Stoves and furnaces – Tool having fluid fuel burner – Curling iron
Patent
1980-01-02
1983-12-20
Dority, Jr., Carroll B.
Stoves and furnaces
Tool having fluid fuel burner
Curling iron
176443, 176441, 176448, 176901, F24J 302
Patent
active
044211023
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a process for heating a transparent gaseous medium by means of highly concentrated solar radiation and an apparatus for carrying out this process.
Concentrated solar radiation is understood to mean the increasing of the power of the solar irradiation which strikes an object per unit of area. The power which is insolated upon an area of 1 m.sup.2 with normal solar irradiation amounts to some 800 W. With solar radiation concentrated a thousandfold, the power which is insolated upon a m.sup.2 is 1000.times.800 W equals 800 kW. The concentrating of the solar radiation can be achieved by lenses, concave reflectors, or, in the case of the known solar power plants, by a plurality of reflectors disposed on the ground which reflect the solar rays onto the top of a centrally disposed tower. References to such power plants are described in the report "Solar thermal Power Stations" of the international Symposium [sic] of Apr. 11-13, 1978 in Cologne of the Deutsche Forschungs- und Versuchsanstalt fur Luft- und Raumfahrt (DFVLR) as well as in the paper "Solar Heated Air-Receivers" which was prepared for the international solar energy convention and the exhibition of July 28, to Aug. 1, 1975 in Los Angeles U.S.A. In the case of these known solar power plants, or in general in the case of installations which serve to convert solar energy into mechanical work by thermal means, there exists, as in other thermal power processes, the necessity of attaining the highest possible operating temperatures so that a high efficiency for the conversion of thermal energy into work results (Carnot vactor [sic]).
Normally, it follows from this that the working medium in thermal power processes at these high temperatures is gaseous at 600.degree. to 1000.degree. C. according to Brayton, Otto, Stirling and vaporous according to Rankine, for example, superheated steam of 500.degree. to 600.degree. C. The heating of a gaseous or vaporous medium by means of highly concentrated solar energy presents very particular difficulties in the types of solar power plants known today.
In the design of the radiation receivers, which are usually disposed on a tower, it can be observed that gigantic, voluminous structures, so-called cavity receivers, are built, in which the highly concentrated solar radiation, after passing through an entrance opening, is closed "defocused" and, in the interior, strikes pipes in which the working medium to be heated circulates.
Because of the poor coefficient of heat transmission at which heat is transferred from a solid body to a gaseous medium, large surfaces are necessary, on the one hand, for heating the gas with the known types of construction and processes. It follows from this that relatively great volume of the cavity, the inside surface of which is substantially greater than the area of the opening through which the rays are captured. On the other hand, very high temperatures are necessary for the heat-transferring pipe walls, which leads to the use of highly heat-resistant ceramic materials. Let these relationships be shown in the following with the aid of a brief calculation:
The radiation power entering the cavity amounts to
This radiation power must be transmitted to the gas via the pipe walls, which happens according to the following equation: medium, and -T.sub.medium.
Thus the result is the following relation
For example, if an admissible difference in temperature of 400.degree. C. between wall and medium is assumed, when, for example, the gas is supposed to be heated to 800.degree. C., the wall would have a temperature of 1200.degree. C., and if a very high coefficient of heat transmission .alpha. of 0.2 kW/m.sup.2.degree. C. is taken as a basis, which is attainable only at very high pressure and gas speeds, then at a radiation density of 2000 kW/m.sup.2, the result is the following aspect ratio between the total surface of the absorber pipe walls and the cross-section of the cavity opening ##EQU1##
If it were desired to reduce the size of this surface of the cavity, and thereby the
REFERENCES:
patent: 2133649 (1938-10-01), Abbot
patent: 3239000 (1966-03-01), Meagher
patent: 4015584 (1977-04-01), Haberman
patent: 4033327 (1977-07-01), Pei
patent: 4136674 (1979-01-01), Korr
Kriesi Ruedi
Posnansky Mario
Dority Jr. Carroll B.
Miskin Howard C.
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