GB2575606A

GB2575606A - Air-conditioning apparatus

Info

Publication number: GB2575606A
Application number: GB1916115.7A
Authority: GB
Inventors: Ishimura Katsuhiro; Morimoto Osamu; Yamashita Koji
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2017-05-31
Filing date: 2017-05-31
Publication date: 2020-01-15
Anticipated expiration: 2037-05-31
Also published as: GB2575606B; WO2018220758A1; JPWO2018220758A1; GB2575606C; JP6972125B2; GB201916115D0

Abstract

This air-conditioning apparatus is provided with: at least one indoor unit which air-conditions a space to be air-conditioned; at least one outdoor unit which functions as a heat source; a refrigerant circuit in which the indoor unit and the outdoor unit are connected via refrigerant piping and through which a refrigerant is circulated; a refrigerant detection device which is disposed within the indoor unit or in the space to be air-conditioned by the indoor unit and which detects leakage of refrigerant from the refrigerant circuit; and a control device which determines that refrigerant leakage has occurred in the case when a detection value of the refrigerant detection device exceeds a threshold value C1 all the time during a determination period ΔTa, or in the case when the detection value of the refrigerant detection device exceeds the threshold value C1 for a period equal to or longer than a standard time during the determination period ΔTa.

Description

DESCRIPTION

Title of Invention

AIR-CONDITIONING APPARATUS

Technical Field [0001]

The present invention relates to refrigerant leakage detection of an airconditioning apparatus.

Background Art [0002]

In an existing air-conditioning apparatus such as a variable refrigerant flow system, the total length of refrigerant pipes that connect outdoor units and indoor units is several hundred meters in some cases, and thus the amount of refrigerant with which a refrigerant circuit is filled is very large. In such an air-conditioning apparatus, there is a possibility that a large amount of the refrigerant will leak to one room when refrigerant leakage occurs.

[0003]

In addition, in recent years, from the viewpoint of global warming, replacement with refrigerant having a low global warming potential has been required, but in many cases, the refrigerant having a low global warming potential has combustibility. In the future, when replacement with the refrigerant having a low global warming potential progresses, further consideration for safety would be required.

[0004]

To overcome such a problem, a technique has been proposed in which a blocking valve for blocking refrigerant flow is provided in a refrigerant circuit, thereby reducing a leakage amount of the refrigerant when the refrigerant leaks (see, for example, Patent Literature 1).

[0005]

In addition, there have been also proposed a technique in which a refrigerant detection sensor that detects refrigerant leakage is provided in an indoor unit or an air-conditioned space, and the refrigerant detection sensor is used to operate the blocking valve appropriately, and a technique related to a method of reducing the number of refrigerant detection sensors to be provided and an optimal location at which the refrigerant detection sensor is provided (see, for example, Patent Literature 2).

Citation List

Patent Literature [0006]

Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2000-97527

Patent Literature 2: Japanese Patent No. 3744330

Summary of Invention

Technical Problem [0007]

However, actual results on the market of the air-conditioning apparatus provided with a refrigerant detection sensor are still insufficient, and the airconditioning apparatus may provide the false detection of the refrigerant detection sensor due to not only electrical noise but also miscellaneous gas such as organic compound-based gas in the air, the miscellaneous gas being generated from a sanitizer, a cleaning agent or other agents. In addition, some air-conditioning apparatuses take measures for protecting a sensor portion with a filter that can adsorb the miscellaneous gas chemically to suppress the false detection of the refrigerant leakage of the refrigerant detection sensor, but there is a problem in that the false detection of the refrigerant leakage cannot be sufficiently suppressed. [0008]

The present invention has been made to solve the above-described problem, and an object of the present invention is to provide an air-conditioning apparatus that can suppress false detection of refrigerant leakage.

Solution to Problem [0009]

An air-conditioning apparatus of an embodiment according to the present invention includes one or a plurality of indoor units configured to condition air in an air-conditioned space, one or a plurality of outdoor units each used as a heat source, a refrigerant circuit in which the one or the plurality of indoor units and the one or the plurality of outdoor units are connected by a refrigerant pipe and in which refrigerant circulates, a refrigerant detection device provided in an interior of the one or any of the plurality of indoor units or the air-conditioned space in which air is conditioned by the one or the plurality of indoor units, the refrigerant detection device being configured to detect refrigerant leakage from the refrigerant circuit, and a controller configured to determine that the refrigerant leakage has occurred when a detection value of the refrigerant detection device always exceeds a threshold C1 during a determination time period ATa or when the detection value of the refrigerant detection device exceeds the threshold C1 for a reference time period or longer during the determination time period ATa.

Advantageous Effects of Invention [0010]

In the air-conditioning apparatus according to an embodiment of the present invention, the controller determines that the refrigerant leakage has occurred when a detection value of the refrigerant detection device always exceeds a threshold C1 during a determination time period ATa or when the detection value of the refrigerant detection device exceeds the threshold C1 for a reference time period or longer during the determination time period ATa so that the false detection of the refrigerant leakage can be avoided. Brief Description of Drawings [0011] [Fig. 1] Fig. 1 is a schematic diagram illustrating a first example of a configuration of an air-conditioning apparatus according to an embodiment of the present invention.

[Fig. 2] Fig. 2 is a schematic diagram illustrating a second example of a configuration of the air-conditioning apparatus according to the embodiment of the present invention.

[Fig. 3] Fig. 3 is a schematic diagram illustrating a third example of a configuration of the air-conditioning apparatus according to the embodiment of the present invention.

[Fig. 4] Fig. 4 is a schematic diagram illustrating a fourth example of a configuration of the air-conditioning apparatus according to the embodiment of the present invention.

[Fig. 5] Fig. 5 is a schematic diagram illustrating a fifth example of a configuration of the air-conditioning apparatus according to the embodiment of the present invention.

[Fig. 6] Fig. 6 is a schematic diagram illustrating a sixth example of a configuration of the air-conditioning apparatus according to the embodiment of the present invention.

[Fig. 7] Fig. 7 is a schematic diagram illustrating a seventh example of a configuration of the air-conditioning apparatus according to the embodiment of the present invention.

[Fig. 8] Fig. 8 is a schematic diagram illustrating an eighth example of a configuration of the air-conditioning apparatus according to the embodiment of the present invention.

[Fig. 9] Fig. 9 is a schematic diagram illustrating an example of a configuration of a refrigerant circuit of the air-conditioning apparatus according to the embodiment of the present invention.

[Fig. 10] Fig. 10 is afunctional block diagram illustrating the air-conditioning apparatus according to the embodiment of the present invention.

[Fig. 11] Fig. 11 is a refrigerant circuit diagram illustrating refrigerant flow during cooling only operation of the air-conditioning apparatus according to the embodiment of the present invention.

[Fig. 12] Fig. 12 is a refrigerant circuit diagram illustrating refrigerant flow during heating only operation of the air-conditioning apparatus 100 according to the embodiment of the present invention.

[Fig. 13] Fig. 13 is a graph showing an example of a false detection operation of refrigerant leakage of some air-conditioning apparatus.

[Fig. 14] Fig. 14 is a graph showing a false detection avoiding operation of the refrigerant leakage of the air-conditioning apparatus according to the embodiment of the present invention.

[Fig. 15] Fig. 15 is a flowchart illustrating a first example of a control flow of a detection operation of refrigerant leakage of the air-conditioning apparatus according to the embodiment of the present invention.

[Fig. 16] Fig. 16 is a flowchart illustrating a second example of a control flow of a detection operation of refrigerant leakage of the air-conditioning apparatus according to the embodiment of the present invention.

[Fig. 17] Fig. 17 is a flowchart illustrating a third example of a control flow of a detection operation of refrigerant leakage of the air-conditioning apparatus according to the embodiment of the present invention.

Description of Embodiments [0012]

Hereinafter, an embodiment of an air-conditioning apparatus 100 of the present invention will be described with reference to the drawings. It should be noted that the drawings are examples and are not intended to limit the present invention. In addition, in each drawing, components designated by the same reference signs are the same or equivalent components, and the reference signs apply throughout the specification. Furthermore, the relationship of the sizes of components in the drawings described below may be different from actual ones.

[0013]

Embodiment

Fig. 1 is a schematic diagram of a first example of a configuration of the airconditioning apparatus 100 according to the embodiment of the present invention.

Hereinafter, a configuration of the air-conditioning apparatus 100 according to the present embodiment will be described.

The air-conditioning apparatus 100 circulates refrigerant in a refrigerant circuit

101, which will be described later, and performs air-conditioning using a refrigeration cycle. The air-conditioning apparatus 100 is an air-conditioning apparatus that is able to select a cooling only operation in which all operating indoor units perform cooling or a heating only operation in which all operating indoor units perform heating, as in a variable refrigerant flow system or other apparatuses.

[0014]

As illustrated in Fig. 1, the air-conditioning apparatus 100 includes a single outdoor unit 1 and two indoor units 2a and 2b (hereinafter, generically referred to as the indoor unit 2), and the outdoor unit 1 and the indoor units 2a and 2b are connected to each other by a refrigerant pipe 3. It should be noted that the present embodiment shows the case where the two indoor units 2 are connected to the outdoor unit 1, but the number of outdoor units 1 and the number of indoor units 2 are not limited to the embodiment. The number of outdoor units 1 may be two or more, and the number of indoor units 2 may be one or three or more.

[0015]

The indoor units 2a and 2b are provided on air-conditioned spaces 4a and 4b (hereinafter, generically referred to as the air-conditioned space 4), respectively, and condition air in the air-conditioned spaces 4a and 4b, respectively. Blocking devices 7a and 7b (hereinafter, generically referred to as a blocking device 7) are provided in branch portions 3a and 3b, respectively, of the refrigerant pipe 3 connecting the outdoor unit 1 and the indoor units 2a and 2b to block the refrigerant flow when the refrigerant leakage occurs, thereby inhibiting the refrigerant leakage. Furthermore, alarm devices 6a and 6b (hereinafter, generically referred to as an alarm device 6) configured to inform a user of the refrigerant leakage when the refrigerant leakage occurs and ventilation devices 8a and 8b (hereinafter, generically referred to as a ventilation device 8) configured to exhaust leaking refrigerant to an outside of the airconditioned spaces 4a and 4b are provided in the air-conditioned spaces 4a and 4b, respectively.

[0016]

Refrigerant detection devices 5a and 5b (hereinafter, generically referred to as a refrigerant detection device 5) for detecting the refrigerant leakage are provided in the indoor unit 2a or the air-conditioned space 4a, and the indoor unit 2b or the airconditioned space 4b, respectively. It should be noted that the present embodiment shows an example in which the refrigerant detection device 5a is provided in the indoor unit 2a, and the refrigerant detection device 5b is provided in the airconditioned space 4b, but the locations of the refrigerant detection devices 5a and 5b are not limited to the embodiment. It is only required that the refrigerant detection device 5a is provided in at least one of the indoor unit 2a and the air-conditioned space 4a, and the refrigerant detection device 5b is provided at least one of the indoor unit 2b and the air-conditioned space 4b.

[0017]

The refrigerant detection device 5, the alarm device 6, the blocking device 7, and the ventilation device 8 are provided as safety measures when the refrigerant leaks out from the air-conditioning apparatus 100. Hereinafter, the refrigerant detection device 5, the alarm device 6, the blocking device 7, and the ventilation device 8 are generically referred to as safety measure devices.

[0018]

In the air-conditioning apparatus 100 according to the present embodiment, when the refrigerant leakage is detected by the refrigerant detection device 5, a refrigerant leakage output signal is output to the alarm device 6, the blocking device 7, and the ventilation device 8. Then, all or at least one of the alarm device 6, the blocking device 7, and the ventilation device 8 operates on the basis of the output refrigerant leakage output signal so that the safety of the air-conditioned space 4 can be maintained.

[0019]

Thus, as the refrigerant detection device 5, the alarm device 6, the blocking device 7, and the ventilation device 8 are provided as the safety measures when the refrigerant leaks out from the air-conditioning apparatus 100, the refrigerant detection device 5, the alarm device 6, the blocking device 7, and the ventilation device 8 do not perform any function while the normal cooling operation or heating operation is performed. For this reason, when the maximum refrigerant concentration during refrigerant leakage that is calculated from an amount of refrigerant with which the airconditioning apparatus 100 is filled and a volume of the air-conditioned space 4 is not a concentration that affects the human body, the refrigerant detection device 5, the alarm device 6, the blocking device 7, and the ventilation device 8 are not necessarily provided.

[0020]

Fig. 2 is a schematic diagram illustrating a second example of a configuration of the air-conditioning apparatus 100 according to the embodiment of the present invention, Fig. 3 is a schematic diagram illustrating a third example of a configuration of the air-conditioning apparatus 100 according to the embodiment of the present invention, Fig. 4 is a schematic diagram illustrating a fourth example of a configuration of the air-conditioning apparatus 100 according to the embodiment of the present invention, Fig. 5 is a schematic diagram illustrating a fifth example of a configuration of the air-conditioning apparatus 100 according to the embodiment of the present invention, Fig. 6 is a schematic diagram illustrating a sixth example of a configuration of the air-conditioning apparatus 100 according to the embodiment of the present invention, and Fig. 7 is a schematic diagram illustrating a seventh example of a configuration of the air-conditioning apparatus 100 according to the embodiment of the present invention.

[0021]

It should be noted that it is only required that any one or more types of devices among the alarm device 6, the blocking device 7, and the ventilation device 8 are provided. Fig. 2 to Fig. 8 each illustrate a case where one type or two types among these devices are provided.

[0022]

Fig. 2 illustrates the air-conditioning apparatus 100 in which, as the safety measures, the alarm devices 6a and 6b are provided in the air-conditioned spaces 4a and 4b, respectively. Fig. 3 illustrates the air-conditioning apparatus 100 in which, as the safety measures, the blocking devices 7a and 7b are provided in the branch portions 3a and 3b, respectively, of the refrigerant pipe 3. Fig. 4 illustrates the airconditioning apparatus 100 in which, as the safety measures, the ventilation devices 8a and 8b are provided in the air-conditioned spaces 4a and 4b, respectively. Fig. 5 illustrates the air-conditioning apparatus 100 in which, as the safety measures, the alarm devices 6a and 6b are provided in the air-conditioned spaces 4a and 4b, respectively, and the blocking devices 7a and 7b are provided in the branch portions 3a and 3b, respectively, of the refrigerant pipe 3.

[0023]

Fig. 6 illustrates the air-conditioning apparatus 100 in which, as the safety measures, the alarm devices 6a and 6b and the ventilation devices 8a and 8b are provided in the air-conditioned spaces 4a and 4b, respectively. Fig. 7 illustrates the air-conditioning apparatus 100 in which, as the safety measures, the blocking device 7 is provided at the refrigerant pipe 3 of the interior of the outdoor unit 1. It should be noted that it is only required that the blocking device 7 is provided outside of the air-conditioned spaces 4a and 4b, and therefore, as illustrated in Fig. 7, the blocking device 7 can be provided in the interior of the outdoor unit 1.

[0024]

Fig. 8 is a schematic diagram illustrating an eighth example of a configuration of the air-conditioning apparatus 100 according to the embodiment of the present invention.

As illustrated in Fig. 8, in the air-conditioning apparatus 100 according to the present embodiment, a plurality of indoor units 2a and 2b may be provided in the same air-conditioned space 4. In this case, as the safety measures, for example, the alarm device 6 is provided in the air-conditioned space 4, and the blocking devices 7a and 7b are provided in the branch portions 3a and 3b, respectively, of the refrigerant pipe 3.

[0025]

Next, a configuration of a refrigerant circuit 101 of the air-conditioning apparatus 100 according to the present embodiment will be described.

Fig. 9 is a schematic diagram illustrating an example of a configuration of the refrigerant circuit 101 ofthe air-conditioning apparatus 100 according to the embodiment ofthe present invention.

As illustrated in Fig. 9, the air-conditioning apparatus 100 according to the present embodiment includes the refrigerant circuit 101 in which 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, an accumulator 13 are sequentially connected by the refrigerant pipe 3, and in which refrigerant circulates. Hereinafter, the expansion devices 41a and 41b are generically referred to as an expansion device 41, and the load side heat exchangers 40a and 40b are generically referred to as a load side heat exchanger 40.

[0026] [Outdoor Unit 1]

The outdoor unit 1 is used as a heat source, and includes the compressor 10, the refrigerant flow switching device 11, the heat source side heat exchanger 12, and the accumulator 13. In addition, an outdoor air-sending device 14 for sending air to the heat source side heat exchanger 12 is provided in the vicinity of the heat source side heat exchanger 12.

[0027]

The compressor 10 sucks low-temperature and low-pressure refrigerant, and compresses the refrigerant into a high-temperature and high-pressure refrigerant state. The compressor 10 is a capacity-controllable inverter compressor or another compressor. The refrigerant flow switching device 11 switches refrigerant flow during the cooling operation and refrigerant flow during the heating operation. The refrigerant flow switching device 11 is a four-way valve or another device. [0028]

The heat source side heat exchanger 12 is used as a condenser during the cooling operation, is used as an evaporator during the heating operation, and exchanges heat between the refrigerant and air supplied from the outdoor air-sending device 14 such as a fan.

[0029]

In the outdoor unit 1, a first pressure detection device 20 and a second pressure detection device 21 that each detect a pressure are provided. The first pressure detection device 20 is provided at part of the refrigerant pipe 3 connecting the discharge port of the compressor 10 and the refrigerant flow switching device 11, and detects the pressure of the high-temperature and high-pressure refrigerant compressed and discharged by the compressor 10. In addition, the second pressure detection device 21 is provided at part of the refrigerant pipe 3 connecting the refrigerant flow switching device 11 and the suction port of the compressor 10, and detects the pressure of the low-temperature and low-pressure refrigerant to be sucked into the compressor 10.

[0030]

In the outdoor unit 1, a first temperature detection device 22 that detects a temperature is provided. The first temperature detection device 22 is provided at part of the refrigerant pipe 3 connecting the discharge port of the compressor 10 and the refrigerant flow switching device 11, and detects the temperature of the hightemperature and high-pressure refrigerant compressed and discharged by the compressor 10. The first temperature detection device 22 is a thermistor or another device.

[0031] [Indoor Units 2a and 2b]

The indoor units 2a and 2b condition air in the air-conditioned spaces 4a and 4b, and include the load side heat exchangers 40a and 40b, and the expansion devices 41 a and 41 b, respectively. In addition, indoor air-sending devices 42a and 42b (hereinafter, generically referred to as an indoor air-sending device 42) for sending air to the load side heat exchangers 40a and 40b are provided in the vicinity of the load side heat exchangers 40a and 40b, respectively. In addition, the indoor units 2a and 2b are connected to the outdoor unit 1 through the refrigerant pipe 3 to allow the refrigerant to flow to and from the indoor units 2a and 2b.

[0032]

The load side heat exchanger 40 is used as an evaporator during the cooling operation, and is used as a condenser during the heating operation. The load side heat exchanger 40 exchanges heat between the refrigerant and air supplied from the indoor air-sending device 42 such as a fan and generates heating air or cooling air to be supplied to the air-conditioned space 4. The expansion device 41 is used as a pressure reducing valve or an expansion valve and reduces the pressure of the refrigerant to expand the refrigerant, and is an expansion device whose opening degree is variably controllable, such as an electronic expansion valve.

[0033]

In the indoor units 2a and 2b, second temperature detection devices 50a and 50b (hereinafter, generically referred to as a second temperature detection device 50), third temperature detection devices 51a and 51b (hereinafter, generically referred to as a third temperature detection device 51), and fourth temperature devices 52a and 52b (hereinafter, generically referred to as a fourth temperature detection device 52) that each detect a temperature are provided, respectively.

[0034]

The second temperature detection device 50 is provided at part of the refrigerant pipe 3 connecting the expansion device 41 and the load side heat exchanger 40, and detects the temperature of the refrigerant flowing into the load side heat exchanger 40 during the cooling operation. The third temperature detection device 51 is provided at part of the refrigerant pipe 3 that is across the load side heat exchanger 40 from the expansion device 41, and detects the temperature of the refrigerant flowing out from the load side heat exchanger 40 during the cooling operation. Furthermore, the fourth temperature detection device 52 is provided at an air-inlet portion of the load side heat exchanger 40, and detects the temperature of air in the air-conditioned space 4.

[0035]

Each of the second temperature detection device 50, the third temperature detection device 51, and the fourth temperature detection device 52 is a thermistor or another device.

[0036] [Controller 30]

The outdoor unit 1 includes a controller 30. The controller 30 includes, for example, dedicated hardware or a central processing unit (CPU, also referred to as a central processor, a processing unit, an arithmetic and logic unit, a microprocessor, a microcomputer, or a processor) that runs a program stored in a memory.

[0037]

Fig. 10 is a functional block diagram illustrating the air-conditioning apparatus 100 according to the embodiment of the present invention.

As illustrated in Fig. 10, the controller 30 includes a main control unit 31, a timer unit 32, a memory 33, and a drive unit 34.

The main control unit 31 instructs the drive unit 34 to control the turning on and off of the alarm device 6, the opening and closing of the blocking device 7, the rotation frequency (including turning on and off) of the ventilation device 8, the frequency of the compressor 10, the rotation frequency (including turning on and off) of the outdoor air-sending device 14 for the heat source side heat exchanger 12, the switching of the refrigerant flow switching device 11, the opening degree of the expansion device 41, and the rotation frequency (including turning on and off) of the indoor air-sending device 42 for the load side heat exchanger 40, on the basis of the detection values of various detection devices and instructions from a remote control (not illustrated).

[0038]

It should be noted that the various detection devices include the refrigerant detection device 5, the first pressure detection device 20, the second pressure detection device 21, the first temperature detection device 22, the second temperature detection device 50, the third temperature detection device 51, and the fourth temperature detection device 52.

[0039]

The timer unit 32 measures a time. The memory 33 stores various types of information such as a threshold C1, which will be described later.

The drive unit 34 controls the turning on and off of the alarm device 6, the opening and closing of the blocking device 7, the rotation frequency (including turning on and off) of the ventilation device 8, the frequency of the compressor 10, the rotation frequency (including turning on and off) of the outdoor air-sending device 14 for the heat source side heat exchanger 12, the switching of the refrigerant flow switching device 11, the opening degree of the expansion device 41, and the rotation frequency (including turning on and off) of the indoor air-sending device 42 for the load side heat exchanger 40, on the basis of the instructions from the main control unit 31.

[0040]

It should be noted that the present embodiment shows an example in which the controller 30 is provided in the outdoor unit 1, but the location of the controller 30 is not limited to the embodiment. The controller 30 can also be provided to each of the outdoor unit 1 and the indoor units 2a and 2b, or can also be provided to either the outdoor unit 1 or the indoor units 2a and 2b. In addition, the present embodiment shows a configuration in which the controller 30 includes the timer unit 32 and the memory 33, but the configuration is not limited to the embodiment. The timer unit 32 and the memory 33 can be provided separately from the controller 30.

[0041]

It should be noted that the blocking device 7 blocks the refrigerant flow in the refrigerant pipe 3 to inhibit leakage of the refrigerant to the air-conditioned space 4 from the outdoor unit 1, when the refrigerant leakage occurs from the indoor unit 2 or the vicinity of the indoor unit 2. For this reason, the blocking device 7 can be any device that can block the refrigerant flow in the refrigerant circuit 101. For example, the blocking device 7 may be a device that can be controlled to only open or close, such as an electromagnetic valve, or a device whose opening degree is variably controllable, such as an electronic expansion valve.

[0042] [Cooling Only Operation]

Fig. 11 is a diagram of the refrigerant circuit 101 illustrating the refrigerant flow during cooling only operation of the air-conditioning apparatus 100 according to the embodiment of the present invention. It should be noted that in Fig. 11, the direction of refrigerant flow is represented by solid arrows. The refrigerant flow switching device 11 is switched in such a manner that the discharge port of the compressor 10 is connected to the heat source side heat exchanger 12. With reference to Fig. 11, the cooling only operation of the air-conditioning apparatus 100 will be described for an exemplary case where cooling loads are generated in the load side heat exchangers 40a and 40b.

[0043]

During the cooling only operation, the low temperature and low pressure refrigerant is compressed into high-temperature and high pressure gas refrigerant by the compressor 10 and discharged from the compressor 10. The high-temperature and high-pressure gas refrigerant discharged from the compressor 10 flows into the heat source side heat exchanger 12 through the refrigerant flow switching device 11. The high-temperature and high-pressure gas refrigerant flowing into the heat source side heat exchanger 12 condenses into high-pressure liquid refrigerant while rejecting heat to the outdoor air. Then, the high-pressure liquid refrigerant flowing out from the heat source side heat exchanger 12 flows out from the outdoor unit 1, flows through the refrigerant pipe 3, and flows into the indoor units 2a and 2b. At this time, the blocking devices 7a and 7b are opened not to obstruct the refrigerant flow.

[0044]

The high-pressure liquid refrigerant flowing into the indoor units 2a and 2b is reduced in pressure by the expansion devices 41a and 41b into low-temperature and low-pressure two-phase refrigerant, then flows into the load side heat exchangers 40a and 40b that are each used as an evaporator, and removes heat from indoor air to cool the indoor air, thereby becoming low-temperature and low-pressure gas refrigerant. The low-temperature and low-pressure gas refrigerant flowing out from the load side heat exchangers 40a and 40b flows into the outdoor unit 1 through the refrigerant pipe 3. The refrigerant flowing into the outdoor unit 1 is sucked into the compressor 10 through the refrigerant flow switching device 11 and the accumulator

13.

[0045]

The controller 30 controls the opening degree of each of the expansion devices 41a and 41b in such a manner that superheat (degree of superheat) becomes constant. The superheat is obtainable as the difference between the temperature detected by each of the second temperature detection devices 50a and 50b and the temperature detected by the corresponding one of the third temperature detection devices 51 a and 51 b. Thus, the capacity corresponding to the heat loads of the airconditioned spaces 4a and 4b can be provided, thereby high efficient operation is enabled.

[0046] [Heating Only Operation]

Fig. 12 is a diagram of the refrigerant circuit 101 illustrating the refrigerant flow during heating only operation of the air-conditioning apparatus 100 according to the embodiment of the present invention. It should be noted that in Fig. 12, the direction of refrigerant flow is represented by solid arrows. The refrigerant flow switching device 11 is switched in such a manner that the discharge port of the compressor 10 is connected to the blocking devices 7a and 7b. With reference to Fig. 12, the heating only operation of the air-conditioning apparatus 100 will be described for an exemplary case where heating loads are generated in the load side heat exchangers 40a and 40b.

[0047]

During the heating only operation, the low temperature and low pressure refrigerant is compressed into high-temperature and high pressure gas refrigerant by the compressor 10 and discharged from the compressor 10. The high-temperature and high-pressure gas refrigerant discharged from the compressor 10 flows through refrigerant pipe 3 to flow into the indoor units 2a and 2b through the refrigerant flow switching device 11. At this time, the blocking devices 7a and 7b are opened not to obstruct the refrigerant flow.

[0048]

The high-temperature and high-pressure gas refrigerant flowing into the indoor units 2a and 2b rejects heat to the indoor air at the load side heat exchangers 40a and 40b to become high-pressure liquid refrigerant, and flows into the expansion devices 41a and 41b. Then, the high-pressure liquid refrigerant is reduced in pressure by the expansion devices 41a and 41b into low-temperature and lowpressure two-phase refrigerant, flows out from the indoor units 2a and 2b, flows through the refrigerant pipe 3, and flows into the outdoor unit 1.

[0049]

The low-temperature and low-pressure two-phase refrigerant flowing into the outdoor unit 1 flows into the heat source side heat exchanger 12, and removes heat from the outdoor air to become low-temperature and low-pressure gas refrigerant. The low-temperature and low-pressure gas refrigerant flowing out from the heat source side heat exchanger 12 is sucked into the compressor 10 through the refrigerant flow switching device 11 and the accumulator 13.

[0050]

The controller 30 also controls the opening degree of each of the expansion devices 41 a and 41 b in such a manner that subcooling (degree of subcooling) becomes constant. The subcooling is obtainable as the difference between the saturated liquid temperature of the refrigerant calculated from the pressure detected by the first pressure detection device 20 and the temperature detected by each of the second temperature detection devices 50. Thus, the capacity corresponding to the heat loads of the air-conditioned spaces 4a and 4b can be provided, thereby high efficient operation is enabled.

[0051]

Next, a false detection avoiding operation of the refrigerant leakage of the airconditioning apparatus 100 according to the present embodiment will be described.

Fig. 13 is a graph showing an example of a false detection operation of the refrigerant leakage of some air-conditioning apparatus, and Fig. 14 is a graph showing a false detection avoiding operation of the refrigerant leakage of the airconditioning apparatus 100 according to the embodiment of the present invention.

In some air-conditioning apparatus, a method of storing a threshold of a refrigerant concentration in a controller and determining that the refrigerant leakage has occurred when a detection value (refrigerant concentration) detected by a refrigerant leakage device exceeds the threshold has been typically used. However, in this method, the determination is made that the refrigerant leakage has occurred, even when the refrigerant concentration temporarily exceeds the threshold due to miscellaneous gas, noise, or other similar causes, as shown in Fig. 13, and the false detection of refrigerant leakage is provided.

[0052]

To solve this problem, the controller 30 of the air-conditioning apparatus 100 according to the present embodiment has a refrigerant leakage determination function for avoiding the above-described false detection of the refrigerant leakage.

Hereinafter, the refrigerant leakage determination function will be described in detail.

[0053] [Refrigerant Leakage Determination Function]

The refrigerant leakage determination function of the controller 30 of the airconditioning apparatus 100 is a function of determining, using two values of a refrigerant leakage determination time period and a threshold of a refrigerant concentration, whether the refrigerant leakage occurs.

[0054]

Hereinafter, the refrigerant leakage determination function will be more specifically described. When the refrigerant leakage has occurred, a time period ΔΤ (s) from the time when the refrigerant leakage occurs to the time when the refrigerant concentration in the air-conditioned space 4 becomes C (kg/m³) is represented by the following expression.

[0055] [Expression 1]

AT = CxAxH/G (1) [0056]

In Expression 1, A represents a floor surface area (m²) of the air-conditioned space 4, H represents a ceiling height (m) of the air-conditioned space 4, and G represents a leakage speed (kg/s) of the refrigerant.

[0057]

When the threshold of the refrigerant concentration is represented as C1 (kg/m³), a time period ΔΤ1 (s) from the time when the refrigerant leakage occurs to the time when the refrigerant concentration reaches the threshold C1 is represented by the following expression.

[0058] [Expression 2]

ΔΤ1 = C1 x A x H/G (2) [0059]

When, using a lower flammable limit (LFL) (kg/m³), the refrigerant leakage is detected before the refrigerant concentration in the air-conditioned space 4 becomes LFL/2 (kg/m³), a flammable area that becomes a problem is not generated in the airconditioned space 4, which is reported in Risk Assessment of Mildly Flammable Refrigerants Final Report 2016 (March, 2017), page 221 (http://www.jsrae.or.jp/committee/binensei/final_report_2016r1_en.pdf) published by Japan Society of Refrigerating and Air Conditioning Engineers.

[0060]

Consequently, when the refrigerant leakage is detected before the refrigerant concentration in the air-conditioned space 4 becomes LFL/2 (kg/m³) and the safety measure devices are operated, the ignition in the air-conditioned space 4 can be inhibited. Here, a time period ΔΤ2 (s) from the time when the refrigerant leakage occurs to the time when the refrigerant concentration in the air-conditioned space 4 becomes LFL/2 is represented by the following expression.

[0061] [Expression 3]

ΔΤ2 = (LFL/2) x A x H/G (3) [0062]

Consequently, in a case where the safety measure devices are immediately operated, it can be said that the safety is ensured when the refrigerant concentration is detected to be the threshold C1 by the refrigerant detection device 5 after the elapse of ΔΤ1 seconds from the time when the refrigerant leakage occurs, and the controller 30 determines that the refrigerant leakage has occurred before the refrigerant concentration in the air-conditioned space 4 becomes LFL/2 after the elapse of ΔΤ2 seconds from the time when the refrigerant leakage occurs.

[0063]

A determination time period ATa (s) that is a maximum time period allowed from the time when the refrigerant leakage occurs to the time when the controller 30 determines that the refrigerant leakage has occurred is represented by the following expression.

[0064] [Expression 4]

ATa = ΔΤ2 - ΔΤ1 = ((LFL/2) - C1) x A x H/G (4) [0065]

The refrigerant leakage occurs due to cracks in the refrigerant pipe 3, corrosion of the heat exchanger in the indoor unit 2, and other similar causes. That is, once the refrigerant leakage has occurred, a hole through which the refrigerant leaks is not blocked. Thus, the refrigerant leakage continues until an amount of the refrigerant in the air-conditioning apparatus 100 becomes low. On the other hand, a sterilizing agent or other agent that may cause false detection of the refrigerant leakage is sprayed for a short time.

[0066]

For this reason, to suppress the false detection of the refrigerant leakage, a method is conceivable in which the controller 30 determines that the refrigerant leakage has occurred when the refrigerant detection device 5 detects the refrigerant concentration exceeding the threshold C1 consecutively for a predetermined period since the refrigerant detection device 5 detects the refrigerant concentration exceeding the threshold C1. However, a transmission error of the detection signal from the refrigerant detection device 5 may occur. Even when the transmission error of the signal occurs, the ratio of a detection period due to the transmission error is small. Consequently, using, as a determination criterion, a condition that the ratio of the time period for which the refrigerant concentration exceeds the threshold C1 is greater than or equal to a predetermined ratio, the transmission error of the signal can be suppressed.

[0067]

That is, the controller 30 determines whether the refrigerant leakage has occurred, on the basis of the determination criterion that the refrigerant concentration detected by the refrigerant detection device 5 always exceeds the threshold C1 or the ratio of the time period for which the refrigerant concentration exceeds the threshold C1 is greater than or equal to a predetermined ratio, until the determination time period ATa (s) elapses since the refrigerant leakage occurs so that the false detection of the refrigerant leakage can be suppressed.

[0068]

It is not always necessary to wait until the determination time period ATa (s) elapses since the refrigerant detection device 5 detects that the refrigerant concentration exceeds the threshold C1, to determine the refrigerant leakage. When the refrigerant detection device 5 has high reliability, the controller 30 can determines whether the refrigerant leakage has occurred, before the elapse of the determination time period ATa (s).

[0069]

The control interval of the controller 30 of the air-conditioning apparatus 100 is at least 10 seconds or longer. To suppress the false detection of the refrigerant leakage, it is necessary to detect the refrigerant leakage a plurality of times at this control interval. In addition, the time period for which the sterilizing agent or other agent is sprayed is believed to be several seconds at most. For this reason, the refrigerant detection device 5 needs to detect the refrigerant concentration exceeding the threshold C1 consecutively for 20 seconds or longer as the shortest determination time period of the refrigerant leakage. Consequently, the determination time period ATa needs to be 20 (s) or longer.

[0070]

In addition, it is necessary to determine the refrigerant leakage before all the refrigerant with which the refrigerant circuit 101 is filled leaks, and therefore an amount M (kg) of the refrigerant with which the refrigerant circuit 101 is filled needs to satisfy the following expression.

[0071] [Expression 5]

Μ > ΔΤ2 x G (5) [0072]

The refrigerant leakage speed in the indoor unit of the air-conditioning apparatus is 10 (kg/h), which equals to 10/3600 (kg/s), which is reported in Risk Assessment of Mildly Flammable Refrigerants Final Report 2016 (March, 2017), page 221 (http://www.jsrae.or.jp/committee/binensei/final_report_2016r1_en.pdf), page 198 published by Japan Society of Refrigerating and Air Conditioning Engineers. In addition, taking into account that the standard ceiling height is 2.2 (m), Expression (1) to Expression (5) are represented as follows.

[0073] [Expression 1A]

ΔΤ = C x A x H/G = C x A x 2.2/(10/3600) = 792 x C x A (6) [0074] [Expression 2A]

ΔΤ1 = C1 x A x H/G = C1 x A x2.2/( 10/3600) = 792 x C1 x A (7) [0075] [Expression 3A]

ΔΤ2 = (LFL/2) x A x H/G = (LFL/2) x Ax2.2/(10/3600) = 396 x LFL x A (8) [0076] [Expression 4A]

ATa = ((LFL/2) - C1) x A x H/G = ((LFL/2) - C1) x A x 2.2/(10/3600) = 792 x (LFL/2 - C1) x A (9) [Expression 5A] Μ > ΔΤ2 x G = (LFL/2 x A x (H/G) x G = 396 x LFL x A x G = (LFL/2) x A x H = (LFL/2) x A x 2.2 = 1.1 x LFL x A (10) [0077]

As an example, when the refrigerant with which the refrigerant circuit 101 is filled is R32 refrigerant, the floor surface area A of the air-conditioned space 4 is 9 (m²), and the threshold C1 of the refrigerant detection device 5 is 0.0307 (kg/m³), as the LFL of R32 refrigerant is 0.307 (kg/m³), ΔΤ1 becomes about 219 seconds (« 3.7 minutes), ΔΤ2 becomes about 1094 seconds (« 18.2 minutes), ATa becomes about 875 seconds (« 14.5 minutes), and M becomes about 3.0 (kg).

[0078]

In the above-described example of R32 refrigerant, even when the determination time period ATa (s) that is the maximum time period allowed from the time when the refrigerant concentration exceeding the threshold C1 is detected to the time when the determination is made that the refrigerant leakage has occurred is specified as about 875 seconds, the safety of the air-conditioned space 4 can be maintained. Needless to say, as the determination time period ATa (s) is the allowable maximum time period, the determination time period ATa (s) may be specified as a value smaller than the above-described value in an actual operation. [0079]

It should be noted that as an amount of the refrigerant with which the refrigerant circuit 101 is to be filled is specified in advance, the LFL of the leaking refrigerant is known in advance. In addition, the threshold C1 is specified in advance for the refrigerant detection device 5 to be used. Then, LFL and C1 in Expression (9) can be specified as constants. When R32 refrigerant is used and the threshold C1 is specified as 0.0307 (kg/m³), Expression (9) corresponds to the following expression, and ATa can be calculated using only a value of the floor surface area A.

[0080] [Expression 4B]

ATa = ((LFL/2) - C1) x A x H/G = 792 x (0.307/2 - 0.037) x A = 92.268 x A (11) [0081]

A typical air conditioning load L of the air-conditioned space 4 corresponds to a value such as 0.1 (kW/m²). As an air conditioning capacity Q (kW) of the indoor unit 2 is stored in the memory 33 of the controller 30, the floor surface area A can be obtained using the air conditioning capacity Q of the indoor unit 2 and the air conditioning load L, and ATa can also be calculated by the following expression. That is, ATa can be calculated using only a value of the air conditioning capacity Q of the indoor unit 2. It should be noted that when a plurality of indoor units 2 are provided in one air-conditioned space 4, the total air conditioning capacity for the plurality of indoor units 2 can be represented as Q.

[0082] [Expression 4C] ATa = ((LFL/2) - C1) x (Q/L) x H/G = 792 x (0.307/2 - 0.037) x (Q/0.1) = 922.68 xQ (12) [0083]

Expression (9) also corresponds to the following expression, and ATa can be defined by a value calculated by Expression (13).

[0084] [Expression 4D] ATa = ((LFL/2) - C1) x (Q/L) x H/G = 792 x ((LFL/2) -C1) x (Q/0.1) = 7920 x ((LFL/2)-01) xQ (13) [0085]

Similarly, Expression (10) also corresponds to the following expression, and M can be defined by a value calculated by Expression (14).

[0086] [Expression 5B]

Μ > ΔΤ2 x G = (LFL/2) x (Q/L) x (H/G) x G = (LFL/2) x (Q/L) x H = (LFL/2) x (Q/0.1) x 2.2 = 11 x LFL x Q (14) [0087]

Consequently, as shown in Fig. 14, the controller 30 does not readily determine that the refrigerant leakage has occurred, even when the refrigerant detection device 5 detects the refrigerant concentration exceeding the threshold C1 due to electrical noise and miscellaneous gas such as organic compound-based gas in the air. Then, the controller 30 can determine whether the refrigerant leakage has actually occurred, on the basis of the detection value Cd of the refrigerant detection device 5 during the determination time period ATa (s) so that the false detection of the refrigerant leakage can be suppressed.

[0088]

Next, a specific example for a method of suppressing the false detection of the refrigerant leakage will be described. As a method of suppressing the false detection of the refrigerant leakage using the determination time period ATa (s), the following measures can be taken.

When the condition for determining that the refrigerant leakage has occurred is set in such a manner that a detection value Cd by the refrigerant detection device 5 always exceeds the threshold C1 (kg/m³) until the determination time period ATa (s) elapses since the detection value Cd exceeds the threshold C1, the false detection of the refrigerant leakage due to miscellaneous gas in the air can be suppressed. [0089]

Besides the above, even when the condition for determining that the refrigerant leakage has occurred is set in such a manner that a ratio at which a detection value Cd by the refrigerant detection device 5 exceeds the threshold C1 (kg/m³) is greater than or equal to a predetermined ratio in a period from the time when the detection value Cd exceeds the threshold C1 until the determination time period ATa (s) elapses, the false detection of the refrigerant leakage due to miscellaneous gas in the air can be suppressed.

[0090]

As a further determination condition, by sampling the detection value Cd by the refrigerant detection device 5 at a regular interval, the determination may be made that the refrigerant leakage has occurred when the detection value Cd by the refrigerant detection device 5 exceeds the threshold C1 consecutively a reference number of times until the determination time period ATa (s) elapses.

[0091]

It should be noted that in the present embodiment, in the description of the above-described refrigerant leakage determination function, R32 refrigerant that is a flammable refrigerant is used as the refrigerant with which the refrigerant circuit 101 is filled, and the lower flammable limit LFL forthe refrigerant is used. However, the refrigerant with which the refrigerant circuit 101 is filled is not limited to a flammable refrigerant. A similar effect can be obtained even when a non-flammable refrigerant or a toxic refrigerant is used and the refrigerant concentration limit RCL for the nonflammable refrigerant or the toxic refrigerant is used.

[0092]

Fig. 15 is a flowchart illustrating a first example of a control flow of a detection operation of the refrigerant leakage of the air-conditioning apparatus 100 according to the embodiment of the present invention.

Next, the first example of the control flow of the detection operation of the refrigerant leakage of the air-conditioning apparatus 100 according to the present embodiment will be described with reference to Fig. 15.

[0093]

Firstly, the main control unit 31 determines whether the detection value Cd by the refrigerant detection device 5 exceeds the threshold C1 stored in the memory 33 (step S1A).

[0094]

When the main control unit 31 determines that the detection value Cd exceeds the threshold C1 (YES in step S1 A), the timer unit 32 starts the measurement of a time period t (step S2A).

[0095]

After step S2A, the main control unit 31 determines whether the time period t exceeds the determination time period ATa stored in the memory 33 (step S3A). [0096]

When the main control unit 31 determines that the time period t does not exceed the determination time period ATa (NO in step S3A), the main control unit 31 determines whether the detection value Cd exceeds the threshold C1 (step S4A). [0097]

In step S4A, when the main control unit 31 determines that the detection value Cd does not exceed the threshold C1 (NO in step S4A), the process ends.

[0098]

On the other hand, when the main control unit 31 determines that the detection value Cd exceeds the threshold C1 (YES in step S4A), the process returns to step S3A.

[0099]

When, in step S3A, the main control unit 31 determines that the time period t exceeds the determination time period ATa (YES in step S3A), the safety measure devices are operated by the drive unit 34. That is, the main control unit 31 turns on the alarm device 6 when the alarm device 6 is the safety measure device, opens the blocking device 7 when the blocking device 7 is the safety measure device, and turns on the ventilation device 8 when the ventilation device 8 is the safety measure device (step S5A).

[0100]

As described above, the main control unit 31 repeats the processes of step S3A to step S4A while the detection value Cd exceeds the threshold C1, and operates the safety measure devices when the detection value Cd always exceeds the threshold C1 during the determination time period ATa.

[0101]

Fig. 16 is a flowchart illustrating a second example of a control flow of a detection operation of the refrigerant leakage of the air-conditioning apparatus 100 according to the embodiment of the present invention.

Next, the second example of the control flow of the detection operation of the refrigerant leakage of the air-conditioning apparatus 100 according to the present embodiment will be described with reference to Fig. 16.

[0102]

Firstly, the timer unit 32 starts the measurement of a time period t, and the main control unit 31 resets on-time period Aton and off-time period Atoff to zero (step S1B). Here, the on-time period Aton refers to a total time period for which the detection value Cd exceeds the threshold C1, and the off-time period Atoff refers to a total time period for which the detection value Cd does not exceed the threshold C1. Next, the main control unit 31 determines whether the detection value Cd by the refrigerant detection device 5 exceeds the threshold C1 stored in the memory 33 (step S2B).

[0103]

When the main control unit 31 determines that the detection value Cd exceeds the threshold C1 (YES in step S2B), the main control unit 31 adds a time period to the on-time period Aton (step S3B), and the process proceeds to step S5B.

[0104]

On the other hand, when the main control unit 31 determines that the detection value Cd does not exceed the threshold C1 (NO in step S2B), the main control unit 31 adds the time period to the off-time period Atoff (step S4B), and the process proceeds to step S5B. It should be noted that the process of step S4B may be omitted.

[0105]

Here, in steps S3B and S4B, the time period to be added to the on-time period Aton or the off-time period Atoff is a time period from the time when the determination process is performed in the previous step S2B to the time when the determination process is performed in the present step S2B. For example, when the main control unit 31 performs the determination process in step S2B every one second, the abovedescribed time period to be added is one second.

[0106]

In step S5B, the main control unit 31 determines whether the time period t exceeds the determination time period ATa stored in the memory 33.

[0107]

When the main control unit 31 determines that the time period t exceeds the determination time period ATa (YES in step S5B), the process proceeds to step S6B. [0108]

On the other hand, when the main control unit 31 determines that the time period t does not exceed the determination time period ATa (NO in step S5B), the process returns to step S2B. That is, the main control unit 31 repeats the processes of steps S2B to S5B until the time period t exceeds the determination time period ATa. Then, the main control unit 31 obtains the Δοη-time period ton that is a total time period for which the detection value Cd exceeds the threshold C1 during the determination time period ATa, and the off-time period Atoff that is a total time period for which the detection value Cd does not exceed the threshold C1 during the determination time period ATa.

[0109]

In step S6B, the main control unit 31 determines whether the on-time period

Aton exceeds a reference time period xATa stored in the memory 33. Here, regarding the reference time period xATa, when the determination time period ATa is 30 seconds and the preset ratio is 80 percent, for example, the reference time period xATa can be calculated by an expression of 30 x (8/10), which equals to 24 seconds. [0110]

When the main control unit 31 determines that the on-time period Aton exceeds the reference time period xATa (YES in step S6B), the safety measure devices are operated by the drive unit 34. That is, the main control unit 31 turns on the alarm device 6 when the alarm device 6 is the safety measure device, opens the blocking device 7 when the blocking device 7 is the safety measure device, and turns on the ventilation device 8 when the ventilation device 8 is the safety measure device (step S7B).

[0111]

On the other hand, when the main control unit 31 determines that the on-time period Aton does not exceed the reference time period xATa (NO in step S6B), the process ends.

[0112]

As described above, when the main control unit 31 measures the total time period for which the detection value Cd exceeds the threshold C1 during the determination time period ATa, and the measured total time period is greater than or equal to the reference time period xATa, the safety measure devices are operated. [0113]

Fig. 17 is a flowchart illustrating a third example of a control flow of a detection operation of the refrigerant leakage of the air-conditioning apparatus 100 according to the embodiment of the present invention.

Next, the third example of the control flow of the detection operation of the refrigerant leakage of the air-conditioning apparatus 100 according to the present embodiment will be described with reference to Fig. 17.

[0114]

Firstly, the timer unit 32 starts the measurement of a time period t, and the main control unit 31 resets a counter K to zero (step S1C). Next, the main control unit 31 determines whether the detection value Cd by the refrigerant detection device 5 exceeds the threshold C1 stored in the memory 33 (step S2C).

[0115]

When the main control unit 31 determines that the detection value Cd exceeds the threshold C1 (YES in step S2C), the main control unit 31 increments the counter K by 1 (step S3C), and the process proceeds to step S5C.

[0116]

On the other hand, when the main control unit 31 determines that the detection value Cd does not exceed the threshold C1 (NO in step S2C), the main control unit 31 resets the counter K (step S4C), and the process proceeds to step S5C. [0117]

In step S5C, the main control unit 31 determines whether a value of the counter K has reached a reference number of times Ka stored in the memory 33.

[0118]

When the main control unit 31 determines that the value of the counter K has reached the reference number of times Ka (YES in step S5C), the safety measure devices are operated by the drive unit 34. That is, the main control unit 31 turns on the alarm device 6 when the alarm device 6 is the safety measure device, opens the blocking device 7 when the blocking device 7 is the safety measure device, and turns on the ventilation device 8 when the ventilation device 8 is the safety measure device (step S7C).

[0119]

On the other hand, when the main control unit 31 determines that the value of the counter K does not reach the reference number of times Ka (NO in step S5C), the process proceeds to step S6C.

[0120]

In step S6C, the main control unit 31 determines whether the time period t exceeds the determination time period ATa stored in the memory 33.

[0121]

When the main control unit 31 determines that the time period t exceeds the determination time period ATa (YES in step S6C), the process ends.

[0122]

On the other hand, when the main control unit 31 determines that the time period t does not exceed the determination time period ATa (NO in step S6C), the process returns to step S2C. That is, the main control unit 31 repeats the processes of steps S2C to S5C until the time period t exceeds the determination time period ATa, and determines whether the detection value Cd exceeds the threshold C1 consecutively a reference number of times Ka during the determination time period ATa.

[0123]

As described above, the main control unit 31 measures the number of times the detection value Cd consecutively exceeds the threshold C1 during the determination time period ATa, and when the measured number of times is greater than or equal to the reference number of times Ka, the safety measure devices are operated.

[0124]

As described above, the air-conditioning apparatus 100 according to the present embodiment includes the refrigerant detection device 5 that detects the refrigerant leakage from the refrigerant circuit 101, and the controller 30 that determines that the refrigerant leakage has occurred when the detection value Cd of the refrigerant detection device 5 always exceeds the threshold C1 during the determination time period ΔΤ or when the detection value Cd of the refrigerant detection device 5 exceeds the threshold C1 for the reference time period xATa or longer during the determination time period ΔΤ.

[0125]

In the air-conditioning apparatus 100 according to the present embodiment, the controller 30 determines that the refrigerant leakage has occurred when the detection value Cd of the refrigerant detection device 5 always exceeds the threshold C1 during the determination time period ΔΤ or when the detection value Cd of the refrigerant detection device 5 exceeds the threshold C1 for the reference time period xATa or longer during the determination time period ΔΤ so that the false detection of the refrigerant leakage can be suppressed.

[0126]

The air-conditioning apparatus 100 according to the present embodiment includes at least one of the alarm device 6, the ventilation device 8, and the blocking device 7, and when the controller 30 determines when the refrigerant leakage has occurred, the controller 30 operates at least one of the alarm device 6, the ventilation device 8, and the blocking device 7.

[0127]

In the air-conditioning apparatus 100 according to the present embodiment, when the controller 30 determines that the refrigerant leakage has occurred, the controller 30 operates the safety measure devices so that the ignition in the airconditioned space 4 can be inhibited, and the safety of the air-conditioned space 4 can be maintained.

[0128]

In the air-conditioning apparatus 100 according to the present embodiment, the controller 30 samples the detection value of the refrigerant detection device 5 at a regular interval, and the controller 30 determines that the refrigerant leakage has occurred when the detection value of the refrigerant detection device 5 exceeds the threshold C1 consecutively a reference number of times Ka during the determination time period ATa.

[0129]

In the air-conditioning apparatus 100 according to the present embodiment, the controller 30 samples the detection value of the refrigerant detection device 5 at a regular interval, and the controller 30 determines that the refrigerant leakage has occurred when the detection value of the refrigerant detection device 5 exceeds the threshold C1 consecutively a reference number of times Ka during the determination time period ATa so that the false detection of the refrigerant leakage can be suppressed.

Reference Signs List [0130]

Outdoor unit, 2 Indoor unit, 2a Indoor unit, 2b Indoor unit, 3

Refrigerant pipe, 3a Branch portion, 3b Branch portion, 4 Air-conditioned space, 4a Air-conditioned space, 4bAir-conditioned space, 5 Refrigerant detection device, 5a Refrigerant detection device, 5bRefrigerant detection device, 6 Alarm device, 6a Alarm device, 6b Alarm device, 7 Blocking device, 7a Blocking device, 7b Blocking device, 8 Ventilation device, 8a Ventilation device, 8b

Ventilation device, 10 Compressor, 11 Refrigerant flow switching device, 12 Heat source side heat exchanger, 13 Accumulator, 14 Outdoor air-sending device, 20 First pressure detection device, 21 Second pressure detection device, 22 First temperature detection device, 30 Controller, 31 Main control unit, 32 Timer unit, 33 Memory, 34 Drive unit, 40 Load side heat exchanger, 40a Load side heat exchanger, 40b Load side heat exchanger, 41

Expansion device, 41a Expansion device, 41b Expansion device, 42

Indoor air-sending device, 42a Indoor air-sending device, 42b Indoor airsending device, 50 Second temperature detection device, 50a Second temperature detection device, 50b Second temperature detection device, 51 Third temperature detection device, 51a Third temperature detection device, 51b

Third temperature detection device, 52 Fourth temperature detection device, 52a Fourth temperature detection device, 52b Fourth temperature detection device, 100 Air-conditioning apparatus, 101 Refrigerant circuit

Claims

CLAIMS [Claim 1]

An air-conditioning apparatus, comprising:

one or a plurality of indoor units configured to condition air in an air-conditioned space;

one or a plurality of outdoor units each used as a heat source;

a refrigerant circuit in which the one or the plurality of indoor units and the one or the plurality of outdoor units are connected by a refrigerant pipe and in which refrigerant circulates;

a refrigerant detection device provided in an interior of the one or any of the plurality of indoor units or the air-conditioned space in which air is conditioned by the one or the plurality of indoor units, the refrigerant detection device being configured to detect refrigerant leakage from the refrigerant circuit; and a controller configured to determine that the refrigerant leakage has occurred when a detection value of the refrigerant detection device always exceeds a threshold C1 during a determination time period ATa or when the detection value of the refrigerant detection device exceeds the threshold C1 for a reference time period or longer during the determination time period ATa.

[Claim 2]

The air-conditioning apparatus of claim 1, further comprising at least one of an alarm device configured to inform a user of the refrigerant leakage, a ventilation device configured to exhaust leaking refrigerant, and a blocking device configured to block refrigerant flow, wherein the controller is configured to operate at least one of the alarm device, the ventilation device, and the blocking device when the controller determines that the refrigerant leakage has occurred.

[Claim 3]

The air-conditioning apparatus of claim 1 or 2, wherein the determination time period ATa is a value obtained using a lower flammable limit LFL (kg/m3) when the refrigerant with which the refrigerant circuit is filled is a flammable refrigerant.

[Claim 4]

The air-conditioning apparatus of claim 3, wherein the determination time period ATa is less than a value calculated by an expression of ((LFL/2) - C1) x A x H/G or an expression of ((LFL/2) - C1) x (Q/L) x H/G, where A (m2) is a floor surface area of the air-conditioned space in which the one or the plurality of indoor units are provided,

H (m) is a ceiling height of the air-conditioned space in which the one or the plurality of indoor units are provided,

G (kg/s) is a leakage speed of the refrigerant with which the refrigerant circuit is filled,

Q (kW) is a total air conditioning capacity of the one or the plurality of indoor units, and

L (kW/m2) is an air conditioning load of the air-conditioned space in which the one or the plurality of indoor units are provided.

[Claim 5]

The air-conditioning apparatus of claim 4, wherein an amount of the refrigerant with which the refrigerant circuit is filled is greater than or equal to a value calculated by an expression of (LFL/2) χ A χ H or an expression of (LFL/2) x (Q/L) χ H. [Claim 6]

The air-conditioning apparatus of claim 4 or 5 wherein the leakage speed G equals to 10/3600 (kg/s), the ceiling height H equals to
2.2 (m), and the air conditioning load L equals to 0.1 (kW/m2).

[Claim 7]

The air-conditioning apparatus of claim 1 or 2, wherein the determination time period ATa is a value obtained using a refrigerant concentration limit RCL (kg/m3) when the refrigerant with which the refrigerant circuit is filled is a non-flammable refrigerant or a toxic refrigerant.

[Claim 8]

The air-conditioning apparatus of any one of claims 1 to 7, wherein the determination time period ATa is 20 seconds or longer.

[Claim 9]

The air-conditioning apparatus of any one of claims 1 to 8, wherein the controller is configured to sample the detection value of the refrigerant detection

5 device at a regular interval, and the controller is configured to determine that the refrigerant leakage has occurred when the detection value of the refrigerant detection device exceeds the threshold C1 consecutively a reference number of times during the determination time period ATa.