Heat exchanger and air conditioner

Abstract

A heat exchanger according to the present disclosure comprises: a plurality of heat transfer tubes arranged in parallel in a first direction; and a refrigerant distributor to which the plurality of heat transfer tubes are connected, which extends in the first direction, and which has a connection port to which a refrigerant pipe is connected. The refrigerant distributor comprises: an outer tube to which the plurality of heat transfer tubes are connected and which extends in the first direction; an inner tube which is housed inside the outer tube and which extends in the first direction; and a partition plate that partitions a first space formed between the inner and outer tubes into a plurality of areas in the first direction. The inner tube has distribution holes that connect the first space with a second space formed inside the inner tube. The second space is connected to the connection port at an end of the inner tube in the first direction, and two areas adjacent to each other in the first direction from among the plurality of areas are connected to each other by an aperture portion.

Description

Heat exchanger and air conditioning device

[0001] The present disclosure relates to a heat exchanger and an air conditioner having a refrigerant distributor with a double-pipe structure including an inner pipe and an outer pipe.

[0002] A known heat exchanger used in a conventional air conditioner is a refrigerant distributor that distributes refrigerant using a double-walled piping structure with an inner pipe and an outer pipe. In such a refrigerant distributor using a double-walled piping structure, a refrigerant outlet hole is provided at the bottom of the inner pipe. The refrigerant flowing out from the refrigerant outlet hole is sprayed into the space between the inner pipe and the outer pipe, and flows from the outer pipe into the heat transfer pipe, where heat exchange with air takes place.

[0003] In a heat exchanger equipped with such a refrigerant distributor, two-phase refrigerant flows into the refrigerant distributor and exits the inner tube through the refrigerant outlet holes. The two-phase refrigerant inside the inner tube is stirred before flowing out of the refrigerant outlet holes into the space between the inner and outer tubes, resulting in a nearly homogeneous refrigerant. This results in a uniform refrigerant flow ratio among the multiple heat transfer tubes, improving the heat exchange performance of the heat exchanger. Furthermore, by providing multiple outer tubes for one inner tube, the refrigerant distributor is configured to form multiple spaces between the inner and outer tubes, thereby reducing the volume (see, for example, Patent Document 1).

[0004] International Publication No. 2019 / 239445

[0005] However, heat exchangers with double-pipe refrigerant distributors have a problem in that when gas-phase refrigerant flows from the heat transfer tubes into the double-pipe refrigerant distributor, oil that accumulates in the spaces between the multiple inner and outer pipes is difficult to remove. This accumulated oil causes uneven distribution of refrigerant to each of the multiple spaces between the inner and outer pipes in the refrigerant distributor.

[0006] 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 suppress oil stagnation in multiple areas provided between the inner tube and the outer tube of a refrigerant distributor.

[0007] The heat exchanger of the present disclosure comprises a plurality of heat transfer tubes arranged in parallel in a first direction, and a refrigerant distributor to which the plurality of heat transfer tubes are connected, extending in the first direction, and having a connection port to which a refrigerant pipe is connected, the refrigerant distributor comprising an outer tube to which the plurality of heat transfer tubes are connected and extending in the first direction, an inner tube housed inside the outer tube and extending in the first direction, and a partition plate that divides a first space formed between the inner tube and the outer tube into a plurality of regions in the first direction, the inner tube having a flow hole that connects the first space to a second space formed inside the inner tube, the second space being connected to the connection port at the end of the inner tube in the first direction, and two of the plurality of regions adjacent to each other in the first direction being connected to each other by an opening.

[0008] The air conditioning apparatus of the present disclosure includes the above-described heat exchanger, wherein the plurality of heat transfer tubes extend in the direction of gravity, and the refrigerant distributor is positioned lower than the plurality of heat transfer tubes in the direction of gravity.

[0009] The heat exchanger and air conditioning apparatus of the present disclosure connect multiple regions of the first space together, thereby allowing accumulated oil to circulate toward the connection port, thereby eliminating imbalances in the accumulated oil and also eliminating imbalances in the flowing in refrigerant.

[0010] Fig. 2 is an example of a refrigerant circuit diagram of the air conditioning apparatus 100 according to Embodiment 1. Fig. 3 is an explanatory diagram of the peripheral structure of the refrigerant distributor 30 of the outdoor heat exchanger 3 of the air conditioning apparatus 100 according to Embodiment 1. Fig. 4 is an explanatory diagram of the cross-sectional structure of the D-D section in Fig. 2. Fig. 5 is an explanatory diagram of the cross-sectional structure of another example of the refrigerant distributor 30 shown in Fig. 3. Fig. 6 is an explanatory diagram of the cross-sectional structure of another example of the refrigerant distributor 30 shown in Fig. 3.

[0011] 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.

[0012] Embodiment 1. <Air Conditioning Apparatus 100> Fig. 1 is an example of a refrigerant circuit diagram of an air conditioning apparatus 100 pertaining to Embodiment 1. As shown in Fig. 1, 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 with one another. A refrigerant circulates inside the outdoor unit 10 and the multiple indoor units 11, 12, and 13. The air conditioning apparatus 100 is a multi-type air conditioning apparatus. Note that Embodiment 1 does not limit the number of indoor units 11, 12, and 13 that can be connected to the outdoor unit 10.

[0013] The air conditioning apparatus 100 has a refrigerant circuit in which a compressor 1, a four-way valve 2, an outdoor heat exchanger 3, an expansion valve 5, an indoor heat exchanger 6, and an accumulator 8 are connected by refrigerant piping 26 and refrigerant piping 27. In the outdoor heat exchanger 3 and the indoor heat exchanger 6, heat is exchanged between the refrigerant flowing therethrough and the air by the wind generated by the fan 4 and the fan 7, respectively.

[0014] During cooling operation, high-temperature, high-pressure gas refrigerant compressed by the compressor 1 flows through the four-way valve 2 and from a refrigerant pipe 26 connecting the four-way valve 2 and the outdoor heat exchanger 3 into the outdoor heat exchanger 3. The refrigerant that has flowed into the outdoor heat exchanger 3 exchanges heat with the air generated by the fan 4, and then flows out from a refrigerant pipe 27 connecting the outdoor heat exchanger 3 and the expansion valve 5. During heating operation, i.e., when the outdoor heat exchanger 3 functions as an evaporator, the refrigerant flows in the opposite direction to the refrigerant flow direction in the condenser.

[0015] <Outdoor Heat Exchanger 3> FIG. 2 is an explanatory diagram of the peripheral structure of the refrigerant distributor 30 of the outdoor heat exchanger 3 of the air conditioning apparatus 100 according to Embodiment 1. FIG. 3 is an explanatory diagram of the cross-sectional structure taken along the line D-D in FIG. 2. The outdoor heat exchanger 3 mounted on the outdoor unit 10 of the air conditioning apparatus 100 exchanges heat between the refrigerant and outside air drawn in through an air inlet by the fan 4. The structure of the outdoor unit 10 is not limited, but for example, the outdoor heat exchanger 3 is disposed along the side of the housing of the outdoor unit 10. The fan 4 is disposed in the upper part of the outdoor unit 10, near an air outlet formed on the top surface of the housing. Air flows in through the side of the housing that serves as the air inlet, passes through the outdoor heat exchanger 3, passes through the upper fan 4, and is blown out through the air outlet. Arrow a in FIG. 3 schematically represents air flowing through the outdoor unit 10.

[0016] As shown in FIG. 2 , the outdoor heat exchanger 3 includes a refrigerant distributor 30 and a plurality of heat transfer tubes 31. The plurality of heat transfer tubes 31 are flat tubes and are aligned in the x direction. The refrigerant distributor 30 extends in the x direction and includes a connection port 36 to which the refrigerant pipe 26 is connected at one end. Fins may be installed between the plurality of heat transfer tubes 31. A refrigerant distributor 30B is also connected to the other end of the plurality of heat transfer tubes 31. Note that the refrigerant distributor 30B connected to the other end of the plurality of heat transfer tubes 31 may have a structure different from that of the refrigerant distributor 30A shown in FIG. 2 . The refrigerant distributor 30 is arranged with its longitudinal direction oriented horizontally. The plurality of heat transfer tubes 31 are spaced apart, and one end of each is inserted into an insertion port 37 of the refrigerant distributor 30. As shown in FIG. 2 , the refrigerant distributor 30A is positioned lower than the plurality of heat transfer tubes 31 in the direction of gravity.

[0017] 2 , the refrigerant distributor 30 has a double-pipe structure including an inner pipe 33 and an outer pipe 34. The outer pipe 34 has a surface facing the z direction formed with a plurality of insertion ports 37, and a plurality of heat transfer pipes 31 are connected to the insertion ports 37. The plurality of heat transfer pipes 31 are connected to a first space 40 formed between the inner pipe 33 and the outer pipe 34. The first space 40 and the plurality of heat transfer pipes 31 are in communication, and the refrigerant flowing through the plurality of heat transfer pipes 31 flows into the first space 40.

[0018] The inner pipe 33 is arranged so that its pipe axis is along the x-direction. The inner pipe 33 has, for example, a hollow pipe structure, and at one end 42a, an end space 43 of the refrigerant distributor 30, which is connected to the connection port 36, communicates with a second space 42c, which is an internal space. In addition, a plurality of communication holes 35 are formed in the side surface of the inner pipe 33. The plurality of communication holes 35 are formed along the axial direction of the inner pipe 33, and communicate the second space 42c of the inner pipe 33 with the first space 40.

[0019] The gap formed between the inner tube 33 and the outer tube 34 is called a first space 40, and is divided into multiple regions 41A, 41B, and 41C in the x direction by partition plates 38A, 38B, 38C, and 38D. The partition plates 38A, 38B, 38C, and 38D may be collectively referred to as partition plates 38. Each of the multiple regions 41A, 41B, and 41C is surrounded by the partition plate 38, the inner surface of the outer tube 34, and the outer surface of the inner tube 33. Two adjacent regions 41A and 41B are separated by partition plate 38B, and two adjacent regions 41B and 41C are separated by partition plate 38C. Region 41A, located at the end, is separated from end space 43 by partition plate 38A. Region 41C, located at the other end, is separated from end space 44 by partition plate 38d.

[0020] The end space 43 and the plurality of regions 41A, 41B, and 41C are in communication with each other via the partition plate 38 or an opening 39 provided at the location where the partition plate 38 is installed.

[0021] Each of the plurality of regions 41A, 41B, and 41C communicates with the plurality of heat transfer tubes 31 and also communicates with the second space 42c of the inner tube 33 via the flow holes 35. In the first embodiment, three regions 41 connected to the plurality of heat transfer tubes 31 are formed, but the number may be two, or four or more.

[0022] In the refrigerant distributor 30 shown in Figure 2, one end 42a of the inner pipe 33 is located in the end space 43, and the other end 42b is located in the end space 44. The second space 42c of the inner pipe 33 is in communication with at least the end space 43, which is in communication with the connection port 36. The other end space 44 does not have to be in communication with the second space 42c of the inner pipe 33. Furthermore, the end 42b of the inner pipe 33 may be closed, and the refrigerant distributor 30 may not have a structure provided with the end space 44. The one end 42a of the inner pipe 33 is open, allowing refrigerant in the second space 42c to flow to the connection port 36.

[0023] 2 and 3 , the inner pipe 33 has flow holes 35, also referred to as orifice holes, formed at intervals on the side surface of the inner pipe 33. The flow holes 35 are formed directly below the heat transfer pipes 31 in the x direction. The flow holes 35 may also be provided so as to be positioned between the heat transfer pipes 31. By providing the flow holes 35 between the heat transfer pipes 31, it is possible to improve the refrigerant distribution performance when a gas-liquid two-phase refrigerant flows into the refrigerant distributor 30, compared to when the flow holes 35 are provided in the inner pipe 33 directly below the heat transfer pipes 31.

[0024] 3, the flow holes 35 are on the side surface of the inner tube 33 and open obliquely downward when the heat transfer tubes 31 are arranged so that their tube axes extend in the z direction. When a gas-liquid two-phase refrigerant flows into the inner tube 33, also called a shower pipe, the refrigerant exists in two states, namely, a gas phase and a liquid phase. In the first embodiment, the angle θ of the liquid level AL of the liquid phase refrigerant is ＡＬ A flow hole 35 is provided in the vicinity of the

[0025] 3 shows an example in which the flow holes 35 are provided at an angle θ with respect to the liquid level AL of the liquid-phase refrigerant. The angle θ at which the flow holes 35 are provided, which is the angle θ from the lower end of the inner pipe 33 to the position at which the flow holes 35 are located on a vertical line passing through the center of the inner pipe 33 as viewed from the center of the inner pipe 33, may be set in the range of 10°≦θ≦80°, for example.

[0026] More specifically, the angle at which the flow holes 35 are provided is determined by formula (1). Formula (1) is a prediction formula that reflects the experimental results of the inventors based on the Nusselt liquid film estimation formula. where x is the distance of the flow hole 35 projected onto a horizontal line passing through the center of the inner pipe 33 and perpendicular to the pipe extension direction, Ja is the Jacob number, Ga is the Galileo number, and Pr is the Ｌ is the liquid Prandtl number, ν Ｌ is the dynamic viscosity of the liquid, L is the inlet distance of the inner pipe, D is the inner diameter of the inner pipe, and Ga = gD ３ / ν Ｌ ２ , Ja=CpL / Δiv, CpL is the specific heat at constant pressure, Δiv is the latent heat, and L<5D. Each state quantity and physical property value is estimated based on the pressure of the refrigerant flowing into the refrigerant distributor 30.

[0027] When the liquid phase of the refrigerant flowing through the inner pipe 33 is a semi-annular flow and the circulation holes 35 are provided at the lowest part of the inner pipe 33 (θ=0°), the amount of liquid refrigerant distributed through each of the multiple circulation holes 35 provided in the inner pipe 33 along the x direction is greater on the side closer to the connection port 36 than on the side farther away.

[0028] When the flow holes 35 are provided at a position of θ=90° on the inner pipe 33, the amount of liquid refrigerant distributed through each of the multiple flow holes 35 provided in the inner pipe 33 along the x direction is smaller on the side closer to the connection port 36 than on the side farther away.

[0029] On the other hand, as shown in FIG. 3 , in the first embodiment, the flow hole 35 is provided near the liquid level AL of the inner pipe 33. Only one flow hole 35 is provided in the vertical cross section of the inner pipe 33. When the flow hole 35 is provided at the position of the liquid level AL of the inner pipe 33, the amount of liquid refrigerant distributed to each of the plurality of flow holes 35 provided in the inner pipe 33 along the x direction is likely to be uniform, even when the refrigerant flow pattern is a semi-annular flow. In the air conditioning apparatus 100 according to the first embodiment, the position of the flow hole 35 is not limited. However, as shown in FIG. 3 , by arranging the flow hole 35 at a position where θ is 10°≦θ≦80° in the cross section perpendicular to the pipe axis of the inner pipe 33, the gas and liquid in the inner pipe 33 can be distributed relatively uniformly to the space formed between the outer pipe 34 and the inner pipe 33.

[0030] (Outer Tube 34) The outer tube 34 is a hollow tube with closed end faces 34a and 34b on both sides in the x direction, and includes a first member 34f that forms the outer shell on the side to which the heat transfer tube 31 is connected, and a second member 34e that is arranged to close the open portion of the first member 34f. As shown in Fig. 3, the first member 34f has a U-shaped cross section perpendicular to the x axis, and the second member 34e is fitted into and joined to the open portion of the U to form a hollow tube.

[0031] (Partition Plate 38) The partition plate 38 is inserted into and joined to the inside of the first member 34f of the outer pipe 34. In the refrigerant distributor 30 shown in Fig. 3, an opening 39 is formed between a lower edge 38a of the partition plate 38 and the second member 34e. The openings 39 are formed at the lower ends of the multiple regions 41A, 41B, and 41C in the z direction, in other words, are located at the portions farthest from the heat transfer tubes 31. When the refrigerant distributor 30 is arranged with the z direction facing vertically upward, oil remaining in the multiple regions 41A, 41B, and 41C can flow through the openings 39.

[0032] 3, the second member 34e is disposed so as to abut against the partition plate 38, but this is not limiting, and the second member 34e may be configured to abut against the end 34fa of the first member 34f. At least the first member 34f has a structure in which the opposite side in the z direction is open in cross section, and is configured so that the heat transfer tube 31 is connected to one end on the z direction side, and the hollow outer tube 34 is configured by closing the open portion with another member.

[0033] Fig. 4 is an explanatory diagram of a cross-sectional structure of another example of the refrigerant distributor 30 shown in Fig. 3. In Fig. 4, the partition plate 38 has an opening 39 at a position spaced apart from the second member 34e in the z direction. The opening 39 may be located in any part of the partition plate 38. However, in terms of circulating the oil remaining in the region 41, it is desirable that the opening 39 be located at least lower in the z direction than the circulation holes 35, and further lower than the inner pipe 33.

[0034] Fig. 5 is an explanatory diagram of the cross-sectional structure of another example of the refrigerant distributor 30 shown in Fig. 3. The arrows in Fig. 5 schematically represent the flow of refrigerant. In the example shown in Fig. 5, the partition plate 38 has a notch 38b formed in a portion of the edge 38a, and the notch 38b and the second member 34e form an opening 39.

[0035] Alternatively, the opening 39 may be formed by providing a groove on the inner surface of the first member 34f or the second member 34e, or may be in the form of a slit provided in the partition plate 38, or the like.

[0036] (Operation) FIG. 2B is a diagram showing a schematic diagram of the position of the heat exchanger 3 in the x direction and the tendency of the pressure distribution of the refrigerant at each part of the refrigerant distributor 30. As shown in FIG.

[0037] Curve A shows the distribution of the outlet pressure of the refrigerant distributor 30B, which serves as a liquid header when the heat exchanger 3 functions as an evaporator. The outlet pressure of the refrigerant distributor 30B is, in other words, the pressure at the inlets of the heat transfer tubes 31. The outlet pressure of the refrigerant distributor 30B tends to decrease from one end, where the refrigerant flows into the refrigerant distributor 30B, to the other end.

[0038] Curve B represents the outlet pressure of the heat transfer tubes 31, and the internal pressure of each of the regions 41A, 41B, and 41C. The internal pressure of the region 41C tends to be low, corresponding to the pressure distribution on the liquid header side. Oil stagnation also occurs in the regions 41A, 41B, and 41C. The region 41C farthest from the connection port 36 has low internal pressure, and oil tends to be difficult to discharge.

[0039] Curve C shows the pressure distribution in the second space 42c, which is the space inside the inner pipe 33. In the second space 42c, a plurality of flow holes 35 are arranged along the pipe axis, so the pressure tends to decrease from the deep side, which is upstream, toward the end 42a, which is the outlet.

[0040] Because each section of the refrigerant distributor 30 has the above-described pressure distribution tendency, the pressure difference ΔP between the second space 42c inside the inner tube 33 and the region 41C is small, suppressing the flow of refrigerant and oil and facilitating oil accumulation. As oil accumulation increases, the volume within the region 41 decreases, increasing flow resistance and reducing the refrigerant flow rate. Therefore, the heat transfer tubes 31 connected to the region 41C where oil accumulation is high tend to have reduced heat exchange efficiency, resulting in a low heat exchange capacity for the entire heat exchanger 3. When the temperature distribution of the heat exchanger 3 was measured using an evaporator, the temperature in the region corresponding to the region 41C tended to be higher when the regions 41 were not connected to each other. In other words, when oil cannot be discharged as in the refrigerant distributor 30 according to the first embodiment, the refrigerant evaporation was insufficient in the heat transfer tubes 31 connected to the region 41C where refrigerant flow is low.

[0041] However, in the refrigerant distributor 30 of the heat exchanger 3 according to the first embodiment, the plurality of regions 41A, 41B, and 41C are connected to each other by the openings 39, so that the accumulated oil can be moved toward the connection port 36. This prevents oil from accumulating in the region 41C, reduces flow resistance within the region 41C, and promotes the flow of the refrigerant. This also ensures proper heat exchange in the heat transfer tubes 31 connected to the region 41C, allowing the heat exchanger 3 to exhibit the expected heat exchange performance.

[0042] The refrigerant distributor 30A of the heat exchanger 3 according to the first embodiment is disposed below the heat transfer tubes 31 in the direction of gravity, and oil tends to accumulate at the bottom. Furthermore, as shown in FIG. 5 , the heat exchanger 3 according to the first embodiment may also have a configuration in which the inlet-side refrigerant distributor 30B is disposed below the heat transfer tubes 31, and the structure of the refrigerant distributor 30B may be similar to that of the refrigerant distributor 30A. This configuration ensures the refrigerant distributor 30's refrigerant distribution performance even when a refrigerant containing a liquid-phase refrigerant flows in, and also suppresses oil accumulation when a gas-phase refrigerant flows in, as described with reference to FIG. 2 . However, the other refrigerant distributor 30B may also be disposed above the heat transfer tubes 31, and in this case, the structure may be different from that of the refrigerant distributor 30A.

[0043] Furthermore, in the first embodiment, the outdoor heat exchanger 3 is used as an example, but the structure of the refrigerant distributor 30 can also be adopted for an indoor heat exchanger, and oil accumulation in the refrigerant distributor from which the gas phase refrigerant flows out can be suppressed.

[0044] The above describes the embodiments, but these are presented as examples and are not intended to limit the scope of the claims. The embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the embodiments. These embodiments and their modifications are included within the scope and spirit of the present disclosure.

[0045] REFERENCE SIGNS LIST 1 Compressor, 2 Four-way valve, 3 (Outdoor) heat exchanger, 4 Fan, 5 Expansion valve, 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, 30A Refrigerant distributor, 30B Refrigerant distributor, 31 Heat transfer tube, 33 Inner tube, 34 Outer tube, 34a End surface, 34b End surface, 34e Second member, 34f First member, 34fa End, 35 Flow hole, 36 Connection port, 37 Insertion port, 38 Partition plate, 38A Partition plate, 38B Partition plate, 38C Partition plate, 38D Partition plate, 38a Edge, 38b Notch, 38d Partition plate, 39 Opening, 40 First space, 41 area, 41A area, 41B area, 41C area, 42a end, 42b end, 42c second space, 43 end space, 44 end space, 100 air conditioning device.

Claims

1. a plurality of heat transfer tubes arranged in parallel in a first direction; a refrigerant distributor to which the plurality of heat transfer tubes are connected, extending in the first direction, and having a connection port to which a refrigerant pipe is connected; The refrigerant distributor comprises: an outer tube to which the plurality of heat transfer tubes are connected and which extends in the first direction; an inner tube housed inside the outer tube and extending in the first direction; a partition plate that divides a first space formed between the inner tube and the outer tube into a plurality of regions in the first direction, The inner tube is a communication hole that communicates a second space formed inside the inner pipe with the first space, The second space is an end of the inner pipe in the first direction communicates with the connection port; Two regions adjacent to each other in the first direction among the plurality of regions are They communicate with each other through openings, The outer tube is a first member having a structure in which, in a cross section perpendicular to the first direction, one end is connected to the plurality of heat transfer tubes and the other end is open; a second member joined to close the other open end of the first member, The partition plate is the first member is joined to a side to which the plurality of heat transfer tubes are connected, The opening is a gap formed between an inner surface of the second member and an edge of the partition plate located on the other end side where the first member is open.

2. The opening is The heat exchanger according to claim 1 , wherein the heat exchanger is provided so as to be located below the flow holes in the direction of gravity.

3. The plurality of regions are: an end region located at an end in the first direction, The end region is The heat exchanger according to claim 1 , wherein the connection port and the second space are in communication with each other.

4. The partition plate is A notch is formed on an edge located on the other open end side of the first member. The heat exchanger of claim 1 .

5. A heat exchanger according to any one of claims 1 to 4, The plurality of heat transfer tubes include: It extends in the direction of gravity, The refrigerant distributor comprises: An air conditioning apparatus arranged lower than the plurality of heat transfer tubes in the direction of gravity.