Flat-Plate Solar Collector Thermal Performance and Optimal Operation Mode by Exergy Analysis and Numerical Simulation

In this paper, the effect of a flat-plate solar collector components exergy destruction rates on the collector performance has been examined. A theoretical model based on energy and exergy balance for glass cover, absorber plate and working fluid resulted in nonlinear ordinary differentials non-autonomous system of equations that was solved numerically. Upon verification of the accuracy of the proposed model with experimental data, the effect of parameters such as solar radiation, mass flow rate, inlet fluid temperature and insulation thickness on the exergy destruction rates and exergy efficiency has been investigated. The model was used to optimize parameters, such as inlet fluid temperature, mass flow rate and number of collector tube. The results reveal that the highest exergy destruction rate occurs in the absorber plate, which is 79.23% of the total exergy destruction rate. Increasing the mass flow rate to 0.0087 kg/s leads to a decrease in the absorber plate exergy destruction rate to a minimum value of 575.74 W/m2 and to an increase in the exergy efficiency to a maximum value of 21.97%. When the inlet fluid temperature increases from 20 to 50 °C, the absorber plate exergy destruction rate reduces from 676.66 to 438.40 W/m2 resulting in a significant increase in the collector exergy efficiency from 6.80 to 37.86%. The optimum operating condition was found to be 37 °C for the inlet fluid temperature, 0.0087 kg/s for mass flow rate and fifteen for the number of tubes.