CH699393B1 - Heat exchangers for the flue of a furnace. - Google Patents

Abstract

The heat exchanger (1) for the flue gases of a heater has a flue gas divider (2) dividing the incoming flue gases (3) into parallel sub-streams (7, 8, 9), each of the partitions (4, 5, 6) being transported by a heat-transporting medium is flowed through, which absorbs the heat of the flue gases and feeds in the heating circuit. The heat exchanger can be used in the flue gas duct of a heater.

Description

The present invention relates to a heat exchanger according to the preamble of claim 1.

Such heat exchangers are arranged in a chimney or in a conduit for the flue gases and should make as much of the residual heat of the flue gas of a heat source such as a heater or a fireplace or other firing reusable. They are known in various embodiments.

Thus, DE 20 103 124 shows a heat exchanger, which consists of a double tube. The inner tube serves as a conduit for the flue gases, the outer tube forms the outside of the heat exchanger. The annular space between the inner tube and the outer tube is used for the heat exchange. In one embodiment, a water conduit is provided which is wound around the inner tube adjacent thereto so that the inner tube heated by the flue gases can deliver the heat to the water conduit where it is removed by the water. Here is advantageous that on the one hand the line for flue gases is still easy to clean, since the inner tube has a smooth inner surface, and on the other hand, the water-carrying coil (which would be expensive to clean) in the annulus is protected from contamination. The disadvantage, however, is that the heat transfer from the inner tube to the helix is problematic because it touches the inner tube substantially along a line.

In another embodiment, therefore, the annular space between the inner and the outer tube of water flows through, so that the inner tube is surrounded by a water jacket. Due to the irregular flow in the water jacket resulting in the operation of the heat exchanger results in an irregular cooling of the inner, the flue gases leading tube, with the result that the heat dissipation is not optimal.

DE 10 2004 023 026 shows a combination of water jacket and helix, with the advantage that the heat exchanger is arbitrarily extendable over its modular design, so that at least in long chimneys despite irregular or less efficient heat transfer, a larger proportion of residual heat available can be made. Here, however, increases the design effort, especially if the often prescribed thermal discharge assurance must be additionally provided.

In CA 02 499 775 it is disclosed, inside, to arrange the flue gases leading tube with this connected Wärmeleitbleche that enforce the inner tube, so that now heat from the inner core of the rising flue gases can be removed, which the fast Heat transfer between flue gases and the inner tube facilitated and could lead to shortening of the heat exchanger. However, the heat transfer from the inner tube to the coil wrapped around it remains unsolved.

The problem of heat transfer from the wall of the flue gases conducting tube to the cooling water cycle is improved solved by the arrangement shown in DE 4 010 151, which consists of four coaxial tubes, which together form three annular spaces. The middle annulus serves as a conduit for the flue gases; the inner and the outer annulus ever as a conduit for the cooling medium, also here usually water. In addition, a helical baffle runs in the middle annulus, so that the flue gases no longer need to flow through this parallel to the longitudinal axis of the tubes, but along this baffle. On the one hand, this extends the path of the flue gases and, on the other hand, they flow between two walls receiving their heat, so that the disadvantages of the irregular heat transfer into the surrounding water jacket are reduced. The disadvantage of this construction is that it is expensive and then necessarily has either an oversized overall diameter or scarce or too small flow cross-section for the flue gases. Finally, this arrangement is to be cleaned only with great effort.

Accordingly, it is the object of the present invention to provide a heat exchanger for the flue gas duct, which efficiently dissipates the heat of the flue gases, is easy to clean and so also as use in pre-existing flue gas ducts, such. Fireplaces can be used.

This object is solved by the characterizing features of claim 1 and claims 14 and 15, respectively.

Characterized in that the heat exchanger has a flue gas divider, which is itself traversed by the heat-exchanging medium, the heat can be taken from the flue gases in the core region with maximum efficiency, since the temperature difference between the flue gases and the walls along which these along delete, always as large as possible remains. In addition, the heat radiation of the flue gases is efficiently absorbed by the appropriate distribution of the flue gas flow. This applies over the entire cross section of the flue gas flow, and not only for its outer periphery. Flow barriers or whirling plates in the flue gas duct are no longer necessary.

Since all walls are parallel to the longitudinal axis of the heat exchanger, there is no significant flow resistance for the flue gases. This is advantageous because the natural chimney draft at the now taking place in the core zone strong cooling of the flue gases considerably loses its effect. Furthermore, simple cleaning is still possible, since the individual chambers formed by the partitions can be easily traversed by the cleaning tools lengthwise.

Surprisingly, it has been shown that during cooling, even in the core zone (i.e., over the entire cross section of the flue gas stream), the ejection of solids such as soot particles decreases considerably. This is attributed to the now reduced flow rate in the core zone, which is now no longer sufficient, at least for larger particulate matter particles, to convey it out through a vertical flue gas duct. These particles fall back into the chimney, settle at the lower end, which leads to an increased need for cleaning, which in turn occupies the reduced solids ejection. For wood heating, it further turns out that the dyeings, e.g. the brown color of the smoke, occur reduced, which also demonstrates the reduced solids ejection and the increased environmental friendliness.

In a method of operation of the heat exchanger according to the invention this can before starting the firing of upstream firing e.g. be flooded with hot storage water. The gases in the flue gas duct are thus kept at a minimum temperature over its entire cross-section and only cooled when the operating temperature of the system is reached. As a result, there is already a train in the starting phase that comes close to that of normal operation, which makes firing itself considerably easier and at the same time can reduce the formation of pollutants in the combustion process during the initiation process.

It turns out that in addition to the heat recovery as such and the fine dust ejection is improved.

Preferred embodiments are described in the dependent claims.

The invention is explained below with reference to the figures. It shows: <Tb> FIG. 1 <sep> a first embodiment of a heat exchanger according to the present invention <Tb> FIG. 2 <sep> a second embodiment of a heat exchanger according to the present invention, and <Tb> FIG. 3 <sep> a third embodiment of a heat exchanger according to the present invention.

Fig. 1 shows a heat exchanger 1 with a flue gas divider 2 for an entering into the flue gas divider 2 flue gas stream 3. Three partitions 4, 5, 6 separate the incoming flue gas stream 3 into three parts 7, 8, 9 of flue gas flow, behind the smoke gas divider 2 reunite to a cooled flue gas stream 10.

The partitions 4, 5, 6 are preferably thin, but hollow; they can consist of V4A welded together at an acute angle welded together sheets. Thereby, in the partitions 4, 5, 6, a heat exchanging medium, e.g. Water, flow through, which enter via the connecting pieces 12, 13, 14 and can exit through the outlet port 15, 16, 17 again. Connecting pieces 12, 13, 14 and output nozzles 15, 16, 17 are shown only schematically in the figure and can be easily designed by the skilled person for the specific application and installed in the flue gas divider 2. In other words, the flue gas divider 2 is designed for the flow of the heat exchanging medium.

In the present case, the partitions 4, 5, 6 are connected to each other via a central tube 20, wherein the central tube 20 is not traversed by the heat-exchanging medium. On the other hand, as an alternative to the illustration in FIG. 1, a central connection or outlet connection can be arranged at the ends of the central tube 20, each with a branch line immediately thereafter leading into (or out of) the ends of the partition walls, so that the heat-transporting medium from the central inlet into the partitions into distributed, and then can be removed centrally. As a result, the heat exchanging medium continues to flow essentially through the partition walls 4, 5, 6.

The flue gas divider 2 is elongated and has a longitudinal axis 21; it may be inserted lengthwise into any flue, e.g. a chimney of a chimney, a chimney or a flue-gas pipe of a heater or channel leading into some hot flue gases. In the case of heating, as in the other cases, the guidance of the supply and return lines for the heat-transporting medium, preferably water, to be determined by a person skilled in the art; the guidance of these lines is dictated by the local conditions prevailing in a building. It is not mandatory, but advantageous that the flue gas divider 2 is dimensioned such that the outer longitudinal edges 25, 26, 27 abut the walls of the given flue gas duct.

As mentioned, a flowing flue gas stream 3 in parts 7, 8, 9 is separated during operation, which are performed parallel to each other and parallel to the longitudinal axis 20; Thus, the parts 7, 8, 9 also flow parallel to the longitudinal axis of the flue gas channel. The hot flue gases heat via heat radiation and contact with the partitions 4, 5, 6 on this, which in turn emit the heat to the heat transporting medium (water).

By this arrangement, in particular, the heat flowing in the middle of the flue gas channel hot core of the flue gases effectively removed without flow obstacles to the turbulence of the flue gases, which in turn make the chimney draft and cleaning difficult or impossible, must be provided.

Particularly advantageously, the partitions 4, 5, 6 made thin, so that the flow cross section for the flue gases is little reduced, with the result that additional blower for the train in the flue gas duct are not necessary or only have low power.

In a further embodiment, the central tube 20 is connected to a further coolant circuit, which is activated due to excess temperature by a temperature sensor 72 (FIG. 3) and thus serves as emergency cooling in the sense of thermal discharge safety. Since the central tube 20 is preferably not flowed through by the heat exchanging medium (the wall surface of the central tube 20 is small in comparison to that of the partitions 4 to 6), it can nevertheless, despite the comparatively small efficiency, serve as an emergency cooling line.

Fig. 2 shows another embodiment of the inventive heat exchanger 30. Shown are partitions 31 to 36 of a flue gas divider 37, which channel parts of the flue gas stream 38.

As the partitions 4 to 7 in Fig. 1, here are the partitions 31 to 36 arranged in a star shape in cross section. Preferably, but not necessarily, these partitions are radially from a central longitudinal axis 21 (Fig. 1) and 39 of the flue gas divider 2 (Fig. 1) and 37 from. This forms in cross section a symmetrical, multi-pointed star, through which the flue gas stream 38 is divided into the corresponding number of parallel flowing partial streams.

The optimum number of partitions, be it (in the star's sense) a minimum of two (Figure 3), or three (Figure 1), or more, will be appreciated by one skilled in the art from the temperature of the incoming flue gases as well as the locally prevailing one Conditions such as determined the given masses of the flue gas channel.

The figure further shows that the partitions 31 to 36 are connected to an inner tube 40, which in turn is arranged coaxially in an outer tube 41. The inner tube 41 and the outer tube 42 form a double tube 43, which encloses an annular space 44. This annular space 44 can also be provided for the flow of heat exchanging medium. Then each partial flow of flue gases is uniformly cooled on all sides.

Particularly here, but also in the arrangement of Fig. 1, is advantageous if the partitions taper outwardly, so that the thickness of the outer longitudinal edge 25, 26, 27 (Fig. 1) is less than at their root. It is particularly advantageous if the thickness decreases continuously.

For example, the thickness of the partitions at the root in a flue gas duct of 200 mm diameter is 22 mm, preferably only 16 mm. Firstly, as mentioned above, the cross section of the flue gas duct is not limited too much; then the water in the partitions will heat up a little quickly so that the flue gases do not fall below a temperature of e.g. 55 ° C fall, so the unwanted cold smoke and the formation of condensation substantially omit.

Not shown in Fig. 2 is an embodiment in which the flue gas divider 37 is not enclosed by a double tube 43, but only by a simple tube. Such a simple tube serves to stabilize the partitions, so that e.g. Central tube 18 can be omitted; Furthermore, this results in a heat exchanger, which can be used as an insert in any, e.g. masonry flue, as it can be found in older buildings, can be used. Alternatively, it is also possible for the heat exchanger tube thus formed to be used as a section to be exchanged in an existing flue gas pipeline. As mentioned above in connection with Fig. 1, the heat exchanger can also be used without an outer tube in the flue gas duct. It is then advantageous that a heat exchanger can also be used in a flue gas duct with irregular walls, e.g. a coarse brick fireplace, easy to use, which would not be possible with an outer tube.

Fig. 3 shows another embodiment of a heat exchanger 50 according to the present invention in a view from the outside. A flue gas divider 51 (corresponding in cross-section to a two-pronged star) is enclosed by a double-walled tube 52 consisting of an inner tube 53 and an outer tube 54. Between the inner tube 53 and the outer tube 54 is an annular space 55, in which in turn a conduit 56 is arranged for a cooling medium such as water. The tube 56 preferably extends around the inner tube 53 such that it lies on a helical line that extends over a length or the entire length of the heat exchanger 50.

Further, the tube 56 has a diameter corresponding to the distance between the inner tube 53 and the outer tube 54. So it is in contact with both tubes 53, 54. Thereby, the medium flowing through the annular space 55 is brought to a helical flow path which passes through the annular space 55. In place of the pipe 56, a simple sheet or similar means may be provided; when using a line 56, however, the advantages described in more detail below arise.

In other words, 55 means are provided in the annular space, which determine the flow path of the heat exchanging medium, such that this flows through the annulus 55 of a helix along. This results in a longer flow path and a longer residence time of the medium through the annular space 55 through, with the advantage of improved heat transfer between flue gas and heat-transporting medium.

Schematically in the connections for the annular space 55 are further shown: A port 57 is the inflow of cold water and a connection 58 the outflow of the heated water. Similarly, a port 59 serves the inflow of cold water into the flue gas divider 51 and a port 60 the outflow of heated water out of this. Depending on the design in the specific case, the already heated in the annulus 55 water from port 58 directly into the port 59, and then passed in countercurrent through the flue gas divider 51, where it finally heated to an operating temperature of about 95 ° C and the Terminal 60 can be removed. Of course, other circuits of the water streams are possible, which in turn determined by the expert according to the local conditions.

The outer tube 54 is cut along line 62 for clarity, so that the view of the inner tube 53 and a portion of the conduit 56 is free. It can be seen further designed as a transverse bulkhead 63 flow obstruction for the annulus 55 flowing medium. The transverse bulkhead consists here of a sheet metal which obstructs the flow path for the medium and has a slot 64 through which the medium can flow. The edges of the slot 64 are preferably curved, as shown in the figure; which promotes the mixing and thus the uniform heating of the medium. Preferably, such a flow obstruction is provided in every fourth turn of the helical flow path. In addition, such a too fast flow through the heat-transporting medium can be avoided if the pump power is set too large.

A flue gas adapter 64 for the incoming flue gases 64 pierces the bottom 65 of the heat exchanger 50 and discharges the flue gases 64 to be introduced into the heat exchanger 50 slightly above the lower edge 66 of the inner tube 53. Through the outer tube 54, the bottom 55 and the upper part of the flue gas adapter 64, a groove 67 is formed which collects on the inner side wall of the inner tube 53 run-down condensation, which can flow through the also schematically indicated port 68.

At the lower end of the flue gas divider 51 laterally from this projecting baffles 70 perform an analogous function: Any condensate draining on the flue gas divider 51 is passed through these baffles 70 against the wall of the inner tube 53 and then runs down into the channel 67th

Next, a temperature sensor 72 is shown in the figure, which detects the temperature of the heated water. The temperature sensor 72 is connected to a control, not shown for relieving the figure, which activates a cooling water connection 74 at excess temperature, so that the line 56 is traversed by cooling water and the medium in the heat exchanger 50 cools. This results in a thermal discharge safety device in the event that the flow is disturbed by the heat exchanging medium. Advantageously, the line 56 thus fulfills two functions: once that of a guide plate for the flow path of the heat exchanging medium through the annular space 55, then the emergency cooling in the sense of the thermal discharge safety device.

In another embodiment, the flue gas divider is not provided, but the double tube 52 is provided with all elements shown in the figure, and thus with a helical line 56, flow obstacles 63, a channel 67 for condensation and a temperature sensor 72 for a through Line 56 formed thermal discharge safety device equipped.

The heat exchanger according to the invention may also be charged with a preheated medium, e.g. in the flue gas duct operating temperature is not reached, as may be the case when starting a heater. If the flue gas duct is too cold, the flue gases will cool down too tightly, there will be insufficient draft, which in turn will result in a prolonged start-up phase with the known disadvantages, such as e.g. can lead to increased pollutant production. The under temperature (and also the once reached lower operating temperature) in the flue gas channel can be detected by heat sensors or determined by the general temperature level in connection with the time that has elapsed since ignition. Depending on the local conditions, the expert can determine the appropriate parameters. Once a lower operating temperature has been reached, the flue gases are cooled by the heat-transporting medium in accordance with normal operation.

Claims (16)

1. Heat exchanger for the flue gas duct of a heater, characterized by an elongated flue gas divider (2, 37, 51) for the flue gas stream (3, 38), the parts during operation of a flowing flue gas stream (38) separated from each other and parallel to each other and to the longitudinal axis (21 , 39) of the heat exchanger and thus leads to that of the flue gas duct with it, wherein the flue gas divider (2, 37, 51) is designed for the flow of a heat exchanging medium, via which heat of the channeled flue gases (7, 8, 9) is dissipated. 2. Heat exchanger according to claim 1, wherein the flue gas divider (2, 37, 51) has partitions (4, 5, 6, 31 to 36) for the flue gas flow (3, 38), which are arranged in a star shape in cross section. 3. Heat exchanger according to claim 2, wherein the flue gas divider (2, 37, 51) at least three radially from the central longitudinal axis (21, 39) of the heat exchanger protruding partitions (4, 5, 6, 31 to 36), which in cross section a form symmetrical dreizackigen star, such that in operation, a flue gas stream (38) is divided into at least three parallel to each other flowing partial streams (7, 8, 9). 4. Heat exchanger according to one of claims 2 or 3, wherein the thickness of the partition walls (4, 5, 6) at its outer longitudinal edge (25, 26, 27) is smaller than in the region of its root, wherein the thickness preferably decreases continuously. 5. Heat exchanger according to one of claims 2 to 4, wherein the thickness of the partitions at the root does not exceed 22 mm, preferably 16 mm. 6. Heat exchanger according to one of claims 2 to 5, wherein the heat exchanging medium flows in the heat exchanger substantially only through the partitions (4, 5, 6, 31 to 36). 7. Heat exchanger according to one of claims 2 to 6, wherein the flue gas divider (2, 37, 51) is connected to the outer longitudinal edges of its partitions along with a tube which encloses the flue gas divider (2, 37, 51). 8. Heat exchanger according to claim 7, wherein the tube is double-walled, designed as a double tube, which forms an annular space (55) which is provided for the flow of heat-exchanging medium. 9. Heat exchanger according to claim 8, wherein in the annular space (55) means are provided which determine the flow path of the heat exchanging medium, such that this flows through the annulus (55) along a helix, and wherein at least one flow obstruction is preferably provided in the flow path , 10. A heat exchanger according to claim 9, wherein the at least one flow obstruction is formed as a slotted transverse bulkhead (63), which is preferably provided after every fourth turn of the helix. 11. A heat exchanger according to one of the preceding claims, wherein in the heat exchanging medium through which a passage (56) is provided for a cooling medium. 12. A heat exchanger according to any one of claims 11 or 9, wherein the means for determining the flow path as a conduit, preferably as a conduit (56) are formed for the cooling medium, wherein the conduit (56) passes through the annular space (55) along a helical line and thereby the inner tube wall (53) and the outer tube wall (54) touched. 13. A heat exchanger according to any one of claims 11 or 12, wherein formed as part of a thermal discharge fuse temperature sensor (72) on the flue gas divider (2, 37, 51) and wherein a central tube (20) or the conduit (56) for the cooling medium can be acted upon by a controller in response to a temperature signal of the temperature sensor with cooling medium. 14. A heater with a flue gas channel having a heat exchanger according to one of the preceding claims. 15. Building with a heater according to claim 14. 16. A method for operating a heat exchanger according to one of claims 1 to 13, characterized in that it is flooded at low temperature in the flue gas duct with a preheated heat exchange medium, until the train has reached a lower operating value in the flue gas duct, after which then the Heat exchanging medium is used for cooling the flue gases.