Air conditioning system

Abstract

To provide an air conditioning system that can accurately detect refrigerant leaks. [Solution] The air conditioning system (100) comprises a refrigerant circuit (10) and a detection unit (61). The refrigerant circuit has a heat source heat exchanger (23), an expansion valve (24), and a utilization heat exchanger (51), and is filled with refrigerant. The detection unit detects refrigerant leakage in the refrigerant circuit. The detection unit detects refrigerant leakage by comparing a first value (P1) corresponding to a first estimated flow rate (F1), which is the estimated flow rate (F) of refrigerant flowing through the expansion valve in a first period (T1), with a second value (P2) corresponding to a second estimated flow rate (F2), which is the estimated flow rate of refrigerant flowing through the expansion valve in a second period (T2) prior to the first period.

Description

Technical Field

[0001] It relates to an air conditioner.

Background Art

[0002] Patent Document 1 (Japanese Patent Application Laid-Open No. 2017-26308) discloses a refrigeration cycle device that detects refrigerant leakage in a refrigerant circuit by comparing the predicted opening degree of an expansion valve when there is no refrigerant leakage with the measured opening degree of the expansion valve.

Summary of the Invention

Problems to be Solved by the Invention

[0003] The opening degree of the expansion valve is likely to vary depending on the amount of refrigerant circulating in the refrigerant circuit, the capacity of the refrigeration cycle device, and the environment of the air-conditioned space. Therefore, in the case of the refrigerant leakage detection method disclosed in Patent Document 1, it has been difficult to accurately detect refrigerant leakage.

[0004] The present disclosure aims to provide an air conditioner that can accurately detect refrigerant leakage.

Means for Solving the Problems

[0005] The air conditioner according to the first aspect includes a refrigerant circuit and a detection unit. The refrigerant circuit has a heat source heat exchanger, an expansion valve, and a utilization heat exchanger, and is filled with refrigerant. The detection unit detects refrigerant leakage in the refrigerant circuit. The detection unit compares a first value corresponding to a first estimated flow rate, which is the estimated flow rate of the refrigerant flowing through the expansion valve in a first period, with a second value corresponding to a second estimated flow rate, which is the estimated flow rate of the refrigerant flowing through the expansion valve in a second period before the first period, to detect refrigerant leakage.

[0006] The detection unit detects refrigerant leakage in the refrigerant circuit using an estimated flow rate based on the flow rate of the refrigerant flowing through the expansion valve. The flow rate of the refrigerant flowing through the expansion valve is less affected by the amount of refrigerant circulating in the refrigerant circuit, the capacity of the refrigeration cycle device, and the environment of the air-conditioned space. Therefore, this air conditioner can accurately detect refrigerant leakage.

[0007] The air conditioning system in the second perspective is the same as the air conditioning system in the first perspective, and the detection unit records a flow characteristic equation that specifies the relationship between the opening degree of the expansion valve and the estimated flow rate of the refrigerant flowing through the expansion valve. The first estimated flow rate is calculated based on the opening degree of the expansion valve and the flow characteristic equation during the first period. The second estimated flow rate is calculated based on the opening degree of the expansion valve and the flow characteristic equation during the second period.

[0008] This air conditioning system can accurately detect refrigerant leaks.

[0009] The third-perspective air conditioning system is an air conditioning system of the first or second perspective, where the first value is calculated based on the first estimated flow rate and the first estimated air conditioning capacity corresponding to the air conditioning capacity in the first period. The second value is calculated based on the second estimated flow rate and the second estimated air conditioning capacity corresponding to the air conditioning capacity in the second period.

[0010] This air conditioning system can detect refrigerant leaks with greater accuracy by incorporating estimated air conditioning capacity based on the actual air conditioning capacity.

[0011] The air conditioning system in the fourth perspective is the air conditioning system in the third perspective, in which the first estimated air conditioning capacity is calculated based on the difference between the temperature of the heat exchanger used during the first period and the temperature of the air-conditioned space in which the heat exchanger is installed during the first period. The second estimated air conditioning capacity is calculated based on the difference between the temperature of the heat exchanger used during the second period and the temperature of the air-conditioned space during the second period.

[0012] This air conditioning system allows for easy estimation of the air conditioning capacity based on the difference between the temperature of the heat exchanger being used and the temperature of the space being air-conditioned.

[0013] The air conditioning system in the fifth perspective is the air conditioning system in the fourth perspective, where the first value is the average value obtained by dividing the first estimated flow rate by the first air conditioning capacity. The second value is the average value obtained by dividing the second estimated flow rate by the second air conditioning capacity.

[0014] This air conditioning system uses the average value of the estimated flow rate, which reduces the influence of external disturbances such as temperature, humidity, and airflow restrictions on the estimated flow rate, thus enabling more accurate detection of refrigerant leaks.

[0015] The sixth air conditioning system is one of the air conditioning systems from the first to the fifth perspectives, and the detection unit detects refrigerant leakage using the change in the first value relative to the second value.

[0016] This air conditioning system can accurately detect refrigerant leaks.

[0017] The seventh air conditioning system is one of the air conditioning systems from the first to the sixth perspectives, and the detection unit detects refrigerant leakage using the rate of change of the first value relative to the second value.

[0018] This air conditioning system can accurately detect refrigerant leaks.

[0019] The air conditioning system of the eighth aspect is any of the air conditioning systems of the first aspect to the seventh aspect, and the refrigerant is flammable.

[0020] This air conditioning system can accurately detect leaks of flammable refrigerants.

[0021] The air conditioning system in the ninth perspective is one of the air conditioning systems in the first, second, or eighth perspectives, and the refrigerant is propane.

[0022] This air conditioning system can accurately detect leaks of propane, a flammable refrigerant.

[0023] The air conditioning system of the tenth perspective is any of the air conditioning systems of the first to ninth perspectives, and the air conditioning system further includes a notification unit that notifies the detection result when the detection unit detects a refrigerant leak.

[0024] This air conditioning system can notify the user of the results of refrigerant leak detection.

[0025] The air conditioner according to the 11th aspect is any one of the air conditioners according to the 1st to 10th aspects, and the air conditioner continues the air conditioning operation even after the notification unit makes a notification.

[0026] The air conditioner according to the 12th aspect is any one of the air conditioners according to the 1st to 10th aspects, and the air conditioner further includes a refrigerant sensor that detects refrigerant leakage. When the refrigerant sensor detects refrigerant leakage during the air conditioning operation, the air conditioner stops the air conditioning operation, and when the detection unit detects refrigerant leakage during the air conditioning operation, the air conditioner continues the air conditioning operation.

[0027] The air conditioner according to the 13th aspect is any one of the air conditioners according to the 1st to 12th aspects, and both the heat source heat exchanger and the utilization heat exchanger have heat transfer tubes. At least one of the heat source heat exchanger and the utilization heat exchanger has heat transfer tubes made of aluminum.

[0028] This air conditioner can accurately detect refrigerant leakage even when refrigerant leaks from the aluminum heat transfer tubes.

Brief Description of Drawings

[0029] [Figure 1] It is a schematic configuration diagram of an air conditioner 100 according to an embodiment of the present disclosure. [Figure 2] It is a block diagram of the control unit 60. [Figure 3] It is a flowchart showing the control flow of the sampling process. [Figure 4] It is a conceptual diagram of the average detection variable PQa. [Figure 5] It is a flowchart showing the control flow of the leakage determination process. [Figure 6] It is a conceptual diagram explaining the determination process. [Figure 7A] It is a graph showing the result of evaluating the influence of the air volume on the detection variable PQ in the heating operation. [Figure 7B] It is a graph showing the result of evaluating the influence of the air volume on the detection variable PQ in the cooling operation. [Figure 8A]This graph shows the results of evaluating the effect of ambient temperature on the sensing variable PQ during heating operation. [Figure 8B] This graph shows the results of evaluating the effect of ambient temperature on the sensing variable PQ during air conditioning operation. [Modes for carrying out the invention]

[0030] <Embodiment> (1) Overall structure Figure 1 is a schematic diagram of an air conditioning system 100 according to one embodiment of the present disclosure. The air conditioning system 100 performs a vapor compression type refrigeration cycle operation in the refrigerant circuit 10. By performing the refrigeration cycle operation, the air conditioning system 100 realizes air conditioning operation for a space to be air-conditioned (not shown). Air conditioning operation includes cooling operation and heating operation. The air conditioning system 100 mainly comprises one heat source unit 20, one utilization unit 50, liquid refrigerant connecting pipe 2, gas refrigerant connecting pipe 4, and a control unit 60.

[0031] The refrigerant circuit 10 is configured such that the equipment of the heat source unit 20 and the utilization unit 50 are connected to the liquid refrigerant connecting pipe 2 and the gas refrigerant connecting pipe 4 via refrigerant piping. More specifically, the refrigerant circuit 10 comprises a compressor 21, a flow direction switching mechanism 22, a heat source heat exchanger 23, an expansion valve 24, a utilization heat exchanger 51, a liquid refrigerant connecting pipe 2, and a gas refrigerant connecting pipe 4, all of which are connected via refrigerant piping. The refrigerant circuit 10 is filled with refrigerant. The refrigerant filled in the refrigerant circuit 10 is a flammable refrigerant such as propane.

[0032] As will be described in more detail later, the control unit 60 has a function to detect refrigerant leakage in the refrigerant circuit 10.

[0033] (2) Detailed configuration (2-1) Usage Unit 50 The utilization unit 50 includes a utilization heat exchanger 51, a utilization fan 52, a notification unit 53, a first temperature sensor 54, a second temperature sensor 55, and a refrigerant sensor 56. The utilization unit 50 is installed, for example, in a space to be air-conditioned.

[0034] (2-1-1) Utilized heat exchanger 51 The heat exchanger 51 performs heat exchange between the refrigerant flowing inside and the air in the space to be air-conditioned. The heat exchanger 51 has a liquid-side end 51a and a gas-side end 51b.

[0035] The liquid-side end 51a is connected to the liquid refrigerant connecting pipe 2 via the refrigerant piping. The gas-side end 51b is connected to the gas refrigerant connecting pipe 4 via the refrigerant piping.

[0036] (2-1-2) Use of fan 52 The utilization fan 52 supplies air to the utilization heat exchanger 51. The utilization fan 52 is driven by a motor 52a. The rotational speed of the motor 52a is controlled by the control unit 60.

[0037] (2-1-3) Hochi Department 53 The notification unit 53 notifies the user or others of the detection result when the control unit 60 detects a refrigerant leak. The notification unit 53 is controlled by the control unit 60. The notification unit 53 includes an LED (not shown). When the control unit 60 detects a refrigerant leak, it causes the LED of the notification unit 53 to blink. In this way, the notification unit 53 notifies the detection result.

[0038] (2-1-4) First temperature sensor 54 The first temperature sensor 54 detects the temperature Th of the heat exchanger 51. The control unit 60 receives the temperature Th detected by the first temperature sensor 54.

[0039] (2-1-5) Second temperature sensor 55 The second temperature sensor 55 detects the temperature Tr of the air-conditioned space. The control unit 60 receives the temperature Tr detected by the second temperature sensor 55.

[0040] (2-1-6) Refrigerant sensor 56 The refrigerant sensor 56 detects the refrigerant. Specifically, the refrigerant sensor 56 detects the refrigerant when the concentration of leaked refrigerant exceeds a predetermined value. The refrigerant sensor 56 is housed in the utilization unit 50 and detects refrigerant (leakage) in the air-conditioned space. The control unit 60 receives the detection result from the refrigerant sensor 56.

[0041] (2-2) Heat source unit 20 The heat source unit 20 includes a compressor 21, a flow direction switching mechanism 22, a heat source heat exchanger 23, an expansion valve 24, an accumulator 25, a shut-off valve 26, and a heat source fan 27. The heat source unit 20 is located, for example, outside the space to be air-conditioned.

[0042] (2-2-1) Compressor 21 The compressor 21 draws in low-pressure refrigerant from the refrigeration cycle through the suction pipe 21a, compresses the refrigerant using a compression mechanism (not shown), and discharges it as high-pressure refrigerant to the discharge pipe 21b. The capacity of the compressor 21 is controlled by the control unit 60. The operating capacity of the compressor 21 is controlled by controlling the rotational speed of the motor (not shown) that drives the compression mechanism.

[0043] (2-2-2) Flow direction switching mechanism 22 The flow direction switching mechanism 22 switches between a first state and a second state, changing the direction in which the refrigerant flows. The flow direction switching mechanism 22 is switched between the first state and the second state by the control unit 60. In this embodiment, the flow direction switching mechanism 22 is a four-way switching valve.

[0044] In the first state, the flow direction switching mechanism 22 connects the inlet 25a of the accumulator 25 to the gas refrigerant connecting pipe 4 and the discharge pipe 21b of the compressor 21 to the gas side end 23b of the heat source heat exchanger 23 (see solid line in the flow direction switching mechanism 22 in Figure 1). In the second state, the flow direction switching mechanism 22 connects the inlet 25a of the accumulator 25 to the gas side end 23b of the heat source heat exchanger 23 and the discharge pipe 21b to the gas refrigerant connecting pipe 4 (see dashed line in the flow direction switching mechanism 22 in Figure 1).

[0045] (2-2-3) Heat source heat exchanger 23 The heat source heat exchanger 23 performs heat exchange between the refrigerant flowing inside and the air (heat source air) at the installation location of the heat source unit 20. The heat source heat exchanger 23 has a liquid side end 23a and a gas side end 23b.

[0046] The liquid-side end 23a is connected to the liquid refrigerant connecting pipe 2 via the refrigerant piping. The gas-side end 23b is connected to the gas refrigerant connecting pipe 4 via the refrigerant piping.

[0047] (2-2-4) Expansion valve 24 The expansion valve 24 regulates the pressure and / or flow rate of the refrigerant flowing through the refrigerant circuit 10. The expansion valve 24 is installed in the refrigerant piping that connects the liquid refrigerant connecting pipe 2 and the liquid side end 23a of the heat source heat exchanger 23. The opening degree of the expansion valve 24 is controlled by the control unit 60.

[0048] More specifically, the expansion valve 24 is an electrically operated expansion valve having a stepping motor and a valve body (neither of which are shown) that opens and closes in accordance with the rotation of the stepping motor. The stepping motor rotates in response to a pulse signal output by the control unit 60, thereby driving the valve body. As a result, the control unit 60 controls the opening degree of the expansion valve 24 via the pulse signal.

[0049] (2-2-5) Accumulator 25 The accumulator 25 separates the incoming refrigerant into gaseous refrigerant and liquid refrigerant. The accumulator 25 also stores excess refrigerant generated in response to fluctuations in the operating load of the utilization unit 50. The accumulator 25 has an inlet 25a and an outlet 25b.

[0050] The inlet 25a is connected to the flow direction switching mechanism 22. The outlet 25b is connected to the suction pipe 21a of the compressor 21.

[0051] (2-2-6) Shut-off valve 26 The shut-off valve 26, when closed, blocks the flow of refrigerant through the refrigerant piping. The shut-off valve 26 includes a liquid-side shut-off valve 26a and a gas-side shut-off valve 26b. The shut-off valve 26 is, for example, a manually operated valve.

[0052] The liquid-side shut-off valve 26a is installed between the expansion valve 24 and the liquid refrigerant connecting pipe 2 in the refrigerant piping that connects the liquid-side end 23a of the heat source heat exchanger 23 to the liquid refrigerant connecting pipe 2.

[0053] The gas-side shut-off valve 26b is provided in the refrigerant piping that connects the flow direction switching mechanism 22 and the gas refrigerant communication pipe 4.

[0054] (2-2-7) Heat source fan 27 The heat source fan 27 supplies air to the heat source heat exchanger 23. The heat source fan 27 is driven by a motor 27a. The rotational speed of the motor 27a is controlled by the control unit 60.

[0055] (2-3) Liquid refrigerant connecting pipe 2 and gaseous refrigerant connecting pipe 4 The liquid refrigerant connecting pipe 2 and the gaseous refrigerant connecting pipe 4 are pipes that connect the heat source unit 20 and the utilization unit 50.

[0056] (2-4) Control Unit The control unit 60 controls the operation of each component of the heat source unit 20 and the utilization unit 50 to realize refrigeration cycle operation and refrigerant recovery operation, and also functions as a detection unit 61 that detects refrigerant leakage in the refrigerant circuit 10. As will be described in detail later, the detection unit 61 performs a leak detection process that detects refrigerant leakage in the refrigerant circuit 10 based on the estimated flow rate of refrigerant flowing through the expansion valve 24. The control unit 60 (detection unit 61) stores a flow characteristic formula, which specifies the relationship between the opening degree of the expansion valve 24 and the estimated flow rate of refrigerant flowing through the expansion valve 24, in a storage device, which will be described later. As described above, since the control unit 60 controls the opening degree of the expansion valve 24 via pulse signals, the flow characteristic formula may specify the relationship between the frequency of the pulse signal corresponding to the opening degree of the expansion valve 24 and the estimated flow rate of refrigerant flowing through the expansion valve 24.

[0057] Figure 2 is a block diagram of the control unit 60. As shown in Figure 2, the control unit 60 is electrically connected to the compressor 21, the flow direction switching mechanism 22, the expansion valve 24, the motor 27a of the heat source fan 27, the motor 52a of the utilization fan 52, and the notification unit 53 to send and receive control signals and to control their operation. The control unit 60 is electrically connected to the first temperature sensor 54 to receive temperature Th. The control unit 60 is electrically connected to the second temperature sensor 55 to receive temperature Tr. The control unit 60 is electrically connected to the refrigerant sensor 56 to receive detection results. The user of the air conditioning system 100 can start or stop the refrigeration cycle operation of the air conditioning system 100 by giving instructions to the control unit 60 via a remote control (not shown). The control unit 60 may be housed in either the utilization unit 50 or the heat source unit 20, or in both the utilization unit 50 and the heat source unit 20, or it may be installed separately from the utilization unit 50 and the heat source unit 20.

[0058] The control unit 60 is implemented by a computer. The control unit 60 includes a control arithmetic unit and a memory device (neither of which are shown in the figure). A processor such as a CPU or GPU can be used for the control arithmetic unit. The control arithmetic unit reads a program stored in the memory device and performs predetermined arithmetic processing according to this program. Furthermore, the control arithmetic unit can write the calculation results to the memory device or read information stored in the memory device according to the program.

[0059] (2-5) Operation of the air conditioning system This section describes the control of the operation of the air conditioning system 100 during cooling, heating, and refrigerant recovery operations.

[0060] (2-5-1) Cooling operation When the control unit 60 detects an instruction to start cooling operation sent from a remote control or the like, it sets the airflow switching mechanism 22 to the first state and starts operating the compressor 21, the heat source fan 27, and the utilization fan 52.

[0061] The control unit 60 controls the rotational speed of the motor 27a of the heat source fan 27 and the rotational speed of the motor 52a of the utilization fan 52 to predetermined rotational speeds. For example, the control unit 60 controls the rotational speed of motor 27a to the maximum rotational speed. The control unit 60 appropriately controls the rotational speed of motor 52a based on the airflow instruction or the like input to the remote control.

[0062] The control unit 60 controls the opening of the expansion valve 24 so that the superheating degree of the refrigerant approaches a predetermined target superheating degree. The control unit 60 controls the operating capacity of the compressor 21 so that the evaporation temperature approaches a predetermined target evaporation temperature.

[0063] When the compressor 21 starts operating, the low-pressure gaseous refrigerant in the refrigeration cycle is drawn into the compressor 21 from the suction pipe 21a and compressed to become the high-pressure gaseous refrigerant in the refrigeration cycle. The high-pressure gaseous refrigerant is discharged from the discharge pipe 21b and sent to the heat source heat exchanger 23 via the flow direction switching mechanism 22. The refrigerant that flows into the heat source heat exchanger 23 condenses through heat exchange with the heat source air supplied by the heat source fan 27, becoming the high-pressure liquid refrigerant. The high-pressure liquid refrigerant that leaves the heat source heat exchanger 23 is depressurized in the expansion valve 24 to become a gas-liquid two-phase refrigerant and is sent to the liquid refrigerant connecting pipe 2. The gas-liquid two-phase refrigerant that has passed through the liquid refrigerant connecting pipe 2 and flowed into the utilization unit 50 is sent to the utilization heat exchanger 51. The refrigerant that flows into the utilization heat exchanger 51 evaporates through heat exchange with the air of the air-conditioned space supplied to the utilization heat exchanger 51 by the utilization fan 52, becoming the low-pressure gaseous refrigerant. The air supplied to the heat exchanger 51 is cooled by heat exchange with the refrigerant flowing through the heat exchanger 51, and then blown out into the space to be air-conditioned. The low-pressure gaseous refrigerant that leaves the heat exchanger 51 is sent to the gaseous refrigerant connecting pipe 4. The refrigerant that has passed through the gaseous refrigerant connecting pipe 4 and flowed into the heat source unit 20 flows into the accumulator 25 from the inlet 25a via the flow direction switching mechanism 22. The low-pressure gaseous refrigerant that has flowed into the accumulator 25 leaves the accumulator 25 from the outlet 25b and is then drawn back into the compressor 21.

[0064] (2-5-2) Heating operation When the control unit 60 detects an instruction to start heating operation sent from a remote control or the like, it sets the flow direction switching mechanism 22 to the second state and starts operating the compressor 21, heat source fan 27, and utilization fan 52.

[0065] The control unit 60 controls the rotational speed of the motor 27a of the heat source fan 27 and the rotational speed of the motor 52a of the utilization fan 52 to predetermined rotational speeds. For example, the control unit 60 controls the rotational speed of motor 27a to the maximum rotational speed. The control unit 60 appropriately controls the rotational speed of motor 52a based on the airflow instruction or the like input to the remote control.

[0066] The control unit 60 controls the opening of the expansion valve 24 so that the degree of subcooling of the refrigerant approaches a predetermined target degree of subcooling. The control unit 60 also controls the operating capacity of the compressor 21 so that the condensation temperature approaches a predetermined target condensation temperature.

[0067] When the compressor 21 starts operating, the low-pressure gaseous refrigerant in the refrigeration cycle is drawn into the compressor 21 from the suction pipe 21a and compressed to become the high-pressure gaseous refrigerant in the refrigeration cycle. The high-pressure gaseous refrigerant is discharged from the discharge pipe 21b and sent to the utilization heat exchanger 51 via the flow direction switching mechanism 22. The refrigerant flowing into the utilization heat exchanger 51 condenses by exchanging heat with the air in the air-conditioned space supplied by the utilization fan 52, becoming the high-pressure liquid refrigerant. The air supplied to the utilization heat exchanger 51 is heated by exchanging heat with the refrigerant flowing through the utilization heat exchanger 51, and then blown out into the air-conditioned space. The high-pressure liquid refrigerant that exits the utilization heat exchanger 51 is sent to the liquid refrigerant connecting pipe 2. The refrigerant that passes through the liquid refrigerant connecting pipe 2 and flows into the heat source unit 20 is depressurized in the expansion valve 24 to become a gas-liquid two-phase refrigerant and is sent to the heat source heat exchanger 23. The refrigerant flowing into the heat source heat exchanger 23 exchanges heat with the heat source air supplied to the heat source heat exchanger 23 by the heat source fan 27, evaporating and becoming a low-pressure gaseous refrigerant. The low-pressure gaseous refrigerant leaving the heat source heat exchanger 23 flows into the accumulator 25 from the inlet 25a via the flow direction switching mechanism 22. The low-pressure gaseous refrigerant that has flowed into the accumulator 25 exits the accumulator 25 from the outlet 25b and is then drawn back into the compressor 21.

[0068] (2-5-3) Leak detection process (2-5-3-1) Overview In the leak detection process, the detection unit 61 detects refrigerant leakage by comparing a first value P1 with a second value P2. The first value P1 corresponds to the first estimated flow rate F1, which is the estimated flow rate of refrigerant flowing through the expansion valve during the first period T1. The second value P2 corresponds to the second estimated flow rate F2, which is the estimated flow rate of refrigerant flowing through the expansion valve during the second period T2, which precedes the first period T1. More specifically, the detection unit 61 detects refrigerant leakage using the change in the first value P1 relative to the second value P2.

[0069] The first estimated flow rate F1 is calculated based on the opening degree of the expansion valve 24 and the flow rate characteristic equation during the first period T1. The second estimated flow rate F2 is calculated based on the opening degree of the expansion valve 24 and the flow rate characteristic equation during the second period T2.

[0070] The first value P1 is calculated based on the first estimated flow rate F1 and the first estimated air conditioning capacity C1 corresponding to the air conditioning capacity during the first period T1. The second value P2 is calculated based on the second estimated flow rate F2 and the second estimated air conditioning capacity C2 corresponding to the air conditioning capacity during the second period T2. More specifically, the first value P1 is the average value of the first estimated flow rate F1 divided by the first estimated air conditioning capacity C1 (the first average detection variable group PQa1 described later). The second value P2 is the average value of the second estimated flow rate F2 divided by the second estimated air conditioning capacity C2 (the second average detection variable group PQa2 described later).

[0071] The first estimated air conditioning capacity C1 is calculated based on the difference between the temperature Th of the heat exchanger used in the first period T1 and the temperature Tr of the air-conditioned space in which the heat exchanger is installed in the first period T1. The second estimated air conditioning capacity C2 is calculated based on the difference between the temperature Th of the heat exchanger used in the second period T2 and the temperature Tr of the air-conditioned space in the second period T2.

[0072] The detection unit 61 performs leak detection processing in both cooling and heating operations. The detection unit 61 performs leak detection processing in cooling operation and leak detection processing in heating operation as separate processes.

[0073] (2-5-3-2) Control Flow The following describes the specific control flow of the leak detection process. The leak detection process includes sampling and leak determination processes.

[0074] (Sampling process) In the sampling process, the detection unit 61 calculates the average detection variable PQa, which is used for refrigerant leakage determination in the leakage determination process, from the sampled detection variable PQ and records it in the storage device. Figure 3 is a flowchart of the control flow of the sampling process. Figure 4 is a conceptual diagram of the average detection variable PQa. The detection unit 61 repeats the sampling process while the air conditioning system 100 is running.

[0075] In step S100, the detection unit 61 proceeds to step S110 or step S100 based on whether or not a predetermined sampling period Ps has been reached. Specifically, the detection unit 61 obtains the time T1 from the start of the sampling process and the time T2 from the previous sampling (execution of the process in step S110). If the detection unit 61 determines that either time T1 or time T2 has reached the sampling period Ps (yes), it proceeds to step S110; if it determines that the sampling period Ps has not been reached (no), it proceeds to step S100. In other words, the detection unit 61 repeats step S100 until the sampling period Ps is reached. The sampling period Ps is, for example, 1 / 12 of a second.

[0076] In step S110, the detection unit 61 acquires (samples) the estimated flow rate F of the refrigerant flowing through the expansion valve 24 during the sampling period Ps, and proceeds to step S120. Specifically, the detection unit 61 calculates the estimated flow rate F from the opening degree of the expansion valve 24 during the sampling period and the flow rate characteristic equation of the expansion valve 24 recorded in the storage device. The estimated flow rate F is an example of a first estimated flow rate F1 and a second estimated flow rate F2.

[0077] In step S120, the detection unit 61 calculates the estimated air conditioning capacity C at the sampling period Ps and proceeds to step S130. Specifically, the detection unit 61 uses the absolute value of the difference between the temperature Th detected by the first temperature sensor 54 at the sampling period Ps and the temperature Tr detected by the second temperature sensor 55 at the sampling period Ps as the estimated air conditioning capacity C (C = |Th - Tr|). The estimated air conditioning capacity C is an example of the first estimated air conditioning capacity C1 and the second estimated air conditioning capacity C2.

[0078] In step S130, the detection unit 61 calculates the detection variable PQ at the sampling period Ps and proceeds to step S140. Specifically, the detection unit 61 uses the value obtained by dividing the estimated flow rate F by the estimated air conditioning capacity C as the detection variable PQ (PQ = F / C).

[0079] In step S140, the detection unit 61 records the calculated detection variable PQ in the storage device and proceeds to step S150.

[0080] In step S150, the detection unit 61 refers to the storage device to calculate the average detection variable PQa, which is the average of all detection variables PQ sampled on that day. The detection unit 61 then saves the detection variables PQ to the storage device for each sampling date and proceeds to step S100. If the average detection variable PQa calculated from detection variables PQ calculated on the same day is already recorded in the storage device, the detection unit 61 overwrites the old average detection variable PQa with the newly calculated average detection variable PQa.

[0081] As shown in Figure 4, the detection unit 61 repeats the sampling process, and the average detection variable PQa calculated from multiple detection variables PQ (PQ(0), PQ(1)...) for one day is recorded in the storage device for each day (PQa(0), PQa(-1)...).

[0082] As described above, the sampling process is performed while the air conditioning system 100 is running. For this reason, the detection unit 61 does not calculate and record the average detection variable PQa for days when the air conditioning system 100 is not running. As a result, the storage device only records the average detection variable PQa for days when the air conditioning system 100 is running. The detection unit 61 treats the multiple average detection variables PQa recorded in the storage device as a data group PQag arranged in the order of the dates on which the average detection variable PQa was calculated.

[0083] In Figure 4, "PQ(0), PQ(1), PQ(2)..." represent multiple detection variables PQ recorded on the same day. "PQa(0), PQa(-1), PQa(-2)..." represent sequences of multiple average detection variables PQa included in the data set PQag. "PQa(n)" indicates that PQa(0) represents the average detection variable PQa for the most recent date, and the smaller the number n in parentheses, the older the average detection variable PQa.

[0084] The detection unit 61 may terminate the sampling process when the number of sampled detection variables PQ reaches a predetermined number or when a predetermined time has elapsed since the start of the sampling process.

[0085] (Leak detection process) In the leak detection process, the detection unit 61 performs refrigerant leakage detection using the average detection variable PQa recorded in the storage device during the sampling process. Figure 5 is a flowchart showing the control flow of the leak detection process. Figure 6 is a conceptual diagram illustrating the detection process.

[0086] The detection unit 61 performs a leak detection process once a day. Although not limited to this, the detection unit 61 can, for example, perform the leak detection process when the air conditioning system 100 is first started up for the day.

[0087] When the detection unit 61 starts the leak detection process, in step S200 it calculates a first value P1 and proceeds to step S210. The first value P1 is the average value of the group of average detection variables PQa for the most recent X days in the data group PQag, the most recent average detection variable PQa, PQa(0), which is referred to as the first average detection variable group PQa1. X is an integer greater than or equal to 2. Figure 6 shows an example where X is 3. X days is an example of the first period T1.

[0088] In step S210, the detection unit 61 calculates the second value P2 and proceeds to step S220. The second value P2 is the average value of the group of average detection variables PQa for Y consecutive days in the data group PQag (hereinafter referred to as the second average detection variable group PQa2), which does not include the average detection variable PQa of the first average detection variable group PQa1.

[0089] As shown in Figure 6, the detection unit 61 determines the second mean detection variable group PQa2 such that there are Z consecutive days of the mean detection variable PQa in the data group PQag between the mean detection variable PQa of the latest date in the second mean detection variable group PQa2 (PQa(-7) in Figure 6) and the mean detection variable PQa of the last date in the first mean detection variable group PQa1 (PQa(-3) in Figure 6). Y is an integer greater than or equal to 2. Z is an integer greater than or equal to 0. Figure 6 shows an example where Y and Z are 3. Y days is an example of the second period T2.

[0090] In step S220, the detection unit 61 determines whether to proceed to step S230 or step S260 based on the change in the first value P1 relative to the second value P2. Specifically, if the first value P1 is greater than the value obtained by multiplying the second value P2 by a predetermined coefficient K (yes), the detection unit 61 proceeds to step S230; otherwise, it proceeds to step S260. The coefficient K is greater than zero.

[0091] In step S230, the detection unit 61 increments the counter c recorded in the storage device and proceeds to step S240. The incremented counter c is recorded in the storage device and is referenced in the leakage detection process on subsequent days.

[0092] In step S240, the detection unit 61 compares counter c with a predetermined number N to determine whether to proceed to step S250 or terminate the control flow. Specifically, if counter c is greater than number N (yes), the detection unit 61 proceeds to step S250; otherwise, if counter c is not greater than number N (no), the control flow terminates. Number N is an integer greater than or equal to 1.

[0093] In step S250, the detection unit 61 detects a refrigerant leak and notifies the notification unit 53 of the detection result, ending the control flow.

[0094] In step S260, the detection unit 61 resets counter c to zero and terminates the control flow.

[0095] As explained above, in the leak detection process, the detection unit 61 determines that there is a risk of refrigerant leakage and increments counter c if the average value of the most recent multiple average detection variables PQa (first value P1) is greater than the value obtained by multiplying the average value of the past multiple average detection variables PQa (second value P2) by a coefficient K. If the detection unit 61 determines that there is a risk of refrigerant leakage for N consecutive days or more (when counter c is greater than N), it determines that a refrigerant leak has been detected and notifies the notification unit 53 of the detection result.

[0096] The coefficient K is the margin ratio of the first value P1 to the second value P2. The smaller the coefficient K, the easier it is for the detection unit 61 to determine that there is a risk of refrigerant leakage.

[0097] The number N defines the sensitivity of the leak detection process. The smaller the number N, the easier it is for the detection unit 61 to determine that a refrigerant leak has been detected.

[0098] (2-5-3-3) About the detection variable PQ The inventors evaluated the influence of airflow and ambient temperature on the detection variable PQ used for detecting refrigerant leaks.

[0099] (Effect of airflow) Figure 7A is a graph showing the results of evaluating the effect of airflow on the sensing variable PQ during heating operation. Figure 7B is a graph showing the results of evaluating the effect of airflow on the sensing variable PQ during cooling operation. In Figures 7A and 7B, the horizontal axis shows the capacity of the compressor 21, and the vertical axis shows the sensing variable PQ.

[0100] In this evaluation, the inventors calculated the detection variable PQ when the motor 52a of the fan 52 was rotated at the M tap and the detection variable PQ when it was rotated at the L tap for each of the following refrigerant circuits: one filled with a specified amount of refrigerant, one filled with 90% of the specified amount of refrigerant, and one filled with 70% of the specified amount of refrigerant. The L tap represents a lower airflow than the M tap.

[0101] In Figures 7A and 7B, the detection variable PQ when the motor 52a of the fan 52 is rotated with an M tap is shown as a square, and the approximation line obtained from this detection variable PQ is shown as a solid line. Also in Figures 7A and 7B, the detection variable PQ when it is rotated with an L tap is shown as a circle, and the approximation line obtained from this detection variable PQ is shown as a dotted line.

[0102] Of these approximation lines, the result obtained using a refrigerant circuit 10 filled with a specified amount of refrigerant is indicated with the sign "La100", the result obtained using a refrigerant circuit 10 filled with 90% of the specified amount of refrigerant is indicated with the sign "La90", and the result obtained using a refrigerant circuit 10 filled with 70% of the specified amount of refrigerant is indicated with the sign "La70".

[0103] As shown in Figures 7A and 7B, it was confirmed that the change in the detection variable PQ associated with changes in airflow was sufficiently small compared to the change associated with the amount of refrigerant charged.

[0104] (Effects of ambient temperature) Figure 8A is a graph showing the results of evaluating the effect of ambient temperature on the sensing variable PQ during heating operation. Figure 8B is a graph showing the results of evaluating the effect of ambient temperature on the sensing variable PQ during cooling operation. In Figures 8A and 8B, the horizontal axis shows the capacity of the compressor 21, and the vertical axis shows the sensing variable PQ.

[0105] In this evaluation, the inventors calculated the detection variable PQ for each of the following refrigerant circuits: one filled with a specified amount of refrigerant, one filled with 90% of the specified amount of refrigerant, and one filled with 70% of the specified amount of refrigerant, when the capacity of the compressor 21 was changed.

[0106] In Figures 8A and 8B, the approximation line obtained from the detection variable PQ calculated when using a refrigerant circuit 10 filled with a specified amount of refrigerant is indicated with the sign "Lb100". The approximation line obtained from the detection variable PQ calculated when using a refrigerant circuit 10 filled with 90% of the specified amount of refrigerant is indicated with the sign "Lb90". The approximation line obtained from the detection variable PQ calculated when using a refrigerant circuit 10 filled with 70% of the specified amount of refrigerant is indicated with the sign "Lb70".

[0107] As shown in Figures 8A and 8B, it was confirmed that the change in the detection variable PQ associated with changes in ambient temperature was sufficiently small compared to the change associated with the amount of refrigerant charged.

[0108] (Summary of evaluation results) From the evaluation results above, it was confirmed that the detection variable PQ is sufficiently less affected by changes in airflow and ambient temperature compared to changes in refrigerant charge amount. Therefore, it was confirmed that refrigerant leakage in the refrigerant circuit 10 can be detected using the detection variable PQ while suppressing the effects of airflow and ambient temperature. In this evaluation, R32, a mildly flammable refrigerant, was used to fill the refrigerant circuit 10, but it is presumed that similar results can be obtained even if the refrigerant circuit 10 is filled with a highly flammable refrigerant such as propane.

[0109] (3) Variant (3-1) Variation A The detection unit 61 may detect refrigerant leakage using the rate of change of the first value P1 relative to the second value P2. Specifically, in step S220, the detection unit 61 may decide whether to proceed to step S230 or step S260 based on the rate of change of the first value P1 relative to the second value P2, instead of the amount of change of the first value P1 relative to the second value P2.

[0110] In this case, the detection unit 61 proceeds to step S230 if the value obtained by dividing the first value P1 by the second value P2 is greater than a predetermined value R (yes), and proceeds to step S260 if the value obtained by dividing the first value P1 by the second value P2 is not greater than the value R (no).

[0111] (3-2) Modification B The notification unit 53 is not limited to the above-described configuration, as long as it can notify the user of the detection results. However, the notification unit 53 may be configured to notify the user of the detection results to a mobile terminal such as a smartphone owned by the user using computer network technologies such as the Internet or Wi-Fi (registered trademark).

[0112] (3-3) Modification C The air conditioning system 100 may continue air conditioning operation even after the notification unit 53 has issued a notification.

[0113] (3-4) Modification D The control unit 60 stops the air conditioning operation when the refrigerant sensor detects a refrigerant leak, and continues the air conditioning operation when the detection unit 61 detects a refrigerant leak during air conditioning operation.

[0114] (3-5) Modification E At least one of the heat source heat exchanger 23 and the utilization heat exchanger 51 may be a fin-and-tube type heat exchanger having a plurality of heat transfer tubes and a plurality of fins (not shown). In this case, the heat transfer tubes may be made of aluminum.

[0115] (3-6) Modification F The estimated flow rate F may be a value calculated from the opening degree of the expansion valve 24 at the sampling period Ps and the flow rate characteristic equation recorded in the storage device, and then corrected based on the differential pressure of the refrigerant before and after the expansion valve 24.

[0116] As mentioned above, the flow rate of the refrigerant flowing through the expansion valve 24, obtained from the flow characteristic equation, is an estimated value. This estimated flow rate may have some error compared to the actual flow rate, mainly due to the differential pressure of the refrigerant before and after the expansion valve 24. Therefore, by correcting the value calculated from the opening degree of the expansion valve 24 and the flow characteristic equation recorded in the storage device based on the differential pressure of the refrigerant before and after the expansion valve 24 to obtain an estimated flow rate F, the detection unit 61 can detect refrigerant leakage with greater accuracy.

[0117] (3-7) Modification G The estimated air conditioning capacity C, obtained from the absolute difference between the temperature Th at the sampling period Ps and the temperature Tr at the sampling period Ps, may be affected by the amount of air (airflow) supplied to the heat exchanger 51. For this reason, the estimated air conditioning capacity C may be a value obtained by correcting the absolute difference between the temperature Th at the sampling period Ps and the temperature Tr at the sampling period Ps based on the airflow generated by the fan 52. Specifically, the detection unit 61 can determine the estimated air conditioning capacity C by multiplying the absolute difference between the temperature Th at the sampling period Ps and the temperature Tr at the sampling period Ps by a coefficient based on the rotational speed or rotational tap of the fan 52.

[0118] (3-8) Modification H The values ​​of X, Y, and Z may be different from each other.

[0119] (4) Features (4-1) The air conditioning system 100 comprises a refrigerant circuit 10 and a detection unit 61. The refrigerant circuit 10 has a heat source heat exchanger 23, an expansion valve 24, and a utilization heat exchanger 51, and is filled with refrigerant. The detection unit 61 detects refrigerant leakage in the refrigerant circuit 10. The detection unit 61 detects refrigerant leakage by comparing a first value P1 corresponding to a first estimated flow rate F1, which is the estimated flow rate of refrigerant flowing through the expansion valve 24 in a first period T1, with a second value P2 corresponding to a second estimated flow rate F2, which is the estimated flow rate of refrigerant flowing through the expansion valve 24 in a second period T2 prior to the first period T1.

[0120] The detection unit 61 detects refrigerant leakage in the refrigerant circuit 10 using an estimated flow rate based on the flow rate of refrigerant flowing through the expansion valve 24. The flow rate of refrigerant flowing through the expansion valve 24 is less affected by the amount of refrigerant circulating in the refrigerant circuit 10, the capacity of the refrigeration cycle device, and the environment of the air-conditioned space. Therefore, the air conditioning system 100 can accurately detect refrigerant leakage.

[0121] (4-2) The detection unit 61 records a flow characteristic equation that identifies the relationship between the opening degree of the expansion valve 24 and the estimated flow rate of the refrigerant flowing through the expansion valve 24. The first estimated flow rate F1 is calculated based on the opening degree of the expansion valve 24 and the flow characteristic equation during the first period T1. The second estimated flow rate F2 is calculated based on the opening degree of the expansion valve 24 and the flow characteristic equation during the second period T2.

[0122] The air conditioning system 100 can accurately detect refrigerant leaks.

[0123] (4-3) The first value P1 is calculated based on the first estimated flow rate F1 and the first estimated air conditioning capacity corresponding to the air conditioning capacity during the first period T1. The second value P2 is calculated based on the second estimated flow rate F2 and the second estimated air conditioning capacity corresponding to the air conditioning capacity during the second period T2.

[0124] The air conditioning system 100 can detect refrigerant leaks with even greater accuracy by incorporating an estimated air conditioning capacity based on the air conditioning capacity itself.

[0125] (4-4) The first estimated air conditioning capacity is calculated based on the difference between the temperature of the heat exchanger 51 used during the first period T1 and the temperature of the air-conditioned space in which the heat exchanger 51 is installed during the first period T1. The second estimated air conditioning capacity is calculated based on the difference between the temperature of the heat exchanger 51 used during the second period T2 and the temperature of the air-conditioned space during the second period T2.

[0126] The air conditioning system 100 can easily determine its estimated air conditioning capacity based on the difference between the temperature of the heat exchanger 51 and the temperature of the space to be air-conditioned.

[0127] (4-5) The first value P1 is the average value obtained by dividing the first estimated flow rate F1 by the first estimated air conditioning capacity. The second value P2 is the average value obtained by dividing the second estimated flow rate F2 by the second estimated air conditioning capacity.

[0128] By using the average value of the estimated flow rate, the air conditioning system 100 can reduce the influence of external disturbances such as temperature, humidity, and airflow restriction on the estimated flow rate, thereby enabling more accurate detection of refrigerant leaks.

[0129] (4-6) The detection unit 61 detects refrigerant leakage using the change in the first value P1 relative to the second value P2.

[0130] The air conditioning system 100 can accurately detect refrigerant leaks.

[0131] (4-7) The detection unit 61 detects refrigerant leakage using the rate of change of the first value P1 relative to the second value P2.

[0132] The air conditioning system 100 can accurately detect refrigerant leaks.

[0133] (4-8) Refrigerants are flammable.

[0134] The air conditioning system 100 can accurately detect leaks of flammable refrigerant.

[0135] (4-9) The refrigerant is propane.

[0136] The air conditioning system 100 can accurately detect leaks of propane, which is a flammable refrigerant.

[0137] (4-10) The air conditioning system 100 further includes a notification unit that notifies the detection result when the detection unit 61 detects a refrigerant leak.

[0138] The air conditioning system 100 can notify the user of the results of refrigerant leak detection.

[0139] (4-11) The air conditioning system 100 continues to operate even after the notification unit has issued a notification.

[0140] (4-12) The air conditioning system 100 further includes a refrigerant sensor 56 for detecting refrigerant leakage. If the refrigerant sensor 56 detects refrigerant leakage during air conditioning operation, the air conditioning system 100 stops air conditioning operation, and if the detection unit 61 detects refrigerant leakage during air conditioning operation, it continues air conditioning operation.

[0141] (4-13) Both the heat source heat exchanger 23 and the utilization heat exchanger 51 have heat transfer tubes. At least one of the heat source heat exchanger 23 and the utilization heat exchanger 51 has aluminum heat transfer tubes.

[0142] The air conditioning system 100 can accurately detect refrigerant leaks even when refrigerant leaks from aluminum heat transfer tubes.

[0143] <Conclusion> While embodiments of this disclosure have been described above, it should be understood that various modifications to the form and details are possible without departing from the spirit and scope of this disclosure as described in the claims. [Explanation of Symbols]

[0144] 10: Refrigerant Circuit 23:Heat source heat exchanger 24: Expansion valve 51: Utilization heat exchanger 53: Hochi Department 56: Refrigerant sensor 61: Detection unit 100: Air conditioning system C1: First estimated air conditioning capacity C2: Second estimated air conditioning capacity F: Estimated flow rate F1: 1st estimated flow rate F2: Second estimated flow rate P1: First value P2: Second value T1: Period 1 T2: Second period Th: Temperature of the heat exchanger used Tr: Temperature of the space to be air-conditioned [Prior art documents] [Patent Documents]

[0145] [Patent Document 1] Japanese Patent Publication No. 2017-26308

Claims

1. A refrigerant circuit (10) filled with refrigerant has a heat source heat exchanger (23), an expansion valve (24), and a utilization heat exchanger (51), A detection unit (61) for detecting refrigerant leakage in the refrigerant circuit and Equipped with, The detection unit, The system detects refrigerant leakage by comparing a first value (P1) corresponding to a first estimated flow rate (F1), which is the estimated flow rate (F) of the refrigerant flowing through the expansion valve during a first period (T1), with a second value (P2) corresponding to a second estimated flow rate (F2), which is the estimated flow rate of the refrigerant flowing through the expansion valve during a second period (T2) prior to the first period. Air conditioning system (100).

2. The detection unit, A flow characteristic equation is recorded that specifies the relationship between the opening degree of the expansion valve and the estimated flow rate of the refrigerant flowing through the expansion valve. The first estimated flow rate is, It is calculated based on the opening degree of the expansion valve and the flow rate characteristic formula during the first period, The second estimated flow rate is, The opening degree of the expansion valve and the flow rate characteristic formula during the second period are calculated, The air conditioning device according to claim 1.

3. The first value is, It is calculated based on the first estimated flow rate and the first estimated air conditioning capacity (C1) corresponding to the air conditioning capacity during the first period. The second value is, Based on the second estimated flow rate and the second estimated air conditioning capacity (C2) corresponding to the air conditioning capacity during the second period, The air conditioning device according to claim 1.

4. The first estimated air conditioning capacity is, It is calculated based on the difference between the temperature of the heat exchanger used during the first period (Th) and the temperature of the air-conditioned space in which the heat exchanger used is installed during the first period (Tr). The second estimated air conditioning capacity is, The temperature of the heat exchanger used during the second period is calculated based on the difference between the temperature of the space to be air-conditioned during the second period. The air conditioning device according to claim 3.

5. The first value is, This is the average value obtained by dividing the first estimated flow rate by the first estimated air conditioning capacity. The second value is, This is the average value obtained by dividing the second estimated flow rate by the second estimated air conditioning capacity. The air conditioning device according to claim 4.

6. The detection unit, The amount of change from the first value to the second value is used to detect the refrigerant leak. The air conditioning device according to claim 1.

7. The detection unit, The rate of change of the first value relative to the second value is used to detect the refrigerant leak. The air conditioning device according to claim 1.

8. The aforementioned refrigerant is Flammable, The air conditioning device according to claim 1.

9. The aforementioned refrigerant is It is propane. The air conditioning device according to claim 7.

10. The system further includes a notification unit (53) that notifies the detection result when the detection unit detects the refrigerant leak. The air conditioning device according to claim 1.

11. The air conditioning operation will continue even after the notification unit has issued a notification. The air conditioning device according to claim 10.

12. The system further includes a refrigerant sensor (56) for detecting the leakage of the aforementioned refrigerant, If the refrigerant sensor detects a refrigerant leak during air conditioning operation, the air conditioning operation will be stopped. If the detection unit detects a refrigerant leak during the aforementioned air conditioning operation, the air conditioning operation will continue. The air conditioning device according to claim 1.

13. The heat source heat exchanger and the utilization heat exchanger are both, It has heat transfer tubes, At least one of the heat source heat exchanger and the utilization heat exchanger is The heat transfer tube is made of aluminum. An air conditioning device according to any one of claims 1 to 12.

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