Modelling of flat-plate collectors based on monolithic silica aerogel

• Published in: Solar energy Vol. 49; no. 5; pp. 387 - 402
• Main Authors: Nordgaard, A., Beckman, W.A.
• Format: Journal Article
• Language: English
• Published: New York Elsevier Ltd 01.11.1992; Pergamon Press Inc
• Subjects: 141000 - Solar Collectors & Concentrators; 990200 - Mathematics & Computers; aerogel collectors; Atmosphere; CALENTAMIENTO; CAPTEUR SOLAIRE; CHALCOGENIDES; CHAUFFAGE; COLECTORES SOLARES; DESECANTES; DESICCANTS; DESSICCANT; ECHANGE THERMIQUE; ENERGIA SOLAR; ENERGIE SOLAIRE; ENERGY TRANSFER; EQUIPO; FLAT PLATE COLLECTORS; FORECASTING; GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE; HEAT TRANSFER; HEATING; INFRARED HEATERS; INSULATING MATERIALS; ISOTROPY; MATERIEL; MATHEMATICAL MODELS; MODELE; MODELOS; OPTICAL PROPERTIES; OXIDES; OXYGEN COMPOUNDS; PREDICTION; PROPIEDADES OPTICAS; PROPRIETE OPTIQUE; RADIACIONES; RADIANT HEAT TRANSFER; RADIATION; RADIATIONS; SILICA; SILICA GEL; SILICE; SILICON COMPOUNDS; SILICON OXIDES; SOLAR COLLECTORS; SOLAR ENERGY; SOLAR EQUIPMENT; SOLAR RADIATION; STELLAR RADIATION; TECHNIQUE DE PREVISION; TECNICAS DE PREDICCION; THERMAL INSULATION; TRANSFER; TRANSFERENCIA TERMICA; TRANSMITTANCE; transparent insulation material
• ISSN: 0038-092X; 1471-1257
• DOI: 10.1016/0038-092X(92)90111-M

This paper presents a new method for predicting the radiative transfer in an absorbing and isotropically scattering, non-gray plane-parallel atmosphere. The technique is based upon the F̂ (“F-hat”) concept and was developed to determine the radiative transfer at short wavelengths for the transparent insulation material, monolithic silica aerogel. The angular dependence of solar transmittance of diffuse and ground reflected radiation is evaluated along with the “transmittance-absorptance product” of a collector. The F̂ technique is also used to determine the IR transmission of the cover from which the overall loss coefficient for a flat-plate collector constructed with aerogel filled covers is determined. The performance of a system using aerogel collectors is compared to systems using other types of high performing collectors. It is shown that, at least for the system investigated, the decrease in solar transmittance of monolithic silica aerogel is more than compensated by the decrease in thermal losses.