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Minor Loss Coefficients for Air Duct Components
Minor loss - pressure or head loss - coefficients for air duct distribution systems components
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Minor Loss - Head or Pressure Loss in Air Duct Components - can be expressed as
hminor_loss = ξ v2/ 2 g (1)
where
hminor_loss = minor head loss (m, ft)
v = flow velocity (m/s, ft/s)
g = acceleration of gravity (m/s2, ft/s2)
Minor loss can also be expressed as pressure loss instead of head loss.
Minor loss coefficients for different components common in air duct distribution systems
| Component or Fitting | Minor Loss Coefficient - ξ - |
| 90o bend, sharp | 1.3 |
| 90o bend, with vanes | 0.7 |
| 90o bend, rounded radius/diameter duct <1 | 0.5 |
| 90o bend, rounded radius/diameter duct >1 | 0.25 |
| 45o bend, sharp | 0.5 |
| 45o bend, rounded radius/diameter duct <1 | 0.2 |
| 45o bend, rounded radius/diameter duct >1 | 0.05 |
| T, flow to branch (applied to velocity in branch) | 0.3 |
| Flow from duct to room | 1.0 |
| Flow from room to duct | 0.35 |
| Reduction, tapered | 0 |
| Enlargement, abrupt (due to speed before reduction) (v1= velocity before enlargement and v2 = velocity after enlargement) | (1 - v2 / v1)2 |
| Enlargement, tapered angle < 8o (due to speed before reduction) (v1= velocity before enlargement and v2 = velocity after enlargement) | 0.15 (1 - v2 / v1)2 |
| Enlargement, tapered angle > 8o (due to speed before reduction) (v1= velocity before enlargement and v2 = velocity after enlargement) | (1 - v2 / v1)2 |
| Grilles, 0.7 ratio free area to total surface | 3 |
| Grilles, 0.6 ratio free area to total surface | 4 |
| Grilles, 0.5 ratio free area to total surface | 6 |
| Grilles, 0.4 ratio free area to total surface | 10 |
| Grilles, 0.3 ratio free area to total surface | 20 |
| Grilles, 0.2 ratio free area to total surface | 50 |
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Related Topics
- Fluid Mechanics - The study of fluids - liquids and gases. Involves various properties of the fluid, such as velocity, pressure, density and temperature, as functions of space and time.
- Ventilation - Systems for ventilation and air handling - air change rates, ducts and pressure drops, charts and diagrams and more
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