Parametric Design and Performance Evaluation of a Streamlined Dual-Outlet Main Duct for Industrial Pre-Drying Systems

A streamlined dual-outlet main air duct was developed for industrial open-width pre-drying systems operating under a “single-duct–multiple-spray-box” configuration, where stringent airflow uniformity is required. Conventional multi-segment linear-bending ducts introduce abrupt geometric transitions, leading to flow separation, vortex formation, and excessive mechanical energy loss. To overcome these limitations, a fully streamlined duct geometry was constructed using Non-Uniform Rational B-Spline (NURBS)-based parametric modeling to ensure smooth curvature continuity and controllable geometric gradients. The aerodynamic performance was evaluated through CFD simulations and experimentally validated on a slide-rail test platform. Results show that the optimized duct reduces turbulent kinetic energy by 22.8% and mechanical energy loss by 38%, indicating improved flow stability and reduced turbulence intensity. In addition, the statistical deviation indices of outlet velocity and pressure decreased by 47.82% and 27.95%, respectively. indicating enhanced flow uniformity. A composite posterior performance index decreased by 25.9%, demonstrating improved coordination between flow organization and thermal distribution. The optimized duct has been successfully implemented in an industrial production line, confirming its engineering feasibility for improving energy efficiency and process stability.