Experimental and CFD analysis of dimple tube parabolic trough solar water heater with various nanofluids

A solar collector is a device used to absorb energy from the sun by collecting solar radiation and turning it into electricity or heat. The material type and coating of a solar collector are utilized to enhance solar energy absorption. This research combines experimental and computational methods to examine the performance of a parabolic-type plate solar water heater (PTSWH). The nanoparticles-DI water at a rate of mass flow (MFR) of 0.5–3.0 kg/min in 0.5 kg/min increments were used in a tube-in-tube heat exchanger featuring dimpled inner tubes with a pressure-to-diameter (P/D) ratio of 3. The researchers examined the fluid flow patterns and heat transfer efficiency in a dimple texture tube using nanoparticles of TiO₂, Al₂O₃, CuO, and SiO₂ with a size range of 10–15 nm and a volume concentration (VC) of 0.1–0.5% in increments of 0.1%. Computational Fluid Dynamics (CFD) was used to explore and verify the impact of nanoparticle concentration on the PTSWH. It was revealed that CuO /DI-H₂O at a nanoparticles VC of 0.3% and a MFR of 2.5 kg/min yielded the best PTSWH performance. With a nanoparticle concentration of 0.3% and MFR of 2.5 kg/min, the efficiency of PTSWH was increased by approximately 34.3% for TiO₂, 32.3% for Al₂O₃, 38.4% for CuO, and 36.4% for SiO₂. The results also show that the solar water heater’s thermal efficiency rose steadily with the rise in MFR. At a MFR of 2.5 kg/min, Cu/DI-H₂O was found to have a higher Nusselt number than TiO₂/DI-H₂O, Al₂O₃/DI-H₂O, and SiO₂/DI-H₂O, respectively, by 10.5%, 8.2%, and 5%. TiO₂/DI-H₂O, Al₂O₃/DI-H₂O, Cu/DI-H₂O, and SiO₂/DI-H₂O nanoparticle-coated dimple texturing tubes all had lower friction coefficients than a plain tube did. Finally, a comparison was made between the experimental and simulated data, and the overall variation of ± 3.1% was found to be within an acceptable range.