JP2003074990A - Refrigeration equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To assure smooth operation and reliability even in the case of using a fluid machine having a constant internal capacity ratio as an expansion machine, in a refrigerating unit recovering power from a high pressure refrigerant by the expansion machine. SOLUTION: Carbon dioxide is filled in a refrigerant circuit (10) of the refrigerating unit as a refrigerant. In the refrigerating unit, high pressure of a refrigeration cycle is set at a pressure not lower than the critical pressure of carbon dioxide. The circuit (10) has the expansion machine (22) and a motor driven expansion valve (23) provided in series. The expansion machine (22) is constituted of a scroll type fluid machine having a constant internal capacity ratio. The expansion ratio of the machine (22) is constant and does not change, but high pressure of the refrigeration cycle can be set at a value suitable for operation by controlling the opening of the valve (23).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerating apparatus for performing a vapor compression refrigerating cycle, and more particularly to a refrigerating cycle in which a high pressure is equal to or higher than a critical pressure of a refrigerant.

[0002]

2. Description of the Related Art Conventionally, a refrigerating device for circulating a refrigerant in a closed circuit to perform a vapor compression refrigerating cycle has been known and is widely used as an air conditioner or the like. As a refrigerating device of this type, there is known a refrigerating device in which the high pressure of the refrigerating cycle is set to be equal to or higher than the critical pressure of the refrigerant, as disclosed in JP-A-10-54617. In this refrigeration system, since the refrigerant is compressed in the compressor up to its critical pressure or higher, the power consumption of the compressor motor increases and a high COP (coefficient of performance) cannot be obtained.

To solve this problem, Japanese Patent Laid-Open No. 2001-10
As disclosed in Japanese Patent No. 7881, a measure to provide an expander in a refrigeration system has been proposed. The expander as used in this specification is synonymous with a prime mover as a type of fluid machine. In this case, the refrigerating apparatus is provided with an expander as a refrigerant expansion mechanism instead of the expansion valve and the capillary tube. Then, in the expander, the internal energy of the high-pressure refrigerant is converted into mechanical power, and the obtained power is used to drive the compressor, thereby reducing the power consumption of the compressor motor.

[0004]

In the above refrigeration system, the high pressure and the low pressure of the refrigeration cycle fluctuate depending on the operating conditions. For example, when the refrigeration system is used as an air conditioner,
The high pressure and the low pressure in the refrigeration cycle fluctuate according to the temperature change inside or outside the room. Further, the high pressure and the low pressure in the refrigeration cycle are different between the cooling operation and the heating operation. For example, the high pressure of the refrigeration cycle is 7
It fluctuates in the range of up to 9 MPa, and its low pressure varies in the range of 2 to 4.6 MPa. As described above, in the refrigeration system described above, the ratio of high pressure to low pressure in the refrigeration cycle fluctuates significantly.

On the other hand, a fluid machine such as a scroll type or a screw type may be used as the expander.
However, this type of fluid machine has a constant internal volume ratio. That is, the expansion ratio in the expander is constant and does not change despite the change in the high pressure / low pressure ratio in the refrigeration cycle. Therefore, when a fluid machine with a constant internal volume ratio is used as an expander, the high-pressure and low-pressure ratio in the refrigeration cycle does not match the expansion ratio of the expander, which causes a problem that the operation of the refrigeration system is not smoothly performed. there were.

Further, the expander constituted by the fluid machine is operated in a state of being largely deviated from its designed expansion ratio. For this reason, cavitation occurs due to overexpansion, and erosion resulting from this causes damage to the fluid machine, resulting in a problem of impairing the reliability of the refrigeration system.

The present invention has been made in view of the above point, and an object of the present invention is to expand a fluid machine having a constant internal volume ratio in a refrigerating apparatus for recovering power from a high pressure refrigerant by an expander. Even when used as a machine, it is to ensure smooth operation and reliability.

[0008]

A first solution provided by the present invention is to provide a refrigerant circuit (10) filled with a refrigerant, and to use a compressor (21) provided in the refrigerant circuit (10). The object is a refrigerating apparatus that performs a refrigeration cycle by compressing a refrigerant to a pressure equal to or higher than a critical pressure of the refrigerant. And the refrigerant circuit (10)
An expansion machine (22) composed of a fluid machine having a constant internal volume ratio and an expansion valve (23) of variable opening which is connected in series with the expansion machine (22) serve as a refrigerant expansion mechanism. It is provided.

A second solving means devised by the present invention is the above first solving means, in which the expansion valve (23) is arranged upstream of the expander (22) in the refrigerant circuit (10). .

A third solving means devised by the present invention is the above first or second solving means, wherein a refrigerant is provided between the expander (22) and the expansion valve (23) in the refrigerant circuit (10). A container member (31) for temporarily storing is provided.

A fourth solving means devised by the present invention is the above-mentioned first or second solving means, which is provided between the expander (22) and the expansion valve (23) in the refrigerant circuit (10) and is an intermediate device. A gas-liquid separator (3 that separates the pressurized refrigerant into a liquid refrigerant and a gas refrigerant)
2) and a gas pipeline (33) for supplying the gas refrigerant separated by the gas-liquid separator (32) to the compressor (21).

A fifth solution provided by the present invention includes a refrigerant circuit (10) filled with a refrigerant, and a compressor (21) provided in the refrigerant circuit (10) transfers the refrigerant to a critical temperature of the refrigerant. It is intended for refrigeration equipment that performs refrigeration cycles by compressing to a pressure or higher. An expander (22) configured by a fluid machine having a constant internal volume ratio to expand a part of the high pressure refrigerant in the refrigerant circuit (10) to an intermediate pressure, and a high pressure refrigerant remaining in the refrigerant circuit (10). An intermediate heat exchanger (40) for exchanging heat with the intermediate pressure refrigerant from the expander (22), and a variable-opening expansion valve (for expanding the high pressure refrigerant from the intermediate heat exchanger (40) to a low pressure ( 23), the low pressure refrigerant from the expansion valve (23) is supplied to the evaporator provided in the refrigerant circuit (10) in the refrigerant circuit (10), and the low pressure refrigerant is supplied to the compressor (21). The low-pressure refrigerant from the evaporator and the intermediate-pressure refrigerant from the intermediate heat exchanger (40) are supplied.

A sixth solving means taken by the present invention is the above first, second, third, fourth or fifth solving means, wherein the refrigerant circuit (10) is filled with carbon dioxide as a refrigerant. It is something.

-Operation- In the first solution, the refrigeration cycle is performed by circulating the refrigerant in the refrigerant circuit (10). Specifically, in the compressor (21) of the refrigerant circuit (10), the sucked refrigerant is compressed to its critical pressure or higher. Compressors (21)
The high-pressure refrigerant discharged from the device releases heat and then is decompressed by the expansion mechanism. The low-pressure refrigerant after depressurization absorbs heat and evaporates, and then is sucked into the compressor (21) and compressed again.

In the refrigerant circuit (10), the expansion mechanism is constituted by the expander (22) and the expansion valve (23) which are connected in series. However, in the present solving means, the expansion valve (23) may be provided on the upstream side of the expander (22) or the expansion valve (23) may be provided on the downstream side of the expander (22). That is, one of the expander (22) and the expansion valve (23) depressurizes the high-pressure refrigerant to an intermediate pressure, and the other one depressurizes the intermediate-pressure refrigerant to a low pressure. At that time, expander (22)
Converts the internal energy of the introduced refrigerant into motive power.

In this solution, the expander (22) is composed of a fluid machine having a constant internal volume ratio. Therefore, the pressure ratio between the refrigerant flowing into the expander (22) and the refrigerant flowing out of the expander (22) remains constant and does not change. On the other hand, the expansion valve (23) is configured so that its opening can be changed. Therefore, the pressure ratio of the refrigerant at the inlet and outlet of the expansion valve (23) changes depending on the opening degree of the expansion valve (23). Further, in the present solving means, the expander (22) and the expansion valve (23) are arranged in series in the refrigerant circuit (10).
Therefore, the pressure ratio of the refrigerant at the inlet and outlet of the expansion mechanism composed of the expander (22) and the expansion valve (23) is
Even if the expansion ratio is constant, it changes by changing the opening of the expansion valve (23).

In the second solution, the refrigerant circuit (10) is provided.
In, an expansion valve (23) is provided on the upstream side of the expander (22). That is, the high-pressure refrigerant flowing through the refrigerant circuit (10) first radiates heat and then passes through the expansion valve (23) to be depressurized to an intermediate pressure. Then, the intermediate pressure refrigerant from the expansion valve (23)
It flows into the expander (22) and is depressurized to a low pressure. In the expander (22), a part of the internal energy of the intermediate pressure refrigerant is converted into mechanical power.

In the third solution means, the container member (31) is provided between the expander (22) and the expansion valve (23). The intermediate-pressure refrigerant that has passed through either the expander (22) or the expansion valve (23) flows into the container member (31). That is, the refrigerant having a pressure lower than the critical pressure flows into the container member (31). Then, the amount of the refrigerant circulating in the refrigerant circuit (10) is adjusted by increasing or decreasing the amount of the liquid refrigerant stored in the container member (31).

In the fourth solution means, a gas-liquid separator (32) is provided between the expander (22) and the expansion valve (23). The gas-liquid separator (32) has an expander (22) or an expansion valve (2
The intermediate pressure refrigerant after flowing through either one of 3) flows in. That is, the refrigerant having a pressure lower than the critical pressure flows into the gas-liquid separator (32). Then, in the gas-liquid separator (32), the intermediate-pressure refrigerant flowing in the gas-liquid two-phase state is separated into the liquid refrigerant and the gas refrigerant.

In this solution, the intermediate pressure liquid refrigerant in the gas-liquid separator (32) passes through the expander (22) or the expansion valve (23) to become a low pressure, after which it absorbs heat and evaporates. It is sent to the compressor (21). On the other hand, the intermediate-pressure gas refrigerant in the gas-liquid separator (32) flows through the gas pipeline (33) and is sucked into the compressor (21). That is, the compressor (21) sucks the low-pressure gas refrigerant and the intermediate-pressure gas refrigerant.

In the fifth solution, the refrigerant circuit (10)
A refrigeration cycle is performed by circulating a refrigerant inside. Specifically, in the compressor (21) of the refrigerant circuit (10),
The sucked refrigerant is compressed to above its critical pressure.
The high-pressure refrigerant discharged from the compressor (21) dissipates heat thereafter and then split into two. One of the split high-pressure refrigerant flows into the expander (22) and expands to an intermediate pressure before being sent to the intermediate heat exchanger (40). On the other hand, the remainder of the divided high-pressure refrigerant is sent to the intermediate heat exchanger (40) as it is.

The intermediate heat exchanger (40) exchanges heat between the high pressure refrigerant and the intermediate pressure refrigerant. The intermediate-pressure refrigerant absorbs heat from the high-pressure refrigerant in the intermediate heat exchanger (40) to evaporate, and is then sucked into the compressor (21). On the other hand, the high pressure refrigerant radiates heat to the intermediate pressure refrigerant in the intermediate heat exchanger (40) and is then sent to the expansion valve (23). The high-pressure refrigerant that has released heat expands to a low pressure when passing through the expansion valve (23). The low-pressure refrigerant from the expansion valve (23) absorbs heat, evaporates, and is then sucked into the compressor (21). The compressor (21) sucks the low-pressure gas refrigerant and the intermediate-pressure gas refrigerant, and compresses the sucked refrigerant again.

In the present solution, the expander (22) is composed of a fluid machine having a constant internal volume ratio. Therefore, the pressure ratio between the refrigerant flowing into the expander (22) and the refrigerant flowing out of the expander (22) remains constant and does not change. On the other hand, the expansion valve (23) is configured so that its opening can be changed. Therefore, the pressure ratio between the refrigerant flowing into the expansion valve (23) and the refrigerant flowing out of the expansion valve (23) is
It changes according to the opening of 3). In the present solution, the high pressure refrigerant expands to the intermediate pressure in the expander (22), while the high pressure refrigerant expands to the low pressure in the expansion valve (23). Therefore, even if the expansion ratio of the expander (22) does not change, the high pressure or low pressure of the refrigeration cycle changes if the opening degree of the expansion valve (23) is changed.

In the sixth means, the refrigerant circuit (10)
Carbon dioxide (CO ₂ ) is used as the refrigerant.

[0025]

According to the present invention, both the expander (22) having a constant internal volume ratio and the expansion valve (23) having a variable opening are provided in the refrigerant circuit (1).
0). Therefore, even if the expansion ratio of the expander (22) cannot be changed, by changing the opening of the expansion valve (23), the high and low pressures of the refrigeration cycle can be set to values suitable for the operating conditions of the refrigeration system. It becomes possible to do. Therefore, according to the present invention, the high pressure and the low pressure of the refrigeration cycle can be set to the optimum values, and the operation of the refrigeration system can always be smoothly performed.

Further, according to the present invention, the expansion ratio of the expander (22) in operation can be kept substantially the same as the designed expansion ratio of the fluid machine constituting the expander (22). Therefore, according to the present invention, it is possible to prevent cavitation due to overexpansion of the refrigerant, avoid damage to the expander (22) due to cavitation, and improve the reliability of the refrigeration system.

Particularly, in the second solving means, the expander (22) is installed downstream of the expansion valve (23). Therefore, according to the present solution, the expander (22) is connected to the expansion valve (23).
The internal energy of the refrigerant can be reliably converted into mechanical power in the expander (22), as compared with the case of installing it on the upstream side of.

This point will be described. When the pressure of the refrigerant is equal to or higher than the critical pressure, the refrigerant is in a state where there is no distinction between the liquid phase and the gas phase, and even if the specific volume is slightly changed, the pressure greatly fluctuates. Therefore, if the expander (22) is used in the process of expanding the high-pressure refrigerant to the intermediate pressure, even if a slight leak occurs inside the fluid machine as the expander (22),
The power obtained in the expander (22) is greatly reduced.

On the other hand, when the refrigerant has a pressure lower than its critical pressure, the refrigerant is in a gas-liquid two-phase state and the specific volume fluctuates greatly as the pressure fluctuates. Therefore, if the expander (22) is used in the process of expanding the intermediate-pressure refrigerant to a low pressure, even if some leakage occurs inside the fluid machine as the expander (22), the accompanying decrease in pressure is slight. There is an expander (2
The power obtained in 2) does not decrease so much.

On the other hand, in the present solution means, the expander (22) is provided in the refrigerant circuit (10) downstream of the expansion valve (23), and the expander (22) is expanded in the process of expanding the intermediate pressure refrigerant to a low pressure. ) Is used. Therefore, according to the present solution,
Even if some leakage of the refrigerant occurs inside the fluid machine used as the expander, the power recovery in the expander can be reliably performed.

Further, according to the third solving means, by temporarily storing the intermediate pressure refrigerant in the container member (31),
The amount of refrigerant circulating in the refrigerant circuit (10) can be adjusted.
Here, in a refrigeration system that performs a normal refrigeration cycle in which the high pressure is lower than the critical pressure of the refrigerant, a receiver is provided in the refrigerant circuit (10) and the high pressure liquid refrigerant is stored in the receiver to circulate the refrigerant circuit (10). The amount of refrigerant is adjusted. However, when the pressure of the refrigerant becomes equal to or higher than its critical pressure, the refrigerant is in a state in which the liquid phase and the gas phase are indistinguishable. Therefore, when the high pressure of the refrigeration cycle is equal to or higher than the critical pressure of the refrigerant, like the refrigeration apparatus of the present solution, even if a conventional receiver into which the high pressure refrigerant flows is provided, the receiver is always a single-phase refrigerant. It becomes impossible to adjust the amount of the refrigerant because it becomes full. Therefore, in the present solving means, by introducing an intermediate pressure refrigerant having a pressure lower than the critical pressure into the container member (31), the amount of refrigerant circulating in the refrigerant circuit (10) can be adjusted.

[0032]

Embodiment 1 of the present invention will be described in detail below with reference to the drawings.

As shown in FIG. 1, the first embodiment is an air conditioner constituted by a refrigeration system according to the present invention. This air conditioner includes a refrigerant circuit (10) and a controller (50), and is configured to switch between cooling operation and heating operation.

The refrigerant circuit (10) includes an indoor heat exchanger (11), an outdoor heat exchanger (12), a first four-way switching valve (13),
Second four-way switching valve (14), compressor (21), expander (22),
An electric expansion valve (23) and a receiver tank (31) are provided. In the refrigerant circuit (10), an expander (22) and an electric expansion valve (23) are arranged in series, and these constitute a refrigerant expansion mechanism. The refrigerant circuit (10) is filled with carbon dioxide (CO ₂ ) as a refrigerant.

The indoor heat exchanger (11) is a so-called cross-fin type fin-and-tube heat exchanger. Indoor air is supplied to the indoor heat exchanger (11) by a fan (not shown). Indoor heat exchanger (11)
In, the heat exchange between the supplied indoor air and the refrigerant in the refrigerant circuit (10) is performed. In the refrigerant circuit (10), one end of the indoor heat exchanger (11) has a first four-way switching valve (1
It is connected to the first port of 3) by piping, and the other end is connected to the first port of the second four-way switching valve (14) by piping.

The outdoor heat exchanger (12) is a so-called cross fin type fin-and-tube heat exchanger. Outdoor air is supplied to the outdoor heat exchanger (12) by a fan (not shown). Outdoor heat exchanger (12)
In, heat exchange is performed between the supplied outdoor air and the refrigerant in the refrigerant circuit (10). In the refrigerant circuit (10), one end of the outdoor heat exchanger (12) has a first four-way switching valve (1
The pipe is connected to the second port of 3), and the other end is connected to the second port of the second four-way switching valve (14).

The compressor (21) is a rolling piston type fluid machine. This compressor (21)
Compresses the sucked refrigerant (CO ₂ ) to the critical pressure or higher. In the refrigerant circuit (10), the discharge side of the compressor (21) is connected to the third port of the first four-way switching valve (13) by piping, and the suction side thereof is the first four-way switching valve (13). Is connected to the fourth port of the pipe.

The expander (22) is composed of a scroll type fluid machine. That is, this expander (22)
Is composed of a positive displacement fluid machine with a constant internal volume ratio. In the refrigerant circuit (10), the expander (2
In 2), the inflow side is pipe-connected to the third port of the second four-way switching valve (14), and the outflow side is pipe-connected to the receiver tank (31). The fluid machine forming the expander (22) is not limited to the scroll type as long as the internal volume ratio is constant, and for example, a screw type, a gear type,
It may be of the roots type.

The receiver tank (31) is a vertically long and cylindrical hermetic container, and constitutes a container member for storing the intermediate pressure refrigerant. In the refrigerant circuit (10),
The receiver tank (31) is connected to the inflow side of the electric expansion valve (23) by piping. Thus, in the refrigerant circuit (10), the electric expansion valve (23) is provided downstream of the expander (22).
Is provided.

The electric expansion valve (23) is constructed so that its opening can be changed by rotating the valve body with a pulse motor or the like. In the refrigerant circuit (10), the outflow side of the electric expansion valve (23) is pipe-connected to the fourth port of the second four-way switching valve (14).

As mentioned above, the first four-way switching valve (13) is
The first port is the indoor heat exchanger (11), the second port is the outdoor heat exchanger (12), the third port is the discharge side of the compressor (21), and the fourth port is the compressor. It is connected to the suction side of (21). The first four-way switching valve (13) has a state in which the first port communicates with the third port and the second port communicates with the fourth port (state shown by a solid line in FIG. 1).
And the first port communicates with the fourth port and the second port communicates with the third port (state shown by a broken line in FIG. 1).

On the other hand, in the second four-way switching valve (14), the first port is the indoor heat exchanger (11), the second port is the outdoor heat exchanger (12), and the third port is the expansion. The inflow side of the machine (22) and the fourth port are connected to the outflow side of the electric expansion valve (23), respectively. This first four-way switching valve (13) has a first
Port communicates with the third port and the second port communicates with the fourth port (state shown by a solid line in FIG. 1)
And the first port communicates with the fourth port and the second port communicates with the third port (state shown by a broken line in FIG. 1).

In this embodiment, the expander (22) and the compressor motor (24) are connected to the drive shaft of the compressor (21). This compressor (21) is an expander (22)
It is rotatably driven by both the power obtained by the expansion of the refrigerant in (1) and the power obtained by energizing the compressor motor (24). Further, the compressor motor (24) is supplied with AC power of a predetermined frequency from an inverter (not shown). Then, the compressor (21) changes the frequency of the electric power supplied to the compressor motor (24),
The capacity is variable.

Although not shown in the figure, the air conditioner of this embodiment
Temperature and pressure sensors are provided. Above compressor (2
The pipe connected to the discharge side of 1) is provided with a temperature sensor for detecting the discharge pipe temperature T _d and a pressure sensor for detecting the discharge pressure p _d . In the indoor heat exchanger (11),
A temperature sensor for detecting the indoor heat exchanger temperature T _hi is provided. The outdoor heat exchanger (12) is provided with a temperature sensor for detecting the outdoor heat exchanger temperature T _ho . Furthermore,
The aforementioned air conditioner, a temperature sensor for detecting a room air temperature T _r, a temperature sensor for detecting the outdoor air temperature T _o is provided.

The detection values of the above-mentioned temperature sensor and pressure sensor are input to the controller (50). In addition, the indoor set temperature _Trset set by the user is input to the controller (50). Then, the controller (50) is configured to adjust the capacity of the compressor (21) and the opening degree of the electric expansion valve (23) based on the detection value of each sensor and the indoor set temperature _Trset . .

The controller (50) uses the indoor heat exchanger temperature T _hi as the refrigerant evaporation temperature during cooling, and the outdoor heat exchanger temperature T _ho as the refrigerant evaporation temperature during heating, so that the predetermined temperature is obtained. Is configured to perform the operation of. Therefore, the temperature sensor for detecting the indoor heat exchanger temperature T _hi is installed at a position where the refrigerant is not superheated during cooling in the indoor heat exchanger (11). In addition, the temperature sensor for detecting the indoor heat exchanger temperature T _ho is the outdoor heat exchanger (1
It is installed at a position where the refrigerant does not get superheated during heating in 2).

-Operational Behavior- << Heating Operation >> Regarding the operation during heating operation of the air conditioner,
This will be described with reference to FIGS. 1 and 2. Note that FIG. 2 shows the refrigeration cycle in the air conditioner on a Mollier diagram (pressure-enthalpy diagram).

During the heating operation, the first four-way switching valve (1
3) and the second four-way switching valve (14) are switched to the state shown by the solid line in FIG. When the compressor (21) is driven in this state, the refrigerant circulates in the refrigerant circuit (10) to perform the refrigeration cycle. At that time, the indoor heat exchanger (11) functions as a radiator, and the outdoor heat exchanger (12) functions as an evaporator.

Specifically, the compressor (21) discharges the high-pressure refrigerant in the state of the point in FIG. The pressure P _H of this high-pressure refrigerant is higher than its critical pressure P _C.
The refrigerant discharged from the compressor (21) is introduced into the indoor heat exchanger (11) through the first four-way switching valve (13).

In the indoor heat exchanger (11), the introduced high pressure refrigerant exchanges heat with indoor air. Due to this heat exchange, the high-pressure refrigerant radiates heat to the room air, and its enthalpy decreases from the point state to the point state. The high-pressure refrigerant in the state of the point passes through the second four-way switching valve (14) and the expander (2
2) to be introduced. On the other hand, the indoor air heated by the high-pressure refrigerant in the indoor heat exchanger (11) is sent back to the room as conditioned air.

The refrigerant in the point state after radiating heat in the indoor heat exchanger (11) expands in the expander (22), and its pressure and enthalpy decrease to the point state. That is,
In the expander (22), the high pressure refrigerant expands to become an intermediate pressure refrigerant having a pressure P _M. This intermediate pressure refrigerant has a pressure lower than its critical pressure P _C and is in a gas-liquid two-phase state. Then, the intermediate-pressure refrigerant in a gas-liquid two-phase state flows out from the expander (22), passes through the receiver tank (31), and the electric expansion valve (23).
Sent to.

In the electric expansion valve (23), the intermediate pressure refrigerant is decompressed, and the pressure thereof decreases from the point state to the point state. That is, by passing through the electric expansion valve (23), the intermediate pressure refrigerant is decompressed and becomes a low pressure refrigerant having a pressure P _L. The low-pressure refrigerant in the point state is introduced into the outdoor heat exchanger (12) through the second four-way switching valve (14).

In the outdoor heat exchanger (12), the introduced low pressure refrigerant exchanges heat with outdoor air. By this heat exchange, the low-pressure refrigerant absorbs heat from the outdoor air, and its enthalpy increases from the point state to the point state. The low-pressure refrigerant in the point state flows out from the outdoor heat exchanger (12) and is sent to the compressor (21) through the first four-way switching valve (13).

The refrigerant in the point state sucked into the compressor (21) is compressed into the point state. That is, in the compressor (21), the low pressure refrigerant having the pressure P _L is compressed to become the high pressure refrigerant having the pressure P _H. And this high-pressure refrigerant is the compressor (21).
To the indoor heat exchanger (11).

As described above, in the expander (22), the pressure and enthalpy of the refrigerant decrease from point to point. Then, in the expander (22), power corresponding to the enthalpy difference between the points is obtained, and the obtained power is used to drive the compressor (21).

<< Cooling Operation >> The operation of the air conditioner during the cooling operation will be described with reference to FIGS. 1 and 2.

During the cooling operation, the first four-way selector valve (1
3) and the second four-way switching valve (14) are switched to the state shown by the broken line in FIG. When the compressor (21) is driven in this state, the refrigerant circulates in the refrigerant circuit (10) to perform the refrigeration cycle. At that time, the outdoor heat exchanger (12) functions as a radiator, and the indoor heat exchanger (11) functions as an evaporator.

Specifically, the compressor (21) discharges the high-pressure refrigerant in the state of the point in FIG. The pressure P _H of this high-pressure refrigerant is higher than its critical pressure P _C.
The refrigerant discharged from the compressor (21) is introduced into the outdoor heat exchanger (12) through the first four-way switching valve (13).

In the outdoor heat exchanger (12), the introduced high pressure refrigerant exchanges heat with outdoor air. By this heat exchange, the high-pressure refrigerant radiates heat to the outdoor air, and its enthalpy decreases from the point state to the point state. The high-pressure refrigerant in the state of the point passes through the second four-way switching valve (14) and the expander (2
2) to be introduced.

The refrigerant in the point state after radiating heat in the outdoor heat exchanger (12) expands in the expander (22), and its pressure and enthalpy decrease to the point state. That is,
In the expander (22), the high pressure refrigerant expands to become an intermediate pressure refrigerant having a pressure P _M. This intermediate pressure refrigerant has a pressure lower than its critical pressure P _C and is in a gas-liquid two-phase state. Then, the intermediate-pressure refrigerant in a gas-liquid two-phase state flows out from the expander (22), passes through the receiver tank (31), and the electric expansion valve (23).
Sent to.

In the motor-operated expansion valve (23), the intermediate pressure refrigerant is decompressed and its pressure is reduced from the point state to the point state. That is, by passing through the electric expansion valve (23), the intermediate pressure refrigerant is decompressed and becomes a low pressure refrigerant having a pressure P _L. The low-pressure refrigerant in the point state is introduced into the indoor heat exchanger (11) through the second four-way switching valve (14).

In the indoor heat exchanger (11), the introduced low-pressure refrigerant exchanges heat with indoor air. By this heat exchange, the low-pressure refrigerant absorbs heat from the indoor air, and its enthalpy increases from the point state to the point state. The low-pressure refrigerant in the state of point flows out from the indoor heat exchanger (11) and is sent to the compressor (21) through the first four-way switching valve (13). On the other hand, the indoor air cooled by the low-pressure refrigerant in the indoor heat exchanger (11) is sent back to the room as conditioned air.

The refrigerant in the point state sucked into the compressor (21) is compressed into the point state. That is, in the compressor (21), the low pressure refrigerant having the pressure P _L is compressed to become the high pressure refrigerant having the pressure P _H. And this high-pressure refrigerant is the compressor (21).
To the outdoor heat exchanger (12).

As described above, in the expander (22), the pressure and enthalpy of the refrigerant decrease from point to point. Then, in the expander (22), power corresponding to the enthalpy difference between the points is obtained, and the obtained power is used to drive the compressor (21).

-Control operation of controller-During the heating operation or the cooling operation, the controller (50) performs a predetermined control operation as described below, and the operating frequency of the compressor (21) and the electric expansion valve ( The opening of 23) is adjusted. Accordingly, the values of the high pressure P _H and the low pressure P _L of the refrigeration cycle fluctuate during the heating operation and the cooling operation.
That is, during the operation of the air conditioner, the ratio P _H / P _L of the high pressure P _H and the low pressure P _L in the refrigeration cycle is changed.

In this embodiment, since the expander (22) is composed of a scroll type fluid machine, the expander (22)
, The pressure ratio P _H / P _M of the refrigerant at the inlet and outlet of the expander (22) is constant and does not change. On the other hand, when the opening degree of the electric expansion valve (23) is changed, the pressure ratio P _M / P _L of the refrigerant at the inlet and outlet of the electric expansion valve (23) changes. Therefore, even if the expansion ratio of the expander (22) is constant, by adjusting the opening degree of the electric expansion valve (23), the high pressure P _H and the low pressure P _L of the refrigeration cycle can be adjusted to values suitable for the operating state. Is set.

<< Control Operation During Heating Operation >> During heating operation, the controller (50) performs a predetermined control operation to adjust the capacity of the compressor (21) and the opening degree of the electric expansion valve (23).

When starting the heating operation, the controller (50) sequentially performs the following operations <a> to <c>. <a> Based on the input indoor air temperature T _r and outdoor air temperature T _o , the control area is divided, and according to the area division,
The initial value F ₀ of the operating frequency of the compressor (21) is determined from the table stored in advance. Substituted into equation for previously storing a <b> and determined operation frequency F and the outdoor air temperature T _o, determining the initial value Ev ₀ of the opening degree of the electronic expansion valve (23). <C> Set the opening of the electric expansion valve (23) to the initial value Ev ₀ ,
AC power of frequency F ₀ is supplied to the compressor motor (24) to start the compressor (21).

On the other hand, during the heating operation, the controller (50) repeats the following operations <d> to <f> at predetermined time intervals. <D> Substituting the input discharge pressure p _d , the indoor air temperature T _r , and the outdoor heat exchanger temperature T _ho into the relational expressions stored in advance,
The control target value T _dset of the discharge pipe temperature is determined. <E> The opening degree operation amount ΔEv of the electric expansion valve (23) is determined based on the difference between the input discharge pipe temperature T _d and the control target value T _dset , and the opening degree of the electric expansion valve (23) is determined according to the value. To change. <F> Input indoor air temperature T _r and indoor set temperature T
The change amount ΔF of the operating frequency of the compressor (21) is determined based on the difference in _rset , and the frequency of the AC power supplied to the compressor motor (24) is changed according to the value.

<< Control Operation During Cooling Operation >> During the cooling operation, the controller (50) performs a predetermined control operation to adjust the capacity of the compressor (21) and the opening degree of the electric expansion valve (23).

When starting the cooling operation, the controller (50) sequentially performs the following operations from <g> to <i>. <G> performs control regions divided based on the room air temperature T _r that is input and the outside air temperature T _o, in accordance with the area division,
The initial value F ₀ of the operating frequency of the compressor (21) is determined from the table stored in advance. Substituted into the relational expression previously stores <h> and determined operation frequency F and the outdoor air temperature T _o, determining the initial value Ev ₀ of the opening degree of the electronic expansion valve (23). <I> Set the opening of the electric expansion valve (23) to the initial value Ev ₀ ,
AC power of frequency F ₀ is supplied to the compressor motor (24) to start the compressor (21).

On the other hand, during the heating operation, the controller (50) repeats the following operations <j> to <l> at predetermined time intervals. <J> Substitute the input discharge pressure p _d , the indoor air temperature T _r , and the indoor heat exchanger temperature T _hi into a relational expression stored in advance,
The control target value T _dset of the discharge pipe temperature is determined. <K> The opening degree operation amount ΔEv of the electric expansion valve (23) is determined based on the difference between the input discharge pipe temperature _Td and the control target value _Tdset , and the opening degree of the electric expansion valve (23) is determined according to the value. To change. <L> Input indoor air temperature T _r and indoor set temperature T
The change amount ΔF of the operating frequency of the compressor (21) is determined based on the difference in _rset , and the frequency of the AC power supplied to the compressor motor (24) is changed according to the value.

-Effect of Embodiment 1-In the present embodiment, in the refrigerant circuit (10), both the expander (22) with a constant internal volume ratio and the electric expansion valve (23) with a variable opening are provided in series. Has been. Because of this, the expander (22)
Even if the expansion ratio is constant, the high pressure and the low pressure of the refrigeration cycle can be set to values suitable for the operating conditions of the air conditioner by changing the opening degree of the electric expansion valve (23). Therefore, according to the present embodiment, it is possible to set the high pressure and the low pressure of the refrigeration cycle to optimum values even in an air conditioner including an expander (22) having a constant expansion ratio, and the heating operation of the air conditioner or The cooling operation can always be performed smoothly.

Further, according to this embodiment, the expansion ratio of the expander (22) in operation is kept substantially the same as the designed expansion ratio of the fluid machine constituting the expander (22), and the air conditioning is performed. It becomes possible to operate the machine. Therefore, according to the present embodiment, it is possible to prevent cavitation due to excessive expansion of the refrigerant, avoid damage to the expander (22) due to cavitation, and improve the reliability of the air conditioner.

In this embodiment, the receiver tank (31) is provided between the expander (22) and the electric expansion valve (23) in the refrigerant circuit (10). Therefore, by temporarily storing the intermediate pressure refrigerant in the gas-liquid two-phase state in the receiver tank (31), the amount of refrigerant circulating in the refrigerant circuit (10) can be adjusted.

Here, in a general refrigeration system in which the high pressure of the refrigeration cycle is lower than the critical pressure of the refrigerant, the refrigerant circuit (10)
A receiver is provided in the receiver, and high-pressure liquid refrigerant is stored in the receiver to adjust the amount of refrigerant circulating in the refrigerant circuit (10). However, when the pressure of the refrigerant becomes equal to or higher than its critical pressure, the refrigerant is in a state in which the liquid phase and the gas phase are indistinguishable. For this reason, in the high-pressure refrigeration cycle such as the air conditioner of the present embodiment having a pressure equal to or higher than the critical pressure of the refrigerant, even if the conventional receiver into which the high-pressure refrigerant flows is provided, the receiver is filled with the refrigerant in the supercritical state. As a result, the amount of refrigerant cannot be adjusted. Therefore, in the present embodiment, the intermediate pressure refrigerant having a pressure lower than the critical pressure is temporarily stored in the receiver tank (31), so that the amount of refrigerant circulated in the refrigerant circuit (10) can be adjusted.

[0077]

Second Embodiment of the Invention In the second embodiment of the present invention, the positions of the expander (22) and the electric expansion valve (23) in the first embodiment are exchanged, and the expander (22) in the refrigerant circuit (10) is replaced. The electric expansion valve (23) is arranged on the upstream side. Here, with respect to the configuration of the air conditioner according to the present embodiment, portions different from those of the first embodiment will be described.

As shown in FIG. 3, the electric expansion valve (23) is
The inflow side is connected to the third port of the second four-way switching valve (14) by piping, and the outflow side is connected to the upper portion of the receiver tank (31) by piping. The inflow side of the expander (22) is connected to the lower portion of the receiver tank (31) by piping, and the outflow side of the expander (22) is connected to the fourth port of the second four-way switching valve (14).

-Driving Operation- << Heating Operation >> The heating operation of the air conditioner of this embodiment will be described with reference to FIGS. 3 and 4.
Note that FIG. 4 shows the refrigeration cycle in the air conditioner on the Mollier diagram (pressure-enthalpy diagram).

During heating operation, the first four-way selector valve (1
3) and the second four-way switching valve (14) are switched to the state shown by the solid line in FIG. When the compressor (21) is driven in this state, the refrigerant circulates in the refrigerant circuit (10) to perform the refrigeration cycle. At that time, the indoor heat exchanger (11) functions as a radiator, and the outdoor heat exchanger (12) functions as an evaporator.

Specifically, the high pressure refrigerant in the state of the point in FIG. 4 is discharged from the compressor (21). The pressure P _H of this high-pressure refrigerant is higher than its critical pressure P _C.
The refrigerant discharged from the compressor (21) is introduced into the indoor heat exchanger (11) through the first four-way switching valve (13).

In the indoor heat exchanger (11), the introduced high pressure refrigerant exchanges heat with indoor air. Due to this heat exchange, the high-pressure refrigerant radiates heat to the room air, and its enthalpy decreases from the point state to the point state. The high-pressure refrigerant in the point state is sent to the electric expansion valve (23) through the second four-way switching valve (14). On the other hand, the indoor air heated by the high-pressure refrigerant in the indoor heat exchanger (11) is sent back to the room as conditioned air.

In the electric expansion valve (23), the high-pressure refrigerant is decompressed, and the pressure thereof drops from the point state to the point state. That is, by passing through the electric expansion valve (23), the high pressure refrigerant is decompressed and becomes the intermediate pressure refrigerant having the pressure P _M. This intermediate pressure refrigerant has a pressure lower than its critical pressure P _C and is in a gas-liquid two-phase state. Then, the intermediate-pressure refrigerant in a gas-liquid two-phase state flows out from the electric expansion valve (23) and is sent to the expander (22) through the receiver tank (31).

The refrigerant in the point state sent from the receiver expands in the expander (22), and its pressure and enthalpy decrease to the point state. That is, in the expander (22), the intermediate pressure refrigerant expands to become a low pressure refrigerant having a pressure P _L. The low-pressure refrigerant in the state of point is the second four-way switching valve (1
It is introduced into the outdoor heat exchanger (12) through 4).

In the outdoor heat exchanger (12), the introduced low pressure refrigerant exchanges heat with outdoor air. By this heat exchange, the low-pressure refrigerant absorbs heat from the outdoor air, and its enthalpy increases from the point state to the point state. The low-pressure refrigerant in the point state flows out from the outdoor heat exchanger (12) and is sent to the compressor (21) through the first four-way switching valve (13).

The refrigerant in the point state sucked into the compressor (21) is compressed into the point state. That is, in the compressor (21), the low pressure refrigerant having the pressure P _L is compressed to become the high pressure refrigerant having the pressure P _H. And this high-pressure refrigerant is the compressor (21).
To the indoor heat exchanger (11).

As described above, in the expander (22), the pressure and enthalpy of the refrigerant decrease from point to point. Then, in the expander (22), power corresponding to the enthalpy difference between the points is obtained, and the obtained power is used to drive the compressor (21).

<< Cooling Operation >> The operation of the air conditioner during the cooling operation will be described with reference to FIGS. 3 and 4.

During the cooling operation, the first four-way selector valve (1
3) and the second four-way switching valve (14) are switched to the state shown by the broken line in FIG. When the compressor (21) is driven in this state, the refrigerant circulates in the refrigerant circuit (10) to perform the refrigeration cycle. At that time, the outdoor heat exchanger (12) functions as a radiator, and the indoor heat exchanger (11) functions as an evaporator.

Specifically, the high pressure refrigerant in the state of the point in FIG. 4 is discharged from the compressor (21). The pressure P _H of this high-pressure refrigerant is higher than its critical pressure P _C.
The refrigerant discharged from the compressor (21) is introduced into the outdoor heat exchanger (12) through the first four-way switching valve (13).

In the outdoor heat exchanger (12), the introduced high pressure refrigerant exchanges heat with outdoor air. By this heat exchange, the high-pressure refrigerant radiates heat to the outdoor air, and its enthalpy decreases from the point state to the point state. The high-pressure refrigerant in the point state is sent to the electric expansion valve (23) through the second four-way switching valve (14).

In the electric expansion valve (23), the high-pressure refrigerant is decompressed, and the pressure thereof decreases from the point state to the point state. That is, by passing through the electric expansion valve (23), the high pressure refrigerant is decompressed and becomes the intermediate pressure refrigerant having the pressure P _M. This intermediate pressure refrigerant has a pressure lower than its critical pressure P _C and is in a gas-liquid two-phase state. Then, the intermediate-pressure refrigerant in a gas-liquid two-phase state flows out from the electric expansion valve (23) and is sent to the expander (22) through the receiver tank (31).

The refrigerant in the point state sent from the receiver expands in the expander (22), and its pressure and enthalpy are lowered to the point state. That is, in the expander (22), the intermediate pressure refrigerant expands to become a low pressure refrigerant having a pressure P _L. The low-pressure refrigerant in the state of point is the second four-way switching valve (1
It is introduced into the indoor heat exchanger (11) through 4).

In the indoor heat exchanger (11), the introduced low pressure refrigerant exchanges heat with indoor air. By this heat exchange, the low-pressure refrigerant absorbs heat from the indoor air, and its enthalpy increases from the point state to the point state. The low-pressure refrigerant in the state of point flows out from the indoor heat exchanger (11) and is sent to the compressor (21) through the first four-way switching valve (13). On the other hand, the indoor air cooled by the low-pressure refrigerant in the indoor heat exchanger (11) is sent back to the room as conditioned air.

The refrigerant in the point state sucked into the compressor (21) is compressed into the point state. That is, in the compressor (21), the low pressure refrigerant having the pressure P _L is compressed to become the high pressure refrigerant having the pressure P _H. And this high-pressure refrigerant is the compressor (21).
To the outdoor heat exchanger (12).

As described above, in the expander (22), the pressure and enthalpy of the refrigerant drop from point to point. Then, in the expander (22), power corresponding to the enthalpy difference between the points is obtained, and the obtained power is used to drive the compressor (21).

-Effect of Second Embodiment- In the present embodiment, in the refrigerant circuit (10), the expander (2
2) is installed downstream of the electric expansion valve (23). Therefore, according to the present embodiment, as compared with the case where the expander (22) is installed on the upstream side of the electric expansion valve (23) as in the first embodiment, the internal energy of the refrigerant in the expander (22) is reduced. It is possible to reliably convert to mechanical power.

This point will be described. When the pressure of the refrigerant is equal to or higher than the critical pressure, the pressure fluctuates greatly even if the specific volume slightly changes. Therefore, if the expander (22) is used in the process of expanding the refrigerant of high pressure P _H to the intermediate pressure P _M , even if a slight leak occurs inside the fluid machine as the expander (22), the expander The power obtained in (22) is greatly reduced.

On the other hand, when the refrigerant has a pressure lower than its critical pressure, the refrigerant is in a gas-liquid two-phase state, and the specific volume greatly changes as the pressure changes. Therefore, if the expander (22) is used in the process of expanding the refrigerant of the intermediate pressure P _M to the low pressure P _L , even if some leakage occurs inside the fluid machine as the expander (22), the pressure accompanying The decrease is slight and the power obtained by the expander (22) is not significantly decreased.
And in an actual fluid machine, due to problems such as machining accuracy,
It is extremely difficult to completely prevent the leakage of the working fluid.

On the other hand, in the present embodiment, the expander (22) is provided downstream of the electric expansion valve (23), and the expander (22) is expanded in the process of expanding the intermediate pressure P _M refrigerant to the low pressure P _L. I am trying to use. Therefore, according to the present embodiment, even if the refrigerant leaks inside the expander (22), it is possible to minimize the decrease in the generated power resulting from this, and to reduce the internal energy of the expanding refrigerant. It can be reliably recovered as power.

[0101]

[Third Embodiment of the Invention] A third embodiment of the present invention is a modification of the configuration of the first embodiment, in which a so-called multi-effect refrigeration cycle is performed. That is, in this embodiment, the power consumption of the compressor motor (24) is reduced by performing the multi-effect refrigeration cycle. Here, regarding the configuration of the air conditioner according to the present embodiment,
The part different from is explained.

As shown in FIG. 5, the refrigerant circuit (10) of this embodiment is provided with a gas-liquid separator (32) instead of the receiver tank (31) of the first embodiment. The gas-liquid separator (32) is composed of a vertically long and cylindrical closed container, and is connected to the outflow side of the expander (22) by piping. The intermediate-pressure refrigerant in a gas-liquid two-phase state is sent from the expander (22) to the gas-liquid separator (32). Among the intermediate pressure refrigerants sent to the gas-liquid separator (32), the liquid refrigerant among them is the gas-liquid separator (3
2) It collects in the lower part and the gas refrigerant collects in the upper part in the gas-liquid separator (32).

The bottom of the gas-liquid separator (32) is connected to the inflow side of the electric expansion valve (23) by piping. The intermediate pressure liquid refrigerant stored in the gas-liquid separator (32) is stored in the electric expansion valve (23).
Sent to. On the other hand, the upper end of the gas-liquid separator (32) is connected to the compressor (21) by piping. The intermediate-pressure gas refrigerant stored in the gas-liquid separator (32) is sent to the compressor (21). That is, the pipe connecting the gas-liquid separator (32) and the compressor (21) constitutes the gas pipe line (33).

The low pressure gas refrigerant from the outdoor heat exchanger (12) or the indoor heat exchanger (11) and the intermediate pressure from the gas-liquid separator (32) are supplied to the compressor (21) of this embodiment. Gas refrigerant is being supplied. The compressor (21) is configured to compress the sucked low-pressure gas refrigerant and suck the intermediate-pressure gas refrigerant during the compression stroke.

In the present embodiment, the gas-liquid separator (3
By increasing or decreasing the amount of liquid refrigerant stored in 2), the refrigerant circuit (1
The amount of the refrigerant circulating in 0) can be changed. Therefore, the gas-liquid separator (32) of this embodiment is the same as that of the first embodiment.
It also has the function of the receiver tank (31).

-Driving Operation- << Heating Operation >> Regarding the heating operation of the air conditioner,
This will be described with reference to FIGS. 5 and 6. FIG. 6 shows the refrigeration cycle of the air conditioner on the Mollier diagram (pressure-enthalpy diagram).

During the heating operation, the first four-way selector valve (1
3) and the second four-way switching valve (14) are switched to the state shown by the solid line in FIG. When the compressor (21) is driven in this state, the refrigerant circulates in the refrigerant circuit (10) to perform the refrigeration cycle. At that time, the indoor heat exchanger (11) functions as a radiator, and the outdoor heat exchanger (12) functions as an evaporator.

Specifically, the compressor (21) discharges the high-pressure refrigerant in the state of the point in FIG. The pressure P _H of this high-pressure refrigerant is higher than its critical pressure P _C.
The refrigerant discharged from the compressor (21) is introduced into the indoor heat exchanger (11) through the first four-way switching valve (13).

In the indoor heat exchanger (11), the introduced high pressure refrigerant exchanges heat with indoor air. Due to this heat exchange, the high-pressure refrigerant radiates heat to the room air, and its enthalpy decreases from the point state to the point state. The high-pressure refrigerant in the state of the point passes through the second four-way switching valve (14) and the expander (2
2) to be introduced. On the other hand, the indoor air heated by the high-pressure refrigerant in the indoor heat exchanger (11) is sent back to the room as conditioned air.

The refrigerant in the point state after radiating heat in the indoor heat exchanger (11) expands in the expander (22), and its pressure and enthalpy decrease to the point state. That is,
In the expander (22), the high pressure refrigerant expands to become an intermediate pressure refrigerant having a pressure P _M. This intermediate pressure refrigerant has a pressure lower than its critical pressure P _C and is in a gas-liquid two-phase state. The intermediate pressure refrigerant flowing out from the expander (22) is sent to the gas-liquid separator (32).

The intermediate pressure refrigerant flowing into the gas-liquid separator (32) is separated into a liquid refrigerant in the state of point 'and a gas refrigerant in the state of point''. The liquid refrigerant in the state of point 'is the gas-liquid separator (3
2) to the electric expansion valve (23). Meanwhile, the point ''
The gas refrigerant in the state of is from the gas-liquid separator (32) to the compressor (2
Sent to 1).

In the electric expansion valve (23), the intermediate pressure liquid refrigerant is decompressed, and the pressure thereof is reduced from the point 'state to the point state. That is, by passing through the electric expansion valve (23), the intermediate-pressure liquid refrigerant is decompressed and becomes a low-pressure refrigerant having a pressure P _L. The low-pressure refrigerant in the state of the point is the second four-way switching valve (14).
And is introduced into the outdoor heat exchanger (12).

In the outdoor heat exchanger (12), the introduced low pressure refrigerant exchanges heat with outdoor air. By this heat exchange, the low-pressure refrigerant absorbs heat from the outdoor air, and its enthalpy increases from the point state to the point state. The low-pressure refrigerant in the point state flows out from the outdoor heat exchanger (12) and is sent to the compressor (21) through the first four-way switching valve (13).

As described above, the low pressure gas refrigerant in the state of the point and the intermediate pressure gas refrigerant in the state of the point ″ are supplied to the compressor (21). First, in the compressor (21), compression of the gas refrigerant in the dot state is started. The refrigerant in the compression process is mixed with the gas refrigerant in the state of point ″ at the point state, that is, when the pressure reaches the pressure P _M. The mixed gas refrigerant is in the state of point '. The refrigerant in this point 'state is continuously compressed in the compressor (21) to reach the point state. Then, the high-pressure refrigerant in the dot state is sent from the compressor (21) to the indoor heat exchanger (11).

In the expander (22), the pressure and enthalpy of the refrigerant decrease from point to point. Then, in the expander (22), power corresponding to the enthalpy difference between the points is obtained, and the obtained power is used to drive the compressor (21).

<< Cooling Operation >> The operation of the air conditioner during the cooling operation will be described with reference to FIGS. 5 and 6.

During the cooling operation, the first four-way selector valve (1
3) and the second four-way switching valve (14) are switched to the state shown by the broken line in FIG. When the compressor (21) is driven in this state, the refrigerant circulates in the refrigerant circuit (10) to perform the refrigeration cycle. At that time, the outdoor heat exchanger (12) functions as a radiator, and the indoor heat exchanger (11) functions as an evaporator.

Specifically, the compressor (21) discharges the high-pressure refrigerant in the state of the point in FIG. The pressure P _H of this high-pressure refrigerant is higher than its critical pressure P _C.
The refrigerant discharged from the compressor (21) is introduced into the outdoor heat exchanger (12) through the first four-way switching valve (13).

In the outdoor heat exchanger (12), the introduced high pressure refrigerant exchanges heat with outdoor air. By this heat exchange, the high-pressure refrigerant radiates heat to the outdoor air, and its enthalpy decreases from the point state to the point state. The high-pressure refrigerant in the state of the point passes through the second four-way switching valve (14) and the expander (2
2) to be introduced.

The refrigerant in the point state after radiating heat in the outdoor heat exchanger (12) expands in the expander (22), and its pressure and enthalpy decrease to the point state. That is,
In the expander (22), the high pressure refrigerant expands to become an intermediate pressure refrigerant having a pressure P _M. This intermediate pressure refrigerant has a pressure lower than its critical pressure P _C and is in a gas-liquid two-phase state. The intermediate pressure refrigerant flowing out from the expander (22) is sent to the gas-liquid separator (32).

The intermediate-pressure refrigerant flowing into the gas-liquid separator (32) is separated into a liquid refrigerant in the state of point 'and a gas refrigerant in the state of point''. The liquid refrigerant in the state of point 'is the gas-liquid separator (3
2) to the electric expansion valve (23). Meanwhile, the point ''
The gas refrigerant in the state of is from the gas-liquid separator (32) to the compressor (2
Sent to 1).

In the electric expansion valve (23), the intermediate pressure liquid refrigerant is decompressed, and the pressure thereof is reduced from the point 'state to the point state. That is, by passing through the electric expansion valve (23), the intermediate pressure refrigerant is decompressed and becomes a low pressure refrigerant having a pressure P _L. The low-pressure refrigerant in the point state is introduced into the indoor heat exchanger (11) through the second four-way switching valve (14).

In the indoor heat exchanger (11), the introduced low pressure refrigerant exchanges heat with indoor air. By this heat exchange, the low-pressure refrigerant absorbs heat from the indoor air, and its enthalpy increases from the point state to the point state. The low-pressure refrigerant in the state of point flows out from the indoor heat exchanger (11) and is sent to the compressor (21) through the first four-way switching valve (13). On the other hand, the indoor air cooled by the low-pressure refrigerant in the indoor heat exchanger (11) is sent back to the room as conditioned air.

As described above, the low pressure gas refrigerant in the point state and the intermediate pressure gas refrigerant in the point state '' are supplied to the compressor (21). First, in the compressor (21), compression of the gas refrigerant in the dot state is started. The refrigerant in the compression process is mixed with the gas refrigerant in the state of point ″ at the point state, that is, when the pressure reaches the pressure P _M. The mixed gas refrigerant is in the state of point '. The refrigerant in this point 'state is continuously compressed in the compressor (21) to reach the point state. Then, the high-pressure refrigerant in the dot state is sent from the compressor (21) to the outdoor heat exchanger (12).

In the expander (22), the pressure and enthalpy of the refrigerant drop from point to point. Then, in the expander (22), power corresponding to the enthalpy difference between the points is obtained, and the obtained power is used to drive the compressor (21).

[0126]

[Fourth Embodiment of the Invention] A fourth embodiment of the present invention is a modification of the configuration of the above-described second embodiment to perform a so-called multi-effect refrigeration cycle. That is, in this embodiment, the power consumption of the compressor motor (24) is reduced by performing the multi-effect refrigeration cycle. Here, regarding the configuration of the air conditioner according to this embodiment,
The part different from is explained.

As shown in FIG. 7, the refrigerant circuit (10) of this embodiment is provided with a gas-liquid separator (32) instead of the receiver tank (31) of the second embodiment. The gas-liquid separator (32) is composed of a vertically long and cylindrical hermetic container, and is connected to the outflow side of the electric expansion valve (23) by piping.
An intermediate pressure refrigerant in a gas-liquid two-phase state is sent to the gas-liquid separator (32) from the electric expansion valve (23). Among the intermediate-pressure refrigerant sent to the gas-liquid separator (32), the liquid refrigerant of the intermediate-pressure refrigerant accumulates in the lower part of the gas-liquid separator (32), and the gas refrigerant accumulates in the upper part of the gas-liquid separator (32).

The bottom of the gas-liquid separator (32) is connected to the inflow side of the expander (22) by piping. Gas-liquid separator (3
The intermediate-pressure liquid refrigerant stored in 2) is sent to the expander (22). On the other hand, the upper end of the gas-liquid separator (32) is connected to the compressor (21) by piping. The intermediate-pressure gas refrigerant stored in the gas-liquid separator (32) is sent to the compressor (21).
That is, the pipe connecting the gas-liquid separator (32) and the compressor (21) constitutes the gas pipe line (33).

The low pressure gas refrigerant from the outdoor heat exchanger (12) or the indoor heat exchanger (11) and the intermediate pressure from the gas-liquid separator (32) are supplied to the compressor (21) of this embodiment. Gas refrigerant is being supplied. The compressor (21) is configured to compress the sucked low-pressure gas refrigerant and suck the intermediate-pressure gas refrigerant during the compression stroke.

In the present embodiment, the gas-liquid separator (3
By increasing or decreasing the amount of liquid refrigerant stored in 2), the refrigerant circuit (1
The amount of the refrigerant circulating in 0) can be changed. Therefore, the gas-liquid separator (32) of this embodiment is the same as that of
It also has the function of the receiver tank (31).

-Driving Operation- The operation of the air conditioner of this embodiment during the heating operation will be described with reference to FIGS. 7 and 8. Note that FIG.
Is a Mollier diagram (pressure-enthalpy diagram) showing the refrigeration cycle of the air conditioner.

During the heating operation, the first four-way selector valve (1
3) and the second four-way switching valve (14) are switched to the state shown by the solid line in FIG. When the compressor (21) is driven in this state, the refrigerant circulates in the refrigerant circuit (10) to perform the refrigeration cycle. At that time, the indoor heat exchanger (11) functions as a radiator, and the outdoor heat exchanger (12) functions as an evaporator.

Specifically, the compressor (21) discharges the high-pressure refrigerant in the state of the point in FIG. The pressure P _H of this high-pressure refrigerant is higher than its critical pressure P _C.
The refrigerant discharged from the compressor (21) is introduced into the indoor heat exchanger (11) through the first four-way switching valve (13).

In the indoor heat exchanger (11), the introduced high pressure refrigerant exchanges heat with indoor air. Due to this heat exchange, the high-pressure refrigerant radiates heat to the room air, and its enthalpy decreases from the point state to the point state. The high-pressure refrigerant in the point state is sent to the electric expansion valve (23) through the second four-way switching valve (14). On the other hand, the indoor air heated by the high-pressure refrigerant in the indoor heat exchanger (11) is sent back to the room as conditioned air.

In the electric expansion valve (23), the high-pressure refrigerant is depressurized, and the pressure thereof drops from the point state to the point state. That is, by passing through the electric expansion valve (23), the high pressure refrigerant is decompressed and becomes the intermediate pressure refrigerant having the pressure P _M. This intermediate pressure refrigerant has a pressure lower than its critical pressure P _C and is in a gas-liquid two-phase state. Then, the intermediate-pressure refrigerant flowing out of the electric expansion valve (23) is sent to the gas-liquid separator (32).

The intermediate-pressure refrigerant flowing into the gas-liquid separator (32) is separated into the liquid refrigerant in the state of point 'and the gas refrigerant in the state of point''. The liquid refrigerant in the state of point 'is the gas-liquid separator (3
It is sent from 2) to the expander (22). On the other hand, the gas refrigerant in the state of the point '' is sent from the gas-liquid separator (32) to the compressor (21).

In the expander (22), the intermediate-pressure liquid refrigerant expands, and its pressure and enthalpy decrease to the point state. That is, in the expander (22), the intermediate-pressure liquid refrigerant expands to become the low-pressure refrigerant at the pressure P _L. The low-pressure refrigerant in the point state passes through the second four-way switching valve (14) and the outdoor heat exchanger (12).
Be introduced to.

In the outdoor heat exchanger (12), the introduced low pressure refrigerant exchanges heat with the outdoor air. By this heat exchange, the low-pressure refrigerant absorbs heat from the outdoor air, and its enthalpy increases from the point state to the point state. The low-pressure refrigerant in the point state flows out from the outdoor heat exchanger (12) and is sent to the compressor (21) through the first four-way switching valve (13).

As described above, the low pressure gas refrigerant in the point state and the intermediate pressure gas refrigerant in the point '' state are supplied to the compressor (21). First, in the compressor (21), compression of the gas refrigerant in the dot state is started. The refrigerant in the compression process is mixed with the gas refrigerant in the state of point ″ at the point state, that is, when the pressure reaches the pressure P _M. The mixed gas refrigerant is in the state of point '. The refrigerant in this point 'state is continuously compressed in the compressor (21) to reach the point state. Then, the high-pressure refrigerant in the dot state is sent from the compressor (21) to the indoor heat exchanger (11).

Further, in the expander (22), the pressure and enthalpy of the refrigerant decrease from the point'to the point state. Then, in the expander (22), power corresponding to the enthalpy difference between the point 'and the point is obtained, and the obtained power is used to drive the compressor (21).

<< Cooling Operation >> The operation of the air conditioner during the cooling operation will be described with reference to FIGS. 7 and 8.

During the cooling operation, the first four-way selector valve (1
3) and the second four-way switching valve (14) are switched to the state shown by the broken line in FIG. When the compressor (21) is driven in this state, the refrigerant circulates in the refrigerant circuit (10) to perform the refrigeration cycle. At that time, the outdoor heat exchanger (12) functions as a radiator, and the indoor heat exchanger (11) functions as an evaporator.

Specifically, the compressor (21) discharges the high-pressure refrigerant in the state of the point in FIG. The pressure P _H of this high-pressure refrigerant is higher than its critical pressure P _C.
The refrigerant discharged from the compressor (21) is introduced into the outdoor heat exchanger (12) through the first four-way switching valve (13).

In the outdoor heat exchanger (12), the introduced high pressure refrigerant exchanges heat with outdoor air. By this heat exchange, the high-pressure refrigerant radiates heat to the outdoor air, and its enthalpy decreases from the point state to the point state. The high-pressure refrigerant in the point state is sent to the electric expansion valve (23) through the second four-way switching valve (14).

In the electric expansion valve (23), the high-pressure refrigerant is decompressed, and the pressure thereof drops from the point state to the point state. That is, by passing through the electric expansion valve (23), the high pressure refrigerant is decompressed and becomes the intermediate pressure refrigerant having the pressure P _M. This intermediate pressure refrigerant has a pressure lower than its critical pressure P _C and is in a gas-liquid two-phase state. The intermediate pressure refrigerant flowing out from the electric expansion valve (23) is sent to the gas-liquid separator (32).

The intermediate pressure refrigerant flowing into the gas-liquid separator (32) is separated into the liquid refrigerant in the state of point 'and the gas refrigerant in the state of point''. The liquid refrigerant in the state of point 'is the gas-liquid separator (3
2) to the electric expansion valve (23). Meanwhile, the point ''
The gas refrigerant in the state of is from the gas-liquid separator (32) to the compressor (2
Sent to 1).

In the expander (22), the intermediate pressure refrigerant expands.
And its pressure and enthalpy drop to the point state.
It In other words, in the expander (22), the intermediate pressure refrigerant expands
Pressure P _LIt becomes a low pressure refrigerant. The low pressure refrigerant in the state of the point is
Guided to the indoor heat exchanger (11) through the second four-way switching valve (14)
Be entered.

In the indoor heat exchanger (11), the introduced low pressure refrigerant exchanges heat with indoor air. By this heat exchange, the low-pressure refrigerant absorbs heat from the indoor air, and its enthalpy increases from the point state to the point state. The low-pressure refrigerant in the state of point flows out from the indoor heat exchanger (11) and is sent to the compressor (21) through the first four-way switching valve (13). On the other hand, the indoor air cooled by the low-pressure refrigerant in the indoor heat exchanger (11) is sent back to the room as conditioned air.

As described above, the low pressure gas refrigerant in the point state and the intermediate pressure gas refrigerant in the point state '' are supplied to the compressor (21). First, in the compressor (21), compression of the gas refrigerant in the dot state is started. The refrigerant in the compression process is mixed with the gas refrigerant in the state of point ″ at the point state, that is, when the pressure reaches the pressure P _M. The mixed gas refrigerant is in the state of point '. The refrigerant in this point 'state is continuously compressed in the compressor (21) to reach the point state. Then, the high-pressure refrigerant in the dot state is sent from the compressor (21) to the outdoor heat exchanger (12).

In the expander (22), the pressure and enthalpy of the refrigerant decrease from the point'to the point. Then, in the expander (22), power corresponding to the enthalpy difference between the point 'and the point is obtained, and the obtained power is used to drive the compressor (21).

[0151]

Fifth Embodiment of the Invention A fifth embodiment of the present invention is a modification of the configuration of the first embodiment, in which a so-called two-stage compression refrigeration cycle is performed. That is, in this embodiment, the power consumption of the compressor motor (24) is reduced by performing the two-stage compression refrigeration cycle. here,
Regarding the configuration of the air conditioner according to the present embodiment, parts different from those in the first embodiment will be described.

As shown in FIG. 9, in the refrigerant circuit (10) of the present embodiment, the receiver tank (31) of the first embodiment is omitted and an intercooler (40) is provided instead. There is. The intercooler (40) includes a shell portion (41) in the form of a closed container, and a pipe portion (42) formed of a heat transfer tube and housed in the shell portion (41). The intermediate cooler (40) constitutes an intermediate heat exchanger. That is, the intercooler (40) is configured to exchange heat between the refrigerant stored in the shell portion (41) and the refrigerant flowing inside the pipe portion (42).

In this embodiment, the inflow side of the expander (22) and one end of the pipe section (42) of the intercooler (40) are both connected to the third port of the second four-way switching valve (14). Piping is connected. The other end of the pipe part (42) of the intercooler (40) is connected to the inflow side of the electric expansion valve (23) by piping. on the other hand,
The shell part (41) of the intercooler (40) has its inflow side pipe-connected to the outflow side of the expander (22) and its outflow side pipe-connected to the compressor (21).

To the compressor (21) of this embodiment, the low pressure gas refrigerant from the outdoor heat exchanger (12) or the indoor heat exchanger (11) and the shell portion (41) of the intercooler (40) are used. The intermediate pressure refrigerant from is supplied. Although not shown, the compressor (21) is provided with two compression mechanisms. And
This compressor (21) sucks the low-pressure refrigerant into the compression mechanism on the low-stage side and compresses it to an intermediate pressure, while discharging the intermediate-pressure refrigerant discharged from the compression mechanism on the low-stage side and the shell portion (41). The intermediate pressure refrigerant is sucked into the high-stage compression mechanism and compressed to a high pressure.

-Driving operation- << Heating operation >> Regarding the operation of the air conditioner during the heating operation,
This will be described with reference to FIGS. 9 and 10. Incidentally, FIG.
Is a Mollier diagram (pressure-enthalpy diagram) showing the refrigeration cycle of the air conditioner.

During the heating operation, the first four-way selector valve (1
3) and the second four-way switching valve (14) are switched to the state shown by the solid line in FIG. When the compressor (21) is driven in this state, the refrigerant circulates in the refrigerant circuit (10) to perform the refrigeration cycle. At that time, the indoor heat exchanger (11) functions as a radiator, and the outdoor heat exchanger (12) functions as an evaporator.

Specifically, the compressor (21) discharges the high-pressure refrigerant in the state of the point in FIG. The pressure P _H of this high-pressure refrigerant is higher than its critical pressure P _C. The refrigerant discharged from the compressor (21) is introduced into the indoor heat exchanger (11) through the first four-way switching valve (13).

In the indoor heat exchanger (11), the introduced high pressure refrigerant exchanges heat with indoor air. Due to this heat exchange, the high-pressure refrigerant radiates heat to the room air, and its enthalpy decreases from the point state to the point state. The high-pressure refrigerant in the state of the point passes through the second four-way switching valve (14) and the expander (2
2) to be introduced. On the other hand, the indoor air heated by the high-pressure refrigerant in the indoor heat exchanger (11) is sent back to the room as conditioned air.

The refrigerant in the state of the point after radiating heat in the indoor heat exchanger (11) passes through the second four-way switching valve (14) and is then split into two parts. One of the split refrigerants is introduced into the expander (22), and the other is inserted into the intercooler (4).
It is introduced into the pipe section (42) of (0).

In the expander (22), the high-pressure refrigerant in the point state expands, and its pressure and enthalpy decrease to the point state. That is, in the expander (22), the high pressure refrigerant expands to become an intermediate pressure refrigerant having a pressure P _M. This intermediate pressure refrigerant is
It is lower than the critical pressure P _C and is in a gas-liquid two-phase state. The intermediate pressure refrigerant flowing out from the expander (22) is
It is introduced into the shell part (41) of the intercooler (40).

In the intercooler (40), heat is exchanged between the high-pressure refrigerant flowing through the pipe section (42) and the intermediate-pressure refrigerant introduced into the shell section (41). Due to this heat exchange, the enthalpy of the high-pressure refrigerant flowing through the pipe portion (42) is lowered from the point state to the point state. The high-pressure refrigerant in this state flows out of the pipe portion (42) and is sent to the electric expansion valve (23). On the other hand, the intermediate pressure refrigerant introduced into the shell part (41) is
The enthalpy increases from the point state to the point state. The intermediate pressure refrigerant in this state is the shell part (41).
And is sent to the compressor (21).

In the electric expansion valve (23), the high-pressure refrigerant in the point state is depressurized, and the pressure is reduced to the point state. That is, by passing through the electric expansion valve (23), the high pressure refrigerant is decompressed and becomes a low pressure refrigerant having a pressure P _L. The low-pressure refrigerant in the point state is introduced into the outdoor heat exchanger (12) through the second four-way switching valve (14).

In the outdoor heat exchanger (12), the introduced low pressure refrigerant exchanges heat with outdoor air. By this heat exchange, the low-pressure refrigerant absorbs heat from the outdoor air, and its enthalpy increases from the point state to the point state. The low-pressure refrigerant in the point state flows out from the outdoor heat exchanger (12) and is sent to the compressor (21) through the first four-way switching valve (13).

As described above, the low pressure refrigerant in the dot state and the intermediate pressure refrigerant in the dot state are supplied to the compressor (21). In the compressor (21), the low-pressure refrigerant in the point state is sucked into the low-stage compression mechanism and is compressed into the point state. That is, in the low-stage compression mechanism, the refrigerant is boosted to the pressure P _M.

The point refrigerant discharged from the low-stage compression mechanism is mixed with the point refrigerant sent from the intercooler (40). By mixing these refrigerants, the refrigerant in the state of point 'is obtained. The refrigerant in the state of point 'is sucked into the compression mechanism on the higher stage side and compressed, and becomes the state of point. Then, the high-pressure refrigerant in the dot state is sent from the compressor (21) to the indoor heat exchanger (11).

In the expander (22), the pressure and enthalpy of the refrigerant drop from point to point. Then, in the expander (22), power corresponding to the enthalpy difference between the points is obtained, and the obtained power is used to drive the compressor (21).

In this embodiment, the expansion ratio of the expander (22) is constant, and the pressure of the refrigerant flowing out of the expander (22) changes in conjunction with the high pressure of the refrigeration cycle. In (), the high-pressure refrigerant is only expanded to the intermediate pressure. On the other hand, the electric expansion valve (23) reduces the pressure of the high-pressure refrigerant to a low pressure, but the opening degree of the electric expansion valve (23) can be adjusted. Therefore, even if the expansion ratio of the expander (22) is constant and does not change, the high pressure of the refrigeration cycle can be set to an optimum value for the operation of the air conditioner by adjusting the opening degree of the electric expansion valve (23). .

<Cooling Operation> The operation of the air conditioner during the cooling operation will be described with reference to FIGS. 9 and 10.

During the cooling operation, the first four-way selector valve (1
3) and the second four-way switching valve (14) are switched to the state shown by the broken line in FIG. When the compressor (21) is driven in this state, the refrigerant circulates in the refrigerant circuit (10) to perform the refrigeration cycle. At that time, the outdoor heat exchanger (12) functions as a radiator, and the indoor heat exchanger (11) functions as an evaporator.

Specifically, the high pressure refrigerant in the state of the point in FIG. 10 is discharged from the compressor (21). The pressure P _H of this high-pressure refrigerant is higher than its critical pressure P _C. The refrigerant discharged from the compressor (21) is introduced into the outdoor heat exchanger (12) through the first four-way switching valve (13).

In the outdoor heat exchanger (12), the introduced high pressure refrigerant exchanges heat with the outdoor air. By this heat exchange, the high-pressure refrigerant radiates heat to the outdoor air, and its enthalpy decreases from the point state to the point state.

After radiating heat in the outdoor heat exchanger (12), the refrigerant in the state of the point passes through the second four-way switching valve (14) and is then split into two. One of the split refrigerants is introduced into the expander (22), and the other is inserted into the intercooler (4).
It is introduced into the pipe section (42) of (0).

In the expander (22), the high-pressure refrigerant in the point state expands, and its pressure and enthalpy decrease to the point state. That is, in the expander (22), the high pressure refrigerant expands to become an intermediate pressure refrigerant having a pressure P _M. This intermediate pressure refrigerant is
It is lower than the critical pressure P _C and is in a gas-liquid two-phase state. The intermediate pressure refrigerant flowing out from the expander (22) is
It is introduced into the shell part (41) of the intercooler (40).

In the intercooler (40), heat is exchanged between the high-pressure refrigerant flowing through the pipe part (42) and the intermediate-pressure refrigerant introduced into the shell part (41). Due to this heat exchange, the enthalpy of the high-pressure refrigerant flowing through the pipe portion (42) is lowered from the point state to the point state. The high-pressure refrigerant in this state flows out of the pipe portion (42) and is sent to the electric expansion valve (23). On the other hand, the intermediate pressure refrigerant introduced into the shell part (41) is
The enthalpy increases from the point state to the point state. The intermediate pressure refrigerant in this state is the shell part (41).
And is sent to the compressor (21).

In the electric expansion valve (23), the high-pressure refrigerant in the point state is decompressed, and the pressure is reduced to the point state. That is, by passing through the electric expansion valve (23), the high pressure refrigerant is decompressed and becomes a low pressure refrigerant having a pressure P _L. The low-pressure refrigerant in the point state is introduced into the indoor heat exchanger (11) through the second four-way switching valve (14).

In the indoor heat exchanger (11), the introduced low pressure refrigerant exchanges heat with indoor air. By this heat exchange, the low-pressure refrigerant absorbs heat from the indoor air, and its enthalpy increases from the point state to the point state. The low-pressure refrigerant in the state of point flows out from the indoor heat exchanger (11) and is sent to the compressor (21) through the first four-way switching valve (13). On the other hand, the indoor air cooled by the low-pressure refrigerant in the indoor heat exchanger (11) is sent back to the room as conditioned air.

As described above, the low pressure refrigerant in the dot state and the intermediate pressure refrigerant in the dot state are supplied to the compressor (21). In the compressor (21), the low-pressure refrigerant in the point state is sucked into the low-stage compression mechanism and is compressed into the point state. That is, in the low-stage compression mechanism, the refrigerant is boosted to the pressure P _M.

The point refrigerant discharged from the low-stage compression mechanism is mixed with the point refrigerant sent from the intercooler (40). By mixing these refrigerants, the refrigerant in the state of point 'is obtained. The refrigerant in the state of point 'is sucked into the compression mechanism on the higher stage side and compressed, and becomes the state of point. Then, the high-pressure refrigerant in the dot state is sent from the compressor (21) to the outdoor heat exchanger (12).

In the expander (22), the pressure and enthalpy of the refrigerant drop from point to point. Then, in the expander (22), power corresponding to the enthalpy difference between the points is obtained, and the obtained power is used to drive the compressor (21).

In the present embodiment, the expansion ratio of the expander (22) is constant, and the pressure of the refrigerant flowing out of the expander (22) changes in conjunction with the high pressure of the refrigeration cycle. In (), the high-pressure refrigerant is only expanded to the intermediate pressure. On the other hand, the electric expansion valve (23) reduces the pressure of the high-pressure refrigerant to a low pressure, but the opening degree of the electric expansion valve (23) can be adjusted. Therefore, even if the expansion ratio of the expander (22) is constant and does not change, the high pressure of the refrigeration cycle can be set to an optimum value for the operation of the air conditioner by adjusting the opening of the electric expansion valve (23). .

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an air conditioner according to a first embodiment.

FIG. 2 is a Mollier diagram showing a refrigeration cycle of the air conditioner according to the first embodiment.

FIG. 3 is a schematic configuration diagram of an air conditioner according to a second embodiment.

FIG. 4 is a Mollier diagram showing a refrigeration cycle of the air conditioner according to the second embodiment.

FIG. 5 is a schematic configuration diagram of an air conditioner according to a third embodiment.

FIG. 6 is a Mollier diagram showing the refrigeration cycle of the air conditioner according to the third embodiment.

FIG. 7 is a schematic configuration diagram of an air conditioner according to a fourth embodiment.

FIG. 8 is a Mollier diagram showing the refrigeration cycle of the air conditioner according to the fourth embodiment.

FIG. 9 is a schematic configuration diagram of an air conditioner according to a fifth embodiment.

FIG. 10 is a Mollier diagram showing the refrigeration cycle of the air conditioner according to the fifth embodiment.

[Explanation of symbols]

(10) Refrigerant circuit (21) Compressor (22) Expander (23) Electric expansion valve (expansion valve) (31) Receiver tank (container member) (32) Gas-liquid separator (33) Gas pipeline (40) Intercooler (intermediate heat exchanger)

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI Theme Coat (Reference) F25B 43/00 F25B 43/00 EG

Claims (6)

[Claims] 1. A refrigeration cycle comprising a refrigerant circuit (10) filled with a refrigerant, wherein a compressor (21) provided in the refrigerant circuit (10) compresses the refrigerant to a pressure equal to or higher than a critical pressure of the refrigerant. A refrigerating apparatus for performing operation, wherein the refrigerant circuit (10) includes an expander (22) configured by a fluid machine having a constant internal volume ratio, and a variable opening degree connected in series with the expander (22). The expansion device (23) is provided as a refrigerant expansion mechanism. 2. The refrigeration apparatus according to claim 1, wherein in the refrigerant circuit (10), the expansion valve (2) is provided upstream of the expander (22).
3) The refrigeration equipment is located. 3. The refrigeration apparatus according to claim 1 or 2, wherein a container member (temporarily storing refrigerant) is provided between the expander (22) and the expansion valve (23) in the refrigerant circuit (10). 31)
Refrigeration equipment provided with. 4. The refrigerating apparatus according to claim 1, wherein the refrigerant circuit (10) is provided between the expander (22) and the expansion valve (23) to convert the intermediate pressure refrigerant into a liquid refrigerant and a gas refrigerant. And a gas-liquid separator (32) for separating into a compressor and a gas pipeline (33) for supplying the gas refrigerant separated by the gas-liquid separator (32) to the compressor (21). . 5. A refrigeration cycle comprising a refrigerant circuit (10) filled with a refrigerant, wherein a compressor (21) provided in the refrigerant circuit (10) compresses the refrigerant to a pressure equal to or higher than a critical pressure of the refrigerant. A refrigerating apparatus for performing, which comprises a fluid machine having a constant internal volume ratio and expands a part of the high-pressure refrigerant of the refrigerant circuit (10) to an intermediate pressure, and the refrigerant circuit (10). The remaining high pressure refrigerant of the expander (2
Intermediate heat exchanger (4) for exchanging heat with the intermediate pressure refrigerant from 2)
0) and an expansion valve (23) having a variable opening degree for expanding the high pressure refrigerant from the intermediate heat exchanger (40) to a low pressure, while the refrigerant circuit (10) includes the refrigerant circuit (10). The low pressure refrigerant from the expansion valve (23) is supplied to the evaporator provided in the compressor, and the low pressure refrigerant from the evaporator and the intermediate pressure refrigerant from the intermediate heat exchanger (40) are supplied to the compressor (21). Refrigeration equipment supplied with. 6. The refrigerating apparatus according to claim 1, 2, 3, 4 or 5, wherein the refrigerant circuit (10) is filled with carbon dioxide as a refrigerant.