MODELING AND EVALUATION OF A PASSIVE FLAT-PLATE SOLAR COLLECTOR

MODELING AND EVALUATION OF A PASSIVE FLAT-PLATE SOLAR COLLECTOR

ABSTRACT

This work investigated the variation of top loss heat transfer coefficient with the emittance of the absorber plate, the collector tilt angle and air gap spacing between the absorber plate and the cover plate. The effects of the emittance of the absorber plate, the collector tilt angle and air gap spacing between the plate and the cover on the collector performance were also considered. Data collected from the thermosyphon solar water heater constructed by the National Centre for Energy Research and Development (NCERD), UNN was used in the analysis.  Evaluations of thermal losses by radiative and convective heat transfer coefficient were performed.  It was observed that increase in the emittance of the absorber plate resulted in dissipation of more heat to the atmosphere and consequent increase in top loss heat transfer coefficient which led to reduced system performance. The collector tilt angle had little effect on the top loss heat transfer coefficient and consequently had insignificant effect on the performance of the collector. Increase in the air gap spacing between the absorber plate and the cover plate resulted in decrease in the top loss heat transfer coefficient. It was also observed that passive flat-plate solar collector had a better performance at a low mean absorber plate temperature. In addition, a correlation that relates the efficiency of the collector with the absorber plate emittance, collector tilt angle and the air gap spacing between the absorber plate and the cover plate was developed for the NCERD thermosyphon water heater.