Pressure losses in heating, ventilation, and air-conditioning (HVAC) duct elbows significantly increase fan power requirements and reduce overall system efficiency. This study presents a comprehensive computational fluid dynamics (CFD) investigation aimed at identifying effective strategies for reducing pressure losses in 90° HVAC duct elbows. The numerical methodology was first validated against published experimental measurements, demonstrating excellent agreement and providing confidence in the predictive capability of the CFD model. The validated model was then employed to evaluate the influence of duct geometry, inlet velocity, guide vane configuration, inter-vane spacing, perforated guide vanes, and duct material roughness on aerodynamic performance using the SST k–ω turbulence model. The results show that round elbows reduce pressure losses by approximately 50% compared with hydraulically equivalent rectangular elbows, highlighting the strong influence of duct geometry on flow separation. Among the flow-control strategies investigated, curved guide vanes produced the greatest improvement, with an optimized three-vane arrangement and a non-dimensional spacing of s/Dh≈0.15 (corresponding to 150 mm for the specific geometry tested) reducing pressure losses by approximately 31% relative to the baseline elbow without guide vanes. In contrast, the investigated perforated guide vane provided only marginal improvement, indicating that its geometry requires further optimization to minimize blockage and mixing losses. The material roughness study showed that smooth, rigid duct materials produced only minor differences in pressure loss, whereas flexible ducts generated noticeably higher losses because of their increased surface roughness. These findings demonstrate that optimizing elbow geometry and guide vane design is considerably more effective than modifying duct material or using the investigated perforated vane configuration. The study provides practical design recommendations for improving the aerodynamic performance and energy efficiency of HVAC duct systems.
Fouad et al. (2026) studied this question.