EP0729000A1 - Tube bundle for steam condenser - Google Patents

Abstract

The assembly consists of a series of tubes contained in a shell in which they extend radially in a plane perpendicular to their axes in a number of spurs (6; 10-18), some of which (6; 10-13) are branched (8,9) and have their inner ends connected to a tube surface (22) which is more or less ring-shaped. The branching tubes have trunks (7) at their bases which diverge and then branch into two sections of equal thickness, with the thickness of the trunk section being between 1.5 times and double the thickness at the base. One tube surface which is trapezoid in shape (27) acts as an air cooler; its upper section is covered by a hood (51) and is located inside the central annular tube surface (22).

Description

The present invention relates to a tube bundle for a steam condenser, in which the trace, in a plane perpendicular to the axis of the tubes, of the envelope of the tubed zones of the bundle, is a trace of the type forming radiating spikes.

French Patent No. 1,391,661 describes a tubular bundle of this type.

In such a bundle, there is, between each radiating ear, which constitutes a tubed zone, an uncubed groove of triangular shape. Such a bleeding is necessary for the passage of steam to the tubes of the two ears located on either side of the bleeding. Thus, a groove "feeds" the tubes of a half-ear on either side of the groove.

• de la section de la zone tubée qui dépend du nombre des tubes et du pas des tubes,
• de la section requise pour lesdites saignées de passage de vapeur entre les épis,
• de la section de zones non tubées résultant de contraintes du tracé : par exemple autour de la zone tubée, appelée réfrigérant d'air.

The total section occupied by a beam is a function:

• the section of the tubed area which depends on the number of tubes and the pitch of the tubes,
• the section required for the said passages for the passage of steam between the ears,
• of the section of non-cased areas resulting from layout constraints: for example around the cased area, called air cooler.

, (i étant la largeur de la saignée : distance séparant deux épis à leur extrémité et H la hauteur de la saignée, correspondant à la hauteur des deux demi-épis encadrant la saignée) a également pour valeur S = NH $\frac{{\text{q}}_{\text{i}}}{\text{2 LV}}$

, avec N = le nombre de tubes des deux demi-épis alimentés par la saignée triangulaire de hauteur H.However, for a given speed V _{(m / s)} of vapor, constant along a passage passage between two ears, a length L _(m) of the tubes and a flow q _i in m ³ / s of vapor condensed by tube, uniform for all the tubes, we show by calculation that the necessary section S of a triangular groove which is equal to 1 x $\frac{\text{<figure-callout id="2" label="H" filenames="imgf0001.png" state="{{state}}">H</figure-callout>}}{\text{2}}$

, (i being the width of the cut: distance separating two ears at their end and H the height of the cut, corresponding to the height of the two half-ears surrounding the cut) also has the value S = NH $\frac{{\text{q}}_{\text{i}}}{}$$\frac{{}_{}}{\text{2 LV}}$

, with N = the number of tubes of the two half-ears supplied by the triangular groove of height H.

It can therefore be seen that the section required for a bleeding, which is a non-cased surface necessary for the passage of steam to the two half-ears framing the bleeding, is proportional to the number N of tubes of the two adjacent half-ears and to the height H of the groove.

It is therefore clear that large bundles with long spikes, and therefore long grooves require, per tube, a larger uncased surface than smaller bundles with shorter spikes.

Thus, for a given steam speed V, the number of tubes which can be installed per unit of area will therefore be smaller the higher the height H of the triangular steam grooves.

However, the power exchanged in a tube bundle is proportional to the exchange surface and therefore to the number of tubes.

The present invention therefore aims to allow a better filling coefficient of the tubed area relative to the total cross section of the bundle thus reducing the dimensions of the tubular bundle for the same number of tubes and improving the exchange performance of the bundle and this by a new tracing of the beam.

The subject of the invention is therefore a tubular bundle for a steam condenser in which the layout, in a plane perpendicular to the axis of the tubes, of the envelope of the tubed areas of the bundle, is a layout of the type forming radiant spikes, characterized in that at least some of the ears have at least one branch and in that said radiating ears radiate from a tubed surface forming a substantially circular ring.

According to another characteristic, the ears which branch off have at their base a trunk which is growing and branches out into two branches of equal thickness as soon as the thickness of the trunk of the ear reaches between one and a half times and twice its thickness at its base.

Advantageously, the thickness of said tubed surface forming a ring is substantially constant.

According to another characteristic, a cased surface of trapezoidal shape, called an air cooler, surrounded by a cover, except on the underside of said air cooler, is located inside said cased ring, an annular non-cased surface. separating said trapezoidal surface from said cased ring, said cased ring comprising an interruption into which penetrates the upper end of said casing and leaving a clearance of communication between the uncased ring and an uncapped casing of steam passages separating two ears, said casing communicating with some extraction pipes passing through said groove.,

We will now give the description of a few examples of implementation of the invention with reference to the appended drawing in which:

FIG. 1 represents the layout of a tubular bundle of steam condenser according to the known prior art.

Figures 2, 3 and 4 show the layout of three tubular beams according to the invention in three cases of height to width ratio.

Thus, Figure 1 shows the layout of a tube bundle for a steam condenser. It is a known prior art bundle of the so-called radiating spike type.

This line constitutes, in a plane perpendicular to the axis of the tubes 50 which are all parallel, the envelopes of the tubed areas. This plane is parallel to the tubular end plates.

This bundle comprises a first tubed zone 1, called an air cooler, in the form of an isosceles trapezoid, surrounded by a cowling, shown diagrammatically by the simple line 51, except on the underside of the air cooler. Around this air cooler is located a second tubed zone forming a plurality of radiating ears 2.

Outside these closed lines, the surface is uncased, in particular the grooves 3 of substantially triangular section for the passage of steam between two consecutive ears as well as the area 4 around the air cooler 1 between it and the base of ears 2.

The air cooler 1 ensures the concentration of the incondensables (air) with a view to their extraction by vacuum pumps. To this end, the cowling 51 communicates with a few extraction pipes 52 passing through the upper groove 3.

In the line shown in FIG. 1, as in the other figures, only a few tubes 50 have been shown in each cased area only 50 and the rest of these areas cased in shaded frame.

Each half-ear 2 is "supplied" with steam by the groove 3 which they frame. The ears 2 moreover comprise a narrow uncapped casing 5 (generally the width of a single row of tubes) dividing the ear into two half-ears.

It can be seen that certain ears 2, in particular the upper ears, are very long and fed by deep grooves 3 for the passage of steam, which is unfavorable as we have seen since the necessary triangular section 3, not cased, for passage of steam is proportional to the height H of the grooves therefore to the length of the ears.

FIG. 2 shows a plot of a tube bundle according to the invention in the case of a height to width ratio equal to one.

This bundle is also of the type with radiating spikes, but essentially comprises the characteristic peculiar to the invention that certain spikes, not all, but most, are divided into ramifications.

Thus, we see that the ear 6 for example has a trunk 7 which widens from its base, then branches into two branches 8 and 9. The branching into two branches is done when the trunk 7 reaches a width e ₁ between one and a half and two times the thickness e at its base. The thickness of the two branches 8 and 9 is equal, and remains approximately constant. It is the same for the ears 10, 11, 12, 13 and the symmetrical ears of the axis Δ.

The lower spikes 14, 15 and 16 are not divided, but they are very short. Likewise, the two upper ears 17 and 18 are not divided and are separated by an uncut rectangular recess 19.

The other uncapped tubings for the passage of vapor are triangular. For example, the groove 20 between the ear 18 and the ear 6 as well as the groove 21 between the two branches 8 and 9 of the ear 6.

Another feature of the invention consists in that the radiating spikes radiate from a surface also cased forming a ring 22. A dotted line 23 simply makes it possible to visualize this ring between this line and the line 24 which forms part of it. tracing of the envelope of the tubes. This ring has a substantially constant thickness, a little stronger however at its lower part.

As in the prior art of FIG. 1, there is a tubed zone of trapezoidal shape 27 constituting the air cooler (1 in FIG. 1). This air cooler is surrounded by a cover, shown diagrammatically by a simple line 51, except on the inner face of the air cooler. The cased ring 22 includes an interruption 25 into which the upper end of the casing 51 penetrates. A clearance between this casing 51 and the cased ring 22 allows the passage of vapor communication between the groove 19 and an uncased annular surface 26 located between the air cooler 27 and the cased ring 22. The cowling 51 has a few extraction pipes 52 passing through the groove 19 and connected to vacuum pumps for extracting the non-condensables.

We note an extra thickness such as e ₁ at the start of the ramifications. The ramifications lead to long grooves 20 and to short grooves 21, thus reducing the section required for the passage of steam.

It is thus possible, due to these divisions of the tubed ears 6, 10, 11, 12, etc. to reduce the thickness of the ears without reducing the number of tubes, therefore increase heat exchange. This reduction in the thickness of the ears makes it possible to accept the extra thickness e ₁ at the location of the branches.

The layout according to the invention thus makes it possible to install, while retaining the same sizing criteria, a greater number of tubes in a given tubular plate section: between 5 and 10% of additional tubes compared to the layout of the art anterior, Figure 1.

It is also noted that the efficiency of the tubes is more homogeneous, in particular avoiding large jams at the base of the ears. A reduction of the condensing pressure of the order of 2 to 3 mbar can be obtained on a 1000 MW condenser.

FIG. 3 shows another example of a beam in the case of a height to width ratio equal to 0.6. Here we see that the ears 11 and 12, as well as their symmetrical with respect to the axis Δ are respectively divided, first into two branches 28, 29 and 30, 31, then again into two branches 32, 33 for branch 28 and 34, 35 for branch 29. The branch 31 of the spike 12 is again divided into two branches 36 and 37. Between all these branches, there are grooves of variable lengths: 38 to 45.

FIG. 4 shows another example in which the height to width ratio of the beam is here 1.7. In this example, the ear 6, as well as its symmetrical branched into two branches 46 and 47, then the branch 46, again into two branches 48 and 49.

In general, the tubes are better distributed in the tube plate since the peripheral part has a higher filling coefficient thus avoiding jams or concentrations of tubes, unfavorable to heat exchanges.

Thus, a calculation has shown that, in the case of the prior art, for the upper ears, the tubes situated between the mid-height and the end of the ears constitute 49.3% of the total of the tubes, whereas in the case of the invention, we arrive at 54.6%. The periphery of the plate is thus better occupied.

Claims (5)

Tubular bundle for a steam condenser in which the layout, in a plane perpendicular to the axis of the tubes, of the envelope of the tubed areas of the bundle, is a layout of the type forming radiating spikes (6; 10 to 18), characterized in that at least some (6; 10 to 13) of the ears have at least one branch (8, 9; 28, 29; 32 to 35, 46, 47, 48, 49) and in that said radiating ears radiate at from a cased surface forming a substantially circular ring (22). Tubular bundle according to claim 1, characterized in that the branching ears have at their base a trunk (7) which widens and branches into two branches (8, 9) of equal thickness as soon as the thickness of the trunk of the ear reaches between one and a half times and twice its thickness at its base. Tubular bundle according to one of claims 1 or 2, characterized in that the thickness of said tubed surface forming a ring (22) is substantially constant. Tubular bundle according to one of claims 1 to 3, characterized in that a trapezoidal cased surface (27), called an air cooler, surrounded by a cover (51), except on the underside of said cooler d air is located inside said cased ring (22), an annular non-cased surface (26) separating said trapezoidal surface (27) from said cased ring (22), said cased ring (22) having an interruption (25) , into which penetrates the upper end of said cowling (51) and leaving a clearance of communication between the uncased ring (26) and an uncased groove (19) for the passage of vapor separating two ears (17, 18), said cowling communicating with some extraction pipes (52) passing through said groove (19). Tubular bundle according to claim 4, characterized in that said two ears (17, 18) separated by said groove (19) are unbranched ears and in that said groove (19) is rectangular.

Images