GL Ground T Transport vehicle

Claims (6)

A primary refrigerant circuit that is provided in a freezer having a cargo handling chamber and that forms a refrigeration cycle using NH ₃ as a refrigerant, and a secondary refrigerant circuit that is connected to the primary refrigerant circuit and in which a CO ₂ liquid cooled by NH ₃ circulates; In a defrosting method for a refrigeration apparatus comprising a first air cooler interposed in the secondary refrigerant circuit and provided in a freezer,
CO ₂ fluid between a second air cooler provided in the handling chamber, a first receiver that the CO ₂ fluid is pressure adjusted so as to be stored at room temperature below the temperature exceed 0 ℃ , And the handling room cooling process for cooling the handling room to a temperature exceeding 0 ° C. and below normal temperature,
A defrosting step of defrosting the first air cooler by circulating the CO ₂ liquid recovered from the heat held in the cargo handling chamber in the cargo handling chamber cooling step from the first liquid receiver to the first air cooler. A method for defrosting a refrigeration apparatus comprising: The defrost process includes a pre-process for returning the CO ₂ liquid remaining in the first air cooler to the first liquid receiver after the normal freezing operation of the freezer is completed, and a first process after the defrost of the first air cooler is completed. And a post process for returning the CO ₂ liquid remaining in the air cooler to the first receiver.
When the liquid level of the CO ₂ liquid in the first receiver exceeds the set value, the CO ₂ liquid in the first receiver is transferred to the second receiver provided in the secondary refrigerant circuit. The defrosting method for a refrigeration apparatus according to claim 1, further comprising a CO ₂ liquid level control step of controlling the CO ₂ liquid level of the first receiver to a set value or less. A primary refrigerant circuit that is provided in a freezer having a cargo handling chamber and that forms a refrigeration cycle using NH ₃ as a refrigerant, and a secondary refrigerant circuit that is connected to the primary refrigerant circuit and in which a CO ₂ liquid cooled by NH ₃ circulates; A refrigeration apparatus comprising a first air cooler interposed in the secondary refrigerant circuit and provided in a freezer,
A second air cooler provided in the cargo handling chamber, a first liquid receiver that is pressure-adjusted so that CO ₂ liquid can be stored at a temperature higher than 0 ° C. and lower than room temperature, and a second air cooler And a first CO ₂ circulation path disposed between the first liquid receiver and the first CO ₂ circulation path, and between the first liquid receiver and the first air cooler. A second CO ₂ circuit connected,
Normal CO ₂ liquid from the first liquid receiver during freezing operation is circulated through the second air cooler, to cool the cargo handling chamber, during defrosting operation, the CO ₂ liquid from the first liquid receiver second A refrigeration apparatus characterized in that the first air cooler is circulated through the CO ₂ circulation path to defrost the first air cooler. A second receiver that is provided in the secondary refrigerant circuit, the internal pressure of which is maintained at a lower pressure than that of the first receiver, and the CO ₂ liquid is maintained at a freezing temperature;
A communication path with an on-off valve that connects between the first liquid receiver and the second liquid receiver;
A level meter provided in the first receiver for detecting the liquid level of the CO ₂ liquid;
When the detected value of the level meter exceeds the set value, the first on-off valve is opened to send the CO ₂ liquid of the first receiver to the second receiver, and the CO _{2 of} the first receiver. The refrigeration apparatus according to claim 3, wherein the liquid level is controlled to be equal to or lower than a set value. The second CO ₂ circulation path includes a branch path branched upstream of the first air cooler and connected to the gas phase part of the first liquid receiver;
The CO remaining in the first air cooler at the start of the defrost operation and at the end of the defrost operation in a state where the first air cooler and the gas phase portion of the first liquid receiver are connected through the branch path. The refrigeration apparatus according to claim 3 or 4, wherein the _two liquids are returned to the first liquid receiver. Connected to said first receiver, the NH ₃ is provided a second primary refrigerant circuit constituting the refrigeration cycle as a refrigerant, and configured to cool the CO ₂ of the first CO ₂ circulation path by NH ₃ The refrigeration apparatus according to claim 3.

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