Patent Application
20110017433
The present invention relates to a heat exchanger for a heating device.
There are types of heat exchanger (for a heating device) that are made up of at least two members cast in one piece, which develop a combustion chamber having a burner connection in the upper region, as well as at least one heating gas flue, having heat exchanger surfaces, that leads from the combustion chamber to an exhaust collector in the lower region. The latter are provided with projections that are cast on, mostly ribs or knobs, for increasing the surface area so as to improve heat transmission. As a rule, the members stand vertically side by side. So-called end members, having heat exchange surfaces on only one side, form the outer limits, and may be supplemented using intermediate members, so as to increase the heat transmission performance. The latter have heat exchange surfaces on both sides.
On the side of the water, up to now, all members in all specific embodiments are connected to one another via two hubs, and on the heating gas side, sealing takes place between two boiler members having encircling packing strips, which may optionally be filled with an elastic sealing material.
In this connection, non-cooled cleaning covers, for closing channels on the end face, that conduct heating gas, are also known, and also cooled parts, such as combustion chamber doors that have heating medium flowing through them. For permanent seals it is important to maintain determined specified values for temperature stresses in the sealing region. Besides the material cast iron for such heat exchangers, fuel value boilers having a blowpipe for fossil fuels and a heat exchanger made of aluminum casting materials are also known. These may be produced using sand casting, extruding/die casting or sand molding casting methods. The methods are technically of different expenditures, and are suitable in each case for a certain number of pieces, and also have clear limits as to the design of the parts. There is a distinction between flow-forced and non-flow-forced heat exchangers, with regard to the flow guidance on the side of the heating medium. In flow-forced heat exchangers, a circulating pump takes care of a specified water volume flow through the mostly narrow water channels that are applied in a meandering shape. For this purpose, heat exchanger blocks, especially cast in one piece, are known, having water channels running around the combustion chamber and the heating gas flue. In spite of low water contents, this makes one able to implement rather high heating flow densities, brought in from the heating gas side.
In the constructive design of such an heat exchanger, the heating performance of the heat generator and the heat exchange surfaces, on the side of the heating gas and of the water, have to be at a certain relationship with respect to each other. On the one hand, the heat flow of the heating gas has to be transmitted to the heat exchanger down to a design temperature, and on the other hand, the heat exchanger has to be able to give off the same heat flow to the surrounding heating water. If these two magnitudes are not adjusted to each other, this may have the result that, either the exhaust setpoint temperature is not achieved, which becomes noticeable if there are increased exhaust gas losses, or the overtemperature of the heat exchanger with respect to the surrounding heating water leads to local simmering. The result will then be undesired simmering noises, material damage and/or deposits. It is also known from EP 0 287 142 A2, for example, that one should design the channel cross section for the heating medium in the entire upper zone of the heat exchanger block, that is hottest and close to the combustion chamber, to be narrower than in the lower, cooler region, at the recirculating water entry. Doing that is intended to achieve a high flow speed in the channel guiding the heating medium, in the entire upper, hot region. Since the channel narrowing gradually increases over the entire course of the channel, the cooling performance also rises accordingly.
An object of the exemplary embodiments and/or exemplary methods of the present invention is based on creating a compact heat exchanger for a heating device, that is light and is especially suitable for the fuel value operation.
According to the exemplary embodiments and/or exemplary methods of the present invention, this object may be attained by the features described herein. Advantageous developments may be derived from the further disclosures and descriptions herein.
The heat exchanger is characterized in that members and cover are connected to one another at the end face to form a block that is leak-proof to the heating gas, whose channels guiding the heating medium correspond to one another, and to which a burner may be connected in the upper region and an exhaust collector at the lower side.
The heat exchanger surfaces, acted upon by heating gas, in this context, of two adjacent members, over their length, in the middle, that is, at the location of the highest thermal stress, have a greater distance from each other and thus form a wider heating gas flue than in the edge regions. The ribs of two members associated with one another, in this instance, each have a greater height in the middle and overlap one another over a greater surface than in the edge regions.
For the channels guiding the heating medium in the members as well, in each case in the middle of a member, according to the exemplary embodiments and/or exemplary methods of the present invention, a lower cross section is also provided, so that, in that location, a higher flow speed prevails than in the edge regions, in order to dissipate the heat from the hottest zone well. The cross section of the channels, guiding the heating medium in the members, tapers in each case towards the middle of a member, and runs conically, for example. This reduction in the cross section essentially corresponds to the draft of the cores required for production by casting technology, an angle of 1.5 to 7 degrees to the center axis of a channel being provided as the draft.
The channels guiding the heating medium are connected to one another with the covers in such a way that, through the entire block, starting from a lower recirculating connection, a flowing through from below to above sets in, to a feed connection, in counter flow to the heating gases. The connected channels one after the other have heating medium flowing through them, in a plurality of planes, in this instance.
In a first specific embodiment, the channels guiding the heating medium are connected to the covers in such a way to one another that, starting from a recirculating connection, the following flow-through sets in: first of all, from a first lower plane via the lower region of the first outer member, using a transfer into at least one middle member and having a flow-through of same in the lower region, using a transfer into the second, outer member as well as a flow-through into its lower region. There then follows a U-shaped vertical deflection in the member to a second plane in the central region, and from this, first of all, a transfer to at least one middle member and a flow through same in the middle region, a transfer into the middle region of the first outer member, and there, a vertical turn round in the member into a third plane in the middle region. On this plane, the flow is reversed to the second plane through the entire block and guided to the second outer member. Starting from there, a U-shaped vertical deflection takes place in the member into a fourth plane in the upper region, on which a direct connecting channel exists through an end-face cover to the opposite first member, as well as a feed connection on the upper plane to the opposite first member, as well as a feed connection on the upper plane.
Consequently, the connecting channel includes and cools the combustion chamber on three sides, so that no insulation material is required. On the fourth, non-cooled side there is the possibility for access to the combustion chamber, for instance, in the form of a recess for installing an inspection glass as well as ignition devices and/or monitoring devices for a burner.
On the fourth plane the at least one middle member is recessed, that is, it has one cooling channel less than the two outer members, in order to form a somewhat lower combustion chamber or to assure the necessary combustion height.
In a second specific embodiment, the channels guiding the heating medium are connected to one another using the covers in such a way that, starting from the recirculating connection, a serpentine-like flow-through sets in in the first outer member, a transfer and also a serpentine-like flow-through sets in in at least one middle member, and a transfer and a serpentine-like flow-through sets in in the second outer member having a connection to a feed connection.
Deflection zones are generally provided in the covers, which are made up of arches of the walls bordering the deflection zones. In the deflection zones, the channels guiding the heating medium have at least an equally great, or a greater cross section than in the end regions of the members, so as to take care of a calmed flow deflection that has little pressure loss. In the upper region, the cover may have no channels guiding the heating medium, but has instead a recess for installing an inspection glass as well as ignition devices and/or monitoring devices for a burner. In order to connect all components to one block in a manner that is leak-proof to heating gas and liquid, the end faces of the members are developed like a flange, and form a contact surface and a sealing surface for an associated cover. The covers are advantageously connected to the members via a friction welding method, but other welding connection methods suitable for aluminum materials are also conceivable for this purpose. Covers may also be screwed together at their two outer edges at several points to the two outer members.
Furthermore, the elements enlarging the surfaces in the heating gas flue may be horizontally interrupted, especially in the form of ribs running in the vertical direction. This interruption is intended to prevent heat conduction from the hot, upper region into the cooler, lower heat exchanger surface region, for instance, in order optimally to cool the heating gases below the dew point and to utilize the fuel value. The interruption of a rib in each case takes place at least in the region between the first and the second plane of the channels guiding the heating medium, which already have a clear temperature difference with respect to each other. In addition, a venting nozzle, a gas/air mixture supply line and/or an exhaust gas line may be integrated into a member or a cover.
The exemplary embodiments and/or exemplary methods of the present invention provides a compact heat exchanger that is light and especially suitable for fuel value operation for a heating device, that is made primarily of aluminum casting materials. A modular construction for representing different performance sizes is easily possible, and the production of boiler members is relatively favorable. The heat exchanger is easy to clean and is accessible starting from the upper side, via the relatively large combustion chamber. The aluminum parts may be produced in mass production using easily formable cores in sand casting and extruding/die casting methods or in sand molding casting methods.
This design according to the exemplary embodiments and/or exemplary methods of the present invention has the advantage that the heat transfer coefficient is the greatest at the center of the heat exchanger. Because of the tapering water channels, the speed of the heating medium is relatively low at the beginning and the end of each channel. It is only high in the center, where a high heat transmission performance is required. Therefore, the channels guiding the heating medium are able to become narrower, and the height of the ribs may increase correspondingly, because the high heat input at the center is able to be transferred to the heating medium easily because of the locally higher speed. The otherwise usual problem of the danger of boiling at this critical location is voided.
The efficiency of the heat exchanger is increased especially on the side of the heating gas, because the ribs are interspersed among one another, and thus offer a large specific heat exchanger surface. Furthermore, in the design according to the exemplary embodiments and/or exemplary methods of the present invention, relatively low temperatures prevail in the sealing zones having heating medium flow around them, which makes possible the use of common sealing materials.
The drawings represent an exemplary embodiment of the present invention.
The heat exchanger is made up essentially of two vertically aligned outer members 1, 1′, two middle members 2 positioned between the latter, as well as a cover 3, 3′ in each case at the end faces. This forms a combustion chamber 4 in the upper region, beginning from which heating gas flues 5 having heat exchanger surfaces furnished with ribs 6 lead to an exhaust collector, that is not shown, in the lower region.
Channels 7 guiding heating medium are integrated into all members 1, 1′, 2 and covers 3, 3′, so that, via covers 3, 3′, at the end face, all members 1, 1′, 2 are mounted, to form a block that is leak-proof to heating gas, and with regard to channels 7 guiding the heating medium, is at least partially connected.
From
The channels 7 guiding the heating medium having the covers 3, 3′, are connected to one another in such a way that, through the entire block, starting from a lower recirculating connection, a flowing through from below to above sets in to a feed connection that is mounted there, in counter flow to the heating gases. In this context, the channels 7 guiding the heating medium have it flowing through them in several planes E1, E2, E3, E4, one after the other. In each case, within one planes E1, E2, E3, E4, the flow snakes through the components of the system, at a horizontal deflection in deflection zones 8 of covers 3, 3′. At the end of the flow path, in a planes E1, E2, E3, alternately within the two outer members 1, 1′, there takes place a U-shaped vertical deflection 8′ up to the next planes E2, E3, E4 lying above it.
In the upper region, cover 3′ has no channels 7 guiding the heating medium, but has instead a recess 9 for installing an inspection glass as well as ignition devices and/or monitoring devices for a burner. The end faces of all members 1, 1′, 2 are developed flange-like, and form a contact surface and sealing surface for an associated cover 3, 3′, the covers 3, 3′ being connected either using a welding method or, at their two outer edges, being screwed together at several points 10 with the two outer members 1, 1′.
In
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2007 060 508.2 | Dec 2007 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2008/067019 | 12/8/2008 | WO | 00 | 10/8/2010 |
