What losses are caused by changes to air movement and turbulence?

What losses are caused by changes to air movement and turbulence?

• A. Friction Losses
• B. Contractions
• C. Dynamic Losses
• D. Dilution Ventilation

Answer: (C)

When air flow is redirected, accelerated, or decelerated by bends, fittings, expansions, contractions, or obstacles, part of the flow’s energy is lost to turbulence and changes in velocity. This creates pressure drops beyond what straight-length friction would produce. That type of loss is called dynamic losses (often referred to as minor losses) because they arise from changes in air movement and turbulence rather than from friction along a long duct. They’re typically expressed with a loss coefficient so the pressure drop scales with the velocity head, ΔP = K (ρ V^2 / 2). This distinguishes them from friction losses, which come from viscous friction along duct walls over length. Dilution ventilation is a design objective, not a loss type. Contractions are one feature that can cause dynamic losses, but the broader concept encompasses all changes in flow that generate turbulence and momentum changes.

When air flow is redirected, accelerated, or decelerated by bends, fittings, expansions, contractions, or obstacles, part of the flow’s energy is lost to turbulence and changes in velocity. This creates pressure drops beyond what straight-length friction would produce. That type of loss is called dynamic losses (often referred to as minor losses) because they arise from changes in air movement and turbulence rather than from friction along a long duct. They’re typically expressed with a loss coefficient so the pressure drop scales with the velocity head, ΔP = K (ρ V^2 / 2). This distinguishes them from friction losses, which come from viscous friction along duct walls over length. Dilution ventilation is a design objective, not a loss type. Contractions are one feature that can cause dynamic losses, but the broader concept encompasses all changes in flow that generate turbulence and momentum changes.