Stoves and furnaces – Solar heat collector – With means to convey fluent medium through collector
Patent
1998-02-23
1999-04-20
Dority, Carroll B.
Stoves and furnaces
Solar heat collector
With means to convey fluent medium through collector
126669, F24J 224
Patent
active
058948376
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a solar collector having a metal pipe system through which a heat carrier flows in serpentine fashion.
Such solar collectors are known. The pipe system through which the heat carrier (usually water) flows in serpentine fashion is formed by a serpentine copper pipe soldered onto a copper sheet. This unit is sprayed black on the upper side and disposed in a glass-covered frame with an insulating layer under the copper sheet. In order to utilize the spaces between the copper pipes at least partly for heat recovery one can additionally apply heat conducting plates to the copper pipes.
Because the contact surface and thus heat transfer surface between the copper sheet and the copper pipe is relatively small, the copper sheet heats up greatly in the known solar collector This necessitates an elaborate insulating layer under the copper sheet, on the one hand, and causes the copper sheet to radiate part of the heat again, on the other hand.
WO93/15368 and U.S. Pat. No. 4,898,153 disclose solar collectors consisting of a hollow section plate made of transparent plastic, in particular polycarbonate. The hollow section plates consist of two layers connected by parallel longitudinal webs so as to form channels through which a heat carrier flows which is mixed with a solar absorbent material, for example a dark color. There is a danger of part of the color settling in the hollow section, thereby heating the plastic hollow section but not the heat carrier.
The problem of the invention is to provide a simply constructed solar collector with high efficiency.
This is obtained according to the invention by the solar collector characterized in claim 1. Advantageous embodiments of the invention are rendered in the subclaims.
The inventive solar collector is produced from plate-shaped metal hollow section portions. The metal hollow section consists of two plane-parallel layers interconnected by longitudinal webs.
The metal hollow section is produced by extrusion. One can thus easily obtain a hollow section wherein the two metal layers are spaced only a small distance apart.
For high heat transfer from the metal hollow section to the heat carrier, and thus high efficiency of the solar collector, it is necessary that the heat carrier quickly removes the heat of the metal hollow section heated by solar radiation. For the heat carrier to be heated to a maximum temperature, heat must in addition be removed through a minimum quantity of heat carrier. This means that the distance between the two layers of the hollow section should be as small as possible, being smaller than 10 mm if possible, preferably smaller than 5 mm.
In addition, extrusion makes it possible to produce a metal hollow section with very thin layers and thin longitudinal walls, a further precondition for fast heat transfer. The thickness of the two layers and the longitudinal webs of the hollow section portions of the inventive solar collector can be for example 0.1 mm to 1 mm.
In order to reduce the distance between the two layers of the hollow section one according to the invention preferably uses a hollow section which has been subjected after extrusion to deformation, in particular cold forming, e.g. by pressing or rolling. In this way one can produce a metal hollow section wherein the distance between the two layers is only 3 mm or less. The minimum distance between the two layers should be 1 mm, however, since otherwise the flow resistance for the heat carrier greatly increases.
The metal from which the hollow section is produced is preferably an aluminum material, i.e. aluminum or an aluminum alloy. As has turned out, an aluminum material can be extruded and cold-formed especially well into such hollow sections. Also, aluminum is much more cost-effective than copper for example, and much more corrosion-resistant than iron for example.
The longitudinal webs between the two layers of the hollow section increase the heat transfer surface, thereby additionally improving efficiency. However, they are also indispensable because the hollow
REFERENCES:
patent: 4051832 (1977-10-01), Stelzer
patent: 4156419 (1979-05-01), Lewis
patent: 4265225 (1981-05-01), Berger et al.
patent: 4271818 (1981-06-01), Hastwell
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