Heat exchange unit

Abstract

Heat exchange unit (14) with a heat exchanger (22) and an exhaust gas chamber (24) adjoining the heat exchanger (22) in the lower region of the heat exchange unit (14), wherein the exhaust gas chamber (24) comprises a drainage device (26) delimiting the exhaust gas chamber (24) for discharging a liquid-solid mixture (31), wherein the drainage device (26) has a collecting container (32) with an outlet (34), and wherein a retaining element (46) is arranged at the outlet (34), which is designed to retain the solid (30) in the collecting container, characterized in that the outlet (34) is arranged at the bottom (50) of the collecting container (32) and extends in the direction of gravity, wherein the bottom (50) of the collecting container (32) has at least two planes (56, 58), wherein the planes (56, 58) are spaced from one another in the direction of gravity and wherein the plane (58), in which the outlet (34) is located,has a greater distance from the heat exchanger (22) than the at least second plane (56).,

Description

[0001] The invention is based on a heat exchange unit with a retaining element and a heating device according to the preamble of the independent claims. State of the art

[0002] Modern boilers are typically designed as condensing boilers, in which the exhaust gas is cooled below its condensation temperature, causing the water vapor contained in the exhaust gas to condense. The resulting condensate must generally be collected and drained away. Due to the generally acidic pH value of the condensate, it reacts with the housing components of the condensing boiler, producing dirt particles as reaction products that can drain away along with the condensate and clog pipes.

[0003] DE 10 2015 216 688 A1 discloses a connection for a condensate drain from a heater with a housing arranged below an outlet of an exhaust system, whereby the accumulating condensate can flow through the outlet into the housing. The housing is provided with chambers in which the condensate accumulates. Dirt particles can settle in these chambers.

[0004] DE 34 06 028 C2 discloses a heat exchange unit according to the preamble of claim 1.

[0005] GB 2 425 588 A discloses a retaining element according to the preamble of claim 11. Disclosure of the inventionAdvantages of the invention

[0006] The invention is based on a heat exchange unit with a heat exchanger and an exhaust gas chamber adjoining the heat exchanger in the lower region of the heat exchange unit, wherein the exhaust gas chamber comprises a drainage device delimiting the exhaust gas chamber for discharging a liquid-solid mixture and wherein the drainage device has a collecting container with an outlet, wherein a retaining element is arranged at the outlet and is designed to retain the solid in the collecting container. It is proposed that the outlet is arranged at the bottom of the collecting container and extends in the direction of gravity, wherein the bottom of the collecting container has at least two levels, wherein the levels are spaced apart from one another in the direction of gravity and wherein the level in which the outlet is located is at a greater distance from the heat exchanger than the at least second level.

[0007] The heat exchanger according to the invention with the retaining element according to the invention having the features of the independent claims has the advantage that the solids can be retained in the collection container of the exhaust gas chamber and are not directed through the outlet into the adjoining siphon container. By retaining the solids in the collection container, clogging of the siphon adjoining the outlet can be prevented in a particularly simple manner. In the past, such blockages could often only be removed during complex maintenance. Thus, the retaining element according to the invention has a positive effect on the maintenance frequency and maintenance effort.

[0008] Since the solids are already retained in the collection container by the retention element according to the invention, the siphon container connected to the outlet can be made smaller, as it does not have to be designed to collect a large amount of solids. The reduction in the size of the siphon container also has a positive effect on the costs of a heat exchanger according to the invention. In addition to the cost reduction due to the smaller dimensions, the resulting lower weight of the siphon container advantageously influences the tightness of the connection between the outlet and the siphon container, since this connection is subject to tensile stress due to gravity.

[0009] In the context of the present invention, an exhaust gas chamber can be understood as a closed unit that is arranged on the heat exchanger according to the invention and delimits it downwards and laterally. According to the invention, the exhaust gas chamber has an exhaust gas discharge line suitable for discharging the exhaust gases and an outlet suitable for discharging the accumulating condensate. The components adjoining the outlet, such as the siphon, are not considered part of the exhaust gas chamber within the meaning of the invention.

[0010] With regard to the present invention, a liquid-solid mixture can be understood as a substantially heterogeneous mixture whose components, liquid and solid, can be separated from one another again.

[0011] The measures listed in the subclaims result in advantageous further developments and improvements of the features given in the independent claims.

[0012] The heat exchange unit according to the invention, or an advantageous development thereof, is characterized in that the liquid is condensate liquid and the solid is material dissolved out of the heat exchange unit, in particular oxidized aluminum. Particularly when using heat exchange units containing aluminum, the aluminum oxide formed by the reaction with the acidic condensate liquid can be retained in the collection basin in a particularly simple manner by the heat exchanger according to the invention.

[0013] In this context, oxidized aluminum can be understood as meaning not only aluminum oxide but also products or electron donors resulting from the oxidation of aluminum alloys, particularly aluminum-silicon cast alloys.

[0014] The outlet is located at the bottom of the collection tank and extends in the direction of gravity. This allows the liquid-solid mixture formed in the heat exchanger to fall into the collection tank particularly easily and energy-efficiently by gravity, eliminating the need for complex conveying. The separation between liquid and solid can be achieved advantageously based on the principle of sedimentation by aligning the outlet at the bottom of the collection tank, allowing the separated liquid to flow out of the outlet free of dirt particles.

[0015] In the context of the invention, the direction of gravity can be understood as the direction in which gravity acts when installed.

[0016] Furthermore, within the scope of the present invention, the bottom can be understood as the side of the housing opposite the exit surface of the liquid-solid mixture from the heat exchange unit, which delimits the exhaust gas space at the bottom.

[0017] In a particularly simple and robust embodiment of the retaining element, the retaining element has a first and a second section, wherein the first section sits in the outlet in the installed state and the second section encloses the outlet in the form of a circumferential wall in the installed state, wherein the wall then extends from the outlet into the space of the collecting container.

[0018] By positioning the first section of the retaining element in the outlet, a solids-tight connection can be provided with particularly simple means via the positive engagement between the first section of the retaining element and the outlet. This connection can be easily removed for maintenance purposes, for example, by pulling the retaining element out of the outlet. The contact area between the outer surface of the retaining element according to the invention and the outer surface of the outlet can certainly have a narrow gap in the sense of a gap seal to fulfill its function.

[0019] In an advantageous embodiment, the bottom of the collection container encloses a reservoir between a side wall of the collection container and the surrounding wall. Sedimentation of the liquid-solid mixture can occur in this reservoir, and the thus settled solids can be retained.

[0020] In the context of the present invention, a reservoir can be understood as a container that is open at the top and capable of retaining the accumulating solids or oxidized aluminum. Essential to the invention in this context is that the peripheral wall, which represents a side wall of the reservoir thus formed, has a height sufficient to retain the solids from the outlet.

[0021] The effect of gravity is particularly preferably utilized for transporting the liquid and for sedimenting the solids from the solid-liquid mixture by the base of the collecting container having at least two levels, wherein the levels are spaced apart from one another in the direction of gravity, and wherein the level in which the outlet is located is at a greater distance from the heat exchanger than the at least second level. In other words, the base can comprise a tray within the tray, wherein the second tray is lower than the first tray when installed.

[0022] In principle, sedimentation begins when the sedimentation velocity, i.e., the rate at which the solids sink from the solid-liquid mixture, exceeds the turbulence-induced vertically opposing components of the transporting medium. Therefore, to optimize the sedimentation process, turbulence should be minimized. A design with a trough within the trough advantageously influences the turbulence in the collection basin through the additional side walls.

[0023] In this particularly preferred embodiment, the circumferential wall forms, with the shoulder between the two levels, which is formed by the fact that the levels are arranged at a distance from one another, a reservoir according to the invention in which the solids can settle and be collected.

[0024] Particularly simple production and handling results from the fact that the retaining element is designed as a truncated cone hollow body.

[0025] In this context, a truncated cone hollow body is understood to be a truncated cone, i.e. a truncated circular cone with a larger circular base area and a smaller circular top area, which has a certain wall thickness.

[0026] According to the invention, the truncated cone body is installed in such a way that the smaller cover surface lies below the larger circular surface in the direction of gravity. Such a truncated cone hollow body allows the retaining element to be positioned and secured in the outlet using simple structural means. At the same time, the hollow body design allows the fluid from the liquid-solid mixture to pass from the collection basin into the siphon container.

[0027] In an advantageous embodiment, the tightness of the reservoir at the outlet and the force transmission in the direction of gravity can be improved by arranging a shoulder between the respective outer surfaces of the first and second sections of the retaining element. When assembled, the shoulder rests positively on the bottom of the collection container and provides a solids-tight connection. The resulting additional positive connection between the shoulder and the bottom of the collection container allows the sealing effect and force transmission in the direction of gravity to be optimized.

[0028] Furthermore, it is considered advantageous if the retention element is designed as a filter. By designing it as a filter, the separation of liquid and solid can be based not only on the principle of self-separation by sedimentation but also on the principle of physical separation by filtration.

[0029] In the context of the present invention, a filter can be understood as a component which retains the solids from the liquid-solid mixture and allows the liquid to pass through due to the pressure difference.

[0030] In a preferred embodiment, the circumferential wall of the retaining element can have at least one through-opening in the radial direction, i.e., transverse to the direction of gravity. In contrast to the retaining element designed as a filter, which separates the liquid from the solid, the through-opening is suitable for retaining solids of a specific grain size and allowing other solids that are not critical for clogging, for example, due to their grain size, to pass through.

[0031] In a further advantageous embodiment, the retaining element can have a circumferential collar at its free end facing the space of the collecting container, wherein the circumferential collar extends radially over the contour of the circumferential wall. Such a collar can have a beneficial effect on the sedimentation process at the overflow edge between the reservoir and the outlet. In particular, the consequences of turbulence caused by the liquid-solid mixture from the heat exchanger impinging on the filled reservoir at the overflow can be minimized.

[0032] In the context of the present invention, a circumferential collar can be understood as a projection which delimits the reservoir at least partially upwards, i.e. in the direction of the heat exchange element.

[0033] The retaining element according to the invention is particularly preferably suitable for use in a heat exchange unit having a collecting basin with a tub within the tub. Due to its design with a first and a second section, wherein the first section sits in the outlet and the second section encloses the outlet in the form of a circumferential wall, and wherein the wall extends from the outlet into the space of the collecting container, the retaining element according to the invention can advantageously minimize turbulence, enable the sedimentation process in the collecting basin, and at the same time, through its design, ensure the required tightness for solids between the collecting basin and the outlet.

[0034] The retaining element is designed as a truncated cone hollow body and a shoulder is arranged between the respective outer surfaces of the first and second sections, wherein the shoulder, in the assembled state, rests positively on the bottom of the collecting container and provides a connection that is tight for solids.

[0035] Advantageously, the heat exchange unit according to the invention can be installed in a heating device, in particular a condensing boiler.

[0036] Embodiments of the invention are illustrated in the figures and explained in more detail in the following description. They show: Fig. 1 a schematic representation of a heating device according to the invention, Fig. 2 an enlarged view of the drainage device according to the invention in the filled state with a retaining element according to the invention, Fig. 3 an embodiment of the retaining element according to the invention in an installed state in a drainage device, Fig. 4 shows a further embodiment of the retaining element according to the invention in an installed state in a drainage device.

[0037] Fig. 1 shows a heater 10 with a burner 12 and a heat exchange unit 14. A fuel gas-air mixture is fed to the burner 12 via a fan (not shown here) and burned in the burner 12. The hot combustion gas 16 produced during combustion flows into a subsequent heat exchange unit 14. As in Fig. As shown in Figure 1, the burner 12 is located at the upper end of this heat exchange unit 14. The hot combustion gas 16 is guided from the burner 12 located at the upper end of the heat exchange unit 14 from top to bottom through the heat exchange unit,

[0038] The heat exchange unit 14 has water-carrying channels 18. The hot combustion gas 16 flowing from the burner 12 is directed downward along the water-carrying channels 18 in a downdraft, thereby heating the water or heating fluid 20 conveyed in the water-carrying channels 18. The combustion gas 16 releases energy along the channels 18, resulting in a cooling of the combustion gases 16.

[0039] In the present application, a distinction is made between the terms heat exchange unit 14 and heat exchanger 22. A heat exchange unit 14 can be understood as the heat exchanger 22 in conjunction with an exhaust gas chamber 24 adjoining the heat exchanger 22 and a drain device 26 delimiting the exhaust gas chamber 24. The combustion gas 16 cooled by the heat exchanger 22 flows into an exhaust gas chamber 24, which is arranged in the lower region of the heat exchange unit 14.

[0040] The heat exchange unit 14 or the heater 10 is designed as a condensing boiler, meaning that the combustion gas 16 is cooled and condensed along the water-conducting channels 18 below the dew point temperature, which is approximately 55°C. The condensate liquid 28 that accumulates in the lower region of the heat exchanger 22 is generally acidic and can chemically react with the walls of the water-conducting channels 18 or other components that conduct the condensate liquid 28. The resulting reaction products are often solids 30, which are dissolved from the housing walls and transported away with the liquid 28 in a liquid-solid mixture 31. For this purpose, the exhaust gas chamber 24 has a drain device 26 that discharges the resulting liquid-solid mixture 31.

[0041] As in Fig. 1, the drain device 26 delimits the heat exchanger downwards and laterally and thus, together with the heat exchanger 22, encloses the exhaust gas chamber 24 between them. In addition to the aforementioned liquid-solid mixture 31, exhaust gases also flow from the heat exchanger 22 into the exhaust gas chamber 24. These exhaust gases are generally guided out of the exhaust gas chamber 24 via an exhaust pipe (not shown here).

[0042] In order to collect and drain the liquid-solid mixture 31, which exits the heat exchanger 22 and falls downwards due to gravity, the drainage device 26 has a collecting basin 32 and an outlet 34. The collecting basin 32 is constructed of an acid-resistant material in order to withstand the acidic condensate liquid 28. As shown in Fig. As shown in Figure 1, the outlet 34 is located at the lowest point of the collection basin 32. The drain device 26 and the associated wall of the collection basin 32 seal off the heat exchange unit 14 downwards and to the sides. For this purpose, the collection basin 32 extends over the entire exit area of ​​the liquid-solid mixture 31 from the heat exchanger 22.

[0043] To prevent exhaust gases from entering the installation room surrounding the heater 10 via the outlet 34 of the drain device 26, a siphon 36 is connected to the drain device 26. As shown in Fig. 1, the siphon 36 has an S-shaped siphon tube 38, wherein the lower bend of the siphon tube 38 is filled with condensate liquid 28 and thus prevents the passage of the exhaust gases. In the Fig. In the embodiment of the heater 10 shown in Figure 1, a so-called siphon container 40 is connected upstream of the siphon tube 38 of the siphon 36. The siphon container 40 is connected at one of its connections via a connecting piece to the outlet 34 of the drainage device 26. The siphon tube 38 is connected to its other connection, which is designed as an overflow and is located in the upper region of the siphon container 40.

[0044] In the Fig. The condensing boiler shown in Figure 1 is an aluminum heat exchanger 14. The acidic condensate liquid 28 accumulating in the heat exchanger 12 reacts with the aluminum of the heat exchanger, resulting in oxidized aluminum 42 as a solid 30. This oxidized aluminum 42 is carried out of the heat exchanger 22 with the condensate liquid 28. The aluminum oxide-condensate mixture 44 exiting the heat exchanger 22 via the outlet surface 35 is generally sludge-like. If this sludge is discharged into the wastewater via the outlet, this leads to contamination of the wastewater, and the aluminum oxide or oxidized aluminum 42 can clog the connected pipes, such as the siphon pipe 38.To prevent this, the heat exchange unit 14 according to the invention has a retaining element 46 which is arranged at the outlet 34 and is suitable for retaining the solid 30 or the aluminum oxide 42 already in the collecting basin 32 and not allowing it to pass through the outlet 34 into the siphon 36.

[0045] Since, despite the retaining element 46, small amounts of aluminum oxide 42 can still enter the adjoining siphon 36, the siphon 36 has the aforementioned siphon container 40, which collects residual solids based on the principle of sedimentation and discharges the condensate via the overflow 48 located further upstream to the siphon tube 38. However, the heating device 10 according to the invention is not limited to use with a siphon container 40. It is also conceivable, and may be sufficient to fulfill its function, for the siphon tube 38 to be connected directly to the outlet 34 without the siphon container 40. Such an embodiment has a particularly positive effect on the costs of the heating device 10, since the siphon container 40 is very cost-intensive.

[0046] In comparison to previous heating devices in which the siphon container 40 had to collect the entire solid 30, the heating device 10 according to the invention, as shown in Fig. 1, has the advantage that the siphon tank 40 can be dimensioned significantly smaller and thus more cost-effectively. Another positive aspect is that the reduction in size of the siphon tank 40, particularly when filled, reduces the weight compared to previous systems, so that the connection between the collecting basin 32 or outlet 34 and the adjoining siphon tank 40 is subjected to lower loads.

[0047] In order to retain the solid 30 in the collection basin 32, the retaining element 46 is located in the form of a plug in the outlet 34. In order to still allow the condensate liquid 28 to pass through, the retaining element 46 has a through-opening extending in the direction of gravity. The separation of the liquid-solid mixture 31 occurs essentially via the principle of sedimentation. A detailed description of the retaining element 46, its positioning in or at the outlet 34, and the separation process of solid 30 and condensate liquid 28 can be found in the description of Fig. 2.

[0048] As in Fig. 1, the collection basin is trough-shaped and has a bottom 50 and surrounding side walls 52. In order to retain the solid 30 in the collection basin 32 and enable the sedimentation process, the bottom 50 of the collection container 32, the side walls 52, and the retaining element 46 enclose a reservoir 46 between them. According to the invention, the solid 30 can be collected in this reservoir 46.

[0049] At the Fig. In the embodiment shown in Figure 1, the bottom 50 of the collecting container 52 has at least two levels 56, 58, which are spaced apart from one another in the direction of the shear force. The outlet is located in the lower, second level 58. In other words, a second, lower, smaller pan is located in the basin of the collecting tank 52, which has the outlet 34. In this case, this second, lower pan forms the reservoir 46 for the solid 30 or the oxidized aluminum 42.

[0050] It is pointed out at this point that the heater 10 in Fig. 1 is shown only schematically without components such as the heating housing, the control system, pumps or piping, since the structure and functionality of such a heating device 10, in particular a condensing boiler within the meaning of the invention, are sufficiently known, so that a detailed explanation of the functions is omitted here for the sake of brevity and simplicity of the description.

[0051] In Fig. 2, the retaining element 46 according to the invention is shown in more detail in the assembled state. The retaining element 46 is located in the outlet 34 of the collecting basin 32. As in Fig. As can be clearly seen in Figure 2, the outlet 34 extends in the direction of gravity, i.e., the outlet 34 has an outlet height 60 over its circumference, which extends in the direction of gravity. The retaining element 46 is arranged in the outlet 60. The retaining element 46 has a first and a second section 62, 64, wherein the first section 62 of the retaining element 46 is inserted into the outlet and the second shoulder 64 extends into the space of the collecting basin 32. The first and second shoulders 62, 64 are an integral part of the retaining element 46.

[0052] As in Fig. 2, the first section 62 rests with its outer wall over its wall height against the outer wall of the outlet 34. This support surface, which extends essentially in the direction of shear force between the two outer surfaces, serves, on the one hand, to position the retaining element 46 in the outlet 34; on the other hand, the large support surface helps to seal the adjoining siphon container 40 against the solids 30, 42.

[0053] It should be mentioned at this point that the retaining element according to the invention is not limited to such Fig. 2 is limited to a first section 62 located in the outlet 34. For example, embodiments are also conceivable in which the retaining element 46 is attached to the collecting basin 62 via additional fastening means. In a further embodiment, it is likewise conceivable for the retaining element 46 to be formed integrally with the collecting container 32. The only essential aspect of the invention is that the retaining element 46 shields the outlet from the accumulating aluminum oxide 42. Furthermore, the heat exchange unit 14 according to the invention is not limited to an embodiment in which the outlet 34 extends in the direction of gravity. Particularly if sufficient tightness of the retaining element 46 in the radial direction, i.e., in the circumferential direction of the outlet 34 for the solids 30, is ensured, the outlet 34 does not necessarily have to extend in the direction of gravity.This may be the case in particular if the collecting basin 32 and the retaining element 34 are formed as one piece.

[0054] The outlet 34 is enclosed by a circumferential wall 65 of the second section 64 of the retaining element 46, wherein the wall 65 extends from the outlet 34 into the space of the collecting container 32. The circumferential wall 65 has a wall height 68 in the direction of extension. This circumferential wall 65, together with the bottom 50 of the collecting container and the respective side walls 52 of the collecting container 32 or the respective side walls 52 of the second level 58 of the bottom 50 of the collecting container 32, encloses the reservoir 54. The liquid-solid mixture 31, 44 emerging from the heat exchanger 22 is collected in this reservoir 54. Under the influence of gravity, the particles or solids 30, 42 separate from the liquid 28 and settle on the bottom 50 of the reservoir 54.When the liquid level in the reservoir 54 reaches the full wall height 68, the liquid 28 flows over the upper edge of the retaining element 46 into the outlet. This upper edge is referred to below as the overflow edge 70.

[0055] If the reservoir 54 is filled with solids 30 or aluminum oxide 42 up to the overflow edge 70, the solids 30, 42 must be removed from the reservoir 46 as part of maintenance. For this purpose, the siphon container 40 is removed, a collecting container is placed under the outlet 34, and the retaining element 46 is removed. The aluminum oxide 42 and other solids 30 can then be rinsed out of the collection basin in a particularly simple manner. To further simplify maintenance, a retaining device 46 can also be provided, which is attached to the outlet 34 in such a way that it can be removed downwards. Such a retaining element 46 can, for example, be a simple hollow cylinder having a circumferential flange, via which it is attached to the underside of the base 50 of the collection basin 32 using fastening means, such as a screw connection.

[0056] The Fig. The retaining element 46 shown in Figure 2 is designed as a truncated cone hollow body, which is inserted into the outlet 34 during assembly without additional fastening means. The truncated cone body is installed such that the smaller cover surface 72 lies below the larger circular surface 74 in the direction of gravity. The inclined sides 76 of the first section 62 of the truncated cone hollow body can transmit the forces in the direction of shear force via the support surface with the outlet 34. In this way, the truncated cone hollow body is held in the outlet 46 without additional fastening means. However, it is also conceivable that additional means are provided for transmitting the normal forces, i.e., for transmitting the forces in the direction of gravity.For example, it is also conceivable for the retaining element to have a cylindrical shape and for the normal forces to be transmitted via an additional shoulder in the retaining element 46 at the transition between the first and second sections 62, 64. Other shapes that can be positioned above the outlet 34 and are capable of forming a corresponding reservoir 54 with an overflow edge 70 can also be conceivable as the retaining element 46.

[0057] As in Fig. 2, a shoulder 78 is arranged between the first and second sections 62, 64. This shoulder 78 extends in the radial circumferential direction of the retaining element 46. In the assembled state, the shoulder 78 is located, as shown in Fig. 2, positively engages the bottom 50 of the collecting container 32. The support surface 80 thus formed, on the one hand, enlarges the sealing surface between the collecting container 32 and the siphon 36; on the other hand, the shoulder 78 simplifies the precise installation of the retaining element 46 in the outlet 34 and transmits normal forces. It is also conceivable for the support surface 80 of the shoulder 78 to have recesses, so that it encloses a gap or labyrinth seal between itself and the bottom 50 of the collecting container.

[0058] The Fig. 3 and Fig. 4 show further embodiments of the heat exchange unit 14 according to the invention and of the retaining element 46 according to the invention.

[0059] Fig. 3 shows a section of the heater 10 in an enlarged view analogous to Fig. 2.

[0060] As in Fig. 3, an outlet 32 ​​is arranged in the collecting basin 32 of the heat exchange unit 14, which outlet is in turn connected to a siphon 36 or a siphon container 40 shown here. A retaining element 46 with the Fig. 2 described features.

[0061] As in Fig. 3, openings 82 are provided in the radial direction in the circumferential wall 65 of the retaining element 46. These openings are preferably provided in the upper region associated with the free end of the retaining element 46 and are dimensioned at least small enough that the accumulating solids 30, 42 are retained in the reservoir 54. The liquid 30, 42 can be drained off via the openings 82 provided in the upper region even if the level of the liquid 28 in the reservoir 54 has not yet reached the overflow edge 70. The separation of the liquid 28 from the solids 30, 42 and the retention of the solids 30, 42 in the collecting basin 32 is based on a combination of sedimentation and mechanical separation.

[0062] Fig. 4 shows a further embodiment of the retaining element 46 according to the invention.

[0063] The retaining element 46 has a circumferential collar 84 at the overflow edge 70, i.e., at its free end facing the space of the collecting container 32. This circumferential collar 84 extends radially over the contour of the circumferential wall 65. This circumferential collar 84 defines the upper boundary of the reservoir 54 in the region of the retaining element 46, in addition to its lateral boundary by the respective side walls 52 of the collecting container 32 on one side and the circumferential wall 65 on the other side, and its downward boundary by the bottom 50 of the collecting container 32. In this way, turbulence in the reservoir 54 can be reduced, particularly in the region of the retaining element 46. This measure has a particularly positive effect on the sedimentation process and the clean separation of the solids 30, 42 from the liquid 28.

Claims

[1] Heat exchange unit (14) with a heat exchanger (22) and an exhaust gas chamber (24) adjoining the heat exchanger (22) in the lower region of the heat exchange unit (14), wherein the exhaust gas chamber (24) comprises a drainage device (26) delimiting the exhaust gas chamber (24) for discharging a liquid-solid mixture (31), wherein the drainage device (26) has a collecting container (32) with an outlet (34), and wherein a retaining element (46) is arranged at the outlet (34), which is designed to retain the solid (30) in the collecting container, characterized bythat the outlet (34) is arranged on the bottom (50) of the collecting container (32) and extends in the direction of gravity, wherein the bottom (50) of the collecting container (32) has at least two levels (56, 58), wherein the levels (56, 58) are spaced apart from one another in the direction of gravity and wherein the level (58) in which the outlet (34) is located has a greater distance from the heat exchanger (22) than the at least second level (56). [2] Heat exchange unit (14) according to claim 1, characterized by that the liquid is condensate liquid (28). [3] Heat exchange unit (14) according to one of the preceding claims, characterized by that the solid (30) is material dissolved out of the heat exchange unit (14), in particular oxidized aluminum (42). [4] Heat exchange unit (14) according to one of the preceding claims, characterized bythat the retaining element (46) has a first and a second section (62, 64), wherein the first section (62) is seated in the outlet (34) and the second section (64) encloses the outlet (34) in the form of a circumferential wall (65), wherein the wall (65) extends from the outlet (34) into the space of the collecting container (32). [5] Heat exchange unit (14) according to one of the preceding claims, characterized by that the bottom (50) of the collecting container (32) with a side wall (52) of the collecting container (32) and the circumferential wall (65) enclose a reservoir (54) between them. [6] Heat exchange unit (14) according to one of the preceding claims, characterized by that the retaining element (46) is designed as a truncated cone hollow body. [7] Heat exchange unit (14) according to claim 4, characterized bythat a shoulder (78) is arranged between the respective outer surfaces of the first and second sections (62, 64), wherein the shoulder (78) in the assembled state bears positively against the bottom (50) of the collecting container (32) and provides a connection which is tight for solids. [8] Heat exchange unit (14) according to one of the preceding claims, characterized by that the retaining element (46) is designed as a filter. [9] Heat exchange unit (14) according to one of the preceding claims, characterized by that the circumferential wall (65) of the retaining element (46) has at least one through opening (82) in the radial direction. [10] Heat exchange unit (14) according to one of the preceding claims, characterized bythat the retaining element (46) has a circumferential collar (84) at its free end facing the space of the collecting container (32), wherein the circumferential collar (48) extends in the radial direction over the contour of the circumferential wall (65). [11] Retaining element (46) for use in a heat exchange unit (14) according to one of the preceding claims, wherein the retaining element (46) has a first and a second section (62, 64), wherein the first section (62) in the installed state sits in the outlet (34) and the second section (64) in the installed state encloses the outlet in the form of a circumferential wall (65), wherein the wall (65) then extends from the outlet (34) into the space of the collecting container (32), characterized bythat the retaining element (46) is designed as a truncated cone hollow body and a shoulder (78) is arranged between the respective outer surfaces of the first and second sections (62, 64), wherein the shoulder (78) in the assembled state bears positively against the bottom (50) of the collecting container (32) and provides a connection which is tight for solids. [12] Heating device (10), in particular a condensing boiler, comprising a burner (12) and a heat exchange unit (14) according to one of claims 1 to 10.

Images