Orifice Flow Calculator
Q = Cd × A × √(2ΔP/ρ). Calculate flow rate, orifice diameter, or differential pressure for orifice plates.
Flow Rate
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m³/h
Flow (GPM)
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US gal/min
Velocity (orifice)
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m/s
Beta Ratio
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d/D
How this was calculated
Q = Cd × A × sqrt(2ΔP / ρ) where A = πd²/4 is the orifice area.
Beta ratio (β) = d/D. Typical range 0.2-0.75. Above 0.75, accuracy decreases.
Cd ~ 0.61 for a sharp-edged orifice (ISO 5167). Varies with beta ratio and Reynolds number.
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Orifice plates are the most common differential pressure flow measurement device in industrial applications. A thin plate with a precisely machined bore creates a pressure drop proportional to the square of the flow rate.
Key design considerations: beta ratio (0.2-0.75), straight pipe runs upstream (20D) and downstream (5D), and proper tap placement (flange, corner, or D-D/2 taps).
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