EP0120435B1 - Shape of fuel gas passages in boilers - Google Patents

Abstract

1. Heating gas flue for heating boilers for burning liquid or gaseous fuels, consisting of a water carrying wall of which the part nearest the combustion chamber is double-walled and is provided with longitudinal ribs which divide the entire cross section of the flue into individual channels, characterised in that the longitudinal ribs are constructed as U-, L- or T-profiles (1) and are arranged so that their webs (2) which extend transversely to the free legs (9) entirely cover the wall (3) nearest the combustion chamber and rest on this wall (3) and in places are welded to the wall (3) in heat-conducting manner, in such a way that the heat-conducting cross sections of the heat conductive bridges (5) thus formed decrease towards the outlet end of the heating gas flue corresponding to the outlet end of the boiler, longitudinal weld slots (16) or weld connections free from added weld material being arranged in order of decreasing length, with increasingly great spacings therebetween, on the webs (2) of the profiles (1), to form the graduatedly effective conductive bridges (5).

Description

The invention relates to a heating gas train for heating boilers according to the preamble of the main claim.

Such heating gas flues for heating boilers are known, for example, from DE-A 1 778 832.

In this known boiler, the longitudinal ribs are formed by a cylindrically rolled sheet metal blank, which is often folded to form the longitudinal ribs, a sealed space being present between the folded tube and the adjacent water-cooled wall to increase the heating surface temperature and thus to reduce the risk of condensate formation , in which an insulating layer can optionally be arranged, d. H. there is no direct heat-conducting connection between the folded tube and the water-cooled wall.

Heating gas flues, which are divided into individual channels by longitudinal ribs, have proven themselves and have been introduced on the market. Such heating boilers are operated today with so-called sliding temperature and are therefore referred to as low-temperature boilers. Such heating boilers can even be completely switched off in the most modern design and provided with a corrosion protection insert which consists of a cast body which is pressed or shrunk into the tubular insert made of sheet steel (DE-A 2 948 864). As has been shown. such boilers have a clear performance limit upwards, i. H. the pipe pull or, in particular, the fitted casting insert can only be produced economically up to a maximum diameter and, if this is exceeded, there is a measurement ratio between the train heating surfaces (secondary heating surfaces) and the combustion chamber volume. These limits are in the order of magnitude between about 40-60 cm in diameter and in terms of performance at about 105-146,000 kJ.

So if you want to keep this construction principle on the one hand, but on the other hand you want to exceed performance limits and therefore size dimensions, you have to do it in other ways, especially with regard to the design of the heating gas flues.

The invention is based on the object, while maintaining the above construction principle, to improve a heating gas flue of the type mentioned in that heating boilers provided with such trains, taking into account the corrosion protection requirements, can also be operated as low-temperature boilers with a sliding temperature and ensure that in certain areas there are different heat transfers. This object is achieved with a heating gas flue of the type mentioned according to the invention by the features stated in the characterizing part of the main claim. Advantageous further developments result from the subclaims.

U-shaped profiles are known from DE-A 15 01 676 and 20 25 472, but these profiles form the wall itself in the boilers in question, which separates the water-carrying from the gas-carrying space. Although the reason for the design of the heating gas flues according to the invention was the aforementioned limits, this should not rule out that the solution principle according to the invention cannot also be used for heating boilers with smaller output ranges. The design principle according to the invention can also be used not only for trains which have only a water-cooled wall, but also for trains which have water-cooled walls on the opposite side.

By means of this design according to the invention, the profiles are used on the one hand to form the heating gas flues, but on the other hand their webs placed on the water-carrying wall simultaneously form a largely condensation-preventing double wall on the water-carrying draft wall, wherein, as will be explained in more detail, a specifically metered heat transfer to the wall takes place. which also has the effect during start-up processes during operation, particularly in the low-temperature area of the boiler, that the areas lying towards the fume cupboard side can heat up more quickly because of the lower heat transfer there, which counteracts or largely prevents the accumulation of condensate.

Since only profile strips can be processed in this solution, larger-volume boilers of the type mentioned can also be formed in this way. The attachment of the profiles is very simple since, apart from certain exemplary embodiments, they are placed with their base webs directly next to one another on the train wall to be fitted and welded with their webs. Thereafter, in a certain embodiment (U-profiles), the legs of a profile are pressed together, which is done with a suitable wedge-shaped tool that is pressed between the free legs of two adjacent U-profiles, whereby care can also be taken if necessary, that the resulting draft channels narrow towards the exhaust side in adaptation to the decreasing gas volume. In this manufacturing process (after the profiles have been attached, the draft wall is rounded to form a tube or partial tube and closed with a longitudinal weld seam), a multitude of heating gas flues with approximately triangular cross sections are created around the pot-like combustion chamber to be used later, each alternating with their distal base points against the combustion chamber and are directed against the wall.

However, the principle of the solution according to the invention can still be used as regards the formation of traction channels which are U-shaped in cross section. by several design variants within the meaning of subclaims 4 to 8.

The hot gas flue according to the invention and special embodiments are explained in more detail below with the aid of exemplary embodiments.

• Fig. 1 einen Querschnitt durch einen Heizungskessel allerdings nur beispielhafter Art ;
• Fig. 2 einen Blechzuschnitt für die U-Profile ;
• Fig. 3 einen Längsschnitt durch den Heizungskessel ;
• Fig. 4 im Schnit die U-Profile nach Anbringung auf dem noch planen, später das Rohr bildenden Blechzuschnitt ;
• Fig. 5 im Schnitt die U-Profile gemäß Fig. 4 nach ihrer Verformung ;
• Fig. 6 eine besondere Ausführungsform hinsichtlich der Zurichtung der U-Profile gemäß Fig. 5 in Draufsicht und
• Fig. 7-11 im Schnitt besondere und bevorzugte Ausführungsformen der Profile und ihrer gegenseitigen Zuordnung an allein oder beidseitig wasserführenden Zugwänden.

It shows schematically

• Figure 1 shows a cross section through a heating boiler, however, only of an exemplary nature.
• 2 shows a sheet metal blank for the U-profiles;
• 3 shows a longitudinal section through the heating boiler.
• Fig. 4 in section the U-profiles after mounting on the still plan, later forming the tube sheet metal blank;
• 5 shows in section the U-profiles according to FIG. 4 after their deformation;
• Fig. 6 shows a special embodiment with regard to the preparation of the U-profiles according to FIG. 5 in plan view and
• Fig. 7-11 in section special and preferred embodiments of the profiles and their mutual assignment on water conductors alone or on both sides.

3 is only an example and consists in a manner known per se of a water-carrying housing 22, the front and rear walls 23, 24 of which are penetrated by the tubular wall 3 in a liquid-tight manner, the projecting ends being closed with lids or doors . The rear cover 25 is provided with a flue gas outlet connection 26. The deflection chamber 27 is arranged in the tube formed by the wall on the burner side (burner not shown). The pot-like combustion chamber 28 sits in the free space between the heating gas flues 8, and the flue gas collecting chamber 28 'is located behind it. This boiler structure is not absolutely essential, just as the combustion chamber 28 must be cylindrical and the heating gas flues 8 must be arranged in a ring structure. Possibly. 8 additional secondary heating surfaces can be arranged behind the combustion chamber 28 or the heating gas flues. Furthermore, the walls of the combustion chamber can also be designed as water-carrying double walls, the interior of which is connected in a suitable manner to the other interior of the housing 22. This would be the case in which the heating gas flues 8 are delimited on both sides by water-cooled walls 3, 3 '.

The sheet metal blanks for the rib profiles 1 look like they can be seen in FIG. 2 before they are deformed into U-profiles. The side slots are used to compensate for thermal expansion, but are not absolutely necessary.

After the edges of the surfaces forming the free legs 29 have been edged, the profiles thus formed are placed close to one another in the sense of FIG. 4 on the sheet metal blanks of the wall 3 which will later form the pipe, are still flat or slightly bulged, and are welded to the wall in the region of the longitudinal welding slots 16. As can be seen from Fig. 2, the length of these slots 26 decreases towards the rear, while their distance from each other increases, i. H. there are thermal bridges 5 of different sizes in connection with the sheet metal blank. This also applies to all of the exemplary embodiments to be described below. Now a wedge-shaped tool (shown in simplified form as a triangle in FIG. 4) is pressed between the free legs 9 of each two adjacent profiles 1, so that the profiles then appear in cross-section, as can be seen in FIGS. 5 and 1. Possibly. longitudinal weld seams can also be laid in the gussets 30 '(FIG. 5) which form. It is also possible to bend the legs in the sense of FIG. 6.

At the rear end of the tube, an annular shell 30 can advantageously be arranged either completely or, as shown, in part freely projecting in the area of the flue gas collecting chamber 28 ', but for which it is essential that its inner edge is welded to the profiles 1, to ensure a flow of heat from the profiles into the shell 30, so that this can also heat up quickly.

The term "thermally connected in some areas" is to be understood as the slot welding connection described above, but it is also possible, and this is also preferred because of the much lower expenditure, that the base webs 2 with, for example, a tungsten electrode (i.e. without the addition of additional welding material ) to be welded or melted. The attachment of longitudinal welding slots 16 of different sizes and distances can be omitted, and the attachment takes place in such a way that the tacking area or the resulting thermal bridge 5 becomes narrower or smaller from front to back. This can be accomplished easily and simply by means of a correspondingly regulated supply of current to the electrode, the weld or tack seam being interrupted in the sense of the different distances of the slots according to FIG. 2.

In the embodiment according to FIG. 7, the flow channels of the heating gas flue which are U-shaped in cross section are formed by rectangular profiles 10, i. H. two adjacent profiles 10 delimit a single channel. The same applies to the T-shaped profiles 11 according to FIG. 11. As can be seen from FIG. 8, however, U-profiles can also be arranged at a distance from one another, the free surfaces of the wall 3 being covered with correspondingly wide intermediate webs 12 in order to avoid this Maintain double wall principle in all areas. 7, 8 are advantageously provided when pressing the profiles in the transition areas 13 of the legs 9 to the webs 2 profile crankings 14, which serve to accommodate the connecting edges 15 of adjacent webs 2 or the intermediate webs 12. This is advantageous in order to prevent arching when welding the webs 2 or the intermediate webs 12.

The legs 9 of the profiles 10, 11, which can form the longitudinal ribs 1, as indicated in Fig. 7, at intervals with flag-like outbreaks conditions 19 are provided. 7, 8, the wall of the combustion chamber 28 which is not water-cooled in this case is designated by 3 ″.

If, in contrast to FIG. 3, the combustion chamber is water-cooled, there is (such boilers are known) an additional water-cooled wall 3 'with respect to the heating gas flue, which are also covered with the profiles described according to the same principle (FIG. 9) . Depending on the free cross section of such a train and depending on the length of the legs 9, the arrangement can be such that the longitudinal edges 17 of the opposing profiles 10, 11 end approximately in the same intermediate plane or protrude somewhat into the space 18 of the other profiles. However, an arrangement according to FIG. 9 is advantageously chosen such that the longitudinal edges 17 run closely above the welded points of the heat-conducting bridge 5. Since these longitudinal edges 17 heat up very quickly when restarting or in general when operating in the low-temperature range of the boiler, in any case significantly faster than the thermal bridges under cooling, the heating of the longitudinal edges 17 via radiation can also have an effect on condensate formed on the thermal bridges, for example that this evaporates faster.

As can be seen from FIG. 10, several legs 9 can also have a common web 2 and the entire profile can also be designed, for example, as an extruded profile with a suitable wall thickness.

7 to 11, the heating gas flues are shown in a straight extension, which of course can also be used in this form depending on the structural conditions on the boiler. It should be noted, however, that trains in this design, based on modern boiler designs, generally have more or less curved walls 3 and 3 ', respectively. that is, the exemplary embodiments shown also apply to such curved surfaces. An essential aspect of the entire heating gas train formation is, as described, to a certain extent draining heating gas-carrying areas to the extent that condensate formation is largely prevented, but on the other hand ensures that any condensate deposits are evaporated as quickly as possible when the boiler starts up again. Test boilers provided with such train designs and operated over a longer period of time have shown that these requirements are met absolutely satisfactorily.

Claims (8)

1. Heating gas flue for heating boilers for burning liquid or gaseous fuels, consisting of a water carrying wall of which the part nearest the combustion chamber is double-walled and is provided with longitudinal ribs which divide the entire cross section of the flue into individual channels, characterised in that the longitudinal ribs are constructed as U-, L- or T-profiles (1) and are arranged so that their webs (2) which extend transversely to the free legs (9) entirely cover the wall (3) nearest the combustion chamber and rest on this wall (3) and in places are welded to the wall (3) in heat-conducting manner, in such a way that the heat-conducting cross sections of the heat conductive bridges (5) thus formed decrease towards the outlet end of the heating gas flue corresponding to the outlet end of the boiler, longitudinal weld slots (16) or weld connections free from added weld material being arranged in order_ of decreasing length, with increasingly great spacings therebetween, on the webs (2) of the profiles (1), to form the graduatedly effective conductive bridges (5).

2. Heating gas flue according to claim 1, characterised in that the free legs (9) are angled towards each other and the angle increases from 0° upwards, from the inlet end of the heating gas flue towards the outlet end.

3. Heating gas flue according to claim 1, characterised in that the free legs (9) of each U-profile are angled towards each other in such a way that the cross sections (7) of the heating gas flues (8) thus formed, both between the legs (9) of a profile and also between the legs (9) of two adjacent profiles, are substantially triangular.

4. Heating gas flue according to claim 1, characterised in that the U-profiles are spaced from one another by approximately the width of one profile and ribfree intermediate webs (12) are arranged between the profiles and these webs (12) are also attached to the tube in places by graduatedly effective conductive bridges (5).

5. Heating gas flue according to claim 1 or 4, characterised in that, in the region of transition (13) from the legs (9) to the web (2), there is a profiled bend (14), and the joining edge (15) of the adjacent web (2) or intermediate web (12) is arranged in this bend (14).

6. Heating gas flue according to one of claims 1 to 6, characterised in that, if the flue walls (3) are water-cooled throughout, the opposite wall (3') is also provided with corresponding ribbed profiles (1, 10, 11) and if required intermediate webs (12).

7. Heating gas flue according to claim 6, characterised in that the free longitudinal edges (17) of the oppositely arranged ribbed profiles are each arranged to project into the gaps (18) of the ribbed profiles (1) on the other side.

8. Heating gas flue according to claim 7, characterised in that the free longitudinal edges (17) of the legs (9) engaging in the gaps (18) of the ribbed profiles (1) opposite are arranged to extend immediately above the weld points (5) of the webs (2).

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