JPH07218053A - Refrigerating apparatus - Google Patents

Abstract

PURPOSE:To prevent overheat operation of a compressor during hot gas defrosting operation. CONSTITUTION:A bypass pipe 20 is connected at one end to a refrigerant output end of a condenser 2, and is connected at the other end to an area in a two- stage compressor 1 where an intermediate pressure prevails. Also, the bypass pipe 20 is provided with a bypass solenoid valve 10 and a bypass expansion valve 11. The bypass solenoid valve 10 is made in a closed condition at the time of normal freezing operation, and in an opened condition at the time of hot gas defrosting operation. Accordingly, a refrigerant flows as shown by arrows of solid line in Fig. 1 during cooling operation, and flows as shown by arrows of dotted line during hot gas defrosting operation. Accordingly, it is possible to perform hot gas defrosting.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerating apparatus which can favorably perform hot gas defrosting.

[0002]

2. Description of the Related Art As such a refrigerating device,
Vol.63, NO731 September 1988, p. 50 ”. In this refrigeration system, the refrigerant gas used for supercooling the main liquid refrigerant in the subcooler is supplied to a portion of the compressor at an intermediate pressure to suppress the temperature rise of the discharge gas of the compressor.

[0003]

However, in the above-described conventional refrigeration system, when hot gas defrosting is performed, hot gas flows into the evaporator to dissolve the frost adhering to the evaporator, and The hot gas releases latent heat of condensation and part of it becomes a liquid refrigerant. After that, the hot gas is depressurized and heated to be vaporized and supplied to the compressor, so that the temperature of the gas sucked by the compressor becomes higher during defrosting of the hot gas than during normal cooling operation. Therefore, the internal temperature of the compressor rises and the life of the bearing of the compressor is shortened. Further, the temperature of the motor winding for the compressor rises due to the overheating operation.

Therefore, an object of the present invention is to provide a refrigeration system capable of preventing the compressor from overheating during the hot gas defrosting operation.

[0005]

A refrigeration system of the present invention has a compressor, a condenser, an expansion valve, and an evaporator to form a refrigeration cycle, and hot gas is used for defrosting the evaporator. In a refrigerating apparatus using defrost, the refrigerant is branched into a liquid phase or gas-liquid mixed phase state in the refrigeration cycle,
A bypass pipe that communicates with a portion of the compressor that has an intermediate pressure; a bypass valve that is a valve that opens and closes a conduit of the bypass pipe; and a bypass expansion valve that is an expansion valve provided in the bypass pipe. However, during the normal cooling operation, the bypass valve is closed, and during the hot gas defrosting operation, the bypass valve is opened.

Further, in the refrigerating apparatus of the present invention, it is preferable that one end of the bypass pipe is connected to the refrigerant output portion of the condenser, and the other end thereof is connected to a portion of the compressor which is at an intermediate pressure. .

Further, in the refrigerating apparatus of the present invention, it is preferable that one end of the bypass pipe is connected to the refrigerant output portion of the evaporator, and the other end thereof is connected to a portion of the compressor which is at an intermediate pressure. .

Further, in the refrigerating apparatus of the present invention, the refrigerating cycle is provided with a subcooler for lowering the temperature of the refrigerant,
The bypass pipe is preferably provided in parallel with the supercooling pipe line in the subcooler.

In the refrigerating apparatus of the present invention, it is preferable that the compressor has a built-in electric motor.

Further, in the refrigerating apparatus of the present invention, it is preferable that the compressor is a two-stage compressor that compresses the refrigerant gas in two stages.

[0011]

In the refrigerating apparatus of the present invention, the bypass valve is opened during the hot gas defrosting operation. As a result, a liquid-phase or gas-liquid mixed-phase refrigerant flows into the bypass pipe, and the refrigerant becomes a low-temperature wet gas by passing through the bypass expansion valve. Then, the moist gas is sucked into a portion of the compressor having an intermediate pressure.

As a result, the amount of the moist gas sucked into the intermediate pressure portion of the compressor is increased as compared with that during the cooling operation, so that the temperature rise and the compression of the compressor motor are stronger than during the cooling operation. The temperature rise of the high-stage compressed gas of the compressor can be suppressed, and the overheating operation of the compressor during the hot gas defrosting operation can be prevented.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a refrigerating apparatus according to an embodiment of the present invention. The solid line arrows in the figure show the flow of the refrigerant during the cooling operation, and the broken line arrows show the flow of the refrigerant during the hot gas defrosting operation.

Here, the two-stage compressor 1, the condenser 2, the supercooler 3, the evaporator 4, the hot gas defrosting device 5, the main liquid solenoid valve 6, the main expansion valve 7, The subcooling solenoid valve 8, the subcooler expansion valve 9, and the pressure adjusting valve 15 form a two-stage compression refrigeration cycle. And the hot gas defrosting device 5
The hot gas solenoid valve 12 is equipment for performing hot gas defrosting on the evaporator 4.

Further, a bypass pipe 20 equipped with a bypass solenoid valve 10 and a bypass expansion valve 11, which are the features of the present refrigeration system, is connected to the refrigerant output end of the condenser 2, and the other end of the bypass pipe 20 is a double end. It is connected to a portion of the stage compressor 1 where the intermediate pressure is obtained.

The two-stage compressor 1 compresses the refrigerant gas sent from the hot gas defrosting device 5 in two stages.
The two-stage compressor 1 has a built-in electric motor for driving itself. The condenser 2 takes in the high-pressure refrigerant gas compressed by the two-stage compressor 1 via the hot gas defrosting device 5 and condenses the condensed gas into a condensed liquid. The supercooler 3 cools the condensed liquid of the refrigerant sent from the condenser 2. The evaporator 4 evaporates the refrigerant that has become low-pressure wet gas by the actions of the subcooler 3 and the main expansion valve 7. The refrigerant is sent to the two-stage compressor 1 again via the hot gas defrosting device 5. The hot gas defrosting device 5 is composed of an accumulator 13 and a heat storage tank 14, and the refrigerant output end of the hot gas defrosting device 5 is connected to the refrigerant input end of the evaporator 4 by a pipe equipped with the hot gas solenoid valve 12. Is also connected.

Further, a pipe provided with a subcooling electromagnetic valve 8 and a subcooler expansion valve 9 is connected to the refrigerant output end of the subcooler 3, and the other end of the pipe is connected to the subcooler 3 The refrigerant supplied by the pipe to the subcooler 3 serves to cool the subcooler 3. The refrigerant that has been cooled by the supercooler 3 is sent by a pipe to a portion of the two-stage compressor 1 that has an intermediate pressure.

Next, the operation of this embodiment will be described.
First, the operation during normal cooling operation will be described. During the cooling operation, the main liquid solenoid valve 6 and the supercooling solenoid valve 8 are open, and the hot gas solenoid valve 12 and the bypass solenoid valve 10 are closed. The high-pressure refrigerant gas compressed by the two-stage compressor 1 warms the inside of the heat storage tank 14 in the hot gas defrosting device 5 and becomes a condensed liquid in the condenser 2. The condensate is sent to the subcooler 3 to be cooled, is further converted into a low-pressure wet gas by the action of the main expansion valve 7, and is sent to the evaporator 4. The moist gas evaporates in the evaporator 4 to exert a cooling action on the object to be cooled, and then is absorbed by the two-stage compressor 1 via the hot gas defrosting device 5.

In the above operation, some of the refrigerant discharged from the subcooler 3 goes to the main expansion valve 7 and also goes to the subcooler expansion valve 9. The refrigerant that has passed through the expansion valve 9 for the subcooler is changed to a wet gas having an intermediate pressure, and causes a cooling action in the subcooler 3. After that, the moist gas is sucked into the intermediate pressure portion of the two-stage compressor 1, and the exhaust gas in the low stage of the two-stage compressor 1 and the compressor motor built in the two-stage compressor 1 are discharged. After cooling, it is sucked into the high-stage pressure portion of the two-stage compressor 1.

The operation during the hot gas defrosting operation will be described below. FIG. 2 is a sequence diagram showing a control circuit of each solenoid valve in the refrigerating apparatus shown in FIG. First, when a defrosting command is issued from a manual switch, a timer or the like, the bypass solenoid valve 10 and the hot gas solenoid valve 12 are opened and the main liquid solenoid valve 6 is closed. Here, the supercooling solenoid valve 8 is in the open state as in the normal cooling operation.

When the hot gas solenoid valve 12 is opened, the discharge gas discharged from the two-stage compressor 1 is discharged into the hot gas defroster 5 and the hot gas solenoid valve 12 as shown by the dotted arrow in FIG. After entering the evaporator 4, the frost adhering to the evaporator 4 is melted to become a liquid refrigerant. The liquid refrigerant is decompressed by the pressure regulating valve 15, and further, the accumulator 13 in the hot gas defrosting device 5 separates the liquid refrigerant into liquid and gas. Further, the liquid refrigerant is heated by the heat storage tank 14 to become a gas and returns to the two-stage compressor 1.

Further, the bypass solenoid valve 10 is opened so that the refrigerant liquefied in the condenser 2 is bypassed by the bypass pipe 20.
Pass through. Here, the refrigerant is changed into a wet gas having an intermediate pressure by the bypass expansion valve 11 and is sucked into a portion of the two-stage compressor 1 having an intermediate pressure.

As a result, in the refrigeration system of this embodiment, during the hot gas defrosting operation, the refrigerant passing through the supercooling electromagnetic valve 8 and the refrigerant passing through the bypass expansion valve 11 are intermediate in the two-stage compressor 1. Since it is sucked into the portion having the pressure, the amount of moist gas supplied to the portion having the intermediate pressure in the two-stage compressor 1 is increased more than that in the cooling operation, and the two-stage compressor 1 in the hot gas defrosting operation Overheat operation can be prevented and stable hot gas defrosting can be performed.

Further, since the refrigerating apparatus of this embodiment can prevent the overheating operation of the two-stage compressor 1, the lubricating oil can be stably supplied to the sliding parts of the two-stage compressor 1. In addition, it is possible to prevent defective lubrication of the bearings of the compressor electric motor and prolong the product life, and it is possible to reduce the power consumption of the compressor electric motor during the hot gas defrosting operation.

FIG. 3 shows the winding temperature of the electric motor of the two-stage compressor 1 and the exhaust gas of the two-stage compressor 1 when the refrigerating apparatus shown in FIG. 1 is changed from the cooling operation to the hot gas defrosting operation. It is a characteristic view which shows temperature. The solid-line characteristic curves (a) and (b) in the characteristic diagram show the characteristic when the hot gas solenoid valve 12 is opened during the hot gas defrosting operation as described above, and the dotted characteristic curve (c) )
(D) shows the case where the hot gas solenoid valve 12 is kept closed even during the hot gas defrosting operation. That is, the solid-line characteristic curves (a) and (b) show the characteristics of the above-described embodiment, and the dotted-line characteristic curves (c) and (d) show the characteristics of the conventional refrigeration system.

In FIG. 3, regarding the temperature of the exhaust gas, the solid line characteristic curve (b) has a lower temperature characteristic than the dotted line characteristic curve (d), and the winding temperature also shows the solid line characteristic. The curve (b) has a lower temperature characteristic than the dotted characteristic curve (d). From these,
It can be seen that the present embodiment, which is characterized in that the hot gas solenoid valve 12 is opened during the hot gas defrosting operation, can prevent the overheating operation of the two-stage compressor 1 during the hot gas defrosting operation. .

FIG. 4 is a block diagram showing a refrigerating apparatus according to another embodiment of the present invention. The same components as those of the refrigeration system shown in FIG. 1 are designated by the same reference numerals. Further, the solid line arrows in the figure show the flow of the refrigerant during the cooling operation, and the broken line arrows show the flow of the refrigerant during the hot gas defrosting operation.

The difference between the refrigerating apparatus of this embodiment and the refrigerating apparatus shown in FIG. 1 is that a bypass pipe 20 including a bypass solenoid valve 10 and a bypass expansion valve 11 is connected to the refrigerant output end of the evaporator 4. And the other end of the pipe is a portion connected to a portion of the two-stage compressor 1 where the intermediate pressure is obtained.

Next, the operation of this embodiment will be described.
During the normal cooling operation, the main liquid solenoid valve 6 and the supercooling solenoid valve 8 are in the open state, and the hot gas solenoid valve 12 and the bypass solenoid valve 10 are in the closed state. The same operation as the operation is performed.

During the hot gas defrosting operation, the subcooling solenoid valve 8, the bypass solenoid valve 10 and the hot gas solenoid valve 12 are opened and the main liquid solenoid valve 6 is closed. As a result, during the hot gas defrosting operation, most of the exhaust gas of the two-stage compressor 1 flows into the evaporator 4 via the hot gas solenoid valve 12, melts the frost adhering to the evaporator 4, and melts the liquid refrigerant. Becomes A part of the liquid refrigerant is sucked through the bypass solenoid valve 10 to a portion of the two-stage compressor 1 which has an intermediate pressure.

As a result, in the refrigerating apparatus of this embodiment, as in the refrigerating apparatus shown in FIG. 1, during the hot gas defrosting operation, the refrigerant passing through the subcooling electromagnetic valve 8 and the bypass expansion valve 11 are passed. Since the refrigerant and the refrigerant are sucked into the part having the intermediate pressure in the two-stage compressor 1, the amount of the moist gas supplied to the part having the intermediate pressure in the two-stage compressor 1 is increased more than that in the cooling operation to remove the hot gas. Overheating operation of the two-stage compressor 1 during frost operation can be prevented, and stable hot gas defrosting can be performed.

In the above embodiment, the bypass pipe 20 is used.
One end is connected to the refrigerant output part of the condenser or the refrigerant output part of the evaporator, but the present invention is not limited to these. For example, the bypass pipe 20 may be used for supercooling in the subcooler 3. It may be provided in parallel with the pipeline. Further, although the two-stage compressor 1 is used in the above embodiment,
The present invention is not limited to this, and for example, a rotary compressor or a scroll compressor may be used.
Further, in the above-described embodiment, the bypass solenoid valve 10 is opened simultaneously with the start of the hot gas defrosting operation, but the present invention is not limited to this, and for example, the hot gas defrosting operation is performed. The bypass solenoid valve 10 may be opened after a fixed time from the start.

[0034]

As described above, according to the present invention, during the hot gas defrosting operation, the refrigerant gas that has passed through the subcooler and the refrigerant gas that has passed through the bypass expansion valve become the intermediate pressure in the compressor. Since it is sucked into the part, it is possible to increase the amount of moist gas supplied to the part of the compressor, which has an intermediate pressure, than that during the cooling operation, and prevent the compressor from overheating during the hot gas defrosting operation. it can.

[Brief description of drawings]

FIG. 1 is a block diagram showing a refrigerating apparatus according to an embodiment of the present invention.

FIG. 2 is a sequence diagram showing a control circuit for each solenoid valve in the refrigerating apparatus shown in FIG.

FIG. 3 is a characteristic diagram showing a temperature change of each part of the refrigeration apparatus when the refrigeration apparatus shown in FIG. 1 is changed from a cooling operation to a hot gas defrosting operation.

FIG. 4 is a block diagram showing a refrigeration system according to another embodiment of the present invention.

[Explanation of symbols]

 1 Two-stage compressor 2 Condenser 3 Supercooler 4 Evaporator 5 Hot gas defroster 6 Main liquid solenoid valve 7 Main expansion valve 8 Supercooling solenoid valve 9 Supercooler expansion valve 10 Bypass solenoid valve 11 Bypass expansion valve 12 hot gas solenoid valve 13 accumulator 14 heat storage tank 15 pressure regulating valve 20 bypass pipe

(72) Inventor Yoshifumi Suzuki, 390 Muramatsu, Shimizu City, Shizuoka Prefecture, Hitachi Shimizu Engineering Co., Ltd. (72) Nobu Otahara, 390, Muramatsu, Shimizu City, Shizuoka, Hitachi, Ltd., Shimizu Plant, Hitachi, Ltd.

Claims (6)

[Claims] 1. A refrigeration system comprising a compressor, a condenser, an expansion valve, and an evaporator to form a refrigeration cycle, and hot gas defrosting is used to defrost the evaporator. A bypass pipe that branches from a portion where the refrigerant is in a liquid phase or a gas-liquid mixed phase state, and that communicates with a portion that has an intermediate pressure in the compressor, and a bypass valve that is a valve that opens and closes the pipeline of the bypass pipe. A bypass expansion valve that is an expansion valve provided in the bypass pipe,
A refrigeration system characterized in that the bypass valve is closed during a normal cooling operation, and the bypass valve is opened during a hot gas defrosting operation. 2. The refrigerating apparatus according to claim 1, wherein one end of the bypass pipe is connected to a refrigerant output part of the condenser, and the other end is connected to a part of the compressor which has an intermediate pressure. Refrigerating device characterized by. 3. The refrigerating apparatus according to claim 1, wherein one end of the bypass pipe is connected to a refrigerant output part of the evaporator, and the other end is connected to a part of the compressor which has an intermediate pressure. Refrigerating device characterized by. 4. The refrigerating apparatus according to claim 1, wherein the refrigerating cycle is provided with a subcooler for lowering the temperature of the refrigerant, and the bypass pipe is provided with respect to the subcooling pipe line in the subcooler. Refrigerating device, which is provided in parallel. 5. The refrigerating apparatus according to claim 1, 2, 3 or 4, wherein the compressor has a built-in electric motor. 6. The refrigerating apparatus according to claim 1, 2, 3, 4 or 5, wherein the compressor is a two-stage compressor that compresses a refrigerant gas in two stages.