Double-layer pipe for heat exchange

Abstract

The present invention provides a heat exchange double-layer pipe having a novel structure, which can suppress pressure loss of fluids flowing through an inner flow path and an outer flow path, and can further improve heat exchange efficiency between the fluids. In a double-layer pipe (10) for heat exchange, an inner pipe (12) is inserted into an outer pipe (14), and heat exchange can be performed between fluids flowing in an inner flow path (16) in the inner pipe (12) and an outer flow path (46) between the inner pipe (12) and the outer pipe (14), in a straight pipe section that forms a heat exchange section by extending linearly in the longitudinal direction of the pipe, the inner pipe (12) is inserted into the outer pipe (14), and the outer pipe (14) is inserted into the inner pipe (12). The tube wall (20a) of the inner tube (12) has a concavo-convex cross-sectional shape in which a plurality of convex sections (24) are provided in the circumferential direction, and an inclined tube wall section (26) in which the convex sections (24) spirally extend in the longitudinal direction of the tube and a turbulent flow generating tube wall section (28) in which the lead angle of the convex sections (24) is different from that of the inclined tube wall section (26) are formed in line in the longitudinal direction of the tube on the tube wall (20a) of the inner tube (12).

Description

Technical Field

[0001] The present invention relates to a double tube for heat exchange used in a heat exchanger such as an air conditioner of a motor vehicle, a refrigerator, etc. Background Art

[0002] In the past, a part of the piping of a heat exchanger of an air conditioner, a car refrigerator, etc., of a motor vehicle sometimes uses a double-layer heat exchange tube in which an inner tube is inserted into an outer tube. The double-layer heat exchange tube, as shown in, for example, Japanese Patent No. 6823906 (Patent Document 1), can perform heat exchange between a heat medium flowing inside the inner tube and a heat medium flowing between the inner tube and the outer tube. If such a double-layer heat exchange tube is used, the heat exchange between the heat mediums in the double-layer heat exchange tube can achieve high efficiency in cooling / heating of the heat medium in the refrigeration cycle.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent No. 6823906 Summary of the invention

[0006] Problems to be solved by the invention

[0007] Incidentally, in order to improve the heat exchange efficiency between the heat medium flowing in the inner flow path in the inner tube and the outer flow path between the inner tube and the outer tube, respectively, in Patent Document 1, a structure is adopted in which a plurality of convex portions are provided in the circumferential direction on the tube wall of the inner tube, and these convex portions extend in a spiral shape. As a result, the surface area of ​​the tube wall of the inner tube is larger than that of the tube wall extending straightly with a constant circular cross section, thereby achieving an improvement in heat exchange efficiency. In addition, the tube wall of the inner tube is formed in a spiral shape, thereby suppressing the increase in the flow resistance of the heat medium, achieving a reduction in pressure loss, and not requiring high pump performance, etc.

[0008] However, the inventors of the present invention have further studied the double-layer tube for heat exchange having a spiral inner tube wall as in Patent Document 1, and found that there is still room for improvement. That is, it is known that in the structure of Patent Document 1, the heat medium flowing near the tube wall in the inner flow path generates a sufficient temperature change through heat exchange with the heat medium flowing in the outer flow path, while the heat medium flowing in the central portion of the inner flow path away from the tube wall does not contribute sufficiently to the heat exchange with the outer flow path, and the temperature change is small.

[0009] In particular, it is found that the temperature difference of the heat medium between the region near the tube wall of the spiral inner tube and the region near the center far from the tube wall is greater in the portion extending linearly in the tube length direction than in the portion where the pipeline is bent or curved.

[0010] On the other hand, in recent years, changes in heat medium and the like have been studied from the viewpoint of environmental protection and the like, and therefore, there is a strong demand for further improvement in the heat exchange efficiency of the entire double tube for heat exchange.

[0011] The present invention is completed based on the new insights obtained as described above under such circumstances, and the problem it solves is to provide a double-layer tube for heat exchange with a new structure that can suppress the pressure loss of the heat medium flowing in the inner flow path and the outer flow path respectively, and can further improve the heat exchange efficiency between these heat media.

[0012] Means used to solve problems

[0013] The following describes the preferred modes for understanding the present invention, but the modes described below are described for exemplary purposes, and can be used in combination with each other as appropriate. The multiple components described in each mode can also be identified and used as independently as possible, and can also be used in combination with any component described in other modes as appropriate. Therefore, the present invention is not limited to the modes described below, and various other modes can be realized.

[0014] The first mode is a double tube for heat exchange, wherein an inner tube is inserted into an outer tube, and heat exchange can be performed between heat media flowing in an inner flow path in the inner tube and an outer flow path between the inner tube and the outer tube, respectively.

[0015] In the straight tube portion extending linearly in the tube length direction to constitute the heat exchange portion,

[0016] The inner tube wall has a concave-convex cross-sectional shape with a plurality of convex portions arranged in the circumferential direction.

[0017] In addition, on the tube wall of the inner tube, an inclined tube wall portion in which the convex portion spirally extends in the tube length direction and a turbulence generating tube wall portion in which the lead angle of the convex portion is different from that of the inclined tube wall portion are formed in series in the tube length direction.

[0018] According to the double-layered heat exchange tube formed in accordance with the present embodiment, the tube wall of the inner tube that separates the inner flow path from the outer flow path is formed into a concave-convex cross-sectional shape having a plurality of convex portions in the circumferential direction, and the surface area becomes larger, thereby achieving an improvement in heat exchange efficiency between the heat medium flowing in the inner flow path and the outer flow path respectively. In addition, the tube wall of the inner tube extends continuously in a spiral shape along the tube length direction in a predetermined concave-convex cross-sectional shape, so that the heat medium flows smoothly in both the inner flow path and the outer flow path, reducing the pressure loss caused by the tube wall of the inner tube being formed into a concave-convex shape. Therefore, excellent heat exchange efficiency can be achieved without the need for a high-performance pump or the like.

[0019] In addition, a turbulence generating wall portion is provided on the wall of the inner tube so that the lead angle of the convex portion is different from that of the inclined wall portion, and the inclined wall portion and the turbulence generating wall portion are arranged in a straight line in the length direction of the tube. As a result, turbulence is generated in the flow of the heat medium in the inner flow path and the outer flow path at the connection portion between the inclined wall portion and the turbulence generating wall portion, and the heat medium in each flow path is stirred. As a result, it is possible to reduce or eliminate the situation in which the heat medium that has transferred heat tends to stay near the wall of the inner tube, and to achieve equalization of temperature distribution in the inner flow path and the outer flow path. Therefore, in each heat medium flowing near the wall of the inner tube in the inner flow path and the outer flow path, the reduction of the temperature difference caused by heat exchange can be suppressed, and the heat exchange efficiency can be improved.

[0020] The second aspect is based on the double tube for heat exchange described in the first aspect,

[0021] The length of the turbulent flow generating tube wall portion in the tube length direction is shorter than the length of the inclined tube wall portion in the tube length direction.

[0022] According to the double-layer heat exchange tube formed in the structure according to this mode, the heat medium can flow smoothly due to the inclined tube wall portion in a longer area in the tube length direction, thereby reducing the pressure loss. In addition, the turbulent flow generating tube wall portion exerts a turbulent stirring effect on the heat medium at the connection portion with the inclined tube wall portion, so even if the turbulent flow generating tube wall portion is shorter than the inclined tube wall portion, the heat exchange efficiency can be effectively improved.

[0023] A third aspect is a double tube for heat exchange according to the first aspect or the second aspect,

[0024] The convex portion of the turbulent flow generating tube wall portion is formed as a straight tube wall portion extending linearly in the tube length direction.

[0025] According to the double-layer tube for heat exchange formed in accordance with the structure of this method, the turbulence generating tube wall portion is formed as a straight tube wall portion, so that the change in the flow direction of the heat medium at the connection portion with the inclined tube wall portion becomes larger, and the improvement in heat exchange efficiency brought about by the generation of turbulence can be more effectively achieved.

[0026] A fourth aspect is the double tube for heat exchange according to any one of the first to third aspects,

[0027] The inclined tube wall portion and the turbulent flow generating tube wall portion in the tube wall of the inner tube are formed in a constant cross-sectional shape over the entire length.

[0028] According to the double tube for heat exchange formed in the structure according to this embodiment, it is possible to avoid pressure loss due to a change in the cross-sectional shape of the tube wall of the inner tube, and to allow the heat medium to flow more efficiently in the inner flow path and the outer flow path.

[0029] A fifth aspect is the double tube for heat exchange according to any one of the first to fourth aspects,

[0030] The convex portion in the inclined tube wall portion extends spirally in the tube length direction at a constant lead angle.

[0031] According to the double heat exchange tube having the structure according to this embodiment, smoother flow of the heat medium in the inner flow path and the outer flow path is achieved at the position corresponding to the inclined tube wall portion, thereby achieving a further reduction in pressure loss.

[0032] A sixth aspect is the double tube for heat exchange according to any one of the first to fifth aspects,

[0033] The inclined tube wall portions are provided on both sides of the turbulent flow generating tube wall portion in the tube length direction.

[0034] According to the double-layer tube for heat exchange formed in accordance with the present method, connection portions connected to the inclined tube wall portions are formed at both ends of the turbulence generating tube wall portion, so that the heat medium in the inner flow path and the outer flow path is stirred twice by one turbulence generating tube wall portion, and the heat exchange efficiency between the heat media can be effectively improved with a smaller number of turbulence generating tube wall portions.

[0035] Effects of the Invention

[0036] According to the present invention, it is possible to suppress the pressure loss of the heat medium flowing in the inner flow path and the outer flow path, respectively, and further improve the heat exchange efficiency between these heat media. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a front view showing a double tube for heat exchange as a first embodiment of the present invention.

[0038] Figure 2 yes Figure 1 A top view of a double-layer tube for heat exchange is shown.

[0039] Figure 3 yes Figure 2 III-III sectional view.

[0040] Figure 4 It is a magnified representation Figure 3 FIG. 4 is a diagram of section IV-IV.

[0041] Figure 5It is a magnified representation Figure 3 Figure 4 is a diagram of a VV cross section.

[0042] Figure 6 It is composed Figure 1 A perspective view of the inner tube of a double tube for heat exchange is shown.

[0043] Figure 7 yes Figure 6 A cutaway perspective view of the inner tube is shown.

[0044] Figure 8 It is a diagram showing the simulation results of the flow of the heat medium in the inner flow path of the double tube for heat exchange.

[0045] Fig. 9 It is a diagram showing the simulation results of the temperature distribution of the heat medium in the inner flow path of the double tube for heat exchange. DETAILED DESCRIPTION

[0046] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0047] exist Figure 1 to Figure 5 FIG. 1 shows a double-layer heat exchange tube 10 as a first embodiment of the present invention. The double-layer heat exchange tube 10 is a straight tube extending in a straight line. Figure 3 to Figure 5 As shown in FIG. 1 , the inner tube 12 is inserted into the outer tube 14. In the following description, in principle, the up and down directions refer to Figure 1 The up-down direction and the left-right direction refer to the length direction of the tube. Figure 1 The left and right directions in the text are Figure 2 The up and down directions in .

[0048] The inner tube 12 extends straightly in the left-right direction and has an inner flow path 16 that penetrates in the length direction of the tube. In order to improve the heat exchange efficiency between the heat medium described later, the forming material of the inner tube 12 is preferably a forming material with high thermal conductivity, and preferably a forming material with excellent corrosion resistance to the heat medium described later. Specifically, for example, aluminum alloy, iron (stainless steel), copper alloy, etc. can be preferably used as the forming material of the inner tube 12. The inner tube 12 is composed of a tube wall 20a of the middle area 18 and tube walls 20b, 20b of the end areas 22, 22. The middle area 18 is a straight tube part that cooperates with the outer tube 14 described later to constitute a heat exchange part, and the end areas 22, 22 constitute the inflow part and outflow part of the heat medium at both ends of the heat exchange part.

[0049] like Figure 4 , Figure 5As shown, the tube wall 20a of the middle region 18 has a concave-convex cross-sectional shape with three convex portions 24, 24, 24 in the circumferential direction. The tube wall 20 of the inner tube 12 is formed into a generally triangular shape with rounded corners by having three convex portions 24, 24, 24 at equal intervals in the circumferential direction. The convex portion 24 is formed into a curved cross-sectional shape with a smaller curvature radius than the inner circumferential surface of the outer tube 14. The curvature radius between the convex portions 24, 24 adjacent to each other in the circumferential direction is larger than the curvature radius of the inner circumferential surface of the outer tube 14.

[0050] Also like Figure 6 , Figure 7 As shown, the tube wall 20a in the middle region 18 in the tube length direction of the inner tube 12 is continuously formed with an inclined tube wall portion 26 and a straight tube wall portion 28 as a turbulent flow generating tube wall portion in the tube length direction. In this embodiment, a plurality of inclined tube wall portions 26 and a plurality of straight tube wall portions 28 are alternately and continuously arranged in a manner of being arranged in series in the tube length direction.

[0051] The inclined tube wall portion 26 is formed into a spiral shape in which the convex portion 24 is inclined in the circumferential direction and extends in the tube length direction. The convex portion 24 of each inclined tube wall portion 26 preferably extends in a spiral shape in the tube length direction at a certain lead angle. The lead angles of the convex portions 24 extending in a spiral shape may be different between the plurality of inclined tube wall portions 26, but are set to be the same as each other in the present embodiment. The lead angle θ of the convex portion 24 in the inclined tube wall portion 26 is set in the range of 0°<θ<90°.

[0052] The convex portion 24 of the straight tube wall portion 28 is not inclined in the circumferential direction but extends linearly in the tube length direction. The lead angle of the straight tube wall portion 28 is 90°, which is different from the lead angle of the inclined tube wall portion 26. The straight tube wall portion 28 is shorter in the tube length direction than the inclined tube wall portion 26.

[0053] like Figure 4 , Figure 5 As shown, the inclined tube wall portion 26 and the straight tube wall portion 28 are formed into substantially the same cross-sectional shape. Both the inclined tube wall portion 26 and the straight tube wall portion 28 are formed into substantially constant cross-sectional shapes throughout the entire length direction of the tube. Therefore, the tube wall 20a of the middle region 18 of the inner tube 12 is formed into a constant cross-sectional shape throughout the entire length.

[0054] The two ends of the tube wall 20a in the middle area 18 of the inner tube 12 are composed of inclined tube wall portions 26, 26, and a plurality of straight tube wall portions 28 are located in the middle of the two ends that deviate from the tube wall 20a in the tube length direction. Therefore, the inclined tube wall portions 26 are located on both sides of the straight tube wall portions 28 in the tube length direction.

[0055] Each tube wall 20b of the end regions 22, 22 of the inner tube 12 that deviate from the middle region 18 along the tube length direction is formed as a cylindrical tube wall portion 30. The cylindrical tube wall portion 30 extends along the tube length direction with a substantially constant circular cross section. The cross-sectional shape of the cylindrical tube wall portion 30 is different from that of the inclined tube wall portion 26 and the straight tube wall portion 28. The cylindrical tube wall portions 30, 30 of the end regions 22, 22 are continuously arranged in one piece with the inclined tube wall portions 26, 26 at both ends of the middle region 18, and the inner holes of the middle region 18 and the end regions 22, 22 are connected to each other to form an inner flow path 16 that penetrates in the axial direction. It should be noted that in the present embodiment, an example of a cylindrical tube wall portion 30 extending in a straight tube shape is shown, but the cylindrical tube wall portion 30 can also be appropriately bent in the middle.

[0056] It should be noted that the manufacturing method of the inner tube 12 is not particularly limited, and the inner tube 12 of a predetermined shape can be easily obtained by, for example, hydraulic forming. That is, by applying a large hydraulic pressure to the inner peripheral surface of the cylindrical tube blank in a state where the tube blank is inserted into the cavity of the mold, the tube blank expanded by the hydraulic pressure is pressed against the inner surface of the cavity of the mold, and the concavo-convex inner surface of the cavity is transferred to the tube blank, thereby forming the inner tube 12 of a predetermined shape. In this way, if the inner tube 12 is formed by hydraulic forming, it is easy to obtain an inner tube 12 of a complex shape in which a plurality of inclined tube wall portions 26 and straight tube wall portions 28 are alternately provided. In addition, the inner tube 12 can also be formed with a large degree of freedom in shape.

[0057] The outer tube 14 extends linearly in the left-right direction and has an inner diameter dimension that allows the inner tube 12 to be inserted through. The outer tube 14 is preferably formed of a material having excellent corrosion resistance to the heat medium described later, for example, an aluminum alloy, iron (stainless steel), a copper alloy, etc. The tube wall 32a of the middle region 18 of the outer tube 14 is formed as a cylindrical middle tube wall portion 34 extending in a straight tube shape with a substantially constant circular cross section. The inner diameter dimension of the tube wall 32a of the outer tube 14 is substantially the same as the maximum outer diameter dimension of the inner tube 12 or the inner diameter dimension of the tube wall 32a of the outer tube 14 is slightly larger than the maximum outer diameter dimension of the inner tube 12, and can be inserted outside the inner tube 12.

[0058] Each tube wall 32b of the end regions 22, 22 of the outer tube 14 is formed as a connecting tube wall portion 36. The connecting tube wall portion 36 has an expanded diameter portion 38 having a larger diameter than the intermediate tube wall portion 34, and both outer sides of the expanded diameter portion 38 in the tube length direction are formed as fitting portions 40 having a smaller diameter than the intermediate tube wall portion 34.

[0059] A connection hole 42 is formed in the enlarged diameter portion 38 of the outer tube 14, which passes through a portion of the circumference. A connection pipe 44 which is separate from the outer tube 14 is inserted and installed in the connection hole 42. Figure 3As shown, one end of the connecting pipe 44 is connected to the inner hole of the outer pipe 14 and is connected in series with the outer pipe 14. The connecting pipe 44 of this embodiment is formed in a shape that is bent at the front end extending radially outward from the expanded diameter portion 38 of the outer pipe 14 and extends to the left and right sides, but the shape (piping path) of the connecting pipe 44 is appropriately set in consideration of interference with other components, the position of the equipment connected to the other end (for example, the condenser 54 and the expansion valve 56 described later), etc.

[0060] The inner tube 12 is inserted through the outer tube 14. The inner tube 12 and the outer tube 14 are positioned relative to each other by fitting the fitting parts 40, 40 of the connecting tube wall parts 36, 36 constituting the two ends of the outer tube 14 into the outer peripheral surfaces of the cylindrical tube wall parts 30, 30 of the inner tube 12. The cylindrical tube wall parts 30, 30 of the tube walls 20b, 20b constituting the end regions 22, 22 of the inner tube 12 extend toward both outer sides in the tube length direction compared to both ends of the outer tube 14. It should be noted that the fitting parts 40 may be formed by performing a diameter reduction process on both ends of the outer tube 14 after the inner tube 12 is inserted through the outer tube 14, and it is not necessary to form them in advance on the outer tube 14. In this case, for example, when the diameter reduction of the fitting parts 40 is formed, the fitting parts 40 are fitted into the cylindrical tube wall parts 30. In order to prevent leakage of the heat medium described later, both ends of the outer tube 14 and the inner tube 12 are sealed in a fluid-tight manner by bonding, brazing, or interposing an O-ring.

[0061] In the middle region 18, the tube wall 20a of the inner tube 12 is inserted into the tube wall 32a of the outer tube 14, thereby forming a double-layer tube structure. Figure 4 , Figure 5 As shown, the convex portions 24, 24, 24 in the tube wall 20a of the inner tube 12 are close to or in contact with the tube wall 32a (intermediate tube wall portion 34) of the outer tube 14, and the portion of the tube wall 20a that is away from the convex portions 24, 24, 24 is separated from the tube wall 32a due to the difference in curvature. As a result, an outer flow path 46 extending in the tube length direction is formed between the tube wall 20a of the inner tube 12 and the tube wall 32a of the outer tube 14. Therefore, in the intermediate region 18, the inner flow path 16 formed by the inner hole of the inner tube 12 and the outer flow path 46 formed between the inner tube 12 and the outer tube 14 around the inner flow path 16 are respectively formed on the inner circumference side and the outer circumference side of the inner tube 12 relative to the tube wall 20a. The outer flow path 46 may be a single flow path continuous in the circumferential direction, or may be formed into a plurality of substantially independent flow paths by partially contacting the outer circumferential surface of the inner tube 12 (convex portion 24) with the inner circumferential surface of the outer tube 14 in the circumferential direction.

[0062] like Figure 3As shown, the inner flow path 16 is connected to the evaporator 50 and the compressor 52 of the refrigeration cycle 48 constituting the heat exchanger (refrigerator or heat pump) through the inner holes of the cylindrical tube wall parts 30, 30 of the inner tube 12. In addition, the outer flow path 46 is connected to the inner hole of the connecting pipe 44 through the radial direction between the cylindrical tube wall part 30 of the inner tube 12 and the expanded diameter part 38 of the outer tube 14, and both ends of the connecting pipe 44 are connected to the condenser 54 and the expansion valve 56. In addition, in the inner flow path 16, the low-pressure and low-temperature heat medium cooled by the expansion valve 56 and passed through the evaporator 50 flows toward the compressor 52, and in the outer flow path 46, the high-pressure and high-temperature heat medium heated by the compressor 52 and the condenser 54 flows toward the evaporator 50.

[0063] The compressor 52, condenser 54, expansion valve 56, and evaporator 50 are not components of the double tubes 10 for heat exchange, but constitute the refrigeration cycle (heat exchange cycle) 48 including the double tubes 10 for heat exchange, and thus will be briefly described.

[0064] The compressor 52 is a device that compresses and heats the heat medium flowing in the refrigeration cycle 48. The compressor 52 is connected to the downstream side of the inner tube 12 in the double tube 10 for heat exchange, and the heat medium that has completed heat exchange and flows out of the inner flow path 16 flows in and is pressurized and heated.

[0065] The condenser 54 is a heat exchanger for heating the conditioned air, and is a device that condenses and liquefies the heat medium that has become a gas phase due to the heating of the compressor 52 by exchanging heat with the outside air. The condenser 54 is connected to the downstream side of the compressor 52 directly or via a pipe, and is connected to the upstream side of the outer flow path 46, and the condensed heat medium flows into the outer flow path 46.

[0066] The expansion valve 56 is a device that cools the liquid phase heat medium flowing out of the condenser 54 to a predetermined temperature by decompressing and expanding it. The expansion valve 56 is connected to the downstream side of the outer flow path 46 in the double-layered heat exchange pipe 10, and the heat medium flowing out of the outer flow path 46 that has completed the heat exchange flows in and is decompressed and cooled.

[0067] The evaporator 50 is a refrigeration heat exchanger for cooling the conditioned air, and is a device that evaporates the liquid phase heat medium that has been decompressed and cooled by the expansion valve 56, and cools the conditioned air using the latent heat during evaporation. The evaporator 50 is provided on the downstream side of the expansion valve 56, into which the heat medium that has been decompressed and cooled by the expansion valve 56 flows, and is provided on the upstream side of the inner flow path 16 of the double-layered heat exchange tube 10, into which the heat medium that has been heated by the cooling of the conditioned air flows.

[0068] It should be noted that the heat medium circulating in the refrigeration cycle 48 is a fluid (gas or liquid), such as various well-known fluids (refrigerants) such as Freon, carbon dioxide, and ammonia, which are usually used in the refrigeration cycle 48 of air conditioners and refrigerators (cold storages).

[0069] In the refrigeration cycle 48 equipped with such various devices, in the double tube 10 for heat exchange, heat transfer (heat exchange) based on the temperature difference between the heat media occurs between the low-temperature heat medium flowing in the inner flow path 16 and the high-temperature heat medium flowing in the outer flow path 46. As a result, the heat medium flowing to the compressor 52 through the inner flow path 16 of the double tube 10 for heat exchange is heated by the heat received from the heat medium flowing in the outer flow path 46 before being pressurized and heated by the compressor 52. In addition, the heat medium flowing to the expansion valve 56 through the outer flow path 46 of the double tube 10 for heat exchange is cooled by heat dissipation to the heat medium flowing in the inner flow path 16 before being depressurized and cooled by the expansion valve 56. It should be noted that in order to improve the heat exchange efficiency between the heat media, it is preferred that the flow direction of the heat medium in the inner flow path 16 and the flow direction of the heat medium in the outer flow path 46 are opposite to each other. It should be noted that in Figure 3 In FIG. 1 , the flow direction of the heat medium in the inner flow path 16 is indicated by a solid arrow, and the flow direction of the heat medium in the outer flow path 46 is indicated by a dotted arrow.

[0070] The heat medium flowing in the inner flow path 16 flows in a substantially laminar flow without being stirred in the outer periphery and the inner periphery in the inclined tube wall portion 26. Thus, the flow of the heat medium flowing in the inclined tube wall portion 26 is not disturbed but is stable, thereby suppressing pressure loss and making it possible to efficiently flow the heat medium in the refrigeration cycle 48.

[0071] The cross-sections of the inclined tube wall portion 26 and the straight tube wall portion 28 that are perpendicular to the tube length direction have the same shape, and the tube wall 20a of the intermediate region 18 is formed into a substantially constant cross-sectional shape throughout the entire tube length direction. Therefore, pressure loss caused by changes in the cross-sectional shapes of the inner flow path 16 and the outer flow path 46 is avoided.

[0072] In addition, in the present embodiment, the total length of the inclined tube wall portion 26 is longer than the total length of the straight tube wall portion 28 in the tube wall 20a of the middle region 18 of the inner tube 12. Therefore, as described later, even if turbulence occurs at the connection portion between the inclined tube wall portion 26 and the straight tube wall portion 28, the heat medium stably flows over a wide area of ​​the inner flow path 16 and the outer flow path 46, thereby suppressing pressure loss.

[0073] The heat medium flowing in the inner flow path 16 is disturbed in the flow due to the rapid change of the lead angle at the connection part of the inclined tube wall part 26 and the straight tube wall part 28. As a result, the heat medium flowing in the inner periphery of the inner flow path 16 and the heat medium flowing in the outer periphery of the inner flow path 16 are stirred at the connection part of the inclined tube wall part 26 and the straight tube wall part 28. Therefore, the temperature of the heat medium in the inner flow path 16 can be uniformized, and it can be prevented that only the heat medium flowing in the outer periphery becomes high temperature due to heat exchange, while the heat medium flowing in the inner periphery hardly contributes to the heat exchange and remains low temperature. As a result, the heat medium flowing near the tube wall 20a in the inner flow path 16 is maintained at a relatively low temperature, and the heat exchange efficiency is improved between the heat medium flowing in the outer flow path 46.

[0074] Similarly, regarding the heat medium flowing in the outer flow path 46, the flow turbulence caused by the sharp change in the lead angle occurs at the connection portion between the inclined tube wall portion 26 and the straight tube wall portion 28, so that the heat medium in the outer flow path 46 is stirred and the temperature is made uniform. As a result, it is possible to prevent the heat medium flowing only in the inner peripheral portion of the outer flow path 46 from becoming low temperature, and by increasing the temperature difference with the heat medium in the inner flow path 16, the heat exchange efficiency can be improved. It should be noted that achieving uniform temperature of the heat medium does not mean that the temperature of the entire heat medium is strictly constant, but means that the temperature difference in the heat medium is reduced.

[0075] As described above, in the present embodiment, in the straight tube portion constituting the heat exchange portion, the inner tube 12 is provided with the inclined tube wall portion 26 in which the plurality of convex portions 24 formed in the circumferential direction extend in a spiral shape in the tube length direction, and the turbulent flow generating tube wall portion 28 having the convex portions 24 with different lead angles is provided in the middle portion in the tube length direction. Furthermore, since the plurality of inclined tube wall portions 26 and the plurality of straight tube wall portions 28 are alternately provided in the tube length direction, turbulent flow is generated at the connection portion between the inclined tube wall portion 26 and the straight tube wall portion 28 at a plurality of locations in the tube length direction. As a result, the temperature difference between the inner and outer peripheries is more effectively reduced in the heat medium in the inner flow path 16 and the heat medium in the outer flow path 46, and the heat exchange efficiency is further improved.

[0076] The inclined tube wall portions 26 are provided on both sides of each straight tube wall portion 28 in the tube length direction, so that the stirring effect of the heat medium caused by the generation of turbulence is exerted at both ends of each straight tube wall portion 28. As a result, the heat exchange efficiency can be advantageously improved by a relatively small number of straight tube wall portions 28. In particular, in the present embodiment, in the inner tube 12, the tube walls 20b, 20b of the end regions 22, 22 continuous with the tube wall 20a of the middle region 18 are formed as straight tube-shaped cylindrical tube wall portions 30, 30, so if both ends of the tube wall 20a are composed of the inclined tube wall portions 26, the stirring effect of the heat medium caused by the difference in lead angles between the inclined tube wall portions 26 and the cylindrical tube wall portions 30 can also be expected.

[0077] exist Figure 8 2 shows the simulation result of the flow of the heat medium in the inner flow path 16 . Figure 8 The comparative example shown in the upper section is a simulation result of a double-layer tube for heat exchange of a conventional structure, which has no straight tube wall portion (turbulence generating tube wall portion) but is formed as an inclined tube wall portion 26 in which a convex portion 24 extends helically at a substantially constant lead angle throughout the entire tube wall 20a. Figure 8 The example shown in the lower part of FIG. 1 is a simulation result of the double-walled heat exchange tube 10 according to the first embodiment having a straight tube wall portion 28. Figure 8 In FIG. 1 , the flow of the heat medium within a predetermined time is represented by a plurality of points and their movement trajectories, and in particular, the heat medium that is likely to be retained in each convex portion 24 of the inclined tube wall portion 26 of the inner tube 12 is observed.

[0078] exist Figure 8 In the comparative example of , the heat medium flowing near the tube wall of the inner tube flows in a spiral shape along the tube wall, and the heat medium flowing in a spiral shape in each convex portion of the tube wall hardly flows from the outer circumference to the inner circumference toward the center side of the inner tube, or vice versa. Figure 8In the embodiment of the invention, the heat medium flowing near the tube wall 20a flows in a spiral shape along the tube wall 20a in the inclined tube wall portion 26 in each convex portion 24, but the flow is turbulent in the straight tube wall portion 28, and a flow of the heat medium flows from the outer circumference to the inner circumference or vice versa toward the center side of the inner tube 12. Specifically, the following situation can be confirmed: in the heat medium flowing in the spiral shape in each convex portion 24, a plurality of smaller vortex flows are generated near the boundary from the inclined tube wall portion 26 to the straight tube wall portion 28, and the turbulent state is promoted by these vortex flows, so that the heat medium flowing in the spiral shape in each convex portion 24 and the heat medium flowing in a straight line in the central part of the inner tube 12 without being affected by these convex portions 24 are stirred with each other. Thus, in the double tube 10 for heat exchange according to the present invention having the turbulent flow generating tube wall portion (straight tube wall portion 28 ), the simulation results also confirmed that the temperature in the inner flow path 16 was equalized due to the stirring of the heat medium.

[0079] It should be noted that in Fig. 9 The simulation results of the temperature distribution of the heat medium flowing in the inner flow path are shown in FIG. Fig. 9 It can be seen that in the comparative example without the turbulent flow generating tube wall portion, the high-temperature heat medium on the outer circumference flowing along the tube wall of the inner tube and the low-temperature heat medium on the inner circumference flowing in the center area of ​​the inner tube are hardly mixed and flow in a substantially separated state. Fig. 9 It can be seen that in the embodiment in which the straight tube wall portion 28 is provided as the turbulent flow generating tube wall portion, the high-temperature heat medium at the outer periphery flowing along the tube wall 20a of the inner tube 12 in the inclined tube wall portion 26 and the low-temperature heat medium at the inner periphery flowing in the central area of ​​the inner tube 12 in the inclined tube wall portion 26 produce a flow change such that they are mixed with each other at the connecting portion of the inclined tube wall portion 26 and the straight tube wall portion 28. That is, according to Fig. 9 The simulation results of the temperature distribution also confirm that the straight tube wall portion 28 generates a flow in which the high-temperature heat medium on the outer periphery flows toward the center of the inner tube 12 and inward, or conversely, the low-temperature heat medium on the inner periphery flows toward the outer periphery.

[0080] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the specific description. For example, the double-layered heat exchange tube does not need to be a straight tube portion extending in a straight line as a whole, and the portion where the inclined tube wall portion and the turbulent flow generating tube wall portion are formed can be a straight tube. Therefore, the double-layered heat exchange tube can be formed into a shape that is appropriately bent and extended in a region that deviates from the portion where the inclined tube wall portion and the turbulent flow generating tube wall portion are formed.

[0081] The turbulence generating tube wall portion only needs to have a lead angle of the convex portion different from that of the inclined tube wall portion, and is not limited to a straight tube wall portion in which the convex portion extends in a straight line. For example, the portion in which the convex portion extends in a spiral shape at a lead angle greater or smaller than that of the convex portion in the inclined tube wall portion may be used as the turbulence generating tube wall portion. However, from the viewpoint of suppressing the increase of pressure loss, it is preferred that the lead angle of the convex portion in the turbulence generating tube wall portion is close to 90° and faces the flow direction toward the central axis of the tube. In addition, it is preferred to set the lead angle to be the same as the inclination direction of the convex portion in the inclined tube wall portion and not to be inclined in the opposite direction. In addition, from the viewpoint of suppressing the increase of pressure loss, a connecting tube wall portion may also be provided at the boundary portion connecting the inclined tube wall portion and the turbulence generating tube wall portion, and the connecting tube wall portion is transferred from the inclined tube wall portion to the turbulence generating tube wall portion by gradually or stage-by-stage changing the lead angle of the convex portion.

[0082] When a plurality of inclined tube wall portions are provided, the lead angles of the convex portions in the plurality of inclined tube wall portions may be the same as or different from each other. In addition, the lead angle of one inclined tube wall portion is preferably substantially constant, but may also vary locally or throughout the entirety. In addition, the plurality of inclined tube wall portions may also have different lengths in the tube length direction.

[0083] In the case where a plurality of turbulence generating tube wall portions are provided, the lead angles of the convex portions in these plurality of turbulence generating tube wall portions may be the same as or different from each other. Thus, one or several of the plurality of turbulence generating tube wall portions may be set as a straight tube wall portion with a lead angle of 90°, and the other turbulence generating tube wall portions may be set as a spiral with a lead angle less than 90°. In addition, the lead angle of a turbulence generating tube wall portion is preferably of a substantially constant size, but may also vary locally or throughout the entirety. In addition, the plurality of turbulence generating tube wall portions may also have different lengths in the tube length direction.

[0084] The number of the inclined tube wall portions and the turbulence generating tube wall portions, the length in the tube length direction, the configuration in the tube length direction, etc. are not particularly limited. In addition, the number, shape, and circumferential configuration of the convex portions in the inclined tube wall portions and the turbulence generating tube wall portions are not particularly limited. In addition, by providing a groove-shaped portion formed into a concave shape toward the outer periphery in the portion of the inclined tube wall portions and the turbulence generating tube wall portions that deviates from the convex portions in the circumferential direction, it is also possible to ensure a greater flow path cross-sectional area of ​​the outer flow path formed between the inner tube and the outer tube. The length of the turbulence generating tube wall portion is preferably shorter than the inclined tube wall portion, but it can also be longer than the length of the inclined tube wall portion.

[0085] In the embodiment, an example is given of a case where a refrigeration cycle 48 having a double-layer tube 10 for heat exchange is used for cooling / heating conditioned air to form an air-conditioning device for a motor vehicle, but the double-layer tube for heat exchange involved in the present invention can be used for heat exchange, for example, it can also be applied to the refrigeration cycle of a car refrigerator, etc.

[0086] Description of Reference Numerals

[0087] 10: Double tube for heat exchange (first embodiment);

[0088] 12: Inner tube;

[0089] 14: External tube;

[0090] 16: inner flow path;

[0091] 18: middle area;

[0092] 20a: tube wall;

[0093] 20b: tube wall;

[0094] 22: end area;

[0095] 24: convex part;

[0096] 26: inclined tube wall portion;

[0097] 28: straight tube wall portion (turbulence generating tube wall portion);

[0098] 30: cylindrical tube wall portion;

[0099] 32a: tube wall;

[0100] 32b: tube wall;

[0101] 34: middle tube wall;

[0102] 36: connecting the pipe wall;

[0103] 38: diameter expansion part;

[0104] 40: Chimeric part;

[0105] 42: connection hole;

[0106] 44: connecting pipeline;

[0107] 46: outer flow path;

[0108] 48: Refrigeration cycle;

[0109] 50: evaporator;

[0110] 52: compressor;

[0111] 54: condenser;

[0112] 56: Expansion valve.

Claims

1. A double-layer tube for heat exchange, wherein an inner tube is inserted into an outer tube, and heat exchange can be performed between heat media flowing in an inner flow path in the inner tube and an outer flow path between the inner tube and the outer tube, respectively, wherein: In the straight tube portion extending linearly in the tube length direction to constitute the heat exchange portion, The inner tube wall has a concave-convex cross-sectional shape with a plurality of convex portions arranged in the circumferential direction. In addition, on the tube wall of the inner tube, an inclined tube wall portion in which the convex portion spirally extends in the tube length direction and a turbulence generating tube wall portion in which the lead angle of the convex portion is different from that of the inclined tube wall portion are formed in series in the tube length direction.

2. The double-layer tube for heat exchange according to claim 1, wherein: The length of the turbulent flow generating tube wall portion in the tube length direction is shorter than the length of the inclined tube wall portion in the tube length direction.

3. The double-layer tube for heat exchange according to claim 1 or 2, wherein: The turbulent flow generating tube wall portion is formed as a straight tube wall portion in which the convex portion extends linearly in the tube length direction.

4. The double-layer tube for heat exchange according to any one of claims 1 to 3, wherein: The inclined tube wall portion and the turbulent flow generating tube wall portion in the tube wall of the inner tube are formed in a constant cross-sectional shape over the entire length.

5. The double-layer tube for heat exchange according to any one of claims 1 to 4, wherein: The convex portion in the inclined tube wall portion extends in a spiral shape in the tube length direction at a constant lead angle.

6. The double-layer tube for heat exchange according to any one of claims 1 to 5, wherein: The inclined tube wall portions are provided on both sides of the turbulent flow generating tube wall portion in the tube length direction.

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