The parabolic trough collector remains one of the most extensively deployed technologies for concentrating solar power and heating. Enhancing the thermal performance of the receiver tube, which is its core component, is critical for improving overall system efficiency. Longitudinal fins represent a simple and cost-effective method for augmenting heat transfer within the receiver. However, due to the inherently non-uniform heat flux distribution along the receiver surface, the positioning of these fins significantly influences thermal performance, but this aspect has not been thoroughly explored in the literature. This study systematically investigates the effects of the location, as well as height and number of fins, and clarifies the distinct roles of fins positioned on the different halves of the receiver tube. Furthermore, a novel performance evaluation metric is proposed, offering a more representative basis for comparison than the conventional approach commonly adopted in the literature. Computational fluid dynamics simulations are employed to assess the thermal performance of receivers equipped with rectangular-profile fins across a range of Reynolds numbers from 20,000 to 60,000. The numerical model is validated against experimental data from the literature. Results from configurations with 2, 4, 6, and 8 fins reveal that optimal thermal management is achieved by placing shorter fins in regions of higher heat flux and longer fins in areas of lower heat flux. The most effective configuration yields a 45.6% enhancement in the overall Nusselt number and an 18.0% reduction in heat losses compared to a smooth receiver. These findings offer valuable insights for the design of more efficient parabolic trough receivers, contributing to improved thermal performance and reduced risk of tube deformation and failure in linear collectors.
