Refrigeration cycle device and air conditioning device

Abstract

A refrigeration cycle apparatus according to the present disclosure is formed from a compressor, a condenser, an expansion valve, and an evaporator which are connected together by pipes, and has a refrigerant circuit through which a refrigerant mixture having a temperature gradient circulates, said refrigeration cycle apparatus comprising: a two-phase pipe temperature sensor for detecting a heat exchanger passing temperature of the refrigerant mixture passing through inside the condenser; a heat exchanger port temperature sensor for detecting a temperature of the refrigerant mixture flowing out from the condenser; and a control device for performing excessive-cooling control while correcting the degree of excessive cooling, that is, the difference between the heat exchanger passing temperature detected by the two-phase pipe temperature sensor and the heat exchanger port temperature detected by the heat exchanger port temperature sensor, wherein the control device has a circulation amount estimation unit for estimating a refrigerant circulation amount of the refrigerant mixture, a determination unit for determining a correction value for correcting the degree of excessive cooling on the basis of the estimated refrigerant circulation amount and a preset threshold value, a correction unit for correcting the degree of excessive cooling with the correction value based on the determination of the determination unit, and an excessive-cooling control unit for performing the excessive-cooling control.

Description

[Technical Field]

[0001] This technology relates to a refrigeration cycle device and an air conditioner, and in particular to supercooling control in a refrigerant circuit using a refrigerant with a temperature gradient. [Background technology]

[0002] Refrigeration cycle devices such as air conditioners operate by circulating a refrigerant filled in a refrigerant circuit and exchanging heat with a fluid such as air or water to heat or cool the fluid. Here, the global warming potential (GWP) of the refrigerant used in refrigeration cycle devices is sometimes taken into consideration. Refrigerants with a high GWP can cause global warming and other problems if released into the atmosphere. For this reason, due to increased environmental awareness, there is a trend toward refrigerants with lower GWP values for refrigeration cycle devices. Therefore, in recent years, non-azeotropic refrigerant mixtures, which are mixtures of multiple refrigerants with different boiling points, have been used as refrigerants with a low GWP.

[0003] In addition, in a refrigeration cycle device, the devices within the device are controlled to control the degree of subcooling of the refrigerant to a preset temperature. The degree of subcooling is the difference between the saturation temperature (condensation temperature) and the temperature of the refrigerant flowing out from the condenser. Therefore, the control device that controls the devices in the refrigeration cycle device obtains the degree of subcooling by physical quantities detected by detection devices such as sensors and calculations from these physical quantities.

[0004] When a refrigeration cycle device operates by circulating a non-azeotropic refrigerant mixture filled in the refrigeration circuit, the temperature of the refrigerant in the condenser gradually decreases under constant pressure during the condensation process of the refrigeration cycle. As a result, the refrigerant inlet temperature is greater than the refrigerant outlet temperature. The difference between the refrigerant inlet temperature and the refrigerant outlet temperature forms a temperature gradient. Therefore, the refrigerant flowing out of the condenser appears to be supercooled even when it is not. Therefore, the control device performs control based on the corrected degree of supercooling (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-185116 Summary of the Invention [Problem to be solved by the invention]

[0006] The refrigeration cycle device of Patent Document 1 described above uniformly corrects the degree of subcooling. However, in the case of a refrigerant circuit using a refrigerant with a temperature gradient, such as a non-azeotropic refrigerant mixture, the temperature of the refrigerant varies during the condensation process, making it impossible to perform control based on an appropriate degree of subcooling, which may result in a decrease in capacity.

[0007] Therefore, an object of the present invention is to provide a refrigeration cycle device and an air conditioner that can perform control based on the degree of subcooling more accurately even when a refrigerant having a temperature gradient is used. [Means for solving the problem]

[0008] The refrigeration cycle device according to this disclosure is a refrigeration cycle device configured by piping a compressor, a condenser, an expansion valve, and an evaporator, and having a refrigerant circuit that circulates a mixed refrigerant having a temperature gradient. The refrigeration cycle device is equipped with a two-phase pipe temperature sensor that detects the heat exchanger exit temperature of the mixed refrigerant passing through the condenser, a heat exchanger inlet temperature sensor that detects the temperature of the mixed refrigerant flowing out of the condenser, and a control device that performs supercooling control by correcting the degree of subcooling, which is the difference between the heat exchanger exit temperature detected by the two-phase pipe temperature sensor and the heat exchanger inlet temperature detected by the heat exchanger inlet temperature sensor. The control device has a circulation amount estimation unit that estimates the refrigerant circulation amount of the mixed refrigerant, a judgment unit that judges a correction value for the degree of subcooling based on the estimated refrigerant circulation amount and a predetermined set threshold value, a correction unit that corrects the degree of subcooling based on the correction value judged by the judgment unit, and a subcooling control unit that performs supercooling control.

[0009] The air conditioner according to the present disclosure cools and heats a target space using the above-described refrigeration cycle device. [Effects of the Invention]

[0010] In the refrigeration cycle apparatus and air conditioner disclosed herein, the control device determines and corrects the correction value for the degree of supercooling and performs supercooling control. This allows for more accurate supercooling control based on the degree of supercooling. As a result, the capacity of the refrigeration cycle apparatus can be improved. [Brief explanation of the drawings]

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

[0012] Refrigeration cycle devices and the like according to embodiments will be described below with reference to the drawings. In the following drawings, components with the same reference numerals are identical or equivalent and will be common throughout the following embodiments. The dimensional relationships between components in the drawings may differ from those in reality. The configurations of components shown throughout the specification are merely illustrative and are not limited to those described in the specification. In particular, the combinations of components are not limited to those in each embodiment; components described in other embodiments may be applied to other embodiments. Furthermore, the levels of pressure and temperature are not determined in relation to absolute values, but are determined relatively in terms of the state and operation of the device. When multiple similar devices are distinguished by subscripts, the subscripts may be omitted if there is no need to distinguish or identify them.

[0013] Embodiment 1 FIG. 1 is a diagram showing the configuration of a refrigeration cycle apparatus according to a first embodiment. Here, as an example of a refrigeration cycle apparatus, an air conditioner 1 that conditions the air of a room, which is a space to be air-conditioned, will be described. As shown in FIG. 1, the air conditioner 1 of the first embodiment has an outdoor unit 200, an indoor unit 100, and two refrigerant pipes 300. A compressor 210, a four-way valve 220, and an outdoor heat exchanger 230 of the outdoor unit 200 are connected to an indoor heat exchanger 110 and an expansion valve 120 of the indoor unit 100 via the refrigerant pipes 300, forming a refrigerant circuit that circulates refrigerant to supply heat. The outdoor unit 200 may also have the expansion valve 120. The air conditioner 1 of the first embodiment is configured such that one outdoor unit 200 and one indoor unit 100 are connected via pipes. However, the number of units that can be connected is not limited to this.

[0014] The air conditioner 1 uses a non-azeotropic refrigerant mixture as the refrigerant circulating within the refrigerant circuit. A non-azeotropic refrigerant mixture is a refrigerant mixture of multiple refrigerant components whose composition changes when evaporating and condensing. A non-azeotropic refrigerant mixture is in a two-phase gas-liquid state under the same pressure and does not maintain a constant temperature as its composition changes. For example, during the evaporation process under the same pressure, the refrigerant temperature at the end of evaporation is higher than the refrigerant temperature at the start of evaporation. Similarly, during the condensation process under the same pressure, the refrigerant temperature at the end of condensation is lower than the refrigerant temperature at the start of condensation. The temperature difference between the start and end of evaporation or condensation is the temperature gradient. Here, the non-azeotropic refrigerant mixture used in the air conditioner 1 in the first embodiment is R454B refrigerant, which is a mixture of HFC (hydrofluorocarbon) refrigerants R32 and R1234yf refrigerants in a ratio of 68.1:31.9.

[0015] The outdoor unit 200 in the first embodiment has, as devices that configure a refrigerant circuit, a compressor 210, a four-way valve 220, and an outdoor heat exchanger 230. The outdoor unit 200 also has an outdoor blower 240 and a control device 400.

[0016] The compressor 210 compresses the drawn refrigerant and discharges it. The compressor 210 is, for example, a scroll compressor, a reciprocating compressor, or a vane compressor. Here, the compressor 210 can change the volume of the refrigerant discharged by arbitrarily changing the drive frequency using, for example, an inverter circuit.

[0017] The four-way valve 220 serving as the flow path switching device is a valve that switches the flow of refrigerant between, for example, cooling operation and heating operation. During heating operation, the four-way valve 220 connects the discharge side of the compressor 210 to the indoor heat exchanger 110 and also connects the suction side of the compressor 210 to the outdoor heat exchanger 230. During cooling operation, the four-way valve 220 connects the discharge side of the compressor 210 to the outdoor heat exchanger 230 and also connects the suction side of the compressor 210 to the indoor heat exchanger 110. While the four-way valve 220 is used here as an example, the flow path switching device is not limited to this. For example, a combination of multiple two-way valves may also be used as the flow path switching device.

[0018] The outdoor heat exchanger 230 is a heat exchanger that exchanges heat between the refrigerant and outdoor air. The outdoor heat exchanger 230 in the first embodiment functions as an evaporator during heating operation, absorbing heat to evaporate the refrigerant, and vaporizing it into a gaseous refrigerant (hereinafter referred to as a gas refrigerant), which is then passed through. On the other hand, during cooling operation, it functions as a condenser, condensing the refrigerant to release heat, and liquefying it into a liquid refrigerant (hereinafter referred to as a liquid refrigerant), which is then passed through. The configuration of the outdoor heat exchanger 230 will be described in further detail later. Furthermore, the outdoor blower 240, when driven, passes air from outside the outdoor unit 200 through the outdoor heat exchanger 230, forming an air flow that flows out of the outdoor unit 200, thereby promoting heat exchange in the outdoor heat exchanger 230.

[0019] The indoor unit 100 conditions the air inside the room. The indoor unit 100 has an indoor heat exchanger 110 and an expansion valve 120 as devices that configure a refrigerant circuit. The indoor unit 100 also has an indoor blower .

[0020] The expansion valve 120, which serves as a throttling device etc., is a valve that reduces the pressure of the refrigerant and expands it. The expansion valve 120 is composed of, for example, an electronic expansion valve etc. Then, the expansion valve 120 adjusts its opening degree based on instructions from a control device 400 etc. described later, performs pressure reduction, and controls the amount of refrigerant passing through. Also, the indoor heat exchanger 110 is a heat exchanger that performs heat exchange between the air in the indoor space to be air-conditioned and the refrigerant. For example, during heating operation, the indoor heat exchanger 110 functions as a condenser, condenses the refrigerant, and allows the liquid refrigerant to pass through. Also, during cooling operation, the indoor heat exchanger 110 functions as an evaporator, evaporates the refrigerant, and allows the gaseous refrigerant to pass through. The indoor blower 130 passes air through the indoor heat exchanger 110 to promote heat exchange in the indoor heat exchanger 110, and supplies the air that has passed through the indoor heat exchanger 110 to the indoor space, which is the space to be air-conditioned.

[0021] Next, the operations of each device in the air conditioner 1 will be described based on the flow of the refrigerant. First, the operations of each device in the refrigerant circuit during heating operation will be described based on the flow of the refrigerant. The solid-line arrows in FIG. 1 indicate the flow of the refrigerant during heating operation. The high-temperature and high-pressure gaseous refrigerant compressed and discharged by the compressor 210 passes through the four-way valve 220 and flows into the indoor heat exchanger 110. While passing through the indoor heat exchanger 110, the gaseous refrigerant condenses and liquefies, for example, by exchanging heat with the air in the space to be air-conditioned. The condensed and liquefied refrigerant passes through the expansion valve 120. The refrigerant is depressurized when passing through the expansion valve 120. The refrigerant that has been depressurized by the expansion valve 120 and has become a gas-liquid two-phase state passes through the outdoor heat exchanger 230. In the outdoor heat exchanger 230, the refrigerant evaporates and gasifies by exchanging heat with the outdoor air sent from the outdoor blower 240, and then passes through the four-way valve 220 and is sucked into the compressor 210 again. In this way, the refrigerant in the air conditioner 1 circulates, and air conditioning related to heating is performed.

[0022] Next, cooling operation will be described. The dotted arrows in FIG. 1 indicate the flow of refrigerant during cooling operation. The high-temperature, high-pressure gas refrigerant compressed and discharged by the compressor 210 passes through the four-way valve 220 and flows into the outdoor heat exchanger 230. The refrigerant then passes through the outdoor heat exchanger 230, where it condenses and liquefies by exchanging heat with outdoor air supplied by the outdoor fan 240. The liquefied refrigerant then passes through the expansion valve 120. As it passes through the expansion valve 120, the refrigerant is reduced in pressure and enters a two-phase gas-liquid state. The refrigerant, once reduced in pressure by the expansion valve 120 and brought into a two-phase gas-liquid state, passes through the indoor heat exchanger 110. In the indoor heat exchanger 110, the refrigerant evaporates by exchanging heat with, for example, the air in the space to be air-conditioned. The gasified refrigerant then passes through the four-way valve 220 and is drawn back into the compressor 210. In this manner, the refrigerant in the air conditioner 1 circulates, performing air conditioning related to cooling. In the following description, it is assumed that a cooling operation is performed in which the outdoor heat exchanger 230 serves as a condenser.

[0023] Fig. 2 is a diagram showing a schematic configuration of an example of a heat exchanger according to Embodiment 1. Here, the heat exchanger in Fig. 2 will be described as the outdoor heat exchanger 230, but the indoor heat exchanger 110 is also assumed to have a similar configuration.

[0024] The outdoor heat exchanger 230 is, for example, a fin-tube heat exchanger. The outdoor heat exchanger 230 has a heat exchanger body 231 that exchanges heat between outdoor air and a refrigerant. The heat exchanger body 231 is composed of a plurality of heat transfer tubes that form a refrigerant flow path and a plurality of fins that promote heat exchange between the refrigerant and the outdoor air. One end of the heat exchanger body 231 is connected to a refrigerant distributor 232 via a plurality of capillary tubes 233, and the other end is connected to a header 234. The distributor 232 and the header 234 distribute or merge the refrigerant to the plurality of heat transfer tubes of the heat exchanger body 231.

[0025] 2, a two-phase pipe temperature sensor 500 and a heat exchanger port temperature sensor 510 are attached to the outdoor heat exchanger 230. The two-phase pipe temperature sensor 500 and the heat exchanger port temperature sensor 510 are detection devices that detect the temperature of the refrigerant at the attached positions and send a signal related to the detection to the control device 400, which will be described later.

[0026] The two-phase pipe temperature sensor 500 detects the temperature of the refrigerant in the heat exchanger as the heat exchanger exit temperature. While not particularly limited, the two-phase pipe temperature sensor 500 is assumed to be mounted so as to detect the temperature of the refrigerant at a position approximately midway through the heat exchanger body 231. For example, the two-phase pipe temperature sensor 500 is mounted in a holder brazed to the U-shaped portion of a hairpin tube in the heat exchanger body 231. The mounting position of the two-phase pipe temperature sensor 500 is, for example, a position intended to detect the temperature of point P2 on the pH diagram in FIG. 4 (described later). Therefore, the heat exchanger exit temperature is typically the saturation temperature (condensation temperature) of the refrigerant in a gas-liquid two-phase state during the condensation process in the refrigeration cycle.

[0027] The heat exchanger port temperature sensor 510 is a detection device that detects the temperature of the refrigerant flowing into or out of the outdoor heat exchanger 230 as the heat exchanger port temperature and sends a signal related to the detection to the control device 400. In this case, the heat exchanger port temperature sensor 510 is a liquid pipe temperature sensor that detects the temperature of the liquid refrigerant flowing out of the outdoor heat exchanger 230, particularly when the outdoor heat exchanger 230 functions as a condenser. The heat exchanger port temperature sensor 510 is attached to a position on the refrigerant flow path between the expansion valve 120 and the outdoor heat exchanger 230 via the refrigerant piping 300. In this case, the heat exchanger port temperature sensor 510 is attached to the capillary tube 233 that connects the heat exchanger main body 231 and the distributor 232. When the outdoor heat exchanger 230 functions as an evaporator, the heat exchanger port temperature sensor 510 detects the temperature of the refrigerant flowing into the outdoor heat exchanger 230.

[0028] 3 is a diagram illustrating the configuration of the control device 400 in the air conditioner 1 according to embodiment 1. The control device 400 is a device that controls the air conditioner 1. Here, the outdoor unit 200 is described as having the control device 400, but this is not limited to this. Another unit may have the control device 400. Furthermore, the control device 400 may be a device independent of the unit that has the devices that make up the air conditioner 1.

[0029] The control device 400 includes a control unit 410 and a memory unit 420. The control unit 410 includes, for example, a control and arithmetic processing device such as a CPU (Central Processing Unit) or a microcomputer. The control unit 410 in the first embodiment includes, among other things, a determination unit 411, a correction unit 412, a supercooling control unit 413, and a circulation amount estimation unit 414. The determination unit 411 performs a determination process related to supercooling control. In particular, the determination unit 411 determines a correction value (degree of correction) that the correction unit 412 uses to correct the degree of supercooling, which is the difference between the heat exchanger exit temperature detected by the two-phase pipe temperature sensor 500 and the heat exchanger inlet temperature detected by the heat exchanger inlet temperature sensor 510. The correction unit 412 corrects the degree of supercooling using the correction value based on the determination by the determination unit 411. The supercooling control unit 413 performs supercooling control. The content of the control performed by the supercooling control unit 413 in response to the change in the supercooling degree is not particularly limited. Here, the supercooling control unit 413 adjusts the opening of the expansion valve 120 to perform supercooling control so that the degree of supercooling of the refrigerant flowing through the refrigerant circuit becomes a target degree of supercooling. Here, the target degree of supercooling is, for example, approximately 5 degrees. When making a change to increase the degree of supercooling, the supercooling control unit 413 reduces the opening of the expansion valve 120. On the other hand, when making a change to decrease the degree of supercooling, the supercooling control unit 413 increases the opening of the expansion valve 120. Then, the circulation amount estimation unit 414 estimates the circulation amount of the refrigerant passing through the heat exchanger serving as a condenser. In the first embodiment, the circulation amount estimation unit 414 has a drive frequency acquisition unit 414A and estimates the circulation amount based on the acquired drive frequency of the compressor 210.

[0030] The storage unit 420 also includes a volatile storage device (not shown) such as a random access memory (RAM) that can temporarily store data, and a non-volatile auxiliary storage device (not shown) such as a flash memory. Here, the storage unit 420 stores the relationship between the refrigerant circulation amount, the condensation temperature in the condenser, and the correction value as table-format data. The storage unit 420 also stores data of a set threshold value used by the determination unit 411 when making a determination. The set threshold value, the correction value, and the like are set in advance through experiments or the like depending on the refrigerant circulation amount and the condensation temperature. The storage unit 420 also includes data in the form of a program that describes the processing procedures to be performed by the control arithmetic processing device. The control unit 410 then executes processing based on the program data. However, the present invention is not limited to this, and the control device 400 may also be a device (hardware) dedicated to control.

[0031] FIG. 4 is a pH diagram for a refrigeration cycle device. The two-phase pipe temperature sensor 500 is positioned to detect the refrigerant temperature at point P2 on the pH diagram (Mollier diagram) shown in FIG. 4. A general characteristic of refrigerants is that the refrigerant pressure in the condenser decreases by the amount of pressure loss on the condenser side (the high-pressure side of the refrigerant circuit) from point P2c, which is the refrigerant inlet of the condenser, through point P2, to point P2d, which is the refrigerant outlet. The difference between the saturated liquid temperature at point P2b and the heat exchanger inlet temperature at point P2d is the degree of subcooling.

[0032] Fig. 5 is a diagram showing the relationship between pressure and temperature in the condensation process using a non-azeotropic refrigerant mixture when the pressure in the condenser is constant in the refrigeration cycle apparatus according to embodiment 1. Fig. 6 is a diagram showing the relationship between pressure and temperature in the condensation process using a non-azeotropic refrigerant mixture when a pressure difference occurs in the condenser in the refrigeration cycle apparatus according to embodiment 1. The arrows in Figs. 5 and 6 indicate the direction of refrigerant flow.

[0033] In the case of a non-azeotropic refrigerant mixture, the condensation temperatures of the refrigerants involved in the mixture are different. Therefore, as enthalpy increases, the refrigerant temperature also increases. Therefore, as shown in FIG. 5, for example, if there is no or negligible pressure difference between the pressure at point P2a and the pressure at point P2b, the refrigerant temperature decreases from the refrigerant inlet to the refrigerant outlet of the condenser due to the physical properties of the non-azeotropic refrigerant mixture. Therefore, for a non-azeotropic refrigerant mixture, the heat exchanger inlet temperature detected by heat exchanger inlet temperature sensor 510 tends to be lower than the heat exchanger exit temperature detected by two-phase pipe temperature sensor 500. Furthermore, in the case of a non-azeotropic refrigerant mixture, even a refrigerant in a gas-liquid two-phase state undergoing condensation exhibits the same temperature trend as a refrigerant in a supercooled state. In the case of a refrigerant with a temperature gradient, it may be difficult to distinguish the temperature change due to supercooling from that due to refrigerant temperature gradient.

[0034] Furthermore, as shown in FIG. 6, if a pressure difference occurs between the refrigerant inlet and refrigerant outlet of the condenser due to pressure loss or other factors within the condenser, the refrigerant temperature will decrease from the inlet to the outlet. Therefore, the refrigerant temperature decrease due to pressure loss and the temperature decrease due to the physical properties of the non-azeotropic refrigerant mixture act in the same direction. Therefore, in FIG. 6, the refrigerant temperature decrease due to pressure loss is added to the temperature decrease due to the physical properties of the non-azeotropic refrigerant mixture. As shown in FIGS. 5 and 6, it is difficult to uniformly correct the degree of subcooling for refrigerants with a temperature gradient, such as non-azeotropic refrigerants. It is therefore necessary to correct the degree of subcooling using a correction value that is tailored to the pressure conditions within the condenser. Therefore, in the control device 400 of the air conditioning apparatus 1 in embodiment 1, the correction unit 412 corrects the degree of subcooling based on the determination by the determination unit 411.

[0035] FIG. 7 is a diagram showing the temporal change in the refrigerant temperature when the refrigerant circulation amount is small in the outdoor heat exchanger 230 of the air conditioner 1 according to Embodiment 1. FIG. 8 is a diagram showing the temporal change in the refrigerant temperature when the refrigerant circulation amount is large in the outdoor heat exchanger 230 of the air conditioner 1 according to Embodiment 1. As described above, here, the outdoor heat exchanger 230 functions as a condenser. In the refrigerant circuit, the pressure difference generated in the condenser changes depending on the refrigerant circulation amount. When the refrigerant circulation amount is large, the pressure loss is large, and when the refrigerant circulation amount is small, the pressure loss is small. Therefore, as shown in FIG. 7, when the refrigerant circulation amount is small and the pressure loss is absent or small, the correction value considering the temperature gradient with respect to the temperature detected by the two-phase pipe temperature sensor 500 becomes small. On the other hand, as shown in FIG. 8, when the refrigerant circulation amount increases and temperature drop due to pressure loss and temperature rise due to the physical properties of the zeotropic refrigerant occur, the correction value considering the temperature gradient becomes a large value.

[0036] As described above, according to the air conditioner 1 of the first embodiment, the determination unit 411 of the control device 400 determines a correction value for the degree of subcooling that corresponds to the operating conditions. Furthermore, the correction unit 412 corrects the degree of subcooling calculated based on the heat exchanger exit temperature detected by the two-phase pipe temperature sensor 500 and the heat exchanger inlet temperature detected by the heat exchanger inlet temperature sensor 510, using the determined correction value. The determination unit 411 of the control device 400 then determines whether to change the degree of subcooling based on the corrected degree of subcooling, and the supercooling control unit 413 performs supercooling control based on the determination. This allows the air conditioner 1 to obtain a more accurate degree of subcooling. The control device 400 of the air conditioner 1 can then perform supercooling control based on a more accurate degree of subcooling. Therefore, in the air conditioner 1, the control device 400 can perform supercooling control based on a more accurate degree of subcooling. Therefore, the air conditioner 1 can improve its compressor capacity. Furthermore, the air conditioner 1 can perform appropriate supercooling accuracy and can operate with a reduced drive frequency of the compressor 210. This allows for energy savings. Furthermore, in the air conditioner 1 of embodiment 1, the control device 400 can more accurately determine supercooling based on the refrigerant temperatures detected by the two-phase pipe temperature sensor 500 and the heat exchanger inlet temperature sensor 510, using a smaller number of temperature sensors.

[0037] Embodiment 2 Fig. 9 is a diagram illustrating the process of supercooling control of the refrigeration cycle apparatus according to embodiment 2. The process in Fig. 9 will be described as being performed by the control device 400. When the control device 400 operates the refrigeration cycle apparatus, the supercooling control unit 413 of the control device 400 controls the opening degree of the expansion valve 120 and performs the process related to the supercooling control (step S1).

[0038] In the supercooling control of the second embodiment, the circulation amount estimation unit 414 of the control device 400 includes the drive frequency acquisition unit 414A, as described above. Therefore, the circulation amount estimation unit 414 estimates the refrigerant circulation amount based on the drive frequency of the compressor 210 (step S2). Here, the refrigerant circulation amount can generally be obtained based on the following equation (1).

[0039] Refrigerant circulation volume = volumetric efficiency × driving frequency × suction refrigerant density × displacement volume …(1)

[0040] (1) In the formula, the driving frequency is a term that affects the estimation of the refrigerant circulation volume. Therefore, in Embodiment 2, when the circulation volume estimation unit 414 estimates the refrigerant circulation volume, it is assumed that the volumetric efficiency, the suction refrigerant density, and the displacement volume are constant values. For this reason, the refrigerant circulation volume can be obtained as an approximate value as a quantity that depends on the driving frequency of the compressor 210.

[0041] In the determination unit 411 of the control device 400, the determination unit 411 compares the estimated refrigerant circulation volume with the set threshold value stored in the storage unit 420, and determines whether the refrigerant circulation volume is equal to or greater than the set threshold value (step S3). The set threshold value is set to a value that is, for example, 50% of the maximum refrigerant circulation volume of the refrigerant passing through the indoor unit 100. Here, when there are a plurality of indoor units 100, the set threshold value is set for each maximum refrigerant circulation volume in each indoor unit 100. As a result of the determination by the determination unit 411, when the determination unit 411 determines that the refrigerant circulation volume is equal to or greater than the set threshold value, the correction unit 412 calculates the degree of subcooling from the heat exchanger passing temperature detected by the two-phase pipe temperature sensor 500 and the heat exchanger outlet temperature detected by the heat exchanger outlet temperature sensor 510. Then, the correction unit 412 corrects the degree of subcooling with the first correction value (step S4). Further, when the determination unit 411 determines that the refrigerant circulation volume is smaller than the set threshold value, the correction unit 412 corrects the degree of subcooling with a second correction value that is smaller than the first correction value (step S5). Here, the temperature gradient varies depending on the condensation temperature in the condenser during operation. Therefore, the correction unit 412 corrects with the values of the first correction value and the second correction value corresponding to the condensation temperature. The first correction value and the second correction value are stored as data in the storage unit 420 as described above.

[0042] Then, returning to step S1, the supercooling control unit 413 performs processing related to the supercooling control (step S1). As described above, here, the supercooling control unit 413 controls the opening degree of the expansion valve 120. The control device 400 continues to perform the processing related to the supercooling control as described above during operation of the refrigeration cycle device.

[0043] As described above, the air conditioner 1 of embodiment 2 can achieve the effects described in embodiment 1. Furthermore, in the air conditioner 1 of embodiment 2, the control device 400 corrects the temperature passing through the heat exchanger based on the drive frequency. This makes it possible to easily obtain a more accurate refrigerant circulation amount.

[0044] Embodiment 3 FIG. 10 is a diagram illustrating the configuration of a control device 400 according to a third embodiment. Components illustrated in FIG. 10 with the same reference numerals as those in FIG. 3 perform the same processing functions as those described in the first embodiment. The circulation volume estimation unit 414 of the control device 400 according to the third embodiment includes a suction temperature determination unit 414B. The suction temperature determination unit 414B determines the suction temperature of the refrigerant suctioned by the compressor 210 based on the heat exchanger exit temperature detected by the evaporator-side two-phase pipe temperature sensor 500. The circulation volume estimation unit 414 according to the second embodiment estimates the refrigerant circulation volume based on the drive frequency of the compressor 210 and the suction density determined by the suction temperature determined by the suction temperature determination unit 414B. When the outdoor heat exchanger 230 functions as a condenser, the evaporator-side two-phase pipe temperature sensor 500 is replaced by the two-phase pipe temperature sensor 500 attached to the indoor heat exchanger 110.

[0045] As described in the first and second embodiments, the control device 400 determines and corrects the correction value based on the refrigerant circulation volume of the refrigerant circulating through the refrigerant circuit. Therefore, if the control device 400 can obtain a more accurate refrigerant circulation volume, it can perform a more accurate correction. Here, in the second embodiment, the circulation volume estimation unit 414 of the control device 400 estimated the refrigerant circulation volume by setting the suction refrigerant density to a constant value. The control device 400 in the third embodiment estimates the refrigerant circulation volume based not only on the drive frequency of the compressor 210 but also on the suction refrigerant density obtained from the suction temperature of the refrigerant sucked into the compressor 210.

[0046] As described above, according to the refrigeration cycle apparatus of the third embodiment, the control unit 410 of the control device 400 has an intake temperature determination unit 414B and determines the intake temperature based on the heat exchanger passing temperature detected by the two-phase pipe temperature sensor 500 on the evaporator side. This allows the control device 400 to estimate the refrigerant circulation volume, including the intake refrigerant density obtained from the intake temperature. Therefore, the control device 400 can more accurately estimate the refrigerant circulation volume and make a determination, and therefore more accurately determine whether to change the degree of subcooling. Furthermore, when the refrigeration cycle apparatus of the third embodiment is an air conditioner 1 that conditions the air of a target space, it can provide comfortable air conditioning for people in the room.

[0047] Embodiment 4 FIG. 11 is a diagram showing the configuration of a control device 400 according to the fourth embodiment. Among the components shown in FIG. 11, those with the same reference numerals as those in FIG. 3 perform the same processing functions as those described in the first embodiment. The control device 400 according to the fourth embodiment has a suction temperature estimation unit 414C. The suction temperature estimation unit 414C estimates the suction temperature of the refrigerant sucked into the compressor 210 based on the opening degree of the expansion valve 120. The circulation amount estimation unit 414 according to the fourth embodiment estimates the refrigerant circulation amount based on the drive frequency of the compressor 210 and the suction temperature estimated by the suction temperature estimation unit 414C.

[0048] In the refrigeration cycle apparatus of the fourth embodiment, the suction temperature estimation unit 414C in the control device 400 can obtain the Cv value of the expansion valve 120 based on the aperture of the expansion valve 120. The Cv value is a value determined by the type and port diameter of the expansion valve 120 and is a capacity coefficient of the valve. The Cv value is a numerical representation of the flow rate of a fluid passing through the valve at a certain differential pressure. The suction temperature estimation unit 414C also estimates the low-pressure pressure on the low-pressure side of the refrigerant circuit from the Cv value and the refrigerant circulation volume, and further estimates the suction temperature. The control device 400 can then estimate not only the drive frequency of the compressor 210 but also the refrigerant circulation volume based on the estimated suction temperature.

[0049] As described above, according to the refrigeration cycle apparatus of the fourth embodiment, the suction temperature estimation unit 414C of the control device 400 estimates the suction temperature based on the opening degree of the expansion valve 120, which expands high-pressure refrigerant and reduces the pressure to low-pressure refrigerant. This allows for a more accurate determination of the refrigerant circulation amount, enabling efficient control. Furthermore, when the refrigeration cycle apparatus of the fourth embodiment is an air conditioner 1 that conditions the air of a target space, it can provide comfortable air conditioning for people in the room.

[0050] Embodiment 5. In the third embodiment described above, the control unit 410 of the control device 400 has the suction temperature determination unit 414B, and in the fourth embodiment, the control unit 410 of the control device 400 has the suction temperature estimation unit 414C. However, the present invention is not limited to having only one of them. The control unit 410 of the control device 400 may be configured to have both the suction temperature determination unit 414B and the suction temperature estimation unit 414C and to perform the respective processes.

[0051] In addition, in the refrigeration cycle device of the above-described Embodiment 1, as the zeotropic mixture refrigerant circulating in the refrigerant circuit, R454B refrigerant in which R32 refrigerant and R1234yf refrigerant are mixed at a ratio of 68.1:31.9 was used. However, the present invention is not limited to this. For example, a zeotropic mixture refrigerant such as R407C may be used. Also, a pseudo-azeotropic mixture refrigerant having a temperature gradient may be used. Since the refrigeration cycle device can be applied to various types of zeotropic mixture refrigerants, a refrigerant with a low GWP can be adopted, and a refrigeration cycle device considering the global environment can be obtained. Also, a refrigeration cycle device corresponding to the standards and criteria for each region of the market can be obtained.

[0052] In addition, the configuration of the refrigerant circuit in the refrigeration cycle device is not limited to the configuration of the air conditioner 1 in FIG. 1 described in the above-described Embodiment 1. For example, the refrigeration cycle device may be configured to have an accumulator between the evaporator on the low-pressure side of the refrigerant circuit and the suction side of the compressor 210. The accumulator is a container that allows the gas refrigerant to pass through and stores the liquid refrigerant. Also, the refrigeration cycle device may be configured to have a receiver between the heat exchanger serving as the condenser on the high-pressure side of the refrigerant circuit and the expansion valve 120. The receiver is a container that stores excess refrigerant in the refrigerant circuit on the high-pressure side.

[0053] In addition, in the above-described Embodiment 2, in the control device 400, the temperature passing through the heat exchanger was corrected with the first correction value or the second correction value based on the set threshold value. However, the present invention is not limited to this. The storage unit 420 may store a plurality of set threshold values as data, divide the refrigerant circulation amount into three or more sections, and correct with correction values corresponding to each section. Also, when the relationship between the environmental state of the refrigerant in the evaporation process and the correction value can be expressed by a mathematical formula or the like, the correction value may be calculated by arithmetic or the like.

Industrial Applicability

[0054] In the first embodiment described above, the heat exchanger is used in the outdoor heat exchanger 230 of the outdoor unit 200, but this is not limiting. The heat exchanger may be used in the indoor heat exchanger 110 of the indoor unit 100, or may be used in both the outdoor heat exchanger 230 and the indoor heat exchanger 110.

[0055] In the above-mentioned first embodiment and the like, the air conditioner 1 has been described, but the invention can also be applied to other refrigeration cycle devices such as a refrigerator, a freezer, or a hot water heater. [Explanation of symbols]

[0056] 1 air conditioning apparatus, 100 indoor unit, 110 indoor heat exchanger, 120 expansion valve, 130 indoor blower, 200 outdoor unit, 210 compressor, 220 four-way valve, 230 outdoor heat exchanger, 231 heat exchanger body, 232 distributor, 233 capillary tube, 234 header, 240 outdoor blower, 300 refrigerant piping, 400 control device, 410 control unit, 411 determination unit, 412 correction unit, 413 subcooling control unit, 414 circulation amount estimation unit, 414A drive frequency acquisition unit, 414B suction temperature determination unit, 414C suction temperature estimation unit, 420 memory unit, 500 two-phase pipe temperature sensor, 510 heat exchanger inlet temperature sensor.

Claims

1. A refrigeration cycle apparatus having a refrigerant circuit configured by pipe-connecting a compressor, a condenser, an expansion valve, and an evaporator and circulating a mixed refrigerant having a temperature gradient, a two-phase pipe temperature sensor that detects the heat exchanger passing temperature of the mixed refrigerant passing through the condenser, a heat exchanger outlet temperature sensor that detects the temperature of the mixed refrigerant flowing out of the condenser, a control device that corrects the degree of subcooling, which is the difference between the heat exchanger passing temperature detected by the two-phase pipe temperature sensor and the heat exchanger outlet temperature detected by the heat exchanger outlet temperature sensor, and performs subcooling control and comprising, the control device, a circulation amount estimation unit that estimates the refrigerant circulation amount of the mixed refrigerant, a determination unit that determines a correction value for the degree of subcooling based on the estimated refrigerant circulation amount and a preset set threshold value, a correction unit that corrects the degree of subcooling with the correction value based on the determination of the determination unit, and a subcooling control unit that performs the subcooling control A refrigeration cycle apparatus having the same.

2. The circulation amount estimation unit, The refrigeration cycle apparatus according to claim 1, wherein the refrigerant circulation amount of the mixed refrigerant is estimated based on the driving frequency of the compressor.

3. Further comprising a two-phase pipe temperature sensor on the evaporator side that detects the heat exchanger passing temperature of the mixed refrigerant passing through the evaporator, the circulation amount estimation unit, further having a suction temperature determination unit that determines the suction temperature of the compressor from the temperature detected by the two-phase pipe temperature sensor on the evaporator side, The refrigeration cycle apparatus according to claim 2, wherein the refrigerant circulation amount is estimated based on the driving frequency and the suction temperature.

4. The circulation amount estimation unit, further having a suction temperature estimation unit that estimates the suction temperature of the compressor from the opening degree of the expansion valve, and the refrigeration cycle apparatus according to claim 2, wherein the refrigerant circulation amount is estimated based on the driving frequency and the suction temperature.

5. The mixed refrigerant is a zeotropic mixed refrigerant obtained by mixing R32 refrigerant and R1234yf refrigerant. The refrigeration cycle apparatus according to any one of claims 1 to 4.

6. An air conditioner that performs air conditioning of a target space by the refrigeration cycle apparatus according to any one of claims 1 to 4.

Images