Patent Application
20240219067
The present disclosure relates to a heat exchanger including a plurality of flat tubes, an outdoor unit of an air-conditioning apparatus including the heat exchanger, and an air-conditioning apparatus including the outdoor unit of the air-conditioning apparatus.
Conventionally, there has been a heat exchanger including a plurality of flat tubes that extend in a vertical direction and that are arrayed at spacings in a horizontal direction, a plurality of fins that are each connected across a space between adjacent ones of the flat tubes and that transfer heat to the flat tubes, and headers provided at upper and lower ends of the plurality of flat tubes (see, for example, Patent Literature 1).
The heat exchanger of Patent Literature 1 is mounted in an outdoor unit of an air-conditioning apparatus that is capable of both a cooling operation and a heating operation. Moreover, in a case in which a heating operation is performed in a low-temperature environment in which the outside air temperature is low and the surface temperature of the heat exchanger is lower than or equal to 0 degrees C., frost forms on the heat exchanger. Therefore, when a particular or larger amount of frost forms on the heat exchanger, a defrosting operation is performed to melt the frost on the surface of the heat exchanger. In a defrosting operation, frost is removed by causing high-temperature and high-pressure gas refrigerant to flow in from one of the headers and flow to the flat tubes.
During a defrosting operation in a conventional heat exchanger such as that of Patent Literature 1, high-temperature and high-pressure gas refrigerant flows in from the lower header, flows as upward flows through the flat tubes, becomes cooler as it flows through the flat tubes, and increases its liquid phase as it flows further downstream. Moreover, there has undesirably been deterioration of defrosting performance due to the occurrence of liquid retention in which when the high-temperature and high-pressure gas refrigerant flows as upward flows through the flat tubes, refrigerant liquefied by the effect of gravity is undesirably retained without being able to go upward.
The present disclosure was made to solve such a problem and has as an object to provide a heat exchanger configured to reduce deterioration of defrosting performance, an outdoor unit of an air-conditioning apparatus including the heat exchanger, and an air-conditioning apparatus including the outdoor unit of the air-conditioning apparatus.
A heat exchanger according to an embodiment of the present disclosure is a heat exchanger that is mounted in an outdoor unit of an air-conditioning apparatus. The heat exchanger includes one heat exchanger core or two or more heat exchanger cores each including a plurality of flat tubes that extend in an up-down direction and through which refrigerant flows as upward flows when the heat exchanger functions as a condenser. The two or more heat exchanger cores are placed along a direction of flow of air. In a case in which a total flow passage cross-sectional area of each of the heat exchanger cores is defined as A [m2]=a×N [m2], where a [m2] is a flow passage cross-sectional area of each of the flat tubes and N is a number of the flat tubes, a height of each of the heat exchanger cores is defined as H [m], a differential pressure of a refrigerant flow passage is defined as ΔPHEX, and a liquid head is defined as ΔPHEAD, ΔPHEX/ΔPHEAD=(5.94635×10−4×A−1.75030)/(8.4303H+0.8779)>1 is satisfied.
Further, an outdoor unit of an air-conditioning apparatus according to an embodiment of the present disclosure includes the heat exchanger.
Further, an air-conditioning apparatus according to an embodiment of the present disclosure includes the outdoor unit of the air-conditioning apparatus, an indoor unit of an air-conditioning apparatus, and a refrigerant circuit that is constituted by the outdoor unit of the air-conditioning apparatus and the indoor unit of the air-conditioning apparatus and through which refrigerant circulates.
According to a heat exchanger according to an embodiment of the present disclosure, an outdoor unit of an air-conditioning apparatus including the heat exchanger, and an air-conditioning apparatus including the outdoor unit of the air-conditioning apparatus, the heat exchanger satisfies ΔPHEX/ΔPHEAD=(5.94635×10−4×A−1.75030)/(8.4303H+0.8779)>1. This makes it possible to, when the heat exchanger functions as a condenser, suppress the occurrence of liquid retention in which when refrigerant flows as upward flows through the flat tubes, refrigerant liquefied by the effect of gravity is undesirably retained without being able to go upward, making it possible to reduce deterioration of defrosting performance.
The following describes embodiments of the present disclosure with reference to the drawings. It should be noted that the present disclosure is not limited by the embodiments described below. Further, relationships in size between one constituent element and another in the following drawings may be different from actual ones.
As shown in
Further, the air-conditioning apparatus 100 includes a refrigerant circuit 101 that is constituted by the outdoor unit 10 and the indoor unit 20 and through which refrigerant circulates. Specifically, the refrigerant circuit 101 is constituted by the compressor 11, the flow switching device 12, the heat exchanger 30, the expansion device 21, and the indoor heat exchanger 22 being connected by refrigerant pipes. The air-conditioning apparatus 100 is enabled by the flow switching device 12 to switch between a cooling operation and a heating operation.
The compressor 11 suctions low-temperature and low-pressure refrigerant, compresses the refrigerant thus suctioned, and discharges high-temperature and high-pressure refrigerant. The compressor 11 is constituted, for example, by an inverter compressor or other machines whose capacity, that is, rate of delivery per unit time, is controlled by varying operating frequency.
The flow switching device 12 is for example a four-way valve, and enables switching between a cooling operation and a heating operation to be done by switching the direction of flow of refrigerant. During a cooling operation, the flow switching device 12 makes switching to a state indicated by the solid lines in
The heat exchanger 30 exchanges heat between outdoor air and refrigerant. During a cooling operation, the heat exchanger 30 functions as a condenser configured to condense the refrigerant by rejecting the heat of the refrigerant to the outdoor air. Further, during a heating operation, the heat exchanger 30 functions as an evaporator configured to evaporate the refrigerant and cool the outdoor air with the resulting heat of vaporization.
The fan 13 is configured to supply outdoor air to the heat exchanger 30, and by controlling the rotation speed of the fan 13, the amount of air that is sent to the heat exchanger 30 is adjusted.
The expansion device 21 is for example an electronic expansion valve whose opening degree of expansion can be adjusted, and by adjusting the opening degree, the pressure of refrigerant flowing into the heat exchanger 30 or the indoor heat exchanger 22 is controlled. Although, in Embodiment 1, the expansion device 21 is provided in the indoor unit 20, the expansion device 21 may be provided in the outdoor unit 10 and is not limited in place of installation.
The indoor heat exchanger 22 exchanges heat between indoor air and refrigerant. During a cooling operation, the indoor heat exchanger 22 functions as an evaporator configured to evaporate the refrigerant and cool the outdoor air with the resulting heat of vaporization. Further, during a heating operation, the indoor heat exchanger 22 functions as a condenser configured to condense the refrigerant by rejecting the heat of the refrigerant to the outdoor air.
The indoor fan 23 is configured to supply indoor air to the indoor heat exchanger 22, and by controlling the rotation speed of the indoor fan 23, the amount of air that is sent to the indoor heat exchanger 22 is adjusted.
As shown in
A first header 34 is provided at a lower end of the heat exchanger core 31. Lower ends of the flat tubes 38 of the heat exchanger core 31 are directly inserted in the first header 34. Further, a second header 35 is provided at an upper end of the heat exchanger core 31. Upper ends of the flat tubes 38 of the heat exchanger core 31 are directly inserted in the second header 35.
A hot-gas refrigerant inlet 32 is formed at one end of the first header 34, and the hot-gas refrigerant inlet 32 is connected to the refrigerant circuit 101 of the air-conditioning apparatus 100 via a gas pipe 37. Therefore, the first header 34 is also called “gas header”. The first header 34 causes high-temperature and high-pressure gas refrigerant (hereinafter also referred to as “hot-gas refrigerant”) from the compressor 11 to flow into the heat exchanger 30 during a cooling operation and causes low-temperature and low-pressure gas refrigerant subjected to heat exchange in the heat exchanger 30 to flow out to the refrigerant circuit 101 during a heating operation. That is, the hot-gas refrigerant inlet 32 serves as a hot-gas refrigerant inflow port. Note here that the hot-gas refrigerant is not limited to single-phase gas refrigerant but may be two-phase gas-liquid refrigerant containing a gas phase of 0 degrees C. or higher.
A liquid refrigerant outlet 33 is formed at one end of the second header 35, and the liquid refrigerant outlet 33 is connected to the refrigerant circuit 101 of the air-conditioning apparatus 100 via a liquid pipe 36. Therefore, the second header 35 is also called “liquid header”. The second header 35 causes low-temperature and low-pressure two-phase refrigerant to flow into the heat exchanger 30 during a heating operation and causes low-temperature and high-pressure liquid refrigerant subjected to heat exchange in the heat exchanger 30 to flow out to the refrigerant circuit 101 during a cooling operation.
The plurality of flat tubes 38, the plurality of fins 39, the first header 34, and the second header 35 are all made of aluminum and joined to each other by brazing.
Next, the actions of the air-conditioning apparatus 100 during each operation are described with reference to
High-temperature and high-pressure gas refrigerant discharged from the compressor 11 flows into the heat exchanger 30 via the flow switching device 12. The high-temperature and high-pressure gas refrigerant having flowed into the heat exchanger 30 condenses while rejecting heat by exchanging heat with outdoor air taken in by the fan 13 and turns into low-temperature and high-pressure liquid refrigerant that then flows out from the heat exchanger 30. The low-temperature and high-pressure liquid refrigerant having flowed out from the heat exchanger 30 is decompressed by the expansion device 21 into low-temperature and low-pressure two-phase gas-liquid refrigerant that then flows into the indoor heat exchanger 22. The low-temperature and low-pressure two-phase gas-liquid refrigerant having flowed into the indoor heat exchanger 22 evaporates while receiving heat by exchanging heat with indoor air taken in by the indoor fan 23, cools the indoor air, and turns into low-temperature and low-pressure gas refrigerant that then flows out from the indoor heat exchanger 22. The low-temperature and low-pressure gas refrigerant having flowed out from the indoor heat exchanger 22 is suctioned into the compressor 11 and turns again into high-temperature and high-pressure gas refrigerant.
High-temperature and high-pressure gas refrigerant discharged from the compressor 11 flows into the indoor heat exchanger 22 via the flow switching device 12. The high-temperature and high-pressure gas refrigerant having flowed into the indoor heat exchanger 22 condenses while rejecting heat by exchanging heat with indoor air taken in by the indoor fan 23, heats the indoor air, and turns into low-temperature and high-pressure liquid refrigerant that then flows out from the indoor heat exchanger 22. The low-temperature and high-pressure liquid refrigerant having flowed out from the indoor heat exchanger 22 is decompressed by the expansion device 21 and turns into low-temperature and low-pressure two-phase gas-liquid refrigerant that then flows into the heat exchanger 30. The low-temperature and low-pressure two-phase gas-liquid refrigerant having flowed into the heat exchanger 30 evaporates while receiving heat by exchanging heat with outdoor air taken on by the fan 13 and turns into low-temperature and low-pressure gas refrigerant that then flows out from the heat exchanger 30. The low-temperature and low-pressure gas refrigerant having flowed out from the heat exchanger 30 is suctioned into the compressor 11 and turns again into high-temperature and high-pressure gas refrigerant.
In a case in which a heating operation is performed in a low-temperature environment in which the surface temperature of the flat tubes 38 and the fins 39 shown in
In the defrosting operation, the fan 13 is suspended, and the flow switching device 12 is switched to the same state as it is during a cooling operation, so that high-temperature and high-pressure gas refrigerant flows into the heat exchanger 30. This causes the frost forming on the flat tubes 38 and the fins 39 to melt. Once the defrosting operation is started, the high-temperature and high-pressure gas refrigerant flows from the gas pipe 37 into each flat tube 38 via the first header 34. It should be noted that the refrigerant having flowed into each flat tube 38 turns into an upward flow that flows upward in a vertical direction. Then, the high-temperature refrigerant having flowed into the flat tubes 38 causes the frost forming on the flat tubes 38 and the fins 39 to melt and turn into water. The water produced by the frost melting is drained toward a lower level in the heat exchanger 30 along the flat tubes 38 or the fins 39. The defrosting operation is ended once the frost melts, and the heating operation is resumed. It should be noted that it is possible to use a known method to determine when to end the defrosting operation and resume the heating operation. For example, such a configuration may be set up to end the defrosting operation and resume the heating operation, for example, when a temperature detected by a temperature sensor (not illustrated) has reached a predetermined temperature or in a case in which the defrosting operation has been executed for a particular period of time.
In a case in which the total flow passage cross-sectional area of the heat exchanger core 31 is defined as A, the total flow passage cross-sectional area A is found by Formula (1) as follows:
where a is the flow passage cross-sectional area [m2] of each of the flat tubes 38 (i.e. a shaded area of
Further, in a case in which a differential pressure of a refrigerant flow passage (hereinafter referred to as “flow passage differential pressure”) is defined as ΔPHEX and a liquid head is defined as ΔPHEAD, ΔPHEX/ΔPHEAD is found by Formula (2) below. In Embodiment 1, the flow passage differential pressure ΔPHEX is the differential pressure of a flow passage through which hot-gas refrigerant flows as an upward flow during a defrosting operation and is the differential pressure across the upper and lower ends of a flat tube 38 in the heat exchanger core 31.
where A is the total flow passage cross-sectional area [m2] of the heat exchanger core 31 and H is the height [m] of the heat exchanger core 31.
Note here that the height H of the heat exchanger core 31 is a length between an upper end of the first header 34 and a lower end of the second header 35 and is the length of an exposed portion of a flat tube 38.
Formula (2) above is an empirical formula obtained by the inventors' numerical analyses and experimental results and, in a range of conditions under which the heat exchanger 30 is used in an outdoor unit 10 for building use, store use, and household use (hereinafter referred to as “use in buildings or other structures”), formulated using the total flow passage cross-sectional area A [m2] of the heat exchanger core 31, which is a shape parameter of the heat exchanger 30 dominated by the flow passage differential pressure ΔPHEX, and the height H [m] of the heat exchanger core 31, which is a shape parameter of the heat exchanger 30 dominated by the liquid head ΔPHEAD. This empirical formula is shown in
According to the inventors' experiments, as shown in
In general, car air conditioners or other air conditioners utilize engine heat during heating and use heat pumps only during cooling. Therefore, most heat exchangers that are used in outdoor units of car air conditioners or other air conditioners and that use corrugated fins are heat exchangers dedicated to cooling and are therefore used for such purposes that a defrosting operation does not take place. Further, even in a case in which heat exchangers are used as heat pumps both during cooling and during heating, most of the heat exchangers are so small in size that the heights of heat exchanger cores are approximately 300 [mm]. On the other hand, in most heat exchangers that are used in outdoor units in buildings or other structures, the heights of heat exchanger cores are greater than or equal to 420 [mm], and in some of the heat exchangers, the heights of heat exchanger cores are greater than or equal to 800 [mm].
According to the inventors' study, it was found, as shown in
Under conditions where ΔPHEX/ΔPHEAD is lower than or equal to 1, the liquid retention area increases as ΔPHEX/ΔPHEAD decreases. This suggests that a decrease in ΔPHEX/ΔPHEAD by 43 [%] to 65 [%] in comparison with a heat exchanger whose heat exchanger core 31 has a height H of 300 [mm] has an extraordinary effect on heat exchanger performance. According to the inventors' experiments, there were examples in which when ΔPHEX/ΔPHEAD became lower than or equal to 1, there were decreases in heat exchanger performance by approximately 30 [%] to 50 [%] in comparison with a heat exchanger whose heat exchanger core 31 has a height H of 300 [mm].
Conventionally, in a case in which the height H of a heat exchanger core 31 is greater than or equal to 420 [mm], there is undesirably remarkable deterioration of defrosting performance in a region of occurrence of liquid retention in which when hot-gas refrigerant flows into a first header 34 provided in a lower part of the heat exchanger and flows via the first header 34 and refrigerant flows as upward flows through flat tubes 38 extending in a vertical direction, refrigerant liquefied by the effect of gravity is retained without being able to go upward. To address this problem, Embodiment 1 is intended to remedy this problem to reduce deterioration of defrosting performance during a defrosting operation.
According to the experimental results, it was found, as shown in
In a case in which a heat exchanger is not configured to satisfy ΔPHEX/ΔPHEAD>1 as has conventionally been the case, liquid retention occurs during a defrosting operation, and in a liquid retention area in which the liquid retention has occurred, frost undesirably remains without being sufficiently removed. Therefore, as shown in
On the other hand, in a case in which a heat exchanger 30 is configured to satisfy ΔPHEX/ΔPHEAD>1 as is the case in Embodiment 1, the occurrence of liquid retention during a defrosting operation is suppressed, so that lingering frost can be reduced. Therefore, as shown in
Further, as shown in
In a heat exchanger, when the height H of a heat exchanger core is high and the aspect ratio of the heat exchanger increases in a height direction, that is, when H/L increases, the liquid head ΔPHEAD increases as shown in
In Embodiment 1, as shown in
In a case in which the hot-gas refrigerant inlet 32 and the liquid refrigerant outlet 33 are provided at ends of the first header 34 and the second header 35 located on the same side as each other, respectively, as shown in
On the other hand, when the hot-gas refrigerant inlet 32 and the liquid refrigerant outlet 33 are provided at ends of the first header 34 and the second header 35 located opposite each other, respectively, as shown in
As noted above, by configuring the heat exchanger 30 to satisfy H/L>1, the first header 34 and the second header 35 can be configured to be small in length with respect to the amount of heat exchange. This makes it possible to reduce pressure losses of working fluids that flow through the first header 34 and the second header 35. That is, the difference between the pressure loss ΔP1-2 of the first header 34 and the pressure loss ΔP3-4 of the second header 35 described in
As noted above, the heat exchanger 30 according to Embodiment 1 is a heat exchanger 30 that is mounted in an outdoor unit 10 of an air-conditioning apparatus 100. The heat exchanger 30 includes one heat exchanger core or two or more heat exchanger cores 31 each including a plurality of flat tubes 38 that extend in an up-down direction and through which refrigerant flows as upward flows when the heat exchanger 30 functions as a condenser. The two or more heat exchanger cores 31 are placed along a direction of flow of air. In a case in which a total flow passage cross-sectional area of each of the heat exchanger cores 31 is defined as A [m2]=a×N [m2], where a [m2] is a flow passage cross-sectional area of each of the flat tubes 38 and N is a number of the flat tubes 38, a height of each of the heat exchanger cores 31 is defined as H [m], a differential pressure of a refrigerant flow passage is defined as ΔPHEX, and a liquid head is defined as ΔPHEAD, ΔPHEX/ΔPHEAD=(5.94635×10−4×A−1.75030)/(8.4303H+0.8779)>1 is satisfied.
According to the heat exchanger 30 according to Embodiment 1, the heat exchanger 30 satisfies ΔPHEX/ΔPHEAD=(5.94635×10−4×A−1.75030)/(8.4303H+0.8779)>1. This makes it possible to, when the heat exchanger 30 functions as a condenser, suppress the occurrence of liquid retention in which when refrigerant flows as upward flows through the flat tubes 38, refrigerant liquefied by the effect of gravity is retained without being able to go upward, making it possible to reduce deterioration of defrosting performance.
Further, the heat exchanger 30 according to Embodiment 1 is configured to satisfy H/L>1 in a case in which a width of each of the heat exchanger cores 31 is defined as L [m].
The heat exchanger 30 according to Embodiment 1 is configured to satisfy H/L>1. Therefore, the first header 34 and the second header 35 can be configured to be small in length with respect to the amount of heat exchange. This makes it possible to reduce pressure losses of working fluids that flow through the first header 34 and the second header 35, making it possible to suppress the occurrence of liquid retention.
Further, the heat exchanger 30 according to Embodiment 1 includes the one heat exchanger core 31, a first header 34 provided at a lower end of the heat exchanger core 31, and a second header 35 provided at an upper end of the heat exchanger core 35. Moreover, the heat exchanger 30 according to Embodiment 1 includes a hot-gas refrigerant inlet 32 formed at one end of the first header 34 and a liquid refrigerant outlet 33 that is formed at one end of the second header 35 located opposite the one end of the first header 34 and through which refrigerant flows out when the heat exchanger 30 functions as a condenser.
According to the heat exchanger 30 according to Embodiment 1, the hot-gas refrigerant inlet 32 and the liquid refrigerant outlet 33 are formed at ends of the first header 34 and the second header 35 located opposite each other. Therefore, the difference between the difference between the pressure loss ΔP1-2 of the first header 34 and the pressure loss ΔP3-4 of the second header 35 decreases. As a result of that, a region in which the flow passage differential pressure ΔPHEX decreases hardly forms. This suppresses the occurrence of liquid retention, making it possible to reduce lingering frost.
Further, an outdoor unit 10 according to Embodiment 1 of an air-conditioning apparatus 100 includes the heat exchanger 30.
Further, an air-conditioning apparatus 100 according to Embodiment 1 includes the outdoor unit 10 of the air-conditioning apparatus 100, an indoor unit 20 of the air-conditioning apparatus 100, and a refrigerant circuit 101 that is constituted by the outdoor unit 10 of the air-conditioning apparatus 100 and the indoor unit 20 of the air-conditioning apparatus 100 and through which refrigerant circulates.
The outdoor unit 10 according to Embodiment 1 of an air-conditioning apparatus 100 and the air-conditioning apparatus 100 according to Embodiment 1 bring about effects that are similar to those of the heat exchanger 30.
The following describes Embodiment 2. A description of overlaps with Embodiment 1 is omitted. Components that are identical or equivalent to those of Embodiment 1 are given identical reference signs.
In the heat exchanger 30 according to Embodiment 2, a partition plate 40 is provided in at least the first header 34.
This partition plate 40 is provided to divide a flow passage of the heat exchanger core 31 into a plurality of regions in a horizontal direction. Further, the partition plate 40 is provided so that a flow passage in each region of the heat exchanger core 31 is opposite in flow to a flow passage in an adjacent region. Moreover, assuming that L1 is the width of the furthest downstream region of the heat exchanger core 31, the heat exchanger 30 is configured to satisfy 20 [%]≤L1/L≤50 [%].
By providing the partition plate 40 in the first header 34, the flow passage cross-sectional area is reduced with the flow rate of refrigerant being the same. This increases the velocity of flow of refrigerant but causes an increase in pressure loss. Accordingly, in consideration of a balance between improvement in heat exchanger performance brought about by improvement in heat-transfer coefficient due to the increase in the velocity of flow of refrigerant and deterioration of heat exchanger performance caused by the increase in pressure loss, the heat exchanger 30 is configured to satisfy 20 [%]≤L1/L≤50 [%] to attain a heat exchanger performance of 90 [%] or higher as shown in
As noted above, the heat exchanger 30 according to Embodiment 2 is a heat exchanger 30 including the one heat exchanger core 31, a first header 34 provided at a lower end of the heat exchanger core 31, and a second header 35 provided at an upper end of the heat exchanger core 35. Further, the heat exchanger 30 includes a partition plate 40 provided in at least the first header 34 and configured to divide a flow passage of the heat exchanger core 31 into a plurality of regions in a width direction. Moreover, in a case in which the width of the heat exchanger core 31 is defined as L [m] and a width of the furthest downstream region of the heat exchanger core 31 is defined as L1, the heat exchanger 30 satisfies 20 [%]≤L1/L≤50 [%].
The heat exchanger 30 according to Embodiment 2 is configured to satisfy 20 [%] ≤L1/L≤50 [%]. This makes it possible to make heat exchanger performance higher than in a case in which no partition plate 40 is provided in the first header 34. Furthermore, an increase in pressure loss suppresses the occurrence of liquid retention during a defrosting operation, making it possible to reduce lingering frost. As a result of that, defrosting performance during a defrosting operation can be improved.
The following describes Embodiment 3. A description of overlaps with Embodiments 1 and 2 is omitted. Components that are identical or equivalent to those of Embodiments 1 and 2 are given identical reference signs.
As shown in
By thus arranging the two heat exchanger cores 31 in the direction of flow of air and providing the bridging header 50 at one end of each of the two heat exchanger cores 31, a refrigerant flow passage represented by the sum of the heights of the two heat exchanger cores 31 can be lengthened. Therefore, the flow passage differential pressure ΔPHEX can be increased. As a result of that, ΔPHEX/ΔPHEAD can be increased, and liquid retention is suppressed. This makes it possible to improve defrosting performance during a defrosting operation. In Embodiment 3, the flow passage differential pressure ΔPHEX is the differential pressure P1-4 between a lower end of a flat tube 38 of the leeward heat exchanger core 31 and a lower end of a flat tube 38 of the windward heat exchanger core 31 (i.e. the differential pressure between position (1) and position (4) in
Further, as shown in
By so doing, the differential pressure P2-3 in the bridging header 50 (i.e. the differential pressure between position (2) and position (3) in
As shown in
In general, during a defrosting operation, the fan 13 stops to reduce leakage of heat from the heat exchanger 30 to the air, but due to the effect of external wind or other currents, an air current that pushes into the heat exchanger 30 may be generated. In such a case, as shown in
Although the heat exchanger 30 according to Embodiment 3 is configured such that two heat exchanger cores 31 are arranged side by side in the direction of flow of air, the heat exchanger 30 according to Embodiment 3 is not limited to this configuration but may be configured such that three or more heat exchanger cores 31 are arranged side by side in the direction of flow of air. In that case, the heat exchanger 30 is configured to include bridging headers 50 whose number is smaller by 1 than the number of heat exchanger cores 31. For example, in a case in which three heat exchanger cores 31 are arranged side by side in the direction of flow of air, the first header 34 is provided at a lower end of one of the heat exchanger cores 31 that is located on the furthest leeward side, and the second header 35 is provided at an upper end of one of the heat exchanger cores 31 that is located on the furthest windward side. Moreover, a bridging header 50 is provided at an upper end of the furthest leeward heat exchanger core 31 and an upper end of a middle one of the heat exchanger cores 31 that is adjacent to the furthest leeward heat exchanger core 31, and a bridging header 50 is provided at a lower end of the middle heat exchanger core 31 and a lower end of the furthest windward heat exchanger core 31 that is adjacent to the middle heat exchanger core 31.
As noted above the heat exchanger 30 according to Embodiment 3 is a heat exchanger 30 including the two or more heat exchanger cores 31 placed along the direction of flow of air, a first header 34 provided at a lower end of one of the heat exchanger cores 31 that is located on a furthest leeward side, a second header 35 provided at an upper or lower end of one of the heat exchanger cores 31 that is located at a furthest windward side, a hot-gas refrigerant inlet 32 formed at one end of the first header 34, and a liquid refrigerant outlet 33 formed at one end of the second header 35 located on the same side as the one end of the first header 34. Moreover, the heat exchanger 30 includes a bridging header 50 provided at upper or lower ends of two adjacent ones of the heat exchanger cores 31 and configured so that refrigerant converging from the flat tubes 38 of one of the heat exchanger cores 31 that is located on a leeward side is distributed to the flat tubes 38 of one of the heat exchanger cores 31 that is located on a windward side.
The heat exchanger 30 according to Embodiment 3 includes a bridging header 50 configured so that refrigerant converging from the flat tubes 38 of one of the heat exchanger cores 31 that is located on a leeward side is distributed to the flat tubes 38 of one of the heat exchanger cores 31 that is located on a windward side. This makes it possible to lengthen a refrigerant flow passage represented by the sum of the heights of the two or more heat exchanger cores 31, thus making it possible to increase the flow passage differential pressure ΔPHEX. As a result of that, ΔPHEX/ΔPHEAD can be increased, and liquid retention is suppressed. This makes it possible to improve defrosting performance during a defrosting operation.
Further, in the heat exchanger 30 according to Embodiment 3, an upper or lower end of each of the flat tubes 38 of the two adjacent heat exchanger cores 31 is inserted in the bridging header 50. Moreover, in a case in which a gap between the upper or lower end of the flat tube 38 and a wall portion 51 of the bridging header 50 that faces the upper or lower end is defined as δ, the heat exchanger 30 satisfies δ≤3 [mm].
The heat exchanger 30 according to Embodiment 3 is configured to satisfy δ≤3 [mm]. This makes it possible to suppress the occurrence of liquid retention even in consideration of the effect of a pressure loss, making it possible to improve heat exchanger performance.
The following describes Embodiment 4. A description of overlaps with Embodiments 1 to 3 is omitted. Components that are identical or equivalent to those of Embodiments 1 to 3 are given identical reference signs.
As shown in
An outlet side of the heat exchanger 30a and an outlet side of the heat exchanger 30b are configured to merge at a first merging section 63a. Further, an outlet side of the first merging section 63a and an outlet side of the heat exchanger 30c are configured to merge at a second merging section 63b. Further, a first expansion device 62a is provided in one of the refrigerant pipes that is located between the first merging section 63a and the second merging section 63b. Further, a second expansion device 62b is provided in one of the refrigerant pipes that is located between an outlet of the heat exchanger 30c and the second merging section 63b. Further, a first open-close valve 61a is provided in one of the refrigerant pipes that is located between a branch point on inlet sides of the heat exchangers 30a to 30c and an inlet of the heat exchanger 30c. Further, a second open-close valve 61b is provided in one of the refrigerant pipes that connects the inlet of the heat exchanger 30c with one of the refrigerant pipes that is located between the first merging section 63a and the first expansion device 62a. It should be noted that the first open-close valve 61a and the second open-close valve 61b are not valves that simply open and shut but may be valves whose opening degrees can be adjusted. In the following, the first expansion device 62a and the second expansion device 62b are collectively referred to as “expansion devices”, and the first open-close valve 61a and the second open-close valve 61b are collectively referred to as “open-close valves”.
Further, the air-conditioning apparatus 100 includes a controller 70 configured to control the expansion devices, the open-close valves, or other devices. The controller 70 is constituted by dedicated hardware or a central processing unit (CPU; also referred to as “processing unit”, “arithmetic device”, “microprocessor”, or “processor”) configured to execute programs that are stored in a storage unit (not illustrated). It should be noted that the controller 70 may be provided in the outdoor unit 10 or may be provided in the indoor unit 20.
In a case in which the controller 70 is the dedicated hardware, the controller 70 corresponds to a single circuit, a complex circuit, an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or a combination thereof. Functional parts that the controller 70 implements may be implemented by each separate piece of hardware or may be implemented by one piece of hardware.
In a case in which the controller 70 is the CPU, functions that the controller 70 executes may be implemented by software, firmware, or a combination of the software and the firmware. The software and the firmware are described as programs and stored in the storage unit. The CPU implements the functions of the controller 70 by reading out and executing the programs stored in the storage unit. Note here that the storage unit is configured to store various types of information and includes data-rewritable nonvolatile semiconductor memory such as a flash memory, an EPROM, or an EEPROM.
Some of the functions of the controller 70 may be implemented by the dedicated hardware, and others of the functions of the controller 70 may be implemented by the software or the firmware.
Moreover, the flow passage differential pressure ΔPHEX is made greater than or equal to the liquid head ΔPHEAD by configuring the heat exchangers 30a to 30c so that during a defrosting operation, a flow of refrigerant through one or more of the heat exchangers 30a to 30c is in series with a flow of refrigerant through the other of the heat exchangers 30a to 30c and a flow of refrigerant through rest of the heat exchangers 30a to 30c is in parallel with the flow of refrigerant through the other of the heat exchangers 30a to 30c. Specifically, the controller 70 causes the second open-close valve 61b to be opened and causes the first open-close valve 61a to be shut. Further, the heat exchangers 30a to 30c are configured so that when the heat exchangers 30a to 30c function as evaporators, such as during a heating operation, a flow of refrigerant through each of the heat exchangers 30a to 30c is in parallel with a flow of refrigerant through the other of the heat exchangers 30a to 30c. Specifically, the controller 70 causes the second open-close valve 61b to be shut and causes the first open-close valve 61a to be opened.
By thus configuring the heat exchangers 30a to 30c so that during a defrosting operation, a flow of refrigerant through one or more of the heat exchangers 30a to 30c is in series with a flow of refrigerant through the other of the heat exchangers 30a to 30c and a flow of refrigerant through rest of the heat exchangers 30a to 30c is in parallel with the flow of refrigerant through the other of the heat exchangers 30a to 30c, the flow passage cross-sectional area is reduced with the flow rate of refrigerant being the same. Therefore, the velocity of flow of refrigerant through a flow passage through which hot-gas refrigerant flows upward increases, and the flow passage differential pressure ΔPHEX can be increased. This suppresses liquid retention, making it possible to improve defrosting performance during a defrosting operation. Further, by configuring the heat exchangers 30a to 30c so that when the heat exchangers 30a to 30c function as evaporators, a flow of refrigerant through each of the heat exchangers 30a to 30c is in parallel with a flow of refrigerant through the other of the heat exchangers 30a to 30c, the flow passage cross-sectional area is increased with the flow rate of refrigerant being the same. This reduces a pressure loss, thus making it possible to improve heating capacity.
As noted above, the air-conditioning apparatus 100 according to Embodiment 4 includes an outdoor unit 10 including a plurality of heat exchangers 30a to 30c and a controller 70 configured so that during a defrosting operation, one of more of the plurality of heat exchangers 30a to 30c are in series with the other of the heat exchangers 30a to 30c and configured so that when the heat exchangers 30a to 30c function as evaporators, a flow of the refrigerant through each of the heat exchangers 30a to 30c is in parallel with a flow of the refrigerant through the other of the heat exchangers 30a to 30c.
According to the air-conditioning apparatus 100 according to Embodiment 4, by configuring the heat exchangers 30a to 30c so that during a defrosting operation, a flow of refrigerant through one or more of the heat exchangers 30a to 30c is in series with a flow of refrigerant through the other of the heat exchangers 30a to 30c and a flow of refrigerant through rest of the heat exchangers 30a to 30c is in parallel with the flow of refrigerant through the other of the heat exchangers 30a to 30c, the flow passage cross-sectional area is reduced with the flow rate of refrigerant being the same. Therefore, the velocity of flow of refrigerant through a flow passage through which hot-gas refrigerant flows upward increases, and the flow passage differential pressure ΔPHEX can be increased. This suppresses liquid retention, making it possible to improve defrosting performance during a defrosting operation. Further, by configuring the heat exchangers 30a to 30c so that when the heat exchangers 30a to 30c function as evaporators, a flow of refrigerant through each of the heat exchangers 30a to 30c is in parallel with a flow of refrigerant through the other of the heat exchangers 30a to 30c, the flow passage cross-sectional area is increased with the flow rate of refrigerant being the same. This reduces a pressure loss, thus making it possible to improve heating capacity.
The following describes Embodiment 5. A description of overlaps with Embodiments 1 to 4 is omitted. Components that are identical or equivalent to those of Embodiments 1 to 4 are given identical reference signs.
As shown in
In Embodiment 5, a third open-close valve 61c is provided in one of the refrigerant pipes that is located between a branch point on the inlet sides of the heat exchangers 30a to 30b and an inlet of the heat exchanger 30b. A description of other components is omitted, as they are identical to those of the refrigerant circuit 101 described in Embodiment 4.
Moreover, the flow passage differential pressure ΔPHEX is made greater than or equal to the liquid head ΔPHEAD by configuring the heat exchangers 30a to 30c so that during a defrosting operation, a flow of refrigerant through one or more of the heat exchangers 30a to 30c is in series with a flow of refrigerant through the other of the heat exchangers 30a to 30c and a flow of refrigerant through rest of the heat exchangers 30a to 30c is in parallel with the flow of refrigerant through the other of the heat exchangers 30a to 30c. Specifically, the controller 70 causes the second open-close valve 61b and the third open-close valve 61c to be opened and causes the first open-close valve 61a to be shut. Further, by fully closing an expansion device or an open-close valve, refrigerant is stopped from flowing through at least one of the heat exchangers 30a to 30c configured in parallel with one another and the other of the heat exchangers 30a to 30c is preferentially subjected to the defrosting operation. Moreover, by switching from fully closing one expansion device or one open-close valve to fully closing another expansion device or another open-close valve, switching from subjecting one of the heat exchangers 30a to 30c to the defrosting operation to subjecting another of the heat exchangers 30a to 30c to the defrosting operation is done. The timing of switching from fully closing one expansion device or one open-close valve to fully closing another expansion device or another open-close valve and switching from preferentially subjecting one of the heat exchangers 30a to 30c to the defrosting operation to preferentially subjecting another of the heat exchangers 30a to 30c to the defrosting operation is when a predetermined period of time has elapsed, based on a temperature sensed by a temperature sensor, such as a thermistor, provided on the outlet side of each of the heat exchangers 30a to 30c, or other timings.
Further, the heat exchangers 30a to 30c are configured so that when the heat exchangers 30a to 30c function as evaporators, such as during a heating operation, a flow of refrigerant through each of the heat exchangers 30a to 30c is in parallel with a flow of refrigerant through the other of the heat exchangers 30a to 30c. Specifically, the controller 70 causes the second open-close valve 61b to be shut and causes the first open-close valve 61a and the third open-close valve 61c to be opened.
Thus, the heat exchangers 30a to 30c are configured so that during a defrosting operation, a flow of refrigerant through one or more of the heat exchangers 30a to 30c is in series with a flow of refrigerant through the other of the heat exchangers 30a to 30c and a flow of refrigerant through rest of the heat exchangers 30a to 30c is in parallel with the flow of refrigerant through the other of the heat exchangers 30a to 30c. By so doing, the flow passage cross-sectional area is reduced with the flow rate of refrigerant being the same. Therefore, the velocity of flow of refrigerant through a flow passage through which hot-gas refrigerant flows upward increases, and the flow passage differential pressure ΔPHEX can be increased. Furthermore, by preferentially subjecting, to the defrosting operation, at least one of the heat exchangers 30a to 30c configured so that flows of the refrigerant through the heat exchangers 30a to 30c are in parallel with one another and then sequentially switching from preferentially subjecting one of the heat exchangers 30a to 30c to the defrosting operation to preferentially subjecting another of the heat exchangers 30a to 30c to the defrosting operation, lingering frost can be reduced. This further suppresses liquid retention, making it possible to further improve defrosting performance during a defrosting operation. Further, by configuring the heat exchangers 30a to 30c so that when the heat exchangers 30a to 30c function as evaporators, a flow of refrigerant through each of the heat exchangers 30a to 30c is in parallel with a flow of refrigerant through the other of the heat exchangers 30a to 30c, the flow passage cross-sectional area is increased with the flow rate of refrigerant being the same. This reduces a pressure loss, thus making it possible to improve heating capacity.
As noted above, in the air-conditioning apparatus 100 according to Embodiment 5, the controller 70 is configured so that during a defrosting operation, a flow of the refrigerant through one or more of the plurality of heat exchangers 30a to 30c is in series with a flow of the refrigerant through the other of the heat exchangers 30a to 30c and configured so that a flow of the refrigerant through rest of the heat exchangers 30a to 30c is in parallel with the flow of the refrigerant through the other of the heat exchangers 30a to 30c, and in a case in which there are a plurality of the heat exchangers 30a to 30c configured so that during a defrosting operation, flows of the refrigerant through the heat exchangers 30a to 30c are in parallel with one another, the refrigerant is stopped from flowing through at least one of the heat exchangers 30a to 30c and the other of the heat exchangers 30a to 30c is preferentially subjected to the defrosting operation.
According to the air-conditioning apparatus 100 according to Embodiment 5, by preferentially subjecting, to the defrosting operation, at least one of the heat exchangers 30a to 30c configured so that flows of refrigerant through the heat exchangers 30a to 30c are in parallel with one another and then sequentially switching from preferentially subjecting one of the heat exchangers 30a to 30c to the defrosting operation to preferentially subjecting another of the heat exchangers 30a to 30c to the defrosting operation, lingering frost can be reduced. This further suppresses liquid retention, making it possible to further improve defrosting performance during a defrosting operation.
The following describes Embodiment 6. A description of overlaps with Embodiments 1 to 5 is omitted. Components that are identical or equivalent to those of Embodiments 1 to 5 are given identical reference signs.
As shown in
Thus, the flat tube 38 of the heat exchanger 30 is made a grooved flat tube or an end-shrunk flat tube. By so doing, the flow passage cross-sectional area is reduced with the flow rate of refrigerant being the same. Therefore, the velocity of flow of refrigerant through a flow passage through which hot-gas refrigerant flows upward increases, and the flow passage differential pressure ΔPHEX can be increased. This suppresses liquid retention, making it possible to improve defrosting performance during a defrosting operation.
As noted above, in the heat exchanger 30 according to Embodiment 6, each of the flat tubes 38 is provided with a plurality of partition posts 38a configured to partition an internal flow passage and an inward projecting portion 38b provided between adjacent ones of the partition posts 38a, or each of the flat tubes 38 has a distal portion 38c subjected to tube shrinking so that an outer diameter of the flat tube 38 decreases toward a distal end.
According to the heat exchanger 30 according to Embodiment 6, each of the flat tubes 38 has a plurality of projecting portions 38b each formed along a flow passage between adjacent ones of the partition posts 38a, or each of the flat tubes 38 has a distal portion 38c subjected to tube shrinking so that an outer diameter of the flat tube 38 decreases toward a distal end. By thus making the flat tube 38 a grooved flat tube or an end-shrunk flat tube, the flow passage cross-sectional area is reduced with the flow rate of refrigerant being the same. Therefore, the velocity of flow of refrigerant through a flow passage through which hot-gas refrigerant flows upward increases, and the flow passage differential pressure ΔPHEX can be increased. As a result of that, liquid retention is suppressed, and defrosting performance during a defrosting operation can be improved.
The following describes Embodiment 7. A description of overlaps with Embodiments 1 to 6 is omitted. Components that are identical or equivalent to those of Embodiments 1 to 6 are given identical reference signs.
As shown in
Accordingly, Embodiment 7 uses any of the pure refrigerants HFO1123, HFO1132(E), R1234yf, R1234ze(E), R1234ze(Z), R1233zd(E), propane (R290), and fluoroethane (R161) as refrigerant that circulates through the refrigerant circuit 101 of the air-conditioning apparatus 100.
By thus using any of the foregoing pure refrigerants as refrigerant that circulates through the refrigerant circuit 101 of the air-conditioning apparatus 100, ΔPHEX/ΔPHEAD can be improved. This makes it possible to suppress the occurrence of liquid retention, making it possible to improve heat exchanger performance.
As noted above, in the air-conditioning apparatus 100 according to Embodiment 7, the refrigerant is a pure refrigerant selected from the group consisting of HFO1123, HFO1132(E), R1234yf, R1234ze(E), R1234ze(Z), R1233zd(E), propane (R290), and fluoroethane (R161).
The air-conditioning apparatus 100 according to Embodiment 7 uses any of the foregoing pure refrigerants as refrigerant that circulates through the refrigerant circuit 101, thus making it possible to improve ΔPHEX/ΔPHEAD. This suppresses the occurrence of liquid retention, making it possible to improve heat exchanger performance.
The following describes Embodiment 8. A description of overlaps with Embodiments 1 to 7 is omitted. Components that are identical or equivalent to those of Embodiments 1 to 7 are given identical reference signs.
During a cooling operation, the heat exchanger 30 according to Embodiment 8 functions as a condenser configured to condense the refrigerant by rejecting the heat of the refrigerant to the outdoor air. As shown in
A first header 34 is provided at a lower end of the heat exchanger core 31. Lower ends of the flat tubes 38 of the heat exchanger core 31 are directly inserted in the first header 34. Further, a second header 35 is provided at an upper end of the heat exchanger core 31. Upper ends of the flat tubes 38 of the heat exchanger core 31 are directly inserted in the second header 35.
A hot-gas refrigerant inlet 32 is formed at one end of the second header 35, and the hot-gas refrigerant inlet 32 is connected to the refrigerant circuit 101 of the air-conditioning apparatus 100 via a gas pipe 37. Further, a liquid refrigerant outlet 33 is formed at the other end of the second header 35, and the liquid refrigerant outlet 33 is connected to the refrigerant circuit 101 of the air-conditioning apparatus 100 via a liquid pipe 36. The second header 35 causes high-temperature and high-pressure gas refrigerant from the compressor 11 to flow into the heat exchanger 30 during a cooling operation and causes low-temperature and high-pressure gas refrigerant subjected to heat exchange in the heat exchanger 30 to flow out to the refrigerant circuit 101. Further, the second header 35 causes low-temperature and low-pressure two-phase refrigerant to flow into the heat exchanger 30 during a heating operation and causes low-temperature and low-pressure liquid refrigerant subjected to heat exchange in the heat exchanger 30 to flow out to the refrigerant circuit 101.
The plurality of flat tubes 38, the plurality of fins 39, the first header 34, and the second header 35 are all made of aluminum and joined to each other by brazing.
In the heat exchanger 30 according to Embodiment 8, as shown in
Moreover, hot-gas refrigerant having flowed into the second header 35 flows as downward flows through ones of the flat tubes 38 of the heat exchanger core 31 that are placed in the region T1, merges in the merging region M1 of the first header 34, flows as upward flows through ones of the flat tubes 38 of the heat exchanger core 31 that are placed in the region T2, and then flows out from the second header 35. That is, the region T1 is a downward flow region, and the region T2 is an upward flow region. Further, the merging region M1 of the first header 34 serves as a hot-gas refrigerant inflow port for the upward flow region.
In the region T2, there is an occurrence of liquid retention in which when hot-gas refrigerant flows as upward flows through the flat tubes 38 of the heat exchanger core 31, refrigerant liquefied by the effect of gravity is undesirably retained without being able to go upward. To address this problem, the heat exchanger 30 according to Embodiment 8 is configured such that in a case in which the total flow passage cross-sectional area of the heat exchanger core 31 in the region T2 is defined as Ar [m2]=a×Nr [m2], where Nr is the number of flat tubes 38 of the heat exchanger core 31 that are placed in the region T2, which is an upward flow region, the height of the heat exchanger core 31 is defined as H [m], a differential pressure of a refrigerant flow passage is defined as ΔPHEX, and a liquid head is defined as ΔPHEAD, ΔPHEX/ΔPHEAD=(5.94635×10−4×Ar−1.75030)/(8.4303H+0.8779)>1 is satisfied. The heat exchanger 30 thus configured makes it possible to suppress the occurrence of liquid retention in which when refrigerant having flowed in from the hot-gas refrigerant inlet 32 formed in an upper part of the heat exchanger 30 flows as upward flows through the flat tubes 38 of the heat exchanger core 31 in the region T2, refrigerant liquefied by the effect of gravity is retained without being able to go upward, making it possible to reduce deterioration of defrosting performance. Further, by providing the partition plate 40 in the second header 35, the flow passage cross-sectional area is reduced with the flow rate of refrigerant being the same. Therefore, the velocity of flow of refrigerant increases, and the flow passage differential pressure ΔPHEX can be increased. This suppresses liquid retention, making it possible to improve defrosting performance during a defrosting operation.
The following describes Embodiment 9. A description of overlaps with Embodiments 1 to 8 is omitted. Components that are identical or equivalent to those of Embodiments 1 to 8 are given identical reference signs.
During a cooling operation, the heat exchanger 30 according to Embodiment 9 functions as a condenser configured to condense the refrigerant by rejecting the heat of the refrigerant to the outdoor air. As shown in
A first header 34 is provided at a lower end of the heat exchanger core 31. Lower ends of the flat tubes 38 of the heat exchanger core 31 are directly inserted in the first header 34. Further, a second header 35 is provided at an upper end of the heat exchanger core 31. Upper ends of the flat tubes 38 of the heat exchanger core 31 are directly inserted in the second header 35.
A hot-gas refrigerant inlet 32 is formed at one end of the second header 35, and the hot-gas refrigerant inlet 32 is connected to the refrigerant circuit 101 of the air-conditioning apparatus 100 via a gas pipe 37. The second header 35 causes high-temperature and high-pressure gas refrigerant from the compressor 11 to flow into the heat exchanger 30 during a cooling operation and causes low-temperature and high-pressure gas refrigerant subjected to heat exchange in the heat exchanger 30 to flow out to the refrigerant circuit 101 during a heating operation.
Further, a liquid refrigerant outlet 33 is formed at one end of the first header 34 located opposite the one end of the second header 35, and the liquid refrigerant outlet 33 is connected to the refrigerant circuit 101 of the air-conditioning apparatus 100 via a liquid pipe 36. The first header 34 causes low-temperature and low-pressure two-phase refrigerant to flow into the heat exchanger 30 during a heating operation and causes low-temperature and high-pressure liquid refrigerant subjected to heat exchange in the heat exchanger 30 to flow out to the refrigerant circuit 101 during a cooling operation.
The plurality of flat tubes 38, the plurality of fins 39, the first header 34, and the second header 35 are all made of aluminum and joined to each other by brazing.
In the heat exchanger 30 according to Embodiment 9, as shown in
Moreover, hot-gas refrigerant having flowed into the second header 35 flows as downward flows through ones of the flat tubes 38 of the heat exchanger core 31 that are placed in the region T1, merges in the merging region M1 of the first header 34, and flows as upward flows through ones of the flat tubes 38 of the heat exchanger core 31 that are placed in the region T2. After that, the hot-gas refrigerant merges in the merging region M2 of the second header 35, flows as downward flows through ones of the flat tubes 38 of the heat exchanger core 31 that are placed in the region T3, and then flows out from the first header 34. That is, the region T1 and T3 are downward flow regions, and the region T2 is an upward flow region. Further, the merging region M1 of the first header 34 serves as a hot-gas refrigerant inflow port for the upward flow region.
In the region T2, there is an occurrence of liquid retention in which when hot-gas refrigerant flows as upward flows through the flat tubes 38 of the heat exchanger core 31, refrigerant liquefied by the effect of gravity is undesirably retained without being able to go upward. To address this problem, the heat exchanger 30 according to Embodiment 9 is configured such that in a case in which the total flow passage cross-sectional area of the heat exchanger core 31 in the region T2 is defined as Ar [m2]=a×Nr [m2], where Nr is the number of flat tubes 38 of the heat exchanger core 31 that are placed in the region T2, which is an upward flow region, the height of the heat exchanger core 31 is defined as H [m], a differential pressure of a refrigerant flow passage is defined as ΔPHEX, and a liquid head is defined as ΔPHEAD, ΔPHEX/ΔPHEAD=(5.94635×10−4×Ar−1.75030)/(8.4303H+0.8779)>1 is satisfied. The heat exchanger 30 thus configured makes it possible to suppress the occurrence of liquid retention in which when refrigerant having flowed in from the hot-gas refrigerant inlet 32 formed in an upper part of the heat exchanger 30 flows as upward flows through the flat tubes 38 of the heat exchanger core 31 in the region T2, refrigerant liquefied by the effect of gravity is retained without being able to go upward, making it possible to reduce deterioration of defrosting performance. Further, by providing the partition plates 40 in the first header 34 and the second header 35, the flow passage cross-sectional area is reduced with the flow rate of refrigerant being the same. Therefore, the velocity of flow of refrigerant increases, and the flow passage differential pressure ΔPHEX can be increased. This suppresses liquid retention, making it possible to improve defrosting performance during a defrosting operation.
10: outdoor unit, 11: compressor, 12: flow switching device, 13: fan, 20: indoor unit, 21: expansion device, 22: indoor heat exchanger, 23: indoor fan, 30: heat exchanger, 30a: heat exchanger, 30b: heat exchanger, 30c: heat exchanger, 31: heat exchanger core, 32: hot-gas refrigerant inlet, 33: liquid refrigerant outlet, 34: first header, 35: second header, 36: liquid pipe, 37: gas pipe, 38 flat tube, 38a: partition post, 38b: projecting portion, 38c: distal portion, 39: fin, 40: partition plate, 50: bridging header, 51: wall portion, 61a: first open-close valve, 61b: second open-close valve, 61c: third open-close valve, 62a: first expansion device, 62b: second expansion device, 63a: first merging section, 63b: second merging section, 70: controller, 100: air-conditioning apparatus, 101: refrigerant circuit
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/020313 | 5/28/2021 | WO |
