JPS6262243B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a shell-type heat exchanger, primarily a heat exchanger for exchanging heat between molten metal and water, and a method for manufacturing the same.

Molten metals, such as sodium, are used in nuclear reactor technology as cooling media in fast breeder reactors, primarily due to their high heat capacity. Due to the high operating temperatures and corrosive nature of molten metals, heat exchangers used in heaters and reheaters are made of austenitic steel, but these units nevertheless present considerable damage. has been discovered. Despite the strictest quality control during production,
The tube-to-tube plate joint was damaged.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved shell heat exchanger for use in heat exchange between molten metal and water, which is less prone to failure which could lead to reactions between sodium and water. .

According to the present invention, in a shell heat exchanger using molten metal, each heat exchange tube extends through a respective opening in the tube sheet with a gap between the tube and the tube sheet; is sealed to the tube sheet by a sleeve that stands upright from the tube sheet surface and has its free end sealed to the tube outer wall surface,
The tube and sleeve are joined by an intervening bonding metal that provides a seal, and the bonding metal does not require high-temperature processing such as that required to create a fusion welded joint. This is the type of thing that is not needed at all. In a preferred construction, the sleeve is brazed to the tube and fusion welded to the tubesheet, and the heat exchange tube is constructed as a continuous length of tube within the shell.

By fitting the tubes to the tubesheet using sleeves brazed to the tubes and by making the tubes in the shell from continuous, seamless lengths of tube, the sodium and water barriers in this heat exchanger are achieved. No fusion welding was used.
Thus, according to another interpretation, the invention uses molten metal on the shell side, and all the tubes enter and exit the shell by passing through the individual tubesheet openings with clearance. having a seamless and continuous length over the entire length of each tube, and being sealed at each opening by a sleeve that stands upright from the tube sheet surface of each tube and has a connection with the outer wall surface of the tube at its free end; , and also at the high temperatures required to create a joint by fusion welding, such that this joint reduces the deterioration of the integrity of the tube wall and thus also the barrier between the molten metal and the heat transfer medium within the tube. The present invention relates to a shell-type heat exchanger formed by interposing a bonding metal of a type that does not require any processing to make the joint.

This structure facilitates stress relief at braze points and fusion joints between the sleeve and tubesheet, so that both the tube and tubesheet are placed under high tension, which can increase cracking due to stress corrosion. It seems like it never happens.

In the barrel heat exchanger according to the invention, each tube and the complementary sleeve can be indirectly coupled by providing a tubular mating piece at each end that is brazed to the tube and sleeve, respectively. In this case, the sleeve is provided with means for lateral support of the U-tube extending over the tube with sufficient clearance to facilitate assembly, and with means for lateral support of the U-tube extending along the inner chamber of the shroud and with sufficient clearance to facilitate assembly. the longer leg of each tube passing through the end wall of the extension forming one tubesheet and the flange of the extension extending along the outer chamber of the shroud forming the second tubesheet of the heat exchanger; a shorter leg of each tube passing therethrough, each leg of each tube passing through the complementary tubesheet through a respective opening with a gap between the tube and the tubesheet, and the tube passing through the supplementary tubesheet with a gap between the tube and the tubesheet. The tube can be placed through a sleeve which is sealed at its free end to the outer wall of the upright tube. The mating piece is constructed to provide an interference fit with the outer surface of the tube and sleeve suitable for brazing.

The present invention comprises an elongated vessel containing a removable heat exchange tube assembly with an inlet and an outlet for molten metal, the heat exchange tube assembly having a flanged extension forming a closure for the vessel; A group of U-shaped heat exchange tubes with legs of unequal length suspended from the U-shaped heat exchange tube group, a flanged extension section disposed coaxially with the container, and a U-shaped heat exchange tube group with legs of unequal length suspended from the extension section. a set of heat exchange tubes in the shape of a shape, an annular shroud arranged coaxially with the vessel and surrounding the U-shaped set of tubes, and suspended from the extension and forming inner and outer annular chambers in the shroud. A cylindrical baffle plate and a U extending parallel to the longitudinal axis of the container.
and a device for laterally supporting the tubes in the shape of a tube, with the longer tube of each tube extending inside the shroud so as to pass through the end wall of the extension forming the first tubesheet of the heat exchanger. the shorter tube of each tube extends along the outer chamber of the shroud so as to pass through the flange of the extension forming the second tube sheet of the heat exchanger; The legs pass through respective openings with gaps between the tubes and the tubesheet, and the tubes are sealed to the tubesheet by sleeves that stand upright from the face of the tubesheet and are secured to the tubes by the free ends of the sleeves. The object of the present invention is to provide a shell-type heat exchanger which is sealed to the outer wall surface of the tube and the sleeve are brazed together.

The structure of the shell-and-tube heat exchanger according to the present invention will be explained with reference to the accompanying drawings.

The barrel heat exchanger shown in the accompanying drawings is used in a steam generation circuit of a liquid metal cooled fast breeder reactor device. Although the disclosed heat exchanger is intended for use in a superheater, heat exchangers according to the present invention for use as evaporators and reheaters are of generally similar construction. The illustrated heat exchanger is closed at the bottom end;
It has a generally cylindrical body 1 with a flange and an open upper end.

The body has a sodium inlet 2 at the base, an outlet 3 at the side,
It is equipped with a drain port 4 and a pressure release connection 5 for releasing the pressure inside the shell when a reaction between sodium and water occurs. The open end of the barrel has a flanged cylindrical extension 6 with a closed top end, the flange of the barrel and the flange of the extension being bolted together and sealed around the periphery with a light weld 7. heat exchange tube 8
is U-shaped with legs of unequal length and is suspended from an extension 6 within the torso. The longer leg 8a extends along the extension and passes through the end cover forming the inner tubesheet 9, and the shorter leg 8b extends along the annular outer tubesheet 10.
passing through an extension flange forming an extension flange. These tubes are connected by two coaxially arranged cylindrical members 11a, 11b and are connected to an annular shroud 11.
There is a cylindrical baffle 12 surrounded by and suspended in the inner tubesheet (as shown in FIG. It extends coaxially between the two. The flow path for the sodium is directed upwardly from the inlet at the base of the barrel and through the inner cylindrical member 11b of the shroud to the distributor 1 in the extension 6.
3 and from there flows downward on the long leg of the tube,
It flows upwards over the short legs and exits the torso through outlet 3. The long and short legs of the U-tube are connected to external outlet and inlet steam headers 14 and 15, respectively, as shown in FIGS. 1 and 2. The U-shaped tube 8 is made of 9% chromium alloy steel, but since this material is difficult to weld and process in the field, the transition section 16 is made of 1% chromium alloy steel.
is placed between the tube plate and the header. The 1% chromium alloy tail can be attached to the 9% alloy steel tube end and tail tube of the header and can be heat treated during its manufacture. Interlocking can be easily done in situ and requires no further heat treatment. A cover gas of argon is placed above the sodium liquid level on each side of the cylindrical baffle 12, and a plant such as that shown at 17 is
It is equipped to test the hydrogen content of the cover gas and to detect the sodium level.

As shown in FIGS. 3 and 4, each tube 8 passes through an associated tube sheet 9, 10 through a clearance opening and is sealed thereto by a sleeve 18. As shown in FIGS. To effect the seal, the lower end of each sleeve is butt welded to an outwardly projecting spigot 19 bounding the opening in the top of the tubesheet, and the free end of the upright sleeve is brazed to the outside wall of the tube. be. Welding of the sleeve to the respective spigot in each tubesheet can be done from the inside of the sleeve before threading the tube, and the welds are all stress relieved at the same time by heating the entire tubesheet. Ru. The braze joints are made individually, but in order to make the braze joint, the outer surface of the tube and the inner surface of the free end of the sleeve are first carefully cleaned of the joint area. To make each joint in succession, a strip of filler material, indicated at 20 (FIG. 4), is attached to the hole in the sleeve. The tube is threaded through the sleeve to a position just above the joint made between the sleeve and the tube, and the tube is moved by internally actuated rolling means to bring the tube into a tight interference fit with the free end of the sleeve. is deformed outwardly by The tube is then pulled into the sleeve such that the expanded portion of the tube engages the free end of the sleeve. A high frequency induction heating coil (designated 21 in Figure 4) is placed around the sleeve and heated for about 1 minute to melt the filler, but the joints are heated with argon to prevent oxidation of the material. Surround with a filled sealed cover shown at 22.

The filler material is the nickel-based alloy Nicrobraz 135 (Nicrobraz is a registered trademark; the melting point of this material is typically around 1065°C), and the brazing operation is performed at temperatures between 1050°C and 1200°C. Perform the test at a temperature within the range of . The bond is then stress relieved.

Each braze joint is subjected to ultrasonic inspection, helium leak testing, and visual inspection to ensure a satisfactory seal. The appearance of the filler material on the outermost edge of the sleeve provides evidence of whether the bond is effective. The tube 8 is made from a long continuous tube so that there are no seams in the shell that could cause the sodium to come into contact with the water in the event of a defect.

The composite tube is laterally supported by a cylindrical baffle plate 12 suspended from the underside of the inner tubesheet 9. The baffle plate is double-walled to reduce conduction through it, and a pad 23 (shown in Figure 5) is provided between the inner and outer walls to separate the inner and outer walls during handling operations. They are placed at intervals. The pad 23 is welded to the inner wall,
It is in sliding contact with the outer wall to adjust the difference in thermal linear expansion of the wall in the axial direction. Annular cell-shaped grid plates 24, 25 on the inner and outer walls for laterally supporting the heat exchange tubes 8 are fixed at intervals in the axial direction by annular shroud plates. Each grid plate has inner and outer rims 33, 34 interconnected by cellular spokes 35 as shown in FIG. 6, which shows a fragment of the inner cellular grid plate 24. The spokes 35 each have an opening for loosely accommodating a tube. Movable vibration isolation plate 2 between spokes
6 is arranged, and this vibration isolation plate is provided with a clearance opening for the tube. The vibration isolation plate 26 is slidably supported from the outer rim 34 by two (vertically spaced) radially projecting dowels 37 and It is secured to the inner rim 33 by a set bolt 27 which is adjustable to move radially inward or outward.
The grids are sequentially arranged on the shroud so that each tube leg passes alternately through the spokes 35 and the vibration isolation plates 26. By radially displacing the vibration isolators, a lateral load can be applied to dampen the vibrations of the tube. In another construction, the inner and outer annular cellular grid plates 24, 25 have a cylindrical baffle plate 1.
The grid plate is axially spaced and fixed to the inner and outer walls of 2, and the grid plate is provided with large clearance openings or slots for passage of the tubes. Each of the lattice plates supports a group of angularly spaced vibration isolators, through which the tubes also pass with clearance. The vibration isolating plate is the cylindrical member 8 of the shrouding plate.
It is provided for radial movement with respect to the grid plate by means of set bolts extending through a, 8b, so that it can be pulled out or pushed in radially relative to the tube 8 to prevent vibrations. The direction of movement performed to load the tube can be either inward or outward. The cylindrical members 8a and 8b of the shroud have removable parts (not shown) to allow access to the vibration isolators, and the vibration isolators are also used to inspect the tubes after operation of the heat exchanger. It is arranged to be axially movable in order to allow damage investigation of the contact part and to be replaced in order to renew the contact part with the tube if the need arises.

The straight portions of the legs of the U-shaped tube 8 below the lower grid plates 24, 25 are supported by reinforcing sleeves 31, as shown in FIGS. 9 and 10. The sleeves tightly enclose the tubes at their upper and lower ends, the upper ends of each sleeve being firmly fixed within the tube guiding cells of the lower grid plates 24,25. The sleeve is spaced apart from the tube between its ends and includes a window 32 to allow molten sodium to contact the tube. The reinforcing sleeve 31 reduces to an acceptable level the runout of the U-tube caused by cross-flow caused by vibration or impact from grid turbulence.

In an alternative support sleeve arrangement shown in FIGS. 11 and 12, an aluminum-nickel based alloy bushing 23 is provided between the U-tube and the sleeve.
The aluminized support surface of this bushing has a low coefficient of friction, so wear damage due to longitudinal tube movement and vibration due to thermal expansion is greatly reduced.

The heat exchange tube 8 is attached to the tube plate 9,1 using the sleeve 18.
By adapting to 0, the formation of a tubesheet boundary between water and sodium is avoided. Because the complex stresses normally associated with fusion welded tube and tubesheet connections are eliminated, the tubesheet itself is not prone to cracking due to stress corrosion. The braze joint between the sleeve and the tube avoids the use of fusion welds within the sodium and water interface, and the braze joint is easy to fabricate and stress relieve. A cover gas space at the top of the outer annular portion of the shroud continues with the inner tubesheet, thus maintaining the temperature at the inner end of the outer tubesheet at an acceptable level.

In another construction of a heat exchanger embodying the invention, the seal between each tube and its associated sleeve is provided by a mating piece. Referring to FIGS. 7 and 8, the tube 8 passes through the tube sheets 9, 10 by means of clearance openings and is sealed to the tube sheets by means of a sleeve 18. The tube extends through the sleeve with sufficient clearance to each end of the sleeve, and there is a collar-shaped mating piece 28 machined for an interference fit between the upper end of the sleeve and the outer surface of the tube. sleeve 1
8 is welded to the tube sheet at its lower end, while its upper end is sealed to the tube 8 by brazing a mating piece to the sleeve and tube. The brazing material 29 can be inserted between the mating piece and the tube before heating to melt the brazing material, as shown in FIG. 7, or alternatively, as shown in FIG. It can be placed in a suitably positioned groove 30 in the mating piece.
Brazing work shall be carried out as per the above-mentioned implementation order.
The process may be carried out in an inert atmosphere and the stress may be relieved after the process. Such a construction has the economic benefit of allowing multiple tubes to be easily threaded through the sleeve during assembly of the structure prior to brazing.

In another construction, the tubes are sealed to the tubesheet by a sleeve facing inwardly into the heat exchanger. Although the fabrication of heat exchangers with inwardly facing sleeves is more complex, such heat exchangers have the advantage that they generally avoid multiple pockets that are difficult to clean of sodium deposits.

Cellular lattice plates of the above structure are machined from plate stock, but if a small pressure drop in the shell is required, a cellular lattice plate with a more complex shape is required. The grid plate could be formed more economically using electrical discharge machining techniques.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of a shell-and-tube heat exchanger structure according to the present invention, FIG. 2 is a plan view, FIG. 3 is an enlarged partial sectional view of the portion shown in FIG. 1, and FIG. Third
FIG. 5 is an enlarged partial sectional view of the part shown in FIG. 1, FIG. 6 is a partial plan view taken along the line of FIG. 1, and FIGS. 9th, 10th, 11th, 12th partial cross-sectional view of the embodiment of
The figure is a partial view of two separate support bags at the lower end of the heat exchange tube. 1... Cylindrical body, 6... Cylindrical extension with flanges,
8... Heat exchange tube, 9... Inner tube sheet, 10... Outer tube sheet,
11... Shrouding plate, 12... Baffle plate, 18... Sleeve,
23... Padded, 24, 25... Grid plate, 26... Vibration proof plate.

Claims (1)

[Scope of Claims] 1. A liquid metal-water/steam heat exchanger used in nuclear reactor equipment, comprising a shell configured to guide liquid metal, and a shell provided within the shell to guide water or steam. a bundle of heat exchange tubes, the shell having at least one tube sheet for passing the heat exchange tubes, each heat exchange tube having a gap between the heat exchange tube and the tube sheet. each tube through a respective opening in the tubesheet, each heat exchange tube being sealed to the tubesheet by a respective sleeve upright from the face of the tubesheet, the free ends of the sleeves being sealingly coupled to the outer surface of the heat exchange tube. In the heat exchanger, the sleeve 8 and the sleeve 18 are made of a nickel-based alloy and are joined together by a brazed lap joint. 1. A liquid metal-water/steam heat exchanger characterized in that the liquid metal-water/steam heat exchanger is 2. All of the heat exchange tubes 8 are of continuous length throughout the tubes in the shell 1, and the ends of the heat exchange tubes are connected outside the shell to a water-conducting header 15 and a steam-conducting header 14, respectively. A heat exchanger according to claim 1. 3. Each sleeve 18 has at its free end a tapered portion for forming a neck portion that overlaps the outer surface of the respective heat exchange tube 8, and the brazing joint is formed between the neck portion and the tube surrounded by this neck portion. 3. A heat exchanger according to claim 1 or 2, which is made between the heat exchanger and the heat exchanger. 4. A heat exchanger according to claim 1, 2 or 3, wherein each heat exchange tube is radially expanded in the region of the brazed lap joint. 5. The heat exchange tube 8 and the sleeve are indirectly connected to each other via a tubular fitting piece 28 having a brazed lap joint with the heat exchange tube and the sleeve, respectively.
A heat exchanger according to claim 1, 2 or 3. 6. In a heat exchanger comprising an elongated vessel having an inlet and an outlet for molten metal and containing a removable heat exchange tube assembly, said heat exchange tube assembly having a flanged tube forming a closure of the vessel. a U-shaped heat exchange tube group with legs of unequal length suspended from the extension, and a U-shaped heat exchange tube group arranged coaxially with the longitudinal axis of the tube group and surrounding the U-shaped tube group. a cylindrical baffle suspended from the extension and defining inner and outer annular chambers within the shroud; and means for laterally supporting the U-tube from the baffle. the legs of the U-tubes extending parallel to the longitudinal axis of the vessel, the longer tubes of each tube being enclosed so as to pass through the end wall of the extension forming the first tubesheet of the heat exchanger. extending along the inner chamber of the plate, with the shorter tube of each tube extending along the outer chamber of the shroud to pass through the flange of the extension forming the second tube sheet of the heat exchanger; Claims 1 to 1 are characterized by:
The heat exchanger according to any of Item 5. 7 The means for supporting the U-tube laterally from the baffle includes a series of axially spaced cells supported by the cylindrical baffle and penetrated by the heat exchange tubes. shaped gratings and vibration isolators spaced apart at a series of angles associated with each grating, the isolators having openings through which the tubes pass, the vibration isolators being connected to the gratings for laterally supporting the tubes. 7. A heat exchanger according to claim 6, further comprising extraction means for radially displacing the heat exchanger. 8. At least some U-tubes are provided with a reinforcing sleeve for supporting the U-bend against vibrations, the reinforcing sleeve suspending from the grid adjacent to the U-bend and extending from the U-bend. 8. The heat exchanger according to claim 7, wherein the heat exchanger extends in the direction of the heat exchanger. 9. The heat exchanger of claim 8, wherein an aluminized nickel-based alloy is disposed between each reinforcing sleeve and its complementary tube. 10 First, one end of each sleeve 18 is welded to the tube sheets 9 and 10, and each heat exchange tube 8 is inserted into the sleeve 18, and the heat exchange tube is expanded locally at a position slightly beyond the sleeve to release heat. repositioning the heat exchange tube so that the enlarged portion of the exchange tube is in an interference fit with the free end of the sleeve, and placing the enlarged portion in overlapping relationship with the free end of the sleeve; A method for manufacturing a heat exchanger, which comprises brazing the overlapping surfaces of a heat exchange tube and a sleeve with a nickel-based alloy using a heater while enveloping the joint in an inert gas atmosphere.