JPH1172202A - Horizontal type heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a horizontal type heat exchanger made free from the possibilities of wear-out reduction of wall thickness, bursting, etc., by making a contrivance for heat transfer tubes disposed on the lateral wall side, in regard to the horizontal type heat exchanger using finned tubes in a boiler. SOLUTION: In this horizontal type heat exchanger, a flow deflection preventing plate 2 is provided above heat exchanger tubes on the side of the lateral wall of a boiler, while the heat exchanger tubes are constituted of bare tubes 4 for several panels located on the lateral wall side and of finned tubes 3 for ones located to the center, and the bare tubes 4 are so arranged as to leave a narrow space between the adjacent ones so that the resistance to a gas flow be equal to or larger than that in the part of the tinned tubes 3. According to this constitution, occurrence of ash erosion, reduction of the wall thickness of the tubes or the like is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a horizontal heat exchanger using finned tubes in a boiler.

[0002]

2. Description of the Related Art A conventional device of this type will be described with reference to FIGS. FIG. 3 is a bird's-eye view of a finned tube of a general horizontal heat exchanger, and FIG. 4 is a cross-sectional view of a main part of a conventional horizontal heat exchanger viewed from the front of a boiler.

[0003] In a coal-fired boiler, powder abrasion, that is, ash erosion occurs due to coal ash caught in the combustion gas.

On the other hand, the boilers currently being constructed are of a horizontal type using finned heat transfer tubes (finned tubes) as shown in FIG. 3 in order to increase the heat transfer area and reduce the overall construction cost. Heat exchangers are often used.

The horizontal type heat exchanger provided with a finned tube is shown in FIG. 4 in which a part of the cross section near the boiler side wall is enlarged and extends in the vertical direction near the boiler side wall. A large number of finned tubes 3 are arranged so as to be spaced apart from each other at a fixed distance from the provided side wall tube 1 over a central portion.

In general, in this type of horizontal heat exchanger, the combustion gas flowing as indicated by the gas flow direction A is divided into a flow a on the side wall and a flow b near the center. Will flow excessively along the side wall surface where the flow resistance is small.

In order to prevent a reduction in the heat transfer efficiency of the entire element and a rapid ash erosion of the side wall tube, a non-uniform flow preventing plate 2 is provided above the finned tube 3 on the side wall side. ing.

[0008]

However, the flow a on the side wall is a gas flow involving the drift preventing plate 2, and a portion having an extremely high flow velocity is generated in a region of several panels from the side wall of the boiler. In addition, this gas flow has a high flow velocity and is often disturbed by an obstacle, resulting in a so-called oblique flow which enters the heat exchange tube in the axial direction.

Due to its shape, the finned tube is very weak against this high-speed oblique flow, generates ash erosion, and is liable to cause thinning.

That is, in the above-mentioned conventional coal-fired boilers, most of them are horizontal type heat exchangers, but the finned tube 3 as a main part thereof is generally weak due to its shape to ash erosion. In particular, in the case of the finned tube 3 disposed on the side wall exposed to excessive flow, there is a problem that the possibility of abrasion thinning and blasting is higher.

The present invention solves such a problem in the prior art and devise a heat transfer tube arranged on the side wall side so that there is no fear of abrasion thinning and blasting. It is an object to provide a mold heat exchanger.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems. In the present invention, a drift preventing plate is provided above a heat exchange tube on a side wall of a boiler. A horizontal heat exchanger in which the panel is composed of a bare tube and the central part is a finned tube, and the distance between adjacent bare tubes is so narrow that the gas flow resistance is equal to or greater than that of the finned tube. Is provided.

That is, the heat transfer tube is a bare tube over several panels on the side wall side, and the interval between the adjacent bare tubes is narrowed so that the gas flow resistance is equal to or more than that of the finned tube. As a result, it is possible to prevent the occurrence of ash erosion and tube thinning, etc. It is possible to obtain a heat transfer tube having a long life.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a cross-sectional view of a main part of a horizontal heat exchanger as viewed from the front of a boiler, and FIG. 2 compares the ash erosion tendency of a bare tube (bare tube) with that of a finned tube (finned tube). It is shown.

In the present embodiment, the same parts as those of the related art are denoted by the same reference numerals and are denoted by the same reference numerals in the drawings, and redundant description will be omitted.

The present embodiment is similar in general construction to the conventional one, but several panels (several) from both sides of the boiler are bare tubes without fins, that is, bare tubes 4.
, And the difference between the two is that the interval between the panels (tube interval) is smaller than the interval between the tubes of the finned tubes 3 arranged on the center side.

That is, since the bare tube 4 has high resistance to a high-speed oblique flow, in the present embodiment, the bare tube 4 is arranged over several panels from the side wall side.

However, in general, the bare tube 4 has a smaller gas flow resistance than the finned tube 3 having the same diameter,
When these are arranged at the same interval as the finned tube 3, the gas flow concentrates on the bare tube 4 and separately,
There is a possibility that an obstacle in terms of heat transfer performance or wall thinning due to ash erosion in the bare tube 4 and the side wall tube portion may occur.

Therefore, in the present embodiment, as described above, the gas flow resistance at the position of the finned tube 3 is compared with the gas flow resistance of the finned tube 3 so as to be equal to or higher than the gas flow resistance of the finned tube 3. By arranging the finned tubes 3 at appropriate intervals, the gas flow does not concentrate on the side wall side, and together with the strength of the bare tube 4 against the oblique flow, the occurrence of ash erosion at this portion is prevented. Is what you do.

The inventors of the present invention conducted an experiment to confirm the wear amount of the heat transfer tube under the conditions of ash concentration: 50 g / Nm ³ , gas flow rate: 30 m / s, and operation time: 64 hours. The results shown in FIG. 2 were obtained in comparison with the experimental results of the conventional apparatus under the same conditions.

That is, in FIG. 2, the vertical axis represents the amount of wear of the heat transfer tube, and the horizontal axis represents the number of steps from the gas entrance surface to the heat transfer tube element, plotted with black circles. The change situation due to the bare tube (bare tube) of the form and the change situation due to the conventional finned tube (finned tube) plotted by white circles are shown for each of the oblique flow (broken line) and the direct flow (solid line). The cases are shown separately.

As shown by the results, the present embodiment has high abrasion resistance against oblique flow, and generates less than about half of the conventional wear, in other words, about twice as long life. It became clear that we could do that.

When the gas flow is a direct flow, the bare tube 4 of the present embodiment and the finned tube 3 of the conventional apparatus have a slight difference depending on the number of stages. Indicates that there is not much difference between the two.

Although the present invention has been described with reference to the illustrated embodiment, the present invention is not limited to such an embodiment.
It goes without saying that various changes may be made to the specific structure within the scope of the present invention.

[0026]

As described above, according to the present invention, the drift preventing plate is provided above the heat exchange tube on the side wall of the boiler, and the heat exchange tube is constituted by a bare tube on several panels on the side wall side and a finned tube on the center. However, the adjacent space between the bare tubes is narrowed so that the gas flow resistance is equal to or more than that of the finned tube portion to constitute a horizontal heat exchanger. And, by the bare tube which narrowed the interval between adjacent bare tubes so that the gas flow resistance becomes equal to or more than that of the finned tube, the gas flow is not unnecessarily concentrated on the side wall side, and Combined with the characteristics of a bare tube that is strong against oblique flow, ash erosion and tube thinning can be prevented, resulting in a long-life heat transfer. It is those that can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a main part of a horizontal heat exchanger according to an embodiment of the present invention, as viewed from the front of a boiler.

FIG. 2 is an explanatory diagram showing a tendency of ash erosion between a bare tube and a finned tube in comparison.

FIG. 3 is a bird's-eye view of a finned tube of a general horizontal heat exchanger.

FIG. 4 is a cross-sectional view of a main part of a conventional horizontal type heat exchanger viewed from the front of a boiler.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 side wall pipe 2 drift prevention plate 3 finned tube 4 bear tube 4 A gas flow direction a side wall side flow b center flow

Claims (1)

[Claims] 1. A drift prevention plate is provided above a heat exchange tube on a side wall of a boiler, and the heat exchange tube comprises a few panels on a side wall side as a bare tube and a central portion as a tube with fins. A horizontal heat exchanger characterized in that the distance between the heat exchangers is narrowed so that the gas flow resistance is equal to or greater than that of the finned tube.