Air Ducts Friction Loss Diagram

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Friction loss (head loss) in standard air ducts are indicated in the diagram below:

The diagram is based on standard air 0.075 lb/ft³ in clean round galvanized metal ducts.

• 1 inch water = 248.8 N/m² (Pa)= 0.0361 lb/in² (psi) = 25.4 kg/m² = 0.0739 in mercury
• 1 ft³/min (cfm) = 1.7 m³/h = 0.47 l/s
• 1 ft/min = 5.08x10^-3 m/s
• 1 inch = 25.4 mm = 2.54 cm = 0.0254 m = 0.08333 ft

Example - Friction Loss in Air Duct

The friction loss in a 20 inches duct with air flow 4000 cfm can be estimated to approximately 0.23 inches water per 100 feet duct as shown in the diagram below. The air velocity can be estimated to approximately 1850 feet per minute.

Related Mobile Apps from The Engineering ToolBox

• Air Duct Flow App
• Air Duct Velocity App
• Air Duct Head Loss App 

- free apps for offline use on mobile devices

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Related Topics

• Ventilation - Systems for ventilation and air handling - air change rates, ducts and pressure drops, charts and diagrams and more

Related Documents

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