Performance enhancement of parabolic trough collectors via a novel multi-blade ninja star turbulator: Thermal and economic–environmental insights

This study introduces a novel Multi-Blade Ninja Star (MBNJ) turbulator as a dual-action enhancement device that simultaneously promotes radial flow and swirl inside the absorber tube of parabolic trough solar collectors (PTSCs). A three‑dimensional steady‑state numerical model based on the finite‑volume method and the RNG k − ε turbulence model is developed to evaluate the thermo‑hydraulic, economic, and environmental performance of the system. The effects of three geometric parameters are investigated, including blade count (2–5), bending angle (0–50°), and rectangular opening area (0.5 × 1.5 to 0.5 × 2.5 mm 2 ). The results reveal that the baseline 2‑blade configuration (without bending or openings) provides the strongest heat‑transfer enhancement, increasing the Nusselt number by up to 135 % compared with a smooth tube. This improvement translates into the best economic and environmental outcomes, with the lowest levelized cost of energy (0.022 $/kWh), the shortest payback period (1.45 years), and the largest CO 2 reduction (66.5 tons). However, due to the associated friction penalty, its thermal enhancement factor (TEF) remains below unity, indicating an unfavorable thermo‑hydraulic balance. When both heat‑transfer enhancement and pressure‑drop penalties are considered simultaneously, the configuration with five blades, a 40° bending angle, and a 0.5 × 2.5 mm 2 opening yields the highest TEF (1.36), representing the most balanced thermo‑hydraulic performance.