Modelling of Energy and Exergy Analysis for a Double-Pass Solar Air Heater System

Energy is conserved in every device and in every action we are doing. The energy itself cannot be abandoned nor destroyed. However, energy conservation alone by using the first law of thermodynamics is insufficient in order to depict the internal losses for maximizing energy usage. Nevertheless, the second law analysis, exergy, provides important information about the optimum conditions and sources of inefficiencies together with their values and locations. The purpose of this study was to perform an exergy analysis of a solar air heater. The geometric and operation parameters including wind speed, solar radiation, collector area, ambient temperature and optical efficiency were considered as variables in this analysis. The focus was to determine the exergy efficiency of a double- pass solar air heater under forced flow condition by considering the affecting factors. The analysis was performed numerically using MATLAB simulation. Results of exergy efficiency were obtained and compared with the thermal efficiency of the solar air heater. It was found that exergy losses could be reduced by altering the variables until it reached the maximum efficiency. Solar collector area has been found to have the minimum effect on both thermal and exergy efficiencies, whereas incident solar radiation has the maximum effect. Values of 10% and 70% of exergy and energy efficiencies respectively have been obtained in the average solar radiation of about 4500 W/m 2 . Copyright © 2015

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