JPS6089681A - Condensor - Google Patents

Abstract

PURPOSE:To improve a rate of thermal flow and prevent a cooling pipe from being cracked by a method wherein annular projections water and some inclination surfaces gradually descending downstream of the raised surfaces are arranged axially in a spaced-apart relation to each other at the inner surfaces of the cooling pipes and the inner surfaces at a part contacting with pipe plates of the cooling pipes, is made as a smooth flat surface. CONSTITUTION:Annular projections 11 are arranged and spaced apart axially, i.e. in a direction of flow of fluid at the inner surfaces of titanium cooling pipes 10 for use in connecting a pipe plate 4 of an inlet water chamber 2 to a pipe plaste 5 for outlet water chamber 3. The annular projections 11 are formed by surfaces 12 crossing at a right angle to a direction of flow positioned upstream of the flow direction of fluid and inclination surfaces 14 communicating gradually with the inner surface 13 of the cooling pipe from the surfaces 12 toward the downstream of the flow direction. Truncated conical space 15 is axially spaced apart and defined by the inclination surfaces of annular projections 11 of which areas are enlarged in a direction of flow of cooling water.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a condenser in which an annular projection is provided on the inner circumferential surface of a cooling pipe to improve the heat transfer effect.

[Technical background of the invention]

For example, in a nuclear power plant, steam that has completed its work in a turbine is guided to a condenser, where it is condensed by cooling water that passes through cooling pipes installed horizontally within the condenser, and the resulting condensed water is returned to the boiler. That's what I do.

As shown in FIG. 1, the above condenser is provided with an inlet water chamber 2 on one side of a main body 1 and an outlet water chamber 3 on the other side, and a tube plate 4 of the inlet water chamber 2 and an outlet water chamber 3. The tube plate 5 is connected to a large number of horizontally installed cooling pipes 6, 6, . . . , and seawater is often used as the cooling water passing through the cooling pipes 6. The seawater contains many impurities such as marine organisms, which adhere to the inner surface of the cooling pipe and cause corrosion of the cooling pipe.

Therefore, ferrous sulfate is mixed into the seawater that serves as the cooling water.
A protective film is formed on the inner surface of the cooling tube to prevent corrosion of the cooling tube due to marine organisms adhering to the inner surface.

However, ferrous sulfate mixed into seawater is discharged into the sea together with the seawater, causing seawater pollution, making it difficult to use it due to problems in pollution control.

On the other hand, in recent power plants, hydrazine, ammonia, etc. are injected for the purpose of water quality control of boiler feed water.Hydrazine generates ammonia under high temperature, and this ammonia is with steam,
It passes through the turbine and is discharged to the condenser, where it accumulates as non-condensable gas and can corrode the outer surface of the cooling pipes.

On the other hand, cooling pipes are made of aluminum plus, cupronickel, etc., but recently cooling pipes have been made of titanium, which has excellent corrosion resistance, because ferrous sulfate cannot be injected and to prevent corrosion due to ammonia. It is also used. Titanium cooling pipes have better corrosion resistance than regular cooling pipes, but the material is expensive, making the product more expensive.

Therefore, condensers equipped with titanium cooling pipes are required to improve the heat transfer coefficient and significantly reduce the heat transfer area.

Generally, the performance of a condenser is evaluated by the heat transfer coefficient, and the heat transfer coefficient is defined by the following formula.

Here: Heat transfer coefficient, h, Cooling water side heat transfer coefficient, ho
= Steam side heat transfer coefficient, N: Thermal conductivity of the pipe material, t: Pipe wall thickness, CH: Fouling coefficient thermal power, The performance of a condenser in a nuclear power plant is defined by the cooling water side heat transfer coefficient. Therefore, the heat transfer coefficient K
In order to improve this, it is necessary to improve the heat transfer coefficient h1 on the cooling water side.

Providing projections on the inner surface of the tube is an effective means of improving heat transfer on the cooling water side, and is also applied to titanium cooling tubes. The end of the pipe is expanded, the expanded part is inserted into the tube plate, and both are welded.

[Problems with background technology]

However, in the above type of condenser, the contact area between the tube plate and the cooling tube is expanded from the inside of the cooling tube and welded, so when expanding the tube,
Stress may concentrate on the protruding parts, causing cracks or defects. Up to now, it has not been possible to sufficiently detect such inherent defects, and if left untreated, this will eventually lead to a cooling water leakage accident into the Maypin system.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned points, and is equipped with a cooling pipe having protrusions on the inner surface, and prevents stress concentration on the protruding portion of the cooling pipe, thereby preventing the occurrence of cracks in the cooling pipe. The purpose is to provide condensers.

[Summary of the invention]

In the present invention, the inner surface of the cooling pipe has an upright surface on the upstream side in the cooling water flow direction and an inclined surface that gently descends from the upright surface to the downstream side, so that the area is expanded in the cooling water flow direction. In addition to providing annular protrusions with inclined surfaces at intervals in the axial direction, the inner surface of the portion of the cooling tube that contacts the tube plate is made a smooth surface to improve heat transfer coefficient and reduce stress concentration on the protrusions during tube expansion. This prevents the cooling pipe from cracking.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 2, the same members as in FIG. 1 are given the same reference numerals.

In FIG. 2, reference numeral 10 denotes a titanium cooling pipe connecting the tube plate 4 of the inlet water chamber 2 and the tube plate 5 of the outlet water chamber 3,
On the inner surface of the cooling pipe 10, annular protrusions 11, 11 are provided at intervals in the axial direction, that is, in the fluid flow direction.

As shown in FIG. 3, the annular protrusion 11 has a surface 12 located on the upstream side in the fluid flow direction and perpendicular to the fluid flow direction;
The cooling pipe inner surface 1 is gently flowed downstream from this surface in the flow direction.
3, and a frusto-conical space 15 is defined in the axial direction by the inclined surface of the annular protrusion 11 whose area is expanded in the direction of flow of the cooling water.

Experimentally, the height of the annular protrusion 11 was set to 0.3 to 0.5 mm,
The optimum condition is that the interval between the annular protrusions 110 is approximately 30 to 60 times the height.

On the other hand, the inner surface of the portion of the cooling pipe 10 that contacts the tube plates 4 and 5 is the same surface as the surface 13 that does not have the annular projection 11, and does not have the annular projection 11 in this portion.

Therefore, when the cooling pipe 10 is expanded and welded to the tube sheets 4 and 5, there is no cracking in the cooling pipe, and no annular protrusion is formed in the part corresponding to the tube sheet, so stress concentration can occur. No inherent defects occur.

In turbulent heat transfer in a pipe, a certain distance from the entrance of the pipe becomes a run-up section where the boundary layer is not fully developed, and in this run-up section, the local heat transfer coefficient is the heat transfer coefficient for the developed turbulence. It reaches several times the transmission coefficient. The area that has an effect on increasing the local heat transfer coefficient is limited to a distance from the tube inlet to about 20 times the tube inner diameter, and the boundary layer gradually develops from the tube inlet side, and the heat transfer increases accordingly. The coefficient gradually decreases, and finally, when the boundary layer is completely developed, the tube inside heat transfer coefficient reaches a value given by the Dittus-Boelfer equation or the like. The condenser tube plate is 3
Since the thickness is approximately 0 to 40 mm, the heat transfer performance is not affected even if the inner surface of the portion that contacts the tube sheet on the cooling tube inlet side is made smooth.

In the above embodiment, a condenser using a cooling pipe having protrusions has been described, but it is of course applicable not only to a condenser but also to a heat exchanger having the same function.

〔Effect of the invention〕

As described above, according to the present invention, even if an annular projection having an inclined surface with an enlarged 'dEiR in the cooling water flow direction is provided inwardly of a cooling pipe, there is no stress concentration on this annular projection during welding. , so there are no cracks or inherent defects in the cooling tubes.
Furthermore, by specifying the shape of the annular protrusion, it is possible to improve the heat transmission coefficient and achieve efficient heat transfer.

[Brief explanation of drawings]

Figure 1 is a side view showing a part of a conventional condenser in cross section;
The figure is an enlarged cross-sectional view of a main part of a condenser according to the present invention, and FIG. 3 is a diagram showing the shape of an annular projection. 4.5... Tube plate, lO... Cooling pipe, 11... Annular projection, 12... Orthogonal surface, 13... Cooling pipe inner surface, 14
... Inclined surface, 15 ... truncated conical space. Applicant's agent Kiyoshi Inomata

Claims (1)

[Claims] 1. An inlet ice chamber is provided on one side of the main body shell, and an outlet ice chamber is provided on the other side, and these rain ice chambers are connected by a plurality of cooling pipes to communicate with each other, and the steam sent to the main body shell is In the condenser, the condenser is configured to condense the cooling water through the cooling pipe, and the cooling pipe has an annular inner surface having inclined surfaces spaced apart in the axial direction and whose area expands in the flow direction of the cooling water. A condenser characterized by being provided with protrusions and having a smooth inner surface at a portion of the cooling tube that contacts the tube plate. 2. The condenser according to claim 1, wherein a truncated conical flow path space is formed by an annular projection provided on the inner surface of the cooling tube.