Delta-T Company

Instruments for research and development in flow measurement.

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Flow Equations for ASME Type Gas Flow Nozzles

Picture of Nozzle (Adopted from "Fluid Meters - Their Theory and Application")

To compute mass flow rate (lb/sec) using the precision air flow nozzle (ASME long-radius flow nozzle, Beta <= 0.5, where Beta is defined as throat diameter to duct diameter)

 	D, upstream pipe diameter, in
   	d, nozzle throat diameter, in
	p1, upstream static pressure, lb/in2
	δp, differential pressure (p1 - p2), in H2O
	T1, upstream gas temperature, deg F

Inputs required are the type of gas (air, CO2, H2, etc.), the upstream static temperature, upstream static pressure and the differential pressure. The procedure incorporates real gas effects (variation of gas viscosity with temperature, boundary layer, etc.), determines whether the flow is choked or subsonic and computes the exit velocity, the volumetric flow rate and the mass flow rate.

For flow computation, written in BASIC and running under MS-DOS, go to software.