JP2001235245A - Freezer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase an economizer effect in a double-stage compression type freezing cycle. SOLUTION: Discharged gas at a lower stage compressor and a double-phase refrigerant at an intermediate pressure are pre-mixed to each other, gas and liquid are separated by a gas-liquid separator (24), wherein the liquid refrigerant is supplied to an evaporator (13) and the gaseous refrigerant is supplied to a higher stage compressor (21).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerating apparatus having a two-stage compression mechanism for performing a refrigerating cycle, and more particularly to a technique for improving an economizer effect.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Application Laid-Open No. 4-80545
As described in the publication, a two-stage compression refrigeration cycle is employed in a refrigeration system that requires a low evaporation pressure and a high compression ratio operation. The compression mechanism of the two-stage compression refrigeration cycle is composed of a low-stage compressor and a high-stage compressor, and uses a single-stage compression operation using only one compressor and uses both compressors in series. It is configured to be able to switch between two-stage compression operation.

In the refrigeration system of the two-stage compression refrigeration cycle, an intermediate-pressure refrigerant is generated in the refrigerant circuit during the two-stage compression operation, and the gas phase of the intermediate-pressure refrigerant and the gas refrigerant discharged from the low-stage compressor are discharged. And supply it to the high-stage compressor to achieve the economizer effect, prevent oil deterioration and refrigerant decomposition due to excessive rise in the discharge refrigerant temperature, improve reliability, and improve COP (performance) Coefficient).

More specifically, as shown in FIG. 8, an intermediate expansion valve and a gas-liquid separator are provided in a liquid line from a condenser to an evaporator to separate the liquid from the two-phase refrigerant flowing into the gas-liquid separator. The refrigerant in the saturated gas state is supplied to the gas line connected from the discharge side of the low-stage compressor to the suction side of the high-stage compressor, or provided in the liquid line as shown in FIG. Some gas-liquid separators connect a low-stage discharge line from the discharge side of a low-stage compressor and a high-stage suction line to the suction side of a high-stage compressor.

[0005]

In the first example shown in FIG. 8, the saturated gas is separated from the two-phase refrigerant by the gas-liquid separator and mixed with the low-stage discharge gas. That is, as shown in the Mollier diagram of FIG. 10, the saturated gas at the point A and the low-stage side discharge gas at the point B are mixed in the middle of the compression stroke. Since the gas is supplied to the high-stage compressor, the temperature of the gas refrigerant sucked into the high-stage compressor is not sufficiently reduced, and the economizer effect is insufficient.

In the second example shown in FIG. 9, the two-phase refrigerant generated from the high-pressure liquid line through the intermediate expansion valve and the gas refrigerant from the low-stage compressor flow into the gas-liquid separator. After that, the gas refrigerant in the gas-liquid separator is sucked by the high-stage compressor. However, in this case, the gas refrigerant separated from the two-phase refrigerant is higher than the pressure of the liquid refrigerant, so that the low-stage discharge gas refrigerant enters the gas refrigerant. Therefore, the discharged gas on the lower stage side cannot be sufficiently cooled by the liquid refrigerant. For this reason, as in the first example, as shown in FIG. 10, the gas refrigerant sucked on the high stage side is in a state of being overheated, and the economizer effect is also insufficient.

[0007] The present invention has been made in view of such problems, and an object of the present invention is to provide a state in which a gas refrigerant supplied to a high-stage compressor is sufficiently cooled.
It is to enhance the economizer effect in a two-stage compression refrigeration cycle.

[0008]

SUMMARY OF THE INVENTION According to the present invention, a gas discharged from a low-stage compressor and a two-phase refrigerant are preliminarily mixed, and then gas-liquid separated by a gas-liquid separator. Flows into the high-stage compressor.

Specifically, a solution taken by the present invention is to provide a refrigeration cycle including a two-stage compression mechanism (11, 21) comprising a low-stage compressor (11) and a high-stage compressor (21). Gas refrigerant from the intermediate-pressure refrigerant generated in the liquid line (40 L) from the condenser (31) to the evaporator (13), and separates the gas refrigerant from the low-stage compressor (11) with the gas discharged from the low-stage compressor (11). It is premised on a refrigerating device to be supplied to the compressor (21). A gas-liquid separator (24) is provided in which the discharge gas of the low-stage compressor (11) and the intermediate-pressure refrigerant are supplied in a premixed state, and is separated in the gas-liquid separator (24). The liquid refrigerant is supplied to the evaporator (13), and the gas refrigerant is supplied to the high-stage compressor (21).

In the above configuration, the liquid passing through the intermediate expansion mechanism (23) from the condenser (31) to the gas line (40G) connected from the low-stage compressor (11) to the gas-liquid separator (24). Connect the line (40L) and connect the liquid outlet of the gas-liquid separator (24) to the evaporator (1
In 3), the gas outlet may be connected to the high-stage compressor (21).

In the above solution, the intermediate-pressure two-phase refrigerant is supplied to the gas-liquid separator (24).
Before the gas-liquid separation in step (a), the gas is previously mixed with the discharge gas on the lower stage side. Therefore, the gas discharged from the low-stage compressor (11) and the two-phase refrigerant can be sufficiently mixed and then supplied to the gas-liquid separator (24).
In addition, since the dryness of the two-phase refrigerant increases during the mixing, the amount of gas increases as compared with the case where the two-phase refrigerant is not mixed before the gas-liquid separator (24). Further, since the low-stage discharge gas is sufficiently mixed with the two-phase refrigerant, the low-stage discharge gas is sufficiently cooled.

[0012]

Therefore, according to the above solution, the gas refrigerant sucked by the high-stage compressor (21) can be cooled to a saturated gas state, and the discharge of the high-stage compressor (21) can be performed. By preventing the temperature from rising excessively, deterioration of the refrigerating machine oil and decomposition of the refrigerant can be reliably prevented, and reliability can be improved.

Further, since the amount of gas sucked in by the high-stage compressor (21) can be increased as compared with the conventional case, it is possible to increase the capacity by improving the efficiency compared with the conventional case. As described above, according to the present invention, the economizer effect can be enhanced as compared with the related art.

[0014]

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

An embodiment of the present invention is an air conditioner (1) in which single-stage compression and two-stage compression can be switched during heating operation and single-stage compression is performed during cooling operation. It was done.

The specific circuit configuration of the air conditioner (1) is as follows.

That is, as shown in FIG. 1, this air conditioner comprises an outdoor unit (10), an intermediate unit (20),
And a plurality of indoor units (30) connected in parallel. The intermediate unit (20) enables two-stage compression operation in the existing air conditioner (1) of the single-stage compression system, and has an existing air conditioner having the outdoor unit (10) and the indoor unit (30). It is configured so that it can be added to the device.

The outdoor unit (10) includes a variable-stage low-stage compressor (11), a first four-way switching valve (12) for switching between a cooling operation and a heating operation, and an outdoor heat exchanger (13). , Outdoor expansion valve (14)
And The intermediate unit (20) is connected to the high-stage compressor (2
1), a second four-way switching valve (22) for switching between the two-stage compression operation and the single-stage compression operation during the heating operation, an intermediate expansion valve (intermediate expansion mechanism) (23), and a gas-liquid separator (24). And Also,
Each indoor unit (30) consists of an indoor heat exchanger (31) and an indoor expansion valve.
(32). Then, these devices are connected in order by a refrigerant pipe (40) and configured to perform a vapor compression refrigeration cycle, and also include a low-stage compressor (11) and a high-stage compressor (21). A two-stage compression mechanism (11, 21) is constituted. The refrigerant pipe (40) is connected to each unit (10, 20, 30)
In between, they are connected by a pipe joint (41).

More specifically, a variable displacement low-stage compressor.
In (11), the suction side and the discharge side are connected to two ports of the first four-way switching valve (12). The other port of the first four-way switching valve (12) is connected to the outdoor heat exchanger (13), and the other port is connected to one port of the second four-way switching valve (22). I have. The other four ports of the second four-way switching valve (22) are connected to the suction side of the high-stage compressor (21) and the high-stage compressor (21) through the gas-liquid separator (24). The discharge side and the indoor heat exchanger (31) are connected.

By switching the four-way switching valves (12, 22) to the state shown by the solid line in the figure, the low-stage compressor (11)
The four-way switching valves (12, 22) and the gas-liquid separator (2
4) and is sucked into the high-stage compressor (21). As described above, the outdoor heat exchanger (13) and the indoor heat exchanger
A gas line (40G) between the gas line and (31) is formed.

On the other hand, the indoor heat exchanger (31) and the outdoor heat exchanger (1)
The liquid line (40L) to the gas inlet of the gas-liquid separator (24) through the indoor expansion valve (32) and the intermediate expansion valve (23) in order from the indoor heat exchanger (31) side. And a gas-liquid separator (2
The liquid outlet of 4) is connected to the outdoor heat exchanger (13) via the check valve (25) and the outdoor expansion valve (14).

As described above, in this embodiment, the gas line (40) connected from the low-stage compressor (11) to the gas-liquid separator (24)
G), a liquid line from the condenser (31) through the intermediate expansion valve (23)
(40L), the liquid outlet of the gas-liquid separator (24) is connected to the evaporator (13), and the gas outlet is connected to the high-stage compressor (21).

As shown in the enlarged view of FIG. 2 in the refrigerant pipe near the gas-liquid separator (24), during the two-stage compression operation, the refrigerant gas discharged from the low-stage compressor (11) is connected to the refrigerant pipe. An intermediate-pressure two-phase refrigerant generated by passing through the intermediate expansion valve (23) from the indoor heat exchanger (31) side is premixed and supplied to the gas-liquid separator (24). After gas-liquid separation in the separator (24), the liquid refrigerant is supplied from the outdoor expansion valve (14) to the outdoor heat exchanger (13), and the gas refrigerant is supplied to the high-stage compressor (21). Economizer is configured.

The liquid line (40L) is provided with an indoor expansion valve.
The position between (32) and the intermediate expansion valve (23) and the position between the check valve (25) and the outdoor expansion valve (14) correspond to a communication passage provided with an on-off valve (42) such as a solenoid valve. (43).

In this embodiment, in order to prevent the high-stage compressor (21) from cooling down and the liquid refrigerant from being accumulated when the high-stage compressor (21) is stopped during single-stage compression. Although not shown, the liquid refrigerant is heated by a crankcase heater or the like of the high-stage compressor (21) so that the gas refrigerant can be discharged to the gas-liquid separator (24).

As the second four-way switching valve (22), for example, a rotary four-way switching valve can be used. This rotary four-way switching valve can be configured to switch the flow path by adopting, for example, an electromagnetic drive system or a motor drive system.

-Operation- Next, the operation of the air conditioner (1) will be described.

First, the operation when the heating operation is performed by the two-stage compression will be described with reference to FIG. 3 showing the flow direction of the refrigerant. At this time, the four-way switching valves (12, 22) are set to the state shown by the solid line in FIG. Further, the indoor expansion valve (32) is set to fully open, the intermediate expansion valve (23) is set to an opening degree to reduce the high-pressure refrigerant to a predetermined intermediate pressure, and the outdoor expansion valve (14)
Is set so as to reduce the intermediate pressure refrigerant to a predetermined low pressure. Further, the solenoid valve (42) of the communication passage (43) is closed.

The low-pressure compressor (11) compresses the low-pressure refrigerant in one stage and discharges it.
High-stage compressor (21) via (12,22) and gas-liquid separator (24)
And compressed in two stages. The gas refrigerant discharged from the high-stage compressor (21) flows into the indoor heat exchanger (31) acting as a condenser via the second four-way switching valve (22), and exchanges heat with indoor air. The room air is heated. The heated indoor air is blown into the room by an indoor fan (not shown), and warm air is supplied to the room.

The refrigerant condensed by the heat exchange in the indoor heat exchanger (31) passes through the indoor expansion valve (32), and then passes through the intermediate expansion valve (2).
A part expands in 3) and becomes a two-phase refrigerant of an intermediate pressure and flows into the gas-liquid separator (24). At this time, the two-phase refrigerant is supplied to the low-stage compressor (1
After being mixed with the discharge gas of 1), it flows into the gas-liquid separator (24). For this reason, a part of the two-phase refrigerant evaporates and the dryness is increased, and the low-stage discharge gas refrigerant is cooled by the two-phase refrigerant.

The refrigerant thus mixed is separated into a liquid refrigerant and a gas refrigerant by a gas-liquid separator (24), and the liquid refrigerant flows out of the gas-liquid separator (24) and flows out of the outdoor expansion valve (14). ), And flows into the outdoor heat exchanger (13) acting as an evaporator. Then, in the outdoor heat exchanger (13), the refrigerant is heated by exchanging heat with the outdoor air, is heated, changes phase into a gas refrigerant, passes through the first four-way switching valve (12), and passes through the low-stage compressor (11). ).

On the other hand, the gas refrigerant that has merged with the gas refrigerant discharged from the low-stage compressor (11) and flows into the gas-liquid separator (24) is sucked into the high-stage compressor (21). At this time, as shown in the Mollier diagram of FIG. 4, during the compression stroke, the low-stage side discharge gas refrigerant at the point B is cooled to the state of the saturated gas shown at the point A beyond the conventional point C. . Therefore, as is apparent from comparison with the state of the related art shown by a broken line, an increase in the discharge temperature due to compression in the high-stage compressor (21) can be suppressed. In addition, since the dryness of the two-phase refrigerant is increased, the amount of the refrigerant flowing through the indoor heat exchanger (31) increases, so that a high heating capacity can be obtained.

Next, the single-stage compression heating operation will be described with reference to FIG. 5 showing the flow direction of the refrigerant. At this time, the low-stage compressor (11) is operated to stop the high-stage compressor (21), and the two-way switching valves (11, 21) are set to the state shown by the solid line in FIG. That is, while the first four-way switching valve (12) is in the same state as in FIG. 3, the second four-way switching valve (22) is switched to the broken line side in FIG. Then, the indoor expansion valve (32) is controlled to be fully opened, the intermediate expansion valve (23) is controlled to be fully closed, and the outdoor expansion valve (14) controls the opening degree so as to reduce the high-pressure refrigerant to a predetermined low pressure. Also,
The solenoid valve (42) of the communication passage (43) is opened.

In this way, the discharge gas of the low-stage compressor (11) is supplied to the indoor heat exchanger (31) via the first four-way switching valve (12) and the second four-way switching valve (22). ) And flows into the indoor heat exchanger (3
In 1), the room air is heated. Then, the refrigerant condensed at that time passes through the indoor expansion valve (32) and the communication passage (43), is depressurized by the outdoor expansion valve (14), and flows into the outdoor heat exchanger (13). The refrigerant is heated by the outdoor heat exchanger (13), changes into a gas phase, and is sucked into the low-stage compressor (11). The single-stage compression heating operation is performed by repeating the above cycle.

When frost is formed on the outdoor heat exchanger (13) by performing the heating operation with the two-stage compression or the single-stage compression as described above, FIG.
The defrost operation is performed by the flow of the refrigerant shown in FIG. During defrost operation, both compressors (11, 21) are operated in a state where the capacity of the low-stage compressor (11) is larger than the capacity of the high-stage compressor (21), and both four-way switching valves (12, 22 is set to the state shown by the solid line in FIG. 6, that is, the first four-way switching valve (12) is set to the state shown by the broken line in FIG. 1, and the second four-way switching valve (22) is set to the state shown by the solid line in FIG. Further, the indoor expansion valve (32) and the outdoor expansion valve (14) are set to fully open, and the solenoid valve (42) of the communication passage (43) is opened,
The opening of the intermediate expansion valve (23) is controlled so that the high-pressure liquid refrigerant is reduced to a predetermined low pressure.

With the above setting, the gas discharged from the low-stage compressor (11) flows into the outdoor heat exchanger (13) via the first four-way switching valve (12), and is discharged from the outdoor heat exchanger (13). 13) Heat to defrost. At this time, the outdoor fan (not shown) is stopped, the refrigerant is cooled somewhat, flows out of the outdoor heat exchanger (13), further passes through the communication passage (43) from the outdoor expansion valve (14), and is Expansion valve (23)
Reach

On the other hand, the gas discharged from the high-stage compressor (21) flows into the indoor heat exchanger (31) via the second four-way switching valve (22). At this time, the indoor fan (not shown) is rotating, and heat exchange between the refrigerant and the indoor air is performed. Therefore, the blowing of the warm air into the room is continued, and the refrigerant is condensed and flows out of the indoor heat exchanger (31). After passing through the indoor expansion valve (32), the refrigerant merges with the refrigerant from the low-stage compressor (11), and is decompressed by the intermediate expansion valve (23). (2
4).

While this refrigerant is heated by the residual heat of the low-stage refrigerant, a part of the refrigerant is directed to the low-stage compressor (11) and another part is transmitted to the high-stage compressor (24) through the gas-liquid separator (24). It is sucked into the side compressor (21). The refrigerant drawn into each of the compressors (11, 21) is compressed again and discharged, and the above cycle is repeatedly performed on the outdoor side and the indoor side, so that the defrost operation is performed while the heating operation is continued.

Next, in the cooling operation, only the low-stage compressor (11) is operated, and the two-way switching valves (12, 22) are switched to the state shown by the solid line in FIG. 7 (the state shown by the broken line in FIG. 1). Do it. At this time, the outdoor expansion valve (14) is set to fully open, and the opening of the indoor expansion valve (32) is controlled so as to reduce the high-pressure refrigerant to a predetermined low pressure. Further, the solenoid valve (42) of the communication passage (43) is opened, and the intermediate expansion valve (23) is closed. With the above setting, the refrigerant is supplied to the low-stage compressor (11), the first four-way switching valve (12), and the outdoor heat exchanger (1).
3), outdoor expansion valve (14), communication passage (43), indoor expansion valve (32),
Cool air is blown into the room by circulating in the order of the indoor heat exchanger (31), the second four-way switching valve (22), and the first four-way switching valve (12).

-Effects of Embodiment- As described above, according to the present embodiment, during the two-stage compression operation, the intermediate-pressure two-phase refrigerant is set to a low pressure before the gas-liquid separator (24) separates it into gas and liquid. It is mixed in advance with the refrigerant discharged from the stage-side compressor (11). Therefore, the low-stage side discharge gas and the two-phase refrigerant can be sufficiently mixed and then supplied to the gas-liquid separator (24).
In addition, since the dryness of the two-phase refrigerant increases during the mixing, the amount of gas increases as compared with the case where the two-phase refrigerant is not mixed in advance.
For this reason, the amount of gas sucked in by the high-stage compressor (21) can be increased as compared with the conventional case, and the capacity can be increased by improving the efficiency compared to the conventional case.

Further, since the discharge gas of the low-stage compressor (11) is sufficiently mixed with the two-phase refrigerant, the low-stage discharge gas is sufficiently cooled. Therefore, the gas refrigerant sucked by the high-stage compressor (21) can be cooled to a saturated gas state as shown by the point A in the Mollier diagram of FIG. By preventing an excessive rise in the discharge temperature, deterioration of the refrigerating machine oil and decomposition of the refrigerant can be reliably prevented, and reliability can be improved.

As described above, according to the present embodiment, it is possible to enhance the economizer effect as compared with the conventional case.

[0043]

Other Embodiments of the Invention The present invention may be configured as follows with respect to the above embodiment.

For example, in the above embodiment, the present invention is applied to an air conditioner capable of cooling and heating, but the present invention is applicable to an air conditioner capable of only heating operation, a refrigeration device other than the air conditioner, and the like. But it is applicable. Further, the circuit configuration of the above embodiment is merely an example. For example, a configuration in which the two-stage compression mechanism (11, 21) is provided in the outdoor unit (10) without using the intermediate unit (20) may be used. As described above, the present invention provides a refrigeration system that can perform a two-stage compression operation, in which the gas discharged from the low-stage compressor (11) and the intermediate-pressure two-phase refrigerant are mixed and then gas-liquid separated to form a liquid refrigerant. The gas refrigerant may be supplied to the evaporator (in the embodiment, the outdoor heat exchanger (13)) and the gas refrigerant to the high-stage compressor (21).

[Brief description of the drawings]

FIG. 1 is a refrigerant circuit diagram of an air conditioner according to an embodiment of the present invention.

FIG. 2 is an enlarged view showing an economizer of the air conditioner of FIG.

3 is an operation state diagram showing an operation when performing a heating operation by two-stage compression in the air-conditioning apparatus of FIG.

FIG. 4 is a Mollier chart showing the operation state of FIG.

5 is an operation state diagram showing an operation when performing a heating operation by single-stage compression in the air-conditioning apparatus of FIG.

6 is an operation state diagram showing an operation when performing a defrost operation in the air-conditioning apparatus of FIG.

FIG. 7 is an operation state diagram showing an operation when performing a cooling operation in the air-conditioning apparatus of FIG. 1;

FIG. 8 is a diagram showing a conventional example of an economizer in a refrigerating apparatus that performs two-stage compression.

FIG. 9 is a diagram showing another conventional example of an economizer in a refrigerating apparatus that performs two-stage compression.

FIG. 10 is a Mollier diagram showing a two-stage compression operation state of the refrigeration apparatus of FIGS. 8 and 9;

[Explanation of symbols]

 (1) Air conditioner (refrigerator) (10) Outdoor unit (11) Low-stage compressor (12) First four-way switching valve (13) Outdoor heat exchanger (evaporator) (14) Outdoor expansion valve ( 20) Intermediate unit (21) High-stage compressor (22) Second four-way switching valve (23) Intermediate expansion valve (intermediate expansion mechanism) (24) Gas-liquid separator (25) Check valve (30) Indoor unit (31) Indoor heat exchanger (condenser) (32) Indoor expansion valve (40) Refrigerant piping (40G) Gas line (40L) Liquid line (41) Piping joint (42) Open / close valve (43) Communication passage

Claims (2)

[Claims] A refrigerating cycle is performed by providing a two-stage compression mechanism (11, 21) comprising a low-stage compressor (11) and a high-stage compressor (21), and a vaporization process is performed from a condenser (31). Liquid line to vessel (13)
A refrigerating device that separates the gas refrigerant from the intermediate-pressure refrigerant generated in (40L) and supplies it to the high-stage compressor (21) together with the discharge gas of the low-stage compressor (11). (11) is provided with a gas-liquid separator (24) which is supplied in a state of being mixed in advance with the intermediate-pressure refrigerant, the liquid refrigerant separated in the gas-liquid separator (24) evaporator (13 ), A refrigeration apparatus configured to supply a gas refrigerant to the high-stage compressor (21). 2. A gas line (40G) connected from the low-stage compressor (11) to the gas-liquid separator (24), and a liquid line (40L) from the condenser (31) through the intermediate expansion mechanism (23). ), The liquid outlet of the gas-liquid separator (24) is connected to the evaporator (13), and the gas outlet is connected to the high-stage compressor (21).