EF200W-C
8
Flow velocity
D
i
v,Q
A0033469
D
i
Internal diameter of measuring tube (corresponds to dimension K→ See page 34)
v
Velocity in mating pipe
Q
Flow
The internal diameter of measuring tube D
i
is denoted in the dimensions as dimension
K.→ See page 34.
Calculation of flow velocity:
v [m/s] =
³
]
h
/
m
[
Q
·
4
π
· D [m]
i
²
·
1
3600 [s/h]
v [ /s] =
4 · Q [
/min]
ft³
π
· D [ft]
i
²
·
1
60 [s/min]
A0034301
Lower range value
A restriction applies to the lower range value due to the turbulent flow profile, which only occurs
with Reynolds numbers greater than 5
000. The Reynolds number is dimensionless and indicates the
ratio of the inertia force of a fluid to its viscous force when flowing and is used as a characteristic
variable for pipe flows. In the case of pipe flows with Reynolds numbers less than 5
000, periodic
vortices are no longer generated and flow rate measurement is no longer possible.
The Reynolds number is calculated as follows:
Re
=
4 · Q [m³/s] · [kg/m³]
ρ
· D [m] · µ [Pa · s]
π
i
Re
=
4 · Q [ft³/s] · [lbm/ft³]
ρ
· D [ft] · µ [lbf · s/ft ]
π
i
²
A0034291
Re
Reynolds number
Q
Flow
D
i
Internal diameter of measuring tube (corresponds to dimension K→ See page 34)
µ
Dynamic viscosity
ρ
Density
The Reynolds number, 5
000 together with the density and viscosity of the fluid and the nominal
diameter, is used to calculate the corresponding flow rate.
