Energy and exergy analysis on performance of spiral solar collector: An experimental investigation

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Abstract
This study investigates the impacts of varying mass flowrate on thermal and exergetic performances of spiral solar collector during summer in Duhok, Iraq. Experimental data are collected in June and July under various mass flowrates, solar irradiance and environmental conditions. Analysis encompasses temperature distributions across system components, useful heat gain, heat loss coefficient, thermal efficiency, exergy destruction and exergy efficiency. Energy and exergy efficiencies are obtained by solving governing equations using MATLAB program. Findings indicated that the glass cover and absorber plate temperatures have positive relationships with solar irradiance reaching peaking values of 67.4°C and 86.2°C, respectively. Results indicated that the useful heat gain is steadily increased with mass flowrate achieving peak value of 341 W at 0.067 kgs −1 . Thermal efficiency of the system is found within a range from 60.1% to 66.3%, where the highest value occurred at 0.042 kgs −1 . Findings revealed that the exergy destruction varied from 388 W to 492.5 W, where this value decreases with increasing mass flowrate and reducing wind speeds. Exergy efficiency and second‐law performance metric are significantly improved from 5.4% at 0.025 kgs −1 to 20.5% at 0.067 kgs −1 . The overall heat loss coefficient is affected by environmental factors and hence, this value increases with increasing wind speed reaching peaking value of 5.36 Wm −2 K −1 at wind speed reached 1.2 m s −1 . Results demonstrated that spiral solar collector can affect the system performance across higher mass flow rates leading to improve the thermal output and exergy efficiency while reducing system irreversibilities.

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