Study on resistance reduction in a jugular profiled bend based on entropy increase analysis and the field synergy principle

Ventilation and air conditioning duct systems have been widely studied for their extensive application, sophisticated duct system and significant resistance effect. The energy consumption of the fan in ventilation and air conditioning systems accounts for approximately 20%–40% of the total building energy consumption, which is equivalent to that of the cooling source. This paper proposes a novel low-resistance bend with a guide vane based on a jugular profile, and through the field synergy principle and the entropy increase principle, the bend internal flow state and the mechanism of resistance reduction are analyzed. The position and shape of the guide vane in the traditional bend are optimized by full-scale experiments and numerical simulations. The effects of resistance reduction for traditional bends and novel bends are compared with different aspect ratios and curvature radii. The results show that the local resistance coefficient of a bend with a tongue-shaped guide vane is significantly smaller than that of the traditional vane, and in the case of the curvature radii of the bend being equal, the resistance reduction effect is better when the aspect ratio of the bend is closer to 1.0. The resistance reduction of a bend with a tongue-shaped guide vane is as high as 31%. This paper provides guidance for the study of resistance reduction in local components of ventilation and air conditioning ducts with guide vanes.