Flow Nozzle Flow Calculator
Calculate flow through an ISA 1932 or long radius flow nozzle from its differential pressure. The discharge coefficient follows ISO 5167-3 and is iterated with the Reynolds number; gases include the expansibility factor.
- β = d ÷ D = 0.6000
- C from the ISO 5167-3 equation, iterated with ReD = 392,400: C = 0.9615
- qm = C ÷ √(1 − β⁴) × ε × π/4 × d² × √(2ΔPρ) = 46.317 kg/s
Flow Nozzle Equations
ISA 1932: C = 0.9900 − 0.2262β4.1 − (0.00175β² − 0.0033β4.15) × (10⁶/ReD)1.15
Long radius: C = 0.9965 − 0.00653 × β0.5 × (10⁶/ReD)0.5
d is the throat diameter, D the pipe inside diameter, β = d/D, ΔP the differential pressure, ρ1 the upstream density and ReD the pipe Reynolds number. ε is 1 for liquids; for gases it uses the same expansibility equation as the venturi in ISO 5167.
Worked example
Water (998.2 kg/m³, 1.002 cP) through an ISA 1932 nozzle, D = 150 mm, d = 90 mm (β = 0.6), at 250 mbar: C = 0.9615 and qm ≈ 166,700 kg/h (167 m³/h) at ReD ≈ 392,000.
Frequently Asked Questions
Where are flow nozzles used?
Mostly on high pressure steam and boiler feedwater, and for high velocity gas, where an orifice edge would erode.
What is the difference between ISA 1932 and long radius nozzles?
The ISA 1932 nozzle has a short curved inlet with corner taps; the long radius nozzle has an elliptical inlet and uses 1D and ½D taps. Their discharge coefficients follow different equations.
How much pressure does a nozzle lose?
More than a venturi but slightly less than an orifice of the same β, because there is no diffuser to recover pressure.
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