EP0056746B1 - Heat exchanger with an array of tubes, having undulations for dilatation, and not subjected to vibration - Google Patents

Description

The present invention relates to a tube bundle device arranged between two tube plates and provided with expansion lyres, for heat exchange between a fluid circulating inside the tubes and a liquid circulating around the tubes.

The expansion lyres of such devices can be driven in vibration for certain flow rates of the fluid circulating around the tubes, in particular when the latter is a liquid alkali metal. If the excitation frequency due to the flow of the fluid approaches the resonance frequency of the expansion lyres, sufficient vibrations may occur to seriously damage the tubes.

It has already been proposed to avoid these phenomena to have the expansion lyres in an area where they are not in contact with the flowing fluid, for example, when the latter is a liquid alkali metal, in an area filled with a rare gas. surmounting the bath of this metal, in the vicinity of the tube plate of the hot end of the exchanger.

This however requires an extension of the tube bundle, often already very long, the length of the expansion lyres not involved in the heat exchange. Furthermore, the expansion lyres are in the hottest part of the exchanger, where the permissible working rate is the lowest.

The object of the present invention is to remedy the above drawbacks, and to provide a device which does not have a special zone reserved for expansion lyres and which does not participate in the heat exchange. It also aims to ensure the operation of the expansion lyres with a more favorable working rate, outside the hottest part of the exchanger, and consequently to use tubes of smaller thickness.

To this end and in accordance with the invention, a heat exchange device is proposed comprising an external ferrule closed at its ends by two tube plates, a bundle of tubes provided with expansion lyres, these tubes being connected to the plates. with tubes for opening into inlet and outlet manifolds of a fluid circulating inside the tubes and inlet and outlet pipes of a liquid circulating in said ferrule and around the tubes, as known from FR-A-2 415 262. This device is characterized in that the expansion lyres are arranged in contact with the liquid in the coldest zone of the exchanger and in that means are provided for deflecting at least part of the liquid flow at the expansion lyres so that the liquid cannot cause them to vibrate.

According to another characteristic of the invention, the means for deflecting at least part of the liquid flow rate comprise a jacket internal to the external shell and in which the expansion lyres are placed and at least one orifice formed in said shell upstream of the expansion lyres to divert at least part of the liquid flow between the inner jacket and the outer shell.

• - Les lyres de dilatation sont au contact du liquide en écoulement, lesdits moyens comprenant en outre au moins un second orifice ménagé dans ladite virole en aval des lyres de dilatation, l'un au moins des orifices comprenant des moyens de répartition du débit entre l'intérieur et l'extérieur de la chemise, tels que le métal passe au contact des lyres de dilatation à une vitesse suffisamment faible pour ne pouvoir les entraîner en vibration.
• - Les lyres de dilatation sont au contact d'un bain de liquide statique, ladite chemise étant obturée en aval des lyres de dilatation de telle sorte que tout le métal est dévié entre la chemise interne et la virole externe.
• - Les lyres de dilatation sont équilibrées par rapport à l'axe général des tubes de façon à n'exercer aucune contrainte de flexion sur leur liaison avec les plaques à tubes.
• - Les lyres de dilatation sont symétriques par rapport à l'axe des tubes.
• - Des barres de stabilisation sont disposées entre les lyres dans des plans parallèles aux plans de celles-ci.

It also preferably meets at least one of the following characteristics:

• - The expansion lyres are in contact with the flowing liquid, said means further comprising at least one second orifice formed in said ferrule downstream of the dilatation lyres, at least one of the orifices comprising means for distributing the flow between the inside and outside of the jacket, such that the metal passes in contact with the expansion lyres at a sufficiently low speed to be unable to cause them to vibrate.
• - The expansion lyres are in contact with a bath of static liquid, said jacket being closed downstream of the expansion lyres so that all the metal is deflected between the inner jacket and the outer shell.
• - The expansion lyres are balanced with respect to the general axis of the tubes so as not to exert any bending stress on their connection with the tube plates.
• - The expansion lyres are symmetrical with respect to the axis of the tubes.
• - Stabilization bars are arranged between the lyres in planes parallel to the planes thereof.

• la figure 1 est une vue en coupe schématique d'un générateur de vapeur réalisé conformément à l'invention ;
• la figure 2 est une vue en coupe à plus grande échelle montrant la partie inférieure du générateur de vapeur de la figure 1 et illustrant une première variante de réalisation selon laquelle les lignes de dilatation des tubes sont au contact du liquide en écoulement ;
• la figure 3 est une vue schématique comparable à la figure 2 montrant une variante de réalisation dans laquelle les lyres de dilatation des tubes sont symétriques ;
• la figure 4 est une vue en coupe selon la ligne IV-IV de la figure 2 ;
• la figure 5 est une vue à plus grande échelle du détail V de la figure 4 ; et
• la figure 6 est une vue de la partie inférieure du générateur de vapeur comparable à la figure 2, montrant une variante de réalisation de l'invention selon laquelle les lyres de dilatation des tubes sont au contact d'un bain de liquide statique.

There will now be described, by way of nonlimiting examples, two alternative embodiments of the device according to the invention, with reference to the appended drawings in which:

• Figure 1 is a schematic sectional view of a steam generator produced in accordance with the invention;
• Figure 2 is a sectional view on a larger scale showing the lower part of the steam generator of Figure 1 and illustrating a first embodiment according to which the expansion lines of the tubes are in contact with the flowing liquid;
• Figure 3 is a schematic view comparable to Figure 2 showing an alternative embodiment in which the tubes of the expansion lyres are symmetrical;
• Figure 4 is a sectional view along the line IV-IV of Figure 2;
• Figure 5 is an enlarged view of detail V of Figure 4; and
• FIG. 6 is a view of the lower part of the steam generator comparable to FIG. 2, showing an alternative embodiment of the invention according to which the lyres for expanding the tubes are in contact with a bath of static liquid.

It can be seen in FIG. 1 that the steam generator has an outer shroud 1, with a vertical axis, closed at its lower and upper ends by tube plates 2,2 'to which the tubes such as 3 are connected to a bundle of tubes arranged inside the shell 1. These tubes open respectively, at the bottom of the steam generator, into an inlet manifold 4 of the water from the secondary circuit of the generator and at its upper part, in an outlet manifold 4 'of the vaporized water. The water to be vaporized therefore circulates from bottom to top inside the tubes 3 between the collectors 4 and 4 '.

The liquid metal (generally sodium) circulating in the primary circuit of the generator moves against the current with respect to the water in the primary circuit, that is to say from top to bottom, inside the shell. 1 and around the tubes 3 between an inlet pipe 5 'and an outlet pipe 5.

As illustrated in particular in FIG. 2, the tubes 3 are generally rectilinear and each define a vertical axis X. However, they each have, near their lower end connected to the tube plate 2, a dilatation lyre shown at 11 in its cold position and 12 in its hot position. The expansion lyres are thus in the coldest area of the exchanger, that is to say in contact with the liquid sodium, cooled in contact with the water to be vaporized. In addition, the expansion lyres are balanced, that is to say that the length of their branches and their position relative to the axes X of the tubes are such that the lyres exert in operation no bending reaction on the teats. 13A for joining the tubes with the tube plate 2.

In accordance with the invention, the expansion lyres 11 are arranged inside a thin jacket 6 which defines with the external ferrule 1 an annular passage through which is deflected at least part of the flow of liquid sodium circulating between the ferrules 5 'inlet and outlet 5. For this purpose, the thin jacket 6 has above the expansion lyres 11 an annular orifice 8 through which at least part of the liquid sodium descending in the outer shell 1 is deflected into the annular passage formed between this ferrule and the jacket 6.

In the alternative embodiment of FIG. 2, the shell 6 extends below the expansion lyres by a perforated shell 7 welded to the shell and by which the part of the liquid sodium descending inside the shell 6 comes out in the annular passage to be discharged through the tubing 5 with the part of the sodium which has been deflected in this passage through the orifice 8. This perforated ferrule 7 ensures the desired distribution of the flow of liquid sodium between the internal and external zones of the jacket 6 More specifically, the passage section of the holes of the perforated shell 7 defines a sufficiently large pressure drop, relative to the passage section around the jacket 6, so that the flow of hot liquid sodium inside of the shirt is low enough not to risk causing vibrations of the expansion lyres.

As shown in FIG. 2, the perforated ferrule 7 is fixed to a circular crown 9, itself connected to the tube plate 2 by bolts 10.

FIG. 3 represents a variant of the steam generator of FIG. 2 in which the expansion lyres such as 13 are symmetrical with respect to the general axis X of the corresponding tube (the position of the hot lyre is represented at 14). This has the advantage of reducing the transverse size of the lyres and therefore the diameter of the ferrule 6. On the other hand, the length of the lyres is increased and they exert in operation a certain bending force on the corresponding teats of the junction of the tube with the tube plate (not shown).

FIG. 4 is a sectional view along the axis IV-IV of FIG. 2 and FIG. 5 a detail view V of FIG. 4. These figures show the staggered distribution of the tubes such as 13, 14, 15, 16, and bars such as 17, 18, 19 slid between the rows of tubes to increase safety against vibrations thereof.

Finally, FIG. 6 shows a variant of FIG. 2 according to which the zone internal to the shell 6 containing the expansion lyres 11 contains liquid sodium in the static state and not in circulation. For this purpose, the perforated shell 7 is eliminated and the shell 6 is connected directly to the tube plate 2. As a result, as the arrows illustrate in FIG. 6, the entire flow of liquid sodium s' made from the outside of the shell 6, through the orifices 8.

In this configuration, the expansion lyres always participate in the heat exchange, but they are in contact with practically static liquid sodium, so that any risk of vibration of these lyres is eliminated.

Although the devices which have been described with reference to the figures appear to be the preferred embodiments of the invention, it will be understood that various modifications can be made to them without departing from the scope of the invention, some of their members being able to be replaced by others who would play a similar technical role. In particular, in the variant embodiment of FIG. 2, the members for distributing the flow between the internal and external zones relative to the envelope may be other than a grid with calibrated holes. They can also be arranged upstream of the internal envelope, and no longer downstream of the latter.

The invention applies to tube bundle heat exchangers with expansion lyres, in particular for a steam generator with a primary fluid consisting of a liquid alkali metal.

Claims (7)

1. Heat exchange device comprising an external shell (1) closed at its ends by two tube plates (2, 2'), a bundle of tube (3) having expansion bends (11), said tubes being connected to the tube plates (2, 2') to open into inlet and outlet manifolds (4, 4') for a fluid circulating inside said tubes, and an inlet and outlet (5, 5') for a liquid circulating inside said shell and around said tubes, characterized in that the expansion bends (11) are located in contact with the liquid in the coolest zone of the exchanger, and in that means (6, 7, 8) are provided to divert at least a part of the flow of liquid from the level of the expansion bends whereby the liquid cannot set them vibrating.

2. Device according to claim 1, characterized in that said means comprise an internal liner (6) for the external shell (1) within which the expansion bends (11) are located, and at least one orifice (8) formed in said shell above the expansion bends to divert at least a part of the flow of liquid between the internal liner and the external shell.

3. Device according to claim 2, characterized in that the expansion bends are in contact with flowing liquid, said means additionally comprising at least one second orifice (7) formed in said shell below the expansion bends, at least one of the orifices (7, 8) comprising means for dividing the flow between the interior and the exterior of the liner, such taht metal passes in contact with the expansion bends at a speed low enough not to set them vibrating.

4. Device according to claim 2, characterized in that the expansion bends are in contact with static liquid, said liner (6) being closed below the expansion bends, whereby all the metal is diverted between the internal liner and the external shell.

5. Device according to any one of claims 2 to 4, characterized in that the expansion bends (11) are equilibrated with respect to the general axis of the tubes whereby they exercise no flexing stress on their linkage with the tube plates.

6. Device according to any one of claims 1 to 5, characterized in that the expansion bends (13) are symmetrically disposed with respect to the axis (X) of the tubes.

7. Device according to any one of claims 1 to 6, characterized in that stabiliser bars (18, 19, Fig 5) are disposed between the bends in planes parallel to the planes of the latter.

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