JPS58160798A - Heat exchanger - Google Patents

Abstract

PURPOSE:To lower the thermal stress that will occur in a tube plate section, by arranging circular such that each of the circular pipes is spaced away from the inner surface of each hole of the tube plate and sealing each of the thus formed spaces with a sealing mechanism to prevent a fluid from flowing in the space, in a heat exchanger that will be operated under high heat transition conditions. CONSTITUTION:Heat conduction pipes 3 extend from the holes 2 in the tube plate 1 into the heat exchanger, and the circular pipes 4 are inserted into the holes 2 with a space between the inner wall surface of the hole 2 and the circular pipe 4. A piston ring 5 is fitted in a groove 4A of the cylider 4 so that the space between the inner wall surface of the hole 2 and the circular pipe 4 is sealed. The high temperature fluid ascending in the heat conduction pipes 3 passes through the circular pipes 4 into a water chamber 10. In this case, the difference of longitudinal thermal expansions of the inner wall surface of the hole 2 and the circular pipe 4 will be absorbed by the sliding of the piston ring 5. The difference of radial thermal expansions of the inner wall surface of the hole 2 and the circular pipe 4 can be offset by the resilient deformation of the piston ring 5. Therefore, in case where the heat exchanger is operated under high heat transition conditions, the thermal stress in the tube plate 1 can be prevented from occuring.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat exchanger 4 having a tube plate, such as a steam generator, and particularly to reduce thermal stress in the tube plate portion of a heat exchanger operated under discoloring thermal transient conditions. The present invention relates to a heat exchanger suitable for.

The structure of the tube plate of a conventional heat exchanger such as a steam generator III is such that a large number of holes are formed in the tube plate and a large number of heat transfer tubes are arranged from these holes toward the center of the vessel. It has become. Therefore, the fluid flowing inside the heat transfer tube is boiled so as to directly contact the inner wall surface of the nine holes formed in the tube plate.

Therefore, the area near the center of a signboard with many holes is ll1
Although it quickly follows the temperature change of the fluid in the ili@ state, there are no holes in the peripheral part of the tube sheet, and
Since it is a fleshy part, it has poor ability to follow the temperature change of the fluid flowing through the hole in the tube sheet. As a result, there is a problem in that large thermal stress is generated due to a large temperature difference between the central portion and the peripheral portion of the tube sheet.

An object of the present invention is to provide a heat exchanger capable of reducing thermal stress generated in a tube sheet portion of a heat exchange section operated under severe thermal transient conditions.

In order to achieve the above objective, it is necessary to
Possible means include improving the ability to follow temperature changes and making the ability to follow temperature changes worse near the center of the tube sheet. Present invention F
Structure of i heat exchanger! i! *=Jt is adopted, which is highly effective in reducing thermal stress without causing any higher problems.

However, the present invention provides a rounded seal mechanism in which a circular tube is disposed in a hole of a tube plate with a gap between the inner wall surface of the hole and the outer circumferential surface of the circular tube and the inner wall surface of the hole. It was established.

Embodiments of this invention will be described below with reference to the accompanying drawings. 1st
2 and 2 show an embodiment of the present invention, in which a large number of holes 2 are formed in a tube plate 1, and a large number of heat exchanger tubes 3 extend from each hole 2 toward the center of the vessel. . A circular tube 4 is inserted into each of these holes 2 with a gap between the inner wall surface and the inner wall surface.

This circle f4 is a groove 4 along the circumferential direction as shown in FIG.
A piston ring 5 is fitted into these grooves 4A. This results in a seal between the inner wall surface of the hole 2 and the circular tube 4. The outer periphery of the nine-round tube 4 protruding from the top of the tube plate lx is fixed to the support plate 6 by welding. In FIG. 1, a support frame 7 is provided extending upward from a position 3111 on the outer peripheral surface of the support plate 6, and a locking member 8 extending in both directions from the upper end of the support frame 7 is fixed. This locking member 8 is installed in the heat exchanger in a state where it is engaged with a stepped portion provided on the seventh rank portion 9.

In the heat exchanger having such a configuration, the heat exchanger tube 3
The high temperature fluid rising inside the ice chamber lO after passing through the circle f4
leading to. During the flow of fluid with a higher temperature, the hole 2
The difference in thermal expansion between the inner wall surface of the circular tube 4 and the axial direction of the circular tube 4 is
extends in the axial direction, in which case it can be absorbed by sliding of the piston ring.

Thermal expansion g in the radial direction of the inner 11 surfaces of the round hole 2 and the circular tube 4
kM is compensated by the elastic deformation of the piston ring 4A. Therefore, the high temperature fluid flowing into the hole from the heat transfer tube 3 flows into the hole 2.
It does not flow into the gap between the inner surface of the tube 4 and the outer wall surface of the circular tube 4. As a result, since gas exists between the inner wall surface of the hole 2 and the inside of the circular tube 4, it serves as a heat insulating layer, and a large thermal excess is generated in the fluid, causing thermal transients during travel to the circular tube 4. Since it takes time to pass through the gap between the circular tube 4 and the hole 2 and reach the inside of the tube sheet, the metal temperature change near the center of the tube sheet 1 is adjusted to the same degree as the metal temperature change at the periphery of the tube sheet 1. It is possible to get closer. Therefore, even when operating under large thermal transient conditions, it is possible to suppress the generation of thermal stress due to the temperature difference between the center and peripheral portions of the tube sheet l.

In this embodiment, during horizontal flaw detection and repair work in the heat transfer tube 3, the circular tube 4, support plate 6, support frame 7, and locking member 8 can be lifted upward in the figure as one body and removed. Therefore, repair work will not be a hindrance. In addition, since the flow rate of the fluid introduced into the circular tube 4 from the heat transfer [3] is quite high, there is a risk that the circular tube 4 may shake, but the piston ring 4A prevents the circular tube 4 from deflecting. It's colored.

FIG. 3 shows another embodiment of the present invention, which differs from the embodiment shown in FIGS. 1 and 2 in that the lower end of the circular tube 11 is expanded into a conical shape. In this case, circular pipe 1
1 and the piston ring can be reduced.

#! FIG. 4 shows another embodiment of the present invention, and FIGS.
The difference from the embodiment shown in the figure is that the hole 1 formed in the tube sheet l
The diameter of the heat exchanger tube 2 is enlarged so that the inner diameter of the circular tube 13 becomes equal to the inner diameter of the heat transfer tube 3. According to this embodiment, it is possible to reduce the flow resistance of the fluid, and since the inner diameter of the circular tube 13 is large, even in the case of flaw detection and erosion of heat transfer tubes, there is no need to remove the circle f13. A flaw detector, etc. can be inserted into the

In the present invention, instead of forming a groove in the circular tube and fitting the piston ring into the groove, the ring may be directly fixed to the circular tube by burning.

In addition, in the case of FIGS. 1 and 2, since gas is interposed in the gap between the inner wall surface of the hole 2 and the circular tube, there is an effect that the temperature followability near the center of the tube sheet l is lowest. If the fluid does not flow within the gap between the inner surface 11 of the hole 2 and the circular tube 4, the temperature followability in the vicinity of the center shaft of the tube plate 1 can be lowered. As such a means, by using a cylindrical support member in place of the support frame 7 in FIG. It is possible to block the flow of fluid at the 9th point where the surface becomes a dead end. Therefore, it is possible to lower the followability of m near the center of the tube sheet 1. However, in this case, there is a risk that the circular tube 4 may bend, so it is desirable to provide a supporting member installed between the circular tube 4 and the inner wall of the hole in place of the four piston rings.

Ideally, the piston ring and support member provided in the gap between the inner wall surface of the hole and the circular pipe should have a small coefficient of thermal expansion and be equivalent to the material forming the tube sheet 1. From a practical point of view, it is desirable that the coefficient of thermal expansion is the same as that of the material of the tube sheet 1.

As described above, according to the present invention, the temperature change followability near the center of the tubesheet can be made lower than the temperature change followability near the periphery of the tubesheet. By reducing the temperature difference, the generation of thermal stress can be reduced, which has the effect of increasing the integrity of the structure.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view of the main part showing one embodiment of the present invention, II
Figure 2#'i#! FIG. 1 is an enlarged view of the main part, and FIGS. 3 and 4 are longitudinal sectional views of the main part showing other embodiments of the present invention. l...tube sheet, 2...hole, 3...heat exchanger tube, 4...
Circular tube, 5... Piston ring, 6... Support plate, 7.
...Support frame, Fig. 1 Fig. 21￥1 Fig. 3 Fig. 6

Claims (1)

[Claims] 1. In a nine-heat exchanger equipped with a tube plate in which a large number of holes are formed and a heat transfer tube extending into the container from the holes, A heat exchanger characterized in that a circular pipe is arranged with a gap between the wall surface and a sealing mechanism that prevents liquid from flowing between the outer peripheral surface of the circular pipe and the inner wall surface of the hole. vessel. 2. C/L? Claim 1, wherein the mechanism is a piston ring provided in the gap between the circular tube and the 411 surface inside the hole.
Heat exchanger as described in section. 3. The heat exchanger according to claim 1, wherein the sealing mechanism is a close structure between the supporting member and the flange, which extends from the tube plate and is provided along the inner surface of the flange. 4. The heat exchanger according to claim 3, wherein a support member is provided between the circular tube and the inner wall surface of the hole.