GB2129925A

GB2129925A - Heat exchange elements and solar panels

Info

Publication number: GB2129925A
Application number: GB08232253A
Authority: GB
Inventors: Robert Dominic Walker
Original assignee: HELYG DEVELOPMENTS Ltd
Current assignee: HELYG DEVELOPMENTS Ltd
Priority date: 1982-11-11
Filing date: 1982-11-11
Publication date: 1984-05-23

Abstract

A heat exchanger element 1, suitable for use as a radiator or in a solar panel, is made by adhesively bonding two oppositely facing plates 2 and 3 of a heat conductive metallic material together around their opposed surfaces 4 and 5 in spaced apart relation to provide a continuous fluid-tight space 15 therebetween for a heat exchange fluid. <IMAGE>

Description

SPECIFICATION Heat exchange elements This invention relates to heat exchange elements and, more particularly but not exclusively, to heat exchange elements suitable for use as part of a solar panel.

There are many forms of solar panels available on the market nowadays which generally consist of a heat exchange element housed in an insulated container having an open top which is closed by a transparent glass panel. One form of heat exchange element in common use comprises a length of tubing e.g. of copper, arranged in a series of loops. Water passed through the tubing from one end to the other is heated during its passage by exposure of the tubing to sunlight through the glass panel.

Such heat exchange elements are expensive to manufacture, thereby militating against wide usage of solar heating in particular for domestic purposes as the initial total cost of solar panels incorporating these heat exchange elements and installation is not justifiable with respect to the time taken to recover the cost from fuel savings.

Moreover, the water flowing through heat exchange elements utilizing tubing does not collect substantially all of the heat irradiated from the tubing.

Accordingly, the main object of this invention is to provide a heat exchange element and a method of making a heat exchange element in which the aforesaid disadvantages are reduced or eliminated.

To this end, and from one aspect, the invention consists in a heat exchange element comprising two oppositely facing plates of a heat conductive metallic material, at least one of which plates presents an exposed heat absorbent surface, said plates being held in spaced apart relationship and being adhesively bonded together around their opposed surfaces to provide a liquid-tight continuous space therebetween.

By means of the invention, and when the heat exchange element is incorporated in a solar panel in use, a film of heat exchange liquid is formed between the opposed surfaces of the plates in contrast to the columns of heat exchange liquid formed in the tubing of known heat exchange elements. Accordingly, heat exchange elements constructed in accordance with the invention provide an optimum relationship between their absorbent area and the quantity of heat exchange liquid being heated so that the heat exchange liquid flowing therethrough collects substantially all of the heat irradiated from the heat absorbent surface.

The invention also consists in a method of making a heat exchange element, said method comprising providing two plates of a heat conductive metallic material of which at least one presents a heat absorbent surface, and adhesively bonding oppositely facing surfaces of the two plates together in spaced apart relationship such that the heat absorbent surface is exposed and to provide a continuous liquid-tight space therebetween.

The adhesive bonding is preferably carried out by means of a substantially solid strip or strips of a suitable adhesive sealant, for example an adhesive foam which extend around the plates along or adjacent the edges of their opposed surfaces.

The plates may be held in spaced apart relation by the adhesive strips, or, as is preferred, separate spacer elements are additionally provided within the space which may be strips or blocks, for example, of the adhesive or, of metal or plastics material.

Alternatively, the separate spacer elements may be integral with one or both of the plates and formed as a multiplicity of projections, e.g. by stamping, on the opposed surface of the or each plate and which engage with the opposed surface of the other plate or the opposed surfaces of the plates between the projections.

The plates themselves may be made of any suitable heat conductive metallic material such as copper or aluminium but mild steel is preferred, in particular to reduce costs of manufacture.

Whether or not the material of the plates provides an efficient exposed heat absorbent surface, the exposed surface of at least one of the plates may be provided with a heat absorbent coating, for example a paint of a suitable colour such as black.

Instead of being of metal the plates could be of a metallised plastics material.

Although the adhesive bonding is sufficient to hold the plates together in normal usage, in arder to ensure that the plates remain together, for example, during transport to site, in a preferred embodiment of the invention the plates are additionally fixed together along their edges by any other suitable means such as rivets or crimping.

In order that the invention may be more readily understood reference will now be made to the accompanying drawings in which: Fig. 1 is an exploded perspective view of a heat exchange element constructed in accordance with the invention and suitable for use as part of a solar panel, Fig. 2 is a cross-section along the line Il-Il of Fig. 1,and Fig. 3 is a diagrammatic cross-section of a solar panel incorporating the heat exchange element of Fig. 1.

Referring to Figs. 1 and 2 of the drawings, there is shown a heat exchange element which is generally indicated at 1 and which comprises two mild steel plates 2 and 3 having oppositely facing surfaces 4 and 5 and of which at least the upper plate 2 (as shown) has a heat absorbent coating 6, e.g. of paint thereon. The plates 2 and 3 are provided with respective part circular recesses 7 and 8 in their opposed surfaces 4 and 5 for accommodating inflow and return pipes 9 and 10 for a heat exchange liquid such as water. Solid strips 11 of an adhesive bonding sealant material such as an adhesive foam are laid as shown for convenience along the edges 12 of the opposed surface 5 of the bottom plate 3 (as shown) so as to provide a continuous run of adhesive strip entirely around the plate 3 including the recesses 8.Short strips 1 a of the same adhesive material are laid in the recesses 7 of the plate 2.

Although the strips 11 and 11 a hold the plates 2 and 3 in spaced apart relationship, in this embodiment, separate spacer strips 13, for example of the same adhesive material as that of the strips 11 are additionally provided on the opposed surface 5 of the plate 3 or, alternatively, the strips 10 may be of a suitable metal such as mild steel which is brazed or otherwise bonded to the plate 3.

To assemble the heat exchange element 1, the inflow and return pipes are accommodated in the recesses 7 of the bottom plate 3 and the opposed surface 4 of the plate 2 is matched to that 5 of the plate 3, and placed in contact with the adhesive strips 11 and the plates pressed together to bond them together.

Conveniently, the assembly is completed by fixing the two plates 2 and 3 together by means of rivets 14 for example but this operation is not essential.

It will be appreciated that the assembled heat exchange element has a continuous space 1 5 between the opposed surfaces 4 and 5 of the two plates. The space 1 5 is made liquid-tight by means of the adhesive bonding sealant strips 11 and 1 a except that heat exchange liquid may flow into and out of the space 1 5 through the pipes 9 and 10 respectively.

In use, heat exchange liquid flowing through the space 1 5 spreads out in a continuous film between the opposed surfaces of the plates.

Fig. 3 shows the heat exchange element 1 forming part of a solar panel or collector 1 5a. The solar panel 1 spa comprises a totally insulated and reflective container 1 6 having a layer 1 7 of reflective insulating material over its entire inner surface. The heat exchange element 1 is secured in any convenient manner against that part of the layer 1 7 on the bottom of the container 1 6. The open top of the container 1 6 is closed by means of a transparent glass panel 1 8.

Although the invention has been particularly described with reference to a heat exchange element suitable for use as part of a solar panel or collector, it should be appreciated, that the heat exchange element itself may be used for other purposes, for example as a central heating radiator since its cost compared with conventional radiators is considerably reduced.

Various modifications may be made without departing from the scope of the invention. For example, instead of the plates 2 and 3 being of rectangular configuration they may be of any other suitable configuration. The heat exchange element described may be used with heat exchange mediums other than liquids for example a gaseous fluid, in which case, the adhesive bonding sealant material must be such as to ensure that the space 1 5 is fluid-tight.

Claims

1. A heat exchanger element comprising two oppositely facing plates of a heat conductive metallic material, at least one of which plates presents an exposed heat absorbent surface, said plates being held in spaced apart relationship and being adhesively bonded together around their opposed surfaces to provide a fluid-tight continuous space therebetween.

2. A heat exchange element as claimed in claim 1, wherein the adhesive bonding is carried out by means of a strip or strips of adhesive sealant.

3. A heat exchange element as claimed in claim 2, wherein the adhesive sealant is an adhesive foam which extend(s) around the plates along or adjacent the edges of their opposed surfaces.

4. A heat exchange element as claimed in claim 2 or 3, wherein the plates are held in spaced apart relation by spacer means.

5. A heat exchanger element as claimed in claim 4, wherein the spacer means are the adhesive strip or strips.

6. A heat exchanger element as claimed in claim 4 or 5, and including additional separate spacer elements within the space.

7. A heat exchange element as claimed in claim 5, wherein the spacer elements are strips or blocks.

8. A heat exchange element as claimed in claim 6, wherein the strips or blocks are of adhesive or of metal or plastics material.

9. A heat exchange element as claimed in claim 4, the spacer means are integral with one or both of the plates and are formed as a multiplicity of projections on the opposed surface of one or each plate, said projections engaging with the opposed surface of the other plate or the opposed surfaces of the plates between the projections.

10. A heat exchange element as claimed in any one of the preceding claims, wherein the plates are of mild steel or of a metalized plastics material.

11. A heat exchange element as claimed in any one of the preceding claims, wherein the exposed surface of at least one of the plates is provided with a heat absorbent coating.

12. A heat exchange element as claimed in claim 11. wherein the heat absorbent surface is a paint of a suitable colour such as black.

1 3. A heat exchange element as claimed in any one of the preceding claims, wherein the plates have additional fixing to each other along their edges.

14. A heat exchange element as claimed in claim 13, wherein the additional fixing is by means of rivets or crimping.

1 5. A heat exchange element as claimed in any one of the preceding claims, wherein the plates are provided with respective oppositely facing part-circular recesses which accommodate inflow and return pipes for a heat exchange fluid and wherein the adhesive bonding extends into the recesses and encircles the pipes.

1 6. A heat exchange element as claimed in claim 15, as appendant to claim 5 or any claim dependent thereon, wherein a continuous run of adhesive bonding strip extends entirely around one of the plates including the recesses therein, and wherein short strips of adhesive are disposed in the recesses in the other plate such that the pipes are encircled by the adhesive.

17. A heat exchange element substantially as hereinbefore described with reference to Figs. 1 and 2 of the accompanying drawings.

18. A solar panel incorporating a heat exchange element as claimed in any one of the preceding claims.

19. A solar panel as claimed in claim 18, and including an insulated and reflective open-topped container having a layer of reflective insulating material extending over its entire surface, with the heat exchange element secured within the container against that part of the layer which extends over the bottom of the container and wherein the open top of the container is closed by a transparent panel.

20. A solar panel substantially as hereinbefore described with reference to Figs. 1 to 3 of the accompanying drawings.

21. A method of making a heat exchange element, said method comprising providing two plates of a heat conductive metallic material of which at least one presents a heat absorbent surface, and adhesively bonding oppositely facing surfaces of the two plates together in spaced apart relationship such that the heat absorbent surface is exposed and to provide a continuous fluid-tight space therebetween.

22. A method of making a heat exchange element according to claim 21 and substantially as hereinbefore described.

23. A method of making a heat exchange element substantially as hereinbefore described with reference to Figures 1 to 3 of the accompanying drawings.