DE2032891B2 - Steam generator tube with helical inner trains and process for its manufacture - Google Patents

Description

linear grooves in a smooth A certain remedy against these dangerous

Tube, which serves as the mother tube, pushed in is known in the aforementioned operations

is, whereby by free rotation of the "stamp steam generator pipes run through the one-way

on the inner wall of the pipe several helical lines - the helical inner trains that make the process

shaped fields are formed, 40 of which favor nucleate boiling, have already been achieved,

in a second production stage through use. The object of the invention is on the other hand

of a second punch each part is pressed down to create a steam generator tube

be so that a plurality of helical which opposed the critical heat flux density

raised in front of a tube with unidirectional screwing

jumps stops. 45-shaped inner cables is significantly increased as a result,

6. The method according to claim 5, characterized in that the occurrence of boiling nuclei in the through shows that for the second production stage a liquid flowing through the pipe is still further geStempel is used, which is promoted at its external. It should be under critical heat flow area several helical densities mean that heating surface load, Grooves with 5 ° to the grooves of the first punch in which the sudden rise of the pipe wall is opposite The cutting angle is provided with the temperature of the bubble evaporation in the film evaporation and which rotates freely during the drawing process. turn over, lets.

7. The method according to claim 5 for the production, this object is achieved according to the invention daeines Steam generator pipe according to claim 4, characterized in that the steam generator pipe with two each other characterized in that for the second Fer- 55 crossing systems in a helical direction a stamp is used, which is equipped on running inner trains, through their its outer surface with several straight grooves overlapping helically behindciiiandcrvom Chamfer angle is provided zero and the lying projections of parallelogram-like, insin the tube inserted ii'ul is pulled straight. special rhombic shape.

60 The advantage of this arrangement over the known Arrangement according to the mentioned USA.-Pa-

The invention is based on a steam generator tcntschrift 3,088,494 based primarily on:

lir with helical inner teeth for the

Mricb with high heat flux below the angle (i.e. the angle the trains make with the pipe

■ itic pressure. 65 ;; form chsc) be quite large to the desired

Dampferzcugerrohrc of this type are already known. To let the effect occur to a sufficient extent: he

For example, US Pat. No. 3,088,494 is approximately 80 "in the known arrangement

igt. They are - as in part also in the above-mentioned assessment - a noticeable increase in the flow rate and

also has manufacturing difficulties. According to the invention, however, can Chamfer angles can be much smaller (they are preferably between 20 and 80 °), because also with the The resulting high steepness of the trains, which is favorable in terms of production technology, due to the formation of the protrusion the desired effect of maintaining nucleate boiling occurs to an even greater extent "and although despite the lower flow resistance.

Regarding the state of the art, reference is also made to German Offenlegungsschrift 1 451 280 and the patent 24 204 of the Office for Inventions and Patents in East Berlin. Both pre-releases deal, however, with ordinary heat exchanger tubes, which address the problem of steam generator tubes is completely alien. It is in these known arrangements therefore not to Influencing of boiling processes, but about favoring the flow and the Enlargement of the heat transfer areas. For this purpose, the heat exchanger tube according to the in the first place mentioned patent specification inside a tape roll with helically extending Cam arranged, and in the heat exchanger tube according to the second patent mentioned is eir between two concentric pipe walls. System of intersecting helicals Arranged channels, between which rhombic baffles or guide bodies have remained However, these bodies have no more than the cams on the heat exchanger tube after the first Point mentioned patent specification - to do something with influencing boiling processes.

The desired effect of the arrangement according to the invention is particularly great when the projections formed on the inner wall of the pipe have the following dimensional ratios: pjh - 5 to 40, ItId ₁ = 0.005 to 0.08, b / p = 0.2 to 0, 8, where i /, the smallest inner diameter of the pipe, Ii the height of the projections, b the width of the projections in the longitudinal section through the pipe and ρ the slope.

The sum of the bevel angles λ and ß, which are included between the opposing inner lines forming the projections and the pipe axis, is expediently 20 to 80 ⁼ .

A situation that is particularly favorable in terms of production technology arises when one of the two lead angles i \ or β is less than 43 ° and the other is 0 °.

In the course of the overall inventive concept there is also a specific method for production of the steam generator tubes according to the invention, which complements the invention in that it is the shaping and ensures arrangement of the projections according to the invention. This is followed by a cold drawing process in a first production stage a stamp that is on its outer surface is provided with several helical grooves in a smooth tube that serves as a mother pipe, pushed in, whereby by free rotation of the punch on the inner wall of the pipe several helical fields are formed, of which in a second production stage by using a second punch each parts are pressed down, so that a plurality of Raised projections lying helically one behind the other remain standing.

Appropriately, a stamp is used for the second production stage, which on its outer surface with several helical grooves with opposite to the grooves of the first punch Cutting angle is provided and which rotates freely during the drawing process.

If a pipe is to be produced in which one of the two angles of incision χ or β is less than 43 ^: and the other is 0 ', then a punch is used for the second production stage which has several straight grooves on its outer surface is provided and which is inserted into the pipe and pulled straight.

The following are exemplary embodiments of the subject matter of the invention described in more detail on the basis of the drawing. It shows

F i g. 1 shows a sectional view of an example of a cross-drawn steam generator tube according to the invention;

F i g. 2 another example of a cross-drawn tube in section,

F i g. 3 shows a diagram which shows a comparison of the inner wall temperatures of a smooth pipe and a pipe cross-drawn according to the invention for a pressure of 210 kg / cm ² and a "mass velocity" of 700 to 710 kg / m ² second,

F i g. 4 shows a diagram which illustrates a comparison of the maximum values of the inner wall temperatures as a function of the heat flow density for a smooth tube and a tube cross-drawn according to the invention in the case of a pressure of 210 kg / cm ^2,

F i g. 5 shows a schematic view of a device for manufacturing a cross-drawn one according to the invention Pipe,

F i g. 6 a sectional view of a working part for the first production stage,

F i g. 7 shows a section through a pipe after the first production stage,

F i g. 8 a sectional view through the mounting of a mandrel;

F i g. 9 is a sectional view showing the pipe and the tool in the second manufacturing stage for a cross-drawn tube according to FIG. 1 shows

F i g. 10 is a sectional view showing the tube and tool in the second manufacturing stage the production of a cross-drawn tube according to FIG. 2 shows.

Tabel

Chemical composition and mechanical properties of the cross-drawn tubes

according to the invention

Chemical components in percent by weight

60.0
68.0

Table dimensions of the cross-drawn test tubes

Λ-2 Tcstpipe c Ii-i 15-2 A-I 20.16 20.09 20.06 20.27 9.54 13.27 13.18 9.66 0.64 0.47 0.52 0.55 12th 12th 12th 12th 3.16 3.75 3.75 3.16 22 ° 20 ' 21 ° 48 ' 21 ° 48 ' 22 ° 20 ' 18 ° 45 ' 18 ° 37 ' 18 ° 37 ' 18 ° 45 ' 41 ° 05 ' 40 ° 25 ' 40 ° 25 ' 41 ° 05 ' 7.32 11.20 11.20 7.32 6.88 8.65 8.65 6.88 11.42 23.80 21.60 13.30 lü, 78 18.40 16.65 12.50 0.067 0.036 0.040 0.057 0.432 0.335 0.335 0.432 0.459 0.433 0.433 0.459

Outside diameter D ₁ in mm

Smallest inside diameter </, in mm

Height h of the projections in mm

Number of aisles of the trains (number per cross section)

Width b of the projections in mm

Lead angle λ

Lead angle β

Lead angle λ ■ + ■ β

Pitch ρ in mm (pitch in mm number of turns)

re

Ii

Ratios p / h right

Ii

Ψι

b \ p re

i

The cross-drawn tube according to the invention has numerous raised projections 18 or 20 on the Inner pipe wall, as shown in FIGS. 1 and 2 can be seen.

In the above Tables 1 and 2 are numerical examples of the chemical composition, the mechanical properties and the dimensions of the test tubes.

In Fig. 3 are the inner wall temperatures of the smooth pipe and the pipe cross-drawn according to the invention for a pressure of 210 kg / cm ² and a "mass velocity" (flow rate per unit of time through the unit of the pipe cross-section) of 700 to 710 kg / m ² as curves for an average specific enthalpy with the heat flux density as a parameter. In the same diagram, the heat flux q is selected in the range from 10 · 10 * to 50 · 10 ⁴ kcal / m ² · h; the test values for the inner wall of the smooth tube are drawn with solid lines, those of the tube crossed according to the invention for comparison of the effectiveness with dashed lines; in addition, a quality measure of the steam content is also indicated on the abscissa. The diagram clearly shows that both in the single-phase range and in the two-phase range, the inner wall temperature of the cross-drawn tube is much lower than that of the smooth tube υπ Λ that the heat transfer is favorably influenced. That means: Even in the area where the wall temperature rises steeply with the smooth pipe, the bubble evaporation is maintained up to the high quality area with the cross-drawn pipe. Therefore, the wall temperature of the cross-drawn pipe is much lower than that of the smooth pipe.

As further from the diagram in FIG. 3, the rapid rise in wall temperature begins in the case of the smooth pipe with a steam content of 50%. From this one can conclude that the burnout a so-called rapid burnout caused by the transition from nucleate boiling to the movie boiling.

The maximum value (T ₁₀ max) of the wall temperature is shown in FIG. 4 plotted against the simultaneously prevailing heat flux density with the "mass velocity" as a parameter. In this diagram, the smooth pipe and the pipe that is cross-drawn according to the invention are compared with one another for three states of the “mass velocity”, namely at 900, 700 and 400 kg / m ² second. In the case of the cross-drawn pipe, the above maximum value (T _w max) of the wall temperature is much lower than that of the smooth pipe. So in this respect, too, the effectiveness of the cross-drawn tube is remarkable.

It has been shown that the cross-drawn tube according to the invention can withstand burnout at a heat flux density of 60 · 10 ⁴ kcal / m ² · h even under conditions as severe as a "mass velocity" of 400 kg / m ² second. Since the maximum local heat flow density of an oil-fired boiler is 50 to 60 · 10 ⁴ kcal / m ² · h, there is no risk of burnout at all when using such a cross-drawn tube in the parts with high heat flow density in a conventional fossil fuel boiler . The pipe of the present invention contributes greatly to the construction of a subcritical pressure boiler.

The superiority of the cross-drawn tube can already be seen from the results of the test with the two-phase air-water flow at normal temperature and normal pressure. After the flow test, concentrate in the case of a flow containing bubbles in the cross-drawn flow Tube the bubbles much sooner in the middle part of the tube than in the smooth tube and in that previously known finned pipe, and in the case of an annular flow, the thickness of the water layer greater. It follows that the tube according to the invention cross-drawn the tubes of other types and

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Form both for rapid burnout and as a mother tube for the intermediate production stage. Fin

as well as the slow burning out is superior to this usable punch 17 is with screw

and increases the critical heat flux density. give away linear grooves that have a gate

l ^; It is also important to note that the angles / ^ are in the opposite direction.

Pressure drop in the criss-cross tube in a 5 than that used for the first stage of manufacture

a; ■ asigcn flow and in a two-phase pistil. This / wide stamp is now on the

Flow is low. This puts a considerable mandrel IO on top and the tube 3 'is again

Preferred over the finned tube drawn with a rotating. That way, the

at the first production stage formed trains 13

The cross-drawn tube according to the invention is partially plastically uncompressed by the screw and a punch attached to the outside of the punch 17 in a cold drawing process with the aid of a mold. First, a punch is formed in shaped projections 16, and many of a first production stage, on which helically arranged raised projections several helical grooves are formed, 18 on the inner wall of the pipe, which cinge a rhombic or a smooth pipe that serves as a mother pipe. 15 parallelogram-like shape with the two leaders, and by turning the punch will have cutting angles ν and β . Also for this second, the inner wall of the mother tube several screw production stage (tube 23) of the punch 17 is shaped trains and fields. A second punch is mounted in a second supporting mandrel so that it can rotate just as smoothly as Fcrtignungsstufc, on which for the first operation.

several helical grooves with the around 20 As already mentioned, on the inner wall of the pipe

inverted lead angle or straight grooves due to the two production stages many sublime

are attached, pushed into the tube, and formed by projections. The shape of these protrusions

Turning or pulling this punch straight depends on the shape of the punch or punch used

part of the helical fields in this the combination of dimensions, such as the prozcn-

Tube pressed down plastically, so that many projections 25 tualcn surface reduction. F i g. 10 shows

rhombic or other shape evenly and a modified version, in which many pa-

stand individually on the inner wall of the pipe. rallclogram-shaped protrusions 20 thereby cnt-

I i g. Fig. 5 is a side view of the main part of a stand with a punch 19. of the grooves

Cold drawing bench of the Celtic type, which is used for production with a lead angle β = -. 0 has. these are

of the subject matter of the invention. A nut pipe 3 30 straight grooves parallel to the pipe axis in the second

is a straight pulling process from a manufacturing stage (tube 24) anchored in bed 1 of the bench

Working part 2 and one of an endless chain 6 was made.

towed clamping slide 4 continuously The results of broad tests have shown pulled. The head end of the mother tube 3 is before that the shape and arrangement of the raised front Pull pressed and in the clamping slide 35 jumps of the pipe according to the invention krcuzgczogcncn clamped. A pawl 5 of the slide is very advantageous for the heat transfer. as the endlessly revolving chain 6 hooked, so that a result has been found "that an earthing Slide 4 is pulled along. according to the invention, cross-drawn tube in order to

As in Fig. 6, the working part 2 includes boiling from the area of low steam value to a mold holder 7, which is attached to the bed 1 of the bench 40 with the high steam value below the predetermined ones and contains a mold 8. It has an opening 9, conditions of pressure, of heat flux density, the diameter of which is slightly larger than the internal speed, and the "mass velocity" of the raised pre-diameter of the mold in the center of the mold holder. must have jumps, the following conditions must be met.A punch 11 sitting on a mandrel 10 will not:
the mother tube 3 pushed in, uH in this to- 45 ,, _
stand the pipe is pulled. The stamp II is '/' _ «^ l _S w η ns
with several helical projections 12 J "· ~ J 5 hun *, i"'i
provided, the fixed dimensions and a fixed 7. «Im ·« n ·
Have angle of cut. While the pipe3 between- * + /) - ^ ms8U,

see the punch 11 and the form 8 is drawn, 50 where ρ represents the slope, which is determined by the number

are determined by the helical lines attached to the outside of the punch, as well as

th helical projections on the pipe through the bevel angles \ and β and the transverse

inner wall helical trains 13 with a cut. /; represents the height of the island, </, is dei

Cutting angle \ plastically pressed and shaped. smallest inner diameter of the pipe and h is dit

For example, in this first production 55 width of the protrusions in a longitudinal section through there:

grade that in Fig. 7 shown tube 3 'with screw tube. However, form and type should be appropriate

shaped trains. For this purpose, the projections are at the bearing point of the order to the bubble boiler

Dorns 10, which bears the mentioned stamp II, to maintain the following condition as well as possible

Rotary device, such as a thrust bearing 14, meet the requirements:

seen as in Fig. 8 so that the 60 "_" ,. _25th

Stamp 11 can rotate freely and uniformly. V ₁ . _ _{n ni,.} '

At the rear end of Be'tes 1 on the side of the thorn V '. * ¹ ~ "'" ^L ,? ^{IS L} ' ^{u /} ·

bracket is an adjusting device 15 for the <a I ^ -r »

Stamp of a known type attached, which is shown in FIG. 5 ^{a + p} - JU 01s ο.

is indicated. 65 For the above limit values of the various sizes

In the next step, which is shown in FIG. 9 illustrates the number of helices on a cross

is, the pipe 3 'of FIG. 7 with the cut that is easy to manufacture: 6, 12, 18 or

Inner wall formed helical trains 24 trains. For the inventive 'pipe sine

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9 10

ied · Kh '.2'..no>/;.;·; οΐί π; - :: ^ ;: ι W er'.e. In . · Ρ ι l: cr kreu / jc / ogjiicn Ruhr, which are the maximum critical TaΚ:! Ie 2 mho c.ä e :: Npr ^ hi: 'de: i ^λ · "getni ^ ahlen heat-iromdicHe, are depending on the pressure used for> icr · .er-chii'cerie Te "! pipes ^! '^" chneren. V. ic, the "e TiSeüe"i;:;. ¹ Te »· .roh: -; ::" Area however hcsiätigi. that in the above-mentioned situations: Behavior i-wcrü jno arrangements / i: for: ed- 5 guiding for a subcritical pressure of 21ukg -telienJ. Mj- »'el!', M de- Prüfjngicrjerin ^ cr. Servant cm- 'according to the llauptaufyabe of the F-lrlindiinc for the R .ihre uberi ",. ii.r; λοιγ: ·; -" · grv'ben L r.tcr ^ c'"; ed fe · - ;. lall A measure of 710 kg in ^J So-Under the above conditions only the last and a heat flow density of 60 · 10 ⁴ kcal / mentioned arrangement of ·. -, -i = 20 to 80 a m ¹ · h of bubble boiling up to a steam switch condition, which remained due to the cold drawing at a free io of 70 ⁰ J ₁ CrIIaItCn. With a "mass speed of rotation of the punch, this is a speed" of 400 kg / m ² second It is possible even with a limit drawn by the manufacturing process. The difficult prerequisite, such as bringing the helical trains to the pipe density of 60 · 10 * kcal / m * · h possible, the permitted inner wall through free rotation of the The stamp will keep the temperature of a conventional boiler tube below 5 (X) C through the friction between the stamp and the 15. By using an inventing mold and de m pipe, and the maximum according to the cross-drawn pipe, almost all limit values for both χ and β is 43 ". Problems with the construction of the boiler tube shape and arrangement of the projections in the solved.

For this purpose 2 sheets of drawings

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Claims (5)

ι 2 patent is executed - the following problems patent claims:,. H is based on: 1. Steam generator tube with helical The operational safety of the steam tube a Inner flues for operation with high heat- steam boiler depends on the wall temperature of the current density below the critical pressure, 5 pipe. That means: She is so close to that characterized by two heat transfer coefficients on the inner surface of the Crossing systems of helical tubes in opposite directions, furthermore with the temperature of the working medium Inner cables, through their overlapping screw (for example a steam-water Oemiscnes) and ben-shaped one behind the other projections (18, linked with the heat flux density that one of the 20) of a parallelogram-like, in particular 10, wall surface, which in the presence of a strong ammenrhombic Form are formed. exposure to radiation always pay close attention 2. Steam generator pipe according to claim 1, must be given. Due to the increased introduction of the fact that the on the pipe interior oil firing and the general spread of wall formed projections (18, 20) following forced flow boilers has increased the risk of dimensional ratios: p / h = 5 to 15 that a local state occurs at which the critical 40, ItId ₁ = 0.005 to 0.08, b / p = 0.2 to 0.8, where the heat flux density is exceeded and which leads to ad, the smallest inner diameter of the pipe, /; Burning out and thus a break in the steam the height of the projections b leads to the width of the pre-generator pipe. Cracks in the longitudinal section through the pipe and ρ The appearance of the burnout of a steam the slope means. 20 generator tube, which has a high heat flux density 3. Steam generator pipe according to claim 2, there is exposed and below the critical pressure is indicated by sec. That the sum of the initial work is based on two factors, namely , the angle of intersection and, which are enclosed between the internal lines and steam content that form the prior rapid burnout in an area of low cracks, and secondly, a slow extension of the pipe axis , 20 "to SO" 25 glow in an area of high vapor content. That amounts to. The effect mentioned in the first place is due to the over- 4. Steam generator tube according to claim 3, caused by nucleate boiling to film boiling. characterized in that one of the two mentioned in the second place, however, is smaller than 43 ° due to the cut angle λ or β and the annular flow distribution of the vapor-liquid other is 0 °. 30 mix. So you have to get the critical one 5. Method for producing a steam heat flux density in a steam generator tube safely generator pipe according to one of the. .nsprüche 1 to 3 to delimit this critical heat flow density through by "cold drawing, characterized in that heat transfer tests detect and on the other hand In the first production stage, a stamp that knows the flow pattern through flow tests its outer surface with several screw 35 learn.