Composite material for resistance heating and resistance heating system with at least one heating element based on this composite material

Abstract

The invention relates to a composite material (1) for resistance heating, which comprises a heating layer (2) which consists of a flat layer of electrically conductive carbon multifilaments or rovings having a basis weight of 50 to 850 g / m2, wherein an insulating layer (3) consisting of a flat layer of electrically non- conductive fibrous material having a basis weight of 200 to 600 g / m2 is arranged on both sides of the heating layer (2), wherein the heating layer (2) and the insulating layers (3) are embedded in a matrix (4) formed of resin, the amount of resin corresponding to 20 to 35 % by weight of the heating layer (2). In addition, the invention relates to a system (5) for resistance heating, which comprises at least one heating element (6) made of the composite material (1) according to the invention, which is connected to an electrical voltage source (7), wherein a temperature controller (8) is arranged between the heating element (6) and the electrical voltage source (7).

Description

[0001] Composite material for resistance heating and resistance heating system with at least one heating element based on this composite material

[0002] Technical field

[0003] The technical solution relates to a composite material for resistance heating.

[0004] The technical solution also relates to a system for resistance heating with at least one heating element based on this composite material, intended in particular for heating the electrical cells of a battery of a battery electric vehicle.

[0005] Background art

[0006] Resistance heating is a method of electrical heating in which an electric current passes through a heating resistor, wherein moving electric charge carriers (most often electrons) collide with particles (most often ions) in the material lattice of the heating resistor and transfer part of their kinetic energy to them, wherein this energy is subsequently converted into thermal energy and increases the temperature of the heating resistor (Joule heat). Heating resistors are currently used mainly in large industrial installations such as glass furnaces, etc. Their disadvantages are their relatively large size and the large mass of the heating resistors, due to which the heating resistors have a relatively large thermal inertia. This makes it difficult or even impossible to use resistance heating in applications with insufficient space to mount the resistors and / or in applications where the emphasis is put on the fastest possible response of the heating system to the current conditions and therefore on the lowest possible thermal inertia. A typical example is the heating of electric battery cells, e.g. of battery electric vehicles, before charging them at low temperatures, etc.

[0007] The object of the technical solution is to provide a composite material for resistance heating which would eliminate the disadvantages of the background art.

[0008] In addition, the object of the technical solution is a system for resistance heating with at least one heating element based on this composite material. of technical solution

[0009] The object of the technical solution is achieved by a composite material which contains a heating layer which is formed by a flat layer of electrically conductive carbon multifilaments or rovings having a fineness of 800 to 3000 tex and a basis weight of 50 to 850 g / m2, wherein an insulating layer formed by a layer of electrically non-conductive fibrous material with a basis weight of 200 to 600 g / m2is arranged on both sides of the heating layer, wherein the heating layer and the insulating layers are embedded in a matrix formed of resin, the amount of resin corresponding to 20 to 35 % by weight of the heating layer.

[0010] In a preferred variant of embodiment, the heating layer consists of a layer of unilaterally laid carbon multifilament or roving with a total fineness of 800 to 3000 tex, the basis weight of the heating layer being 50 to 150 g / m2.

[0011] In another preferred embodiment, the heating layer is formed of a carbon multifilament fabric or roving with a total fineness of 800 to 3000 tex, the basis weight of the layer being 120 to 850 g / m2. A suitable type of fabric is a fabric with a twill weave.

[0012] In a preferred variant of embodiment, the insulating layer is formed by a fabric made of glass multifilaments or rovings or a fabric made of aramid fibres with a total fineness of 300 to 2300 tex, the basis weight of this layer being 200 to 600 g / m2. A suitable type of fabric is a fabric with a twill weave.

[0013] The matrix is preferably formed of epoxy resin or melamine-formaldehyde resin.

[0014] In addition, the object of the technical solution is achieved by a system for resistance heating, which comprises at least one heating element formed of the composite material according to the technical solution, which is connected to an electrical voltage source, wherein between the heating element and the electrical voltage source, a temperature controller is arranged; e.g., a bimetallic temperature controller. Brief description of drawings

[0015] In the enclosed drawing, Fig. 1 shows a schematic cross-section of the composite material for resistance heating according to the technical solution and Fig. 2 shows a scheme of the heating system with one heating element based on this composite material.

[0016] Examples of embodiment of technical solution

[0017] The composite material 1. for resistance heating according to the technical solution contains a heating layer 2, which is formed by a planar layer made of electrically conductive carbon multifilaments or rovings, i.e., a linear structure composed of several hundred to thousands of endless carbon fibres with a diameter of typically 4 to 9 micrometres, which is not reinforced by twisting or the twisting is only minimal. On both sides of the heating layer 2, an insulating layer 3 is arranged, formed by a planar layer of electrically non-conductive material, preferably fibrous material. All three layers 2, 3 of the composite material 1. are embedded together in a matrix 4 which connects them and at the same time provides the composite material 1_ thus prepared with rigidity and advantageous mechanical properties and at the same time protects the individual layers 2, 3 from mechanical damage.

[0018] The heating layer_2 is, according to the intended use, formed by a layer of unilaterally laid carbon multifilament or roving or a fabric formed from such multifilament or roving in a suitable weave. For low power applications with output in the order of a few tens of watts, the heating layer 2 is formed by a layer of unilaterally laid carbon multifilament or roving with a total fineness of 800 to 3000 tex and a basis weight of 50 to 150 g / m2, preferably 90 to 120 g / m2For higher power outputs in the order of hundreds of watts, the heating layer 2 contains a fabric from these carbon multifilaments or rovings having a basis weight of 150 to 850 g / m2, preferably in the range of 200 to 700 g / m2. A suitable type of fabric is a fabric with a twill weave.

[0019] The heating layer 2 is provided at its two opposite ends with means for connection to an electrical voltage source, e.g., in the form of conductive interfaces 20. Preferably, the interfaces 20 are implemented by an electrically conductive epoxy paste containing silver, which is encapsulated on the carbon filaments by pressing with copper or aluminium foil. However, in other embodiments, these interfaces 20 may be formed in a different way.

[0020] The insulating layers 3 are formed of an electrically non-conductive material, preferably fibrous. These layers protect the heating layer 2 from mechanical damage and at the same time electrically insulate it from the environment. Suitable materials for the insulating layers 3 are high heat resistant fibres (preferably non-flammable) with suitable mechanical and electrical insulating properties, such fabric made of glass multifilaments or rovings with a total fineness of 300 to 2300 tex or fabric made of aramid fibres. The insulating layer 3 has a basis weight of 200 to 600 g / m2, preferably 250 to 400 g / m2A suitable fabric type for the insulating layer 3 is a fabric with a twill weave.

[0021] The two insulating layers 3 on opposite surfaces of the heating layer 2 may be identical or may differ in material and / or structure and / or basis weight.

[0022] The heating layer 2 and the insulating layers 3 are together embedded in a matrix 4 which provides rigidity to the resulting composite material and at the same time protects these layers 2, 3 from mechanical damage. A suitable matrix 4 is, for example, an epoxy-based resin matrix with a glass transition temperature (Tg) higher than 100 °C, for example, a dispersion epoxy resin with potassium thiocyanate (KSCN) as a catalyst or melamine-formaldehyde resins. In general, it is also possible to use other types of resins offered for bonding carbon and glass composites with heat resistance above 220 °C. In a preferred variant of preparation, the matrix 4 is introduced into the composite structure in a liquid state by impregnating a dry sandwich consisting of a heating layer 2 and electrical insulating layers 3. The matrix fills the free spaces of the individual layers 2, 3, wraps their fibres and connects these layers 2, 3 into a single whole. After solidification, it provides the resulting composite with rigidity and protection of its layers 2, 3 from mechanical damage. At the same time, however, this matrix does not prevent heat transfer from the heating layer to the surroundings. The amount of the matrix corresponds to 20 to 35 % by weight of the heating layer 2.

[0023] Applicable fabrics made from carbon multifilaments or rovings as well as fabrics made from glass multifilaments or rovings are currently commonly available on the market (see, for example, the company Havel composites CZ). If necessary, the composite material 1_ for resistance heating according to the technical solution may be provided with more than one heating layer 2, in which case each heating layer 2 is covered on its outer side by an insulating layer 3.

[0024] In any variant of embodiment, the composite material 1_ for resistance heating can be supplemented on at least one side with another suitable layer of material that provides it with an added function. Such a layer can be, for example, a layer of reflective material for reflection or concentration of heat produced by the heating layer / layers 2, etc.

[0025] Figure 2 shows a scheme of a system 5 for resistance heating, which comprises a heating element 6 formed of the present composite material 1_. This heating element 6 is connected via an interface 20 of the heating layer 2 to an electrical voltage source 7, wherein a suitable known controller 8, such as a bimetallic temperature controller, is arranged between the heating element 6 and the electrical voltage source 7 to connect or disconnect the circuit depending on the actual temperature. When an electric current passes through the material of the heating layer 7, this material is heated.

[0026] If necessary, multiple heating elements 6 may be included within a single system 5 for resistance heating.

[0027] Due to the small mass of the composite material 1. for resistance heating according to the technical solution, this composite material, or the heating element 6_made of it, has a low thermal inertia, so that it can be rapidly heated or cooled as required.

Claims

CLAIMS1 . The composite material (1 ) for resistance heating, characterized in that it comprises a heating layer (2) which is formed by a flat layer of electrically conductive carbon multifilaments or rovings having a basis weight of 50 to 850 g / m2, wherein an insulating layer (3) consisting of a flat layer of electrically non- conductive fibrous material having a basis weight of 200 to 600 g / m2is arranged on both sides of the heating layer (2), wherein the heating layer (2) and the insulating layers (3) are embedded in a matrix (4) formed of resin, the amount of resin corresponding to 20 to 35 % by weight of the heating layer (2).

2. The composite material (1 ) according to claim 1 , characterized in that the heating layer (2) is formed by a layer of unilaterally laid carbon multifilament or roving with a total fineness of 800 to 3000 tex, the basis weight of the heating layer (2) being 50 to 150 g / m2.

3. The composite material (1 ) according to claim 1 , characterized in that the heating layer (2) is formed of a fabric made from carbon multifilament or roving with a total fineness of 800 to 3000 tex, the basis weight of the heating layer (2) being 120 to 850 g / m2.

4. The composite material (1 ) according to claim 3, characterized in that the heating layer (2) is formed of a fabric with a twill weave.

5. The composite material (1 ) according to claim 1 , characterized in that the insulating layer (3) is formed by a fabric made of glass multifilaments or rovings with a total fineness of 300 to 2300 tex, wherein the basis weight of the insulating layer (3) is 200 to 600 g / m2.

6. The composite material (1 ) according to claim 1 , characterized in that the insulating layer (3) is formed of a fabric of aramid fibres with a total fineness of 300 to 2300 tex, wherein the basis weight of the insulating layer (3) is 200 to 600 g / m2.

7. The composite material (1 ) according to claim 5 or 6, characterized in that the insulating layer (3) is formed of a fabric with a twill weave.

8. The composite material (1 ) according to claim 1 , characterized in that the matrix is formed of epoxy resin or melamine-formaldehyde resin.

9. A system (5) for resistance heating, characterized in that the system (5) comprises at least one heating element (6) made of the composite material (1 ) according to any of claims 1 to 8, which is connected to an electrical voltage source (7), wherein a temperature controller (8) is arranged between the heating element (6) and the electrical voltage source (7).

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