Experimental study on the thermal performance of a flat plate solar water collector with a bifunctional flow insert

Abstract

A flat plate solar water collector is a simple solar energy conversion system for hot water production. In this experimental work, the effect of bifunctional rectangular cut flow deviator longitudinal flow inserts with a tilt angle of 30° fixed inside the absorber tube is studied with different water flow rates (0.0083, 0.0167, and 0.025 kg/s). The maximum instantaneous efficiency obtained is 72.93% at 0.025 kg/s, which is 23.6% higher than that of the conventional collector, and a lower mass flow rate results in better exergy efficiency of 3.3% at 0.0083 kg/s. The maximum instantaneous efficiency for a modified collector is observed when the outlet water temperature of 56.7 °C and the proposed flow inserts result in a maximum temperature difference of 10.5 °C between the water inlet and outlet points. The flow inserts serve as a turbulence promoter to enhance the heat transfer coefficient and the heat absorption rate of a conventional collector. The significant contribution of the flow inserts towards increasing the instantaneous efficiency of the collector confirms the bifunctionality with minimum pressure drop and pumping power. The enviro-economic analysis ensures a clean production, and solar collectors with passive inserts provide a lower payback period due to higher thermal energy output. The proposed collector's annual CO₂ mitigation and carbon credit are higher than the conventional collector, and such collectors are feasible for commercialization.