AIR-CONDITIONING APPARATUS

Abstract

An air-conditioning apparatus includes a refrigerant circuit configured to cause refrigerant to circulate therein, and an outdoor unit and an indoor unit forming the refrigerant circuit. The outdoor unit includes a heat exchanger provided with one heat exchanger core or two or more heat exchanger cores arranged along a flow direction of air. Each heat exchanger core has a plurality of flat tubes extending in an up-down direction. The heat exchanger is configured to cause the refrigerant to flow as an upward flow in the flat tubes when functioning as a condenser. The refrigerant is a two-component refrigerant mixture in which two refrigerants selected from R32, HFO1123, and R1234yf are mixed, or a three-component refrigerant mixture in which the three refrigerants are mixed.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national stage application of International Application No. PCT/JP2022/022119 filed on May 31, 2022, which is based on and claims priority to International Application No. PCT/JP2021/020652 filed on May 31, 2021, the contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to an air-conditioning apparatus provided with an outdoor unit including a heat exchanger having a plurality of flat tubes.

BACKGROUND

Conventionally, there is an air-conditioning apparatus in which an outdoor unit is provided with a heat exchanger including a plurality of flat tubes that extends in a vertical direction and is arranged at intervals in a horizontal direction, a plurality of fins that is connected between adjacent flat tubes and transfers heat to the flat tubes, and headers provided at an upper end part and a lower end part of the plurality of flat tubes (see, for example, Patent Literature 1).

The air-conditioning apparatus of Patent Literature 1 is capable of operating both a cooling operation and a heating operation, and a pure refrigerant R410A or a similar refrigerant is enclosed in its refrigerant circuit. When the air-conditioning apparatus performs the heating operation in a low-temperature environment where an outside air temperature is low and a surface temperature of the heat exchanger becomes zero degrees C. or below, frost forms on the heat exchanger. For this reason, when the amount of frost formed on the heat exchanger reaches a certain level, a defrosting operation for melting the frost on the surface of the heat exchanger is performed. In the defrosting operation, defrosting is performed by causing the refrigerant in a high-temperature, high-pressure gas state to enter one of the headers and flow in the flat tubes.

PATENT LITERATURE

• • Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2018-96638

In a conventional air-conditioning apparatus such as that of Patent Literature 1, during the defrosting operation, refrigerant in a high-temperature, high-pressure gas state enters the flat tubes from the lower header and flows as an upward flow in the flat tubes. When the refrigerant flows in the flat tubes, the refrigerant is cooled, and the amount of the refrigerant in a liquid phase increases as the refrigerant goes to the downstream side. Then, when the refrigerant in a high-temperature, high-pressure gas state flows as an upward flow in the flat tubes, liquid stagnation occurs in which liquefied refrigerant cannot move upward due to the effect of gravity and thus stagnates, causing degradation of the defrosting performance.

SUMMARY

The present disclosure has been made to solve the problem described above, and has an object to provide an air-conditioning apparatus capable of preventing degradation of the defrosting performance.

An air-conditioning apparatus according to an embodiment of the present disclosure includes a refrigerant circuit configured to cause refrigerant to circulate therein, and an outdoor unit and an indoor unit forming the refrigerant circuit. The outdoor unit includes a heat exchanger provided with one heat exchanger core or two or more heat exchanger cores arranged along a flow direction of air. Each heat exchanger core has a plurality of flat tubes extending in an up-down direction. The heat exchanger is configured to cause the refrigerant to flow as an upward flow in the flat tubes when functioning as a condenser. The refrigerant is a two-component refrigerant mixture in which two refrigerants selected from R32, HFO1123, and R1234yf are mixed, or a three-component refrigerant mixture in which the three refrigerants are mixed.

According to the air-conditioning apparatus according to an embodiment of the present disclosure, the refrigerant circulating in the refrigerant circuit is a two-component refrigerant mixture in which two refrigerants selected from R32, HFO1123, and R1234yf are mixed, or a three-component refrigerant mixture in which the three refrigerants are mixed. Therefore, compared with a case where a pure R410A refrigerant is used, liquid stagnation can be reduced, which is caused by the refrigerant in a liquid state that cannot move upward due to the effect of gravity and thus stagnates when the refrigerant entering from a hot gas refrigerant inlet formed at a lower part of the heat exchanger flows as an upward flow in the flat tubes of the heat exchanger core, and thus degradation of the defrosting performance can be prevented.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a refrigerant circuit diagram of an air-conditioning apparatus according to Embodiment 1.

FIG. 2 is a perspective view of a heat exchanger of the air-conditioning apparatus according to Embodiment 1.

FIG. 3 is a front view of the heat exchanger of the air-conditioning apparatus according to Embodiment 1.

FIG. 4 is a diagram illustrating a relationship between a height H of a heat exchanger core of the heat exchanger and a value of APHEX/APHEAD obtained from experimental results.

FIG. 5 is a diagram illustrating degradation of defrosting performance due to liquid stagnation in the heat exchanger.

FIG. 6 is a first graph illustrating a relationship between a concentration of R1234yf in a three-component refrigerant mixture and a value of ΔP_HEX/ΔP_HEAD obtained from experimental results.

FIG. 7 is a second graph illustrating a relationship between a concentration of R1234yf in a three-component refrigerant mixture and a value of ΔP_HEX/ΔP_HEAD obtained from experimental results.

FIG. 8 is a graph illustrating a relationship between a concentration of R1234yf in a two-component refrigerant mixture of R32 and R1234yf and a value of ΔP_HEX/ΔP_HEAD obtained from experimental results.

FIG. 9 is a graph illustrating a relationship between a concentration of R1234yf in a two-component refrigerant mixture of HFO1123 and R1234yf and a value of ΔP_HEX/ΔP_HEAD obtained from experimental results.

FIG. 10 is a cross-section diagram of flat tubes in the heat exchanger of the air-conditioning apparatus according to Embodiment 1.

FIG. 11 is a graph illustrating a relationship between a concentration of R32 in a two-component refrigerant mixture of R32 and R1234yf and a refrigerant pressure drop multiplication factor Y obtained from experimental results.

FIG. 12 is a graph illustrating a relationship between a concentration of HFO1123 in a three-component refrigerant mixture (R32=50 wt %) and the refrigerant pressure drop multiplication factor Y obtained from experimental results.

FIG. 13 is a graph illustrating a relationship between a concentration of HFO1123 in a three-component refrigerant mixture (R32=40 wt %) and the refrigerant pressure drop multiplication factor Y obtained from experimental results.

FIG. 14 is a graph illustrating a relationship between a concentration of HFO1123 in a three-component refrigerant mixture (R32=30 wt %) and the refrigerant pressure drop multiplication factor Y obtained from experimental results.

FIG. 15 is a graph illustrating a relationship between a concentration of HFO1123 in a three-component refrigerant mixture (R32=20 wt %) and the refrigerant pressure drop multiplication factor Y obtained from experimental results.

FIG. 16 is a graph illustrating a relationship between a concentration of HFO1123 in a three-component refrigerant mixture (R32=10 wt %) and the refrigerant pressure drop multiplication factor Y obtained from experimental results.

FIG. 17 is a front view of the heat exchanger of the air-conditioning apparatus according to Embodiment 2.

FIG. 18 is a front view of the heat exchanger of the air-conditioning apparatus according to Embodiment 3.

DETAILED DESCRIPTION

Embodiments of the present disclosure will be described with reference to the drawings. Note that the present disclosure is not limited to the embodiments described below. Furthermore, the relationship of sizes of the components in the drawings may differ from that of actual ones.

Embodiment 1

<Configuration of Air-Conditioning Apparatus 100>

FIG. 1 is a refrigerant circuit diagram of an air-conditioning apparatus 100 according to Embodiment 1. Note that, solid arrows in FIG. 1 indicate flows of refrigerant in a cooling operation, and broken line arrows in FIG. 1 indicate flows of refrigerant in a heating operation.

As shown in FIG. 1, the air-conditioning apparatus 100 according to Embodiment 1 includes an outdoor unit 10 and an indoor unit 20. The outdoor unit 10 includes a compressor 11, a flow switching device 12, a fan 13, and a heat exchanger 30. The indoor unit 20 includes an expansion device 21, an indoor heat exchanger 22, and an indoor fan 23.

In addition, the air-conditioning apparatus 100 includes a refrigerant circuit 101 in which refrigerant circulates. The refrigerant circuit 101 is formed with the outdoor unit 10 and the indoor unit 20. More specifically, the refrigerant circuit 101 is formed by connecting the compressor 11, the flow switching device 12, the heat exchanger 30, the expansion device 21, and the indoor heat exchanger 22 by a refrigerant pipe. The air-conditioning apparatus 100 is capable of performing both a cooling operation and a heating operation by switching of the flow switching device 12.

The refrigerant that circulates in the refrigerant circuit 101 is a two-component refrigerant mixture in which two refrigerants selected from R32, HFO1123, and R1234yf are mixed, or a three-component refrigerant mixture in which these three refrigerants are mixed. Note that details of these refrigerants will be described later.

The compressor 11 is configured to suck the refrigerant in a low-temperature, low-pressure state, compress the sucked refrigerant, and discharge the refrigerant in a high-temperature, high-pressure state. The compressor 11 is, for example, an inverter compressor, in which the displacement, which is a delivery amount per unit time, is controlled by changing the operation frequency.

The flow switching device 12 is, for example, a four-way valve, and is configured to switch the cooling operation and the heating operation by switching directions of refrigerant flow. In the cooling operation, the flow switching device 12 is switched to a state shown by the solid lines in FIG. 1 to connect a discharge side of the compressor 11 to the heat exchanger 30. In addition, in the heating operation, the flow switching device 12 is switched to a state shown by the broken lines in FIG. 1 to connect a suction side of the compressor 11 to the indoor heat exchanger 22.

The heat exchanger 30 is configured to exchange heat between outdoor air and the refrigerant. In the cooling operation, the heat exchanger 30 functions as a condenser that rejects heat of the refrigerant to outdoor air to condense the refrigerant. Furthermore, in the heating operation, the heat exchanger 30 functions as an evaporator that evaporates the refrigerant, and cools outdoor air by using the vaporization heat generated thereby.

The fan 13 is configured to supply outdoor air to the heat exchanger 30, and the amount of air to be supplied to the heat exchanger 30 is adjusted by controlling the rotation speed.

The expansion device 21 is, for example, an electronic expansion valve capable of adjusting an opening degree of the valve. By adjusting the opening degree, the pressure of the refrigerant flowing into the heat exchanger 30 or the indoor heat exchanger 22 is controlled. Note that, although, in the embodiments, the expansion device 21 is provided at the indoor unit 20, the expansion device 21 may be provided at the outdoor unit 10, and the installation site is not limited to any specific position.

The indoor heat exchanger 22 is configured to exchange heat between indoor air and the refrigerant. In the cooling operation, the indoor heat exchanger 22 functions as an evaporator that evaporates the refrigerant and cools indoor air by using the vaporization heat generated thereby. Furthermore, in the heating operation, the indoor heat exchanger 22 functions as a condenser that rejects heat of the refrigerant to indoor air to condense the refrigerant.

The indoor fan 23 is configured to supply indoor air to the indoor heat exchanger 22, and the amount of air to be supplied to the indoor heat exchanger 22 is adjusted by controlling the rotation speed.

<Configuration of Heat Exchanger 30>

FIG. 2 is a perspective view of the heat exchanger 30 of the air-conditioning apparatus 100 according to Embodiment 1. FIG. 3 is a front view of the heat exchanger 30 of the air-conditioning apparatus 100 according to Embodiment 1. Note that, the broken line arrows of FIG. 2 and the white arrows of FIG. 3 each indicate a flow of the refrigerant in the cooling operation. In addition, a height H and a width L of a heat exchanger core 31, which will be described later, are indicated in FIG. 3.

As shown in FIGS. 2 and 3, the heat exchanger 30 is provided with the heat exchanger core 31 having a plurality of flat tubes 38 and a plurality of fins 39. The flat tubes 38 are arranged at intervals in a horizontal direction (right-left direction in FIGS. 2 and 3) such that airflows generated by the fan 13 pass between flat tubes 38. The refrigerant flows in a vertical direction (up-down direction in FIGS. 2 and 3) in each flat tube 38 extending in the vertical direction. Each fin 39 is connected between the adjacent flat tubes 38, and configured to transfer heat to the flat tubes 38. Note that, the fin 39 is provided to improve heat exchange efficiency between air and the refrigerant, and a corrugated fin, for example, is used as the fin 39. However, the fin 39 is not limited to the corrugated fin. Because heat exchange between air and the refrigerant is performed through the surfaces of the flat tubes 38, the fins 39 may be omitted.

A lower end part of the heat exchanger core 31 is provided with a first header 34. Lower end parts of the flat tubes 38 of the heat exchanger core 31 are directly inserted into the first header 34. An upper end part of the heat exchanger core 31 is provided with a second header 35. Upper end parts of the flat tubes 38 of the heat exchanger core 31 are directly inserted into the second header 35.

A hot gas refrigerant inlet 32 is formed at one end of the first header 34, and is connected to the refrigerant circuit 101 of the air-conditioning apparatus 100 via a gas pipe 37. Thus, the first header 34 is also called a gas header. The first header 34 is configured to cause the refrigerant in a high-temperature, high-pressure gas state (hereinafter referred to also as hot gas refrigerant) flowing out of the compressor 11 to flow into the heat exchanger 30 in the cooling operation, and cause the refrigerant in a low-temperature, low-pressure gas state, on which heat exchange has been performed in the heat exchanger 30, to flow out to the refrigerant circuit 101 in the heating operation. Here, the hot gas refrigerant is not limited to a single-phase gas refrigerant, and may be a two-phase gas-liquid refrigerant containing a gas-phase and having a temperature of zero degrees C. or above.

A liquid refrigerant outlet 33 is formed at one end of the second header 35, and is connected to the refrigerant circuit 101 of the air-conditioning apparatus 100 via a liquid pipe 36. Thus, the second header 35 is also called a liquid header. The second header 35 is configured to cause the refrigerant in a low-temperature, low-pressure two-phase state to flow into the heat exchanger 30 in the heating operation, and cause the refrigerant in a low-temperature, high-pressure liquid state, on which heat exchange has been performed in the heat exchanger 30, to flow out to the refrigerant circuit 101 in the cooling operation.

The plurality of flat tubes 38, the plurality of fins 39, the first header 34, and the second header 35 are made of aluminum, and are joined by brazing.

Next, operations of each operation mode of the air-conditioning apparatus 100 will be described based on FIGS. 1 and 2.

<Cooling Operation>

The refrigerant in a high-temperature, high-pressure gas state discharged from the compressor 11 flows into the heat exchanger 30 via the flow switching device 12. The refrigerant in a high-temperature, high-pressure gas state flowed into the heat exchanger 30 exchanges heat with outdoor air supplied by the fan 13, is condensed while rejecting heat, then enters a low-temperature, high-pressure liquid state, and flows out of the heat exchanger 30. The refrigerant in a low-temperature, high-pressure liquid state flowed out of the heat exchanger 30 is decompressed by the expansion device 21, then enters a low-temperature, low-pressure, two-phase gas-liquid state, and flows into the indoor heat exchanger 22. The refrigerant in a low-temperature, low-pressure, two-phase gas-liquid state flowed into the indoor heat exchanger 22 exchanges heat with indoor air supplied by the indoor fan 23, is evaporated while receiving heat, and cools the indoor air. Then, the refrigerant enters a low-temperature, low-pressure, gas state and flows out of the indoor heat exchanger 22. The refrigerant in a low-temperature, low-pressure gas state flowed out of the indoor heat exchanger 22 is sucked into the compressor 11, and enters a high-temperature, high-pressure gas state again.

<Heating Operation>

The refrigerant in a high-temperature, high-pressure gas state discharged from the compressor 11 flows into the indoor heat exchanger 22 via the flow switching device 12. The refrigerant in a high-temperature, high-pressure gas state flowed into the indoor heat exchanger 22 exchanges heat with indoor air supplied by the indoor fan 23, is condensed while rejecting heat, and heats the indoor air. Then, the refrigerant enters a low-temperature, high-pressure liquid state and flows out of the indoor heat exchanger 22. The refrigerant in a low-temperature, high-pressure liquid state flowed out of the indoor heat exchanger 22 is decompressed by the expansion device 21, then enters a low-temperature, low-pressure, two-phase gas-liquid state, and flows into the heat exchanger 30. The refrigerant in a low-temperature, low-pressure, two-phase gas-liquid state flowed into the heat exchanger 30 exchanges heat with outdoor air supplied by the fan 13, is evaporated while receiving heat, then enters a low-temperature, low-pressure gas state, and flows out of the heat exchanger 30. The refrigerant in a low-temperature, low-pressure gas state flowed out of the heat exchanger 30 is sucked into the compressor 11, and enters a high-temperature, high-pressure gas state again.

<Defrosting Operation>

In a low-temperature environment where surface temperatures of the flat tubes 38 and the fins 39 shown in FIG. 2 become zero degrees C. or below, frost forms on the heat exchanger 30 when the heating operation is performed. When the amount of frost formed on the heat exchanger 30 reaches a certain level, the frost obstructs air passages that allow airflows generated by the fan 13 to pass through the heat exchanger 30, and thus the performance of the heat exchanger 30 is lowered and the heating performance is diminished. For this reason, when the heating performance is lowered, the defrosting operation that melts frost on the surface of the heat exchanger 30 is performed.

In the defrosting operation, the fan 13 is stopped, and the flow switching device 12 is switched to the same state as the cooling operation so that the refrigerant in a high-temperature, high-pressure gas state flows into the heat exchanger 30. Thus, the frost formed on the flat tubes 38 and the fins 39 is melted. When the defrosting operation is started, the refrigerant in a high-temperature, high-pressure gas state flows into the flat tubes 38 from the gas pipe 37 via the first header 34. Note that, the refrigerant flowed into each of the flat tubes 38 moves upward in the vertical direction as an upward flow. Then, the frost formed on the flat tubes 38 and the fins 39 is melted into water by the refrigerant in a high-temperature state flowed in the flat tubes 38. The water generated by melting the frost is drained along the flat tube 38 or the fin 39 to a lower part of the heat exchanger 30. When the formed frost is melted, the defrosting operation is terminated and the heating operation is resumed. Note that timing for terminating the defrosting operation and resuming the heating operation can be determined by using a known method. For example, the air-conditioning apparatus 100 may be configured such that the defrosting operation is terminated and the heating operation is resumed when a detection temperature of a temperature sensor (not shown) reaches a predetermined temperature, or when the defrosting operation has been performed for a fixed time period.

FIG. 4 is a diagram illustrating a relationship between a height H of the heat exchanger core 31 of the heat exchanger and a value of ΔP_HEX/ΔP_HEAD obtained from experimental results. FIG. 5 is a diagram illustrating degradation of defrosting performance due to liquid stagnation in the heat exchanger. Note that, the white arrows of FIG. 5 indicate flows of the refrigerant in the defrosting operation. In this case, the height H of the heat exchanger core 31 is the length between an upper end of the first header 34 and a lower end of the second header 35, that is, the length of an exposed part of the flat tubes 38.

As shown in FIG. 4, according to the inventor's experiment, a value of ΔP_HEX/ΔP_HEAD tends to decrease as the height H [m] (see FIG. 3) of the heat exchanger core 31 increases, where a differential pressure (hereinafter referred to as flow passage differential pressure) in a refrigerant flow passage is given as ΔP_HEX, and a liquid head is given as ΔP_HEAD. Note that, in Embodiment 1, the flow passage differential pressure ΔP_HEX is a differential pressure in a flow passage in which the hot gas refrigerant flows as an upward flow in the defrosting operation, that is, a differential pressure between the upper end and lower end of the flat tube 38 in the heat exchanger core 31. In addition, the experimental results find that, if the value of ΔP_HEX/ΔP_HEAD decreases to a predetermined value or below, when the hot gas refrigerant flowed in the first header 34 flows as an upward flow in the flat tubes 38 of the heat exchanger core 31, liquid stagnation occurs in which liquefied refrigerant cannot move upward due to the effect of gravity and thus stagnates, and thereby the defrosting performance is significantly reduced. Note that, as shown in FIG. 5, when the liquid stagnation occurs, a frost remaining area is formed in which the frost formed on the flat tubes 38 and the fins 39 remains unmelted even when the defrosting operation is performed for the area (hereinafter referred to as liquid stagnation area) where the liquid stagnation occurs.

In general, many of the heat exchangers using a corrugated fin that are used in the outdoor units for car air-conditioners often have heat exchanger cores having a height of about 300 [mm], but the heat exchangers used in the outdoor units for buildings often have heat exchanger cores having a height of 420 [mm] or over.

The inventor's research finds that, if the heat exchanger used for the outdoor unit of a car air-conditioner is applied to the outdoor unit for building, when the height H of the heat exchanger core 31 is increased to about, for example, 420 [mm], the value of ΔP_HEX/ΔP_HEAD is reduced by 43[%] compared to the case using the heat exchanger core having a height of 300 [mm], as shown in FIG. 4. The research finds that, due to the increase in the height H of the heat exchanger core 31, liquid stagnation that prevents the refrigerant in a liquid state from flowing occurs in a part of the heat exchanger. In addition, the inventor's research finds that, when the height H of the heat exchanger core 31 is 800 [mm], the value of ΔP_HEX/ΔP_HEAD is reduced by 65[%] compared to the case using the heat exchanger core having a height of 300 [mm].

Conventional technology has a problem that, if the height H of the heat exchanger core 31 is equal to or greater than 420 [mm], liquid stagnation occurs in which liquefied refrigerant cannot move upward due to the effect of gravity and thus stagnates, and thereby significantly reducing the defrosting performance in the region where liquid stagnation is occurring when the hot gas refrigerant flows into the first header 34 provided at the lower part of the heat exchanger and, via the first header 34, flows as an upward flow in the flat tubes 38 extending in the vertical direction. Therefore, Embodiment 1 is provided to solve the problem to prevent reduction in the defrosting performance in the defrosting operation.

In Embodiment 1, the refrigerant that circulates in the refrigerant circuit 101 of the air-conditioning apparatus 100 is a two-component refrigerant mixture in which two refrigerants selected from R32, HFO1123, and R1234yf are mixed, or a three-component refrigerant mixture in which these three refrigerants are mixed. By using such a refrigerant, the value of ΔP_HEX/ΔP_HEAD can be increased due to differences in the gas density, the liquid density and the latent heat, compared with the case using a pure R410A refrigerant or a similar refrigerant used in common practice. Thus, liquid stagnation can be reduced, and degradation of the defrosting performance in the defrosting operation can be prevented.

FIG. 6 is a first graph illustrating a relationship between the concentration of R1234yf in the three-component refrigerant mixture and the value of ΔP_HEX/ΔP_HEAD obtained from experimental results. FIG. 7 is a second graph illustrating a relationship between the concentration of R1234yf in the three-component refrigerant mixture and the value of ΔP_HEX/ΔP_HEAD obtained from experimental results.

As illustrated in FIGS. 6 and 7, it is understood that when the three-component refrigerant mixture, in which three kinds of refrigerants R32, HFO1123, and R1234yf are mixed, is used as the refrigerant that circulates in the refrigerant circuit 101 of the air-conditioning apparatus 100, the value of ΔP_HEX/ΔP_HEAD increases as the concentration of R32 decreases. It is understood that, especially when the concentration of R32 is equal to or less than 30 wt[%], ΔP_HEX>ΔP_HEAD IS always satisfied, that is, the value of ΔP_HEX/ΔP_HEAD is always greater than 100[%] (or 1). The line (1) shown in FIG. 6 indicates a target liquid stagnation remediation line, and is a line of ΔP_HEX/ΔP_HEAD=100[%]. Therefore, by keeping the concentration of R32 at 30 [wt %] or less, occurrence of liquid stagnation can be further prevented.

In addition, even when the concentration of R32 is greater than 30 [wt %], if the concentration of R32 is equal to or less than 60 [wt %] and the concentration of R1234yf is equal to or greater than 40 [wt %], the value of ΔP_HEX/ΔP_HEAD is greater than 100[%] (or 1). Thus, the value of ΔP_HEX/ΔP_HEAD can be made larger compared with the case using a pure R410A refrigerant.

The line (2) shown in FIG. 7 indicates a target liquid stagnation remediation line for a case where the height H of the heat exchanger core 31 is 420 [mm], and is a line of ΔP_HEX/ΔP_HEAD=140[%]. In addition, the line (3) shown in FIG. 7 indicates a target liquid stagnation remediation line for a case where the height H of the heat exchanger core 31 is 490 [mm], and is a line of ΔP_HEX/ΔP_HEAD=150[%]. The line (4) shown in FIG. 7 indicates a target liquid stagnation remediation line for a case where the height H of the heat exchanger core 31 is 800 [mm], and is a line of ΔP_HEX/Δ P_HEAD=160[%].

As shown in FIG. 7, in the case where the height H of the heat exchanger core 31 is 420 [mm], when the concentration of R32 is equal to or less than 20 [wt %] and the concentration of R1234yf is equal to or greater than 50 [wt %], the value of ΔP_HEX/ΔP_HEAD exceeds the line (2). Therefore, even when the height H of the heat exchanger core 31 is 420 [mm], liquid stagnation can be significantly reduced to the same level as that in a heat exchanger used in the outdoor unit of a car air-conditioner. In addition, in the case where the height H of the heat exchanger core 31 is 490 [mm], when the concentration of R32 is equal to or less than 20 [wt %] and the concentration of R1234yf is equal to or greater than 65 [wt %], the value of ΔP_HEX/ΔP_HEAD exceeds the line (3). Therefore, even when the height H of the heat exchanger core 31 is 490 [mm], liquid stagnation can be significantly reduced to the same level as that in a heat exchanger for vehicle. Furthermore, in the case where the height H of the heat exchanger core 31 is 800 [mm], when the concentration of R32 is equal to or less than 10 [wt %] and the concentration of R1234yf is equal to or greater than 60 [wt %], the value of ΔP_HEX/ΔP_HEAD exceeds the line (4). Therefore, even when the height H of the heat exchanger core 31 is 800 [mm], liquid stagnation can be significantly reduced to the same level as that in a heat exchanger used for the outdoor unit of a car air-conditioner. In short, by adjusting the concentration of R1234yf in the three-component refrigerant mixture to exceed the corresponding liquid stagnation remediation line, liquid stagnation can be significantly reduced to the same level as that in a heat exchanger for vehicle.

FIG. 8 is a graph illustrating a relationship between the concentration of R1234yf in the two-component refrigerant mixture of R32 and R1234yf and the value of ΔP_HEX/ΔP_HEAD obtained from experimental results.

As shown in FIG. 8, it is understood that, in the case where the two-component refrigerant mixture in which two kinds of refrigerants R32 and R1234yf are mixed is used as the refrigerant that circulates in the refrigerant circuit 101 of the air-conditioning apparatus 100, the value of ΔP_HEX/ΔP_HEAD exceeds 100[%] (or 1) when the concentration of R1234yf is equal to or greater than 40 wt[%].

FIG. 9 is a graph illustrating a relationship between the concentration of R1234yf in the two-component refrigerant mixture of HFO1123 and R1234yf and the value of ΔP_HEX/ΔP_HEAD obtained from experimental results.

As shown in FIG. 9, it is understood that, in the case where the two-component refrigerant mixture in which two kinds of refrigerants HFO1123 and R1234yf are mixed is used as the refrigerant that circulates in the refrigerant circuit 101 of the air-conditioning apparatus 100, the value of ΔP_HEX/ΔP_HEAD always exceeds 100[%] (or 1) regardless of the concentration of R1234yf.

FIG. 10 is a cross-section diagram of the flat tubes 38 in the heat exchanger 30 of the air-conditioning apparatus 100 according to Embodiment 1. FIG. 11 is a graph illustrating a relationship between the concentration of R32 in the two-component refrigerant mixture of R32 and R1234yf and a refrigerant pressure drop multiplication factor Y obtained from experimental results. FIG. 12 is a graph illustrating a relationship between the concentration of HFO1123 in the three-component refrigerant mixture (R32=50 wt %) and the refrigerant pressure drop multiplication factor Y obtained from experimental results. FIG. 13 is a graph illustrating a relationship between the concentration of HFO1123 in the three-component refrigerant mixture (R32=40 wt %) and the refrigerant pressure drop multiplication factor Y obtained from experimental results. FIG. 14 is a graph illustrating a relationship between the concentration of HFO1123 in the three-component refrigerant mixture (R32=30 wt %) and the refrigerant pressure drop multiplication factor Y obtained from experimental results. FIG. 15 is a graph illustrating a relationship between the concentration of HFO1123 in the three-component refrigerant mixture (R32=20 wt %) and the refrigerant pressure drop multiplication factor Y obtained from experimental results. FIG. 16 is a graph illustrating a relationship between the concentration of HFO1123 in the three-component refrigerant mixture (R32=10 wt %) and the refrigerant pressure drop multiplication factor Y obtained from experimental results.

As shown in FIG. 10, the total flow passage cross-sectional area A [m²] of the heat exchanger core 31 in which the hot gas refrigerant flows as an upward flow is expressed as follows: A [m²]=a [m²]×N [piece], where a [m²] is the flow passage cross-sectional area of one flat tube 38, and N [piece] is the number of the flat tubes 38 that form the heat exchanger core 31. The heat exchanger 30 according to Embodiment 1 is configured to satisfy a condition ΔP_HEX/ΔP_HEAD=A^−1.75/(−4.9056×L²+15.53×L−0.6204)×Y>100[%] (or 1).

Here, L [m] is the width of the heat exchanger core 31 described above. In addition, Y is the refrigerant pressure drop multiplication factor for the refrigerant R410A for a case where a two-component refrigerant mixture of R32 and R1234yf or a three-component refrigerant mixture of HFO1123, R32 and R1234yf is used. FIG. 11 shows the formula of Y for a case where the two-component refrigerant mixture of R32 and R1234yf is used. FIGS. 12 to 16 each show the formula of Y for a case where the three-component refrigerant mixture of HFO1123, R32 and R1234yf is used and the concentration of R32 is 50, 40, 30, 20, or 10 [wt %].

Note that, although FIGS. 12 to 16 show relational formulas of the refrigerant pressure drop multiplication factor Y for cases where the concentration of R32 is 50 [wt %], 40 [wt %], 30 [wt %], 20 [wt %], and 10 [wt %], the concentration of R32 is not limited thereto. For example, when the concentration of R32 falls between the concentrations described above, the concentration of R32 may be rounded off. For example, when the concentration of R32 is 14 [wt %], the concentration is rounded to 10 and the formula of the refrigerant pressure drop multiplication factor Y for the case where the concentration of R32 is 10 [wt %] is used. Likewise, when the concentration of R32 is 15 [wt %], the concentration is rounded to 20 and the formula of the refrigerant pressure drop multiplication factor Y for the case where the concentration of R32 is 20 [wt %] is used.

Conventional technology has a problem that, if the height H of the heat exchanger core 31 is large, liquid stagnation occurs in which liquefied refrigerant cannot move upward due to the effect of gravity and thus stagnates when the hot gas refrigerant flows into the first header 34 provided at the lower part of the heat exchanger and, via the first header 34, flows as an upward flow in the flat tubes 38 extending in the vertical direction, and thereby significantly reducing the defrosting performance in the region where liquid stagnation is occurring. To solve this problem, the heat exchanger 30 according to Embodiment 1 is configured to satisfy the condition ΔP_HEX/Δ_HEAD=A^−1.75/(−4.9056×L²+15.53×L−0.6204)×Y>100 [%] (or 1) to reduce the liquid stagnation and thus to prevent degradation of the defrosting performance during the defrosting operation.

Note that, although, in Embodiment 1, the case where the heat exchanger 30 is provided with one heat exchanger core 31 is described, the configuration is not limited thereto. The heat exchanger 30 may be provided with two or more heat exchanger cores 31 arranged along a flow direction of air. In that case, a lower end part of the heat exchanger core 31 on the most leeward side is provided with the first header 34, and an upper end part or a lower end part of the heat exchanger core 31 on the most windward side is provided with the second header 35. In addition, a bridge header is provided between upper end parts or lower end parts of two adjacent heat exchanger cores 31. The bridge header is configured to distribute the refrigerant merged together from the flat tubes 38 of the heat exchanger core 31 on the leeward side, to the flat tubes 38 of the heat exchanger core 31 on the windward side.

Furthermore, although, in Embodiment 1, the heat exchanger 30 is configured to satisfy the condition ΔP_HEX/Δ P_HEAD>100[%] (or 1) in the defrosting operation, the circulation flow rate of the refrigerant generally varies (decreases) during the defrosting operation in the air-conditioning apparatus 100. For this reason, the heat exchanger 30 is designed to satisfy the condition ΔP_HEX/ΔP_HEAD>100[%] (or 1) when, for example, the circulation flow rate of the refrigerant is the maximum flow rate or at least 75% thereof.

As described above, the air-conditioning apparatus 100 according to Embodiment 1 includes the refrigerant circuit 101 in which the refrigerant circulates, and the outdoor unit 10 and the indoor unit 20 forming the refrigerant circuit 101. Furthermore, the outdoor unit 10 includes the heat exchanger 30 provided with one heat exchanger core 31 having the plurality of flat tubes 38 extending in the vertical direction or two or more heat exchanger cores 31 having the plurality of flat tubes 38 extending in the vertical direction and arranged along a flow direction of air. In the heat exchanger 30, the refrigerant flows as an upward flow in the flat tubes 38 when the heat exchanger 30 functions as a condenser. The refrigerant is the two-component refrigerant mixture in which two refrigerants selected from R32, HFO1123, and R1234yf are mixed, or the three-component refrigerant mixture in which these three refrigerants are mixed.

According to the air-conditioning apparatus 100 of Embodiment 1, the refrigerant circulating in the refrigerant circuit 101 is the two-component refrigerant mixture in which two refrigerants selected from R32, HFO1123, and R1234yf are mixed, or the three-component refrigerant mixture in which these three refrigerants are mixed. Therefore, compared with a case where a pure R410A refrigerant or a similar refrigerant is used, liquid stagnation, which is caused by the refrigerant in a liquid state that cannot move upward due to the effect of gravity and thus stagnates when the refrigerant entering from the hot gas refrigerant inlet 32 formed at the lower part of the heat exchanger 30 flows as an upward flow in the flat tubes 38 of the heat exchanger core 31, can be reduced, and thus degradation of the defrosting performance can be prevented.

Furthermore, in the air-conditioning apparatus 100 according to Embodiment 1, the refrigerant is the three-component refrigerant mixture in which three kinds of refrigerants R32, HFO1123, and R1234yf are mixed and the concentration of R32 is equal to or less than 30 [wt %]. Alternatively, the refrigerant is the three-component refrigerant mixture in which three kinds of refrigerants R32, HFO1123, and R1234yf are mixed, the concentration of R32 is between 40 [wt %] and 60 [wt %], inclusive, and the concentration of R1234yf is equal to or greater than 40 [wt %]. As another alternative, the refrigerant is the two-component refrigerant mixture of R32 and R1234yf and the concentration of R1234yf is equal to or greater than 40 [wt %]. As another option, the refrigerant is the two-component refrigerant mixture of HFO1123 and R1234yf.

According to the air-conditioning apparatus 100 of Embodiment 1, by using one of the refrigerants described above as the refrigerant circulating in the refrigerant circuit 101, ΔP_HEX/ΔP_HEAD can be increased to 100[%] (or 1). As a result, the liquid stagnation can be further reduced, and thus the degradation of the defrosting performance can be further prevented.

Moreover, the air-conditioning apparatus 100 according to Embodiment 1 includes the refrigerant circuit 101 in which the refrigerant circulates, and the outdoor unit 10 and the indoor unit 20 forming the refrigerant circuit 101. The outdoor unit 10 includes the heat exchanger 30 provided with one heat exchanger core 31 having the plurality of flat tubes 38 extending in the vertical direction or two or more heat exchanger cores 31 having the plurality of flat tubes 38 extending in the vertical direction and arranged along a flow direction of air. In the heat exchanger 30, the refrigerant flows as an upward flow in the flat tubes 38 when the heat exchanger 30 functions as a condenser. When the differential pressure in the refrigerant flow passage in which the hot gas refrigerant flows as an upward flow when the heat exchanger 30 functions as a condenser is given as ΔP_HEX and the liquid head is given as ΔP_HEAD, the two-component refrigerant mixture in which two refrigerants selected from R32, HFO1123, and R1234yf are mixed or the three-component refrigerant mixture in which these three refrigerants are mixed is used as the refrigerant such that ΔP_HEX is larger than ΔP_HEAD.

According to the air-conditioning apparatus 100 of Embodiment 1, the refrigerant circulating in the refrigerant circuit 101 is the two-component refrigerant mixture in which two refrigerants selected from R32, HFO1123, and R1234yf are mixed, or the three-component refrigerant mixture in which these three refrigerants are mixed. Therefore, compared with a case where a pure R410A refrigerant or a similar refrigerant is used, liquid stagnation, which is caused by the refrigerant in a liquid state that cannot move upward due to the effect of gravity and thus stagnates when the refrigerant entering from the hot gas refrigerant inlet 32 formed at the lower part of the heat exchanger 30 flows as an upward flow in the flat tubes 38 of the heat exchanger core 31, can be reduced, and thus degradation of the defrosting performance can be prevented.

Furthermore, the air-conditioning apparatus 100 according to Embodiment 1 includes the refrigerant circuit 101 in which the refrigerant circulates, and the outdoor unit 10 and the indoor unit 20 forming the refrigerant circuit 101. The outdoor unit 10 includes the heat exchanger 30 provided with one heat exchanger core 31 having the plurality of flat tubes 38 extending in the vertical direction or two or more heat exchanger cores 31 having the plurality of flat tubes 38 extending in the vertical direction and arranged along a flow direction of air. In the heat exchanger 30, the refrigerant flows as an upward flow in the flat tubes 38 when the heat exchanger 30 functions as a condenser. In addition, the refrigerant is the two-component refrigerant mixture in which two refrigerants selected from R32, HFO1123, and R1234yf are mixed, or the three-component refrigerant mixture in which these three refrigerants are mixed. Then, when the total flow passage cross-sectional area of the heat exchanger core 31, in which the hot gas refrigerant flows as an upward flow, is expressed as A [m²]=a [m²]×N [piece], where a [m²] is the flow passage cross-sectional area of one flat tube 38, and N [piece] is the number of the flat tubes 38 that form the heat exchanger core 31, and Y represents the refrigerant pressure drop multiplication factor for the refrigerant R410A, the heat exchanger 30 is configured to satisfy the condition ΔP_HEX/ΔP_HEAD=A^−1.75/(−4.9056×L²+15.53×L−0.6204)×Y>100[%] (or 1).

According to the air-conditioning apparatus 100 of Embodiment 1, because the heat exchanger 30 satisfies the condition ΔP_HEX/Δ_HEAD=A^−1.75/(−4.9056×L²+15.53×L−0.6204)×Y>100[%] (or 1), the liquid stagnation can be further reduced, and thus the degradation of the defrosting performance can be further prevented.

Embodiment 2

Embodiment 2 will now be described. Description that has been given in Embodiment 1 is omitted. Elements that are the same as or equivalent to those described in Embodiment 1 are denoted by the same reference signs.

FIG. 17 is a front view of the heat exchanger 30 of the air-conditioning apparatus 100 according to Embodiment 2. Note that, white arrows of FIG. 17 each indicate a flow of the refrigerant in the cooling operation. In addition, FIG. 17 shows the height H and the width L of the heat exchanger core 31. The width of each region of the heat exchanger core 31 is indicated as L₁, L₂ . . . in order from the downstream side.

The heat exchanger 30 according to Embodiment 2 is configured to function as a condenser that rejects heat of the refrigerant to outdoor air to condense the refrigerant in the cooling operation. As shown in FIG. 17, the heat exchanger 30 is provided with the heat exchanger core 31 having a plurality of flat tubes 38 and a plurality of fins 39. The flat tubes 38 are arranged at intervals in a horizontal direction (right-left direction in FIG. 17) such that airflows generated by the fan 13 pass between the flat tubes 38. The refrigerant flows in a vertical direction (up-down direction in FIG. 17) in each flat tube 38 extending in the vertical direction. Each fin 39 is connected between the adjacent flat tubes 38, and configured to transfer heat to the flat tubes 38. Note that, the fin 39 is provided to improve heat exchange efficiency between air and the refrigerant, and a corrugated fin, for example, is used as the fin 39. However, the fin 39 is not limited to the corrugated fin. Because heat exchange between air and the refrigerant is performed through the surfaces of the flat tubes 38, the fins 39 may be omitted.

A lower end part of the heat exchanger core 31 is provided with the first header 34. Lower end parts of the flat tubes 38 of the heat exchanger core 31 are directly inserted into the first header 34. An upper end of the heat exchanger core 31 is provided with the second header 35. Upper end parts of the flat tubes 38 of the heat exchanger core 31 are directly inserted into the second header 35.

The hot gas refrigerant inlet 32 is formed at one end of the second header 35, and is connected to the refrigerant circuit 101 of the air-conditioning apparatus 100 via the gas pipe 37. In addition, the liquid refrigerant outlet 33 is formed at the other end of the second header 35, and is connected to the refrigerant circuit 101 of the air-conditioning apparatus 100 via the liquid pipe 36. The second header 35 is configured to cause the refrigerant in a high-temperature, high-pressure gas state flowing out of the compressor 11 to flow into the heat exchanger 30, and cause the refrigerant in a low-temperature, high-pressure liquid state, on which heat exchange has been performed in the heat exchanger 30, to flow out to the refrigerant circuit 101 in the cooling operation. Furthermore, the second header 35 is configured to cause the refrigerant in a low-temperature, low-pressure, two-phase state to flow into the heat exchanger 30 and cause the refrigerant in a low-temperature, low-pressure gas state, on which heat exchange has been performed in the heat exchanger 30, to flow out to the refrigerant circuit 101 in the heating operation.

The plurality of flat tubes 38, the plurality of fins 39, the first header 34, and the second header 35 are made of aluminum, and are joined by brazing.

In the heat exchanger 30 according to Embodiment 2, the second header 35 is provided with a partition plate 40, as shown in FIG. 17. The partition plate 40 is provided for partitioning the flow passages of the heat exchanger core 31 into a plurality of regions in the horizontal direction. In addition, the partition plate 40 is provided such that the flow direction of the flow passages in each region in the heat exchanger core 31 is opposite to the flow direction of the flow passages in an adjacent region. In Embodiment 2, the flow passages of the heat exchanger core 31 are partitioned into two regions T₁ and T₂ by the partition plate 40. Furthermore, when the second header 35 is provided with the partition plate 40, a merging region M₁ for the hot gas refrigerant is formed in the first header 34.

The hot gas refrigerant flowed into the second header 35 flows as a downward flow in the flat tubes 38 of the heat exchanger core 31 in the region T₁. Then, flows of the refrigerant flowing out of the flat tubes 38 are merged together in the merging region M₁ in the first header 34. After the refrigerant flows as an upward flow in the flat tubes 38 of the heat exchanger core 31 in the region T₂, the refrigerant flows out of the second header 35. That is, the region T₁ is a downward flow region and the region T₂ is an upward flow region. In addition, the merging region M₁ in the first header 34 functions as an inlet of the upward flow region for the hot gas refrigerant.

In the region T₂, liquid stagnation occurs in which liquefied refrigerant cannot move upward due to the effect of gravity and thus stagnates when the hot gas refrigerant flows as an upward flow in the flat tubes 38 of the heat exchanger core 31. Accordingly, in the air-conditioning apparatus 100 of Embodiment 2, the two-component refrigerant mixture in which two refrigerants selected from R32, HFO1123, and R1234yf are mixed, or the three-component refrigerant mixture in which the three refrigerants are mixed is used as the refrigerant that circulates in the refrigerant circuit 101. Therefore, compared with a case where a pure R410A refrigerant or a similar refrigerant is used, liquid stagnation, which is caused by the refrigerant in a liquid state that cannot move upward due to the effect of gravity and thus stagnates when the refrigerant entering from the hot gas refrigerant inlet 32 formed at the heat exchanger 30 flows as an upward flow in the flat tubes 38 of the heat exchanger core 31 in the region T₂, can be reduced, and thus degradation of the defrosting performance can be prevented. In addition, because the flow passage cross-sectional area is reduced for the same refrigerant flow rate by providing the partition plate 40 in the second header 35, the flow velocity of the refrigerant is increased, and thus the flow passage differential pressure ΔP_HEX can be increased. As a result, the liquid stagnation is reduced, and the defrosting performance in the defrosting operation can be improved.

Embodiment 3

Embodiment 3 will now be described. Description that has been given in any of Embodiments 1 and 2 is omitted. Elements that are the same as or equivalent to those described in any of Embodiments 1 and 2 are denoted by the same reference signs.

FIG. 18 is a front view of the heat exchanger 30 of the air-conditioning apparatus 100 according to Embodiment 3. Note that, white arrows of FIG. 18 each indicate a flow of the refrigerant in the cooling operation. In addition, FIG. 18 shows the height H and the width L of the heat exchanger core 31. The width of each region of the heat exchanger core 31 is indicated as L₁, L₂ . . . in order from the downstream side.

The heat exchanger 30 according to Embodiment 3 is configured to function as a condenser that rejects heat of the refrigerant to outdoor air to condense the refrigerant in the cooling operation. As shown in FIG. 18, the heat exchanger 30 is provided with the heat exchanger core 31 having a plurality of flat tubes 38 and a plurality of fins 39. The flat tubes 38 are arranged at intervals in a horizontal direction (right-left direction in FIG. 18) such that airflows generated by the fan 13 pass between the flat tubes 38. The refrigerant flows in a vertical direction (up-down direction in FIG. 18) in each flat tube 38 extending in the vertical direction. Each fin 39 is connected between the adjacent flat tubes 38, and configured to transfer heat to the flat tubes 38. Note that, the fin 39 is provided to improve heat exchange efficiency between air and the refrigerant, and a corrugated fin, for example, is used as the fin 39. However, the fin 39 is not limited to the corrugated fin. Because heat exchange between air and the refrigerant is performed through the surfaces of the flat tubes 38, the fins 39 may be omitted.

A lower end part of the heat exchanger core 31 is provided with the first header 34. Lower end parts of the flat tubes 38 of the heat exchanger core 31 are directly inserted into the first header 34. An upper end part of the heat exchanger core 31 is provided with the second header 35. Upper end parts of the flat tubes 38 of the heat exchanger core 31 are directly inserted into the second header 35.

The hot gas refrigerant inlet 32 is formed at one end of the second header 35, and is connected to the refrigerant circuit 101 of the air-conditioning apparatus 100 via the gas pipe 37. The second header 35 is configured to cause the refrigerant in a high-temperature, high-pressure gas state flowing out of the compressor 11 to flow into the heat exchanger 30 in the cooling operation, and cause the refrigerant in a low-temperature, low-pressure, gas state, on which heat exchange has been performed in the heat exchanger 30, to flow out to the refrigerant circuit 101 in the heating operation.

The liquid refrigerant outlet 33 is formed at one end of the first header 34, the one end being located on the opposite side to the one end of the second header 35, and is connected to the refrigerant circuit 101 of the air-conditioning apparatus 100 via the liquid pipe 36. The first header 34 is configured to cause the refrigerant in a low-temperature, low-pressure, two-phase state to flow into the heat exchanger 30 in the heating operation, and cause the refrigerant in a low-temperature, high-pressure liquid state, on which heat exchange has been performed in the heat exchanger 30, to flow out to the refrigerant circuit 101 in the cooling operation.

The plurality of flat tubes 38, the plurality of fins 39, the first header 34, and the second header 35 are made of aluminum, and are joined by brazing.

In the heat exchanger 30 according to Embodiment 3, each of the first header 34 and the second header 35 is provided with one partition plate 40, as shown in FIG. 18. Each partition plate 40 is provided for partitioning the flow passages of the heat exchanger core 31 into a plurality of regions in the horizontal direction. In addition, the partition plate 40 is provided such that the flow direction of the flow passages in each region in the heat exchanger core 31 is opposite to the flow direction of the flow passages in an adjacent region. In Embodiment 3, the flow passages of the heat exchanger core 31 in each region are partitioned into three regions T₁, T₂, and T₃ by two partition plates 40. Furthermore, when each of the first header 34 and the second header 35 is provided with the partition plate 40, merging regions M₁ and M₂ for the hot gas refrigerant are formed in the first header 34 and the second header 35.

The hot gas refrigerant flowed into the second header 35 flows as a downward flow in the flat tubes 38 of the heat exchanger core 31 in the region T₁. Then, flows of the refrigerant flowing out of the flat tubes 38 are merged together in the merging region M₁ in the first header 34. Then, the refrigerant flows as an upward flow in the flat tubes 38 of the heat exchanger core 31 in the region T₂. After that, flows of the hot gas refrigerant are merged together in the merging region M₂ in the second header 35. After the refrigerant flows as a downward flow in the flat tubes 38 of the heat exchanger core 31 in the region T₃, the refrigerant flows out of the first header 34. That is, the regions T₁ and T₃ are downward flow regions and the region T₂ is an upward flow region. In addition, the merging region M₁ in the first header 34 functions as an inlet of the upward flow region for the hot gas refrigerant.

In the region T₂, liquid stagnation occurs in which liquefied refrigerant cannot move upward due to the effect of gravity and thus stagnates when the hot gas refrigerant flows as an upward flow in the flat tubes 38 in the heat exchanger core 31. Accordingly, in the air-conditioning apparatus 100 of Embodiment 3, the two-component refrigerant mixture in which two refrigerants selected from R32, HFO1123, and R1234yf are mixed, or the three-component refrigerant mixture in which the three refrigerants are mixed is used as the refrigerant that circulates in the refrigerant circuit 101. Therefore, compared with a case where a pure R410A refrigerant or a similar refrigerant is used, liquid stagnation can be reduced, which is caused by the refrigerant in a liquid state that cannot move upward due to the effect of gravity and thus stagnates when the refrigerant entering from the hot gas refrigerant inlet 32 formed at the heat exchanger 30 flows as an upward flow in the flat tubes 38 of the heat exchanger core 31 in the region T₂, and thus degradation of the defrosting performance can be prevented. In addition, because the flow passage cross-sectional area is reduced for the same refrigerant flow rate by providing the partition plate 40 in each of the first header 34 and the second header 35, the flow velocity of the refrigerant is increased, and thus the flow passage differential pressure ΔP_HEX can be increased. As a result, the liquid stagnation is reduced, and the defrosting performance in the defrosting operation can be improved.

Claims

1-10. (canceled)

11. An air-conditioning apparatus comprising:

a refrigerant circuit configured to cause refrigerant to circulate therein; and

an outdoor unit and an indoor unit forming the refrigerant circuit,

wherein the outdoor unit includes a heat exchanger provided with one heat exchanger core or two or more heat exchanger cores arranged along a flow direction of air, each heat exchanger core having a plurality of flat tubes extending in an up-down direction, and configured to cause the refrigerant to flow as an upward flow in the flat tubes when functioning as a condenser,

the refrigerant is a two-component refrigerant mixture in which two refrigerants selected from R32, HFO1123, and R1234yf are mixed, or a three-component refrigerant mixture in which the three refrigerants are mixed, and

the heat exchanger is configured to satisfy a condition ΔPHEX/ΔPHEAD=A−1.75/(−4.9056×L2+15.53×L−0.6204)×Y>100[%] (or 1), where Y represents a refrigerant pressure drop multiplication factor for a refrigerant R410A, and A [m2] represents a total flow passage cross-sectional area of the heat exchanger core in which a hot gas refrigerant flows as an upward flow when the heat exchanger functions as a condenser and is obtained by a formula A [m2]=a [m2]×N [piece], where a [m2] represents a flow passage cross-sectional area of one flat tube, and N [piece] represents a number of the flat tubes that form the heat exchanger core.

12. The air conditioning apparatus of claim 11, wherein

the refrigerant is a two-component refrigerant mixture of R32 and R1234yf, and

the factor Y is 0.00019x2−0.03026x+2.17100.

13. The air conditioning apparatus of claim 11, wherein

the refrigerant is a three-component refrigerant mixture in which three refrigerants R32, HFO1123, and R1234yf are mixed,

the concentration of R32 is 50 [wt %], and

the factor Y is 0.00002x2−0.00467x+1.14905.

14. The air conditioning apparatus of claim 11, wherein

the refrigerant is a three-component refrigerant mixture in which three refrigerants R32, HFO1123, and R1234yf are mixed,

the concentration of R32 is 40 [wt %], and

the factor Y is 0.00003x2−0.00602x+1.27790.

15. The air conditioning apparatus of claim 11, wherein

the refrigerant is a three-component refrigerant mixture in which three refrigerants R32, HFO1123, and R1234yf are mixed,

the concentration of R32 is 30 [wt %], and

the factor Y is 0.00003x2−0.00751x+1.44400.

16. The air conditioning apparatus of claim 11, wherein

the refrigerant is a three-component refrigerant mixture in which three refrigerants R32, HFO1123, and R1234yf are mixed,

the concentration of R32 is 20 [wt %], and

the factor Y is 0.00005x2−0.01056x+1.66882.

17. The air conditioning apparatus of claim 11, wherein

the refrigerant is a three-component refrigerant mixture in which three refrigerants R32, HFO1123, and R1234yf are mixed,

the concentration of R32 is 10 [wt %], and

the factor Y is 0.00006x2−0.01342x+1.94049.