Investigation of a star flow insert in a parabolic trough solar collector

The use of flow inserts is a common passive technique for enhancing the thermal performance of parabolic trough solar collectors. The objective of this work is to investigate a novel insert with a star shape. The shape of this insert is optimized by examining different combinations of its geometric characteristics. Totally 16 different cases are studied with the fin length to be varied from 15 mm to 30 mm and the fin thickness from 2 mm to 5 mm. The evaluation criteria of the examined cases are the thermal efficiency, the exergy efficiency and the overall efficiency of the solar collector. The exergy efficiency and the overall efficiency are suitable criteria for evaluation the Nusselt number increase with the simultaneous friction factor increase. The collector is examined for inlet temperatures between 400 K and 650 K with a volumetric flow rate equal to 150 L/min. According to the final results, the thermal efficiency, the exergy efficiency and the overall efficiency are increased for all the examined flow inserts. The thermal efficiency enhancement is higher with the inlet temperature increase and it can reach up to 1%. Moreover, it is found that greater dimensions of the insert lead to higher performance enhancements. The pressure drop is found to increases many times with the use of inserts but the pumping work value is extremely low in all the cases. The analysis is conducted with SolidWorks Simulation Studio with a validated model.