JPH0727300A - Mixed flow piping structure - Google Patents

Abstract

(57) [Summary] [Structure] A thermal sleeve arranged coaxially with the main pipe from the branch pipe is attached to the main pipe of the mixing pipe where high-temperature water and low-temperature water join. Set up. [Effect] In the mixed flow pipe section, it is possible to sufficiently reduce the temperature difference before the two fluids having a temperature difference are brought into contact with each other and to have high mixing performance without requiring a complicated shape.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to piping for thermal power plants and nuclear power plants, and more particularly to suppressing the occurrence of thermal stress and thermal fatigue due to wall temperature fluctuations in the mixing portion piping when hot water and low temperature water come into contact with each other. And a mixing performance mechanism suitable for promoting mixing of both fluids.

[0002]

2. Description of the Related Art FIG. 3 shows a basic confluent piping structure which has been used in the prior art in consideration of reduction in temperature difference. In the structure of FIG. 3, the heat transfer area is not so large, and when the two fluids having a large temperature difference are mixed, the two fluids come into contact with each other without sufficiently reducing the temperature difference. Further, in the structure shown in FIG. 3, it is considered that the two fluids are separated into the center and the wall side, respectively, and the reaching distance for reaching the thermal equilibrium between the two fluids is considerably long. Therefore, it can be said that it is preferable from the viewpoint of the mixing performance. Absent. Next, FIG. 4 is shown as an example similar to the present invention. The figure below shows the temperature changes in the flow direction of each fluid. FIG. 4 shows a mixing promoting structure of a connecting pipe disclosed in Japanese Patent Laid-Open No. 59-39331. From the structure of FIG. 4, the mixing performance seems to be good. However, the fluid B discharged from the small holes remains directly mixed with the mainstream fluid with a large temperature difference, and the fluid D has a temperature difference from the fluid B ejected from the small holes as shown in the figure below. It is considered that they will come into direct contact as they are and cause temperature fluctuations. Therefore, it is considered that thermal fatigue is caused on the thermal sleeve 4 due to temperature fluctuation, and it is considered to be not so preferable from the viewpoint of thermal fatigue. Further, the pressure loss of the tributary flow is large, and it is not preferable from the viewpoint of pressure loss. Although the invention of FIG. 4 is structurally similar to the present invention, the inflow path of the fluid in the branch pipe is fundamentally different from that of the present invention due to the presence or absence of the fluid stop portion 5. Further, the present invention aims at improving the heat transfer performance by increasing the contact area through the wall surface on the thermal sleeve, and at the time of direct contact mixing of both fluids, the effect of rapid mixing by increasing the contact area of both fluids. The effect to do is also different.

[0003]

In a mixed flow pipe in which a high temperature water pipe and a low temperature water pipe merge with each other with a large temperature difference, two points of view, that is, a large reduction in temperature difference and high mixing performance, are taken into consideration. Therefore, it cannot be said that the conventional invention has sufficient performance. Further, even if the temperature difference can be sufficiently reduced, there are problems that the shape is complicated and the pressure loss increases. The invention as shown in FIG. 4 has a structure in which hot water and cold water are almost directly contact-mixed with each other without reducing the temperature difference, which is not preferable from the viewpoint of thermal fatigue.

An object of the present invention is to suppress temperature fluctuations while
It is possible to sufficiently reduce the temperature difference between the two fluids having a temperature difference and to achieve high mixing performance.

[0005]

In order to suppress thermal fatigue due to temperature fluctuations in a certain part, which is the above-mentioned object, FIG.
By improving the heat transfer performance by modifying the method for reducing the temperature difference by directly contacting and mixing as shown in the figure, removing the direct contact mixing part and expanding the heat transfer area when the fluid in the branch pipe flows into the thermal sleeve. , To reduce the temperature difference. That is, the above-mentioned problem is solved by providing an inner cylinder at the center of the thermal sleeve extending from the branch pipe in the axial direction in the main pipe, and increasing the heat transfer area of the thermal sleeve and the contact area of both fluids at the time of merging contact.

[0006]

[Operation] A thermal sleeve is attached to the mixed flow pipe where the high temperature water pipe and the low temperature water pipe merge with each other with a large temperature difference,
When an inner cylinder is provided at the center of the thermal sleeve, the fluid from the main stream is divided into two regions, a central part and an outer wall part. When the tributary flow enters the thermal sleeve in the main pipe, the tributary flow is sandwiched by the main flow through the pipe walls, and as a result, the heat transfer area becomes large while the temperature gradient of both pipe walls remains high. , Enables high heat transfer. Therefore, the temperature difference between the two fluids is sufficiently reduced before they come into direct contact. After that, both fluids directly contact and mix at the thermal sleeve outlet, at which time the contact area of both fluids is large,
Since the tributary flow has a distribution that spreads throughout the main pipe, high mixing performance can be expected. By these actions, two fluids having a temperature difference are prevented from directly contacting and mixing and causing a large temperature fluctuation, and at the same time, it is possible to sufficiently reduce the temperature difference before contacting and to achieve high mixing performance.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. FIG. 1 shows a vertical sectional view of a mixed flow pipe section.

The structure of the mixed flow pipe section will be described. Here, the fluid A in the main pipe is divided into a fluid C and a fluid D at the confluence. After that, the fluid C and the fluid D are the fluid B in the branch pipe.
And a mixed fluid E is generated. This basic structure is
A main pipe 1 which is a main stream is connected to a branch pipe 2 having a thermal sleeve 4 arranged in the main pipe axial direction by welding. The thermal sleeve 4 has an inner cylinder 3 into which the mainstream flow A flows. When the fluid B in the branch pipe flows into the thermal sleeve 4 in the main pipe, the fluid B is sandwiched between the fluid C flowing near the outer wall and the fluid D flowing in the central portion of the pipe, and the fluid B is transferred through the heat transfer between the pipe walls 3 and 4. And the temperature difference between the fluid D and the fluid C decreases. At this time, the temperature gradient and the heat transfer area of both fluids are large, and the heat transfer is large, so that it is possible to sufficiently reduce the temperature difference. As a result, the fluid B, the fluid D, and the fluid C do not directly contact and mix with each other until the outlet of the thermal sleeve 4, and the temperature difference is sufficiently reduced before the thermal sleeve 4
Combine and mix at the exit. That is, the fluid A and the fluid B, which have a large temperature difference, are mixed at the merging portion while suppressing the fluid temperature fluctuation as shown in the figure below. Fluid A is divided into fluid C and fluid D and flows into the thermal sleeve. Due to high heat transfer on the thermal sleeve, the fluid B
The temperature gradually decreases, and the temperatures of the fluid C and the fluid D gradually increase. Since the fluids B and D are sufficiently mixed with each other after the temperature difference is reduced, the amplitude of the temperature fluctuation is not so large. Then, the mixed fluid merges and mixes with the fluid C, but at that time, it is considered that there is almost no temperature difference and the amplitude of the temperature fluctuation is at a considerably low level. Therefore, the two fluids having a temperature difference are merged and mixed while suppressing the fluid temperature fluctuation. After that, the fluid B joins and contacts the fluid C and the fluid D, and at that time, the contact area of both fluids is large, and the distribution is such that the tributary flow spreads throughout the main pipe. Further, when the velocities of the mainstream flow and the tributary flows are different, the velocity distribution has a large velocity gradient widely, the turbulent component is strong, and the velocity distribution is expected to have high mixing performance. Therefore, it is possible to sufficiently reduce the temperature difference before the two fluids having the temperature difference are brought into contact with each other and to achieve high mixing performance. As a result, the safety and reliability of plant piping are secured. The present invention is structurally similar to the invention of FIG. 4, but the inflow path of the fluid in the branch pipe is fundamentally different from the invention of FIG. 4 depending on the presence or absence of the fluid stop portion 5. As a result,
In the structure of (1), it is considered that both fluids directly contact with each other on the thermal sleeve while having a large temperature difference, and a large fluid temperature fluctuation occurs, but in the present invention, both fluids directly contact with each other with a large temperature difference. It has a structure that can prevent and suppress large temperature fluctuations. Further, the present invention aims at the effect of improving the heat transfer performance by increasing the contact area through the wall surface on the thermal sleeve, and the effect of improving the mixing performance by increasing the contact area of both fluids during direct contact mixing of both fluids. And the effect is different.

[0009]

According to the present invention, in the mixed flow pipe section, (1) it is possible to sufficiently reduce the temperature difference while suppressing direct contact mixing of the high temperature water and the low temperature water with a large temperature difference. To do.

(2) A high degree of mixing performance is possible while suppressing large temperature fluctuations.

(3) The shape is not so complicated, and it is possible to sufficiently reduce the temperature difference before direct contact with a relatively low pressure loss and to achieve high mixing performance.

As described above, the present invention can ensure higher safety of the plant piping.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a mixed flow pipe section according to an embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view of a mixed flow pipe section according to another embodiment of the present invention.

FIG. 3 is a vertical cross-sectional view of a conventional mixed flow pipe section.

FIG. 4 is a vertical cross-sectional view of a conventional mixed flow pipe similar to the present invention.

[Explanation of symbols]

1 ... Main pipe, 2 ... Branch pipe, 3 ... Thermal sleeve inner cylinder, 4 ...
Thermal sleeve, 5 ... Fluid stop.

Front Page Continuation (72) Hidekazu Fujimura Inventor Hidekazu Fujimura 502 Kazutachi-cho, Tsuchiura-shi, Ibaraki Hiritsu Seisakusho Co., Ltd. Mechanical Research Laboratory (72) Inventor Yukihiro Asada 3-1-1 Sachimachi, Hitachi, Ibaraki Hitachi Factory Hitachi Factory

Claims (1)

[Claims] 1. A mixing pipe in which high-temperature water and low-temperature water of a pipe for thermal power and nuclear power plants merge, in order to prevent both fluids from directly contacting and mixing with each other with a large temperature difference, the main pipe is inserted from a branch pipe in the coaxial direction of the main pipe. By disposing the inner cylinder into which the mainstream fluid flows in at the center of the thermal sleeve arranged along, the flow inside the main pipe is divided into two regions, the center and the outer wall side, and the fluid with the temperature difference from the branch pipe is divided into the inner and outer wall sides. The mixed flow piping structure is characterized in that the temperature difference between the two fluids is significantly reduced by high heat transfer through the two, and then the two fluids are mixed in direct contact with each other.