Heat exchange structure, heat transfer tube, and heat exchanger

Abstract

A heat transfer tube according to the present invention is characterized by heat exchange structures (S4, S5) which are provided in flow paths (1a, 1b, 1c) allowing a heat exchange fluid to flow therethrough, and in which a plurality of radially arranged pin layers (1, 2, 3, 4, 5, 6, 7, 8, 9) having pins (15, 16, 17) that have three or more different lengths arranged radially from the center side to the outer periphery side of the flow paths (1a, 1b, 1c) and having said pins (15, 16, 17) arranged radially in the circumferential direction of the flow paths (1a, 1b, 1c) are disposed along the longitudinal direction of the flow paths (1a, 1b, 1c). The heat transfer tube is also characterized in that, in the plurality of radially arranged pin layers (1, 2, 3, 4, 5, 6, 7, 8, 9) disposed in the longitudinal direction of the flow paths (1a, 1b, 1c), each of the adjacent radially arranged pin layers (1, 2, 3, 4, 5, 6, 7, 8, 9) disposed in the longitudinal direction of the flow paths (1a, 1b, 1c) rotates in the circumferential direction of the flow paths (1a, 1b, 1c), and the pins (15, 16, 17) in the adjacent layers are disposed to be shifted from each other.

Description

Heat exchange structures, heat transfer tubes and heat exchangers

[0001] The present invention relates to a heat exchange structure for performing heat exchange with a fluid with low pressure loss and high heat transfer coefficient, and to a heat transfer tube and a heat exchanger equipped with the heat exchange structure. This application claims priority to Japanese Patent Application No. 2024-155154, filed on September 9, 2024, the contents of which are incorporated herein by reference.

[0002] A known fin-and-tube heat exchanger for a room air conditioner includes a plurality of aluminum plate-like fins and aluminum tubular refrigerant pipes inserted through holes in each fin, as described in Patent Document 1. The heat exchanger described in Patent Document 1 includes a heat-conducting portion that contacts the refrigerant inside the tubes that serve as the refrigerant pipes, and partition plates that define the cross section of the tubes in a direction perpendicular to the longitudinal direction of the tubes. According to the configuration described in Patent Document 1, the radially arranged partition plates contact the refrigerant, thereby increasing the contact area between the refrigerant and the partition plates and improving heat exchange efficiency.

[0003] Furthermore, the following Patent Document 2 discloses a structure as an example of an EGR gas cooling device for an EGR (Exhaust Gas Recirculation) system installed in an automobile engine, in which a plurality of plate-like fins are arranged in parallel on a metal substrate by welding or brazing, and the metal substrate is rolled into a cylindrical shape and tightly attached to the inner circumferential surface of a heat transfer tube. According to the configuration described in Patent Document 2, by fixing a cylindrical metal substrate to the inner circumferential surface of the heat transfer tube, a plurality of plate-like fins can be arranged at intervals inside the heat transfer tube, which has the characteristic of improving the efficiency of heat exchange with the fluid flowing inside.

[0004] Japanese Unexamined Patent Publication No. 2015-117873 (A) Japanese Unexamined Patent Application No. 2004-317060 (A)

[0005] In the structure described in Patent Document 1, the height of the partition plates along the radial direction of the refrigerant pipe is all the same, and there are no additional fins or the like in the spaces between adjacent partition plates in the circumferential direction of the refrigerant pipe. Therefore, even if the configuration of Patent Document 1 includes multiple partition plates that come into contact with the refrigerant, the surface area where the partition plates come into contact with the refrigerant is not very large, and further improvement in heat exchange efficiency is desired.

[0006] In the configuration described in Patent Document 2, the examples illustrate a configuration in which multiple fins of different heights are arranged alternately, but only up to two heights are disclosed. Furthermore, welding or brazing is required to set up the fins, and setting up multiple fins of three or more different heights means an increase in the number of fins, making the joining work more difficult and therefore impractical. Furthermore, in a structure with fins of about two different heights, the gap between the bases of the fins is wide, resulting in a large area that does not contribute to heat exchange, making it difficult to expect further improvements in heat exchange efficiency.

[0007] For this reason, the inventors have considered a configuration in which a plurality of pins of three or more different lengths are alternately arranged radially on the inner wall of a pipe through which the medium flows, and have arrived at the present invention.

[0008] The present invention was devised in view of the above-mentioned problems, and its object is to provide a heat exchange structure capable of exchanging heat with a fluid with low pressure loss and high heat transfer coefficient, and a heat transfer tube and a heat exchanger equipped with the heat exchange structure.

[0009] (1) A heat exchange structure according to one embodiment of the present invention is a heat exchange structure provided in a flow path through which a heat exchange fluid flows, and in which pin layers in which three or more types of pins of different lengths are arranged radially from the center of the flow path toward the outer periphery and in a circumferential direction of the flow path are arranged in a plurality of layers along the length of the flow path, and in which the pins are arranged radially in the circumferential direction of the flow path, the plurality of radially arranged pin layers arranged in the longitudinal direction of the flow path are rotated in the circumferential direction of the flow path for each radially arranged pin layer adjacent in the longitudinal direction of the flow path, and the pins in adjacent layers are arranged so as to be misaligned.

[0010] (2) In the heat exchanger structure according to (1) of the present invention, it is preferable that the angle between adjacent pins in the radially arranged pin layer is defined as a radiation angle A, and that the radiation angle A is constant, and that the angle of rotation around the circumferential direction of the flow channel for each adjacent radially arranged pin layer in the longitudinal direction of the flow channel is defined as a rotation angle B, and that the rotation angle B is constant. (3) In the heat exchanger structure according to (1) or (2) of the present invention, when the radially arranged structure of the radially arranged pin layer has n-fold symmetry around the circumferential direction of the flow channel, it is preferable that the rotation angle B is a rotation angle less than 360° / n and an angle other than a multiple of the radiation angle A, where n is a natural number.

[0011] (4) In the heat exchange structure of any one of (1) to (3) of the present invention, when the cross-sectional shapes of all pins constituting the radially arranged pin layer are squares of the same size, it is preferable that the distance between adjacent layers along the length of the flow path is small compared to the length of one side of all pins constituting adjacent radially arranged pin layers along the length of the flow path.

[0012] (5) In the heat exchange structure of any one of (1) to (3) of the present invention, when the cross-sectional shapes of all pins constituting the radially arranged pin layer are squares of the same size, it is preferable that the spacing between adjacent layers along the length of the flow path is small compared to the thickness value of all pins constituting adjacent radially arranged pin layers along the length of the flow path.

[0013] (6) In the heat exchange structure according to any one of (1) to (3) of the present invention, it is preferable that the cross-sectional shape of the pin is elliptical. (7) In the heat exchange structure according to any one of (1) to (3) of the present invention, it is preferable that the pin has a tapered shape that is thick at the tip side close to the outer periphery of the flow path and becomes thinner as it approaches the center of the flow path.

[0014] (8) In the heat exchanger structure described in any one of (1) to (3) of the present invention, it is preferable that a reinforcing ring is provided to reinforce all pins in the radially arranged pin layer. (9) In the heat exchanger structure described in any one of (1) to (3) of the present invention, in the radially arranged pin layer composed of pins of three or more different lengths, it is preferable that the longest pin among the three or more different lengths is radially arranged so as to extend from the center of the flow path to the outer periphery of the flow path, and the pins of the second and subsequent lengths are radially arranged so as to extend successively to the vicinity of the other pins closer to the center of the flow path that are longer than the longest pin. Furthermore, it is preferable that the pin arrangement in the pin layer is such that pins of the same length are not adjacent to each other, and that the number of pins is the greatest for the shortest pins and the least for the longest pins. (10) In the heat exchanger structure described in any one of (1) to (3) of the present invention, it is preferable that the area ratio (radial area / tube body inner diameter area) is higher than 0.2 and the number of layers is 7 or more.

[0015] (11) A heat transfer tube according to one aspect of the present invention comprises a plurality of heat exchanger structures according to any one of (1) to (3) inside an aluminum tube body that forms a flow path through which a heat exchange fluid flows, along the length of the tube body, the pins being made of aluminum, and the tips of the outer circumferential sides of the pins being joined and integrated with the inner wall of the tube body. (12) A heat exchanger according to one aspect of the present invention comprises the heat transfer tube according to (11). (13) A heat exchanger according to one embodiment of the present invention comprises a plurality of parallel-arranged aluminum fins and an aluminum tube body penetrating the plurality of fins, wherein the inside of the tube body has a plurality of radially arranged pin layers at predetermined intervals along the length of the tube body, in which aluminum pins of three or more different lengths are arranged radially from the center of the tube body toward the outer periphery, and the pins are arranged radially around the tube body, and the plurality of radially arranged pin layers arranged along the length of the tube body are rotated around the tube body for each radially arranged pin layer adjacent to each other along the length of the tube body, and the pins in adjacent layers are arranged so as to be misaligned.

[0016] According to one aspect of the present invention, it is possible to provide a heat exchange structure for exchanging heat with a fluid with low pressure loss and high heat transfer coefficient, and a heat transfer tube and a heat exchanger including the heat exchange structure.

[0017] 1 is a perspective view showing a heat exchanger structure according to a first embodiment of the present invention; FIG. 2 is a plan view showing a first radially arranged pin layer constituting the heat exchanger structure; FIG. 3 is a plan view showing a second radially arranged pin layer constituting the heat exchanger structure; FIG. 4 is a plan view showing a third radially arranged pin layer constituting the heat exchanger structure; FIG. 5 is a schematic view showing pins constituting the radially arranged pin layer having a rectangular cross section; FIG. 6 is a schematic view showing pins constituting the radially arranged pin layer having an elliptical cross section; FIG. 7 is a perspective view showing an example of a heat exchanger equipped with a heat transfer tube to which the heat exchanger structure according to the first embodiment is applied; FIG. 8 is a front view showing a part of the heat exchanger; FIG. 9 is a plan view showing a heat exchanger structure according to a second embodiment of the present invention; FIG. 10 is a plan view showing a first radially arranged pin layer constituting the heat exchanger structure according to the first embodiment of the present invention; FIG. 11 is a perspective view showing an example of a rotation angle of 0° in the heat exchanger structure; FIG. 12 is a perspective view showing an example of a rotation angle of 9° in the heat exchanger structure; and FIG. 13 is a bottom view showing a radially arranged pin layer in an example of a rotation angle of 0° in the heat exchanger structure. 19 is a perspective view showing a radially arranged pin layer in an example of a rotation angle of 9° in the same heat exchanger structure. FIG. 20 is a bottom view showing a radially arranged pin layer in an example of a rotation angle of 9° in the same heat exchanger structure. FIG. 21 is a perspective view showing a heat exchanger structure according to a first embodiment of the present invention. FIG. 22 is a schematic view showing the spacing between pins in adjacent radially arranged pin layers in the heat exchanger structure shown in FIG. 15. FIG. 23 is a view showing an example of a heat transfer tube in which a heat exchanger structure according to the first embodiment is integrated inside a tube main body. FIG. 24 is a partially enlarged perspective view showing the stacking state of the radially arranged pin layers provided on the same heat transfer tube. FIG. 25 is a perspective view showing the rotation angle in the heat exchanger structure according to the first embodiment. FIG. 26 is a schematic view showing an example of a pin with an elliptical cross section applied to the radially arranged pin layer. FIG. 27 is a view showing an example of a heat transfer tube provided with a radially arranged pin layer composed of the pins shown in FIG. 21. FIG. 28 is a view showing an example of the first radially arranged pin layer applied to the heat transfer tube shown in FIG. 21. 1 is a schematic diagram showing a method for manufacturing a heat exchanger structure by an additive manufacturing method, the method being described in detail below, and the ...Schematic diagram showing heat transfer in a heat exchange structure employing a radially arranged pin layer. Schematic diagram explaining that the pin arrangement of the radially arranged pin layer returns to its original arrangement by a 180° rotation. A perspective view showing an example of a heat transfer tube manufactured in the examples. A perspective view showing the configuration of a heat exchange structure used for evaluation in the examples. A photograph showing an example of a heat exchange structure manufactured in the examples and used for evaluation. A photograph showing an example of a test piece with one layer of reinforcing rings manufactured in the examples. A photograph showing an example of a test piece with two layers of reinforcing rings manufactured in the examples. A photograph showing an example of a test piece manufactured in the examples and with distortion.

[0018] "First Embodiment" The present invention will be described in detail below based on an embodiment, but the present invention is not limited to the embodiment described below. Note that the drawings used in the following description may conveniently show enlarged characteristic portions to make the features easier to understand. FIG. 1 shows a heat exchanger structure S1 according to a first embodiment of the present invention. This heat exchanger structure S1 is composed of nine identically shaped radially arranged pin layers 1-9 stacked together, with the rotation angle of each layer slightly changed. In the configuration shown in FIG. 1, the radially arranged pin layers 1-9 are stacked sequentially from the lower surface to the upper surface of the heat exchanger structure S1. In FIG. 1, the stacking direction of the radially arranged pin layers 1-9 is the vertical direction. The heat exchanger structure S1 shown in FIG. 1 is installed, for example, in a flow path through which a heat exchange fluid flows from the lower surface to the upper surface. That is, the heat exchanger structure S1 is installed in a flow path through which a fluid (refrigerant) such as air flows along the direction in which the radially arranged pin layers 1-9 are stacked.

[0019] Figure 2 shows the first layer of radially arranged pin layer 1, Figure 3 shows the second layer of radially arranged pin layer 2, and Figure 4 shows the third layer of radially arranged pin layer 3. The fourth layer of radially arranged pin layer 4, the fifth layer of radially arranged pin layer 5, the sixth layer of radially arranged pin layer 6, the seventh layer of radially arranged pin layer 7, the eighth layer of radially arranged pin layer 8, and the ninth layer of radially arranged pin layer 9 all have the same shape, and only the rotation angles of these layers differ in their integrated structures, which will be explained below.

[0020] As shown in Figure 2, which shows the heat exchanger structure S1 of Figure 1 viewed from the bottom, the radially arranged pin layer 1, which is the first layer from the bottom, has eight first pins 15 (the longest), 12 second pins 16 (the second longest), and 20 third pins 17 (the third longest), which are arranged radially in parallel to form a circle. As shown in Figure 2, a total of 40 pins, including all pins 15, 16, and 17, are arranged radially from the center to the outer periphery of the circle. The positions of the pins 15, 16, and 17 are arranged as described below, but the pins 15, 16, and 17 are arranged radially at equal intervals (constant intervals) around the circumference of a circle drawn at the positions connecting the tips of the pins 15, 16, and 17. As described above, the radially arranged pin layer 1 is composed of 40 pins, and the 40 pins are arranged radially at 9° intervals around the circumference of the circle. In this embodiment, the pins 15, 16, and 17 are preferably made of aluminum, which has excellent thermal conductivity. In this embodiment, aluminum refers to pure aluminum or an aluminum alloy. Furthermore, in this embodiment, the pins 15, 16, and 17 are each formed in the shape of a long, thin rod having a square cross section along its entire length.

[0021] The longest pin 15 has a length extending from the center position of the radially arranged pin layer 1 to the outer periphery of the radially arranged pin layer 1. In the example shown in Fig. 2, if the circle drawn by connecting the tip ends 15a of the radially arranged pins 15 is likened to the face of a clock, the pins 15 are radially arranged so that they are positioned at 36°, 90°, 126°, 162°, 216°, 270°, 306°, and 342° clockwise (right-handed) from the reference 12 o'clock position. The base ends 15b of the pins 15 located at the center of the circle are integrated at the center of the circle.

[0022] If the circle drawn by connecting the tip ends 16a of the radially arranged pins 16 is likened to the face of a clock, the second longest pins 16 are radially arranged so that, clockwise from the reference position of 12 o'clock, they are at 0°, 18°, 54°, 72°, 108°, 144°, and 180°. Furthermore, the pins 16 are radially arranged so that, clockwise from the reference position of the circle, they are at 198°, 234°, 252°, 288°, and 324°. The base end 16b of the second longest pin 16 extends from the outer periphery of the circle toward the center of the circle. However, since there is a portion at the center of the circle where the base end 15b of the pin 15 is integrated, the base end 16b of the pin 16 extends to a position close to (near) the portion where the base end 15b is integrated. In the example shown in Fig. 1, the base end 16b of the pin 16 is located near the center of the circle and sandwiched between the pins 15, 15 adjacent in the circumferential direction of the circle.

[0023] If the circle drawn by connecting the tips 17a of the radially arranged pins 17 is likened to the face of a clock, the third longest pin 17 is radially arranged so that, clockwise from the reference position of 12 o'clock, it is at 9°, 27°, 45°, 63°, 81°, 99°, 117°, 135°, 153°, and 171°. Furthermore, the pins 17 are radially arranged so that, clockwise from the reference position of the circle, it is at 189°, 207°, 225°, 243°, 261°, 279°, 297°, 315°, 333°, and 351°. The base end 17b of the third longest pin 17 extends from the outer periphery of the aforementioned circle toward the center of the circle. Since the base end 15b of pin 15 and the base end 16b of pin 16 are located toward the center of the circle, the base end 17b of pin 17 extends to a position close to (near) the base ends of pins 15 and 16. The pins 16 and 17, which are second longest and below pin 15, can be described as extending to positions closer to the center of the longer pins.

[0024] As described above with reference to Figure 2, the pins 15, 16, and 17 are arranged radially, and therefore, in a plan view of the circle, a center-side flow passage 1a is formed on the center side of the circle, partitioned by the base end 15b of pin 15 and the base end 16b of pin 16. Also, an inner-side flow passage 1b is formed slightly outside the center of the circle, partitioned by the base end side of pin 15, the base end side of pin 16, and the base end of pin 17. Furthermore, outer-side flow passages 1c are formed outside the inner-side flow passage 1b and between the pins 15 and 16, between the pins 16 and 17, and between the pins 15 and 17 that are adjacent in the circumferential direction of the circle.

[0025] In comparison with the radially arranged pin layer 1, which is the first layer from the bottom, as shown in Figure 2, the radially arranged pin layer 2, which is the second layer from the bottom, is configured as shown in Figure 3. The radially arranged pin layer 2 is composed of pins 15, 16, and 17, just like the radially arranged pin layer 1. The number of pins 15, 16, and 17 and the arrangement of the pins 15, 16, and 17 around the circumference of the circle formed by the tips of the pins 15, 16, and 17 are also the same as those of the radially arranged pin layer 1. In the second radially arranged pin layer 2, as viewed from the bottom as shown in Figure 3, the pins 15, 16, and 17 are formed at positions rotated 7° clockwise from the 12 o'clock position, which is the reference when the circle is likened to the face of a clock, compared to the first radially arranged pin layer 1, as viewed from the bottom as shown in Figure 2.

[0026] For example, in the radially arranged pin layer 1 shown in Fig. 2, pin 16, which extends in the 12 o'clock direction, is located at a position rotated 7° clockwise from the 12 o'clock direction in the radially arranged pin layer 2 shown in Fig. 3. The other pins 15, 16, and 17 are similarly formed along the aforementioned circle at positions shifted 7° clockwise from the position in the radially arranged pin layer 1 shown in Fig. 2. Therefore, the second layer of radially arranged pin layer 2 shown in Fig. 3 can be described as a rotationally symmetric body rotated 7° clockwise on the aforementioned circle with respect to the first layer of radially arranged pin layer 1 shown in Fig. 2.

[0027] In contrast to the second radially arranged pin layer 2 shown in Fig. 3, the third radially arranged pin layer 3 is configured as shown in Fig. 4. The third radially arranged pin layer 3 is made up of pins 15, 16, and 17, similar to the radially arranged pin layers 1 and 2. The number of pins 15, 16, and 17 and the arrangement of the pins 15, 16, and 17 around the circumference of the circle formed by the tips of the pins 15, 16, and 17 are also similar to the radially arranged pin layers 1 and 2.

[0028] In the third radially arranged pin layer 3 as viewed from the bottom as shown in Fig. 4, the pins 15, 16, and 17 are formed at positions rotated 7° clockwise from the 12 o'clock position, which is the reference position when the circle is likened to the clock face, relative to the second radially arranged pin layer 2 as viewed from the bottom as shown in Fig. 3. For example, in the radially arranged pin layer 1 shown in Fig. 3, the pin 16 extending in a clockwise direction of 7° from the 12 o'clock position is located at a position rotated 14° clockwise from the 12 o'clock position in the third radially arranged pin layer 3 shown in Fig. 4. The other pins 15, 16, and 17 are also formed along the circle at positions shifted 7° clockwise from the positions of the radially arranged pin layer 2 shown in Fig. 3. The third radially arranged pin layer 3 shown in Fig. 4 can be described as a rotationally symmetric body rotated 14° clockwise on the circle relative to the first radially arranged pin layer 1 shown in Fig. 2. Similarly, the third radially arranged pin layer 3 shown in FIG. 4 can be explained as a rotationally symmetric body rotated 7° clockwise on the circle described above with respect to the second radially arranged pin layer 2 shown in FIG.

[0029] Similarly, in the fourth radially arranged pin layer 4 to the ninth radially arranged pin layer 9, the pins 15, 16, and 17 are formed so that they are shifted in position by 7° in the circumferential direction of the circle in each layer. Although the bottom structures of the fourth radially arranged pin layer 4 to the ninth radially arranged pin layer 9 are not shown in the figures, as shown in the overall structure of the heat exchanger structure S1 in Fig. 1, the pins 15, 16, and 17 in each layer are stacked so that they are shifted in position by 7° in each layer relative to the radially arranged pin layer immediately before. For example, the pin 16 extending in the 12 o'clock direction shown in Fig. 2 in the first radially arranged pin layer 1 is positioned 7° clockwise from the 12 o'clock direction in the second radially arranged pin layer 2 as shown in Fig. 3, and is positioned 14° clockwise from the 12 o'clock direction in the third radially arranged pin layer 3 as shown in Fig. 4.

[0030] For example, in the fourth radially arranged pin layer and the fourth to ninth radially arranged pin layers 9, the pins 16 in the next layer are sequentially arranged so that they are shifted in position relative to the pins 16 in the previous layer by 7° in the circumferential direction of the circle. Regarding the radially arranged structure of the radially arranged pin layers 1 to 9, if the radially arranged structure has n-fold symmetry around the circle (in other words, around the flow path), and the rotation angle is defined as B, the rotation angle is preferably less than 360° / n and is not a multiple of the radial angle A. Here, n is a natural number. Furthermore, in the structure of this embodiment, the pin arrangement of the radially arranged pin layer is preferably such that pins of the same length are not adjacent to each other around the circle, the number of pins is the most for the shortest pins 17, the least for the longest pins 15, and the number of pins of intermediate lengths is between the number of pins 15 and the number of pins 17.

[0031] FIG. 5 shows an example of pins 15, 16, and 17 with rectangular cross sections. FIG. 6 shows an example of pins 15, 16, and 17 with elliptical cross sections. Pins 15, 16, and 17 may have square cross sections as shown in FIGS. 1 to 4 , rectangular cross sections as shown in FIG. 5 , or elliptical cross sections as shown in FIG. 6 . Alternatively, other polygonal or irregular cross sections may be used. Regardless of the cross section, it is preferable that the spacing G between adjacent pins in the direction of the flow of the heat exchange fluid, such as air, be smaller than the pin's thickness D along the direction of the heat exchange fluid (the spacing G is less than the thickness D). This can be expressed as a relationship of G<D. In FIG. 5 , when the pins 15, 16, and 17 have rectangular cross sections, the long sides are 0.7 mm and the short sides are 0.3 mm, as an example. In Fig. 6, when the pins 15, 16, and 17 have an elliptical cross section, the length of the major axis of the ellipse is indicated as 0.3 mm, for example. The thickness of the pin along the length of the flow path is 0.3 mm for the pins 15, 16, and 17 shown in Fig. 5, and 0.3 mm for the pins 15, 16, and 17 shown in Fig. 6. When the pin has a square cross section as shown in Fig. 1, the thickness is equal to the length of one side of the square.

[0032] 7 shows a heat exchanger 22 including a plurality of plate-shaped aluminum fins 20 and a plurality of aluminum heat transfer tubes 21 that are provided to penetrate these fins 20. In this heat exchanger 22, the ends of the heat transfer tubes 21 that penetrate the fins 20 are connected by U-shaped elbow pipes 23, and a serpentine flow path is formed by the heat transfer tubes 21 and the elbow pipes 23 to enable efficient heat exchange throughout the entire fin 20. In this heat exchanger 22, the opening of one heat transfer tube 21 that penetrates the upper end side of the fin 20 serves as an inlet for the heat exchange fluid, and the opening of the other heat transfer tube 21 serves as an outlet for the heat exchange fluid.

[0033] 7, the heat exchanger 22 shown in Fig. 1 is formed intermittently inside the heat transfer tube 21 in the required number, integrally with the heat transfer tube 21. Any number of heat exchange structures S1 may be provided inside the heat transfer tube 21, and the heat exchange structures S1 may be formed continuously in the longitudinal direction of the heat transfer tube 21. The heat transfer tube 21 provided with the heat exchange structure S1 therein will be described in detail later, but a structure in which the tip sides of the pins 15, 16, 17 are integrated with the inner circumferential surface of the tube body constituting the heat transfer tube 21 can be employed.

[0034] If the heat transfer tube 21 is provided with a heat exchange structure S1, the pins 15, 16, and 17 are arranged around the heat transfer structure S1 so that they are offset by a small angle, which efficiently disrupts the flow of the heat exchange fluid. This results in a heat transfer tube 21 with excellent heat exchange efficiency. Also, three types of pins 15, 16, and 17 with different lengths are provided, and in the radially arranged pin layers 1 to 9, a center-side flow path 1a is provided on the inner periphery side of each, an inner-side flow path 1b is provided outside of that, and an outer-side flow path 1c is provided outside of that.

[0035] As a result, when a fluid passes through the heat exchange structure S1, the fluid can flow along the center of the heat exchange structure S1, and can also flow along the inner-side flow path 1b on the outside of the heat exchange structure S1, and can also flow along the outer-side flow path 1c on the outside. As a result, the entire length of the pins 15, 16, and 17 provided on the heat exchange structure S1 can be effectively utilized to efficiently exchange heat with the fluid. This improves the heat exchange efficiency of the heat transfer tubes 21. Furthermore, since multiple fins 20 are provided in contact with the heat transfer tubes 21, heat can be dissipated via the multiple fins 20 using the air surrounding the fins 20. This, combined with the excellent heat exchange characteristics of the heat transfer tubes 21, makes it possible to provide a heat exchanger 22 with excellent heat exchange efficiency.

[0036] Second Embodiment Figure 9 shows the configuration of the first radially arranged pin layer 30 used in the construction of a heat exchanger structure of a second embodiment. Similar to the first radially arranged pin layer 1 of the first embodiment shown in Figure 2, the radially arranged pin layer 30 also consists of three types of pins 35, 36, and 37 of different lengths. The radially arranged pin layer 30 has eight first pins 35, the longest, twelve second pins 36, and the third longest, twenty third pins 37, which are radially arranged in parallel to form a circle as a whole, which is the same as the radially arranged pin layer 1 of the first embodiment. As shown in Figure 9, the configuration in which a total of 40 pins, including the pins 35, 36, and 37, are radially arranged is also the same as the structure of the first embodiment.

[0037] A characteristic feature of the radially arranged pin layer 30 is that the base end 35b of each pin 35 is the thinnest, gradually thickening toward the tip end 35a of the pin 35, and a tapered shape is imparted to the pin 35, with the tip end 35a being the thickest. Furthermore, the structure in which the pins 35, 36, and 37 are radially arranged at equal intervals around the circumference of the radially arranged pin layer 30 is equivalent to the arrangement structure of the pins 15, 16, and 17 in the radially arranged pin layer 1 of the first embodiment. As an example, if the thickness of the pin 35 along the length of the flow channel is 0.3 mm and the thickness of the base end 35b of the pin 35 in the direction perpendicular to the length is 0.3 mm, the thickness of the tip end 35a can be 0.7 mm. The base end of each pin 36 is also the thinnest, gradually thickening toward the tip end 36a of the pin 36, with the tip end 36a being the thickest. The base end 37b of the pin 37 is also the thinnest, and gradually becomes thicker toward the tip end 37a of the pin 37, with the tip end 37a being the thickest.

[0038] The heat exchanger structure of the second embodiment can be constructed by sequentially stacking the second to ninth radially arranged pin layers, each having a shape obtained by rotating the radially arranged pin layer 30 shown in FIG. 9 around itself by 7° increments, in the same manner as in the first embodiment. The heat exchanger structure of the second embodiment is disposed in a flow path within the tube body of a heat transfer tube, similar to the heat exchanger structure S1 of the first embodiment. Therefore, in other words, the pins 35, 36, and 37 can be described as having a tapered shape that is thicker at the tip end near the outer periphery of the flow path and becomes thinner as it approaches the center of the flow path. The heat exchanger structure of the second embodiment can also achieve the same effects as the heat exchanger structure S1 of the first embodiment. Furthermore, a heat transfer tube can be constructed by providing the heat exchanger structure of the second embodiment inside the tube body, and a heat exchanger that achieves the same effects as the heat exchanger 22 shown in FIG. 7 can be obtained using this heat transfer tube.

[0039] Next, the detailed structure of a comparative example compared to the heat exchanger structure S1 of the first embodiment described above will be further described with reference to Figures 10 to 14. As shown in Figure 10, in the first radially arranged pin layer 1 applied to the heat exchanger structure S1 of the first embodiment, all of the radiation angles in the first radially arranged pin layer 1 were 9°. In the first radially arranged pin layer 1, a total of 40 pins, including pins 15, 16, and 17, were arranged radially at equal intervals around the circumference, resulting in a radiation angle of 9°. In addition, the rotation angles of the first to ninth radially arranged pin layers were all the same, at 7°.

[0040] Assuming that the heat exchanger structure S1 is formed as described above using the radially arranged pin layer 1 shown in FIG. 10 , if the rotation angle of each layer is set to 0° as shown in FIG. 11 , the pins in the first radially arranged pin layer 1 to the ninth radially arranged pin layer 9 will not be misaligned with each other in adjacent layers. FIG. 11 shows a heat exchanger structure S2 in which the rotation angle of each layer is set to 0°, so the pins in the first to ninth layers are aligned in the stacking direction. In contrast, consider an example in which the rotation angle of the radially arranged pin layer is set to 9°. FIG. 12 shows a heat exchanger structure S3 as an example in which the rotation angle of each layer in the first to ninth layers is set to 9°. At first glance, the heat exchanger structure S3 shown in the perspective view of FIG. 12 appears to be the same as the heat exchanger structure S2 shown in the perspective view of FIG. 11 .

[0041] FIG. 13 shows a bottom view of a heat exchange structure S2 with a rotation angle of 0°, and FIG. 14 shows a bottom view of a heat exchange structure S3 with a rotation angle of 9°. Comparing the heat exchange structure S2 shown in FIG. 13 with the heat exchange structure S3 shown in FIG. 14 reveals differences not identified by comparing FIGS. 11 and 12 . In the heat exchange structure S2 with a rotation angle of 0° shown in FIG. 13 , the presence of a center-side flow path 1a, an inner-side flow path 1b, and an outer-side flow path 1c can be confirmed in the center. That is, in the heat exchange structure S2, the center-side flow path 1a, the inner-side flow path 1b, and the outer-side flow path 1c are each individually connected in a straight line along the entire length of the heat exchange structure S2 in the stacking direction. In contrast, in the heat exchange structure S3 with a rotation angle of 9° shown in FIG. 14 , it is impossible to recognize that the center-side flow path 1a and the inner-side flow path 1b are each individually connected in a straight line along the stacking direction of the heat exchange structure S3.

[0042] Therefore, the heat exchange structure S2 with a rotation angle of 0° and the heat exchange structure S3 with a rotation angle of 9°, which are considered to be equivalent structures when displayed as in Figures 11 and 12, can be considered to be different structures. The same can be said for structures with rotation angles of 18°, 27°, and subsequent rotation angles that are multiples of 9°. The same applies to structures with rotation angles of 4.5° and 13.5° (13.5° corresponds to 4.5° + 9°). As will be demonstrated in the examples below, when the rotation angle is a multiple of the radiation angle, good heat exchange characteristics cannot be obtained, so it is preferable that the rotation angle be an angle other than a multiple of the radiation angle.

[0043] In the case of the heat exchanger structure S1 described above, as shown in FIG. 1 , the radially arranged pin layers 1 to 9 are stacked, forming a spiral flow path in the thickness direction of the heat exchanger structure S1, with the low flow path resistance portions of the exterior-side flow paths 1c formed in each layer. Furthermore, the low flow path resistance portions of the interior-side flow paths 1b formed in each layer are connected in a spiral manner in the thickness direction of the heat exchanger structure S1, forming a spiral flow path. Furthermore, the low flow path resistance portions of the center-side flow paths 1a formed in each layer are connected in a spiral manner in the thickness direction of the heat exchanger structure S1, forming a spiral flow path. With the heat exchanger structure S1 configured as described above, fluid can flow in a nearly spiral manner on all sides of the heat exchanger structure S1, including the center, interior, and exterior sides, which is thought to improve the heat exchange efficiency with the fluid. Because the effect of the spiral flow path cannot be achieved with a small number of layers, a stack number of 7 or more is preferred. While not particularly limited, the number of layers may be 8 or more, or even 9 or more. Furthermore, although not particularly limited, the number of layers may be 60 or less, 30 or less, or 15 or less. Furthermore, when the radially arranged pin layer is viewed from the front from the fluid flow side, the area ratio of the projected area of ​​the radial structures per layer to the inner diameter area of ​​the tube main body having the radial structures therein is preferably higher than 0.2, since this provides a large heat exchange area. Although not particularly limited, the area ratio of the projected area of ​​the radial structures per layer to the inner diameter area of ​​the tube main body having the radial structures therein when the radially arranged pin layer is viewed from the front from the fluid flow side may be higher than 0.25 or higher than 0.3. Furthermore, although not particularly limited, the area ratio of the projected area of ​​the radial structures per layer to the inner diameter area of ​​the tube main body having the radial structures therein when the radially arranged pin layer is viewed from the front from the fluid flow side may be lower than 0.8, lower than 0.7, or lower than 0.6.

[0044] Figure 15 shows the same heat exchange structure S1 as the heat exchange structure S1 shown in Figure 1, but Figure 16, which is drawn in contrast to Figure 15, shows the pins 15, 16, and 17 provided on the heat exchange structure S1 as seen from the side. When the pins 15, 16, and 17 are elongated rods with square cross sections as shown in Figure 16, the thickness D of each pin can be selected to be 0.3 x 0.3 mm as shown in the previous example, and in this case the spacing G between adjacent radially arranged pin layers can be selected to be 0.15 mm. It is preferable that the relationship G<D.

[0045] 17 shows a heat transfer tube 41 having a structure in which an aluminum heat exchange structure S4 is integrated into an aluminum tube body 40. The heat exchange structures S4 may be arranged intermittently at predetermined intervals in the longitudinal direction of the tube body 40 inside the tube body 40, or the heat exchange structures S4 may be arranged continuously along the longitudinal direction of the tube body 40.

[0046] The heat exchange structure S4 shown in Fig. 17 includes first to ninth radially arranged pin layers each including pins 15, 16, and 17 having the same structure as the heat exchange structure S1 of the first embodiment shown in Fig. 1. However, in the heat exchange structure S4, in order to increase the structural strength of the pins 15, 16, and 17, a reinforcing ring 42 is provided on the inner periphery of each radially arranged pin layer to individually connect the pins 15, 16, and 17. Fig. 18 shows a state in which the multiple radially arranged pin layers constituting the heat exchange structure S4 are arranged intermittently in the longitudinal direction of the pipe body 40 and are misaligned at a predetermined rotation angle.

[0047] In the heat transfer tube 41, aluminum constituting the tube body 40 and each pin 15, 16, 17 has excellent thermal conductivity, so excellent heat exchange characteristics can be obtained by flowing a fluid through the heat transfer tube 41 shown in Fig. 17. Furthermore, since the heat transfer tube 41 is provided with the heat exchange structure S4, the flow of the heat exchange fluid can be efficiently disturbed, similar to the heat transfer tube 21 using the heat exchange structure S of the first embodiment. This allows the heat transfer tube 41 to have excellent heat exchange efficiency.

[0048] Fig. 19 shows the same heat exchange structure S1 as the heat exchange structure S1 shown in Fig. 1 , but Fig. 20, which is drawn in comparison with Fig. 19, shows an enlarged view of the rotation angles of the pins 15, 16, and 17 provided on the heat exchange structure S1. In the heat exchange structure S1 shown in these figures, if the rotation angle of each pin is denoted as B, the rotation angle B can be expressed by the following formula: B = (n - 1) x A + C In this formula, n is an integer of 1 or more, A is the radiation angle (9° in the case of the first embodiment), and C indicates 0 < C < A. As an example, when n = 1, the rotation angle E preferably satisfies the relationship 0 < B < 9°, and when n = 2, the rotation angle E preferably satisfies the relationship 9 < B < 18°.

[0049] FIG. 21 shows pins 55, 56, and 57 with an elliptical cross section. FIG. 22 shows a heat transfer tube 51 in which a heat exchange structure S5 (shown in FIG. 22) that can be constructed using these pins 55, 56, and 57 is integrated into the tube body 50. The arrangement of the first pins 55, second pins 56, and third pins 57 and the relationship of their lengths may be similar to those of the first to ninth radially arranged pin layers 1 to 9 and the first pins 15, second pins 16, and third pins 17 described in the first embodiment. For illustrative purposes, FIG. 23 shows an example of the arrangement of pins 55, 56, and 57 in the first radially arranged pin layer 58. For example, the cross-sectional dimensions of the pins 55, 56, and 57 may be elliptical, with the major axis length of the ellipse being 0.3 mm and the minor axis length being 0.2 mm. The heat transfer tube 51 shown in FIG. 22 can also achieve the same effects as the heat transfer tube 21 described in the first embodiment.

[0050] "Manufacturing Method" The heat exchange structure S1 having the configuration described above can be manufactured by a binder jet additive manufacturing method using metal powder and a 3D printer. For example, when manufacturing a lattice-shaped structure by additive manufacturing, as shown in FIG. 24, a layer of metal powder particles 61 is stacked on a powder bed 60, and binder ink 63 is applied from an inkjet printer head 62 to match the shape to be manufactured. Next, a second layer of metal powder particles is deposited on the powder bed 60, and binder ink is applied to the required locations. The above process is repeated the required number of times to form a laminate 66 of the required thickness, as shown in FIG. 25.

[0051] After this, curing is performed and the laminate 66 is dried in a drying oven. After drying, a molded object (green body) 67 shown in FIG. 26 is removed from the powder, and the molded object 67 is separated from the metal powder particles 61 that are not coated with the binder ink 63. The separated molded object 67 is degreased, then loaded into a heating furnace and sintered by heating to the required temperature, thereby obtaining a sintered body of the desired shape. For example, by sintering the molded object 67 shown in FIG. 26, a lattice-shaped structure 68 shown in FIG. 27 can be obtained.

[0052] The radially arranged pin layer 1 to be manufactured in this embodiment is shown in Figure 28. Using the additive manufacturing method described with reference to Figures 24 to 26, binder ink is sprayed onto the stacked metal powder particle layers as needed to match the planar shape of the desired radially arranged pin layer 1. Metal powder particles coated with binder ink are sequentially stacked to the required thickness, followed by curing, degreasing, and sintering, to form the radially arranged pin layer 1 shown in Figure 28. In this embodiment, nine radially arranged pin layers are preferably deposited. Therefore, the binder jet additive manufacturing method described so far can be repeated until the thickness of nine layers is reached to manufacture the heat exchange structure S1 shown in Figure 1. For example, additive manufacturing can be performed using a typical commercially available 3D printer with a layer thickness of several tens of microns or more to form each radially arranged pin layer.

[0053] If the tube body is also manufactured simultaneously using binder jet additive manufacturing in addition to the heat exchange structure S1, it is possible to manufacture a heat transfer tube 41 having a configuration in which the heat exchange structure S1 is integrated inside the tube body 40 as previously explained with reference to Fig. 17. Using binder jet additive manufacturing not only makes it possible to manufacture the heat exchange structure S1 independently, but also makes it possible to manufacture a heat transfer tube 41 having a configuration in which the heat exchange structure S1 is integrated into the tube body 40 as needed.

[0054] Comparing the heat conduction of the lattice structure 68 shown in Fig. 27 with that of the radially arranged pin layer 1 shown in Fig. 28, it is believed that the heat resistance is greater in the structure 68 because heat is conducted in a zigzag pattern through the lattice portion. However, in the radially arranged pin layer 1 shown in Fig. 28, heat is conducted linearly through any of the pins 15, 16, and 17, over the shortest distance, which is believed to enable more efficient heat transfer with the heat exchange fluid.

[0055] Figure 29 is a diagram again showing the first radially arranged pin layer 1 previously described in Figure 2. Considering the rotational symmetry of the radially arranged pin layer 1 based on Figure 29, it can be seen that the first radially arranged pin layer 1 returns to its original shape in plan view when rotated 180 degrees clockwise or counterclockwise.

[0056] Examples of the present invention will be described below, but the present invention is not limited to the following examples. A heat transfer tube (outer diameter 21 mm, inner diameter 18 mm, length 27 mm) 71 was assumed, which had a heat exchange structure S1 similar in structure to the heat exchange structure shown in FIG. 1 integrated inside an aluminum tube body 70 shown in FIG. 30 . The outer wall temperature of the heat transfer tube 71 was assumed to be 140°C, and air (25°C, 50 L / min) flowing into the heat transfer tube 71 was assumed. A simulation was performed to calculate the pressure loss and heat transfer coefficient. The simulation software used to calculate the heat transfer coefficient and pressure loss was ANSYS, Inc.'s coupled analysis software "Ansys 2022 R2." The simulation conditions were: element size of 0.1 mm or less, polyhedral meshing, number of iterations of 1000 or more, viscosity model "Transition SST," and calculation method "SIMPLE." In conducting the simulation, the heat transfer coefficient, pressure loss, Nu (Nusselt number), f (friction loss coefficient), and TPE (Thermal Performance Factor) were calculated using the following variables for the simulation: pin shape, pin length (mm), radiation angle (°), rotation angle (°), pin thickness (mm), spacing between layers (mm), presence or absence of reinforcing rings, number of layers, and area ratio (radial area / inner diameter area of ​​the tube body), as shown in Table 1. The lengths of the pins, from longest to shortest, were 9 mm, 8 mm, 6 mm, and 3 mm for Example No. 10; 9 mm, 8 mm, and 6 mm for Examples 1 to 9, 11, and 12 and Comparative Examples 1 and 2; and 9 mm and 8 mm for Comparative Example 3. The 9 mm pins are located at 36°, 90°, 126°, 162°, 216°, 270°, 306°, and 342° clockwise from the 12 o'clock reference position. The 8 mm pins are located at 0°, 18°, 54°, 72°, 108°, 144°, 180°, 198°, 234°, 252°, 288°, and 324° clockwise from the 12 o'clock reference position. The 6 mm pins are located every 18° starting at 9° clockwise from the 12 o'clock reference position.The 3mm long pins are located every 9° starting at 4.5° clockwise (right-hand) from the nominal 12 o'clock position.

[0057] The Nusselt (Nu) number was calculated from the pressure loss, and the heat transfer performance index (TPF), which can be expressed by the following formula, was evaluated from these. The smaller the pressure loss, the higher the heat transfer coefficient, and the better the heat exchange performance of the heat transfer tube, the higher the TPF value tends to be. TPF = Nu / f （１／３） The simulation results for heat exchange structures No. 1 to No. 15, which were set using the variables shown in Table 1, are also shown in Table 1 below. No. 8 is a structure in which the pins are tapered so that they are thinnest at the base end, gradually thicken toward the tip end, and are thickest at the tip end, with the pin thickness along the length of the flow path being 0.3 mm, and the thickness of the base end of the pin in the direction perpendicular to the length direction being 0.3 mm and 0.7 mm at the tip end.

[0058]

[0059] The results shown in Table 1 indicate that the heat transfer tubes of Examples 1 to 12 all met the desired conditions for the number of different pin lengths, radiation angle, and rotation angle, resulting in excellent heat transfer coefficients and favorable heat transfer performance indexes (TPEs). In contrast to these heat transfer tubes, the heat transfer tube of Comparative Example 1, which had a rotation angle of 0°, and the heat transfer tube of Comparative Example 2, which had a rotation angle of 90°, both exhibited low pressure loss but low heat transfer coefficients and low TPEs. The heat transfer tube of Comparative Example 3, which had two different pin lengths and was similar to the aforementioned heat transfer tubes in terms of the radiation angle, rotation angle, pin thickness, layer spacing, and number of layers, also exhibited low heat transfer coefficients and low TPEs.

[0060] From these results, it was found that if a heat transfer tube uses three or more types of pins of different lengths and satisfies the desirable relationship between the radiation angle and the rotation angle described in the previous embodiment, it is possible to obtain a heat transfer tube that has an excellent heat transfer coefficient and a good value for the heat transfer performance index.

[0061] A prototype test was conducted to manufacture the heat exchanger structure shown in FIG. 1 , which was constructed by stacking nine radially arranged pin layers as shown in FIG. 2 , using a binder jet additive manufacturing method with aluminum powder and a 3D printer. The first, second, and third pins were formed into square rods with diameters of 0.3 x 0.3 mm. The rotation angle per layer in the radially arranged pin layers from the first to ninth layers was 7°, and a total of 40 pins of three types were used. The radiation angle was set to 9°. Figure 32 shows the heat exchanger structure obtained as a result of the prototype. In this prototype, a circular through-hole 81 was formed in the center of a plate-shaped base 80 as shown in FIG. 31 , and the heat exchanger structure S1 was constructed to occupy the interior of this through-hole 81. As shown in FIG. 32 , a heat exchanger structure having a structure in which multiple pins having the desired shape are arranged was successfully manufactured.

[0062] Figure 33 shows an example of a heat exchanger structure obtained as a result of trial manufacture using the binder jet additive manufacturing method, with the intention of producing a heat exchanger structure S4 equipped with the reinforcing ring 42 shown in Figure 17. Figure 34 shows another example of a heat exchanger structure obtained as a result of trial manufacture with the intention of producing a heat exchanger structure equipped with two reinforcing rings, in addition to the example of the heat exchanger structure shown in Figure 33. As shown in Figures 33 and 34, a heat exchanger structure equipped with a reinforcing ring could be manufactured using the binder jet additive manufacturing method.

[0063] Figure 35 shows a heat exchanger structure that was distorted as a result of fabricating multiple prototypes of the heat exchanger structure shown in Figure 32. In binder jet additive manufacturing, aluminum powder is layered and then sintered, so it is thought that distortion occurs in the elongated pins as shown in Figure 35 depending on the bonding state of the powders during sintering. Multiple prototypes were fabricated with the reinforcing rings shown in Figures 23 and 24, but none of the pins were distorted as shown in Figure 35. This shows that when fabricating a heat exchanger structure with a large number of elongated rod-shaped pins, it is important to provide a structure to reinforce the pins.

[0064] According to the present invention, it is possible to provide a heat exchange structure capable of exchanging heat with a fluid with low pressure loss and high heat transfer coefficient, and a heat transfer tube and a heat exchanger equipped with the heat exchange structure.

[0065] S1 Heat exchange structure, 1, 2, 3, 4, 5, 6, 7, 8, 9 Radially arranged pin layer 1a Center side flow path 1b Internal side flow path 1c External side flow path 15 First pin 16 Second pin 17 Third pin 20 Fin 21 Heat transfer tube 22 Heat exchanger 30 Radially arranged pin layer 35 First pin 36 Second pin 37 Third pin 40 Tube body 41 Heat transfer tube S4 Heat exchange structure 50 Tube body 51 Heat transfer tube S5 Heat exchange structure 58 Radially arranged pin layer 70 Tube body 71 Heat transfer tube.

Claims

1. A heat exchange structure provided in a flow path through which a heat exchange fluid flows, in which a plurality of radially arranged pin layers are arranged along the length of the flow path, with the pins of three or more different lengths arranged radially from the center of the flow path to the outer periphery and also arranged radially around the flow path, characterized in that in the plurality of radially arranged pin layers arranged along the length of the flow path, adjacent radially arranged pin layers in the length of the flow path rotate around the flow path for each adjacent radially arranged pin layer, and the pins in adjacent layers are arranged so as to be misaligned.

2. A heat exchange structure as described in claim 1, characterized in that the angle between adjacent pins in the radially arranged pin layer is defined as a radiation angle A, the radiation angle A is constant, and the angle by which each adjacent radially arranged pin layer rotates around the flow path in the longitudinal direction of the flow path is defined as a rotation angle B, and the rotation angle B is constant.

3. The heat exchange structure according to claim 2, wherein when the radially arranged structure of the radially arranged pin layer has an n-fold symmetry around the circumference of the flow path, the rotation angle B is a rotation angle less than 360° / n and is an angle other than a multiple of the radiation angle A, where n is a natural number.

4. A heat exchange structure as described in any one of claims 1 to 3, characterized in that when the cross-sectional shapes of all pins constituting the radially arranged pin layer are squares of the same size, the spacing between adjacent layers along the length of the flow path is smaller than the length of one side of all pins constituting adjacent radially arranged pin layers along the length of the flow path.

5. A heat exchange structure as described in any one of claims 1 to 3, characterized in that when the cross-sectional shapes of all pins constituting the radially arranged pin layer are the same shape and size, the spacing between adjacent layers along the length of the flow path is small compared to the thickness along the length of the flow path of all pins constituting the radially arranged pin layer adjacent along the length of the flow path.

6. A heat exchange structure according to any one of claims 1 to 3, characterized in that the cross-sectional shape of the pin is elliptical.

7. A heat exchange structure as described in any one of claims 1 to 3, characterized in that the pin has a tapered shape that is thicker at the tip near the outer periphery of the flow path and becomes thinner as it approaches the center of the flow path.

8. A heat exchange structure according to any one of claims 1 to 3, further comprising a reinforcing ring for reinforcing all of the pins in the radially arranged pin layer.

9. A heat exchange structure as described in any one of claims 1 to 3, characterized in that in the radially arranged pin layer composed of pins of three or more different lengths, the longest pin of the three or more different lengths is arranged radially so as to extend from the center of the flow path to the outer periphery of the flow path, and the pins of the second and subsequent lengths are arranged radially so as to extend successively to the vicinity of the other pins that are longer than the longest pin and are closer to the center of the flow path.

10. A heat exchange structure according to any one of claims 1 to 3, in which the area ratio (radial area / inner diameter area of ​​the tube body) is higher than 0.2 and the number of layers is 7 or more.

11. A heat transfer tube comprising a plurality of heat exchange structures according to any one of claims 1 to 3 arranged along the length of an aluminum tube body that forms a flow path for a heat exchange fluid, the pins being made of aluminum and being integrated with the tube body.

12. A heat exchanger comprising the heat transfer tube according to claim 11.

13. A heat exchanger comprising a plurality of aluminum fins arranged in parallel and an aluminum tube body penetrating a plurality of said fins, wherein inside said tube body, a plurality of radially arranged pin layers are arranged at predetermined intervals along the length of said tube body, each of which has aluminum pins of three or more different lengths arranged radially from the center of said tube body to the outer periphery and radially arranged around the circumference of said tube body, and wherein in said plurality of radially arranged pin layers arranged along the length of said tube body, adjacent radially arranged pin layers along the length of said tube body rotate around the circumference of said tube body, and the pins in adjacent layers are arranged so as to be misaligned.

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