JPS60228898A - Heat transfer tube made of titanium - Google Patents

Abstract

PURPOSE:To obtain the heat transfer tube of titanium, which is prevented from stress concentration of annular protuberance and improved in the rigidity thereof, by a method wherein a plural rails of axial protuberances, intersecting orthogonally to the annular protuberances of inner surface of the tube, are provided in the heat transfer tube. CONSTITUTION:The annular protuberances 11 are arranged axially on the inner wall of main body 10 of the tube with constant spaces. The annular protuberances 11 are formed so as to have vertical surfaces 12 in order to improve the overall heat-transfer coifficient efficiently and slanted surfaces 13 are formed from the vertical surfaces 12 toward the downstream side of heat medium. Four rails of axial protuberances 14 are formed axially along the inner wall of main body 10 of the tube. The section of the axial protuberance 14 is circular and is connected to the inner wall of the tube main body 10 smoothly with a curvature (r). In case the impact force of steam or the like, for example, is exerted vertically on the outer periphery of the heat transfer tube of titanium of such constitution, the impact force may be supported by the axial protuberances of the tube and, as a result, the stress concentration, effecting on the roots of vertical surfaces 12 of the annular protuberances 11, may be mitigated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a titanium heat exchanger tube used in a condenser or the like.

[Technical advancement of the invention and its problems] For example, in a nuclear power plant, a condenser is installed to condense the steam that has finished its work in the turbine using cooling water and convert it into condensate.

FIG. 2 shows such a condenser, and in the figure, reference numeral 1 indicates the main body. An artificial water chamber 2 is formed on one side of the body trunk 1, and an outlet water chamber 3 is formed on the other side. A tube plate 4.5 is provided in each of the inlet water chamber 2 and the outlet water chamber 3, and a large number of heat transfer tubes 6 are connected between these tube plates 4.5.

In such a condenser, steam 7 flowing from the upper part of the main body shell 1 is condensed by the cooling water flowing in the heat transfer tubes 6 and turned into condensed water.

Generally, in such a condenser, seawater is often used as the cooling water that passes through the heat exchanger tubes 6, and this seawater contains many impurities such as marine organisms. This causes the heat exchanger tubes 6 to corrode.

Therefore, conventionally, ferrous sulfate is mixed into the seawater used as cooling water to form a protective film on the inner surface of the heat exchanger tube 6 to prevent marine organisms from adhering to the inner wall of the heat exchanger tube 6. prevents corrosion.

On the other hand, in recent power plants, hydrazine, ammonia, etc. are injected into the water supply for the purpose of water quality control of the boiler supply water. Hydrazine decomposes under high temperature and generates ammonia, which is discharged together with steam into the condenser via the turbine, accumulates in the condenser as a non-condensable gas, and corrodes the outer wall of the heat transfer tube 6. There is a problem.

On the other hand, conventionally, the heat exchanger tube 6 has been formed of aluminum plus, gupronickel, etc., but in such a heat exchanger tube 6, ferrous sulfate cannot be injected due to corrosion problems, and ammonia Therefore, there is a problem in that it suffers from a large amount of corrosion.

Therefore, recently, heat exchanger tubes 6 made of titanium, which has excellent corrosion resistance, have been used. Heat exchanger tubes made of titanium have much better corrosion resistance than conventional heat exchanger tubes, but the problem is that the material is expensive, making the product relatively expensive.

For these reasons, condensers equipped with heat transfer tubes made of titanium are required to improve the heat transfer coefficient and reduce the heat transfer area to a greater extent than in the past.

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

1/to = 1/h + + 1/h o +t /k
+RF Here, K: Heat transfer coefficient hI: Cooling water side heat transfer coefficient ho: Steam side heat transfer coefficient: Thermal conductivity of the pipe material [: Pipe wall thickness RF: Contamination coefficient.

In general, the performance of condensers in thermal power plants, nuclear power plants, etc. is determined by the heat transfer coefficient on the cooling water side. Therefore, in order to increase the heat transfer coefficient, it is necessary to improve the heat transfer coefficient on the cooling water side.

As a means of improving the heat transfer coefficient on the cooling water side,
As shown in FIG. 3, it is effective to provide an annular protrusion 8 vertically rising on the inner wall of the heat exchanger tube 6 to disturb the flow of cooling water, and this can also be applied to the heat exchanger tube 6 made of titanium.

However, in power plants, especially nuclear power plants, when a turbine generator load is cut off due to a power system accident, the steam generated by the reactor is bypassed to the condenser without shutting down the reactor, and the reactor output is reduced. A turbine bypass system is installed to reduce the amount of steam and safely shift to isolated operation within the plant, but there is a problem that the heat transfer tubes 6 may be damaged due to the impact force of the incoming steam when the turbine bypass system is activated.

That is, when the turbine bypass system is in operation, the steam generated in the nuclear reactor is introduced into the condenser after its temperature and pressure are reduced. As shown in FIG. It receives bending stress due to impact force in the vertical direction,
This bending stress causes stress concentration on the vertically rising portion 9 of the annular protrusion 8, which may cause the heat exchanger tube 6 to break from this portion and cause a cooling water leakage accident.

[Object of the invention] The present invention has been made in response to such conventional circumstances,
Prevents stress concentration on the annular protrusion formed inside the heat exchanger tube,
The present invention aims to provide a titanium heat exchanger tube with increased rigidity.

[Summary of the Invention] The titanium heat exchanger tube of the present invention has an inner surface of the titanium tube with
The tube comprises a plurality of annular projections formed at intervals in the axial direction, and a plurality of axial projections formed linearly over the entire length of the tube at intervals in the circumferential direction and perpendicular to the annular projections, The annular protrusion has a vertical surface that rises slightly perpendicularly from the inner surface of the tube, and an inclined surface that is connected to the vertical surface and gradually expands the flow path toward the downstream side, and whose terminal end is connected to the inner surface of the tube, The axial protrusion is characterized in that its cross section is formed into a substantially semicircular shape, and both sides of the semicircular shape are smoothly connected to the inner surface of the tube.

[Embodiment of the Invention] The details of the present invention will be described below with reference to an embodiment shown in the drawings.

FIG. 4 shows an embodiment of the titanium heat transfer tube of the present invention, and in the figure, reference numeral 10 indicates a tube body made of, for example, titanium, through which a heat medium such as cooling water made of seawater flows. Annular protrusions 11 are arranged on the inner wall of the tube body 10 at regular intervals in the axial direction. This annular projection 1
Reference numeral 1 designates a heat medium inflow end as a vertical surface 12 that stands up perpendicularly from the inner wall of the tube body 10 . An inclined surface 13 connected to the inner wall of the tube body 10 is formed on the downstream side of the heat medium from this vertical surface 12 . Note that the reason why the annular projection 11 is made to stand perpendicularly to the inner wall of the tube body 10 is that the heat transmission coefficient can thereby be efficiently improved. In addition, the tube diameter of the heat exchanger tube may be set, for example, from 25 mm to 38 mm. Assuming mi, it is desirable that the height of the annular projections 11 be set to 0.3 mm to 0.5 mm, and the interval between the annular projections 11 be set to about 30 to 60 times the height of the annular projections 11.

Four axial protrusions 14 are formed along the inner wall of the tube body 10 in the axial direction.

As shown in FIG. 1, this axial projection 14 has a semicircular cross section and is smoothly connected to the inner wall of the tube body 10 by a curve r. This can prevent stress concentration at the connection portion. Note that the number of axial protrusions 14 is preferably increased or decreased depending on the magnitude of the impact force acting on the heat exchanger tube.

In the titanium heat exchanger tube configured as J: above, for example, when an impact force such as steam is applied perpendicularly to the outer periphery of the titanium heat exchanger tube, this impact force is supported by the axial protrusion 14, and this impact force is supported by the axial projection 14. As a result, the stress concentration that conventionally acts on the root portion of the vertical surface 9 of the annular projection 11 can be alleviated. As a result, the rigidity of the heat exchanger tube can be significantly increased compared to the conventional one, and damage to the heat exchanger tube can be prevented.

[Effects of the Invention] As described above, according to the titanium heat exchanger tube of the present invention, it is possible to alleviate the stress concentration that occurs at both vertical rising portions of the annular projection of the titanium heat exchanger tube, and the titanium heat exchanger tube has high rigidity and is resistant to breakage. It is possible to provide fewer titanium heat exchanger tubes.

[Brief Description of the Drawings] Figure 1 is a cross-sectional view taken along the line I-I in Figure 4, Figure 2 is a longitudinal cross-sectional view showing a conventional condenser, and Figure 3 is a conventional heat exchanger tube. FIG. 4 is a vertical cross-sectional view taken along the line ■-■ in FIG. 1, and FIG. 5 is a vertical cross-sectional view showing a condenser using the titanium heat exchanger tube of the present invention. 10......Tube body 11......Annular protrusion 12...
・・・・・・Vertical plane 13 ・・・・・・・・・・・・ Inclined plane 14 ・・・・・・・・・・・・ Axial protrusion Attorney Patent attorney Sa Suyama − 3rd Figure 1

Claims (2)

[Claims] (1) A plurality of annular protrusions formed on the inner surface of a titanium tube at intervals in the axial direction, and a plurality of stripes formed linearly over the entire length of the tube at intervals in the circumferential direction and perpendicular to the annular protrusions. The annular protrusion has a vertical surface slightly perpendicular to the inner surface of the tube, and the annular protrusion is connected to this vertical surface to gradually expand the flow path toward the downstream side, and the end of the annular protrusion is connected to the inner surface of the tube. and an inclined surface connected to the
The titanium heat exchanger tube is characterized in that the axial protrusion has a substantially semicircular cross section, and both sides of the semicircle are smoothly connected to the inner surface of the tube. (2) The titanium heat exchanger tube according to claim 1, wherein the height of the axial projection is substantially the same as the height of the annular projection.