JP6252627B2 - Multi-type air conditioner - Google Patents

Description

  The present invention relates to a multi-type air conditioner, and more particularly, to a multi-type air conditioner including a plurality of indoor units having an indoor heat exchanger capable of exchanging heat between air and a refrigerant.

  In the conventional air conditioner, when the cooling load is low during the cooling operation, as described in Patent Document 1 (Japanese Patent Laid-Open No. 59-122864), for example, the operating frequency of the compressor is lowered, There are cases where operation is performed in accordance with a low cooling load. In the explanation below, the operation frequency of the indoor unit heat exchanger of the indoor unit is decreased more than the normal cooling operation by lowering the operation frequency of the compressor, so that the operation with a reduced cooling capacity corresponding to a low cooling load is performed at a low capacity. This is called cooling operation. As described in Patent Document 1, when one outdoor unit and one indoor unit are connected, for example, even when the indoor temperature of the indoor unit changes during low-performance cooling operation, In response to the demand of the indoor unit, the operation frequency of the compressor can be changed to easily cope with it.

  However, for example, in a multi-type air conditioner in which a plurality of indoor units are connected to a single outdoor unit and the plurality of indoor units are operated in parallel, the operation of the compressor of the outdoor unit is performed in accordance with the requirements of any indoor unit. It becomes difficult to change the frequency. Therefore, in any indoor unit of the multi-type air conditioner, for example, when the indoor temperature changes or the set temperature is changed, and the cooling capacity required for the arbitrary indoor unit changes, the request It is conceivable to cope with the changed cooling load by changing the opening of the expansion valve of the indoor unit in which the cooling capacity has changed.

  However, when low-capacity cooling operation is being performed in a multi-type air conditioner, if the cooling valve is increased by increasing the opening of the expansion valve, it passes through the overheat region and the wet region of the indoor heat exchanger, respectively. Condensation may occur in the rotor of the indoor fan due to the mixed air.

  An object of the present invention is to prevent the occurrence of condensation on the rotor of the indoor fan when the multi-type air conditioner is performing a low-performance cooling operation.

A multi-type air conditioner according to a first aspect of the present invention includes an outdoor unit having a compressor that compresses a refrigerant that circulates in order to perform a refrigeration cycle, and a plurality of indoor heats in which refrigerant discharged from the compressor circulates. A plurality of indoor units having a exchanger and a plurality of decompression mechanisms and having a plurality of indoor fans through which air that has passed through the plurality of indoor heat exchangers passes, and at least one of the plurality of indoor units In the low-capacity cooling operation that increases the overheating area compared to the normal cooling operation , cooling is performed with the mixed air that has passed through the wet area and the overheating area, and when the room temperature is higher than the set temperature in the low-capacity cooling operation, while expanding the wet area by narrowing the superheat region of the indoor heat exchanger by increasing the opening degree, the humid region in the range of apparatus condensation downstream of the indoor heat exchanger by increasing the air volume of the indoor fan does not occur It is configured so that can limit the expansion.

  According to this multi-type air conditioner, by increasing the opening of the decompression mechanism, the wet area of the indoor heat exchanger can be expanded to improve the cooling capacity, but when the wet area increases, the overheat area of the indoor heat exchanger is reduced. The temperature of the mixed air formed by mixing the air that has passed through and the air that has passed through the wet region is lowered. Therefore, the control by the opening of the decompression mechanism is performed in the device downstream of the indoor heat exchanger so that the temperature of the mixed air does not decrease too much below the dew point temperature of the mixed air and condensation in the device does not occur downstream of the indoor heat exchanger. The necessary cooling capacity can be ensured by stopping the expansion to the upper limit at which condensation does not occur and suppressing the expansion of the wet area and increasing the air volume of the indoor fan for further improvement of the cooling capacity. Thereby, when the multi-type air conditioner is performing the low-capacity cooling operation, it is possible to prevent condensation in the apparatus downstream from the indoor heat exchanger while ensuring the required cooling capacity.

  The multi-type air conditioner according to a second aspect of the present invention is the multi-type air conditioner according to the first aspect, wherein at least one indoor unit is depressurized when the room temperature is lower than a set temperature in the low-capacity cooling operation. The cooling mechanism can be lowered by reducing the opening of the mechanism and / or lowering the air volume of the indoor fan.

  According to this multi-type air conditioner, when the room temperature is lower than the set temperature in the low-capacity cooling operation during cooling, the opening degree of the decompression mechanism is reduced and / or the air volume of the indoor fan is lowered to reduce the cooling capacity. Therefore, the wet area is reduced and / or the air volume is reduced from the state in which the expansion of the wet area is limited to the upper limit at which no dew condensation occurs in the apparatus downstream of the indoor heat exchanger.

The multi-type air conditioner according to a third aspect of the present invention is the multi-type air conditioner according to the first aspect or the second aspect, wherein at least one indoor unit is a room using the temperature of the mixed air or the humidity of the mixed air. It is determined that the expansion of the wet region is limited to the upper limit at which no dew condensation occurs in the apparatus downstream of the heat exchanger.

  According to this multi-type air conditioner, is the expansion of the wet area limited to the upper limit at which no dew condensation occurs in the apparatus downstream of the indoor heat exchanger using the temperature of the mixed air or the humidity of the mixed air? It can be determined whether or not.

  The multi-type air conditioner according to a fourth aspect of the present invention is the multi-type air conditioner according to any one of the first to third aspects, wherein at least one indoor unit is connected to the indoor heat exchanger at the indoor heat exchanger temperature. The sensor further has a sensor, and when the low-capacity cooling operation is performed, the detection of the indoor heat exchanger temperature sensor is used to limit the expansion of the wet area to the upper limit where no condensation occurs in the apparatus downstream of the indoor heat exchanger. Judgment.

  According to this multi-type air conditioner, whether or not the expansion of the wet area is limited to the upper limit at which no dew condensation occurs in the apparatus downstream of the indoor heat exchanger, using the detection result of the indoor heat exchanger temperature sensor. It can be determined whether or not.

  A multi-type air conditioner according to a fifth aspect of the present invention is the multi-type air conditioner according to any one of the first to fourth aspects, wherein at least one indoor unit has a room for obtaining a required cooling capacity. When it is not possible to limit the expansion of the wet area to the upper limit where condensation in the device does not occur downstream of the indoor heat exchanger by increasing the airflow of the fan, the mode is switched from the low capacity cooling operation mode to the normal cooling operation mode. .

  According to this multi-type air conditioner, by switching from the low-capacity cooling operation mode to the normal cooling operation mode, the entire indoor heat exchanger can be made a wet region, so the overheating region of the indoor heat exchanger can be reduced. Air passing through can be eliminated.

  In the multi-type air conditioner according to the first aspect of the present invention, it is possible to prevent dew condensation in the apparatus downstream from the indoor heat exchanger when the low-capacity cooling operation is performed.

  In the multi-type air conditioner according to the second aspect of the present invention, it is possible to reduce the cooling capacity while maintaining a state in which dew condensation does not occur downstream of the indoor heat exchanger.

  In the multi-type air conditioner according to the third aspect or the fourth aspect of the present invention, the certainty of preventing dew condensation in the apparatus downstream of the indoor heat exchanger is improved.

  In the multi-type air conditioning apparatus according to the fifth aspect of the present invention, it is possible to prevent dew condensation in the apparatus downstream of the indoor heat exchanger while ensuring necessary cooling capacity.

The circuit diagram showing the schematic structure of the multi type air harmony device concerning the embodiment of the present invention. Sectional drawing which shows an example of a structure of the indoor unit of the multi type air conditioning apparatus of FIG. FIG. 3 is a perspective view illustrating a configuration around an indoor heat exchanger by removing a front panel and the like of the indoor unit in FIG. 2. The conceptual diagram of the indoor heat exchanger for demonstrating the normal cooling operation of a multi type air conditioning apparatus. The conceptual diagram of the indoor heat exchanger for demonstrating the low-capacity cooling operation of a multi type air conditioning apparatus. The graph for demonstrating the concept of the control at the time of low capacity cooling operation. The graph for demonstrating an example of the control at the time of low capacity cooling operation. The graph for demonstrating the other example of the control at the time of low capacity cooling operation. The circuit diagram showing the schematic structure of the air harmony device concerning modification 1C of the present invention. The perspective view which shows the external appearance of the outdoor unit of the modification 1C.

(1) Overall Configuration of Air Conditioner FIG. 1 is a schematic configuration diagram of a multi-type air conditioner according to an embodiment of the present invention. The multi-type air conditioner 10 is an apparatus used for air conditioning in a room such as a building by performing a vapor compression refrigeration cycle operation. The multi-type air conditioner 10 includes an outdoor unit 20 as a single heat source unit, and indoor units 40, 50, 60 as a plurality of (three in the present embodiment) usage units connected in parallel to the outdoor unit 20. The liquid refrigerant communication pipe 71 and the gas refrigerant communication pipe 72 are provided as refrigerant communication pipes for connecting the outdoor unit 20 and the indoor units 40, 50, 60.

  The refrigerant circuit 11 of the multi-type air conditioner 10 is configured by connecting an outdoor unit 20, indoor units 40, 50, 60, a liquid refrigerant communication pipe 71 and a gas refrigerant communication pipe 72. The refrigerant circuit 11 includes indoor refrigerant circuits 11a, 11b, 11c and an outdoor refrigerant circuit 11d. The refrigerant circulates through the refrigerant circuit 11.

  The multi-type air conditioner 10 includes an operation control device 80 that performs overall operation control of the multi-type air conditioner 10. The indoor side control devices 47, 57, and 67 and the outdoor side control device 37 are connected by a transmission line 80a to constitute an operation control device 80. And the indoor side control apparatuses 47, 57, and 67 of the indoor units 40, 50, and 60 can exchange control signals and the like through the transmission line 80a.

  The operation control device 80 includes a suction pressure sensor 29, a discharge pressure sensor 30, a suction temperature sensor 31, a discharge temperature sensor 32, an outdoor temperature sensor 36, liquid side temperature sensors 44, 54, 64, and gas side temperature sensors 45, 55, 65. It is connected so that it can receive detection signals. In addition, the operation control device 80 can control the outdoor unit 20 and the indoor units 40, 50, 60 based on these detection signals and the like, the compressor 21, the four-way switching valve 22, the outdoor fan 28, the outdoor unit. The expansion valve 38, the indoor expansion valves 41, 51, 61 and the indoor fans 43, 53, 63 are connected.

(2) Detailed configuration (2-1) Outdoor unit 20
The outdoor unit 20 has an outdoor refrigerant circuit 11 d that constitutes a part of the refrigerant circuit 11. A compressor 21, a four-way switching valve 22, an outdoor heat exchanger 23, an outdoor expansion valve 38, and an accumulator 24 are connected to the outdoor refrigerant circuit 11d.

  The compressor 21 is a compressor whose operating capacity can be varied, and is a positive displacement compressor driven by a motor 21m whose rotation speed is controlled by an inverter. The four-way switching valve 22 is a valve for switching the direction of refrigerant flow.

  During the cooling operation, the four-way switching valve 22 in FIG. 1 is switched to the connection state indicated by the solid line. That is, the discharge side of the compressor 21 and the outdoor heat exchanger 23 are connected by the four-way switching valve 22, and the suction side (specifically, the accumulator 24) of the compressor 21 and the gas refrigerant communication pipe 72 are connected. Thus, during the cooling operation, the outdoor heat exchanger 23 functions as a radiator for the refrigerant compressed by the compressor 21, and the indoor heat exchange is performed as an evaporator for the refrigerant deprived of heat in the outdoor heat exchanger 23. The devices 42, 52, 62 function.

  During the heating operation, the four-way switching valve 22 in FIG. 1 is switched to the connected state indicated by the broken line. The four-way switching valve 22 connects the discharge side of the compressor 21 and the gas refrigerant communication pipe 72 side, and connects the suction side of the compressor 21 and the outdoor heat exchanger 23. The indoor heat exchangers 42, 52, 62 function as the refrigerant radiator, and the outdoor heat exchanger 23 functions as the refrigerant evaporator deprived of heat in the indoor heat exchangers 42, 52, 62.

  The outdoor heat exchanger 23 is, for example, a cross fin type fin-and-tube heat exchanger, and is a device for exchanging heat between air and a refrigerant in order to use air as a heat source. The outdoor heat exchanger 23 has a gas side connected to the four-way switching valve 22 and a liquid side connected to the outdoor expansion valve 38.

  The outdoor expansion valve 38 is downstream of the outdoor heat exchanger 23 in the refrigerant flow direction in the refrigerant circuit 11 when performing a cooling operation in order to adjust the pressure, flow rate, and the like of the refrigerant flowing in the outdoor refrigerant circuit 11d. It is an electric expansion valve arrange | positioned in. The outdoor expansion valve 38 is connected to the liquid side of the outdoor heat exchanger 23.

  The outdoor unit 20 has an outdoor fan 28 as a blower for sucking outdoor air into the apparatus and exchanging heat with the refrigerant in the outdoor heat exchanger 23 and then discharging it to the outside. The outdoor fan 28 is a fan capable of changing the air volume of air supplied to the outdoor heat exchanger 23, and is, for example, a propeller fan driven by a motor 28m composed of a DC fan motor or the like.

  The outdoor unit 20 includes, for example, a suction pressure sensor 29 that detects a suction pressure of the compressor 21 (that is, a refrigerant pressure corresponding to the evaporation pressure Pe during the cooling operation), and a discharge pressure that detects a discharge pressure of the compressor 21. A sensor 30, a suction temperature sensor 31 that detects the suction temperature of the compressor 21, a discharge temperature sensor 32 that detects the discharge temperature of the compressor 21, and the like are provided. An outdoor temperature sensor 36 that detects the temperature of the outdoor air that flows into the interior of the outdoor unit 20 is provided at the outdoor air intake port.

  Furthermore, the outdoor unit 20 has an outdoor side control device 37 in order to control the operation of each part constituting the outdoor unit 20. The outdoor control device 37 includes a microcomputer (not shown) provided for controlling the outdoor unit 20, a memory (not shown), an inverter circuit (not shown) for controlling the motor 21m, and the like. doing.

  The set temperature, set humidity, indoor temperature, indoor humidity, and the like of the plurality of indoor units 40, 50, 60 vary, and since these vary, the capacity required for the outdoor unit 20 is the individual indoor unit 40, It is difficult to adjust to fit all 50,60. Therefore, the outdoor side control device 37 is adapted to some requests of the plurality of indoor units 40, 50, 60, such as the most requested indoor unit of the plurality of indoor units 40, 50, 60, for example. The operating capacity of the compressor 21 and / or the air volume of the outdoor fan 28 will be controlled. Therefore, for many of the plurality of indoor units 40, 50, 60, the setting of the operating capacity of the compressor 21 and / or the air volume of the outdoor fan 28 may be higher than necessary.

(2-2) Indoor unit (2-2-1) Overview of indoor unit The indoor units 40, 50, 60 are embedded in the ceiling of a room such as a building or suspended, or are hung on a wall surface of a room. For example, it is installed in a room such as a conference room. The plurality of indoor units 40, 50, 60 may be arranged in the same room or may be arranged separately in different rooms. Since the indoor unit 40 and the indoor units 50 and 60 have the same configuration, only the configuration of the indoor unit 40 will be described below. About the structure of the indoor units 50 and 60, the code | symbol of the 50th series or the 60th series is attached instead of the code | symbol of the 40th series which shows each part of the indoor unit 40, respectively, and description of each part of the indoor units 50 and 60 is abbreviate | omitted. .

  The indoor units 40, 50, 60 are connected to the outdoor unit 20 via a liquid refrigerant communication pipe 71 and a gas refrigerant communication pipe 72. For example, the indoor unit 40 has an indoor refrigerant circuit 11a (a indoor refrigerant circuit 11b in the indoor unit 50 and an indoor refrigerant circuit 11c in the indoor unit 60) that constitutes a part of the refrigerant circuit 11. The indoor refrigerant circuit 11a includes an indoor expansion valve 41 as a decompression mechanism and an indoor heat exchanger 42. In this embodiment, the indoor expansion valves 41, 51, 61 are provided in the indoor units 40, 50, 60, respectively, as the pressure reducing mechanism. However, the present invention is not limited to this, and a plurality of units corresponding to the indoor units 40, 50, 60 are provided. The decompression mechanism may be provided in the outdoor unit 20, or may be provided in a connection unit independent of the indoor units 40, 50, 60 and the outdoor unit 20.

  The indoor expansion valve 41 is an electric expansion valve connected to the liquid side of the indoor heat exchanger 42 in order to adjust the flow rate of the refrigerant flowing in the indoor refrigerant circuit 11a, and blocks passage of the refrigerant. Is also possible. The indoor expansion valve 41 is controlled by the indoor control device 47, and is configured to be able to adjust the flow rate of the refrigerant and the pressure reduction by changing the opening degree.

  The indoor heat exchanger 42 is a heat exchanger for exchanging heat between air and a refrigerant, and is, for example, a cross-fin type fin-and-tube heat composed of heat transfer tubes and a large number of fins. It is an exchanger. The indoor heat exchanger 42 functions as a refrigerant evaporator during cooling operation to cool room air, and functions as a refrigerant radiator during heating operation to heat room air.

  The indoor unit 40 sucks indoor air into the indoor unit, exchanges heat with the refrigerant in the indoor heat exchanger 42, and then supplies the indoor air 43 as a blower for supplying the indoor air after heat exchange into the room as supply air. have. The indoor fan 43 is a fan capable of changing the air volume supplied to the indoor heat exchanger 42 within a predetermined air volume range. For example, a centrifugal fan or a multiblade fan driven by a motor 43m formed of a DC fan motor or the like. Etc. In the indoor unit 40 shown in FIG. 2, a cross flow fan is used as the indoor fan 43.

(2-2-2) Detailed Configuration of Indoor Unit FIG. 2 shows a cross section of the indoor unit 40. The indoor unit 40 shown in FIG. 2 is a wall-hanging type. In FIG. 2, an arrow Ar <b> 1 indicated by a two-dot chain line represents a flow of indoor air to be sucked, and an arrow Ar <b> 2 indicated by a one-dot chain line represents a flow of conditioned air to be blown out. The indoor unit 40 includes a casing 411, an air filter 412, an indoor heat exchanger 42, an indoor fan 43, vertical blades 416, and horizontal blades 417 shown in FIG. FIG. 3 is a perspective view illustrating a configuration of the front heat exchange unit 421 and the rear heat exchange unit 422 and the surroundings of the indoor unit 40 illustrated in FIG. 2.

  The wall-mounted indoor unit 40 shown in FIG. 2 has an opening of the casing 411, that is, a suction port 431 at the upper side. The indoor air sucked from the suction port 431 enters the suction space S1. The space on the downstream side of the air filter 412 is also included in the suction space S1. An indoor temperature sensor 451 for measuring the temperature of the intake air and an indoor humidity sensor 452 for measuring the relative humidity of the intake air are installed in the intake space S1, for example. The temperature measured by the room temperature sensor 451 is the room temperature Tr1 and also the suction temperature Ti.

  The intermediate space S <b> 2 is located downstream of the indoor heat exchanger 42 and upstream of the indoor fan 43. And it is the blowing space S3 located downstream of the indoor fan 43. The indoor air sucked from above the casing 411 is adjusted in temperature and humidity by the indoor heat exchanger 42 in the casing 411 until it flows from the suction space S1 to the intermediate space S2. The air in the intermediate space S2 is mixed to be mixed air when passing through the indoor fan 43, and the mixed air is blown out as conditioned air from the lower outlet 432 through the blowing space S3.

(2-2-3) Casing 411 and air filter 412
The casing 411 forms the outline and frame of the indoor unit 40. The rear guider 433 and the stabilizer 434 of the casing 411 form a blowout space S3 that is a blowout flow path following the blowout port 432. The air filter 412 is disposed between the suction port 431 and the indoor heat exchanger 42. Prior to passing through the indoor heat exchanger 42, the indoor air passes through the air filter 412 to remove dust. Therefore, the air filter 412 is attached to the casing 411 so as to surround the indoor heat exchanger 42. Since the temperature and humidity of the air do not change before and after the air filter 412, the spaces before and after the air filter 412 are treated in the same way as the suction space S <b> 1. Therefore, the indoor temperature sensor 451 and the indoor humidity sensor 452 may be provided either upstream or downstream of the air filter 412.

(2-2-4) Indoor heat exchanger 42
The indoor heat exchanger 42 includes a front heat exchange unit 421 and a rear heat exchange unit 422. The indoor heat exchanger 42 includes a plurality of fins 481 and a plurality of heat transfer tubes 482. Each fin 481 is made of a thin metal plate, and is disposed in parallel to the adjacent fin 481 and perpendicular to the longitudinal direction of the indoor unit 40. Therefore, the air passing through the indoor heat exchanger 42 passes between the fins 481 adjacent to each other. Each of the plurality of heat transfer tubes 482 is a metal pipe, extends through the fin 481 along the longitudinal direction of the indoor unit 40, and passes through the gap between the refrigerant flowing inside and the fin 481 and the heat transfer tube 482. It is a member for exchanging heat with air. The refrigerant and air exchange heat through a large number of fins 481 and a large number of heat transfer tubes 482. Further, moisture in the room air is condensed and attached to the fins 481 and the heat transfer tubes 482, so that the indoor heat exchanger 42 can perform dehumidification. The front heat exchanging part 421 includes an upper front heat exchanging part 426 that inclines toward the front lower side, and a lower front heat exchanging part 427 that inclines from the lower end of the upper front heat exchanging part 426 toward the lower rear side. Yes. The rear side heat exchange part 422 is inclined toward the lower rear side.

  In this embodiment, in order to simplify the description, the case where the heat transfer tubes 482 of the indoor heat exchanger 42 are arranged in a row will be described. However, the arrangement of the heat transfer tubes 482 of the indoor heat exchanger 42 to which the present invention can be applied is not limited to a single row, and may be two or more rows. In the cooling operation, it is assumed that the refrigerant enters from the lowermost heat transfer tube 483 of the lower front heat exchange unit 427 and exits from the lowermost heat transfer tube 484 of the rear heat exchange unit 422. The heat transfer tubes 482 of each stage are connected to the heat transfer tubes 482 of other stages. For example, the heat transfer tubes 482 of different stages are connected to each other by a U-shaped tube 485 shown in FIG. In the indoor heat exchanger 42, the refrigerant sequentially flows to the adjacent heat transfer tubes 482.

(2-2-5) Indoor fan 43
The indoor fan 43 is located between the front heat exchange unit 421 and the rear heat exchange unit 422 and the air outlet 432. The indoor fan 43 includes a cylindrical fan rotor 43a that extends long in the longitudinal direction of the indoor unit 40, and a motor 43m that rotates the fan rotor 43a. The fan rotor 43a is composed of a plurality of fan blades arranged along the circumference, and the fan rotor 43a rotates clockwise around the center point O in FIG. By rotating around the center point O, an air flow from the front heat exchange unit 421 and the rear heat exchange unit 422 toward the outlet 432 is generated. The air flow toward the air outlet 432 passes through the fan rotor 43a. Therefore, dew condensation occurs when the fan rotor 43a has a temperature lower than the dew point temperature of the mixed air (conditioned air). In other words, in this case, fan rotor condensation occurs downstream of the indoor heat exchanger 42. The rotation of the indoor fan 43 is controlled by the indoor side control device 47, and the air volume can be changed according to a command from the indoor side control device 47.

(2-2-6) Vertical blade 416 and horizontal blade 417
The vertical blade | wing 416 is arrange | positioned in the blowing flow path which is blowing space S3. The vertical blades 416 are rotated by a stepping motor (not shown) to adjust the longitudinal wind direction of the indoor unit 40. The horizontal blade | wing 417 is arrange | positioned along the blower outlet 432, and rotates by a stepping motor (not shown) and adjusts the wind direction of an up-down direction. The vertical blades 416 and the horizontal blades 417 also form condensation when the temperature is lower than the dew point temperature of the mixed air. Such condensation also corresponds to fan rotor condensation that occurs downstream of the indoor heat exchanger 42.

(2-2-7) Indoor Control Device 47 and Various Sensors The indoor control device 47 is housed in an electrical component box (not shown) installed inside the casing 411. The indoor side control device 47 controls the indoor unit 40 in accordance with, for example, an instruction stored in a memory (not shown) and an instruction from a remote controller (not shown).

  The indoor unit 40 is provided with various sensors in addition to the indoor temperature sensor 451 and the indoor humidity sensor 452 described above, but the description of sensors that are not important for the description is omitted here. On the liquid side of the indoor heat exchanger 42, a liquid side temperature sensor 44 that detects the temperature of the refrigerant (the refrigerant temperature corresponding to the evaporation temperature Te during the cooling operation) is provided. A gas side temperature sensor 45 that detects the temperature of the refrigerant is provided on the gas side of the indoor heat exchanger 42. The blowing space S3 is provided with a blowing temperature sensor 453 that measures the air temperature of the blowing space S3 (the temperature of the mixed air). The blowing space S3 is provided with a blowing humidity sensor 454 that measures the air humidity of the blowing space S3 (humidity of the mixed air). For example, a thermistor can be used for the liquid side temperature sensor 44, the gas side temperature sensor 45, the indoor temperature sensor 451, and the blowout temperature sensor 453.

(3) Operation of the air conditioner In the multi-type air conditioner 10, the user individually sets each indoor unit 40, 50, 60 by an input device such as a remote controller in the cooling operation and the heating operation. Indoor temperature control for bringing the indoor temperatures Tr1, Tr2, Tr3 closer to the set temperatures Ts1, Ts2, Ts3 is performed on the indoor units 40, 50, 60. In this indoor temperature control, when the indoor fans 43, 53, 63 are set to the automatic air volume mode, the air volume of the indoor fan 43 and the indoor expansion valve 41 are opened so that the indoor temperature Tr1 converges to the set temperature Ts1. The air volume of the indoor fan 53 and the opening of the indoor expansion valve 51 are adjusted so that the indoor temperature Tr2 converges to the set temperature Ts2, and the indoor fan 63 is adjusted so that the indoor temperature Tr3 converges to the set temperature Ts3. The air volume and the opening degree of the indoor expansion valve 61 are adjusted. In the low-capacity cooling operation mode, the air volume of the indoor fans 43, 53, and 63 is automatically adjusted by the operation control device 80.

  What is important for the present invention is the low-capacity cooling operation, and since the heating operation may have the same configuration as the conventional one, only the cooling operation will be described below. The multi-type air conditioner 10 is configured to perform a cooling operation in the low-capacity cooling operation mode in addition to the normal refrigerant operation mode during the cooling operation. The normal cooling operation mode is a mode for performing normal cooling operation, and the low-capacity cooling operation mode is a mode for performing low-capacity cooling operation. The low-capacity cooling operation is a cooling operation in which the overheated area of the indoor heat exchanger 42 is increased as compared with the normal cooling operation and the mixed air is mixed with the air that has passed through the overheated area and the air that has passed through the wet area.

(3-1) Cooling Operation During the cooling operation, the four-way switching valve 22 is in the state shown by the solid line in FIG. 1, that is, the discharge side of the compressor 21 is connected to the gas side of the outdoor heat exchanger 23, and the compression is performed. The suction side of the machine 21 is connected to the gas side of the indoor heat exchangers 42, 52, 62 via the gas refrigerant communication pipe 72. In this case, the outdoor expansion valve 38 is fully opened during the cooling operation. The opening of the indoor expansion valve 41 is adjusted so that the superheat degree SH1 of the refrigerant at the outlet of the indoor heat exchanger 42 (that is, the gas side of the indoor heat exchanger 42) becomes the target superheat degree SHt1, and the indoor expansion valve 51 Is adjusted so that the superheat degree SH2 of the refrigerant at the outlet of the indoor heat exchanger 52 (that is, the gas side of the indoor heat exchanger 52) becomes constant at the target superheat degree SHt2, and the indoor expansion valve 61 is The opening degree is adjusted such that the superheat degree SH3 of the refrigerant at the outlet of the indoor heat exchanger 62 (that is, the gas side of the indoor heat exchanger 62) becomes the target superheat degree SHt3.

  The target superheat degrees SHt1, SHt2, and SHt3 are set to optimum temperature values so that the indoor temperatures Tr1, Tr2, and Tr3 converge to the set temperatures Ts1, Ts2, and Ts3 within a predetermined superheat degree range. The superheat degrees SH1, SH2, and SH3 of the refrigerant at the outlets of the indoor heat exchangers 42, 52, and 62 are calculated from the refrigerant temperature values detected by the gas side temperature sensors 45, 55, and 65, for example. , 54, 64 are detected by subtracting the refrigerant temperature value (corresponding to the evaporation temperature Te). However, the superheat degrees SH1, SH2, and SH3 of the refrigerant at the outlets of the indoor heat exchangers 42, 52, and 62 are not limited to being detected by the above-described method.

  When the compressor 21, the outdoor fan 28, and the indoor fans 43, 53, 63 are operated in the state of the refrigerant circuit 11, the low-pressure gas refrigerant is sucked into the compressor 21 and compressed to become a high-pressure gas refrigerant. Thereafter, the high-pressure gas refrigerant is sent to the outdoor heat exchanger 23 via the four-way switching valve 22, performs heat exchange with the outdoor air supplied by the outdoor fan 28, and dissipates heat to generate high-pressure liquid refrigerant. Become. The high-pressure liquid refrigerant is sent to the indoor units 40, 50 and 60 via the liquid refrigerant communication pipe 71.

  The high-pressure liquid refrigerant sent to the indoor units 40, 50, 60 is decompressed to near the suction pressure of the compressor 21 by the indoor expansion valves 41, 51, 61, respectively, and becomes low-pressure gas-liquid two-phase refrigerant. Are sent to the indoor heat exchangers 42, 52, and 62, exchange heat with indoor air in the indoor heat exchangers 42, 52, and 62, respectively, and evaporate into low-pressure gas refrigerant.

  The low-pressure gas refrigerant is sent to the outdoor unit 20 via the gas refrigerant communication pipe 72 and flows into the accumulator 24 via the four-way switching valve 22. Then, the low-pressure gas refrigerant that has flowed into the accumulator 24 is again sucked into the compressor 21. Thus, in the multi-type air conditioner 10, the outdoor heat exchanger 23 is used as a radiator for the refrigerant compressed in the compressor 21, and the indoor heat exchangers 42, 52, and 62 are condensed in the outdoor heat exchanger 23. Then, it is possible to perform a cooling operation to function as an evaporator of the refrigerant sent through the liquid refrigerant communication pipe 71 and the indoor expansion valves 41, 51, 61 after being performed. In the multi-type air conditioner 10, the indoor units 40, 50, 60 do not have a mechanism for adjusting the refrigerant pressure on the gas side of the indoor heat exchangers 42, 52, 62. The evaporation pressure Pe in 42, 52 and 62 is a common pressure.

(3-2) Normal Cooling Operation and Low-Performance Cooling Operation In the normal cooling operation, as shown in FIG. 4, substantially all of the indoor heat exchanger 42 has a wet region 491 (hatched lines are drawn). Area). On the other hand, in the low-capacity cooling operation, as shown in FIG. 5, the lowermost heat transfer tube 483 of the lower front heat exchange section 427 closest to the refrigerant inlet 4 to the bottom of the upper front heat exchange section 426 Up to the stage heat transfer tube 486 is a wet region 491 (a region in which diagonal lines are drawn). However, from the lower front heat exchange section 426 to the lowermost heat transfer pipe 484 of the rear heat exchange section 422 from the fifth stage heat transfer pipe 487 to the rear heat exchange section 422 is an overheated region 492 (region not hatched). . This overheated region 492 may be referred to as a dry region in the following description. In the normal cooling operation, almost the entire area becomes the wet region 491 in order to obtain a high cooling capacity, but the portion near the outlet of the indoor heat exchanger 42 is in the overheat region (dry region) in relation to the overheat control. Sometimes it becomes.

  A gas-liquid two-phase refrigerant flows in the wet region 491, and a gas-state refrigerant flows in the overheat region 492. For this reason, in the overheating region 492, heat exchange between the refrigerant and the air is hardly performed, and the temperature of the air that has passed through the overheating region 492 is substantially the same as the temperature of the air before passing through.

  When the low-capacity cooling operation mode is selected, the opening degree of the indoor expansion valve 41 and the air volume of the indoor fan 43 are adjusted by the operation control device 80, and the low-capacity cooling operation in the state shown in FIG. 5 is performed. It is. In the low-capacity cooling operation, condensation is more likely to occur in the device downstream of the indoor heat exchanger 42 than in the normal cooling operation in which the condensed water is removed by the indoor heat exchanger 42. Therefore, control for avoiding the occurrence of condensation in the apparatus of the multi-type air conditioner 10, particularly in the indoor unit 40, in the low-performance cooling operation will be described below.

(3-3) Control at the time of low-capacity cooling operation (3-3-1) Overview of control at the time of low-capacity cooling operation A plurality of arrows shown in FIG. Wet area passing air Ar8 and superheated area passing air Ar9 are shown conceptually. In the low-performance cooling operation, the operation control device 80 increases the opening of the indoor expansion valve 41 when the room temperature Tr1 is higher than the set temperature Ts1, thereby narrowing the overheat region 492 and expanding the wet region 491. I do. Here, the value of the room temperature Tr1 is the value of the suction temperature Ti of the suction air Ar6, is measured by the room temperature sensor 451, and is transmitted to the operation control device 80.

  Since the temperature of the mixed air Ar7 is lowered by expanding the wet area 491 having a higher heat exchange capacity than the overheat area 492, the indoor unit 40 is operated by increasing the opening of the indoor expansion valve 41. The temperature Tr1 can be brought close to the set temperature Ts1. However, if the wet region 491 is excessively expanded in the low-capacity cooling operation, a state in which condensation occurs in the fan rotor 43a of the indoor fan 43 occurs.

  Here, it will be described with reference to the air diagram calculation table shown in FIG. 6 that the fan rotor 43a will cause condensation when the wet region 491 is excessively expanded. In FIG. 6, RH100, RH90, RH80, and RH70 are curves indicating relative humidity of 100% RH, 90% RH, 80% RH, and 70% RH, respectively. Assuming that the suction temperature of the suction air Ar6 is 27 ° C. and the relative humidity is about 85% RH, the point P1 in FIG. 6 corresponds to the state of the suction air Ar6. When the evaporation temperature of the indoor heat exchanger 42 is 7 ° C., a point P2 where the dry bulb temperature 7 ° C. and the curve RH100 (saturation line) intersect is taken. The intersection of the straight line LN20 connecting the point P1 and the point P2 and the curve RH100 is defined as a point P3. Condensation does not occur if the state of the mixed air Ar7 is in the range D1 from the point P1 to the point P3, but condensation occurs if the state of the mixed air Ar7 is in the range D2 from the point P2 to the point P3. The size of the wet region 491 at this point P3 is an upper limit that does not cause condensation. In order to control so as not to exceed the upper limit, the size of the wet region 491 is determined by a method described later. Then, the opening degree of the indoor expansion valve 41 and the air volume of the indoor fan 43 are set so that the determined wet area 491 size (occupation ratio of the wet area 491) does not exceed the wet area 491 size at the point P3. Adjust. If the occupation ratio of the wet area 491 during the low-capacity cooling operation approaches the occupation ratio of the wet area 491 at the point P3, the air volume of the indoor fan 43 is increased without opening the indoor expansion valve 41 and the cooling is performed. Control to increase ability.

  In the following, (3-4) shows the avoidance control of the fan rotor condensation performed by determining the size of the wet region 491 by measuring the temperature or humidity of the mixed air Ar7, and two or more indoor heat exchanger temperatures are shown. The fan rotor condensation avoidance control performed by determining the size of the wet region 491 using the detection result of the sensor 455 is shown in (3-5).

  When the room temperature Tr1 is lower than the set temperature Ts1 in the low-capacity cooling operation, the opening degree of the indoor expansion valve 41 is reduced and / or the air volume of the indoor fan 43 is lowered to lower the cooling capacity. In the control corresponding to the case where the indoor temperature Tr1 is lower than the set temperature Ts1, the fan rotor condensation is changed to a state that is less likely to occur, and therefore the determination of the size of the wet region 491 may be omitted.

(3-4) Avoidance Control During Low-Performance Cooling Operation (3-4-1) Outline of Avoidance Control of Fan Rotor Condensation The plurality of arrows shown in FIG. 5 indicate the intake air Ar6, the mixed air Ar7, Wet area passing air Ar8 and superheated area passing air Ar9 are shown conceptually. The operation control device 80 determines the size of the wet region 491 using the temperature of the mixed air Ar7 during the low-capacity cooling operation, and the temperature of the mixed air Ar7 exceeds the dew point temperature of the mixed air Ar7. Control is performed to prevent fan rotor condensation from occurring downstream of 42. More specifically, the size of the wet region 491 is determined using the suction temperature and suction humidity (relative humidity) of the suction air Ar6, the temperature of the mixed air Ar7, and the evaporation temperature, and the determination result of the size of the wet region 491 is used. Control based on. The size of the wet region 491 (the area of the wet region 491) is, for example, (the area of the wet region 491) / ((the area of the wet region 491) + (the area of the overheating region 492)) × 100 (= the wet region 491) Occupancy). That is, the size of the wet area 491 can be determined by calculating the occupation ratio of the wet area 491. The control by the operation control device that calculates the occupation ratio of the wet region 491 and prevents the fan rotor condensation from occurring downstream of the indoor heat exchanger 42 will be described in detail below.

(3-4-2) Calculation in Avoidance Control of Condensation of Fan Rotor In the following description, the suction temperature of the suction air Ar6 is expressed as Ti ° C., and the suction humidity of the suction air Ar6 is expressed as Hi% RH. The temperature of the mixed air Ar7 is expressed as Tm ° C., and the absolute humidity of the mixed air Ar7 is expressed as Xmkg / kgDA. The air temperature of the wet region passing air Ar8 is expressed as Tw ° C., and the absolute humidity of the wet region passing air Ar8 is expressed as Xwmkg / kgDA. The air temperature Td ° C. of the overheated area passing air Ar9 is expressed, and the absolute humidity of the overheated area passing air Ar9 is expressed as Xdmkg / kgDA. However, it can be expressed using Ti instead of Td, assuming that the air temperature Td ° C. of the overheated region passing air Ar9 is equal to the suction temperature Ti ° C. Even if such a replacement is used, the accuracy is hardly changed, and by this replacement, a temperature sensor for measuring the air temperature Td ° C. of the overheated region passing air Ar9 can be omitted.

  The operation control device 80 stores information related to the bypass factor BF of the indoor heat exchanger 42 in, for example, an internal memory. The bypass factor BF is obtained in advance by experiment or simulation, and the obtained value is input to the operation control device 80. The operation control device 80 is configured to be able to read and obtain a necessary bypass factor BF from, for example, an internal memory when performing avoidance control of fan rotor condensation during low-performance cooling operation.

  As already described, the intake temperature Ti of the intake air Ar6 is detected by the indoor temperature sensor 451. The operation control device 80 acquires the value of the suction temperature Ti detected by the room temperature sensor 451 from the room temperature sensor 451.

  The evaporation temperature Te ° C. of the indoor heat exchanger 42 is detected by the liquid side temperature sensor 44. The operation control device 80 acquires the value of the evaporation temperature Te detected by the liquid side temperature sensor 44 from the liquid side temperature sensor 44.

  The temperature Tm ° C. of the mixed air Ar7 is detected by the blowing temperature sensor 453. The operation control device 80 acquires the value of the temperature Tm of the mixed air Ar7 detected by the blowing temperature sensor 453 from the liquid side temperature sensor 44.

  The operation control device 80 calculates the value of the air temperature Tw that has passed through the wet region 491 using the following equation (1). The operation control device 80 can acquire the value of the air temperature Tw that has passed through the wet region 491 by calculating the equation (1).

  Tw = (Ti−Te) × BF + Te (1).

  The operation control apparatus 80 calculates the value of the occupation ratio Rw% of the wet region 491 using the following equation (2). The operation control device 80 can acquire the value of the occupation ratio Rw of the wet region 491 by calculating the equation (2).

  Rw = (Tm−Ti) / (Tw−Ti) (2).

  The operation control device 80 uses the occupation ratio Rw of the wet region 491 to prevent the temperature Tm of the mixed air Ar7 from being lower than the dew point temperature Tp of the mixed air Ar7 using a result obtained by calculation described later. Control is performed so that fan rotor condensation does not occur downstream of the indoor heat exchanger 42. That is, in the low-capacity cooling operation, the operation control device 80 determines the size of the wet region 491 using the temperature Tm of the mixed air Ar7, and the temperature Tm of the mixed air Ar7 exceeds the dew point temperature Tp of the mixed air Ar7. Thus, control is performed so that fan rotor condensation does not occur downstream of the indoor heat exchanger 42.

  Next, a method for obtaining the relationship between the temperature Tm of the mixed air Ar7 and the dew point temperature Tp of the mixed air Ar7 using the occupation ratio Rw of the wet region 491 will be described.

  The intake humidity Hi of the intake air Ar6 is detected by the indoor humidity sensor 452. The operation control device 80 acquires the value of the suction humidity Hi detected by the indoor humidity sensor 452 from the indoor humidity sensor 452.

  When the function for obtaining the absolute humidity with the dry bulb temperature and the relative humidity as parameters is expressed as fx, the operation control device 80 uses the following equation (3) to calculate the absolute humidity Xd of the air that has passed through the overheating region 492. Calculate the value of. The operation control device 80 can acquire the value of the absolute humidity Xd by calculating the equation (3). The function fx is, for example, an approximation of an air diagram calculation table by a calculation formula.

  Xd = fx (Ti, Hi) (3).

  The operation control device 80 calculates the value of the absolute humidity Xw of the air that has passed through the wet region 491 using the following equation (4). The operation control device 80 can acquire the value of the occupation ratio Rw of the wet region 491 by calculating the equation (4).

  Xw = (Xd−fx (Te, 100)) × BF + fx (Te, 100) (4).

  The operation control device 80 calculates the value of the absolute humidity Xm of the mixed air Ar7 using the following equation (5). The operation control device 80 can obtain the value of the absolute humidity Xm of the mixed air Ar7 by calculating the equation (5).

  Xm = Rw * Xw + (1-Rw) * Xd (5).

  When the function for obtaining the dew point temperature with the dry bulb temperature and the absolute humidity as parameters is expressed as fp, the operation control device 80 uses the following equation (6) to calculate the value of the dew point temperature Tp of the mixed air Ar7. calculate. The function fp is, for example, an approximation of an air diagram calculation table by a calculation formula. The operation control device 80 can obtain the value of the dew point temperature Tp of the mixed air Ar7 by calculating the equation (6).

  Tp = fp (Tm, Xm) (6).

  The operation control device 80 prevents the fan rotor condensation on the downstream side of the indoor heat exchanger 42 by preventing the temperature Tm of the mixed air Ar7 from falling below the dew point temperature Tp of the mixed air Ar7 obtained by the equation (6). Control to not.

(3-4-3) Device control for avoiding fan rotor dew condensation during low-capacity cooling operation Size of wet area determined using the above formulas (1) to (6) (occupation ratio of the wet area) Using the calculation result calculated based on the above, device control for avoiding fan rotor condensation during low-performance cooling operation is performed. For example, by comparing the temperature Tm of the mixed air Ar7 (the temperature detected by the blowout temperature sensor 453) with the dew point temperature Tp of the mixed air Ar7 obtained using the above formulas (1) to (6), The operation control device 80 controls the indoor expansion valve 41 and / or the indoor fan 43.

  FIG. 7 shows a fan rotor dew condensation limit line with respect to the temperature of the mixed air, which is obtained from the evaporation temperature, the suction temperature, and the suction temperature. The graph shown in FIG. 7 is a schematic representation of the relationship obtained using the above equations (1) to (6). The limit lines LN1, LN2, LN3, and LN4 are limit lines when the suction humidity Hi is 85% RH, 80% RH, 70% RH, and 60% RH, respectively. If the temperature Tm of the mixed air Ar7 is higher than these limit lines LN1 to LN4, condensation does not occur. Conversely, if the temperature Tm of the mixed air Ar7 is lower than these limit lines, condensation occurs.

  With reference to FIG. 7, for example, if the evaporation temperature Te is about 7 ° C. and the suction humidity Hi is 80% RH, the temperature of the mixed air Ar7 is made higher than about 17 ° C., thereby avoiding fan rotor condensation. I can see that In other words, the limit lines LN1 to LN4 represent the dew point temperature Tp of the mixed air Ar7 under each condition.

  In the operation control device 80, the indoor unit 40 is operated under the above-described conditions that the evaporation temperature Te is about 7 ° C., the suction humidity Hi is 80% RH, and the dew point temperature Tp of the mixed air Ar7 is about 17 ° C. In addition, it is assumed that the indoor unit 40 is operated at the operation point OP1 of FIG. In such a case, there is no concern that fan rotor condensation will occur. In such a case, if the temperature Tm of the mixed air Ar7 at the operating point OP1 of the indoor unit 40 is higher than 17 ° C., it is possible to perform control to continue the operation as it is, but it is possible to reliably avoid fan rotor condensation. Therefore, even if the temperature Tm of the mixed air at the operation point OP1 of the indoor unit 40 is higher than 17 ° C., the temperature Tm of the mixed air does not fall below the dew point temperature Tp due to a sudden change in environment or setting conditions. It is conceivable to change the operating condition to an operating point where fan rotor condensation is unlikely to occur.

  Further, for example, when the evaporation temperature Te is about 7 ° C. and the suction humidity Hi is not changed at 80% RH under the above-described conditions, the operation control device 80 can detect the temperature Tm of the mixed air Ar7 and the limit line LN2 (dew point temperature). When the temperature difference of (Tp) falls below the first threshold value, the opening of the indoor expansion valve 41, which is a pressure reducing mechanism, may be reduced and the air volume of the indoor fan 43 may be increased. For example, if the first threshold value is 7 ° C., the operation control device 80 determines that (Tm−Tp) <7 ° C. when the temperature Tm of the mixed air Ar7 at the operation point OP1 becomes 23 ° C. Thus, control is performed to reduce the opening of the indoor expansion valve 41 and increase the air volume of the indoor fan 43. When the operation control device 80 controls the opening degree of the indoor expansion valve 41 to be small, the refrigerant circulation amount is decreased and the overheating region 492 of the indoor heat exchanger 42 is increased, thereby preventing the temperature Tm of the mixed air from being lowered. , Fan rotor condensation can be suppressed. A decrease in the cooling capacity due to a decrease in the refrigerant circulation amount can be compensated by increasing the air volume of the indoor fan 43.

  For example, when the evaporating temperature Te is about 7 ° C. and the suction humidity Hi is not changed at 80% RH under the above-described conditions, the operation control device 80 can detect the temperature Tm of the mixed air Ar7 and the limit line LN2 (dew point temperature Tp). When the temperature difference is less than the second threshold value, the air volume of the indoor fan 43 may be controlled to increase. For example, if the second threshold value is 8 ° C., the operation control device 80 determines that (Tm−Tp) <8 ° C. when the temperature Tm of the mixed air Ar7 at the operation point OP1 becomes 24 ° C. Thus, control is performed to increase the air volume of the indoor fan 43. When the operation control device 80 controls the air volume of the indoor fan 43 to increase, the air volume increases and the cooling capacity increases, so that the superheat region 492 of the indoor heat exchanger 42 changes in the increasing direction. The temperature Tm can be prevented from decreasing and the occurrence of fan rotor condensation can be suppressed.

  Further, for example, when the evaporation temperature Te is about 7 ° C. and the suction humidity Hi is not changed at 80% RH under the above-described conditions, the operation control device 80 can detect the temperature Tm of the mixed air Ar7 and the limit line LN2 (dew point temperature). When the temperature difference of Tp) falls below the third threshold value, control may be performed to switch from the low-capacity cooling operation mode to the normal cooling operation mode. For example, if the value of the third threshold value is set to 0.5 ° C., the operation control device 80 (Tm−Tp) <0.5 when the temperature Tm of the mixed air Ar7 at the operation point OP1 becomes 17 ° C. Control is performed to switch from the low-capacity cooling operation mode to the normal cooling operation mode based on the judgment of ° C. When the operation control device 80 performs control to switch from the low-capacity cooling operation mode to the normal cooling operation mode, the state shown in FIG. 5 changes to the state shown in FIG. 4 to substantially change the indoor heat exchanger. Since the entire area 42 can be made into the wet area 491, air passing through the overheat area 492 of the indoor heat exchanger 42 can be eliminated, so that it is possible to prevent the fan rotor condensation while ensuring the necessary cooling capacity. it can.

(3-4-4)
The graph shown in FIG. 8 is a schematic representation of the relationship obtained using the above equations (1) to (6). The limit lines LN11, LN12, LN13, and LN14 are limit lines when the suction humidity Hi is 85% RH, 80% RH, 70% RH, and 60% RH, respectively. If the occupation ratio Rw of the wet region 491 is smaller than these limit lines LN11 to LN14, condensation does not occur. Conversely, if the occupation ratio Rw of the wet region 491 is larger than these limit lines LN11 to LN14, condensation occurs.

  With reference to FIG. 8, for example, if the evaporation temperature Te is about 7 ° C. and the suction humidity Hi is 80% RH, the fan rotor condensation can be avoided by making the occupation ratio Rw of the wet region 491 smaller than about 50%. You can see that you can.

  The operation control device 80 is configured so that the indoor unit 40 operates under the above-described conditions that the evaporation temperature Te is about 7 ° C., the suction humidity Hi is 80% RH, and the limit occupation ratio Rmw of the wet region 491 where condensation occurs is about 50 ° C. It is assumed that the indoor unit 40 is in operation and is operated at the operation point OP2 in FIG. In such a case, there is no concern that fan rotor condensation will occur. In such a case, if the occupation ratio Rw of the wet area 491 at the operation point OP2 of the indoor unit 40 is smaller than 50%, it is possible to perform control to continue the operation as it is, but it is possible to reliably avoid fan rotor condensation. Therefore, even if the occupation ratio Rw of the operating point OP2 of the indoor unit 40 is smaller than 50%, it is conceivable to change the operating condition to an operating point where fan rotor condensation is less likely to occur.

  For example, when the evaporation temperature Te is about 7 ° C. and the suction humidity Hi is not changed at 80% RH under the above-described conditions, the operation control device 80 indicates that the difference between the occupation ratio Rw of the wet region 491 and the limit line LN12 is the first. It may be configured to perform control to reduce the opening degree of the indoor expansion valve 41 that is a pressure reducing mechanism and increase the air volume of the indoor fan 43 when the value falls below the four threshold values. For example, if the value of the fourth threshold is 15%, the operation control device 80 determines that (Rmw−Rw) <15 when the occupation ratio Rw of the wet region 491 at the operation point OP2 becomes 40%. Thus, control is performed to reduce the opening of the indoor expansion valve 41 and the air volume of the indoor fan 43 is increased. A decrease in the cooling capacity due to a decrease in the refrigerant circulation amount can be compensated by increasing the air volume of the indoor fan 43.

  Further, for example, when the evaporation temperature Te is about 7 ° C. and the suction humidity Hi is not changed at 80% RH under the above-described conditions, the operation control device 80 determines the difference between the occupation ratio Rw of the wet region 491 and the limit line LN12. May be configured to perform control to increase the air volume of the indoor fan 43 when the value falls below the fifth threshold. For example, if the value of the fifth threshold is 25%, the operation control device 80 determines that (Rmw−Rw) <25% when the occupation ratio Rw of the wet region 491 at the operation point OP2 becomes 30%. Then, control for increasing the air volume of the indoor fan 43 is performed.

  Further, for example, when the evaporation temperature Te is about 7 ° C. and the suction humidity Hi is not changed at 80% RH under the above-described conditions, the operation control device 80 determines the difference between the occupation ratio Rw of the wet region 491 and the limit line LN12. May be configured to perform control to switch from the low-capacity cooling mode to the normal cooling mode when the value falls below the sixth threshold. For example, if the value of the sixth threshold is 1%, the operation control device 80 determines that (Rmw−Rm) <1% when the occupation ratio Rw of the wet region 491 of the operation point OP2 becomes 50%. Then, control for switching from the low-capacity cooling operation mode to the normal cooling operation mode is performed.

(3-4-5)
In the above-described control, in the low-capacity cooling operation in which the overheating region 492 of the indoor heat exchanger 42 is increased more than the normal cooling operation, the suction temperature Ti, the suction humidity Hi, the temperature Tm of the mixed air Ar7, and the evaporation temperature Te are used, for example, FIG. As shown in FIG. 7, the fan rotor dew condensation avoidance control is performed, and the temperature Tm of the mixed air Ar7 exceeds the dew point temperature Tp of the mixed air so that the fan rotor dew condensation does not occur downstream of the indoor heat exchanger 42. The case where the operation control device 80 performs control has been described. However, the operation control device 80 uses the suction temperature Ti, the suction humidity Hi, the humidity of the mixed air Ar7 and the evaporation temperature Te instead of using the suction temperature Ti, the suction humidity Hi, the temperature Tm and the evaporation temperature Te of the mixed air Ar7. Then, the fan rotor condensation avoidance control may be performed so that the fan rotor condensation does not occur downstream of the indoor heat exchanger 42 when the humidity of the mixed air Ar7 exceeds the saturated humidity of the mixed air. For this purpose, for example, as shown in FIG. 2, a blowing humidity sensor 454 may be provided in the blowing space S3.

(3-5) Fan rotor dew condensation avoidance control during low-capacity cooling operation (3-5-1) Overview of fan rotor dew condensation avoidance control The operation control device 80 performs two or more indoor heat exchanges during low-performance cooling operation. The size of the wet region 491 is determined using the detection result of the temperature sensor 455, and the temperature of the mixed air Ar7 shown in FIG. 5 exceeds the dew point temperature of the mixed air Ar7, so that In order to prevent the fan rotor condensation from occurring, control is performed. More specifically, the size of the wet region 491 is determined using the suction temperature, the suction humidity (relative humidity) and the evaporation temperature of the suction air Ar6, and the detection results of two or more indoor heat exchanger temperature sensors 455, and the wet region Control is performed based on the determination result of the size of 491.

(3-5-2) Calculation in Operation Control Device 80 Operation control device 80 inputs the temperature of U-shaped tube 485 attached from a plurality of indoor heat exchanger temperature sensors 455. The temperature of the U-shaped tube 485 is the temperature of the refrigerant flowing through the U-shaped tube 485. The temperature of the heat transfer tube 482 in the wet region 491 becomes an evaporation temperature Te that is substantially the temperature of the gas-liquid two-phase refrigerant. On the other hand, the temperature of the heat transfer tube 482 in the overheating region 492 is higher than the evaporation temperature Te. For example, assuming that there are 10 heat transfer tubes 482, if there are 11 indoor heat exchanger temperature sensors 455, the indoor heat exchanger temperature sensors 455 can be arranged before and after each heat transfer tube 482. For example, in any heat transfer tube 482, if there is a height difference of a predetermined threshold or more between the detected temperatures of the two indoor heat exchanger temperature sensors 455 before and after that, the heat transfer tube 482 is determined to be the wet region 491. It can be constituted as follows. For example, if the indoor heat exchanger temperature sensor 455 on the side near the outlet of the tenth stage heat transfer tube 482 near the outlet of the indoor heat exchanger 42 detects the evaporation temperature Te, the operation control device 80 It is determined that the occupation ratio Rw of 491 is 100%. For example, if there is a height difference equal to or greater than a predetermined threshold in the detected temperatures of the two indoor heat exchanger temperature sensors 455 at both ends of the sixth-stage heat transfer tube 482, the superheat region 492 extends to the sixth-stage heat transfer tube 482. Therefore, the operation control device 80 can acquire a value that the occupation ratio Rw of the wet region 491 is 50%.

  In addition, although the indoor heat exchanger temperature sensor 455 may be arrange | positioned equally, you may concentrate and arrange | position to a part. For example, since the indoor heat exchanger 42 in FIG. 2 has eight heat transfer tubes 482 in the upper front heat exchange section 426, the indoor heat exchangers 482 are provided before and after the eight heat transfer tubes 482 in the upper front heat exchange section 426. An exchanger temperature sensor 455 may be arranged. When arranged in this manner, it becomes possible to determine in detail whether the occupation ratio Rw is around 50% with a small number of sensors.

  The operation control device 80 can acquire values of the air temperature Tw ° C. that has passed through the wet region 491, the absolute humidity Xwkg / kgDA of the air that has passed through the wet region 491, and the absolute humidity Xdkg / kgDA of the air that has passed through the overheat region 492. It is configured. For example, the operation control device 80 calculates the air temperature Tw that has passed through the wet region 491 and the absolute value of the air that has passed through the wet region 491 by performing calculations of the following equations (14), (15), and (16). The values of the humidity Xw and the absolute humidity Xd of the air that has passed through the overheating region 492 can be acquired.

  The operation control device 80 determines the occupation ratio Rw of the wet region 491 acquired from the detection result of the indoor heat exchanger temperature sensor 455, the acquired temperature Tm of the mixed air Ar7, the absolute humidity Xw of the air that has passed through the wet region 491, and the overheating. Using the value of the absolute humidity Xd of the air that has passed through the region 492, the temperature Tm of the mixed air Ar7 is obtained by the following equation (11).

  Tm = Rw × Tw + (1−Rw) × Ti (11).

  Further, the absolute humidity Xm of the mixed air Ar7 is obtained by the following equation (12).

  Xm = Rw * Xw + (1-Rw) * Xd (12).

  Then, using the temperature Tm of the mixed air Ar7 and the value of the absolute humidity Xm obtained by the equations (11) and (12), the dew point temperature Tp of the mixed air is obtained by the following equation (13). However, fp is a function for obtaining the dew point temperature using the dry bulb temperature and the absolute humidity as parameters. The function fp is, for example, an approximation of an air diagram calculation table by a calculation formula.

  Tp = fp (Tm, Xm) (13).

  The operation control device 80 uses the result obtained by the equation (13) to prevent the dew point temperature Tp of the mixed air Ar from dropping below the temperature Tm of the mixed air Ar7, thereby reducing the fan downstream of the indoor heat exchanger 42. Control to prevent rotor condensation.

  Next, one mode in which the operation control device 80 acquires the values of the temperature Tm of the mixed air Ar7, the absolute humidity Xw of the air that has passed through the wet region 491, and the absolute humidity Xd of the air that has passed through the superheat region 492 will be described. As described above, the operation control device 80 reads and acquires the necessary bypass factor BF from, for example, the internal memory, acquires the value of the suction temperature Ti detected by the indoor temperature sensor 451 from the indoor temperature sensor 451, The value of the suction humidity Hi detected by the indoor humidity sensor 452 can be acquired from the indoor humidity sensor 452, and the value of the evaporation temperature Te detected by the liquid side temperature sensor 44 can be acquired from the liquid side temperature sensor 44. It is configured.

  The operation control device 80 obtains the air temperature Tw that has passed through the wet region 491 according to the following equation (14).

  Tw = (Ti−Te) × BF + Te (14).

  Moreover, the operation control apparatus 80 calculates | requires the absolute humidity Xd of the air which passed the overheating area | region 492 by following (15) Formula. However, fx is a function for obtaining absolute humidity using dry bulb temperature and relative humidity as parameters.

  Xd = fx (Ti, Hi) (15).

  Using the absolute humidity Xd of the air that has passed through the overheating region 492 determined by the equation (15), the absolute humidity Xw of the air that has passed through the wet region is determined by the following equation (16).

  Xw = (Xd−fx (Te, 100)) × BF + fx (Te, 100) (16).

  The operation control device 80 calculates the temperature Tm of the mixed air Ar7, the absolute humidity Xw of the air that has passed through the wet region 491, and the overheating region by calculating the above equations (14), (15), and (16). The value of the absolute humidity Xd of the air that has passed through 492 can be acquired.

(3-5-3) Device control for avoiding fan rotor dew condensation during low-performance cooling operation FIG. It is shown. The graph shown in FIG. 7 is a schematic representation of the relationship obtained using the above equations (11) to (16). Since the graph in FIG. 7 is also a diagram showing the relationship obtained using the above-described equations (1) to (6), the relationship obtained using the above-described equations (1) to (6) is used. In the same manner as described in the above-mentioned “(3-4-3) Device control for avoiding condensation of fan rotor at the time of low-performance cooling operation”, the above equations (11) to (16) are used. Equipment control for avoiding fan rotor condensation during low-performance cooling operation can be performed using the required relationship.

(3-5-4)
The graph shown in FIG. 8 is a schematic representation of the relationship obtained using the above equations (11) to (16). Since the graph of FIG. 8 is also a diagram illustrating the relationship obtained using the above-described equations (1) to (6), the relationship obtained using the above-described equations (1) to (6) is used. In the same manner as described above in “(3-4-4) Device control for avoiding condensation of fan rotor at the time of low-capacity cooling operation”, the above equations (11) to (16) are used. Equipment control for avoiding fan rotor condensation during low-performance cooling operation can be performed using the required relationship.

(4) Features (4-1)
As described above, in the multi-type air conditioner 10, the cooling capacity is improved by widening the wet region 491 of the indoor heat exchanger 42 by increasing the opening of the indoor expansion valve 41 (an example of a pressure reducing mechanism). On the other hand, when the wet area increases 491, the temperature of the mixed air formed by mixing the air that has passed through the superheated area 492 of the indoor heat exchanger 42 and the air that has passed through the wet area 491 decreases. Therefore, the control by the opening degree of the indoor expansion valve 41 does not cause condensation on the fan rotor 43a so that the temperature Tm of the mixed air Ar7 falls too much to the dew point temperature Tp or less of the mixed air Ar7 and condensation does not occur on the fan rotor 43a. The required cooling capacity is ensured by stopping the upper limit to suppress the expansion of the wet area 491 and increasing the air capacity of the indoor fan 43 to further improve the cooling capacity. As a result, when the multi-type air conditioner 10 is performing the low-capacity cooling operation, it is possible to prevent condensation from occurring in the fan rotor 43a of the indoor fan 43 while ensuring the necessary cooling capacity.

(4-2)
When the indoor temperature Tr1 is lower than the set temperature Ts1 in the low-capacity cooling operation during cooling, the opening of the indoor expansion valve 41 is reduced and / or the air volume of the indoor fan 43 is reduced to lower the cooling capacity. What has been done? Condensation occurs in the fan rotor 43a because the wet region 491 is reduced from the state in which the expansion of the wet region 491 is limited to the upper limit at which no condensation occurs in the fan rotor 43a of the indoor fan 43 and / or the air volume is reduced. It is possible to reduce the cooling capacity while maintaining the absence. At this time, since the operation control device 80 does not perform the fan rotor condensation avoidance control, an increase in the load on the operation control device 80 can be suppressed.

(4-3)
If the blower temperature sensor 453 or the blown humidity sensor 454 for measuring the temperature Tm of the mixed air Ar7 or the humidity of the mixed air Ar7 is provided in the indoor unit 40, the humid region using the temperature Tm of the mixed air Ar7 or the humidity of the mixed air Ar7. The occupation ratio Rw of 491 can be determined. As a result, using the temperature Tm of the mixed air Ar7 or the humidity of the mixed air Ar7, it is simply determined whether or not the expansion of the wet region 491 is limited to the upper limit at which no condensation occurs in the fan rotor 43a. Thus, the certainty of preventing the condensation of the fan rotor 43a is improved.

(4-4)
If the indoor heat exchanger 42 is provided with two or more indoor heat exchanger temperature sensors 455, the occupation ratio Rw of the wet region 491 can be determined using the detection result of the indoor heat exchanger temperature sensor 455. As a result, using the detection results of two or more indoor heat exchanger temperature sensors 455, it is simply determined whether or not the expansion of the wet region 491 is limited to the upper limit at which no condensation occurs in the fan rotor 43a. Thus, the certainty of preventing the condensation of the fan rotor 43a is improved.

(4-5)
If the operation control device 80 cannot limit the expansion of the wet area to the upper limit where condensation does not occur on the rotor even if the air volume of the indoor fan 43 is increased in order to obtain the required cooling capacity, the operation control device 80 is in the low-performance cooling operation mode. By switching to the normal cooling operation mode, the entire indoor heat exchanger 42 can be made substantially wet. As a result, air passing through the overheating region 492 of the indoor heat exchanger 42 can be eliminated, and condensation of the fan rotor 43a can be prevented while ensuring necessary cooling capacity.

(5) Modification (5-1) Modification 1A
In the above-described embodiment, the avoidance control of fan rotor condensation has been described for the indoor unit 40. However, for the indoor units 50 and 60, the operation control device 80 can perform the same avoidance control of fan rotor condensation as for the indoor unit 40. it can. In that case, each indoor expansion valve 51, 61 functions as a pressure reducing mechanism for each indoor unit 50, 60. In addition, the indoor fans 53 and 63 include a fan rotor through which the mixed air similar to the fan rotor 43a of the indoor fan 43 passes.

(5-2) Modification 1B
In the above-described embodiment, the indoor unit 40 is provided with the blowout temperature sensor 453, the blowout humidity sensor 454, and two or more indoor heat exchanger temperature sensors 455. Since the size can be determined, any one of the blowout temperature sensor 453, the blowout humidity sensor 454, and two or more indoor heat exchanger temperature sensors 455 may be provided.

(5-3) Modification 1C
In the above embodiment, the multi-type air conditioner 10 includes the indoor expansion valves 41, 51, 61, the liquid side temperature sensors 44, 54, 64, the gas side temperature sensors 45, 55, and the indoor units 40, 50, 60, respectively. Although what 65 was attached was demonstrated, as FIG.9 and FIG.10 shows, these may be provided in the outdoor unit 20. FIG. The expansion valves 41a, 51a, 61a are provided in the outdoor unit 20, but function as a pressure reducing mechanism for the refrigerant flowing through the indoor heat exchangers 42, 52, 62, respectively.

(5-3-1) Outdoor unit 20
The outdoor unit 20 shown in FIG. 9 and FIG. 10 is different from the outdoor unit 20 shown in FIG. 1 in that the outdoor unit 20 has the expansion valves 41a, 51a, 61a and the liquid side temperature. The sensor 44, 54, 64 and the gas side temperature sensor 45, 55, 65 are provided. Regarding the connection between the other compressor 21, the four-way switching valve 22, the outdoor heat exchanger 23, and the accumulator 24, the outdoor unit 20 shown in FIGS. 9 and 10 is shown in FIG. This is the same as the outdoor unit 20.

  In the outdoor unit 20 shown in FIGS. 9 and 10, the liquid side of the outdoor heat exchanger 23 is connected to one end of the liquid pipe 271 in the outdoor unit 20. The other end of the liquid pipe 271 is branched into three here, and the tip of the branch destination is connected to one end of each of the expansion valves 41a, 51a, 61a. The other ends of the expansion valves 41a, 51a, 61a are connected to three liquid side connection ports 222 provided in the outdoor unit 20, respectively. Liquid side temperature sensors 44, 54, and 64 are attached between the other ends of the expansion valves 41a, 51a, and 61a and the three liquid side connection ports 222, respectively. Three liquid side connection ports 222 are connected to the liquid side of the indoor heat exchangers 42, 52, 62 of the indoor units 40, 50, 60, respectively.

  The outdoor unit 20 shown in FIGS. 9 and 10 includes three gas side connection ports 221 that are connected to the gas side of the indoor heat exchangers 42, 52, and 62 of the indoor units 40, 50, and 60, respectively. Yes. The three gas side connection ports 221 are respectively connected to three other ends of the gas pipe 272 branched into three. The refrigerant flowing through the three other ends flows through one end of the gas pipe 272. One end of the gas pipe 272 is connected to the four-way switching valve 22. One end of the gas pipe 272 is connected to the accumulator 24 during the cooling operation, and is connected to the discharge side of the compressor 21 during the heating operation. In order to detect the temperature of the refrigerant flowing through the three other ends of the gas pipe 272, gas side temperature sensors 45, 55, and 65 are attached to the three other ends, respectively.

(5-3-2) Indoor units 40, 50, 60
The indoor units 40, 50, 60 shown in FIG. 9 have the same configuration as that of the expansion valves 41a, 51a, 61a, the liquid side temperature sensors 44, 54, 64, and the gas side temperature sensors 45, 55, 65 shown in FIG. Are the same as those of the indoor units 40, 50, 60 shown in FIG.

(5-3-3) Operation of Multi-Type Air Conditioner 10 In the outdoor unit 20 shown in FIG. 9 and FIG. The Further, the temperature values detected by the liquid side temperature sensors 44, 54, 64 and the gas side temperature sensors 45, 55, 65 are acquired by the outdoor side control device 37.

  In the multi-type air conditioner 10 shown in FIG. 1, the operation control device 80 is connected to the liquid side temperature sensors 44, 54, 64 and the gas side temperature sensors 45, 55, 55 via the indoor side control devices 47, 57, 67. Although the temperature value detected by 65 was acquired and the expansion valves 41a, 51a, 61a were controlled via the indoor side control devices 47, 57, 67, the multi-type air conditioner 10 shown in FIG. Then, the operation control device 80 acquires the temperature values detected by the liquid side temperature sensors 44, 54, 64 and the gas side temperature sensors 45, 55, 65 via the outdoor side control device 37, and sets the outdoor side control device 37. The expansion valves 41a, 51a, and 61a are controlled via these. However, the operation control device 80 acquires temperature values detected by the liquid side temperature sensors 44, 54, 64 and the gas side temperature sensors 45, 55, 65, and controls the expansion valves 41a, 51a, 61a via the temperature values. 1 is the same as the multi-type air conditioner 10 shown in FIG. 1 and the multi-type air conditioner 10 shown in FIG. 9, and the multi-type air conditioner 10 shown in FIG. The same control as that of the above embodiment can be performed as in the multi-type air conditioner 10 shown in FIG.

  Further, in the multi-type air conditioner 10 shown in FIG. 9, the outdoor expansion valve 38 is omitted. However, in the multi-type air conditioner 10 shown in FIG. 9 is not fully contributed to the operation of the cooling operation, and the operations other than the outdoor expansion valve 38 during the cooling operation are also shown in FIG. 1 for the multi-type air conditioner 10 shown in FIG. This can be performed in the same manner as the multi-type air conditioner 10.

(5-4) Modification 1D
In the embodiment described above, the case where the wet region size is determined using any one of the blowing temperature sensor 453, the blowing humidity sensor 454, and the indoor heat exchanger temperature sensor 455 provided in the indoor unit 40 has been described. However, in order to improve accuracy, these may be used in combination.

(5-5) Modification 1E
In the above-described embodiment, the dew condensation in the fan rotor 43a of the indoor fan 43 has been described as an example of the dew condensation in the apparatus downstream of the indoor heat exchanger 42. However, the dew condensation in the apparatus is limited to the dew condensation in the fan rotor 43a. Absent. For example, the case where condensation occurs on the vertical blades 416 and / or the horizontal blades 417 downstream of the indoor heat exchanger 42 is also included in the in-device condensation.

(5-6) Modification 1F
In the above embodiment, the occupation ratio Rw of the upper limit wet region 491 in which dew condensation does not occur in the apparatus downstream of the indoor heat exchanger 42 of the indoor unit 40 is obtained by calculation using two or more indoor heat exchanger temperature sensors 455. Explained the case. However, it is also possible to use one indoor heat exchanger temperature sensor 455 so that the expansion of the wet region 491 can be limited to the upper limit where no dew condensation occurs in the apparatus downstream of the indoor heat exchanger 42. For example, if the occupation ratio of the wet region 491 where the condensation in the apparatus cannot occur downstream of the indoor heat exchanger 42 in the specified operation range of the specific indoor unit 40 is determined, the condensation in the apparatus occurs. The indoor heat exchanger temperature sensor 455 is disposed in a place where it can be determined that the occupancy ratio of the wet region 491 is not possible, and the indoor heat exchanger temperature sensor 455 in the place is overheated during the low-performance cooling operation period The temperature indicating the region 492 is detected. With this configuration, during the period of the low-capacity cooling operation, the expansion of the wet region 491 can be limited to the upper limit that does not cause condensation in the apparatus downstream of the indoor heat exchanger 42. Such control can be similarly performed not only in the indoor unit 40 but also in the indoor units 50 and 60.

DESCRIPTION OF SYMBOLS 10 Air conditioning apparatus 20 Outdoor unit 21 Compressor 40, 50, 50 Indoor unit 41, 51, 61 Indoor expansion valve (example of pressure reduction mechanism)
41a, 51a, 61a Expansion valve (example of pressure reducing mechanism)
42, 52, 62 Indoor heat exchanger 43, 53, 63 Indoor fan 80 Operation control device

JP 59-122864 A

Claims (5)

An outdoor unit (20) having a compressor (21) for compressing a circulating refrigerant to perform a refrigeration cycle;
A plurality of indoor heat exchangers (42, 52, 62) and a plurality of decompression mechanisms (41, 51, 61, 41a, 51a, 61a) through which the refrigerant discharged from the compressor circulates A plurality of indoor units (40, 50, 60) having a plurality of indoor fans (43, 53, 63) through which air passing through the exchanger passes;
With
At least one indoor unit of the plurality of indoor units performs cooling with the mixed air that has passed through the wet region and the overheated region during low-capacity cooling operation that increases the overheated region as compared with normal cooling operation , and when the room temperature is higher than the set temperature in the cooling operation, while spreading the wet area by narrowing the superheat region of the indoor heat exchanger by increasing the opening degree of the pressure reducing mechanism, by increasing the air volume of the indoor fan the apparatus condensation downstream of the indoor heat exchanger is configured so that to limit the expansion of the wet area in a range that does not occur, the multi-type air conditioner. When the indoor temperature is lower than a set temperature in the low-capacity cooling operation, the at least one indoor unit reduces the opening of the pressure reducing mechanism and / or reduces the air volume of the indoor fan to reduce the cooling capacity. Is configured to be
The multi-type air conditioning apparatus according to claim 1. In the at least one indoor unit, expansion of the wet region is limited to an upper limit that does not cause condensation in the apparatus downstream of the indoor heat exchanger using the temperature of the mixed air or the humidity of the mixed air. Determine
The multi-type air conditioning apparatus according to claim 1 or 2. The at least one indoor unit further includes an indoor heat exchanger temperature sensor (455) in the indoor heat exchanger, and the indoor heat using the detection result of the indoor heat exchanger temperature sensor during the low-capacity cooling operation. It is determined that the expansion of the wet area is limited to an upper limit that does not cause condensation in the apparatus downstream of the exchanger.
The multi-type air conditioning apparatus according to any one of claims 1 to 3. In order to obtain the required cooling capacity, the at least one indoor unit cannot restrict the expansion of the wet area to the upper limit where the air volume of the indoor fan is increased and no dew condensation occurs in the apparatus downstream of the indoor heat exchanger. When switching from the low-capacity cooling mode to the normal cooling mode,
The multi-type air conditioning apparatus according to any one of claims 1 to 4.

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