WO2009083107A1

WO2009083107A1 - Heating device

Info

Publication number: WO2009083107A1
Application number: PCT/EP2008/010435
Authority: WO
Inventors: Jürgen Hetzler; Frank Bartmann; Norbert Ernst
Original assignee: Eichenauer Heizelemente Gmbh & Co. Kg; Beru Aktiengesellschaft
Priority date: 2007-12-21
Filing date: 2008-12-09
Publication date: 2009-07-09
Also published as: DE102007062302A1; DE112008002833A5

Abstract

The invention relates to a heating device for heating a fluid, with at least one electric heating element (2) and at least one heat exchanger (1) through which the fluid which is to be heated can flow in order for heat generated by the at least one heating element (2) to be transmitted to the fluid. According to the invention, the heat exchanger (1) is an open-pore foam material.

Description

heater

The invention relates to a heating device with the features specified in the preamble of claim 1.

Such a heating device is known from WO 2007/071335. In the known heating device is used as a heat exchanger, an extruded profile having openings through which flows a fluid to be heated.

A heating device with the features specified in the preamble of claim 1 is also known from DE 101 02 671 A1. In this heater, numerous lamellar sheets are pushed as clamping heat transfer to mutually parallel heating rods, which are filled with PTC heating elements as a heat exchanger.

The object of the invention is to improve a heater of the type mentioned. This object is achieved in that the heat exchanger is an open-cell foam material. Advantageous developments of the invention are the subject of the dependent claims.

A heating device according to the invention can deliver the heat generated by one or more electric heating elements particularly efficiently to a fluid flow to be heated, for example an air flow, since the open-cell foam material used as heat exchanger has an advantageously large surface area. The use of an open-pore foam material, preferably a metal or ceramic foam, as a heat exchanger also enables a significant weight saving in comparison with conventional heating devices with lamellae or extruded profiles as a heat exchanger.

In the case of an open-pore foam material, at least some of the cells contained in the foam material are connected to one another so that a fluid can flow through the foam material. A method for producing a suitable metal foam is known from DE 199 39 155.

A heating device according to the invention is particularly suitable as interior heating of a motor vehicle for heating an air flow.

A heating device according to the invention preferably has a plurality of electrical heating elements, in particular PTC heating elements. The heating elements can be arranged in a housing, for example a rod-shaped housing as is known, for example, from DE 101 02 671 A1. The heat exchanger may be non-positively, positively or materially secured to the housing, for example, heat exchanger and housing may be jammed, pressed, locked, glued, soldered or welded. Preferred attachment options are in particular clamping or sticking and to the housing to spray a foam material for forming the heat exchanger. In a clamping connection, it is possible to connect individual heat exchanger and housing, for example by means of brackets with each other, or to hold the entire heater, which may be constructed, for example, in layers, clamping in a frame. But it is also possible that the heat exchanger forms a housing in which the one or more heating elements are arranged. It is also possible to dispense with a housing so that the heating elements are exposed directly to the fluid flow to be heated. The heating elements can be non-positively, positively or materially connected to the heat exchanger. It is preferred to jam the entire assembly in a frame or to arrange the individual heating elements in cavities and to press together. It is also possible that the heating elements are made of an open-cell foam material and form the heat exchanger or a part of the heat exchanger.

An advantageous development of the invention provides that the foam material has a closed surface area, which faces the at least one heating element. This measure has the advantage that heat generated by the heating elements or the heating elements can be absorbed by the heat exchanger in a particularly efficient manner. The closed surface area can rest, for example, on a housing surrounding the heating elements or a metal strip contacting the heating elements. It is also possible that the foam material rests with its closed surface area directly on the one or more heating elements.

Preferably, the foam material has a density which decreases with increasing distance from the heating element (s). In this way, the thermal conductivity of the heat exchanger can be adapted to the amount of heat to be transported. The amount of heat flowing through the heat exchanger decreases with the distance from the heating element (s). Therefore, close to the heating elements, a higher density is advantageous, so that a large amount of heat can be dissipated by the heating element or elements. With increasing distance from the heating element or elements, the quantity of heat to be transported decreases, which is why a lower density, in particular a larger pore size, are increasingly advantageous in order to reduce the flow resistance of the heat exchanger and to save weight. The density of the foam material can change continuously or suddenly. In order to utilize the above-described advantages of a location-dependent density at least in part, it is sufficient if the density changes only once, which can be achieved for example by joining two plates of a foam material with different density, in particular different pore size.

The density of a foam material depends primarily on the pore size and the thickness of the walls present between the pores. A change in density can therefore be effected by a variation of the pore size. Another way to change the density is to vary the wall thicknesses between the pores.

A further advantageous embodiment of the invention provides that in the heat exchanger straight running flow channels are present. This measure has the advantage of reducing the flow resistance of the heat exchanger. This is particularly advantageous if the air heater is to be used to heat an air stream, as is required, for example, for heating the interior of a vehicle. The flow channels may be formed, for example, as slots, slots or holes. In the simplest case, the flow channels can run perpendicular to the surface of the heat exchanger. But it is also possible that the flow channels run obliquely to the surface of the heat exchanger. In this way, the flow path of the fluid can be extended, so that heat can be released to the fluid more intensively, or the flow direction can be influenced. Linear flow channels can be produced in the foam material during its production or can be produced in the heat exchanger with little effort, for example by drilling, milling or punching.

A heating device according to the invention preferably contains a plurality of heating elements. In each case a plurality of heating elements are preferably combined in an elongated assembly, which contains a plurality of heating elements in a straight line arrangement one behind the other. In a heating device according to the invention a plurality of such assemblies, for example a plurality of heating elements with PTC elements, may be present. The heating elements can be contacted in such an assembly by a common conductor, preferably a metal strip, and supplied with power. The circuit can be connected via the heat exchangers or another line terbahn, for example, another metal strip to be closed. In such an arrangement, the conductor used for the power supply is to be insulated from the heat exchanger. This can be done by an extending over the length of the conductor strip strips of an electrically insulating material or in that the conductor track, with the exception of the bearing surfaces for the heating elements is encapsulated with an insulating material. Preferably, a direct contact of the current-supplying conductor to the heat exchanger is prevented by using as heating elements PTC resistors, which are arranged in pairs next to each other. In such a case, the trace may pass between the PTC elements of each pair, which are thereby both contacted so that the current-carrying trace is separated from the heat exchanger by the PTC heating elements.

Preferably, the foam material is molded onto the at least one housing to form the heat exchanger. It is particularly preferred that two opposite longitudinal sides of the housing remain free. In this way, it is possible to introduce a heater into the housing only after the injection of the foam material. Even after the molding of the foam material, the housing can still be pressed by pressure on its free narrow sides in order to achieve a good thermal coupling of heating elements arranged therein. In addition, heating elements can be easily introduced with a mounting frame made of plastic in the housing, as it is not exposed to the high temperatures occurring during injection molding. It is also possible to inject foam material to form a heat exchanger on three or even all longitudinal sides, so that the housing is surrounded by the heat exchanger. In this case, heating elements can be positioned without a mounting frame in the housing, for example. However, even with an encapsulation of the housing, it is not necessary to dispense with the advantages of a mounting frame. For example, a mounting frame made of a polymer ceramic can be used. Polymeric ceramics are sufficiently resistant to heat to withstand the temperatures occurring in the housing during injection molding of a metal foam. It is even possible to use a mounting frame made of conventional plastic, even with an encapsulation of the housing. On the one hand, the heat capacity of the housing can prevent the encapsulation of the housing in its interior excessive temperatures occur. On the other hand, a slight overheating of the mounting frame, which leads to a loss of shape, unproblematic, since the mounting frame has fulfilled its function after insertion into the housing and is no longer needed in the subsequent operation of the heater itself.

Further details and advantages of the invention will be explained with reference to embodiments with reference to the accompanying drawings. Identical and corresponding components are identified by matching reference numerals. Show it:

Figure 1 shows an embodiment of a heating device according to the invention;

Figure 2 shows the embodiment shown in Figure 1 from the side;

Figure 3 shows the embodiment shown in Figure 1 from above;

Figure 4 is a sectional view of the embodiment shown in Figure 1;

Figure 5 is a sectional view of a modified embodiment;

FIG. 6 shows a further embodiment of a heating device according to the invention;

Figure 7 shows the embodiment shown in Figure 6 in an exploded view.

Figure 1 shows an embodiment of a heating device, which is designed for heating an air flow as interior heating of a vehicle. The heating device is shown in Figure 1 in the direction of the flow direction of an air stream to be heated, in Figure 2 in a side view and in Figure 3 in a view from above.

The heater shown has a heat exchanger 1 made of an open-cell foam material, such as a metal foam. In operation, the heat exchanger 1 is flowed through by the air stream to be heated. The heat emitted by the heat exchanger 1 to the air flow is by means of PTC Produces heating elements 2, which are enclosed by the heat exchanger 1 and can be seen in the schematic sectional view shown in Figure 4. In the illustrated embodiment, the PTC heating elements 2 are arranged in rod-shaped housings 3, which are stuck in the heat exchanger 1. The housings 3 protect the PTC heating elements 2 from contact with the air flow to be heated.

So that the heat generated by the heating elements 2 can be transferred well to the housing 3, this is preferably pressed, so that it rests flat against the heating elements 2. For better clarity, this is not shown in the schematic sectional view of Figure 4, so that there is a distance between the heating elements 2 and the inner surface facing the housing 3 can be seen.

The rod-shaped housing 3 are connected by clamping with the heat exchanger 1, so that a good heat-conducting contact between the housings 3 and the heat exchanger 1 results. Alternatively, the housing 3 may also be materially connected to the heat exchanger 1, in particular soldered, which also causes a good thermal contact. In particular, it is also possible to spray metal foam onto the rod-shaped housing 3 in order to form the heat exchanger 1. A molded-on heat exchanger 1 can enclose the housing as shown in FIG. 4, that is to say be injection-molded onto all longitudinal sides, or be injection-molded onto only one longitudinal side.

The heat exchanger 1 carries a connection housing 5 and at its opposite end a hood 7, which protects the heat exchanger 1 against damage during installation.

The metal foam of the heat exchanger 1 has a pore size, which increases with increasing distance from the rod-shaped housing 3. As the distance from the heating elements 2 increases, the amount of heat to be transported by the metal foam decreases. Close to the heating elements 2, therefore, a smaller pore size is advantageous in order to be able to conduct heat generated quickly, while with increasing distance a larger pore size, which allows a lower flow resistance for the fluid to be heated, becomes more advantageous. The Po Reindeer size may increase continuously or skyrocket. In the illustrated embodiment, the heat exchanger 1 in the region of the housing 3 receiving recesses has a closed surface area. By the heat exchanger 2 with a closed surface against the housings 3, a particularly good heat-conducting contact results.

The PTC elements 2 are arranged one behind the other in the rod-shaped housings 3 and are supplied with power by rigid electrical leads 4, which project into a connection housing 5 shown in FIG. In the connection housing 5 further protrudes a ground line 6, which is electrically connected via the heat exchanger 1 to the outer sides of the housing 3 and thus also connected to the heating elements 2. The leads 4 and the ground line 6 can be connected via connectors, for example, to the electrical system of a motor vehicle or to a control unit. The heating elements 2 are preferably arranged in pairs in the housings 3, the supply lines 4 formed as metal strips each extending between the heating element pairs. In this way, no additional electrical insulation is required. It is also possible to arrange the PTC heating elements 2 one after another in the housings 3 and to insulate the lead 4 from the housing 3 by means of an insulating layer.

FIG. 4 shows a cross section through the heat exchanger 1 and the heating elements arranged therein with their housings 3 and heating elements 2 contained therein. The heat exchanger 1 is formed as a block having openings which receive the housings 3. But it is also possible, the heat exchanger 1 of two heat exchanger parts 1a, 1b together, between which the heating elements 2 are arranged. A cross section through a correspondingly modified embodiment is shown in FIG.

FIG. 5 shows a cross section through a further exemplary embodiment, which differs from the exemplary embodiment illustrated in FIGS. 1 to 3 only in that the heat exchanger 1 is composed of two plate-shaped heat exchangers 1 a, 1 b, between which the heating elements 2 are arranged in housings 3 , The two heat exchanger parts 1 a, 1 b are of identical design and each have recesses which are adapted to the shape of the housing 3. Figures 6 and 7 show a further embodiment of a heating device, which also serves to heat a fluid flow and is designed as Innenraumbeheizer a motor vehicle. For simplicity, in the embodiment shown in FIGS. 6 and 7, no electrical connections are shown. Similar to the embodiment described above, the heat exchanger 1 is also an open-pore metal foam in the embodiment shown in Figure 6. In the exemplary embodiment illustrated in FIG. 6, two heat exchangers 1 are present, between which PTC heating elements 2 are arranged in accordance with the exploded illustration shown in FIG. On the side surfaces of the longitudinal sides of the heat exchanger 1 respectively metal strips 10, in the illustrated embodiment of aluminum or an aluminum alloy, soldered. The PTC heating elements 2 are arranged between two metal strips 10 and held there by a plastic frame 11.

In order to reduce the flow resistance, straight-flow flow channels 12 are present in the heat exchangers 1 of the exemplary embodiment shown in FIGS. 6 and 7. Such flow channels 12 may also be present in the above described embodiments of Figures 1 to 5. The rectilinear flow channels 12 can run perpendicular or obliquely to the surface of the heat exchanger 1 and be executed as holes or slots.

The two heat exchangers 1 of the exemplary embodiment shown in FIGS. 6 and 7 are arranged next to one another in the flow direction of the fluid flow to be heated. If necessary, the heater can be arbitrarily increased by further heat exchanger 1 are arranged with intermediate heating elements 2 side by side. Bezuαszahlen

1 heat exchanger

1a, 1 I b heat exchanger ^

2 heating elements

3 housing

4 supply line

5 connection housing

6 ground line

7 hood

10 metal strip

11 plastic frame

12 flow channels

Claims

claims

A heating device for heating a fluid, comprising at least one electric heating element (2) and at least one heat exchanger (1) through which the fluid to be heated can deliver heat generated by the at least one heating element (2) to the fluid, characterized in that the heat exchanger (1) is an open-pore foam material.

2. Heating device according to claim 1, characterized in that the foam material has a density which decreases with increasing distance from the at least one heating element (2).

3. Heating device according to claim 2, characterized in that the density of the foam material decreases with increasing distance from the at least one heating element (2) at least once in a leap.

4. Heating device according to claim 2, characterized in that the density of the foam material decreases continuously.

5. Heating device according to one of claims 2 to 4, characterized in that the change in the density of the foam material is based on a change in the pore size.

6. Heating device according to one of the preceding claims, characterized in that the foam material has a closed surface area, which faces the at least one heating element (2).

7. Heating device according to one of the preceding claims, characterized in that in the heat exchanger (1) rectilinear flow channels (12) are present.

8. Heating device according to claim 7, characterized in that the flow channels (12) are slots or holes.

9. Heating device according to claim 7 or 8, characterized in that the flow channels (12) extend perpendicular to the surface of the heat exchanger (1).

10. Heating device according to claim 7 or 8, characterized in that the flow channels (12) run obliquely to the surface of the heat exchanger (1) fen.

11. Heating device according to one of the preceding claims, characterized in that the at least one heating element (2) in a housing (3) is arranged, on which the heat exchanger (1) is attached.

12. Heating device according to claim 11, characterized in that the housing (3) is rod-shaped.

13. Heating device according to claim 11 or 12, characterized in that the at least one heating element (2) is pressed in the housing.

14. Heating device according to one of claims 11 to 13, characterized in that the housing (3) is pressed in the heat exchanger (1).

15. Heating device according to one of claims 11 to 13, characterized in that the housing (3) with the heat exchanger (1) is glued.

16. Heating device according to one of claims 11 to 13, characterized in that the heat exchanger (1) is molded onto the housing (3).

17. Heating device according to claim 16, characterized in that two opposite longitudinal sides of the housing are free of foam material.

18. Heating device according to one of claims 11 to 17, characterized in that a plurality of housing (3) are present, in each of which at least one heating element (2) is arranged.

19. Heating device according to one of claims 1 to 9, characterized in that the at least one heating element (2) is arranged in a housing formed by the heat exchanger (1).

20. Heating device according to one of the preceding claims, characterized in that the at least one heating element (2) of the heat exchanger

(1) is surrounded.

21. Heating device according to one of the preceding claims, characterized in that the heat exchanger (1) is designed as a block having an opening in which the at least one heating element (2) is arranged.

22. Heating device according to one of the preceding claims, characterized in that the at least one heating element (2) between two heat exchangers (1, 1a, 1b) is arranged.

23. Heating device according to claim 22, characterized in that the heat exchangers (1a, 1b) are arranged one behind the other in the flow direction of the fluid to be heated.

24. Heating device according to claim 22, characterized in that the heat exchangers (1) are arranged side by side in the flow direction of the fluid to be heated.

25. Heating device according to one of claims 22 to 24, characterized in that at least one of the two heat exchangers (1 a, 1 b), between which the at least one heating element (2) is arranged, a recess for the heating element (2).

26. Heating device according to one of claims 22 to 25, characterized in that both heat exchanger (1), between which the at least one heating element (2) is arranged, a recess for the heating element (2) or the heating elements (2).

27. Heating device according to one of the preceding claims, characterized in that at least one heating element (2) between two metal strips (10) is arranged, which are arranged between two heat exchangers (1).

28. Heating device according to claim 27, characterized in that the at least one heating element (2) is held between the two metal strips (10) in a plastic frame (11).

29. Heating device according to claim 27 or 28, characterized in that the metal strips (10) are each materially connected to a narrow side of a heat exchanger (1).

30. Heating device according to one of claims 27 to 29, characterized in that the metal strips (10) with the heat exchangers (1) are soldered

31. Heating device according to one of the preceding claims, characterized in that the foam material is a metal foam.

32. Heating device according to one of the preceding claims, characterized in that the at least one heating element (2) has a positive temperature coefficient.

33. Heating device according to claim 32, characterized in that the at least one heating element (2) is a ceramic PTC element.

34. Heating device according to one of the preceding claims, characterized in that the at least one heating element (2) is made of an open-cell foam material.

35. Heating device according to claim 33, characterized in that the at least one heating element (2) forms the heat exchanger (1) or a part of the heat exchanger (1).

36. Heating device according to one of the preceding claims, characterized in that the heating device is designed for heating an air flow as an interior space heating of a vehicle.