JPH09303701A - Exhaust gas boiler evaporator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make all the tubes from the upstream to the downstream of an exhaust gas flow, uniformly perform a heat-exchange, and stabilize the operation of an evaporator by a method wherein the winding number of fins of respective fin tubes, are made smaller for the ones at the upstream side than the ones on the downstream side. SOLUTION: The winding number of fins 8 on a fin tube 7 which is located at the upstream side of an exhaust gas flow 9, is made smaller than the winding number of fins 8 of the fin tube 7 which is located at the downstream side of the exhaust gas flow 9. That is, the relationship between the fin tubes 7 and the fins 8 at the most downstream point A, an intermediate point B and the most upstream point C is constituted in such a manner that the winding number of the fins 8 is largest at the most downstream point A of the exhaust gas flow 9, is intermediate at the intermediate point B, and is smallest at the most upstream point C. By doing so, heat-exchanges are uniformly performed at all the tubes 7 from the upstream to the downstream of the exhaust gas flow 9, and the operation of an evaporator can be stabilized.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a heat exchanger such as an exhaust gas boiler evaporator having a plurality of fin tubes arranged therein.

[0002]

2. Description of the Related Art A conventional device will be described with reference to FIGS. FIG. 3 shows the whole view of the exhaust gas boiler and a schematic system of fluid, and FIG. 4 shows the main part thereof.

Reference numeral 1 denotes a water drum. Water introduced from the water drum 1 to the inlet header 3 through the descending pipe 2 is divided into a plurality of fin tubes 7 at the inlet header 3.

The fin tubes 7 are arranged in an exhaust gas passage not shown in the figure to form the evaporator 4, and the water separated into the fin tubes 7 by the exhaust gas flow 9 flowing through the exhaust gas passage is heat-exchanged. It is (heated) and vaporized.

The steam vaporized in each fin tube 7 and the moisture which has not been vaporized merge at the outlet header 5,
Returning to the water drum 1 through the rising pipe 6, the steam content is sent to another system such as a steam turbine (not shown), and the water content is circulated again through the above system path and is repeatedly heat-exchanged to be vaporized.

As for the fin tube 7 which constitutes the evaporator 4 which performs the basic operation for producing steam in this manner, the fin tube 7 is constructed by mounting fins 8 in a spiral shape on the peripheral surface.

Then, even if any of points A, B and C shown in FIG. 4A is taken, the number of peaks of the fins 8 in each fin tube 7 is as shown in FIG. 4B. Everything is configured the same.

That is, a point C on the upstream side (high temperature), a point B on the way (medium temperature), and a downstream side (low temperature) with respect to the exhaust gas flow 9
All of the fin tubes 7 have the same number of turns 8 at any point A.

[0009]

In designing an exhaust gas boiler, one of the most difficult and paying attentions to date is to make the fluid in the evaporator flow stably. However, since the number of fin turns of the evaporator tube was the same from the exhaust gas upstream side to the downstream side as described above, the heat exchange amount was large in the exhaust gas upstream side (high temperature gas side) tube, and The amount of heat exchange is small.

Therefore, when the heat quantity of the exhaust gas is excessive, the vaporization of the fluid rapidly progresses inside the tube where the heat exchange is large, the vapor volume ratio inside the tube becomes excessive, and the circulation force of the fluid is impeded. Will be done.

Due to this phenomenon, heat absorption imbalance occurs in the tube group, and the planned heat absorption amount of the entire evaporator deviates, so that the evaporation amount and the steam temperature deviate from the planned values, and further the supplied heat amount If the number increases, the inside of the tube will be in an empty state, which may cause a problem of burning out.

The present invention solves the above-mentioned problems in the conventional one, and heat is uniformly exchanged in all the tubes from the upstream side to the downstream side of the exhaust gas flow to stabilize the operation of the evaporator. The challenge is to provide things.

[0013]

The present invention has been made to solve the above problems, and in an exhaust gas boiler evaporator in which a plurality of fin tubes are arranged in an exhaust gas passage, the fin winding number of each fin tube is set. The upstream side provides an exhaust gas boiler evaporator that is smaller than the downstream side, and the heat absorption amount of each tube is designed so that the number of fin turns of the exhaust gas upstream side tube is reduced and it is gradually increased toward the downstream side. So that it is uniform,
Even for exhaust gas with an excessive amount of heat, it is possible to plan a compact evaporator that does not cause imbalance in the internal fluid flow rate in the evaporator, heat absorption amount imbalance, and tube damage. .

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to FIGS. The same members and the like as the conventional ones described above are designated by the same reference numerals in the drawings,
Duplicate description will be omitted.

In the present embodiment, as shown in FIG. 1, the number of turns of the fin 8 in the fin tube 7 on the upstream side of the exhaust gas flow 9 is smaller than that on the downstream side,
In other words, the number of windings of the fins 8 in the fin tube 7 on the downstream side of the exhaust gas flow 9 is larger than that on the upstream side.

That is, the relationship between the fin tubes 7 and the fins 8 at the most downstream point A, the middle point B, and the most upstream point C of the exhaust gas flow 9 shown in FIG. 1A is shown in FIGS. c),
As shown in (d), the number of windings of the fin 8 is largest at the most downstream point A as shown in FIG.
As shown in FIG. 1 (c), it is in the middle position, and at the most upstream point C, FIG.
Is the least configured.

Although the description between the points A, B, and C is omitted, in short, from point A to point B through C
This indicates that the number of turns of the fin 8 is gradually reduced as the number of points is reached.

When determining the number of turns of the fins 8, it is necessary to select the number of turns capable of obtaining the absorbed heat amount so that the vaporization of the fluid does not become excessive with respect to the mass flow rate of the water in the fin tube 7. This work must be carried out sequentially from the fin tubes 7 on the upstream side of the exhaust gas flow, and consideration must be given to securing the required amount of absorbed heat as a whole.

When this work is carried out, it is carried out by using the reference graph of the fluid layer separation judgment shown in FIG. In FIG. 2, the horizontal axis represents the heat flux on the inner surface of the tube and the vertical axis represents the mass velocity in the tube, and the layer separation is determined by the operating pressure in the evaporator. When it is on the upper side, the circulating water in the evaporation pipe can secure a stable flow, and when the plot point is on the lower side,
The mass flow rate of circulating water in the evaporating pipe is not sufficient, the volume ratio of fluid bubbles becomes too large, and the fluid sticks in the pipe, causing poor circulation.

The following table shows an example of selecting the number of fin crests (number of turns) that can obtain stable circulation for a certain evaporator.

[0021]

[Table 1]

Heaviness and He in the tube resulting from the above calculation
The relationship of at Flux is plotted in FIG. 2, and there is no problem when it is above the reference judgment line, but when it is below, the number of fin crests m / inch is reduced and the heat flux (Heat) on the inner surface of the pipe is reduced. By decreasing Flux), it is above the judgment line. This work may be sequentially performed from the upstream side of the exhaust gas, and adjustment may be performed by the number of fins on the downstream side so that the planned heat absorption amount of the entire evaporator can be obtained.

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

[0024]

As described above, according to the present invention, the fluid in the tube can stably flow, and the imbalance of the fluid in the tube, the band flow, etc. can be prevented. When the present invention is applied to a natural circulation type evaporator with a water drum, the amount of heat absorbed in each tube is made uniform, so that a stable water circulation force can be obtained and an unbalanced flow rate in the tube can be obtained. It can be corrected and avoid accidents such as tube damage.

[Brief description of drawings]

FIG. 1 shows a schematic structure of an evaporator according to an embodiment of the present invention, (a) is a general view, (b) is a detailed A part of (a),
(C) is an explanatory view of details of the B part of (a), and (d) is a detailed view of the C part of (a).

FIG. 2 is a graph showing the criteria for fluid layer separation in each fin tube in FIG.

FIG. 3 is a schematic system diagram of a conventional exhaust gas boiler evaporator.

4A and 4B show the main parts of FIG. 3, in which FIG. 4A is an overall view of the evaporator, and FIG.

[Explanation of symbols]

 1 Water Drum 2 Downcomer 3 Inlet Header 4 Evaporator 5 Outlet Header 6 Upcomer 7 Fin Tube 8 Fin 9 Exhaust Gas Flow

Claims (1)

[Claims] 1. An exhaust gas boiler evaporator comprising a plurality of fin tubes arranged in an exhaust gas passage, wherein the number of fin turns of each fin tube is smaller on the upstream side than on the downstream side. Boiler evaporator.