JP2011075122A - Aluminum internally-grooved heat transfer tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum internally-grooved heat transfer tube capable of exerting superior heat exchanging performance, with respect to the internally-grooved heat transfer tube having prescribed internal grooves formed on a tube internal face by extruding aluminum or its alloy. <P>SOLUTION: In this aluminum internally-grooved heat transfer tube 10 having three or more internal grooves 12 extending in the tube axial direction, in the tube circumferential direction by extruding aluminum or its alloy, a ratio Ha/Di of a fin height Ha of the internal fin 14 formed between the internal grooves 12, 12 adjacent to each other, and a tube minimum inner diameter Di is 0.02-0.45, an uneven section 18 is formed on one 16a out of side faces 16 of the internal grooves 14, 14 adjacent to each other, and the side face 16b of the other internal fin 14 is a smooth face. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to an internally grooved heat transfer tube suitably used for various fin-and-tube heat exchangers for refrigeration, air conditioning, and hot water supply equipment, and more particularly to an internally grooved heat transfer tube made of aluminum. It is.

  Conventionally, heat exchangers that operate as evaporators or condensers have been used in air conditioners such as home air conditioners, automobile air conditioners, packaged air conditioners, and refrigerators. In commercial packaged air conditioners, cross-fin tube heat exchangers have been most commonly used.

  And the cross fin tube which comprises such a cross fin tube type heat exchanger is comprised by assembling | attaching the air side aluminum plate fin and the refrigerant | coolant side heat exchanger tube integrally. In addition, as a heat transfer tube used to constitute such a cross fin tube, a large number of grooves, for example, spiral grooves extending so as to have a predetermined lead angle with respect to the tube axis are formed on the inner surface thereof. Thus, so-called internally grooved heat transfer tubes in which internal fins having a predetermined height are formed between the grooves have been widely used.

  By the way, the internally grooved heat transfer tube used to construct such a cross fin tube is generally formed by rolling a metal material such as copper or a copper alloy, thereby grooving the inner surface. Will be formed. And, after cutting the inner surface grooved heat transfer tube so formed and performing hairpin bending processing, the heat transfer tube is expanded and fixed to the aluminum plate fin to form a cross fin tube, The target cross fin tube type heat exchanger is manufactured through the process of brazing the U-bend tube to the end of the heat transfer tube opposite to the side subjected to the hairpin bending process.

  Until now, in the cross fin tube type heat exchanger having such a configuration, various efforts have been made to improve the heat exchange performance. For example, in a heat transfer tube, various improvements are made to the shape of the groove formed on the inner surface of the tube to promote heat transfer between the refrigerant and the heat transfer tube that can be circulated in the tube. Various types of internally grooved heat transfer tubes designed to improve the heat transfer rate have been proposed.

  In addition, for such heat transfer tube materials, copper-based materials such as copper and copper alloys with high thermal conductivity are often used in order to improve heat exchange performance. In order to meet the demands for reducing the size and weight of air-conditioning heat exchangers, it has been studied to employ aluminum-based materials made of aluminum or aluminum alloy as the tube material.

  As such an aluminum inner surface grooved heat transfer tube, for example, in Japanese Unexamined Patent Application Publication No. 2008-267788 (Patent Document 1), a tube inner surface made of a JIS A6000 (Al—Mg—Si) aluminum alloy is used. A heat transfer tube in which fins are formed, wherein a ratio [D / t] of an outer diameter (D) of the heat transfer tube and a bottom wall thickness (t) is 18.4 or more and 24.8 or less, and A heat transfer tube characterized by a fin bottom width W of 0.1 mm or more has been clarified.

  However, in the aluminum internally grooved heat transfer tube disclosed in Patent Document 1, the internal groove is formed by rolling as in the conventional copper internally grooved heat transfer tube. However, in such a rolling process of aluminum, the material tends to extend in the longitudinal direction, so there is a problem that the metal flow to the inner groove processing portion deteriorates, and the conventional inner surface made of copper Like a grooved heat transfer tube, it was difficult to obtain an inner surface groove / fin shape having a high fin height, a small fin apex angle, and good heat exchange performance.

  Therefore, the inner surface groove in the heat transfer tube with inner surface groove made of aluminum is not formed by rolling, but is generally formed by a processing step by extrusion. In the case of forming, since the lead angle of the inner fin cannot be increased due to processing limitations, the lead angle is usually 0 °, that is, a parallel groove, or 10 ° or less. For this reason, the conventional inner surface groove shape does not provide a sufficient effect of promoting turbulent flow to the refrigerant flowing in the pipe.

  Under such circumstances, in the aluminum inner surface grooved heat transfer tube that forms the inner surface groove by such an extrusion process, it is possible to effectively promote turbulent flow to the refrigerant flowing in the tube and improve the heat exchange performance. The development of a heat transfer tube with an inner surface groove made of aluminum is demanded.

JP 2008-267788 A

  Here, the present invention has been made in the background of such circumstances, and a solution to that problem is that a predetermined inner surface groove is formed on the inner surface of the tube by extrusion of aluminum or an alloy thereof. It is an object of the present invention to provide an aluminum internally grooved heat transfer tube capable of exhibiting good heat exchange performance, particularly good condensation performance, in the internally grooved heat transfer tube.

  In the present invention, in order to solve such problems, aluminum made of aluminum or an alloy thereof having three or more inner surface grooves extending in the pipe axis direction by extrusion processing is provided. In the inner surface grooved heat transfer tube, an inner surface fin extending in the tube axis direction between adjacent ones of the inner surface grooves has a fin height: Ha and a minimum tube inner diameter: Di: Ha / Di is 0.02. Are formed so as to be .about.0.45, and one side surface of each inner surface groove is provided with a concavo-convex portion on the side surface of one adjacent inner surface fin, while the other inner surface groove The gist is an aluminum internally grooved heat transfer tube in which the side surface of the other adjacent inner surface fin that provides the side surface is a smooth surface.

  In addition, according to one of the desirable aspects of the aluminum inner surface grooved heat transfer tube according to the present invention, the uneven portions formed on the side surfaces of the inner surface fins are a plurality of protrusions extending in the fin longitudinal direction. In still another preferred embodiment, the inner fin has a fin height of 0.2 mm or more.

  Furthermore, in one of the preferred embodiments of the aluminum internally grooved heat transfer tube according to the present invention, the inner surface of the tube located between adjacent ones of the inner surface fins is higher than the inner surface fin. A low second inner fin will be provided.

  Furthermore, according to another preferred embodiment of the present invention, the concave and convex portions are formed on one side surface of each inner fin, and the other side surface is a smooth surface. The concave and convex portions are formed only on the side surface on one side in the circumferential direction of each inner fin.

  Therefore, in such an aluminum inner surface grooved heat transfer tube according to the present invention, while maintaining the relationship between the fin height of the inner surface fin extending in the tube axis direction and the minimum inner diameter of the tube within an appropriate range, Since the side surface of the inner fin is a smooth surface and the other side surface is an uneven surface, when the refrigerant flows through the inner groove portion formed between the inner fins, the refrigerant against the two side surfaces of the inner fins In other words, the frictional resistance of the refrigerant against the uneven surface is greater than the frictional resistance of the refrigerant against the smooth surface. Thus, the turbulent flow of the refrigerant flowing through the air is promoted. And by promoting the turbulent flow of the refrigerant in this way, the heat transfer between the refrigerant and the heat transfer tube can also be effectively promoted, and the heat exchange performance of the internally grooved heat transfer tube, in particular, the condensation performance can be improved. This can be advantageously improved.

It is sectional explanatory drawing which shows an example of the aluminum inner surface grooved heat exchanger tubes according to this invention. It is a cross-section part enlarged explanatory drawing which expands and shows a part of inner surface grooved heat exchanger tube shown in FIG. FIG. 2 is an explanatory diagram schematically showing how the flow velocity changes in the inner groove portion when the refrigerant flows in the inner groove groove heat transfer tube shown in FIG. 1. It is sectional explanatory drawing which shows another example of the heat transfer tube made from aluminum inner surface groove | channel according to this invention. It is sectional explanatory drawing which shows another example of the heat transfer tube made from aluminum inner surface groove | channel according to this invention. It is explanatory drawing which shows the cross-sectional photograph of the aluminum internally grooved heat exchanger tube according to this invention actually manufactured in the Example. It is explanatory drawing which shows the distribution | circulation state of the refrigerant | coolant at the time of performing a condensation test in the test apparatus used in order to measure the single pipe | tube performance of the heat transfer tube with an inner surface groove in an Example.

  Hereinafter, in order to clarify the configuration of the present invention more specifically, an aluminum internally grooved heat transfer tube according to the present invention will be described in detail with reference to the drawings.

  First, FIG. 1 shows an example of an aluminum internally grooved heat transfer tube according to the present invention in a cross-sectional form cut along a plane perpendicular to the tube axis direction. That is, the heat transfer tube 10 shown in FIG. 1 has a plurality of inner surface grooves 12 formed on the inner surface of the tube so as to extend in parallel to the tube axis, and the inner surface grooves 12, 12. A large number of internal fins 14 are formed so as to be located therebetween.

  More specifically, the heat transfer tube 10 has a predetermined heat conductivity selected appropriately from aluminum or an alloy thereof according to the required heat transfer performance, the type of heat transfer medium circulated in the heat transfer tube, and the like. An aluminum grooved heat transfer tube formed into a tubular shape by extruding an aluminum material according to a known method, the tube outer diameter: D is generally about 4.0 to 10.0 mm, and Bottom thickness: t is generally about 0.2 to 0.6 mm.

  And the inner surface groove | channel 12 formed in the inner surface of this heat exchanger tube 10 with the predetermined depth and extended in parallel with a tube axis is the figure which expanded a part of end surface cut | disconnected by the surface perpendicular | vertical to a tube axis direction. 2, here, it is formed in a substantially trapezoidal shape that gradually becomes narrower toward the groove bottom, and the tube wall thickness between the bottom of the inner surface groove 12 and the pipe outer peripheral surface is as follows. , Bottom wall thickness: t. Further, between the adjacent inner surface grooves 12 in the inner surface grooves 12, inner surface fins 14 are formed at a fin height: Ha and a fin apex angle: α. In FIG. 1, the inner fin 14 has a substantially trapezoidal shape with a semicircular or arcuate head, but instead of a substantially trapezoidal shape with a flattened head. Or, even if it has a triangular shape, there is no problem.

  In addition, in the side surface 16 of the fin 14 formed on the inner surface of the heat transfer tube 10, one of the side surfaces 16 a of the opposing side surfaces of the adjacent inner surface fins 14, 14 is roughened. As a result, the concavo-convex portion 18 is formed, and the other side surface 16b is a smooth surface having a smoother surface roughness than the side surface 16a. As described above, since the surface roughness of the side surfaces 16 a and 16 b of the inner fin 14 is different, the refrigerant flowing through the inner groove 12 formed between the inner fins 14 and 14 is When flowing in the extending direction, that is, in the tube axis direction, a difference in frictional resistance occurs between the side surface 16a and the side surface 16b, thereby obtaining the effect of effectively promoting turbulence. That is, as shown in FIG. 3 schematically showing an image of the refrigerant flowing on the inner surface of the pipe, the refrigerant flowing in the inner surface groove 12 (in the vertical direction in the figure) is in the vicinity of the side surface 16a having a rough surface. In FIG. 2, resistance is generated in the flow of the refrigerant, and the flow velocity becomes slow (the flow of V1 in the figure). Moreover, in the same inner surface groove | channel 12, since the resistance with respect to the flow of a refrigerant | coolant is small in the side surface 16b made into the smooth surface, it becomes a refrigerant | coolant flow with a faster flow velocity than the vicinity of the side surface 16a (in the figure, V2 flow). As described above, when a speed difference is generated in the inner surface groove 12, a flow V3 in the pipe circumferential direction is generated in the inner surface groove 12, and this causes a turbulent flow of the refrigerant.

  In addition, such an inner surface fin 14 is formed so that the fin apex angle: α is generally about 0 to 40 °, and the number of lines is at least 3 or more per pipe circumference. . This is because, when the number of the inner fins 14 is less than three, the inner grooves 12 formed between the adjacent inner fins 14 and 14 are too wide, and the inner surfaces have different surface roughness. This is because the side surfaces 16a and 16b of the fins 14 are too far apart, and the effect of promoting turbulence due to the difference in frictional resistance between the circulating refrigerant and the side surface 16 cannot be obtained sufficiently.

  Further, the fin height Ha of the inner fin 14 is desirably 0.2 mm or more. This is because, when the fin height: Ha is less than 0.2 mm, the area of the fin side surface becomes too small, and the effect of promoting turbulence due to the difference in surface roughness from the opposing fin side surface cannot be sufficiently obtained. Because it will end up. On the other hand, if the fin height Ha of the inner surface fin 14 becomes too high, the pressure loss of the refrigerant flowing in the pipe increases, leading to a decrease in heat transfer performance. Therefore, the minimum inner diameter of the heat transfer tube 10, that is, the ratio of the inner diameter Di and the fin height Ha defined by the top of the inner fin 14 is in the range of 0.02 to 0.45. It is configured.

  By the way, the heat transfer tube 10 having such a configuration is suitably formed by a conventionally known extrusion process. That is, a predetermined inner surface groove 12 is formed on the inner surface of the pipe by extruding a predetermined aluminum material (billet) of a known material appropriately selected from aluminum or an alloy thereof from a die that gives a desired inner surface groove shape. An internally grooved heat transfer tube is manufactured. And in order to form the uneven | corrugated | grooved part 18 in one side 16a of the inner surface fin 14 formed between the inner surface grooves 12 and 12, for example, after forming an inner surface grooved heat exchanger tube by extrusion, By applying a surface treatment to one of the side surfaces 16a, the surface roughness is roughened, and a method of forming the target uneven portion 18 or forming simultaneously with the extrusion process is adopted. It becomes. In addition, when forming a heat transfer tube with an inner surface groove by extrusion, the lead angle between the inner surface groove 12 and the tube axis is normally 0 °, that is, the inner surface groove 12 parallel to the tube axis. By applying a torsional force during the extrusion process, it is possible to provide a lead angle of about 0 to 10 ° to form the inner surface groove 12 extending spirally with respect to the tube axis. Thus, by making the inner surface groove 12 into a spiral shape, it becomes possible to promote turbulent flow more effectively with respect to the refrigerant circulating in the pipe.

  According to such an internally grooved heat transfer tube 10 according to the present invention, the refrigerant is applied to the side surface 16a provided with the uneven portions 18 on both sides of the internal surface groove 12 and the side surface 16b which is a smooth surface not provided with such uneven portions. Based on the frictional resistance difference, it is possible to effectively promote turbulent flow with respect to the refrigerant flowing in the inner surface groove 12 and thus in the pipe, and heat transfer between the refrigerant and the heat transfer tube by such turbulent flow. Therefore, heat exchange performance can be advantageously improved also in the internally grooved heat transfer tube formed by extruding aluminum or an alloy thereof.

  The internally grooved heat transfer tube 10 according to the present invention having the above-described features is a heat transfer tube in a cross-fin tube type heat exchanger for various known applications such as a refrigerator, an air conditioner, and a hot water supply device. As a result, it can be advantageously used.

  The exemplary embodiments of the present invention have been described in detail above. However, these are merely examples, and the present invention is not limited to any specific description according to the specific embodiments. It should be understood that this is not to be interpreted.

  For example, in the above-described embodiment, the uneven portion 18 is formed on the one side surface 16a of the inner surface fin 14 by increasing the surface roughness, but as shown in FIG. One side surface 16b is a smooth side surface, and the other side surface is formed with a plurality of protrusions 22 extending in the longitudinal direction along the inner surface fins 14 protruding from the surface with a predetermined height: Hc. The heat transfer tube 20 having a concavo-convex structure with the protrusions 22 can be used. In addition, the uneven | corrugated | grooved part of such a shape can be formed by giving a fine unevenness | corrugation to the predetermined thing of the internal surface groove formation surface of an extrusion die, for example. That is, by applying fine unevenness to the die surface of the portion forming the one side surface 16a of the inner fin 14, and extruding using such an extrusion die, in the extrusion direction corresponding to the uneven surface of the die. A continuously extending ridge 22 is formed. In the case where the concavo-convex portion is formed by such a plurality of protrusions 22, it is possible to form the heat transfer tube 10 only by extrusion processing, so that the productivity of the heat transfer tube is also advantageously improved. I can do it. Here, the height of the protrusion: Hc is about 1/10 of the fin height of the inner fin 14: Ha, but in order to obtain a sufficient turbulence promoting effect, The fin height of the inner fin 14 is about 1/20 to 1/2 of Ha.

  Further, according to one of the desirable embodiments of the internally grooved heat transfer tube according to the present invention, as shown in FIG. 5, a second height lower than that of the internal fins 14 is provided between the adjacent internal fins 14 and 14. A plurality of the inner fins 32 may be the heat transfer tubes 30 provided so as to protrude from the inner surface of the tube. By providing such second inner surface fins 32, the contact area between the refrigerant and the heat transfer tube can be further increased, and the refrigerant side heat transfer coefficient can be improved. When the second inner fins 32 are provided between the inner fins 14 and 14, the number of inner fins 14 is generally about 3 to 6 in the pipe circumferential direction. FIG. 6 shows a photograph of a cross section obtained by actually cutting the heat transfer tube 30 having such a groove shape and cutting it along a plane perpendicular to the tube axis. In addition, the actually manufactured aluminum internally grooved heat transfer tube is also used in performance evaluation tests in Examples described later.

  And it is desirable that the fin height Hb of the second inner fin 32 is not more than ½ of the fin height Ha of the inner fin 14. This is because, when Hb becomes higher than 1/2 of Ha, turbulent flow promotion by the side surfaces 16a and 16b having different roughness in the inner fin 14 is prevented. Further, in FIG. 5, the number of the second inner fins 32 is two between the inner fins 14 and 14, but is not limited to this number. It is appropriately determined according to the diameter and the height and number of the inner fins 14. Such a second inner surface fin 32, together with the inner surface fin 14, contributes to an increase in the heat transfer area between the heat transfer tube and the refrigerant, so that the larger the total number, the greater the effect. Moreover, the higher the effect, the greater. However, since the fin heights (Ha, Hb) are limited as described above, increasing the number after limiting the fin height is effective for increasing the heat transfer area.

  Furthermore, in the above-described embodiment, the concave and convex portions 18 and the ridges 22 are formed on one end surface 16a of the both side surfaces of each inner surface fin 14, so that the inner surface fins 14 and 14 are adjacent to each other. Although the uneven surface and the smooth surface of each side face each other, in addition to such an arrangement, for example, the inner surface fin 14 in which uneven portions 18 and protrusions 22 are formed on the side surfaces on both sides of the fin. And the inner surface fins 14 whose side surfaces on both sides are smooth surfaces are alternately arranged in the pipe circumferential direction, so that the concave and convex surfaces and the smooth surface face each other on the side surfaces facing each other between the adjacent inner surface fins 14 and 14. It is also possible to use an internally grooved heat transfer tube.

  In addition, although not listed one by one, the present invention is implemented in a mode to which various changes, modifications, improvements and the like are added based on the knowledge of those skilled in the art. It goes without saying that any one of them falls within the scope of the present invention without departing from the spirit of the invention.

  In the following, one of the representative embodiments of the present invention will be shown to clarify the features of the present invention. However, the present invention is not restricted by the description of such embodiments. It goes without saying that it is not a thing.

  First, in order to fabricate an internally grooved heat transfer tube having a structure according to the present invention, an aluminum alloy material of JIS A3003 is prepared, and this is subjected to a conventionally known hot extrusion process to obtain FIGS. As shown in FIG. 6), aluminum inner surface grooved heat transfer tubes each having a structure according to the present invention were produced. That is, the height: Ha of the inner fin (14) as shown in FIG. 4 is one type, and there are a plurality of protrusions (22) as concavo-convex portions on one side surface (16a) of the inner fin (14). While what is provided is referred to as Example 1, a combination of an inner fin (14) and a second inner fin (22) as shown in the photograph of FIG. did. On the other hand, the side surface of the inner fin 14 having smooth side surfaces was similarly produced by extrusion, and this was used as a comparative example. The specifications of the heat transfer tubes of Examples 1 and 2 and the comparative example, such as tube outer diameter and fin height, were as shown in Table 1 below. Further, in Table 1, the fin corresponding to the inner surface fin (14) provided with the concavo-convex portion on one fin side surface is the fin A, the second inner surface fin (22) whose fin side surface is the smooth surface, and the comparative example. Each inner fin is referred to as a fin B, and each specification is shown.

And about each heat exchanger tube prepared in this way, the heat exchange performance evaluation in the single tube of a heat exchanger tube was performed, respectively. In this single tube performance evaluation test, each test heat transfer tube is assembled as a single tube with respect to a test section of a conventionally known heat transfer performance test apparatus, and under the flow of refrigerant as shown in FIG. The condensation performance test was performed under the test conditions of saturation temperature: 50 ° C., inlet condition: degree of superheat = 40 ° C., outlet condition: degree of supercooling = 5 ° C. Note that R-410A, which is an HFC-based refrigerant, was used as the refrigerant, and the test was performed at a refrigerant mass speed of 200 kg / (m ² · s), which almost coincided with the actual operating conditions of the air conditioning equipment.

  As a result, assuming that the heat transfer coefficient in the tube of the heat transfer tube of the comparative example is 100, Example 1 is 140, and Example 2 is 155. In the heat transfer tube having the structure according to the present invention, a good condensation heat transfer coefficient is obtained. It was confirmed that it was obtained.

DESCRIPTION OF SYMBOLS 10 Heat transfer tube 12 Inner surface groove 14 Inner surface fin 16a, 16b Side surface 18 Uneven part

Claims (5)

An aluminum inner surface grooved heat transfer tube made of aluminum or an alloy thereof, in which three or more inner surface grooves extending in the tube axis direction are provided in the tube circumferential direction by extrusion processing,
The inner surface fins extending in the tube axis direction between adjacent ones of the inner surface grooves are such that the ratio of the fin height: Ha to the minimum tube inner diameter: Di: Ha / Di is 0.02 to 0.45. An uneven portion is formed on the side surface of one adjacent inner surface fin that is formed and that provides one side surface of each inner surface groove, while the other adjacent surface that provides the other side surface of each inner surface groove A heat transfer tube with an aluminum inner surface groove, wherein the side surface of the inner surface fin is a smooth surface.   The heat transfer tube with an aluminum inner surface groove according to claim 1, wherein the uneven portions formed on the side surfaces of the inner surface fins are a plurality of protrusions extending in the longitudinal direction of the fin.   The aluminum inner surface grooved heat transfer tube according to claim 1 or 2, wherein the inner surface fin has a fin height of 0.2 mm or more.   The pipe | tube inner surface site | part located between the adjacent ones of the said inner surface fin is provided with the 2nd inner surface fin whose height is lower than this inner surface fin. Heat transfer tube with aluminum inner groove. While the concave and convex portions are formed on one side surface of each of the inner surface fins, the other side surface is a smooth surface, and only on one side surface in the circumferential direction of each inner surface fin, The aluminum inner surface grooved heat transfer tube according to any one of claims 1 to 4, wherein the uneven portion is formed.

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