RU2304367C1 - Electric heating device - Google Patents

Abstract

FIELD: current-conducting composite heating devices based on carbon fibers, which have various function designations.

SUBSTANCE: the electric heating device has two layers of the electric insulating base with a current conducting resistive layer based on carbon fibers and current leads electrically coupled to it and located on two sides at the edges of the current-conducting resistive layer. The current leads are made in the form of a flexible current-conducting chain of soft wire. The current-conductive resistive layer is made in the form of zigzag sections of the resistive chain of carbon fibers, 0.45±0.05 mm thick, 7-8 m long. The ends of each section of the resistive chain are metallized and wound on the current leads. All the sections of the resistive chain are made of continuous unidirectional carbon fibers consisting of elementary fibers, each finished with an impregnation compound at a definite content of the components.

EFFECT: enhanced heating power end reduced consumption of electric power per unit of the heated area.

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Description

The present invention relates to electrically conductive composite heating devices based on carbon fibers, which have different functional purposes (heated clothes; household heating devices; heating pads, electric blankets, electric blankets, in technology - to prevent icing of ships, for heating batteries, in aircraft, space technology , in construction, agriculture and medicine.

Known electric heating device, which consists of an electric heating element and a busbar. The electric heating element is made of non-metallic material with a volume electric resistance from 1 × 10 ⁵ to 1 × 10 ⁸ Ohm × cm, while the current-carrying busbars are mated with opposite surfaces of the electric heating element. Such an electric heating device is used to heat the floor of residential and non-residential premises.

The electric heating element of this electric heating device can be made of high pressure polyethylene and is a cylindrical pipe. Current-carrying tires are made in the form of layers of electrically conductive material deposited, respectively, on the inner and outer surfaces of the cylindrical tube. Current-carrying tires can be made with slots (Patent RU 2224386).

Known electric heating device containing an electrically conductive circuit connected to a current source, with a current carrier of a flexible electrically conductive material with a layer of a binder applied to it. The electrically conductive circuit is equipped with an electrically insulating substrate made of layers of polymer material, between which a zigzag-shaped polymetallic tape 15-50 microns thick is located as a flexible electrically conductive carrier. A polymetallic tape is attached at the top and bottom to the polymer material with a binder, which is used as a polymer film material with an adhesive layer.

In such an electric heating device between the layers of the polymeric material and the polymetallic tape, a laminated bonding layer obtained by cold or hot pressing can be used (Patent RU 35582).

The above-described electric heating devices do not imply the use of carbon fibers as an electric heating element. Such electric heating devices have a fairly narrow range of applications, i.e. their use is limited. Also, these devices are characterized by low power. And their main disadvantage is low strength characteristics.

Known electric heating device, taken by us as a prototype, consisting of two layers of an insulating base, placed between them an electrically conductive layer and electrically connected current leads, located on both sides along the edges of the electrically conductive layer. Each current lead is formed by a pair of metal strips superimposed on each other, the electrically conductive layer is made of carbon bundles or threads, the ends of which are placed between a pair of metal strips on each side, connected by spot welding, and the layers of the insulating base are connected to the resistive layer using glue.

In this electric heating device, carbon tows or threads can be sutured with liquid glass, a fluoroelastomer, or a non-combustible elastic adhesive. The layers of the electrical insulating base can be made of non-combustible asbot fiberglass fabric, fabric with basalt fibers or fabric impregnated with a non-combustible elastomer. To connect the layers of the electric heating device with each other, non-burning elastomers or liquid glass are used as glue. Two layers of fabric with asbestos, glass or basalt fibers are additionally glued to the current leads.

The electric heating device has an external decorative insulating coating made of rubberized fabric or cullet with heat resistance of 250-300 ° C (Application RU 2001128126/09).

The use of carbon tows and threads as an electrically conductive material reduces the working surface of the heating, which leads to high energy consumption per unit of the heated area. Such an electric heating device has a low power and a flexible shape, which limits its use. It should be noted that no methods are indicated for reducing the transition resistance at the contact points of carbon tows, threads and metal strips.

When creating the invention, the objectives were to expand the range of application of the electric heating device; increase the working surface of the heating; reduce energy consumption per unit of heated area; increase the power of the electric heating device we received; reduce transient resistance in the contact zone of carbon fiber and a flexible current-supply circuit.

To solve the tasks, the electric heating device contains two layers of an insulating base, between which there is a conductive resistive layer based on carbon fibers and electrically connected current leads, located on both sides along the edges of the conductive resistive layer. The current leads are made in the form of a flexible current-carrying circuit made of soft wire. The conductive resistive layer is made in the form of zigzag sections of the resistive circuit of carbon fibers with a thickness of 0.45 ± 0.05 mm, a length of 7-8 m. The ends of each section of the resistive circuit are metallized with copper and wound on current leads. Moreover, all sections of the resistive circuit are made of continuous unidirectional carbon fibers, consisting of elementary fibers, each of which is dressed with an impregnating mixture with the following components, wt.%:

- 25% heat-resistant silicone sealant and 75% glue based on methyl methacrylate; or

- 50% heat-resistant silicone sealant and 50% glue based on methyl methacrylate; or

- 75% heat-resistant silicone sealant and 25% glue based on methyl methacrylate; or

- 45% heat-resistant silicone sealant, 45% glue based on methyl methacrylate and 10% graphite powder.

The content of the impregnation mixture on carbon fiber is 45 ± 5%.

In this work, silicone sealant manufactured according to TU 2384-031-05666764-96, glue based on methyl methacrylate according to TD ITB nr AT-15-629 / 2002 were used.

The composition of the impregnating mixture depends on the properties of the resulting electric heating device. This mixture allows to increase the operational and deformation-strength characteristics of the electric heating device and allows you to expand the scope of its application.

To increase the working surface of the heating, carbon fibers are impregnated with elementary fibers, which reduces the energy consumption per unit of the heated area. Such impregnation is achieved due to the proposed concentration of the impregnating mixture and the extraction of unidirectional carbon fibers, consisting of elementary fibers, impregnated with this mixture, with the same effort.

Graphite powder can increase the flexural stability and power of an electric heating device.

The power of the electric heating device is controlled by the composition of the impregnating mixture and the number of sections of the resistive circuit based on carbon fibers, i.e. the number of sections of the resistive circuit is directly proportional to the power of the electric heating device.

An electric heating device can have both a rigid structure and a flexible shape, depending on the material of the electrical insulating base, which can be made of glass, basalt fabric, PET, PE films and ceramic, metal and glassy materials, thereby expanding the range of applications.

The proposed electric heating device is illustrated in figures 1-3.

Figure 1 presents a diagram of an electric heating device.

Fig. 2a shows the structure of a finished carbon tow or thread.

On figb - the structure of the fiber, consisting of sizing elementary fibers.

Figure 3 shows the dependence of the tensile strength of the electrically conductive resistive layer based on carbon fibers on the number of double bend cycles with a tensile force of 0.5% of the breaking stress.

The electric heating device (Fig. 1) contains two layers of an electrical insulating base 1, between which an electrically conductive resistive layer based on carbon fibers and electrically connected current leads, made in the form of a flexible current supply circuit 2. An electrically conductive resistive layer consists of sections of the resistive circuit 3. Input current leads 4. The ends of sections 5 of the resistive circuit 3 are metallized with copper and wound on a flexible current-supply circuit 2.

The structure of the finished carbon tow or thread (figa) proposed in the prototype. The sizing layer 1 is located on the surface of the carbon tow or thread 2. The surface area of the heating of such an electric heating device is S ₁ , where S ₁ is the area of the fitted tow. The structure of the carbon fiber (figb) consists of n elementary fibers 2, finished with a layer of impregnating mixture 1 (figure 2b). The surface area of the heating is S ₂ .

,

,

where S ₂ i is the area of the finished elementary fiber.

The dependence of the tensile strength (P _r N) of the electrically conductive resistive layer based on carbon fibers (Fig. 3) on the number of double kink cycles N with a tensile force of 0.5% of the breaking stress, with the content of: 1 - non-impregnated carbon fibers; 2 - carbon fibers impregnated with silicone sealant; 3, 4, 5 - carbon fibers impregnated with an impregnating mixture silicone sealant: adhesive based on methyl methacrylate in the ratio, wt.%: 25:75; 4-50: 50; 5-75: 25 respectively.

In the electric heating device (Fig. 1), a supply voltage is supplied to the input current leads 4, which is distributed through the flexible current supply circuits 2 to the sections of the resistive circuit 3. The resulting electric current leads to heating of the resistive sections 3. The ends of the sections 5 of the resistive circuit 3 are metallized with copper to reduce transition resistance in the contact zone of the carbon fiber and the flexible current-supply circuit 2.

The structure of the finished carbon tow or thread (figa) proposed by the prototype. The sizing layer 1 is located on the surface of the carbon tow or thread 2. The heating surface area of such an electric heating device is S ₁ . The structure of the carbon fiber (figb) consists of n elementary fibers 2, finished with a layer of impregnating mixture 1 (figure 2b). The surface area of the heating is S ₂ .

,

,

where S ₂ i is the area of the finished elementary fiber.

The use of a carbon fiber structure in the electric heating device, consisting of finished elementary fibers (Fig.2b), will increase the working surface of the heating, as S ₁ <S ₂ , which reduces the energy consumption per unit of the heated area.

Figure 3 presents the dependence of the tensile strength (P _r N) of the electrically conductive resistive layer based on carbon fibers on the number of double kink cycles N with a tensile force of 0.5% of the breaking stress, with the content: 1 - non-impregnated carbon fibers; 2 - carbon fibers impregnated with silicone sealant; 3, 4, 5 - carbon fibers impregnated with an impregnating mixture silicone sealant: adhesive based on methyl methacrylate in the ratio, wt.%: 25:75; 4-50: 50; 5-75: 25 respectively.

It can be observed that the tensile strength of non-impregnated carbon fiber decreases by 2 times (curve 1), and the strength of carbon fibers impregnated with heat-resistant silicone sealant decreases by 1.5 times (curve 2). The strength of carbon fibers with an impregnating mixture of various contents (curves 3, 4, 5, respectively) practically does not change after 2-5 thousand cycles of double bends. The advantages of the proposed device:

- increased working surface of the heating due to the use of the carbon fiber structure, consisting of elementary fibers, finished with a layer of impregnating mixture;

- reduced energy consumption per unit area of heating;

- increased deformation-strength and operational characteristics of the electric heating device through the use of an impregnating mixture of heat-resistant silicone sealant and glue based on methyl methacrylate;

- reduced resistance in the contact zone of the carbon fiber and the flexible current-supply circuit due to the metallization of the ends of the resistive circuit;

- the range of applications of the electric heating device is expanding, both in terms of power and depending on the material of the insulating base, which can be made of glass, basalt fabric, PET, PE films and ceramic, metal and glassy materials.

Information sources

1. Pat. RF №2224386, MKI 7 Н05В 3/10.

2. Pat. RF №355582, MKI 7 Н05В 3/36.

3. RF application No. 2001128126/09, MKI 7 Н05В 3/34.

Claims (1)

An electric heating device containing two layers of an electrical insulating base, between which is placed an electrically conductive resistive layer based on carbon fibers and electrically connected current leads, located on both sides along the edges of the electrically conductive resistive layer, characterized in that the current leads are made in the form of a flexible current-conducting circuit of soft wire , the conductive resistive layer is made in the form of zigzag sections of the resistive circuit of carbon fibers with a thickness of 0.45 ± 0.05 mm and a length of 7-8 , The ends of each section are plated with copper and the resistive circuit current leads are wound on, wherein all the sections of the resistive circuits are made of continuous and unidirectional carbon fibers consisting of filaments, each of which is a coated impregnating mixture with the following contents, wt.%: 25% heat-resistant silicone sealant and 75% methyl methacrylate adhesive; or 50% heat-resistant silicone sealant and 50% glue based on methyl methacrylate; or 75% heat-resistant silicone sealant and 25% methyl methacrylate adhesive; or 45% heat-resistant silicone sealant, 45% glue based on methyl methacrylate and 10% graphite powder, while the content of the impregnating mixture on carbon fiber is 45 ± 5%.

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