JPH11183062A - Double piped heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily meet a request for increasing a heat exchanging capacity in a double piped heat exchanger having an inner pipe provided with heat transfer fin formed with a corrugated tube with a radial shape in cross section. SOLUTION: A double piped heat exchanger having an inner pipe 12. an outer pipe 14 and either a high temperature side fluid passage or a low temperature side fluid passage respectively in the inner pipe side and the outer pipe side. In the inner pipe 12, a heat transfer fin 22 formed with a corrugated tube radial in cross-section is arranged in contact with the inside of the wall of the inner pipe 12. A column body 26 is formed for closing the central part of the inner pipe to form an annular orifice.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a double-pipe heat exchanger. In particular, a heat exchanger that exchanges heat by passing 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 exhaust gas of an internal combustion engine with cooling water (High heat exchange capability is required).

Here, a case where heat exchange is performed by passing cooling water through an outer tube and high-temperature gas through an inner tube is taken as an example, but the combination of heat exchange media is not limited to this.
That is, in the combination of fluids, liquid / liquid, gas /
Gas, liquid / gas, etc. are arbitrary, and the fluid passage on the high temperature side / low temperature side may be on either the inner tube side or the outer tube side.

[0003]

2. Description of the Related Art As shown in FIGS. 1 and 2, a double-pipe heat exchanger is one in which an inner pipe 12 is inserted into an outer pipe 14 and both ends of the outer pipe 14 are welded to the outer wall of the inner pipe 12. is there. Outer tube 14
The cooling water inlet nozzle 16 and outlet nozzle 18 are formed at both ends so that they can be used in countercurrent / cocurrent (countercurrent in the example in the figure). In addition, 20 is a pipe flange.

In the configuration 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 center of the inner tube 12 is difficult, and the heat exchange efficiency is low. That is, it was difficult to obtain a large heat exchange capacity as a whole.

For this reason, as shown in FIGS. 3 and 4, a multi-tube type in which a plurality (four in the illustrated example) of small-diameter inner tubes 12A are inserted into the outer tube 14 is usually used. Have been.
With this configuration, the heat transfer area is increased, and heat exchange can be performed with respect to the fluid flowing on the central portion side, so that a large heat exchange capability is easily obtained.

However, the multi-tube type shown in FIGS. 3 and 4 tends to increase the number of manufacturing steps and increase the weight.

[0007] For this reason, the inventors of the present invention have previously described FIG.
In the double-pipe heat exchanger having the configuration shown in FIG. 2, a heat transfer fin 22 formed of a corrugated tube having a radial cross section is brought into contact with the inner pipe 12 as shown in FIG. (Japanese Patent Application No. 9-182571)
No .: See Japanese Unexamined Patent Publication No. Hei. The heat transfer area can be increased and the fluid flowing through the center of the inner tube 12 can be exchanged with heat, thereby increasing the heat exchange capacity.

[0008]

In the heat exchanger having the structure shown in FIG. 5, when the heat exchange efficiency is to be further increased, as shown in FIG. 6, the wave number of the corrugated tube forming the heat transfer fins 22A is increased. It is conceivable to increase the heat transfer area to cope with the increase.

However, as a result of the study by the present inventor, it was found that not only the heat exchange capacity did not increase but also decreased. The reason is presumed to be as follows.

When the number of waves is increased, the heat transfer fins 22A
The gap between the waves becomes narrower, especially on the center side, and the pressure loss of the heat transfer fins in this portion increases. For this reason, the high-temperature gas preferentially flows from the pipe wall side of the inner pipe 12 on the side where the heat transfer fins 22A are disposed to the center side of the inner pipe 12 on the side where the heat transfer fins 22A are not disposed (inside). . And the heat transfer fins 22
The flow rate of the high-temperature gas in the portion where A is disposed is small, and the heat transfer coefficient in that portion increases. It is common knowledge in the art that the heat transfer coefficient increases as the flow velocity in the tube increases (for example, the Chemical Engineering Association, “Chemical Engineering Handbook, Revised Fourth Edition” (Showa 5)
3-10-25) Maruzen, p. 359).

Therefore, the heat exchange is substantially performed by the heat transfer fins 22.
This is performed only on the inner diameter side of A, and the increase in the heat transfer area does not contribute to the increase in the heat exchange capacity.

Further, it is presumed that the thickness of the heat transfer fins 22A becomes relatively thin, and the heat transfer resistance of the heat transfer fins 22A itself also increases, thereby contributing to a reduction in heat exchange ability.

As described above, in the heat exchanger having the structure shown in FIG. 5, it is difficult to increase the heat exchange capacity by increasing the wave number of the corrugated tube forming the heat transfer fin.

SUMMARY OF THE INVENTION In view of the above, the present invention provides a double-pipe heat exchanger in which heat transfer fins formed of corrugated tubes with a radial cross section are disposed on the inner pipe, and can easily respond to the demand for increased heat exchange capacity. It is an object of the present invention to provide a double-pipe heat exchanger capable of performing heat treatment.

[0015]

The double-pipe heat exchanger according to the present invention solves the above-mentioned problems by the following constitution.

In a double-pipe heat exchanger comprising an inner pipe and an outer pipe, each of which has one of a high-temperature fluid path and a low-temperature fluid path on the inner and outer pipe sides, A heat transfer fin formed of a corrugated tube having a radial cross section is disposed in contact with the inner wall of the inner tube, and a central portion of the inner tube is closed inside the heat transfer fin to form an annular orifice. An annular orifice forming means is provided.

The annular orifice forming means may be in the form of a column disposed at the center of the inner tube, and may be in the form of a column.

Further, the annular orifice forming means may include:
As a hollow column closed at both ends, the hollow column may be configured such that a pipe having the same fluid path as the inside of the outer tube is connected to the hollow column.
Desirable further increase in heat exchange capacity.

[0019]

Operation / Effect of the Invention The double-pipe heat exchanger of the present invention has the following operation / effect with the above configuration.

For example, high-temperature gas is passed through the inner tube 12 and cooling water is passed through the outer tube 14. Then, due to the presence of the heat transfer fins 22 provided in the inner pipe, the flow of the high temperature gas is subjected to resistance on the side where the heat transfer fins 22 are provided. At this time, an annular orifice forming means 26 for closing the central portion of the inner tube is disposed inside the corrugated tube (see FIG. 8). For this reason, the high-temperature gas which is going to flow inside the heat transfer fins 22 is forcibly guided to the heat transfer fins 22 side, flows through the heat transfer fins 22 and the heat transfer fins 22 and the high-temperature gas. Contact efficiency is improved.

Further, since the high-temperature gas does not substantially escape inside the heat transfer fins and is substantially constricted by the heat transfer fins,
The flow rate of the hot gas is increased, the heat transfer coefficient is increased, and the heat transfer coefficient is improved.

Therefore, the high-temperature gas and the cooling water are efficiently exchanged heat through the heat transfer fins and the inner tube wall.

The balance between the heat transfer area determined by the inner tube diameter and the specifications of the heat transfer fins (wave height and number of corrugated tubes) and the reduction in the heat transfer coefficient of the heat transfer fins due to the decrease in flow velocity are balanced. The required heat exchange capacity can be easily designed.

For example, a decrease in the contact rate of the high-temperature gas with the heat transfer fins due to an increase in the wave number of the corrugated tube;
Further, the decrease in the heat transfer coefficient due to the decrease in the flow velocity is complemented by the presence of the annular orifice forming means. For this reason, the wave number of the corrugated tube can be increased substantially in proportion to the increase in the heat transfer area, and the heat exchange capacity can be easily designed.

Therefore, in the double-pipe heat exchanger in which the heat transfer fins formed of the corrugated tubes having a radial cross section are disposed on the inner pipe, measures for improving the heat exchange efficiency can be easily made.

Further, the column is a hollow body closed at both ends,
If the hollow body is connected to a pipe having the same fluid passage as the inside of the outer tube, the heat transfer area of the cooling water to the high-temperature gas can be improved, and the heat exchange capacity can be further increased.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Various embodiments of the present invention will be described below with reference to the drawings. The same parts as those in the above-described example are denoted by the same reference numerals, and all or part of the description thereof will be omitted.

(1) FIGS. 7 and 8 show an embodiment of the present invention.

A double-pipe heat exchanger having an inner pipe 12 and an outer pipe 14, wherein the inner pipe 12 side and the outer pipe 14 side are each one of a high-temperature side fluid passage and a low-temperature side fluid passage. It is. In the illustrated example, the inner pipe 12 side is a high-temperature gas fluid passage, and the outer pipe 14 side is a cooling water fluid passage.

A heat transfer fin 22 formed of a corrugated tube having a radial cross section is disposed on the inner pipe 12 in contact with the inner wall of the inner pipe 12.

Here, the corrugated tube, which is the heat transfer fin 22, is generally formed by forming a metal (for example, steel) metal corrugated plate 24 having a large thermal conductivity and a spring property as shown in FIG. It is desirable to bend and insert into the inner tube 12 and then fix it by brazing. This is because temporary fixing work before the brazing process is not required. Of course, a corrugated tube formed by drawing or the like from the beginning may be inserted into the inner tube 12 and fixed. In this case, it is desirable that the corrugated tube be tightly fitted to the inner tube because the temporary fixing before the brazing step is not required similarly to the above.

Here, the thickness of the corrugated tube 22 varies depending on the material.
mm, desirably 0.05 to 0.2 mm. If the thickness is too small, the heat transfer resistance is increased together with the shape retention, and if the thickness is too large, the weight increases, which is not desirable.

The relationship between the inner radius r of the inner tube 12 and the height L of the corrugated plate 24 depends on the inner diameter of the inner tube 12.
L / r = 0.1 to 10 to 50 mm
0.8, preferably L / r = 0.2 to 0.7.
And according to the range of the inner diameter, the height of the wave peak is L = 4 ~
20 mm.

The wave pitch of the corrugated tube 22 is set to 2 to 5 mm corresponding to the required heat transfer area.

The shape of the corrugated tube is the shape of the corrugated peak.
The valleys may not be R-shaped, but the peaks and valleys may be square. Alternatively, the ridges may be formed by using a metal corrugated plate in which the peaks are shifted at regular intervals in the longitudinal direction. For example, as shown in FIG.
A corrugated plate 24A in which a and 25b are alternately formed is desirable. The pitch in this case is, for example, 5 to 20 mm.

The thickness of the inner tube 12 is desirably as thin as possible from the viewpoint of heat transfer. However, since the inner tube 12 is required to have higher rigidity than the corrugated tube, it is made thicker than the corrugated tube.
For example, when the inner diameter of the inner tube 12 is within the above range, it is usually 0.1
To 1.0 mm, preferably 0.3 to 0.8 mm.

The gap between the outer tube 14 and the inner tube 12 is, for example,
When the inner diameter of the inner tube 12 is in the above range, it is usually in the range of 1 to 5 mm.

(2) Inside the heat transfer fins 22, an annular orifice forming means for closing the center of the inner tube 12 to form an annular orifice is provided.

As a specific embodiment, there are pillars 26 and 26A shown in FIGS. At this time, the pillars 26, 26A
May be a prism (for example, a triangular prism or a polygonal prism corresponding to a mountain), but is usually a cylinder. And the pillar 26
A is reduced in diameter as shown in FIG. 11 so as to secure a flow rate to pass through the inner pipe 12, that is, to reduce the pressure loss to a predetermined value or less, and there is a gap between the heat transfer fins 22. It may be configured. The gap at this time is usually within 3 mm. If the gap is too large, the amount flowing on the central portion side will increase, and it will be difficult to achieve the above-described functions and effects of the present invention.

The pillars 26 and 26A do not necessarily need to be provided over the entire length of the outer tube forming portion (heat exchange portion), and may be formed on the fluid inflow side beyond the heat exchange portion (FIG. 7-2). See dotted line). When the length of the heat exchange portion is short, the heat exchange portion may be provided only on the near side or only in the center portion within a range in which the function and effect of the present invention can be obtained.

The pillar may be a hollow body 26B having both ends closed as shown in FIG. When the hollow body 26B is used, a pipe having the same fluid path as the outer pipe may be connected to the hollow body 28, that is, although not shown, an inlet / outlet of the cooling water may be provided. In this case, the heat exchange capacity is further increased as shown in FIG.

The material for forming the pillars 26, 26A, 26B and the like is made of ceramics having heat resistance when the cooling water is not allowed to pass through the hollow body 28, and plastics if heat resistant. It may be. in this case,
From the viewpoint of weight reduction, a hollow body or a foam is desirable.

The mode of use of this embodiment is the same as in the prior art, and its operation and effects are as described above.

The heat exchange capacity in each of the embodiments shown in FIGS. 5, 8 and 12 is represented by a comparative model graph as shown in FIG.

[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 of FIG. 1;

FIG. 3 is a front view showing an example of a conventional multi-tube heat exchanger.

FIG. 4 is a 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 in FIG. 1;

FIG. 6 is an end view in which the number of peaks of the corrugated tube in FIG. 5 is increased.

FIG. 7 is a longitudinal sectional view showing one embodiment of the heat exchanger of the present invention.

FIG. 8 is an enlarged end view taken along line 8-8 in FIG. 7;

FIG. 9 is a perspective view of a metal corrugated sheet used in the heat exchanger of the present invention.

FIG. 10 is a partial perspective view of another metal corrugated sheet.

FIG. 11 is an end view of the form in which the diameter of the cylindrical body is reduced in FIG. 8;

FIG. 12 is an end view of a form in which a cylindrical body is hollowed in FIG. 8;

FIG. 13 is a comparative model graph showing heat exchange efficiency as a moving calorie index.

[Explanation of symbols]

12 Inner tube 14 Outer tube 22 Heat transfer fin 24, 24A Corrugated plate 26, 26A, 16B Cylinder (annular orifice forming means)

Claims (4)

[Claims] 1. A double-pipe heat exchange system comprising an inner tube and an outer tube, wherein the inner tube and the outer tube each have one of a high-temperature fluid passage and a low-temperature fluid passage. In the vessel, a heat transfer fin formed of a corrugated tube having a radial cross section is disposed in contact with the inner wall of the inner pipe, and a central portion of the inner pipe is closed inside the heat transfer fin. An annular orifice forming means for forming an annular orifice by heating. 2. The double-pipe heat exchanger according to claim 1, wherein said annular orifice forming means is a column disposed at the center of the inner pipe. 3. The double-pipe heat exchanger according to claim 1, wherein the column as the annular orifice forming means is a column. 4. The double according to claim 2, wherein the column is a hollow body having both ends closed, and a pipe having the same fluid passage as the inside of the outer tube is connected to the hollow body. Tube heat exchanger.