JPH08226783A - Heat exchanger - Google Patents

Abstract

PURPOSE: To obtain a heat exchanger, which allows a reduction in weight and size of an apparatus and is excellent in heat transfer characteristics, and its arrangement construction. CONSTITUTION: An inclined fin 4 is a serrated flat plate and consists of a number of divided parts 3 along one edge and a common base part 2 that is along the other edge and connects the divided parts 3. The fin 4 is wound around a tube 1 so that the edge of the common base 2 comes in contact with the circumference of the tube 1. The ratio (H /h) is restricted within 1.5-15, where H represents the overall height of the fin 4 in the radial direction and h the height of the common base part 2 in the radial direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger used in, for example, a heat recovery device for recovering heat from combustion exhaust gas, and more particularly to a heat exchanger formed by winding serrated fins around a tube. Regarding

[0002]

2. Description of the Related Art FIG. 12 shows a U-shaped dividing fin 12 disclosed in Japanese Patent Laid-Open No. 55-43310 and Japanese Utility Model Laid-Open No. 60-28365, and FIG. 13 shows the U-shaped dividing fin 12 in a tube 10. It is a figure showing the state where it was attached to.

As shown in FIG. 12, this U-shaped split fin 12 has a central mounting portion 1 of a band-shaped fin material.
A U-shaped split fin 12 is formed by leaving notches 1 on both sides and bending in the same direction from the root of the notch.

The U-shaped dividing fin 12 is shown in FIG.
As shown in FIG. 3, by winding and fixing the portion of the central mounting portion 11 around the tube 10, a large number of fins 12 are oriented in the radial direction, and the outer peripheral portion of the fins 12 is positioned above the central mounting portion 11. It is inclined to face.

[0005]

[Problems to be Solved by the Invention] By the way, this fin 1
As shown in FIG. 13, in the heat exchanger having the 2 attached thereto, the flat mounting portions 11 are attached to the outer periphery of the tube 10 so as to be adjacent to each other, so that the tube wall has a double structure. The thickness of the tube wall increases, and a boundary surface is formed between the tube wall of the tube 10 and the mounting portion 11, which increases the thermal resistance and deteriorates the heat transfer characteristics.

Further, when the fins are wound around the outer circumference of the tube, they are wound around the outer circumference of the tube while applying a considerable tension to the band-shaped fin material, but as described above, there are cuts from both sides of the fin material. Therefore, when winding it around the tube with high tension, the central mounting part 11
Cracks tend to occur, the fin material may be cut in the middle, and work efficiency and yield are poor.

Further, since the fins 12 are cut to the roots, the inclination angles of the fins tend to be uneven, and the flow resistance of the fluid passing between the fins becomes high. In addition, it has drawbacks such as deterioration of heat transfer characteristics.

It is an object of the present invention to solve the above-mentioned drawbacks of the prior art, to reduce the weight of the apparatus, to downsize the apparatus, and to provide a heat exchanger having good heat transfer characteristics and an arrangement structure thereof.

[0009]

To achieve the above object, the present invention provides a flat plate having a large number of divided portions on one side and a common base portion connecting the divided portions on the other side in the radial direction. A serrated fin is wound around the tube so that the edge of the common base is joined to the outer circumference of the tube, and the radial height h of the common base and the radial height of the entire fin are increased. The ratio (H / h) with H is 1.5 to
It is characterized by being regulated in the range of 15.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, as described in claim 1 above, H / h is restricted to a range of 1.5 to 15 to reduce the width of wrinkles at the root of the fin and to reduce the fin width. It is possible to suppress the flow resistance of the fluid at the root portion to be small and maintain the heat transfer characteristics in good condition.

Further, as described in claim 2, by restricting the inclination angle θ of the fin in the range of 2 to 20 degrees, the number N of fin peaks can be increased and the weight W of the apparatus can be reduced.

A specific example of the present invention will be described below with reference to the drawings. 1 is a perspective view of a heat exchanger according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along the line AA of FIG. 1, and FIG. 3 is an enlarged plan view of the heat exchanger of FIG.

As shown in these figures, a large number of divided portions 3 are provided on one side, and a common base portion 2 which is not toothed and which connects the divided portions 3 is provided on the other side in the radial direction. The plate-shaped serrated fins 4 are wound around the tube 1 so that the edge of the common base portion 2 is joined to the outer peripheral portion of the tube 1 to form a heat exchanger.

As shown in FIG. 2, the fin 4 is a tube 1
Is inclined at an angle θ with respect to a straight line that is perpendicular to the axis of the.

FIG. 6 shows the inclination angle θ of the fin 4 (see FIG. 2).
FIG. 6 is a characteristic diagram showing the relationship between the number of fins (the number of turns per unit length in the tube axis direction) N. As is clear from this figure, the fin number N increases as the inclination angle θ of the fin 4 increases.
The number of fin crests N is remarkably increased particularly in the range of θ of 2 to 20 degrees.

FIG. 7 shows the number N of fins and the weight W of the entire apparatus.
It is a characteristic view which shows the relationship with. As is clear from this figure, the fact that the number of fin crests N per unit length in the pipe axis direction is large means that a predetermined heat transfer area can be secured even if the device is made small, and the device weight is correspondingly increased. W becomes lighter. Therefore, by restricting the inclination angle θ of the fin 4 in the range of 2 to 20 degrees, the number of fin crests N can be increased and the device weight W can be reduced.

FIG. 8 shows the radial height h of the common base portion 2.
Is a characteristic diagram showing the relationship between the ratio (H / h) between the height of the fins in the radial direction (see FIG. 3 for both) and the width of the wrinkles at the root when the fins 4 are wound around the tube 1. is there. The width of the wrinkles at the base of the fin 4 is the width shown in FIG.

FIG. 9 is a characteristic diagram showing the relationship between the width of the fin wrinkle and the draft loss. As is clear from this figure, there is a correlation between the width of the fin root wrinkle and the draft loss, and as the width of the fin root wrinkle increases, the draft loss becomes large, and the large draft loss means that This means that the flow of the fluid becomes poor, and eventually the heat transfer characteristics deteriorate.

As is clear from FIGS. 8 and 9, when H / h is less than 1.5, that is, when the ratio of the height h of the common base portion 2 is large, the width of the fin root wrinkles is large. Therefore, the draft loss becomes large and the heat transfer characteristics deteriorate.

If this point H / h exceeds 1.5, the width of the wrinkles at the root of the fin becomes extremely small, so that the draft loss, that is, the flow resistance at the root of the fin becomes small,
Good heat transfer efficiency at the root of the fin. This tendency is H
Even if / h exceeds 15, the value of H / h becomes larger than this, which means that the common base portion 2 becomes extremely low, which reduces the tensile strength of the fin material. However, when the fin 4 is wound around the tube 1, the fin material may be cut, resulting in a decrease in work efficiency.

Therefore, the width of the wrinkles at the base of the fin is suppressed to be small,
Moreover, in order to wind the fin material around the tube with good workability, the value of H / h should be regulated within the range of 1.5 to 15.

FIG. 4 is a plan view showing the arrangement structure of the above-mentioned heat exchanger, and FIG. 5 is a view taken in the direction of arrows in FIGS. 4B-B. As shown in FIGS. 4 and 5, four heat exchangers with inclined fins 4 are arranged in a staggered manner in four rows along the flow direction of the gas 6, and as shown in FIG. The heat exchanger 1 has the fins 4 facing downward, and the heat exchanger 1 on the downstream side has the fins 4
Are facing upward, and the inclination directions of the fins 4 are different from each other.

FIG. 10 shows a case A in which the fins have different inclination directions and a case B in which the fins have the same inclination direction.
FIG. 6 is a characteristic diagram showing the relationship between the gas flow velocity v and the heat transfer coefficient α with respect to. As is clear from this figure, by making the fins tilted in different directions (case A), the gas diffusion becomes very good, and as a result, the heat transfer coefficient α can be significantly improved compared to case B. It was

Further, as shown in FIGS. 1 and 2, when the outer peripheral portion of the fin 4 is inclined downward from the inner peripheral portion joined to the tube 1, for example, when gas ventilation is stopped. Less dust accumulation on the common base part 2 of
In addition, there is no concern that water will collect on the common base portion 2 when it is washed with water.

[0025]

According to the present invention, as described in claim 1 above,
By controlling H / h within the range of 1.5 to 15, the width of wrinkles at the fin root portion is reduced, the flow resistance of the fluid at the fin root portion is reduced, and heat transfer characteristics are maintained well. can do.

Further, as described in claim 2, by restricting the inclination angle θ of the fin in the range of 2 to 20 degrees, the number N of fin peaks can be increased and the weight W of the apparatus can be reduced.

[Brief description of drawings]

FIG. 1 is a perspective view of a heat exchanger according to a specific example of the present invention.

FIG. 2 is a sectional view taken along the line AA in FIG.

FIG. 3 is an enlarged plan view of the heat exchanger.

FIG. 4 is a plan view showing an array structure of the heat exchanger.

FIG. 5 is a view on arrow in FIG. 4B-B.

FIG. 6 is a characteristic diagram showing a relationship between a fin inclination angle and the number of fin crests.

FIG. 7 is a characteristic diagram showing the relationship between the number of fins and the device weight.

FIG. 8 is a characteristic diagram showing a relationship between H / h and the width of a fin root wrinkle.

FIG. 9 is a characteristic diagram showing a relationship between the width of a fin root wrinkle and draft loss.

FIG. 10 is a characteristic diagram showing a relationship between a gas flow velocity and a heat transfer coefficient in case A and case B.

FIG. 11 is an explanatory diagram showing the width of a fin base wrinkle.

FIG. 12 is a perspective view of a conventionally proposed fin.

FIG. 13 is a cross-sectional view of a heat exchanger with the fins attached.

[Explanation of symbols]

 1 ... Tube 2 ... Common base part 3 ... Dividing part 4 ... Fin

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kimiya Sakamoto 6-9 Takaracho, Kure-shi, Hiroshima Bab Hitachi Industrial Co., Ltd.

Claims (2)

[Claims] 1. A flat serrated fin having a plurality of divided portions on one side and a common base portion connecting the divided portions on the other side in a radial direction, and an edge of the common base portion. Is wound around the tube so as to be joined to the outer peripheral portion of the tube, and the ratio (H / h) of the radial height h of the common base portion and the radial height H of the whole fin is 1.5 to A heat exchanger characterized by being regulated in the range of 15. 2. The saw-toothed fin according to claim 1, wherein the serrated fin is 2 with respect to a straight line which is perpendicular to the axis of the tube.
A heat exchanger characterized by being inclined in a range of up to 20 degrees.