CA1228518A

CA1228518A - Solar-energy collector

Info

Publication number: CA1228518A
Application number: CA000437307A
Authority: CA
Inventors: Gosta Janson
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-09-22
Filing date: 1983-09-22
Publication date: 1987-10-27

Abstract

ABSTRACT OF THE DISCLOSURE

A solar-energy collector with an absorber unit comprising two plates of rigid material has an intermediate space for a flowing medium to be heated. In order to obtain a form-stable unit having temperature equalizing properties, the two plates are wave-shaped in mutually intersecting directions, symmetrically in relation to the main direction of flow of the medium, and the plates abut each other at the points of intersection, at which points the plates are joined together by welding, adhesive bonding or the like.

Description

~r~5.~L~3 The present invention relates to a solar-energy collector comprising two corrosion and heat-resistant plates whictl are sealed around their peripheries, to enclose a shallow cavity for containing a medium to be heated.
Solar-energy collectors of this kind are still encumbered with a number of cost increasing disadvantages.
In order to withstand the mechanical stresses and strains which are created partly as a result of external influences an partly as a result of internal pressures in the absorber unit, it is necessary to use a particularly strong and robust material, normally copper sheet or aluminum sheet, and sometimes steel sheet, particularly when the heat-transport medium is air. For the same reason, the cavity is normally divided into a plurality ox mutually parallel ducts. Particularly when such ducts are provided, and even in the absence ox said ducts, the flow of medium through the cavity can readily become unevenly distributed across the whole of the cross-section of the cavity, requiring manual adjustments to be made so that the whole of the collector surface can be utilized.
It is an object of the invention to provide a solar-energy collector slaving an absorber unit which despite the use of lightweight and weak materials, is able TV withstand strong external and internal pressures, and which is constructed so as to provide more uniform distribution of the medium flow across the whole cross-section and area of the collector.
The present invention provides a solar-energy collector having an absorber unit which comprises two plates of rigid corrosion-and lleat-resistallt material sealingly connected together around their peripheries to form an intermediate, wide, elongate, shallow, cavity or a medium to be heated and which is provided at two mutually opposite ends with inlet and outlet openings for the medium, wherein the two plates are wave-formed over at least substantially the whole of their surfaces in mutually crossing directions, and the waves of the I,:

respective plates are oriented at equal but opposite angles in relation to the main direction of flow of the medium; the plates abut each other at those location where the waves cross each other, the plates being joined together at at least a part owe the locations, by welding, adhesive bonding or the like, and the two plate are joined around their peripheries with a common ring-like frame having abutment surfaces adapted to the wave-form of the plates, the frame also being provided with abutment surfaces for receiving front and rear cover plates for the collector.
This wave-form in combination with the connections at the abutment locations provides fixation of the wave-form and also affords considerable resistance to bending. In addition, as a result of the waveform of respective plates the flow of medium is also divide into a plurality of mutually intersecting portals, and each time two part-flows intersect each other, they are divided into further portals At the same time, there is obtained additional contribution from adjacent part-flows.
Even if the collector is unveil irradiated, so that part of the collector becomes too hot with sub~eguent impairment of its efficiency, the temperature will be rapidly elude throughout, so as to constantly obtain the highest possible efficiency.
Various embodiments of solar-energy collectors according to the invention will now be described more clearly with reference to the accompanying drawings in which Figure 1 is a front view ox a first embodiment;
Figure 2 is a cross-sectional view taken on the line Isle in Figure l;
Figure 3 is a detail view in perspective of the two plates illustrated in Figures 1 and 2 Figures 4 and 5 are each front views of a plate havirlg pressed therein recesses to form a wave ape sector part on respective plates; and I

_ I

Figures 6 and 7 are respectively a cross-sectional view and a view taken on the line VII-VII in Figure 6 of a preferred embodiment of the invention.
Figures 1 - 3 illustrate two mutually parallel 5 plates 1, 2 made from thin alu~inium sheet and having mutually facing, inwardly pressed ridges 3, 4 which cross each other and which are connected to one another at the locations of intersection by means of an adhesive or spot welds. The plates are connected around their periphery, in some suitable manner r with a ring like frame 5 corlstructed from aluminum section having abutment surfaces adapted to the waveform of the plates. The height of the reloan 5 is sufficient to form an air-filled cavity 6 between the absorber unit 1, 2, 3, 4 and a cover plate 7 made of transparent material, for example glass, joined to the frame 5, and a cavity or accommodating heat-insulating material B between absorber unit end a rear side 9 attached to the frame.
At each end of the solar-energy collector, the frame 5 is provided Witty through-passing passages 10, which connect the cavity between the plates 1 end 2 to inlet and outlet passages 11, 12, respectively, for the medium to be heated.
The main direction of flow ox the medium is indicated ho an arrow if in Figure 3, from WlliCil Figure it will be seen that the flow of medium will be diced into a plurality of part-flows which are constantly divided up and Maxwell in a plurality of eddy-currents, which results in rapid and complete temperature equalization should irregularities occur.
similar embodiment can Allah be obtained with the pressed plates 41, I or 51 r 52 as illustrated in Figures 4 and S; in the Faker 4 embodiment ridge 43 have been pressed into planar plates 41, 42l while in the Figure 5 embodiment groove 54 have bell pressed into planar plates 51, 52 to leave ridges 53 there between. In this latter case, the plates 51, 52 can be joined directly together arourld the peripheries thereof although it it . . . ,/
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then necessary to provide separate inlet and outlet openings 55 and 56, respectively.
The ridges are pressed into the plates Al, 42 in a manner such that the plates are mutually identical and so that, subsequent to turning one plate through 180 in relation to the other plate, the ridges 43 will cross one another. The same applies to the plates 51, 52.
The absorber units need not necessarily comprise two metal plates. One or both plates may optionally comprise a plastics material. The plate onto which radiation from the sun falls may be transparent and the other darkly colored. When a liquid medium is used r the liquid may also be darkly colored, so that the liquid itself is heated by tile sun' 5 rays in a known manner.
lo As will be understood, when a gaseous medium, such as air, is used the distance between the wave-shaped surfaces must be greater than when a liquid medium is used.
The preferred embodiment of a solar energy Jo collector according to the invention illustrate in Figures 6 and 7 is based mainly on the type ox absorber plots Sly 9 52' illustrated in Figure 5.
In this embodiment! the plates, made of steel sheet approximately lam in thickness, are supplemented with upstanding rims 61, 62, each of which extend aroulld the periphery of its respective plate and which are terminated with planar-ring-like flanges 63, 64. The two plates are also provided with mutually opposite, transversely extending raised portions 65, 66, which together form two distributing ducts 67~ 68 which comlnunicate with the Initial intersecting grooves or channels 54 and with a respective inlet and outlet pipe-connector 69, 70.
A continuous weld extends around the bottom portions 71 of the rims 61, 62 and there joins the plates So', 52' together. Spot welds are also made at the major part of toe intersection locations 72 of the ridges I
thereby to provide a particularly rigid absorber.
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Each absorber can be manufactured from two plates 51', 52' which are similarly profiled and produced in a large press and which subsequent to turning or rotating one ox the plates are welded back-to-back in an automatic welding machine and provided with inlet and outlet pipe-connectors 59, 70. A plastics cover 75 is then arranged on the flanges 63, and on the opposite side there is temporarily arranged a mound (not shown by means ox which a block 76 of cellular plastics can be formed on the rear side of the absorber, the rim 62 and the Lange 64 serving as reinforcing means within the block 76.
Because the absorber is particularly rigid no casing is required.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A solar-energy collector having an absorber unit which comprises two plates of rigid corrosion-and heat-resistant material sealingly connected together around their peripheries to form an intermediate, wide, elongate, shallow, cavity for a medium to be heated, and which is provided at two mutually opposite ends with inlet and outlet openings for said medium, wherein the two plates are wave-formed over at least substantially the whole of their surfaces in mutually crossing directions, and the waves of the respective plates are oriented at equal but opposite angles in relation to the main direction of flow of the medium, the plates abut each other at those locations where the waves cross each other, the plates being joined together at at least a part of said locations, by welding, adhesive bonding or the like; and the two plates are joined around their peripheries with n common ring-like frame having abutment surfaces adapted to the wave-form of the plates, said frame also being provided with abutment surfaces for receiving front and rear cover plates for the collector.

2. R solar-energy collector according to claim l, wherein the wave-form of the plates is such that mutually abutting wave surfaces are planar.

3. A solar-energy collector having an absorber unit which comprises two plates of rigid material having the requisite resistance to corrosion and heat, said plates being sealingly connected together around their peripheries to form an intermediate, wide, elongate cavity of low height for a medium to be heated, and which is provided at two mutually opposite ends with inlet and outlet openings for said medium, wherein the two plates are wave-formed over at least substantially the whole of their surfaces in mutually crossing directions oblique to the main direction of flow of the medium, and the waves of the respective plates are oriented at equal but opposite angles in relation to said main direction of flow of the medium;
the plates abut each other at those locations where the waves cross each other, the plates being joined together at at least a part of said locations, by welding, adhesive bonding or the like;
the peripheries of the plates are located in a common plane with the intersection locations of the waves, and the plates are joined together around said peripheries; and said plates are provided around said peripheries with rims which project away from each other and which are terminated with flanges one of which forms fastening means for a transparent cover plate, and the other of which, together with its associated rim, constitutes a reinforcement for a block of cellular plastics material, or like insulating material, arranged on the absorber, preferably by moulding.