JPS6017964B2 - Anti-corrosion structure of bellows that absorbs thermal expansion differences for heat exchangers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an anti-corrosion structure for a bellows absorbing thermal expansion difference for a heat exchanger, and in particular to an anti-corrosion structure for a bellows of this type suitable for use in an intermediate heat exchanger for a sodium-cooled fast breeder reactor.

Figure 1 shows the structure of an intermediate heat exchanger for a sodium-cooled fast breeder reactor.

An inner shell 2 is provided within the outer shell 1, and a heat transfer tube 3 is disposed within the inner shell 2. Primary sodium, which is a heating medium, enters the outer shell 1 through a primary sodium inlet nozzle 4.
and the inner shell 2, and is further supplied into the inner shell 2 from the inner shell inlet hole 5. Subsequently, the sodium descends inside the body 2, is led back to the space between the outer chest 1 and the inner chest 2 through the inner body outlet hole 6, and is further passed through the primary sodium outlet nozzle 7. It is guided outside the outer trunk 1. In addition, the outer chest 1 and the inner trunk 2 are connected to each other so that the sodium supplied to the inner ear 2 and the sodium flowing out from the inner ear outlet hole 6 do not mix in the space between the outer chest 1 and the inner trunk 2. A sodium bypass prevention plate 8 is attached between them. On the other hand, the secondary sodium descends in the downcomer pipe 9 and reaches the lower plenum. Subsequently, the sodium passes through the heat exchanger tubes 3 arranged within the inner shell 2 and is led to the upper plenum 11. The inner shell 2 and the upper plenum 11 are provided with an insulating cylinder 12 and an isolation cylinder 13, respectively, and between these and the downcomer pipe 9 an annular gap 14 is provided. The downcomer pipe 9 and the upper plenum 11 are:
It is connected via a bellows 15, and this bellows 1
The annular gap 14 sealed by the bellows 15 is filled with primary sodium, and the bellows 15 absorbs the dark heat difference between the inner and outer fuselage 2, 1 sides and the downcomer pipe 9. In the figure, 16 is a lower tube plate, 17 is a body rest, and 18 is an upper tube plate. In the above configuration, the sodium filled in the annular gap 14 is in a stagnant state, but as the oxygen content in this sodium increases, the corrosion of the heat exchanger components that come into contact with it also increases. do. To explain this with reference to FIG. 1, the annular gap 14
The amount of oxygen in the sodium filled in the bellows is the sum of the small amount of initial oxygen contained in the sodium and the large amount of oxygen adsorbed on the metal surface of the bellows that has been diffused. Therefore, the influence of corrosion on the metal material constituting the bellows is significant and cannot be ignored. However, increasing the thickness of the bellows would solve this problem, but increasing the thickness of the bellows, which performs expansion and contraction, is undesirable in terms of its functionality.
An alternative solution is desired. In consideration of the above points, an object of the present invention is to prevent the bellows from being corroded by oxygen without impairing the expansion and contraction function of the bellows. The gist of the present invention is to provide a heat exchanger equipped with a mechanism in which a bellows absorbs the difference in thermal expansion between a downcomer pipe and a body in which heat transfer tubes are disposed. The point is that an oxygen adsorbent material is inserted in between. Hereinafter, the present invention will be explained with reference to an embodiment shown in FIG. 2. The same reference numerals as in FIG. frame! 9 is an oxygen adsorbent having a high affinity for oxygen, such as zirconium or titanium.

In the above configuration, the coolant filled in the annular gap 14 contains a high concentration of oxygen, but in the present invention, "an oxygen adsorbent 20 is inserted, the high concentration of oxygen present in the area is adsorbed by the oxygen adsorbent 20', and the bellows 1
5 parts can be prevented from being corroded by oxygen.

Therefore, in the present invention, there is no need to increase the wall thickness of the bellows 15, and the original function of the bellows, which expands and contracts to absorb the difference in thermal expansion, is not impaired. In order to improve the effectiveness of the oxygen adsorbent 20, it is desirable that the surface area of the adsorbent be as large as possible, and for example, a thin wire or foil may be used.

When the oxygen adsorbing material 20 is made into a foil, as shown in FIG. 3, diagonal continuous waves are applied to the material foil, and this is wound as shown in FIGS. 4 and 5. Basket frame 19
It is best to store it inside. According to this structure, as shown in FIG. 6a, there is a portion where the peaks of the corrugated sheet 20a located on the inside and the valleys of the corrugated sheet 20b located on the outside intersect with each other. Since they have a cross-sectional shape as shown in FIG. 6b, the inner and outer corrugated plates 20a and 20b do not completely overlap, but there is a passage 21 between them that penetrates obliquely in the vertical direction as shown by the arrow in FIG. A large number of layers are formed for each layer. Therefore, oxygen in the coolant stagnant in the bellows 15 is removed from the inner and outer corrugated plates 20a and 20.
Since it makes efficient contact with both the front and back surfaces of each corrugated plate in the passages 21 formed in large numbers between b, the oxygen adsorption effect per unit capacity can be improved. Here, an intermediate heat exchanger for a sodium-cooled fast breeder reactor is used as a heat exchanger,
In addition, zirconium is used as an oxygen adsorbent between the downcomer pipe and the bellows, and the amount of sodium is reduced to 30〆 (=
If the oxygen concentration in the sodium stagnant between the downcomer and the bellows is 130 legs, then the oxygen concentration in the sodium is the initial oxygen concentration of the sodium, which is the initial oxygen concentration of the sodium. When calculating the required amount of zirconium for purification, the amount of oxygen to be removed 0w is: ○w=30×10-3×10-6(130-10)×y
.

[yo = specific weight of oxygen 1.33k9/(however,
20 pm ○, in the case of a lab)] is expressed as 4.8 x 10-6k9.

The reaction rate of zirconium is 5902/meh, and the removal capacity is 1202/lk9 (provided that the design temperature of the intermediate heat exchanger is 55 pi), so the required surface area of zirconium (required time) is 2 dishes r) is 4.8/5
〆h÷2 sail; 0.048〆, and the weight of zirconium is 4.8xlo-3 no 12io. It will be 4 evenings.

As is clear from this formula, the required amount of zirconium under the above conditions is approximately 0.05 mm in surface area and 0.4 mm in weight.

As described above, according to the present invention, it is possible to prevent the bellows from being corroded by oxygen without increasing the wall thickness of the bellows for absorbing thermal expansion difference for a heat exchanger. There is a practical benefit in that the safety of this type of equipment can be improved without impairing its functionality.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view showing the internal structure of an intermediate heat exchanger for a sodium-cooled fast breeder reactor, FIG. A developed view showing a specific example of the oxygen adsorbent used, FIG. 4 is a plan view of the oxygen adsorbent shown in FIG. 3 in a rolled state, and FIG. 5 is a perspective view of the same.
FIGS. 6a and 6b are both partial cross-sectional views of the oxygen adsorbent shown in FIG. 4. 1... Outer body, 2... Inner chest, 3... Heat transfer tube, 9... Downpipe, 15... Bellows, 20... ...Oxygen adsorbent. Pig, Figure 2, Figure 3, Figure 4, Leopard, Figure 6.

Claims (1)

[Scope of Claims] 1. A heat exchanger equipped with a mechanism in which a bellows absorbs the difference in thermal expansion between a body in which heat transfer tubes are disposed and a downcomer, in which oxygen adsorption occurs between the downcomer and the bellows. An anti-corrosion structure of a bellows for absorbing thermal expansion difference for a heat exchanger, which is characterized by having a material interposed therein. 2 Form the oxygen adsorbing material into a foil shape, add continuous diagonal waves to the material foil, and wind it so that the peaks of the inner corrugated sheet and the troughs of the outer corrugated sheet meet and cross. An anti-corrosion structure of a bellows for absorbing thermal expansion difference for a heat exchanger according to claim 1, which has a three-dimensional structure.