Heat Transfer Enhancement in a Parabolic Trough Solar Collector Using Inner Wall Fins and Nanofluids

In this study, two different absorber tube configurations were examined: a smooth absorber tube and an absorber tube with inner wall fins at the bottom. The study primarily focused on the effects of nanoparticle additives (Al2O3 and SiO2) to the base fluid, Syltherm 800. The nanoparticles were introduced at concentrations of 1, 2, 3, and 4% within a smooth tube. The study also explored their impact when introduced in a tube with inner wall fins at the bottom. The investigation centered on 2D heat transfers under turbulent flow conditions, with Reynolds numbers ranging from 6.104 to 15.104. The research uncovered several key observations. The incorporation of nanofluids resulted in a 4.90% increase in the Nusselt number for the smooth tube. Additionally, the friction factor experienced a 2.64% increase, and the Performance Evaluation Criteria (PEC) improved by 1.04. Interestingly, a combination of SiO2 with Syltherm 800 and the addition of fins exhibited even better performance, showcasing, 88.76% enhancement compared to individual nanofluids. This configuration led to a Nusselt number and PEC increase of 1.80, while the friction factor initially decreased by 9.10% at Reynolds numbers below 105, and subsequently increased by 16.73%.