Thermal performance enhancement of elliptical absorbers in cylindrical-parabolic solar collectors: A CFD-Based comparative study

Abstract

In this research paper, the computational fluid dynamics (CFD) technique was implemented for analyzing and improving the thermal efficiency of a parabolic trough collector (PTC). The effect of the elliptical absorber geometry under turbulent flow and non-uniform heat flux was investigated numerically and compared with empirical correlations to verify the proposed method. Additionally, it was noted that the elliptical absorber tube design increased the Nusselt number (Nu) by 25 %, improving convective heat transfer compared with the conventional cylindrical absorber tube. Heat transfer performance increased by an additional 15 % using an HTF with 1 % aluminum oxide nanoparticles (Al₂O₃). Integrating the elliptical geometry with the nanofluids enhanced the overall thermal efficiency by 40 %. The thermal performance evaluation criterion (PEC) exceeded 20 %, confirming the design's suitability. The elliptical configuration reduced the absorber wall temperature by 10 %, resulting in a decrease in thermal stress and a corresponding increase in durability. However, there was a small effect on the pressure drop of 4.5 %. From the velocity field, it is evident that the fluid distribution is more uniform in the elliptical tube than in the circular tube, resulting in higher convective heat transfer coefficients. These findings validated that the elliptical absorber outperforms the circular design in thermal performance. When nanofluids are used in the elliptical absorber, the thermal performance is further improved, demonstrating the possibility of great potential in improving solar energy systems as a successful approach to increasing the efficiency of energy production for sustainable results.