Numerical investigation on enhancing the performance of a parabolic trough collector using a threaded absorber tube

The growing global demand for energy and heightened environmental concerns have elevated the importance of solar energy harvesting in recent years. Parabolic trough collectors (PTCs) are widely utilized for capturing direct solar radiation; however, conventional PTC efficiency is limited by low convection heat transfer rate in the absorber section, which is then delivered to heat transfer fluid (HTF). This study numerically investigates the use of a threaded tube as a fluid flow disruption technique to enhance heat transfer rate within the absorber, with Reynolds numbers ranging from 4000 to 10,000. Three key geometric parameters of the thread: pitch (300, 150 and 80 mm), depth (0.5, 1 and 1.5 mm) and width (10, 20 and 30 mm) are evaluated as surface modification variables, with results compared with those of a conventional PTC under identical working conditions. The study's comparative analysis shows that changing the depth of the thread has the most effect on overall performance and exergy efficency, while the effects of depth and width are comparatively lower. Overall, the thread's depth emerges as the most influential parameter, with PEC values reaching a maximum of 3.18 at Re = 6000, and remaining above 2.6 across all tested Reynolds numbers and parameter combinations.