JP2000121268A - Finned heat transfer tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a heat transfer area and to improve a heat transfer efficiency by providing many fin chips each having a root and a tip in sawtooth state and forming the tips of the chips to be convergent and wider toward its tip. SOLUTION: The finned heat transfer tube has flat serrated fins having many fin chips by continuously and spirally winding a cut fin material on a heat transfer tube 1 and fixing them by continuous resistance welding. Tips 4 of the fin chips 3 of the serrated fins are twisted in predetermined directions to incline the tips 4 to the root at 20 degrees, and then pressed so that thicknesses of the tips 4 become thinner toward the tips and simultaneously wider toward the tips. Thus, its heat transfer area can be increased as much as possible to improve its heat transfer efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a finned heat transfer tube, and more particularly to a finned heat transfer tube capable of increasing the amount of heat exchange with a small number of heat transfer tubes.

[0002]

2. Description of the Related Art Heat transfer tubes typified by superheater tubes and reheater tubes of boiler devices have conventionally been provided with fins on the surface thereof in order to increase the heat transfer area. Have been.

[0003] When the extra-pipe fluid flowing around the fins provided in the heat transfer tube is higher in temperature than the intra-pipe fluid, the heat of the extra-pipe fluid is transmitted to the fins, transmitted through the fin material, and passed through the pipe wall to the intra-pipe fluid. Convey. Therefore, in order to improve the heat transfer performance of the heat transfer tube, it is effective to improve the heat transfer coefficient, the surface area of the fin surface, the heat conductivity of the fin, the cross-sectional area of the passage, the heat transfer coefficient and the surface area of the inner surface of the tube, and the like. . In particular, when the fluid outside the tube is a gas, the heat transfer coefficient is small. Therefore, increasing the surface area outside the tube by the fins is effective for improving the heat transfer performance. The shape of the fins formed on the surface of the heat transfer tube is, for example, a solid fin in which a fin material of a steel strip is continuously wound on the surface of the heat transfer tube, or a serrated cut is formed in the fin material of the steel band and wound around the heat transfer tube surface. Serrated fins.

FIG. 13 is a partial cross-sectional view perpendicular to the length direction of a heat transfer tube having solid fins in which fin materials are not cut, and FIG. 14 is a sectional view taken along the length direction of the heat transfer tube. FIG. In the figure, a solid fin 9 made of a steel strip that is not cut is wound around and fixed to the heat transfer tube 1. Since the solid fin 9 is formed by forcibly stretching a strip of steel not cut and winding it around the heat transfer tube 1 and fixing the same by, for example, welding, the winding conditions are limited, and the winding speed and fin shape at the time of manufacture are limited. Is restricted. In addition, such a solid fin has a slightly thinner wall thickness than the root portion due to the extension of the tip portion of the fin, but is not intentionally made thinner.

[0005] On the other hand, FIG. 11 is a partial cross-sectional view perpendicular to the length direction of a conventional heat transfer tube having serrated fins, and FIG. 12 is an enlarged view of the fin tip. In the figure, there is shown a serrated fin 7 having a plurality of fin tips (hereinafter, also simply referred to as tips) 8 to which a fin material having a sawtooth cut is spirally wound and fixed on the surface of the heat transfer tube 1. I have. This serrated fin 7
In order to further improve the heat transfer performance disturbs the gas flow through the heat transfer tube surface, the fin tip 8 is twisted Serrated fins twisted in a predetermined direction, and the width W _fo cut base portion The width W _ft at the tip is substantially the same. Further, since the fin material is cut, the cross-sectional thickness of each chip is almost the same at the root portion and the tip portion.

[0006] Serrated fins such as such twisted serrated fins have less deformation during winding by cutting the fin material,
The winding speed during processing can be increased as compared with the solid fin. In addition, the heat transfer area of serrated fins such as twisted serrated fins increases and decreases according to the increase in the area of the cut surface of the cut chip and the decrease in the area of the gap between the chips. Since the base of the chip extends because it is wrapped around the surface, it slightly increases or decreases compared to the solid fins depending on the manufacturing method, but the heat transfer performance is equal to or higher than that of the solid fins.

However, the above-mentioned conventional solid fins and serrated fins cannot be said to have a shape sufficient for increasing the heat transfer area, which is the original purpose of the fin, and the heat transfer performance is improved due to the turbulence of the gas flow. However, there is still room for improvement in improving the heat transfer performance based on the increase in the heat transfer area, and the improvement of the heat transfer efficiency was naturally limited.

In order to further improve the heat transfer efficiency of the finned heat transfer tube, it is necessary to increase the fin density in the length direction of the heat transfer tube or to increase the heat transfer area outside the tube by increasing the fin height. However, such a method is a basic provision for adopting an expanded heat transfer surface, and has been studied and adopted in the past.For example, when the height is increased, the fin efficiency decreases. In addition, since the outer diameter is increased, it is necessary to increase the pipe pitch, and the root of the fin is easily deformed at the time of manufacture, and there are problems in the processing speed, the degree of fin adhesion, and the like.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to increase the heat transfer area, which is the original object of the fin, as much as possible without increasing the resistance of the extravascular fluid. Accordingly, an object of the present invention is to provide a finned heat transfer tube that can further improve heat transfer efficiency.

[0010]

Means for Solving the Problems In order to achieve the above object, the present inventor has conducted intensive studies on the relationship between the shape of the fins provided on the surface of the heat transfer tube and the heat transfer area and the like. Pressing and extending the fin increases the fin height, but does not increase the heat transfer coefficient, but lowers the fin efficiency.At a certain height or higher, the heat transfer performance and economic efficiency are both wide from the beginning. In the case of serrated fins consisting of a large number of fin tips, the tip width is smaller than the height of the tip part, so it is easy to change the width and height direction by pressing the tip part. Can be extended, which increases the heat transfer area, and can be extended only in the width direction, and twists each tip of the serrated fin Or, by bending, each chip comes into contact with a new extra-fluid fluid, and the knowledge that the heat transfer coefficient can be increased was obtained. In the heat transfer tube with fins formed with a large number of fin tips in a shape, the tip portion of the fin tip was formed using the same fin material by pressing or rolling so that the tip portion was thinner and wider as the tip end portion became wider. The inventors have found that the heat transfer area is remarkably increased as compared with the heat transfer tube having the fins of different shapes, and the heat transfer efficiency is improved, and the present invention has been achieved.

That is, the invention claimed in the present application is as follows. (1) In a finned heat transfer tube in which a fin material having a cut is continuously wound and fixed on the surface of the heat transfer tube and a number of fin chips including a root portion and a chip portion are provided in a saw-tooth shape, A heat transfer tube with fins, characterized in that the tip portion is made thinner and wider at the tip. (2) The thickness ratio of the tip portion of the fin tip to the thickness of the root portion is set to 0.67 or less, and the thickness of the tip portion is set to 0.2 mm or more. The finned heat transfer tube according to (1).

(3) The tip portion of the fin tip provided in a sawtooth shape is twisted so that the tip portion surface is inclined at a predetermined angle with respect to the root portion surface. ) Or the finned heat transfer tube according to (2). (4) The finned heat transfer tube according to the above (3), wherein the inclination angle is 15 to 35 degrees. (5) The finned heat transfer tube according to the above (1) or (2), wherein adjacent chip portions of the fin chips provided in a sawtooth shape are alternately bent in opposite directions.

FIG. 6 is an explanatory view showing the principle of the present invention. The flat serrated fins having a fin height of 12.7 mm and a fin thickness of 1.2 mm are used. And the ratio of the heat transfer area to the change in the thickness _Tt of the tip portion of the tip portion when the tip portion is rolled so that the thickness gradually decreases toward the tip portion and the width is increased toward the tip portion. This shows the change of

Table 1 shows the relationship between the thickness (T _t ) of the tip portion of the fin tip in FIG. 6 and the ratio of the heat transfer area and the relationship between these and the width W _{ft of the} tip portion of the fin tip. The ratio of the thickness of the tip portion to the thickness of the root portion (root portion) is shown. At this time, the height is unchanged. The heat transfer area ratio is shown as a ratio of the heat transfer area of the flat serrated fin after rolling to the heat transfer area of the flat serrated fin in which the tip portion is not rolled.

[0015]

[Table 1] In FIG. 6 and Table 1, by gradually reducing the thickness of the tip portion of the fin tip, the width W _ft and the heat transfer area ratio of the tip portion gradually increase, and the thickness of the tip portion of the tip portion is reduced. When rolled to 0.6 mm, that is, half the thickness of the root (root), the width W _{ft of the} tip of the tip becomes twice the width W _f0 of the root (root). , Heat transfer area ratio of about 20% due to increase of fin surface
It can be seen that it increases.

In the present invention, the tip portion of the fin tip refers to a radially extending portion composed of a fin material having a saw-toothed cut, and the root portion refers to a root portion at which the fin tip extends radially. No, it refers to a continuous strip that is common to each fin tip without being separated.
However, in the present invention, the root portion corresponding to the tip portion of each fin tip is referred to as the fin tip root portion or simply the root portion for convenience. The fin is fixed to the surface of the heat transfer tube by, for example, continuous resistance welding of this root portion. Then, a fin tip is formed by the tip part and the root part. The height of the root is usually 4-5 mm.

In the present invention, if the tip of the fin tip is made too thin, for example, by rolling,
A contact portion with a support attached for preventing vibration may become small, resulting in insufficient strength. Therefore, the thickness of the tip of the fin tip is thinner than the thickness of the fin material,
It is preferably 0.2 mm or more. More preferably, the ratio of the thickness of the fin material, that is, the ratio of the thickness of the fin tip portion (tip portion tip) to the thickness of the fin root portion (root portion) is 0.67 or less, and the thickness of the fin tip tip portion is 0.1 mm. 2 mm or more.

In the present invention, when the tip portion of the fin chip is rolled, it can be extended in the height direction of the chip, but if it is extended in the height direction, the engagement with the support and the like will all be changed. It is more preferable to extend only in the width direction. In the present invention, it is preferable that each of the fin tips provided in a saw-tooth shape is twisted in a predetermined direction so that the tip portion surface is inclined by a predetermined angle with respect to the root portion surface. The inclination angle (twist angle) is 15 to 35 degrees, preferably 20 to 30 degrees. If the inclination angle is too large, the flow of the extravascular fluid is hindered due to the relationship with the adjacent fin tip, and the heat transfer performance is reduced. On the other hand, if the inclination angle is too small, the increase in the heat transfer performance becomes insufficient.

In the present invention, the tip portions of the sawtooth-shaped fin tips may be alternately bent in opposite directions. This increases both the heat transfer area and the heat transfer coefficient.

[0020]

Next, the present invention will be described in more detail by way of examples. 1 to 5 are explanatory views of a heat transfer tube with fins showing one embodiment of the present invention. FIG. 1 is a sectional view perpendicular to the length direction of the heat transfer tube, and FIG. 2 is a part of FIG. FIG. 3 is an enlarged view, FIG. 3 is a conceptual diagram when a finned heat transfer tube is installed in a gas flue, FIG. 4 is a partially detailed view showing a wide portion of the fin tip, and FIG. 5 is a cross section of the fin tip of FIG. FIG.

In this heat transfer tube with fins, a cut fin material is continuously wound spirally around the heat transfer tube 1 and fixed by, for example, continuous resistance welding to have a thickness of, for example, 1.2 m.
m, width 4 mm, and height 7.7 mm are flat serrated fins (FIGS. 1 and 2).
Of the flat serrated fins, the tip portions 4 of the fin tips 3 of the flat serrated fins are each twisted in a predetermined direction so that the tip portion surface is inclined, for example, by 20 degrees with respect to the root portion surface, and then pressed to form a tip portion. 4 is made thinner toward the tip, and at the same time the width is increased toward the tip (see FIGS. 4 and 5). The tip portion has a thickness of, for example, 0.6 mm and a width of, for example, 8 mm.

In FIG. 3 and FIG.
Width W at the tip of_ftIs the width W of the root _foWider than
ing. In FIG. 5, the tip of the fin tip 2 is shown.
Thickness T_tIs the thickness T of the root part (root part)₀compared to
And gradually thinner from the root to the tip
I have. The height H of the fin tip 2_fIs the height h of the root
_rAnd tip height h_cExpressed as the sum of This
As shown in FIG.
For example, it is arranged in the flue gas flue 6 and reduces the calorific value of the flue gas.
Used for recovery, for example as a superheater tube.

According to the present embodiment, the cut fin material is continuously wound spirally around the surface of the heat transfer tube 1 and fixed by, for example, continuous resistance welding to provide serrated fins. After the tip portion 4 of the fin tip 3 is twisted and inclined in a predetermined direction with respect to the root portion 5, the tip portion 4 is pressed to be thinner at the tip end portion and to be wider at the tip end portion. By
Approximately 15-20% heat transfer area while suppressing increase in material weight
Can be increased. Therefore, the heat transfer performance is improved,
The required number of heat transfer tubes can be reduced by 10 to 15%.

Since the size of the entire heat transfer device is mainly determined by the number of heat transfer tubes, this embodiment in which the number of heat transfer tubes can be reduced makes the heat transfer device more compact, and the overall economic effect is greater. Become.

Next, another embodiment of the present invention will be described. 7 and 8 are explanatory views showing another embodiment of the present invention. FIG. 7 is a cross-sectional view perpendicular to the length direction of the heat transfer tube, and FIG. 8 is a cross-sectional view of the fin tip. This finned heat transfer tube has a flat serrated fin in which a cut fin material is continuously wound spirally around the heat transfer tube 1 and fixed, that is, in the above embodiment, the tip portion 4 of the fin tip 3 is replaced with a flat serrated fin. The tip portion 4 is pressed in a flat state without being twisted, and the tip portion is made thinner and wider.
And the route section 5 are on the same plane.

In the present embodiment, the performance is not much different from that of the pressed solid fin, but the deformation of the root portion of the fin is small, and high-speed winding is possible. Next, FIGS. 9 and 10 are explanatory views showing another embodiment of the present invention.
FIG. 9 is a partial sectional view perpendicular to the length direction of the heat transfer tube, and FIG.
FIG. 4 is an explanatory view showing a cross section of a fin tip. In the figure, the fins provided in the heat transfer tube in this embodiment are the same as the fins of the flat serrated fins in which the tip portion 4 of each fin tip 3 is rolled to reduce the thickness toward the tip and widen. The chip 3 is bent in the opposite direction with respect to the root 5 every other central axis of the chip 4 of the chip 3 to provide a step.

The shape of the fin in this embodiment has an intermediate characteristic between the flat serrated fin obtained by rolling the tip portion 4 and the twisted fin, and the heat transfer area is obtained by rolling the tip portion 4 of the fin tip 3. And the heat transfer coefficient can both be increased.

[0028]

According to the first aspect of the present invention, the tip portion of the fin tip is made thinner and wider at the tip end, so that the fin tip can be transferred without increasing the weight of the fin. The heat transfer efficiency can be improved by increasing the heat area. Therefore, since the number of heat transfer tubes can be relatively reduced, the weight of the heat transfer device can be reduced, and the economy due to the compactness can be improved.

According to the invention of claim 2 of the present application, the thickness ratio of the tip portion of the fin tip to the thickness of the root portion is set to 0.67 or less, and the thickness of the tip portion is reduced to 0.67 or less. When the thickness is 0.2 mm or more, in addition to the effect of the above-described invention, a point of contact with the support for preventing vibration of the heat transfer tube with fins can be secured to avoid insufficient strength.

According to the third aspect of the present invention, the tip portion of the fin tip provided in a sawtooth shape is twisted so that the tip portion surface is inclined at a predetermined angle with respect to the root portion surface. Thereby, in addition to the effect of the above invention, the heat transfer coefficient can be increased without increasing the resistance of the extra-fluid fluid, and the heat transfer efficiency can be improved. According to the invention as set forth in claim 4 of the present application, by setting the inclination angle to 15 to 35 degrees, in addition to the effect of the above invention, the flow of the extravascular fluid is not obstructed.

According to the invention as set forth in claim 5 of the present application, the adjacent tip portions of the fin tips provided in a saw-tooth shape are alternately bent in opposite directions, so that in addition to the effect of the above-described invention, heat transfer is achieved. Both area and heat transfer coefficient can be increased.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view perpendicular to the length direction of a heat transfer tube showing an embodiment of the present invention.

FIG. 2 is a partially enlarged view of FIG. 1;

FIG. 3 is a diagram showing a concept when a finned heat transfer tube according to one embodiment of the present invention is installed in a gas flue.

FIG. 4 is an enlarged view of a fin tip in one embodiment of the present invention.

FIG. 5 is a diagram showing a cross section of a fin tip in one embodiment of the present invention.

FIG. 6 is an explanatory diagram showing the principle of the present invention.

FIG. 7 is an explanatory view showing another embodiment of the present invention.

FIG. 8 is a sectional view of a fin tip according to another embodiment of the present invention.

FIG. 9 is an explanatory view showing another embodiment of the present invention.

FIG. 10 is a sectional view of a fin tip according to another embodiment of the present invention.

FIG. 11 is an explanatory diagram of a conventional technique.

FIG. 12 is an explanatory diagram of a conventional technique.

FIG. 13 is an explanatory diagram of a conventional technique.

FIG. 14 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Heat transfer tube, 2 ... Serrated fin, 3 ... Fin tip, 4 ... Tip part, 5 ... Root part, 6 ... Exhaust gas flue, 7
... serrated fins, 8 ... fin tips, 9 ... solid fins.

Claims (5)

[Claims] 1. A finned heat transfer tube in which a fin material having a cut is continuously wound and fixed on the surface of the heat transfer tube, and a plurality of fin chips each including a root portion and a tip portion are provided in a saw-tooth shape. A heat transfer tube with fins, characterized in that the tip portion of the tip is made thinner and wider at the tip. 2. A method according to claim 1, wherein the thickness ratio of the tip of the fin tip to the root is 0.67 or less, and the thickness of the tip of the fin tip is 0.2 mm or more. The finned heat transfer tube according to claim 1. 3. The chip portion of the fin tip provided in a sawtooth shape is twisted by a predetermined angle with respect to the root portion surface by twisting the tip portion surface. 3. The heat transfer tube with fins according to 2. 4. The finned heat transfer tube according to claim 3, wherein the inclination angle is set to 15 to 35 degrees. 5. The heat transfer tube with fins according to claim 1, wherein adjacent chip portions of the fin chips provided in a sawtooth shape are alternately bent in opposite directions.