ELECTRIC HEATING DEVICE

Abstract

An electric heating device and a method for manufacturing an electric heating device with at least two plate pairs forming a fluid passage through which fluid can flow, which plate pairs are assembled from two plates and form a fluid passage between the two, wherein the plate pairs take on a predefined distance from one another and form a free space, wherein at least one heating unit is arranged in the free space between at least two of the plate pairs, which heating unit has at least one heating element and contact electrodes electrically connected thereto for making electrical contact with the at least one heating element. The invention also relates to such an electric heating device.

Claims

1. A method for manufacturing an electric heating device comprising at least two plate pairs forming a fluid passage through which fluid is adapted to flow, the two plate pairs being assembled from two plates and form a fluid passage there between, wherein the plate pairs take on a predefined distance from one another and form a free space, wherein at least one heating unit is arranged in the free space between at least two of the plate pairs, which heating unit has at least one heating element and contact electrodes electrically connected thereto for making electrical contact with the at least one heating element, the method comprising: providing and stacking the plates into a stack of plates and/or plate pairs; soldering the stack of plates; and inserting and attaching the heating unit in the free space.

2. The method according to claim 1, wherein the heating unit in the free space is attached to the plate pairs via at least one adhesive.

3. The method according to claim 2, wherein the at least one adhesive is fed into the free space before insertion of the heating unit or wherein the at least one adhesive is fed into the remaining free space after insertion of the heating unit.

4. The method according to claim 3, wherein a partial sealing of one side at a time of at least one free space is accomplished via sealing elements before the at least one adhesive is fed into the free space.

5. The method according to claim 4, wherein the partially sealed free space is filled with at least one adhesive.

6. The method according to claim 5, wherein an insertion of the heating unit into the free space filled with the at least one adhesive takes place, or the heating unit is inserted into the free space before the feeding of the at least one adhesive and subsequently the at least one adhesive is fed into the free space that has been partially sealed beforehand.

7. The method according to claim 5, wherein a curing of the at least one adhesive subsequently occurs.

8. The method according to claim 2, wherein the at least one adhesive is an adhesive substance, a silicone compound, a potting compound, a cross-linkable plastic molding compound, and/or a flowable substance.

9. The method according to claim 2, wherein a plurality of different adhesives are used.

10. The method according to claim 2, wherein the sealing elements are removed after the at least one adhesive has cured.

11. The method according to claim 2, wherein the at least one adhesive is electrically insulating and thermally conductive.

12. The method according to claim 2, wherein the at least one adhesive contains agents and/or particles for improving the thermal conductivity of the adhesive.

13. The method according to claim 1, wherein the free space is at least partially evacuated prior to the filling with the adhesive.

14. The method according to claim 1, wherein excess adhesive is expelled from the free space during insertion of the heating unit into the free space.

15. The method according to claim 1, wherein the heating unit has a frame for arrangement of the heating elements of the heating unit relative to one another and/or for defined positioning of the heating elements of the heating unit in the free space.

16. The method according to claim 1, wherein the stack of plate pairs is provided with an inlet connection and an outlet connection prior to soldering, and/or wherein the fluid passages of the plate pairs are in fluid connection with one another.

17. The method according to claim 9, wherein the inlet connection and the outlet connection are arranged on the same plate pair of the stack or on an end plate pair of the stack or wherein the inlet connection and the outlet connection are arranged on different plate pairs of the stack or on opposing end plate pairs of the stack.

18. An electric heating device comprising: at least two plate pairs forming a fluid passage through which fluid is adapted to flow, the at least two plate pairs being assembled from two plates and form a fluid passage there between; a free space formed between the plate pairs that are spaced a predefined distance from one another; and at least one heating unit arranged in the free space between at least two of the plate pairs, the heating unit having at least one heating element and contact electrodes electrically connected thereto for making electrical contact with the at least one heating element, wherein the heating unit is held in the free space via at least one adhesive, and wherein the at least one adhesive simultaneously forms an electrical insulation of contact electrodes with respect to a relevant adjacent plate.

19. The electric heating device according to claim 18, wherein the stack of plates is soldered and the at least one heating unit or the heating units is or are inserted into the relevant free space after the soldering.

20. The electric heating device according to claim 18, wherein the at least one adhesive is electrically insulating and thermally conductive.

21. The electric heating device according to claim 18, wherein the at least one adhesive is an adhesive substance, a silicone compound, a potting compound, a cross-linkable plastic molding compound, and/or a flowable substance.

22. The electric heating device according to claim 18, wherein the at least one adhesive contains agents and/or particles for improving the thermal conductivity of the adhesive.

23. The electric heating device according to claim 18, wherein the heating unit has a frame for arrangement of the heating elements of the heating unit relative to one another and/or for defined positioning of the heating elements of the heating unit in the free space and/or for distribution of the adhesive.

24. The electric heating device according to claim 23, wherein the frame surrounds or delimits the heating unit on at least three sides or on four sides.

25. The electric heating device according to claim 23, wherein the frame is a rigid frame or a collapsible frame.

26. The electric heating device according to claim 23, wherein at least one projecting edge, a beveled edge, at least one ridge, or at least one nub is provided on the frame for distribution of the adhesive.

27. The electric heating device according to claim 26, wherein a ridge, in particular central ridge, is provided that projects from the edge.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

[0055] FIG. 1 is a perspective view of an exemplary embodiment of an electric heating device according to the invention,

[0056] FIG. 2 is an exploded view of the electric heating device according to the invention,

[0057] FIG. 3 is a partial sectional view of the electric heating device according to the invention,

[0058] FIG. 4 is a side view of a heating unit of the electric heating device according to the invention,

[0059] FIG. 5 is a perspective view of the heating unit,

[0060] FIG. 6 is a partial sectional view of the electric heating device according to the invention,

[0061] FIG. 7 is a graph to explain the invention,

[0062] FIG. 8 is a graph to explain the invention, and

[0063] FIG. 9 is a graph to explain the invention.

DETAILED DESCRIPTION

[0064] FIGS. 1 through 6 show different views of an exemplary embodiment of an electric heating device 1 according to the invention or details thereof.

[0065] According to FIGS. 1 and 2, the electric heating device 1 according to the invention has at least two plate pairs 2 forming a fluid passage 4 through which fluid can flow, which plate pairs are assembled from two plates 3 and form between them the fluid passage 4.

[0066] The plate pairs 2 are arranged at a predefined distance from one another and form a free space 5 between them. The distance is achieved through formed features 6 on the plates 3, which are provided on the two narrow end regions of the plates 3, wherein the formed features 6 of two adjacent plates 3 of adjacent plate pairs 2 touch one another, and thus hold the plates 3 or the plate pairs 2 at a distance.

[0067] The plate pairs 2 form a stack 7 of plate pairs 2. These plate pairs 2 and the stack 7 are soldered.

[0068] After the soldering, at least one heating unit 8 is arranged in the free space 5 between at least two of the plate pairs 2, which heating unit has at least one heating element 9 or a multiplicity of heating elements 9 and contact electrodes 10 electrically connected thereto for making electrical contact with the at least one heating element 9. It is possible, in particular, for several such heating elements 9 to be provided, in particular in each of the free spaces 5.

[0069] The heating unit 8 is held in the free space 5 by means of an adhesive, wherein the adhesive simultaneously forms the electrical insulation 11 of the contact electrodes 10 with respect to the relevant adjacent plate 3.

[0070] To manufacture the electric heating device 1, the stack 7 of plates 3 is attached by soldering, and the at least one heating unit 8 or the heating units 8 is or are inserted into the relevant free space 5 after the soldering. FIGS. 3 and 4 show a side view and a cross-section through the stack 7.

[0071] The stack 7 of plate pairs 2 is provided with an inlet connection 16 and with an outlet connection 17, in particular prior to soldering. In this case, the fluid passages of the plate pairs 2 are advantageously in fluid connection with one another.

[0072] Advantageously, the inlet connection 16 and the outlet connection 17 can be arranged on the same plate pair 2 of the stack 7, such as in particular on an end plate pair of the stack 7, or the inlet connection 16 and the outlet connection 17 can be arranged on different plate pairs 2 of the stack 7, such as in particular on opposing end plate pairs of the stack 7.

[0073] The adhesive that is used to bond the relevant heating unit 8 preferably is designed to be electrically insulating and thermally conductive. The adhesive preferentially is a flowable substance, such as, in particular, a flowable silicone compound, which is fed into the free spaces 5 and subsequently inserted or pushed into the heating units 8, wherein the adhesive fed into the free space 5 is distributed therewith and fills in cavities and expels excess adhesive.

[0074] It is also advantageous when the adhesive contains agents and/or particles for improving the thermal conductivity of the adhesive. Such agents can be ceramic particles, graphite, etc., for example.

[0075] FIGS. 4 and 5 show that the heating unit 8 has a frame 12 for arrangement of the heating elements 9 of the heating unit 8 relative to one another and/or for defined positioning of the heating elements 9 of the heating unit 8 in the free space 5 and/or for distribution of the adhesive. In this design, the frame 12 surrounds or delimits the heating unit 8 on at least three sides or on four sides, see FIGS. 4 and 5.

[0076] In this case the frame 12 can be designed as a rigid frame, see FIGS. 4 and 5, or alternatively as a collapsible frame. In this case at least one projecting edge 13, in particular beveled edge, at least one ridge 14, at least one nub are provided on the frame 12, in particular for distribution of the adhesive.

[0077] In this case a ridge 15, in particular central ridge, can also be provided that projects from the edge.

[0078] To manufacture the electric heating device 1, a method for manufacturing an electric heating device 1 is used, wherein the electric heating device 1 with at least two plate pairs 2 forming a fluid passage 4 through which fluid can flow, which plate pairs are assembled from two plates 3 and form a fluid passage 4 between the two, wherein the plate pairs 2 take on a predefined distance from one another and form a free space 5, wherein at least one heating unit 8 is arranged in the free space 5 between at least two of the plate pairs 2, which heating unit has at least one heating element 9 and contact electrodes 10 electrically connected thereto for making electrical contact with the at least one heating element 9, having the steps: providing and stacking the plates 3 into a stack 7 of plates 3 and/or plate pairs 2, soldering the stack 7 of plates 3, partial sealing of one side at a time of at least one free space by means of sealing elements, filling of the partially sealed free space 5 with an adhesive, inserting the heating unit 8 into the free space 5 filled with the adhesive, and curing of the adhesive.

[0079] In this case, the sealing elements are removed, in particular after the curing of the adhesive.

[0080] In order to improve the bonding and to avoid air bubbles, the free space 5 is at least partially evacuated prior to the filling with the adhesive.

[0081] Subsequently, excess adhesive is expelled from the free space 5 during insertion of the heating unit 8 into the free space 5.

[0082] According to another exemplary embodiment, the insertion of the heating unit 8 into the relevant free space 5 can also take place prior to the feeding of the adhesive.

[0083] The method can include the following steps: providing and stacking the plates 3 into a stack 7 of plates 3 and/or plate pairs 2, soldering the stack 7 of plates 3, and inserting and attaching the heating unit 8 in the free space 5.

[0084] In this case, the attachment of the heating unit 8 in the free space 5 to the plate pairs 2 can be accomplished with at least one adhesive.

[0085] In this case, as described above, the at least one adhesive can be fed into the free space 5 before the insertion of the heating unit 8 or the at least one adhesive can be fed into the remaining free space 5 after the insertion of the heating unit 8.

[0086] In one exemplary embodiment, it is also possible that an insertion of the heating unit 8 takes place into the free space filled with the at least one adhesive, or the heating unit 8 is inserted into the free space 5 before the feeding of the at least one adhesive and subsequently the at least one adhesive is fed, in particular, into the free space 5 that has been partially sealed beforehand.

[0087] FIGS. 7 to 9 show different graphs regarding the layer thickness d in m of the insulating material, the dielectric strength D in kV/mm of the insulating material, and the thermal conductivity in W/mK of the insulating material, respectively. Here, the insulating material is the layer of the adhesive that is formed between the heating unit 8 and the opposite plate 3.

[0088] In this context, the layer thickness d should be in the range from approximately 0.2 mm to 0.8 mm, which is to say between 200 m and 800 m. The dielectric strength along the creepage path 50 should be between 15 kV/mm and 25 kV/mm in this context. The creepage path 50 is drawn in FIG. 6 by way of example here. The thermal conductivity is advantageously between 1.7 W/mK and 3.9 W/mK. FIG. 7 indicates the advantageous range for d between 200 m and 800 m and for D between 15 kV/mm and 25 kV/mm.

[0089] In this context, the value of D*d specifies the dielectric strength that is to be expected for a recommended layer thickness, in particular for d between 200 m and 800 m, see FIG. 8. Thus, in a high voltage application with a voltage of 400 V, for example, it can be sufficient for the layer thickness d to be 0.3 mm. The test voltage would be 2000 V, for example. However, manufacturing tolerances and process-related minimum layer thicknesses also play a role in the choice of layer thickness d here.

[0090] FIG. 9 shows a graph with the value d/ as a function of d. The thermal conductivity of the insulating material should advantageously be between 1.7 W/mK and 3.9 W/mK. Here, d/ specifies the thermal resistance through the insulation that is to be expected. The thermal conductivity and the thermal resistance are inversely proportional here.

[0091] The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.