Study and Exergy Optimization of a Flat Plate Solar Collector in a Closed Circuit Utilized with Reflectors and Lenses Using Experimental Results

In this study، exergy analysis of a flat plat solar collector in a closed circuit has been performed using existing experimental data and the effects of utilization of the collector with upper، lower and side reflectors alone and together with lenses on exergy efficiency have been considered. Then، based on a mathematical model، optimization analysis has been performed. Unlike the past studies، the collector overall heat loss coefficient is not constant and the fluid inlet temperature to the collector is not the same as the ambient temperature; instead the experimental results are used. The optimization analysis has been undertaken by studying the effects of the fluid inlet temperature and flow rate، ambient temperature، optical efficiency، solar radiation flux and collector area. The results show that exergy efficiency increases always with increasing solar radiation flux as well as optical efficiency، but decreases with increased ambient temperature. For every condition there are an optimum flow rate and inlet temperature for which the exergy efficiency becomes optimum. Utilization of the collector with reflectors and reflectors-lenses improves the collector exergy efficiency، but using reflectors alone is better.