Indoor unit and air conditioning device

Abstract

An indoor unit is an indoor unit of an air conditioning apparatus. The indoor unit is configured to adopt a zeotropic refrigerant as a refrigerant. The indoor unit includes a main heat exchanger, a flow divider, and a sensor. The main heat exchanger includes a plurality of tube passes through which the refrigerant flows. The flow divider is configured to divide the refrigerant before the refrigerant flows into the plurality of tube passes. The sensor is configured to detect a temperature of the refrigerant. The sensor is disposed near the flow divider, is disposed between the flow divider and the main heat exchanger, or is disposed on one of the tube passes defined by heat transfer tubes of the main heat exchanger, at a position that is closer to the flow divider than a midpoint of an entire length of the one of the tube passes is.

Description

TECHNICAL FIELD

[0001] Embodiments disclosed herein relate to an indoor unit and an air conditioning apparatus.BACKGROUND ART

[0002] Recent air conditioning apparatuses have adopted a refrigerant with a low global warming potential (GWP) for the purpose of curbing global warming. A variety of inexpensive refrigerants with a GWP of 150 or less and with improved cooling efficiency have been considered and proposed. As a refrigerant that may satisfy such a demand, there is a zeotropic refrigerant obtained by mixing refrigerants of different types. Patent Literature 1 (JP 2022-115320 A) discloses an indoor unit for an air conditioner, and this indoor unit is configured to adopt a zeotropic refrigerant.SUMMARY OF THE INVENTION <Technical Problem>

[0003] There is a possibility of frost formation on the indoor unit for the air conditioner disclosed in Patent Literature 1.<Solution to Problem>

[0004] An indoor unit according to a first aspect is an indoor unit of an air conditioning apparatus. The indoor unit is configured to adopt a zeotropic refrigerant as a refrigerant. The indoor unit includes a main heat exchanger, a flow divider, and a sensor. The main heat exchanger includes a plurality of tube passes through which the refrigerant flows. The flow divider is configured to divide the refrigerant before the refrigerant flows into the plurality of tube passes. The sensor is configured to detect a temperature of the refrigerant. The sensor is disposed near the flow divider in a refrigerant flow, is disposed on a pipe connecting the flow divider and the main heat exchanger on a refrigerant flow path, or is disposed on one of the plurality of tube passes defined by heat transfer tubes of the main heat exchanger, at a position that is closer to the flow divider than a midpoint of an entire length of the one of the plurality of tube passes is.

[0005] This indoor unit can reduce a possibility of frost formation.

[0006] An indoor unit according to a second aspect is the indoor unit according to the first aspect, in which the main heat exchanger includes a front surface upper portion, a front surface lower portion, and a rear surface portion. The sensor is disposed in a refrigerant flow near the flow divider that divides the refrigerant before the refrigerant flows into the tube pass located in the front surface upper portion among the plurality of tube passes, is disposed on a pipe connecting the flow divider and the tube pass located in the front surface upper portion on the refrigerant flow path, or is disposed on the tube pass located in the front surface upper portion.

[0007] An indoor unit according to a third aspect is the indoor unit according to the second aspect, in which the sensor is disposed on the one of the plurality of tube passes defined by the heat transfer tubes of the main heat exchanger, at the position that is closer to the flow divider than the midpoint of the entire length of the one of the plurality of tube passes is, and on a windward side of the front surface upper portion.

[0008] An indoor unit according to a fourth aspect is the indoor unit according to any of the first to third aspects, in which during an evaporation operation, a refrigerant temperature at a position where the sensor is disposed is lower than a refrigerant temperature at an inlet of the main heat exchanger.

[0009] An indoor unit according to a fifth aspect is the indoor unit according to any of the first to fourth aspects, in which during an evaporation operation, a refrigerant temperature at a position where the sensor is disposed is lower than a refrigerant temperature at a merging portion of the plurality of tube passes of the main heat exchanger.

[0010] An indoor unit according to a sixth aspect is the indoor unit according to the first or second aspect, further including an auxiliary heat exchanger. During an evaporation operation, the refrigerant flows through the auxiliary heat exchanger, the flow divider, and the main heat exchanger in this order. The sensor is disposed on the pipe connecting the flow divider and the main heat exchanger on the refrigerant flow path.

[0011] An indoor unit according to a seventh aspect is the indoor unit according to the first or second aspect, further including an auxiliary heat exchanger. During an evaporation operation, the refrigerant flows through the auxiliary heat exchanger, the flow divider, and the main heat exchanger in this order. The sensor is disposed near the flow divider in the refrigerant flow and on a pipe connecting the auxiliary heat exchanger and the flow divider on the refrigerant flow path.

[0012] An indoor unit according to an eighth aspect is the indoor unit according to the first or second aspect, further including an auxiliary heat exchanger. During an evaporation operation, the refrigerant flows through the auxiliary heat exchanger, the flow divider, and the main heat exchanger in this order. The sensor is disposed on the one of the plurality of tube passes defined by the heat transfer tubes of the main heat exchanger, at the position that is closer to the flow divider than the midpoint of the entire length of the one of the plurality of tube passes is.

[0013] An indoor unit according to a ninth aspect is the indoor unit according to the first or second aspect, in which the sensor is disposed on one of the plurality of tube passes except the tube pass having a longest length among the plurality of tube passes.

[0014] An indoor unit according to a tenth aspect is the indoor unit according to the ninth aspect, in which the sensor is disposed on the tube pass having a shortest length among the plurality of tube passes.

[0015] An indoor unit according to an eleventh aspect is the indoor unit according to the first or second aspect, in which the sensor is disposed on one of the plurality of tube passes where an amount of the refrigerant circulating in the main heat exchanger is largest.

[0016] An indoor unit according to a twelfth aspect is the indoor unit according to any of the first to eleventh aspects, further including a fan. During an evaporation operation, a traveling direction of the refrigerant and a traveling direction of an airflow generated by the fan are opposite to each other.

[0017] An indoor unit according to a thirteenth aspect is the indoor unit according to any of the first to twelfth aspects, further including a fan. During an evaporation operation and a condensation operation, a traveling direction of the refrigerant and a traveling direction of an airflow generated by the fan are opposite to each other.

[0018] An indoor unit according to a fourteenth aspect is the indoor unit according to any of the first to thirteenth aspects, in which the zeotropic refrigerant is mainly made up of a hydrofluoroolefin refrigerant.BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1 is a schematic diagram of an air conditioning apparatus 10 including an indoor unit 30. FIG. 2 is a front view of the indoor unit 30 from which a front portion of a casing 33 is removed. FIG. 3 is a sectional view of the indoor unit 30 taken along line A-A in FIG. 2. FIG. 4 is a diagram illustrating refrigerant temperature distribution in a utilization heat exchanger 31. FIG. 5 is a sectional view of an indoor unit 30 according to Modification A. FIG. 6 is a sectional view of an indoor unit 30 according to Modification B. FIG. 7 is a sectional view of an indoor unit 30 according to Modifications C and D. FIG. 8 is a sectional view of an indoor unit 30 according to Modification E. FIG. 9 is a sectional view of the indoor unit 30 according to Modification E. FIG. 10 is a sectional view of an indoor unit 30 according to Modification F. FIG. 11 is a sectional view of the indoor unit 30 according to Modification F. FIG. 12 is a sectional view of an indoor unit 30 according to Modification G. FIG. 13 is a sectional view of the indoor unit 30 according to Modification G. FIG. 14 is a schematic diagram of an air conditioning apparatus 10 including an indoor unit 30 according to Modification I. FIG. 15 is a sectional view of the indoor unit 30 according to Modification I. FIG. 16 is a sectional view of the indoor unit 30 according to Modification I. DESCRIPTION OF EMBODIMENTS

[0020] Embodiments of the present invention are described below with reference to the drawings. The following embodiments are preferable examples in nature and are not intended to limit the scope of the present invention, products to which the present invention is applied, or the use of the present invention. Configurations described in the embodiments, modifications, and other examples below may be combined or partially substituted within a range where the present invention is implementable. As used herein, terms representing directions, such as "up", "down", "left", "right", "front", and "rear", correspond to the directions indicated by arrows in the respective drawings.(1) General Configuration

[0021] An indoor unit 30 according to an embodiment of the present disclosure is used for an air conditioning apparatus 10.

[0022] As illustrated in FIG. 1, the air conditioning apparatus 10 achieves a vapor compression refrigeration cycle in a refrigerant circuit 11 to perform an evaporation operation and a condensation operation as an air conditioning operation. During the evaporation operation, the air conditioning apparatus 10 cools air within an indoor space. During a condensation operation, the air conditioning apparatus 10 heats air within the indoor space.

[0023] The air conditioning apparatus 10 includes an outdoor unit 20, the indoor unit 30, and refrigerant pipes 12 and 13. The refrigerant pipes 12 and 13 connect the indoor unit 30 and the outdoor unit 20 to form the refrigerant circuit 11 in which a refrigerant circulates.

[0024] The refrigerant circuit 11 is filled with a zeotropic refrigerant mixture. The GWP of the zeotropic refrigerant mixture is less than 150.

[0025] The zeotropic refrigerant mixture is a mixture of refrigerants of at least two types. The refrigerant circuit 11 of the air conditioning apparatus 10 according to the embodiment is filled with a zeotropic refrigerant mixture including only refrigerants of two types (i.e., a first refrigerant and a second refrigerant). However, the present disclosure is not limited thereto. For example, the zeotropic refrigerant mixture may be a mixture of refrigerants of three or more types. For example, the second refrigerant may be an azeotropic refrigerant mixture or a pseudo-azeotropic refrigerant mixture including refrigerants of two or more types, rather than a refrigerant of one type. That is, the zeotropic refrigerant mixture may be a refrigerant mixture of the first refrigerant that is in a zeotropic relationship with the second refrigerant and the second refrigerant that corresponds to an azeotropic refrigerant mixture or a pseudo-azeotropic refrigerant mixture including refrigerants of two or more types. The second refrigerant is higher in boiling point than the first refrigerant.

[0026] A non-limiting example of the first refrigerant may be difluoromethane (R32), and a non-limiting example of the second refrigerant may be hydrofluoroolefin (HFO). HFO is a refrigerant with a considerably low GWP. A non-limiting example of HFO to be used as the second refrigerant may be 2,3,3,3-tetrafluoropropene (R1234yf). Difluoromethane (R32) is a refrigerant with a relatively low boiling point, and R1234yf is a refrigerant with a relatively high boiling point.

[0027] The zeotropic refrigerant mixture according to the embodiment is mainly made up of a hydrofluoroolefin refrigerant. A non-limiting example of the zeotropic refrigerant mixture according to the embodiment may be R454C. R454C contains R32 of 21.5% by mass as the first refrigerant, and also contains R1234yf of 78.5% by mass as the second refrigerant.

[0028] In the air conditioning apparatus 10, preferably, a ratio of a total weight of the first refrigerant in the refrigerant circuit 11 to a total weight of the entire refrigerant in the refrigerant circuit 11 is 15 to 30% by mass. Also in the air conditioning apparatus 10, preferably, a ratio of a total weight of the second refrigerant in the refrigerant circuit 11 to the total weight of the entire refrigerant in the refrigerant circuit 11 is 70 to 85% by mass.(2) Specific Configuration(2-1) Indoor unit 30

[0029] The indoor unit 30 is installed in an air conditioning target space.

[0030] As illustrated in FIGS. 1 and 2, the indoor unit 30 is of a wall-hung type and has a substantially rectangular parallelepiped shape elongated in the horizontal direction (left-right direction). For the installation, the indoor unit 30 is attached to a wall surface of a room that defines therein the air conditioning target space.

[0031] The indoor unit 30 includes a casing 33, a utilization heat exchanger 31, a flow divider 50, a refrigerant temperature sensor 40, a utilization fan 32, and a control device 39.(2-1-1) Casing 33

[0032] The casing 33 serves as an outer perimeter of the indoor unit 30. The casing 33 defines therein an internal space where the utilization heat exchanger 31 is accommodated.

[0033] The casing 33 has a box shape elongated laterally. The casing 33 includes a front plate, a rear plate, an upper plate, and a lower plate.

[0034] The casing 33 has a suction port 33a and a blow-out port 33b. The casing 33 is installed in the air conditioning target space such that the rear plate is in contact with the wall surface.

[0035] The suction port 33a is an opening that is open in an upper portion of the casing 33, and serves as an inlet port through which air flows into the casing 33. The blow-out port 33b is an opening that is open in a lower portion of the casing 33, and serves as an airflow (conditioned air) outlet port. The indoor unit 30 is configured to suck air within the air conditioning target space into the casing 33 through the suction port 33a and blow conditioned air out of the casing 33 through the blow-out port 33b.(2-1-2) Utilization heat exchanger 31

[0036] The utilization heat exchanger 31 causes the refrigerant to exchange heat with air within the air conditioning target space. The utilization heat exchanger 31 allows passage of an airflow generated by the utilization fan 32.

[0037] As illustrated in FIG. 2, the utilization heat exchanger 31 includes a plurality of heat transfer tubes 31a, a plurality of heat transfer fins 31b, a plurality of U-shaped tubes 31c, and tube plates 31d. The utilization heat exchanger 31 is a fin-and-tube heat exchanger. Materials for the heat transfer tubes 31a, heat transfer fins 31b, U-shaped tubes 31c, and tube plates 31d are not limited. For example, the heat transfer tubes 31a, heat transfer fins 31b, U-shaped tubes 31c, and tube plates 31d are made of aluminum or an aluminum alloy. Alternatively, for example, the heat transfer tubes 31a and U-shaped tubes 31c may be made of copper or a copper alloy, the heat transfer fins 31b may be made of aluminum or an aluminum alloy, and the tube plates 31d may be made of a steel material. The utilization heat exchanger 31 is an example of a heat exchanger. The plurality of heat transfer tubes 31a and U-shaped tubes 31c each constitute a part of the refrigerant circuit 11.

[0038] The plurality of heat transfer tubes 31a are disposed in the casing 33 such that the longitudinal direction of each heat transfer tube 31a extends along the left-right direction and the heat transfer tubes 31a are spaced apart from each other at predetermined intervals.

[0039] The plurality of heat transfer fins 31b are arranged in the direction perpendicular to the left-right direction and disposed in the casing 33 such that the heat transfer fins 31b are spaced apart from each other in the left-right direction at predetermined intervals. The heat transfer fins 31b each have a plurality of holes through which the heat transfer tubes 31a are inserted. The plurality of heat transfer fins 31b are arranged in the left-right direction between the two tube plates 31d.

[0040] Each of the U-shaped tubes 31c connects ends of corresponding two of the heat transfer tubes 31a. Some of the heat transfer tubes 31a each have an end to which a pipe connected to either the refrigerant pipe 12 or the refrigerant pipe 13 is connected. With this configuration, the refrigerant flows into the some heat transfer tubes 31a through either the refrigerant pipe 12 or the refrigerant pipe 13 and flows through the plurality of heat transfer tubes 31a while turning around at the U-shaped tubes 31c.

[0041] The tube plates 31d support the plurality of heat transfer tubes 31a at the longitudinal ends of the heat transfer tubes 31a. The tube plates 31d are arranged in the direction perpendicular to the left-right direction and disposed in the casing 33. The tube plates 31d are substantially equal in shape to the heat transfer fins 31b and each have a plurality of holes through which the heat transfer tubes 31a are inserted.

[0042] As illustrated in FIG. 3, the utilization heat exchanger 31 includes a main heat exchanger 37 and an auxiliary heat exchanger 38. The auxiliary heat exchanger 38 is disposed forward of a front surface upper portion 37a and a front surface lower portion 37b of the main heat exchanger 37. The auxiliary heat exchanger 38 is located on the windward side, and the main heat exchanger 37 is located on the leeward side.

[0043] The main heat exchanger 37 includes a plurality of tube passes P through which the refrigerant flows. In the present embodiment, the main heat exchanger 37 includes three tube passes P, i.e., a first tube pass P1, a second tube pass P2, and a third tube pass P3.

[0044] The length of path P increases in the order of first path P1, second path P2, and third path P3. In one tube pass P, the heat transfer tubes 31a inserted through the heat transfer fins 31b substantially contribute to heat exchange performance. Therefore, in simply comparing the lengths of the tube passes P, the comparison can be made by substituting "the number of heat transfer tubes 31a inserted through the heat transfer fins 31b (hereinafter, simply referred to as the number of heat transfer tubes 31a)". In the present embodiment, the number of heat transfer tubes 31a in the first tube pass P1 is 10. The number of heat transfer tubes 31a in the second tube pass P2 is 12. The number of heat transfer tubes 31a in the third tube pass P3 is 14. Therefore, the first tube pass P1 corresponds to the shortest one of the plurality of tube passes P. The third tube pass P3 corresponds to the longest one of the plurality of tube passes P.

[0045] The main heat exchanger 37 includes the front surface upper portion 37a and the front surface lower portion 37b each corresponding to a front surface portion, and a rear surface portion 37c. The front surface upper portion 37a and the front surface lower portion 37b are disposed on the front side of the indoor unit 30. The rear surface portion 37c is disposed on the rear side of the indoor unit 30. The front surface upper portion 37a and the front surface lower portion 37b are arranged in the form of inverted V so as to surround the utilization fan 32.

[0046] During the evaporation operation, the refrigerant flows through the auxiliary heat exchanger 38, the flow divider 50, and the main heat exchanger 37 in this order. Specifically, the refrigerant flows into the auxiliary heat exchanger 38 at a position indicated by an arrow in the bottom left area of FIG. 3. After flowing out of the auxiliary heat exchanger 38, the refrigerant is divided by the flow divider 50. The divided refrigerants respectively flow through the first to third tube passes P1 to P3 in the main heat exchanger 37. After flowing out of the main heat exchanger 37, the refrigerants are merged into one again. The merged refrigerant is sucked into a compressor 21 via a four-way switching valve 22 and an accumulator 25.(2-1-3) Flow divider 50

[0047] The flow divider 50 connects a collecting pipe M and a plurality of branch pipes BP. The branch pipes BP each connect the flow divider 50 and a corresponding one of the tube passes P.

[0048] The flow divider 50 divides the refrigerant before the refrigerant flows into the tube passes P of the main heat exchanger 37. Specifically, the flow divider 50 divides the refrigerant, which has flowed from the collecting pipe M, such that the divided refrigerants flow into the plurality of branch pipes BP.(2-1-4) Refrigerant temperature sensor 40

[0049] The refrigerant temperature sensor 40 is disposed on the refrigerant pipe 12 at a position near the flow divider 50 in a refrigerant flow. The refrigerant temperature sensor 40 is configured to measure a temperature of the refrigerant flowing through the refrigerant pipe 12. As used herein, the term "near the flow divider 50" means that the refrigerant temperature sensor 40 is within 6 cm of the flow divider 50. More preferably, the term "near the flow divider 50" means that the refrigerant temperature sensor 40 is within 5 cm of the flow divider 50. Still more preferably, the term "near the flow divider 50" means that the refrigerant temperature sensor 40 is within 4 cm of the flow divider 50. With reference to FIG. 3, specifically, the refrigerant pipe 12 connecting the refrigerant temperature sensor 40 and the flow divider 50 on the refrigerant flow has a length B1a within 6 cm. The length B1a of the refrigerant pipe 12 connecting the refrigerant temperature sensor 40 and the flow divider 50 on the refrigerant flow is preferably within 5 cm, more preferably within 4 cm. It should be noted that the refrigerant pipe 12 connecting the flow divider 50 and the main heat exchanger 37 has a length of 7 to 30 cm.

[0050] Specifically, the refrigerant temperature sensor 40 is disposed in the refrigerant flow near the flow divider 50 that divides the refrigerant before the refrigerant flows into the tube pass P located in the front surface upper portion 37a. More specifically, the refrigerant temperature sensor 40 is disposed on a pipe connecting the main heat exchanger 37 and the flow divider 50 on a refrigerant flow path. The refrigerant temperature sensor 40 is disposed on one of the branch pipes BP.

[0051] The refrigerant temperature sensor 40 is, for example, a resistive sensor (thermistor). The thermistor is brazed to the refrigerant pipe 12. In the case where the refrigerant temperature sensor 40 is a thermistor, the length B1a of the refrigerant pipe 12 connecting the refrigerant temperature sensor 40 and the flow divider 50 on the refrigerant flow corresponds to a length of the refrigerant pipe 12 from a temperature measurement point of the thermistor to the flow divider 50 on the refrigerant flow.

[0052] During the evaporation operation, a refrigerant temperature at a position where the refrigerant temperature sensor 40 is disposed is lower than a refrigerant temperature at an inlet of the utilization heat exchanger 31. More preferably, the refrigerant temperature at the position where the refrigerant temperature sensor 40 is disposed is lower than a refrigerant temperature at an inlet 37E of the main heat exchanger 37.

[0053] During the evaporation operation, the refrigerant temperature at the position where the refrigerant temperature sensor 40 sensor is disposed is lower than a merging portion 37M of the tube passes P of the main heat exchanger 37.(2-1-5) Utilization fan 32

[0054] As illustrated in FIG. 1, the utilization fan 32 generates an airflow that flows into the casing 33 through the suction port 33a, passes through an air filter and the utilization heat exchanger 31, and then blows out of the casing 33 through the blow-out port 33b. The utilization fan 32 is a cross-flow fan.

[0055] The utilization fan 32 is disposed such that a rotation shaft of the utilization fan 32 extends in the left-right direction and the utilization fan 32 is surrounded by the utilization heat exchanger 31 at a position downstream of the utilization heat exchanger 31 in the airflow. The utilization fan 32 includes a motor serving as an actuator for rotationally driving a main body of the utilization fan 32. The motor is connected to the control device 39. The control device 39 controls a rotation speed of the motor.(2-1-6) Control device 39

[0056] The control device 39 controls each actuator (the motor of the utilization fan 32). The control device 39 is electrically connected to each actuator via a wire. The control device 39 is accommodated in an electrical component box and is disposed rightward of the motor (see FIG. 2).

[0057] The control device 39 is practicable using a computer. The control device 39 includes a control computation device and a storage device. The control computation device may include a processor such as a CPU or a GPU. The control computation device reads a program stored in the storage device and performs predetermined computation processing in accordance with the program. In addition, the control computation device is capable of writing a result of the computation processing to the storage device, and reading information stored in the storage device, in accordance with the program.

[0058] The control device 39 determines whether frost formation occurs, based on a temperature result of a refrigerant gas detected by the refrigerant temperature sensor 40.(2-2) Outdoor unit 20

[0059] The outdoor unit 20 is installed outside the air conditioning target space.

[0060] As illustrated in FIG. 1, the outdoor unit 20 includes the compressor 21, the four-way switching valve 22, a heat source heat exchanger 23, an expansion valve 24, the accumulator 25, and a heat source fan 28. The refrigerant circuit 11 connects the compressor 21, the four-way switching valve 22, the heat source heat exchanger 23, the expansion valve 24, the accumulator 25, and the utilization heat exchanger 31 with pipes. The refrigerant circuit 11 is filled with the refrigerant.

[0061] In an evaporation operation mode, the four-way switching valve 22 is switched to a connection state indicated by a solid line to connect the compressor 21 and the heat source heat exchanger 23 to each other and connect the utilization heat exchanger 31 and the accumulator 25 to each other. In a condensation operation mode, the four-way switching valve 22 is switched to a connection state indicated by a broken line to connect the compressor 21 and the utilization heat exchanger 31 to each other and connect the heat source heat exchanger 23 and the accumulator 25 to each other.(3) General Operation

[0062] Next, a description is given of basic operation of the air conditioning apparatus 10. The air conditioning apparatus 10 performs the evaporation operation and the condensation operation.(3-1) Circulation of refrigerant during evaporation operation

[0063] During the evaporation operation, the gas refrigerant compressed by the compressor 21 flows into the heat source heat exchanger 23 via the four-way switching valve 22. In the heat source heat exchanger 23, the refrigerant condenses by heat exchange with air (heat source) that is outside the air conditioning target space and is sent by the heat source fan 28. After the heat exchange in the heat source heat exchanger 23, the refrigerant is decompressed by expansion in the expansion valve 24. The decompressed refrigerant then flows into the utilization heat exchanger 31 of the indoor unit 30 via the refrigerant pipe 12. The refrigerant flowed into the utilization heat exchanger 31 flows into the flow divider 50 via the auxiliary heat exchanger 38 as illustrated in FIG. 3. In the flow divider 50, the refrigerant is divided into three directions, and the divided refrigerants flow into the first tube pass P1, second tube pass P2, and third tube pass P3 in the main heat exchanger 37. After flowing out of the main heat exchanger 37, the refrigerants are merged into one. The low-temperature and low-pressure refrigerant flows from the expansion valve 24 to the utilization heat exchanger 31 of the indoor unit 30. In the utilization heat exchanger 31, the refrigerant evaporates by heat exchange with air that is within the air conditioning target space and is sent by the utilization fan 32. At this time, the air is cooled by the heat exchange with the refrigerant. After the heat exchange in the utilization heat exchanger 31, the gas refrigerant or the refrigerant in a gas-liquid two-phase state is sucked into the compressor 21 via the refrigerant pipe 13, the four-way switching valve 22, and the accumulator 25. The indoor unit 30 blows the conditioned air cooled in the utilization heat exchanger 31 toward the air conditioning target space to cool the room.

[0064] During the evaporation operation, the traveling direction of the refrigerant (indicated by solid arrow RF of FIG. 3) and the traveling direction of the airflow generated by the utilization fan 32 (indicated by broken arrow AF of FIG. 3) are parallel to each other. In other words, since the refrigerant flows from the outside (the front side of FIG. 3) to the inside (the rear side of FIG. 3) while repeatedly turning around in side view (as seen in the longitudinal direction of the heat transfer tubes), the refrigerant and the airflow travel in the same direction.(3-2) Circulation of refrigerant during condensation operation

[0065] During the condensation operation, the gas refrigerant compressed by the compressor 21 flows into the utilization heat exchanger 31 via the four-way switching valve 22 and the refrigerant pipe 13. In the utilization heat exchanger 31, the refrigerant condenses by heat exchange with air that is within the air conditioning target space and is sent by the utilization fan 32. At this time, the air is heated by the heat exchange with the refrigerant. After the heat exchange in the utilization heat exchanger 31, the refrigerant flows into the expansion valve 24 via the refrigerant pipe 12. The refrigerant is decompressed by expansion in the expansion valve 24, and the low-temperature and low-pressure refrigerant then flows into the heat source heat exchanger 23. In the heat source heat exchanger 23, the refrigerant evaporates by heat exchange with air that is outside the air conditioning target space and is sent by the heat source fan 28. After the heat exchange in the heat source heat exchanger 23, the gas refrigerant or the refrigerant in the gas-liquid two-phase state is sucked into the compressor 21 via the four-way switching valve 22 and the accumulator 25. The indoor unit 30 blows the conditioned air heated in the utilization heat exchanger 31 toward the air conditioning target space to heat the room.

[0066] During the condensation operation, the traveling direction of the refrigerant and the traveling direction of the airflow generated by the utilization fan 32 are opposite to each other. In other words, since the refrigerant flows from the inside (the rear side of FIG. 3) to the outside (the front side of FIG. 3) while repeatedly turning around in side view (as seen in the longitudinal direction of the heat transfer tubes), the refrigerant and the airflow travel in opposite directions.(4) Features

[0067] (4-1) An indoor unit 30 is configured to adopt a zeotropic refrigerant as a refrigerant. The indoor unit 30 includes a main heat exchanger 37, a flow divider 50, and a refrigerant temperature sensor 40. The main heat exchanger 37 includes a plurality of tube passes P through which the refrigerant flows. The flow divider 50 is configured to divide the refrigerant before the refrigerant flows into the plurality of tube passes P. The refrigerant temperature sensor 40 is configured to detect a temperature of the refrigerant. The refrigerant temperature sensor 40 is disposed near the flow divider 50 in a refrigerant flow.

[0068] In a case of adopting a refrigerant of one type, such as R32, as indicated by a broken line of FIG. 4, the refrigerant temperature slightly varies due to a slight pressure loss, but is almost constant from the upstream side where the evaporation starts to the downstream side where the evaporation ends.

[0069] On the other hand, a zeotropic refrigerant mixture such as R454C is a refrigerant obtained by mixing a first refrigerant and a second refrigerant that are different in type from each other. In R454C, the boiling point of R32 is about -52°C and the boiling point of R1234yf is about -29°C. These boiling points are largely different from each other. This difference causes stepwise progression of evaporation for each type of refrigerant in the evaporator, which results in a clear gradient in the refrigerant temperature. This temperature gradient provides a characteristic of the refrigerant temperature that increases from the evaporation start point to the evaporation end point. In the heat exchanger that functions as an evaporator, therefore, the zeotropic refrigerant mixture has a temperature gradient indicating that the refrigerant temperature on the upstream side where the evaporation starts is different from the refrigerant temperature on the downstream side where the evaporation ends. As indicated by a solid line of FIG. 4, specifically, the refrigerant temperature is lowest at a position near the inlet of the utilization heat exchanger 31 and gradually increases toward the outlet of the utilization heat exchanger 31.

[0070] In the indoor unit 30 according to the present embodiment, the refrigerant temperature sensor 40 is disposed at a position near the position where the refrigerant temperature is lowest, i.e., is disposed near he flow divider 50 in the refrigerant flow. The refrigerant temperature of the zeotropic refrigerant is inconstant in the heat exchanger due to the difference in boiling point between the different types of refrigerants of the zeotropic refrigerant, and the zeotropic refrigerant has the temperature gradient indicating that the refrigerant temperature increases in accordance with the progression of the evaporation. Therefore, the refrigerant temperature becomes lowest at a position immediately ahead of the inlet of the main heat exchanger 37, i.e., immediately before the refrigerant flows into the evaporator. At this position, since the refrigerant is in a liquid-phase state and is present in a supercooling region before the evaporation starts, the refrigerant temperature varies slightly. As a result, the refrigerant temperature sensor 40 detects the temperature with high stability. This enables detection of a minimum value of the refrigerant temperature with high accuracy and good reproducibility.

[0071] At this position, moreover, the state of the refrigerant is stable, and the refrigerant temperature varies slightly. This configuration therefore minimizes variations in temperature measurement by the sensor, which enables highly reliable detection. This configuration thus enables an accurate grasp of refrigerant temperature changes and early detection of a sign of frost formation. As a result, this configuration enables reduction in possibility of frost formation.

[0072] (4-2) The main heat exchanger 37 includes a front surface upper portion 37a, a front surface lower portion 37b, and a rear surface portion 37c. The refrigerant temperature sensor 40 is disposed near the flow divider 50 in a refrigerant flow that divides the refrigerant before the refrigerant flows into the tube pass P located in the front surface upper portion 37a among the plurality of tube passes P.

[0073] In the main heat exchanger 37, the air velocity at the front surface upper portion 37a, which is located near the suction port 33a, is greater than the air velocity at the front surface lower portion 37b and the air velocity at the rear surface portion 37c, so that the front surface upper portion 37a is significantly susceptible to reduction in performance upon occurrence of frost formation. According to this configuration, the refrigerant temperature sensor 40, which is disposed on the front surface upper portion 37a, can preferentially detect the change in refrigerant temperature at the front surface upper portion 37a.

[0074] (4-3) During an evaporation operation, a refrigerant temperature at a position where the refrigerant temperature sensor 40 is disposed is lower than a refrigerant temperature at an inlet 37E of the main heat exchanger 37.

[0075] According to this configuration, the refrigerant temperature sensor 40 is disposed at a position where the refrigerant temperature is lower. This configuration therefore improves accuracy in detecting the change in refrigerant temperature.

[0076] (4-4) During the evaporation operation, the refrigerant temperature at the position where the refrigerant temperature sensor 40 is disposed is lower than a refrigerant temperature at a merging portion 37M of the plurality of tube passes P of the main heat exchanger 37.

[0077] According to this configuration, the refrigerant temperature sensor 40 is disposed at the position where the refrigerant temperature is lower than the merging portion 37M of the plurality of tube passes P. This configuration therefore improves accuracy in detecting the change in refrigerant temperature.

[0078] (4-5) The indoor unit 30 further includes an auxiliary heat exchanger 38. During the evaporation operation, the refrigerant flows through the auxiliary heat exchanger 38, the flow divider 50, and the main heat exchanger 37 in this order. The refrigerant temperature sensor 40 is disposed on the pipe connecting the flow divider 50 and the main heat exchanger 37 on a refrigerant flow path.

[0079] According to this configuration, the refrigerant temperature sensor 40 can detect the refrigerant temperature in the vicinity of the position where the refrigerant temperature is lowest.

[0080] (4-6) During the evaporation operation, a traveling direction RF of the refrigerant and a traveling direction AF of an airflow generated by a utilization fan 32 are opposite to each other.

[0081] According to this configuration, the refrigerant having the low refrigerant temperature can be fed toward the leeward side during the evaporation operation. As a result, this configuration improves a cooling effect.

[0082] (4-7) The zeotropic refrigerant is mainly made up of a hydrofluoroolefin refrigerant.

[0083] According to this configuration, the indoor unit 30 can adopt a refrigerant suitable for air conditioning.(5) Modifications(5-1) Modification A

[0084] In the foregoing embodiment, the refrigerant temperature sensor 40 is disposed near the flow divider 50 in the refrigerant flow. As illustrated in FIG. 5, however, a refrigerant temperature sensor 40 may be disposed on any portion of a pipe connecting a flow divider 50 and a main heat exchanger 37 on a refrigerant flow path. In this case, the refrigerant temperature sensor 40 is disposed on a pipe connecting the flow divider 50 and a tube pass P located in a front surface upper portion 37a on the refrigerant flow path.

[0085] The refrigerant temperature sensor 40, which is disposed on the pipe connecting the flow divider 50 and the main heat exchanger 37 on the refrigerant flow path, can measure a refrigerant temperature at a position sufficiently close to a position where the refrigerant temperature is lowest. This configuration therefore enables reduction in possibility of frost formation.(5-2) Modification B

[0086] In the foregoing embodiment, the refrigerant temperature sensor 40 is disposed near the flow divider 50 in the refrigerant flow. As illustrated in FIG. 6, however, a refrigerant temperature sensor 40 may be disposed on one of a plurality of tube passes P defined by heat transfer tubes of a main heat exchanger, at a position that is closer to a flow divider 50 than a midpoint of an entire length of the one of the plurality of tube passes is. Preferably, a location "on one of a plurality of tube passes P defined by heat transfer tubes of a main heat exchanger, at a position that is closer to a flow divider 50 than a midpoint of an entire length of the one of the plurality of tube passes is" is, for example, a U-shaped tube 31c through which a refrigerant flows first after flowing into a main heat exchanger 37 or a U-shaped tube 31c through which the refrigerant flows second after flowing into the main heat exchanger 37.

[0087] In this case, the refrigerant temperature sensor 40 is disposed on a tube pass P located in a front surface upper portion 37a. In this case, the refrigerant temperature sensor 40 is also disposed on the windward side of the front surface upper portion 37a.

[0088] When the refrigerant temperature sensor 40 is disposed on the one of the plurality of tube passes P defined by the heat transfer tubes of the main heat exchanger, at the position that is closer to the flow divider 50 than the midpoint of the entire length of the one of the plurality of tube passes P is, the refrigerant temperature sensor 40 is disposed on a tube pass P where an air velocity is high among the plurality of tube passes P defined by the heat transfer tubes of the main heat exchanger, at a position that is closer to the flow divider 50 than a midpoint of an entire length of a part of the tube pass P is. Therefore, the refrigerant temperature sensor 40 can preferentially detect a change in refrigerant temperature at a first half of the tube pass P near the flow divider 50.

[0089] In Modification B, preferably, the refrigerant temperature sensor 40 is disposed on one of the plurality of tube passes P except a third tube pass P3 having the longest length among the plurality of tube passes P. According to this configuration, the refrigerant temperature sensor 40 can be disposed on one of a first tube pass P1 and a second tube pass P2 rather than the third tube pass P3 since the third tube pass P3 is higher in resistance when the refrigerant flows than the first tube pass P1 and the second tube pass P2. This configuration therefore enables reduction in possibility that the refrigerant temperature is detected relatively high due to a pressure loss.

[0090] More preferably, the refrigerant temperature sensor 40 is disposed on the first tube pass P1 having the shortest length among the plurality of tube passes P. According to this configuration, the resistance when the refrigerant flows through the first tube pass P1 is reduced, so that the refrigerant flows through the first tube pass P1 with ease. Accordingly, a pressure loss hardly occurs, so that the refrigerant temperature sensor 40 can detect the refrigerant temperature at the first tube pass P1 lower than the refrigerant temperature at each of the second tube pass P2 and the third tube pass P3. This configuration therefore enables reduction in possibility that the refrigerant temperature is detected relatively high due to a pressure loss.

[0091] In Modification B, preferably, the refrigerant temperature sensor 40 is disposed on one of the plurality of tube passes P where an amount of the refrigerant circulating in the main heat exchanger 37 is largest. The tube pass P where the amount of the circulating refrigerant is large is, for example, the tube pass P located in each of the front surface upper portion 37a and a front surface lower portion 37b of the main heat exchanger 37 and on the windward side of the main heat exchanger 37. For example, the first tube pass P1 corresponds to the tube pass P where the amount of the circulating refrigerant is large. In the tube pass P where the amount of the circulating refrigerant is small, the refrigerant promptly evaporates and turns into a heated gas. In Modification B, the refrigerant temperature sensor 40 is disposed on the tube pass P where the amount of the circulating refrigerant is large. Therefore, the refrigerant temperature sensor 40 can detect the refrigerant temperature before the refrigerant turns into a heated gas.(5-3) Modification C

[0092] In the foregoing embodiment, the refrigerant temperature sensor 40 is disposed near the flow divider 50 in the refrigerant flow and on the pipe connecting the main heat exchanger 37 and the flow divider 50 on the refrigerant flow path. As illustrated in FIG. 7, however, a refrigerant temperature sensor 40 may be disposed on a pipe connecting an auxiliary heat exchanger 38 and a flow divider 50 on a refrigerant flow path.

[0093] The refrigerant temperature sensor 40, which is disposed near the flow divider 50 in a refrigerant flow and on the pipe connecting the auxiliary heat exchanger 38 and the flow divider 50 on the refrigerant flow path, can measure a refrigerant temperature in the vicinity of a position where the refrigerant temperature is lowest. This configuration therefore enables reduction in possibility of frost formation.(5-4) Modification D

[0094] In the foregoing embodiment, the refrigerant temperature sensor 40 is disposed near the flow divider 50 in the refrigerant flow and on the pipe connecting the main heat exchanger 37 and the flow divider 50 on the refrigerant flow path. As illustrated in FIG. 7, however, another refrigerant temperature sensor 40A may be disposed on one of a plurality of tube passes P defined by heat transfer tubes of a main heat exchanger, at a position that is closer to a flow divider 50 than a midpoint of an entire length of the one of the plurality of tube passes P is, although an indoor unit 30 includes an auxiliary heat exchanger 38.(5-5) Modification E

[0095] In the foregoing embodiment, the indoor unit 30 includes the auxiliary heat exchanger 38. However, the indoor unit 30 does not necessarily include the auxiliary heat exchanger 38.

[0096] As illustrated in FIG. 8, in a case where an indoor unit 30 does not include an auxiliary heat exchanger 38, a refrigerant temperature sensor 40 is disposed near a flow divider 50 in a refrigerant flow and on a pipe connecting the flow divider 50 and a main heat exchanger 37 on a refrigerant flow path.

[0097] As illustrated in FIG. 9, alternatively, the refrigerant temperature sensor 40 may be disposed on a U-shaped tube 31c through which a refrigerant flows immediately after flowing through an inlet 37E of the main heat exchanger 37.(5-6) Modification F

[0098] In the foregoing embodiment, during the evaporation operation, the refrigerant flows through the auxiliary heat exchanger 38, the flow divider 50, and the main heat exchanger 37 in this order. As illustrated in FIG. 10, however, a refrigerant which has flowed through an auxiliary heat exchanger 38 may flow through a flow divider 50 via a main heat exchanger 37 and then flow through the main heat exchanger 37 again. In FIG. 10, numerals enclosed in rectangles indicate the order in which the refrigerant passes. The same applies to the drawings referred to in the following description.

[0099] In Modification F, for example, during an evaporation operation, the refrigerant which has flowed from a heat source heat exchanger 23 flows into the flow divider 50 via the auxiliary heat exchanger 38 by a route passing rectangles 1 to 4 of FIG. 10 in this order. The refrigerant is divided into three directions in the flow divider 50, and the divided refrigerants flow into a fourth tube pass P4, a fifth tube pass P5, and a sixth tube pass P6, respectively. The fourth tube pass P4 is on a route passing rectangles 11 to 16 of FIG. 10 in this order. The fifth tube pass P5 is on a route passing rectangles 5 to 10 of FIG. 10 in this order. The sixth tube pass P6 is on a route passing rectangles 17 to 22 of FIG. 10 in this order. After passing through the fourth tube pass P4, the fifth tube pass P5, and the sixth tube pass P6, the refrigerants are merged into one again in a merging portion 37M, and the refrigerant then flows toward an outdoor unit 20.

[0100] In Modification F, a refrigerant temperature sensor 40 is disposed near the flow divider 50 in a refrigerant flow and on a pipe, which connects the flow divider 50 and the main heat exchanger 37 and through which the refrigerant passes when flowing into the main heat exchanger 37 in the second time, on a refrigerant flow path.

[0101] As illustrated in FIG. 11, alternatively, the refrigerant temperature sensor 40 may be disposed on a U-shaped tube 31c through which the refrigerant flows immediately after flowing through an inlet 37E of the main heat exchanger 37 when flowing into the main heat exchanger 37 in the second time.(5-7) Modification G

[0102] An indoor unit 30 may include an electromagnetic valve 26. In Modification G, as illustrated in FIG. 12, the electromagnetic valve 26 is disposed on a pipe connecting a front surface upper portion 37a and a front surface lower portion 37b, which serve as a front surface portion of a utilization heat exchanger 31, and a rear surface portion 37c on a refrigerant flow path.

[0103] In Modification G, during an evaporation operation, a high-pressure refrigerant discharged from a compressor 21 flows through a refrigerant pipe 12 via a heat source heat exchanger 23 and reaches the utilization heat exchanger 31. After reaching the utilization heat exchanger 31, the high-pressure refrigerant flows into an auxiliary heat exchanger 38 from rectangle 1 or rectangle 13 of FIG. 13.

[0104] After flowing into the auxiliary heat exchanger 38 from rectangle 1, the refrigerant flows out of the auxiliary heat exchanger 38 from rectangle 3 and then is divided into three directions in a first flow divider 51. The divided refrigerants flow into a main heat exchanger 37 by a route passing rectangles 4 to 6, a route passing rectangles 7 to 9, and a route passing rectangles 10 to 12, respectively. The high-pressure refrigerants condense while passing through three tube passes P, and then turn into the liquid refrigerants. After flowing out of the three tube passes P of the main heat exchanger 37, the refrigerants are merged into one again in a merging portion 37M. Thereafter, the refrigerant flows into the electromagnetic valve 26.

[0105] After flowing into the auxiliary heat exchanger 38 from rectangle 13, the refrigerant flows out of the auxiliary heat exchanger 38 from rectangle 15 and then is divided into three directions in a second flow divider 52. The divided refrigerants flow into the main heat exchanger 37 by a route passing rectangles 16 to 18, a route passing rectangles 19 to 21, and a route passing rectangles 22 to 24, respectively. The high-pressure refrigerants condense while passing through the three tube passes P, and then turn into the liquid refrigerants. After flowing out of the three tube passes P of the main heat exchanger 37, the refrigerants are merged into one again in the merging portion 37M. Thereafter, the refrigerant flows into the electromagnetic valve 26.

[0106] The liquid refrigerant is decompressed in the electromagnetic valve 26 and is then divided into four by a third flow divider 53. Thereafter, the divided refrigerants flow into four tube passes P. The divided refrigerants reach the rear surface portion 37c of the utilization heat exchanger 31. The rear surface portion 37c also includes a plurality of tube passes P. The divided refrigerants flow into the four tube passes P by a route passing rectangles 27 to 29, a route passing rectangles 30 to 32, a route passing rectangles 33 to 35, and a route passing rectangles 36 to 38, respectively. In the plurality of tube passes P, the refrigerants evaporate while passing through the plurality of tube passes P, and then turn into the gas refrigerants. Thereafter, the gas refrigerants flow out of the rear surface portion 37c. After flowing out of the rear surface portion 37c, the gas refrigerants are merged into one again at rectangle 39. Thereafter, the refrigerant reaches an outdoor unit 20 via a refrigerant pipe 13.

[0107] The performance of an air conditioning apparatus 10 can be improved by causing the refrigerant to flow as described above.

[0108] In Modification G, the air conditioning apparatus 10 includes the plurality of flow dividers 50. In this case, the arrangement of refrigerant temperature sensors 40 may be considered in relation to the second flow divider 52 disposed near the front surface upper portion 37a of the utilization heat exchanger 31 and the front surface upper portion 37a of the utilization heat exchanger 31.

[0109] Specifically, in a case where the refrigerant temperature sensors 40 are disposed near the second flow divider 52 in the refrigerant flow, the refrigerant temperature sensors 40 are disposed on the pipes connecting the second flow divider 52 and the front surface upper portion 37a of the main heat exchanger 37 on the refrigerant flow path, at any positions illustrated in FIG. 12.

[0110] In the case where the refrigerant temperature sensors 40 are disposed on the front surface upper portion 37a of the utilization heat exchanger 31, the refrigerant temperature sensors 40 are disposed near inlets, through which the refrigerants from the second flow divider 52 flow first, of the front surface upper portion 37a of the main heat exchanger 37, as illustrated in FIG. 13. The refrigerant temperature sensors 40 are disposed at any positions illustrated in FIG. 13. It should be noted that FIG. 13 does not illustrate the rear surface portion 37c as well as the refrigerant pipes and the like reaching the rear surface portion 37c.(5-8) Modification H

[0111] In the foregoing embodiment, the refrigerant flows such that, during the evaporation operation, the traveling direction RF of the refrigerant and the traveling direction AF of the airflow generated by the utilization fan 32 are parallel to each other. However, the refrigerant may flow such that, during the evaporation operation, the traveling direction RF of the refrigerant and the traveling direction AF of the airflow generated by the utilization fan 32 are opposite to each other.

[0112] This configuration enables improvement in performance of the air conditioning apparatus 10.

[0113] In Modification H, an air conditioning apparatus 10 is equal in configuration to the air conditioning apparatus 10 according to the foregoing embodiment except that the air conditioning apparatus 10 does not include an auxiliary heat exchanger 38. Therefore, a refrigerant temperature sensor 40 is disposed in the same manner as that described in the foregoing embodiment except the components associated with the auxiliary heat exchanger 38.(5-9) Modification I

[0114] In the foregoing embodiment, during the evaporation operation, the traveling direction RF of the refrigerant and the traveling direction AF of the airflow generated by the utilization fan 32 are parallel to each other. However, during both the evaporation operation and the condensation operation, the traveling direction RF of the refrigerant and the traveling direction AF of the airflow generated by the utilization fan 32 may be opposite to each other.

[0115] In Modification I, as illustrated in FIG. 14, an indoor unit 30 includes a utilization heat exchanger 31 and a bridge circuit 80. The utilization heat exchanger 31 includes a refrigerant inlet pipe 31e and a refrigerant outlet pipe 31f. A refrigerant flows into the utilization heat exchanger 31 through the refrigerant inlet pipe 31e, and flows out of the utilization heat exchanger 31 through the refrigerant outlet pipe 31f. A utilization fan 32 urges heat exchange between air and the refrigerant by generating a flow of air passing through the utilization heat exchanger 31.

[0116] The bridge circuit 80 never changes a traveling direction RF of the refrigerant in the utilization heat exchanger 31. By the function of the bridge circuit 80, even when the traveling direction RF of the refrigerant is oriented as indicated by either arrow CO or arrow HO, the refrigerant always flows into the utilization heat exchanger 31 through the refrigerant inlet pipe 31e and always flows out of the utilization heat exchanger 31 through the refrigerant outlet pipe 31f.

[0117] The bridge circuit 80 includes a first node A', a second node B', a third node C', and a fourth node D'. The first node A' is connected to the refrigerant outlet pipe 31f. The second node B' is connected to a compressor 21 via a four-way switching valve 22. The third node C' is connected to the refrigerant inlet pipe 31e. The fourth node D' is connected to an expansion valve 24.

[0118] The bridge circuit 80 also includes a first flow path A'B' extending from the first node A' to the second node B', a second flow path B'C' extending from the second node B' to the third node C', a third flow path D'C' extending from the fourth node D' to the third node C', and a fourth flow path A'D' extending from the first node A' to the fourth node D'.

[0119] The bridge circuit 80 also includes a first check valve 81, a second check valve 82, a third check valve 83, and a fourth check valve 84. These check valves maintain the traveling direction RF of the refrigerant on the flow paths where the check valves are disposed, and prevent backflow of the refrigerant. The first check valve 81 is disposed on the first flow path A'B' to allow the refrigerant to flow only in the direction from the first node A' to the second node B'. The second check valve 82 is disposed on the second flow path B'C' to allow the refrigerant to flow only in the direction from the second node B' to the third node C'. The third check valve 83 is disposed on the third flow path D'C' to allow the refrigerant to flow only in the direction from the fourth node D' to the third node C'. The fourth check valve 84 is disposed on the fourth flow path A'D' to allow the refrigerant to flow only in the direction from the first node A' to the fourth node D'.

[0120] During an evaporation operation, the four-way switching valve 22 establishes a connection indicated by a solid line of FIG. 14 and allows the refrigerant to flow in a direction indicated by arrow CO.

[0121] The compressor 21 sucks the refrigerant in a low-pressure gas state through a suction pipe, and discharges the refrigerant in a high-pressure gas state through a discharge pipe. The refrigerant in the high-pressure gas state passes through the four-way switching valve 22 and then flows into a heat source heat exchanger 23. The heat source heat exchanger 23 condenses the refrigerant, using the cold heat of air to generate the refrigerant in a high-pressure liquid state. The refrigerant in the high-pressure liquid state flows out of the heat source heat exchanger 23 through a refrigerant outlet pipe. The refrigerant is then decompressed in an expansion valve 24 to turn into the refrigerant in a gas-liquid two-phase state. Thereafter, the refrigerant reaches the fourth node D'. Thereafter, the refrigerant passes through the third check valve 83 and reaches the third node C'. Thereafter, the refrigerant flows into the utilization heat exchanger 31 through the refrigerant inlet pipe 31e. The utilization heat exchanger 31 evaporates the refrigerant in the gas-liquid two-phase state to provide the cold heat carried by the refrigerant to a user and to generate the refrigerant in the low-pressure gas state. Thereafter, the refrigerant flows out of the utilization heat exchanger 31 through the refrigerant outlet pipe 31f and then reaches the first node A'. Thereafter, the refrigerant passes through the first check valve 81 and reaches the second node B'. Thereafter, the refrigerant passes through a refrigerant pipe 13 and reaches an outdoor unit 20.

[0122] The refrigerant flows through the utilization heat exchanger 31 as follows.

[0123] In the utilization heat exchanger 31, after reaching rectangle 1 of FIG. 15, the refrigerant is divided into two direction by a first flow divider 51 of FIG. 15. The divided refrigerants flow toward rectangle 2 and rectangle 18.

[0124] After passing through rectangle 2, the refrigerant is further divided into three directions in a second flow divider 52. The divided refrigerants pass through a main heat exchanger 37 and an auxiliary heat exchanger 38 by a route passing rectangles 3 to 7, a route passing rectangles 8 to 12, and a route passing rectangles 13 to 17, respectively. After flowing out of the auxiliary heat exchanger 38, the refrigerants are merged into one again in a merging portion 37M. Thereafter, the refrigerant reaches the outdoor unit 20.

[0125] After passing through rectangle 18, the refrigerant is further divided into three directions in a third flow divider 53. The divided refrigerants flow through the main heat exchanger 37 and the auxiliary heat exchanger 38 by a route passing rectangles 19 to 23, a route passing rectangles 24 to 28, and a route passing rectangles 29 to 33, respectively. After flowing out of the auxiliary heat exchanger 38, the refrigerants are merged into one again in the merging portion 37M. Thereafter, the refrigerant flows out of the utilization heat exchanger 31 through the refrigerant outlet pipe 31f and then reaches the first node A'.

[0126] During a condensation operation, the four-way switching valve 22 establishes a connection indicated by a broken line of FIG. 14 and allows the refrigerant to flow in a direction indicated by arrow HO. Also in this case, the refrigerant flows into the utilization heat exchanger 31 through the refrigerant inlet pipe 31e, and flows out of the utilization heat exchanger 31 through the refrigerant outlet pipe 31f. Therefore, during both the evaporation operation and the condensation operation, the traveling direction of the refrigerant (indicated by solid arrow RF of FIG. 15) and the traveling direction of an airflow generated by the utilization fan 32 (indicated by broken arrow AF of FIG. 15) are opposite to each other.

[0127] In Modification I, an air conditioning apparatus 10 includes the plurality of flow dividers. In this case, the arrangement of refrigerant temperature sensors 40 may be considered in relation to the second flow divider 52 and third flow divider 53 disposed near the main heat exchanger 37 and a front surface upper portion 37a of the utilization heat exchanger 31.

[0128] Specifically, in a case where the refrigerant temperature sensors 40 are disposed near the second flow divider 52 or third flow divider 53 in refrigerant flows, the refrigerant temperature sensors 40 are disposed on pipes connecting the second flow divider 52 or the third flow divider 53 and the front surface upper portion 37a of the main heat exchanger 37 on a refrigerant flow path, at any positions illustrated in FIG. 15.

[0129] In the case where the refrigerant temperature sensors 40 are disposed on the front surface upper portion 37a of the utilization heat exchanger 31, the refrigerant temperature sensors 40 are disposed near inlets, through which the refrigerant from the second flow divider 52 or the third flow divider 53 passes first, of the front surface upper portion 37a of the main heat exchanger 37, as illustrated in FIG. 16. The refrigerant temperature sensors 40 are disposed at any positions illustrated in FIG. 16.

[0130] The configurations of the foregoing modifications may be employed in combination in a case where these modifications are relevant to each other.

[0131] While an embodiment of the present disclosure has been described herein above, it is to be appreciated that various changes in form and detail may be made without departing from the spirit and scope of the present disclosure presently or hereafter claimed. In addition, the foregoing embodiment and modifications may be appropriately combined or substituted as long as the combination or substitution does not impair the functions of the present disclosure. The foregoing ordinal numbers such as "first", "second", ... are merely used for distinguishing the elements designated with the ordinal numbers, and are not intended to limit the number and order of the elements.INDUSTRIAL APPLICABILITY

[0132] As described above, the present disclosure is useful for an indoor unit 30 and an air conditioning apparatus.REFERENCE SIGNS LIST

[0133] 10: air conditioning apparatus 11: refrigerant circuit 12: refrigerant pipe 13: refrigerant pipe 20: outdoor unit 26: electromagnetic valve 30: indoor unit 31: utilization heat exchanger (example of heat exchanger) 31a: heat transfer tube 31b: heat transfer fin 31c: U-shaped tube 32: utilization fan (example of fan) 33: casing 37: main heat exchanger 37E: inlet 37M: merging portion 37a: front surface upper portion 37b: front surface lower portion 37c: rear surface portion 38: auxiliary heat exchanger 40: refrigerant temperature sensor (example of sensor) 50: flow divider 80: bridge circuit AF: traveling direction of airflow BP: branch pipe M: collecting pipe P: tube pass P1: first tube pass (example of tube pass having shortest length) P2: second tube pass P3: third tube pass (example of tube pass having longest length) RF: traveling direction of refrigerant CITATION LIST PATENT LITERATURE

[0134] Patent Literature 1: JP 2022-115320 A

Claims

1. An indoor unit (30) of an air conditioning apparatus (10), configured to adopt a zeotropic refrigerant as a refrigerant, the indoor unit comprising: a main heat exchanger (37) including a plurality of tube passes (P) through which the refrigerant flows; a flow divider (50) configured to divide the refrigerant before the refrigerant flows into the plurality of tube passes; and a sensor (40) configured to detect a temperature of the refrigerant, wherein the sensor is disposed the flow divider in a refrigerant flow, is disposed on a pipe connecting the flow divider and the main heat exchanger on a refrigerant flow path, or is disposed on one of the plurality of tube passes defined by heat transfer tubes (31a) of the main heat exchanger, at a position that is closer to the flow divider than a midpoint of an entire length of the one of the plurality of tube passes is.

2. The indoor unit according to claim 1, wherein the main heat exchanger includes a front surface upper portion (37a), a front surface lower portion (37b), and a rear surface portion (37c), and the sensor is disposed in a refrigerant flow near the flow divider that divides the refrigerant before the refrigerant flows into the tube pass located in the front surface upper portion among the plurality of tube passes, is disposed on a pipe connecting the flow divider and the tube pass located in the front surface upper portion on the refrigerant flow path, or is disposed on the tube pass located in the front surface upper portion.

3. The indoor unit according to claim 2, wherein the sensor is disposed on the one of the plurality of tube passes defined by the heat transfer tubes of the main heat exchanger, at the position that is closer to the flow divider than the midpoint of the entire length of the one of the plurality of tube passes is, and on a windward side of the front surface upper portion.

4. The indoor unit according to any one of claims 1 to 3, wherein during an evaporation operation, a refrigerant temperature at a position where the sensor is disposed is lower than a refrigerant temperature at an inlet (37E) of the main heat exchanger.

5. The indoor unit according to any one of claims 1 to 4, wherein during an evaporation operation, a refrigerant temperature at a position where the sensor is disposed is lower than a refrigerant temperature at a merging portion (37M) of the plurality of tube passes of the main heat exchanger.

6. The indoor unit according to claim 1 or 2, further comprising an auxiliary heat exchanger (38), wherein during an evaporation operation, the refrigerant flows through the auxiliary heat exchanger, the flow divider, and the main heat exchanger in this order, and the sensor is disposed on the pipe connecting the flow divider and the main heat exchanger on the refrigerant flow path.

7. The indoor unit according to claim 1 or 2, further comprising an auxiliary heat exchanger, wherein during an evaporation operation, the refrigerant flows through the auxiliary heat exchanger, the flow divider, and the main heat exchanger in this order, and the sensor is disposed near the flow divider in the refrigerant flow and the sensor is disposed on a pipe on the refrigerant flow path connecting the auxiliary heat exchanger and the flow divider.

8. The indoor unit according to claim 1 or 2, further comprising an auxiliary heat exchanger, wherein during an evaporation operation, the refrigerant flows through the auxiliary heat exchanger, the flow divider, and the main heat exchanger in this order, and the sensor is disposed on the one of the plurality of tube passes defined by the heat transfer tubes of the main heat exchanger, at the position that is closer to the flow divider than the midpoint of the entire length of the one of the plurality of tube passes is.

9. The indoor unit according to claim 1 or 2, wherein the sensor is disposed on one of the plurality of tube passes except the tube pass (P3) having a longest length among the plurality of tube passes.

10. The indoor unit according to claim 9, wherein the sensor is disposed on the tube pass (P1) having a shortest length among the plurality of tube passes.

11. The indoor unit according to claim 1 or 2, wherein the sensor is disposed on one of the plurality of tube passes where an amount of the refrigerant circulating in the main heat exchanger is largest.

12. The indoor unit according to any one of claims 1 to 11, further comprising a fan (32), wherein during an evaporation operation, a traveling direction RF of the refrigerant and a traveling direction AF of an airflow generated by the fan are opposite to each other.

13. The indoor unit according to any one of claims 1 to 12, further comprising a fan, wherein during an evaporation operation and a condensation operation, a traveling direction RF of the refrigerant and a traveling direction AF of an airflow generated by the fan are opposite to each other.

14. The indoor unit according to any one of claims 1 to 13, wherein the zeotropic refrigerant is mainly made up of a hydrofluoroolefin refrigerant.

Images