Evaluation of a solar flat plate collector's performance using wavy riser tubes and coil inserts

Solar water heater systems are essential for harnessing renewable solar energy to produce domestic hot water, offering an eco-friendly alternative to traditional heating methods. Flat plate collectors (FPCs), commonly used in solar water heater systems, heavily rely on the effectiveness of the absorber surface to maximize solar energy absorption while minimizing thermal losses. The main aim of this study is to evaluate the performance of flat plate solar collectors. The performance parameters, including Nusselt number and collector efficiency, were examined at different mass flow rates of the working fluid. The assessment of flat plate solar collectors (FPSCs) was performed experimentally and through CFD analysis, utilizing wavy-shaped riser tubes with coil inserts. The experiments involved riser tubes with coil inserts of 10, 20, and 30 mm pitches, with Reynolds numbers ranging from 5500 to 14,500. Compared to plain tubes, the increase in Nusselt number with a 30 mm pitch is 15.38% and 34.48 % at Reynolds numbers of 5500 and 14,500, respectively. For a 10 mm pitch, the Nusselt number increases by 41.02 % and 49.4 % at the same Reynolds numbers. The collector’s efficiency reaches 84 % for a 10 mm pitch at a Reynolds number of 14,500, compared to a plain tube.