Pressure Loss Measurements in Typical Flexible and Sheet Metal Light-Commercial Duct Systems

摘要

Tests were performed to measure pressure losses in light-commercial duct systems comprised of wire-wound flexible duct and rigid sheet metal duct. The tests determined the pressure loss associated with various lengths of flexible duct used in multi-branch systems. ASHRAE Handbook guidelines recommend a maximum 6 ft (1.83 m) length of flexible duct for commercial applications. The total pressure loss penalty for a system that utilized 11 ft (3.35 m) of flexible duct branches connected to diffusers was 3%, compared to a duct system meeting this recommendation. A system using complete lengths of properly sized flexible duct yielded a total pressure loss that was 22% less than a multi-branch system which conformed to prevailing requirements. Regarding the measured flow imbalance in the branches, systems that used flexible duct branch lengths greater than the existing limit of 6 ft (1.83 m) exhibited negligible adverse effects.