The energy and exergy performance of a parabolic dish collector is investigated experimentally and theoretically. The e ect of receiver type, inlet temperature and mass ow rate of heat transfer uid (HTF), receiver temperature, receiver aspect ratio and solar radiation are investigated. To evaluate the e ect of the receiver aperture area on the system performance, three aperture diameters are considered. It is deduced that the fully opened receivers have the greatest exergy and thermal e ciency. The cylindrical receiver has greater energy and exergy e ciency than the conical one due to less exergy destruction. It is found that the highest exergy destruction is due to heat transfer between the sun and the receivers and counts for 35 % to 60 % of the total wasted exergy. For three selected receiver aperture diameters, the exergy e ciency is minimum for a speci ed HTF mass ow rate. High solar radiation allows the system to work at higher HTF inlet temperatures. To use this system in applications that need high temperatures, in cylindrical and conical receivers, the HTF mass ow rates lower than 0.05 and 0.09 kg/s are suggested, respectively. For applications that need higher amounts of energy content, higher HTF mass ow rates than the above mentioned values are recommended.

This study undertakes the experimental and theoretical investigation of heat losses from a cylindrical cavity receiver employed in a solar parabolic dish collector. Simultaneous energy and exergy equations are used for a thermal performance analysis of the system. The e ects of wind speed and its direction on convection loss has also been investigated. The e ects of operational parameters, such as heat transfer uid mass ow rate and wind speed, and structural parameters, such as receiver geometry and inclination, are investigated. The portion of radiative heat loss is less than 10%. An empirical and simpli ed correlation for estimating the dimensionless convective heat transfer coe cient in terms of the Re number and the average receiver wall temperature is proposed. This correlation is applicable for a wind speed range of 0.1 to 10 m/s. Moreover, the proposed correlation for Nu number is validated using experimental data obtained through the experiments carried out with a conical receiver with two aperture diameters. The coe cient of determination 2 and the normalized root mean square error (NRMSE) parameters were calculated, and the results show that there is a good agreement between predicted results and experimental data. 2 is greater than 0.95 and the NRMSE parameters is less than 0.06 in this analysis.

The performance of a pilot scale at plate solar water heater system is investigated theoretically and experimentally. The e ect of the operating conditions and characteristic factors of the collector on the system e ciency is studied. A conceptual mathematical model is developed in order to analyze the system behavior in di erent operating conditions by considering the physical and constructive aspects of the system. The accuracy of the model result is estimated by comparing the model results with the existing experimental data. The highest obtained system thermal e ciency is 45%, and the optimum local values for surface azimuth and tilt angles are obtained at 180 degrees from north and 33 degrees, respectively, for the constructed solar water heater in Isfahan, Iran, with the local latitude of 32.6333 ∘ N.

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