Abstract
A focusing collector for air heater, the concentrator being Fresnel lenses, is here examined. The sunlight is focalized on black-body metallic sheets, contained in an insulated box, through which the energy is transferred to the fluid (dry air). The sheets, having the same height, are arranged at a distance one from another increasing from the center to the edges in order to trap all the incident energy. The energy reflected by the sheets is also trapped. A thermotechnical analysis of the system in order to determine the optimal conditions for the heat transfer is reported.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
Abbreviations
- D :
-
aperture of the lens
- f :
-
focal length of the lens
- Q :
-
reflection coefficient
- Nu:
-
Nusselt number
- Pr:
-
Prandtl number
- Re:
-
Reynold number
- h :
-
heat transfer coefficient (sheet-air)
- v :
-
velocity of the airflow
- k :
-
thermal conductivity
- μ :
-
density of the air
- η :
-
dynamic viscosity
- c p :
-
specific heat of air at constant pressure
- T j :
-
inlet temperature
- T o :
-
outlet temperature
References
J.A.Duffie, W.A.Beckman:Solar Energy Thermal Processes (John Wiley&Sons, New York 1974) pp. 271–273
G.O.G.Löf: Use of Solar energy for heating purposes: Space Heating. Proc. UN Conf. New Source of Energy5, 114 (1964)
A.B.Meinel, M.P.Meinel:Applied Solar Energy, an Introduction (Addison Wesley Publ., Reading, MA 1976) pp. 378–410
J.F.Kreider, F.Kreith:Solar Heating and Colling (Hemisphere Publishing Corporation 1977) pp. 139–144
G.O.G.Löf, R.A.Tybout: ASME Paper 72-WA/Sol-8 (1972)
F.Kreith:Principi di trasmissione del calore (Liguori editori 1974) pp. 427–430 and 563–565