Exploration and enhancement of the thermal properties of heat transfer fluids used in solar collectors

Abstract This study investigates the thermal performance enhancement of parabolic trough collectors (PTCs) through nanoparticle-enriched Syltherm 800, addressing the critical yet underexplored challenge of achieving uniform heat distribution in solar thermal systems. Computational fluid dynamics (CFD) simulations using ANSYS Fluent and ray-tracing analysis with Tonatiuh were conducted under 968.2 W m −2 irradiance to evaluate CuO, Fe₃O₄, and MWCNTs nanoparticles at a 5% concentration. Among the tested nanoparticles, CuO exhibited the highest enhancement, increasing volumetric specific heat capacity by 8%, compared to 7.6% for Fe₃O₄ and 1.5% for MWCNTs. Thermal efficiency improved from 70.73 to 80.70%, representing a 14.1% gain, with Fe₃O₄ and MWCNTs achieving increases in 13.6% and 12.5%, respectively. Additionally, CuO uniquely reduced absorber tube temperature gradients by 4.2% at the bottom surface, surpassing reductions of 3.2% for Fe₃O₄ and 0.4% for MWCNTs, effectively mitigating thermal stress beyond conventional efficiency-focused improvements. These findings highlight CuO’s superior potential in enhancing specific heat capacity, improving thermal efficiency, and minimizing temperature gradients, offering a promising approach to optimizing PTC performance.