Optimizing heat transfer in solar air heater ducts through staggered arrangement of discrete V-ribs

This research paper details an experimental study on airflow dynamics in a solar air heater. The heater's design incorporates unique, discrete V-shaped ribs with staggered elements to enhance thermal performance. The study investigates the influence of various roughness parameters on flow characteristics. These parameters include a relative coarseness pitch (P/e) ratio of 12, a rib inclination angle (α) of 60°, a relative coarseness height (e/D_h) of 0.043, and a staggered element arrangement with a positioning ratio (p′/P) of 0.65. Additionally, the investigation includes scenarios with three gaps (N_g) between elements and a gap-to-rib width (g/e) ratio of 4. The research focuses on how changes to the Reynolds number, ranging from 3000 to 14,000, and alterations to the ratio of staggered element positioning to rib height (r/e), from 2 to 5, impact the flow dynamics. The outcomes indicate a significant boost in heat transfer performance, with the Nusselt number rising to 3.76 compared with a conventional smooth duct. The highest thermal efficiency recorded was 86%, at an r/e ratio of 3.5. These results underscore the potential of using discrete V-ribs with staggered elements in rectangular ducts to improve heat transfer efficiency.