Up to now, nearly all the experimental and theoretical work treating convective heat loss of cavity receivers had been effected for downward and sideward-facing receivers, as they are used in dish concentrators and solar power towers. With a test facility it was possible to show flow patterns and a temperature field in a hot cavity for a variety of parameter settings and over the whole range of tilt angles. Two types of geometries were examined: a spherical and a hemispherical cavity, both with an inner diameter of 400 mm, the aperture diameter ranging between 60 and 195 mm. Temperatures were varied between 573 K and 873 K. The dependence of losses on temperature, tilt angle, aperture-radius, geometry, ribs, and ventilation is reported. Special emphasis is invested to get an understanding of the air flow in an upward facing cavity. Based on the works of Clausing et al. (1987), and Stine and McDonald (1989), two algorithms are developed that allow the calculation of convective loss from upward-facing receivers. Over the whole range of tilt angles, calculated results are compared with measurements. Good agreement between the calculated and measured data is found.

Issue Section:
Research Papers
Topics:
Cavities, Heat losses, Solar energy, Temperature, Air flow, Algorithms, Flow (Dynamics), Geometry, Solar power, Test facilities, Ventilation
1.
Clausing
A. M.
,
1981
, “
An Analysis of Convective Losses from Cavity Solar Central Receivers
,”
Solar Energy
, Vol.
27
, No.
4
, pp.
295
–
300
.
2.
Clausing
A. M.
,
1983
, “
Convective Losses from Cavity Solar-Receivers—Comparisons Between Analytical Predictions and Experimental Results
,”
ASME JOURNAL OF SOLAR ENERGY ENGINEERING
, Vol.
105
, pp.
29
–
33
.
3.
Clausing
A. M.
,
Waldvogel
J. M.
, and
Lister
L. D.
,
1987
, “
Natural Convection from Isothermal Cubical Cavities with a Variety of Side-Facing Apertures
,”
ASME Journal of Heat Transfer
, Vol.
109
, pp.
407
–
412
.
4.
Kleinwa¨chter, H., and Radebold, R., 1981, “Fix-Focus Concentrator for Production of Hydrazine and Other Applications,” Proceedings of the 20th COMLES International Meeting, Rabat (Maroc).
5.
Lankhorst, A., 1991, “Laminar and Turbulent Natural Convection in Cavities,” Thesis, Technical University Delft, Holland.
6.
Leibfried, U., 1992, “Einsatzmo¨glichkeiten eines Solarkraftwerkes mit thermochemischem Speicher—Simulationsergebnisse,” Proceedings of the 8th Internationales Sonnenforum, DGS-Sonnenenergie-Verlags GmbH, Berlin.
7.
Mitzel, M., 1989, “Solarthermische H2S-Zersetzung mit einem Fix-Fokus-Konzentrator,” Solarchemische Technik, Vol. 2, Springer-Verlag, Berlin.
8.
Siebers, D. L., and Kraabel, J. S., 1984, “Estimating Convective Energy Losses from Solar Central Receivers,” Sandia National Laboratories Report, SAND 84–8717.
9.
Stine, W. B., and McDonald, C. G., 1988, “Cavity Receiver Heat Loss Measurements,” Proceedings of the 1988 ASME Solar Energie Division Conference, Denver.
10.
Stine, W. B., and McDonald, C. G., 1989, “Cavity Receiver Convective Heat Loss,” Proceedings of the 1989 Congress of the ISES, Kobe, Japan.
11.
Stine, W., 1992, private communication, California State Polytechnic University, Pomona, CA.
12.
Stine, W., 1992, “Listing of Experimental Data Used in the 1988 Kobe ISES Conference Paper,” private communication, California State Polytechnic University, Ponoma, CA.
13.
Stine, W., 1992, “Wind Effects on Convective Loss, Project Output,” private communication, California State Polytechnic University, Ponoma, CA.
14.
Vafai
K.
, and
Ettefagh
J.
,
1990
, “
Thermal and Fluid Flow Instabilities in Buoyancy Driven Flows in Open-Ended Cavities
,”
Int. Journal of Heat and Mass Transfer
, Vol.
33
, No.
10
, pp.
2329
–
2344
.
15.
Yang, K. T., 1987, “Natural Convection in Enclosures,” Handbook of Single Phase Convective Heat Transfer, John Wiley and Sons, New York.
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