Computational Investigation of Aerodynamic Performance Improvement in Low-Speed Axial Flow Fans Used in Industrial Ventilation Systems in Nigerian Manufacturing Plants

Axial flow fans are ubiquitous in industrial ventilation systems across Nigerian manufacturing facilities, yet their energy performance is frequently compromised by blade profile deterioration, incorrect operating point selection, and suboptimal inlet and outlet duct configurations, resulting in excessive electrical energy consumption for delivered airflow. This study presents a computational fluid dynamics investigation of aerodynamic performance characteristics and improvement opportunities for low-speed axial flow fans installed in representative manufacturing plant ventilation systems, with reference to installations in Ogun and Oyo State factories. Fan geometry was modelled using reverse engineering measurements of a commonly used industrial fan type, and three-dimensional CFD simulations were conducted in ANSYS CFX using the shear stress transport k-omega turbulence model. Parametric studies evaluated the effects of blade pitch angle variation from 20 to 35 degrees, blade profile modification from flat-plate to NACA 4412 aerofoil cross-section, and inlet bellmouth geometry on fan total pressure rise, flow coefficient, and overall efficiency across the operating range. Results showed that substituting NACA 4412 aerofoil blades for flat-plate blades improved peak fan efficiency by 11.8 percentage points at the design flow coefficient. Blade pitch angle optimisation shifted the peak efficiency point to align with the actual duty condition, eliminating a 22 percent efficiency penalty attributable to off-design operation. Inlet bellmouth installation improved fan static efficiency by a further 4.1 percentage points at design flow. Combined modifications projected annual electricity savings of approximately 24 percent for a representative 15-kilowatt fan installation. Keywords: axial flow fan, CFD, aerodynamic optimisation, blade profile, industrial ventilation.