Exergy analysis and parametric study of concentrating type solar collectors

The exergetic performance of concentrating type solar collector is evaluated and the parametric study is made using hourly solar radiation. The exergy output is optimized with respect to the inlet fluid temperature and the corresponding efficiencies are computed. Although most of the performance parameters, such as, the exergy output, exergetic and thermal efficiencies, stagnations temperature, inlet temperature, ambient temperature etc. increase as the solar intensity increases but the exergy output, exergetic and thermal efficiencies are found to be the increasing function of the mass flow rate for a given value of the solar intensity. The performance parameters, mentioned above, are found to be the increasing functions of the concentration ratio but the optimal inlet temperature and exergetic efficiency at high solar intensity are found to be the decreasing functions of the concentration ration. On the other hand, for low value of the solar intensity, the exergetic efficiency first increases and then decreases as the concentration ratio is increased. This is because of the reason that the radiation losses increase as the collection temperature and hence, the concentration ratio increases. Hence, for lower value of solar intensity, there is an optimal value of concentration ratio for a given mass flow rate at which the exergetic efficiency is optimal. Again it is also observed that the mass flow rate is a critical parameter for a concentrating type solar collector and should be chosen carefully. (C) 2006 Elsevier Masson SAS. All rights reserved.