EP3630513A1

EP3630513A1 - Electric heating device

Info

Publication number: EP3630513A1
Application number: EP18728816.2A
Authority: EP
Inventors: Martin Zoske; Volodymyr Ilchenko; Uwe Strecker; Bengt Meier; Nikolaus Gerhardt; Michael Schwanecke
Original assignee: Webasto SE
Current assignee: Webasto SE
Priority date: 2017-05-24
Filing date: 2018-05-23
Publication date: 2020-04-08
Also published as: JP2020520846A; JP2020521272A; DE102017121038A1; CN110662927A; DE102017121063A1; EP3631314A1; WO2018215551A1; DE102017121041A1; CN110678703A; WO2018215546A1; WO2018215537A1; WO2018215198A1; CN110678704A; DE102017121042A1; KR20190139983A; WO2018215541A1; CN110691949A; EP3631317A1; US20200224926A1; US20200113019A1

Abstract

The invention relates to an electric air heating device, in particular a liquid or air heating device, in particular for a motor vehicle, comprising a first heating element (9a) and at least one second heating element (9b), the heating elements (9a, 9b) respectively comprising one, in particular insulating substrate (18a - 18d) and a polymer layer (14a, 14b) which contains a polymer component and a conductive component, in particular a carbon component. An intermediate space (16a), through which the fluid can flow for heating, is formed between the heating elements (9a, 9b). The heating elements (9a, 9b) are interconnected by one or more in particular conductive spacers (10c) which are arranged therebetween and/or one or more respective recesses and/or openings of the heating element penetrating, in particular conductive positioning elements (11a, 11b).

Description

Electric heater

description

The invention relates to an electric heater, in particular for a

Motor vehicle, a method for producing an electric heater, a set for producing a heater, a method for operating a

Heater and a use of a heater.

Electric heaters (in particular those used in mobile applications) are often based on ceramic heating elements with a comparatively strongly temperature-dependent electrical resistance, by which a self-regulation of the heat release is made possible. These resistors are typically PTC elements (PTC for Positive Temperature Coefficient). These are usually made with heat exchanger surfaces

Aluminum sheet connected and are also contacted electrically. A PTC element comprises a PTC resistor, ie a temperature-dependent resistor with a positive temperature coefficient, which at low

Temperatures conduct electricity better than at high temperatures.

A disadvantage of conventional heaters with ceramic PTC elements u .a. their complex production due to a comparatively complicated heat exchanger manufacturing and the complex installation of the ceramic elements, a usually necessary sorting of the ceramic elements due to manufacturing tolerances, a comparatively unfavorable power density in a heating element heat exchanger composite by a local heat generation, a comparatively strong Limitation of a maximum heating power by a thickness of the PTC material (due to a limited heat dissipation from the ceramic) and a comparatively high risk of short circuit, in particular due to a small geometric distance of components with a high voltage potential.

It is an object of the invention to provide a heater, in particular liquid or air heater, which enables effective heating of the fluid. In particular, a high level of space is required for a comparatively small installation space Power density can be enabled. It is another object of the invention, a corresponding method for producing a heater, in particular liquid or air heater, a corresponding set for producing a heater, in particular liquid or air heater, a corresponding method for operating a heater, in particular liquid or air heater, and to suggest a suitable use of a heater.

This object is achieved in particular by an electric heater, in particular liquid or air heater, according to claim 1.

In particular, the object is achieved by an electric heater, in particular a liquid or air heater, preferably for a vehicle

preferably for a motor vehicle, comprising a first heating element and at least one second heating element, the heating elements each having a, in particular insulating, substrate and a polymer layer, wherein the polymer layer contains a polymer component and a conductive component, in particular carbon component, wherein between the heating elements an intermediate space is formed, through which fluid can be flowed for heating thereof, wherein the heating elements by interposed, in particular conductive, spacers and / or the (individual) heating elements penetrating (or (a) respective recess (s) and / or opening (s) of the respective heating elements penetrating), in particular conductive, positioning elements (guide elements) are interconnected.

A central idea of the invention is to provide at least two heating elements which have at least one (conductive) polymer layer and can be connected to each other in a modular manner, in particular via corresponding ones

(Conductive) spacers and / or (conductive) positioning elements (in particular positioning or guide pin). By means of such a modular design, the individual heating elements can be designed in particular as (pure) parallel connection and can be modularly adapted in terms of performance (in particular with regard to their performance). Furthermore, a simple contacting or power supply of the individual heating elements is possible. Overall, a high power density in an existing space by the use of heating elements (especially when thin Heat transfer fins are used) and provided a comparatively large effective heat transfer area.

In particular, when the heating elements have a PTC behavior, no additional safety elements for temperature monitoring are necessary.

Preferably, the (electrically conductive) polymer layer is printed on the (respective) substrate. Furthermore, electrodes for contacting or supplying power to the polymer layer may also be printed (on the substrate and / or the polymer layer).

The (respective) spacer can be designed as a (eg strip-shaped or rod-shaped) pad (contact pad) and possibly both the power supply

ensure as well as ensure a distance between the heating elements. In this respect, the spacer may have a dual function, which allows a total of a simple construction of the electric heater. Possibly. Spacers of different sizes (in particular thickness) can be provided, so that a distance between the heating elements can be variably selected, in particular to prevent an electrical short circuit (breakdown) and / or to set a pressure loss (of the fluid flowing through).

The (respective) positioning element (guide element) can be, in particular, a positioning bolt (guide pin) which is round, oval or rectangular, in particular rectangular, preferably square

Manufacturing tolerance compensation (in the sense of a guide or positioning of the individual heating elements) ensures, as well as possibly necessary contact (power supply) allows. Here, too, different functions are realized again via an element.

By at least one or more or all heating elements can preferably at least two or exactly two positioning (guide pins) run. Thereby, the position of the heating elements can be set in a simple manner. To protect against mechanical damage, moisture and / or

Short circuits may include painting or sealing the polymer layer (or parts thereof).

Preferably, the heating elements (one above the other) are stackable. Furthermore, the heating elements can be designed as a (total) resistor connected in parallel (which in particular allows stacking).

Preferably, first and / or second heating elements extend (at least substantially) along a fluid flow direction. This can be done in an effective manner, a heating of the fluid. Alternatively or additionally, the heating elements may be at an angle to the

Air flow direction extend, z. B at an angle less than or equal to 90 ° and greater than 0 °, in particular greater than 10 °.

In embodiments, at least three, preferably at least five heating elements (with corresponding gaps) may be provided.

Preferably, a diameter of the gap between the first and second heating elements is greater than a thickness of the first and / or second heating elements.

The conductive component, in particular carbon component can in

Particle form and / or as a (carbon) framework.

The conductive component may include metal particles and / or fibers.

Furthermore, the carbon component may be present in the form of carbon black and / or graphite and / or graphene and / or carbon fibers and / or carbon nanotubes and / or fullerenes.

Furthermore, the polymer component can be in the form of an electrically insulating polymer component and / or a first polymer subcomponent based on ethylene acetate or ethylene acetate copolymer and / or ethylene acrylate or ethylene acrylate copolymer and / or a second polymer subcomponent based on polyolefin, in particular polyethylene and / or polypropylene, and / or polyester and / or polyamide and / or

Include fluoropolymer. The polymer component can also be formed completely from the first or second polymer component (or only partially).

In a specific embodiment, the polymer layer forms a PTC resistor.

The heating elements are preferably electrically connected in parallel.

The spacers may, in particular integral, be part of the heating elements.

The above-mentioned object further comprises a method for producing an electric heater, in particular a liquid or air heater, in particular of the above type, comprising a first heating element and at least one second heating element, the heating elements each having a, in particular insulating, substrate and a polymer layer, the

Polymer layer containing a polymer component and a conductive (filling) component, in particular carbon component, wherein between the heating elements, a gap is formed through which fluid can be flowed to the heating, wherein the heating elements are stacked. In the context of stacking or as an independent alternative, between the

Heating elements, in particular conductive, spacers the heating elements spaced from each other. Alternatively or additionally, (in particular conductive) positioning or guide elements can pass through the heating elements (be guided).

Preferably, spacers of different sizes are provided and of these spacers at least one spacer of a particular one

(desired) size, which is then arranged between the heating elements accordingly. Alternatively or additionally

Guide elements of different sizes are provided and from these guide elements at least one guide element of a particular

(desired or suitable) size can be selected and passed through the heating elements accordingly. Then can different requirement Be taken into account, for example, a distance between the

Heating elements are chosen variably, in particular to prevent an electrical short circuit (strike through) and / or to set a pressure drop (of the fluid flowing through) targeted.

The positioning elements (guide elements or guide pins) preferably run in the sense of the heating elements that the heating elements corresponding openings (holes), which corresponds to the corresponding

Enclose positioning element. In this case, the openings (holes) can have a cross-section corresponding to the outer circumference of the positioning elements (for example angular, in particular quadrangular, preferably rectangular, more preferably square and / or oval, in particular elliptical, preferably (circular) round).

Preferably, the polymer layer and / or at least one electrical connection element is / are printed.

The above object is further achieved by a set for producing a heater, in particular liquid or air heater, in particular of the above type, comprising a plurality of heating elements, wherein the

Heating elements each one, in particular insulating, substrate, and a

Polymer layer, wherein the polymer layer contains a polymer component and a conductive component, in particular carbon component, wherein between the heating elements, a gap can be formed through the fluid is flowable to the heating, wherein the heating elements are modularly interconnected, such that at a first number of interconnected heating elements a second number (greater than or equal to 1)

added or removed from there. Preferably, this is done by means of arranged between the heating elements (arranged), in particular conductive, spacers, and / or by means of the (individual) heating elements penetrating, in particular conductive, positioning.

Preferably, the set comprises spacers and / or positioning elements of different sizes, in particular spacers of different thicknesses and / or positioning elements of different lengths. The above object is further achieved by a method for operating a heater, in particular liquid or air heater, the above type or prepared by the method of the above type or prepared with the above set, wherein fluid, in particular a liquid, for. As water (especially cooling water), or air flows through the at least one intermediate space and is heated.

The above object is further achieved by the use of a heater of the above type or prepared according to a method of the above type or prepared with the above set for heating fluid, in particular a liquid such. As water (especially cooling water) or air, especially in a vehicle, preferably in a motor vehicle, more preferably for a motor vehicle interior.

In embodiments, the polymer component may be a first polymer subcomponent based on ethylene acetate (copolymer) and / or

Ethylene acrylate (copolymer) and / or comprise a second polymer component based on polyolefin, in particular polyethylene and / or polypropylene, and / or polyester and / or polyamide and / or fluoropolymer. The term "subcomponent" is intended here in particular for

Distinction between first and second polymer subcomponent can be used. The respective subcomponent can form either partially or completely the polymer component. The ethylene acrylate may be ethyl methyl acrylate or ethylene ethyl acrylate. In which

Ethylene acetate may be ethylene vinyl acetate. The polyethylene may be high density polyethylene, medium density polyethylene, low density polyethylene. The fluoropolymer may be PFA (copolymer of tetrafluoroethylene and perfluoropropyl vinyl ester) MFA (copolymer of tetrafluoroethylene and perfluorovinyl ester), FEP (copolymer of tetrafluoroethylene and hexafluoropropylene), ETFE (copolymer of ethylene and tetrafluoroethylene) or PVDF (polyvinylidene fluoride) act.

In embodiments, the first polymer subcomponent, as in FIG

WO 2014/188190 AI (described as a first-electrically insulating material) may be formed. The second polymer subcomponent can also, as in WO 2014/188190 AI (as a second-term insulating material) describe, be formed.

The substrate preferably serves as a heat exchanger.

Overall, a large (actively) heated by the polymer layer

Surface can be realized, whereby a necessary surface temperature can be lowered with constant overall heating capacity and constant overall space. At (maximum) surface temperatures of, for example, below 200 ° C still comparatively high total heat outputs are still possible.

The polymer layer can be applied (printed) to the substrate by a coating and / or printing process. Optionally, a curing step may be carried out at elevated temperature (eg, above 120 ° C) in an oven. For application, for example, a screen printing or doctoring can be used.

In general, the polymer layer or one for producing the

Polymer layer used as described in DE 689 23 455 T2, be formed. This applies in particular also to their production and / or specific composition. For example, this also applies to possible

Binders (especially according to p. 4, 2nd paragraph and p. 5, 1st paragraph of

DE 689 23 455 T2) and / or solvent (in particular according to page 5, 2nd paragraph and page 6 2nd paragraph of DE 689 23 455 T2).

The substrate or the substrates can / at least partially, preferably be made entirely of plastic, in particular a polymer such as, for example, polyether ketone and / or polyamide. Particularly preferred is a production of polyethylene (PE) and / or polypropylene (PP) and / or polyetheretherketone (PEEK) and / or (short) fiber-reinforced polyamide (eg PA-GF).

The substrate may be made of an electrically insulating material.

An electrically insulating material is to be understood in particular as meaning a material which, at room temperature (25 ° C.), has an electrical conductivity of less than 10 ^"1 S ¹ nr ¹ (possibly less than 10 ^{" 8} S ¹ nr ¹ ). Accordingly, an electrical conductor or a material (or coating) with electrical conductivity is to be understood as meaning a material which has an electrical conductivity

Conductivity of preferably at least 10 S ¹ nr ¹ , more preferably at least 10 ³ S ¹ nr ¹ (at room temperature, in particular 25 ° C).

The substrate may be made of a material that is at a temperature of below

500 ° C, preferably foams below 200 ° C and / or melts, be made.

The polymer layer or the polymer layers can be or are contacted by at least one metal structure, preferably a (in particular bent) metal sheet, preferably copper sheet, and / or metal strip and / or metal wire and / or metal grid (electrical).

Alternatively or additionally, the metal structure (or corresponding

Electrodes), z. B. on the substrate and / or the polymer layer, printed and / or applied by vapor deposition and / or imprinting and / or by coating.

The (optionally carbon-containing) polymer layer or the (optionally carbon-containing) polymer layers and / or a corresponding paste for the production thereof may comprise (in particular crystalline binder) at least one polymer, preferably based on at least one olefin; and / or at least one copolymer of at least one olefin and at least one monomer which can be copolymerized therewith, e.g. Ethylene / acrylic acid and / or ethylene / ethyl acrylate and / or ethylene / vinyl acetate; and / or at least one polyalkenamer (polyacetylene or polyalkenylene), such as. For example, polyoctenamer; and / or at least one, in particular melt-deformable, fluoropolymer, such as. As polyvinylidene fluoride and / or copolymers thereof.

The polymer layer or the polymer layers are preferably on the

(respective) substrate printed (eg by screen printing) or scrape.

In general, the polymer layer (s) may have a continuous surface (without interruptions) or be patterned, for example, have gaps (apertures) or recesses. A plan view of the respective heating element (preferably several or all heating elements) may be polygonal, in particular quadrangular, preferably rectangular or oval, in particular elliptical, preferably (circular) circular.

At least one intermediate space (possibly several or all intermediate spaces) can be limited by (exactly) two or more heating elements.

A cross section of the intermediate space (generally fluid channel) may be polygonal, in particular quadrangular, preferably rectangular or oval, in particular elliptical, preferably (circular) circular.

A cross section within a space (fluid channel) may vary or be constant (over its length). Also cross sections of different

Gaps or fluid passages (ie, gaps or fluid passages that are not formed by the same pair or group of heating elements) may differ or be the same. For example, cross-sections of the intermediate spaces or fluid channels may be slit-shaped (in particular as rectangular slits).

The respective polymer layer (at least one of the heating elements, preferably several or all of the heating elements) may be (at least on average) thinner than the corresponding substrate, for example by a factor of 1.1; more preferably by a factor of 1.5.

In principle, the term "conductive" with regard to the conductive components of the heater is to be understood as an abbreviation for "electrically conductive".

The (respective) polymer layer is preferably a conductive layer with PTC behavior.

The heater is preferably for low-voltage operation (eg.

<100 volts or <60 volts).

The heater may be designed for operation with DC and / or AC voltage and / or PWM. The substrate or the substrates may be formed as a plate, in particular a plastic plate, and / or have a thickness of at least 0.1 mm, preferably at least 0.5 mm, more preferably at least 1.0 mm and / or at most 5.0 mm, more preferably at most 3.0 mm. In particular, the respective thickness is an average thickness or a thickness of the largest area of constant thickness.

A (layer) thickness of the respective polymer layer may be <1 mm, preferably <0.5 mm, more preferably <0.2 mm.

The first and / or second polymer layer and / or the substrate (or the

Substrates) may be formed at least substantially planar. If

Elevations (recesses) are provided, they may be less than 10% of an (average) thickness of the respective coating or of the respective substrate.

A sum of the cross sections of fluid channels (in particular gaps between the heating elements) may be at least 2 times, preferably at least 4 times, as large as a sum of the cross sections of the heating elements

(viewed in particular transversely to the fluid flow direction or transversely to the

Width direction).

The proportion of the conductive component or the carbon content in the

Polymer layer of at least one heating element (preferably several or all heating elements) may be formed so that it allows a flow of current (eg., In particle form, wherein the particles are correspondingly touching or close to each other).

A diameter of the gap between the first and second heating elements may be greater than a thickness of the first and / or second

Heating element.

The (respective) polymer layer is preferably over at least 20%, more preferably at least 50%, even more preferably at least 80% of a surface of the substrate facing the polymer layer with the (respective) Substrate in contact. This can effectively heat over the substrate (which then serves as another heat exchanger) are transferred.

The above object is further achieved by a vehicle,

in particular motor vehicle comprising the above (electric) heater.

Further embodiments emerge from the subclaims.

The invention will be described with reference to embodiments, which are explained in more detail with reference to the accompanying figures. Hereby show:

Fig. 1 is a schematic oblique view of an electric air heater according to the invention;

FIG. 2 is a schematic oblique view of an electric air heater according to another embodiment of the invention; FIG. and

Fig. 3 is a schematic oblique view of an electric air heater according to another embodiment of the invention.

In the following description, the same reference numerals are used for identical and equivalent parts.

Fig. 1 shows a schematic oblique view of an inventive

Air heater. The electric air heater has a plurality of (in this case four, but not necessarily) heating elements 9a to 9d. Between

Heating elements corresponding spaces 16a to 16c are formed.

Through these spaces air can flow to their heating. The individual heating elements 9a to 9d are further spaced apart by spacers 10a, 10b, 10c arranged within the intermediate spaces 16a to 16c. In Fig. 1 for each gap 16a, 16b, 16c exactly one spacer 10a, 10b, 10c shown. However, it is conceivable, for example, two or more

Provide spacers. For example, can also be at a

opposite edge of the respective intermediate space 16a to 16c (in Fig. 1 at the left edge) may be provided a corresponding spacer. The Spacers are preferably made of a conductive material (especially metal).

Furthermore, positioning elements I Ia, I Ib are shown. The positioning in particular form guide pins and penetrate (in the present

Embodiment all) heating elements 9a to 9d or openings 12a to 12d and 13a to 13d thereof. In the present embodiment (which is not mandatory) exactly two positioning elements I Ia, I Ib are provided.

In the embodiment, both (not shown in detail) a (conductive) polymer layer 14a to 14d as well as corresponding for contacting

provided electrodes 15a to 15d (in the present case only one, possibly

both) surface (s) of a respective substrate 18a to 18d printed. In addition to the printed electrodes, contacting preferably takes place via the (conductive) positioning elements I Ia, I Ib (preferably made of metal) and the (conductive) spacers (contact pads) 16a to 16c (preferably made of metal).

The positioning elements preferably have a strip-like or rod-shaped form. A cross section may be rectangular, in particular square.

The positioning elements I Ia, I Ib are preferably (round) rod-shaped and may have a round (circular) cross-section.

The electric air heater is contacted via the contacts 17a, 17b.

Fig. 2 shows a schematic oblique view of an electric air heater according to another embodiment of the invention. At this

Forming embodiment (upturned or bent)

Spacers 10a to 10d have an integral (monolithic) structure with the heating elements 9a to 9d.

Fig. 3 shows a schematic oblique view of an electric air heater according to another embodiment of the invention. At this

Embodiment run the heating elements 9a to 9d at an angle greater than 0 °, for example, between 2 ° and 45 °, (or employed) against a

Main flow direction of the inflowing fluid according to arrow 19. It should be noted at this point that all parts described above, taken alone and in any combination, especially in the

Drawings shown details are claimed as essential to the invention. Variations thereof are familiar to the person skilled in the art.

LIST OF REFERENCE NUMBERS

9a to 9d heating element

10a to 10d spacers

I Ia, I Ib positioning element

12a to 12d opening

13a to 13d opening

14a to 14d polymer layer

15a to 15d electrical connection structure

16a to 16c gap

17a, 17b contacts

18a to 18d substrate

19 arrow

Claims

claims

Electric heater, in particular liquid or air heater, in particular for a motor vehicle, comprising a first heating element (9a) and at least one second heating element (9b), wherein the

Heating elements (9a, 9b) each one, in particular insulating, substrate (18a to 18d) and a polymer layer (14a, 14b), the one

Polymer component and a conductive component, in particular carbon component, include,

wherein between the heating elements (9a, 9b) an intermediate space (16a) is formed through which fluid is flowable for heating, wherein the heating elements (9a, 9b) arranged by one or more, in particular conductive, spacers (10c) and between them / or one or more (one) respective recess (s) and / or openings of the heating elements penetrating, in particular conductive,

Positioning element (s) (IIa, IIb) are interconnected.

Heater according to claim 1,

d a d u rc h e ke n ze i ch n et that,

first (9a) and / or second (9b) heating element at least in

Extend substantially along a fluid flow direction and / or extend at an angle to the air flow direction, for.

B at an angle less than or equal to 90 ° and greater than 0 °, in particular greater than 10 °.

Heater according to claim 1 or 2,

d a d u rc h e ke n ze ze ch n et that

the respective polymer layer (14a, 14b) is printed, in particular on the substrate, and / or

electrical connection structures (15a, 15b) on the substrate (18a, 18b) and the polymer layer (14a, 14b) are printed.

Heater according to one of the preceding claims,

d a d u rc h e ke n ze ze ch n et that

at least three (9a-9c) heating elements with appropriate

Gaps (16a, 16b) are provided.

5. Heater according to one of the preceding claims, d a d u r c h e c e n e c e s in that e

the component, in particular carbon component, is present in particle form and / or as a framework, in particular a carbon skeleton, and / or the carbon component is present in the form of carbon black and / or graphite and / or graphene and / or carbon fibers and / or carbon nanotubes

and or

the polymer component in the form of an electrically insulating

Polymer component is formed and / or a first polymer subcomponent based on ethylene acetate or ethylene acetate copolymer and / or ethylene acrylate or ethylene acrylate copolymer and / or

a second polymer component based on polyolefin,

in particular polyethylene and / or polypropylene, and / or polyester and / or polyamide and / or fluoropolymer.

6. Heating device according to one of the preceding claims,

d a d u r c h e c e n c i n e s that

the heating elements (9a, 9b) are electrically connected in parallel.

7. Heating device according to one of the preceding claims,

d a d u r c h e c e n c i n e s that

the spacers, in particular integral, are part of the heating elements.

8. A process for producing an electric heater, preferably liquid or air heater, in particular according to one of

Claims 1 to 7, comprising a first heating element (9a) and at least a second heating element (9b), wherein the heating elements (9a, 9b) each have a, in particular insulating, substrate and a

Polymer layer (14a, 14b) comprising a polymer component and a conductive component, in particular carbon component,

wherein between the heating elements (9a, 9b), a gap (16a) is formed through which fluid can be flowed for heating, wherein the heating elements are stacked on one another and / or by between they are arranged, in particular conductive, spacers are spaced apart from each other and / or wherein, in particular conductive,

Positioning be performed by the heating elements.

9. The method according to claim 8,

d a d u rc h e ke n ze ze ch n et that

Spacers (10a-10c) of different sizes are provided and from these spacers at least one spacer of a certain size is / are selected and / or

Positioning elements of different sizes are provided and at least one positioning element of a certain size is selected from these positioning elements.

10. The method according to claim 8 or 9,

d a d u rc h e ke n ze ze ch n et that

the polymer layer (14a, 14b) and / or at least one electrical connection element (15a, 15b) is / are printed.

11. Set for producing a heater, preferably liquid or air heater, in particular according to one of claims 1 to 7, comprising a plurality of heating elements (9a), wherein the heating elements (9a, 9b) each one, in particular insulating, substrate and a

wherein between the heating elements (9a, 9b) an intermediate space (16a) can be formed through which fluid can be flowed for heating, wherein the heating elements are modularly connected to each other, such that at a first number of interconnected heating elements added a second number or from can be removed there, preferably by means disposed between the heating elements, in particular conductive, spacers and / or by means of the heating elements

penetrating, in particular conductive, positioning.

12. Set according to claim 11,

d a d u rc h e ke n ze ze ch n et that

the set comprises spacers (10a-10c) and / or positioning elements (IIa, IIb) of different sizes, in particular length and / or thickness.

13. A method for operating a heater according to any one of claims 1 to 7 or prepared according to any one of claims 8 to 10 or prepared with the kit according to any one of claims 11 or 12, wherein fluid, in particular air or a liquid, for. As water flows through the at least one intermediate space (16 a, 16 n) and is heated.

14. Use of a heater according to any one of claims 1 to 7 or prepared according to any one of claims 8 to 10 or prepared with the kit according to any one of claims 10 or 11 for heating fluid, in particular air or a liquid, for. As water, especially in a motor vehicle, preferably for a motor vehicle interior.