WO2024075235A1

WO2024075235A1 - Air conditioning device

Info

Publication number: WO2024075235A1
Application number: PCT/JP2022/037402
Authority: WO
Inventors: 正典佐藤
Original assignee: 三菱電機株式会社
Priority date: 2022-10-06
Filing date: 2022-10-06
Publication date: 2024-04-11

Abstract

An air conditioning device (1000) comprises a refrigerant circuit (500), and a control device (100) for controlling the refrigerant circuit (500). A condenser (211) includes a first heat exchanging unit and a second heat exchanging unit configured to be capable of allowing a refrigerant to flow in parallel, and a flow rate adjusting mechanism (272) configured to adjust a flow rate of the refrigerant passing through the second heat exchanging unit. The control device (100) is configured to be capable of causing the flow rate adjusting mechanism (272) to reduce the flow rate of the refrigerant passing through the second heat exchanging unit to below the flow rate of the refrigerant passing through the first heat exchanging unit if an operating frequency of a compressor (200) is a predetermined lower limit frequency. The control device (100) is configured to cause the flow rate adjusting mechanism (272) to reduce the flow rate of the refrigerant passing through the second heat exchanging unit if an air conditioning capability of the refrigerant circuit (500) is greater than an indoor load, and then to increase an opening degree of an expansion valve (230).

Description

Air Conditioning Equipment

This disclosure relates to air conditioning devices.

　A method widely used in air conditioning systems is to control the operating frequency of the compressor according to the load inside the room to adjust the indoor temperature. Compressors have a set frequency range within which they can operate. When the indoor load is small, such as in spring and autumn, and the indoor temperature cannot be maintained even when the compressor is operating at the minimum frequency, on-off operation is implemented to stabilize the room temperature by repeatedly operating (thermo on) and stopping (thermo off) the compressor.

However, on-off operation has issues such as room temperature fluctuating up and down, reducing comfort, and the air conditioning system's coefficient of performance (COP) being lower than with continuous operation.

To this end, Japanese Patent Laid-Open Publication No. 10-141740 (Patent Document 1) discloses a technique for forcibly reducing the opening of the expansion valve when operating near the lower limit frequency, thereby reducing the amount of refrigerant circulating and thereby lowering capacity and reducing the frequency of on-off operation.

Japanese Patent Application Laid-Open No. 10-141740

However, in the technology disclosed in JP 10-141740 A (Patent Document 1), the opening of the expansion valve is made smaller than the optimal state, so the proportion of gas refrigerant in the evaporator increases. This causes the evaporator performance to decrease, and the evaporation temperature to decrease, resulting in a problem of a decrease in COP.

The present disclosure aims to solve the above problem by providing an air conditioner that both reduces the frequency of on-off operation and prevents a decrease in COP.

The present disclosure relates to an air conditioner. The air conditioner includes a refrigerant circuit including at least a compressor, a condenser, an expansion valve, and an evaporator, and configured to circulate a refrigerant, and a control device that controls the refrigerant circuit. The condenser includes a first heat exchange unit and a second heat exchange unit configured to allow the refrigerant to flow in parallel, and a flow rate adjustment mechanism configured to adjust the flow rate of the refrigerant passing through the second heat exchange unit. The control device is configured to be able to reduce the flow rate of the refrigerant passing through the second heat exchange unit by the flow rate adjustment mechanism to be lower than the flow rate of the refrigerant passing through the first heat exchange unit when the operating frequency of the compressor is a preset lower limit frequency. The control device is configured to increase the opening of the expansion valve after reducing the flow rate of the refrigerant passing through the second heat exchange unit by the flow rate adjustment mechanism when the air conditioning capacity of the refrigerant circuit is greater than the indoor load.

The air conditioning device disclosed herein is capable of further reducing the air conditioning capacity even when the compressor is operating at the lower limit frequency. This makes it possible to suppress the frequency of on-off operation while also suppressing the decrease in COP.

1 is a diagram showing the configuration of an air conditioning device 1000 according to a first embodiment. 2 is a diagram showing a configuration example of an outdoor heat exchanger 211 in FIG. 1 . 4 is a flowchart for explaining control of the expansion valve 230. 13 is a diagram showing changes in the capacity of the air conditioner when the opening degree of the flow rate adjustment mechanism 272 is changed when the operating frequency of the compressor is at the lower limit frequency Fmin during cooling operation. FIG. This is a ph diagram of an air conditioning device when the circulation flow ratio is 100%. This is a ph diagram of an air conditioning device when the circulation flow rate ratio is 19%. 13 is a flowchart for explaining control of a flow rate adjustment mechanism 272. 13 is a diagram showing a change in the Cv value of the expansion valve 230 when the opening degree of the flow rate adjustment mechanism 272 is changed in a case where the operating frequency of the compressor 200 is the lower limit frequency Fmin during cooling operation. FIG. FIG. 13 is a diagram showing an approximation formula for a region where the circulation flow rate ratio is large. FIG. 13 is a diagram showing an approximation formula for a region where the circulation flow rate ratio is small. FIG. 13 is a diagram showing the results during heating operation. FIG. 11 is a diagram showing a first modified example in which the configuration of the outdoor heat exchanger 211 is changed. FIG. 13 is a diagram showing a second modified example in which the configuration of the outdoor heat exchanger 211 is changed. 13A and 13B are diagrams illustrating a third modified example in which the configuration of the flow rate adjusting mechanism is changed. FIG. 12 is a diagram showing the configuration of an air conditioning device 1200 according to a second embodiment. 16 is a diagram showing a configuration example of an outdoor heat exchanger 211 in FIG. 15 . 10 is a flowchart for explaining control of a flow rate adjustment mechanism 272 and

fans

221 and 222. 18 is an example of a map referred to in steps S44 and S47 of FIG. 17. 13 is a diagram showing changes in the capacity of the air conditioner when the opening degree of the flow rate adjustment mechanism 272 and the rotation speed of the fan 221 are changed when the operating frequency F of the compressor 200 is at the lower limit frequency Fmin during cooling operation. FIG. FIG. 11 is a diagram showing a Cv value ratio of an expansion valve 230 relative to a circulation flow rate ratio in the second embodiment. FIG. 13 is a diagram showing fitting results and approximate equation results in a region where the circulation flow rate ratio is 28% to 100%. FIG. 13 is a diagram showing fitting results and approximate equation results in a region where the circulation flow rate ratio is 0 to 28%. 11 is a diagram showing changes in the capacity of the air conditioner relative to the Cv value ratio of the expansion valve 230. FIG. 20 corresponds to FIG. 19 when the rotation speed of the fan 221 is set to 0. FIG. 20 when the rotation speed of the fan 221 is set to 0. FIG. 21 when the rotation speed of the fan 221 is set to 0. FIG. 22 when the rotation speed of the fan 221 is set to 0. FIG. 23 when the rotation speed of the fan 221 is set to 0. FIG. FIG. 1 is a diagram illustrating an example of the configuration of a rotary vane type compressor.

Below, the embodiments of the present disclosure will be described in detail with reference to the drawings. Several embodiments will be described below, but it is planned from the beginning of the application that the configurations described in each embodiment will be appropriately combined. Note that the same or equivalent parts in the drawings will be given the same reference numerals and their description will not be repeated. Note that the size relationships between the components in the following drawings may differ from the actual ones.

Embodiment 1.
Fig. 1 is a diagram showing the configuration of an air-conditioning apparatus 1000 according to embodiment 1. The air-conditioning apparatus 1000 shown in Fig. 1 includes a refrigerant circuit 500 and a control device 100.

As shown in FIG. 1, the refrigerant circuit 500 of the air conditioning device 1000 includes a compressor 200, an outdoor heat exchanger 211, an outdoor blower (fan) 220, an expansion valve 230, a four-way valve 240, a flow rate adjustment mechanism 272, an indoor heat exchanger 110, and an indoor blower (fan) 120. The four-way valve 240 has ports P1 to P4. As the expansion valve 230, for example, an electronic expansion valve (LEV: Linear Expansion Valve) can be used.

The refrigerant circuit 500 is arranged separately for an outdoor unit 1001 and an indoor unit 1002. The outdoor unit 1001 includes a compressor 200, a four-way valve 240, an outdoor heat exchanger 211, an outdoor fan 220, an expansion valve 230, and a control device 100. The indoor unit 1002 includes an indoor heat exchanger 110 and an indoor fan 120. The outdoor unit 1001 and the indoor unit 1002 are connected by

pipes

310 and 320.

Compressor 200 is configured to change its operating frequency according to a control signal received from control device 100. Specifically, compressor 200 has a built-in drive motor with a variable rotation speed that is inverter-controlled, and when the operating frequency is changed, the rotation speed of the drive motor changes. The output of compressor 200 is adjusted by changing the operating frequency of compressor 200.

The four-way valve 240 is controlled to be in either a cooling operation state or a heating operation state by a control signal received from the control device 100. The cooling operation state is a state in which port P1 and port P4 are in communication, and port P2 and port P3 are in communication, as shown by solid lines in FIG. 1. The heating operation state is a state in which port P1 and port P3 are in communication, and port P2 and port P4 are in communication, as shown by dashed lines in FIG. 1. By operating the compressor 200 in the cooling operation state, the refrigerant circulates through the refrigerant circuit in the direction shown by the solid arrow. Also, by operating the compressor 200 in the heating operation state, the refrigerant circulates through the refrigerant circuit in the direction shown by the dashed arrow.

The air conditioning device 1000 further includes temperature sensors 261-265. The temperature sensor 261 is disposed in the indoor unit 1002 and detects the room temperature T261 of the room to be air-conditioned. The temperature sensor 262 is disposed on the side connected to the pipe 320 (liquid pipe) of the indoor heat exchanger 110 and measures the refrigerant temperature T262. The temperature sensor 263 is disposed on the side connected to the pipe 310 (gas pipe) of the indoor heat exchanger 110 and measures the refrigerant temperature T263. The temperature sensor 264 is disposed on the side connected to the expansion valve 230 of the outdoor heat exchanger 211 and measures the refrigerant temperature T264. The temperature sensor 265 is disposed on the side connected to the port P4 of the four-way valve 240 of the outdoor heat exchanger 210 and measures the refrigerant temperature T265.

The control device 100 controls the opening of the expansion valve 230 to adjust the SH (superheat) of the refrigerant at the evaporator outlet according to the outputs of the temperature sensors 261-265, and also controls the rotation of the

fans

221 and 222.

The control device 100 is composed of a CPU (Central Processing Unit) 101, memory 102 (ROM (Read Only Memory) and RAM (Random Access Memory)), an input/output buffer (not shown), etc. The CPU 101 deploys programs stored in the ROM into the RAM etc. and executes them. The programs stored in the ROM are programs in which the processing procedures of the control device 100 are written. The control device 100 controls each device in the air conditioning device 1000 in accordance with these programs. This control is not limited to processing by software, but can also be processed by dedicated hardware (electronic circuits).

In FIG. 1, the flow of refrigerant during cooling operation is shown by a solid line, and the flow of refrigerant during heating operation is shown by a dashed line. The control device 100 changes the frequency of the compressor 200 so that the indoor temperature becomes the target (set) temperature.

Note that while FIG. 1 illustrates an air conditioner equipped with a four-way valve 240, the air conditioner may be a cooling-only air conditioner that does not have a four-way valve 240.

The outdoor heat exchanger 211 includes two heat exchange sections connected in parallel and a flow rate adjustment mechanism 272. The flow rate adjustment mechanism 272 is disposed at the refrigerant outlet of one of the heat exchange sections.

FIG. 2 is a diagram showing an example of the configuration of the outdoor heat exchanger 211 in FIG. 1. The outdoor heat exchanger 211 includes a first heat exchange section 211A and a second heat exchange section 211B that are configured to allow a refrigerant to flow in parallel. FIG. 2 shows a side view of the outdoor heat exchanger 211 as seen from a lateral direction perpendicular to the wind direction.

The flow rate adjustment mechanism 272 in FIG. 1 is installed between the refrigerant outlet POB of the second heat exchange section 211B and the junction of the refrigerant flow paths. The flow rate adjustment mechanism 272 is fully open unless otherwise specified.

The outdoor heat exchanger 211 further includes a plurality of fins 211F that are provided in common to the first heat exchange section 211A and the second heat exchange section 211B. The plurality of fins 211F are arranged in layers from the front to the back of the page with intervals provided to allow air to pass through.

The first heat exchange section 211A includes multiple pipes that pass through multiple fins 211F and connections that connect these multiple pipes on both sides. In FIG. 2, a circle indicates one pipe, a solid line indicates a connection that connects the pipes on the side facing the page, and a dashed line indicates a connection that connects the pipes on the side facing the page. This forms a single refrigerant flow path in which the refrigerant that flows in from the refrigerant inlet PIA flows out from the refrigerant outlet POA.

The second heat exchange section 211B, like the first heat exchange section 211A, includes multiple pipes penetrating multiple fins 211F and connections connecting these multiple pipes on both sides. In FIG. 2, a circle indicates one pipe, a solid line indicates a connection connecting the pipes on the side facing the page, and a dashed line indicates a connection connecting the pipes on the side facing the page. This forms a single refrigerant flow path in which the refrigerant flowing in from the refrigerant inlet PIB flows out from the refrigerant outlet POB.

Here, the flow rate adjustment mechanism 272 in FIG. 1 is installed on the refrigerant outlet POB side of the second heat exchange section 211B, but it may be installed on the refrigerant inlet PIB side. Also, the flow rate adjustment mechanism 272 may be installed upstream or downstream of the first heat exchange section 211A.

In FIG. 1, the flow of refrigerant in cooling operation mode is shown by a solid line, and the flow of refrigerant in heating operation mode is shown by a dashed line. Compressor 200 changes the frequency of compressor 200 so that the indoor temperature becomes the target (set) temperature.

Next, the control of the expansion valve 230 will be described. Figure 3 is a flowchart for explaining the control of the expansion valve 230.

First, in step S21, the control device 100 sets the opening of the expansion valve 230 to a default value. This default value will be described later with reference to Figures 8 to 10. After a certain period of time has elapsed, in step S22, the control device 100 initializes the variable Count to 0. If the variable Count is 1 or greater, this indicates that the expansion valve opening has been decreased multiple times, and if the variable Count is 0, this indicates that the expansion valve opening has not been decreased multiple times.

Then, in step S23, the control device 100 reduces the opening of the expansion valve 230 by a fixed value. After a fixed time has elapsed, in step S24, the control device 100 determines whether the degree of refrigerant superheat SH at the evaporator outlet has changed.

During cooling operation, the degree of refrigerant superheat SH at the evaporator outlet is calculated by subtracting the evaporation temperature T262 obtained by the temperature sensor 262 from the evaporator outlet temperature T263 obtained by the temperature sensor 263. On the other hand, during heating operation, the degree of refrigerant superheat SH at the evaporator outlet is calculated by subtracting the evaporation temperature T264 obtained by the temperature sensor 264 from the evaporator outlet temperature T265 obtained by the temperature sensor 265.

If the answer in step S24 is NO, that is, if there is no change in the degree of refrigerant superheat SH at the evaporator outlet, it is considered that the state of the refrigerant at the evaporator outlet has not changed from the two-phase gas-liquid state. Therefore, in step S25, the control device 100 adds 1 to the variable Count, and then returns to the process in step S23, decreasing the opening degree of the expansion valve 230 by a fixed value.

By repeating the processes of steps S23 to S25, if liquid refrigerant is present up to the evaporator outlet at the default opening in step S21, the refrigerant superheat degree SH at the evaporator outlet can be brought to an optimal state where the refrigerant superheat degree SH at the evaporator outlet is approximately 0. On the other hand, if the determination in step S24 is YES (if the refrigerant state at the evaporator outlet is a superheated gas state), the control device 100 proceeds to step S26 and determines whether the variable Count is 0.

If step S26 returns NO, i.e., if the variable Count is not 0, the refrigerant superheat degree SH at the evaporator outlet has been appropriately controlled in steps S23 to S25, and the control device 100 ends the process of determining the opening degree of the expansion valve 230.

On the other hand, if the answer is YES in step S26, the variable Count is 0, so step S24 is passed through in one go without going through step S25. At the default opening in step S21, the evaporator outlet is in a superheated gas state, and the degree of superheat (SH) is further increased in step S23, so this cannot be said to be an appropriate state. Therefore, in step S27, the opening of the expansion valve 230 is increased by a fixed value. Then, after a fixed time has elapsed, in step S28, it is determined whether there has been a change in the value of the refrigerant superheat SH at the evaporator outlet.

If step S28 returns YES, that is, if there has been a change in the refrigerant superheat degree SH at the evaporator outlet, the process returns to step S27 and increases the opening degree of the expansion valve 230 by a fixed value since there has been a change in the value of the refrigerant superheat degree SH at the evaporator outlet. By repeating this process, an optimal state in which the refrigerant superheat degree SH at the evaporator outlet is approximately 0 can be achieved. On the other hand, if step S28 returns NO, that is, if there has been no change in the refrigerant superheat degree SH at the evaporator outlet, the evaporator outlet refrigerant can be determined to be in two phases (superheat degree 0) and the heat exchange efficiency in the evaporator is good, so the process of determining the opening degree of the expansion valve 230 is terminated.

The reason that the heat exchange efficiency in the evaporator is good when the degree of superheat = 0 is that in the gas phase, only sensible heat is exchanged, but in the two-phase, sensible heat + latent heat can be exchanged. When the degree of superheat = 0, the evaporator is in a two-phase state from the inlet to the outlet, so it has good heat exchange capacity, and the refrigerant sent to the compressor is in a gas state, so liquid compression can be prevented.

The above describes the flow of control of the expansion valve 230. In the flowchart of FIG. 3, control is performed based on the value of the refrigerant superheat degree SH at the evaporator outlet, but it is also possible to predetermine a target value for the superheat degree or discharge refrigerant temperature of the discharge refrigerant of the compressor 200 corresponding to the value of the refrigerant superheat degree SH at the evaporator outlet, and control the expansion valve 230 based on the superheat degree or discharge refrigerant temperature of the discharge refrigerant.

The refrigerant superheat degree SH at the evaporator outlet used in the flowchart of Figure 3 changes if there is a pressure loss between the temperature sensors or if there is a temperature gradient in the refrigerant. For refrigerants (low pressure refrigerants, e.g. 1234yf, propane, etc.) that have a larger pressure loss than currently mainstream refrigerants such as R32, the value of the refrigerant superheat degree SH at the evaporator outlet calculated using this method will be smaller, and for refrigerants with a large temperature gradient (non-azeotropic refrigerant mixtures), the value of the refrigerant superheat degree SH at the evaporator outlet calculated using this method will be larger.

In addition, in reality, if the degree of superheat (SH) is about 5 degrees, the performance of the evaporator does not decrease significantly, so some error is acceptable. Therefore, in steps S24 and S28, the control device 100 may control the degree of superheat (SH) to 5 degrees or less.

Next, the control of the flow rate adjusting mechanism 272 will be described.
Fig. 4 is a diagram showing the change in capacity of the air conditioner when the opening degree of the flow rate adjustment mechanism 272 is changed when the operating frequency of the compressor is at the lower limit frequency Fmin during cooling operation. The vertical axis of Fig. 4 shows the capacity of the air conditioner, with 100% being when the flow rate adjustment mechanism 272 is fully open. The horizontal axis shows the circulation flow rate ratio (%) that changes according to the opening degree of the flow rate adjustment mechanism 272.

The capacity ratio (%) shown on the vertical axis is a numerical value obtained by dividing (capacity of air conditioning device 1000) by (capacity of air conditioning device 1000 at a circulation flow rate ratio of 100%), expressed as a percentage. The circulation flow rate ratio (%) shown on the horizontal axis is a numerical value obtained by dividing (refrigerant flow rate flowing through second heat exchange section 211B) by (refrigerant flow rate flowing through first heat exchange section 211A), expressed as a percentage. If the circulation flow rate ratio is reduced to 50%, it is possible to reduce the capacity of air conditioning device 1000 by approximately 20%. If the flow rate adjustment mechanism 272 is fully closed and the refrigerant flow rate flowing through second heat exchange section 211B is set to 0, it is possible to reduce the capacity of air conditioning device 1000 to almost 0.

Fig. 5 is a ph diagram of an air conditioner when the circulation flow rate ratio is 100%. Fig. 6 is a ph diagram of an air conditioner when the circulation flow rate ratio is 19%. Figs. 5 and 6 show the case where the air volume is fixed at the same 24 m ³ /min.

The reason why the capacity decreases when the opening degree of the flow rate adjustment mechanism 272 is reduced is explained below. When the opening degree of the flow rate adjustment mechanism 272 is reduced, the refrigerant flow rate flowing through the second heat exchange section 211B is reduced, and the amount of heat exchange in the second heat exchange section 211B is reduced. Then, the refrigerant passing through the second heat exchange section 211B is more likely to complete heat exchange on the way from the refrigerant inlet PIB to the refrigerant outlet POB (or completes heat exchange completely), and the refrigerant temperature at the refrigerant outlet POB approaches the air temperature (or becomes completely the same as the air temperature). In other words, the amount of liquid refrigerant increases, and the amount of refrigerant in the second heat exchange section 211B increases. Therefore, the amount of refrigerant in the first heat exchange section 211A decreases, that is, the enthalpy of the refrigerant outlet POA also increases. As a result, the outlet enthalpy at the junction where the temperature sensor 264 is installed increases, and the evaporator inlet enthalpy also increases. As a result, as shown in FIG. 6, the enthalpy difference between the evaporator outlet and inlet decreases, and the air conditioning capacity decreases.

In other words, compared to the refrigeration cycle (C1-C2-C3-C4) shown in Figure 5 (circulation flow ratio 100%), the refrigeration cycle (C11-C12-C13-C14) shown in Figure 6 (circulation flow ratio 19%) is shorter in length in the horizontal direction (specific enthalpy direction). Note that points C1 and C11 indicate the state of the evaporator outlet. Points C2 and C12 indicate the state of the compressor outlet. Points C3 and C13 indicate the state of the refrigerant confluence point where temperature sensor 264 is installed. Points C4 and C14 indicate the state of the evaporator inlet.

Heat exchange capacity and heat exchange amount Q [kW] are expressed as the refrigerant circulation flow rate Gr [kg/s] x enthalpy difference Δh [kJ/kg]. Therefore, the capacity decreases as the enthalpy difference, which is the length in the horizontal direction, decreases.

This means that even with the same air volume and compressor frequency, by changing the circulation flow ratio, it is possible to create a heat exchanger that reduces the air conditioning capacity by about half.

In this way, when the compressor 200 is operating at the lower limit frequency Fmin, it is possible to reduce the capacity of the air conditioning device by decreasing the opening of the flow rate adjustment mechanism 272 and lowering the circulation flow rate ratio.

FIG. 7 is a flowchart for explaining the control of the flow rate adjustment mechanism 272. First, in step S31 of FIG. 7, the control device 100 determines whether the operating frequency F of the compressor 200 is the lower limit frequency Fmin.

If step S31 returns NO, that is, if the operating frequency F is greater than the lower limit frequency Fmin, the compressor 200 can perform normal control, increasing or decreasing the operating frequency F of the compressor 200 so that the indoor temperature becomes the set temperature. For this reason, the control device 100 ends the process by fully opening the flow rate adjustment mechanism 272 in step S37. As described above, the control device 100 controls the opening rate of the flow rate adjustment mechanism 272 to be fully open when the operating frequency F of the compressor 200 is other than the lower limit frequency Fmin. In this case, the control device 100 sets the rotation speed of the outdoor fan 220 to the rotation speed N corresponding to the operating frequency F of the compressor 200.

On the other hand, if the answer is Yes in step S31, the control device 100 determines whether the indoor heat exchange capacity of the air conditioner is greater than the indoor load.

Specifically, whether or not the indoor heat exchange capacity of the air conditioner is greater than the indoor load is determined by the following formula (1).
|Ta(end)-Ts|>|(Ta(start)-Ts)| ... (1)
Here, Ts indicates the indoor set temperature of the air conditioner, Ta(start) indicates the temperature detected by the temperature sensor 261 at the start of step S32, and Ta(end) indicates the temperature detected by the temperature sensor 261 when a certain time has elapsed since the start of step S32. The certain time is, for example, about several minutes.

The above formula (1) holds true when the difference between the indoor temperature after a certain time has passed and the set temperature (|Ta(end) - Ts|) is greater than the difference between the indoor temperature at the start and the set temperature (|(Ta(start) - Ts)|). In other words, this is the case when the indoor temperature has deviated from the set temperature after a certain time has passed, in which case the indoor heat exchange capacity is greater than the indoor load.

If step S32 returns YES, the capacity of the air conditioning device is greater than the indoor load even at the lower limit frequency Fmin, so the process proceeds to step S33, where the control device 100 determines whether the flow rate adjustment mechanism 272 is fully closed. If step S33 returns NO, the control device 100 reduces the opening of the flow rate adjustment mechanism 272 by a fixed value in step S34. This reduces the amount of heat exchanged in the second heat exchange section 211B, and reduces the air conditioning capacity. Then, in step S35, the control device 100 controls the opening of the expansion valve 230. The reason for performing step S35 after step S34 will be explained below.

If the opening of the flow rate adjustment mechanism 272 is reduced by a certain value in step S34 without controlling the opening of the expansion valve 230, that is, with the opening fixed at the time of the initial transition to step S32, the circulation flow rate will decrease, resulting in operation with the refrigerant superheat SH at the evaporator outlet becoming too high, and the COP of the air conditioner will deteriorate. Therefore, by implementing the control of the expansion valve 230 shown in Figure 3 in step S35, it is possible to maintain the refrigerant superheat SH at the evaporator outlet at an appropriate value.

At this time, in order to quickly bring the refrigerant superheat SH at the evaporator outlet to an appropriate value, the opening value of the expansion valve 230 in step S21 should be set to an opening corresponding to the Cv value ratio calculated using the approximation formula when first moving to step S32. Alternatively, in step S35, the control of the expansion valve 230 shown in FIG. 3 may not be performed, and the opening may be directly changed to an opening corresponding to the Cv value ratio calculated using the approximation formula. In this case, if the accuracy of the approximation formula is high, the same results will be obtained as when the control in FIG. 3 is performed.

The approximation formula will be explained using Figs. 8 to 10. Fig. 8 shows the change in the Cv value of the expansion valve 230 when the opening degree of the flow rate adjustment mechanism 272 is changed when the operating frequency of the compressor 200 is at the lower limit frequency Fmin during cooling operation. Fig. 9 shows the approximation formula for the region where the circulation flow rate ratio is large. Fig. 10 shows the approximation formula for the region where the circulation flow rate ratio is small.

FIG. 8 shows that the smaller the opening of the flow rate adjustment mechanism 272 (the smaller the circulation flow rate ratio), the larger the opening of the expansion valve 230 must be. This is because the expansion valve 230 is controlled to keep the refrigerant superheat degree SH at the evaporator outlet constant by the control shown in FIG. 3. When the opening of the flow rate adjustment mechanism 272 is changed when the operating frequency of the compressor 200 is at the lower limit frequency, it is desirable to make the refrigerant superheat degree SH at the evaporator outlet reach an appropriate value quickly in order not to lower the COP of the air conditioner. For example, if the circulation flow rate ratio is 19%, the setting value of the opening of the expansion valve 230 in step S21 of FIG. 3 may be set to the opening of the expansion valve 230 corresponding to 338% of the Cv value when the circulation flow rate ratio is 100%. To find the setting value of the Cv value of the expansion valve 230 at any circulation flow rate ratio, an approximation formula of the graph in FIG. 8 may be created.

In Figure 8, the slope of the graph is significantly different between the range where the circulation flow ratio is 19% to 100% and the range where the circulation flow ratio is 0 to 19%. When this range is converted in Figure 4, it becomes the range where the capacity ratio is 41% to 100% and the range where the capacity ratio is 0% to 41%. An approximation formula was created by dividing the region into these two regions.

9, when the circulation flow rate ratio is indicated by x and the Cv value ratio of the expansion valve 230 is indicated by y, in the region of x>19%, the approximation is expressed as y=-2.8009x+3.7344. In this case, ^R2 is 0.9763.

10, when the circulation flow rate ratio is indicated by x and the Cv value ratio of the expansion valve 230 is indicated by y, in the region where x<19%, the approximation is expressed as y=-34.246x+9.5616. In this case, ^R2 is 0.9782.

The coefficient of determination ^R2 of the fitting results shown in FIG. 9 and FIG. 10 is 0.97 or more, which indicates that good approximation is achieved by linear approximation.

Returning to FIG. 7, after controlling the opening degree of the expansion valve 230 in step S35, the process proceeds to step S32, where the balance between the air conditioning capacity and the indoor load is determined again.

In this case, reversing the order of steps S34 and S35, i.e. increasing the opening of the expansion valve 230 and then decreasing the opening of the flow rate control mechanism 272, is not desirable because it can cause a breakdown in the compressor 200. The reason for this is that the refrigerant superheat SH at the evaporator outlet decreases, increasing the risk of liquid refrigerant returning to the suction section of the compressor 200, which could result in liquid compression.

On the other hand, if the answer is No in step S32, the capacity of the air conditioner is equal to or less than the indoor load, so the compressor 200 can perform normal control, accelerating the operating frequency F of the compressor 200 (or maintaining it at Fmin) so that the indoor temperature becomes the set temperature, and the control device 100 ends the processing in FIG. 7.

Also, if the determination in step S33 is YES, the flow rate adjustment mechanism 272 is fully closed, and the air conditioning capacity cannot be reduced any further. Therefore, the control device 100 turns off the thermostat of the compressor 200 in step S36, and ends the processing in FIG. 7.

The control flow of the flow rate adjusting mechanism 272 has been described above.
11 is a diagram showing the results during heating operation. Unlike during cooling operation, it is shown that the capacity does not decrease as much as during cooling operation even if the opening degree of the flow rate adjustment mechanism 272 is reduced. The reason for this will be explained below.

When the opening degree of the flow rate adjustment mechanism 272 is reduced, the refrigerant flow rate flowing through the second heat exchange section 211B decreases, and the amount of heat exchanged in the second heat exchange section 211B decreases. As a result, the refrigerant passing through the second heat exchange section 211B is more likely to complete heat exchange on the way from the refrigerant inlet PIB to the refrigerant outlet POB (or completes heat exchange completely), and the refrigerant temperature at the refrigerant outlet POB approaches the air temperature (or becomes completely the same as the air temperature). In other words, the amount of gas refrigerant increases, and the amount of refrigerant in the second heat exchange section 211B decreases. As a result, the amount of refrigerant in the first heat exchange section 211A increases, and the enthalpy difference between the evaporator inlet and outlet (the place where the temperature sensor 264 is installed and the place where the temperature sensor 265 is installed) decreases, resulting in a decrease in the air conditioning capacity.

The above is the same as during cooling operation. However, the amount of reduction in capacity is smaller than during cooling operation. This is because the first heat exchanger 211A and the second heat exchanger 211B are used as evaporators during heating operation, so the density of the refrigerant is small and the amount of change in the refrigerant is small.

As explained above, by decreasing the opening of the flow rate control mechanism 272 during cooling operation, it is possible to reduce the capacity. Similarly, if the indoor heat exchanger is configured to allow refrigerant to flow in parallel and a flow rate control mechanism is provided in at least one of the flow paths, it is also possible to reduce the capacity during heating operation.

<Modification>
2 shows an example in which the first heat exchange section 211A and the second heat exchange section 211B are configured in one outdoor heat exchanger 211. Several modified examples of the heat exchanger will be described.

FIG. 12 is a diagram showing a first modified example in which the configuration of the outdoor heat exchanger 211 is changed. As shown in FIG. 12, a first heat exchange section 211A and a second heat exchange section 211B may be configured as a divided heat exchanger. A divided configuration refers to one in which the fins are provided separately as fins 211FA and fins 211FB. With such a configuration, when a large heat exchanger is required, it is possible to realize heat exchangers of various capacities by increasing or decreasing the number of small heat exchangers without having to design a new one.

FIG. 13 is a diagram showing a second modified example in which the configuration of the outdoor heat exchanger 211 is changed. In the configuration shown in FIG. 13, the outdoor heat exchanger 211 has one refrigerant inlet, and the refrigerant flow path is divided into two midway. The outdoor heat exchanger 211 may also be configured as shown in FIG. 13.

FIG. 14 is a diagram showing a third modified example in which the configuration of the flow rate adjustment mechanism has been changed. The modified air conditioner 1010 shown in FIG. 14 includes a flow rate adjustment mechanism 270 that controls the flow rate of refrigerant flowing through the first heat exchange section 211A and the second heat exchange section 211B, instead of the flow rate adjustment mechanism 272 in the configuration of the air conditioner 1000. Even with this configuration, it is possible to reduce capacity by decreasing the circulation flow rate of the refrigerant flowing on one side.

As explained above, the air conditioner according to embodiment 1 can reduce the capacity when the operating frequency of the compressor is at the lower limit frequency, and can improve comfort by reducing the frequency of on-off operation. When the heat exchanger in which the flow rate adjustment mechanism 272 is installed acts as a condenser, as shown in FIG. 4, it is possible to reduce the capacity ratio of the second heat exchange section 211B to almost 0, that is, to reduce the capacity (air conditioning capacity) of the air conditioner to almost 0.

Embodiment 2.
Figure 15 is a diagram showing the configuration of an air conditioning apparatus 1200 according to embodiment 2. Regarding air conditioning apparatus 1200, only the differences from air conditioning apparatus 1000 shown in Figure 1 will be explained. Whereas air conditioning apparatus 1000 shown in Figure 1 has one outdoor blower (fan) 220, configuration 2 has two outdoor blowers (fans) 221 and 222.

FIG. 16 is a diagram showing an example of the configuration of the outdoor heat exchanger 211 in FIG. 15. Fan 221 is provided corresponding to the first heat exchange section 211A, and fan 222 is provided corresponding to the second heat exchange section 211B. The rotation speeds of

fans

221 and 222 can be controlled independently of each other by the control device 100. Therefore, in addition to adjusting the refrigerant flow rate with the flow rate adjustment mechanism 272, the air conditioning capacity of the air conditioner can be further changed by setting the rotation speeds of

fans

221 and 222 to different speeds, or by rotating one of

fans

221 and 222 and stopping the other.

FIG. 17 is a flowchart for explaining the control of the flow rate adjustment mechanism 272 and the

fans

221, 222. In the flowchart shown in FIG. 17, step S34 in the flowchart shown in FIG. 7 is changed to step S44, step S35 to step S45, and step S37 to step S47. Other processes are similar, so the description will not be repeated.

In step S44, the control device 100 reduces the opening degree of the flow rate adjustment mechanism 272 by a fixed value, and also reduces the rotation speed N of the fan 221 corresponding to the first heat exchange section 211A by a fixed value. This not only reduces the amount of heat exchanged in the second heat exchange section 211B, but also reduces the amount of heat exchanged in the first heat exchange section 211A by reducing the airflow rate of the fan 221. This makes it possible to further reduce the air conditioning capacity compared to step S34 in FIG. 7.

The decrease in the rotation speed N of the fan 221 when the compressor is at the lower limit frequency Fmin will be explained later in Figure 18.

The reason for reducing the rotation speed N of fan 221 instead of fan 222 will be explained. By reducing the opening of flow rate adjustment mechanism 272, the refrigerant flow rate of second heat exchange section 211B corresponding to fan 222 decreases, and the heat exchange amount of second heat exchange section 211B decreases. Therefore, even if the rotation speed of fan 222 is reduced, the effect is small because the heat exchange amount has already decreased. On the other hand, the air volume needs to be maintained at a constant amount in order to reflect the user's settings to some extent. Therefore, in step S44, control device 100 reduces rotation speed N of fan 221 while maintaining the rotation speed of fan 222.

After performing the process of step S44 in FIG. 17, in step S45 the control device 100 controls the opening of the expansion valve 230 according to the flowchart shown in FIG. 3. The value of the opening of the expansion valve 230 in step S21 may be set to the opening at the time of the initial transition to step S32, which corresponds to the Cv value ratio calculated using the approximation formula (shown later in FIGS. 20 to 22). Alternatively, in step S45, the control of the expansion valve 230 shown in FIG. 3 may not be performed, and the opening may be directly changed to the opening corresponding to the Cv value ratio calculated using the approximation formula. In this case, if the accuracy of the approximation formula is high, the same result as when the control of FIG. 3 is performed will be obtained.

In this case, if the order of steps S44 and S45 is reversed, that is, the opening of the expansion valve 230 is increased and then the opening of the flow rate control mechanism 272 is decreased, the refrigerant superheat SH at the evaporator outlet will decrease, increasing the risk of liquid refrigerant returning to the intake of the compressor 200, which is undesirable as it could cause a breakdown in the compressor 200.

In step S47, the control device 100 fully opens the flow rate adjustment mechanism 272 and sets the rotation speed of the

fans

221, 222 to the rotation speed N that corresponds to the operating frequency F of the compressor 200.

FIG. 18 is an example of a map referenced in steps S44 and S47 of FIG. 17. In FIG. 18, the horizontal axis shows the operating frequency F of the compressor 200, and the vertical axis shows the fan rotation speed N.

When the operating frequency F of the compressor 200 is higher than the lower limit frequency Fmin, the control device 100 sets the

fans

221 and 222 to the same rotation speed according to the map shown in FIG. 18. That is, when the operating frequency F is higher than Fmin and equal to or lower than F1, the control device 100 sets the rotation speeds of the

fans

221 and 222 to the rotation speed N4 (low rotation). When the operating frequency F is higher than F1 and equal to or lower than F2, the control device 100 sets the rotation speeds of the

fans

221 and 222 to the rotation speed N5 (medium rotation). When the operating frequency F is higher than F2, the control device 100 sets the rotation speeds of the

fans

221 and 222 to the rotation speed N6 (high rotation).

On the other hand, when the operating frequency F is Fmin, the control device 100 reduces the rotation speed of the fan 221 in stages from N4 to N3, N2, N1, and 0, while maintaining the rotation speed of the fan 222 at N4. Alternatively, the rotation speed of the fan 221 may be reduced all at once from N4 to 0. At this time, the reduction rate of the rotation speed of the fan 221 may be determined based on the ratio between the flow rate of the refrigerant passing through the first heat exchanger 211A and the flow rate of the refrigerant passing through the second heat exchanger 211B.

Figure 19 shows the change in capacity of the air conditioner when the opening of the flow rate adjustment mechanism 272 and the rotation speed of the fan 221 are changed when the operating frequency F of the compressor 200 is at the lower limit frequency Fmin during cooling operation. The results indicated by the triangles in Figure 19 are the same as those in Figure 4, and show the results when only the flow rate is adjusted and the fan is controlled in the same way as in embodiment 1. The results indicated by the squares in Figure 19 show the results when the rotation speed of the fan 221 is controlled as in Figure 18 in addition to the flow rate adjustment. Note that the reduction in the rotation speed of the fan 221 is set to the same as the circulation flow rate ratio. In other words, the rotation speed of the fan 221 when the circulation flow rate ratio is 50% is set to 50% of the rotation speed of the fan 222.

It can be seen that by adding control that changes the rotation speed of fan 221, the air conditioning capacity is further reduced even with the same circulation flow rate ratio.

Figure 20 is a diagram showing the Cv value ratio of the expansion valve 230 versus the circulation flow rate ratio in embodiment 2. It shows that the smaller the opening of the flow rate adjustment mechanism 272 (the smaller the circulation flow rate ratio), the larger the opening of the expansion valve 230 needs to be. This is because the expansion valve 230 keeps the refrigerant superheat degree SH at the evaporator outlet constant by the control flow shown in Figure 3. If the opening of the flow rate adjustment mechanism 272 is changed when the operating frequency of the compressor 200 is at the lower limit frequency, it is desirable to allow the refrigerant superheat degree SH at the evaporator outlet to reach an appropriate value as soon as possible in order not to lower the COP of the air conditioning device.

In the second embodiment, the default opening value of the expansion valve 230 in step S21 of FIG. 3 may be set to 304% of the Cv value of the expansion valve 230 when the circulation flow ratio is 100%, as shown in FIG. 20, if the circulation flow ratio is 28%. To find the set value of the Cv value of the expansion valve 230 for all circulation flow ratios, an approximation formula of the graph in FIG. 20 may be created.

In Figure 20, the slope of the graph is significantly different between the region where the circulation flow ratio is 28% to 100% and the region where the circulation flow ratio is 0 to 28%. For this reason, an approximation formula was created by dividing the range into two. Note that the region where the circulation flow ratio is 28% to 100% is the region where the capacity ratio is 41% to 100% when converted in Figure 19. Furthermore, the region where the circulation flow ratio is 0% to 28% is the region where the capacity ratio is 0% to 41% when converted in Figure 19.

21 is a diagram showing the fitting results and the approximation results for the region where the circulation flow rate ratio is 28% to 100%. In this region, the approximation formula is y = -2.7807x + 3.8615, and the coefficient of determination R ² = 0.988.

22 is a diagram showing the fitting results and the approximation results for the region where the circulation flow rate ratio is 0 to 28%. In this region, the approximation formula is y = -19.514x + 8.0881, and the coefficient of determination R ² = 0.9456.

In both cases of FIG. 21 and FIG. 22, the coefficient of determination ^R2 is 0.94 or more, which indicates that good approximation is achieved by linear approximation.

Figure 23 is a diagram showing the change in the capacity of the air conditioner with respect to the Cv value ratio of the expansion valve 230. It can be seen that the capacity of the air conditioner can be reduced by adding the change in the rotation speed of the fan 221, as shown by the square marks, compared to the case of only flow rate adjustment, as shown by the triangle marks, for the same Cv value ratio of the expansion valve 230. Since the operating frequency F of the compressor 200 is the lower limit frequency Fmin, the refrigerant flow rate is small, and the opening degree of the expansion valve 230 at a capacity ratio of 100% is small. Therefore, when the opening degree of the flow rate adjustment mechanism 272 is reduced, the opening degree of the expansion valve 230 can be increased and the capacity can be reduced, but only up to the capacity corresponding to the maximum opening degree of the expansion valve 230. For example, when the maximum opening degree is 500% in the Cv value ratio, the capacity ratio can be reduced to 30% by reducing the opening degree of the flow rate adjustment mechanism 272, but it is possible to further reduce the capacity ratio to 20% by adding a reduction in the rotation speed of the fan 221. Also, if the capacity ratio is to be reduced to 30%, the same as when the opening degree of the flow rate adjustment mechanism 272 is reduced, the Cv value ratio of the expansion valve 230 should be 410%. In other words, in the second embodiment, a small expansion valve with a small diameter can be used, which has the advantages of reducing costs and making it easier to handle the refrigerant piping around the expansion valve 230.

The above describes the case where the rotation speed of the fan 221 is gradually reduced as shown in FIG. 18. However, if the flow rate of the refrigerant passing through the second heat exchange section 211B is reduced to be lower than the flow rate of the refrigerant passing through the first heat exchange section 211A by the flow rate adjustment mechanism 272, the rotation speed of the fan 221 may be set to 0 while maintaining the rotation of the fan 222.

FIG. 24 corresponds to FIG. 19 when the rotation speed of the fan 221 is set to 0. FIG. 25 corresponds to FIG. 20 when the rotation speed of the fan 221 is set to 0.

Fig. 26 is a diagram corresponding to Fig. 21 when the rotation speed of the fan 221 is set to 0. As shown in Fig. 26, in the region where the circulation flow rate ratio is 28% to 100%, the approximation formula is y = -2.4127x + 4.0329, and the coefficient of determination R ² = 0.7603.

Fig. 27 is a diagram corresponding to Fig. 22 when the rotation speed of the fan 221 is set to 0. As shown in Fig. 27, in the region where the circulation flow rate ratio is 0 to 28%, the approximation formula is y = -18.992x + 7.7526, and the coefficient of determination R ² = 0.9664.

FIG. 28 is a diagram corresponding to FIG. 23 in the case where the rotation speed of the fan 221 is set to 0. In FIG.
24 to 28 with FIG. 19 to FIG. 23, it can be seen that, in FIG. 24 to 28, by setting the rotation speed of the fan 221 to 0, the capacity is further reduced at the same circulation flow rate ratio.

As explained above, the air conditioning apparatus of embodiment 2 has the same effect as embodiment 1, and in addition, when using the same expansion valve 230 as embodiment 1, it is possible to further reduce the air conditioning capacity by reducing the fan air volume.

In addition, if the reduction in air conditioning capacity is the same as in embodiment 1, there are advantages such as the expansion valve 230 being smaller and the refrigerant piping around the expansion valve 230 being easier to handle.

(Regarding the compressor used in the first and second embodiments)
Various types of compressors 200 can be adopted, such as a rotary type, a reciprocating type, a scroll type, a screw type, and the like. In particular, the compressor 200 is particularly effective when it is a rotary vane type. Fig. 29 is a diagram showing an example of the configuration of a rotary vane type compressor. The compression mechanism in the rotary compressor includes a cylinder 201, a piston 202, a vane 203, a spring 204, a suction port 206, a discharge port 207, and a rotating shaft 208.

The cylinder 201 is provided with a vane groove 201c that extends radially and is connected to the cylinder chamber, which is a circular space in FIG. 29, and that penetrates the cylinder in the axial direction. A vane 203 is slidably fitted into the vane groove 201c. A back pressure chamber 205 that introduces discharge pressure to the base of the vane groove 201c is provided, and the back pressure chamber 205 has a circular space in a plan view.

In the compression process of the rotary compressor, the inside of the cylinder 201 is divided into a high pressure region 201a and a low pressure region 201b by the vane 203. The high pressure region 201a is filled with refrigerant at discharge pressure (Pd), and the low pressure region 201b is filled with refrigerant at suction pressure (Ps). The vane 203 is in constant contact with the piston 202, enabling the refrigerant gas to be compressed. A check valve is provided at the discharge port 207, and when the pressure in the high pressure region 201a increases, the pressurized gas refrigerant is discharged from the discharge port 207. The resultant force of the forces acting toward the center of the cylinder 201 is called the pressing force, and the resultant force of the forces acting in the opposite direction of the cylinder 201 is called the separating force. As the operating frequency of the compressor decreases, the pressing force also decreases, so the lower limit frequency of the compressor is determined within the range where pressing force > separating force holds.

　The minimum frequency of a rotary vane compressor is determined by the above conditions, and it tends to be higher than that of other types of compressors. For this reason, the range in which the operating frequency of a rotary vane compressor can be lowered to reduce the air conditioning capacity is narrow.

The use of the air conditioning system shown in embodiments 1 and 2 has a significant effect in reducing the frequency of on-off operation when using a rotary vane compressor with a high lower limit frequency.

(summary)
The present embodiment will be summarized below with reference to the drawings again. Note that the units in parentheses are those applicable during cooling.

The present disclosure relates to an air conditioning device 1000. The air conditioning device 1000 includes a refrigerant circuit 500 including at least a compressor 200, a condenser (211), an expansion valve 230, and an evaporator (110) configured to circulate a refrigerant, and a control device 100 that controls the refrigerant circuit 500. As shown in FIG. 2, the condenser (211) includes a first heat exchanger 211A and a second heat exchanger 211B configured to allow the refrigerant to flow in parallel, and a flow rate adjustment mechanism 272 configured to adjust the flow rate of the refrigerant passing through the second heat exchanger 211B. The control device 100 is configured to be able to reduce the flow rate of the refrigerant passing through the second heat exchanger 211B by the flow rate adjustment mechanism 272 to be lower than the flow rate of the refrigerant passing through the first heat exchanger 211A when the operating frequency of the compressor 200 is a preset lower limit frequency Fmin. As shown in steps S34 and S35 of FIG. 7, when the air conditioning capacity of the refrigerant circuit 500 is greater than the indoor load, the control device 100 is configured to reduce the flow rate of the refrigerant passing through the second heat exchange section 211B using the flow rate adjustment mechanism 272, and then increase the opening of the expansion valve 230.

Preferably, the increase in the opening degree of the expansion valve 230 is determined based on the ratio between the flow rate of the refrigerant passing through the first heat exchange section 211A and the flow rate of the refrigerant passing through the second heat exchange section 211B. For example, the increase in the opening degree of the expansion valve 230 may be determined using the map shown in FIG. 8. Also, for example, the increase in the opening degree of the expansion valve 230 may be determined using the approximation formulas shown in FIG. 9 and FIG. 10.

Preferably, the flow rate adjustment mechanism 272 is installed downstream of the second heat exchange section 211B in the example of FIG. 1. The flow rate adjustment mechanism 272 may also be installed upstream of the second heat exchange section 211B.

Preferably, the air conditioning device 1000 further includes a temperature sensor 261 that detects the room temperature. The control device 100 is configured to determine whether the air conditioning capacity is greater than the indoor load based on the change in the difference between the temperature detected by the temperature sensor 261 and a set temperature that is a target temperature for the room temperature.

Preferably, the control device 100 is configured to control the expansion valve 230 so that the degree of superheat of the refrigerant at the outlet of the evaporator (110) or the refrigerant sucked into the compressor 200 is 5 degrees or less.

15 and 16, the condenser (211) preferably further includes a first fan (221) and a second fan (222) whose rotation speeds can be controlled independently of each other by the control device. The first fan (221) is provided corresponding to the first heat exchange section 211A, and the second fan (222) is provided corresponding to the second heat exchange section 211B. When the operating frequency of the compressor 200 is a preset lower limit frequency Fmin and the air conditioning capacity of the refrigerant circuit 500 is greater than the indoor load, the control device 100 uses the flow rate adjustment mechanism 272 to reduce the flow rate of the refrigerant passing through the second heat exchange section 211B to be lower than the flow rate of the refrigerant passing through the first heat exchange section 211A. When the flow rate of the refrigerant passing through the second heat exchange section 211B is reduced to less than the flow rate of the refrigerant passing through the first heat exchange section 211A by the flow rate adjustment mechanism 272, the control device 100 is configured to reduce the rotation speed of the first fan (221) to less than the rotation speed of the second fan (222), as described in FIG. 18.

More preferably, the rate of reduction in the rotation speed of the first fan (221) is determined based on the ratio between the flow rate of the refrigerant passing through the first heat exchange section 211A and the flow rate of the refrigerant passing through the second heat exchange section 211B.

More preferably, when the flow rate of the refrigerant passing through the second heat exchange section 211B is reduced to be lower than the flow rate of the refrigerant passing through the first heat exchange section 211A by the flow rate adjustment mechanism 272, the control device 100 is configured to stop the rotation of the first fan (221) while maintaining the rotation of the second fan (222), as shown in FIG. 24.

Preferably, the compressor 200 is of the rotary vane type as shown in FIG.
The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is defined by the claims, not by the description of the embodiments described above, and is intended to include all modifications within the meaning and scope of the claims.

100 control device, 101 CPU, 102 memory, 110, 210, 211, 212 heat exchanger, 120 indoor fan, 200 compressor, 201 cylinder, 201a high pressure area, 201b low pressure area, 201c vane groove, 202 piston, 203 vane, 204 spring, 205 back pressure chamber, 206 intake port, 207 discharge port, 208 rotating shaft, 211A first heat exchange section, 211B second heat exchange section, 211F, 21 1FA, 211FB fins, 220 outdoor fan, 221, 222 fan, 230 expansion valve, 240 four-way valve, 261, 262, 263, 264, 265 temperature sensor, 270, 272 flow rate adjustment mechanism, 310, 320 piping, 500 refrigerant circuit, 1000, 1010, 1200 air conditioning unit, 1001 outdoor unit, 1002 indoor unit, P1, P2, P3, P4 ports, PIA, PIB refrigerant inlet, POA, POB refrigerant outlet.

Claims

A refrigerant circuit including at least a compressor, a condenser, an expansion valve, and an evaporator, configured to circulate a refrigerant;
A control device for controlling the refrigerant circuit,
The condenser is
a first heat exchange unit and a second heat exchange unit configured to allow a refrigerant to flow in parallel;
a flow rate adjusting mechanism configured to adjust a flow rate of the refrigerant passing through the second heat exchange portion,
the control device is configured to be able to reduce a flow rate of the refrigerant passing through the second heat exchange unit to be lower than a flow rate of the refrigerant passing through the first heat exchange unit by the flow rate adjustment mechanism when an operation frequency of the compressor is a preset lower limit frequency,
The control device is configured to, when the air conditioning capacity of the refrigerant circuit is greater than the indoor load, reduce the flow rate of the refrigerant passing through the second heat exchange section using the flow control mechanism, and then increase the opening degree of the expansion valve.
The air conditioner of claim 1, wherein the increase in the opening degree of the expansion valve is determined based on the ratio of the flow rate of the refrigerant passing through the first heat exchange section to the flow rate of the refrigerant passing through the second heat exchange section.
The air conditioner according to claim 1 or 2, wherein the flow rate adjustment mechanism is installed upstream or downstream of the second heat exchanger.
Further comprising a temperature sensor for detecting a room temperature;
The air conditioning apparatus according to any one of claims 1 to 3, wherein the control device is configured to determine whether the air conditioning capacity is greater than the indoor load based on a change in the difference between the temperature detected by the temperature sensor and a set temperature which is a target temperature for the room temperature.
The air conditioner according to any one of claims 1 to 4, wherein the control device is configured to control the expansion valve so that the degree of superheat of the refrigerant at the outlet of the evaporator or the refrigerant sucked into the compressor is 5 degrees or less.
the condenser further includes a first fan and a second fan whose rotation speeds are independently controllable by the control device;
the first fan is provided corresponding to the first heat exchange unit, and the second fan is provided corresponding to the second heat exchange unit,
The air conditioning apparatus of any one of claims 1 to 5, wherein the control device is configured to reduce the rotation speed of the first fan to be lower than the rotation speed of the second fan when the flow rate of the refrigerant passing through the second heat exchange section is reduced by the flow control mechanism to be lower than the flow rate of the refrigerant passing through the first heat exchange section.
The air conditioner of claim 6, wherein the rate of reduction in the rotational speed of the first fan is determined based on the ratio of the flow rate of the refrigerant passing through the first heat exchange section to the flow rate of the refrigerant passing through the second heat exchange section.
The air-conditioning device according to claim 6, wherein the control device is configured to stop the rotation of the first fan while maintaining the rotation of the second fan when the flow rate of the refrigerant passing through the second heat exchange unit is reduced by the flow rate adjustment mechanism to be lower than the flow rate of the refrigerant passing through the first heat exchange unit.
An air conditioner according to any one of claims 1 to 8, wherein the compressor is of a rotary vane type.