WO2004109199A1

WO2004109199A1 - Air conditioner

Info

Publication number: WO2004109199A1
Application number: PCT/JP2004/007490
Authority: WO
Inventors: Hiromune Matsuoka
Original assignee: Daikin Industries, Ltd.
Priority date: 2003-06-06
Filing date: 2004-05-31
Publication date: 2004-12-16
Also published as: CN1723373A; JP2004361036A; AU2004245797B2; KR20050044931A; EP1632732B1; EP1632732A1; ES2380331T3; ATE541167T1; AU2004245797A1; US20060000224A1; KR100605797B1; EP1632732A4; CN100419344C

Abstract

In an air conditioner with utilization units, an increase in cost of components constituting a refrigerant circuit is restricted even when the maximum use pressure of the refrigerant circuit is raised. An air conditioner (1) has utilization units (5), a steam compression-type refrigerant circuit (10), and an accumulator (25). The refrigerant circuit (10) has a high-pressure portion (10a) and a low-pressure portion (10b). The high-pressure portion (10a) is constructed by connecting components through which a high-pressure refrigerant with the maximum use pressure of not less than 3.3 MPa can be passed. The low-pressure portion (10b) is constructed by connecting components through which only a low-pressure refrigerant with the maximum use pressure of less than 3.3 MPa can be passed. The accumulator (25) is one of the components constituting the low-pressure portion (10b) and capable of storing, as a liquid refrigerant, a refrigerant circulating in the refrigerant circuit (10). The refrigerant flowing in the low-pressure portion (10b) and the high-pressure portion (10a) is R410A.

Description

Air conditioner

Technical field

The present invention relates to an air conditioner, particularly to an air conditioner having a plurality of use units.

Background art

[0002] In an air conditioner used for air conditioning of buildings and the like, from the viewpoint of environmental issues, it is assumed that instead of R22, R407C, one of the HFC-based refrigerants, is replaced with a refrigerant used as a working refrigerant. Become, become.

An air conditioner used for air conditioning of such a building or the like has a plurality of usage units, so the operating load fluctuates greatly and the amount of circulating refrigerant in the refrigerant circuit fluctuates. And the amount of surplus refrigerant increases and decreases in the refrigerant circuit. This surplus refrigerant may be stored as a liquid refrigerant in an accumulator connected to the suction side of the compressor.

However, if the surplus refrigerant is stored in the accumulator, R407C is a non-azeotropic mixed refrigerant, so the evaporation process in the refrigeration cycle process, that is, the evaporation process of the refrigerant in the use side heat exchanger of the utilization unit ( During the cooling process (during cooling operation) and during the evaporation process of the refrigerant in the heat source side heat exchanger of the heat source unit (during heating operation), the composition of the refrigerant changes, and the gas phase in the accumulator is rich in R32, a low boiling point component. In the liquid phase in the accumulator, the high boiling point component R134a becomes rich. As a result, the refrigerant rich in R32 is sucked into the compressor and circulates in the refrigerant circuit, and the original performance of the R407C may not be obtained as the whole air conditioner.

On the other hand, in the past, the accumulator and the refrigerant pipe through which the high-pressure liquid refrigerant flows were connected by a bypass pipe to suppress the change in the composition of the refrigerant, or to detect the refrigerant composition and optimize it in response to the composition change. (See, for example, Patent Documents 1, 2, 3, and 4.) o In addition, surplus refrigerant is stored in a receiver connected to a refrigerant pipe through which high-pressure liquid refrigerant flows. Air conditioning equipment that suppresses the change in refrigerant composition during the evaporation process Some location (e.g., see Patent Document 5.) ₀

Patent Document 1: JP-A-8-35725

Patent Document 2: JP-A-10-220880

Patent Document 3: JP-A-10-332211

Patent Document 4: JP-A-11-173698

Patent Document 5: Japanese Patent Application Laid-Open No. 2001-183020

Disclosure of the invention

When the accumulator and the refrigerant pipe through which the high-pressure liquid refrigerant flows are connected by a bypass pipe as in the former air conditioner using R407C, there is a problem that the configuration and operation control of the refrigerant circuit become complicated. is there.

On the other hand, when a receiver is connected to a refrigerant pipe through which high-pressure liquid refrigerant flows instead of an accumulator, as in the latter air conditioner using R407C, the structure and operation of the refrigerant circuit are higher than the former. The control is not complicated and is excellent in that respect. However, recently, in the field of air conditioners used for air conditioning in buildings and the like, refrigerants with higher saturation pressure characteristics than R407C (for example, R410A) have been used to improve air conditioning capacity and downsize equipment. And HC-based refrigerants) have begun to be developed or commercialized. However, when a refrigerant having a saturation pressure characteristic higher than that of R407C is used, the maximum value of the operating pressure of the refrigerant flowing in the refrigerant circuit (with respect to the standard operating pressure) is higher than when R407C is used. In many cases, the pressure will be about IMPa higher. Hereinafter, the maximum working pressure will be higher.) Accordingly, the pressure resistance of the components that make up the refrigerant circuit must be increased. In particular, since air conditioners in buildings and the like have a larger size of components constituting the refrigerant circuit than relatively small air conditioners such as room air conditioners, a refrigerant circuit portion (hereinafter, referred to as a high pressure refrigerant) flows. When the maximum working pressure of the high pressure section increases, the pressure resistance of the components constituting the refrigerant circuit must be increased, and the cost tends to increase. For this reason, in an air conditioner provided with a receiver which is one of the components constituting the high-pressure section as described above, the thickness must be increased in order to increase the pressure resistance of the receiver. Costs will increase. An object of the present invention is to use a refrigerant having a saturation pressure characteristic higher than that of R407C in an air conditioner having a plurality of utilization units, so that even if the maximum operating pressure of the refrigerant circuit is high, the refrigerant circuit is An object of the present invention is to suppress an increase in the cost of the components that make up the system.

An air conditioner according to a first aspect of the present invention is an air conditioner including a plurality of use units, and includes a vapor compression type refrigerant circuit and an accumulator. The refrigerant circuit consists of a high-pressure section composed of parts that can flow high-pressure refrigerant with a maximum operating pressure of 3.3 MPa or more, and a low-pressure refrigerant with a maximum operating pressure of less than 3.3 MPa. And a low-pressure section configured by connecting flowable components. The accumulator is one of the components constituting the low-pressure section, and can store the refrigerant circulating in the refrigerant circuit as a liquid refrigerant. The refrigerant flowing through the low-pressure section and the high-pressure section is a pseudo-azeotropic mixed refrigerant, an azeotropic mixed refrigerant, or a single refrigerant.

When R407C is used as the working refrigerant of the air conditioner, the standard working pressure of the high pressure section is about 2. OMPa. For this reason, in an air conditioner that uses R407C as the working refrigerant, the maximum operating pressure in the high-pressure section is a standard operating pressure, which is about IMPa higher than OMPa. It is often 3MPa. For this reason, in the air conditioner using R407C as the working refrigerant, the components that make up the high-pressure section have a pressure resistance that can withstand 3.3 MPa! /

On the other hand, if a refrigerant having a saturation pressure characteristic higher than that of R407C is used, the maximum operating pressure of the high pressure section will exceed 3.3 MPa. It must have withstand pressure resistance. In particular, for containers and piping, instead of producing a material with the optimum thickness calculated from the maximum operating pressure of the high-pressure section and caulking, the standard operating pressure of standard products such as JIS, etc. A thick material that satisfies the above conditions is selected. For this reason, the use of a refrigerant having a saturation pressure characteristic higher than that of R407C results in a significant increase in the wall thickness, and the cost of the components constituting the refrigerant circuit increases unnecessarily. Would.

In order to suppress such an unnecessary increase in cost, an air conditioner that is effective in the present invention uses a pseudo-azeotropic mixed refrigerant or a common azeotropic mixed refrigerant as a refrigerant having a saturation pressure characteristic higher than R407C. In addition to using a boiling mixed refrigerant or a single refrigerant, an accumulator that can store excess refrigerant that increases or decreases due to fluctuations in the operating load of multiple utilization units is installed in the low-pressure section with a maximum operating pressure of less than 3.3 MPa. This eliminates the need for a receiver in the high-pressure section, and eliminates the need for components such as bypass pipes for preventing a change in refrigerant composition as in the case of using a non-azeotropic refrigerant mixture.

As a result, by using a refrigerant having a saturation pressure characteristic higher than that of R407C, even if the maximum operating pressure of the refrigerant circuit is increased, it is possible to suppress an increase in the cost of components constituting the refrigerant circuit.

An air conditioner according to a second invention includes a compressor, a heat source side heat exchange, an expansion mechanism, a plurality of use side heat exchanges, a cutting structure, and an accumulator. The compressor compresses the low-pressure gas refrigerant and discharges the high-pressure gas refrigerant. The heat source side heat exchanger can function as an evaporator and a condenser. The plurality of utilization side heat exchangers are connected in parallel with each other and can function as a condenser and an evaporator. The expansion mechanism is connected between the use side heat exchange ^^ and the heat source side heat exchange ^^. In the cutting system, the gas side of the heat source side heat exchanger is connected to the discharge side of the compressor, and the suction side of the compressor is connected to the gas side of the utilization side heat exchanger to draw the low-pressure gas refrigerant into the compressor. The state and the gas side of the heat source side heat exchanger are connected to the suction side of the compressor, and the discharge side of the compressor is connected to the gas side of the use side heat exchanger, so that high-pressure gas refrigerant is connected to the use side heat exchanger. It is possible to switch between the flowing state. The accumulator is connected between the cutting structure and the suction side of the compressor, and can store low-pressure refrigerant as liquid refrigerant. The low-pressure section including the accumulator and configured by connecting the cutting mechanism and the suction side of the compressor can flow only a low-pressure refrigerant having a maximum operating pressure of less than 3.3 MPa. Excluding the low-pressure section, the high-pressure section, which is connected to the compressor, heat source-side heat exchanger, multiple use-side heat exchangers, and switching mechanism, has a maximum operating pressure of 3.3 MPa or higher. It is possible to flow a refrigerant. The refrigerant flowing through the low-pressure section and the high-pressure section is a pseudo-azeotropic mixed refrigerant, an azeotropic mixed refrigerant, or a single refrigerant having a saturation pressure characteristic higher than that of R407C.

When using R407C as the working refrigerant for the air conditioner, the standard working pressure of the high pressure section is about 2. OMPa. Therefore, air conditioning equipment that uses R407C as the working refrigerant In most cases, the maximum working pressure of the high pressure section is 3.0-3.3 MPa, which is about IMPA higher than the standard working pressure of 2. OMPa. For this reason, in the air conditioner using R407C as the working refrigerant, the components that make up the high-pressure section have a pressure resistance that can withstand 3.3 MPa! /

In order to suppress such an unnecessary increase in cost, an air conditioner that is effective in the present invention uses a pseudo-azeotropic mixed refrigerant, an azeotropic mixed refrigerant, or a single azeotropic mixed refrigerant as a refrigerant having a saturation pressure characteristic higher than R407C. In addition to the use of refrigerant, an accumulator capable of storing excess refrigerant that increases or decreases due to fluctuations in the operating load of the multiple use-side heat exchangers is installed in the low-pressure section with a maximum operating pressure of less than 3.3 MPa. Therefore, a receiver is not required in the high-pressure section, and components such as a bypass tube for preventing a change in the composition of the refrigerant as in the case of using a non-azeotropic mixed refrigerant are unnecessary.

The air conditioner according to the third invention is the air conditioner according to the second invention, further comprising: a heat source side temperature detector, a use side temperature detector, and a high pressure detector. ing. The heat source side temperature detector detects a refrigerant temperature on the liquid side of the heat source side heat exchanger. The use-side temperature detector detects the refrigerant temperature on the liquid side of each use-side heat exchanger. The high pressure detector detects the refrigerant pressure on the discharge side of the compressor. Then, the air conditioner uses the heat source side temperature detector, the use side temperature detector, and the cooling Based on medium temperature and refrigerant pressure! When the heat source side heat exchanger functions as a condenser, the degree of opening of the expansion mechanism is adjusted so that the liquid refrigerant on the liquid side of the heat source side heat exchanger is in a predetermined supercooled state. When the use-side heat exchange functions as a condenser, the opening degree of the expansion mechanism is adjusted so that the liquid refrigerant on the liquid side of the use-side heat exchange becomes a predetermined supercooled state.

In this air conditioner, when the heat-source-side heat exchanger functions as a condenser, such as during cooling operation, the condensed refrigerant is placed in a predetermined supercooled state to increase or decrease according to the operating load. Surplus refrigerant can be reliably stored in the accumulator. In addition, even when the use-side heat exchanger functions as a condenser, such as during a heating operation, by setting the condensed refrigerant to a predetermined supercooled state, surplus refrigerant that increases or decreases according to the operating load can be reliably reduced. It can be stored in the accumulator.

An air conditioner according to a fourth invention is the air conditioner according to any one of the first to third inventions, wherein the refrigerant flowing through the low-pressure section and the high-pressure section includes R32.

In this air conditioner, since the refrigerant having high heat transfer capacity and using R32 is used, the air conditioning capacity can be improved.

An air conditioner according to a fifth invention is the air conditioner according to any of the first to third inventions, wherein the refrigerant flowing through the low-pressure section and the high-pressure section is R410A.

Since this air conditioner uses R410A, the air conditioning capacity can be improved more than R407C.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic refrigerant circuit diagram of an air conditioner as one embodiment of the present invention.

FIG. 2 is a Mollier chart showing a refrigeration cycle of the air conditioner.

FIG. 3 is a diagram showing the relationship between operating pressure and wall thickness.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the air conditioner of the present invention will be described with reference to the drawings.

(1) Overall configuration of the air conditioner

FIG. 1 is a schematic refrigerant circuit diagram of an air conditioner 1 as one embodiment of the present invention. The air conditioner 1 is, for example, a device used for cooling and heating a building or the like, and includes a heat source unit. 2 and a plurality of (two in this embodiment) use units 5 connected in parallel with the liquid refrigerant communication pipe 6 and the gas refrigerant communication pipe for connecting the heat source unit 2 and the use unit 5 And 7.

In this embodiment, the air conditioner 1 uses R410A (R32: 50 wt%, R125: 50 wt%), which is a pseudo-azeotropic mixed refrigerant having a saturation pressure characteristic higher than that of R407C, as a working refrigerant. R410A contains more R32 with high heat transfer capacity than R407C, and the air conditioning capacity of the air conditioner 1 is improved.

(2) Usage unit configuration

The usage unit 5 mainly includes a usage-side expansion valve 51, a usage-side heat exchanger 52, and a pipe connecting these components.

The use-side expansion valve 51 is an electric expansion valve connected to the liquid side of the use-side heat exchanger 52 for adjusting the refrigerant pressure / controlling the refrigerant flow rate in the present embodiment.

In the present embodiment, the use-side heat exchanger 52 functions as a refrigerant evaporator during cooling operation to cool indoor air, and functions as a refrigerant condenser to heat indoor air during heating operation. It is an exchanger. Further, the use side heat exchanger 52 is provided with a use side temperature detector 53 for detecting a refrigerant temperature. In the present embodiment, the use-side temperature detector 53 is a thermistor arranged on the liquid side of the use-side heat exchange 52.

(3) Configuration of heat source unit

The heat source unit 2 mainly includes a compressor 21, a four-way switching valve 22, a heat source side heat exchange 23, a heat source side expansion valve 24, an accumulator 25, a liquid side gate valve 26, and a gas side gate. It is composed of a valve 27 and a pipe connecting these.

In the present embodiment, the compressor 21 is a variable displacement compressor that compresses a low-pressure gas refrigerant and discharges a high-pressure gas refrigerant. On the discharge side of the compressor 21, a high-pressure pressure detector 28 including a pressure sensor for detecting the pressure of the high-pressure gas refrigerant is provided. The four-way switching valve 22 is a valve for switching the direction of the refrigerant flow when switching between the cooling operation and the heating operation. During the cooling operation, the discharge side of the compressor 21 and the heat source side heat exchanger 2 3 And the suction side of the compressor 21 (specifically, the accumulator 25) and the gas refrigerant communication pipe 7 side (see the solid line of the four-way switching valve 22 in FIG. 1). operation In some cases, it is possible to connect the discharge side of the compressor 21 and the gas refrigerant communication pipe 7 side and to connect the suction side of the compressor 21 and the gas side of the heat source side heat exchange 23 (four-way in FIG. 1). (See dashed line for switching valve 22).

In the present embodiment, the heat source side heat exchanger 23 functions as a condenser for the refrigerant using the outdoor air or water as a heat source during the cooling operation, and as a refrigerant evaporator using the outdoor air or water as the heat source during the heating operation. A functioning heat exchange ^^. The heat source side heat exchanger is provided with a heat source side temperature detector 29 for detecting a refrigerant temperature. In the present embodiment, the heat source side temperature detector 29 is a thermistor arranged on the liquid side of the heat source side heat exchange 23. The heat-source-side expansion valve 24 is connected to the liquid side of the heat-source-side heat exchanger 23, and in this embodiment, adjusts the refrigerant flow rate between the heat-source-side heat exchanger 23 and the use-side heat exchanger 52. It is an electric expansion valve for performing such operations.

The accumulator 25 is connected between the four-way switching valve 22 and the compressor 21, and is a container for storing low-pressure refrigerant and excess refrigerant sucked into the compressor 21.

The liquid-side gate valve 26 and the gas-side gate valve 27 are connected to the liquid refrigerant communication pipe 6 and the gas refrigerant communication pipe 7, respectively. The liquid refrigerant communication pipe 6 connects between the liquid side of the use side heat exchange 52 of the use unit 5 and the liquid side of the heat source side heat exchange 23 of the heat source unit 2. The gas refrigerant communication pipe 7 connects between the gas side of the use side heat exchanger 52 of the use unit 5 and the four-way switching valve 22 of the heat source unit 2.

The use-side expansion valve 51, use-side heat exchanger 52, compressor 21, four-way switching valve 22, heat-source-side heat exchanger 23, heat-source-side expansion valve 24, accumulator 25, liquid-side gate valve 26, The refrigerant circuit to which the gas-side gate valve 27 is sequentially connected is referred to as the refrigerant circuit 10 of the air conditioner 1.

(3) Operation of air conditioner

Next, the operation of the air conditioner 1 under standard use conditions will be described with reference to FIGS. Here, FIG. 2 is a Mollier chart showing a refrigeration cycle of the air conditioner 1.

During the cooling operation, the four-way switching valve 22 is in the state shown by the solid line in FIG. The discharge side is connected to the gas side of the heat source side heat exchanger 23, and the suction side of the compressor 21 is connected to the gas side of the use side heat exchanger 52. Also liquid

The side gate valve 26 and the gas side gate valve 27 are opened, and the use side expansion valve 51 is fully opened. The opening of the heat source side expansion valve 24 can be adjusted by supercooling control of the high pressure detector 28 and the heat source side temperature detector 29. More specifically, the temperature difference between the saturation temperature corresponding to the pressure value of the high-pressure gas refrigerant detected by the high-pressure pressure detector 28 and the temperature value of the high-pressure liquid refrigerant detected by the heat source-side temperature detector 29 Based on this, the degree of subcooling of the high-pressure liquid refrigerant is calculated, and the degree of opening of the heat-source-side expansion valve 24 can be adjusted so that the degree of subcooling becomes a predetermined value.

When the compressor 21 is started in the state of the refrigerant circuit 10, the low-pressure gas refrigerant (pressure Ps = approximately 0.9 MPa, temperature Ts = approximately 15 ° C) is sucked into the compressor 21 to be compressed, and the high-pressure gas refrigerant is compressed. Gas refrigerant (pressure Pd = about 3. OMPa, temperature Td = about 70 ° C) (see points A and B in Fig. 2). Thereafter, the high-pressure gas refrigerant is sent to the heat-source-side heat exchanger 23 via the four-way switching valve 22, and is condensed by performing heat exchange with outdoor air or water as a heat source, and is condensed at the pressure Pd. Slightly lower than the saturation temperature Tsat (temperature about 50 ° C) !, it is cooled to temperature Tc (temperature about 45 ° C) (see point C in Fig. 2). Here, the degree of supercooling ATc of the high-pressure liquid refrigerant in the state at the point C (that is, Tsat-Tc) is kept constant (here, ATc = about 5 ° C) by the supercooling control of the heat source side expansion valve 24. I'm dripping.

Then, the condensed liquid refrigerant is reduced in pressure according to the opening of the heat source side expansion valve 24 to become a low-pressure gas-liquid two-phase refrigerant (pressure Ps = about 0.9 MPa, temperature TD = about 3 ° C.) It is sent to the user unit 5 via the liquid side gate valve 26 and the liquid refrigerant communication pipe 6 (see point D in FIG. 2). The gas-liquid two-phase refrigerant sent to the usage unit 5 passes through the usage-side expansion valve 51, exchanges heat with the indoor air in the usage-side heat exchanger 52, evaporates, and returns to the low-pressure gas. Refrigerant (pressure Ps = about 0.9MPa, temperature Ts = about 15 ° C) (see point A in Fig. 2). The low-pressure gas refrigerant flows into the accumulator 25 via the gas refrigerant communication pipe 7, the gas-side gate valve 27, and the four-way switching valve 22. Then, the low-pressure gas refrigerant flowing into the accumulator 25 is sucked into the compressor 21 again.

As described above, the state of the point C is set by the supercooling control of the heat-source-side expansion valve 24. Since the degree of subcooling ATc of the high-pressure liquid refrigerant is maintained at a constant level, even if the operating load of the usage unit 5 fluctuates and the amount of circulating refrigerant changes, the state is as shown in the refrigeration cycle shown in Fig. 2. The change is maintained, and the excess refrigerant is accumulated in the accumulator 25.Also, when the low-pressure liquid refrigerant flows into the accumulator 25 together with the low-pressure gas refrigerant from the use-side heat exchanger 52, or when the excess refrigerant is accumulated in the accumulator 25. When the refrigerant is accumulated, gas-liquid separation of the low-pressure gas refrigerant and the liquid refrigerant is performed in the accumulator 25, and only the low-pressure gas refrigerant is sucked into the compressor 21. At this time, in this embodiment, R410A, which is one of the pseudo-azeotropic mixed refrigerants, is used as the working refrigerant, and therefore, the low-pressure low-pressure suctioned into the compressor 21 is performed by the gas-liquid separation in the accumulator 25. The refrigerant composition of the gas refrigerant and the refrigerant composition of the liquid refrigerant accumulated in the accumulator 25 are kept constant.

During the heating operation, the four-way switching valve 22 is in the state shown by the broken line in FIG. 1, that is, the discharge side of the compressor 21 is connected to the gas side of the use side heat exchanger 52, and the suction side of the compressor 21 is heated. The source side heat exchange 23 is connected to the gas side. Further, the liquid-side gate valve 26 and the gas-side gate valve 27 are opened, and the heat-source-side expansion valve 24 is fully opened. The use-side expansion valve 51 is in a state in which the opening degree can be adjusted by supercooling control of the high-pressure pressure detector 28 and the use-side temperature detector 53. More specifically, the temperature difference between the saturation temperature corresponding to the pressure value of the high-pressure gas refrigerant detected by the high-pressure pressure detector 28 and the temperature value of the high-pressure liquid refrigerant detected by the use-side temperature detector 53 is calculated. The degree of supercooling of the high-pressure liquid refrigerant is calculated based on this, and the degree of opening of the usage-side expansion valve 51 can be adjusted so that the degree of subcooling becomes a predetermined value.

When the compressor 21 is started in the state of the refrigerant circuit 10, the low-pressure gas refrigerant is sucked into the compressor 21 and compressed to become a high-pressure gas refrigerant. It is sent to the use unit 5 via the valve 27 and the gas refrigerant communication pipe 7. The high-pressure gas refrigerant sent to the use unit 5 is condensed by exchanging heat with room air in the use-side heat exchanger 52, and is slightly lower than the saturation temperature of the high-pressure gas refrigerant! It is cooled down. Here, the degree of supercooling of the high-pressure liquid refrigerant in the state at the point C is determined by the use-side expansion valve 51 Is kept constant by the supercooling control. The condensed liquid refrigerant is reduced in pressure according to the degree of opening of the use-side expansion valve 51 to become a low-pressure gas-liquid two-phase refrigerant, passes through the liquid refrigerant communication pipe 6 and the liquid-side gate valve 26, and passes through the heat source unit 2. Sent to Then, the gas-liquid two-phase refrigerant sent to the heat source unit 2 passes through the heat source side expansion valve 24 and then evaporates by performing heat exchange with outdoor air or water as a heat source in the heat source side heat exchanger 23. Then, the gas refrigerant again becomes a low-pressure gas refrigerant and flows into the accumulator 25 via the four-way switching valve 22. Then, the low-pressure gas refrigerant flowing into the accumulator 25 is sucked into the compressor 21 again.

As described above, during the heating operation, the flow of the refrigerant is opposite to that during the cooling operation, and the difference is that the supercooling control is performed by the use-side expansion valve 51. Is similar to the state change of the refrigeration cycle shown in FIG.

(4) Design pressure of parts that make up the refrigerant circuit

As can be understood from the description of the operation of the air conditioner 1 during the cooling operation and the heating operation, the refrigerant circuit 10 includes only the high-pressure part 10a, which is a refrigerant circuit part through which the high-pressure refrigerant flows, and the low-pressure refrigerant. And a low-pressure section 10b, which is a refrigerant circuit section. Specifically, the low-pressure section 10b is a section where the four-way switching valve 22 including the accumulator 25 and the suction side of the compressor 21 are connected, and the high-pressure section 10a is connected to the low-pressure section 10b of the refrigerant circuit 10. Excluded parts.

Here, the components constituting the high-pressure section 10a (specifically, the compressor 21, the four-way switching valve 22, the heat source side heat exchanger 23, the heat source side expansion valve 24, the liquid side gate valve 26, and the gas side gate valve 27, The use-side expansion valve 51, use-side heat exchanger 52) and piping should take into account the allowance of about IMPa with respect to the standard working pressure (about 3. OMPa) of the high-pressure refrigerant described above. It is designed to be able to flow high-pressure refrigerant at the maximum operating pressure (about 4MPa). In addition, the components (specifically, the accumulator 25) and the piping constituting the low-pressure section 10b have a margin of about IMPa with respect to the standard operating pressure of the low-pressure refrigerant (about 0.9 MPa). Considering this, it is designed to be able to flow a low-pressure refrigerant at the maximum working pressure (about 2 MPa)!

(5) Features of air conditioners

The air conditioner 1 of the present embodiment has the following features.

(A) In the air conditioner 1 of the present embodiment, R410A is used as a refrigerant having a saturation pressure characteristic higher than that of R407C, and a plurality of usage units 5 are operated in the low pressure section 10b having a maximum operating pressure of less than 3.3 MPa. Since the accumulator 25 capable of storing the surplus refrigerant that increases and decreases due to the fluctuation of the load is provided, it is not necessary to provide a receiver in the high-pressure section 10a.

As a result, in the air conditioner 1, the use of a refrigerant having a saturation pressure characteristic higher than that of R407C increases the cost of components constituting the refrigerant circuit even when the maximum operating pressure of the refrigerant circuit is increased. It is possible to suppress.

The effect of suppressing this increase in cost is that when the maximum operating pressure of the refrigerant circuit is increased by using R410A as the working refrigerant, the case where the accumulator 25 is provided in the low-pressure section 10b as in the present embodiment is considered. This will be described by comparing with a conventional case where a receiver (not shown) is provided in the high-voltage unit 10a.

For example, if a cylindrical accumulator 25 with a nominal diameter of 10 inches and a receiver are processed using JIS standard STPG370E (carbon steel pipe for pressure piping) as a material, schedule 20 (wall thickness 6. 4mm) or schedule 30 (wall thickness 7.8mm) may be selected. Then, as shown in the relationship diagram between the working pressure and the wall thickness in FIG. 3, the material of schedule 20 can be used up to the working pressure of 3.3 MPa, and the material of schedule 30 can be used at 4.3 MPa. It is possible to use up to.

Here, since the maximum operating pressure of the accumulator 25 is about 2. OMPa (the maximum operating pressure of the low-pressure section 10b), even the material of schedule 20 has a sufficient pressure resistance and can be selected. . On the other hand, the maximum working pressure of the receiver is about 4.OMPa (maximum working pressure of the high-pressure section 10a), so the material of schedule 20 cannot be used, and the force is about 7. Even though a wall thickness of 4mm is enough, you must select a material for schedule 30.

As described above, when R407C is used as the working refrigerant of the air conditioner, since the maximum working pressure of the high-pressure section is 3.0-3.3 MPa, it is possible to use the material of schedule 20. However, when a refrigerant having a saturation pressure characteristic higher than that of R407C such as R410A is used as in this embodiment, a receiver is used as a container for storing excess refrigerant. If used, the wall thickness will increase significantly, and the cost of the components constituting the refrigerant circuit will increase unnecessarily. In other words, as described above, when using a refrigerant having a higher saturation pressure characteristic than R407C such as R410A, it is more costly to use an accumulator instead of a receiver as a container for storing excess refrigerant. Being repressed

(B)

In addition, since R410A is a pseudo-azeotropic mixed refrigerant, even if the accumulator 25 is used as a container for storing the surplus refrigerant, the composition of the refrigerant is prevented from changing as in the case of using a non-azeotropic mixed refrigerant such as R407C. This eliminates the need for components such as bypass pipes, thereby making it possible to suppress an increase in the cost of components constituting the refrigerant circuit.

(C)

Further, in the air conditioner 1, during the cooling operation, the temperature difference between the pressure value of the high-pressure gas refrigerant detected by the high-pressure pressure detector 28 and the temperature value of the high-pressure liquid refrigerant detected by the heat source side temperature detector 29 is determined. The degree of supercooling of the high-pressure liquid refrigerant is calculated based on the above equation, and the degree of opening of the heat source side expansion valve 24 can be adjusted so that the degree of subcooling becomes a predetermined value. As a result, the surplus refrigerant that increases and decreases can be reliably stored in the accumulator 25. Also, during the heating operation, the high-pressure gas refrigerant detected by the high-pressure pressure detector 28 and the high-pressure liquid refrigerant detected by the use-side temperature detector 53 have a high-pressure difference based on the temperature difference. The degree of supercooling of the liquid refrigerant is calculated, and the degree of opening of the usage side expansion valve 51 can be adjusted so that the degree of supercooling becomes a predetermined value. Can be reliably stored in the accumulator 25.

(6) Other embodiments

Although the embodiments of the present invention have been described with reference to the drawings, the specific configuration can be changed without departing from the spirit of the invention, which is not limited to these embodiments.

(A)

The air-conditioning apparatus of the embodiment has a refrigerant circuit capable of cooling and heating operations, but is not limited to this, and is a cooling-only or heating-only refrigerant circuit without a four-way switching valve. The present invention may be applied to an air conditioner having

(B)

In the above-described embodiment, R410A, which is one of the pseudo-azeotropic mixed refrigerants, is employed as the working refrigerant, but is not limited thereto, and R32: R125 such as R410B (R32: 45 wt%, R125: 55 wt%), etc. A pseudo-azeotropic mixed refrigerant having a composition ratio different from that of R410A, a single refrigerant such as R32, or another pseudo-azeotropic mixed refrigerant or another azeotropic mixed refrigerant may be employed.

Industrial applicability

According to the present invention, the maximum operating pressure of the refrigerant circuit can be increased by using a refrigerant having a saturation pressure characteristic higher than that of R407C in an air conditioner having a plurality of usage units. In addition, it is possible to suppress an increase in the cost of the components constituting the refrigerant circuit.

Claims

The scope of the claims

[1] An air conditioner (1) having a plurality of utilization units (5),

It is possible to flow only the high-pressure section (10a), which is connected to parts that can flow high-pressure refrigerant with a maximum operating pressure of 3.3 MPa or more, and low-pressure refrigerant with a maximum operating pressure of less than 3.3 MPa. A vapor compression type refrigerant circuit (10) having a low pressure part (10b) configured by connecting possible parts;

An accumulator (25), which is one of components constituting the low-pressure section and is capable of storing a refrigerant circulating in the refrigerant circuit as a liquid cooling medium,

The refrigerant flowing through the low-pressure section and the high-pressure section is a pseudo-azeotropic mixed refrigerant, an azeotropic mixed refrigerant, or a single refrigerant having a saturation pressure characteristic higher than R407C.

Air conditioner (1).

[2] A compressor (21) that compresses a low-pressure gas refrigerant and discharges a high-pressure gas refrigerant,

Heat source side heat exchange that can function as an evaporator and condenser (23), and multiple use side heat exchanges that are connected in parallel and can function as a condenser and evaporator (52) When,

An expansion mechanism (24, 5) connected between the use side heat exchange ^^ and the heat source side heat exchange ^^.

1) and

The gas side of the heat source side heat exchanger is connected to the discharge side of the compressor, and the suction side of the compressor is connected to the gas side of the utilization side heat exchanger to suck a low-pressure gas refrigerant into the compressor. And the gas side of the heat source side heat exchanger is connected to the suction side of the compressor, and the discharge side of the compressor is connected to the gas side of the utilization side heat exchanger to supply high pressure gas refrigerant to the compressor. It is connected between the switching mechanism (22) and the switching mechanism and the suction side of the compressor that can switch the state of flowing to the use side heat exchange, and can store low-pressure refrigerant as liquid refrigerant. With an accumulator (25),

The low-pressure part (10b) including the accumulator and configured by connecting the switching mechanism and the suction side of the compressor can flow only low-pressure refrigerant having a maximum operating pressure of less than 3.3 MPa. Yes, The high-pressure section (10a), which is a section excluding the low-pressure section and which is connected to the compressor, the heat-source-side heat exchanger, the plurality of use-side heat exchangers ^, and the cutting structure, has a maximum capacity. It is possible to flow a high-pressure refrigerant whose operating pressure is 3.3MPa or more.

Air conditioner (1).

[3] A heat source side temperature detector (29) for detecting a refrigerant temperature on a liquid side of the heat source side heat exchanger (23), and a refrigerant temperature on a liquid side of each of the use side heat exchangers (52). A usage-side temperature detector (53); and a high-pressure pressure detector (28) for detecting a refrigerant pressure on a discharge side of the compressor (21).

Based on the refrigerant temperature and the refrigerant pressure values detected by the heat source side temperature detector, the utilization side temperature detector, and the high pressure detector, the heat source side heat exchanger serves as a condenser. When functioning, the opening degree of the expansion mechanism (24) is adjusted so that the liquid refrigerant on the liquid side of the heat source side heat exchanger is in a predetermined supercooled state, and the use side heat exchanger is When functioning as, the opening degree of the expansion mechanism (51) is adjusted so that the liquid refrigerant on the liquid side of the use side heat exchange is in a predetermined supercooled state.

The air conditioner (1) according to claim 2.

[4] The air-conditioning apparatus (1) according to any one of claims 13 to 13, wherein the refrigerant flowing through the low-pressure section (10b) and the high-pressure section (10a) contains R32.

5. The air conditioner (1) according to claim 13, wherein the refrigerant flowing through the low-pressure section (10b) and the high-pressure section (10a) is R410A.