CAST IRON OR ALUMINUM SECTIONAL BOILER
A cast iron or aluminum sectional boiler, in particular a condensing boiler, having generally annular sections, one front section, one cover-like rear section and at least one center section being provided which form a furnace chamber having generally surrounding heating gas passages, and their annular water compartments are connected to one another via hubs. The sections have one lower return connection and one upper feed connection as well as at least two anchor rods for holding the section block together. The cast iron or aluminum sectional boiler is optimized with respect to compactness and robustness. Annular gaps are in each case provided as heating gas passages between two adjacent sections, each of which, starting from the furnace chamber, runs approximately radially outwards and leads into an exhaust gas collection chamber on the outside of the sections.
The present invention relates to a cast iron or aluminum sectional boiler, in particular a condensing boiler.
BACKGROUND INFORMATIONSectional boilers are generally made up of a plurality of boiler sections cast in one piece which are situated one behind the other and connected to one another by hubs on the water side. Flow takes place through the water channels and water pockets formed by the boiler sections between the return connection and the feed connection. Sectional boilers generally have a lower return connection and a feed connection situated at the top, preferably in the particular hub. The heating gases flow from the furnace chamber via downstream heating gas passages to an exhaust gas connection piece and emit heat to the boiler water on their way.
In conventional boilers of this type, the sections are situated in series one after the other. There is an annular front section to which a furnace chamber door or a burner plate may be attached, one or more similarly designed center sections as a function of output class and a rear section. The furnace chamber extends through front and center sections to the rear section, which with its cover-like design forms the floor of the furnace chamber. In these specific embodiments, all boiler sections have similar outside dimensions because they form parts of the furnace chamber, heating gas passages and water compartment across the entire boiler cross section.
Furthermore, boilers for low output ranges which are made up of only two or even only one boiler section are also known.
With respect to the exhaust gas routing and the efficiency of the heating units, a differentiation is made between caloric value technology and condensing technology. More and more condensing heating devices are being used for reasons of saving energy. The design of their heat exchanger allows for the possibility of cooling down the moist exhaust gases arising in operation during the combustion of fuel and air to below the exhaust gas dew point. During this process, the moisture of the exhaust gases is condensed out and in addition to the perceptible heat, the heat of condensation is transferred to the heating water.
When used as a condensing boiler, special attention must be given to the selection of materials, as the exhaust gases are contaminated due to the composition of the fuel used and due to the combustion process, and the accumulating water of condensation contains various acids at a low concentration. The components in contact with water of condensation such as heating surfaces, exhaust gas collectors and the exhaust gas flue must thus be resistant to the acids, which is why these components are usually produced from stainless steel, aluminum or plastic. Welded stainless steel heat exchangers are generally used, especially in oil condensing technology, as is described, for example, as a helically wound pipe in German Patent Application No. DE 10 2004 023 711 B3. They offer the advantage of standing up to the high level of acidity without corrosion. Disadvantages are the high costs associated with the material as well as the less favorable scaling conditions in particular in welded sheet metal constructions and the larger physical sizes which make installation difficult in confined spaces.
The heat exchangers of conventional caloric value boilers are frequently manufactured from cast iron. They are distinguished by high robustness and long life. Being assembled from mostly identical cast segments, they allow cost-effective production and easy scalability with respect to different output classes and offer good installation possibilities even in confined installation conditions. The material stands up very well to brief exhaust gas condensation phases when operation is started and the heat exchanger is cold. In its present form and design, the only area where cast iron is not suitable is in a condensing operation with extended accumulation of water of condensation.
Furthermore, a condensing boiler having a compact heat exchanger made of corrosion-resistant material, which is integrated and connected downstream hydraulically, is described in German Patent Application No. DE 296 21 817 U1. As a separate component, this compact heat exchanger is surrounded by two bowl-shaped boiler sections and connected separately on the water side. All boilers having a downstream heat exchanger have the disadvantages that the installation expense is increased by the necessary pipe components and resistance on the water side rises. As a separate, external component, the system also causes cooling losses which must be reduced by suitable thermal insulation.
SUMMARYAn object of the present invention is to optimize a cast iron or aluminum sectional boiler, in particular with respect to compactness and robustness.
An example cast iron or aluminum sectional boiler is characterized in that annular gaps are provided between each of two adjacent sections as heating gas passages, each of which starting from the furnace chamber runs approximately radially outwards and discharges into an exhaust gas collection chamber on the outside of the sections. Each of two adjacent sections has a matching geometry for forming an annular gap.
To that end, different specific embodiments are possible, namely in the first case that an annular gap runs radially at a right angle to the central axis of the furnace chamber and in a straight line to the outside. In a second variant, an annular gap is radially curved and runs to the outside in the form of an arch, similar to the geometry of a turbine blade. In a third specific embodiment, it is provided that an annular gap runs in a straight line to the outside, tilted toward the central axis of the furnace chamber. This is suitable in particular if the entire section block is in a standing position because the condensate is well able to drain downwards all around from one gap. Furthermore, an annular gap may also run radially to the outside in a wave-like fashion, in particular to increase the flow turbulence within a gap so that an intensive heat transfer is achieved on the surfaces.
Advantageously, the width and/or the open cross section of an annular gap diminish from the furnace chamber to the outlet on the outside of the sections to achieve an adaptation to the decreasing heating gas volume accompanying the cooling. The surfaces of the sections contacted by the heating gas, at least the surfaces forming the gap, may be provided with a corrosion-resistant coating.
The exhaust gas collection chamber on the outside of the sections, into which the annular gaps discharge, extends in the form of a hollow cylinder around the outer jacket surfaces. of the sections and is limited to the outside by a jacket. This jacket is sealingly accommodated between annular webs projecting radially outwards on the outside of the front and rear sections.
The two anchor rods used for holding the section block together are situated within the hubs. Alternatively, a feed pipe for return water and/or a withdrawal pipe for feed water situated within the hubs may be used for holding the section block together if they are provided with appropriate threads for clamping the system.
The upper and lower hubs may be alternately closed for providing a forced flow between the return and feed connection, closure means being attached to the anchor rods, feed pipe and/or withdrawal pipe. This process ensures an alternating overflow between two adjacent sections in the upper and lower hub over the length of the section block.
At least two centering points or surfaces which represent the unfinished casting dimensions and tolerances particularly well are provided on each section for maintaining an exact gap size between two adjacent sections. The thickness of the section in particular has a direct influence on the gap width between two sections. These centering points or surfaces determine the mechanical machining of the sealing or contact surfaces on the hubs, as this allows detection of the actual end measure after the casting process at the decisive point and then sets it to the desired and individually exactly fitting setpoint size via machining.
The present invention creates a sectional boiler optimally suitable for a condensing operation, the positive material properties of cast iron or aluminum being specifically applied and utilized to ensure good thermal transfer properties, compactness and robustness. Corrosion-inducing exposures are brought under control. According to the present invention, the corrosion-resistant coating itself is not only easy to apply and control, it is also protected against possible mechanical stresses in the gaps. In addition to simple manufacturing, the design of the sections offers the advantage that it is possible to variably adjust for different firing capacities and heat exchanger outputs by inserting additional center sections of varying lengths. Nonetheless, all attachment components situated on the face part and all water connections remain the same. Only the jacket surrounding the exhaust gas collection chamber varies. Due to the low exhaust gas temperatures, the exhaust gas collection chamber may even be manufactured from plastic.
The figures show one exemplary embodiment of the present invention. It shows a cast iron or aluminum sectional boiler.
The sectional boiler is generally made up of annular sections, namely a front section 1, a cover-like rear section 2 and a plurality of center sections 3. These sections constitute a furnace chamber 4 and their annular water compartments 5 are connected to one another via hubs 6, 6′.
Annular gaps 7 are provided between each of two adjacent sections 1, 2, 3 as heating gas passages which run approximately radially outwards starting from furnace chamber 4 and discharge into an exhaust gas collection chamber 8. Each two adjacent sections 1, 2, 3 have a matching geometry for forming an annular gap 7. In the exemplary embodiment shown, the concavities of sections 1, 2, 3 produce four radially curved, annular gaps 7.
Exhaust gas collection chamber 8 extends in the form of a hollow cylinder around the outer jacket surfaces of sections 1, 2, 3 and is limited to the outside by a jacket 9 which is sealingly accommodated between annular webs 10 projecting radially outwards on the outside of front and rear sections 1, 2.
Two anchor rods 11 are situated within hubs 6, 6′ for holding the section block together. Disk-like sealing means 12 are attached to anchor rods 11 in order to alternately close upper and lower hubs 6, 6′ for providing a forced flow between the return and feed connection.
In addition, on each section 1, 2, 3, three centering surfaces 13 are situated on cast cams for maintaining an exact gap size between two adjacent sections 1, 2, 3, in order to identify exactly the dimensions present after the casting process and use them for machining the hub areas.
Claims
1-13. (canceled)
14. A cast iron or aluminum sectional condensing boiler, comprising:
- annular sections, including a front section, a cover-like rear section and at least one center section, the sections forming a furnace chamber having surrounding heating gas passages and annular water compartments connected to one another via hubs, the sections having one lower return connection and one upper feed connection and at least two anchor rods for holding the sections together;
- wherein annular gaps are provided between each of two adjacent ones of the sections as heating gas passages which run approximately radially outwards starting from the furnace chamber and discharge into an exhaust gas collection chamber on an outside of the sections.
15. The sectional boiler as recited in claim 14, wherein each of two adjacent ones of the sections has a matching geometry for forming an annular gap.
16. The sectional boiler as recited in claim 14, wherein an annular gap runs radially at a right angle to a central axis of the furnace chamber and in a straight line to the outside.
17. The sectional boiler as recited in claim 14, wherein an annular gap runs to the outside radially curved.
18. The sectional boiler as recited in claim 14, wherein an annular gap runs in a straight line to the outside, tilted toward a central axis of the furnace chamber.
19. The sectional boiler as recited in claim 14 wherein an annular gap runs radially to the outside in a wave-like fashion.
20. The sectional boiler as recited in claim 14, wherein at least one of a width and an open cross section of an annular gap diminishes from the furnace chamber to the opening on the outside of the sections.
21. The sectional boiler as recited in claim 14, wherein surfaces of the sections are contacted by a heating gas gap are provided with a corrosion-resistant coating.
22. The sectional boiler as recited in claim 14, wherein the exhaust gas collection chamber on the outside of the sections, into which the annular gaps discharge, extends in a form of a hollow cylinder around outer jacket surfaces of the sections and is limited to the outside by a jacket which is sealingly accommodated between annular webs projecting radially outwards on the outside of the front and the rear sections.
23. The sectional boiler as recited in claim 14, wherein the at least two anchor rods are situated within the hubs for holding the sections together.
24. The sectional boiler as recited in claim 14, wherein a feed pipe for at least one of return water and a withdrawal pipe for feed water situated within the hubs is used for holding the sections together.
25. The sectional boiler as recited in claim 24, wherein an upper one of the hubs and a lower one of the hubs are alternately closed for providing a forced flow between the return and feed connection, and wherein a closure arrangement is attached to at least one of the anchor rods, feed pipe, and the withdrawal pipe.
26. The sectional boiler as recited in claim 14, wherein at least two centering points or surfaces representing unfinished casting dimensions and tolerances are provided on each of the sections for maintaining an exact gap size between two adjacent ones of the sections and the centering points or surfaces determine mechanical machining of sealing or contact surfaces on the hubs.
Type: Application
Filed: Feb 24, 2009
Publication Date: Jun 16, 2011
Inventors: Rainer Rausch (Alsfeld), Gerhard Jung (Fronhausen)
Application Number: 12/921,054
