Thermally conductive composite element based on expanded graphite and production method

Abstract

A thermally conductive composite element is particularly suited for use in a surface heating system or in a surface cooling system. The composite element has at least one main part which contains expanded graphite and at least one flat textile structure disposed on one face of the main part. The textile structure is connected to the face of the main part by an inorganic adhesive.

Claims

1. A thermally conductive composite element for a surface cooling and/or surface heating system, the composite element, comprising: at least one mold containing expanded graphite and being formed with at least one side; at least one textile fabric disposed on said at least one side of said mold; an inorganic adhesive connecting said at least one textile fabric to said mold; and a pipe body configured for conducting a heat transfer medium and embedded in said at least one mold containing expanded graphite.

2. The composite element according to claim 1, wherein said pipe body has a meandering shape or a spiral shape.

3. The composite element according to claim 1, wherein said at least one mold containing expanded graphite is configured at least substantially as a plate-shaped mold and said at least one textile fabric disposed on an upper side and/or on a lower side of said plate-shaped mold.

4. The composite element according to claim 1, wherein said at least one mold contains expanded graphite with a density of 0.02 to 0.5 g/cm.sup.3.

5. The composite element according to claim 4, wherein said at least one mold contains expanded graphite with a density of 0.05 to 0.2 g/cm.sup.3.

6. The composite element according to claim 1, wherein said at least one mold contains expanded graphite with a surface weight of 100 to 4,000 g/cm.sup.2.

7. The composite element according to claim 1, wherein said at least one mold contains expanded graphite with a surface weight of 500 to 2,000 g/cm.sup.2.

8. The composite element according to claim 1, wherein said at least one mold is one of two molds each consisting of expanded graphite connected to one another by way of an inorganic adhesive.

9. The composite element according to claim 8, wherein said a pipe body for conducting a heat transfer medium is embedded between said two molds.

10. The composite element according to claim 1, which further comprises edge protection.

11. The composite element according to claim 10, wherein said edge protection is an L-shaped component made of metal or plastic, a U-shaped component made of metal or plastic or a coating on at least one of the edge sides of the composite element.

12. The composite element according to claim 1, further comprising a frame of metal and/or a non-woven fabric disposed to encase the composite element.

13. A method for producing a thermally conductive composite element, the method comprising: i) providing a first plate-shaped premolding and a second plate-shaped premolding, each of the premoldings containing expanded graphite; ii) placing a pipe body for conducting a transfer medium between an upper side of the first premolding and a lower side of the second premolding to form a pre-assembly; and iii) pressing of the pre-assembly obtained in step ii), applying at least one textile fabric in step i) to at least one of the sides of the premoldings lying opposite a side on which the pipe body is to be placed and/or, subsequent to step iii), applying at least one textile fabric to an upper side and/or a lower side of the assembly obtained in step iii).

14. The method according to claim 13, which comprises carrying out steps i) to iii) for forming the thermally conductive element according to claim 1.

15. The method according to claim 13, further comprising: a) applying an inorganic adhesive to the upper side and the lower side of the first premolding; b) applying a textile fabric to the upper side or lower side of the first premolding provided with adhesive and placing the pipe body on the side of the first premolding lying opposite the textile fabric; c) applying an inorganic adhesive to the upper side or the lower side of the second premolding; d) applying a textile fabric to the upper side or lower side of the second premolding provided with adhesive; e) placing the second premolding obtained in step d) with its side lying opposite the textile fabric downwards on the pipe body of the assembly obtained in step b); and f) pressing of the assembly obtained in step e).

16. The method according to claim 13, wherein step f) comprises pressing at a pressure of 0.02 to 5 MPa.

17. The method according to claim 16, which comprises pressing at a pressure of 0.1 to 1 MPa.

18. The thermally conductive composite element according to claim 1 in combination with, and configured for: a surface cooling or surface heating system; surface cooling and surface heating of machinery and equipment; cooling medical equipment; air-conditioning in motor vehicles; air-conditioning in ships and aircraft cabins; or temperature-control basins in swimming pools.

19. The thermally conductive composite element according to claim 18, wherein: the surface cooling or surface heating system comprise underfloor, wall or ceiling heating; wherein the machinery and equipment comprise photovoltaic cells, temperature chambers, housings for power electronics, battery cells, battery packs containing lithium-ion battery cells; the medical equipment includes CT scanners and MRI scanners; and the motor vehicles include buses and heavy-goods vehicles.

20. A thermally conductive composite element for a surface cooling and/or surface heating system, the composite element, comprising: two molds containing or consisting of expanded graphite; at least one textile fabric disposed on at least one side of at least one of said two molds; an inorganic adhesive connecting said at least one textile fabric to said mold; and a pipe body for conducting a heat transfer medium embedded between said two molds.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIG. 1 is a schematic cross section of a composite element according to an exemplary embodiment of the present invention;

(2) FIG. 2 is a diagram of a pipe body formed for conducting heat exchange medium through the composite element; and

(3) FIG. 3 is a diagram of an alternatively shaped pipe body.

DETAILED DESCRIPTION OF THE INVENTION

(4) Referring now to the figures of the drawing in detail, there is shown a composite element 10 that comprises two molds 12, 12 which are each made of expanded graphite, i.e., they essentially consist of expanded graphite. They do not contain any further constituents apart from expanded graphite and in particular no organic filling materials. In this case, the two molds 12, 12 are connected to one another by an inorganic adhesive 14, wherein the adhesive layer 14 in the figure is drawn in thicker in the interests of visual clarity than it is in reality. Moreover, at the interface between the two molds 12, 12 a meander-shaped pipe body 16 is provided and embedded in the two molds 12, 12, wherein of the pipe body 16 in the figure a total of 6 windings 18, 18 are shown. The pipe body has an internally hollow configuration and can therefore have a heat transfer medium flowing through it. On the upper side of the upper mold 12 and on the lower side of the lower mold 12, a non-woven fiberglass fabric is provided as the textile fabric 20, 20 in each case. The two textile fabrics 20, 20 are connected to the molds 12, 12 via an inorganic adhesive 14, 14, respectively. In this case as well, the adhesive layers 14, 14 are illustrated with an greater thickness than they would appear in reality.

(5) The edges and corners of the assembly may be protected by way of an edge protection element 21. The latter may also be integrated and formed directly in the textile fabrics 20 and/or 20. In a preferred embodiment, the edge protection is an L-shaped component made of metal or plastic, a U-shaped component which is preferably made of metal or plastic or a coating is provided as the edge protection on at least one of the edge sides of the composite element 10.

(6) There may also be provided a frame 22 of metal and/or a non-woven fabric disposed to encase the composite element 10. An exemplary frame is shown in highly diagrammatic form in FIG. 1.

(7) The present invention is described below with the help of an example explaining the invention. The example is not to be understood as limiting the invention.

EXAMPLE

(8) Two plate-shaped premoldings made of expanded graphite were provided. Each of the plates has a surface area of 625625 mm.sup.2, a thickness of 15 mm and a surface weight of 1,000 g/m.sup.2.

(9) On the upper and lower sides of a first of the two premoldings, water glass with an application quantity of 60 g per side was applied as an adhesive, wherein a product manufactured by Merck was used as the water glass. After this, a non-woven fiberglass fabric with a surface weight of 60 g/m.sup.2 and a thickness of 0.6 mm made of glass fibers with a diameter of 13 m was applied to one of the two sides of the premolding coated with adhesive, pressed on and the adhesive allowed to dry.

(10) In addition, the aforementioned product with an application quantity of 100 g was applied to one of the upper and lower sides of the second premolding as the adhesive and then two holes were punched in this premolding, which holes act as the inlet and outlet for the pipe body being fitted. After this, a non-woven fiberglass fabric with a surface weight of 60 g/m.sup.2 and with a thickness of 0.6 mm made of glass fibers with a diameter of 13 m was applied to the side of the premolding coated with adhesive, pressed on and the adhesive allowed to dry.

(11) A meander-shaped copper pipe body was then arranged on the side of the first premolding lying opposite the non-woven fiberglass fabric and the premolding was then arranged with its side opposite the non-woven fiberglass fabric downwards. This structure was then pressed in a press mold with spacers inserted in it to the desired height. The retention time in this case was 5 to 10 seconds.

(12) The composite element produced in this way was stiff and had no fire load. Both the individual components of the composite element, in other words adhesive, graphite and non-woven fabric, and also the entire composite element were not combustible or inflammable. In particular, samples of the composite element produced with a diameter of 45 mm and a height of 40 mm to 60 mm did not burn when they were heat-treated at 800 C. in a box-type furnace. The composite element showed no sag when supported on a wooden frame with a web width of 2 cm. When the composite element was loaded with 10 kg on a surface of 70.9 cm.sup.2 in the centre of the plate, the measurable sag was only 2 mm.

COMPARATIVE EXAMPLE

(13) A composite element such as that described in the above example was produced, except that rather than the water glass adhesive, an organic adhesive was used and the premoldings created from a mixture of expanded graphite and 20% by weight polyvinyl chloride particles as an organic filling material.

(14) Samples of the composite element produced in this manner with the dimensions referred to in the first-mentioned example burned for 26 seconds with an open flame when they were heat-treated at 800 C. in a box-type furnace.

(15) The following is a summary list of reference numerals and the corresponding structure used in the above description of the invention: 10 Composite element 12, 12 Mold made of expanded graphite 14, 14, 14 Adhesive/adhesive layer 16 Meander-shaped pipe body 18, 18 Windings of the pipe body 20, 20 Textile fabric 21 Edge protection element 22 Encasement frame