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Feature
DESIGN CONSIDERATIONS AND GOOD ENGINEERING PRACTICES FOR AIR DISTRIBUTION Effective air distribution systems prioritise maintaining space conditions and minimising noise. Ducting can be manufactured to a wide range of sizes from 70mm x 70mm to 5000mm x
2000mm in South Africa.
Key design guidelines for optimisation include: Airflow control and stability: Designs must ensure proper airflow regulation and system stability
A fabric / textile installation in a large indoor sports facility.
• Site-specific design: Each design is unique to the site and its conditions, considering available space and aesthetics
• Efficient layouts: Trunk-and-branch configurations with shorter runs are generally best. Long, winding duct sections can lead to issues like collapse or blockages
• Minimise bends: Air naturally flows straight, and bends cause energy loss. While straight runs are cheaper, minimise turns to optimise airflow
• Correct sizing: Ducts must be appropriately sized; too small restricts airflow, while too large wastes energy and air
• Sufficient return ducts: Every conditioned room needs at least one return duct to circulate expended air back to the HVAC unit
• Thermal zoning: Consider dividing buildings into zones with similar heating / cooling needs for efficient control
• Air balancing: Crucial for even air distribution. Adjusting volume control dampers equalises friction losses, often required for both supply and return
• Operating pressure: Duct material thickness depends on operating pressure, dimensions, section length and branch requirements; lower pressure allows for weaker materials
• Connection types: Once material thickness is determined, select suitable flange connections and joining techniques
• Conflict avoidance: Account for other on-site services to prevent installation conflicts that could impact system performance, such as wet services hindering duct installation
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RACA Journal I July 2025 www. refrigerationandaircon. co. za