JP7796887B2 - Refrigeration cycle device and air conditioning device - Google Patents

Description

This technology relates to a refrigeration cycle device and an air conditioner, and in particular to condensation suppression control in a refrigerant circuit using a refrigerant with a temperature gradient.

Refrigeration cycle devices such as air conditioners operate by circulating a refrigerant filled in a refrigerant circuit, exchanging heat with a fluid such as air or water to heat or cool the fluid. 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 if released into the atmosphere. For this reason, with growing environmental awareness, there has been 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.

In addition, the control device that controls the equipment of the refrigeration cycle device corrects the evaporation temperature by calculating physical quantities such as temperature detected by a detection device such as a sensor and from these physical quantities (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2018-185116

In a refrigeration cycle device, condensation suppression control is performed to prevent condensation in the refrigerant circuit based on factors such as evaporation temperature. However, in a refrigerant circuit using a refrigerant with a temperature gradient, such as a non-azeotropic refrigerant mixture, the refrigerant temperature varies during the evaporation process, which can lead to inappropriate correction. As a result, there is a risk that parts of the refrigerant circuit will have a temperature lower than the temperature used to determine the condensation suppression control, causing condensation.

Therefore, an object of the present invention is to provide a refrigeration cycle device and an air conditioner that can perform dew suppression control more accurately even when a refrigerant having a temperature gradient is used.

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 passage temperature of the mixed refrigerant passing through the evaporator, and a control device that corrects the heat exchanger passage temperature detected by the two-phase pipe temperature sensor, determines whether to perform condensation suppression control based on the corrected temperature, and performs condensation suppression control based on the determination . The control device has a drive frequency acquisition unit that acquires the compressor drive frequency, and a circulation volume estimation unit that estimates the refrigerant circulation volume of the mixed refrigerant based on the drive frequency, a correction determination unit that determines a correction value for the heat exchanger passage temperature detected by the two-phase pipe temperature sensor based on the estimated refrigerant circulation volume and a predetermined threshold value, and a correction unit that corrects the heat exchanger passage temperature based on the determination of the correction determination unit .

Furthermore, the air conditioning system disclosed herein uses the above-mentioned refrigeration cycle device to heat and cool a target space.

In the disclosed refrigeration cycle apparatus and air conditioner, the control device corrects the heat exchanger exit temperature detected by the two-phase pipe temperature sensor, determines whether to perform condensation suppression control based on the corrected temperature, and performs condensation suppression control based on the determination. This makes it possible to correct the heat exchanger exit temperature to a more accurate temperature and then determine whether to perform condensation suppression control. Therefore, the refrigeration cycle apparatus can perform condensation suppression control based on a more accurate dry state.

1 is a diagram showing a configuration of a refrigeration cycle device according to a first embodiment; 1 is a diagram showing a schematic configuration of an example of a heat exchanger according to a first embodiment; FIG. 2 is a diagram illustrating the configuration of a control device 400 in the air conditioning apparatus 1 according to the first embodiment. This is a pH diagram of a refrigeration cycle device. 4 is a diagram showing the relationship between pressure and temperature during the evaporation process of a non-azeotropic refrigerant mixture when the pressure inside the evaporator is constant in the refrigeration cycle device according to the first embodiment. FIG. 4 is a diagram showing the relationship between pressure and temperature during the evaporation process of a non-azeotropic refrigerant mixture when a pressure difference occurs inside the evaporator in the refrigeration cycle device of embodiment 1. FIG. FIG. 10 is a diagram showing the change over time in refrigerant temperature when the amount of refrigerant circulating is small in the indoor heat exchanger 110 of the air conditioning apparatus 1 according to Embodiment 1. FIG. 10 is a diagram showing the change over time in refrigerant temperature when the amount of refrigerant circulating is large in the indoor heat exchanger 110 of the air conditioning apparatus 1 according to Embodiment 1. 10A and 10B are diagrams illustrating the process of condensation suppression control of the refrigeration cycle device according to the second embodiment. FIG. 10 is a diagram showing the configuration of a control device 400 according to a third embodiment. FIG. 10 is a diagram showing the configuration of a control device 400 according to a fourth embodiment.

Refrigeration cycle devices and other related embodiments will be described below with reference to the drawings. In the following drawings, items with the same reference numerals are the same or equivalent, and will be common throughout the embodiments described below. Furthermore, the dimensional relationships between components in the drawings may differ from those in reality. Furthermore, 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, and 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, etc. Furthermore, when multiple similar devices are distinguished by subscripts, the subscripts may be omitted if there is no need to distinguish or identify them.

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 that 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. The outdoor unit 200 includes a compressor 210, a four-way valve 220, an outdoor heat exchanger 230, and an expansion valve 240, and the indoor unit 100 includes an indoor heat exchanger 110. These components are connected by the refrigerant pipes 300 to form a refrigerant circuit that circulates refrigerant and supplies heat. The indoor unit 100 may also include the expansion valve 240. The air conditioner 1 of the first embodiment is configured with one outdoor unit 200 and one indoor unit 100 connected by pipes. However, the number of units that can be connected is not limited to this.

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 composed of multiple refrigerant components whose composition changes when evaporating and condensing. A non-azeotropic refrigerant mixture does not maintain a constant temperature under the same pressure in a two-phase gas-liquid state due to changes in composition. 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 embodiment 1 is R454B refrigerant, a mixture of HFC (hydrofluorocarbon) refrigerants R32 and R1234yf in a ratio of 68.1:31.9.

In embodiment 1, the outdoor unit 200 has a compressor 210, a four-way valve 220, and an outdoor heat exchanger 230 as components that make up the refrigerant circuit. The outdoor unit 200 also has an outdoor blower 250 and a control device 400.

Compressor 210 compresses the refrigerant it draws in and discharges it. Compressor 210 may be, for example, a scroll compressor, rotary compressor, or vane compressor. The compressor 210 can vary the amount of circulating refrigerant discharged by, for example, changing the drive frequency using an inverter circuit or the like.

The four-way valve 220, which serves as a flow path switching device, is a valve that switches the flow of refrigerant between cooling operation and heating operation, for example. During heating operation, the four-way valve 220 connects the discharge side of the compressor 210 to the indoor heat exchanger 110 and 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 connects the suction side of the compressor 210 to the indoor heat exchanger 110. While the use of a four-way valve 220 is illustrated here as an example, the flow path switching device is not limited to this. For example, a flow path switching device may be formed by combining multiple two-way valves, etc.

The outdoor heat exchanger 230 is a heat exchanger that exchanges heat between the refrigerant and outdoor air. In embodiment 1, the outdoor heat exchanger 230 functions as an evaporator during heating operation, absorbing heat and evaporating the refrigerant, vaporizing it into gaseous refrigerant (hereinafter referred to as gas refrigerant) and passing it through. On the other hand, during cooling operation, the outdoor heat exchanger 230 functions as a condenser, condensing the refrigerant and releasing heat, liquefying it into liquid refrigerant (hereinafter referred to as liquid refrigerant) and passing it through. In addition, when driven, the outdoor blower 250 passes air from outside the outdoor unit 200 through the outdoor heat exchanger 230, creating an air flow that flows out of the outdoor unit 200, promoting heat exchange in the outdoor heat exchanger 230.

Expansion valve 240, which acts as a throttle device, is a valve that reduces the pressure of the refrigerant to expand it. Expansion valve 240 is, for example, an electronic expansion valve. Expansion valve 240 adjusts its opening based on instructions from control device 400 (described below) and other devices, reducing the pressure and controlling the amount of refrigerant passing through.

The indoor unit 100 conditions the air inside the room. The indoor unit 100 has an indoor heat exchanger 110 as a component of the refrigerant circuit. The indoor unit 100 also has an indoor fan 120. The indoor heat exchanger 110 is a heat exchanger that exchanges heat between the refrigerant and the air inside the room, which is the space to be air-conditioned. For example, during heating operation, the indoor heat exchanger 110 functions as a condenser, condensing the refrigerant and passing the liquid refrigerant. During cooling operation, the indoor heat exchanger 110 functions as an evaporator, evaporating the refrigerant and passing the gas refrigerant. The indoor fan 120 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 room, which is the space to be air-conditioned. The configuration of the indoor heat exchanger 110 will be explained further below.

Next, the operation of each device in the air conditioning unit 1 will be explained based on the flow of refrigerant. First, the operation of each device in the refrigerant circuit during heating operation will be explained based on the flow of refrigerant. The solid arrows in Figure 1 indicate the flow of refrigerant during heating operation. High-temperature, high-pressure gas 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 gas refrigerant condenses and liquefies by exchanging heat with, for example, the air in the air-conditioned space. The condensed and liquefied refrigerant passes through the expansion valve 240. The refrigerant is decompressed as it passes through the expansion valve 240. The refrigerant, which has been decompressed by the expansion valve 240 and is now in a two-phase gas-liquid state, passes through the outdoor heat exchanger 230. In the outdoor heat exchanger 230, the refrigerant evaporates by exchanging heat with outdoor air sent from the outdoor blower 250. The gasified refrigerant passes through the four-way valve 220 and is again drawn into the compressor 210. In this way, the refrigerant in the air conditioning unit 1 circulates and performs air conditioning related to heating.

Next, cooling operation will be described. The dotted arrows in Figure 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 blower 250. The liquefied refrigerant then passes through the expansion valve 240. As it passes through the expansion valve 240, the refrigerant is depressurized and enters a two-phase gas-liquid state. The refrigerant depressurized in the expansion valve 240 and enters a two-phase gas-liquid state passes through the indoor heat exchanger 110. In the indoor heat exchanger 110, the refrigerant evaporates, for example, by exchanging heat with 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 circulates in the air-conditioning unit 1, performing air conditioning related to cooling. In the following explanation, cooling operation will be performed with the indoor heat exchanger 110 acting as an evaporator.

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

The indoor heat exchanger 110 is, for example, a fin-tube type heat exchanger. The indoor heat exchanger 110 has a heat exchanger body 111 that exchanges heat between the indoor air and the refrigerant. The heat exchanger body 111 is composed of multiple heat transfer tubes that form the refrigerant flow path and multiple fins that promote heat exchange between the refrigerant and the indoor air. One end of the heat exchanger body 111 is connected to a refrigerant distributor 112 via multiple capillary tubes 113, and the other end is connected to a header 114. The distributor 112 and header 114 distribute or merge the refrigerant to the multiple heat transfer tubes of the heat exchanger body 111.

As shown in FIG. 2, the indoor heat exchanger 110 is equipped with a two-phase pipe temperature sensor 500 and a liquid pipe temperature sensor 510. The two-phase pipe temperature sensor 500 and the liquid pipe temperature sensor 510 are detection devices that detect the refrigerant temperature at the installation location and send a detection signal to the control device 400, which will be described later.

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, it is assumed here that the two-phase pipe temperature sensor 500 is mounted so as to detect the temperature of the refrigerant at a position approximately midway through its path through the heat exchanger body 111. For example, the two-phase pipe temperature sensor 500 is mounted in a holder brazed to the U-shaped portion of the hairpin tube of the heat exchanger body 111. In this way, the mounting position of the two-phase pipe temperature sensor 500 is, for example, a position intended to detect the temperature of point P3 on the p-h diagram in Figure 4 (described below). Therefore, the heat exchanger exit temperature is typically the saturation temperature (evaporation temperature) of the refrigerant in a two-phase gas-liquid state during the evaporation process of the refrigeration cycle.

The liquid pipe temperature sensor 510 is a detection device that detects the temperature of the refrigerant flowing into and out of the indoor heat exchanger 110 as the liquid pipe temperature and sends a detection signal to the control device 400. The liquid pipe temperature sensor 510 detects the surface temperature of the outlet pipe of the heat exchanger functioning as a condenser. This temperature corresponds to the temperature of the liquid refrigerant after condensation. On the other hand, when the heat exchanger functions as an evaporator, the liquid pipe temperature sensor 510 detects the surface temperature of the inlet pipe of the heat exchanger. This temperature corresponds to the temperature of the highly humid two-phase refrigerant before evaporation. In this case, the liquid pipe temperature sensor 510 is a two-phase refrigerant temperature sensor that detects the temperature of the highly humid two-phase refrigerant, including the liquid refrigerant, flowing into the indoor heat exchanger 110 when the indoor heat exchanger 110 functions as an evaporator. The liquid pipe temperature sensor 510 is installed in a position that forms the refrigerant flow path between the expansion valve 240 and the indoor heat exchanger 110 via the refrigerant piping 300. Here, the liquid pipe temperature sensor 510 is attached to the capillary tube 113 connecting the heat exchanger body 111 and the distributor 112. When the indoor heat exchanger 110 functions as a condenser, the liquid pipe temperature sensor 510 detects the temperature of the refrigerant flowing out of the indoor heat exchanger 110.

Figure 3 is a diagram illustrating the configuration of the control device 400 in the air conditioning apparatus 1 according to embodiment 1. The control device 400 is a device that controls the air conditioning apparatus 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 equipment that makes up the air conditioning apparatus 1.

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 condensation suppression control unit 413, and a circulation amount estimation unit 414. The determination unit 411 performs a determination process related to condensation suppression control . Therefore, for example, the determination unit 411 includes a correction determination unit 411A that determines a correction value (degree of correction) that the correction unit 412 applies to the heat exchanger passing temperature detected by the two-phase pipe temperature sensor 500. The determination unit 411 also includes a condensation determination unit 411B that determines whether the condensation suppression control unit 413 performs condensation control. The correction unit 412 corrects the heat exchanger passing temperature using the correction value based on the determination by the correction determination unit 411A. The condensation suppression control unit 413 performs condensation suppression control when the condensation determination unit 411B determines that condensation will occur. The content of the condensation suppression control performed by the condensation suppression control unit 413 is not particularly limited. For example, the condensation suppression control unit 413 performs control such as lowering the drive frequency of the compressor 210 and increasing the opening of the expansion valve 240. By performing condensation suppression control such as lowering the drive frequency of the compressor 210 or increasing the opening of the expansion valve 240, the condensation suppression control unit 413 can take early action to prevent condensation by increasing the temperature of the refrigerant flowing on the low-pressure side of the refrigerant circuit, such as the evaporation temperature. Furthermore, if condensation cannot be suppressed even after lowering the drive frequency of the compressor 210 or increasing the opening of the expansion valve 240, the condensation suppression control unit 413 may stop driving the compressor 210 or operating the air conditioning apparatus 1. The circulation volume estimation unit 414 estimates the circulation volume of the refrigerant passing through the heat exchanger serving as an evaporator. 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.

The memory unit 420 also includes a volatile storage device (not shown) such as random access memory (RAM) that can temporarily store data, and a non-volatile auxiliary storage device (not shown) such as flash memory. Here, the memory unit 420 stores the relationship between the refrigerant circulation volume, the evaporation temperature in the evaporator, and the correction value as table-format data. It also stores set threshold data used by the determination unit 411 when making a determination. The set threshold value, correction value, etc. are set in advance through experiments or the like depending on the refrigerant circulation volume and evaporation temperature. The memory unit 420 also includes program data 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, this is not limited to this, and the control device 400 may also be a device (hardware) dedicated to control.

Figure 4 is a p-h diagram of a refrigeration cycle device. The refrigerant temperature used as the reference for determining the dryness state of the refrigerant is the heat exchanger passing temperature detected by the two-phase pipe temperature sensor 500 described above. The two-phase pipe temperature sensor 500 is positioned to detect the refrigerant temperature at point P3 on the p-h diagram (Mollier diagram) shown in Figure 4. Here, a general characteristic of refrigerants is that the refrigerant pressure in the evaporator tends to decrease by the amount of pressure loss on the evaporator side (the low-pressure side of the refrigerant circuit) from point P3a, which is the refrigerant inlet of the evaporator, through point P3, to point P3b, which is the refrigerant outlet.

Figure 5 shows the relationship between pressure and temperature during the evaporation process using a non-azeotropic refrigerant mixture when the pressure inside the evaporator is constant in the refrigeration cycle device of embodiment 1. Figure 6 shows the relationship between pressure and temperature during the evaporation process using a non-azeotropic refrigerant mixture when a pressure difference occurs inside the evaporator in the refrigeration cycle device of embodiment 1. The arrows in Figures 5 and 6 indicate the direction of refrigerant flow.

In the case of a non-azeotropic refrigerant mixture, the boiling points of the refrigerants involved in the mixture are different. Therefore, as enthalpy increases, the refrigerant temperature also increases. Therefore, as shown in Figure 5, for example, if there is no or negligible pressure difference between point P3a and point P3b, the refrigerant temperature increases from the refrigerant inlet to the refrigerant outlet of the evaporator due to the physical properties of the non-azeotropic refrigerant mixture. Therefore, for a non-azeotropic refrigerant mixture, the liquid pipe temperature detected by the liquid pipe temperature sensor 510 tends to be lower than the heat exchanger exit temperature detected by the two-phase pipe temperature sensor 500. Furthermore, in the case of a non-azeotropic refrigerant mixture, even a refrigerant in a two-phase gas-liquid state during the evaporation process exhibits the same temperature trend as a superheated refrigerant. For example, under normal conditions, a two-phase gas-liquid refrigerant flows through the evaporator at point P3. However, if there is a refrigerant shortage in the refrigerant circuit due to a refrigerant leak or other reason, the refrigerant may already be superheated at point P3. With a refrigerant with a temperature gradient, it may be difficult to distinguish this from a refrigerant shortage.

On the other hand, as shown in Figure 6, if a pressure difference occurs between the refrigerant inlet and outlet of the evaporator due to factors such as pressure loss within the evaporator, the refrigerant temperature will remain constant or decrease from the refrigerant inlet to the refrigerant outlet. Therefore, the refrigerant temperature decrease due to pressure loss and the temperature increase due to the physical properties of the non-azeotropic refrigerant mixture cancel each other out. Figure 6 shows an example in which the refrigerant temperature decrease due to pressure loss and the temperature increase due to the physical properties of the non-azeotropic refrigerant mixture balance out, resulting in a constant refrigerant temperature within the evaporator. As shown in Figures 5 and 6, for refrigerants with a temperature gradient, such as non-azeotropic refrigerants, the refrigerant temperature used to determine condensation is not uniform. Therefore, it is necessary to correct the refrigerant temperature using a correction value that matches the pressure state within the evaporator. Therefore, in the control device 400 of the air conditioning unit 1 in embodiment 1, the correction unit 412 corrects the heat exchanger passing temperature based on the determination by the determination unit 411.

7 shows the change in refrigerant temperature over time in the indoor heat exchanger 110 of the air conditioning apparatus 1 according to embodiment 1 when the refrigerant circulation volume is low. Also, FIG. 8 shows the change in refrigerant temperature over time in the indoor heat exchanger 110 of the air conditioning apparatus 1 according to embodiment 1 when the refrigerant circulation volume is high. As mentioned above, the air conditioning apparatus 1 performs cooling. Therefore, as mentioned above, the indoor heat exchanger 110 functions as an evaporator. In the refrigerant circuit, the pressure difference occurring within the evaporator varies depending on the refrigerant circulation volume. When the refrigerant circulation volume is high, the pressure loss is large, and when the refrigerant circulation volume is low, the pressure loss is small. Therefore, as shown in FIG. 7, when the refrigerant circulation volume is low and there is no or little pressure loss, the correction value that takes into account the temperature gradient for the temperature detected by the two-phase pipe temperature sensor 500 is large. On the other hand, as shown in FIG. 8, when an increase in the refrigerant circulation volume results in a temperature decrease due to pressure loss and a temperature increase due to the physical properties of the non-azeotropic refrigerant mixture, the correction value that takes into account the temperature gradient can be small.

As described above, according to the air conditioning apparatus 1 of the first embodiment, the determination unit 411 of the control device 400 determines a correction value for the heat exchanger passage temperature related to the temperature gradient based on the heat exchanger passage temperature detected by the two-phase pipe temperature sensor 500, and the correction unit 412 performs the correction. The determination unit 411 of the control device 400 then determines whether to perform condensation suppression control based on the corrected heat exchanger passage temperature, and the condensation suppression control unit 413 performs condensation suppression control based on the determination. This allows the actual heat exchanger passage temperature detected by the two-phase pipe temperature sensor 500 to be corrected to a more accurate temperature. This allows the control device 400 of the air conditioning apparatus 1 to more accurately determine the temperature state of the refrigerant flowing through the low-pressure side of the refrigerant circuit and perform condensation suppression control based on the determination. Furthermore, condensation, freezing and frosting caused by condensation or dew around the air outlet through which air that has passed through the indoor heat exchanger 110 flows out of the indoor unit 100, and other problems can be suppressed or prevented. Furthermore, in the air conditioning apparatus 1 of embodiment 1, the control device 400 can make more accurate decisions related to condensation suppression control, etc., using a smaller number of temperature sensors, based on the refrigerant temperature detected by the two-phase pipe temperature sensor 500.

Embodiment 2.
Fig. 9 is a diagram illustrating the process of condensation suppression control of the refrigeration cycle apparatus according to the second embodiment. The process in Fig. 9 is described as being performed by the control device 400 when the air conditioning apparatus 1 is performing cooling operation. As described above, the circulation amount estimation unit 414 of the control device 400 includes the drive frequency acquisition unit 414A. Therefore, the circulation amount estimation unit 414 estimates the refrigerant circulation amount based on the drive frequency of the compressor 210 (step S1). Here, the refrigerant circulation amount can generally be obtained based on the following equation (1):

Refrigerant circulation amount = volumetric efficiency x driving frequency x suction refrigerant density x displacement volume
…(1)

In equation (1), the drive 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, the volumetric efficiency, suction refrigerant density, and displacement volume are assumed to be constant values. Therefore, the refrigerant circulation volume can be calculated as an approximate value that depends on the drive frequency of the compressor 210.

In the determination unit 411 of the control device 400, the correction determination unit 411A of the determination unit 411 compares the estimated refrigerant circulation volume with the set threshold stored in the memory unit 420 to determine whether the refrigerant circulation volume is equal to or greater than the set threshold (step S2). The set threshold is set, for example, to a value that is 50% of the maximum refrigerant circulation volume of the refrigerant passing through the indoor unit 100. Here, if there are multiple indoor units 100, a set threshold is set for each maximum refrigerant circulation volume in each indoor unit 100. If the correction determination unit 411A determines that the refrigerant circulation volume is equal to or greater than the set threshold, the correction unit 412 corrects the heat exchanger passage temperature detected by the two-phase pipe temperature sensor 500 using a first correction value (step S3). Here, the first correction value also includes the case where no correction is performed (correction value = 0). Furthermore, if the correction determination unit 411A determines that the refrigerant circulation volume is less than the set threshold, it corrects the heat exchanger passage temperature detected by the two-phase pipe temperature sensor 500 using a second correction value greater than the first correction value (step S4). In some cases, the second correction value may be 0. Here, the temperature gradient varies depending on the evaporation temperature during operation. For example, when the evaporation temperature is 10°C, the temperature gradient of the azeotropic refrigerant mixture is 1.5 K, and when the evaporation temperature is 5°C, the temperature gradient of the azeotropic refrigerant mixture is 1.7 K. Therefore, the correction unit 412 performs correction using the first and second correction values corresponding to the evaporation temperature. As described above, the first and second correction values are stored as data in the memory unit 420.

Then, the condensation determination unit 411B of the determination unit 411 determines whether or not to perform condensation suppression control based on the corrected heat exchanger passing temperature (step S5). If the determination unit 411 determines that the corrected heat exchanger passing temperature is higher than the preset condensation threshold value, as shown in Figures 7 and 8, the determination unit 411 determines that condensation suppression control will not be performed. If the condensation determination unit 411B determines that condensation suppression control will not be performed, the process returns to step S1.

On the other hand, if the condensation determination unit 411B determines that condensation suppression control should be performed, the condensation suppression control unit 413 starts the condensation suppression control and performs processing related to the condensation suppression control (step S6). For example, the condensation suppression control unit 413 reduces the drive frequency of the compressor 210 or increases the opening degree of the expansion valve 240. Depending on the balance between cooling capacity and load, the refrigerant temperature on the low-pressure side of the refrigerant circuit may decrease even if the drive frequency of the compressor 210 is reduced to its lower limit. Therefore, the condensation determination unit 411B of the determination unit 411 continues to determine whether condensation has occurred. If the condensation determination unit 411B determines that the corrected heat exchanger exit temperature is lower than a stop threshold that is lower than the set condensation threshold, the condensation determination unit 411B, for example, stops the operation of the compressor 210 to further suppress condensation. As described above, the content of the condensation suppression control performed by the condensation suppression control unit 413 is not particularly limited. When the condensation suppression control unit 413 of the control device 400 ends the condensation suppression control, the process returns to step S1.

As described above, the air conditioning apparatus 1 of embodiment 2 can achieve the effects described in embodiment 1. Furthermore, in the air conditioning apparatus 1 of embodiment 2, the control device 400 corrects the temperature passing through the heat exchanger based on the drive frequency. This makes it easy to obtain a more accurate refrigerant circulation volume.

Embodiment 3.
FIG. 10 is a diagram showing the configuration of a control device 400 according to the third embodiment. Among the components shown in FIG. 10 , components 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 drawn into the compressor 210 based on the heat exchanger exit temperature detected by the two-phase pipe temperature sensor 500 attached to the evaporator. 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.

As explained 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 more accurate corrections. 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. In the third embodiment, the control device 400 estimates the refrigerant circulation volume based not only on the drive frequency of the compressor 210 but also on the suction refrigerant density, which is obtained from the suction temperature of the refrigerant drawn into the compressor 210.

As described above, according to the refrigeration cycle apparatus of the third embodiment, the control unit 410 of the control device 400 has the suction temperature determination unit 414B and determines the suction temperature based on the temperature passing through the heat exchanger. This allows the control device 400 to estimate the refrigerant circulation volume, including the suction refrigerant density obtained from the suction temperature. Therefore, the control device 400 can more accurately estimate the refrigerant circulation volume and make a determination, thereby more accurately determining whether to perform condensation suppression control. Furthermore, when the refrigeration cycle apparatus of the third embodiment is an air conditioner 1 that conditions air in a target space, it can provide comfortable air conditioning for people in the room.

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 drawn into the compressor 210 based on the opening degree of the expansion valve 240. 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.

In the refrigeration cycle apparatus of embodiment 4, the suction temperature estimation unit 414C in the control device 400 can obtain the Cv value of the expansion valve 240 based on the opening degree of the expansion valve 240. The Cv value is a value determined by the type and port diameter of the expansion valve 240 and is the capacity coefficient of the valve. The Cv value is a numerical representation of the flow rate of 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.

As described above, according to the refrigeration cycle apparatus of embodiment 4, the suction temperature estimation unit 414C of the control device 400 estimates the suction temperature based on the opening degree of the expansion valve 240, which expands high-pressure refrigerant and reduces its pressure to low-pressure refrigerant. This allows for a more accurate determination of the refrigerant circulation volume, enabling more efficient control. Furthermore, when the refrigeration cycle apparatus of embodiment 4 is an air conditioner 1 that conditions the air of a target space, it can provide comfortable air conditioning for people in the room.

Embodiment 5.
In the third embodiment described above, the control unit 410 of the control device 400 includes the suction temperature determination unit 414B, and in the fourth embodiment, the control unit 410 of the control device 400 includes the suction temperature estimation unit 414C. However, the control unit 410 is not limited to including either one. The control unit 410 of the control device 400 may be configured to include both the suction temperature determination unit 414B and the suction temperature estimation unit 414C and perform the respective processes.

The refrigeration cycle device of the first embodiment described above uses R454B refrigerant, a mixture of R32 refrigerant and R1234yf refrigerant in a ratio of 68.1:31.9, as the non-azeotropic refrigerant mixture circulating through the refrigerant circuit. However, this is not limited to this. For example, a non-azeotropic refrigerant mixture such as R407C may also be used. A near-azeotropic refrigerant mixture with a temperature gradient may also be used. Because the refrigeration cycle device can be used with various types of non-azeotropic refrigerant mixtures, it is possible to use refrigerants with low GWP, making it a refrigeration cycle device that takes the global environment into consideration. It can also be a refrigeration cycle device that complies with regional market standards and regulations.

Furthermore, the configuration of the refrigerant circuit in the refrigeration cycle device is not limited to the configuration of the air conditioner 1 in Figure 1 described in the first embodiment above. For example, the refrigeration cycle device may be configured to have an accumulator between the evaporator, which is the low-pressure side of the refrigerant circuit, and the suction side of the compressor 210. The accumulator is a container that passes gas refrigerant and stores liquid refrigerant. The refrigeration cycle device may also be configured to have a receiver between the heat exchanger, which is the condenser, on the high-pressure side of the refrigerant circuit, and the expansion valve 240. The receiver is a container on the high-pressure side of the refrigerant circuit that stores excess refrigerant in the refrigerant circuit.

In addition, in the second embodiment described above, the control device 400 corrects the heat exchanger exit temperature using a first correction value or a second correction value based on the set threshold value, but this is not limited to this. The memory unit 420 may store multiple set threshold values as data, divide the refrigerant circulation volume into three or more categories, and correct the temperature using a correction value corresponding to each category. Furthermore, if the relationship between the environmental state of the refrigerant during the evaporation process and the correction value can be expressed by a formula or the like, the correction value may be calculated by calculation or the like.

In the above-described first embodiment, the heat exchanger in Figure 2 was used as the indoor heat exchanger 110 of the indoor unit 100, but this is not limited to this. The heat exchanger may also be used as the outdoor heat exchanger 230 of the outdoor unit 200, or as both the outdoor heat exchanger 230 and the indoor heat exchanger 110.

In the above-mentioned first embodiment and others, the air conditioning unit 1 was described, but it can also be applied to other refrigeration cycle devices, such as refrigerators and refrigeration units.

1 Air conditioning apparatus, 100 Indoor unit, 110 Indoor heat exchanger, 111 Heat exchanger body, 112 Distributor, 113 Capillary tube, 114 Header, 120 Indoor blower, 200 Outdoor unit, 210 Compressor, 220 Four-way valve, 230 Outdoor heat exchanger, 240 Expansion valve, 250 Outdoor blower, 300 Refrigerant piping, 400 Control device, 410 Control unit, 411 Determination unit, 411A Correction determination unit, 411B Dew formation determination unit, 412 Correction unit, 413 Dew formation suppression control unit, 414 Circulation amount estimation unit, 414A Drive frequency acquisition unit, 414B Intake temperature determination unit, 414C Intake temperature estimation unit, 420 Memory unit, 500 Two-phase pipe temperature sensor, 510 Liquid pipe temperature sensor.

Claims (5)

A refrigeration cycle device having a refrigerant circuit configured by connecting a compressor, a condenser, an expansion valve, and an evaporator through pipes, which circulates a mixed refrigerant having a temperature gradient,
a two-phase pipe temperature sensor for detecting a temperature of the mixed refrigerant passing through the evaporator at the time of passing through the heat exchanger;
a control device that corrects the heat exchanger passing temperature detected by the two-phase pipe temperature sensor, determines whether to perform dew condensation suppression control based on the corrected temperature, and performs the dew condensation suppression control based on the determination ,
The control device
a circulation amount estimation unit including a drive frequency acquisition unit that acquires a drive frequency of the compressor and that estimates a refrigerant circulation amount of the mixed refrigerant based on the drive frequency;
a correction determination unit that determines a correction value of the heat exchanger passing temperature detected by the two-phase pipe temperature sensor based on the estimated refrigerant circulation amount and a predetermined set threshold value;
a correction unit that corrects the heat exchanger passing temperature based on the determination of the correction determination unit;
A refrigeration cycle device having the same . The circulation volume estimation unit
The compressor further includes an intake temperature determination unit that determines an intake temperature of the compressor from the heat exchanger passing temperature detected by the two-phase pipe temperature sensor.
The refrigeration cycle apparatus according to claim 1 , wherein the refrigerant circulation amount is estimated based on the drive frequency and the suction temperature. The circulation volume estimation unit
3. The refrigeration cycle device according to claim 1 , further comprising an intake temperature estimation unit that estimates an intake temperature of the compressor from an opening degree of the expansion valve, and that estimates the refrigerant circulation amount based on the drive frequency and the intake temperature. 3. The refrigeration cycle device according to claim 1 , wherein the mixed refrigerant having the temperature gradient is a non-azeotropic mixed refrigerant obtained by mixing an R32 refrigerant and an R1234yf refrigerant. An air conditioner that cools and heats a target space using the refrigeration cycle device according to claim 1 or 2 .