Refrigeration cycle apparatus

Abstract

The present invention secures sufficient safety even when a flammable refrigerant is used as a refrigerant of an air conditioner. This refrigeration cycle apparatus is provided with: an indoor unit (2) that includes a refrigerant circuit (C) through which a flammable refrigerant circulates, an indoor fan (22), and a refrigerant sensor (23) that detects the concentration of the refrigerant; and a control device (6) that controls the indoor unit (2). When it is determined, as a result of comparison between the concentration of the refrigerant detected by the refrigerant sensor and a preset threshold value, that the concentration of the refrigerant is greater than or equal to the threshold value, the control device (6) controls the indoor fan (22) so as to exhibit an air volume (Q) [m3 / h] and executes mixing operation. When the lower flammability limit (LFL) [kg / m3] of the refrigerant, the assumed leakage rate (W) [kg / h] of the refrigerant, and the assumed suction rate (w) [kg / h] of the refrigerant to be suctioned into the indoor unit (2) are defined, the air volume (Q), the lower flammability limit (LFL), the assumed leakage rate (W), and the assumed suction rate (w) satisfy Q>(W+w) / LFL.

Description

Refrigeration cycle equipment

[0001] An embodiment of the present invention relates to a refrigeration cycle device.

[0002] In recent years, as one of the countermeasures against global warming, for example, conversion of refrigerants used in refrigeration cycle devices such as air conditioners and heat pump devices to refrigerants with low global warming potential (GWP; hereinafter, referred to as "GWP" where appropriate) has been considered. Refrigerants with low GWP include flammable refrigerants such as propane (R290), and measures must be taken to prevent the refrigerant from leaking into living spaces. Alternatively, measures must be prepared to ensure sufficient safety even if the refrigerant does leak into living spaces.

[0003] One safety measure to be taken in the event of a refrigerant leak from the indoor unit into the living space is to operate the indoor fan to perform an agitation operation, because if the leaked refrigerant accumulates in a specific location inside the indoor unit housing or in the living space, the risk of fire increases in the location where the refrigerant accumulates.

[0004] In the agitation operation, the indoor fan rotates to agitate the air in the indoor unit housing and the living space so that no area is formed in the living space where the refrigerant concentration exceeds the lower flammability limit (hereinafter referred to as "LFL" as appropriate). By performing such agitation operation, the concentration of refrigerant that has leaked and accumulated in the living space is reduced.

[0005] Regarding the stirring operation, for example, Patent Document 1 below can be cited. The invention disclosed in Patent Document 1 specifies a minimum airflow rate of the indoor fan during stirring operation. Specifically, the indoor fan is controlled so that the airflow rate is greater than the refrigerant leakage rate divided by the LFL. By controlling the indoor fan in this manner, it is possible to keep the refrigerant concentration of the air blown into the living space below the LFL.

[0006] International Publication No. 2017 / 187618

[0007] However, even if the stirring operation is performed as in the invention disclosed in the above-mentioned Patent Document 1, there may be cases where the refrigerant concentration of the blown air exceeds the LFL. That is, when the stirring operation is performed, the blown air containing the refrigerant is blown into the living space, and the blown air stirs the air in the living space. However, even if the air is stirred in this way, if the air present in the living space does not leave the living space, the refrigerant concentration in the living space will gradually increase.

[0008] That is, after a period of continuous stirring, the leaked refrigerant gradually mixes with the air suctioned by the indoor unit. This may increase the absolute amount of leaked refrigerant in the air blown out. For example, this may create an area inside the indoor unit and near the air outlet where the refrigerant concentration exceeds the LFL, resulting in a decrease in safety.

[0009] An object of the present invention is to provide a refrigeration cycle device that can ensure sufficient safety even when a flammable refrigerant is used as the refrigerant for an air conditioner.

[0010] A refrigeration cycle apparatus according to one aspect of the present invention includes a refrigerant circuit through which a flammable refrigerant circulates; an indoor unit that houses some of the equipment connected to the refrigerant circuit and has an indoor fan and a refrigerant sensor that detects the concentration of the refrigerant; and a control device that controls the indoor unit. The control device compares the concentration of the refrigerant detected by the refrigerant sensor with a preset threshold, and when it determines that the refrigerant concentration is equal to or greater than the threshold, the control device controls the indoor fan to achieve an airflow rate Q [m3 / h] to perform a stirring operation. When the lower flammable limit concentration of the refrigerant is LFL [kg / m3], the assumed refrigerant leakage rate W [kg / h], and the assumed suction rate w of the refrigerant drawn into the indoor unit is w [kg / h], the airflow rate Q, the lower flammable limit concentration LFL, the assumed leak rate W, and the assumed suction rate w satisfy the relationship Q > (W + w) / LFL.

[0011] According to the present invention, it is possible to provide a refrigeration cycle device that can ensure sufficient safety even when a flammable refrigerant is used as the refrigerant for an air conditioner.

[0012] 1 is a refrigerant circuit diagram of a refrigeration cycle device according to an embodiment of the present invention. 2 is a block diagram showing the internal configuration of a control device in the refrigeration cycle device according to an embodiment of the present invention. 3 is a schematic diagram showing an assumed refrigerant leakage rate and an assumed refrigerant suction rate in an indoor unit installed in a living space in a refrigeration cycle device according to an embodiment of the present invention. 4 is an explanatory diagram illustrating a comparison result with Patent Document 1 in terms of flammable volume regarding control in a refrigeration cycle device according to an embodiment of the present invention. 5 is an explanatory diagram illustrating a comparison result with Patent Document 1 in terms of risk reduction rate regarding control in a refrigeration cycle device according to an embodiment of the present invention. 6 is a flowchart showing a control flow in a refrigeration cycle device according to an embodiment of the present invention.

[0013] The structure of a refrigeration cycle apparatus S according to an embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is a refrigerant circuit diagram of the refrigeration cycle apparatus S according to an embodiment of the present invention. The refrigeration cycle apparatus S is used for cooling operation when an indoor heat exchanger 21 (described later) is used as an evaporator and an outdoor heat exchanger 41 is used as a condenser. On the other hand, when the indoor heat exchanger 21 is used as a condenser and the outdoor heat exchanger 41 is used as an evaporator, the refrigeration cycle apparatus S is used for heating operation.

[0014] 1 includes a compressor 1, an indoor heat exchanger 21, a pressure reducing mechanism 3, and an outdoor heat exchanger 41. These devices are connected in sequence by refrigerant piping to form a refrigerant circuit C through which the refrigerant circulates.

[0015] Further, a four-way valve 5 is provided between the compressor 1 and the indoor heat exchanger 21, and between the compressor 1 and the outdoor heat exchanger 41. The four-way valve 5 switches whether the refrigerant discharged from the compressor flows to the indoor heat exchanger 21 side or the outdoor heat exchanger 41 side.

[0016] The refrigerant circulating through the refrigerant circuit C of the refrigeration cycle apparatus S in this embodiment of the present invention is a flammable refrigerant such as R290 (propane). Examples of flammable refrigerants include mildly flammable refrigerants such as R32, R1234yf, and R1234ze(E), as well as highly flammable refrigerants such as the above-mentioned R290 and R1270. Any flammable refrigerant may be used. The refrigerant may be a single refrigerant or a mixed refrigerant containing two or more refrigerants.

[0017] The compressor 1 draws in the refrigerant circulating through the refrigerant circuit C, compresses it, and discharges it into the refrigerant circuit C. The indoor unit 2 is installed in the living space L, and in the case of heating operation, for example, heat is exchanged between the refrigerant and the air flowing into the indoor unit 2, and the air heated by absorbing heat from the refrigerant is supplied to the living space L.

[0018] In the refrigeration cycle apparatus S according to the embodiment of the present invention, an indoor unit 2 is assumed that has a function of drawing in air from the living space L, exchanging heat therein, and then blowing the air out into the living space L. Specifically, for example, the indoor unit 2 is a wall-mounted type that is installed with its back surface fixed to the wall surface of the living space L. However, any type of indoor unit may also be used, such as a cassette type that is placed inside the ceiling or a hanging type that is suspended from the ceiling.

[0019] The indoor unit 2 is provided with an indoor heat exchanger 21, an indoor fan 22, and a refrigerant sensor 23 that detects the concentration of the refrigerant. The indoor heat exchanger 21 is connected to the refrigerant circuit C, and exchanges heat between the refrigerant flowing into the indoor heat exchanger 21 and the air in the living space L.

[0020] When the refrigeration cycle device S performs cooling operation, the indoor heat exchanger 21 functions as an evaporator and supplies cool air into the living space L. On the other hand, when the refrigeration cycle device S performs heating operation, the indoor heat exchanger 21 functions as a condenser and supplies warm air into the living space L.

[0021] The indoor fan 22 takes in air from the living space L into the indoor unit 2 and supplies the air that has undergone heat exchange with the refrigerant in the indoor heat exchanger 21 into the living space L. Various types of fans, such as an axial fan or a centrifugal fan, can be used as the indoor fan 22 depending on the configuration of the indoor unit 2. In the refrigeration cycle apparatus S according to the embodiment of the present invention, for example, a cross-flow fan is used when the indoor unit 2 is a wall-mounted type.

[0022] The refrigerant sensor 23 detects the concentration of refrigerant in the air surrounding the refrigerant sensor 23. The control device 6, which will be described later, determines whether or not there is a refrigerant leak based on the refrigerant concentration detected by the refrigerant sensor 23. The refrigerant sensor 23 may be, for example, a semiconductor gas sensor, an infrared gas sensor, or another gas sensor.

[0023] Alternatively, an oxygen concentration meter or a temperature sensor such as a thermistor may be used as the refrigerant sensor 23. When a temperature sensor is used as the refrigerant sensor 23, a refrigerant leak is detected by detecting a decrease in temperature due to adiabatic expansion of the leaked refrigerant.

[0024] As described above, the presence or absence of a refrigerant leak is determined based on the refrigerant concentration detected by the refrigerant sensor 23, but possible causes of refrigerant leakage include, for example, a poor connection in the piping connecting the connecting piping to the indoor unit 2 or poor welding of the heat transfer tubes of the indoor heat exchanger 21. It is also possible that corrosion has occurred in the piping inside the indoor heat exchanger 21, causing refrigerant leakage.

[0025] Therefore, the refrigerant sensor 23 is disposed in a location where there are many piping connections in the indoor unit 2, such as to the side of the indoor heat exchanger 21, or in a space where piping is stored inside the indoor unit 2. Alternatively, the refrigerant sensor 23 is disposed near an air outlet through which air blown out from the indoor unit 2 into the living space L passes.

[0026] The refrigerant sensor 23 continuously detects the refrigerant concentration. This is because a refrigerant leak could create a region in the indoor space where the refrigerant concentration in the air becomes flammable (hereinafter referred to as the "flammable concentration region"), increasing the risk of fire. Note that "constantly" here includes not only continuous detection of the refrigerant concentration, but also detection of the refrigerant concentration intermittently at a predetermined interval.

[0027] The above-described indoor heat exchanger 21, indoor fan 22, and refrigerant sensor 23 are the only components provided in the indoor unit 2. However, this is merely a list of components necessary to explain the refrigeration cycle apparatus S in the embodiment of the present invention. Therefore, other devices that are normally provided in the indoor unit 2 are of course provided.

[0028] In the refrigerant circuit C, a pressure reducing mechanism 3 is provided between the indoor heat exchanger 21 and the outdoor heat exchanger 41. The pressure reducing mechanism 3 is, for example, an expansion valve, and reduces the pressure of the high-pressure refrigerant that has passed through the indoor heat exchanger 21 and the outdoor heat exchanger 41. The outdoor unit 4 is installed outside the living space L, and as shown by the dashed dotted line in Fig. 1 , the outdoor unit 4 contains the compressor 1, the pressure reducing mechanism 3, the outdoor heat exchanger 41, the four-way valve 5, an outdoor fan (not shown), and the like.

[0029] The flow of refrigerant in the refrigerant circuit C when the refrigeration cycle apparatus S performs heating operation is as follows: When heating operation is performed, high-temperature, high-pressure gas refrigerant discharged from the compressor 1 flows into the indoor heat exchanger 21 via the four-way valve 5. The indoor heat exchanger 21 exchanges heat between the refrigerant and air in the living space L that is drawn into the indoor unit 2 by the indoor fan 22. The air that has been warmed by absorbing heat from the refrigerant is supplied into the living space L by the rotation of the indoor fan 22. The high-temperature, high-pressure gas refrigerant releases heat through heat exchange as it passes through the indoor heat exchanger 21, becoming a high-pressure liquid refrigerant.

[0030] The high-pressure liquid refrigerant that flows out of the indoor heat exchanger 21 flows into the pressure reduction mechanism 3. The high-pressure liquid refrigerant is reduced in pressure as it passes through the pressure reduction mechanism 3, becoming a low-pressure two-phase refrigerant. The low-pressure two-phase refrigerant that flows out of the pressure reduction mechanism 3 then flows into the outdoor heat exchanger 41. In the outdoor heat exchanger 41, heat is exchanged between the low-pressure two-phase refrigerant and the outside air, causing the low-pressure two-phase refrigerant to absorb heat and become a low-pressure gas refrigerant, which is then drawn into the compressor 1 via the four-way valve 5.

[0031] On the other hand, when the refrigeration cycle apparatus S performs cooling operation, the flow of refrigerant in the refrigerant circuit C is as follows: When cooling operation is performed, high-temperature, high-pressure gas refrigerant discharged from the compressor 1 flows into the outdoor heat exchanger 41 via the four-way valve 5. The refrigerant that has flowed into the outdoor heat exchanger 41 exchanges heat with the outside air, dissipates heat, and becomes high-pressure liquid refrigerant.

[0032] The high-pressure liquid refrigerant flowing out from the outdoor heat exchanger 41 flows into the pressure reducing mechanism 3, where it is reduced in pressure to become a low-pressure two-phase refrigerant. It then flows into the indoor heat exchanger 21, and exchanges heat with the air in the living space L as it passes through the indoor heat exchanger 21, and the low-pressure two-phase refrigerant absorbs heat and becomes a gas refrigerant. The air cooled by the heat exchange with the refrigerant is then supplied into the living space L. The gas refrigerant flowing out from the indoor heat exchanger 21 is drawn into the compressor 1 via the four-way valve 5.

[0033] The control device 6 controls the compressor 1 and each device constituting the refrigeration cycle device S. The control device 6 also controls the rotation speed of the indoor fan 22 based on the control content described below. By the control device 6 controlling the indoor fan 22, even if a flammable refrigerant leaks into the living space L, an appropriate stirring operation can be performed, thereby taking sufficient safety measures to reduce the concentration of the refrigerant in the living space L.

[0034] However, in the following embodiment of the present invention, only the functions necessary for controlling the operation of the refrigeration cycle apparatus S using a flammable refrigerant will be described. Therefore, in the following Fig. 2, only the configuration necessary for executing the stirring operation in the control device 6 is shown.

[0035] Therefore, the control device 6 may have a configuration in which, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and an input / output interface are connected via a bus, which are not shown in Fig. 2. Furthermore, the input / output interface may be connected to the above-mentioned units as well as units such as a display unit, a communication control unit, or an input unit.

[0036] 2 is a block diagram showing the internal configuration of the control device 6 in the refrigeration cycle apparatus S according to the embodiment of the present invention. The control device 6 includes a refrigerant concentration information acquisition unit 61, a storage unit 62, a determination unit 63, and an indoor fan control unit 64.

[0037] The refrigerant concentration information acquisition unit 61 acquires information about the refrigerant concentration detected by the above-described refrigerant sensor 23. As described above, the refrigerant sensor 23 constantly detects the refrigerant concentration. Therefore, the refrigerant concentration information acquisition unit 61 also constantly acquires information about the refrigerant concentration detected by the refrigerant sensor 23.

[0038] The information regarding the refrigerant concentration may be acquired by the refrigerant concentration information acquisition unit 61 from the refrigerant sensor 23 , or the refrigerant sensor 23 may transmit the information to the refrigerant concentration information acquisition unit 61 .

[0039] The memory unit 62 stores, for example, information regarding the refrigerant concentration acquired by the refrigerant concentration information acquisition unit 61 and a threshold value used by the determination unit 63 when determining whether or not there is a refrigerant leak, as described below.

[0040] The threshold value described above is used by the determination unit 63 to determine whether a refrigerant leak has occurred and is set in advance. That is, the threshold value used here (hereinafter referred to as the "concentration threshold value") is set on the assumption that, if the refrigerant concentration indicates a value equal to or greater than the concentration threshold value, a flammable concentration region may be formed near the air outlet if the refrigerant leak continues. Specifically, the value is set within a range from the lower limit of the refrigerant concentration measurable by the refrigerant sensor 23 to a concentration of ¼ of the LFL, for example.

[0041] Furthermore, the agitation operation is performed when the determination unit 63 determines that the refrigerant concentration is equal to or greater than the concentration threshold value. Therefore, the storage unit 62 also stores information regarding the rotation speed of the indoor fan 22 when the agitation operation is performed, an execution program for performing the agitation operation, and the like.

[0042] The stirring operation is performed to prevent the refrigerant concentration from becoming locally high and creating a flammable concentration region in the living space L. Therefore, after a preset time has elapsed since the stirring operation was started, the refrigerant concentration in the air in the living space L is generally averaged out and the refrigerant concentration decreases.

[0043] Therefore, for the stirring operation, whether or not the refrigerant concentration has increased is determined when a preset time has elapsed, in order to determine whether or not to continue the stirring operation. The memory unit 62 also stores the preset time for starting this determination.

[0044] The storage unit 62 also stores a threshold value (increase threshold value) for the increase in the refrigerant concentration, which is used to determine whether the refrigerant concentration has increased. For example, the increase threshold value is set to zero. If the determination unit 63 determines that the change in the refrigerant concentration per unit time (increase) detected by the refrigerant sensor 23 is smaller than the increase threshold value, as will be described later, the refrigerant concentration has not increased, and the stirring operation is terminated.

[0045] The determination unit 63 determines whether or not to perform an agitation operation based on a refrigerant leak. Specifically, the determination unit 63 obtains information about the refrigerant concentration acquired by the refrigerant concentration information acquisition unit 61, and compares the information with the concentration threshold value that is set in advance and stored in the storage unit 62 to determine whether or not an agitation operation is necessary.

[0046] If the refrigerant concentration indicates a value equal to or greater than the concentration threshold value, the determination unit 63 determines that it is necessary to perform the agitation operation. When the determination unit 63 makes such a determination, the determination unit 63 accesses the storage unit 62 to acquire information on the rotation speed of the indoor fan 22 required for the agitation operation, which information is stored in the storage unit 62. Then, the determination unit 63 instructs the indoor fan control unit 64 to drive the indoor fan 22 at the acquired rotation speed.

[0047] The rotation speed of the indoor fan 22 is a rotation speed that can supply the air volume required for the stirring operation described below to the living space L. When the stirring operation is performed, the indoor fan control unit 64 controls the driving of the indoor fan 22 so that a preset air volume is achieved.

[0048] On the other hand, if the determination unit 63 determines that the refrigerant concentration is lower than the concentration threshold value, the stirring operation is not necessary. Therefore, the stirring operation is not performed, and the determination unit 63 does not issue an instruction to the indoor fan control unit 64.

[0049] Here, when a stirring operation is required due to a refrigerant leak, the air volume Q [m 3 / h] of the indoor fan 22 is set as follows.

[0050] Q>(W+w) / LFL...(1)

[0051] Here, W [kg / h] is the assumed leakage rate of the refrigerant, w [kg / h] is the assumed suction rate of the refrigerant drawn into the indoor unit 2, and LFL [kg / m3] indicates the lower limit flammable concentration of the refrigerant.

[0052] From equation (1), it can be seen that not only the assumed refrigerant leakage rate W but also the assumed suction rate w is taken into consideration when setting the air volume Q. This point will be explained using Fig. 3. Fig. 3 is a schematic diagram showing the assumed refrigerant leakage rate W and the assumed suction rate w of the refrigerant in the indoor unit 2 installed in the living space L of the refrigeration cycle apparatus S according to the embodiment of the present invention.

[0053] The indoor unit 2 shown in Fig. 3 is an indoor unit of a type that is installed with its back surface fixed to the wall of the living space L in which it is installed. As described above, when the indoor fan 22 rotates, the indoor unit 2 blows out air that has exchanged heat with the refrigerant in the indoor heat exchanger 21 into the living space L. In Fig. 3, the air blown out from the indoor unit 2 is indicated by a long downward arrow M.

[0054] Naturally, with regard to the air that exchanges heat with the refrigerant in the indoor heat exchanger 21, the rotation of the indoor fan 22 causes the air in the living space L to be drawn into the indoor unit 2 from the ceiling side of the indoor unit 2. In Figure 3, the air drawn into the indoor unit 2 is indicated by a short arrow N on the ceiling side of the living space L.

[0055] If refrigerant leaks in the indoor unit 2, the leaked refrigerant is blown out from the indoor unit 2 into the living space L, together with the air drawn into the indoor unit 2, as shown by the arrow M in Figure 3. Therefore, if refrigerant leaks inside the indoor unit 2 and the concentration of refrigerant inside the indoor unit 2 increases, a corresponding amount of refrigerant will be blown out together with the air. The refrigerant and air blown out from the indoor unit 2 are supplied to the living space L, and the concentration of refrigerant in the air in the living space L will also gradually increase.

[0056] Therefore, the concentration of the refrigerant in the air drawn in for heat exchange with the refrigerant in the indoor unit 2 also gradually increases, as indicated by the arrow N in Fig. 3. The control in Patent Document 1 described above takes into account the refrigerant in the air that is blown out, but does not take into account the refrigerant in the air that is drawn in.

[0057] As described above, if refrigerant leaks, it is blown out together with air into the living space L, which may increase the absolute amount of leaked refrigerant in the blown air. Therefore, for example, it is possible that an area where the refrigerant concentration is equal to or higher than the LFL may be formed near the air outlet of the indoor unit.

[0058] Therefore, if the air volume during stirring operation is controlled without considering the refrigerant contained in the air being drawn in, as in the control described in Patent Document 1, a flammable concentration region may occur in the living space L. Therefore, when performing stirring operation in the refrigeration cycle device S in the embodiment of the present invention, not only the expected leakage rate W of the refrigerant but also the expected suction rate w is taken into consideration.

[0059] As described above, the air volume Q can be calculated from equation (1). The rotation speed of the indoor fan 22 during the agitation operation is set to a rotation speed at which air can be blown into the living space L at the set air volume Q. Here, the estimated leakage rate W, the estimated suction rate w, and the lower flammable limit concentration LFL of the refrigerant in equation (1) are preset values. Therefore, the air volume Q can also be calculated in advance and stored in the memory unit 62, for example.

[0060] Here, the assumed leak rate W is assumed to be, for example, "15 kg / h," "10 kg / h," or "7.5 kg / h." Of these, "15 kg / h" is a value that is an international standard defined by the International Electrotechnical Commission (IEC).

[0061] This value is a value adopted as a test condition for IEC leakage simulation tests, and is the refrigerant leakage rate under the condition that when 1 kg of flammable refrigerant R290 is charged in refrigerant circuit C, the entire amount of 1 kg leaks in 4 minutes. In other words, the refrigerant leakage rate when the entire amount of 1 kg of refrigerant leaks in 4 minutes is "15 kg / h."

[0062] The refrigerant leakage rate of 7.5 kg / h is half the 15 kg / h used as the test condition for the IEC leakage simulation test. This is the refrigerant leakage rate under the condition that 500 g of flammable refrigerant R290 is charged in the refrigerant circuit C and the entire 500 g leaks out in 4 minutes.

[0063] The reason why the assumed leak rate W of "7.5 kg / h" was also considered was that not all air conditioners that use flammable refrigerants have 1 kg of R290 sealed in the refrigerant circuit. Smaller air conditioners are not filled with such an amount, so this is a more realistic assumed leak rate W for some indoor units.

[0064] In other words, the case where the assumed leakage rate W is "15 kg / h" is the case where the risk is highest when a flammable refrigerant is filled into the refrigerant circuit C. Therefore, if the air volume Q can be set to correspond to this assumed leakage rate W, it is possible to suppress the formation of a flammable concentration region, and it is thought that safety can be further improved.

[0065] In contrast, "10 kg / h" is a refrigerant leakage rate that was once adopted as an international standard. In the above-mentioned Cited Document 1, this value is adopted as the refrigerant leakage rate.

[0066] As described above, the international standard stipulates that the test condition for the refrigerant leakage rate is that the entire amount of refrigerant leaks within four minutes. Therefore, in the event of a refrigerant leak, the air volume Q is set taking into consideration not only the assumed leakage rate W but also the assumed suction rate w to determine the air volume at which the agitation operation should be performed to reduce the flammable concentration region or to prevent its formation.

[0067] That is, based on the above international standards, the amount of leaked refrigerant is greatest four minutes after a refrigerant leak, and this is the most dangerous time after a refrigerant leak. The risk of ignition in the living space L at this time can be calculated by dividing the flammable volume (volume of the flammable concentration range) after four minutes by the indoor space volume (m3). Therefore, to ensure safety at this time, the refrigeration cycle apparatus S according to the embodiment of the present invention controls the stirring operation so that the range above the LFL (flammable concentration range) is minimized after four minutes.

[0068] As explained using Figure 3, the higher the refrigerant concentration in the air in the living space L, the higher the assumed suction speed w. That is, if the assumed leak speed W is large, the assumed suction speed w also becomes large, and if the assumed leak speed W is small, the assumed suction speed w also becomes small. Therefore, the assumed suction speed w is determined based on the assumed leak speed W.

[0069] In the embodiment of the present invention, the assumed suction speed w is set to satisfy the relationship 0.35W<w<0.75W, with the assumed leakage speed W as a reference. As can be seen from equation (1), when the assumed suction speed w is set to "0.35W", the air volume Q is smaller than when the assumed suction speed w is set to "0.75W". Therefore, the assumed suction speed w is set depending on the estimated level of risk in the event of a flammable refrigerant leak.

[0070] Therefore, the effect of the control of the refrigeration cycle apparatus S according to the embodiment of the present invention will be described below in comparison with prior art documents using Figures 4 and 5. Figure 4 is an explanatory diagram illustrating the results of a comparison of the control of the refrigeration cycle apparatus S according to the embodiment of the present invention with Patent Document 1 in terms of flammable volume. Also, Figure 5 is an explanatory diagram illustrating the results of a comparison of the control of the refrigeration cycle apparatus S according to the embodiment of the present invention with Patent Document 1 in terms of risk reduction rate.

[0071] First, we will explain Figure 4, which shows the simulation results for the flammable volume. In the explanatory diagram of Figure 4, the column direction indicates the air volume Q [m3 / h], and the air volume gradually decreases from left to right. The maximum air volume is 700 [m3 / h], and the minimum air volume is 200 [m3 / h].

[0072] The row direction indicates the assumed refrigerant leakage speed W (however, in the explanatory diagram of FIG. 4, it is simply indicated as "leak speed"). The assumed leakage speed W includes the three types of speeds as described above.

[0073] For example, the prior art document cited above calculates the required air volume Q when the refrigerant is R290, and in this case, the LFL is 0.038 kg / m. As mentioned above, the assumed leak rate W is 10 kg / h. The air volume Q in this case is 263 m / h. In the simulation results of FIG. 4, the approximate air volume Q is 265 m / h, and the flammable volume in this case is 0.0477 m.

[0074] Furthermore, when a simulation is performed based on the above assumptions for the case of R290 in the prior art document, the air volume Q in the case of "15 kg / h" in the prior art document is approximately 395 [m3 / h]. Also, the combustible volume in this case is estimated to be "0.0474 [m3]."

[0075] In addition, the cases of "10 kg / h" and "15 kg / h," which are the assumed leakage rates W in the above-mentioned prior art documents, are indicated in the margin of the explanatory diagram in Figure 4 as, for example, (prior art document_15 kg / h).

[0076] In this case, if 1 kg of R290 filled in the refrigerant circuit leaks completely within 4 minutes, the flammable volume is estimated to be 0.0474 m3 when stirring is performed at the air volume Q indicated in the prior art document. However, as mentioned above, the prior art document takes into account the assumed leakage rate W, but does not consider the assumed suction rate w at all. Therefore, even if the air volume Q in the case of 15 kg / h in the above prior art document is approximately 395 m3 / h, it is unclear whether the occurrence of a flammable concentration range can be reliably suppressed.

[0077] Thus, when the air volume Q in the prior art document is 395 m3 / h, the flammable volume is 0.0474 m3. As is clear from the explanatory diagram in FIG. 4, the larger the air volume Q, the smaller the flammable volume. Assuming the assumed leak rate W is 15 kg / h, for example, when the air volume Q is 500 m3 / h, the flammable volume is 0.0187 m3, and when it is 700 m3 / h, the flammable volume is 0.0049 m3. Therefore, the larger the air volume Q, the smaller the flammable volume.

[0078] Next, the risk when such a flammable volume exists will be explained with reference to the diagram in Figure 5. The diagram in Figure 5 has the same contents shown in the column and row directions as the diagram in Figure 4. Then, assuming that the risk is set to "1" when the air volume Q in the above-mentioned prior art document is 395 m3 / h and the assumed suction speed w is "15 kg / h," we will consider the case where the air volume Q increases.

[0079] For example, when the air volume Q is 500 m / h, the flammable volume is 0.0187 m. Compared to the flammable volume of 0.0474 m when the air volume Q is 395 m / h, this flammable volume is approximately 0.39 times smaller. This smaller flammable volume reduces the risk accordingly. Therefore, the risk reduction rate is shown as 0.39 in the explanatory diagram of FIG. 5.

[0080] Similarly, when the air volume Q is 600 m3 / h, the risk reduction rate is 0.22. Therefore, as described above, when the air volume Q is 550 m3 / h, the risk reduction rate drops to roughly 3 / 10 compared to when the air volume Q is 395 m3 / h.

[0081] Furthermore, when the air volume Q is 700 [m3 / h], the risk reduction rate is "0.10", so when the air volume Q is 395 [m3 / h] as the standard, the risk is reduced to 1 / 10.

[0082] Furthermore, in the prior art documents, the air volume Q is calculated on the assumption that the assumed leak rate W is 10 kg / h, as described above. That is, when the assumed leak rate W is 10 kg / h, the air volume Q is 265 m / h, and the combustible volume in this case is 0.0477 m, as shown in the explanatory diagram in FIG.

[0083] Therefore, if the risk reduction rate is set to "1" when the air volume Q is 265 [m3 / h], it can be estimated that the risk reduction rate will be approximately 3 / 100 when the air volume Q is 550 [m3 / h], and approximately 1 / 100 when the air volume Q is 700 [m3 / h].

[0084] Therefore, when the fastest assumed leakage rate W in the event of refrigerant leaking into the living space L is used as a reference, the rotation speed of the indoor fan 22 is controlled so that the air volume Q is at least 550 [m3 / h] or more, and more preferably 700 [m3 / h] or more. By performing such control, it is possible to achieve even better effects than those disclosed in prior art documents.

[0085] Therefore, as explained above, when setting the air volume during stirring operation, the indoor fan is controlled to achieve the above-mentioned air volume, taking into consideration not only the expected leakage rate but also the expected suction rate, thereby ensuring greater safety even in the event of a refrigerant leak into the living space.

[0086] As described above, the determination unit 63 starts the stirring operation when it determines that the refrigerant concentration detected by the refrigerant sensor 23 is equal to or greater than the concentration threshold. However, it is not necessary to control the rotation speed of the indoor fan 22 so that the air volume Q is at least 550 [m3 / h] or more, and more preferably 700 [m3 / h] or more, as described above, from the start of the stirring operation.

[0087] That is, these preferable values ​​of the air volume Q are set taking into consideration the flammable volume four minutes after the refrigerant leaks, which does not mean that the amount of refrigerant leaking will be the same as that four minutes after the initial leak.

[0088] Therefore, the indoor fan control unit 64 may control the air volume when blowing air from the indoor fan 22 into the living space L to gradually increase from the time when the refrigerant sensor 23 detects a refrigerant leak. This reduces the power consumption caused by driving the indoor fan 22. Various methods can be used to increase the air volume, such as gradually increasing the air volume every time a predetermined time elapses.

[0089] Furthermore, the agitation operation is started when the determination unit 63 determines that the refrigerant concentration detected by the refrigerant sensor 23 is equal to or greater than the concentration threshold. However, by executing the agitation operation, the refrigerant concentration does not increase from when the agitation operation started, or the refrigerant concentration in the living space L gradually decreases. If the living space L reaches this state, it can be considered that safety is ensured even if a refrigerant leak has occurred.

[0090] Therefore, the determination unit 63 performs the stirring operation for a preset time (for example, 10 minutes), and then determines the concentration of the refrigerant detected by the refrigerant sensor 23. The preset time here is the time stored in the memory unit 62 as described above.

[0091] The determination of the refrigerant concentration is a determination of whether or not an increase in the refrigerant concentration detected by the refrigerant sensor 23 is recognized. Specifically, the determination unit 63 first calculates the increase per unit time of the refrigerant concentration detected by the refrigerant sensor 23. Then, the determination unit 63 compares the increase with an increase threshold value (e.g., 0) stored in the storage unit 62.

[0092] When the determination unit 63 compares the increase in the refrigerant amount with the increase threshold and finds that the former is greater than the latter, it can determine that the refrigerant concentration detected by the refrigerant sensor 23 is increasing. In such a case, the stirring operation continues.

[0093] On the other hand, when the determination unit 63 compares the increase in the refrigerant amount with the increase threshold value and the former value is equal to or less than the latter value, it can be determined that the refrigerant leakage has ended. In this case, since no increase in the refrigerant concentration is recognized, the determination unit 63 instructs the indoor fan control unit 64 to stop the stirring operation.

[0094] When the determination unit 63 determines to stop the execution of the agitation operation, the indoor fan control unit 64 can immediately stop the indoor fan 22. Alternatively, the indoor fan control unit 64 can perform intermittent operation in which the indoor fan 22 is alternately driven and stopped after performing the agitation operation for a preset time period until the execution of the agitation operation is stopped.

[0095] When the stirring operation is performed intermittently, the determination unit 63 determines the refrigerant concentration while the indoor fan 22 is stopped. That is, the determination is made based on the refrigerant concentration detected by the refrigerant sensor 23 while the indoor fan 22 is stopped.

[0096] This is because the indoor fan 22 is driven while the stirring operation is being performed, and indoor air is constantly being drawn into the indoor unit 2. Therefore, it may not be possible to accurately determine whether or not the refrigerant leak is continuing from the detection value (amount of increase in concentration) of the refrigerant sensor 23.

[0097] [Operation] Next, the flow of the agitation operation in the event of the above-described flammable refrigerant leak will be described with reference to Fig. 6. Fig. 6 is a flowchart showing the flow of control of the refrigeration cycle apparatus S according to the embodiment of the present invention.

[0098] The determination unit 63 determines whether or not a refrigerant leak has occurred (ST1). More specifically, as described above, the refrigerant sensor 23 constantly detects the refrigerant concentration. Information about the refrigerant concentration detected by the refrigerant sensor 23 is acquired by the refrigerant concentration information acquisition unit 61.

[0099] The determination unit 63 obtains information about the refrigerant concentration from the refrigerant concentration information acquisition unit 61 and obtains a concentration threshold value used to determine whether to perform the stirring operation from the storage unit 62. Then, it determines whether a refrigerant leak has occurred (ST2). Specifically, the obtained information about the refrigerant concentration is compared with the concentration threshold value.

[0100] If the determination unit 63 determines that the refrigerant concentration is smaller than the concentration threshold value as a result of the comparison, it determines that there is no refrigerant leakage (NO in ST2). Therefore, in this case, the determination as to whether there is a refrigerant leakage continues.

[0101] On the other hand, if the determination unit 63 determines that the refrigerant concentration is equal to or greater than the concentration threshold value as a result of the comparison, it determines that refrigerant is leaking (YES in ST2), and therefore starts processing to perform the stirring operation.

[0102] That is, the determination unit 63 controls the indoor fan control unit 64 to control the indoor fan to a preset air volume Q, and starts the stirring operation (ST3). As described above, the air volume Q is set in advance and stored in the storage unit 62 in association with the rotation speed of the indoor fan 22. Therefore, the determination unit 63 transmits information about the air volume Q to the indoor fan control unit 64. The indoor fan control unit 64 controls the rotation speed of the indoor fan 22 to a rotation speed associated with the air volume Q.

[0103] Thereafter, the determination unit 63 determines whether a preset time has elapsed (ST4). In Fig. 6, the "preset time" is represented as a "predetermined time." If the predetermined time has not elapsed (NO in ST4), the stirring operation continues.

[0104] On the other hand, if the determination unit 63 determines that the predetermined time has elapsed (YES in ST4), the determination unit 63 further determines whether the refrigerant concentration is increasing (ST5). Specifically, as described above, the determination unit 63 acquires information about the refrigerant concentration detected by the refrigerant sensor 23 via the refrigerant concentration information acquisition unit 61. The determination unit 63 then calculates the amount of increase per unit time of the detected refrigerant concentration and compares the amount of increase with the increase threshold stored in the storage unit 62. As a result, if the determination unit 63 determines that the amount of increase in the refrigerant concentration is higher than the increase threshold (YES in ST5), the stirring operation continues.

[0105] On the other hand, if the determination unit 63 determines that the refrigerant concentration has not increased as a result of comparing the increase in the refrigerant concentration with the increase threshold value (NO in ST5), the determination unit 63 instructs the indoor fan control unit 64 to end the stirring operation. The indoor fan control unit 64 then stops the rotation of the indoor fan 22, thereby ending the stirring operation (ST6).

[0106] At this time, as described above, after the stirring operation is performed for a predetermined period of time, it is also possible to perform intermittent operation in which the indoor fan 22 is alternately driven and stopped until the stirring operation is stopped.

[0107] As explained above, when setting the airflow rate during agitation operation, a more appropriate airflow rate can be set by taking into consideration not only the expected leakage rate but also the expected suction rate. Therefore, sufficient safety can be ensured even when a flammable refrigerant is used as the refrigerant for the air conditioner.

[0108] It should be noted that the present invention is not limited to the above-described embodiment, but is merely an example of the present invention. In the implementation stage, the components can be modified and embodied without departing from the spirit of the invention, and various changes and improvements can be made to the above-described embodiment. Furthermore, various inventions can be created by appropriately combining multiple components disclosed in the above-described embodiment.

[0109] For example, some components may be deleted from all of the components shown in the embodiments. Furthermore, components from different embodiments may be combined as appropriate, and such modified or improved forms may also be included in the present invention. Such embodiments and their modifications are included in the scope and spirit of the inventions, and are also included in the scope of the inventions and their equivalents as defined in the claims.

[0110] In the above description, the determination of the presence or absence of refrigerant leakage as a determination of whether to start the stirring operation is based on the premise that the refrigeration cycle apparatus S is in operation. However, this determination is not limited to when the refrigeration cycle apparatus S is in operation, and may also be performed when the operation is stopped.

[0111] In this way, while operation is stopped, the judgment unit 63 judges whether or not there is a refrigerant leak, and if it is determined that there is a leak, the indoor fan control unit 64 controls the indoor fan 22 to operate at a rotation speed that results in an air volume Q.

[0112] In contrast, if a leak is detected during operation of the refrigeration cycle device S, the indoor fan control unit 64 controls the rotation speed of the indoor fan 22, which has been driven up to that point, to a rotation speed that results in the air volume Q.

[0113] The techniques described in the embodiments of the present invention may also be configured as follows: (1) A refrigeration cycle apparatus comprising: a refrigerant circuit through which a flammable refrigerant circulates; an indoor unit accommodating some of the equipment connected to the refrigerant circuit and including an indoor fan and a refrigerant sensor for detecting the concentration of the refrigerant; and a control device for controlling the indoor unit, wherein the control device compares the concentration of the refrigerant detected by the refrigerant sensor with a preset threshold and, when determining that the concentration of the refrigerant is equal to or greater than the threshold, controls the indoor fan to achieve an airflow rate Q [m3 / h] to perform an agitation operation, wherein, when a flammable lower limit concentration of the refrigerant is LFL [kg / m3], an assumed leak rate of the refrigerant is W [kg / h], and an assumed suction rate of the refrigerant being drawn into the indoor unit is w [kg / h], the airflow rate Q, the flammable lower limit concentration LFL, the assumed leak rate W, and the assumed suction rate w satisfy the relationship Q > (W + w) / LFL. (2) The refrigeration cycle apparatus according to (1) above, wherein the assumed suction speed w has a relationship of 0.35W<w<0.75W with the assumed leakage speed W. (3) The refrigeration cycle apparatus according to (2) above, wherein the refrigerant is R290 and the air volume Q satisfies the relationship Q>550 [m3 / h]. (4) The refrigeration cycle apparatus according to (2) above, wherein the refrigerant is R290 and the air volume Q satisfies the relationship Q>700 [m3 / h]. (5) The refrigeration cycle apparatus according to any one of (1) to (4) above, wherein, when performing the stirring operation, the control device controls the air volume from the indoor fan to gradually increase from the time when the refrigerant sensor detects the refrigerant leakage. (6) The control device is a refrigeration cycle device described in any one of (1) to (5) above, characterized in that after performing the stirring operation for a predetermined time, the control device judges the concentration of the refrigerant detected by the refrigerant sensor, and if it determines that an increase in the concentration of the refrigerant is not observed, the control device stops the stirring operation.(7) The refrigeration cycle device described in (6) above, characterized in that the control device performs intermittent operation by alternately driving and stopping the indoor fan after performing the stirring operation for a predetermined period of time until the stirring operation is stopped.

[0114] 1... Compressor, 2... Indoor unit, 21... Indoor heat exchanger, 22... Indoor fan, 23... Refrigerant sensor, 3... Pressure reducing mechanism, 4... Outdoor unit, 5... Four-way valve, C... Refrigerant circuit, L... Refrigeration cycle device, S... Refrigeration cycle device

Claims

1. A refrigeration cycle device comprising: a refrigerant circuit through which a flammable refrigerant circulates; an indoor unit accommodating some of the equipment connected to the refrigerant circuit and having an indoor fan and a refrigerant sensor for detecting the concentration of the refrigerant; and a control device for controlling the indoor unit, wherein the control device compares the concentration of the refrigerant detected by the refrigerant sensor with a preset threshold and, when it determines that the concentration of the refrigerant is equal to or greater than the threshold, controls the indoor fan to an airflow rate Q [m3 / h] to perform a stirring operation, wherein the airflow rate Q, the lower flammable concentration LFL, the assumed leak rate W, and the assumed suction rate w satisfy the relationship Q > (W + w) / LFL, where LFL is the lower flammable concentration of the refrigerant, W is the assumed leak rate W, and w is the assumed suction rate w.

2. The refrigeration cycle device according to claim 1, wherein the assumed suction speed w and the assumed leakage speed W have a relationship of 0.35W<w<0.75W.

3. The refrigeration cycle device according to claim 2, wherein the refrigerant is R290 and the air volume Q satisfies the relationship Q>550 [m3 / h].

4. The refrigeration cycle device according to claim 2, wherein the refrigerant is R290 and the air volume Q satisfies the relationship Q>700 [m3 / h].

5. The refrigeration cycle device according to claim 1, characterized in that, when performing the stirring operation, the control device controls the air volume from the indoor fan to gradually increase from the time when the refrigerant sensor detects a refrigerant leak.

6. The refrigeration cycle device of claim 1, characterized in that the control device performs the stirring operation for a predetermined time, then determines the concentration of the refrigerant detected by the refrigerant sensor, and if it determines that an increase in the concentration of the refrigerant is not observed, stops the stirring operation.

7. The refrigeration cycle device described in claim 6, characterized in that the control device performs intermittent operation in which the indoor fan is alternately driven and stopped after performing the stirring operation for a predetermined period of time until the stirring operation is stopped.

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