EP0711954B1 - Air/flue gas stack - Google Patents

Abstract

The waste gas pipe (3) is positioned in the chimney shaft forming the air-feed duct (2), a little apart from the shaft wall. The outer periphery of the waste gas pipe has ridges (7), parallel with the pipe's longitudinal axis. The ridges may be lateral to the pipe's longitudinal axis. The cross-sections of the ridges is triangular or rectangular, with rounded free edges.

Description

The invention relates to an air / exhaust chimney with the Features according to the preamble of claim 1.

Air / exhaust chimneys of the type specified above known (see DE-U 77 06 857, DE-A 35 39 311). With these known chimneys flows into the chimney head Fresh air in counterflow to that inside the exhaust pipe discharged exhaust gas stream, the fresh air through Heat exchange with the warm pipe wall of the exhaust pipe is heated. This enables waste heat to be recovered and thus an energy saving.

A heat recovery is also known in the Connection with the routing of the exhaust gas and the supply air a kiln for firing ceramic articles (FR-A 493 632). In this kiln, the exhaust duct consists of ceramic socket pipe sections, which increase the desired heat transfer to the flowing along the outside Supply air are provided with ribs. The exhaust duct runs horizontally so that with a support of the socket pipe sections must be counted over the ribs. Out of it follows that the socket pipe sections for strength reasons have a relatively large wall thickness and that in only small number of wing-like ribs provided project relatively far from the peripheral surface.

In general, premature cooling of the smoke or exhaust gas inside the exhaust pipe of air / exhaust chimneys therefore not desirable because of a corresponding falling below the dew point considerable condensation can occur, which is a Disposal of the condensate is necessary. Is also through excessive cooling of the exhaust gas thereof Flow velocity in the exhaust pipe is reduced too much. A recovery of the waste heat from the exhaust gas should therefore for chimneys in general within certain limits being held.

However, other ratios apply in cases where a Air / flue gas chimney for removing the flue gas from Condensing plants are used, which are usually gas-fired and especially with the exhaust gas from the heating systems a pressure above atmospheric pressure in the Exhaust pipe is fed. Under these circumstances becomes a relatively high level simply due to the excess pressure Flow velocity of the exhaust gas in the exhaust pipe ensures that the exhaust gas flawlessly from the Chimney is removed. In addition, the Composition of any condensate that may occur the choice of fuel considerably less aggressive and therefore does not interfere to the usual extent.

The object of the invention is therefore an air / exhaust chimney of the type mentioned, which is mainly in Connection with condensing plants as far as possible Improved thermal efficiency allowed without that this increases the risk of breakage for the Construction of the smoke tube used ceramic Pipe sections is caused.

This is achieved by the design according to claim 1. Due to the circumstances at Condensing plants it is possible to push the limits for the Recovery of the waste heat from the exhaust gases considerably further to pull than before. Due to the increased recovery of the Waste heat can therefore improve the energy balance. An increased recovery in the inventive Chimney is possible because of the Enlargement of the heat transfer peripheral surface of the Exhaust pipe a more intense heat transfer to the Fresh air takes place.

The ribs provided on the outer surface of the exhaust pipe can be used to achieve increased heat transfer their design and their course can be varied. A preferred design provides that the ribs axially parallel to the longitudinal axis of the exhaust pipe on its Outer surface run. The small radial extension and the multitude of ribs is largely one Compromise on the sensitivity to breakage in the Handling of the exhaust pipe and by the type of manufacture certainly. It has been shown that a variety relatively little protruding ribs that the Outside surface of the exhaust pipe the impression of a grooving convey a significant increase in heat transfer in the Comparison with a smooth pipe wall and are relatively unlikely to break. The distance adjacent ribs from each other must be selected so that there is also a flow between the neighboring ribs takes place, which gives the desired heat transfer.

To increase the heat transfer can also be considered to a certain extent in the area of the ribs To cause turbulence of air flow. That can be done through Transverse or oblique arrangement of the ribs relative to the Fresh air flow can be achieved. An advantage here turns out to be a helical course of each other parallel ribs on the outer circumference of the exhaust pipe.

The exhaust pipes proposed here are ceramic exhaust pipes, in the way of preferred manufacturing of isostatic pressing is very extensive Design freedom for the ribs. While e.g. in the case of ceramic tubes manufactured in the extrusion process Ribs can only run axially parallel to the pressing direction, allows the isostatic pressing also the described Oblique course of the ribs with respect to the pipe axis.

The exhaust pipe is in the usual form by individual Pipe sections with sleeves provided at one end built up an assembly by way of Allow plug connection.

The pipe cross section can be round or square be.

Fig. 1 einen schematischen Längsschnitt durch einen Teil eines Schornsteins, bei dem ein Abgasrohr nach der Erfindung eingesetzt ist;

Fig. 2 einen Querschnitt längs der Linie II-II in Fig. 1, und

Fig. 3 in gegenüber Fig. 2 vergrössertem Maßstab einen Teil-Querschnitt des Abgasrohres.

An embodiment of the invention is explained below with reference to the accompanying drawings. The drawings show:

Figure 1 is a schematic longitudinal section through part of a chimney, in which an exhaust pipe is used according to the invention.

Fig. 2 shows a cross section along the line II-II in Fig. 1, and

Fig. 3 on a larger scale than Fig. 2 shows a partial cross section of the exhaust pipe.

The part of an air / exhaust chimney shown in Fig. 1 has one of a number of mantle stones 1 built-up mantelpiece, in its shaft 2 one off individual pipe sections 3 built exhaust pipe is arranged concentrically. At least on some of the Pipe sections 3 are metal strips 4 on their outer surface attached, of which spacers 5 diagonally after extend outside. The spacers 5 (in the shown Embodiment four pieces per metal band) serve to keep the exhaust pipe concentrically in the shaft 2, but at the same time not to hinder relative thermal expansion.

The connection of the built by the pipe sections 3 Exhaust pipe to the respective heating systems and their connection to the fresh air duct 2 are sufficient known and need no further explanation here.

In the exemplary embodiment shown, the exhaust pipe through relatively thin-walled ceramic pipe sections 3 formed, which are manufactured by isostatic pressing. They each have a sleeve 6 at one end, in which each have the other end of the next one Pipe section is insertable. A gas tightness at the Plug connection can be achieved by putty.

As can be seen from FIG. 3 and only locally in FIG. 1 is indicated, the outer surface of the pipe sections 3 a plurality of ribs 7 on the present Embodiment lie close together and one Have a triangular cross-section. The wall thickness of the Pipe sections 3, measured between the inner wall surface and the bottom of the grooves formed by the ribs 7 for example 7 mm, the height and width of the ribs on Groove base is about 3 mm. Because of the dense Side by side arrangement of the ribs 7 and the described Dimensioning have the pipe sections 3 on their Outside surface has a serrated appearance. As can be seen in FIG. 1 results, which extend parallel to the longitudinal axis of the Pipe sections 3 extending ribs 7 between the neck the sleeve 6 and one place in front of the opposite End of the pipe section 3, which is still in the assembled state lies outside the next following sleeve 6.

To the risk of breakage of the ribs 7 when handling construction, the free edges of the Triangle cross-section, deviating from the representation in Fig. 3, flattened or rounded.

Claims (6)

1. An air/flue gas stack for heating installations operating at a low flue gas temperature, comprising a flue gas tube which is arranged in a shaft of the stack, the shaft forming the feed air duct (2), at a spacing from the shaft wall, and which comprises a plurality of tube portions, characterised in that

   a) the tube portions (3) comprise thin-walled ceramic material and each have a respective socket (6) for the purposes of a push-in connection; and

   b) the outside surface of the tube portions (3) has a channelling with a plurality of ribs (7) which project slightly and which are disposed in closely juxtaposed relationship.
2. A stack according to claim 1 characterised in that the ribs (7) extend parallel to the longitudinal axis of the flue gas tube (3).
3. A stack according to claim 1 characterised in that the ribs (7) extend in a helical configuration on the peripheral surface of the flue gas tube.
4. A stack according to claim 1 characterised in that the ribs extend transversely to the longitudinal axis of the flue gas tube.
5. A stack according to one of claims 1 to 4 characterised in that the rib cross-section is triangular or quadrangular.
6. A stack according to claim 5 characterised in that the free edges of the ribs are rounded.

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