Heat exchanger and air conditioner

Abstract

A heat exchanger according to the present disclosure comprises a plurality of heat transfer tubes and a refrigerant distributor that extends in a transverse, horizontal direction and distributes a refrigerant to the plurality of heat transfer tubes, wherein the heat exchanger is configured from at least one heat exchanger part in which a structure part is provided upstream or in an upstream section of the refrigerant distributor in a refrigerant flow direction when functioning as an evaporator. An air conditioner according to the present disclosure is provided with this heat exchanger. The refrigerant distributor has: an outer pipe in which the refrigerant flows and to which the plurality of heat transfer tubes are connected at predetermined intervals; and an inner pipe in which the refrigerant flows and which is disposed on the inner peripheral side of the outer pipe. The inner pipe is provided with a plurality of refrigerant outflow holes that cause the refrigerant flowing therein to flow out to a space between the outer pipe and the inner pipe. The number of holes of the plurality of refrigerant outflow holes provided in the inner pipe satisfies (Nt -1) / 6 ≤ No < (Nt -1) when No is defined as the number of holes and Nt is defined as the number of the plurality of heat transfer tubes. The structure part brings the state of the refrigerant flowing in the inner pipe into a state in which a gas-liquid two-phase flow does not develop when functioning as an evaporator.

Description

Heat exchanger and air conditioning device

[0001] The present disclosure relates to a heat exchanger and an air conditioner equipped with a double-pipe refrigerant distributor.

[0002] A heat exchanger is known that includes a double-pipe refrigerant distributor having an outer pipe and an inner pipe with multiple orifice holes (hereinafter also referred to as refrigerant outlet holes), and distributes a refrigerant to multiple heat transfer pipes using the refrigerant distributor (see, for example, Patent Document 1). The refrigerant distributor disclosed in Patent Document 1 is provided on the inner pipe or the outer pipe and includes a structure that causes the refrigerant to flow into the inner pipe in an undeveloped gas-liquid two-phase flow state. In this refrigerant distributor, the refrigerant outlet holes are located at an angle θ of 10 degrees or more and 80 degrees or less from the center of the inner pipe on a vertical line passing through the center of the inner pipe from the lower end of the inner pipe to the position where the refrigerant outlet hole is located. There is only one refrigerant outlet hole in the vertical cross section of the inner pipe at the position where the refrigerant outlet hole is located. In Patent Document 1, the optimum angle Φ of the angle θ is determined by assuming that the slip ratio of the gas and liquid of the refrigerant is 1 and the gas-liquid interface is flat and horizontal, where ΦDo is the liquid surface angle of the refrigerant, ΦDs is the liquid surface angle of the refrigerant, and As [mm ２ ], then ΦDo<θ<ΦDs is satisfied, ΦDo is (-0.0408×As+74.124)×0.62, and ΦDs is (-0.0408×As+74.124)×1.2. In the refrigerant distributor of Patent Document 1, the refrigerant outflow holes are provided in the inner tube so as to correspond to the gaps between adjacent heat transfer tubes.

[0003] International Publication No. 2021 / 235463

[0004] However, in Patent Document 1, although the angle θ of the refrigerant outflow holes can be set to an optimal angle, the number of refrigerant outflow holes provided in the inner tube is No = Nt - 1, where No is the number of holes and Nt is the number of heat transfer tubes, and the opening diameter of the refrigerant outflow holes is set according to this number of holes No. Therefore, in the heat exchanger of Patent Document 1, when the refrigerant flow state changes significantly, such as during heating operation under low temperature conditions, the opening diameter of the refrigerant outflow holes is small relative to fluctuations in the refrigerant flow rate and dryness fraction, and refrigerant distribution may deteriorate.

[0005] The present disclosure has been made in consideration of the above-mentioned situation, and aims to provide a heat exchanger and an air conditioning apparatus that can suppress a decrease in distribution performance due to fluctuations in refrigerant flow rate and dryness fraction.

[0006] The heat exchanger disclosed herein is a heat exchanger comprising at least one heat exchanger section including a plurality of heat transfer tubes and a refrigerant distributor extending laterally in a horizontal direction and distributing a refrigerant to the plurality of heat transfer tubes, the heat exchanger having a structural part provided upstream or upstream of the refrigerant distributor in the direction of refrigerant flow when functioning as an evaporator, the refrigerant distributor having an outer tube through which the refrigerant flows and to which a plurality of heat transfer tubes are connected at predetermined intervals, and an inner tube through which the refrigerant flows and disposed on the inner periphery of the outer tube, the inner tube having a plurality of refrigerant outlet holes provided therein for allowing the refrigerant flowing therethrough to flow out into a space between the outer tube and the inner tube, the number of the plurality of refrigerant outlet holes provided in the inner tube satisfies (Nt-1) / 6≦No<(Nt-1), where No is the number of holes and Nt is the number of the plurality of heat transfer tubes, and the structural part causes the refrigerant flowing inside the inner tube to be in a state in which gas-liquid two-phase flow is not yet developed when functioning as an evaporator.

[0007] The air conditioner of the present disclosure includes the above-described heat exchanger.

[0008] The heat exchanger and air conditioner disclosed herein include a refrigerant distributor having an outer tube and an inner tube with multiple refrigerant outlet holes. A structural component is provided upstream or upstream of the refrigerant distributor in the refrigerant flow direction when the heat exchanger functions as an evaporator, to prevent the refrigerant flowing inside the inner tube from becoming a gas-liquid two-phase flow. The number of refrigerant outlet holes provided in the inner tube satisfies (Nt-1) / 6≦No<(Nt-1). This allows the opening area per refrigerant outlet hole to be designed larger than in conventional designs, thereby expanding the liquid surface capture area of ​​each refrigerant outlet hole and suppressing degradation of distribution performance due to fluctuations in refrigerant flow rate and dryness fraction.

[0009] 7 is a schematic front view of a heat exchanger according to a first embodiment.

[0023] FIG. 1 is a refrigerant circuit diagram of an air conditioner equipped with the heat exchanger of FIG. 1.

[0024] FIG. 2 is a partial cross-sectional view schematically showing the A-A cross section of the heat exchanger of FIG. 1.

[0025] FIG. 3 is a diagram showing the relationship between the refrigerant flow rate and heat exchanger performance of the heat exchanger of FIG. 1.

[0026] FIG. 4 is a partial cross-sectional view schematically showing the B-B cross section of the heat exchanger of FIG. 1, showing refrigerant liquid level fluctuations in an inner tube.

[0027] FIG. 5 is a diagram showing refrigerant liquid level fluctuations when the inner diameter of the inner tube in the refrigerant distributor of the heat exchanger of FIG. 5 is enlarged.

[0028] FIG. 6 is a partial cross-sectional view schematically showing the B-B cross section of the heat exchanger of FIG. 1, showing the liquid level capture region of the refrigerant outlet hole.

[0029] FIG. 7 is a diagram showing the liquid level capture region when the opening diameter of the refrigerant outlet hole in the refrigerant distributor of the heat exchanger of FIG. 7 is enlarged.

[0029] FIG. 8 is a diagram showing the relationship between the flow path cross-sectional area of ​​the inner tube and the opening diameter of the refrigerant outlet hole, which is particularly expected to improve robustness in the heat exchanger of FIG. 1.

[0029] FIG. 9 is a schematic front view of the heat exchanger of FIG. 1 in which the refrigerant outlet hole is longer in the vertical direction than in the horizontal direction. 19 is a partial enlarged view showing a case where the shape of the refrigerant outlet hole in FIG. 10 is an ellipse. 20 is a partial enlarged view showing a case where the shape of the refrigerant outlet hole in FIG. 10 is a rectangle. 21 is a partial enlarged view showing a case where the shape of the refrigerant outlet hole in FIG. 10 is a shape where a plurality of circles are connected in a straight line. 22 is a partial cross-sectional view showing a first modified example of the refrigerant distributor in the heat exchanger of FIG. 5. 23 is a partial cross-sectional view showing a second modified example of the refrigerant distributor in the heat exchanger of FIG. 5. 24 is a schematic front view of a heat exchanger according to embodiment 2. 25 is a schematic front view showing a first modified example of a structural part of the heat exchanger of FIG. 16. 26 is a schematic front view showing a second modified example of a structural part of the heat exchanger of FIG. 16. 27 is a schematic view of a heat exchanger according to embodiment 3. 28 is a schematic view showing a first modified example of the heat exchanger of FIG. 19.

[0010] Hereinafter, an air conditioner having a heat exchanger according to an embodiment will be described with reference to the drawings. In the drawings, identical components are denoted by the same reference numerals, and duplicated descriptions will be given only when necessary. The present disclosure may include any combination of the configurations described in the following embodiments that can be combined.

[0011] Embodiment 1. <Air Conditioning Apparatus 100> Fig. 1 is a schematic front view of a heat exchanger 3 according to Embodiment 1. Fig. 2 is a refrigerant circuit diagram of an air conditioning apparatus 100 equipped with the heat exchanger 3 of Fig. 1. Fig. 3 is a partial cross-sectional view schematically showing the A-A cross section of the heat exchanger 3 of Fig. 1. The heat exchanger 3 of Fig. 1 is used in an air conditioning apparatus 100 having a refrigerant circuit as shown in Fig. 2. In Fig. 1, the flow of refrigerant when the heat exchanger 3 functions as an evaporator is indicated by outline arrows and dashed arrows. In Fig. 2, the flow of refrigerant during cooling operation is indicated by solid arrows, and the flow of refrigerant during heating operation is indicated by dashed arrows. In Fig. 2, the heat exchanger 3 is assumed to be provided in an outdoor unit 10.

[0012] Any refrigerant may be used, for example, a single refrigerant selected from R1234yf, R1234ze, R32, and R290, a mixed refrigerant of two or more of these, a mixed refrigerant of any of these with another refrigerant, a mixed refrigerant containing R1132(E), or a mixed refrigerant containing R1123.The refrigerant may also be a mixed refrigerant of two or more of R516A, R445A, R444A, R454C, R444B, R454A, R455A, R457A, R459B, R452B, R454B, R447B, R447A, R446A, R459A, R474A, and R479A.

[0013] As shown in Fig. 2, the air conditioning apparatus 100 includes an outdoor unit 10 and multiple indoor units 11, 12, and 13. The indoor units 11, 12, and 13 are connected in parallel to one another. A refrigerant circulates inside the outdoor unit 10 and the multiple indoor units 11, 12, and 13. In Fig. 2, the air conditioning apparatus 100 is a multi-type air conditioning apparatus. Note that the first embodiment does not limit the number of indoor units 11, 12, and 13 connected to the outdoor unit 10.

[0014] The air conditioning apparatus 100 has a refrigerant circuit in which a compressor 1, a flow path switching device 2 such as a four-way valve, an indoor heat exchanger 6, a pressure reducing device 5 such as an expansion valve, a heat exchanger 3, and an accumulator 8 are connected by refrigerant piping 26 and 27. The heat exchanger 3 and the indoor heat exchanger 6 exchange heat between the wind generated by the fans 4 and 7 and the refrigerant flowing therethrough. The configuration of the refrigerant circuit is not limited to the above configuration. The flow path switching device 2 may also be configured with, for example, a two-way valve or a three-way valve.

[0015] During heating operation, i.e., when the heat exchanger 3 functions as an evaporator, the refrigerant compressed in the compressor 1 flows out of the outdoor unit 10 via the flow switching device 2 and into the indoor units 11, 12, and 13. The refrigerant that flows into the indoor units 11, 12, and 13 exchanges heat with air generated by the fan 7 in the indoor heat exchanger 6 and is then decompressed by the pressure reducing device 5. The refrigerant that has been decompressed by the pressure reducing device 5 of the indoor units 11, 12, and 13 flows out of the indoor units 11, 12, and 13 via the refrigerant piping 27 connecting the pressure reducing device 5 and the heat exchanger 3 and flows into the heat exchanger 3 of the outdoor unit 10. The refrigerant that flows into the heat exchanger 3 of the outdoor unit 10 exchanges heat with air generated by the fan 4, then flows out of the refrigerant piping 26 connecting the heat exchanger 3 and the flow switching device 2 and is drawn into the compressor 1 via the accumulator 8. The above cycle is repeated during heating operation.

[0016] During cooling operation, i.e., when the heat exchanger 3 functions as a condenser, the refrigerant compressed in the compressor 1 flows into the heat exchanger 3 through the flow switching device 2 and the refrigerant pipe 26 connecting the flow switching device 2 and the heat exchanger 3. The refrigerant that flows into the heat exchanger 3 exchanges heat with the air generated by the fan 4, then flows out of the outdoor unit 10 through the refrigerant pipe 27 connecting the heat exchanger 3 and the pressure reducing device 5, and flows into the indoor units 11, 12, and 13. The refrigerant that flows into the indoor units 11, 12, and 13 is decompressed by the pressure reducing device 5, then exchanges heat with the air generated by the fan 7 in the indoor heat exchanger 6, and flows out of the indoor units 11, 12, and 13. The refrigerant that flows out of the indoor units 11, 12, and 13 flows into the outdoor unit 10, passes through the flow switching device 2 and the accumulator 8, and is drawn into the compressor 1. The above cycle is repeated during cooling operation.

[0017] <Heat Exchanger 3> The heat exchanger 3 mounted in the outdoor unit 10 of the air conditioning apparatus 100 exchanges heat between the refrigerant and the wind (outside air) generated by the fan 4. The heat exchanger 3 is disposed below the fan 4. The heat exchanger 3 is, for example, a corrugated fin type heat exchanger.

[0018] 1 , the heat exchanger 3 has a refrigerant distributor 30, a plurality of heat transfer tubes 31, and a plurality of fins 32. The heat transfer tubes 31 are, for example, flat tubes. Note that a heat exchanger formed by connecting two heat exchangers 3, each having a refrigerant distributor 30, a plurality of heat transfer tubes 31, and a plurality of fins 32, may be mounted on the outdoor unit 10. The heat exchanger may be configured with one heat exchanger section (heat exchanger 3), or may have two or more heat exchanger sections (heat exchangers 3).

[0019] The refrigerant distributor 30 is disposed horizontally (i.e., in the direction of arrow X). A plurality of heat transfer tubes 31 are provided at intervals, and one end of each is inserted into the refrigerant distributor 30. The fins 32 are attached to the heat transfer tubes 31 and provided between the heat transfer tubes 31. The fins 32 transfer heat to the heat transfer tubes 31.

[0020] 2, the heat exchanger 3 has a gas header 40 arranged horizontally (i.e., in the direction of arrow X) above the refrigerant distributor 30. The upper ends of the heat transfer tubes 31 (see FIG. 1) are connected to the gas header 40. Although not shown, a refrigerant outlet pipe connected to the refrigerant piping 26 of the refrigerant circuit is provided at one end of the gas header 40 in the extension direction (direction of arrow X). The refrigerant outlet pipe has a smaller diameter than the gas header 40.

[0021] <Refrigerant distributor 30> The refrigerant distributor 30 has a double-pipe structure including an inner pipe 33 and an outer pipe 34. A plurality of heat transfer pipes 31 are connected to the outer pipe 34 in the extension direction of the outer pipe 34. In FIG. 1 , the refrigerant distributor 30 constitutes the lower part of the heat exchanger 3, and the lower ends of the plurality of heat transfer pipes 31 are connected to the refrigerant distributor 30. The inner pipe 33 is disposed within the outer pipe 34 and its extension direction is maintained horizontal. The inner pipe 33 has refrigerant outflow holes 35, also called orifices, formed at intervals in the extension direction of the inner pipe 33.

[0022] 1, eight heat transfer tubes 31 are connected to an outer tube 34, and three refrigerant outlet holes 35 are provided at equal intervals in an inner tube 33. Specifically, when the refrigerant distributor 30 is viewed from above, the refrigerant outlet holes 35 are arranged at three locations: between the two central heat transfer tubes 31, between the second and third heat transfer tubes 31 from the left, and between the second and third heat transfer tubes 31 from the right. In FIG. 1, each refrigerant outlet hole 35 is circular.

[0023] The refrigerant outlet holes 35 may be formed in the inner pipe 33 directly below the heat transfer pipes 31 instead of being formed in the portion below the gap G between the heat transfer pipes 31 .

[0024] 3, in the refrigerant distributor 30, the outer pipe 34 has a rectangular cross section perpendicular to its extension direction (a vertically elongated rectangle in FIG. 3), and the inner pipe 33 has a circular cross section perpendicular to its extension direction. The multiple refrigerant outlet holes 35 are spaced apart in the extension direction of the inner pipe 33 so that the number of holes per vertical cross section perpendicular to the extension direction of the inner pipe 33 is one or less.

[0025] As shown in FIG. 1 , the inner tube 33 extends in the extension direction of the outer tube 34 beyond the region where the multiple heat transfer tubes 31 are connected to the outer tube 34. One end (left end) of the inner tube 33 in the extension direction is open, and the other end (right end) of the inner tube 33 in the extension direction is sealed with a cap 36. The outer tube 34 extends further than the inner tube 33, and one and the other ends of the outer tube 34 in the extension direction are sealed. Note that any sealing structure may be used to seal the end (right end) of the inner tube 33 in the extension direction. Instead of providing the cap 36, the end (end) of the inner tube 33 in the extension direction may be crushed and sealed. Alternatively, the other end (right end) of the inner tube 33 in the extension direction may be sealed by contacting the other end (right end) of the outer tube 34 in the extension direction. Alternatively, the right end of the inner tube 33 in the extension direction may be open, similar to the left end.

[0026] An opening (not shown) is formed in the upper surface of the outer pipe 34, and a refrigerant inlet pipe 63 extending linearly is connected to this opening. The refrigerant inlet pipe 63 is connected to the refrigerant piping 27 (see FIG. 2) of the refrigerant circuit. When the heat exchanger 3 functions as an evaporator, refrigerant including liquid refrigerant flows into one end of the outer pipe 34 via the refrigerant inlet pipe 63, as shown by the outline arrow in FIG. 1.

[0027] The refrigerant inlet pipe 63 may be connected to the lower surface of the outer pipe 34 , or may be connected to the front or rear surface of the outer pipe 34 .

[0028] The refrigerant distributor 30 is provided with a first partition 61 and a second partition 62, which are provided on both sides of the region where the plurality of heat transfer tubes 31 are connected in the extension direction of the outer tube 34 and which divide the space within the outer tube 34. The first partition 61 and the second partition 62 are each made of a plate-like member having a hole (not shown) formed therein through which the inner tube 33 is placed, and divide the space within the outer tube 34 horizontally between the inner periphery of the outer tube 34 and the outer periphery of the inner tube 33. The first partition 61 and the second partition 62 also have the function of supporting the inner tube 33 and determining the position of the inner tube 33 within the outer tube 34.

[0029] The first partition 61 is disposed in the extension direction of the outer pipe 34 between the refrigerant inlet pipe 63 and the heat transfer pipe 31 closest to the refrigerant inlet pipe 63 among the plurality of heat transfer pipes 31. The second partition 62 is disposed between the end of the outer pipe 34 farther from the refrigerant inlet pipe 63 in the extension direction and the heat transfer pipe 31 farthest from the refrigerant inlet pipe 63 among the plurality of heat transfer pipes 31.

[0030] The interior of the outer pipe section 34a of the outer pipe 34 on the refrigerant inlet pipe 63 side (left side in FIG. 1 ) of the first partition 61 forms a mixing space S1. When the other end (right end) of the inner pipe 33 in the extension direction is open, the refrigerant flows into the interior of the outer pipe section 34b on the side of the outer pipe 34 farther from the refrigerant inlet pipe 63 than the second partition 62 (right side in FIG. 1 ) from the other end (right end) of the inner pipe 33 in the extension direction. The interior space of this outer pipe section 34b is separated by the second partition 62 from the space outside the inner pipe 33 in the section between the second partition 62 and the first partition 61 (i.e., the ejection space between the inner pipe 33 and the outer pipe 34 through which the refrigerant flowing out through the multiple refrigerant outlet holes 35 of the inner pipe 33 flows). Therefore, the refrigerant that flows into the interior space of the outer pipe section 34b does not directly flow into the ejection space.

[0031] 1, the other end (right end) of the inner pipe 33 in the extension direction is sealed, so that the refrigerant does not flow into the interior of the outer pipe portion 34b. This prevents the refrigerant from leaking into the ejection space due to manufacturing variations or the like, specifically, prevents the refrigerant from flowing directly from the interior space of the outer pipe portion 34b to the ejection space through the gap between the second partition 62 and the inner pipe 33 or the gap between the second partition 62 and the outer pipe 34.

[0032] <Operation of Heat Exchanger 3> The operation of the heat exchanger 3 when the air conditioning apparatus 100 shown in FIG. 2 is operating in heating mode, i.e., when the heat exchanger 3 functions as an evaporator, will be described below with reference to FIG. 1 and FIG. 2. Refrigerant flows from the refrigerant piping 27 (see FIG. 2) of the refrigerant circuit into the mixing space S1 via the refrigerant inlet pipe 63. The refrigerant that flows into the mixing space S1 is mixed into gas and liquid within the mixing space S1, and flows into the inner tube 33 from its left end in an underdeveloped gas-liquid two-phase flow state. The refrigerant that flows into the inner tube 33 from its left end flows in the extension direction toward its right end. At this time, the refrigerant flows into the space between the inner tube 33 and the outer tube 34 through multiple refrigerant outlet holes 35 provided at regular intervals in the extension direction of the inner tube 33. The refrigerant that flows into the space between the inner tube 33 and the outer tube 34 is distributed to the multiple heat transfer tubes 31 connected to the outer tube 34. The refrigerant distributed to the plurality of heat transfer tubes 31 flows from the lower end to the upper end within each heat transfer tube 31, evaporating and gasifying through heat exchange with air (outside air) passing through gaps G between the heat transfer tubes 31. The refrigerants gasified in each of the plurality of heat transfer tubes 31 join together in the gas header 40 and flow in the extension direction, and then flow out of the heat exchanger 3 through a refrigerant outflow pipe (not shown) into the refrigerant piping 26 (see FIG. 2 ) of the refrigerant circuit.

[0033] When the heat exchanger 3 functions as an evaporator, the heat exchanger 3 has a structural portion C upstream or downstream of the refrigerant distributor 30, which causes a gas-liquid two-phase flow to be underdeveloped in the refrigerant flow. The structural portion C particularly causes the refrigerant flowing inside the inner pipe 33 to be underdeveloped in the gas-liquid two-phase flow. Here, the "underdeveloped gas-liquid two-phase flow" refers to a state in which the refrigerant flowing through the inner pipe 33 is not a gas-liquid two-phase flow, such as a stratified flow.

[0034] In the heat exchanger 3 shown in Fig. 1, structural portion C where the gas-liquid two-phase flow is underdeveloped is the mixing space S1 provided upstream of the refrigerant distributor 30. The refrigerant distributor 30 is configured so that A2 > As, where A2 is the flow path cross-sectional area of ​​the mixing space S1 and As is the flow path cross-sectional area of ​​the inner pipe 33. By providing such a mixing space S1, when the refrigerant flows from the mixing space S1, which has a large flow path cross-sectional area, into the inner pipe 33, which has a small flow path cross-sectional area, the gas-liquid two-phase flow is reduced, but the gas-liquid two-phase flow remains underdeveloped in the mixing space S1.

[0035] Methods for estimating the flow regime of a refrigerant include flow regime diagrams such as the Baker diagram. Many of these flow regime diagrams represent flow regimes in which gas-liquid flow is fully developed. Therefore, if the heat exchanger 3 has a structural portion C in which gas-liquid two-phase flow is underdeveloped, the refrigerant flowing through the inner tube 33 may exhibit stratified or wavy flow even when the flow regime diagram indicates an annular flow. If the intended gas-liquid two-phase flow is not achieved, the vertical liquid phase distribution (liquid level) within the refrigerant distributor 30 will not be as intended, and distribution performance will be reduced if the opening diameter φo of the refrigerant outlet hole 35 is small.

[0036] Therefore, the angle θ at which the refrigerant outlet holes 35 are provided in the inner pipe 33 is set so as to obtain good refrigerant distribution even when the structure C that keeps the gas-liquid two-phase flow underdeveloped is provided upstream or downstream of the refrigerant distributor 30. Here, the angle θ of the refrigerant outlet holes 35 is defined as the angle, as seen from the center of the inner pipe 33, from the lower end of the inner pipe 33 to the center of the refrigerant outlet holes 35 on a vertical line passing through the center of the inner pipe 33. For example, assuming that the slip ratio between the gas and liquid of the refrigerant is 1 and the gas-liquid interface is flat and horizontal, and the liquid level angle of the refrigerant is defined as ΦDo and the liquid level angle of the refrigerant is defined as ΦDs, the refrigerant outlet holes 35 are provided so that the angle θ satisfies ΦDo<θ<ΦDs. Here, when the flow path cross-sectional area of ​​the inner tube 33 is defined as As [mm2], the liquid surface angle ΦDo and the liquid surface angle ΦDs are expressed as ΦDo = (-0.0408 × As + 74.124) × 0.62 and ΦDs = (-0.0408 × As + 74.124) × 1.2.

[0037] 1 operates in heating mode under low-temperature conditions, the progress of frosting on the surfaces of the fins 32 reduces the airflow passing through the gaps G between the heat transfer tubes 31, causing a drop in refrigerant pressure and a resulting drop in heating capacity (a drop in refrigerant flow rate). At this time, the refrigerant flow rate and quality fraction at the refrigerant inlet of the heat exchanger 3 gradually change, resulting in significant fluctuations in the vertical liquid phase distribution (liquid level) within the refrigerant distributor 30. In a conventional configuration in which refrigerant outlet holes 35 are provided in the inner tube corresponding to each of the heat transfer tubes, during heating mode under low-temperature conditions where the refrigerant flow rate and quality fraction fluctuate significantly, the liquid phase distribution may not be optimally positioned for the refrigerant outlet holes 35, resulting in a drop in distribution performance and a significant drop in heating capacity.

[0038] Therefore, in the heat exchanger 3 of the present disclosure, in order to improve robustness against fluctuations in the refrigerant flow pattern, refrigerant flow rate, and dryness fraction in the inner tube 33 of the refrigerant distributor 30, i.e., to suppress deterioration in distribution performance and heating capacity over a wider operating range, the optimal number of refrigerant outlet holes 35 provided in the inner tube 33 of the refrigerant distributor 30 is specified based on the number of heat transfer tubes 31. Specifically, as shown in Fig. 1 , the number No of refrigerant outlet holes 35 provided in the inner tube 33 of the refrigerant distributor 30 is smaller than the number Nt of heat transfer tubes 31 connected to the outer tube 34, and is set so as to satisfy the following formula (1):

[0039] [Equation 1] (Nt-1) / 6≦No<(Nt-1) Equation (1)

[0040] Conventionally, pressure is adjusted by, for example, providing one refrigerant outlet hole 35 between every heat transfer tube 31 in the inner tube 33. However, in the present disclosure, the number N of the refrigerant outlet holes 35 is reduced (i.e., (Nt-1)). In the example of FIG. 1 , eight heat transfer tubes 31 are connected to the outer tube 34, and three refrigerant outlet holes 35 are provided in the inner tube 33. Generally, the opening areas of the multiple refrigerant outlet holes 35 in the refrigerant distributor 30 are determined based on the pressure loss balance. Therefore, when the number N of the refrigerant outlet holes 35 is reduced, the opening area per refrigerant outlet hole 35 (e.g., the opening diameter φo) is designed to be larger.

[0041] Here, the relationship between the opening area of ​​the multiple refrigerant outlet holes 35 and pressure loss will be briefly described. For ease of explanation, a refrigerant outlet pipe (not shown) is provided at the left end of the gas header 40. The refrigerant flows into the heat exchanger 3 from the left end of the refrigerant distributor 30, is distributed to the multiple heat transfer tubes 31, and flows out of the heat exchanger 3 from the left end of the gas header 40. Between path P1, where the refrigerant flows through the refrigerant distributor 30, the leftmost heat transfer tube 31, and the gas header 40, and path P2, where the refrigerant flows through the refrigerant distributor 30, the rightmost heat transfer tube 31, and the gas header 40, path P1 has a shorter flow distance and allows more refrigerant to flow. However, by providing the refrigerant distributor 30 in the heat exchanger 3 and distributing the refrigerant through the multiple refrigerant outlet holes 35, flow resistance is applied, thereby relatively reducing the effect of the flow distance. This reduces the difference between the refrigerant flow rate through the shortest path P1 and the longest path P2. The opening area of ​​the plurality of refrigerant outlet holes 35 is designed to cause a certain degree of pressure loss in order to adjust the flow resistance balance (pressure loss balance) in this way.

[0042] Fig. 4 is a diagram showing the relationship between the refrigerant flow rate and the heat exchanger performance of the heat exchanger 3 shown in Fig. 1. In Fig. 4, the horizontal axis represents the refrigerant flow rate, and the vertical axis represents the heat exchanger performance. Based on Fig. 4, the reason for specifying the number No of the refrigerant outlet holes 35 within the range of the above formula (1) will be explained.

[0043] As shown by the dashed line in Figure 4, in the conventional configuration in which one refrigerant outlet hole 35 is arranged between every heat transfer tube 31 (i.e., No = Nt - 1), changes in refrigerant flow rate have a greater effect on heat exchanger performance than in the case of No = (Nt - 1) / 3 shown by the dashed line. Therefore, in order to obtain stable heat exchanger performance over a wider range of operations, the heat exchanger 3 of the present disclosure has a smaller number of refrigerant outlet holes 35 No than the conventional number of holes (i.e., No = Nt - 1). It is more preferable that the number of refrigerant outlet holes 35 No be (Nt - 1) / 2 or less.

[0044] Furthermore, as shown by the solid line in Figure 4, if the number No of the refrigerant outlet holes 35 is up to about (Nt-1) / 6, it is possible to maintain distribution performance while suppressing deterioration in heat exchanger performance. On the other hand, as shown by the two-dot chain line in Figure 4, if the number No of the refrigerant outlet holes 35 is less than (Nt-1) / 7, distribution loss occurs in some of the heat transfer tubes 31 that are farther from the refrigerant outlet holes 35, preventing proper distribution and reducing heat exchanger performance. Therefore, in the heat exchanger 3 of the present disclosure, the lower limit of the number No of the refrigerant outlet holes 35 is set to (Nt-1) / 6 in consideration of distribution loss.

[0045] FIG. 5 is a partial cross-sectional view schematically showing the B-B cross section of the heat exchanger 3 of FIG. 1, illustrating the refrigerant liquid level fluctuation AL in the inner tube 33. FIG. 6 is a diagram illustrating the refrigerant liquid level fluctuation AL when the inner diameter Di of the inner tube 33 in the refrigerant distributor 30 of the heat exchanger 3 of FIG. 5 is enlarged. FIG. 7 is a partial cross-sectional view schematically showing the B-B cross section of the heat exchanger 3 of FIG. 1, illustrating the liquid level capture region RL of the refrigerant outlet hole 35. FIG. 8 is a diagram illustrating the liquid level capture region RL when the opening diameter φo of the refrigerant outlet hole 35 in the refrigerant distributor 30 of the heat exchanger 3 of FIG. 7 is enlarged. FIG. 9 is a diagram illustrating the relationship between the flow path cross-sectional area As of the inner tube 33 and the opening diameter φo of the refrigerant outlet hole 35, which is particularly expected to improve robustness in the heat exchanger 3 of FIG. 1. In FIG. 9, the horizontal axis represents the flow path cross-sectional area As [mm ２ ], and the vertical axis represents the opening diameter φo [mm] of the refrigerant outflow hole 35 formed in the inner pipe 33.

[0046] As shown in Figures 5 and 6, when the inner diameter Di of the inner pipe 33 in the refrigerant distributor 30 is enlarged, the flow path cross-sectional area As of the inner pipe 33 becomes larger, and therefore the vertical liquid level fluctuation AL of the refrigerant in the inner pipe 33 becomes smaller.

[0047] 7 and 8 , when the opening diameter φo of the refrigerant outlet hole 35 provided in the inner pipe 33 is enlarged, the liquid surface capture region RL of the refrigerant outlet hole 35 also becomes larger. Here, the liquid surface capture region RL is the region that covers the liquid surface or liquid phase of the refrigerant in the refrigerant outlet hole 35, and is defined as the vertical width of the opening edge of the refrigerant outlet hole 35 on the inner circumferential surface of the inner pipe 33.

[0048] 7 and 8, increasing the opening diameter φo of the refrigerant outflow hole 35 increases the liquid level capture region RL, and increasing the inner diameter Di of the inner pipe 33 decreases the refrigerant liquid level fluctuation AL itself in the inner pipe 33, as described with reference to Figures 5 and 6. Therefore, it is possible to suppress a decrease in distribution performance and a decrease in heating capacity not only when the flow pattern differs between the diagram and the actual state, but also during heating operation under low-temperature conditions with large fluctuations in the refrigerant flow rate and dryness fraction.

[0049] As described above, in the heat exchanger 3 of the present disclosure, the number No of the refrigerant outlet holes 35 is set to be smaller than the conventional number of holes (i.e., No = Nt - 1). In this case, in order to improve robustness, as shown in FIG. 9, the opening diameter φo of the refrigerant outlet holes 35 is set to be 144.71 × As －１．２５ In order to achieve a balance between the improvement of robustness and the effect of the heat exchanger and the suppression of the deterioration of the heat exchanger performance, it is preferable that the opening diameter φo of the refrigerant outflow hole 35 is greater than 144.71×As －１．２５ <Φo<1.1287×As ０．５ It is preferable to satisfy the following condition.

[0050] As described above, the opening diameter φo of the refrigerant outlet hole 35 is largely determined by the pressure loss balance, so the adjustment range of the opening diameter φo is limited, but robustness can be further improved by adjusting the flow path cross-sectional area As by the inner diameter Di of the inner pipe 33. Furthermore, if the inner diameter Di of the inner pipe 33 is increased, the opening diameter φo of the refrigerant outlet hole 35 can be made smaller even when the same robustness is obtained.

[0051] The shape of the refrigerant outlet hole 35 is not limited to the circular shape described above and may be non-circular. Fig. 10 is a schematic front view of the heat exchanger 3 in Fig. 1 , where the refrigerant outlet hole 35 is longer in the vertical direction (arrow Z direction) than in the horizontal direction (arrow X direction). Fig. 11 is a partially enlarged view of the refrigerant outlet hole 35 in Fig. 10 , where the shape is elliptical. Fig. 12 is a partially enlarged view of the refrigerant outlet hole 35 in Fig. 10 , where the shape is rectangular. Fig. 13 is a partially enlarged view of the refrigerant outlet hole 35 in Fig. 10 , where the shape is a plurality of circles connected in a straight line.

[0052] As shown in Fig. 10 , the refrigerant outlet hole 35 provided in the inner pipe 33 has a vertically elongated shape in which the dimension in the vertical direction (arrow Z direction) is greater than the dimension in the extension direction (arrow X direction) of the inner pipe 33. The shape of the refrigerant outlet hole 35 may be a vertically elongated ellipse as shown in Figs. 10 and 11 , a vertically elongated rectangle as shown in Fig. 12 , or a shape in which a plurality of circles are linearly connected in the vertical direction as shown in Fig. 13 . By forming the refrigerant outlet hole 35 in this vertically elongated shape, the liquid level capture region RL (see Fig. 8 ) is enlarged even when the opening area per refrigerant outlet hole 35 is the same, compared to a shape with the same vertical and horizontal dimensions, such as a circle, and the robustness of refrigerant distribution is improved.

[0053] The cross-sectional shapes of the outer pipe 34 and the inner pipe 33 of the refrigerant distributor 30 are not limited to those shown in Figures 3 and 5. Two modifications will be described below.

[0054] Fig. 14 is a partial cross-sectional view schematically showing a first modified example of the refrigerant distributor 30 in the heat exchanger 3 of Fig. 5. In the refrigerant distributor 130 of the first modified example, the outer tube 134 has a horizontally long rectangular cross section perpendicular to its extension direction, and the inner tube 133 has a horizontally long rectangular cross section perpendicular to its extension direction.

[0055] 15 is a partial cross-sectional view schematically illustrating a second modified example of the refrigerant distributor 30 in the heat exchanger 3 of FIG. 5. In the refrigerant distributor 230 of the second modified example, the inner tube 233 has a D-shaped cross section perpendicular to its extension direction. Specifically, the inner tube 233 has a flat upper surface 233a facing the lower ends of the heat transfer tubes 31, a downwardly convex curved inner tube lower surface 233d, and a flat inner tube front surface 233b connecting the leading edge of the inner tube upper surface 233a to the leading edge of the inner tube lower surface 233d, and a flat inner tube rear surface 233c connecting the trailing edge of the inner tube upper surface 233a to the trailing edge of the inner tube lower surface 233d. The inner tube lower surface 233d has, for example, an arc-shaped cross section. The inner pipe 233 is formed so that the cross section perpendicular to the extension direction thereof has a horizontally elongated shape in which the dimension in the front-to-rear direction (arrow Y direction) is greater than the dimension in the vertical direction (arrow Z direction). In other words, the inner pipe 233 is formed as a D-shaped pipe that is wide in the front-to-rear direction (arrow Y direction).

[0056] In the refrigerant distributor 230 of the second modification, the outer pipe 234 has a cross section perpendicular to its extension direction that is D-shaped and convex downward. More specifically, the outer pipe 234 has a flat outer pipe upper surface 234a to which the lower ends of the heat transfer pipes 31 are connected, and a downwardly convex outer pipe lower surface 234d. In Fig. 15, the outer pipe 234 has a cross section perpendicular to its extension direction that is elongated such that the dimension in the vertical direction (arrow Z direction) is greater than the dimension in the front-rear direction (arrow Y direction).

[0057] In both the first modified example shown in Fig. 14 and the second modified example shown in Fig. 15, the inner pipes 133, 233 have a cross-sectional shape perpendicular to their extension direction that is elongated in such a way that the dimension in the front-to-rear direction (direction of arrow Y) is greater than the dimension in the vertical direction (direction of arrow Z). By making the inner pipes 133, 233 have a cross-sectional shape that is elongated in this way, the liquid level fluctuation AL (see Fig. 6) of the refrigerant in the inner pipes 133, 233 in the vertical direction is smaller even when the vertical dimension is the same, compared to a shape in which the vertical and horizontal dimensions are the same, such as a circular cross-sectional shape, and the robustness of the refrigerant distribution is improved.

[0058] As described above, the heat exchanger 3 according to the first embodiment includes a plurality of heat transfer tubes 31 and a refrigerant distributor 30 extending horizontally (in the direction of arrow X) and distributing a refrigerant to the plurality of heat transfer tubes 31. The refrigerant distributor 30 includes at least one heat exchanger section provided with a structural section C, in which a gas-liquid two-phase flow is underdeveloped, upstream or downstream of the refrigerant distributor 30 in the refrigerant flow direction when the heat exchanger 30 functions as an evaporator. The refrigerant distributor 30 includes an outer tube 34 through which a refrigerant flows and to which the plurality of heat transfer tubes 31 are connected at predetermined intervals, and an inner tube 33 through which the refrigerant flows and which is disposed on the inner periphery of the outer tube 34. The inner tube 33 is provided with a plurality of refrigerant outlet holes 35 through which the refrigerant flowing therethrough flows into a space between the outer tube 34 and the inner tube 33. The number of the refrigerant outlet holes 35 provided in the inner tube 33 satisfies (Nt-1) / 6≦No<(Nt-1), where No is the number of holes and Nt is the number of the heat transfer tubes 31. The structural part C causes the refrigerant flowing inside the inner tube 33 to be in a state where gas-liquid two-phase flow is not yet developed when the heat exchanger 3 functions as an evaporator.

[0059] As described above, the heat exchanger 3 includes a refrigerant distributor 30 having an outer pipe 34 and an inner pipe 33 provided with a plurality of refrigerant outlet holes 35. A structural portion C is provided upstream or upstream of the refrigerant distributor 30 to prevent the refrigerant flowing inside the inner pipe 33 from becoming a gas-liquid two-phase flow. The number No of the plurality of refrigerant outlet holes 35 provided in the inner pipe 33 satisfies (Nt-1) / 6≦No<(Nt-1). As a result, the opening area per refrigerant outlet hole 35 is designed to be larger than in the conventional design, thereby expanding the liquid level capture region RL of each refrigerant outlet hole 35 and suppressing degradation of distribution performance due to fluctuations in refrigerant flow rate and dryness fraction.

[0060] The refrigerant outlet holes 35 are arranged in the extension direction of the inner pipe 33 so that the number of holes per vertical cross section perpendicular to the extension direction (direction of arrow X) of the inner pipe 33 is one or less. By dispersing the refrigerant outlet holes 35 in the extension direction of the inner pipe 33 in this manner, the refrigerant can be distributed more evenly to the heat transfer pipes 31 even when the number No of the refrigerant outlet holes 35 provided in the inner pipe 33 is limited.

[0061] The opening diameter of each of the plurality of refrigerant outlet holes 35 is defined as 144.71×As, where Φo is the opening diameter and As is the flow path cross-sectional area of ​​the inner pipe 33. －１．２５ <Φo<1.1287×As ０．５ This makes it possible to achieve a balance between the effect of improving the robustness of refrigerant distribution against fluctuations in the refrigerant flow rate and dryness fraction, and the suppression of deterioration in heat exchanger performance.

[0062] Each of the refrigerant outlet holes 35 has a vertically elongated shape, with the vertical dimension (arrow Z direction) being larger than the horizontal dimension (arrow X direction). By forming the refrigerant outlet holes 35 in this vertically elongated shape, the liquid level capture region RL (see FIG. 8) is enlarged, improving the robustness of refrigerant distribution.

[0063] Furthermore, the cross-sectional shape of the inner pipes 133, 233 in the vertical direction perpendicular to the extension direction is a horizontally elongated shape in which the dimension in the horizontal direction perpendicular to the extension direction (the front-to-rear direction, the direction of arrow Y) is greater than the dimension in the vertical direction (the direction of arrow Z). By making the inner pipes 133, 233 have a horizontally elongated cross-sectional shape, the liquid level fluctuation AL (see FIG. 6 ) of the refrigerant in the inner pipes 133, 233 in the vertical direction is reduced, improving the robustness of refrigerant distribution.

[0064] Furthermore, the inner pipe 233 may be a wide D-shaped pipe whose dimension in the horizontal direction perpendicular to the extension direction (the front-to-rear direction, the direction of arrow Y) is greater than its dimension in the vertical direction. When combined with the outer pipe 234 having a vertically elongated cross section, using a D-shaped pipe as the inner pipe 233 allows the flow path cross-sectional area As of the inner pipe 233 to be configured larger, which in turn reduces the refrigerant liquid level fluctuation AL, which is even more advantageous.

[0065] The structural portion C is a mixing space S1 provided in the outer pipe 34 of the refrigerant distributor 30. In this way, even in the refrigerant distributor 30 having the mixing space S1, by limiting the number No of the refrigerant outlet holes 35, deterioration of the refrigerant distribution is suppressed.

[0066] The heat exchanger 3 also includes a sealing structure that seals the end (right end) of the inner tube 33 in the extension direction, and the sealing structure is either a crushed end of the inner tube 33 itself or a cap 36 that covers the end. By providing such a sealing structure, it is possible to prevent internal leakage of the refrigerant into the ejection space due to manufacturing variations or the like.

[0067] The air conditioning apparatus 100 also includes the above-described heat exchanger 3. As a result, the air conditioning apparatus 100 suppresses a decrease in the distribution performance of the heat exchanger 3, and thereby suppresses a decrease in heating capacity, even during operation with large fluctuations in the refrigerant flow rate and dryness fraction, such as heating operation under low-temperature conditions.

[0068] Embodiment 2 Fig. 16 is a schematic front view of a heat exchanger 303 according to embodiment 2. In embodiment 2, the configurations of the refrigerant distributor 330 and structural section C of the heat exchanger 303 are different from those in embodiment 1. The configuration of the heat exchanger 303 of embodiment 2 will be described with reference to Fig. 16. Note that the same components as those in embodiment 1 are denoted by the same reference numerals, and description thereof will be omitted.

[0069] 16 , the inner pipe 333 is housed in the outer pipe 334, and the side connected to the refrigerant pipe 27 (see FIG. 2 ) extends beyond the end 334 e of the outer pipe 334. The extended portion of the inner pipe 333 is a linear inlet portion 362, which serves as an inlet portion for the refrigerant flowing into the outer pipe 334.

[0070] A through-hole (not shown) is formed in the end 334e of the outer pipe 334, in which the inner pipe 333 is disposed. When the heat exchanger 303 functions as an evaporator, the inner pipe 333 is supported by the end 334e of the outer pipe 334 on the upstream side of the refrigerant distributor 330 in the refrigerant flow, and therefore the first partition 61 of the first embodiment can be omitted.

[0071] When the inner diameter of the inlet section 362 (i.e., the inner diameter Di of the inner pipe 333) and the length of the inlet section 362 in the extension direction of the inner pipe 333 (direction of arrow X) are defined as L, L<20×Di. Generally, many flow pattern diagrams used to estimate the flow pattern of a refrigerant represent a state in which the gas-liquid flow is fully developed, in other words, a flow pattern with a sufficient run-up distance. In the second embodiment, the length L of the linear inlet section 362 is set to L<20×Di, and there is not a sufficient run-up distance upstream of the inner pipe 333.

[0072] In the second embodiment, the inlet section 362, which is an extended portion of the inner pipe 333, is structural section C where gas-liquid two-phase flow is underdeveloped. That is, in the second embodiment, structural section C is the inlet section 362 provided upstream of the refrigerant distributor 330. The refrigerant that flows through the inlet section 362 enters an underdeveloped gas-liquid two-phase flow state and flows into the inner pipe 333 within the outer pipe 334. The refrigerant in an underdeveloped gas-liquid two-phase flow state then passes through the multiple refrigerant outlet holes 35 from the inner pipe 333 and flows into the space between the outer pipe 334 and the inner pipe 333. The refrigerant that flows into the space between the outer pipe 334 and the inner pipe 333 passes through the multiple heat transfer tubes 31 and flows into the gas header 40. The refrigerant that flows into the gas header 40 flows to the right in the extension direction within the gas header 40 and flows out into the refrigerant piping 26 of the refrigerant circuit via the refrigerant outlet pipe 41 provided at the right end of the gas header 40.

[0073] In the refrigerant distributor 330 of the second embodiment, the number No of the refrigerant outlet holes 35 provided in the inner tube 333 is specified in the same manner as in the first embodiment. Specifically, the number No of the refrigerant outlet holes 35 provided in the inner tube 333 is less than the number Nt of the heat transfer tubes 31 and is set so as to satisfy (Nt - 1) / 6 ≦ No < (Nt - 1). Because the number No of the refrigerant outlet holes 35 is therefore less than the conventional number (No = Nt - 1), the opening area per refrigerant outlet hole 35 is designed to be larger than in the conventional case, thereby expanding the liquid level capture region RL (see FIG. 8 ). Therefore, even when the length L of the inlet portion 362 is L < 20 × Di and the gas-liquid two-phase flow of the refrigerant in the inner tube 333 is underdeveloped, the deterioration of distribution performance can be suppressed.

[0074] In the example of FIG. 16 , the portion of the inner pipe 333 extending beyond the end 334e of the outer pipe 334 is entirely linear, but the shape of the extended portion of the inner pipe 333 is not limited to this. FIG. 17 is a schematic front view showing a first modified example of the structural section C of the heat exchanger 303 of FIG. 16 . In the heat exchanger 303a, the extended portion of the inner pipe 333a is an L-shaped bent pipe. Specifically, the extended portion of the inner pipe 333a has a linear inlet section 337a extending laterally from the portion of the inner pipe 333a disposed within the outer pipe 334, and an extension section 338 extending upward from the inlet section 337a. The linear inlet section 337a of the extended portion of the inner pipe 333a serves as an inlet section for the refrigerant flowing into the outer pipe 334. The length L of the inlet section 337a satisfies L<20×Di.

[0075] The extension 338 of the extended portion of the inner pipe 333a may be a curved pipe. The extension 338 may extend downward from the inlet 337a, or may extend forward or backward.

[0076] FIG. 18 is a front view showing a second modified example of the structural section C of the heat exchanger 303 shown in FIG. 16 . As shown in FIG. 18 , in the heat exchanger 303b, a valve 339 is provided in the extended portion of the inner pipe 333b. The valve 339, for example, adjusts the dryness of the refrigerant in the inner pipe 333b. The extended portion of the inner pipe 333b is entirely linear, extending laterally in the same direction as the portion of the inner pipe 333a disposed within the outer pipe 334. Of the extended portion of the inner pipe 333b, an inlet section 337b located closer to the outer pipe 334 than the valve 339 serves as an inlet section for the refrigerant flowing into the outer pipe 334. The length L of this inlet section 337b satisfies L<20×Di.

[0077] In both the first modified example shown in Figure 17 and the second modified example shown in Figure 18, because there is not a sufficient inlet distance upstream of the inner pipes 333a, 333b, the gas-liquid two-phase flow enters the inner pipes 333a, 333b within the outer pipe 334 in an underdeveloped state. However, in the refrigerant distributors 330a, 330b of the present disclosure, the number N of the refrigerant outlet holes 35 is smaller than the conventional number of holes (N = Nt - 1). This allows the opening area per refrigerant outlet hole 35 to be designed larger than in the conventional configuration, and the liquid surface capture region RL (see Figure 8) is enlarged. Therefore, even if the length L of the inlet portions 337a, 337b cannot be sufficiently secured due to the shape of the extended portions of the inner pipes 333a, 333b or devices such as the valve 339, a decrease in distribution performance can be suppressed.

[0078] As described above, the heat exchanger 303 according to the second embodiment, like the first embodiment, includes a refrigerant distributor 330 having an outer pipe 334 and an inner pipe 333 provided with a plurality of refrigerant outlet holes 35. A structural portion C is provided upstream of the refrigerant distributor 330 to prevent the refrigerant flowing inside the inner pipe 333 from becoming a gas-liquid two-phase flow. The number No of the plurality of refrigerant outlet holes 35 provided in the inner pipe 333 satisfies (Nt-1) / 6≦No<(Nt-1). This provides the same effect as the first embodiment in suppressing degradation of distribution performance due to fluctuations in refrigerant flow rate and quality fraction.

[0079] In the heat exchanger 303 of the second embodiment, the structural portion C is an inlet portion 337 that extends linearly from the inner pipe 333 of the refrigerant distributor 330 to the outside of the outer pipe 334, and satisfies L < 20 × Di, where Di is the inner diameter of the inner pipe 333 and L is the length of the inlet portion 337. In this way, even if a sufficient inlet distance cannot be secured when providing the inlet portion 337, which is an inlet portion extending from the inner pipe 333, the deterioration of distribution performance can be suppressed by limiting the number No of the multiple refrigerant outlet holes 35 provided in the inner pipe 333.

[0080] Embodiment 3. Figure 19 is a schematic diagram of a heat exchanger 403 according to embodiment 3. Embodiment 3 differs from embodiments 1 and 2 in that the heat exchanger 403 includes multiple heat exchanger sections 403a and 403b. In Figure 19, the flow directions of air supplied to heat exchanger section 403a and heat exchanger section 403b are indicated by outline arrows, respectively. The configuration of the heat exchanger 403 according to embodiment 3 will be described with reference to Figures 1 and 2, based on Figure 19. Hereinafter, the configurations of the heat exchanger sections 403a and 403b are assumed to be the same as those of the heat exchanger 3 according to embodiment 1. That is, each of the heat exchanger sections 403a and 403b includes a refrigerant distributor 30 having resistance to liquid level fluctuations.

[0081] 19, a refrigerant inlet pipe 463a of the heat exchanger unit 403a and a refrigerant inlet pipe 463b of the heat exchanger unit 403b are connected to the refrigerant piping 27 (see FIG. 2) of the refrigerant circuit via a connecting pipe 463c. When the heat exchanger 403 functions as an evaporator, the refrigerant from the refrigerant piping 27 flows through the connecting pipe 463c, branches into two refrigerant inlet pipes 463a and 463b at an upstream branching portion 463d, and flows into the heat exchanger unit 403a and the heat exchanger unit 403b, respectively.

[0082] The heat exchanger section 403a and the heat exchanger section 403b each include a plurality of heat transfer tubes 31, a plurality of fins 32, and a refrigerant distributor 30 (see FIG. 1). The heat exchanger section 403a and the heat exchanger section 403b have different airflow rates, for example, depending on their arrangement. Furthermore, when refrigerant from the refrigerant pipe 27 branches at the upstream branch section 463d, variations in the refrigerant flow rate or dryness fraction may occur. Therefore, these variations may cause a concern of poor refrigerant distribution. However, in the heat exchanger 403 disclosed herein, the heat exchanger section 403a and the heat exchanger section 403b each include a refrigerant distributor 30 (see FIG. 1) that is more resistant to liquid level fluctuations than conventional refrigerant distributors, thereby suppressing the deterioration of refrigerant distribution. This also suppresses a decrease in heat exchange efficiency.

[0083] Fig. 20 is a schematic diagram showing a first modified example of the heat exchanger 403 of Fig. 19. As shown in Fig. 20, the heat exchanger 503 of the first modified example has a heat exchanger section 503a and a heat exchanger section 503b with different volumes. In Fig. 20, the flow direction of the refrigerant branched to the heat exchanger section 503a and the flow direction of the refrigerant branched to the heat exchanger section 503b are indicated by outline arrows. In the following, the configurations of the heat exchanger sections 503a and 503b are assumed to be the same as the configuration of the heat exchanger 3 of the first embodiment, except for the difference in volume.

[0084] A refrigerant inlet pipe 563a of the heat exchanger unit 503a and a refrigerant inlet pipe 563b of the heat exchanger unit 503b are connected to the refrigerant piping 27 (see FIG. 2) of the refrigerant circuit via a connecting pipe 563c. In a first modified example shown in FIG. 20, a flow rate adjustment valve 564 is provided in the refrigerant inlet pipe 563b of the heat exchanger unit 503b. The opening degree of the flow rate adjustment valve 564 is controlled to adjust the refrigerant flow rate to the heat exchanger unit 503b. The opening degree of the flow rate adjustment valve 564 adjusts the refrigerant flow rate branched to the heat exchanger unit 503b, and therefore the refrigerant flow rate to the heat exchanger unit 503a also changes.

[0085] When the heat exchanger 503 functions as an evaporator, the refrigerant flows from the refrigerant pipe 27 through a connecting pipe 563c, branches into two refrigerant inlet pipes 563a and 563b at an upstream branching portion 563d, and flows into the heat exchanger portions 503a and 503b. At this time, the opening of the flow rate control valve 564 is controlled so that the refrigerant flow rate of the heat exchanger portion 503a and the refrigerant flow rate of the heat exchanger portion 503b correspond to the volume.

[0086] A flow rate adjustment valve 564 may be provided in each of the refrigerant inlet pipe 563a and the refrigerant inlet pipe 563b.

[0087] Each of the heat exchanger units 503a and 503b includes a plurality of heat transfer tubes 31, a plurality of fins 32, and a refrigerant distributor 30 (see FIG. 1). In the example of FIG. 20, the heat exchanger units 503a and 503b have different capacities, and when the refrigerant from the refrigerant pipe 27 branches at the upstream branch unit 563d, the refrigerant is branched at a ratio corresponding to the capacities of the heat exchanger units 503a and 503b. When the flow rate is not distributed 1:1, variations in the refrigerant flow rate or dryness fraction tend to increase. Therefore, in a configuration in which the heat exchanger units 503a and 503b have different capacities, this variation may cause deterioration of the refrigerant distribution. However, in the heat exchanger 503 of the present disclosure, the heat exchanger section 503a and the heat exchanger section 503b each include a refrigerant distributor 30 (see FIG. 1) that is more resistant to liquid level fluctuations than conventional refrigerant distributors, thereby preventing deterioration of refrigerant distribution and suppressing a decrease in heat exchange efficiency.

[0088] As described above, the heat exchangers 403 and 503 according to the third embodiment, like the first embodiment, include a refrigerant distributor 30 having an outer pipe 34 and an inner pipe 33 provided with a plurality of refrigerant outlet holes 35. A structural portion C is provided upstream of the refrigerant distributor 30 to keep the refrigerant flowing inside the inner pipe 33 from becoming a gas-liquid two-phase flow. The number No of the plurality of refrigerant outlet holes 35 provided in the inner pipe 33 satisfies (Nt-1) / 6≦No<(Nt-1). This provides the same effect as the first embodiment in suppressing degradation of distribution performance due to fluctuations in refrigerant flow rate and quality fraction.

[0089] The heat exchanger 403 of the second embodiment includes two heat exchanger sections 403a and 403b, which are connected to each other on the upstream side of the structural section C of the two heat exchanger sections.

[0090] In such a configuration, there is a concern that the refrigerant distribution may deteriorate due to variations in the refrigerant flow rate and dryness at the refrigerant branching point (upstream branching section 463d). However, by providing a refrigerant distributor 30 with liquid level fluctuation resistance in each heat exchanger section 403a, 403b, deterioration of the refrigerant distribution can be suppressed.

[0091] The heat exchanger 503 according to the first modification of the second embodiment includes a flow rate adjustment valve 564 that adjusts the ratio of the refrigerant flow rates of the two heat exchanger sections 503 a and 503 b. The two heat exchanger sections 503 a and 503 b have different capacities.

[0092] In this way, in a configuration in which the ratio of refrigerant flow rates between heat exchanger section 503a and heat exchanger section 503b is different, there is a tendency for the refrigerant flow rate and dryness to vary greatly. However, in the heat exchanger 503 disclosed herein, a refrigerant distributor 30 with liquid level fluctuation resistance is provided in each heat exchanger section 503a, 503b, thereby preventing deterioration of refrigerant distribution.

[0093] In the third embodiment, each heat exchanger section 403a, 403b is defined as having the same configuration as the heat exchanger 3 in the first embodiment, but may also have the same configuration as the heat exchanger 303, the heat exchanger 303a, or the heat exchanger 303b in the second embodiment.

[0094] REFRIGERATED SYMBOLS 1 Compressor, 2 Flow switching device, 3 Heat exchanger, 4 Fan, 5 Pressure reducing device, 6 Indoor heat exchanger, 7 Fan, 8 Accumulator, 10 Outdoor unit, 11 Indoor unit, 12 Indoor unit, 26 Refrigerant piping, 27 Refrigerant piping, 30 Refrigerant distributor, 31 Heat transfer tube, 32 Fin, 33 Inner tube, 34 Outer tube, 34a Outer tube section, 34b Outer tube section, 35 Refrigerant outflow hole, 36 Cap, 40 Gas header, 41 Refrigerant outflow tube, 61 First partition, 62 Second partition, 63 Refrigerant inflow tube, 100 Air conditioning device, 130 Refrigerant distributor, 133 Inner tube, 134 Outer tube, 230 Refrigerant distributor, 233 Inner tube, 233a Inner tube top surface, 233b Inner tube front surface, 233c Inner tube rear surface, 233d Inner tube lower surface, 234 Outer tube, 234a Outer tube upper surface, 234d Outer tube lower surface, 303 Heat exchanger, 303a Heat exchanger, 303b Heat exchanger, 330 Refrigerant distributor, 330a Refrigerant distributor, 330b Refrigerant distributor, 333 Inner tube, 333a Inner tube, 333b Inner tube, 334 Outer pipe, 334e End, 337 Inflow part, 337a Inflow part, 337b Inflow part, 338 Extension part, 339 Valve, 362 Inflow part, 403 Heat exchanger, 403a Heat exchanger part, 403b Heat exchanger part, 463a Refrigerant inflow pipe, 463b Refrigerant inflow pipe, 463c Connection pipe, 463d Upstream branch, 503 Heat exchanger, 503a Heat exchanger section, 503b heat exchanger section, 563a refrigerant inlet pipe, 563b refrigerant inlet pipe, 563c connecting pipe, 563d upstream branch section, 564 flow control valve, AL liquid level fluctuation, As flow path cross-sectional area, C structural section, C structural section, Di inner diameter, G gap, P1 path, P2 path, RL liquid level capture area, RL liquid level capture area, S1 mixing space, X arrow, Y arrow, Z arrow, Φ optimal angle, ΦDo liquid level angle, ΦDs liquid level angle, θ angle, φo opening diameter.

Claims

1. A heat exchanger comprising at least one heat exchanger section including a plurality of heat transfer tubes and a refrigerant distributor extending in a horizontal direction and distributing a refrigerant to the plurality of heat transfer tubes, the refrigerant distributor having a structural part provided upstream or upstream of the refrigerant distributor in the flow direction of the refrigerant when functioning as an evaporator, the refrigerant distributor having an outer tube through which the refrigerant flows and to which a plurality of heat transfer tubes are connected at predetermined intervals, and an inner tube through which the refrigerant flows and disposed on the inner periphery of the outer tube, the inner tube having a plurality of refrigerant outlet holes for allowing the refrigerant flowing therethrough to flow out into a space between the outer tube and the inner tube, the number of the plurality of refrigerant outlet holes provided in the inner tube satisfies (Nt-1) / 6≦No<(Nt-1), where the number of holes is defined as No and the number of the plurality of heat transfer tubes is defined as Nt, and the structural part causes the state of the refrigerant flowing inside the inner tube to be in an underdeveloped state of a gas-liquid two-phase flow when functioning as an evaporator. heat exchanger.

2. A heat exchanger as described in claim 1, wherein the plurality of refrigerant outlet holes are arranged in the extension direction of the inner tube so that the number of holes per vertical cross section perpendicular to the extension direction of the inner tube is one or less.

3. The opening diameter of each of the plurality of refrigerant outlet holes is defined as Φo and the flow passage cross-sectional area of ​​the inner tube is defined as As, and the opening diameter of each of the plurality of refrigerant outlet holes is defined as Φo and the flow passage cross-sectional area of ​​the inner tube is defined as As. －１．２５ <Φo<1.1287×As ０．５ The heat exchanger according to claim 1 or 2, which satisfies the above.

4. A heat exchanger as claimed in any one of claims 1 to 3, wherein each of the plurality of refrigerant outlet holes has an elongated shape with the vertical dimension being greater than the horizontal dimension.

5. A heat exchanger as claimed in any one of claims 1 to 4, wherein the shape of a vertical cross section perpendicular to the extension direction of the inner tube is a horizontally elongated shape in which the dimension in the horizontal direction perpendicular to the extension direction is greater than the dimension in the vertical direction.

6. A heat exchanger as claimed in claim 5, wherein said inner tube is a wide D-shaped tube whose dimension in the horizontal direction perpendicular to said extension direction is greater than its dimension in the vertical direction.

7. A heat exchanger according to any one of claims 1 to 6, wherein the structural portion is a mixing space provided in the outer tube of the refrigerant distributor.

8. A heat exchanger as claimed in any one of claims 1 to 6, wherein the structural portion is an inlet portion extending linearly from the inner pipe of the refrigerant distributor to the outside of the outer pipe, and satisfies L < 20 x Di, where Di is the inner diameter of the inner pipe and L is the length of the inlet portion.

9. A heat exchanger as claimed in any one of claims 1 to 8, wherein the at least one heat exchanger section includes two heat exchanger sections, and the two heat exchanger sections are connected to each other upstream of the structural section of the two heat exchanger sections.

10. The heat exchanger according to claim 9, further comprising a flow rate adjusting valve for adjusting a ratio of refrigerant flow rates of the two heat exchanger sections, the two heat exchanger sections having different volumes.

11. The heat exchanger according to any one of claims 1 to 10, wherein the refrigerant is any one of R1234yf, R1234ze, R32, and R290, or a mixed refrigerant of two or more of these, or a mixed refrigerant of any one of these with another refrigerant, a mixed refrigerant containing R1132(E), or a mixed refrigerant containing R1123.

12. The heat exchanger according to any one of claims 1 to 10, wherein the refrigerant is a mixed refrigerant of two or more of R516A, R445A, R444A, R454C, R444B, R454A, R455A, R457A, R459B, R452B, R454B, R447B, R447A, R446A, R459A, R474A, and R479A.

13. A heat exchanger as claimed in any one of claims 1 to 12, comprising a sealing structure for sealing the end of the inner tube in the extension direction, the sealing structure being a crushed end of the inner tube itself or a cap covering the end.

14. An air conditioner comprising a heat exchanger according to any one of claims 1 to 13.

Images