GB2534789A

GB2534789A - Refrigeration cycle device, air conditioning device, and method for calculating circulation composition in refrigeration cycle device

Info

Publication number: GB2534789A
Application number: GB1608160.6A
Authority: GB
Inventors: Ishimura Katsuhiro; Tanaka Kosuke; Yamashita Koji
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2014-01-30
Filing date: 2014-01-30
Publication date: 2016-08-03
Anticipated expiration: 2034-01-30
Also published as: JP6072311B2; JPWO2015114774A1; WO2015114774A1; GB2534789B; GB201608160D0

Abstract

A refrigeration cycle device equipped with a control device (50) having: an excess refrigerant determination means, which determines whether excess refrigerant is present in an accumulator (14); and a refrigerant composition calculation means that uses a different method to calculate a circulation composition when the excess refrigerant determination means determines that excess refrigerant is not present than when the excess refrigerant determination means determines that excess refrigerant is present, said circulation composition being the composition of at least one refrigerant component of multiple refrigerant components when a non-azeotropic refrigerant mixture is circulating in a refrigerant circulation circuit (1).

Description

DESCRIPTION Title of Invention REFRIGERATION CYCLE APPARATUS, AIR-CONDITIONING APPARATUS, AND METHOD FOR CALCULATING CIRCULATION COMPOSITION IN

REFRIGERATION CYCLE APPARATUS

Technical Field

[0001] The present invention relates to a refrigeration cycle apparatus, an air-conditioning apparatus applied to, for example, a multi-air-conditioning apparatus for building, and a method for calculating a circulation composition in a refrigeration cycle apparatus.

Background Art

[0002] As an existing refrigeration cycle apparatus, there is a refrigeration cycle apparatus that includes: a refrigerant circuit filled with a refrigerant mixture such as a zeotropic refrigerant mixture; and a controller. The controller calculates a circulation composition that is a composition of at least one refrigerant component among a plurality of refrigerant components in a state where the refrigerant mixture circulates through the refrigerant circuit. The controller controls, for example, an operation of a compressor in the refrigerant circuit, an operation of a heat source side fan, etc. by using the calculated value of the circulation composition. A value of the circulation composition is calculated by, for example, converting a detection value of a liquid level of excess refrigerant detected by a liquid level detection device provided within an accumulator, with a previously created relationship between a liquid level and a value of the circulation composition (see, e.g., Patent Literature 1). Citation List Patent Literature [0003] Patent Literature 1: Japanese Unexamined Patent Application Publication No. 8-35725 (paragraphs [0044] to [0047], Fig. 9, Fig. 10, etc.)

Summary of Invention

Technical Problem [0004] In the existing refrigeration cycle apparatus, the controller calculates a value of the circulation composition without changing a calculation method on the basis of whether excess refrigerant is absent within the accumulator. If excess refrigerant occurs within the accumulator, the difference between the circulation composition and a filling composition that is a known value and is a composition of at least one refrigerant component among the plurality of refrigerant components in a state where the refrigerant circuit is filled with the refrigerant mixture, increases. Thus, it is effective to calculate the value of the circulation composition by, for example, the above-described method. However, if excess refrigerant does not occur within the accumulator, the difference between the circulation composition and the filling composition that is a known value decreases. Thus, if a value of the circulation composition is calculated by, for example, the above-described method, the accuracy of the calculation may decrease due to an error factor such an error occurring in a detection device and an error occurring through conversion. In addition, a processing amount of calculation may wastefully increase.

[0005] That is, in the existing refrigeration cycle apparatus, since a value of the circulation composition is calculated by the single calculation method regardless of whether excess refrigerant is absent within the accumulator, it is difficult to achieve improvement of performance or the like of the refrigeration cycle apparatus, for example, by increasing the accuracy of the calculation of the value of the circulation composition or reducing a processing amount of the calculation of the value of the circulation composition, both when excess refrigerant does not occur within the accumulator and when excess refrigerant occurs within the accumulator.

[0006] The present invention has been made in view of the above-described problems, and obtains a refrigeration cycle apparatus that is able to achieve improvement in performance or the like of the refrigeration cycle apparatus both when excess refrigerant does not occur within an accumulator and when excess refrigerant occurs within the accumulator. In addition, the present invention obtains such an air-conditioning apparatus. Moreover, the present invention obtains a method for calculating a circulation composition used in such a refrigeration cycle apparatus.

Solution to Problem [0007] A refrigeration cycle apparatus according to the present invention includes a refrigerant circuit in which a compressor, a heat source side heat exchanger, an expansion device, a load side heat exchanger, and an accumulator configured to store excess refrigerant are connected by a pipe, the refrigerant circuit being filled with a zeotropic refrigerant mixture having a plurality of refrigerant components having different boiling points, and a controller including: an excess refrigerant presence/absence determination unit configured to determine whether excess refrigerant is absent within the accumulator, and a circulation composition calculation unit configured to, if the excess refrigerant presence/absence determination unit determines that the excess refrigerant is absent, calculate a circulation composition that is a composition of a at least one refrigerant component among the plurality of refrigerant components in a state where the zeotropic refrigerant mixture circulates through the refrigerant circuit, by using a calculation method different from that if the excess refrigerant presence/absence determination unit does not determine that the excess refrigerant is absent.

Advantageous Effects of Invention [0008] The refrigeration cycle apparatus according to the present invention includes the controller including the excess refrigerant presence/absence determination unit configured to determine whether excess refrigerant is absent within the accumulator, and the circulation composition calculation unit configured to, if the excess refrigerant presence/absence determination unit determines that the excess refrigerant is absent, calculate the circulation composition by using the calculation method different from that if the excess refrigerant presence/absence determination unit does not determine that the excess refrigerant is absent. Therefore, it is possible to achieve improvement of the performance, etc. of the refrigeration cycle apparatus both when excess refrigerant does not occur within the accumulator and when excess refrigerant occurs within the accumulator.

Brief Description of Drawings

[0009] [Fig. 1] Fig. 1 is a schematic circuit configuration diagram showing an example of a circuit configuration of an air-conditioning apparatus according to Embodiment 1.

[Fig. 2] Fig. 2 is a schematic circuit configuration diagram showing flow of refrigerant during cooling operation of the air-conditioning apparatus according to Embodiment 1.

[Fig. 3] Fig. 3 is a schematic circuit configuration diagram showing flow of the refrigerant during heating operation of the air-conditioning apparatus according to Embodiment 1.

[Fig. 4] Fig. 4 is a p-h diagram of a refrigeration cycle of the air-conditioning apparatus according to Embodiment 1.

[Fig. 5] Fig. 5 is a diagram showing an operation flow of an excess refrigerant presence/absence determination unit of the air-conditioning apparatus according to Embodiment 1.

[Fig. 6] Fig. 6 is a diagram showing an operation flow of Modification-1 of the excess refrigerant presence/absence determination unit of the air-conditioning apparatus according to Embodiment 1.

[Fig. 7] Fig. 7 is a diagram showing an operation flow of Modification-2 of the excess refrigerant presence/absence determination unit of the air-conditioning apparatus according to Embodiment 1.

[Fig. 8] Fig. 8 is a diagram showing an operation flow of a circulation composition calculation unit of the air-conditioning apparatus according to Embodiment 1.

[Fig. 9] Fig. 9 is a diagram showing an operation flow of an operation control unit of the air-conditioning apparatus according to Embodiment 1.

[Fig. 10] Fig. 10 is a schematic circuit configuration diagram showing an example of a circuit configuration of an air-conditioning apparatus according to Embodiment 2.

[Fig. 11] Fig. 11 is a diagram showing an operation flow of an excess refrigerant presence/absence determination unit of the air-conditioning apparatus according to Embodiment 2.

[Fig. 12] Fig. 12 is a diagram showing an operation flow of a circulation composition calculation unit of the air-conditioning apparatus according to Embodiment 2.

Description of Embodiments

[0010] Hereinafter, a refrigeration cycle apparatus according to the present invention will be described with reference to the drawings.

In the present invention, a composition of at least one refrigerant component among a plurality of refrigerant components in a state where a zeotropic refrigerant mixture circulates through a refrigerant circuit is defined as "circulation composition". In addition, a composition of the at least one refrigerant component among the plurality of refrigerant components in a state where the zeotropic refrigerant mixture is filled in the refrigerant circuit is defined as "filling composition". Moreover, a composition of the at least one refrigerant component among the plurality of refrigerant components is defined as "refrigerant composition". The "refrigerant composition" includes both the "circulation composition" and the "filling composition".

[0011] Hereinafter, a case where the refrigeration cycle apparatus according to the present invention is an air-conditioning apparatus will be described.

However, the refrigeration cycle apparatus according to the present invention is not limited to such a case, and may be a refrigeration cycle apparatus other than the air-conditioning apparatus. In addition, configurations, operations, and the like described below are merely examples, and the refrigeration cycle apparatus according to the present invention is not limited to cases with such configurations, operations, and the like. Moreover, the detailed description of the configurations, the operations, and the like are simplified or omitted as appropriate. Furthermore, overlapping or similar description is simplified or omitted as appropriate.

[0012] Embodiment 1 Hereinafter, an air-conditioning apparatus according to Embodiment 1 will be described.

Fig. 1 is a schematic circuit configuration diagram showing an example of a circuit configuration of the air-conditioning apparatus according to Embodiment 1.

As shown in Fig. 1, the air-conditioning apparatus 100 includes a refrigerant circuit 1 filled with a zeotropic refrigerant mixture having a plurality of refrigerant components having different boiling points, and a controller 50. The air-conditioning apparatus 100 performs air-conditioning by circulating the zeotropic refrigerant mixture. Examples of the zeotropic refrigerant mixture include a refrigerant mixture of R32 refrigerant and R1234yf refrigerant and a refrigerant mixture of R32 refrigerant and R1234ze refrigerant. In the following description, a case with refrigerant in R32 refrigerant and R1234yf refrigerant are mixed in weight ratios of 44 wt% and 56 wt% will be described as an example. In addition, although the case where the zeotropic refrigerant mixture is the refrigerant mixture of R32 refrigerant and R1234yf refrigerant, and the case where the zeotropic refrigerant mixture is the refrigerant mixture of R32 refrigerant and R1234ze refrigerant have been exemplified, the zeotropic refrigerant mixture does not necessarily need to be such a zeotropic refrigerant mixture, and may be a refrigerant mixture in which R32 refrigerant and R1234yf refrigerant are principal components and another refrigerant is mixed in a small amount, or may be a refrigerant mixture in which R32 refrigerant and R1234ze refrigerant are principal components and other refrigerant is mixed in a small amount. Moreover, the zeotropic refrigerant mixture is not limited to the above-described refrigerant mixtures, and may be a refrigerant mixture in which any refrigerants are mixed. Furthermore, the number of refrigerant components to be mixed may be two or three, or may be greater than three.

[0013] The air-conditioning apparatus 100 includes an outdoor unit 2 and an indoor unit 3. In the outdoor unit 2, each device constituting the refrigerant circuit 1 is connected by a refrigerant pipe 4. In the indoor unit 3, each device constituting the refrigerant circuit 1 is connected by a refrigerant pipe 5. The refrigerant pipe 4 and the refrigerant pipe 5 are connected via a refrigerant main pipe 6. A plurality of indoor units 3 may be connected to the outdoor unit 2 via the refrigerant main pipe 6. In such a case, for example, a cooling only operation mode in which all the indoor units 3 perform cooling operation may be executable, and a heating only operation mode in which all indoor units 3 perform the heating operation may be executable.

[0014] [Outdoor Unit] The outdoor unit 2 is equipped with a compressor 11, a refrigerant flow path switching device 12 such as a four-way valve, a heat source side heat exchanger (outdoor heat exchanger) 13, and an accumulator 14.

[0015] The compressor 11 sucks low-temperature and low-pressure refrigerant, compresses the refrigerant into a high-temperature and high-pressure state, and discharges the refrigerant. The compressor 11 may be, for example, a capacity-controllable inverter compressor. The refrigerant flow path switching device 12 switches flow of the refrigerant during cooling operation and flow of the refrigerant during heating operation. The heat source side heat exchanger 13 functions as a condenser during cooling operation and functions as an evaporator during heating operation. In the heat source side heat exchanger 13, heat is exchanged between the refrigerant and air supplied by a heat source side air-sending device (not shown) composed of a fan or the like. The accumulator 14 is provided at the suction side of the compressor 11. The accumulator 14 stores excess refrigerant occurring due to the difference in operation status between cooling operation and heating operation, excess refrigerant due to a transient change in operation, or the like.

[0016] The outdoor unit 2 is provided with a first pressure detection device 21 and a second pressure detection device 22. The first pressure detection device 21 is provided to the refrigerant pipe 4 that provides communication between the compressor 11 and the refrigerant flow path switching device 12. The first pressure detection device 21 detects a pressure Pi of the high-temperature and high-pressure refrigerant compressed and discharged by the compressor 11.

The second pressure detection device 22 is provided to the refrigerant pipe 4 that provides communication between the refrigerant flow path switching device 12 and the accumulator 14. The second pressure detection device 22 detects a pressure P2 of the low-temperature and low-pressure refrigerant sucked by the compressor 11. The second pressure detection device 22 corresponds to a "pressure detection device" in the present invention. Although the case where the second pressure detection device 22 is provided to the refrigerant pipe 4 that provides communication between the refrigerant flow path switching device 12 and the accumulator 14 has been described above as an example, the position of the second pressure detection device 22 is not necessarily limited to such a case. For example, in the case where the air-conditioning apparatus 100 is an air-conditioning apparatus that performs only cooling operation, the second pressure detection device 22 may be provided at any location on the refrigerant pipe that provides communication between the outlet side of a load side heat exchanger 31 and the inlet side of the accumulator 14, or in the case where the air-conditioning apparatus 100 is an air-conditioning apparatus that performs only heating operation, the second pressure detection device 22 may be provided at any location on the refrigerant pipe that provides communication between the outlet side of the heat source side heat exchanger 13 and the inlet side of the accumulator 14. Even in such these cases, the same advantageous effects are exerted.

[0017] The outdoor unit 2 is provided with a first temperature detection device 23 and a second temperature detection device 24. The first temperature detection device 23 is provided to the refrigerant pipe 4 that provides communication between the compressor 11 and the refrigerant flow path switching device 12.

The first temperature detection device 23 detects a temperature Ti of the high-temperature and high-pressure refrigerant compressed and discharged by the compressor 11. The second temperature detection device 24 is provided to the refrigerant pipe 4 that provides communication between the refrigerant flow path switching device 12 and the accumulator 14. The second temperature detection device 24 detects a temperature T2 of the low-temperature and low-pressure refrigerant sucked by the compressor 11. Each of the first temperature detection device 23 and the second temperature detection device 24 may be composed of a therm istor or the like. The second temperature detection device 24 corresponds to a "temperature detection device" in the present invention. In the above, the case where the second temperature detection device 24 is provided to the refrigerant pipe 4 that provides communication between the refrigerant flow path switching device 12 and the accumulator 14 has been described, but the position of the second temperature detection device 24 is not necessarily limited to such a case. For example, in the case where the air-conditioning apparatus 100 is an air-conditioning apparatus that performs only cooling operation, the second temperature detection device 24 may be provided at any location on the refrigerant pipe that provides communication between the outlet side of the load side heat exchanger 31 and the inlet side of the accumulator 14, or in the case where the air-conditioning apparatus 100 is an air-conditioning apparatus that performs only heating operation, the second temperature detection device 24 may be provided at any location on the refrigerant pipe that provides communication between the outlet side of the heat source side heat exchanger 13 and the inlet side of the accumulator 14. Even in such these cases, the same advantageous effects are exerted.

[0018] [Indoor Unit] The indoor unit 3 is equipped with the load side heat exchanger (indoor heat exchanger) 31 and an expansion device 32.

[0019] In the load side heat exchanger 31, heat is exchanged between the refrigerant and air supplied by a load side air-sending device (not shown) composed of a fan or the like, and heating air or cooling air to be supplied to an indoor space is generated. The expansion device 32 is, for example, a valve, and reduces the pressure of the refrigerant to expand the refrigerant. The expansion device 32 may be composed of an opening degree-controllable valve, for example, an electronic expansion valve, etc. [0020] The indoor unit 3 is provided with a third temperature detection device 41, a fourth temperature detection device 42, and a fifth temperature detection device 43. The third temperature detection device 41 is provided to the refrigerant pipe 5 that provides communication between the expansion device 32 and the load side heat exchanger 31. The third temperature detection device 41 detects the temperature of the refrigerant flowing into the load side heat exchanger 31 during cooling operation. The fourth temperature detection device 42 is provided to the refrigerant pipe 5 that provides communication between the load side heat exchanger 31 and the refrigerant flow path switching device 12. The fourth temperature detection device 42 detects the temperature of the refrigerant flowing out of the load side heat exchanger 31 during cooling operation. The fifth temperature detection device 43 is provided at an air suction portion of the load side heat exchanger 31, and detects the temperature of indoor air. Each of the third temperature detection device 41, the fourth temperature detection device 42, and the fifth temperature detection device 43 may be composed of a therm istor, etc. [0021] [Controller] The controller 50 includes an excess refrigerant presence/absence determination unit 51, a circulation composition calculation unit 52, and an operation control unit 53. Each unit constituting the controller 50 may be composed of, for example, a microcomputer, or a microprocessor unit, etc may be composed of an updatable one such as firmware, or may be a program module, etc. executed on the basis of a command from a CPU, etc. In addition, the controller 50 may be provided in the outdoor unit 2 or in the indoor unit 3, may be provided separately in the outdoor unit 2 and the indoor unit 3, or may be provided in a component other than these units. The excess refrigerant presence/absence determination unit 51 corresponds to "an excess refrigerant presence/absence determination unit" in the present invention. The circulation composition calculation unit 52 corresponds to "a circulation composition calculation unit" in the present invention.

[0022] The excess refrigerant presence/absence determination unit 51 determines presence/absence of excess refrigerant within the accumulator 14, for example, by using at least a detection value P2 of the second pressure detection device 22 and a detection value T2 of the second temperature detection device 24.

[0023] The circulation composition calculation unit 52 selects a calculation method for a circulation composition in accordance with a result of the determination of the excess refrigerant presence/absence determination unit 51, and calculates a circulation composition of the zeotropic refrigerant mixture circulating through the refrigerant circuit 1, for example, by using at least the detection value P2 of the second pressure detection device 22 and the detection value T2 of the second temperature detection device 24.

[0024] The operation control unit 53 controls overall operation of the air-conditioning apparatus 100. The operation control unit 53 controls a frequency fc of the compressor 11, a rotation speed ff (including switching of ON/OFF) of the fan, etc. constituting the heat source side air-sending device (not shown), switching of the refrigerant flow path switching device 12, the opening degree of the expansion device 32, etc. on the basis of, for example, the detection values of various detection devices or commands inputted through a remote control, to cause the air-conditioning apparatus 100 to execute each operation mode. The operation control unit 53 controls the frequency fc of the compressor 11, the rotation speed ff (including switching of ON/OFF) of the fan, etc. constituting the heat source side air-sending device (not shown), etc. on the basis of, for example, the circulation composition calculated by the circulation composition calculation unit 52, the detection value Pi of the first pressure detection device 21, and the detection value P2 of the second pressure detection device 22.

[0025] [Cooling Operation Mode] Fig. 2 is a schematic circuit configuration diagram showing flow of the refrigerant during cooling operation of the air-conditioning apparatus according to Embodiment 1. In Fig. 2, a flow direction of the refrigerant is indicated by solid arrows. In addition, a cooling operation mode will be described below with, as an example, the case where a cooling energy load occurs in the load side heat exchanger 31.

[0026] As shown in Fig. 2, in the cooling operation mode, the low-temperature and low-pressure refrigerant is compressed by the compressor 11 into high-temperature and high-pressure gas refrigerant and discharged therefrom. The high-temperature and high-pressure gas refrigerant discharged from the compressor 11 flows via the refrigerant flow path switching device 12 into the heat source side heat exchanger 13. The high-temperature and high-pressure gas refrigerant having flowed into the heat source side heat exchanger 13 condenses while rejecting heat to outdoor air, to become high-pressure liquid refrigerant. The high-pressure liquid refrigerant having flowed out of the heat source side heat exchanger 13 flows out of the outdoor unit 2 and flows through the refrigerant main pipe 6 into the indoor unit 3. The high-pressure liquid refrigerant having flowed into the indoor unit 3 is reduced in pressure by the expansion device 32 into low-temperature and low-pressure two-phase gas-liquid refrigerant, then flows into the load side heat exchanger 31 serving as an evaporator, removes heat from indoor air to cool the indoor air, and becomes low-temperature and low-pressure gas refrigerant. The low-temperature and low-pressure gas refrigerant having flowed out of the load side heat exchanger 31 flows through the refrigerant main pipe 6 into the outdoor unit 2. The refrigerant having flowed into the outdoor unit 2 is sucked into the compressor 11 through the refrigerant flow path switching device 12 and the accumulator 14. [0027] The operation control unit 53 of the controller 50 controls, for example, the opening degree of the expansion device 32 such that superheat (a degree of superheat) that is the difference between the detection value of the fourth temperature detection device 42 and a saturated gas temperature of the refrigerant calculated from the circulation composition calculated by the circulation composition calculation unit 52 and the detection value P2 of the second pressure detection device 22, is constant.

[0028] [Heating Operation Mode] Fig. 3 is a schematic circuit configuration diagram showing flow of the refrigerant during heating operation of the air-conditioning apparatus according to Embodiment 1. In Fig. 3, a flow direction of the refrigerant is indicated by solid arrows. In addition, a heating operation mode will be described below with, as an example, the case where a heating energy load occurs in the load side heat exchanger 31.

[0029] As shown in Fig. 3, in the heating operation mode, the low-temperature and low-pressure refrigerant is compressed by the compressor 11 into high-temperature and high-pressure gas refrigerant and discharged therefrom. The high-temperature and high-pressure gas refrigerant discharged from the compressor 11 flows via the refrigerant flow path switching device 12 through the refrigerant main pipe 6 into the indoor unit 3. The high-temperature and high-pressure gas refrigerant having flowed into the indoor unit 3 rejects heat to indoor air in the load side heat exchanger 31 to become high-pressure liquid refrigerant, and flows into the expansion device 32. Then, the high-pressure liquid refrigerant is reduced in pressure by the expansion device 32 into low-temperature and low-pressure two-phase gas-liquid refrigerant, then flows out of the indoor unit 3, and flows through the refrigerant main pipe 6 into the outdoor unit 2. The low-temperature and low-pressure two-phase gas-liquid refrigerant having flowed into the outdoor unit 2 removes heat from outdoor air in the heat source side heat exchanger 13 to become low-pressure two-phase gas-liquid refrigerant. The low-pressure two-phase gas-liquid refrigerant having flowed out of the heat source side heat exchanger 13 flows through the refrigerant flow path switching device 12 into the accumulator 14, the gas phase and the liquid phase thereof are separated by the accumulator 14, and only the gas-phase refrigerant is sucked into the compressor 11.

[0030] The operation control unit 53 of the controller 50 controls, for example, the opening degree of the expansion device 32 such that subcooling (a degree of subcooling) that is the difference between the detection value of the third temperature detection device 41 and a saturated liquid temperature of the refrigerant calculated from the circulation composition calculated by the circulation composition calculation unit 52 and the detection value Pi of the first pressure detection device 21, is constant.

[0031] [P-h diagram of refrigeration cycle] Fig. 4 is a p-h diagram of a refrigeration cycle of the air-conditioning apparatus according to Embodiment 1.

As shown in Fig. 4, there is a characteristic that the temperature of the saturated liquid refrigerant and the temperature of the saturated gas refrigerant at the same pressure are different values due to the zeotropic refrigerant mixture having a plurality of refrigerant components having different boiling points. In addition, there is a characteristic that a state of the refrigerant on the p-h diagram cannot be determined at one point unless three parameters that are pressure, temperature, and refrigerant composition are provided. Moreover, if the refrigerant circuit 1 includes a portion where a gas-liquid interface occurs as in the accumulator 14, a low-boiling-point component is likely to become gas phase and a high-boiling-point component is likely to become liquid phase in the portion where a gas-liquid interface occurs, and thus there is a characteristic that the low-boiling-point component flows through the refrigerant circuit 1 in a large amount.

[0032] [Excess Refrigerant Presence/Absence Determination Unit] Hereinafter, operation of the excess refrigerant presence/absence determination unit 51 will be described.

A case where the "filling composition" in the present invention is a filling composition ao of a refrigerant component having a lowest boiling point among a plurality of refrigerant components, will be described below as an example. [0033] Fig. 5 is a diagram showing an operation flow of the excess refrigerant presence/absence determination unit of the air-conditioning apparatus according to Embodiment 1.

As shown in Fig. 5, first, in step A101, the excess refrigerant presence/absence determination unit 51 acquires the detection value P2 of the second pressure detection device 22 and the detection value T2 of the second temperature detection device 24. Next, in step A102, the excess refrigerant presence/absence determination unit 51 calculates a saturated gas temperature Tsat of the refrigerant at an inflow portion of the accumulator 14 from the detection value P2 of the second pressure detection device 22 and the filling composition ao of the zeotropic refrigerant mixture that is a known amount. Next, in step A103, the excess refrigerant presence/absence determination unit 51 determines whether the detection value T2 of the second temperature detection device 24 exceeds the saturated gas temperature Tsat of the refrigerant at the inflow portion of the accumulator 14. If a result of the determination is YES, it is possible to determine that the gas refrigerant is flowing into the accumulator 14, and thus, in step A104, the excess refrigerant presence/absence determination unit 51 provides an output indicating that excess refrigerant is absent within the accumulator 14. If the result of the determination is NO, it is possible to determine that the two-phase gas-liquid refrigerant is flowing into the accumulator 14, and thus, in step A105, the excess refrigerant presence/absence determination unit 51 provides an output indicating that excess refrigerant is present within the accumulator 14.

[0034] In step A102, the saturated gas temperature Tsat of the refrigerant at the inflow portion of the accumulator 14 may be calculated by a calculation formula such as the following formula (1), or may be calculated by being read from a relationship between the detection value P2 of the second pressure detection device 22, the filling composition ao, and the saturated gas temperature Tsat which relationship is previously stored as a table or the like. The resolution in calculating the saturated gas temperature Tsat may be improved by performing interpolation between tabled values as necessary. In addition, an approximation expression representing a relationship between the detection value P2 of the second pressure detection device 22 and the saturated gas temperature Tsat may be previously stored or calculated, and the saturated gas temperature Tsat may be calculated by using the approximation expression.

[0035] [Math. 1] Tsat = f(P2, (10) (1) [0036] The excess refrigerant presence/absence determination unit 51 uses the filling composition when calculating the saturated gas temperature Tsat of the refrigerant at the inflow portion of the accumulator 14. Since the saturated gas temperature Tsat at the same pressure increases as the proportion of the low-boiling-point component decreases, the saturated gas temperature Tsai of the refrigerant flowing into the accumulator 14 is estimated to be higher with such a configuration than in the case where the saturated gas temperature Tsat is calculated by using the circulation composition. Thus, a determination that excess refrigerant is absent within the accumulator 14 is made at the safe side.

[0037] The excess refrigerant presence/absence determination unit 51 may calculate the saturated gas temperature Tsat of the refrigerant at the inflow portion of the accumulator 14 by using another refrigerant composition that is not the filling composition. For example, the excess refrigerant presence/absence determination unit 51 may calculate the saturated gas temperature Tsat of the refrigerant at the inflow portion of the accumulator 14 by using a value of the circulation composition calculated by the circulation composition calculation unit 52 described later according to a first calculation method (a calculation method selected if the excess refrigerant presence/absence determination unit 51 determines that excess refrigerant is absent within the accumulator 14).

[0038] The case where the excess refrigerant presence/absence determination unit 51 calculates the saturated gas temperature Tsat of the refrigerant at the inflow portion of the accumulator 14 on the basis of the detection value P2 of the second pressure detection device 22 and the filling composition, has been described, but the present invention is not limited to such a case. For example, the excess refrigerant presence/absence determination unit 51 may previously store information obtained by, for example, tabling a relationship between the filling composition, the detection value P2 of the second pressure detection device 22, and at least one refrigerant physical property of pressure, temperature, enthalpy, and quality, may derive a refrigerant physical property corresponding to the filling composition and the detection value P2 of the second pressure detection device 22 from the filling composition, the detection value P2 of the second pressure detection device 22, and the stored information, and may calculate the saturated gas temperature Tsat of the refrigerant at the inflow portion of the accumulator 14 on the basis of the derived refrigerant physical property.

Alternatively, the excess refrigerant presence/absence determination unit 51 may calculate at least one refrigerant physical property of pressure, temperature, enthalpy, and quality from the filling composition and the detection value P2 of the second pressure detection device 22 and may calculate the saturated gas temperature Tsat of the refrigerant at the inflow portion of the accumulator 14 on the basis of the calculated refrigerant physical property.

[0039] The case where the filling composition ao of the refrigerant component having the lowest boiling point among the plurality of refrigerant components is used in calculation of the saturated gas temperature Tsar, has been described, but the present invention is not limited to such a case. For example, the filling compositions of two or more refrigerant components among the plurality of refrigerant components may be used.

[0040] (Modification-1 of Excess Refrigerant Presence/Absence Determination Unit) Fig. 6 is a diagram showing an operation flow of Modification-1 of the excess refrigerant presence/absence determination unit of the air-conditioning apparatus according to Embodiment 1.

As shown in Fig. 6, first, in step A201, the excess refrigerant presence/absence determination unit 51 acquires the detection value P2 of the second pressure detection device 22 and the detection value T2 of the second temperature detection device 24. Next, in step A202, the excess refrigerant presence/absence determination unit 51 calculates a saturated gas pressure Psat of the refrigerant at the inflow portion of the accumulator 14 from the detection value T2 of the second temperature detection device 24 and the filling composition ao of the zeotropic refrigerant mixture that is a known amount.

Next, in step A203, the excess refrigerant presence/absence determination unit 51 determines whether the detection value P2 of the second pressure detection device 22 is less than the saturated gas pressure Psat of the refrigerant at the inflow portion of the accumulator 14. If a result of the determination is YES, it is possible to determine that the gas refrigerant is flowing into the accumulator 14, and thus, in step A204, the excess refrigerant presence/absence determination unit 51 provides an output indicating that excess refrigerant is absent within the accumulator 14. If the result of the determination is NO, it is possible to determine that the two-phase gas-liquid refrigerant is flowing into the accumulator 14, and thus, in step A205, the excess refrigerant presence/absence determination unit 51 provides an output indicating that excess refrigerant is present within the accumulator 14.

[0041] In step A202, the saturated gas pressure Psat of the refrigerant at the inflow portion of the accumulator 14 may be calculated by a calculation formula such as the following formula (2), or may be calculated by being read from a relationship between the detection value 12 of the second temperature detection device 24, the filling composition ao, and the saturated gas pressure Psat which relationship is previously stored as a table or the like. The resolution in calculating the saturated gas pressure Psat may be improved by performing interpolation between tabled values as necessary. In addition, an approximation expression representing a relationship between the detection value 12 of the second temperature detection device 24 and the saturated gas pressure Psat may be previously stored or calculated, and the saturated gas pressure Psat may be calculated by using the approximation expression.

[0042] [Math. 2] Psat = f(T2, ao) (2) [0043] The case where the excess refrigerant presence/absence determination unit 51 calculates the saturated gas pressure Psat of the refrigerant at the inflow portion of the accumulator 14 on the basis of the detection value T2 of the second temperature detection device 24 and the filling composition, has been described, but the present invention is not limited to such a case. For example, the excess refrigerant presence/absence determination unit 51 may previously store information obtained by, for example, tabling a relationship between the filling composition, the detection value T2 of the second temperature detection device 24, and at least one refrigerant physical property of pressure, temperature, enthalpy, and quality, may derive a refrigerant physical property corresponding to the filling composition and the detection value T2 of the second temperature detection device 24 from the filling composition, the detection value T2 of the second temperature detection device 24, and the stored information: and may calculate the saturated gas pressure Psat of the refrigerant at the inflow portion of the accumulator 14 on the basis of the derived refrigerant physical property.

Alternatively, the excess refrigerant presence/absence determination unit 51 may calculate at least one refrigerant physical property of pressure, temperature, enthalpy, and quality from the filling composition and the detection value T2 of the second temperature detection device 24 and may calculate the saturated gas pressure Psat of the refrigerant at the inflow portion of the accumulator 14 on the basis of the calculated refrigerant physical property.

[0044] The case where the filling composition CCO of the refrigerant component having the lowest boiling point among the plurality of refrigerant components is used in calculation of the saturated gas pressure Psat, has been described, but the present invention is not limited to such a case. For example, the filling compositions of two or more refrigerant components among the plurality of refrigerant components may be used.

[0045] (Modification-2 of Excess Refrigerant Presence/Absence Determination Unit) Fig. 7 is a diagram showing an operation flow of Modification-2 of the excess refrigerant presence/absence determination unit of the air-conditioning apparatus according to Embodiment 1.

As shown in Fig. 7, first, in step A301, the excess refrigerant presence/absence determination unit 51 acquires the detection value P2 of the second pressure detection device 22 and the detection value T2 of the second temperature detection device 24. Next, in step A302, the excess refrigerant presence/absence determination unit 51 calculates a temperature calculation saturated gas enthalpy HGT, which is a saturated gas enthalpy of the refrigerant at the inflow portion of the accumulator 14, from the detection value T2 of the second temperature detection device 24 and the filling composition CCO of the zeotropic refrigerant mixture that is a known amount. In addition, the excess refrigerant presence/absence determination unit 51 calculates a pressure calculation saturated gas enthalpy HGP, which is a saturated gas enthalpy of the refrigerant at the inflow portion of the accumulator 14, from the detection value P2 of the second pressure detection device 22 and the filling composition ao of the zeotropic refrigerant mixture that is a known amount. Next, in step A303, the excess refrigerant presence/absence determination unit 51 determines whether the temperature calculation saturated gas enthalpy HGT exceeds the pressure calculation saturated gas enthalpy Hcp. If a result of the determination is YES, it is possible to determine that the gas refrigerant is flowing into the accumulator 14, and thus, in step A304, the excess refrigerant presence/absence determination unit 51 provides an output indicating that excess refrigerant is absent within the accumulator 14. If the result of the determination is NO, it is possible to determine that the two-phase gas-liquid refrigerant is flowing into the accumulator 14, and thus, in step A305, the excess refrigerant presence/absence determination unit 51 provides an output indicating that excess refrigerant is present within the accumulator 14.

[0046] In step A302, the temperature calculation saturated gas enthalpy HGT may be calculated by a calculation formula such as the following formula (3), or may be calculated by being read from a relationship between the detection value T2 of the second temperature detection device 24, the filling composition ao, and the temperature calculation saturated gas enthalpy HGT which relationship is previously stored as a table or the like. The resolution in calculating the temperature calculation saturated gas enthalpy HGT may be improved by performing interpolation between tabled values as necessary. In addition, an approximation expression representing a relationship between the detection value T2 of the second temperature detection device 24 and the temperature calculation saturated gas enthalpy HGT may be previously stored or calculated, and the temperature calculation saturated gas enthalpy HOT may be calculated by using the approximation expression.

[0047] [Math. 3] HGT = f(T2, ao) (3) [0048] Alternatively, in step A302, the pressure calculation saturated gas enthalpy HOP may be calculated by a calculation formula such as the following formula (4), or may be calculated by being read from a relationship between the detection value P2 of the second pressure detection device 22, the filling composition ao, and the pressure calculation saturated gas enthalpy HGP which relationship is previously stored as a table or the like. The resolution in calculating the pressure calculation saturated gas enthalpy HOP may be improved by performing interpolation between tabled values as necessary. In addition, an approximation expression representing a relationship between the detection value P2 of the second pressure detection device 22 and the pressure calculation saturated gas enthalpy HGP may be previously stored or calculated, and the pressure calculation saturated gas enthalpy FIGF, may be calculated by using the approximation expression.

[0049] [Math. 4] HGP = f(P2, ao) (4) [0050] The case where the excess refrigerant presence/absence determination unit 51 calculates the temperature calculation saturated gas enthalpy HGT on the basis of the detection value T2 of the second temperature detection device 24 and the filling composition, has been described, but the present invention is not limited to such a case. For example, the excess refrigerant presence/absence determination unit 51 may previously store information obtained by, for example, tabling a relationship between the filling composition, the detection value T2 of the second temperature detection device 24, and at least one refrigerant physical property of pressure, temperature, enthalpy, and quality, may derive a refrigerant physical property corresponding to the filling composition and the detection value T2 of the second temperature detection device 24 from the filling composition, the detection value 12 of the second temperature detection device 24, and the stored information, and may calculate the temperature calculation saturated gas enthalpy FIGT on the basis of the derived refrigerant physical property.

Alternatively, the excess refrigerant presence/absence determination unit 51 may calculate at least one refrigerant physical property of pressure, temperature, enthalpy, and quality from the filling composition and the detection value T2 of the second temperature detection device 24 and may calculate the temperature calculation saturated gas enthalpy Hor on the basis of the calculated refrigerant physical property.

[0051] The case where the excess refrigerant presence/absence determination unit 51 calculates the pressure calculation saturated gas enthalpy Hop on the basis of the detection value P2 of the second pressure detection device 22 and the filling composition, has been described, but the present invention is not limited to such a case. For example, the excess refrigerant presence/absence determination unit 51 may previously store information obtained by, for example, tabling a relationship between the filling composition, the detection value P2 of the second pressure detection device 22, and at least one refrigerant physical property of pressure, temperature, enthalpy, and quality, may derive a refrigerant physical property corresponding to the filling composition and the detection value P2 of the second pressure detection device 22 from the filling composition, the detection value P2 of the second pressure detection device 22, and the stored information, and may calculate the pressure calculation saturated gas enthalpy Hop on the basis of the derived refrigerant physical property. Alternatively, the excess refrigerant presence/absence determination unit 51 may calculate at least one refrigerant physical property of pressure, temperature, enthalpy, and quality from the filling composition and the detection value P2 of the second pressure detection device 22 and may calculate the pressure calculation saturated gas enthalpy HGP on the basis of the calculated refrigerant physical property [0052] The case where the filling composition ao of the refrigerant component having the lowest boiling point among the plurality of refrigerant components is used in calculation of the temperature calculation saturated gas enthalpy HOT and the pressure calculation saturated gas enthalpy HOP, has been described, but the present invention is not limited to such a case. For example, the filling compositions of two or more refrigerant components among the plurality of refrigerant components may be used.

[0053] [Circulation Composition Calculation Unit] Hereinafter, operation of the circulation composition calculation unit 52 will be described.

Hereinafter, a description will be given with, as an example, the case where the "circulation composition" in the present invention is the circulation composition a of the refrigerant component having the lowest boiling point among the plurality of refrigerant components. In addition, a description will be given with, as an example, the case where the "filling composition" in the present invention is the filling composition ao of the refrigerant component having the lowest boiling point among the plurality of refrigerant components.

[0054] Fig. 8 is a diagram showing an operation flow of the circulation composition calculation unit of the air-conditioning apparatus according to Embodiment 1.

As shown in Fig. 8, first, in step B101, the circulation composition calculation unit 52 acquires output of the excess refrigerant presence/absence determination unit 51. If the output indicates that excess refrigerant is absent within the accumulator 14, the circulation composition calculation unit 52 proceeds to step B102. If the output indicates that excess refrigerant is present within the accumulator 14, the circulation composition calculation unit 52 proceeds to step B104.

[0055] In step B102, the circulation composition calculation unit 52 selects the first calculation method as a calculation method for the circulation composition a, and proceeds to step B103. In step B103, the circulation composition calculation unit 52 calculates a value obtained by adding a composition correction value p to the filling composition ao, as the circulation composition a, and in step B107, the circulation composition calculation unit 52 outputs the circulation composition a. The composition correction value [3 is a positive value.

[0056] In step B103, as the circulation composition a in the case where excess refrigerant is absent within the accumulator 14, the circulation composition calculation unit 52 calculates the value obtained by adding the composition correction value ft which is a positive value, to the filling composition ao, not the filling composition ao. Even when excess refrigerant is absent within the accumulator 14, due to the refrigerant being dissolved into refrigerating machine oil, the circulation composition a does not become equal to the filling composition ao. Thus, it is possible to improve the accuracy of calculation of the circulation composition a by adding the composition correction value [3, which is a parameter corresponding to composition variation caused due to the refrigerant being dissolved into the refrigerating machine oil, to the filling composition ao.

[0057] For example, in the case where the zeotropic refrigerant mixture is the refrigerant mixture of R32 refrigerant and R1234yf refrigerant, since the boiling point of R32 refrigerant is -52 degrees C, the boiling point of R1234yf refrigerant is -29.4 degrees C, and the refrigerant component having the lowest boiling point is R32 refrigerant, the filling composition ao is defined as the weight ratio of R32 refrigerant in a state of being filled in the refrigerant circuit 1. If the weight ratio of the R32 refrigerant is any value included in the range of 35 wt% to 75 wt% in a state of being filled in the refrigerant circuit 1, the circulation composition a in a state where excess refrigerant is absent within the accumulator 14 is revealed to be greater than the filling composition ao by any value included in the range of 1 wt% to 4 wt%, from an experiment. Thus, the composition correction value 13 may be any value included in the range of 1 wt% to 4 wt%. In addition, also in the case where the zeotropic refrigerant mixture is the refrigerant mixture of R32 refrigerant and R1234ze refrigerant, since R1234yf refrigerant and R1234ze refrigerant have similar physical properties, if the weight ratio of R32 refrigerant is any value included in the range of 35 wt% to 75 wt% in a state of being filled in the refrigerant circuit 1, the circulation composition a in a state where excess refrigerant is absent within the accumulator 14 is revealed to be greater than the filling composition ao by any value included in the range of 1 wt% to 4 wt%. [0058] The amount of the refrigerant dissolved into the refrigerating machine oil varies depending on an operation state of the refrigeration cycle (a pressure value at the high-pressure side, a pressure value at the low-pressure side, etc.). Thus, the circulation composition calculation unit 52 may change the composition correction value 13 in accordance with the operation state of the refrigeration cycle. In addition, in the case where the circulation composition calculation unit 52 does not change the composition correction value p in accordance with the operation state of the refrigeration cycle, the composition correction value 13 may be set at any value included in the range of 2 wt% to 3 wt%.

[0059] The solubility of the refrigerant to the refrigerating machine oil varies depending on also the types of the refrigerant and the refrigerating machine oil, a temperature condition, and a pressure condition, etc. Thus, the composition correction value R may be set at a value obtained by taking into account a solubility calculated on the basis of the types of the refrigerant and the refrigerating machine oil, the temperature condition, and the pressure condition, etc. During operation of the refrigeration cycle, the circulation composition calculation unit 52 may calculate a solubility, and may change the composition correction value p in accordance with this solubility.

[0060] In step B104, the circulation composition calculation unit 52 selects a second calculation method as the calculation method for the circulation composition a, and proceeds to step B105. In step B105, the circulation composition calculation unit 52 acquires the detection value P2 of the second pressure detection device 22 and the detection value T2 of the second temperature detection device 24. Next, in step B106, the circulation composition calculation unit 52 calculates, as the circulation composition a, a saturated gas composition ac calculated from the detection value P2 of the second pressure detection device 22 and the detection value T2 of the second temperature detection device 24, and in step B107, the circulation composition calculation unit 52 outputs the circulation composition a.

[0061] The saturated gas composition ac is a circulation composition in the case where the refrigerant flowing into the accumulator 14 is saturated gas (i.e., a quality of 1). Actually, in a state where excess refrigerant occurs within the accumulator 14, two-phase gas-liquid refrigerant having a quality of about 0.9 flows into the accumulator 14. However, even if the quality is high and the refrigerant flowing into the accumulator 14 is approximated as being saturated gas (i.e., a quality of 1), the refrigerant less affects the accuracy of calculation of the circulation composition a, and thus no problem arises even when the saturated gas composition ac is calculated as the circulation composition a. [0062] The saturated gas composition ac may be calculated by a calculation formula such as the following formula (5), or may be calculated by being read from a relationship between the detection value P2 of the second pressure detection device 22, the detection value T2 of the second temperature detection device 24, and the saturated gas composition ac which relationship is previously as a table or the like. In a p-h diagram, it is possible to identify a saturated gas state from two factors, temperature and pressure. Thus, it is possible to calculate the saturated gas composition ac by identifying a saturated gas state from the detection value P2 of the second pressure detection device 22 and the detection value T2 of the second temperature detection device 24 and identifying a circulation composition with which the saturated gas state is obtained. The resolution in calculating the saturated gas composition cm may be improved by performing interpolation between tabled values as necessary. In addition, an approximation expression representing a relationship between the detection value P2 of the second pressure detection device 22, the detection value T2 of the second temperature detection device 24, and the saturated gas composition ac may be previously stored or calculated, and the saturated gas composition ac may be calculated by using the approximation expression.

[0063] [Math. 5] ac = f(P2, T2) (5) [0064] The case where the circulation composition a of the refrigerant component having the lowest boiling point among the plurality of refrigerant components is used as the circulation composition, has been described, but the present invention is not limited to such a case. For example, the circulation compositions of two or more refrigerant components among the plurality of refrigerant components may be used. In addition, the case where the filling composition ao of the refrigerant component having the lowest boiling point among the plurality of refrigerant components is used as the filling composition, has been described, but the present invention is not limited to such a case. For example, the filling compositions of two or more refrigerant components among the plurality of refrigerant components may be used.

[0065] [Specific Example of Operation of Excess Refrigerant Presence/Absence Determination Unit and Circulation Composition Calculation Unit] Hereinafter, a specific example of operation of the excess refrigerant presence/absence determination unit 51 and the circulation composition calculation unit 52 will be described.

The case will be described where the zeotropic refrigerant mixture is a refrigerant mixture of R32 refrigerant and R1234yf refrigerant, the weight ratios of R32 refrigerant and R1234yf refrigerant are 44 wt% and 56 wt%, the detection value P2 of the second pressure detection device 22 is 0.70 MPaabs, and the detection value T2 of the second temperature detection device 24 is 1.0 degree C. The physical values described below are values calculated by REFPROP Version 9.0 sold by the NIST (National Institute of Standards and Technology). [0066] First, in step A101, the excess refrigerant presence/absence determination unit 51 acquires the detection value P2 of the second pressure detection device 22 that is 0.70 MPaabs and the detection value T2 of the second temperature detection device 24 that is 1.0 degree C. Next, in step A102, the excess refrigerant presence/absence determination unit 51 calculates the saturated gas temperature Tsat of the refrigerant at the inflow portion of the accumulator 14 as the saturated gas temperature Tsat = 4.3 degrees C from the detection value P2 of the second pressure detection device 22 that is 0.70 MPaabs and the filling composition ao of the R32 refrigerant. Next, in step A103, the excess refrigerant presence/absence determination unit 51 determines whether the detection value T2 of the second temperature detection device 24 is equal to or higher than the saturated gas temperature Tsat. In this example, since 12 (= 1.0 degree C) < Tsat (= 4.3 degrees C), the excess refrigerant presence/absence determination unit 51 proceeds to step A105 and provides an output indicating that excess refrigerant is present within the accumulator 14.

[0067] In step B101, the circulation composition calculation unit 52 acquires the output of the excess refrigerant presence/absence determination unit 51, and proceeds to step B104 since the output indicates that excess refrigerant is present within the accumulator 14. In step B104, the circulation composition calculation unit 52 selects the second calculation method as the calculation method for the circulation composition a, and proceeds to step B105. In step B105, the circulation composition calculation unit 52 acquires the detection value P2 of the second pressure detection device 22 that is 0.70 MPaabs and the detection value T2 of the second temperature detection device 24 that is 1.0 degree C. Next, in step B106, the circulation composition calculation unit 52 calculates the saturated gas composition ac of R32 refrigerant as a saturated gas composition ac = 56.4 wt% from the detection value P2 of the second pressure detection device 22 that is 0.70 MPaabs and the detection value T2 of the second temperature detection device 24 that is 1.0 degree C, and regards this saturated gas composition etc as a value of the circulation composition a.

Next, in step B107, the circulation composition calculation unit 52 outputs the circulation composition a.

[0068] The circulation composition calculation unit 52 approximates the refrigerant flowing into the accumulator 14 as being saturated gas (i.e., a quality of 1), and calculates the circulation composition a. For example, in the case where the detection value P2 of the second pressure detection device 22 is 0.70 MPaabs and the detection value T2 of the second temperature detection device 24 is 1.0 degree C, the circulation composition a (i.e., the saturated gas composition ac) of R32 refrigerant in the case where the refrigerant flowing into the accumulator 14 is saturated gas (i.e., a quality of 1) is 56.4 wt%, and the circulation composition a of R32 refrigerant in the case where the refrigerant flowing into the accumulator 14 is two-phase gas-liquid refrigerant having a quality of 0.9 is 54.8 wt%. Thus, even if the refrigerant flowing into the accumulator 14 is approximated as being saturated gas (i.e., a quality 1), only an error of 1.6 wt% occurs in the circulation composition a.

[0069] Meanwhile, in general, a detection value of a temperature detection device includes an error of about ±1 degree C. If the detection value P2 of the second pressure detection device 22 is fixed as 0.70 MPaabs and the circulation composition a of R32 refrigerant in the case where the refrigerant flowing into the accumulator 14 is two-phase gas-liquid refrigerant having a quality 0.9 is calculated in the case where the detection value T2 of the second temperature detection device 24 is 2 degrees C and in the case where the detection value T2 of the second temperature detection device 24 is 0 degrees C, the circulation composition a is 50.5 wt% in the case where the detection value T2 of the second temperature detection device 24 is 2 degrees C, and the circulation composition a is 59.6 wt% in the case where the detection value T2 of the second temperature detection device 24 is 0 degrees C. That is, due to an error included in the detection value T2 of the second temperature detection device 24, an error occurs in the circulation composition a in the range of -4.3 wt% to 4.8 wt% with respect to the true value. The value is high as compared to the above error of 1.6 wt%, and thus it appears that no problem arises in calculation of the circulation composition a even when the refrigerant flowing into the accumulator 14 is approximated as being saturated gas (i.e., a quality of 1).

[0070] [Operation Control Unit] Hereinafter, operation of the operation control unit 53 will be described. Fig. 9 is a diagram showing an operation flow of the operation control unit of the air-conditioning apparatus according to Embodiment 1.

As shown in Fig. 9, first, in step C101, the operation control unit 53 acquires the detection value Pi of the first pressure detection device 21, the detection value P2 of the second pressure detection device 22, and the circulation composition a calculated by the circulation composition calculation unit 52.

[0071] Next, in step C102, the operation control unit 53 calculates a condensing temperature Te from the detection value Pi of the first pressure detection device 21 and the circulation composition a. In addition, the operation control unit 53 calculates an evaporating temperature Te from the detection value P2 of the second pressure detection device 22 and the circulation composition a. The condensing temperature Te may be calculated by being read from a relationship between the detection value Pi of the first pressure detection device 21, the circulation composition a, and the condensing temperature To which relationship is previously stored as a table or the like. In addition, the evaporating temperature Te may calculated by being read from a relationship between the detection value P2 of the second pressure detection device 22, the circulation composition a, and the evaporating temperature Te which relationship is previously stored as a table or the like.

[0072] Next, in step C103, the operation control unit 53 calculates AL that is a value obtained by subtracting a target value Tom for a condensing temperature from the condensing temperature To, and ATe that is a value obtained by subtracting a target value Tern for an evaporating temperature from the evaporating temperature Te. The target value Tern for the condensing temperature and the target value Tern for the evaporating temperature are target values set in accordance with the outdoor temperature and the indoor temperature. The target value Tern for the condensing temperature and the target value Tern for the evaporating temperature may be calculated by being read from relationships between the outdoor temperature, the indoor temperature, and the target value 'Cm for the condensing temperature and the target value Tern for the evaporating temperature which relationships are previously stored as a table or the like.

[0073] Next, in step C104, the operation control unit 53 controls the frequency fo of the compressor 11, the rotation speed ft of the fan or the like constituting the heat source side air-sending device (not shown), etc. such that ATo and ATe become close to zero. The operation control unit 53 may control both the frequency fo of the compressor 11 and the rotation speed ft of the fan or the like constituting the heat source side air-sending device (not shown), or may control only either of them.

[0074] In step C104, for example, if the heat source side heat exchanger 13 serves as a condenser, when ATe is a positive value, the operation control unit 53 controls the frequency fc of the compressor 11 so as to decrease the frequency fe.

In addition, the operation control unit 53 controls the rotation speed ff of the fan or the like constituting the heat source side air-sending device (not shown) so as to increase the rotation speed ff. In step C104, for example, if the heat source side heat exchanger 13 serves as a condenser, when AL is a negative value, the operation control unit 53 controls the frequency fe of the compressor 11 so as to increase the frequency fe. In addition, the operation control unit 53 controls the rotation speed ff of the fan or the like constituting the heat source side air-sending device (not shown) so as to decrease the rotation speed ff.

[0075] In step C104, for example, if the heat source side heat exchanger 13 serves as an evaporator, when ATe is a positive value, the operation control unit 53 controls the frequency fc of the compressor 11 so as to increase the frequency fc. In addition, the operation control unit 53 controls the rotation speed ff of the fan or the like constituting the heat source side air-sending device (not shown) so as to decrease the rotation speed ff. In step C104, for example, if the heat source side heat exchanger 13 serves as an evaporator, when ATe is a negative value, the operation control unit 53 controls the frequency fe of the compressor 11 so as to decrease the frequency fe. In addition, the operation control unit 53 controls the rotation speed ff of the fan or the like constituting the heat source side air-sending device (not shown) so as to increase the rotation speed ff.

[0076] Embodiment 2 Hereinafter, an air-conditioning apparatus according to Embodiment 2 will be described.

Hereinafter, description overlapping with or similar to Embodiment 1 is simplified or omitted as appropriate.

[0077] Fig. 10 is a schematic circuit configuration diagram showing an example of a circuit configuration of the air-conditioning apparatus according to Embodiment 2.

As shown in Fig. 10, the air-conditioning apparatus 100 includes a plurality of outdoor units 2 and a plurality of indoor units 3. The plurality of outdoor units 2 and the plurality of indoor units 3 are connected to each other via a refrigerant main pipe 6. The number of the outdoor units 2 is not limited to two. The number of the indoor units 3 is not limited to three, and may be one.

[0078] In the case where a plurality of outdoor units 2 are provided as in the air-conditioning apparatus 100, for example, in heating operation or the like, low-pressure two-phase gas-liquid refrigerant flows from the indoor unit 3 through the refrigerant main pipe 6 into the plurality of outdoor units 2. Thus, distribution of the refrigerant is not uniform, and a situation occurs in which liquid refrigerant flows into one outdoor unit 2 in a large amount and gas refrigerant flows into another outdoor unit 2. If operation is continued in such a state, a state arises in which the outdoor units 2 in which excess refrigerant is absent within the accumulator 14 and the outdoor units 2 in which excess refrigerant is present within the accumulator 14 coexist. Thus, in the case where a plurality of outdoor units 2 are provided as in the air-conditioning apparatus 100, the configuration and operation, etc. of the controller 50 need to be different from those in the air-conditioning apparatus according to Embodiment 1.

[0079] [Controller] The controller 50 includes an excess refrigerant presence/absence determination unit 51, a circulation composition calculation unit 52, and an operation control unit 53. The respective units constituting the controller 50 may be provided separately in the plurality of outdoor units 2 and collectively in one representative outdoor unit 2 among the plurality of outdoor units 2, may be provided separately in the plurality of indoor units 3 or collectively in one representative indoor unit 3 among the plurality of indoor units 3, or may be provided separately in components other than these outdoor and indoor units or collectively in one of the components. The excess refrigerant presence/absence determination unit 51 corresponds to the "an excess refrigerant presence/absence determination unit" in the present invention. The circulation composition calculation unit 52 corresponds to the "a circulation composition calculation unit" in the present invention.

[0080] [Excess Refrigerant Presence/Absence Determination Unit] Hereinafter, operation of the excess refrigerant presence/absence determination unit 51 will be described.

Fig. 11 is a diagram showing an operation flow of the excess refrigerant presence/absence determination unit of the air-conditioning apparatus according to Embodiment 2.

As shown in Fig. 11, first, in step D101, the excess refrigerant presence/absence determination unit 51 acquires the detection value P2 of the second pressure detection device 22 and the detection value T2 of the second temperature detection device 24 from each of the plurality of outdoor units 2. Next, in step D102, the excess refrigerant presence/absence determination unit 51 determines presence/absence of excess refrigerant in each accumulator 14 through the operation flows as shown in Figs. 5 to 7. In step D103, the excess refrigerant presence/absence determination unit 51 determines whether excess refrigerant is absent within all the accumulators 14. If a result of the determination is YES, the excess refrigerant presence/absence determination unit 51 proceeds to step D104 and provides an output indicating that excess refrigerant is absent. If the result of the determination is NO, the excess refrigerant presence/absence determination unit 51 proceeds to step D105 and provides an output indicating that excess refrigerant is present.

[0081] [Circulation Composition Calculation Unit] Hereinafter, operation of the circulation composition calculation unit 52 will be described.

Fig. 12 is a diagram showing an operation flow of the circulation composition calculation unit of the air-conditioning apparatus according to Embodiment 2.

As shown in Fig. 12, in step E105, the circulation composition calculation unit 52 acquires the detection value P2 detected in the outdoor unit 2 in which it is determined that excess refrigerant is present, among the detection values P2 of the second pressure detection devices 22, and the detection value 12 detected in the outdoor unit 2 in which it is determined that excess refrigerant is present, among the detection values T2 of the second temperature detection devices 24. If the number of the outdoor units 2 in which it is determined that excess refrigerant is present is plural, for example, the averages of the detection values P2 and the detection values T2 detected in the outdoor units 2 in which it is determined that excess refrigerant is present may be acquired. In addition, among the detection values P2 and the detection values T2 detected in the outdoor units 2 in which it is determined that excess refrigerant is present, the detection value P2 and the detection value T2 detected in the representative outdoor unit 2 or the outdoor unit 2 having a largest amount of excess refrigerant, etc. may be acquired.

[0082] Although Embodiment 1 and Embodiment 2 have been described above, the present invention is not limited to the description of each Embodiment. For example, the entirety or a part of each Embodiment may be combined.

[0083] Although the case where the air-conditioning apparatus 100 has a direct expansion circuit in which the outdoor unit 2 and the indoor unit 3 are connected in series by the refrigerant main pipe 6 has been described above as an example, the present invention is not limited to such a case. For example, in the air-conditioning apparatus 100, the load side heat exchanger 31 and the expansion device 32 may be provided in a component other than the indoor unit 3, heat may be exchanged in the load side heat exchanger 31 between the refrigerant circulating through the refrigerant circuit 1 and another heat medium, and the heat medium may be supplied to another heat exchanger provided in the indoor unit 3. In addition, the air-conditioning apparatus 100 may include a multistage refrigerant circuit 1. Even in these cases, the same advantageous effects are exerted.

[0084] Although the case where the refrigerant filled in the refrigerant circuit 1 is a zeotropic refrigerant mixture in which R32 refrigerant and R1234yf refrigerant are mixed in weight ratios of 44 wt% and 56 wt% has been described above as an example, the present invention is not limited to such a case. The refrigerant filled in the refrigerant circuit 1 may be any type of a refrigerant mixture as long as the refrigerant is a zeotropic refrigerant mixture obtained by mixing a plurality of refrigerants and in which the temperature of saturated gas and the temperature of saturated liquid at the same pressure are different from each other, and the mixing ratios may be any ratios.

[0085] Although the case where the single compressor 11 is provided in the outdoor unit 2 has been described above as an example, the present invention is not limited to such case, and a plurality of compressors 11 may be provided in the outdoor unit 2. Although the case where the single accumulator 14 is provided in the outdoor unit 2 has been described above as an example, the present invention is not limited to such case, and a plurality of accumulators 14 may be provided in the outdoor unit 2.

[0086] Although the case where the refrigerant circuit 1 includes the refrigerant flow path switching device 12 has been described above as an example, the present invention is not limited to such a case. The refrigerant circuit 1 may not include the refrigerant flow path switching device 12, and the air-conditioning apparatus 100 may perform only either cooling operation or heating operation. In the case where presence/absence of excess refrigerant within the accumulator 14 changes in accordance with an operation state in the air-conditioning apparatus 100, the same advantageous effects are exerted.

Reference Signs List [0087] 1 refrigerant circuit 2 outdoor unit 3 indoor unit 4 refrigerant pipe 5 refrigerant pipe 6 refrigerant main pipe 11 compressor 12 refrigerant flow path switching device 13 heat source side heat exchanger 14 accumulator 21 first pressure detection device 22 second pressure detection device 23 first temperature detection device 24 second temperature detection device 31 load side heat exchanger 32 expansion device 41 third temperature detection device 42 fourth temperature detection device 43 fifth temperature detection device 50 controller 51 excess refrigerant presence/absence determination unit 52 circulation composition calculation unit 53 operation control unit 100 air-conditioning apparatus