DE29722802U1 - Heater for heating air and / or water - Google Patents

Description

22 December 1997 Tnima Gerätetechnik GmbH & Co. T 26526 Ro/Le/bb

Heater for heating air and/or water

The invention relates to a heating device for heating air and/or water for small spaces, in particular for caravans, mobile homes, boats or the like according to the preamble of claim 1.

The applicant manufactures such heaters and uses them in caravans and mobile homes. EP 0 544 853 B1 discloses an air heater with a heat exchanger insert, in which the hot combustion gases produced during the combustion taking place in the combustion chamber are dissipated and the actual heating process takes place by releasing this heat energy via the essentially radially arranged fins of the heat exchanger insert. Heating water is not provided for in these pure air heaters.

The applicant provides such heating devices with a water boiler, which is arranged around the heat exchanger insert on its outer periphery. The thermal energy absorbed by the heat exchanger insert from the hot combustion gases is transferred via the fins essentially directly to the inside of the water boiler, which surrounds the heat exchanger insert.

Especially during the cold season, it is necessary that the heaters used in caravans and mobile homes are used for heating on the one hand and for producing hot water on the other. Especially during this cold season, permanent heating is often required

required. However, with permanent heating, heat energy is constantly transferred from the heat exchanger insert to the water boiler, so that there is a risk that the water in the water boiler will start to boil.

In addition, with such heating devices for heating air and/or water there is the problem that the internal dimensions of the water boiler must be matched with relatively high precision to the external dimensions of the relatively complicated profiled and complicated to manufacture heat exchanger insert. This results in relatively high production costs on the one hand,

&iacgr;&ogr; and on the other hand, the uneven heat transfer from the combustion gas to the heat exchanger insert caused by the combustion gases as they flow over the surface of the heat exchanger insert leads to uneven heating of the water in the water boiler that is to be heated. This means that when a tap is opened, water that is heated to different degrees must always be expected. In addition to the risk of scalding, there is also the problem that the supply of cold water must be constantly changed in order to achieve the desired mixing temperature.

Furthermore, the heater should also be able to be used in summer to simply generate heated water. Another problem with heaters for heating air and/or water according to the state of the art is that, due to the small distance between the inside of the water boiler and the outside of the heat exchanger insert, a "diameter problem" occurs in the frequently occurring situation that caravans, mobile homes, etc. are at an angle, because in such a situation individual areas of the inside of the water boiler are directly adjacent to the outside surface of the heat exchanger, while other areas are at a greater distance from the heat exchanger than was originally intended in the design.

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The invention is therefore based on the object of overcoming the disadvantages described and of creating a heating device for heating air and/or water, in which the heat transfer from a heat exchanger insert to a water boiler can be optimized in such a targeted manner that an essentially constant temperature can be achieved in the water boiler and boiling of the water is avoided, and in which the manufacturing costs of the water boiler can be reduced with regard to its accuracy of the dimensions to be maintained.

&iacgr;&ogr; This object is achieved by a heating device with the features according to claim 1. Appropriate further developments are defined in the dependent claims.

In particular, the heating device according to the invention, which is used to heat air and/or water, is used in small spaces, with caravans, mobile homes, boats or the like being the preferred areas of use. The heating device has a boiler, which is arranged in a combustion chamber, which is designed in the form of a flame tube, a heating chamber, which surrounds the combustion chamber, a heat exchanger insert, which surrounds the heating chamber and which has an inner casing, and a water boiler, which surrounds the heat exchanger insert. The water boiler and thus the heating device are surrounded by an outer casing forming a housing. The inner casing of the heat exchanger insert separates the heating chamber, through which the hot combustion gases are passed after leaving the combustion chamber, from the heat exchanger surfaces of the heat exchanger insert, which face the inside of the water boiler. According to the invention, the water boiler has areas on its inside, which faces the heat exchanger insert, by means of which the heat transfer from the heat exchanger insert to the water boiler is facilitated by different

defined gap geometry can be determined. By means of the gap geometry between the outside of the heat exchanger insert and the inside of the water boiler, which face each other, the heat transfer as such as well as the type of heat transfer is determined in such a way that an equilibrium situation of the water in the water boiler can be achieved. In this context, equilibrium situation is understood to mean a water temperature that is as constant as possible essentially in the entire water boiler.

&iacgr;&ogr; The gap geometry of the individual areas determining the heat transfer is designed in such a way that, depending on the required heat transfer and taking into account the nominal load to be achieved with the heater, the gap geometry has gap thicknesses from 0 mm, where the inside of the water boiler is directly on the outer surface of the heat exchanger insert, up to gap thicknesses of finite dimensions. Furthermore, it is possible for the gap geometry to have continuous transitions between the individual heat transfer areas or sharply defined transitions. Within the individual areas, the gap geometry can be constant with respect to the longitudinal axis of the combustion chamber or have variable gaps. Due to the differently defined gap geometry in the respective heat transfer areas, the heat transfer from the heat exchanger to the water boiler is directly influenced in such a way that the water temperature in the water boiler is as constant as possible and that the water boiler is not overheated during continuous heating operation, i.e. that the water in the water boiler does not boil.

According to an embodiment of the invention, the water boiler has a first heat transfer area in the area of the burner of the flame tube, i.e. the lower area of the heating device, in which the inside of the water boiler is manufactured with a narrow tolerance, i.e. high manufacturing

accuracy, essentially rests on the surface of the heat exchanger insert. Because the inside of the water boiler rests on the outside surface of the heat exchanger insert in this heat transfer area, heat conduction dominates in this first heat transfer area. Even if there is a very small gap between the outside surface of the heat exchanger insert and the inside surface of the water boiler in this first heat transfer area, this very small gap is still not large enough for convection and radiation to participate to a large extent in the heat transfer, but rather

&iacgr;&ogr; in such a case, heat conduction also dominates. Furthermore, the water boiler has, at least in the area where the combustion gases exit the flame tube, i.e. the upper area of the heater, a second heat transfer area, the gap geometry of which is designed as a gap between the outer surface of the heat exchanger insert and the inside of the water boiler, so that convection and heat radiation dominate in this second heat transfer area. This means that the gap provided between the inner surface of the water boiler and the outer surface of the heat exchanger insert in this second heat transfer area is large enough that heat conduction is dominated by convection and heat radiation.

Depending on the operating conditions of the heater and the heat transfer to be achieved, the first heat transfer area and the second heat transfer area are of different lengths. The term "long" refers to the length in the longitudinal direction of the combustion chamber or flame tube.

One advantage of such an inventive design of the water boiler is that the high manufacturing precision with regard to narrow manufacturing tolerances is limited to the first heat transfer area

is, which reduces the overall manufacturing costs of the kettle. In the case of direct contact between the inner surface of the kettle and the outer surface of the heat exchanger insert in the first heat transfer area, the kettle already has sufficient tipping stability compared to the heat exchanger insert. For reasons of increased rigidity, the kettle has an additional bead either in the transition area between the first heat transfer area and the second heat transfer area or within the first heat transfer area or within the second heat transfer area. For reasons of the required food safety, the kettle is preferably made of stainless steel and has a wall thickness of preferably 1 mm.

According to a further embodiment, a third heat transfer area is provided between the area of the burner and the area where the combustion gases exit the flame tube, i.e. between the first heat transfer area and the second heat transfer area, in which the gap geometry is defined by a gap that is larger than the gap of the first heat transfer area and smaller than the gap of the second heat transfer area. The number of defined heat transfer areas provided, i.e. the areas with different gap geometries, has a direct influence on the uniformity of the temperature distribution of the water in the water boiler. In addition, the different gap geometry takes into account the different heat transfer conditions due to the different temperature and flow conditions that occur due to the flow of the combustion gases along the heating chamber in the course of the flow from the upper part of the heater to the lower part of the heater on the outside of the combustion chamber.

According to a further embodiment, the heat transfer areas are separated from one another by shoulders or beads or are limited by these. However, the beads or shoulders can also be provided within the respective heat transfer areas in order to ensure increased stability and strength, in particular bulge resistance, of the water boiler.

Preferably, the flame tube is essentially cylindrical and the heating chamber, the heat exchanger insert with its inner casing, the

&iacgr;&ogr; water boiler and the outer casing of the heater are arranged coaxially therewith. According to a further embodiment, the heat exchanger insert is essentially cylindrical, so that its inner casing is also cylindrical. The inner casing has radial, oppositely attached inner and outer ribs, with a transverse web protruding at least on one side being formed on the outer edges of the outer ribs. These transverse webs on the outer ribs are not connected to one another and their outer surfaces essentially follow the inside of the water boiler. Such a heat exchanger insert can, for example, be designed as described in EP 0 544 853 B1 of the applicant.

According to a further embodiment, the individual heat transfer areas each have a constant gap geometry. Constant gap geometry is understood to mean the radial expansion of the gap in the direction of the longitudinal axis of the combustion chamber of the heater.

Preferably, the gap of the first heat transfer area measures 0 to 1.5 mm and the gap of the second heat transfer area measures 3 to 4 mm. Different heating conditions and other heat exchanger inserts than

However, the dimensions described may require gaps that differ considerably from those given as examples.

Further advantages, features and possible applications of the invention will now be explained in detail using an embodiment with reference to the accompanying drawings. They show:

Fig. 1 is an axial section through the heater according to the invention;

&iacgr;&ogr; Fig. 2 is an axial section through the kettle according to the invention; and

Fig. 3 a segment of the heat exchanger insert used in the heating device according to the invention.

Fig. 1 shows an axial section through a heating device according to the invention. Inside the heating device, a burner 1 is provided, which is arranged inside a flame tube 2 designed as a combustion chamber 3. The flame tube 2 is essentially cylindrical and extends upwards from the burner inside the heat exchanger insert 5, where it ends with its upper outlet opening just before a cover 24 that covers the heat exchanger insert 5 or its inner casing 6 in the form of a cap. The cover cap 24 is preferably welded on. This cover cap 24 diverts the combustion gases 23 rising in the flame tube 2 into a heating chamber 4. The heating chamber 4 is formed between the inner casing 6 of the heat exchanger insert 5 and the outer surface of the flame tube 2. The combustion gases 23 then flow in the heating chamber in a coaxial direction with respect to the flame tube 2 in the direction of the burner side of the heat exchanger insert, from where the

combustion gases 23 are discharged, for example, into the open air via an exhaust connection 25.

The heat exchanger insert 5 has inner ribs 17 extending radially into the heating chamber, which can have different radial dimensions, and outer ribs 18 extending radially outwards from the inner casing 6. Air flows in the longitudinal spaces between the outer ribs 18 of the heat exchanger insert 5, which on the one hand absorbs heat energy through heat transfer from the heat exchanger insert 5 as a result of heat emission from the combustion gases 23 and on the other hand, depending on the gap geometry, removes heat energy from the water boiler 7. The air flowing along the outer ribs of the heat exchanger insert 5 flows in parallel with the combustion gases 23 in the heating chamber 4. For this purpose, the air enters the space formed between the outer ribs 18 on the burner side, for example also acted upon by a fan, and exits directly from this space at the other end of the heater.

The outer ribs 18, which are arranged radially around the circumference and extend outwards from the inner casing 6 of the heat exchanger insert 5, have transverse webs 19 on their outer edges, which extend on both sides of the ribs. To increase the heat exchanger surface, further transverse extensions are formed on the outer ribs 18 on the ribs between the transverse webs 19 and the inner casing 6. It is of course also possible for the inner ribs 17 to have such transverse extensions or transverse webs. The outside of the transverse webs 19 facing outwards forms the maximum outer diameter or the outer surface of the cylindrically designed heat exchanger insert 5. In the heat transfer area 9, in which the transverse webs 19 essentially lie against the inside of the water boiler 7 or have a small gap thereto.

so, the crossbars form the surfaces over which the essentially

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chen realized as heat conduction. In the heat transfer area 10, in which a gap 14 is provided between the crossbars 19 and the inner diameter of the water boiler 7, the crossbars 19 additionally form heat transfer surfaces, via which, for example, radiation is realized. By providing the gap 14, the air flowing in the area of the outer fins, i.e. between the inner jacket 6 of the heat exchanger insert 5 and the water boiler 7, contributes, depending on the heating conditions, to either ensuring the heat transfer to the water boiler or dissipating heat energy from the water boiler.

&iacgr;&ogr; to avoid boiling of the water in the kettle 7.

The number of outer fins of the heat exchanger insert is dimensioned such that the air flow flowing over it is fanned out and thus, in conjunction with the selected gap geometry, the desired defined heat transfer processes from the heat exchanger insert 5 to or from the water boiler 7 are realized.

Fig. 2 shows an axial section through the water boiler 7 according to the invention for the heating device according to the invention. The water boiler 7 has a first heat transfer area 9, the diameter of which is dimensioned such that it fits with a narrow tolerance to the outer diameter or to the outer surface 12 of the heat exchanger insert 5 so that the crossbars 19 rest against the inner surface of the water boiler 7 or only a narrow gap with narrow tolerances is present. The precise manufacture of the water boiler 5 is thus limited only to the first heat transfer area 9, which thus contributes to a significant reduction in the manufacturing costs of the water boiler 7, since the other heat transfer areas require such narrow manufacturing tolerances. On the underside of the water boiler 7, which is arranged in the area of the burner 1 of the heating device, a centering collar 20 is provided, which can be placed on a plate (not

) and thus serves to fix the water boiler 7 in the housing of the heater.

The first heat transfer area 9 is limited by a bead 16, which simultaneously serves to increase the rigidity of the water boiler 7. A third heat transfer area 11 extends from the bead 16 to a shoulder 15, the inner diameter of which is selected such that a gap is present between the inside of the water boiler 7 and the outer surface 12, which are formed by the crosspieces 19 of the heat exchanger element 5, which gap is > 0. The inner diameter is preferably selected such that heat conduction, convection and radiation are present in the heat transfer area 11, preferably with almost equal shares.

In the upper area of the water tank 7, which is located in the area of the upper end of the flame tube 2, a second heat transfer area 10 extends from a shoulder 15 to a fixing collar (not shown), the inner diameter of which is larger than the outer diameter formed by the outer surface 12 of the heat exchanger insert 5, so that a gap 14 with a defined gap width is present between the outer surface 12 of the crossbars 19 and the inner surface of the water tank 7. The gap 14 has such dimensions that convection and radiation dominate, since the heat conduction via the air layer present in the gap is small compared to the heat energy transferred by radiation and convection. The water tank 7 also has fasteners 21, 22.

The water tank 7 for the heating device according to the invention can, with the selected gap geometry, also be operated without

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Water, in which case the heater is only used for heating purposes without heating water.

Fig. 3 shows a radial section of a cross-sectional view of the heat exchanger insert 5 used in the heating device according to the invention, the basic structure of which has already been described in connection with Figs. 1 and 2 and which corresponds in detail to the design according to EP 0 544 853 B1 of the applicant.

Claims (9)

22 December 1997 Truma Gerätetechnik GmbH & Co. T 26526 Ro/Le/bb Protection claims 1. Heating device for heating air and/or water for small spaces, in particular for caravans, mobile homes, boats or the like, which has a burner (1) in a combustion chamber (3) designed as a flame tube (2), a heating chamber (4) surrounding it, a heat exchanger insert (5) enclosing the heating chamber (4) with an inner casing (6) and a water boiler (7) surrounding the heat exchanger insert (5), wherein an outer casing (8) enclosing the water boiler (7) is provided, is characterized by the fact that the water boiler (7) has, on its inner side facing the heat exchanger insert (5), areas (9, 11, 10) of different defined gap geometries that determine the heat transfer from the heat exchanger insert (5) to the water boiler (7). 2. Heating device according to claim 1, characterized in that the water boiler (7) in the area of the burner (1) of the flame tube (2) has a first heat transfer area (9), in which the gap geometry is designed such that the inside of the water boiler (7) lies with a narrow tolerance essentially on the outer surface (12) of the heat exchanger insert (5), and in which heat conduction therefore dominates, and that the water boiler (7) at least in the area of the exit (13) of the combustion gases from the flame tube (2) has a second heat transfer area (10), in which the gap geometry is designed such that between the outer surface of the heat exchanger insert (5) and the inside of the water boiler (7) a · A gap (14) is provided so that convection and thermal radiation dominate in the second heat transfer region (10). 3. Heating device according to claim 2, characterized in that the water boiler (7) is arranged between the area of the burner (1) and the area of the Outlet (13) of the combustion gases from the flame tube (2) has a third heat transfer region (11) in which the gap geometry is defined by a gap which is larger than the gap of the first heat transfer region (9) and smaller than the gap (14) of the second heat transfer region (14). 4. Heating device according to claim 2 or 3, characterized in that the heat transfer areas (9, 11, 10) are offset from one another by shoulders (15). 5. Heating device according to claim 2 or 3, characterized in that the heat transfer areas are limited by beads (16). 6. Heating device according to one of claims 1 to 5, characterized in that the flame tube (2) is essentially cylindrical and the heating chamber (4), the heat exchanger insert (5) with its inner casing (6), the water boiler (7) and the outer casing (8) are arranged coaxially thereto. 7. Heating device according to one of claims 1 to 6, characterized in that the heat exchanger insert (5) has radial, oppositely placed inner (17) and outer ribs (18) on the essentially cylindrical inner casing (6), with a transverse web projecting at least on one side being provided on the outer edges of the outer ribs (18). (19) and the crosspieces (19) are not connected to each other. are connected and their outer surfaces essentially face the inside of the water boiler (7). 8. Heating device according to one of claims 1 to 7, characterized in that the heat transfer areas (9, 11, 10) each have a constant gap geometry. 9. Heating device according to claim 8, characterized in that the gap of the first heat transfer area is 0 to 1.5 mm and the gap (14) of the &iacgr;&ogr; second heat transfer area should be 3 to 4 mm.