Inner-groove tube and heat exchanger having excellent heat transfer

Abstract

The inner spiral finned tube of the present invention includes a tube body, a plurality of grooves arranged in the inner peripheral direction of the aforementioned tube body, and a plurality of fins, characterized in that the aforementioned plurality of grooves and the aforementioned plurality of fins are formed in a spiral shape in the longitudinal direction of the aforementioned tube body, the outer diameter of the aforementioned tube body is 3 mm or more and 10 mm or less, the number of the aforementioned fins formed on the inner peripheral surface of the aforementioned tube body is 30 to 60, the aforementioned inner spiral finned tube is made of metal, the cross-sectional shape of each of the aforementioned fins in the cross section of the aforementioned tube body is a rectangle with an apex angle of 0 ± 10º, the ratio h / f is 0.90 or more and 3.40 or less, h is the fin height, f is the fin width, the ratio c / f is 0.50 or more and 3.80 or less, c is the fin pitch between adjacent fins in the aforementioned inner peripheral direction of the aforementioned tube body, and the average value obtained by summing the aforementioned ratio h / f and the aforementioned ratio c / f and dividing the sum by two is 0.8 or more and 3.3 or less.

Description

Technical Field

[0001] This invention relates to internally spiral grooved tubes and heat exchangers with excellent heat transfer properties.

[0002] This application claims priority based on Japanese Patent Application No. 2019-217340 filed on November 29, 2019, the contents of which are incorporated herein by reference. Background Technology

[0003] In the past, copper alloy heat transfer tubes were used in finned tube heat exchangers. However, due to the depletion of copper resources, the high price of copper ingots, and the issue of reusability, lightweight, inexpensive, and highly reusable aluminum alloy heat transfer tubes have begun to be used.

[0004] In heat transfer tubes using copper or aluminum alloys, heat transfer tubes with spiral grooves on the inner surface have been proposed to improve their thermal properties. By spiraling the grooves on the inner surface, the area of ​​the inner circumference of the tube is increased, and wettability is improved through capillary action. As a result, the refrigerant is coiled up, and an increase in the circumference that facilitates heat transfer can be achieved.

[0005] As a method for manufacturing internal spiral grooved tubes, the following groove rolling method is known in the past: a grooved plug supported on a connecting rod is arranged on the inner side of the tube body, and a rolling ball is arranged circumferentially and freely arranged on the outer surface of the tube body. The outer peripheral wall of the tube body is pushed and pulled by the rolling ball, thereby performing groove processing (see Patent Document 1).

[0006] However, if the small-diameter internal spiral groove tube is manufactured by the groove rolling method, it is difficult to make the spiral groove shape neat. Therefore, the following technology is proposed: by simultaneously performing drawing and torsion processing on the drawn tube with straight grooves on the inner surface, a neat internal spiral groove is formed (see Patent Document 2).

[0007] Furthermore, by using a method that simultaneously performs drawing and torsion processing, it is possible to manufacture an inner spiral groove tube that cannot be manufactured by the groove rolling method, which has a groove shape with a groove opening width smaller than the groove bottom width, in other words, has spiral fins with an inverted trapezoidal cross-section (see Patent Document 3).

[0008] Patent Document 1: Japanese Patent Application Publication No. 6-190476.

[0009] Patent Document 2: Japanese Patent No. 6391140.

[0010] Patent document 3: Japanese Patent Application Publication No. 2018-091610.

[0011] As explained above, the manufacturing technology of aluminum alloy internal spiral grooved tubes has been improved in various ways, but due to the need to address environmental impacts in recent years, there is a need to further improve the heat transfer characteristics of internal spiral grooved tubes. Summary of the Invention

[0012] The purpose of this invention is to provide an internal spiral groove tube with better heat transfer properties.

[0013] The proposed internal spiral grooved tube comprises a tube body, a plurality of grooves and a plurality of fins arranged along the inner circumferential direction of the tube body. The grooves and fins are spirally formed along the longitudinal direction of the tube body. The outer diameter of the tube body is 3 mm or more and 10 mm or less. The number of fins formed on the inner circumferential surface of the tube body is 30 to 60. The internal spiral grooved tube is made of metal. In the cross-section of the tube body, each fin has a rectangular cross-section with a apex angle of 0 ± 10°. The ratio h / f is 0.90 or more and 3.40 or less, where h is the fin height and f is the fin width. The ratio c / f is 0.50 or more and 3.80 or less, where c is the fin spacing between adjacent fins in the inner circumferential direction of the tube body. Furthermore, the average value obtained by summing the ratios h / f and c / f and dividing the sum by two is 0.8 or more and 3.3 or less.

[0014] The rectangular fins described in this invention are different from, for example, slender fins produced by groove rolling.

[0015] In the internal spiral groove tube of this solution, preferably, the aforementioned plurality of fins are arranged at equal intervals in the aforementioned inner circumferential direction of the aforementioned tube body.

[0016] In the internal spiral groove tube of this solution, preferably, the cross-sectional shape of each of the aforementioned fins in the cross-section of the aforementioned tube body is a rectangle with a vertex angle of 0±10º, and the aforementioned average value of the aforementioned ratio h / f and the aforementioned ratio c / f is 2.0 or more and 2.8 or less.

[0017] In the inner spiral groove tube of this solution, preferably, the cross-sectional shape of each of the aforementioned fins is a rectangle with a vertex angle of 0±5º, and the average value of the aforementioned ratio h / f and the aforementioned ratio c / f is 2.4 or more and 2.6 or less.

[0018] In the internal spiral groove tube of this solution, preferably, the tube body is made of aluminum or aluminum alloy.

[0019] The heat exchanger of this scheme is characterized by having an internal spiral groove tube as described in a previous work.

[0020] Invention Effects

[0021] According to this solution, an internal spiral groove tube with excellent heat transfer properties can be provided as follows: In a metal internal spiral groove tube with an outer diameter of 3mm to 10mm and 30 to 60 fins, the cross-sectional rectangular shape is set with the fin apex angle of the spiral fins within the range of 0±10°, the height-to-width ratio h / f is set to 0.90 to 3.40, and the fin spacing-to-fin width ratio c / f is set to 0.50 to 3.80. Therefore, the wetting edge length of the internally flowing refrigerant can be ensured to be relatively long, and the refrigerant can easily enter between the fins.

[0022] If the opening between the fins is small, the refrigerant will have difficulty entering the spiral groove, thus tending to deteriorate the heat transfer performance. If the wetting edge length is long, the heat transfer performance will be good.

[0023] For metal internal spiral groove tubes with an outer diameter of 3mm to 10mm and 30 to 60 spiral fins, it is not possible to manufacture fins with a rectangular cross-section of the size described above by conventional rolling methods. However, by using a manufacturing method that simultaneously performs torsion and drawing from an extruded raw material tube, it is possible to achieve spiral groove tubes with spiral fins and spiral grooves of the above dimensions.

[0024] If the height of the spiral fins is increased, the fins extend higher toward the center of the inner spiral groove tube, thus narrowing the opening between the ends of adjacent fins. For metal inner spiral groove tubes with an outer diameter of 3mm to 10mm and 30 to 60 fins, a minimum opening is required for refrigerant entry. In this case, preferably, the above-mentioned range is selected based on the relationship between the height of the fins, the width of the fin top, and the number of fins present on the inner surface of the inner spiral groove tube. Attached Figure Description

[0025] Figure 1 This is a front view showing an example of a heat exchanger equipped with the internal spiral groove tube of the first embodiment.

[0026] Figure 2 This is a partial perspective view showing an example of the heat exchanger.

[0027] Figure 3 This is a cross-sectional view of the inner spiral groove tube of the first embodiment.

[0028] Figure 4 This is a longitudinal sectional view of the internal spiral grooved tube.

[0029] Figure 5 This is an explanatory diagram showing an example of spiral fins and spiral grooves formed on the inner surface of the spiral grooved tube.

[0030] Figure 6 This is an explanatory diagram showing other examples of spiral fins and spiral grooves formed on the inner surface of a conventionally constructed internally spiral grooved tube.

[0031] Figure 7 This is a perspective view of the raw material tube (straight groove tube) used in the manufacturing method of internal spiral groove tube.

[0032] Figure 8 This is a side view showing an example of a manufacturing apparatus used in the manufacture of internally spiral grooved tubes.

[0033] Figure 9 This is a top view showing the state of the raw material tube being released from the manufacturing apparatus of the internal spiral grooved tube relative to the release side winch.

[0034] Figure 10 This is a magnified photograph of a portion of the inner spiral groove tube of Example 1.

[0035] Figure 11 This is a magnified photograph of a portion of the inner spiral groove tube of Example 2.

[0036] Figure 12 This is a partially enlarged photograph showing the inner spiral groove tube of Example 11.

[0037] Figure 13 This is a partially enlarged photograph showing the inner spiral groove tube of Example 12.

[0038] Figure 14 This is a magnified photograph of a portion of the internal spiral groove tube of Comparative Example 1.

[0039] Figure 15 This is a magnified photograph of a portion of the internal spiral groove tube in Comparative Example 4.

[0040] Figure 16 This is a graph showing the results of measuring the condensation heat transfer coefficient of the internal spiral groove tubes of Examples 1, 11, 12 and Comparative Example 1.

[0041] Figure 17 This is a graph showing the results of measuring the evaporative heat transfer coefficient of the internal spiral groove tubes of Examples 1, 11, 12 and Comparative Example 1.

[0042] Figure 18 This is a graph showing an example of the results of measuring condensation pressure loss with respect to the internal spiral groove tubes of Examples 1, 11, 12 and Comparative Example 1.

[0043] Figure 19 This is a graph showing an example of the results of measuring evaporation pressure loss with respect to the inner spiral groove tubes of Examples 1, 11, 12 and Comparative Example 1. Detailed Implementation

[0044] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0045] Furthermore, the accompanying drawings used in the following description sometimes feature parts that are enlarged for emphasis. Also, for the same purpose, sometimes non-feature parts are omitted from the illustration.

[0046] Figure 1 and Figure 2 This is a schematic diagram illustrating an example of a heat exchanger equipped with an internal spiral groove tube according to the first embodiment of the present invention.

[0047] The heat exchanger 1 in this example is constructed as follows: an inner spiral grooved tube 2, which serves as the tube through which the refrigerant passes, is bent, and multiple aluminum plate-shaped heat dissipation plates 3 are arranged in parallel around the inner spiral grooved tube 2. The inner spiral grooved tube 2 is bent so that multiple through holes pass through it, and the aforementioned multiple through holes pass through each heat dissipation plate 3 arranged in parallel.

[0048] At the heat exchanger 1, an inner spiral grooved tube 2 connects multiple U-shaped main pipes 2A that pass straight through the heat dissipation plate 3, with adjacent end openings of adjacent main pipes 2A connected to each other by U-shaped elbows 2B. The U-shaped main pipes 2A and elbows 2B are formed by bending the inner spiral grooved tube 2 into a U-shape, as will be described later. Furthermore, a refrigerant inlet 4 is formed on one end side of the inner spiral grooved tube 2 through which the heat dissipation plate 3 passes in a bent state, and a refrigerant outlet 5 is formed on the other end side of the inner spiral grooved tube 2, thereby constituting the heat exchanger 1.

[0049] In this structure, the heat exchanger 1 has an inner spiral grooved tube, slightly smaller in diameter than the main pipe 2A, passing through the insertion hole of the heat dissipation plate 3. The inner spiral grooved tube is expanded to form the main pipe 2A, and the main pipe 2A and the heat dissipation plate 3 are mechanically joined together. Furthermore, the joining of the main pipe 2A and the heat dissipation plate 3 at the heat exchanger 1 is not limited to mechanical joining; other joining methods such as welding can also be used. In addition, the tube expansion can also be achieved using a known tube expansion method such as hydraulic expansion, plug expansion, or air expansion.

[0050] [Internal spiral groove tube]

[0051] The following is a detailed description of the inner spiral groove tube 2 used in the heat exchanger 1 described above.

[0052] Figure 3 This is an enlarged cross-sectional view of a portion of the inner spiral groove tube 2 of the first embodiment. Figure 4 This is a longitudinal sectional view of the inner spiral groove tube 2.

[0053] The internal spiral grooved tube 2 of this embodiment is a twisted part of the extruded raw material tube described later. The internal spiral grooved tube 2 can be made of aluminum or an aluminum alloy. When using an aluminum alloy for the internal spiral grooved tube 2, there is no particular limitation on the type of aluminum alloy used; pure aluminum alloys such as 1050, 1100, and 1200 as specified in JIS, or 3000 series aluminum alloys, such as 3003 which contains Mn, can be used. Furthermore, in addition to these, one of the 5000 series to 7000 series aluminum alloys specified in JIS can also be used to construct the internal spiral grooved tube 2.

[0054] Furthermore, the inner spiral groove tube 2 can also be formed from an aluminum alloy other than the aluminum alloy specified in JIS. This embodiment uses an inner spiral groove tube 2 made of aluminum or an aluminum alloy as an example, but the heat transfer tube intended for use in this invention can be made of any material that can be drawn using a drawing die, so obviously tubes made of other alloys such as copper alloys or iron alloys can also be used in this method.

[0055] Figure 3 The cross-sectional shape of the shown internally spiral-grooved tube 2 is formed by a circular tube body 6. The outer diameter of the tube body 6 (the diameter of the circle depicting the outer circumferential surface 6a of the tube body 6) is, for example, 3 mm to 10 mm. On the inner circumferential surface 6b of the tube body 6, 30 to 60 fins 7, spirally formed along the length of the tube body 6, are provided at predetermined intervals in the inner circumferential direction of the tube body 6. Furthermore, a spiral groove 8 of predetermined width, for example, a certain width, is formed between adjacent spiral fins 7, 7 in the inner circumferential direction of the tube body 6.

[0056] like Figure 4 As shown, at the inner spiral groove tube 2, the spiral fins 7 and spiral grooves 8 extend with a certain twist angle θ1 in the length direction of the tube body 6.

[0057] The torsion angle θ1 of each fin 7 or spiral groove 8 is as follows: Figure 4 In the case where the longitudinal section of the inner spiral groove tube 2 is depicted as shown, the angle between the extension line of the portion of the spiral groove or spiral fin shown in a straight line at the center of the inner side of the tube and the central axis of the tube body 2 (or a line parallel to the central axis) is indicated.

[0058] Multiple spiral fins 7 are formed at predetermined intervals on the inner circumferential surface 6b of the tube body 6, thereby improving the heat exchange efficiency between the inner spiral groove tube 2 and the refrigerant flowing inside it. The inner spiral groove tube 2, equipped with spiral fins 7, can improve the heat exchange efficiency by forming straight fins and straight grooves that extend linearly in the length direction through extrusion processing. Figure 7 The raw material tube 9 shown is formed by applying a torsion process while being drawn. Figure 7The image shows an example of fins 9A and grooves 9B formed at point 9 of the raw material pipe.

[0059] like Figure 3 As shown in cross-section, a portion of the tube body 6 is observed, and the fins 7 are formed into a rectangular cross-section consisting of an end portion 7a, a bottom portion 7b, and a pair of sidewall portions 7c. The aforementioned end portion 7a is located on the inner side of the tube body 6, the aforementioned bottom portion 7b is located on the outer periphery, and the aforementioned pair of sidewall portions 7c are located between the end portion 7a and the bottom portion 7b.

[0060] The bottom 7b of the fin 7 is located on the inner circumference of the tube body 6 and is continuous with the inner circumferential surface 6b; in other words, it is continuous with the bottom surface of the spiral groove 8. The sidewall portion 7c... Figure 3 The tube body 6 extends radially in a straight line in its cross-section. The wall thickness from the bottom surface of the spiral groove 8 to the outer circumferential surface of the tube body 6 in the cross-section of the tube body 6 can be expressed as the bottom wall thickness (d).

[0061] Figure 3 , Figure 4 In the internal spiral groove tube 2 shown in the diagram, multiple fins 7 are arranged circumferentially on the inner circumferential surface of the tube body 6, with the width of their end portion 7a being equal to or approximately equal to the width of their bottom portion 7b. Therefore, the groove width of the spiral groove 8 formed between adjacent fins 7 in the circumferential direction of the tube body 6 is equal to or approximately equal to the groove bottom side and the groove opening side.

[0062] like Figure 5 As shown, when two adjacent fins 7 are shown side-by-side in the inner circumferential direction of the tube body 6, the distance from the bottom of the spiral groove 8 to the end portion 7a of the fin 7 can be defined as the fin height (h), the width of the end portion 7a of the fin 7 can be defined as the fin top width (a), the width of the bottom portion 7b of the fin 7 can be defined as the fin bottom width (b), and the interval between two adjacent fins 7 can be defined as the fin spacing (c). Furthermore, Figure 5 As shown in the diagram, at fin 7, the left and right sidewall portions 7c are parallel or approximately parallel, so the fin width (f) is equal to or approximately equal to the fin bottom width (b). The definition of the left and right sidewall portions 7c being approximately parallel will be explained later.

[0063] also, Figure 5 In the state shown, the model displays fins 7 and 7 to depict the states of the left and right adjacent fins, but as... Figure 3 As shown, the inner circumferential surface 6b of the tube body 6 is an arc shape with a predetermined curvature. Therefore, the width of the spiral groove 8 formed between adjacent fins 7 is slightly wider at the bottom of the groove and gradually narrows towards the opening of the groove.

[0064] In the inner spiral groove tube 2 of this embodiment, the outer diameter of the tube body 6 is more than 3 mm and less than 10 mm, and about 30 to 60 fins 7 are formed in the inner circumferential direction of the tube body 6.

[0065] The height of fin 7 (i.e., the radial dimension of tube body 6) is approximately 0.13 mm to 0.55 mm. Furthermore, the bottom wall thickness of the inner spiral groove tube 2 (the wall thickness of tube body 6 corresponding to the bottom of the spiral groove 8) is approximately 0.3 mm to 0.6 mm. The thickness of fin 7, i.e., the width of the fin top, is approximately 0.07 mm to 0.20 mm.

[0066] On the other hand, with Figure 5 The fins shown are different, such as... Figure 6 As shown, in the case of a conventionally constructed fin 14 with an isosceles trapezoidal shape, a rounded corner is formed at the end portion 14a, and the sidewall portions 14c, 14c are inclined in a manner that tapers towards the end portion. Therefore, at the fin 14, the center of the rounded corner constituting the end portion 14a is considered as the end of the fin 14, and the distance from this center to the bottom of the spiral groove 8 can be defined as the fin height (h). The fin top width (a) can be defined as the inner diameter of the rounded corner constituting the end portion 14a.

[0067] At fin 14, the bottom edges of sidewall portions 14c and 14c are close to each other, but the distance between the bottom edges of sidewall portions 14c and 14c can be defined as the fin spacing (c). Furthermore, strictly speaking, as... Figure 6 As shown, at the bottom of the sidewall portions 14c, a rounded corner of about 0.05 mm is formed at the part that connects with the bottom surface of the spiral groove 16. Therefore, the position where the extended surface of the sidewall portion 14c intersects with the bottom surface of the spiral groove 16 is assumed to be the bottom of the sidewall portion 14c, and the distance between the lowest parts of the left and right sidewall portions 14c is defined as the fin spacing (c).

[0068] exist Figure 6 As shown in fin 14, the fin width is different on the upper and lower sides. Therefore, at fin 14, the fin width (f) is taken as the average of the upper and lower widths and is defined as f = (a + b) / 2.

[0069] In addition, it is possible to Figure 6 The angle formed by the sidewall portions 14c and 14c at fin 14 shown is defined as the fin apex angle (θ).

[0070] However, in Figure 5At fin 7, the sidewall portions 7c and 7c are parallel or substantially parallel, so although the fin apex angle (θ) cannot be illustrated, the fin apex angle is defined as 0° when the sidewall portions 7c and 7c are parallel at fin 7. Furthermore, at fin 7 in this embodiment, the fin apex angle defined as the angle formed by the sidewall portions 7c and 7c is preferably in the range of 0 ± 10°, and more preferably in the range of 0 ± 5°.

[0071] A fin apex angle (θ) of 0 ± 10° means an isosceles trapezoidal shape as follows: based on the fin apex angle (0°) where the sidewalls 7c are completely parallel to each other, each sidewall 7c is inclined from 0 to +5°, narrowing slightly above each other. Furthermore, it means an inverted isosceles trapezoidal shape as follows: based on the fin apex angle (0°), each sidewall 5c is inclined at an angle less than 0° but less than -5°, widening slightly above each other. That is, Figure 3 , Figure 5 When viewed in cross-section, the rectangle of fin 7 means that it includes cases where the fin apex angle (θ) is tilted from 0° to +5.0° and cases where it is tilted from 0° to -5.0°.

[0072] As explained above, a fin apex angle smaller than 0° up to -5° means that the fin 7 is an inverted isosceles trapezoid when viewed in cross-section, and a fin apex angle larger than 0° up to +5° means that the fin 7 is an isosceles trapezoid when viewed in cross-section. Strictly speaking, they are not rectangular shapes, but in this specification, any fin 7 with an apex angle in the range of 0±10° is also included in the category of fins with a rectangular cross-section.

[0073] Similarly, the range of fin apex angle of 0±5° means that it includes the case of the sidewall portions 7c being slightly narrower above each other in an isosceles trapezoidal shape and the case of the sidewall portions 7c being slightly wider above each other in an inverted isosceles trapezoidal shape, including the case of each sidewall portion 7c being inclined at 0° or more and +2.5° or less and the case of being inclined at 0° or less and -2.5° or more.

[0074] As explained above, in this embodiment, for convenience, the state from which the fin apex angles of the sidewall portions 7c and 7c are completely parallel to each other at 0° to the state where the sidewall portion 7c is tilted at a positive angle and becomes an isosceles trapezoidal shape that narrows at the top is represented by a positive fin apex angle, and the state where the sidewall portion 7c is tilted at a negative angle and becomes an inverted isosceles trapezoidal shape that widens at the top is represented by a negative fin apex angle.

[0075] In this embodiment, the inner spiral groove tube 2 preferably has an outer diameter of 3 mm to 10 mm, 30 to 60 fins 7 formed in the inner circumferential direction, a fin height of 0.13 mm to 0.55 mm, a bottom wall thickness of 0.3 mm to 0.6 mm, and a fin top width of 0.07 mm to 0.2 mm.

[0076] At the aforementioned size of the inner spiral groove tube 2, if the fin tip width is too large, the radial opening of the spiral groove 8 becomes too narrow, making it difficult for the refrigerant to enter the spiral groove 8, potentially leading to deterioration in heat transfer. Furthermore, there is a problem of increased refrigerant pressure loss. By setting the fin tip angle to 0±10° and configuring the fin 7 with the aforementioned size, the opening of the spiral groove 8 can be made sufficiently large, allowing the refrigerant to reliably flow into the spiral groove 8, thereby improving heat transfer towards the refrigerant and ensuring smooth refrigerant flow.

[0077] Furthermore, by setting the fin height and fin top width within the aforementioned range, the fins 7 can be made thinner and longer, ensuring the wetted edge length between the refrigerant and the fins, and ensuring the heat transfer area, thereby ensuring a good heat transfer coefficient.

[0078] At the inner spiral groove tube 2, the ratio (h / f) of fin height (h) to fin width (f) is set to 0.90 or higher and 3.40 or lower.

[0079] By setting (h / f) to 0.90 or higher, the wetting edge length of fin 7 can be ensured as much as possible, but if the lower limit is insufficient, the wetting edge length will be inadequate. If (h / f) exceeds 3.40, poor refrigerant flow will occur due to narrowing of the orifice, thereby reducing heat exchange performance.

[0080] At the inner spiral groove tube 2, the ratio (c / f) of the distance (c) between adjacent fins in the circumferential direction of the tube body to the fin width (f) is set to 0.50 or more and 3.80 or less.

[0081] Setting (c / f) to 0.50 or higher ensures that the refrigerant can easily enter the spiral groove, but if the lower limit is insufficient, the refrigerant will have difficulty entering the spiral groove. If (c / f) exceeds 3.80, the wetting edge length will be insufficient. In addition, this, coupled with a decrease in the number of fins, leads to a reduction in the refrigerant winding effect and a decrease in heat exchange performance.

[0082] Furthermore, the heat exchange performance varies depending on the balance of fin height, fin width, and fin spacing, so an average value of (h / f) and (c / f) of 0.8 to 3.3 is preferred. More preferably, 2.0 to 2.8 is preferred, and even more preferably, 2.4 to 2.6 is preferred.

[0083] Previously, spiral grooved tubes made of copper alloys and aluminum alloys were generally manufactured using a method called groove rolling to form the spiral grooves. The groove rolling method involves using a rolling ball to push a grooved plug from the outer circumference of the tube towards the inner surface of the tube. Grooves are formed at the valleys of the grooved plug through plastic flow. Therefore, all grooves are ideally manufactured to achieve the desired effect. Figure 6 The fins 14 and helical grooves 16 shown have the same shape, but the opening on the apex side (center side of the tube) of the fin 14 is larger than that on the bottom side. Furthermore, it is difficult to achieve this using the groove rolling method. Figure 6 The ideal shape of the fin 14 shown is generally made in a significantly skewed shape.

[0084] On the other hand, since the spiral groove tube 2 of this embodiment has fins 7 of the above-mentioned size, the presence of the spiral fins 7 promotes turbulence, suppresses the film thickness of the refrigerant generated around the fins 7, allows the refrigerant to easily enter and exit relative to the spiral groove 8 due to the size of the opening between the fins 7, and increases the wetting edge length due to the presence of the rectangular fins 7, a high evaporation heat transfer coefficient and a high condensation heat transfer coefficient can be obtained.

[0085] <Manufacturing Method>

[0086] from Figure 7 The raw material pipe 9 is shown in the middle. Figure 3 , Figure 5 As an example, when fin 7 is shown as rectangular in cross-section, it can be processed using torsion drawing. Figure 8 , Figure 9 Manufacturing apparatus A is represented in the diagram.

[0087] <Extrusion Molding Process>

[0088] Manufacturing is achieved by extruding a billet made of aluminum or an aluminum alloy. Figure 7 The material pipe 9 is shown in the figure. On the inner surface of the material pipe 9, there are multiple straight fins 9A and straight grooves 9B at equal intervals in the inner circumferential direction.

[0089] During extrusion processing, the corners of the fins 9A and the straight grooves 9B formed at the raw material tube 9 can achieve a curvature radius accuracy of approximately 0.005~0.025mm, thus enabling the manufacture of multiple fins with... Figure 3 or Figure 5 The inner spiral groove tube represents a fin with a rectangular cross-section, which is the same as the cross-sectional shape shown in the figure.

[0090] <Torsion drawing process>

[0091] Next, the torsion drawing process will be explained.

[0092] The torsion drawing process is as follows: by applying torsion to the aforementioned raw material tube 9 during drawing, an inner spiral groove tube 2 with spiral fins 7 and spiral grooves 8 is formed.

[0093] <Manufacturing apparatus for performing torsional drawing>

[0094] Figure 8 This is a side view of the manufacturing apparatus A, which applies two torsional drawing processes to the raw material tube 9 to manufacture the internally spiral grooved tube 2. First, an overview of the manufacturing apparatus A will be given.

[0095] Manufacturing apparatus A includes a revolution mechanism 30, a suspension frame 34, a release drum (first drum) 11, a first guide winch 18, a first drawing die 17, a first revolution winch 21, a revolution flywheel 23, a second revolution winch 22, a second drawing die 19, a second guide winch 61, and a winding drum (second drum) 71. The details of each part are described below.

[0096] (Public-to-private partnership)

[0097] The revolution mechanism 30 has a rotating shaft 35 including a front shaft 35A and a rear shaft 35B, a drive unit 39, a front platform 37A, and a rear platform 37B.

[0098] The revolution mechanism 30 causes the rotating shaft 35 and the first revolution winch 21, the second revolution winch 22 and the revolution flywheel 23 fixed to the rotating shaft 35 to rotate.

[0099] Furthermore, the revolution mechanism 30 maintains the stationary state of the suspension frame 34, which is located on the same axis as the rotation axis 35 and supported by the rotation axis 35. Thus, the stationary state of the release drum 11, the first guide winch 18, and the first drawing die 17, which are supported by the suspension frame 34, is maintained.

[0100] Both the front shaft 35A and the rear shaft 35B have a hollow cylindrical shape inside. Both the front shaft 35A and the rear shaft 35B are arranged coaxially around the central axis of rotation C (the rolling line of the first drawing die). The front shaft 35A is rotatably supported on the front platform 37A via a bearing 36 and extends rearward (towards the rear platform 37B). Similarly, the rear shaft 35B is rotatably supported on the rear platform 37B via a bearing and extends forward (towards the front platform 37A) from the rear platform 37B. A suspension frame 34 is mounted between the front shaft 35A and the rear shaft 35B.

[0101] The drive unit 39 includes a drive motor 39c, a direct-drive shaft 39f, belts 39a and 39d, and pulleys 39b and 39e. The drive unit 39 rotates the front shaft 35A and the rear shaft 35B.

[0102] The drive motor 39c rotates the linear shaft 39f. The linear shaft 39f extends in the front-rear direction at the lower part of the front stage 37A and the rear stage 37B.

[0103] A pulley 39b is installed at the front end 35Ab of the front shaft 35A, at the end through which the front platform 37A passes. The pulley 39b is linked to the linear shaft 39f via a belt 39a. Similarly, a pulley 39e is installed at the rear end 35Bb of the rear shaft 35B, at the end through which the rear platform 37B passes, and is linked to the linear shaft 39f via a belt 39d. Thus, the front shaft 35A and the rear shaft 35B rotate synchronously around the central axis of revolution C.

[0104] At the rotating shaft 35 (front shaft 35A and rear shaft 35B), the first revolving winch 21, the second revolving winch 22, and the revolving flywheel 23 are fixed. The rotating shaft 35 rotates, thereby causing these components fixed to the rotating shaft 35 to revolve around the central axis of rotation C.

[0105] (Floating window)

[0106] The suspension frame 34 is supported by bearings 34a on the opposing ends 35Aa and 35Ba of the front shaft 35A and rear shaft 35B of the rotating shaft 35. In addition, the suspension frame 34 supports the release drum 11, the first guide winch 18 and the first drawing die 17.

[0107] Figure 9 From Figure 8 The top view of the floating frame 34, viewed in the X direction of the arrow. (See also...) Figure 8 , Figure 9 As shown, the suspended frame 34 has a box shape with openings at the top and bottom. The suspended frame 34 has a front wall 34b and a rear wall 34c facing each other, and a pair of support walls 34d facing each other left and right and extending in the front-back direction.

[0108] Through holes are provided at the front wall 34b and the rear wall 34c, through which the ends 35Aa and 35Ba of the front shaft 35A and the rear shaft 35B are respectively inserted. Bearing 34a is located between the ends 35Aa and 35Ba and the through holes in the front wall 34b and the rear wall 34c. Therefore, the rotation of the rotating shaft 35 (front shaft 35A and rear shaft 35B) is difficult to transmit to the suspension frame 34. Even when the rotating shaft 35 is rotating, the suspension frame 34 can remain stationary relative to the ground G. Alternatively, a counterweight can be provided to tilt the center of gravity of the suspension frame 34 to one side relative to the revolution axis C to stabilize the stationary state of the suspension frame 34.

[0109] like Figure 9 As shown, a pair of support walls 34d will release the drum 11, the first guide winch 18, and the first drawing die 17 in the left-right direction. Figure 9(In the vertical direction in the paper) arranged on both sides. A pair of support walls 34d will rotatably support the drum support shaft 12 of the unloading drum 11 and the rotation shaft J18 of the first guide winch 18. In addition, the support walls 34d support the first drawing die 17 via a die support body (not shown).

[0110] (Release the roll)

[0111] The raw material tube 9 is wound around the release drum 11. The release drum 11 releases the raw material tube 9 and supplies it to the downstream section. The release drum 11 is detachably mounted on the drum support shaft 12.

[0112] like Figure 8 As shown, the drum support shaft 12 extends in a direction orthogonal to the rotation axis 35. Furthermore, the drum support shaft 12 is rotatably supported on the suspension frame 34. Here, "rotatably" means rotating about its own central axis. The drum support shaft 12 holds the release drum 11 and rotates in the supply direction of the release drum 11, thereby assisting the release of the raw material pipe 9 from the release drum 11.

[0113] A braking unit 15 is provided at the drum support shaft 12. The braking unit 15 applies a braking force to the rotation of the drum support shaft 12 relative to the suspension frame 34. That is, the braking unit 15 restricts the rotation of the release drum 11 in the release direction. With the braking force of the braking unit 15, a rear tension is applied to the raw material pipe 9 being transported in the release direction.

[0114] (First guide winch)

[0115] The first guide winch 18 has a disc shape. The released raw material pipe 9 is wound around the first guide winch 18 once from the release drum 11. The tangential direction of the outer periphery of the first guide winch 18 is consistent with the revolution rotation center axis C. The first guide winch 18 guides the raw material pipe 9 along the first direction D1 on the revolution rotation center axis C.

[0116] The first guide winch 18 is rotatably supported on the suspension frame 34. Furthermore, rotatable guide rollers 18b are arranged side-by-side on the outer periphery of the first guide winch 18. In this embodiment, the first guide winch 18 has multiple guide rollers 18b rotating individually, but if all the guide rollers 18b rotate, the raw material pipe 9 can be smoothly transported. Additionally, Figure 8 The diagram of guide roller 18b is omitted.

[0117] like Figure 8 As shown, a pipe guide section 18a is provided between the first guide winch 18 and the release drum 11. The pipe guide section 18a is, for example, a plurality of guide rollers configured to surround the raw material pipe 9. The pipe guide section 18a guides the raw material pipe 9 supplied from the release drum 11 to the first guide winch 18.

[0118] (First drawing die)

[0119] The first drawing die 17 reduces the diameter of the raw material tube 9. The first drawing die 17 is fixed to the suspension frame 34. The first drawing die 17 sets the first direction D1 as the drawing direction. The center of the first drawing die 17 is aligned with the revolution rotation center axis C of the rotation axis 35. Furthermore, the first direction D1 is parallel to the revolution rotation center axis C.

[0120] Lubricating oil is supplied to the first drawing die 17 by means of a lubricating oil supply device 34A fixed to the suspension frame 34.

[0121] The material is introduced into the interior of the front shaft 35A through the through hole provided in the front wall 34b of the suspension frame 34 via the intermediate torsion tube 9D of the first drawing die 17.

[0122] (First revolution winch)

[0123] The first revolution winch 21 has a disc shape. The first revolution winch 21 is disposed in a transverse hole 35Ac that radially passes through the inside and outside of the hollow front shaft 35A. The first revolution winch 21 is supported on a support body 21a fixed to the outer periphery of the rotation shaft 35 (front shaft 35A) with the center of the disc as the rotation axis J21.

[0124] A tangent on the outer periphery of the first revolution winch 21 coincides with the revolution rotation center axis C.

[0125] At the first revolution winch 21, the pipe 5 being transported in the first direction D1 on the revolution rotation center axis C is wound up more than once. The first revolution winch 21 winds the pipe and pulls it out from the inside of the front shaft 35A to the outside, guiding it to the revolution flywheel 23.

[0126] The first revolving winch 21 and the front shaft 35A revolve together around the central axis C. The central axis C extends in a direction orthogonal to the rotation axis J21 of the first revolving winch 21. The tube is twisted between the first revolving winch 21 and the first drawing die 17. Through this first drawing and twisting process, the raw material tube 9 is processed into an intermediate twisted tube 9D.

[0127] The drive motor 20 and the first revolving winch 21 are mounted together on the front shaft 35A. The drive motor 20 drives the first revolving winch 21 to rotate in the winding direction (transporting direction) of the pipe. As a result, the first revolving winch 21 applies a front tension to the pipe to allow the first drawing die 17 to pass through.

[0128] (Revolutionary flywheel)

[0129] The orbiting flywheel 23 reverses the flow of the intermediate torsion tube 9D between the first drawing die 17 and the second drawing die 19. The orbiting flywheel 23 reverses the intermediate torsion tube 9D, orienting the transport direction towards a second direction D2, which is the drawing direction of the second drawing die 19. More specifically, the orbiting flywheel 23 guides the intermediate torsion tube 9D from the first orbiting winch 21 to the second orbiting winch 22.

[0130] The orbital flywheel 23 has multiple guide rollers 23a and guide roller supports (not shown). To avoid complexity, the guide roller supports are not shown here, but they are supported by the rotation shaft 35. However, regarding the flywheel's construction, guide rollers are not essential; they can also be a plate-like structure used only for pipe passage, with rings installed for the pipe to pass through.

[0131] The guide rollers 23a are arranged side by side in an arc shape that bends outward relative to the revolution rotation center axis C. The guide rollers 23a roll on their own to smoothly transport the intermediate torsion tube 9D. The revolution flywheel 23 rotates around the revolution rotation center axis C, around the suspension frame 34, and the first drawing die 17 and the release drum 11 supported in the suspension frame 34.

[0132] One end of the orbital flywheel 23 is located outside the first orbital winch 21 relative to the orbital rotation center axis C. Furthermore, the other end of the orbital flywheel 23 extends towards the interior of the hollow rear shaft 35B through a radially penetrating transverse hole 35Bc. The orbital flywheel 23 guides the intermediate torsion tube 9D, which is wound outwards from the first orbital winch 21, towards the rear shaft 35B. Additionally, the orbital flywheel 23 releases the intermediate torsion tube 9D inside the rear shaft 35B in a manner aligned with the orbital rotation center axis C along the second direction D2.

[0133] (Second revolution winch)

[0134] The second revolving winch 22, like the first revolving winch 21, has a disc shape. The second revolving winch 22 is supported in a rotatable manner on a support body 22a located at the end of the rear shaft 35B, specifically at the end 35Bb. Furthermore, rotatable guide rollers 22c are arranged side-by-side on the outer periphery of the second revolving winch 22. In this embodiment, the second revolving winch 22 rotates individually with multiple guide rollers 22c, yet this rotation allows for smooth transport of pipe materials.

[0135] A tangent on the outer periphery of the second revolution winch 22 coincides with the rotation center axis C.

[0136] At the second revolution winch 22, the pipe 5, which is being transported along the second direction D2 on the rotation center axis C, is wound up more than once. The second revolution winch 22 releases the wound pipe in the second direction D2 on the rotation center axis C.

[0137] The second revolution winch 22 rotates together with the rear shaft 35B about the rotation center axis C. The rotation center axis C extends in a direction orthogonal to the rotation axis J22 of the second revolution winch 22. The intermediate torsion tube 9D released from the second revolution winch 22 is reduced in diameter at the second drawing die 19. The second drawing die 19 is stationary relative to the ground G, so torsion can be applied to the intermediate torsion tube 9D between the second revolution winch 22 and the second drawing die 19. Through this second drawing and torsion process, the intermediate torsion tube 9D is processed into an internally spiral grooved tube 2.

[0138] The support body 22a supporting the second revolution winch 22 supports the counterweight 22b at a position symmetrical to the second revolution winch 22 with respect to the rotation center axis C. The counterweight 22b stabilizes the rotation of the rear shaft 35B.

[0139] (Second drawing die)

[0140] The second drawing die 19 is located at the rear of the second revolving winch 22. The second drawing die 19 sets the drawing direction as the opposite second direction D2. The second direction D2 is parallel to the rotation center axis C. The second direction D2 is opposite to the drawing direction of the first drawing die 17, i.e., the first direction D1. The intermediate torsion tube 9D passes through the second drawing die 19 along the second direction D2. The second drawing die 19 is stationary relative to the ground G. The center of the second drawing die 19 coincides with the rotation center axis C of the rotation shaft 35.

[0141] The second drawing die 19 is supported on a stand 62, for example, via a die support body (not shown). Furthermore, lubricating oil is supplied to the second drawing die 19 by means of a lubricating oil supply device 62A mounted on the stand 62. This reduces the drawing force on the second drawing die 19.

[0142] (Second guide winch)

[0143] The second guide winch 61 has a disc shape. The tangential direction of the outer periphery of the second guide winch 61 is consistent with the revolution rotation center axis C. At the second guide winch 61, the inner spiral groove tube 2, which is transported in the second direction D2 on the revolution rotation center axis C, is wound more than one turn.

[0144] The second guide winch 61 is rotatably supported on the frame 62 with a rotation axis J61 as its center. Furthermore, the rotation axis J61 of the second guide winch 61 is connected to a drive motor 63 via a drive belt or the like. The second guide winch 61 is driven to rotate in the winding direction (transportation direction) of the inner spiral tube 2 by the drive motor 63. Preferably, the drive motor 63 is a torque motor capable of torque control.

[0145] Driven by the second guide winch 61, forward tension is applied to the inner spiral groove tube 2. As a result, the inner spiral groove tube 2 is transported forward by the drawing stress necessary for processing by the second drawing die 19.

[0146] (winding roll)

[0147] A winding drum 71 is located at the end of the inner spiral groove tube 2 to retract the inner spiral groove tube 2. A pulley 72 is located at the front end of the winding drum 71.

[0148] The winding drum 71 is detachably mounted on the drum support shaft 73. The drum support shaft 73 is supported on the frame 75 and connected to the drive motor 74 via a drive belt or the like.

[0149] <Torsion drawing process>

[0150] The method for manufacturing the internal spiral groove tube 2 using the manufacturing apparatus A described above will be explained.

[0151] The raw material pipe 9 is released from the release drum 11 and installed in the pipeline of the pre-installed raw material pipe 9. The raw material pipe 9 is installed by passing through the first guide winch 18, the first drawing die 17, the first revolution winch 21, the revolution flywheel 23, the second revolution winch 22, the second drawing die 19, the second guide winch 61, and the winding drum 71 in that order.

[0152] The first guide winch 18 guides the raw material tube 9 to the die hole of the first drawing die 17 located on the rotation center axis C.

[0153] Next, the raw material tube 9 is passed through the first drawing die 17. Then, at the rear end of the first drawing die 17, the tube is wound onto the first revolving winch 21 to rotate it around the aforementioned rotation axis. As a result, the diameter of the raw material tube 9 is reduced and torsion is applied (first torsion drawing process).

[0154] In the first torsion drawing process, appropriate tension can be applied to the raw material tube 9, and a stable torsion angle can be applied without causing the tube 5 to bend or break.

[0155] The raw material tube 9 is drawn by the first drawing die 17 and twisted by the first revolving winch 21. As a result, the straight fins 9A and straight grooves 9B inside the raw material tube 9 are twisted.

[0156] Through the first torsion drawing process, the raw material tube 9 is transformed into the intermediate torsion tube 9D. The intermediate torsion tube 9D is a tube material in the intermediate stage of the manufacturing process of the inner spiral groove tube 2, which is to form fins and spiral grooves with a torsion angle shallower than the fins 7 and spiral grooves 8 of the inner spiral groove tube 2.

[0157] Next, the intermediate torsion tube 9D is wound onto the revolution flywheel 23, so that the transport direction is toward the second direction D2 on the rotation center axis C. Then, the intermediate torsion tube 9D is wound onto the second revolution winch 22, and the intermediate torsion tube 9D is guided into the second drawing die 19.

[0158] Next, the intermediate torsion tube 9D, which rotates together with the second revolving winch 22, is passed through the second drawing die 19. This reduces the diameter of the intermediate torsion tube 9D and applies torsion, resulting in a larger lead angle (second torsion drawing process). Through this second torsion drawing process, the intermediate torsion tube 9D becomes an internally spiral grooved tube 2. Therefore, an internally spiral grooved tube 2 with a target lead angle can be obtained.

[0159] <Air pulling process>

[0160] Next, the inner spiral groove tube 2 is passed through the finishing drawing die 70 (finishing drawing process). By passing through the finishing drawing die 70, the surface of the inner spiral groove tube 2 can be shaped.

[0161] If the torsion drawing process of manufacturing apparatus A as described above is performed, drawing is carried out simultaneously with torsion. Therefore, in order to apply a combined stress of torsion and diameter reduction to the raw material tube 9, the shear stress necessary for torsion processing can be reduced, and a large torsion can be applied to the raw material tube 9 before reaching the bending stress of the raw material tube 9.

[0162] The internal spiral grooved tube 2 can be made lighter and cheaper by reducing the material cost through thinning the wall thickness. That is, according to this embodiment, a lightweight, inexpensive internal spiral grooved tube 2 with high heat exchange efficiency can be manufactured.

[0163] according to Figure 8 , Figure 9 The manufacturing apparatus A shown aligns the torsion directions in the first and second torsion drawing processes, applying torsion to the raw material tube 9, facilitating mass production.

[0164] If only a torsion is applied to a material tube 9 with a diameter of about 3 to 10 mm made of aluminum or aluminum alloy, it is easy to bend or break. By using the manufacturing device A to apply a drawing action simultaneously with the torsion, the bending and breakage caused by the torsion are suppressed. Therefore, even for a material tube 9 of the above-mentioned size, torsion can be applied without bending or breaking it.

[0165] Furthermore, in this specification, the manufacturing apparatus used in the case of manufacturing the inner spiral groove tube 2 from the raw material tube 9 is as follows: Figure 8 , Figure 9 The manufacturing apparatus A shown is not limited to this example. In addition, the manufacturing apparatus for torsion drawing described in Japanese Patent Application Publication No. 2016-22505 and other similar documents may also be used.

[0166] Extrusion of a raw material tube made of JIS A 3003 series aluminum alloy from a billet produces multiple extruded raw material tubes of various sizes, which have multiple straight fins and multiple straight grooves that are alternately and equally spaced along the entire length of the inner circumference.

[0167] Next, using Figure 8 , Figure 9 Manufacturing apparatus A, as shown in the table, performs torsion drawing on these raw material tubes to produce the internally spiral grooved tubes of Examples 1-13 and Comparative Examples 1-11. Furthermore, for the internally spiral grooved tubes of Examples 1, 2, 11, 12 and Comparative Examples 1, 4 shown in Table 1 below, the results of measuring the bottom wall thickness (mm), fin height (mm), and fin top width (mm) at eight circumferential locations, and the results of calculating their average values, are presented.

[0168] Table 1

[0169] .

[0170] Furthermore, in Tables 2 and 3 below, for the internal spiral groove tubes of Examples 1, 2, 11, 12 and Comparative Examples 1 and 4, the values ​​of bottom wall thickness, fin height (h: mm), fin top width (a: mm), fin spacing (c: mm), fin width (f: mm), h / f value, c / f value, outer diameter, number of grooves, fin apex angle (°), and flow path area (mm²) of each internal spiral groove tube are shown according to the average values ​​in Table 1. 2 The values ​​of wetting edge length (mm), heat exchange performance of a single tube, and average values ​​of h / f and c / f are also included. Furthermore, in Table 2, the results for other embodiments and comparative examples are obtained in the same manner as in Table 1, and the results obtained in the same manner as for Examples 1, 2, 11, 12 and Comparative Examples 1, 4 are also recorded.

[0171] The evaluation of the heat exchange performance of a single tube is carried out using a double-tube structure, in which the refrigerant flows in the inner tube (heat transfer tube) and the water flows in the outer tube in a counter-current manner. The heat transfer coefficient inside the inner tube is calculated based on the temperature changes at the water inlet and outlet. In addition, the pressure loss is calculated based on the refrigerant pressure difference at the inlet and outlet of the inner tube for evaluation.

[0172] In the evaluation of heat exchange performance of a single pipe with a refrigerant flow rate of approximately 20 kg / h, the condensation heat transfer coefficient is 6.5 kW / m³. 2Temperatures below ×℃ and an evaporative heat transfer coefficient of 8.0 kW / m² 2 Cases below ×℃ are judged as ×.

[0173] The condensation heat transfer coefficient exceeds 6.5 kW / m². 2 The value is 8.0 kW / m² at ×℃. 2 Temperatures below ×℃ and evaporative heat transfer coefficients exceeding 8.0 kW / m² 2 The value is 12.0 kW / m² at ×℃. 2 Cases below ×℃ are classified as △, and the condensation heat transfer coefficient exceeds 8.0 kW / m³. 2 The value is 9.5 kW / m² at ×℃. 2 Temperatures below ×℃ and evaporative heat transfer coefficients exceeding 8.0 kW / m² 2 The value is 12.0 kW / m² at ×℃. 2 Conditions below ×℃ are judged as 0, and the condensation heat transfer coefficient exceeds 9.5kw / m². 2 ×℃, and the evaporative heat transfer coefficient exceeds 12.0 kW / m². 2 The case of ×℃ is judged as ◎.

[0174] Table 2

[0175] .

[0176] Table 3

[0177] .

[0178] Figure 10 The image shows a portion of the cross-section of the inner spiral groove tube of Example 1. Figure 11 The image shows a portion of the cross-section of the inner spiral groove tube in Example 2. Figure 12 The image shows a portion of the cross-section of the inner spiral groove tube of Example 11. Figure 13 The image shows a portion of the cross-section of the inner spiral groove tube of Example 12. Figure 14 The image shows a portion of the cross-section of the internal spiral groove tube in Comparative Example 1. Figure 15 The figure below represents a portion of the cross-section of the inner spiral groove tube of Comparative Example 4.

[0179] If Figures 10-13 The internal spiral groove tubes of Examples 1 to 13 shown have fin apex angles of 0 ± 10° and rectangular cross-sections, thus providing fins with good heat transfer efficiency.

[0180] In Examples 1-13, the internal spiral groove tubes are designed such that the ratio (h / f) of the fin height (h) to the fin width (f) is 0.90 or more and 3.40 or less. This allows the wetting edge length of the refrigerant to be increased, resulting in internal spiral groove tubes with good heat transfer efficiency.

[0181] In Examples 1-13, the internal spiral groove tube is designed such that the ratio (c / f) between the distance (c) between adjacent fins in the circumferential direction of the tube body is 0.50 to 3.80. This allows the distance between the fins to be increased, ensuring that the refrigerant can easily enter the spiral groove, thus providing an internal spiral groove tube with good heat transfer efficiency.

[0182] In Examples 1, 2, 7, 8, and 9, the fin apex angle is set to 0±5°. In addition, the average values ​​of the ratio of fin height (h) to fin width (f) (h / f) and the ratio of the distance between adjacent fins in the circumferential direction of the tube body (c) to fin width (f) (c / f) are set to 2.4~2.6, thus providing an internally spiral grooved tube with better heat transfer efficiency.

[0183] Compared to them, the inner spiral groove tube of Example 11 is set with a fin apex angle of 0±5°, and the average values ​​of (h / f) and (c / f) are within the desired range. Therefore, even if the wetting edge length is the same as that of Examples 1 and 2, the heat exchange performance is slightly reduced.

[0184] Next, the inner spiral groove tube of Example 12 shows that the fin apex angle is 0±5°, (h / f) is 1.8, and (c / f) is 1.1, all of which show the preferred range of values. However, the average value of (h / f) and (c / f) is less than 1.8, so the heat exchange performance is lower than that of Examples 1 and 2, and also slightly lower than that of Example 11.

[0185] Next, the average values ​​of (h / f) and (c / f) of the inner spiral groove tube in Comparative Example 1 are within the preferred range, but the fin apex angle is large, so due to the large amount of refrigerant flowing in, it cannot form a thin liquid film, and the drying phenomenon (drying phenomenon) does not occur efficiently, thereby deteriorating the heat exchange performance.

[0186] Next, the (h / f) of the inner spiral groove tube of Comparative Example 2 is 3.6, which deviates from the preferred range to the upper side. As a result, there are relatively fine and tall fins in the circumferential direction, but the spacing of the fin valleys becomes larger. As a result, the heat exchange performance deteriorates due to the same tendency.

[0187] In Comparative Example 3, the number of fins is small, and the (c / f) value is 4.1, which deviates from the preferred range to the upper side, but the thermal properties deteriorate due to the same tendency.

[0188] Next, in Comparative Example 4, the fin apex angle of the inner spiral groove tube is large, with (h / f) showing 0.85, deviating downwards from the preferred range. Low-height fins are present in the circumferential direction, resulting in a decrease in the wetting edge length and deterioration of heat exchange performance. In Comparative Examples 6-9, one or both of (h / f) and (c / f) deviate downwards or upwards from the preferred range, leading to deterioration of heat exchange performance due to the same tendency.

[0189] Next, in Comparative Example 5, the fin apex angle of the internal spiral groove tube is larger on the negative side, with a (c / f) value of 0.47, deviating downwards from the preferred range. This narrows the opening at the fin apex, resulting in inefficient refrigerant flow and deteriorated heat exchange performance. In Comparative Example 10, the number of fins is high, and the (h / f) value is 3.6, deviating upwards from the preferred range, but heat exchange performance deteriorates due to the same tendency.

[0190] Next, the (c / f) of the inner spiral groove tube of Comparative Example 11 deviates upward from the preferred range, the wetting edge length is long, but the fin spacing becomes wider, making it difficult to form a thin refrigerant film and thus not drying efficiently, resulting in deteriorated heat exchange performance.

[0191] Regarding the heat exchange performance of the internal spiral grooved tube, a portion of the results from the evaluation conducted according to the previously stated evaluation method are presented below.

[0192] exist Figure 16 In the charts, the results of the measured condensation heat transfer coefficients are shown for the inner spiral grooved tubes of Example 1 (◎), Example 11 (〇), Example 12 (△), and Comparative Example 1 (×). Figure 17 In the charts, the results of measuring the evaporative heat transfer coefficient are shown for the inner spiral groove tubes of Example 1 (◎), Example 11 (〇), Example 12 (△), and Comparative Example 1 (×).

[0193] like Figure 16 and Figure 17 As shown in the charts, the heat transfer coefficients of the inner spiral groove tubes of Examples 1, 11, and 12 are improved compared to the inner spiral groove tube of Comparative Example 1, based on the results of both condensation heat transfer and evaporation heat transfer.

[0194] Therefore, it can be seen that in a metal internal spiral groove tube with an outer diameter of 3mm to 10mm and 30 to 60 fins, the cross-sectional rectangular shape of the spiral fins with a fin apex angle of 0±10°, the height-to-width ratio (h / f) is 0.90 to 3.40, and the fin spacing-to-fin width ratio (c / f) is 0.50 to 3.80. This ensures a longer wetting edge length for the internally flowing refrigerant and provides an internal spiral groove tube with excellent heat transfer properties, allowing the refrigerant to easily enter between the fins.

[0195] like Figure 16 and Figure 17 As shown in the graphs, these relationships remain unchanged even when the refrigerant flow rate increases or decreases. Therefore, it can be seen that the heat transfer coefficient of the inner spiral groove tube of Example 1 is improved in both condensation heat transfer and evaporation heat transfer compared to the inner spiral groove tube of Comparative Example 1.

[0196] Furthermore, based on the variation in heat exchange performance according to the shape of the inner surface grooves, in the evaluation results with a refrigerant flow rate of 20 kg / h, the condensation heat transfer coefficient is 6.5 kW / m². 2 Temperatures below ×℃ and an evaporative heat transfer coefficient of 8.0 kW / m² 2 Cases below ×℃ are judged as ×, and the condensation heat transfer coefficient exceeds 6.5kw / m². 2 The value is 8.0 kW / m² at ×℃. 2 Temperatures below ×℃ and evaporative heat transfer coefficients exceeding 8.0 kW / m² 2 The value is 12.0 kW / m² at ×℃. 2 Cases below ×℃ are classified as △, and the condensation heat transfer coefficient exceeds 8.0 kW / m³. 2 The value is 9.5 kW / m² at ×℃. 2 Temperatures below ×℃ and evaporative heat transfer coefficients exceeding 8.0 kW / m² 2 The value is 12.0 kW / m² at ×℃. 2 Conditions below ×℃ are judged as 0, and the condensation heat transfer coefficient exceeds 9.5kw / m². 2 ×℃, and the evaporative heat transfer coefficient exceeds 12.0 kW / m². 2 The case of ×℃ is judged as ◎.

[0197] exist Figure 18 The charts for Example 1 (◎), Example 11 (〇), Example 12 (△), and Comparative Example 1 (×) show the results of measuring condensation pressure loss. Figure 19 The charts for Example 1 (◎), Example 11 (〇), Example 12 (△), and Comparative Example 1 (×) show the results of the evaporation pressure loss measurement.

[0198] according to Figure 18 The charts and diagrams shown in the middle Figure 19 As can be seen from the comparison of the charts, if the inner spiral groove tubes of Examples 1, 11, and 12 are compared with the inner spiral groove tube of Comparative Example 1, the values ​​of condensation pressure loss and evaporation pressure loss are roughly the same. Therefore, no difference in pressure loss can be observed within a wide range of refrigerant flow rate of 10~25 kg / h, and they have equivalent performance.

[0199] Therefore, the internal spiral groove tubes of Examples 1, 11, and 12 can achieve excellent thermal conductivity over a wide range of refrigerant flow rates.

[0200] Explanation of reference numerals in the attached figures

[0201] 1… Heat exchanger, 2… Inner spiral groove tube, 3… Heat dissipation plate, 6… Tube body, 6a… Outer circumferential surface, 6b… Inner circumferential surface, 7… Fin, 7a… End portion, 7b… Bottom, 7c… Side wall portion, 8… Spiral groove, 9… Raw material tube, 9A… Straight fin, 9B… Straight groove, A… Manufacturing device, 14… Fin, 14a… End portion, 14b… Bottom, 14c… Side wall portion, 16… Spiral groove, a… Fin top width, b… Fin bottom width, c… Fin spacing, h… Fin height, θ… Fin apex angle, 11… Release drum, 17… First drawing die, 18… First guide winch, 19… Second drawing die, 21… First revolution winch, 22… Second revolution winch, 23… Revolutionary flywheel.

Claims

1. An internally spiral grooved tube, comprising a tube body, a plurality of grooves and a plurality of fins arranged along the inner circumferential direction of the tube body, characterized in that, The aforementioned grooves and fins are formed in a spiral shape along the longitudinal direction of the aforementioned tube body. The outer diameter of the aforementioned pipe body is 3mm or more and 10mm or less. The number of fins formed on the inner circumferential surface of the aforementioned tube body is 30 to 60. The aforementioned internal spiral groove tube is made of metal. In the cross-section of the aforementioned tube body, the cross-sectional shape of each of the aforementioned fins is a rectangle with a vertex angle of 0 ± 2.5º. The ratio h / f is greater than 1.75 and less than 3.161, where h is the fin height and f is the fin width. The ratio c / f is 1.547 or higher and 2.965 or lower, where c is the fin spacing between adjacent fins in the aforementioned inner circumferential direction of the aforementioned tube body. Furthermore, the average value obtained by summing the aforementioned ratios h / f and c / f and dividing the sum by two is greater than 2.4 and less than 2.

6. The aforementioned rectangle with a vertex angle of 0±2.5º refers to, Based on the apex angle of the case where the sidewalls of the aforementioned fins are completely parallel to each other, the shape includes an isosceles trapezoidal shape in which each sidewall is tilted to an angle of 0 to +2.5° by slightly narrowing the sidewalls above each other, and an inverted isosceles trapezoidal shape in which each sidewall is tilted at an angle of less than 0° to -2.5° by slightly widening the sidewalls above each other.

2. The internal spiral grooved tube as described in claim 1, characterized in that, The aforementioned plurality of fins are arranged at equal intervals in the aforementioned inner circumferential direction of the aforementioned tube body.

3. The internal spiral grooved tube as described in claim 1 or 2, characterized in that, The aforementioned tube body is made of aluminum or aluminum alloy.

4. A heat exchanger, characterized in that, The tube having an inner spiral groove as described in any one of claims 1 to 3.

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