Heat exchanger and refrigeration cycle device

Abstract

The first header (21) of the heat exchanger (1) has: a first flow path (57) for flowing refrigerant from one end portion (41) side to the other end portion (42) side in the length direction (25); a second flow path (58) for flowing refrigerant from the other end portion (42) side to the one end portion (41) side; a first return flow path (51) for flowing refrigerant from the first flow path (57) to the second flow path (58) on the other end portion (42) side; a second return flow path (52) for flowing refrigerant from the second flow path (58) to the first flow path (57) on the one end portion (41) side; and an inflow port (61) for flowing refrigerant from an inflow space (43) to the one end portion (41) side of the first flow path (57), the first flow path (57) communicates with the second header (22) via a plurality of heat transfer pipes (23), and the first flow path (57) is formed such that, when the heat exchanger (1) functions as an evaporator, the degree of superheat of refrigerant flowing from the heat transfer pipe located farthest from the inflow space (43) among the plurality of heat transfer pipes (23) to the second header (22) is 0 degrees.

Description

Technical Field

[0001] The technology disclosed herein relates to a heat exchanger and a refrigeration cycle device. Background Technology

[0002] As a heat exchanger for exchanging heat between air and refrigerant, a heat exchanger with a manifold is known, which splits the gas-liquid two-phase refrigerant into multiple heat transfer tubes (Patent Document 1). Inside the manifold, multiple insertion spaces at one end of each of the multiple heat transfer tubes are connected to a circulation path. The circulation path includes a first flow path, a second flow path, a first reversing flow path connecting the upper end of the first flow path to the upper end of the second flow path, and a second reversing flow path connecting the lower end of the second flow path to the lower end of the first flow path. The gas-liquid two-phase refrigerant flowing into the manifold circulates within the circulation path as follows: it rises in the first flow path, flows from the upper end of the first flow path to the upper end of the second flow path via the first reversing flow path, and falls in the second flow path, flowing from the lower end of the second flow path to the lower end of the first flow path via the second reversing flow path. This heat exchanger prevents refrigerant from stagnating in the upper part of the first flow path by circulating the gas-liquid two-phase refrigerant flowing into the manifold within the circulation path. It also allows the gas-liquid two-phase refrigerant to be appropriately distributed to multiple heat transfer tubes so that the flow rates of the refrigerant flowing to each heat transfer tube are equal.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2019-056544 Summary of the Invention

[0004] However, in this type of heat exchanger, when the flow rate of the gas-liquid two-phase refrigerant circulating in the circulation path is low, the liquid refrigerant may not be able to rise in the first flow path, resulting in a decrease in the proportion of liquid refrigerant flowing into the upper heat transfer tube among the multiple heat transfer tubes. When the amount of liquid refrigerant flowing into the multiple heat transfer tubes is uneven, in the upper heat transfer tube with less liquid refrigerant flowing in, the liquid refrigerant will evaporate completely during its flow. On the other hand, in the lower heat transfer tube with more liquid refrigerant flowing in, the liquid refrigerant will not evaporate completely during its flow, and some liquid refrigerant will flow out of the heat transfer tube. This leads to the following problem: with some heat transfer tubes experiencing complete liquid refrigerant evaporation while others have incompletely evaporated liquid refrigerant flowing out, the evaporation performance of the heat exchanger as an evaporator will be reduced.

[0005] The disclosed technology was made in view of the above aspects, and its purpose is to provide a heat exchanger and refrigeration cycle device to improve the evaporation performance of the heat exchanger that functions as an evaporator.

[0006] One embodiment of the heat exchanger disclosed herein includes: a plurality of heat transfer tubes; a first manifold; and a second manifold, the first manifold having: a first flow path for allowing refrigerant to flow from one end side to another end side along the length of the first manifold; a second flow path for allowing refrigerant to flow from the other end side to the first end side; a first reversal flow path for allowing refrigerant to flow from the first flow path to the second flow path at the other end side; a second reversal flow path for allowing refrigerant to flow from the second flow path to the first flow path at the first end side; an inflow space for refrigerant to flow into; and an inlet for allowing refrigerant to flow from the inflow space to the end of the first flow path at the first end side, the first flow path being connected to the second manifold via the plurality of heat transfer tubes, wherein, in this heat exchanger, the first flow path is configured such that, when the heat exchanger functions as an evaporator, the superheat of the refrigerant flowing into the second manifold from the heat transfer tube located furthest from the inflow space among the plurality of heat transfer tubes is 0 degrees.

[0007] The disclosed heat exchanger and refrigeration cycle device can improve the evaporation performance of the heat exchanger that functions as an evaporator. Attached Figure Description

[0008] Figure 1 This is a refrigerant circuit diagram of an air conditioner equipped with a heat exchanger according to an embodiment.

[0009] Figure 2 This is a front view showing the heat exchanger in the embodiment.

[0010] Figure 3 This is a top view showing the heat exchanger in the embodiment.

[0011] Figure 4 This is a cross-sectional view of the heat transfer tubes of the heat exchanger in the embodiment.

[0012] Figure 5 This is an exploded perspective view showing the internal structure of the expansion valve side manifold of the heat exchanger in the embodiment. Detailed Implementation

[0013] The heat exchanger and refrigeration cycle apparatus of the embodiments disclosed in this application will now be described in detail with reference to the accompanying drawings. Furthermore, the technology disclosed herein is not limited to the following description. Additionally, in the following description, the same symbols are used to refer to the same structural elements, and repeated descriptions are omitted.

[0014] Example like Figure 1 As shown, the heat exchanger in this embodiment is the outdoor heat exchanger 1 installed in the air conditioner 10. Figure 1This is a refrigerant circuit diagram of an air conditioner 10 equipped with an outdoor heat exchanger 1 according to an embodiment. The air conditioner 10 includes an outdoor unit 2 and an indoor unit 3. The outdoor unit 2 is located outdoors. The indoor unit 3 is located inside a room.

[0015] Air conditioner 10 includes a refrigerant circuit 4 (refrigeration cycle device). The refrigerant circuit 4 includes a compressor 5, a four-way valve 6, an indoor heat exchanger 7, an expansion valve 8, and an outdoor heat exchanger 1. The compressor 5 is located inside the outdoor unit 2. A suction pipe 11 and a discharge pipe 12 are connected to the compressor 5. The compressor 5 compresses the refrigerant supplied through the suction pipe 11 and discharges the refrigerant at a flow rate corresponding to the compressor speed to the discharge pipe 12. The higher the compressor speed, the greater the flow rate of refrigerant discharged to the discharge pipe 12 per unit time.

[0016] A four-way valve 6 is located inside the outdoor unit 2. The four-way valve 6 connects to the suction pipe 11 and the discharge pipe 12, is connected to the outdoor heat exchanger 1 via refrigerant piping 14, and is connected to the indoor heat exchanger 7 via refrigerant piping 15. The four-way valve 6 switches the refrigerant circuit 4 between heating and cooling cycles. When the refrigerant circuit 4 is switched to heating cycle, the discharge pipe 12 is connected to the indoor heat exchanger 7 via the four-way valve 6, and the suction pipe 11 is connected to the outdoor heat exchanger 1 via the four-way valve 6. When the refrigerant circuit 4 is switched to cooling cycle, the discharge pipe 12 is connected to the outdoor heat exchanger 1 via the four-way valve 6, and the suction pipe 11 is connected to the indoor heat exchanger 7 via the four-way valve 6.

[0017] An indoor heat exchanger 7 is located inside the indoor unit 3. One refrigerant inlet / outlet of the indoor heat exchanger 7 is connected to the expansion valve 8 via refrigerant piping 16, and the other refrigerant inlet / outlet is connected to the four-way valve 6 via refrigerant piping 15 as described above. The indoor unit 3 causes air from the room in which the indoor unit 3 is located to flow through the indoor heat exchanger 7 by rotating a fan (not shown), where it exchanges heat with the refrigerant, and then blows the air after heat exchange into the room. The expansion valve 8 is located inside the outdoor unit 2. The expansion valve 8 is connected to the outdoor heat exchanger 1 via refrigerant piping 17. The air conditioner 10 adjusts the amount of refrigerant flowing through the indoor heat exchanger 7 according to the required air conditioning capacity of the indoor unit 3 by adjusting the opening of the expansion valve 8.

[0018] Outdoor unit 2 includes an outdoor fan 18. The outdoor fan 18 is located inside outdoor unit 2. The outdoor fan 18 blows outdoor air to the ventilation space 19 inside outdoor unit 2. When outdoor unit 2 is properly installed, the outdoor fan 18 directs the airflow in a roughly horizontal direction 20. An outdoor heat exchanger 1 is located inside and fixed to outdoor unit 2, allowing air flowing through the ventilation space 19 to pass through the outdoor heat exchanger 1. The outdoor heat exchanger 1 facilitates heat exchange between the refrigerant flowing through it and the air flowing through the ventilation space 19.

[0019] Figure 2 This is a front view showing the outdoor heat exchanger 1 of the embodiment. The outdoor heat exchanger 1 includes an expansion valve side manifold 21 (first manifold), a compressor side manifold 22 (second manifold), multiple heat transfer tubes 23, and multiple fins 24. The expansion valve side manifold 21 is formed in a cylindrical shape, and is configured such that the extension direction of the expansion valve side manifold 21, i.e., the manifold length direction 25 (length direction), is perpendicular to the bottom surface of the outdoor unit 2 (not shown), and the expansion valve side manifold 21 is fixed to the outdoor unit 2. A refrigerant pipe 17 is connected to the expansion valve side manifold 21, and the expansion valve 8 is connected to the expansion valve side manifold 21 via the refrigerant pipe 17.

[0020] The compressor-side manifold 22 is cylindrical, configured such that its extension direction is parallel to the length direction 25, and it is fixed to the outdoor unit 2. A flow distribution space is formed inside the compressor-side manifold 22. The refrigerant piping 14 is connected to the compressor-side manifold 22 so that the four-way valve 6 is connected to the flow distribution space via the refrigerant piping 14.

[0021] like Figure 2 and Figure 3 As shown, multiple heat transfer tubes 23 are configured such that the extension direction of the heat transfer tubes, i.e., the length direction 26 of the heat transfer tubes, is orthogonal to the length direction 25 of the manifold, and are arranged at equal intervals along the length direction 25 of the manifold. One end of each of the multiple heat transfer tubes 23 is connected to the expansion valve side manifold 21. The other end of each of the multiple heat transfer tubes 23 is connected to the compressor side manifold 22. By connecting the two ends of the multiple heat transfer tubes 23 to the expansion valve side manifold 21 and the compressor side manifold 22 respectively, the multiple heat transfer tubes 23 are fixed to the expansion valve side manifold 21 and the compressor side manifold 22, and the outdoor heat exchanger 1 is fixed to the outdoor unit 2 through the expansion valve side manifold 21 and the compressor side manifold 22.

[0022] Multiple fins 24 are formed into flat plates. Figure 3 This is a top view showing the outdoor heat exchanger 1 of the embodiment. Multiple fins 24 are configured perpendicular to the length direction 26 of the heat transfer tubes (parallel to the ventilation direction 20) and are arranged at equal intervals along the length direction 26 of the heat transfer tubes. The multiple fins 24 are fixed to multiple heat transfer tubes 23 for thermal connection.

[0023] like Figure 4 As shown, each of the multiple heat transfer tubes 23 is formed in a flat shape. Figure 4 This is a cross-sectional view of the heat transfer tube 23 of the outdoor heat exchanger 1 in this embodiment. Multiple flow paths 33 are formed inside the heat transfer tube 23, arranged along the ventilation direction 20. By connecting the other ends of the multiple heat transfer tubes 23 to the compressor-side manifold 22, the multiple flow paths 33 are connected to the distribution space of the compressor-side manifold 22.

[0024] Figure 5This is an exploded perspective view showing the internal structure of the expansion valve side manifold 21 of the outdoor heat exchanger 1 according to an embodiment. The expansion valve side manifold 21 includes multiple plate-shaped components 71 to 76, all of which are rectangular in shape. The multiple plate-shaped components 71 to 76 are stacked and joined together, with the stacking direction being approximately parallel to the length direction 26 of the heat transfer tube. The multiple plate-shaped components 71 to 76 include a refrigerant piping side plate-shaped component 71, a heat transfer tube side plate-shaped component 72, multiple circulating flow path plate-shaped components 73, multiple reversing flow path plate-shaped components 74, multiple insertion space plate-shaped components 75, and an inlet port plate-shaped component 76. Figure 5 As shown, the plate-shaped components are stacked from upstream to downstream in the inlet direction 48 (the direction in which the refrigerant flows in the outdoor heat exchanger 1 when it functions as an evaporator), in the following order: refrigerant piping side plate-shaped component 71, multiple reversible flow path plate-shaped components 74, multiple circulating flow path plate-shaped components 73, inlet hole plate-shaped component 76, multiple insertion space plate-shaped components 75, and heat transfer tube side plate-shaped component 72. Furthermore, in the following description, when referring to components formed by joining multiple plate-shaped components 71 to 76, the term "multiple" may be omitted.

[0025] Each circulating flow path is formed with plate-shaped components 73 having the same shape as each other (in this embodiment, Figure 5 The three circulating flow path plate-shaped components 73 shown are of the same shape. A reversing flow path plate-shaped component 74 is disposed between the circulating flow path plate-shaped component 73 and the refrigerant piping side plate-shaped component 71. Each insertion space plate-shaped component 75 is formed to be the same shape as the others (in this embodiment, ...). Figure 5 The three plate-shaped members 75 for inserting spaces shown are of the same shape. The plate-shaped member 75 for inserting spaces is disposed between the plate-shaped member 76 for inlet holes and the plate-shaped member 72 for the heat transfer tube side. The plate-shaped member 76 for inlet holes is disposed between the plate-shaped member 73 for the circulation path and the plate-shaped member 75 for inserting spaces.

[0026] Furthermore, in the following description, the end face of the lower end of the expansion valve side manifold 21 along the length direction 25 is referred to as one end 41, and the end face of the opposite side of the upper end of the expansion valve side manifold 21 is referred to as the other end 42.

[0027] The expansion valve side manifold 21 is formed by stacking the above-described plate-shaped components from upstream to downstream in the inlet direction 48 in the following order: refrigerant piping side plate-shaped component 71, reversible flow path plate-shaped component 74, circulating flow path plate-shaped component 73, inlet hole plate-shaped component 76, insertion space plate-shaped component 75, and heat transfer tube side plate-shaped component 72. This creates an inflow space 43, a refrigerant piping through hole 44, a circulating flow path 45, an inlet 61, multiple insertion spaces 46, multiple heat transfer tube through holes 47, and multiple inlet holes 62 inside the expansion valve side manifold 21. The inflow space 43 is located in the region inside the expansion valve side manifold 21 near one end 41. The inflow space 43 is formed by inflow space holes 83 formed on each circulating flow path plate-shaped component 73.

[0028] The refrigerant piping through-hole 44 is formed by a refrigerant piping hole 77 formed on the refrigerant piping side plate-like component 71 and a refrigerant piping hole 78 formed on the reversible flow path plate-like component 74. Therefore, the refrigerant piping through-hole 44 is positioned upstream of the inflow space 43 in the inlet direction 48. The refrigerant piping 17 passes through the refrigerant piping through-hole 44, and the inflow space 43 is connected to the expansion valve 8 via the refrigerant piping 17.

[0029] The circulating flow path 45 is formed by a circulating flow path plate-shaped member 73 and a reversing flow path plate-shaped member 74, and includes a first flow path 57, a second flow path 58, a first reversing flow path 51, and a second reversing flow path 52. The first flow path 57 is formed by first flow path holes 84 formed on a plurality of circulating flow path plate-shaped members 73. The second flow path 58 is formed by second flow path holes 85 formed on a plurality of circulating flow path plate-shaped members 73. Therefore, the first flow path 57 and the second flow path 58 are arranged along the manifold length direction 25 with the inflow space 43 and are positioned above the inflow space 43. The first flow path 57 is formed along a straight line parallel to the manifold length direction 25. The second flow path 58 is positioned on the windward side of the first flow path 57 in the ventilation direction 20 and is formed along another straight line parallel to the manifold length direction 25.

[0030] The first reversible flow path 51 is formed by first reversible flow path holes 81 formed on a plurality of reversible flow path plate-like members 74, causing the refrigerant flowing through the first flow path 57 to be reversed to the second flow path 58. That is, the direction of refrigerant flow through the first reversible flow path 51 is perpendicular to the inlet direction 48 and parallel to the ventilation direction 20. The second reversible flow path 52 is formed by second reversible flow path holes 82 formed on a plurality of reversible flow path plate-like members 74, causing the refrigerant flowing through the second flow path 58 to be reversed to the first flow path 57. That is, the direction of refrigerant flow through the second reversible flow path 52 is perpendicular to the inlet direction 48 and parallel to the ventilation direction 20. Therefore, the first reversible flow path 51 and the second reversible flow path 52 are arranged along the length direction 25 of the manifold and are positioned upstream of the first flow path 57 and the second flow path 58 in the inlet direction 48. The first reversing flow path 51 is formed in the region near the other end 42 and is connected to the upper end of the first flow path 57 and the upper end of the second flow path 58. The second reversing flow path 52 is formed in the lower region near one end 41 and is connected to the lower end of the first flow path 57 and the lower end of the second flow path 58.

[0031] The inlet 61 is formed by inlet holes 86 formed on a plurality of circulating flow path plate members 73. Therefore, the inlet 61 is disposed between the inflow space 43 and the first flow path 57, and the refrigerant flowing into the inlet 61 flows to the first flow path 57 via the inlet 61.

[0032] The plurality of insertion spaces 46 are connected by a plurality of insertion space holes 87 formed on a plurality of insertion space plate members 75. Therefore, when viewed from the area where the inflow space 43 and the circulation path 45 are configured, the plurality of insertion spaces 46 are configured on the downstream side of the inlet direction 48 and are arranged along the length direction 25 of the manifold. The plurality of insertion spaces 46 have approximately equal volumes.

[0033] Multiple inlet holes 62 are formed in the inlet hole plate-shaped component 76. Therefore, the multiple inlet holes 62 are arranged along the length direction 25 of the manifold and are respectively disposed between the first flow path 57 and the multiple insertion spaces 46. The multiple insertion spaces 46 and the first flow path 57 are connected through the multiple inlet holes 62.

[0034] Multiple heat transfer tube through holes 47 are formed in the heat transfer tube side plate-like component 72. Therefore, when viewed from the multiple insertion spaces 46, the multiple heat transfer tube through holes 47 are arranged downstream of the introduction direction 48 and are evenly spaced along the length direction 25 of the manifold. The multiple insertion spaces 46 are respectively connected to each heat transfer tube 23 via the multiple heat transfer tube through holes 47.

[0035] The expansion valve side manifold 21 has an inflow space side insertion space 53, an inflow space side guide flow path 64, and an inflow space side through hole 54. The inflow space side insertion space 53 is formed by a lowermost insertion space hole formed at the lowermost section of the manifold length direction 25 of each insertion space plate member 75. Therefore, the inflow space side insertion space 53 is located at the lowermost section of the manifold length direction 25 among the plurality of insertion spaces 46, and is disposed downstream of the inflow space 43 in the guide direction 48. The inflow space side guide flow path 64 is formed at the lowermost point of the manifold length direction 25 of the plurality of guide holes 62, and is disposed between the inflow space 43 and the inflow space side insertion space 53 in the guide direction 48. The inflow space side insertion space 53 and the inflow space 43 are connected via the inflow space side guide flow path 64. The inflow space side through hole 54 is formed at the lowermost point of the manifold length direction 25 of the plurality of heat transfer tube through holes 47, and is disposed downstream of the inflow space side insertion space 53 in the guide direction 48. The inflow space side insertion space 53 is connected to the heat transfer pipe 23 connected to the inflow space side through hole 54.

[0036] A solder filler metal is applied to the surface of each of the multiple plate-shaped components 71-76. By stacking the plate-shaped components and heating them in a furnace, the solder filler metal melts and joins them together, thereby forming the expansion valve side manifold 21. In this way, the expansion valve side manifold 21 is formed by stacking multiple plate-shaped components 71-76 with their outer peripheries aligned. Therefore, for example, compared to a manifold formed by combining plate-shaped components with U-shaped components to create a box shape, the expansion valve side manifold 21 can improve its strength and durability. Furthermore, since the expansion valve side manifold 21 is formed by stacking multiple plate-shaped components 71-76, changes to the refrigerant flow path in the expansion valve side manifold 21 or the number of heat transfer tubes 23 to be joined can be accommodated simply by changing some of the plate-shaped components. Therefore, the design freedom of the outdoor heat exchanger 1, including the expansion valve side manifold 21, can be increased, and development and manufacturing costs can be reduced.

[0037] Multiple heat transfer tubes 23 pass through multiple heat transfer tube through holes 47 and inflow space side through holes 54, and are connected to the expansion valve side manifold 21. Specifically, the inflow space side heat transfer tube disposed at the bottom of the multiple heat transfer tubes 23 passes through the inflow space side through hole 54 and is connected to the expansion valve side manifold 21. In addition, the remaining heat transfer tubes of the multiple heat transfer tubes 23, which are different from the inflow space side heat transfer tubes, pass through multiple heat transfer tube through holes 47 and are connected to the expansion valve side manifold 21.

[0038] Air conditioner 10 can perform heating and cooling operations as described below.

[0039] Heating operation For example, when the user operates the air conditioner 10 to run in heating mode, heating operation is performed. When the air conditioner 10 is running in heating mode, the four-way valve 6 switches the refrigerant circuit 4 to the heating cycle. The compressor 5 compresses the low-pressure gaseous refrigerant flowing from the four-way valve 6 into the suction pipe 11. The low-pressure gaseous refrigerant is compressed by the compressor 5 into a high-pressure gaseous refrigerant. The compressor 5 discharges the high-pressure gaseous refrigerant to the discharge pipe 12. Because the refrigerant circuit 4 is switched to the heating cycle, the high-pressure gaseous refrigerant discharged to the discharge pipe 12 flows into the indoor heat exchanger 7 via the four-way valve 6.

[0040] Indoor unit 3 allows air from the room in which it is located to flow through indoor heat exchanger 7. Indoor heat exchanger 7 allows the high-pressure vapor refrigerant flowing into it to exchange heat with the air flowing through it, cooling the high-pressure vapor refrigerant and heating the air. Indoor unit 3 then blows the heated air out of indoor heat exchanger 7 into the room in which it is located, providing heating. The high-pressure vapor refrigerant is cooled and condensed by indoor heat exchanger 7, becoming a subcooled high-pressure liquid refrigerant. That is, when air conditioner 10 is operating in heating mode, indoor heat exchanger 7 functions as a condenser. High-pressure liquid refrigerant flows out of indoor heat exchanger 7 and into expansion valve 8.

[0041] Expansion valve 8 reduces the pressure of the high-pressure liquid refrigerant flowing into it. After being reduced in pressure by expansion valve 8, the high-pressure liquid refrigerant becomes a low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant flows out of expansion valve 8 and into refrigerant piping 17. Outdoor fan 18 directs outdoor air into ventilation space 19.

[0042] Low-pressure gas-liquid two-phase refrigerant flowing through refrigerant piping 17 flows into the inflow space 43 of the expansion valve-side manifold 21 via refrigerant piping through-hole 44. The low-pressure gas-liquid two-phase refrigerant flowing into the inflow space 43 further flows into the lower end region 59 of the first flow path 57 via inlet 61. The low-pressure gas-liquid two-phase refrigerant flowing into the lower end region 59 via inlet 61 flows towards the other end 42 of the manifold length direction 25 in the first flow path 57. At this time, the refrigerant is diverted from the first flow path 57 to each inlet hole 62. The remaining gas-liquid two-phase refrigerant (excluding the diverted to each inlet hole 62) flowing through the first flow path 57 to the upper end region 60 of the first flow path 57 flows into the second flow path 58 via the first reversal flow path 51. The low-pressure gas-liquid two-phase refrigerant flowing into the second flow path 58 flows towards one end 41 in the second flow path 58. The low-pressure gas-liquid two-phase refrigerant flowing through the second flow path 58 flows from the second flow path 58 through the second reversal flow path 52 into the lower end region 59 of the first flow path 57, and flows towards the other end 42 in the first flow path 57. In this way, the expansion valve side manifold 21 causes the low-pressure gas-liquid two-phase refrigerant to circulate in the circulation flow path 45 in the order of first flow path 57 → first reversal flow path 51 → second flow path 58 → second reversal flow path 52 → first flow path 57, while simultaneously diverting the refrigerant to each inlet hole 62.

[0043] When the amount of refrigerant circulating in the refrigerant circuit 4 is small and the amount of gas-liquid two-phase refrigerant flowing into the expansion valve side manifold 21 is small, the flow rate of the gas-liquid two-phase refrigerant flowing through the first flow path 57 is slow. At this time, the liquid refrigerant, which has a higher specific gravity than the gaseous refrigerant (and is therefore heavier than the gaseous refrigerant), cannot reach the upper region 60, or the amount of liquid refrigerant reaching this region is small. The amount of liquid refrigerant flowing into the upper heat transfer pipe 23 will be less than the amount flowing into the lower heat transfer pipe 23. As a result, when the amount of liquid refrigerant flowing into the multiple heat transfer pipes 23 is uneven, in the upper heat transfer pipe 23 where less liquid refrigerant flows in, the liquid refrigerant will evaporate completely due to latent heat change along its path. Thereafter, until the refrigerant outlet side of the heat transfer pipe 23 (the connection with the compressor side manifold 22), the gaseous refrigerant is heated and becomes a superheated gas due to sensible heat change. In other words, in the upper heat transfer tube 23 where less liquid refrigerant flows in, although the liquid refrigerant could normally evaporate in the area where the gaseous refrigerant is superheated, the small amount of liquid refrigerant means that this area cannot be effectively utilized. On the other hand, in the lower heat transfer tube 23 where more liquid refrigerant flows through, the liquid refrigerant cannot evaporate completely due to changes in latent heat during its flow through the heat transfer tube, resulting in liquid refrigerant flowing out of the heat transfer tube. When the outdoor heat exchanger 1 functions as an evaporator, if all the liquid refrigerant in each heat transfer tube 23 evaporates at the refrigerant outlet, the evaporation performance is fully utilized. However, in the state described above, where there are heat transfer tubes 23 where all the liquid refrigerant evaporates along the way or where some incompletely evaporated liquid refrigerant flows out, the evaporation performance of the outdoor heat exchanger 1 decreases.

[0044] To address the aforementioned issues, in this embodiment, by adjusting the shape of the first flow path 57, even when the amount of refrigerant circulating in the refrigerant circuit 4 is relatively small, the liquid refrigerant in the low-pressure gas-liquid two-phase refrigerant flowing into the expansion valve side manifold 21 will reach the upper region 60 of the first flow path 57. Specifically, the shape of the first flow path 57 is designed such that, by adjusting the cross-sectional area of ​​the first flow path 57, the flow velocity of the liquid refrigerant flowing through the first flow path 57 is sufficient to reach the upper region 60.

[0045] By adjusting the shape of the first flow path 57 as described above, even when the refrigerant circulation volume in the refrigerant circuit 4 is small, the flow rate of the liquid refrigerant flowing through the first flow path 57 can be ensured, allowing the liquid refrigerant to reach the upper region 60. Therefore, the reduction in the flow rate of the liquid refrigerant in the upper heat transfer pipe 23 can be suppressed. Furthermore, there may be a situation where, due to the large number of heat transfer pipes 23 (i.e., the large height of the expansion valve side manifold 21), even adjusting the shape of the first flow path 57 may not guarantee a sufficient flow rate for the liquid refrigerant to reach the upper region 60. In this case, simply adjusting the diameter of the inlet 61 to increase the initial velocity of the liquid refrigerant in the lower region 59 of the first flow path 57 can be achieved. By increasing the initial velocity, the flow rate of the liquid refrigerant flowing through the first flow path 57 can be ensured, thereby allowing the liquid refrigerant to reach the upper region 60 of the first flow path 57.

[0046] When a larger amount of refrigerant circulates in refrigerant circuit 4, resulting in a larger amount of gas-liquid two-phase refrigerant flowing into the expansion valve side manifold 21, the amount of low-pressure gas-liquid two-phase refrigerant flowing through the first flow path 57 is greater than when the refrigerant circulation volume is smaller. At this time, because the compressor 5 rotates at a higher speed when the refrigerant circulation volume in refrigerant circuit 4 is greater than when the volume is smaller, the flow velocity of the low-pressure gas-liquid two-phase refrigerant flowing through the first flow path 57 is faster. Since the liquid refrigerant in the low-pressure gas-liquid two-phase refrigerant has a higher density and greater mass per unit volume compared to the gaseous refrigerant, the flow velocity of the liquid refrigerant is slower than that of the gaseous refrigerant, which has a smaller mass per unit volume. Therefore, the flow of the gaseous refrigerant pushes the liquid refrigerant towards the upper region 60 of the first flow path 57, where it tends to stagnate. In this way, if the liquid refrigerant remains in the upper region 60 of the first flow path 57, the amount of liquid refrigerant flowing from the upper region 60 of the first flow path 57 to the heat transfer tube 23 will be greater than the amount of liquid refrigerant flowing from a position lower than the upper region 60 of the first flow path 57, thus causing a deviation in the flow rate of liquid refrigerant between the heat transfer tubes 23.

[0047] To address the aforementioned issues, in this embodiment, a circulation path 45 is provided. This circulation path 45 directs the gas-liquid two-phase refrigerant flowing upwards along the first flow path 57 to the second flow path 58 and back to the first flow path 57. By providing the circulation path 45, the liquid refrigerant retained in the upper region 60 of the first flow path 57 can return to the first flow path 57 via the second flow path 58. When the liquid refrigerant is retained in the upper region 60, the flow rate of the liquid refrigerant in the upper heat transfer tube 23 will be higher than that in other heat transfer tubes 23. However, by allowing the liquid refrigerant retained in the upper region 60 to flow back in the circulation path 45, the amount of liquid refrigerant retained in the upper region 60 is reduced. This reduced amount can be diverted to each insertion space 46, thus suppressing the deviation in the amount of liquid refrigerant in each heat transfer tube 23.

[0048] The low-pressure gas-liquid two-phase refrigerant flowing into the inflow space 43 flows through the inlet 61 to the first flow path 57, and then through the inflow space-side guide flow path 64 to the inflow space-side insertion space 53 adjacent to the inflow space 43 in the guide direction 48. When the gas-liquid two-phase refrigerant flows from the inlet 61 to the first flow path 57, the flow direction bends at a right angle from the horizontal direction to the vertical direction in the inflow space 43, and after becoming vertical, it flows upward against gravity. On the other hand, when the gas-liquid two-phase refrigerant flows from the inlet 61 to the inflow space-side insertion space 53 through the inflow space-side guide flow path 64, the flow direction remains horizontal and does not flow against gravity. As described above, the resistance experienced by the gas-liquid two-phase refrigerant flowing towards the insertion space 53 (only the pressure loss at each point in the inflow space 43, the inflow space-side guide flow path 64, and the insertion space 53, hereinafter referred to as the first flow path resistance) is less than the resistance experienced by the gas-liquid two-phase refrigerant flowing towards the first flow path 57 (pressure loss at each point in the inflow space 43, the inlet 61, and the first flow path 57, pressure loss caused by flow path bends, and the effect of gravity, hereinafter referred to as the second flow path resistance). In this way, if the resistance of the first flow path is less than the resistance of the second flow path, most of the liquid refrigerant in the gas-liquid two-phase refrigerant flowing into the inflow space 43 will flow to the inflow space side insertion space 53. In contrast, less liquid refrigerant flows to the first flow path 57. Therefore, more liquid refrigerant flows to the heat transfer tube 23 connected to the inflow space side insertion space 53 than to the other heat transfer tubes 23 (heat transfer tubes connected to the multiple insertion spaces 46 connected to the first flow path 57).

[0049] To address the aforementioned issues, in this embodiment, the shape of the insertion space 53 on the inflow side is adjusted to regulate the first flow path resistance, thereby reducing the amount of liquid refrigerant flowing to the heat transfer tube 23 connected to the insertion space 53 on the inflow side. This suppresses unevenness in the liquid refrigerant flow between this heat transfer tube 23 and other heat transfer tubes 23. Specifically, the shape (size or cross-sectional area) of the insertion space 53 on the inflow side is adjusted so that the value obtained by multiplying the number of heat transfer tubes 23 that supply liquid refrigerant from the first flow path 57 by the first flow path resistance is equal to the second flow path resistance. For example, if there is one heat transfer tube 23 connected to the inflow space side insertion space 53, and eight heat transfer tubes 23 for diverting liquid refrigerant from the first flow path 57, and it is desired that an equal amount A of liquid refrigerant flows to all heat transfer tubes 23, the shape of the inflow space side insertion space 53 is adjusted so that the value obtained by multiplying the first flow path resistance by the number of heat transfer tubes 23 (eight) for diverting liquid refrigerant from the first flow path 57 is equal to the second flow path resistance. Thus, the flow path resistance of each heat transfer tube 23 becomes equal, thereby correcting any deviation in the amount of liquid refrigerant flowing to each heat transfer tube 23.

[0050] Furthermore, the shape adjustment of the inflow-side insertion space 53 is also limited because it needs to connect the heat transfer tube 23. For example, the dimension of the inflow-side insertion space 53 in the ventilation direction 20 needs to be set to a dimension corresponding to the dimension of the inserted heat transfer tube 23 in the ventilation direction 20; for example, it cannot be smaller than the dimension of the heat transfer tube 23 in the ventilation direction 20. In addition, regarding the dimension of the inflow-side insertion space 53 in the inlet direction 48, the front end of the inflow-side insertion space 53 needs to be separated from the inflow-side inlet flow path 64 by a certain distance (if the front end of the inflow-side insertion space 53 is too close to the inflow-side inlet flow path 64, a large amount of refrigerant will flow into the flow path 33 near the inflow-side inlet flow path 64). In some cases, even if the shape is adjusted while satisfying these constraints, it is not possible to obtain a first flow path resistance that satisfies the condition that the value obtained by multiplying the number of heat transfer tubes 23 for which liquid refrigerant is diverted from the first flow path 57 by the first flow path resistance is equal to the second flow path resistance.

[0051] If, as described above, the first flow path resistance cannot be adjusted by merely adjusting the shape of the inflow space side insertion space 53, the first flow path resistance can be adjusted by adjusting the diameter of the inflow space side guide flow path 64. Alternatively, a component to obstruct refrigerant flow can be placed in the inflow space 43 between the front end of the refrigerant pipe 17 inserted into the refrigerant pipe through hole 44 and the inflow space side guide flow path 64, such as a triangular prism or a square prism, to adjust the first flow path resistance. Furthermore, the aforementioned inflow space side guide flow path 64 and the component obstructing refrigerant flow are equivalent to the resistance adjuster of the present disclosure.

[0052] The low-pressure gas-liquid two-phase refrigerant flowing into the multiple insertion spaces 46 and the insertion space 53 on the inflow side flows into the multiple flow paths 33 formed inside the multiple heat transfer tubes 23 and flows towards the compressor-side manifold 22. At this time, by adjusting the shape of the first flow path 57 or the insertion space 53 on the inflow side as described above, the flow deviation of the liquid refrigerant flowing through the multiple flow paths 33 is suppressed, that is, the diversion of the liquid refrigerant to the multiple heat transfer tubes 23 is improved. The liquid refrigerant flowing through the multiple heat transfer tubes 23 exchanges heat with the air flowing through the ventilation space 19 and evaporates into a low-pressure gas phase (gaseous) refrigerant, which flows out from the multiple heat transfer tubes 23 to the compressor-side manifold 22.

[0053] As described above, since the flow deviation of liquid refrigerant in each heat transfer tube 23 is suppressed, an appropriate amount of liquid refrigerant flows to the multiple heat transfer tubes 23. At this time, the state of the refrigerant at the refrigerant outlet side of each heat transfer tube 23, i.e., the connection between each heat transfer tube 23 and the compressor-side manifold 22, is such that the liquid refrigerant has just completely evaporated into gaseous refrigerant at this location, or the gaseous refrigerant contains some incompletely evaporated liquid refrigerant. In this state, the heat exchange performance of the outdoor heat exchanger 1 is fully utilized. Furthermore, if the liquid refrigerant has just completely evaporated into gaseous refrigerant at the refrigerant outlet side of each heat transfer tube 23, or the gaseous refrigerant contains some incompletely evaporated liquid refrigerant, then in this state, the refrigerant superheat at this location is 0 degrees. Therefore, when verifying the effect of the technology disclosed herein, it is sufficient to detect the refrigerant superheat at the refrigerant outlet side of each heat transfer tube 23 and confirm its value. For example, when the refrigerant circulation rate in the refrigerant circuit 4 is at its minimum, if the refrigerant superheat at the refrigerant outlet side of the uppermost heat transfer tube 23 is confirmed to be 0 degrees, then it can be confirmed that when the refrigerant circulation rate is at its minimum, there is a sufficient amount of liquid refrigerant flowing through the uppermost heat transfer tube 23, through which the liquid refrigerant is most difficult to flow. It can be considered that there is at least as much refrigerant as the liquid refrigerant flowing through the uppermost heat transfer tube 23 in the other heat transfer tubes 23. Therefore, it is considered that there is exactly the right amount of liquid refrigerant flowing through all the heat transfer tubes 23, and the heat exchange performance of the outdoor heat exchanger 1 is fully utilized.

[0054] The low-pressure gaseous refrigerant flowing from multiple heat transfer pipes 23 converges at the compressor-side manifold 22 and flows out from the compressor-side manifold 22. The low-pressure gaseous refrigerant flowing out from the compressor-side manifold 22 flows into the four-way valve 6 via the refrigerant piping 14. Since the refrigerant circuit 4 is switched to the heating cycle, it flows into the suction pipe 11 of the compressor 5 via the four-way valve 6.

[0055] Refrigeration operation When the user operates the air conditioner 10 to run in cooling mode, the four-way valve 6 is switched so that the refrigerant circuit 4 is in cooling cycle mode. The compressor 5 compresses the low-pressure gaseous refrigerant drawn in from the four-way valve 6 through the suction pipe 11. The low-pressure gaseous refrigerant is compressed by the compressor 5 into high-pressure gaseous refrigerant and discharged to the discharge pipe 12. Because the refrigerant circuit 4 is switched to cooling cycle mode, the high-pressure gaseous refrigerant discharged to the discharge pipe 12 flows into the outdoor heat exchanger 1 through the four-way valve 6 and the refrigerant piping 14.

[0056] The high-pressure gaseous refrigerant flowing into the outdoor heat exchanger 1 flows into the compressor-side manifold 22 and is distributed to multiple heat transfer tubes 23. The high-pressure gaseous refrigerant distributed to the multiple heat transfer tubes 23 condenses through heat exchange with the air flowing through the ventilation space 19 via the rotation of the outdoor fan 18, thus becoming a subcooled high-pressure liquid refrigerant. That is, when the air conditioner 10 is operating in cooling mode, the outdoor heat exchanger 1 functions as a condenser. The high-pressure liquid refrigerant flows out from the multiple heat transfer tubes 23 and flows into multiple insertion spaces 46 on the expansion valve-side manifold 21 and the insertion space 53 on the inflow space side. The high-pressure liquid refrigerant flowing into the multiple insertion spaces 46 flows into the first flow path 57 of the circulation flow path 45 through multiple inlet holes 62 and converges. The high-pressure liquid refrigerant converging in the first flow path 57 flows into the inflow space 43 through the inlet 61. The high-pressure liquid refrigerant flowing into the insertion space 53 of the inflow space flows into the first flow path 57 of the circulation flow path 45 through multiple inlet holes 62, and merges with the high-pressure liquid refrigerant flowing into the inflow space 43 through the inlet 61. The high-pressure liquid refrigerant flowing in the inflow space 43 flows into the refrigerant pipe 17 through the refrigerant pipe through hole 44, and flows into the expansion valve 8 after passing through the refrigerant pipe 17.

[0057] The high-pressure liquid refrigerant flowing into expansion valve 8 is depressurized and becomes a low-pressure gas-liquid two-phase refrigerant. It flows out of expansion valve 8, through refrigerant piping 16, and into indoor heat exchanger 7. The rotation of an indoor fan (not shown) causes the low-pressure gas-liquid two-phase refrigerant flowing into indoor heat exchanger 7 to exchange heat with the room air drawn into indoor unit 3. Thus, the air flowing through indoor heat exchanger 7 is cooled using the low-pressure gas-liquid two-phase refrigerant, and the room is cooled by blowing the cooled air into the room where indoor unit 3 is located. On the other hand, the low-pressure gas-liquid two-phase refrigerant flowing into indoor heat exchanger 7 is heated and evaporated, becoming a low-pressure gas-phase refrigerant. That is, when air conditioner 10 is operating in cooling mode, indoor heat exchanger 7 functions as an evaporator. The low-pressure gas-phase refrigerant flowing out of indoor heat exchanger 7 flows sequentially to refrigerant piping 15, four-way valve 6, and suction pipe 11, and is drawn into compressor 5 for further compression.

[0058] Effect of the heat exchanger in the embodiment The heat exchanger of this embodiment includes multiple heat transfer tubes 23, an expansion valve-side manifold 21, and a compressor-side manifold 22. The expansion valve-side manifold 21 has a first flow path 57, a second flow path 58, a first reversible flow path 51, a second reversible flow path 52, an inflow space 43, and an inlet 61. The first flow path 57 allows refrigerant to flow from one end 41 to the other end 42 along the length 25 of the expansion valve-side manifold 21. The second flow path 58 allows refrigerant to flow from the other end 42 to the first end 41. The first reversible flow path 51 allows refrigerant to flow from the first flow path 57 to the second flow path 58 at the other end 42. The second reversible flow path 52 allows refrigerant to flow from the second flow path 58 to the first flow path 57 at the first end 41. The inflow space 43 allows refrigerant to flow in. The inlet 61 allows refrigerant to flow from the inflow space 43 to the end of the first flow path 57 at the end 41. The first flow path 57 is connected to the compressor-side manifold 22 via a plurality of heat transfer tubes 23. The first flow path 57 is configured such that, when the heat exchanger of the embodiment functions as an evaporator, the superheat of the refrigerant flowing from the uppermost heat transfer tube, which is located furthest from the inflow space 43, into the compressor-side manifold 22 is 0 degrees.

[0059] That is, in the heat exchanger of this embodiment, even when the liquid refrigerant is least likely to flow to the uppermost heat transfer tube 23, by adjusting the shape of the first flow path 57, the liquid refrigerant can flow in such a way that the refrigerant superheat at the refrigerant outlet side of the heat transfer tube 23 is 0 degrees, i.e., so that the liquid refrigerant reaches the refrigerant outlet side exactly. Therefore, the heat exchanger of this embodiment can suppress the deflection of liquid refrigerant into the multiple heat transfer tubes 23, thereby improving the evaporation performance when functioning as an evaporator.

[0060] Furthermore, the shape of the first flow path 57 of the heat exchanger in this embodiment is based on the minimum refrigerant flow rate from the inflow space 43 to the first flow path 57 per unit time when the heat exchanger functions as an evaporator. When the refrigerant circulation amount in the refrigerant circuit 4 is at its minimum, the amount of refrigerant flowing into the first flow path 57 is at its minimum as described above. However, since this situation was considered when adjusting the shape of the first flow path 57, even when the circulation amount of refrigerant circulating in the refrigerant circuit 4 is at its minimum, it is possible to suppress the deflection of liquid refrigerant into the multiple heat transfer tubes 23, thereby improving the evaporation performance when functioning as an evaporator.

[0061] Furthermore, for the multiple heat transfer tubes 23 of the heat exchanger in this embodiment, by adjusting the shape of the inflow space-side insertion space 53, the value obtained by multiplying the first flow path resistance by the number of other heat transfer tubes 23 is equal to the second flow path resistance. This ensures that the amount of liquid refrigerant flowing to the heat transfer tubes 23 connected to the inflow space-side insertion space 53 does not exceed the amount flowing to the other heat transfer tubes 23. Therefore, it is possible to suppress the deflection of liquid refrigerant to each heat transfer tube 23, thereby improving the evaporation performance when functioning as an evaporator.

[0062] Furthermore, in the heat exchanger of the described embodiment, since the heat transfer tubes 23 need to be connected, the shape adjustment of the insertion space 53 on the inflow space side is also limited. Even if the shape is adjusted within the allowable range, it is possible that the value obtained by multiplying the first flow path resistance by the number of other heat transfer tubes 23 may not be equal to the second flow path resistance (for example, if there are more other heat transfer tubes 23, the second flow path resistance will be a larger value). In this case, a resistance adjustment part for adjusting the first flow path resistance can be further provided in the expansion valve side manifold 21. For example, the first flow path resistance can be adjusted by adjusting the diameter of the inflow space side guide flow path 64. Alternatively, the first flow path resistance can be adjusted by placing a member that obstructs the flow of refrigerant, such as a triangular prism or a square prism, between the front end of the refrigerant pipe 17 inserted into the refrigerant pipe through hole 44 and the inflow space side guide flow path 64 in the inflow space 43.

[0063] The embodiments have been described above, but the embodiments are not limited to the above content. Furthermore, the above structural elements include structural elements that are substantially the same and of the same scope, which can be easily conceived by those skilled in the art. Further, the above structural elements can be appropriately combined. Furthermore, at least one of various omissions, substitutions, and modifications of structural elements can be made without departing from the spirit of the embodiments.

[0064] Symbol Explanation 1: Outdoor heat exchanger (heat exchanger) 4: Refrigerant circuit (refrigeration cycle device) 5: Compressor 21: Expansion valve side manifold (first manifold) 22: Compressor-side manifold (second manifold) 23: Multiple heat transfer tubes 25: Manifold length direction (length direction) 41: One end 42: The other end 43: Inflow Space 44: Refrigerant piping through hole 46: Insertion space 47: Multiple heat transfer tube through holes 48: Import Direction 51: First Turnback Flow Path 52: Second Turnback Flow Path 53: Inserting space into the inflow space side 54: Through hole on the side of the inflow space 57: First flow path 58: Second Flow Path 61: Inlet 62: Inlet hole 64: Inflow space side inlet flow path.

Claims

1. A heat exchanger comprising: Multiple heat transfer tubes; First collection pipe; and Second episode, The first manifold has: A first flow path is provided for allowing refrigerant to flow from one end side to the other end side along the length of the first manifold. A second flow path is provided for allowing refrigerant to flow from the other end side to the first end side; A first foldback flow path is used to allow refrigerant to flow from the first flow path to the second flow path at the other end side; A second reversing flow path is used to allow refrigerant to flow from the second flow path to the first flow path at one end; The inflow space is for the refrigerant to flow into; and An inlet, which allows refrigerant to flow from the inlet space to the end of the first flow path at one end. The first flow path is connected to the second manifold via the plurality of heat transfer tubes. The heat exchanger is characterized in that... The first flow path is configured such that, when the heat exchanger functions as an evaporator, the superheat of the refrigerant flowing from the heat transfer tube located furthest from the inflow space among the plurality of heat transfer tubes into the second manifold is 0 degrees.

2. The heat exchanger according to claim 1, characterized in that, For the first flow path, the cross-sectional area of ​​the first flow path is determined based on the minimum refrigerant flow rate from the inflow space to the first flow path per unit time when the heat exchanger functions as an evaporator.

3. The heat exchanger according to claim 1, characterized in that, It also includes an inflow space-side heat transfer pipe, which is located closer to the inflow space than the plurality of heat transfer pipes. The first manifold also has: An inflow space-side insertion space is provided for one end of the inflow space-side heat transfer pipe; and An inflow space-side guide flow path is used to connect the inflow space with the inflow space-side insertion space; The refrigerant flowing from the inflow space into the insertion space via the inflow space side guide path flows to the second manifold via the inflow space side heat transfer pipe. The inflow space side insertion space is formed such that the second flow path resistance experienced by the refrigerant flowing through the first flow path is equal to the target resistance, wherein the target resistance is calculated by multiplying the first flow path resistance experienced by the refrigerant flowing through the inflow space side insertion space by the number of the plurality of heat transfer tubes.

4. The heat exchanger according to claim 3, characterized in that, It also includes a resistance adjustment section for adjusting the resistance of the first flow path.

5. A refrigeration cycle device, which compresses refrigerant after heat exchange in a heat exchanger using a compressor, thereby circulating the refrigerant in a refrigerant circuit, characterized in that... The heat exchanger includes: Multiple heat transfer tubes; First collection pipe; and Second episode, The first manifold has: A first flow path is provided for allowing refrigerant to flow from one end side to the other end side along the length of the first manifold. A second flow path is provided for allowing refrigerant to flow from the other end side to the first end side; A first foldback flow path is used to allow refrigerant to flow from the first flow path to the second flow path at the other end side; A second reversing flow path is used to allow refrigerant to flow from the second flow path to the first flow path at one end; The inflow space is for the refrigerant to flow into; and An inlet, which allows refrigerant to flow from the inlet space to the end of the first flow path at one end. The first flow path is configured such that when the heat exchanger functions as an evaporator and the amount of refrigerant flowing through the refrigerant circuit is at its minimum, the superheat of the refrigerant flowing from the heat transfer tube located furthest from the inflow space into the second manifold is 0 degrees.

6. The refrigeration cycle device according to claim 5, characterized in that, The compressor circulates refrigerant in the refrigerant circuit at a flow rate corresponding to the compressor speed. The first flow path is configured such that the superheat is 0 degrees when the compressor speed is at its minimum speed.

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