Design Advancement and Geometric Optimization of the Absorber Tube of a Parabolic Trough Collector for Enhanced Hydrothermal Performance

The hydrothermal performance of Parabolic Trough Collector (PTC) system is strongly governed by the absorber-tube design. This study numerically optimizes geometrical features of an absorber tube to enhance conjugate heat transfer to the Heat Transfer Fluid (HTF) while limiting hydraulic losses. Rectangular fins are installed inside the absorber tube, and a novel axial sectioning concept is introduced in which the tube is divided into three equal-length sections. Taking the first section as a reference, the second and third sections are rotated by a sectional angular shift (γ) in the clockwise and counterclockwise directions, respectively, to promote controlled flow redistribution. The geometric design factors fin height (H), circumferential fin placement angle (β), and sectional angular shift (γ) are varied at four levels. A Taguchi L16 orthogonal array is employed to efficiently sample the design space. Thermal efficiency (η th ) and the Performance Enhancement Coefficient (PEC) are used to assess thermal and hydrothermal performances, respectively. Response Surface Methodology (RSM), supported by ANOVA and Pareto analysis, is applied to identify optimal configurations and statistically significant parameters. The fin height is identified as the most significant parameter, enhancing thermal performance through enhanced surface area, followed by the angular parameters β and γ, which contribute to improved flow mixing and mitigating local hot spots. Maximum thermal efficiency (68.28%) occurs at γ = 30°, β = 45°, and H = 20 mm, while the highest PEC (1.25) is obtained for the same geometry except β = 60°, yielding a 22.54% heat-loss reduction over the smooth tube.