Air-conditioning apparatus

Abstract

An air-conditioning apparatus includes a refrigerant circuit in which a compressor, a heat source side heat exchanger, an expansion device, and a load side heat exchanger are connected sequentially by a pipe, the refrigerant circuit being filled with a non-azeotropic refrigerant mixture as refrigerant, the air-conditioning apparatus including: a first pressure detection device configured to detect a pressure of refrigerant on a discharge side of the compressor or detect a pressure of refrigerant on a suction side of the compressor; an outdoor-air temperature detection device configured to detect an outdoor-air temperature; and a controller configured to execute a refrigerant leakage detection function of determining whether there is refrigerant leakage based on a pressure detected by the first pressure detection device and an outdoor-air temperature detected by the outdoor-air temperature detection device, when the air-conditioning apparatus is deactivated.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an air-conditioning apparatus to be used as a variable refrigerant flow (VRF) system or other systems.BACKGROUND ART

[0002] In a conventional air-conditioning apparatus such as a VRF system, for example, an outdoor unit located outside a building to serve as a heat source unit and a plurality of indoor units located inside the building are connected by refrigerant pipes to form a refrigerant circuit through which refrigerant circulates. The total length of the refrigerant pipes connecting the outdoor unit and the plurality of indoor units may extend to several hundreds of meters, and accordingly a considerable amount of refrigerant is used. In view of this circumstance, to prevent a large amount of refrigerant from being emitted to the atmosphere when refrigerant leakage has occurred in the air-conditioning apparatus, a technique to estimate whether there is refrigerant leakage based on the operating condition of the air-conditioning apparatus has been proposed (see, for example, Patent Literature 1).CITATION LISTPatent Literature

[0003] Patent Literature 1: International Publication No. WO 2009 / 157200SUMMARY OF INVENTIONTechnical Problem

[0004] However, in the technique disclosed in Patent Literature 1, the operation mode needs to be cooling operation mode. This results in a problem that it is impossible to determine whether there is refrigerant leakage during the intermediate period during which the air-conditioning apparatus is not operated, or during winter season during which heating operation is performed.

[0005] The present disclosure has been made to solve the above problem, and it is an object of the present disclosure to provide an air-conditioning apparatus that can detect the occurrence of refrigerant leakage from the air-conditioning apparatus regardless of the operational status of the air-conditioning apparatus.Solution to Problem

[0006] An air-conditioning apparatus according to an embodiment of the present disclosure is an air-conditioning apparatus including a refrigerant circuit in which a compressor, a heat source side heat exchanger, an expansion device, and a load side heat exchanger are connected sequentially by a pipe, the refrigerant circuit being filled with a non-azeotropic refrigerant mixture as refrigerant, the air-conditioning apparatus including: a first pressure detection device configured to detect a pressure of refrigerant on a discharge side of the compressor or detect a pressure of refrigerant on a suction side of the compressor; an outdoor-air temperature detection device configured to detect an outdoor-air temperature; and a controller configured to execute a refrigerant leakage detection function of determining whether there is refrigerant leakage based on a pressure detected by the first pressure detection device and an outdoor-air temperature detected by the outdoor-air temperature detection device, when the air-conditioning apparatus is deactivated.Advantageous Effects of Invention

[0007] The air-conditioning apparatus according to an embodiment of the present disclosure determines whether there is refrigerant leakage based on a pressure detected by the first pressure detection device and an outdoor-air temperature detected by the outdoor-air temperature detection device, when the air-conditioning apparatus is deactivated. With this configuration, it is possible to detect refrigerant leakage throughout the year regardless of the season, and it is thus possible to detect the occurrence of refrigerant leakage from the air-conditioning apparatus regardless of the operational status of the air-conditioning apparatus.BRIEF DESCRIPTION OF DRAWINGS

[0008] FIG. 1 is a schematic configuration diagram illustrating an example of the configuration of an air-conditioning apparatus according to an embodiment.

[0009] FIG. 2 is a refrigerant circuit diagram illustrating an example of the circuit configuration of the air-conditioning apparatus according to the embodiment.

[0010] FIG. 3 is a refrigerant circuit diagram illustrating a flow of refrigerant during cooling operation of the air-conditioning apparatus according to the embodiment.

[0011] FIG. 4 is a refrigerant circuit diagram illustrating a flow of refrigerant during heating operation of the air-conditioning apparatus according to the embodiment.

[0012] FIG. 5 is a flowchart illustrating operation of a refrigerant leakage detection function in the air-conditioning apparatus according to the embodiment.DESCRIPTION OF EMBODIMENT

[0013] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. Note that the present disclosure is not limited by the embodiment described below. In addition, the relationship of sizes of the components in the drawings described below may differ from that of actual ones.Embodiment 1

[0014] FIG. 1 is a schematic configuration diagram illustrating an example of the configuration of an air-conditioning apparatus 100 according to an embodiment.

[0015] The configuration of the air-conditioning apparatus 100 according to Embodiment 1 is described below with reference to FIG. 1.

[0016] The air-conditioning apparatus 100 according to the embodiment is configured to circulate a non-azeotropic refrigerant mixture made up of a plurality of refrigerants with different boiling points in a refrigerant circuit (see FIG. 2 which will be described later), and to condition air by using a refrigeration cycle. The non-azeotropic refrigerant mixture is, for example, an R454B refrigerant obtained by mixing an R32 refrigerant and an R1234yf refrigerant at a mass ratio of 68.9 [wt %]:31.1[wt %]. The air-conditioning apparatus 100 can select either cooling only operation mode in which all the indoor units to be operated perform cooling operation or heating only operation mode in which all the indoor units perform heating operation similarly to, for example, a variable refrigerant flow (VRF) system. As illustrated in FIG. 1, the air-conditioning apparatus 100 includes one outdoor unit 1 and two indoor units 2a and 2b. The outdoor unit 1 is connected to the indoor units 2a and 2b by a main refrigerant pipe 3 and branch refrigerant pipes 4a and 4b located in a space above a ceiling 61. The indoor units 2a and 2b are installed in air-conditioned spaces 60a and 60b , respectively. Note that while in the embodiment, one outdoor unit 1 and two indoor units 2a and 2b are provided as illustrated in FIG. 1, this is not a limitation. The number of outdoor units 1 may be two or more. The number of indoor units 2a and 2b may be one or three or more.

[0017] FIG. 2 is a refrigerant circuit diagram illustrating an example of the circuit configuration of the air-conditioning apparatus 100 according to the embodiment.

[0018] The air-conditioning apparatus 100 includes the refrigerant circuit through which refrigerant flows, as illustrated in FIG. 2. The refrigerant circuit is formed by connecting a compressor 10, a refrigerant flow switching device 11, a heat source side heat exchanger 12, expansion devices 41a and 41b, load side heat exchangers 40a and 40b, and an accumulator 13 sequentially by pipes including the main refrigerant pipe 3, the branch refrigerant pipes 4a and 4b, and a refrigerant pipe 5.Outdoor Unit 1

[0019] The outdoor unit 1 includes the compressor 10, the refrigerant flow switching device 11, the heat source side heat exchanger 12, and the accumulator 13. A heat source side air-sending device 14 constituted by, for example, a fan is located near the heat source side heat exchanger 12. The heat source side air-sending device 14 delivers air to the heat source side heat exchanger 12. The compressor 10, the refrigerant flow switching device 11, the heat source side heat exchanger 12, and the accumulator 13 are connected by the refrigerant pipe 5.

[0020] The compressor 10 is configured to suction low-temperature low-pressure refrigerant and compress the refrigerant into a high-temperature high-pressure state. It is preferable that the compressor 10 is constituted by, for example, an inverter compressor whose capacity is controllable. The refrigerant flow switching device 11 is, for example, a four-way valve, and configured to switch between a refrigerant flow in cooling operation mode and another refrigerant flow in heating operation mode.

[0021] The heat source side heat exchanger 12 serves as a condenser in cooling operation mode, while serving as an evaporator in heating operation mode. The heat source side heat exchanger 12 is configured to exchange heat between refrigerant and air supplied from the heat source side air-sending device 14.

[0022] The accumulator 13 is located on the suction side of the compressor 10, and is configured to reserve surplus refrigerant generated due to differences in operational condition between cooling operation mode and heating operation mode, or surplus refrigerant for a transitional operational change.

[0023] The outdoor unit 1 includes a discharge-pressure detection device 20 and a suction-pressure detection device 21. The discharge-pressure detection device 20 is located on the refrigerant pipe 5 connecting the discharge side of the compressor 10 and the refrigerant flow switching device 11. The discharge-pressure detection device 20 is configured to detect a pressure of high-temperature high-pressure refrigerant on the discharge side of the compressor 10. The suction-pressure detection device 21 is located on the refrigerant pipe 5 connecting the suction side of the compressor 10 and the refrigerant flow switching device 11. The suction-pressure detection device 21 is configured to detect a pressure of low-temperature low-pressure refrigerant on the suction side of the compressor 10. The discharge-pressure detection device 20 and the suction-pressure detection device 21 are, for example, pressure sensors.

[0024] The outdoor unit 1 further includes an outdoor-air temperature detection device 22 and a first temperature detection device 23. The outdoor-air temperature detection device 22 is located at an air inlet portion (not illustrated) of the outdoor unit 1 and is configured to detect an air temperature at a location where the outdoor unit 1 is installed (hereinafter, referred to as “outdoor-air temperature”). The first temperature detection device 23 is located on the refrigerant pipe 5 connecting the discharge side of the compressor 10 and the refrigerant flow switching device 11. The first temperature detection device 23 is configured to detect a temperature of high-temperature high-pressure refrigerant on the discharge side of the compressor 10 (hereinafter, referred to as “discharge temperature”). The outdoor-air temperature detection device 22 and the first temperature detection device 23 are, for example, thermistors.Indoor Units 2a and 2b

[0025] The indoor units 2a and 2b include load side heat exchangers 40a and 40b, and expansion devices 41a and 41b, respectively. Near the load side heat exchangers 40a and 40b, load side air-sending devices 42a and 42b are located respectively and constituted by, for example, a fan. The load side air-sending devices 42a and 42b deliver air to the load side heat exchangers 40a and 40b, respectively. The indoor units 2a and 2b are connected to the outdoor unit 1 through the main refrigerant pipe 3 through which refrigerant flows into and out from the indoor units 2a and 2b. The load side heat exchangers 40a and 40b are configured to exchange heat between refrigerant and air supplied from the load side air-sending devices 42a and 42b, respectively, and generate heated air or cooled air to be supplied to a room space. The expansion devices 41a and 41b serve as a pressure reducing valve or an expansion valve, and are configured to reduce the pressure of refrigerant to expand the refrigerant. It is preferable that the expansion devices 41a and 41b are constituted by, for example, an electronic expansion valve whose opening degree is variably controllable.

[0026] The indoor units 2a and 2b include second temperature detection devices 50a and 50b, third temperature detection devices 51a and 51b, and fourth temperature detection devices 42a and 42b, respectively. The second temperature detection devices 50a and 50b are located respectively on the branch refrigerant pipes 4a and 4b through which the expansion devices 41a and 41b connect to the load side heat exchangers 40a and 40b respectively. The second temperature detection devices 50a and 50b are configured to detect a temperature of refrigerant flowing into the load side heat exchangers 40a and 4b, respectively, in cooling operation mode. The third temperature detection devices 51a and 51b are located respectively on the branch refrigerant pipes 4a and 4b on the opposite side to the expansion devices 41a and 41b with reference to the load side heat exchangers 40a and 40b, respectively. The third temperature detection devices 51a and 51b are configured to detect a temperature of refrigerant flowing out from the load side heat exchangers 40a and 40b, respectively, in cooling operation mode. The fourth temperature detection devices 52a and 52b are located at air inlet portions (not illustrated) of the load side heat exchangers 40a and 40b, respectively, and are configured to detect an air temperature in a room. The second temperature detection devices 50a and 50b, the third temperature detection devices 51a and 51b, and the fourth temperature detection devices 52a and 52b are, for example, thermistors.

[0027] Note that in the descriptions below, the indoor units 2a and 2b are collectively referred to as “indoor unit 2,” the load side heat exchangers 40a and 40b are collectively referred to as “load side heat exchanger 40,” the expansion devices 41a and 41b are collectively referred to as “expansion device 41,” and the load side air-sending devices 42a and 42b are collectively referred to as “load side air-sending device 42.” In addition, the second temperature detection devices 50a and 50b are collectively referred to as “second temperature detection device 50,” the third temperature detection devices 51a and 51b are collectively referred to as “third temperature detection device 51,” and the fourth temperature detection devices 52a and 52b are collectively referred to as “fourth temperature detection device 52.” Further, either the discharge-pressure detection device 20 or the suction-pressure detection device 21 is also referred to as “first pressure detection device.” Furthermore, the discharge-pressure detection device 20 and the suction-pressure detection device 21 are collectively referred to as “pressure detection device.”

[0028] The air-conditioning apparatus 100 includes a controller 30 made up of a microcomputer and other devices. The controller 30 is configured to control the frequency of the compressor 10, the rotation speed of the heat source side air-sending device 14 (including on / off of the heat source side air-sending device 14) for the heat source side heat exchanger 12, switching of the refrigerant flow switching device 11, the opening degree of the expansion device 41, and other conditions based on a value detected by various types of detection devices and an instruction from a remote control, so that the air-conditioning apparatus 100 enters each operation mode which will be described later. Note that while in the embodiment, an example is described in which the controller 30 is provided in the outdoor unit 1 as illustrated in FIG. 2, this is not a limitation. The controller 30 may be provided in the indoor unit 2, or may be provided in both the outdoor unit 1 and the indoor unit 2.Cooling Operation Mode

[0029] FIG. 3 is a refrigerant circuit diagram illustrating a flow of refrigerant in cooling operation mode of the air-conditioning apparatus 100 according to the embodiment. Note that in FIG. 3, the solid arrow illustrates the refrigerant flow direction.

[0030] The cooling operation mode of the air-conditioning apparatus 100 according to the embodiment is described below with reference to FIG. 3, using an example in which a cooling load is generated in the load side heat exchangers 40a and 40b.

[0031] In the cooling operation mode, the refrigerant flow switching device 11 is switched to a refrigerant flow in which the refrigerant discharged from the compressor 10 flows into the heat source side heat exchanger 12. Low-temperature low-pressure refrigerant is compressed by the compressor 10 into high-temperature high-pressure gas refrigerant and then discharged. The high-temperature high-pressure gas refrigerant discharged from the compressor 10 flows into the heat source side heat exchanger 12 via the refrigerant flow switching device 11. The high-temperature high-pressure gas refrigerant flowing into the heat source side heat exchanger 12 condenses into high-pressure liquid refrigerant, while transferring heat to outdoor air. The high-pressure liquid refrigerant having flowed out from the heat source side heat exchanger 12 flows out from the outdoor unit 1, passes through the main refrigerant pipe 3 and the branch refrigerant pipes 4a and 4b, and then flows into the indoor units 2a and 2b.

[0032] The high-pressure liquid refrigerant flowing into the indoor units 2a and 2b is reduced in pressure by the expansion devices 41a and 41b, respectively, into low-temperature low-pressure two-phase refrigerant. Thereafter, the two-phase refrigerant flows into the load side heat exchangers 40a and 40b that serve as an evaporator, receives heat from room air to cool the room air, and turns into low-temperature low-pressure gas refrigerant. The low-temperature low-pressure gas refrigerant flowing out from the load side heat exchangers 40a and 40b passes through the branch refrigerant pipes 4a and 4b and the main refrigerant pipe 3, and then flows into the outdoor unit 1. The refrigerant flowing into the outdoor unit 1 passes through the refrigerant flow switching device 11 and the accumulator 13 and is suctioned into the compressor 10.

[0033] The opening degree of the expansion devices 41a and 41b is controlled by the controller 30 such that the degree of superheat becomes constant. The degree of superheat is obtained by calculating a difference between a temperature detected by the second temperature detection devices 50a and 50b and a temperature detected by the third temperature detection devices 51a and 51b. Controlling the opening degree in this manner allows the air-conditioning apparatus 100 to show appropriate performance in response to a heat load in the room, and perform efficient operation.Heating Operation Mode

[0034] FIG. 4 is a refrigerant circuit diagram illustrating a flow of refrigerant in heating operation mode of the air-conditioning apparatus 100. In FIG. 4, the solid arrow illustrates the refrigerant flow direction. Note that in FIG. 4, the solid arrow illustrates the refrigerant flow direction.

[0035] The heating operation of the air-conditioning apparatus 100 according to the embodiment is described below with reference to FIG. 4, using an example in which a heating load is generated in the load side heat exchangers 40a and 40b.

[0036] In the heating operation mode, the refrigerant flow switching device 11 is switched to a refrigerant flow in which the refrigerant discharged from the compressor 10 flows into the load side heat exchangers 40a and 40b. Low-temperature low-pressure refrigerant is compressed by the compressor 10 into high-temperature high-pressure gas refrigerant and then discharged. The high-temperature high-pressure gas refrigerant discharged from the compressor 10 passes through the main refrigerant pipe 3 and the branch refrigerant pipes 4a and 4b via the refrigerant flow switching device 11, and then flows into the indoor units 2a and 2b. The high-temperature high-pressure gas refrigerant flowing into the indoor units 2a and 2b transfers heat to room air in the load side heat exchangers 40a and 40b , respectively, turning into high-pressure liquid refrigerant, and then flows into the expansion devices 41a and 41b, respectively. The high-pressure liquid refrigerant is reduced in pressure by the expansion devices 41a and 41b into low-temperature low-pressure two-phase refrigerant. Thereafter, the two-phase refrigerant flows out from the indoor units 2a and 2b, passes through the branch refrigerant pipes 4a and 4b and the main refrigerant pipe 3, and flows into the outdoor unit 1.

[0037] The low-temperature low-pressure two-phase refrigerant having flowed into the outdoor unit 1 flows into the heat source side heat exchanger 12, receives heat from the outdoor air, and tums into low-temperature low-pressure gas refrigerant. The low-temperature low-pressure gas refrigerant flowing out from the heat source side heat exchanger 12 passes through the refrigerant flow switching device 11 and the accumulator 13, and is suctioned into the compressor 10.

[0038] The opening degree of the expansion devices 41a and 41b is controlled by the controller 30 such that the degree of subcooling becomes constant. The degree of subcooling is obtained by calculating a difference between a saturated liquid temperature of refrigerant calculated based on a pressure detected by the discharge-pressure detection device 20 and a temperature detected by the second temperature detection devices 50a and 50b. Controlling the opening degree in this manner allows the air-conditioning apparatus 100 to show appropriate performance in response to a heat load in the room, and perform efficient operation.Refrigerant Leakage Detection Function

[0039] Next, a refrigerant leakage detection function is described. The refrigerant leakage detection function is one of the functions of the controller 30. When the air-conditioning apparatus 100 is in a deactivated state, the refrigerant leakage detection function detects whether there is refrigerant leakage based on a value detected by the pressure detection device installed in the outdoor unit 1 and a value detected by the outdoor-air temperature detection device 22.

[0040] FIG. 5 is a flowchart illustrating operation of the refrigerant leakage detection function in the air-conditioning apparatus 100 according to the embodiment.

[0041] The operation of the refrigerant leakage detection function in the air-conditioning apparatus 100 according to the embodiment is described below with reference to FIG. 5.(Step S1)

[0042] The controller 30 determines whether the air-conditioning apparatus 100 is in a deactivated state. The wording “the air-conditioning apparatus 100 is in a deactivated state” refers to a state in which the compressor 10 stops working. When the controller 30 determines that the air-conditioning apparatus 100 is in a deactivated state (YES), the processing advances to step S2. In contrast, when the controller 30 determines that the air-conditioning apparatus 100 is not in a deactivated state (NO), the processing repeats step S1.(Step S2)

[0043] The controller 30 determines whether a predetermined time (hereinafter, also referred to as “first time set in advance”) or longer has elapsed since the air-conditioning apparatus 100 was brought into a deactivated state. The controller 30 has a timer function of measuring time. When the controller 30 determines that a predetermined time or longer has elapsed since the air-conditioning apparatus 100 was brought into a deactivated state (YES), the processing advances to step S3. In contrast, when the controller 30 determines that a predetermined time or longer has not elapsed yet since the air-conditioning apparatus 100 was brought into a deactivated state (NO), the processing returns to step S1. Note that while in the embodiment, the controller 30 has the timer function, this is not a limitation. For example, a real-time clock may be provided outside the controller 30.(Step S3)

[0044] The controller 30 determines whether the outdoor-air temperature detected by the outdoor-air temperature detection device 22 is stable. Whether the outdoor-air temperature detected by the outdoor-air temperature detection device 22 is stable is determined based on, for example, whether the outdoor-air temperature detected by the outdoor-air temperature detection device 22 falls within a predetermined range for a predetermined period of time. When the controller 30 determines that the outdoor-air temperature detected by the outdoor-air temperature detection device 22 is stable (YES), the processing advances to step S4. In contrast, when the controller 30 determines that the outdoor-air temperature detected by the outdoor-air temperature detection device 22 is not stable (NO), the processing returns to step S1.(Step S4)

[0045] The controller 30 calculates a saturation temperature of refrigerant based on a value detected by the discharge-pressure detection device 20. Note that in a non-azeotropic refrigerant mixture, there is a difference between a saturated vapor temperature and a saturated liquid temperature at an equal pressure, and it is thus necessary to clearly define which saturation temperature is used, the saturated vapor temperature or the saturated liquid temperature, or whether to use an average value of these two saturated vapor and liquid temperatures. Any of the saturated vapor temperature, the saturated liquid temperature, or the average value of these two saturated vapor and liquid temperatures may be used for the refrigerant leakage detection function according to the embodiment when the air-conditioning apparatus 100 is in a deactivated state. While in the above description, the saturation temperature of refrigerant is calculated using the discharge-pressure detection device 20, the saturation temperature of refrigerant may be calculated using the suction-pressure detection device 21 instead of the discharge-pressure detection device 20.(Step S5)

[0046] The controller 30 determines whether a difference between the saturation temperature of refrigerant calculated in step S4 and the outdoor-air temperature detected by the outdoor-air temperature detection device 22 is equal to or larger than a predetermined value. When the controller 30 determines that a difference between the saturation temperature of refrigerant and the outdoor-air temperature is equal to or larger than a predetermined value (YES), the processing advances to step S6. In contrast, when the controller 30 determines that a difference between the saturation temperature of refrigerant and the outdoor-air temperature is not equal to or larger than a predetermined value (NO), the processing returns to step S1.(Step S6)

[0047] The controller 30 determines that refrigerant leakage has occurred in the air-conditioning apparatus 100, and then the processing ends. Thereafter, the controller 30 executes, for example, a refrigerant leakage announcing function which will be described later.Principles of Refrigerant Leakage Detection Function

[0048] Next, principles of the refrigerant leakage detection function are described.

[0049] First, a refrigerant to be filled in the refrigerant circuit of the air-conditioning apparatus 100 according to the embodiment is a non-azeotropic refrigerant mixture. The non-azeotropic refrigerant mixture is made up of a plurality of types of refrigerants with different boiling points. For example, the non-azeotropic refrigerant mixture is an R454B refrigerant that is a mixture of an R32 refrigerant and an R1234yf refrigerant. Note that the R32 refrigerant has a boiling point of −57.1 [degrees C.] under atmospheric pressure, while the R1234yf refrigerant has a boiling point of −29.4 [degrees C.] under atmospheric pressure. When there is a difference in boiling point between the constituent refrigerants of the non-azeotropic refrigerant mixture as described above, if refrigerant leakage has occurred in the air-conditioning apparatus 100, then the R32 refrigerant with a lower boiling point tends to be emitted more to the outside of the system than the R1234yf refrigerant.

[0050] In view of that, the ratio between constituent refrigerants of the non-azeotropic refrigerant mixture to be filled in the refrigerant circuit of the air-conditioning apparatus 100 varies depending on whether there is refrigerant leakage. The non-azeotropic refrigerant mixture present in the air-conditioning apparatus 100 has a physical property value that is variable depending on whether there is refrigerant leakage. The refrigerant leakage detection function utilizes a change in the physical property value of the non-azeotropic refrigerant mixture caused by this refrigerant leakage.

[0051] The principles of the refrigerant leakage detection function are explained below in more detail. In general, when the air-conditioning apparatus 100 is in a deactivated state, refrigerant in the refrigerant circuit and outdoor air at the location where the outdoor unit 1 is installed are thermally balanced. Consequently, the saturation temperature calculated based on the refrigerant pressure in the refrigerant circuit becomes equal to the outdoor-air temperature.

[0052] However, when refrigerant leakage has occurred, there is a change in the physical property value of the non-azeotropic refrigerant mixture as described above. Thus, the pressure in the refrigerant circuit when the air-conditioning apparatus 100 is deactivated at a certain outdoor-air temperature varies depending on whether there is refrigerant leakage. For this reason, the principles of the refrigerant leakage detection function are that a pressure difference in the refrigerant circuit when the air-conditioning apparatus 100 is deactivated is detected to detect whether there is refrigerant leakage.

[0053] The R454B refrigerant is described as an example. When refrigerant leakage does not occur, the R32 refrigerant and the R1234yf refrigerant are present at a mass ratio of 68.9 [wt %]:31.1 [wt %] in the refrigerant circuit of the air-conditioning apparatus 100. In contrast, when refrigerant leakage has occurred, and where a composition change due to the refrigerant leakage is represented as α(>0), the R32 refrigerant and the R1234yf refrigerant are present at a mass ratio of (68.9-α) [wt %]:(31.1+α) [wt %] in the refrigerant circuit of the air-conditioning apparatus 100. In other words, when refrigerant leakage has occurred, the ratio of the R32 refrigerant with a lower boiling point in the composition is decreased.

[0054] In a state in which refrigerant leakage causes a change in the composition of refrigerant, there is also a change in the physical property value of the non-azeotropic refrigerant mixture. For example, there is a change in the saturation pressure at a certain temperature.

[0055] A case where the outdoor-air temperature is 35 [degrees C.] is described as an example. When refrigerant leakage does not occur, the outdoor air and the outdoor unit 1 are thermally balanced provided that the air-conditioning apparatus 100 is in a deactivated state. Thus, the pressure in the refrigerant circuit is 2.0 [MPaA] that is a saturation pressure of the R454B refrigerant at a temperature of 35 [degrees C.]. In contrast, when refrigerant leakage has occurred, the outdoor air at the same temperature (35 [degrees C.]) and the outdoor unit 1 are still thermally balanced. However, the ratio of the R32 refrigerant in the composition of the R454B refrigerant is decreased by the composition change α, while the ratio of the R1234yf refrigerant in the composition of the R454B refrigerant is increased by the composition change α. Accordingly, the pressure in the refrigerant circuit varies even at the same outdoor-air temperature of 35 [degrees C.]. In this example case, since the ratio of the R32 refrigerant in the composition is decreased, the pressure in the refrigerant circuit is decreased from 2.0 [MPaA] that is a pressure detected when refrigerant leakage does not occur.

[0056] The controller 30 has stored therein a relationship between a saturation temperature and a pressure of non-azeotropic refrigerants in the filling composition in a format of table or approximate expression. When the saturation temperature calculated based on a pressure detected by the discharge-pressure detection device 20 or the suction-pressure detection device 21 is not equal to the outdoor-air temperature, the controller 30 can determine that refrigerant leakage has occurred.

[0057] That is, the controller 30 is configured to determine whether the outdoor air and the outdoor unit 1 are thermally balanced in steps S1 to S3 illustrated in FIG. 5, and calculate the difference between the saturation temperature and the outdoor-air temperature caused by the refrigerant leakage described above in steps S4 to S6, thereby to detect the occurrence of refrigerant leakage.

[0058] The amount of decrease in saturation pressure when refrigerant leakage has occurred varies depending on the types of non-azeotropic refrigerants to be used in the air-conditioning apparatus 100, the size of refrigerant circuit of the air-conditioning apparatus 100, how much refrigerant has leaked to the outside of the system, and other factors. It is thus difficult to set a certain fixed value as the predetermined value in step S5 illustrated in FIG. 5.

[0059] Assuming that the predetermined value in step S5 in FIG. 5 to be used for determining whether refrigerant leakage has occurred is set to a relatively small value, it is possible to detect even a small amount of refrigerant leakage. However, if the outdoor air and the outdoor unit 1 are not sufficiently thermally balanced, or due to a measurement error made by the pressure detection device or the outdoor-air temperature detection device 22, there is a possibility for the controller 30 to incorrectly determine whether refrigerant leakage has occurred. In contrast, when the predetermined value in step S5 is set to a relatively large value, there is a reduced risk of an incorrect determination regarding refrigerant leakage. However, this has a disadvantage that the controller 30 can determine that there is refrigerant leakage only when a large amount of refrigerant leaks from the air-conditioning apparatus 100. In view of this disadvantage, the predetermined value in step S5 needs to be variable depending on the type of refrigerant to be used, the size of refrigerant circuit of the air-conditioning apparatus 100, how much refrigerant has leaked to the outside of the system, and other factors. Since the predetermined value in step S5 is also affected by the installation condition of the air-conditioning apparatus 100, it is preferable that the predetermined value is adjustable even on site at the stage of finishing the installation work.

[0060] A supplementary explanation on the predetermined value in step S5 is given by using the R454B refrigerant as an example. There is an R454C refrigerant made up of the same constituent refrigerants as the R454B refrigerant. The R454C refrigerant is a refrigerant mixture of an R32 refrigerant and an R1234yf refrigerant at a mass ratio of 21.5 [wt %]:78.5 [wt %]. In an example case where the outdoor-air temperature is 7 [degrees C.], the R454B refrigerant has a saturated vapor pressure of 0.91 [MPaA], while the R454C refrigerant has a saturated vapor pressure of 0.57 [MPaA] at the same outdoor-air temperature of 7 [degrees C.]. This pressure of 0.57 [MPaA] corresponds to the saturation temperature of-8.1 [degrees C.] for the R454B refrigerant.

[0061] That is, when the air-conditioning apparatus 100 is deactivated under the condition that the outdoor-air temperature is 7 [degrees C.], and when there is not leakage of the R454B refrigerant, its saturation temperature is 7 [degrees C.] based on a value detected by the discharge-pressure detection device 20. In contrast, when leakage of the R454B refrigerant has occurred, the R32 refrigerant is emitted to the atmosphere earlier than the R1234yf refrigerant, and accordingly the refrigerant composition becomes equivalent to that of the R454C refrigerant. In that case, the saturation temperature of the R454B refrigerant is −8.1 [degrees C.] based on a value detected by the discharge-pressure detection device 20. Therefore, in the present embodiment, even the predetermined value in step S5 that is set to 1 [degree C.] is still sufficient to detect refrigerant leakage.

[0062] Note that it is preferable to use, as the outdoor-air temperature detection device 22, a temperature detection device with higher detection accuracy than the detection accuracy of the other temperature detection devices, to thereby improve the detection accuracy of the refrigerant leakage detection function. Likewise, it is preferable to use a pressure detection device with higher detection accuracy as at least either the discharge-pressure detection device 20 or the suction-pressure detection device 21. and to determine whether refrigerant leakage has occurred by using a value detected by the pressure detection device.

[0063] For a determination of whether the outdoor air and the outdoor unit 1 are thermally balanced in steps S2 and S3 in FIG. 5, which is a necessary condition for the refrigerant leakage detection function, it is preferable to set the predetermined time in step S2 to a time required for a value detected by the discharge-pressure detection device 20 installed in the outdoor unit 1 to become equal to a value detected by the suction-pressure detection device 21. As a value detected by the outdoor-air temperature detection device22 is more stable in step S3, a determination of whether refrigerant leakage has occurred is performed with more improved accuracy. For this reason, it is preferable to perform a determination of whether the outdoor-air temperature detected by the outdoor-air temperature detection device 22 is stable based on, for example, whether the outdoor-air temperature varies by 1 degree C. or less per hour.

[0064] Even in a case where the refrigerant circuit of the air-conditioning apparatus 100 is filled with a single-component refrigerant, as refrigerant leakage has occurred, the pressure in the refrigerant circuit decreases, so that it may still be possible to determine that refrigerant leakage has occurred based on a value detected by the pressure detection device. However, in a large-sized air-conditioning device having the accumulator 13 installed therein, such as a VRF system, surplus refrigerant in a liquid phase is present in the refrigerant circuit. When the pressure in the refrigerant circuit is likely to decrease due to the refrigerant leakage, the surplus refrigerant evaporates into gas refrigerant which prevents the decrease in pressure in the refrigerant circuit. Due to this phenomenon, the pressure in the refrigerant circuit is less likely to vary until the surplus refrigerant present in a liquid phase evaporates completely. Thus, when a single-component refrigerant is used in the air-conditioning apparatus having the accumulator 13 installed therein, it is difficult to detect refrigerant leakage by using the refrigerant pressure.

[0065] In contrast to that, in a case where the refrigerant circuit of the air-conditioning apparatus 100 is filled with a non-azeotropic refrigerant mixture, when the accumulator 13 is installed in the air-conditioning apparatus 100, the pressure in the refrigerant circuit is less likely to be reduced due to evaporation of surplus refrigerant in a liquid phase similarly to the case where the refrigerant circuit is filled with a single-component refrigerant. However, the non-azeotropic refrigerant mixture has such properties that a constituent refrigerant with a lower boiling point in the non-azeotropic refrigerant mixture leaks more to the outside of the system than the other constituent refrigerant. This causes a variation in the refrigerant composition (a change in the physical property value), which helps detect even a small amount of refrigerant leakage.

[0066] The principles of the refrigerant leakage detection function according to the present embodiment use a difference in boiling point between non-azeotropic refrigerants. Thus, the air-conditioning apparatus 100 using a non-azeotropic refrigerant mixture does not necessarily include the accumulator 13 as an essential constituent element, and can still detect refrigerant leakage through the operation illustrated in FIG. 5 without including the accumulator 13.

[0067] The controller 30 configured to execute a regular inspection function of executing the refrigerant leakage detection function every predetermined time (hereinafter, also referred to as “second time set in advance”). This regular inspection function allows a determination of whether refrigerant leakage has occurred in the air-conditioning apparatus 100 to be performed even during periods in which the air-conditioning apparatus 100 is not operated such as intermediate periods like spring or autumn, or during the night. With this function, it is possible to check whether refrigerant leakage has occurred every day or once in several days, which helps detect refrigerant leakage earlier. It is also possible to detect refrigerant leakage regardless of the location where the refrigerant leakage has occurred.

[0068] The controller 30 further has the refrigerant leakage announcing function of announcing the occurrence of refrigerant leakage when the controller 30 executes the refrigerant leakage detection function and determines that there is refrigerant leakage. Examples of means of announcing refrigerant leakage include warning with a buzzer, and issuing an alert that indicates detection of the occurrence of refrigerant leakage to a centralized control device when the centralized control device is connected to the air-conditioning apparatus 100 to urge a facilities manager to inspect the air-conditioning apparatus 100. This allows the facilities manager to be notified of the occurrence of refrigerant leakage earlier, so that the facilities manager can take prompt action on the devices such as a repair as appropriate.

[0069] It is general for conventional air-conditioning apparatuses using a flammable refrigerant or other types of refrigerant to ensure safety in a room against refrigerant leakage by installing a refrigerant leakage detection device in an indoor unit or an air-conditioned space where the indoor unit is installed. However, this leads to a problem that it is impossible to detect refrigerant leakage in a space where the refrigerant leakage detection device is not installed, such as a space above a ceiling or a room with a large floor area.

[0070] To cope with this problem, the refrigerant leakage detection function according to the present embodiment is used, although it is still necessary to use a non-azeotropic refrigerant mixture. This allows for detection of refrigerant leakage even from a location where the refrigerant leakage detection device is not installed, so that the indoor side safety can be improved.

[0071] In a case where safety devices stipulated in the international standards such as ISO5149 or IEC60335-2-40, including an alarm device, a ventilation device, and a shut-off device, are installed in the air-conditioning apparatus 100, this air-conditioning apparatus 100 is configured to activate the above safety devices when the refrigerant leakage detection function according to the present embodiment determines that there is refrigerant leakage, so that the indoor side safety can further be improved.

[0072] In the air-conditioning apparatus 100 according to the present embodiment, while an example case has been described in which both the indoor units 2a and 2b perform the same operation, that is, perform operation in either cooling operation mode or heating operation mode, this is not a limitation. The indoor units 2a and 2b may perform operation in different modes, that is, perform operation simultaneously in cooling operation mode and heating operation mode.

[0073] While in the present embodiment, an example case has been described in which one outdoor unit 1 is provided, the number of the outdoor units 1 is not limited to one. Operation of the refrigerant leakage detection function illustrated in FIG. 5 requires two detection devices including the pressure detection device and the outdoor-air temperature detection device 22 as necessary constituent elements for the outdoor unit 1, and other constituent elements of the air-conditioning apparatus 100 are not particularly limited. Therefore, in a large-sized air-conditioning system made up of a plurality of outdoor units 1, the refrigerant leakage detection function may be operated in each of the outdoor units 1, or one of the plurality of outdoor units 1 is set as a representative outdoor unit and the refrigerant leakage detection function may be operated only in the representative outdoor unit 1.

[0074] In the air-conditioning apparatus 100 according to the present embodiment, while an example case has been described in which one compressor 10 is provided in the outdoor unit 1, this is not a limitation. Two or more compressors 10 may be provided in the outdoor unit 1.

[0075] As described above, the air-conditioning apparatus 100 according to the embodiment includes the refrigerant circuit in which the compressor 10, the heat source side heat exchanger 12, the expansion device 41, and the load side heat exchanger 40 are connected sequentially by the pipe, the refrigerant circuit being filled with a non-azeotropic refrigerant mixture as refrigerant, the air-conditioning apparatus 100 including: the first pressure detection device configured to detect a pressure of refrigerant on the discharge side of the compressor 10 or detect a pressure of refrigerant on the suction side of the compressor 10; the outdoor-air temperature detection device 22 configured to detect an outdoor-air temperature; and the controller 30 configured to execute the refrigerant leakage detection function of determining whether there is refrigerant leakage based on a pressure detected by the first pressure detection device and an outdoor-air temperature detected by the outdoor-air temperature detection device 22, when the air-conditioning apparatus 100 is deactivated.

[0076] The air-conditioning apparatus 100 according to the present embodiment determines whether there is refrigerant leakage based on a pressure detected by the first pressure detection device and an outdoor-air temperature detected by the outdoor-air temperature detection device 22, when the air-conditioning apparatus 100 is deactivated. With this configuration, it is possible to detect refrigerant leakage throughout the year regardless of the season, and it is thus possible to detect the occurrence of refrigerant leakage from the air-conditioning apparatus regardless of the operational status of the air-conditioning apparatus.

[0077] According to the conventional technique, some air-conditioning apparatuses have an object to ensure safety in an air-conditioned space where an indoor unit is installed, and are not intended to detect refrigerant leakage in places such as a large space where the concentration of refrigerant in the air-conditioned space is still relatively low even if refrigerant leakage has occurred, or to detect refrigerant leakage from a refrigerant pipe that is present in a non-air-conditioned space such as a space above a ceiling. However, the air-conditioning apparatus 100 according to the embodiment can still detect refrigerant leakage regardless of the location where refrigerant leakage has occurred.

[0078] According to the conventional technique, some air-conditioning apparatuses have a plurality of shut-off valves therein, and are configured to detect a reduction in the pressure in a section closed by the shut-off valves, thereby to identify the location of refrigerant leakage. However, the air-conditioning apparatus 100 according to the embodiment does not need a plurality of shut-off valves, and can consequently reduce the manufacturing cost.

[0079] The air-conditioning apparatus 100 according to the embodiment includes the accumulator 13 located on the suction side of the compressor 10.

[0080] The air-conditioning apparatus 100 according to the present embodiment includes the accumulator 13 located on the suction side of the compressor 10, which causes a variation in the refrigerant composition (a change in the physical property value), and thus helps detect even a small amount of refrigerant leakage.

[0081] The air-conditioning apparatus 100 according to the embodiment includes a temperature detection device in addition to the outdoor-air temperature detection device 22. The outdoor-air temperature detection device 22 has higher detection accuracy than the temperature detection device.

[0082] The air-conditioning apparatus 100 according to the embodiment can improve detection accuracy of the refrigerant leakage detection function.

[0083] The air-conditioning apparatus 100 according to the embodiment includes a pressure detection device in addition to the first pressure detection device. The first pressure detection device has higher detection accuracy than the pressure detection device.

[0084] The air-conditioning apparatus 100 according to the embodiment can improve detection accuracy of the refrigerant leakage detection function.

[0085] In the air-conditioning apparatus 100 according to the embodiment, the controller 30 configured to execute the regular inspection function of executing the refrigerant leakage detection function every second time set in advance.

[0086] In the air-conditioning apparatus 100 according to the embodiment, this regular inspection function allows a determination of whether refrigerant leakage has occurred in the air-conditioning apparatus 100 to be performed even during the intermediate period such as spring or autumn during which the air-conditioning apparatus 100 is not operated, or even during the night. With this function, it is possible to check whether refrigerant leakage has occurred every day or once in several days, which helps detect refrigerant leakage earlier. It is also possible to detect refrigerant leakage regardless of the location where the refrigerant leakage has occurred.

[0087] In the air-conditioning apparatus 100 according to the embodiment, the controller 30 executes the refrigerant leakage detection function and announces the occurrence of refrigerant leakage when determining that there is refrigerant leakage.

[0088] In the air-conditioning apparatus 100 according to the embodiment, the controller 30 announces the occurrence of refrigerant leakage when determining that there is refrigerant leakage. This allows the facilities manager to be notified of the occurrence of refrigerant leakage earlier, so that the facilities manager can take prompt action on the devices such as a repair as appropriate.REFERENCE SIGNS LIST

[0089] 1: outdoor unit, 2, 2a, 2b: indoor unit, 3: main refrigerant pipe, 4a, 4b: branch refrigerant pipe, 5: refrigerant pipe, 10: compressor, 11: refrigerant flow switching device, 12: heat source side heat exchanger, 13: accumulator, 14: heat source side air-sending device, 20: discharge-pressure detection device, 21: suction-pressure detection device, 22: outdoor-air temperature detection device, 23: first temperature detection device, 30: controller, 40, 40a, 40b: load side heat exchanger, 41, 41a, 41b: expansion device, 42, 42a, 42b: load side air-sending device, 50, 50a, 50b: second temperature detection device, 51, 51a, 51b: third temperature detection device, 52, 52a, 52b: fourth temperature detection device, 60a, 60b: air-conditioned space, 61: space above a ceiling. 100: air-conditioning apparatus

Claims

1. An air-conditioning apparatus including a refrigerant circuit in which a compressor, a heat source side heat exchanger, an expansion device, and a load side heat exchanger are connected sequentially by a pipe, the refrigerant circuit being filled with a non-azeotropic refrigerant mixture as refrigerant, the air-conditioning apparatus comprising:a first pressure detection device configured to detect a pressure of refrigerant on a discharge side of the compressor or detect a pressure of refrigerant on a suction side of the compressor;an outdoor-air temperature detection device configured to detect an outdoor-air temperature; anda controller configured to execute a refrigerant leakage detection function of determining whether there is refrigerant leakage based on a pressure detected by the first pressure detection device and an outdoor-air temperature detected by the outdoor-air temperature detection device, when the air-conditioning apparatus is deactivated,wherein the controller is configured to, in execution of the refrigerant leakage detection function, determine whether there is refrigerant leakage when the outdoor-air temperature detected by the outdoor-air temperature detection device is stable after a lapse of a first time set in advance from when the air-conditioning apparatus is deactivated.

2. The air-conditioning apparatus of claim 1, wherein the controller is configured to, in execution of the refrigerant leakage detection function, determine whether there is refrigerant leakage by comparing a saturation temperature of refrigerant obtained from a pressure detected by the first pressure detection device with an outdoor-air temperature detected by the outdoor-air temperature detection device.

3. (canceled)4. (canceled)5. The air-conditioning apparatus of claim 1, comprising an accumulator located on the suction side of the compressor.

6. The air-conditioning apparatus of claim 1, comprising a temperature detection device in addition to the outdoor-air temperature detection device, whereinthe outdoor-air temperature detection device has higher detection accuracy than the temperature detection device.

7. The air-conditioning apparatus of claim 1, comprising a pressure detection device in addition to the first pressure detection device, whereinthe first pressure detection device has higher detection accuracy than the pressure detection device.

8. The air-conditioning apparatus of claim 1, wherein the controller is configured toexecute a regular inspection function of executing the refrigerant leakage detection function every second time set in advance.

9. The air-conditioning apparatus of claim 1, wherein the controller is configured toexecute the refrigerant leakage detection function and announce an occurrence of refrigerant leakage when determining that there is refrigerant leakage.

Images