Improvement of the thermal performances of a parabolic trough solar concentrator with concentric receiver tube and nanofluid

Parabolic trough solar concentrators (PTCs) encounter significant challenges arising from Non-Uniform Heat Flux (NUHF) around the receiver, which causes local overheating and pronounced circumferential temperature gradients.This study proposes the solution to this problem by uniforming the heat flux distribution, minimizing the temperature gradient, and improving performance.A numerical analysis is carried out on a novel small-scale PTC model featuring a concentric absorber tube design.The study compares the heat recovery performance of conventional, concentric, and eccentric absorber configurations using two heat transfer fluids enhanced with nanofluids: water and Syltherm-800 oil.A three-dimensional simulation model was presented by coupling Monte Carlo Ray-Tracing (MCRT) with (CFD) in ANSYS Fluent to predict the thermo-hydraulic response of parabolic trough receivers.Furthermore, Particular attention is given to the effects of Particular attention is given to the effects of critical operational factors, namely inlet fluid temperature, mass flow rate, and nanofluid concentration on heat transfer and overall efficiency.The results confirm that the concentric parabolic trough receiver (PTR) operates with lower peak wall temperatures and smaller circumferential thermal gradients, which lessen thermal stresses and supports higher overall efficiency.When compared to the reference design, the concentric and eccentric receiver tube configurations lower the absorber tube's temperature gradient by roughly 45% and 60.6%, respectively.These new configuration enhance heat collecting efficiency by up to 2.62% and 3.26% relative to the smoothe PTC tube.Moreover, the use of nanofluids added significant enhancements of efficiency, by 6.12% and 8.23% for the concentric and eccentric