Numerical Investigation on the Effect of Elliptical Dimple Vortex Generator’s Attack Angle on Heat Transfer in Parabolic Trough Solar Collectors

为提升抛物面槽式太阳能集热器吸收管的传热性能，本文通过数值模拟研究了椭球丁胞攻角对湍流状态下导热油(Syltherm-800)传热与流动特性的影响。基于Realizable k-ε湍流模型和非均匀热流边界条件，分析了不同雷诺数(Re = 10000~50000)下丁胞结构的流场扰动、温度分布、努塞尔数(Nu)、摩擦系数(f)及综合性能因子(PEC)的变化规律。结果表明：丁胞攻角的增大会显著增强流体换热效果，其中α = 90˚时Nu最大，较光管提升38.8%~83.5%，显著缓解了局部过热问题，但伴随较高的压降，f增加156.4%~89.7%。本研究为抛物面槽式集热器吸热管的被动强化传热设计提供了理论依据。To enhance the thermal performance of the absorber tube in parabolic trough solar collectors, this study numerically investigates the influence of ellipsoidal dimple attack angles on the heat transfer and flow characteristics of thermal oil (Syltherm-800) under turbulent conditions. Based on the Realizable k-ε turbulence model and non-uniform heat flux boundary conditions, the variations in flow field disturbance, temperature distribution, Nusselt number (Nu), friction factor (f), and thermal performance factor (PEC) were analyzed at different Reynolds numbers (Re = 10,000~50,000). The results demonstrate that increasing the dimple attack angle significantly enhances fluid heat transfer, with the maximum Nu achieved at α = 90˚, showing an improvement of 38.8%~83.5% compared to the smooth tube, while the solid-domain temperature difference decreases by 18.5~97.7 K, effectively mitigating local hot spots. However, this configuration incurs a higher pressure drop, with f increasing by 156.4%~89.7%. This study provides a theoretical foundation for the passive heat transfer enhancement design of absorber tubes in parabolic trough collectors.