JP3927700B2 - Manufacturing method of heat exchanger - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a heat exchanger. In particular, a heat exchanger that exchanges heat by passing a high-speed high-temperature gas (gas) through the inner pipe and cooling water (liquid) through the outer pipe, for example, an exhaust cooler that cools the exhaust gas of an internal combustion engine with the cooling water (A high heat exchange capacity is required) and the like.
[0002]
[Background]
As a double-pipe heat exchanger, as shown in FIGS. 1 and 2, there is one in which the inner tube 12 is inserted into the outer tube 14 and both ends of the outer tube 14 are welded to the outer wall of the inner tube 12. At both ends of the outer tube 14, the cooling water inlet nozzle 16 and outlet nozzle 18 are formed so as to be able to use countercurrent / cocurrent flow (counterflow in the illustrated example). Reference numeral 20 denotes a pipe flange.
[0003]
In the configuration as shown in FIGS. 1 and 2, heat exchange is performed only on the wall surface of the inner tube 12, the heat transfer area is small, and heat exchange of the fluid flowing through the central portion of the inner tube 12 is difficult to perform. Is low. That is, it was difficult to obtain a large heat exchange capacity as a whole.
[0004]
For this reason, as shown in FIGS. 3 and 4, a multi-tube type in which a plurality of (four in the illustrated example) small-diameter inner tube 12A is inserted inside the outer tube 14 is normally used. . In this configuration, the heat transfer area is increased, heat can be exchanged with respect to the fluid flowing in the center portion side, and a large heat exchange capability is easily obtained.
[0005]
However, the multi-tube type shown in FIGS. 3 and 4 tends to increase the number of manufacturing steps and increase the weight.
[0006]
For this reason, the inventors of the present application previously formed a double-tube heat exchanger having the configuration shown in FIGS. 1 and 2 on the inner tube 28 with a corrugated tube having a radial cross section as shown in FIG. A heat exchanger in which the heat transfer fins 22 are arranged in contact with the inner wall of the inner tube 28 has been proposed (Japanese Patent Application No. 9-182571 (filed on July 8, 1997 ): Japanese Patent Application Laid- Open No. 11-23181 Reference, unpublished at the time of application). The heat transfer area can be increased and the heat exchange of the fluid flowing through the central portion of the inner tube 28 can be performed, thereby increasing the heat exchange capacity.
[0007]
In the heat exchanger shown in FIG. 5, the heat transfer fins 22 are formed into end tubes by winding a corrugated sheet 24 cut into a predetermined length at a predetermined pitch P and a predetermined height H as shown in FIG. 6. This was placed in contact with the outside of the crest 25 on the tube wall of the inner tube 28, and the outside of the crest was brazed and fixed.
[0008]
Then, the brazing is performed by applying a brazing material to the outside of the wave crest portion 25 and placing the heat exchange tube semi-finished product in which the heat transfer fins 22 are inserted into the inner tube 28 into a brazing heating furnace for a predetermined time. After the lapse, it was taken out.
[0009]
[Problems to be solved by the invention]
However, in the case of the brazing method described above, it has been found that stable brazing properties and strength cannot be obtained between the wave crest portion 25 of the heat transfer fin 22 and the tube wall of the inner tube 28 .
[0010]
In particular, as shown in FIG. 7, the present inventors, from the standpoint of brazing, this time, the brazing surface side (the outer peripheral surface side) is divided into a U-shaped bent portion U (first bent shape) and a V-shaped bent portion. In the case of the corrugated sheet 26 in which (second bent shape) V is alternately formed, it has been found that the brazing property and the stability of the strength are further lowered.
[0011]
In view of the above, an object of the present invention is to provide a method of manufacturing a heat exchanger that can stably obtain brazing properties and strength of heat transfer fins.
[0012]
[Means for Solving the Problems]
In the process of diligently developing in order to solve the above problems, the present inventors have found that in the above manufacturing method, when the wound heat transfer fin has distortion variation and is inserted into the inner tube , The inventors found out that the wave crest portions to be brazed do not come into contact with each other with a uniform gap, and came up with a method for manufacturing a heat exchanger having the following configuration.
[0013]
A double-tube heat exchanger having an inner tube and an outer tube, in which heat transfer fins formed of corrugated tubes having a radial cross section in the inner tube are disposed in contact with the inner wall of the inner tube is manufactured. In the method
Predetermined height-shaped heat transfer fins winding a predetermined length corrugated sheet at a predetermined pitch in a closed-end tubular wound in a wave direction, after insertion into the inner tube, the wave of the heat transfer fins on the tube wall of the inner tube When placing the outer side of the top in contact and brazing the outer side of the wave top ,
The heat transfer fin after winding is wound around a correction collar and inserted, and then the brazing is performed.
[0014]
In the heat exchanger manufacturing method described above, it is preferable to use a straightening collar provided with a plurality of positioning ribs fitted inside the wave portion of the heat transfer fin.
[0015]
Further, in any one of the above heat exchanger manufacturing methods, the first bent shape and the second bent shape, in which the bent shapes of the heat transfer fins are different from each other, are alternately formed. Is desirable.
[0016]
[Operation and effect of the invention]
The method for manufacturing a double-pipe heat exchanger of the present invention has the following operations and effects with the above-described configuration.
[0017]
Since the heat transfer fin after winding is wound around the correction collar and inserted into the inner tube , it is easy to ensure the roundness of the outer periphery when the heat transfer fin is spring-backed.
[0018]
For this reason, the contact degree between the wave crest portion of the heat transfer fin and the tube wall of the inner tube is made substantially uniform, and the brazing property and strength of the heat transfer fin can be stably obtained.
[0019]
Further, by using a material having a plurality of positioning ribs for fitting the wave portion inside of the heat transfer fins as corrective color, with easy to secure more roundness when the spring back in the inner pipe, waves The interval (wave pitch) can also be controlled. Therefore, it is easier to secure the brazing property and strength of the heat transfer fins, and also can suppress variations in the gaps between the wave crest portions of the heat transfer fins, thereby making it easier to manufacture a heat exchanger with improved heat exchange efficiency. Become.
[0020]
Further, as described above, the corrugated plate is formed by alternately applying the first bent shape and the second bent shape having different bent shapes to the manufacturing method of the present invention. The effect of the invention becomes more remarkable.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0022]
(1) The case where the corrugated plate 26 as shown in FIG. 7 is brazed and fixed to the inner tube 28 as shown in FIG. In the cross section of FIG. 8, the outer tube is omitted.
[0023]
The corrugated plate 26 is a U-shaped bent portion (first bent shape) U provided with bent portions on both sides of the wave crest portion 27 on the brazing surface side (the outer peripheral surface side), and is a surface on the inner peripheral surface side. The side is a V-shaped bent portion (second bent shape) V.
[0024]
The method for preparing the corrugated plate 26 is not particularly limited, and can be prepared by a conventional method. For example, as shown in FIG. 9, an upper die (push die) 32 and a lower die (receiver die) 34 are formed by a press machine. It is desirable that the metal strips (materials) 36 are formed by progressively feeding (lifting them one step at a time by a cylinder or the like and feeding them at a fixed length) so that corrugated sheets with a predetermined pitch can be accurately formed.
[0025]
Here, the brazing surface side is a U-shaped bent portion, but the same applies to a corrugated sheet having only a V-shaped bent portion or a U-shaped bent portion as shown in FIG.
[0026]
The corrugated sheet 26 press-molded as described above is usually wound in the wave direction to have a tubular shape, that is, is wound (braded). And the method of brazing is not specifically limited, Usually, it performs by roll forming etc.
[0027]
Next, brazing materials 36 and 36 </ b> A are applied or set on the wave crest portion (outer surface of the U-shaped bent portion U) 27 of the wound heat transfer fin 30. That is, at this time, a brazing material holding groove 29 is formed in the wave crest portion 27, and the holding groove 29 is filled with a paste-like brazing material 36 as shown in FIG. For example, copper wire) 36A is preferably fitted as shown in FIG. 11 from the viewpoint of brazing stability.
[0028]
The end-shaped tubular heat transfer fins 30 on which the brazing materials 36 and 36A are set are wound around the correction collar 38 and inserted, and then brazed.
[0029]
That is, as shown in FIG. 12, the heat-transfer fin 30 in a half-open state after winding is wound around the correction collar 38 so that the ends are substantially in contact with each other and inserted into the inner tube 28. At this time, the outer diameter d of the correction collar 38 is the same as or slightly smaller than the inner diameter D of the inner tube 28 minus two times the height H of the corrugated plate (D-2H). Although it depends on the inner diameter of the inner tube 28 , d = D−2H + (− 0 to −0.6 mm), preferably (−0.1 to −0.3 mm). When the outer diameter d of the correction collar 38 is larger than D-2H, the insertion workability deteriorates, and when the brazing material retaining groove 29 is not present in the wave crest 27, the brazing material that has been brazed (set) is detached, There is a risk of inhibiting brazing stability and strength. On the contrary, if the outer shape of the correction collar 38 is too small, it is difficult to achieve the effect of the present invention (rounding of the heat transfer fin).
[0030]
The correction collar 38 may be continuous, but may be composed of a plurality as shown in FIG. The correction collar 38 is usually hollow from the viewpoint of weight reduction. In this case, it is desirable that at least the insertion direction side of the correction collar 38 is a blind body. The thickness when the correction collar 38 is hollow depends on the diameter of the correction collar, but is usually 0.1 to 1.0 mm, preferably about 0.5 mm.
[0031]
Furthermore, it is desirable to use a straightening collar 38 having a plurality of positioning ribs 39 that fit inside the wave portions of the heat transfer fins 30 as indicated by a two-dot chain line in FIG. The presence of the positioning rib 39 is desirable because it can correct the shifted wave pitch. The number of positioning ribs 39 may correspond to the wave number of the heat transfer fins 30, but may be provided every other or every second.
[0032]
The heat transfer fins 30 are brought into close contact with the inside of the inner tube 28 by the spring back. At this time, since the correction collar 38 exists on the inner peripheral side of the heat transfer fin 30, the uneven distribution of the wave crest portion 27 of the heat transfer fin due to the spring back distortion of the heat transfer fin 30 is corrected, and the heat transfer fin 30 The outer circumference is rounded. In this state, the heat exchanger brazing process is completed by passing through the brazing furnace.
[0033]
Since the wave crests of the heat transfer fins are brazed in a state where they are uniformly in contact with the inner peripheral surface of the inner tube , stable brazing properties and strength can be obtained as a result.
[0034]
In the above description, the correction collar 38 is usually removed after the brazing process, but may be left without being extracted as long as it does not adversely affect the flow of the inner pipe fluid . The material of the straightening collar 38 is usually the inner tube 28 and metal (usually iron, steel), but it disappears or shrinks at the temperature just before the brazing melting temperature when brazing is heated. It may be a material.
[0035]
In addition, although the plate | board thickness of the corrugated sheet 26 used as the said heat-transfer fin 30 changes with materials, when steel, it is 0.01-0.8 mm normally, It is 0.05-0.5 mm desirably. If the thickness is too thin, the heat transfer resistance increases as well as the form retainability. On the other hand, if it is too thick, the weight increases, which is not desirable.
[0036]
The relationship between the height H of the inner radius r and corrugated 24 of the inner tube 28 depends on the inner diameter of the inner tube 28, in the range of the inside diameter 10~50mm of the inner tube 28, typically H / r = 0 0.1 to 0.8, preferably H / r = 0.2 to 0.7. Corresponding to the range of the inner diameter, the height of the wave peak is H = 4 to 20 mm.
[0037]
The wave pitch P of the corrugated plate 26 is 2 to 6 mm corresponding to the required heat transfer area.
[0038]
Further, the thickness of the inner tube 28 and the like is preferably as thin as possible from the viewpoint of heat transfer properties, but since rigidity is required as compared with the heat transfer fins 30, it is thicker than the heat transfer fins 30. . For example, when the inner diameter of the inner tube 28 is in the above range, it is usually 0.1 to 1.0 mm, preferably 0.3 to 0.8 mm.
[Brief description of the drawings]
FIG. 1 is a front view showing a conventional double-tube heat exchanger. FIG. 2 is an enlarged sectional view taken along line 2-2 in FIG. 1. FIG. 3 is a front view showing an example of a conventional multi-tube heat exchanger. 4 is a cross-sectional view taken along line 4-4 in FIG. 3. FIG. 5 is an enlarged end view corresponding to FIG. 2 in which a heat transfer fin of a corrugated tube is provided on the inner tube. FIG. 7 is an end view showing an example of a corrugated plate suitable for application of the present invention. FIG. 8 is an end view showing a state in which the corrugated plate of FIG. 7 is attached to the inner tube . FIG. 10 is a perspective view showing one embodiment of a brazing material set on the wave crest in the heat transfer fin of the present invention. FIG. 11 is a perspective view showing another brazing material setting manner. FIG. 12 is an explanatory view showing a mode in which the correction collar of the present invention is set on the heat transfer fin. FIG. 13 is a diagram showing how the discontinuous correction collar is set. Schematic perspective view showing the state where the heat fin is inserted into the heat exchange tube body [Explanation of symbols]
12 Inner tube 14 Outer tube 22 Heat transfer fin 24 Corrugated plate 25 Wave crest 26 Wave plate 27 Wave crest 28 Inner tube 29 Brazing material retaining groove 30 Heat transfer fin 36, 36A Brazing material 38 Straightening collar V V-shaped bending portion U U shape Bending part

Claims (5)

A double-tube heat exchanger having an inner tube and an outer tube, in which heat transfer fins formed of corrugated tubes having a radial cross section in the inner tube are disposed in contact with the inner wall of the inner tube is manufactured. In the method
Predetermined height-shaped heat transfer fins at a predetermined pitch winding a corrugated plate having a predetermined length in a closed-end tubular wound in a wave direction, after insertion into said tube, the heat transfer fins on the tube wall of the inner tube placed in contact with the crest portion outside when the brazing said corrugated top outside,
Method of manufacturing a heat exchanger for the heat transfer fins after the take-molding, after insertion wound to correct color, and performs the braze.   2. The method of manufacturing a heat exchanger according to claim 1, wherein the straightening collar includes a plurality of positioning ribs fitted inside the wave portion of the heat transfer fin.   3. The heat exchanger according to claim 1, wherein the corrugated plate has a wave shape in which a first bent shape and a second bent shape having different bent shapes are alternately formed. Method.   4. The method of manufacturing a heat exchanger according to claim 3, wherein a brazing material holding groove is formed outside the wave crest that contacts the tube wall of the heat transfer fin.   The method for manufacturing a heat exchanger according to claim 1, wherein a brazing material holding groove is formed outside the wave crest that contacts the tube wall of the heat transfer fin.

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