Orifice, Nozzle, and Venturi Flow Meters: Principles, Calculations & Data

Flow meter calculations based on Bernoulli and Continuity equations for orifice plates, venturi meters, and nozzles. Includes discharge coefficients, mass flow calculations, and performance comparisons.

Meter Type	Discharge Coeff (cd)	Rangeability	Pressure Loss	Accuracy	Upstream Pipe Length	Viscosity Effect	Relative Cost
Orifice Plate	0.60	4:1	Medium	2-4% FS	10-30D	High	Low
Venturi Meter	0.975	4:1	Low	1% FR	5-20D	High	Medium
Nozzle (ISA 1932)	0.95-0.995	4:1	Medium	1-2% FR	10-30D	High	Medium

Diameter Ratio (d)	Re=10⁴	Re=10⁵	Re=10⁶	Re=10⁷
0.2	0.60	0.595	0.594	0.594
0.4	0.61	0.603	0.598	0.598
0.5	0.62	0.608	0.603	0.603
0.6	0.63	0.61	0.608	0.608
0.7	0.64	0.614	0.609	0.609

Orifice Diameter (mm)	Kv (m³/h)
0.8	0.02
1.2	0.05
1.6	0.08
2.4	0.17
3.2	0.26
3.6	0.31
4.8	0.45
6.4	0.60
8	1.5
9	1.7
13	3
16	4
18	4.5
19	6.5
25	11
32	15
38	22
51	41
64	51
76	86
80	99
100	150
125	264
150	383

Calculator

Inputs

Discharge Coefficient (cd)

Orifice/Meter Diameter (m) (m)

Pipe Diameter (m) (m)

Upstream Pressure (Pa) (Pa)

Downstream Pressure (Pa) (Pa)

Fluid Density (kg/m³) (kg/m³)

Results

Diameter Ratio (d)--

Upstream Area (m²)-- m²

Meter Area (m²)-- m²

Pressure Difference (Pa)-- Pa

Mass Flow (kg/s)-- kg/s

Volume Flow (m³/s)-- m³/s