JP2013092335A - Aluminum capillary tube for heat exchanger, and heat exchanger using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum capillary tube for a heat exchanger which has a reduced outer diameter of 2 to 5 mm and allows diameter expansion without causing buckling or deformation.SOLUTION: The capillary tube consists of a tube body as a heat transfer tube for a heat exchanger made of aluminum or aluminum alloy and having an outer diameter not less than 2 mm and not more than 5 mm. On an inner surface of the tube body, a plurality of radiation fins in the form of a protruding stripe extending in a longitudinal direction of the tube body are formed at substantially regular intervals along an inner circumferential direction of the tube body and a plurality of fin grooves are formed between these radiation fins and the thickness of the tube body at each of the fin grooves is not less than 0.1 mm and not more than 0.6 mm, the height of each radiation fin is not less than 0.05 mm and not more than 0.35 mm, the number of fin grooves is not less than 20 and not more than 60, and a ratio of the total width of top flat parts of the plurality of radiation fins in the circumferential direction of the inner circumference of the tube body to the entire circumferential length of the inner bottom surface of the tube body is not less than 20% and not more than 80%.

Description

  The present invention relates to an inner grooved type heat exchanger aluminum thin tube and a heat exchanger using the same.

  A heat exchanger for an air conditioner mainly includes a heat transfer tube made of a copper tube bent into a hairpin shape and a fin made of aluminum or an aluminum alloy plate (hereinafter abbreviated as aluminum fin). For example, the heat transfer part of the heat exchanger is a jig called a buret in a U-shaped heat transfer tube, by inserting a heat transfer tube made of a copper tube bent into a U shape into a through hole of an aluminum fin. By inserting and expanding the tube, the heat transfer tube and the aluminum fin are brought into close contact with each other. Then, the open end of the U-shaped heat transfer tube is expanded, a bend tube bent in the same U shape is inserted into the expanded tube opening, and the copper tube is connected by brazing the bend tube. A heat exchanger.

  Conventionally, when configuring the heat transfer part of a heat exchanger for an air conditioner from a copper tube, it is necessary to improve the composition and metal structure of the copper tube, improve the composition of the constituent material of the copper tube, improve the structure, In order to improve the tensile strength by adjusting the composition and improving the crystal structure to induce a texture, as described in Japanese Patent Application Laid-Open No. 2003-228688, there have been improved measures.

In order to improve the performance of heat exchangers for air conditioners, copper pipes that make up heat transfer parts have been improved in terms of their shape, structure, and composition. Due to the rapid development of infrastructure in other countries such as Southeast Asia, the demand for copper for use in power transmission lines has increased rapidly, and the cost of copper has begun to rise.
Therefore, an attempt has been made to construct a heat transfer tube using aluminum, which is cheaper than copper and rich in workability, and is frequently used as a partial constituent material for heat exchangers.

When replacing the heat transfer tube made of copper with an aluminum heat transfer tube, in view of the fact that aluminum is more easily deformed than copper, a groove is formed on the inner surface of the aluminum heat transfer tube, and the burette passes through the groove. Japanese Patent Application Laid-Open No. H10-228561 discloses a technique for examining a suitable groove shape when suppressing expansion of a heat transfer tube and suppressing deformation of the heat transfer tube.
That is, when expanding the heat transfer tube, an extension called a burette is inserted inside the heat transfer tube and the tube wall of the heat transfer tube is plastically deformed and expanded. If the shape is devised, a technique that can obtain a heat transfer tube having a good groove shape after the pipe expansion is disclosed.

JP 2009-102690 A JP 2001-289585 A

When a heat transfer tube made of aluminum is applied to a heat exchanger, if the diameter of the heat transfer tube is reduced, the pressure of the heat transfer tube is increased, so that the heat transfer tube can be thinned. In addition, if the refrigerant passage is narrowed to improve the performance of the heat exchanger, it directly leads to an increase in the flow rate of the refrigerant, so reducing the heat transfer tube as a thin tube improves the internal heat transfer efficiency of the heat exchanger. It means to become.
From the background as described above, heat transfer tubes for heat exchangers have been made thinner, and aluminum tubes with an outer diameter of about 2 to 5 mm have been studied from the viewpoint of further improving performance as heat exchangers.
However, when a thin tube having an outer diameter of about 2 to 5 mm is used as a heat transfer tube, when a groove is formed on the inner surface of the thin tube, there is a problem that the resistance when the burette is inserted at the time of tube expansion increases and the thin tube is deformed or buckled. .

  According to the technique described in Patent Document 2, a groove shape desirable for a heat exchanger in the case where the outer diameter of the heat transfer tube is about 7 mm has been studied. Further improvement in performance of the heat exchanger, heat transfer tube When thin tubes with an outer diameter of about 2 to 5 mm are used, the heat transfer tubes are thin and the problem of being easily buckled and deformed becomes obvious. Therefore, it was necessary to consider a special groove shape in the heat transfer tube with a reduced diameter.

  The present invention has been made in order to solve the above-described problems, and is used for a heat exchanger. In an aluminum thin tube having an outer diameter of 2 to 5 mm, the tube is expanded without causing buckling or deformation. It is an object of the present invention to provide an aluminum thin tube for a heat exchanger and a heat exchanger including the same.

  The thin tube for a heat exchanger of the present invention is a thin tube composed of a tube body made of aluminum or an aluminum alloy and having an outer diameter of 2 mm or more and 5 mm or less, and is formed on the inner surface of the tube body in the longitudinal direction of the tube body. A plurality of elongated radiating fins extending in the inner circumferential direction of the tube main body are formed substantially evenly at intervals, and a plurality of fin grooves are formed between these radiating fins. The wall thickness of the tube body is 0.1 mm or more and 0.6 mm or less, the height of the heat radiating fin is 0.05 mm or more and 0.35 mm or less, the number of the fin grooves is 20 or more and 60 or less, The total width of the top flat portions of the plurality of heat dissipating fins present in the circumferential direction is 20% or more and 80% or less as a ratio with respect to the total inner peripheral length of the tube main body.

In the thin tube for a heat exchanger of the present invention, the cross-sectional shape of the radiating fin is formed in an isosceles trapezoidal shape having a top flat portion and two inclined portions sandwiching the top flat portion, and a peak angle formed by the two inclined portions is 10. It is characterized in that it is not less than 60 ° and not more than 60 °.
The thin tube for a heat exchanger according to the present invention is characterized in that the central axis of all the radiation fins is inclined at an angle of not less than 10 ° and not more than 30 ° with respect to the radial direction of the tube body in the cross section of the tube body. And
The thin tube for a heat exchanger of the present invention has a top flat portion and two inclined portions sandwiching the top flat portion in the cross-sectional shape of the radiating fin, and the two inclined portions have the same inclination angle. It is formed in a trapezoidal shape with different heights, and the crest angle of the two inclined portions with respect to the inner bottom surface of the pipe body is 10 ° or more and 30 ° or less.
A heat exchanger according to the present invention is characterized in that the heat exchanger thin tube according to any one of the above is provided as a heat transfer tube.

According to the present invention, even if the heat transfer tube is composed of a thin tube having an outer diameter of 2 to 5 mm, the radiating fin is a grooved thin tube formed with a suitable size and spacing for a heat exchanger. It can be expanded without causing deformation and can be used as a heat exchanger tube for a heat exchanger.
In addition, if it is a thin tube according to the present invention, it is possible to secure a suitable radiating fin shape, fin height and number of fins, and radiating fin height and number of fin grooves after tube expansion, so that it is a heat transfer tube for a heat exchanger It is possible to provide a heat exchanger with good heat exchange efficiency.

The cross-sectional view which shows the aluminum thin tube for heat exchangers of 1st Embodiment which concerns on this invention. The cross-sectional view which shows the aluminum thin tube for heat exchangers of 2nd Embodiment which concerns on this invention. FIG. 3A shows an example of a heat radiating fin formed on the aluminum thin tube for a heat exchanger shown in FIGS. 1 and 2, FIG. 3A is a diagram showing a peak angle of the heat radiating fin, and FIG. 3B is a twisted state. The figure which shows the inclination angle of the inclined part of the radiating fin, FIG.3 (c) is a figure which shows the other example of the twist state of a radiating fin, FIG.3 (d) is the case where the radiating fin inclination form is only a top flat part. The figure which shows an example. Explanatory drawing which shows an example of the processing method for obtaining the thin tube made into the twisted state shown in FIG. FIG. 5 shows the heat dissipating fins before and after twisting, and FIG. 5 (a) is an explanatory view showing an example of an inclined state given to the heat dissipating fins before twisting in consideration of twisting, FIG. ) Is an explanatory view showing the heat dissipating fin after twisting in the case of a structure considering twisting. FIG. 6 is a side view showing an example of a heat exchanger provided with an aluminum thin tube according to the present invention.

Hereinafter, specific embodiments of the present invention will be described, but the present invention is not limited to the embodiments described below.
FIG. 1 is an enlarged view showing the cross-sectional structure of a thin tube made of aluminum or aluminum alloy according to the first embodiment of the present invention. The thin tube 1 of the first embodiment has a diameter of several mm, for example, a diameter of 2 A plurality of protrusion-shaped radiating fins 3 are formed inside the tube body 2 of about ˜5 mm. The radiating fins 3 are formed so as to protrude from the inner peripheral surface of the tube main body 2 toward the center of the tube main body 2 and extend over the entire inner surface of the tube main body 2 in the circumferential direction of the inner peripheral surface of the tube main body 2. Are formed at predetermined intervals.
In the cross section of the tube main body 2, the heat radiating fin 3 of the present embodiment has a flat top flat portion 3a facing the center of the tube main body 2 and inclined portions 3b and 3b extending so as to sandwich the top flat portion 3a. It is formed in a trapezoidal shape such as a cross-sectional view. Since a plurality of these radiating fins 3 are formed at predetermined intervals in the circumferential direction of the inner peripheral surface of the tube main body 2, the fins are disposed between the radiating fins 3, 3 adjacent along the inner peripheral surface of the tube main body 2. A groove 4 is formed.

  The tube body 2 constituting the narrow tube 1 is made of aluminum or an aluminum alloy. In this specification, the thin tube 1 made of aluminum or an aluminum alloy is abbreviated as an aluminum thin tube. There is no particular limitation on the aluminum alloy constituting the thin tube 1, and a pure aluminum system such as 1050, 1100, 1200, etc. defined by JIS, or a 3000 series aluminum alloy represented by 3003, in which Mn is added to these, etc. Can be applied. Of course, in addition to these, the tube main body 2 may be configured by using any one of the 5000 series to 7000 series aluminum alloys defined in JIS.

The outer diameter of the tube body 2 is preferably 2 mm to 5 mm. If the outer diameter of the tube body 2 is less than 2 mm, it becomes difficult to extrude the tube body 2 as a thin tube made of aluminum or aluminum alloy by the current extrusion technology, and if the outer diameter of the tube body 2 exceeds 5 mm, heat will be generated. In the case of a heat exchanger tube for an exchanger, the pressure resistance is insufficient and it becomes difficult to reduce the thickness.
The wall thickness of the tube body 2 excluding the radiation fins 3, in other words, the wall thickness (bottom wall thickness) of the tube body 2 corresponding to the fin groove 4 is preferably in the range of 0.1 mm to 0.6 mm. When the wall thickness is less than 0.1 mm, the burst pressure becomes insufficient when viewed as a heat exchanger tube for heat exchanger, and when the wall thickness exceeds 0.6 mm, a large amount of aluminum material is required and the manufacturing cost increases.

In the tube main body 2, the inner surface groove height, in other words, the height of the radiation fin 3 is preferably in the range of 0.05 mm to 0.35 mm. If the height of the radiating fin 3 is less than 0.05 mm, it may be crushed during tube expansion, the fin may disappear, the tube expansion load may increase, and if the height of the radiating fin 3 seems to exceed 0.35 mm, As a heat transfer tube for an exchanger, the pressure loss increases, and it tends to be impossible to form by extrusion.
In the radiating fin 3, the angle (peak angle) formed by the two inclined portions 3b and 3b sandwiching the top flat portion 3a is preferably in the range of 10 ° to 60 °. FIG. 3A shows an example of the peak angle θ ₁ of the radiating fin 3. When the radiating fin 3 is viewed in cross section, the extension lines of the two inclined portions 3 b sandwiching the top flat portion 3 a are formed to intersect. The angle θ ₁ is defined as the peak angle.
When the summit angle is less than 10 °, the radiating fins 3 are liable to be crushed during tube expansion, and the tube expansion tends to be insufficient. When the summit angle exceeds 60 °, the tube expansion load becomes large, which may cause a buckling problem.

The ratio of the total width of the top flat portion in the tube main body 2 (it exists along the inner periphery of the tube main body 2 with respect to the bottom circumference of the tube main body 2 corresponding to the position where the fin groove 4 exists in the cross section of the tube main body 2). The ratio of the total width of all the top flat portions 3a) is desirably in the range of 20% to 80%. Specifically, the ratio of the total width of the top flat portion is such that n (n is a natural number) radiating fins 3 are formed along the inner periphery of the tube body 2 as shown in FIG. the width of the part and a ₁ ~a _n, if the fin grooves 4 therebetween radiation fins 3, 3 are formed, against the bottom circumference of the tube body 2, represented by the following formula (1) relationship It becomes.
Ratio of total width of top flat portion = {(a ₁ + a ₂ + a ₃ + a ₄ +... + _An ) / bottom circumference} × 100 (1)
If the ratio of the total width of the top portion is less than 20%, the load concentrates on the heat radiating fins 3 at the time of pipe expansion, so there is a possibility of crushing, and if the ratio of the total width of the top portion exceeds 80%, the tube expansion load increases. There is a possibility that the tube body 2 buckles.

The number of fin grooves 4 along the circumferential direction of the tube body 2 in the tube body 2 (in other words, the number of radiating fins 3 along the circumferential direction of the tube body 2) is preferably in the range of 20-60. If the number of fin grooves 4 is less than 20, the load concentrates on the heat radiating fins 3. Therefore, there is a possibility that the heat radiating fins 3 may be crushed at the time of pipe expansion, and if the number of fin grooves 4 exceeds 60, the pipe expansion load increases. Is more likely to buckle.
If the tube body 2 satisfies the ratio of the outer diameter, the thickness, the heat radiation fin height, and the total width of the top flat portion in the above range, the tube body 2 having the above structure is combined with the fin as a heat transfer tube for a heat exchanger, Even if expanded and used, there is no buckling during expansion, and refrigerant can be transported with little pressure loss, good heat exchange performance can be secured, and there is no cost problem. it can.

  FIG. 2 shows a cross-sectional structure of a thin tube made of aluminum or an aluminum alloy according to the second embodiment of the present invention. The narrow tube 10 of this embodiment is similar to the thin tube 1 of the first embodiment in the inner periphery of the tube body 12. The point that the ridge-shaped radiating fins 13 are formed on the surface, the point that the fin grooves 14 are formed between the adjacent radiating fins, the outer diameter and thickness of the tube body 12 in the same range as the structure of the first embodiment. The points satisfying the height of the heat dissipating fin and the total width of the top flat part are the same structure. Further, the shape of the heat radiating fin 13 including the top flat portion 13a and the inclined portions 13b and 13b in the cross section of the tube main body 12 is the same as the structure of the first embodiment.

In the thin tube 10 of the second embodiment, the difference from the thin tube 1 of the first embodiment is that the radiating fins 3 are formed along the inner peripheral surface of the thin tube 10 so as to draw a spiral. It is a point.
The plurality of radiating fins 13 formed inside the tube main body 12 are all formed in a spiral shape with the same pitch, and the fin groove 14 formed between the radiating fins 13 is also the tube main body. 12 is formed so as to draw a spiral at a predetermined pitch.
Further, when the tube main body 12 is viewed in a cross section, as shown in FIG. 3A, the radiation fins 13 are not inclined (the central axis S <b> 1 of the cross section of the radiation fins 13 is along the radial direction of the tube main body 12. In the state where the heat dissipating fins 13 of the present embodiment are in a cross-sectional view of the tube main body 12 as shown in FIG. 3B, the central axis S2 of the heat dissipating fins 13 is relative to the peripheral surface of the tube main body 12. It is inclined at an inclination angle θ ₂ in the range of 60 ° to 80 °. In other words, the central axis S2 of the radiating fin 13 is inclined in the range of 10 to 30 ° (90 ° −θ ₂ ) with respect to the radial direction of the tube main body 12 in a state in which the radiating fin 13 is viewed in cross section.

  Even if it is the thin tube 10 provided with the radiation fin 13 of this embodiment, the effect equivalent to the thin tube 1 of previous 1st Embodiment can be obtained. The fin fins 14 are also formed in a spiral shape in the length direction of the tube body 12 by forming the heat radiation fins 13 in a spiral shape in the length direction of the tube body 12 as in the second embodiment. Therefore, when the refrigerant flows through the tube body 12, the heat exchange efficiency with the refrigerant can be improved.

Next, about the shape of the radiation fin 13, it is preferable to comprise so that it may endure the process at the time of pipe expansion. For example, although the heat dissipating fins 13 having a three-dimensional shape are formed inside the tube main body 12, the tube main body 12 including the heat dissipating fins 13 having such a three-dimensional shape is expanded by a burette. In this case, if the radiating fins 13 are arranged in a spiral shape, the buret may expand the tubes while laying down the radiating fins 13 along their twisting directions.
In order to prevent this, it is necessary to incline the radiating fins 13 in advance on the side opposite to the direction in which the burette is assumed to tilt the radiating fins 13. By inclining the heat dissipating fins 13 in advance in this way, it is possible to provide a target structure in which the heat dissipating fins 13 are not crushed even after pipe expansion by a burette.

For example, as an example, when the heat radiation fin 13 is formed in a spiral shape with respect to the tube body 12, the burette is expanded by inserting the burette from one end side to the other end side of the tube body 12. Since a force acts in the direction of tilting the spiral radiating fins 13 along the insertion direction, the radiating fins 13 should be tilted in advance in the direction opposite to the direction in which they fall, ie, in the direction opposite to the direction in which the burette is inserted. It ’s fine.
Thus, by setting the radiation fin 13 to be inclined in the direction opposite to the insertion direction of the burette in advance, it is possible to prevent the radiating fin 13 from falling down due to the buret when the pipe is expanded. Therefore, it is possible to obtain a heat exchanger having a heat transfer tube provided with an aluminum thin tube for a heat exchanger composed of a tube body having a structure in which the heat radiation fins 13 are not collapsed and the heat radiation fins 13 are arranged in a spiral shape.
In addition, about the shape of the radiation fin 13 demonstrated previously, it is not restricted to the shape shown in FIG.3 (b), As shown in FIG.3 (c), the top flat part 23a and the two inclined parts 23b and 23b which pinch | interpose it are shown. It is also possible to use a heat radiation fin 23 having a shape that is processed into a left-right asymmetric trapezoidal shape by varying the lengths of the left and right inclined portions 23b.
The radiating fins 23 may be denoted as a heat radiation fin is inclined at an inclination angle theta ₃ to the radial direction of the pipe main body Itadakitaira portion 23a.
Further, the shape of the radiating fin 13 described above is not limited to the shape shown in FIG. 3C, and as shown in FIG. 3D, the top flat portion 33a and the two inclined portions 33b and 33b sandwiching the top flat portion 33a. The left and right inclined portions 33b have the same inclination angle, and the left and right inclined portions 33b have different heights and are processed into a trapezoidal shape. May be.
The radiating fins 33 may be denoted as a heat radiation fin is inclined at an inclination angle theta ₄ against the inner bottom surface of the tube main body Itadakitaira portion 33a (FIG. 3 (d) in the inner bottom surface and a line parallel).

  FIG. 4 shows an example of a method for processing the tube main body 12 on which the radiating fins 13 are formed to incline the radiating fins 13, and the tube main body 2 having the cross-sectional structure shown in FIG. 2 is a sectional view of the cross-sectional structure shown in FIG. 2 and is spirally swiveled inside the tube main body 12 by applying a tensile process of drawing the tube main body 2 in a direction parallel to the axial direction of the winding drum 35 after winding. 13 can be obtained. In addition, when producing the thin tube 10 by this method, the thin tube can be produced in a state in which the radiating fins 13 are previously tilted in a target direction.

For example, when expanding the narrow tube, as shown in FIG. 5 (a), the radiating fins 13 'are inclined at a predetermined angle so as to be tilted in one direction, and are directed from the left side to the right side in FIG. 5 (a). When the burette is inserted and the tube is expanded, the radiating fins 13 can be deformed so as to be almost upright as shown in FIG. FIG. 5B simply shows a partial cross section of the tube body 12, so that the radiating fins 13 are not drawn in a spiral shape, but the radiating fins 13 spiral along the inner peripheral surface of the tube body 12. It shall be formed in the shape.
As described above, a plurality of heat radiation fins 13 ′ can be spirally formed on the inner surface of the tube main body in a state where the heat radiation fins 13 are preliminarily tilted in a predetermined direction as shown in FIG. As shown in FIG. 5 (b), the heat dissipating fins 13 arranged in a spiral shape are provided by inserting and expanding the thin tubes provided with a 'through the fin insertion holes as heat transfer tubes of the heat exchanger. The thin tube 10 can be incorporated as a heat transfer tube for a heat exchanger.

FIG. 6 shows an example of a heat exchanger provided with the heat dissipating fins 3 or the heat dissipating fins 13 having the above-described structure, and the heat exchanger 30 in this example has a structure in which fins made of aluminum or aluminum alloy are laminated in multiple layers. The thin tube 1 or the thin tube 10 is joined to the fin 31 so as to penetrate the fin 31.
By connecting an elbow tube 32 to the end of the thin tube 1 or the thin tube 10 penetrating the fins 31, the thin tube 1 or the thin tube 10 is configured as a meandering tube.
Since the heat exchanger 30 having the configuration shown in FIG. 6 has the thin tube 1 or the thin tube 10 having the above-described structure, the heat exchanger 30 can be manufactured at a lower cost than a structure having a copper thin tube. Therefore, it is possible to provide a heat exchanger 30 that includes a heat transfer tube including the thin tubes 1 and 10 that are not buckled during tube expansion and includes a heat transfer tube that is well bonded to the fins 31.

A plurality of aluminum thin tubes having the shape shown in FIG. 1 and the shape shown in FIG. 2 were produced by extruding JIS standard 3003 alloy.
A thin tube having the structure shown in FIG. 1 was produced by ordinary extrusion. In addition, the structure of the thin tube shown in FIG. 2 is obtained by manufacturing the aluminum thin tube having the structure shown in FIG. 1, winding the thin tube around a cylindrical winding drum, and then winding the winding tube in a direction parallel to the central axis of the winding drum. It was formed by pulling a thin tube so as to peel off from the surface.

Table 1 below shows the outer diameter of the thin tube, the wall thickness, the height of the radiating fin (the height at the center of the top flat part), the total width ratio of the top flat part, the summit angle, the summit flat part inclination angle, and the radiating fin inclination form. Samples were prepared by setting as shown.
In Table 1, the thickness refers to the thickness of the tube body in the fin groove portion, the peak angle refers to the angle formed by the two inclined portions of the radiating fin, and the peak angle defines the spiral shape by twisting the tube body. The tilt angle when the radiating fin is tilted at a predetermined angle with respect to the radial direction of the tube body, and the radiating fin inclination form are the shape shown in FIG. 3B (when one radiating fin is viewed in cross section, the radiating fin is It means that the whole is in a state inclined with its central axis inclined) or a state shown in FIG. 3C (a state in which only the top flat portion of the radiation fin is inclined).
In Table 1, the pipe expandability evaluation criteria are as follows.
◎ Good tube expandability.
○ Slightly below the target value for tube expansion rate, the adhesion to the external fin is slightly worse.
Δ Although the core does not buckle, the tube expansion load is high or the tube expansion rate is low, and the adhesion with the external fin is poor.
× The tube expansion load is high, the core is buckled, or the tube expansion rate is clearly below the target value, and the adhesion with the external fin is poor.
In Table 1, the failure pressure evaluation standard was 5 MPa or less NG, and the pressure loss judgment standard was 100 MPa or more NG.

From the results shown in Table 1, since the outer diameter of the tube body was less than 2 mm in the sample of Comparative Example 1, the pressure loss when flowing the refrigerant increased, and in the sample of Comparative Example 2, the outer diameter of the tube body exceeded 5 mm. As a result, the pressure resistance was insufficient. From this, it can be judged that the outer diameter of the thin tube is preferably in the range of 2 to 5 mm.
In the sample of Comparative Example 3, since the wall thickness was less than 0.1 mm, the pressure resistance was insufficient, and in the sample of Comparative Example 4, the wall thickness was 0.8 mm exceeding 0.6 mm, resulting in an increase in cost. From this, it can be judged that the thickness is preferably in the range of 0.1 mm to 0.6 mm.

In the sample of Comparative Example 5, since the height of the radiating fin is 0.03 mm, which is less than 0.05 mm, the radiating fin is crushed at the time of tube expansion, the tube expansion load is increased, and the core buckling occurs. In the sample, the heat dissipation fin height was 0.4 mm exceeding 0.35 mm, so the pressure loss increased. From this, it can be judged that the range of 0.05 mm to 0.35 mm is desirable for the height of the radiation fin.
In the sample of Comparative Example 7, the ratio of the total width of the top flat portion is 15%, which is less than 20%. As a result, the heat dissipating fins are crushed during tube expansion, the tube expansion load is increased, and the core is buckled. In this sample, the ratio of the total width of the top flat portion was 85% exceeding 80%, so that the pipe expansion load was large. From this, it can be judged that the range of 20 to 80% is desirable for the ratio of the total width of the top flat portion.

In the sample of Comparative Example 9, since the number of fin grooves is 15 less than 20, the result is that the core buckles at the time of pipe expansion, and in the sample of Comparative Example 10, the number of fin grooves exceeds 65, so the pressure loss increases. It was. From this, it can be judged that the range of 20 to 60 is desirable for the number of fin grooves.
In the sample of Example 23, the summit angle is 5 °, which is less than 10 °, which results in a shortage of tube expansion. In the sample of Example 24, the summit angle is 65 ° exceeding 60 °, so the tube expansion load is somewhat It became bigger. From this, it can be judged that a range of 10 ° to 60 ° is desirable for the peak angle.
In the sample of Example 25, the slope state of the summit flat part is 5 °, which is less than 10 °, which results in a somewhat insufficient expansion of the tube. It was a little overwhelming because there was.

  As described above, the samples of Examples 1 to 28 within the scope of the present invention have a suitable outer diameter, thickness, radiating fin height, number of fin grooves, total width ratio of the top flat portion, and a suitable peak angle. Therefore, it can be joined to the fins without crushing the radiating fins when expanding the tube, and can be provided as an aluminum thin tube for a heat exchanger that does not cause buckling or breakage when expanding the tube.

DESCRIPTION OF SYMBOLS 1, 10 ... Thin tube, 2, 12 ... Tube main body, 3, 13, 13 ', 23 ... Radiation fin, 3a, 13a, 23a ... Top flat part, 3b, 13b, 23b ... Inclined part, 4, 14 ... Fin groove , S 1, S 2, S 3... Central axis, θ ₁ .. peak angle, θ ₂ , θ ₃ , θ ₄ ... Tilt angle, 30.

Claims (5)

  It is a thin tube made of a tube body made of aluminum or an aluminum alloy and having an outer diameter of 2 mm or more and 5 mm or less, and is a ridge-shaped radiating fin extending on the inner surface of the tube body in the longitudinal direction of the tube body Are formed substantially evenly at intervals along the inner circumferential direction of the tube body, and a plurality of fin grooves are formed between the heat dissipating fins, and the thickness of the tube body at the fin groove portion is 0.1 mm. As described above, a plurality of heat dissipating fins present in the circumferential direction of the inner periphery of the tube main body, 0.6 mm or less, the heat dissipating fin height of 0.05 mm or more and 0.35 mm or less, and the number of fin grooves is 20 or more and 60 or less. An aluminum thin tube for a heat exchanger, in which the total width of the top flat part is 20% or more and 80% or less as a percentage of the total circumference of the inner bottom surface of the pipe body.   The cross-sectional shape of the radiating fin is formed in an isosceles trapezoidal shape having a top flat portion and two inclined portions sandwiching the top flat portion, and the peak angle formed by the two inclined portions is 10 ° or more and 60 ° or less. The aluminum thin tube for heat exchangers according to claim 1.   The central axis of all the radiation fins is inclined at an angle of 10 ° or more and 30 ° or less with respect to the radial direction of the tube main body in a cross section of the tube main body. Aluminum tubes for heat exchangers.   The cross-sectional shape of the radiating fin has a top flat portion and two inclined portions sandwiching the top flat portion, the two inclined portions have the same inclination angle, and the two inclined portions have different heights to be trapezoidal. The aluminum thin tube for a heat exchanger according to claim 1 or 2, wherein an inclination angle of a top flat portion formed by the two inclined portions with respect to an inner bottom surface of the tube main body is 10 ° or more and 30 ° or less.   A heat exchanger comprising the heat exchanger aluminum thin tube according to any one of claims 1 to 4 as a heat transfer tube.

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