Duct Velocity Pressure
Air velocity from velocity pressure or the inverse via V = 4005 x sqrt(VP) for standard air. Per ACCA Manual D / ASHRAE Fundamentals.
Formula and source
V = 4005 * sqrt(VP) and VP = (V / 4005)^2, for standard air (0.075 lb/ft^3 at sea level, 70 F). The 4005 constant embeds the standard-air density; at altitude or elevated temperature a density correction applies.
ACCA Manual D / ASHRAE Fundamentals duct-design velocity-pressure relation, by name.
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