Friction Loss - Temperature and Pressure

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Most of the friction loss diagrams and tables available for air ducts are estimated for air at Normal Temperature and Pressure - NTP - conditions (20^oC and 1 bar).

Temperature

If the actual temperature condition is otherwise the  friction loss can be compensated like

Δp = k_t Δp_NTP         (1)

where

Δp = actual friction loss (pressure or head)

k_t = temperature compensating coefficient

Δp_NTP = friction loss at NTP conditions (pressure or head)

The temperature compensating coefficient can be estimated with the diagram below:

Pressure

If the actual pressure is otherwise the  friction loss can be compensated like

Δp = k_p Δp_NTP         (2)

where

Δp = actual friction loss (pressure or head)

k_p = pressure compensating coefficient

Δp_NTP = friction loss at NTP conditions (pressure or head)

The pressure compensating coefficient can be estimated with the diagram below:

• 1000 mbar = 1 bar = 10⁵ Pa (N/m²) = 0.1 N/mm² = 10,197 kp/m² = 10.20 m H₂O = 0.9869 atm = 14.50 psi (lb_f/in²) = 10⁶ dyn/cm² = 750 mmHg

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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

• Air Ducts Friction Loss Diagram - Major loss diagram air ducts - SI units
• D'Arcy-Weisbach Equation for Pressure and Head Loss - The D'Arcy-Weisbach formula can be used to calculate pressure or head loss due to friction in ducts, pipes and tubes
• STP - Standard Temperature and Pressure & NTP - Normal Temperature and Pressure - The definition of STP - Standard Temperature and Pressure and NTP - Normal Temperature and Pressure