Flat tubes for heat exchangers and heat exchangers

Abstract

This suppresses the decrease in heat exchange performance between the refrigerant and the fluid caused by the difference in heat load between the upstream and downstream sides of the multiple flow channels through which the refrigerant flows. [Solution] A flat tube for a heat exchanger, comprising a plurality of flow channels through which a refrigerant, with which heat exchange occurs, flows, wherein each of the plurality of flow channels includes a first partial flow channel extending from the upstream side to the downstream side in the direction of fluid flow, and a second partial flow channel extending from the upstream side to the downstream side in the direction of fluid flow, and from the upstream side to the downstream side in the direction of fluid flow.

Description

Technical Field

[0001] The present invention relates to a flat tube for a heat exchanger and a heat exchanger.

Background Art

[0002] Patent Document 1 describes a heat exchanger that performs heat exchange between an external fluid and an internal fluid. The heat exchanger includes a plurality of heat exchange sections arranged in series with respect to the flow direction of the external fluid. Each of the plurality of heat exchange sections has a plurality of tubes stacked inside through which the internal fluid flows, and a plurality of outer fins joined to the outer surface of the tubes to increase the heat exchange area with the external fluid.

[0003] Patent Document 2 describes a heat exchanger in which each of a plurality of heat exchange members has a flat tube extending from a first header tank to a second header tank, and a heat transfer plate integrated with the flat tube along the longitudinal direction of the flat tube. The width direction of the flat tube intersects the direction in which the plurality of heat exchange members are arranged. The heat transfer plate has an extending portion that extends outward in the width direction of the flat tube from at least one of one end portion and the other end portion in the width direction of the flat tube. The flat tube has one or more flat tube bending portions that form grooves along the longitudinal direction of the flat tube.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Generally, in multiple flow channels through which a refrigerant undergoes heat exchange with a fluid, the heat load tends to differ between the upstream and downstream sides in the direction of fluid flow. Consequently, the refrigerant upstream in the direction of fluid flow may evaporate faster than the refrigerant downstream, resulting in a dry-out state. This leads to a decrease in the heat exchange performance between the refrigerant and the fluid.

[0006] The objective of the present invention is to suppress the decrease in heat exchange performance between the refrigerant and the fluid caused by the difference in heat load between the upstream and downstream sides of the multiple flow channels through which the refrigerant flows. [Means for solving the problem]

[0007] To this end, the present invention provides a flattened tube for a heat exchanger, comprising a plurality of flow channels through which a refrigerant, with which heat exchange is performed, flows, wherein each of the plurality of flow channels includes a first partial flow channel extending from the upstream side to the downstream side in the direction of fluid flow, and a second partial flow channel extending from the upstream side to the downstream side in the direction of fluid flow, both in the direction of refrigerant flow and downstream.

[0008] The flattened tube for the heat exchanger may be composed of multiple plates, with a first partial flow path formed in a first plate among the multiple plates, and a second partial flow path formed in a second plate among the multiple plates.

[0009] Each of the multiple flow channels may further include a connecting portion that connects a first partial flow channel and a second partial flow channel.

[0010] In this case, the flattened tube for the heat exchanger may be composed of a plurality of plates, the first partial flow path may be formed in the first plate among the plurality of plates, the second partial flow path may be formed in the second plate among the plurality of plates, and the connecting portion may be formed in the third plate sandwiched between the first plate and the second plate among the plurality of plates. In this case, the third plate may be thinner than at least one of the first plate, the second plate, the wall separating the first partial flow paths provided on the first plate, and the wall separating the second partial flow paths provided on the second plate. In this case, the width dimension or cross-sectional area of ​​the connecting portion may be larger than the width dimension or cross-sectional area of ​​the first partial flow path and the second partial flow path.

[0011] In that case, the flattened tube for the heat exchanger may be composed of multiple plates, and the first partial flow path, the second partial flow path, and the connecting section may be formed in a third plate sandwiched between the first and second plates. In that case, the wall separating the first partial flow path and the second partial flow path provided in the third plate may be thinner than at least one of the walls separating the first partial flow paths and the walls separating the second partial flow paths. In that case, the width dimension or cross-sectional area of ​​the connecting section may be larger than the width dimension or cross-sectional area of ​​the first partial flow path and the second partial flow path.

[0012] Furthermore, in that case, all of the multiple flow paths may include a first partial flow path, a second partial flow path, and a connecting section.

[0013] The first and second partial flow channels may be constructed by twisting together multiple flow channels.

[0014] Multiple channels may be independent of each other.

[0015] The angle that the first subflow channel makes with the fluid flow direction may be approximately the same as the angle that the second subflow channel makes with the fluid flow direction.

[0016] The cross-sections of the first partial flow path and the second partial flow path may have a semi-circular or semi-elliptical shape.

[0017] The present invention also provides a heat exchanger including: a first header into which a refrigerant that exchanges heat with a fluid flows; a plurality of flat tubes in which a plurality of flow paths through which the refrigerant flows are formed; and a second header from which the refrigerant that has flowed through the plurality of flow paths flows out. Each of the plurality of flow paths includes: a first partial flow path that extends from the upstream side to the downstream side in the flow direction of the fluid as it goes from the upstream side to the downstream side in the flow direction of the refrigerant; and a second partial flow path that extends from the downstream side to the upstream side in the flow direction of the fluid as it goes from the upstream side to the downstream side in the flow direction of the refrigerant.

[0018] The heat exchanger may further include fins installed between the plurality of flat tubes, and the first header and the second header may be vertical headers that extend in a substantially vertical direction.

[0019] The plurality of flat tubes may be arranged without passing through fins, and the first header and the second header may be horizontal headers that extend in a substantially horizontal direction.

Advantages of the Invention

[0020] According to the present invention, it is possible to suppress a decrease in the heat exchange performance between the refrigerant and the fluid due to the heat load of the plurality of flow paths through which the refrigerant flows being different between the upstream side and the downstream side in the flow direction of the fluid.

Brief Description of the Drawings

[0021] [Figure 1] It is a perspective view showing a configuration example of a heat exchanger 1 to which the present embodiment is applied. [Figure 2-1] It is a perspective view of a conventional flat tube. [Figure 2-2] It is a diagram showing a situation where dryout occurs. [Figure 3] It is a perspective view showing a configuration example of a flat tube in the first embodiment. [Figure 4](a) to (c) are top views showing configuration examples of the lower plate, middle plate, and upper plate of the flat tube in the first embodiment, respectively. [Figure 5] It is a diagram showing the premise of the trial calculation of the cooling capacity of the indoor unit by the effect of the flat tube. [Figure 6] It is a graph showing the relationship between the position in the refrigerant flow direction and the dryness. [Figure 7] It is a perspective view showing a configuration example of the flat tube in the second embodiment. [Figure 8] (a) to (c) are top views showing configuration examples of the lower plate, middle plate, and upper plate of the flat tube in the second embodiment, respectively. [Figure 9] It is a top view showing a configuration example of the flat tube in the third embodiment. [Figure 10] It is a cross-sectional view showing a configuration example of the flat tube in the fourth embodiment.

Embodiments for Carrying Out the Invention

[0022] <了 Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0023] [Heat Exchanger] FIG. 1 is a perspective view showing a configuration example of a heat exchanger 1 to which the present embodiment is applied. Here, as the heat exchanger 1, a heat exchanger used as an evaporator of an air conditioner is shown. As shown in the figure, the heat exchanger 1 includes a heat exchange section 2, a liquid side header 5, and a gas side header 6.

[0024] The heat exchange section 2 is constructed by stacking flattened tubes 3 and fins 4 alternately in the vertical direction. The flattened tubes 3 are refrigerant tubes with multiple flow channels formed inside through which the refrigerant flows. The fins 4 are components installed in contact with the flattened tubes 3. With this configuration, the heat exchange section 2 exchanges heat between the refrigerant flowing through the flow channels of the flattened tubes 3 and the fluid flowing between the fins 4, as indicated by arrow F. In the following explanation, air will be used as an example of the fluid flowing between the fins 4. However, the term "fluid" will be used in the drawings instead of "air".

[0025] The liquid-side header 5 is connected to one end of the multiple flattened tubes 3 that constitute the heat exchange section 2. Inside the liquid-side header 5, a space is formed that communicates with the flow paths of the multiple flattened tubes 3. The liquid-side header 5 is an example of a first header into which the refrigerant, which undergoes heat exchange with the fluid, flows.

[0026] The gas-side header 6 is connected to the other ends of the multiple flattened tubes 3 that constitute the heat exchange section 2. Inside the gas-side header 6, a space is formed that communicates with the flow paths of the multiple flattened tubes 3. The gas-side header 6 is an example of a second header through which the refrigerant that has flowed through the multiple flow paths is discharged.

[0027] Furthermore, heat exchanger 1 is not limited to a heat exchanger used as an evaporator in an air conditioner, but may also be a heat exchanger used as a condenser in an air conditioner. In addition, heat exchanger 1 may be a heat exchanger used in equipment other than an air conditioner.

[0028] [Flat tube] In heat exchanger 1, the temperature difference between the air passing through heat exchange section 2 and heat exchange section 2 differs between the upstream and downstream sides in the direction of airflow. On the upstream side in the direction of airflow, this temperature difference is larger, increasing the amount of heat exchanged. As a result, the refrigerant on the upstream side in the direction of airflow evaporates faster than the refrigerant on the downstream side in the direction of airflow, leading to a dry-out state. Since no heat exchange occurs after the dry-out state, the entire heat transfer area cannot be effectively utilized, and performance deteriorates.

[0029] This is explained in detail. Figure 2-1 is a perspective view of a conventional flattened pipe 3. Figure 2-2 is a diagram showing the conditions under which dryout occurs. Figures 2-1 and 2-2 show the flow paths 31a to 31f formed in the flattened pipe 3. Hereinafter, the upstream side in the direction of airflow will be referred to as the "air upstream side," and the downstream side in the direction of airflow will be referred to as the "air downstream side." Similarly, the upstream side in the direction of refrigerant flow will be referred to as the "refrigerant upstream side," and the downstream side in the direction of refrigerant flow will be referred to as the "refrigerant downstream side."

[0030] Refer to Figure 2-2 to explain the reason for dryout. In flow paths 31a to 31f, the refrigerant flows from the bottom to the top of the diagram. Therefore, the bottom of the diagram is the upstream side of the refrigerant, and the top of the diagram is the downstream side of the refrigerant. Note that liquid refrigerants are indicated by diagonal hatching, and gaseous refrigerants are indicated by dot hatching. Furthermore, air enters the flattened tube 3 from the left side of the diagram, as indicated by arrow F1, and exits to the right side of the diagram, as indicated by arrow F2. Therefore, the left side of the diagram is the upstream side of the air, and the right side is the downstream side of the air.

[0031] First, on the upstream side of the air, the air temperature is high, resulting in a large temperature difference between the air and the heat exchange unit 2. Therefore, the amount of heat exchanged on the upstream side of the air is greater than on the downstream side of the air. As a result, the degree of dryness on the downstream side of the refrigerant on the upstream side of the air becomes high. When the degree of dryness exceeds 1, the amount of heat exchanged decreases significantly, and the efficiency decreases. On the other hand, on the downstream side of the air, the degree of dryness remains low, so the refrigerant exits the heat exchange unit 2 while retaining its heat exchange potential.

[0032] In the diagram, gaseous refrigerant is present downstream of the refrigerant in channels 31a to 31d. In channel 31a, the liquid refrigerant is depleted the fastest, and the gaseous refrigerant region increases. However, in channels 31e and 31f, liquid refrigerant still remains downstream before flowing out to the downstream header. In heat exchanger 1, the occurrence of such uneven heat load conditions hinders performance improvement. Hereafter, this problem will be referred to as "Problem 1".

[0033] Therefore, in this embodiment, the refrigerant inside the flattened tube 3 is swapped between the air-upstream and air-downstream sides.

[0034] Furthermore, heat exchanger 1 has the limitation that the heat exchange area cannot be increased. This is a particular challenge when transferring heat to air. In the following, this challenge will be referred to as "Challenge 2". Furthermore, in heat exchanger 1, there is a problem in that heat conduction occurs through the fins 4 when heat exchange occurs via the fins 4. This causes a temperature distribution on the fins 4, which reduces efficiency. Hereafter, this problem will be referred to as "Problem 3".

[0035] Regarding problem 2, in order to increase the heat exchange area while maintaining the external shape of the heat exchanger 1, one solution is to reduce the pitch of the flattened tubes 3 to increase the flattened tube area. Alternatively, reducing the pitch of the fins 4 to increase the fin area is also a solution. However, these measures increase air pressure loss, which increases the rotation speed of the fan (not shown). As a result, noise and the power consumption of the fan motor increase. Regarding issue 3, it is unavoidable as long as fin 4 is used. One possible solution is to reduce the height of the flow path, i.e., make it thinner, so that fin 4 is not used.

[0036] Therefore, in this embodiment, the number of flattened tubes 3 is increased and the pitch is reduced by dramatically reducing the height of the flow path. This increases the heat exchange area and solves problem 2. Furthermore, in this embodiment, the flattened tube 3 is given a pitch similar to that of conventional fins 4. As a result, it is as if there were no fins 4, so no temperature distribution occurs, and problem 3 is solved.

[0037] (First Embodiment) Figure 3 is a perspective view showing an example of the configuration of the flattened pipe 100, which is the flattened pipe 3 in the first embodiment. As shown in the figure, the flattened pipe 100 comprises a lower plate 110, a middle plate 120, and an upper plate 130. The lower plate 110, the middle plate 120, and the upper plate 130 are actually stacked to form the flattened pipe 100, but they are shown separately here for illustrative purposes. Figures 4(a) to 4(c) are top views showing examples of configurations for the lower plate 110, the middle plate 120, and the upper plate 130, respectively.

[0038] Here, the flattened pipe 100 is constructed by stacking three plates, but generally it may be constructed by stacking multiple plates. The lower plate 110 may be any plate below the middle plate 120 among the multiple plates. The upper plate 130 may be any plate above the middle plate 120 among the multiple plates. In this case, the lower plate 110 is an example of the first plate among the multiple plates. The upper plate 130 is an example of the second plate among the multiple plates. The middle plate 120 is an example of the third plate sandwiched between the first and second plates among the multiple plates.

[0039] As shown in Figures 3 and 4, the flattened pipe 100 has a plurality of flow channels 101. It is desirable that the plurality of flow channels 101 are independent of each other. Each of the plurality of flow channels 101 is formed extending in an oblique direction.

[0040] Each of the multiple flow paths 101 includes a lower flow path 111 within the lower plate 110 and an upper flow path 133 within the upper plate 130. The lower flow path 111 extends from the upstream side of the refrigerant to the downstream side of the refrigerant, and from the upstream side of the air to the downstream side of the air. The lower flow path 111 is an example of a first partial flow path formed in the first plate. The upper flow path 133 extends from the upstream side of the refrigerant to the downstream side of the refrigerant, and from the downstream side of the air to the upstream side of the air. The upper flow path 133 is an example of a second partial flow path formed in the second plate. Note that the upper flow path 133 is formed on the underside of the upper plate 130 and is therefore not actually visible in Figures 3 and 4(c), but is shown with a dashed line for illustrative purposes.

[0041] Furthermore, the middle plate 120 is provided with a folded connecting section 122. The lower flow channel 111, which extends diagonally within the lower plate 110, and the upper flow channel 133, which extends diagonally within the upper plate 130, are connected via the folded connecting section 122. The folded connecting section 122 is an example of a connecting section that connects a first partial flow channel and a second partial flow channel. The folded connecting section 122 is an example of a connecting section formed on the third plate.

[0042] In Figures 3 and 4, the direction of refrigerant flow through the folding communication section 122 between the lower flow path 111 and the upper flow path 133 is shown only for a portion of the multiple flow paths 101. Specifically, for flow path 101a of the multiple flow paths 101, the direction of refrigerant flow is indicated by a solid arrow. Also, for flow path 101b of the multiple flow paths 101, the direction of refrigerant flow is indicated by a dashed arrow. It is desirable for the refrigerant entering from the refrigerant inlet to fold back at least once. Here, the refrigerant is folded back twice. However, increasing the number of folds increases the length of flow path 101, which increases the pressure loss of the refrigerant. Therefore, increasing the number of folds is not necessarily always better.

[0043] Here, we focus on one lower channel 111 and one upper channel 133 connected to one folded connecting section 122. In this case, it is desirable that the angle at which the lower channel 111 extends on the lower plate 110 is approximately the same as the angle at which the upper channel 133 extends on the upper plate 130. For example, it is desirable that the angle θ1 between the side of the lower plate 110 and the lower channel 111 is the same as the angle θ3 between the side of the upper plate 130 and the upper channel 133. Alternatively, this can be interpreted as it is desirable that the angle between the lower channel 111 and the direction of airflow is approximately the same as the angle between the upper channel 133 and the direction of airflow.

[0044] Furthermore, it is preferable to configure the folding communication section 122 so that its width is greater than the widths of the lower channel 111 and the upper channel 133. Here, the width of the folding communication section 122 may be dimension L21 or dimension L22. Also, the width of the lower channel 111 may be dimension L1, and the width of the upper channel 133 may be dimension L3. Alternatively, the cross-sectional area of ​​the folded communication section 122 may be configured to be larger than the cross-sectional areas of the lower flow path 111 and the upper flow path 133. If the cross-sectional area of ​​the folded communication section 122 is larger, the refrigerant flow velocity will decrease. The folded communication section 122 also experiences bending losses of the refrigerant, and the most important factor in minimizing this effect is the flow velocity.

[0045] Furthermore, it is preferable to configure the intermediate plate 120 so that its thickness is thinner than that of the lower plate 110 or the upper plate 130. Alternatively, the intermediate plate 120 may be configured so that its thickness is thinner than that of the flow channel wall 114 of the lower plate 110 or the flow channel wall 134 of the upper plate 130. This is because the pressure resistance can be low because there is almost no pressure difference through the intermediate plate 120.

[0046] Furthermore, the cross-sections of the lower channel 111 of the lower plate 110 and the upper channel 133 of the upper plate 130 should preferably be shaped to reduce pressure loss, taking into account the constraints of the channel manufacturing method. In the figure, the cross-section is shown as a semicircle or semiellipse, but it may also be a polygon or other shape.

[0047] In the case of the flattened tube 100, the lower plate 110, middle plate 120, and upper plate 130 are separate components, but they may be integrated into a single unit. In this case, the flattened tube 100 can be created, for example, by a 3D printer or by twisting and then crushing a flattened tube with parallel channels.

[0048] Thus, in the flattened tube 100 of the first embodiment, the refrigerant flowing in from the refrigerant inlet moves back and forth between the air upstream side and the air downstream side to reach the refrigerant outlet. That is, the flow of the refrigerant differs between the lower plate 110 and the upper plate 130, either from the air upstream side to the air downstream side or from the air downstream side to the air upstream side. Specifically, the flow path 101 is formed in a spiral shape with approximately the same angle of extension. This increases the amount of heat exchange between the refrigerant flowing through the flow path 101 and the air.

[0049] Next, we show the results of our calculations regarding the effect of the flattened pipe 100, based on the cooling capacity of the indoor unit. Figure 5 shows the assumptions for this calculation. In this calculation, as shown in the figure, the flattened pipe 100 is divided into regions R1 to R5 in the direction of airflow and into regions S1 to S10 in the direction of refrigerant flow.

[0050] Figure 6 is a graph showing the relationship between position in the flow direction of the refrigerant and the degree of dryness. Graphs P1 to P5 show the change in dryness when the refrigerant flows perpendicular to the direction of airflow, from bottom to top, in regions R1 to R5, respectively. The Paverage graph shows the average of graphs P1 through P5. Graph Spiral shows the change in dryness when using flattened tube 100.

[0051] According to Figure 6, the dryness when using the flattened tube 100 is higher than the average dryness when using a flattened tube in which the refrigerant flows perpendicular to the direction of airflow. Therefore, when using the flattened tube 100, the cooling capacity is improved compared to when using a flattened tube in which the refrigerant flows perpendicular to the direction of airflow. The calculations showed that the cooling capacity improved by more than 8%.

[0052] (Second Embodiment) Figure 7 is a perspective view showing an example of the configuration of the flattened pipe 200, which is the flattened pipe 3 in the second embodiment. As shown in the figure, the flattened pipe 200 comprises a lower plate 210, a middle plate 220, and an upper plate 230. The lower plate 210, the middle plate 220, and the upper plate 230 are actually stacked to form the flattened pipe 200, but are shown separately here for illustrative purposes. Figures 8(a) to 8(c) are top views showing examples of the configurations of the lower plate 210, the middle plate 220, and the upper plate 230, respectively.

[0053] Here, the flattened pipe 200 is constructed by stacking three plates, but generally it may be constructed by stacking multiple plates. The lower plate 210 may be any plate below the middle plate 220 among the multiple plates. The upper plate 230 may be any plate above the middle plate 220 among the multiple plates. In this case, the lower plate 210 is an example of the first plate among the multiple plates. The upper plate 230 is an example of the second plate among the multiple plates. The middle plate 220 is an example of the third plate sandwiched between the first and second plates among the multiple plates.

[0054] As shown in Figures 7 and 8, the flattened pipe 200 has a plurality of flow channels 201. It is desirable that the plurality of flow channels 201 are independent of each other. Each of the plurality of flow channels 201 is formed extending in an oblique direction.

[0055] Each of the multiple flow channels 201 includes a lower flow channel 221 and an upper flow channel 223 within the middle plate 220. The lower flow channel 221 extends from the upstream side of the refrigerant to the downstream side of the refrigerant, and from the upstream side of the air to the downstream side of the air. The lower flow channel 221 is an example of a first partial flow channel formed in the third plate. The upper flow channel 223 extends from the upstream side of the refrigerant to the downstream side of the refrigerant, and from the downstream side of the air to the upstream side of the air. The upper flow channel 223 is an example of a second partial flow channel formed in the third plate. Note that the lower flow channel 221 is formed on the underside of the middle plate 220 and is therefore not actually visible in Figure 8(b), but is shown with a dashed line for illustrative purposes.

[0056] Furthermore, the intermediate plate 220 is also provided with a folded connecting section 222. The lower channel 221 and the upper channel 223, which extend diagonally within the intermediate plate 220, are connected via the folded connecting section 222. The folded connecting section 222 is an example of a connecting section that connects a first partial channel and a second partial channel. The folded connecting section 222 is an example of a connecting section formed on the third plate.

[0057] Here, we focus on one lower channel 221 and one upper channel 223 connected to one folded connecting section 222. In this case, it is desirable that the angle at which the lower channel 221 extends on the intermediate plate 220 is approximately the same as the angle at which the upper channel 223 extends on the intermediate plate 220. For example, it is desirable that the angle between the side of the intermediate plate 220 and the lower channel 221 is the same as the angle between the side of the intermediate plate 220 and the upper channel 223. Alternatively, this can be interpreted as it is desirable that the angle between the lower channel 221 and the direction of airflow is approximately the same as the angle between the upper channel 223 and the direction of airflow.

[0058] Furthermore, it is preferable to configure the width of the folded connecting section 222 to be greater than the width of the lower channel 221 and the upper channel 223. Alternatively, the cross-sectional area of ​​the folded connecting section 222 may be configured to be larger than the cross-sectional area of ​​the lower channel 221 and the upper channel 223.

[0059] Furthermore, it is preferable to configure the intermediate plate 220 such that the thickness of the wall 225 separating the lower channel 221 and the upper channel 223 is thinner than the thickness of the channel wall 224 of the lower channel 221 or the channel wall 226 of the upper channel 223. This is because there is almost no pressure difference through the wall 225 of the intermediate plate 220, so the pressure resistance can be low.

[0060] Furthermore, the cross-sections of the lower channel 221 and upper channel 223 of the intermediate plate 220 should preferably be shaped to reduce pressure loss, taking into account the constraints of the channel manufacturing method. In the figure, the cross-section is shown as a semicircle or semiellipse, but it may also be a polygon or other shape.

[0061] In the case of the flattened tube 200, the lower plate 210, middle plate 220, and upper plate 230 are separate components, but they may be integrated into a single unit. In this case, the flattened tube 200 can be created, for example, by a 3D printer or by twisting and then crushing a flattened tube with parallel channels.

[0062] Thus, in the flattened pipe 200 of the second embodiment, a lower channel 221 and an upper channel 223 are provided on both sides of the middle plate 220, respectively. Furthermore, a folded connecting section 222 is also formed in the middle plate 220. As a result, if the middle plate 220 can be manufactured in a single process, the manufacturing speed may be increased.

[0063] (Third embodiment) Figure 9 is a top view showing an example of the configuration of a flattened pipe 300, which is a flattened pipe 3 in the third embodiment. As shown in the figure, the flattened pipe 300 has a plurality of flow channels 301. The plurality of flow channels 301 are independent of each other. Each of the plurality of flow channels 301 is formed extending in an oblique direction.

[0064] In the flattened pipe 300, the multiple flow channels 301 are bundled together and twisted. For convenience, the flattened pipe 300 is divided into a lower section 310 located towards the back in the figure and an upper section 320 located towards the front in the figure. Consequently, the multiple flow channels 301 are also divided, for convenience, into a lower flow channel 311 within the lower section 310 and an upper flow channel 322 within the upper section 320. The lower flow channel 311 extends from the upstream side of the refrigerant to the downstream side of the refrigerant, and from the upstream side of the air to the downstream side of the air. The lower flow channel 311 is an example of a first sub-flow channel. The upper flow channel 322 extends from the upstream side of the refrigerant to the downstream side of the refrigerant, and from the downstream side of the air to the upstream side of the air. The upper flow channel 322 is an example of a second sub-flow channel. Note that the portion of the lower flow channel 311 formed below the upper flow channel 322 is not actually visible in Figure 9, but is shown with a dashed line for illustrative purposes.

[0065] Here, we focus on the lower channel 311 and the upper channel 322 that constitute a single channel 301. In this case, it is desirable that the angle at which the lower channel 311 extends within the flattened pipe 300 is approximately the same as the angle at which the upper channel 322 extends within the flattened pipe 300. For example, this can be interpreted as it is desirable that the angle between the lower channel 311 and the direction of airflow be approximately the same as the angle between the upper channel 322 and the direction of airflow.

[0066] (Fourth embodiment) In the fourth embodiment, the flattened tube 3, which is the flattened tube 400, adopts a shape that causes turbulence in the flattened tube 100 or the flattened tube 200.

[0067] In the first example of the flattened tube 400 in the fourth embodiment, the outer wall of the flattened tube 100 or the flattened tube 200 is made into an uneven or wave-shaped form. As a result, air turbulence is generated in the first example of the flattened tube 400.

[0068] In the second example of the flattened tube 400 in the fourth embodiment, the flow path 101 of the flattened tube 100 or the flow path 201 of the flattened tube 200 is formed in a zigzag pattern. As a result, refrigerant turbulence is generated in the second example of the flattened tube 400.

[0069] Figure 10 is a cross-sectional view showing an example of the configuration of a flat pipe 400 in the fourth embodiment. Here, the flat pipe 400 is an example in which the outer wall of the flat pipe 100 has an uneven shape. Specifically, the lower plate 410 located below the middle plate 420 and the upper plate 430 located above the middle plate 420 have an uneven shape. Here, the lower plate 410 and upper plate 430 of the flat pipe 400 correspond to the lower plate 110 and upper plate 130 of the flat pipe 100, respectively. Also, the middle plate 420 corresponds to the middle plate 120 of the flat pipe 100. As a result, the lower channel 411 and upper channel 433 also have shapes corresponding to the uneven shapes of the lower plate 410 and upper plate 430, respectively. Here, the lower channel 411 and upper channel 433 of the flattened pipe 400 correspond to the lower channel 111 and upper channel 133 of the flattened pipe 100, respectively. Furthermore, while the lower plate 410 and upper plate 430 of the flattened pipe 400 are preferably made of SUS (stainless steel), they may also be made of copper, aluminum, or the like.

[0070] Thus, in the flattened tube 400 of the fourth embodiment, the refrigerant or air enters a turbulent state, and heat transfer is promoted.

[0071] (Manufacturing method) Next, we will describe the manufacturing method for the flattened tube 100. The same applies to the flattened tube 200, but here we will use the flattened tube 100 as an example. The flattened tube 100 is difficult to manufacture integrally using currently prevalent methods such as extrusion. Therefore, it is assumed that the flattened tube 100 will be manufactured by etching and diffusion bonding. Accordingly, as shown in Figure 3, the cross-section of the flow channel 101 is semicircular or semielliptical in shape. Furthermore, it is desirable that the length of the lower plate 110 and the upper plate 130 outside the folded connecting portion 122 be longer than the width of the flow channel 101 and the height of the flow channel wall 104. This is for fixing to the heat exchanger 1 and ensuring a leak margin. Furthermore, for the material of the flattened pipe 100, stainless steel (SUS) is envisioned as being usable at a relatively realistic price for this thickness.

[0072] (Solutions to problems 2 and 3) Next, we will discuss solutions to problems 2 and 3 when using the flattened pipe 100. The same applies to the flattened pipe 200, but here we will explain using the flattened pipe 100 as an example. To solve problems 2 and 3, it is advisable to increase the density of the flattened tubes 100. For high density, it is necessary to manufacture the flattened tubes 100 with a thickness of approximately 100 to 200 μm. Furthermore, for high density, it is also necessary to increase the number of flattened tubes 100 so that the pitch of the flattened tubes 100 becomes as small as the current pitch of the fins 4. This increases the heat exchange area between the air and the refrigerant, enabling 100% fin efficiency. In other words, because air pressure loss does not increase, the heat exchange area can be increased without increasing the power consumption or noise of the fan (not shown). Also, since fin 4 is not needed, the temperature distribution of fin 4 is eliminated, and the heat loss due to heat conduction by fin 4 is eliminated. In other words, 100% fin efficiency can be achieved. Therefore, it is desirable to have a configuration that can solve both Problem 2 and Problem 3 simultaneously.

[0073] Furthermore, in heat exchangers without fins 4 as described above, considering drainage, the line connecting the refrigerant inlet and outlet must have a component in the direction of gravity. Therefore, it is desirable that the liquid-side header 5 and the gas-side header 6 be horizontal headers that are mounted vertically and extend in a substantially horizontal direction.

[0074] On the other hand, in the heat exchanger 1 shown in Figure 1, a drainage path can be formed by the fins 4, so there are no constraints on the line connecting the refrigerant inlet and outlet from a drainage perspective. However, from the perspective of refrigerant pressure loss, it becomes necessary to select either a vertical header or a horizontal header. In Figure 1, vertical headers are used as the liquid-side header 5 and the gas-side header 6. [Explanation of Symbols]

[0075] 1…Heat exchanger, 2…Heat exchange section, 3, 100, 200, 300, 400…Flat tube, 4…Fin, 5…Liquid side header, 6…Gas side header, 101, 201, 301…Flow path, 110, 210, 410…Lower plate, 111, 221, 411…Lower flow path, 120, 220, 420…Middle plate, 122, 222…Folded connecting section, 130, 230, 430…Upper plate, 133, 223, 433…Upper flow path, 310…Lower part, 311…Lower flow path, 320…Upper part, 322…Upper flow path

Claims

1. It has multiple channels through which a refrigerant, which exchanges heat with a fluid, flows. Each of the aforementioned plurality of flow paths is A first partial flow path extends from the upstream side to the downstream side in the flow direction of the refrigerant, A second partial flow path extends from the downstream side to the upstream side in the flow direction of the fluid, with the flow path extending from the upstream side to the downstream side in the flow direction of the refrigerant. Flat tubes for heat exchangers, including...

2. Composed of multiple plates, The first partial flow path is formed in the first plate among the plurality of plates, The flat tube for a heat exchanger according to claim 1, wherein the second partial flow path is formed in the second plate among the plurality of plates.

3. The flat tube for a heat exchanger according to claim 1, wherein each of the plurality of flow paths further includes a connecting portion that connects the first partial flow path and the second partial flow path.

4. Composed of multiple plates, The first partial flow path is formed in the first plate among the plurality of plates, The second partial flow channel is formed in the second plate among the plurality of plates, The flattened tube for a heat exchanger according to claim 3, wherein the connecting portion is formed on a third plate sandwiched between the first plate and the second plate among the plurality of plates.

5. The flattened tube for a heat exchanger according to claim 4, wherein the third plate is thinner than at least one of the first plate, the second plate, the walls separating the first partial flow channels provided on the first plate, and the walls separating the second partial flow channels provided on the second plate.

6. The flat tube for a heat exchanger according to claim 4, wherein the width dimension or cross-sectional area of ​​the connecting portion is greater than the width dimension or cross-sectional area of ​​the first partial flow path and the second partial flow path.

7. Composed of multiple plates, The flattened tube for a heat exchanger according to claim 3, wherein the first partial flow path, the second partial flow path, and the communication portion are formed in a third plate sandwiched between the first plate and the second plate among the plurality of plates.

8. The flattened tube for a heat exchanger according to claim 7, wherein the wall separating the first partial flow path and the second partial flow path provided in the third plate is thinner than at least one of the wall separating the first partial flow paths and the wall separating the second partial flow paths.

9. The flat tube for a heat exchanger according to claim 7, wherein the width dimension or cross-sectional area of ​​the connecting portion is greater than the width dimension or cross-sectional area of ​​the first partial flow path and the second partial flow path.

10. The flat tube for a heat exchanger according to claim 3, wherein all of the plurality of flow paths include the first partial flow path, the second partial flow path, and the connecting portion.

11. The flat tube for a heat exchanger according to claim 1, wherein the first partial flow path and the second partial flow path are formed by twisting the plurality of flow paths together.

12. The flat tube for a heat exchanger according to any one of claims 1 to 11, wherein the plurality of flow paths are independent of each other.

13. The flat tube for a heat exchanger according to any one of claims 1 to 11, wherein the angle that the first partial flow path makes with the fluid flow direction is substantially the same as the angle that the second partial flow path makes with the fluid flow direction.

14. The flattened tube for a heat exchanger according to any one of claims 1 to 11, wherein the cross-sections of the first partial flow path and the second partial flow path have a semicircular or semielliptical shape.

15. A first header into which a refrigerant undergoes heat exchange with a fluid flows, Multiple flattened tubes having multiple flow paths through which the refrigerant flows, A second header through which the refrigerant that has flowed through the plurality of flow paths is discharged, Equipped with, Each of the aforementioned plurality of flow paths is A first partial flow path extends from the upstream side to the downstream side in the flow direction of the refrigerant, A second partial flow path extends from the downstream side to the upstream side in the flow direction of the fluid, with the flow path extending from the upstream side to the downstream side in the flow direction of the refrigerant. A heat exchanger, including one.

16. The system further comprises fins installed between the plurality of flattened tubes, The heat exchanger according to claim 15, wherein the first header and the second header are vertical headers extending substantially vertically.

17. The aforementioned multiple flattened tubes are arranged without fins, The heat exchanger according to claim 15, wherein the first header and the second header are horizontal headers extending substantially horizontally.

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