Air conditioner

Abstract

An outdoor unit (10) includes a compressor (11) and an outdoor heat exchanger (13). An indoor unit (20) includes an expansion valve (24), a first indoor heat exchanger (21), a second indoor heat exchanger (22), a blower (28), and a blower (29). A refrigerant circuit (110) is configured to circulate a refrigerant during a cooling operation in the order of the compressor (11), the outdoor heat exchanger (13), the second indoor heat exchanger (22), the expansion valve (24), and the first indoor heat exchanger (21). The second indoor heat exchanger (22) is configured such that each of outdoor air (OA) flowing through an air supply path and indoor air (RA) flowing through an air exhaust path can pass therethrough. The indoor unit (20) further comprises a switching device that can switch between a state in which the second indoor heat exchanger (22) is positioned in the air supply path and a state in which the second indoor heat exchanger is positioned in the air exhaust path. The first indoor heat exchanger (21) is disposed on the upstream side from the second indoor heat exchanger (22) in the air supply path.

Description

air conditioner

[0001] The present disclosure relates to an air conditioner.

[0002] One type of air conditioner is an outdoor air processing unit that adjusts the temperature of air drawn in from outdoors and brings it indoors, while also discharging indoor air outdoors. As an outdoor air processing unit, Japanese Patent Application Laid-Open Publication No. 2021-076290 (Patent Document 1) discloses a technology related to a reheat dehumidification operation in which outdoor air is cooled and dehumidified using a first heat exchanger, and then reheated using a second heat exchanger installed downstream of the first heat exchanger in the air duct. Reheating refers to heating air that has been cooled once.

[0003] Reheat dehumidification operation is required when the load conditions are high, with a high latent heat load, and low sensible heat load. Latent heat refers to heat that undergoes a change in state, while sensible heat refers to heat that undergoes a change in temperature. A load condition with a high latent heat load and a low sensible heat load is when there is a high demand for dehumidification but the temperature does not need to be lowered too much. In such cases, the technology disclosed in Japanese Patent Laid-Open Publication No. 2021-076290 (Patent Document 1) can be applied.

[0004] Japanese Patent Application Laid-Open No. 2021-076290

[0005] However, under load conditions where the latent heat load is low and the sensible heat load is sufficiently large, reheating is not necessary. A load condition where the latent heat load is low and the sensible heat load is sufficiently large is a condition where the dehumidification requirement is not high, but the temperature needs to be lowered. The technology of JP 2021-076290 A (Patent Document 1) cannot meet the requirements in such cases.

[0006] An object of the present disclosure is to provide an air conditioner that is capable of highly efficient operation both when reheating is required and when reheating is not required.

[0007] The present disclosure provides a refrigerant circuit including an outdoor unit and an indoor unit. The outdoor unit includes a compressor that compresses and discharges a refrigerant, and an outdoor heat exchanger. The indoor unit includes a first expansion valve that decompresses the refrigerant, a first indoor heat exchanger, a second indoor heat exchanger, an air supply device that takes outdoor air into the room through an air supply duct, and an exhaust device that discharges indoor air to the outside through an exhaust duct. The refrigerant circuit is configured so that refrigerant circulates through the compressor, the outdoor heat exchanger, the second indoor heat exchanger, the first expansion valve, and the first indoor heat exchanger in this order during cooling operation. The second indoor heat exchanger is configured to allow both outdoor air flowing through the air supply duct and indoor air flowing through the exhaust duct to pass through. The indoor unit further includes a switching device that can switch the second indoor heat exchanger between being positioned in the air supply duct and being positioned in the exhaust duct. When the switching device positions the second indoor heat exchanger in the supply air duct, the first indoor heat exchanger is positioned upwind of the second indoor heat exchanger in the supply air duct.

[0008] According to the air conditioner of the present disclosure, it is possible to operate with high efficiency both when reheating is required and when reheating is not required.

[0009] 1 is a schematic diagram showing the configuration of an air conditioner in embodiment 1. FIG. 1 is a schematic diagram showing the configuration of an indoor unit in embodiment 1. FIG. 2 is a diagram showing a refrigerant circuit of the air conditioner in embodiment 1. FIG. 3 is a flowchart showing damper control during cooling operation in embodiment 1. FIG. 4 is a diagram showing an example of damper operation in embodiment 1. FIG. 5 is a diagram showing an example of damper operation in embodiment 1. FIG. 6 is a refrigerant state transition diagram in embodiment 1. FIG. 7 is a flowchart showing damper control during cooling operation in embodiment 2. FIG. 8 is a diagram showing an example of damper operation in embodiment 2. FIG. 9 is a schematic diagram showing the configuration of an indoor unit in embodiment 3. FIG. 10 is a flowchart showing damper control during cooling operation in embodiment 3. FIG. 11 is a diagram showing an example of damper operation in embodiment 3. FIG. 12 is a diagram showing a refrigerant circuit of an air conditioner in embodiment 4. FIG. 13 is a flowchart showing damper control during heating operation in embodiment 4.

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the embodiments described below, when numbers, quantities, etc. are mentioned, the scope of the present disclosure is not necessarily limited to those numbers, quantities, etc., unless otherwise specified. The same reference numerals are used for the same or equivalent parts, and redundant descriptions may not be repeated. It is intended from the beginning that the configurations in the embodiments may be used in appropriate combinations.

[0011] Embodiment 1. Figure 1 is a schematic diagram showing the configuration of an air conditioner 100 in embodiment 1. The air conditioner 100 includes an outdoor unit 10, an indoor unit 20, and refrigerant piping 30. Figure 1 shows a schematic diagram of the indoor unit 20 as seen from the side. The outdoor unit 10 and the indoor unit 20 are connected by the refrigerant piping 30. The indoor unit 20, which is an outdoor air processing unit, is located in the attic 101. The indoor unit 20 takes in outdoor air OA into a duct 40 and blows it out from an outlet 41 as supply air SA. The indoor unit 20 takes in room air RA into the duct 40 via an inlet 42 and blows it out to the outdoors as exhaust air EA.

[0012] The indoor unit 20 includes, within its main casing, an intake air temperature detection unit 50 and an outdoor air temperature detection unit 51. The intake air temperature detection unit 50 is a device configured with a temperature sensor for measuring the temperature of the intake air SA blown into the room. The outdoor air temperature detection unit 51 is a device configured with a temperature sensor for measuring the temperature of the outdoor air OA taken into the room from outdoors.

[0013] Figure 2 is a schematic diagram showing the configuration of the indoor unit 20 in Embodiment 1. Figure 2 shows a schematic diagram of the indoor unit 20 as seen from above. The indoor unit 20 includes, within its main body casing, a first indoor heat exchanger 21, a second indoor heat exchanger 22, an intake air blower 28, an exhaust air blower 29, and a reheat damper made up of a first damper 23a and a second damper 23b. The various arrows in Figure 2 indicate the flow of air.

[0014] The first indoor heat exchanger 21 and the second indoor heat exchanger 22 are indoor heat exchangers that exchange heat between the refrigerant and the air. Outdoor air OA is passed through the first indoor heat exchanger 21 by a blower 28 serving as an air supply device and then supplied into the room as supply air SA. The air path through which the outdoor air OA flows into the room is called the supply air path. On the other hand, the room air RA is exhausted to the outside as exhaust air EA by a blower 29 serving as an exhaust device. The air path through which the room air RA flows to the outside is called the exhaust air path.

[0015] 2, the reheat damper, which is a switching device made up of a first damper 23a and a second damper 23b, can switch between a state in which the second indoor heat exchanger 22 is positioned in the supply air duct and a state in which the second indoor heat exchanger 22 is positioned in the exhaust air duct. In this way, the second indoor heat exchanger 22 is configured to allow both the air flowing through the supply air duct and the air flowing through the exhaust air duct to pass through.

[0016] By switching between the first damper 23a and the second damper 23b, the outdoor air OA flows through the supply air duct in one of two ways: after passing through the first indoor heat exchanger 21, it flows into the room without passing through the second indoor heat exchanger 22, or after passing through the first indoor heat exchanger 21, it flows into the room through the second indoor heat exchanger 22.

[0017] By switching between the first damper 23a and the second damper 23b, the indoor air RA flows through the exhaust air duct in either a pattern in which it passes through the second indoor heat exchanger 22 and then flows to the outdoors, or a pattern in which it flows to the outdoors without passing through the second indoor heat exchanger 22.

[0018] Figure 3 is a diagram showing a refrigerant circuit 110 of an air conditioner 100 according to Embodiment 1. As shown in Figure 3, the air conditioner 100 includes an outdoor unit 10 and an indoor unit 20. The outdoor unit 10 and the indoor unit 20 are connected by refrigerant piping 30 to form the refrigerant circuit 110. The outdoor unit 10 includes a compressor 11, a four-way valve 12, an outdoor heat exchanger 13, and a blower 14 serving as an outdoor unit fan. The indoor unit 20 includes a first indoor heat exchanger 21, a second indoor heat exchanger 22, an expansion valve 24, and temperature sensors 31 and 32.

[0019] The refrigerant circuit 110 is configured so that during cooling operation, the refrigerant circulates through the compressor 11, the outdoor heat exchanger 13, the second indoor heat exchanger 22, the expansion valve 24, and the first indoor heat exchanger 21 in this order. During cooling operation, the outdoor heat exchanger 13 and the second indoor heat exchanger 22 function as condensers, and the first indoor heat exchanger 21 functions as an evaporator. During heating operation, the air conditioner 100 is configured so that the refrigerant circulates through the compressor 11, the first indoor heat exchanger 21, the expansion valve 24, the second indoor heat exchanger 22, and the outdoor heat exchanger 13 in this order. During heating operation, the first indoor heat exchanger 21 functions as a condenser, and the second indoor heat exchanger 22 and the outdoor heat exchanger 13 function as evaporators.

[0020] The compressor 11 draws in and compresses a low-temperature, low-pressure refrigerant and discharges it as a high-temperature, high-pressure gas refrigerant. The compressor 11 is driven, for example, by an inverter, and its capacity (the amount of refrigerant discharged per unit time) is controlled. The four-way valve 12 switches the flow of the refrigerant depending on the operating mode of the air conditioner 100.

[0021] The outdoor heat exchanger 13 exchanges heat between the refrigerant flowing through the refrigerant circuit 110 and outdoor air. A blower 14 is adjacent to the outdoor heat exchanger 13. The blower 14 sends air to the outdoor heat exchanger 13. The expansion valve 24 is, for example, an electronic expansion valve whose valve opening is controllable. Temperature sensors 31, 32 detect the temperatures of the refrigerant flowing before and after the second indoor heat exchanger 22. The air conditioner 100 is equipped with a control device 60 that comprehensively controls the drive components such as the blower 14 and the expansion valve 24.

[0022] The control device 60 is configured to include a CPU (Central Processing Unit) 61, memory 62 (ROM (Read Only Memory) and RAM (Random Access Memory)), and an input / output device (not shown) for inputting and outputting various signals. The CPU 61 loads a program stored in the ROM into the RAM or the like and executes it. The program stored in the ROM is a program in which the processing procedures of the control device 60 are written. The control device 60 controls each device in accordance with these programs. This control is not limited to processing by software, but can also be processed by dedicated hardware (electronic circuits).

[0023] The control device 60 adjusts the air blowing amount, for example, by controlling the rotation speed of the fans 14, 28, and 29. The control device 60 controls the amount of decompression of the refrigerant, for example, by controlling the opening of the expansion valve 24. The control device 60 switches the positions of the first damper 23a and the second damper 23b, for example, by controlling the first damper 23a and the second damper 23b. The first damper 23a and the second damper 23b switch their positions under the control of the control device 60, thereby switching the second indoor heat exchanger 22 between being positioned in the supply air duct and being positioned in the exhaust air duct.

[0024] Fig. 4 is a flowchart showing damper control during cooling operation in Embodiment 1. Figs. 5 and 6 are diagrams showing an example of damper operation in Embodiment 1. During cooling operation, the control device 60 controls the opening of the expansion valve 24 to a throttling state, thereby causing the outdoor heat exchanger 13 and the second indoor heat exchanger 22 to function as condensers and the first indoor heat exchanger 21 to function as an evaporator. The processing of the flowchart in Fig. 4 is repeatedly called and executed as a subroutine from the main routine in the control of the control device 60.

[0025] In step S1, the control device 60 determines whether reheating is necessary. The control device 60 may determine whether reheating is necessary based on information transmitted from a remote control (not shown) operated by a user. Alternatively, a humidity sensor and a temperature sensor may be provided, and the control device 60 may determine whether reheating is necessary based on the values ​​of these sensors.

[0026] When the control device 60 determines that reheating is necessary (YES in step S1), that is, when performing cooling and dehumidifying operation, it controls to switch the reheat damper composed of the first damper 23a and the second damper 23b so that the outdoor air OA passes through the second indoor heat exchanger 22 (step S2), as shown in Fig. 5, and returns the process from the subroutine to the main routine. In other words, as shown in Fig. 5, the control device 60 controls to switch the reheat damper so that the room air RA does not pass through the second indoor heat exchanger 22.

[0027] As a result, when reheating is required, the outdoor air OA passes through the first indoor heat exchanger 21 and then the second indoor heat exchanger 22. After being cooled by the first indoor heat exchanger 21, the outdoor air OA is reheated by the second indoor heat exchanger 22 and blown out into the indoor space.

[0028] When the control device 60 determines that reheating is not necessary (NO in step S1), that is, when cooling and dehumidifying operation is not to be performed, it controls to switch the reheat damper composed of the first damper 23a and the second damper 23b so that the outdoor air OA does not pass through the second indoor heat exchanger 22 (step S3), as shown in Fig. 6, and returns the process from the subroutine to the main routine. In other words, as shown in Fig. 6, the control device 60 controls to switch the reheat damper so that the room air RA passes through the second indoor heat exchanger 22.

[0029] Here, the transition of the refrigerant state when reheating is not required will be described using Figure 7. Figure 7 is a refrigerant state transition diagram for the first embodiment. The vertical axis represents pressure p, and the horizontal axis represents specific enthalpy h. As shown by the line connecting points A and E on the p-h diagram, a refrigeration cycle is depicted in which the outdoor heat exchanger 13 and the second indoor heat exchanger 22 function as condensers, and the first indoor heat exchanger 21 functions as an evaporator.

[0030] In Figure 7, points A to B indicate the compression stroke performed in the compressor 11, points B to C indicate the condensation stroke performed in the outdoor heat exchanger 13, points C to D indicate the condensation stroke performed in the second indoor heat exchanger 22, points D to E indicate the expansion stroke performed in the expansion valve 24, and points E to A indicate the evaporation stroke performed in the first indoor heat exchanger 21.

[0031] As shown in FIG. 7, in the condensation process, air is caused to flow from point B to point C into the outdoor heat exchanger 13, and the amount of heat exchanged Q Ａ The amount of heat exchanged between the refrigerant and the outdoor air OA is thus reduced from h3 to h2 by the specific enthalpy of the refrigerant flowing into the outdoor heat exchanger 13. In the condensation process, the air is further passed from point C to point D through the second indoor heat exchanger 22, thereby increasing the amount of heat exchanged Q Ｂ The amount of heat exchanged between the refrigerant and the outdoor air OA is equal to the amount of heat exchanged between the refrigerant and the outdoor air OA. This causes the specific enthalpy of the refrigerant flowing into the second indoor heat exchanger 22 to decrease from h2 to h1.

[0032] In this way, in the condensation process, the specific enthalpy of the refrigerant is decreased from h3 to h2 in the outdoor heat exchanger 13, and the specific enthalpy of the refrigerant is decreased from h2 to h1 in the second indoor heat exchanger 22. This makes it possible to increase the degree of subcooling of the refrigerant from the outlet of the outdoor heat exchanger 13 at point C to the outlet of the second indoor heat exchanger 22 at point D. This increases the amount of heat exchanged when reheating is not required, and makes it possible to efficiently lower the temperature of the outdoor air OA.

[0033] Embodiment 2. Fig. 8 is a flowchart showing damper control during cooling operation in Embodiment 2. Fig. 9 is a diagram showing an example of damper operation in Embodiment 2. The indoor unit 20A of Embodiment 2 is similar in configuration to the indoor unit 20 of Embodiment 1, except that it is equipped with a third damper 23c whose angle can be adjusted in stages in addition to the first damper 23a and second damper 23b. The control device 60 adjusts the amount of air passing through the second indoor heat exchanger 22 by adjusting the angle of the third damper 23c in stages. Fig. 8 explains damper control using control during cooling operation as an example.

[0034] As shown in Fig. 8, the control device 60 determines whether reheating is necessary in step S11. If the control device 60 determines that reheating is necessary (YES in step S11), that is, if cooling and dehumidifying operation is to be performed, the control device 60 checks the amount of heat required for reheating (step S12). The amount of reheating required may be determined by the control device 60 based on information transmitted from a remote controller operated by a user. For example, the remote controller may be provided with a button for adjusting the amount of heat to be reheated for reheat dehumidifying operation, and information corresponding to the amount of heat may be transmitted.

[0035] Next, the control device 60 controls the switching of the third damper 23c so as to adjust the air volume of the outdoor air OA passing through the second indoor heat exchanger 22 in accordance with the amount of heat required for reheating, as shown in Fig. 9, and returns the process from the subroutine to the main routine. At this time, the control device 60 controls the switching of the first damper 23a and the second damper 23b, the reheat dampers, so that the room air RA does not pass through the second indoor heat exchanger 22, as shown in Fig. 9.

[0036] When the control device 60 determines that reheating is not necessary (NO in step S11), that is, when the cooling and dehumidifying operation is not performed, the control device 60 controls the switching of the first damper 23a and the second damper 23b so that the outdoor air OA does not pass through the second indoor heat exchanger 22 (step S14), and returns the process from the subroutine to the main routine. In other words, the control device 60 controls the switching of the first damper 23a and the second damper 23b so that the room air RA passes through the second indoor heat exchanger 22.

[0037] As a result, the indoor unit 20A can gradually change the volume of outdoor air OA flowing through the second indoor heat exchanger 22 located in the supply air duct according to the amount of heat required for reheating, so that reheat dehumidification operation can be performed according to the user's needs.

[0038] Embodiment 3. Figure 10 is a schematic diagram showing the configuration of an indoor unit 20C in embodiment 3. The indoor unit 20C in embodiment 3 has the same configuration as the indoor unit 20 in embodiment 1, except that it is equipped with a total heat exchanger 25 and a total heat damper 26 that is provided upwind of the total heat exchanger 25 in the exhaust air duct.

[0039] The total heat exchanger 25 has a structure in which, for example, multiple ventilation channels that intersect at right angles to one another are stacked alternately. In the total heat exchanger 25, the room air RA and the outdoor air OA pass through the ventilation channels, thereby performing total heat exchange between the room air RA and the outdoor air OA. In the total heat exchange, not only sensible heat but also latent heat is exchanged. The total heat damper 26 switches the total heat exchanger 25 between a state in which the room air RA flowing through the exhaust air channel passes through and a state in which the room air RA does not pass through.

[0040] Fig. 11 is a flowchart showing damper control during cooling operation in embodiment 3. Fig. 12 and Fig. 13 are diagrams showing an example of damper operation in embodiment 3. Fig. 11 explains damper control using control during cooling operation as an example.

[0041] In step S21, the control device 60 determines whether reheating is necessary. The control device 60 may determine whether reheating is necessary based on information transmitted from a remote control (not shown) operated by a user. Alternatively, a humidity sensor and a temperature sensor may be provided, and the control device 60 may determine whether reheating is necessary based on the values ​​of these sensors.

[0042] When the control device 60 determines that reheating is necessary (YES in step S21), that is, when performing cooling and dehumidifying operation, it controls to switch the reheat damper composed of the first damper 23a and the second damper 23b so that the outdoor air OA passes through the second indoor heat exchanger 22 (step S22), and returns the process from the subroutine to the main routine. In other words, the control device 60 controls to switch the reheat damper so that the room air RA does not pass through the second indoor heat exchanger 22.

[0043] As a result, when reheating is required, the outdoor air OA passes through the total heat exchanger 25 and the first indoor heat exchanger 21, and then passes through the second indoor heat exchanger 22. The outdoor air OA is cooled by the first indoor heat exchanger 21 after total heat exchange between the room air RA and the outdoor air OA in the total heat exchanger 25, and then reheated by the second indoor heat exchanger 22 and blown out into the indoor space.

[0044] When the control device 60 determines that reheating is not necessary (NO in step S21), that is, when cooling and dehumidifying operation is not performed, it controls to switch the reheat damper composed of the first damper 23a and the second damper 23b so that the outdoor air OA does not pass through the second indoor heat exchanger 22 (step S23), and proceeds to the processing of S24. In other words, the control device 60 controls to switch the reheat damper so that the room air RA passes through the second indoor heat exchanger 22. The room air RA is heated by passing through the second indoor heat exchanger 22.

[0045] In step S24, the control device 60 calculates the temperature T of the indoor air RA after passing through the second indoor heat exchanger 22. ＲＡ is the temperature T of the outdoor air OA ＯＡ The temperature T of the room air RA is compared with the temperature T of the room air RA and a determination is made as to whether it is lower or not. ＲＡ The temperature T of the outdoor air OA may be measured by an indoor air temperature detector 52 disposed on the downwind side of the second indoor heat exchanger 22 in the exhaust air duct. ＯＡ The temperature may be measured by the outside air temperature detection unit 51 shown in FIG.

[0046] The control device 60 detects the temperature TＲＡ is the temperature T of the outdoor air OA ＯＡ 12, the total heat damper 26 is switched so that the room air RA passes through the total heat exchanger 25 (step S25), and the process returns from the subroutine to the main routine. As a result, total heat exchange occurs between the room air RA and the outside air OA in the total heat exchanger 25, thereby cooling the outside air OA passing through the supply air duct.

[0047] The control device 60 detects the temperature T ＲＡ is the temperature T of the outdoor air OA ＯＡ 13, the total heat damper 26 is switched so that the room air RA does not pass through the total heat exchanger 25 (step S26), and the process returns from the subroutine to the main routine. This makes it possible to prevent total heat exchange between the room air RA and the outside air OA in the total heat exchanger 25 when there is no need to cool the outside air OA passing through the supply air duct.

[0048] The temperature T of the indoor air RA after passing through the second indoor heat exchanger 22 ＲＡmay be calculated from data such as the indoor temperature and the amount of heat exchanged in the second indoor heat exchanger 22. Specifically, the indoor temperature may be measured by a temperature detector (not shown) installed at the air inlet 42. The amount of heat exchanged in the second indoor heat exchanger 22 may be calculated by the product of the refrigerant specific enthalpy difference at the inlet and outlet of the second indoor heat exchanger 22 and the refrigerant flow rate. The refrigerant specific enthalpy at the inlet of the second indoor heat exchanger 22 may be calculated from the measured values ​​of a low-pressure side pressure sensor (not shown) installed in the refrigerant circuit 110 and the temperature sensor 31 (shown in FIG. 1) that measures the temperature of the refrigerant flowing into the second indoor heat exchanger 22. The refrigerant specific enthalpy at the outlet of the second indoor heat exchanger 22 may be calculated from the measured values ​​of a low-pressure side pressure sensor (not shown) installed in the refrigerant circuit 110 and the temperature sensor 32 (shown in FIG. 1) that measures the temperature of the refrigerant flowing out of the second indoor heat exchanger 22. The refrigerant flow rate can be determined, for example, by calculating the refrigerant density at the inlet of the compressor 11 from the measured values ​​of a low-pressure side pressure sensor installed in the refrigerant circuit 110 and a temperature sensor (not shown) that measures the temperature at the inlet of the compressor 11, and multiplying the refrigerant density by the displacement volume of the compressor 11.

[0049] Embodiment 4 In Embodiment 4, control during heating operation will be described. Fig. 14 is a diagram showing the refrigerant circuit 110A of the air conditioner 100A in Embodiment 4. Fig. 15 is a flowchart showing damper control during heating operation in Embodiment 4. The indoor unit 20E in the refrigerant circuit 110A of the air conditioner 100A in Embodiment 4 has the same configuration as the refrigerant circuit 110 of Embodiment 1, except that an expansion valve 27 is added. The indoor unit 20E in Embodiment 4 has the same configuration as the indoor unit 20C of Embodiment 3, except that an expansion valve 27 is provided.

[0050] The expansion valve 27 is disposed in the indoor unit 20E on the refrigerant piping 30 between the outdoor heat exchanger 13 and the second indoor heat exchanger 22. The control device 60 controls the apertures of the expansion valves 24 and 27. During heating operation, the control device 60 controls the apertures of the expansion valves 24 and 27 so that the expansion valve 24 is fully opened and the expansion valve 27 is throttled. During heating operation, the refrigerant circuit 110A is configured so that the refrigerant circulates through the compressor 11, the first indoor heat exchanger 21, the expansion valve 24, the second indoor heat exchanger 22, the expansion valve 27, and the outdoor heat exchanger 13 in this order. During heating operation, the first indoor heat exchanger 21 and the second indoor heat exchanger 22 function as condensers, and the outdoor heat exchanger 13 functions as an evaporator.

[0051] 15 , the control device 60 controls the switching of the reheat damper composed of the first damper 23a and the second damper 23b so that the outdoor air OA does not pass through the second indoor heat exchanger 22 (step S31), and then proceeds to the processing of S32. In other words, the control device 60 controls the switching of the reheat damper so that the room air RA passes through the second indoor heat exchanger 22. The room air RA is heated by passing through the second indoor heat exchanger 22. This makes it possible to raise the temperature of the room air RA that may flow into the total heat exchanger 25 by exchanging heat with the refrigerant passing through the second indoor heat exchanger 22.

[0052] In step S32, the control device 60 determines the temperature T ＯＡ is the preset threshold temperature T Ｌ It is compared with the preset threshold temperature T Ｌ is a temperature (for example, 0°C) that is set as a temperature at which moisture in the air flowing through the exhaust air duct may freeze. ＯＡ is the preset threshold temperature T Ｌ If the temperature T of the outdoor air OA is lower than the room air RA flowing through the exhaust air duct, the indoor air RA may be cooled by the outdoor air OA, causing the moisture contained in the air to freeze. This may cause a problem of clogging the total heat exchanger 25. ＯＡ The temperature may be measured by the outside air temperature detection unit 51 shown in FIG.

[0053] The control device 60 detects the temperature T ＯＡ is the preset threshold temperature T Ｌ If it is determined that the temperature is lower than the reference temperature (YES in step S32), the total heat damper 26 is switched so that the room air RA passes through the total heat exchanger 25 (step S33), and the process returns from the subroutine to the main routine. As a result, total heat exchange occurs between the room air RA, whose temperature has increased and flows into the total heat exchanger 25, and the low-temperature outdoor air OA. Therefore, the room air RA is cooled by the low-temperature outdoor air OA, and its temperature drops below freezing, which reduces the possibility of moisture freezing in the exhaust air duct and clogging of the total heat exchanger 25.

[0054] The control device 60 detects the temperature T ＯＡ is the preset threshold temperature T Ｌ If it is determined that the temperature is higher than the reference temperature (NO in step S32), there is no possibility of moisture in the exhaust air duct freezing or clogging of the total heat exchanger 25, so control is exercised to switch the total heat damper 26 so that the room air RA does not pass through the total heat exchanger 25 (step S34), and the process returns from the subroutine to the main routine. This makes it possible to prevent total heat exchange between the room air RA and the outside air OA in the total heat exchanger 25 when there is no need to heat the outside air OA passing through the supply air duct.

[0055] Summary The present disclosure includes a refrigerant circuit 110 including an outdoor unit 10 and an indoor unit 20. The outdoor unit 10 includes a compressor 11 that compresses and discharges a refrigerant, and an outdoor heat exchanger 13. The indoor unit 20 includes an expansion valve 24 that decompresses the refrigerant, a first indoor heat exchanger 21, a second indoor heat exchanger 22, a blower 28 that takes in outdoor air OA into the room through an intake air duct, and a blower 29 that discharges indoor air RA to the outside through an exhaust air duct. The refrigerant circuit 110 is configured so that, during cooling operation, the refrigerant circulates through the compressor 11, the outdoor heat exchanger 13, the second indoor heat exchanger 22, the expansion valve 24, and the first indoor heat exchanger 21 in that order. The second indoor heat exchanger 22 is configured to allow both the outdoor air OA flowing through the intake air duct and the indoor air RA flowing through the exhaust air duct to pass through. The indoor unit 20 further includes a first damper 23a and a second damper 23b as a switching device that can switch between a state in which the second indoor heat exchanger 22 is located in the supply air duct and a state in which the second indoor heat exchanger 22 is located in the exhaust air duct. When the switching device switches the second indoor heat exchanger 22 to a state in which the second indoor heat exchanger 22 is located in the supply air duct, the first indoor heat exchanger 21 is positioned upwind of the second indoor heat exchanger 22 in the supply air duct.

[0056] Preferably, the indoor unit 20 further includes a control device 60 that controls the operation of the first damper 23 a and the second damper 23 b. When the outdoor air OA that has been cooled by heat exchange with the refrigerant in the first indoor heat exchanger 21 needs to be heated by the second indoor heat exchanger 22, the control device 60 controls the first damper 23 a and the second damper 23 b so that the second indoor heat exchanger 22 is located in the supply air duct.

[0057] Preferably, when there is no need to heat the outdoor air OA cooled by heat exchange with the refrigerant in the first indoor heat exchanger 21 using the second indoor heat exchanger 22, the control device 60 controls the first damper 23a and the second damper 23b so that the second indoor heat exchanger 22 is positioned in the exhaust air duct.

[0058] Preferably, the indoor unit 20A further includes a control device 60 that controls the operation of the first damper 23a, the second damper 23b, and the third damper 23c. The third damper 23c is capable of adjusting the volume of outdoor air OA passing through the second indoor heat exchanger 22. When the outdoor air OA that has been cooled by exchanging heat with the refrigerant in the first indoor heat exchanger 21 needs to be heated by the second indoor heat exchanger 22, the control device 60 controls the third damper 23c to change in stages the volume of outdoor air OA flowing through the second indoor heat exchanger 22 that is positioned in the supply air duct.

[0059] Preferably, the indoor unit 20C further includes a total heat exchanger 25 that exchanges heat between the outdoor air OA and the room air RA. The damper, which is a switching device, includes a reheat damper composed of a first damper 23a and a second damper 23b that can switch between a state in which the second indoor heat exchanger 22 is located in the supply air duct and a state in which it is located in the exhaust air duct, and a total heat damper 26 that can switch between a state in which the total heat exchanger 25 passes through the room air RA flowing in the exhaust air duct and a state in which it does not pass through.

[0060] Preferably, when it is not necessary to heat the outdoor air OA cooled by heat exchange with the refrigerant in the first indoor heat exchanger 21 in the second indoor heat exchanger 22, the control device 60 controls the reheat damper so that the second indoor heat exchanger 22 is positioned in the exhaust air duct, and adjusts the temperature T of the indoor air RA after passing through the second indoor heat exchanger 22. ＲＡ is the temperature T of the outdoor air OA ＯＡ If the temperature T of the indoor air RA after passing through the second indoor heat exchanger 22 is lower than the temperature T ＲＡ is the temperature T of the outdoor air OA ＯＡ If the temperature is higher than the reference temperature, the total heat damper 26 is controlled so that the total heat exchanger 25 does not pass the room air RA flowing through the exhaust air duct.

[0061] Preferably, the indoor unit 20E further includes an expansion valve 27 that decompresses the refrigerant. The refrigerant circuit 110A is configured so that, during heating operation, the refrigerant circulates through the compressor 11, the first indoor heat exchanger 21, the expansion valve 24, the second indoor heat exchanger 22, the expansion valve 27, and the outdoor heat exchanger 13 in this order. During heating operation, the control device 60 controls the temperature T ＯＡ is a preset threshold temperature T Ｌ When the temperature is less than 100°C, the reheat damper consisting of the first damper 23a and the second damper 23b is controlled so that the second indoor heat exchanger 22 is positioned in the exhaust air duct, and the total heat damper 26 is controlled so that the total heat exchanger 25 passes through the indoor air RA flowing in the exhaust air duct.

[0062] By being provided with the above-described configuration, the air conditioners 100, 100A of the present embodiment can operate with high efficiency both when reheating is required and when reheating is not required.

[0063] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims.

[0064] REFERENCE SIGNS LIST 10 outdoor unit, 11 compressor, 12 four-way valve, 13 outdoor heat exchanger, 14, 28, 29 blower, 20, 20A, 20C, 20E indoor unit, 21 first indoor heat exchanger, 22 second indoor heat exchanger, 23a first damper, 23b second damper, 23c third damper, 24, 27 expansion valve, 25 total heat exchanger, 26 total heat damper, 30 refrigerant piping, 31, 32 temperature sensor, 40 duct, 41 air outlet, 42 intake port, 50 supply air temperature detection unit, 51 outdoor air temperature detection unit, 52 indoor air temperature detection unit, 60 control device, 61 CPU, 62 memory, 100, 100A air conditioner, 110, 110A refrigerant circuit, EA exhaust, SA supply air, OA Outdoor air, RA indoor air.

Claims

1. A refrigerant circuit including an outdoor unit and an indoor unit is provided. The outdoor unit is A compressor that compresses and discharges a refrigerant; an outdoor heat exchanger; The indoor unit includes: a first expansion valve for reducing the pressure of the refrigerant; A first indoor heat exchanger; A second indoor heat exchanger; an air intake device that takes in outdoor air into the room through an air intake duct; an exhaust device that exhausts indoor air to the outside through an exhaust air duct, the refrigerant circuit is configured such that, during a cooling operation, a refrigerant circulates through the compressor, the outdoor heat exchanger, the second indoor heat exchanger, the first expansion valve, and the first indoor heat exchanger in this order; the second indoor heat exchanger is configured to allow each of the outdoor air flowing through the supply air duct and the indoor air flowing through the exhaust air duct to pass therethrough; The indoor unit further includes a switching device that can switch between a state in which the second indoor heat exchanger is located in the supply air duct and a state in which the second indoor heat exchanger is located in the exhaust air duct, When the second indoor heat exchanger is positioned in the supply air duct by the switching device, the first indoor heat exchanger is disposed on the windward side of the second indoor heat exchanger in the supply air duct, The indoor unit includes: A control device for controlling an operation of the switching device; The system further includes a total heat exchanger for exchanging heat between the outdoor air and the indoor air, the switching device includes a first damper that is switchable between a state in which the second indoor heat exchanger is located in the supply air duct and a state in which the second indoor heat exchanger is located in the exhaust air duct, and a second damper that is switchable between a state in which the total heat exchanger passes through the indoor air flowing through the exhaust air duct and a state in which the total heat exchanger does not pass through, When it is not necessary to heat the outdoor air that has been cooled by heat exchange with a refrigerant in the first indoor heat exchanger, by the second indoor heat exchanger, controlling the first damper so that the second indoor heat exchanger is located in the exhaust air duct; When the temperature of the indoor air after passing through the second indoor heat exchanger is lower than the temperature of the outdoor air, the second damper is controlled so that the total heat exchanger passes through the indoor air flowing through the exhaust air duct; An air conditioner that controls the second damper so that the total heat exchanger does not pass the indoor air flowing through the exhaust air duct when the temperature of the indoor air after passing through the second indoor heat exchanger is higher than the temperature of the outdoor air.

2. A refrigerant circuit including an outdoor unit and an indoor unit, The outdoor unit is A compressor that compresses and discharges a refrigerant; an outdoor heat exchanger; The indoor unit includes: a first expansion valve for reducing the pressure of the refrigerant; A first indoor heat exchanger; A second indoor heat exchanger; an air intake device that takes in outdoor air into the room through an air intake duct; an exhaust device that exhausts indoor air to the outside through an exhaust air duct, the refrigerant circuit is configured such that, during a cooling operation, a refrigerant circulates through the compressor, the outdoor heat exchanger, the second indoor heat exchanger, the first expansion valve, and the first indoor heat exchanger in this order; the second indoor heat exchanger is configured to allow each of the outdoor air flowing through the supply air duct and the indoor air flowing through the exhaust air duct to pass therethrough; The indoor unit further includes a switching device that can switch between a state in which the second indoor heat exchanger is located in the supply air duct and a state in which the second indoor heat exchanger is located in the exhaust air duct, When the second indoor heat exchanger is positioned in the supply air duct by the switching device, the first indoor heat exchanger is disposed on the windward side of the second indoor heat exchanger in the supply air duct, The indoor unit includes: A control device for controlling an operation of the switching device; The system further includes a total heat exchanger for exchanging heat between the outdoor air and the indoor air, the switching device includes a first damper that is switchable between a state in which the second indoor heat exchanger is located in the supply air duct and a state in which the second indoor heat exchanger is located in the exhaust air duct, and a second damper that is switchable between a state in which the total heat exchanger passes through the indoor air flowing through the exhaust air duct and a state in which the total heat exchanger does not pass through, The indoor unit further includes a second expansion valve that reduces the pressure of the refrigerant, the refrigerant circuit is configured such that, during a heating operation, a refrigerant circulates through the compressor, the first indoor heat exchanger, the first expansion valve, the second indoor heat exchanger, the second expansion valve, and the outdoor heat exchanger in this order; When the control device is in a heating operation and the first expansion valve is in an open state and the second expansion valve is in a throttling state, thereby causing the first indoor heat exchanger and the second indoor heat exchanger to function as condensers, when the temperature of the outdoor air is lower than a preset threshold value, controlling the first damper so that the second indoor heat exchanger is located in the exhaust air duct; the second damper is controlled so as to set the total heat exchanger in a state in which the indoor air flowing through the exhaust air duct passes through the total heat exchanger.