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Flow-X─ Function Reference
4-233
Flow-X General functions - fxISO5167_VenturiNozzle
fxISO5167_VenturiNozzle
The function calculates the mass flow rate for Venturi Nozzle pressure differential flow devices
according to the ISO-5167 standard.
Compliance
ISO-5167 - 1991 Measurement of fluid flow by means of pressure differential devices, 1st edition, 1991
ISO-5167 Amd.1 : 1998(E)
ISO-5167 - 2003 Measurement of fluid flow by means of pressure differential devices inserted in
circular cross-section conduits running full, 2nd edition, 2003
Function
inputs Remark EU Default
Name Optional tag name, tag description and tag group
Differential
Pressure Differential pressure over the primary flow device
measured at the up- and downstream pressure tappings,
which need to be in the positions as specified in the
standard mbar 0
Pressure Upstream pressure value of the fluid at metering
conditions bar(a) 0
Temperature Down- or upstream temperature of the fluid at metering
conditions °C 0
Density Down or upstream density of the fluid at metering
conditions kg/m3 0
Dynamic
Viscosity Dynamic viscosity of the fluid Pa.s 0
Isentropic
Exponent
Also referred to as

(kappa). For an ideal gas this
coefficient is equal to the ratio of the specific heat
capacity at constant pressure to the specific heat at
constant volume. According to the ISO standard this ratio
may be used, when the real value is unknown.
0
Pipe Diameter Internal diameter of the pipe at reference temperature mm 0
Pipe Expansion
factor The thermal expansion coefficient of the pipe material 1/°C 0.0000108
Pipe Reference
temperature The reference temperature that corresponds to the 'Pipe
diameter' input value °C 20
Venturi Nozzle
Diameter Venturi Nozzle diameter at reference temperature mm 0
Venturi Nozzle
Expansion
factor The thermal expansion coefficient of the Venturi Nozzle
material 1/°C 0.0000163
Venturi Nozzle
Reference
Temperature The reference temperature that corresponds to the
'Venturi Nozzle diameter' input value °C 20
Pressure
Location 1 Input 'Pressure' represents the pressure at the
upstream pressure tapping (p
1
).
Since the absolute pressure is usually measured at
the upstream tapping this is the most common
setting.
- 1
2 Input 'Pressure' represents the pressure at the
downstream tapping (p
2
).
Temperature
Location 1 Input 'Temperature' represents the upstream
temperature (t
1
).
- 2
2 Input 'Temperature represents the temperature at
the downstream tapping (t
2
).
3 Input 'Temperature' represents the downstream
temperature at a location Where the pressure has