EF200R-C
10
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 5000. 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 5000, 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 41)
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.
Q
[m /h] =
Re = 5000
³
5000
[Pa
· · D [m] ·
· s]
i
π
μ
· 3600 [s/h]
4
[kg/m ]
·
³
ρ
Q
[ /h] =
Re = 5000
³
5000
[lbf
· · D [ft] ·
· s/ft ]
i
²
π
μ
· 60 [s/min]
4
[lbm/ ]
·
³
ρ
A0034302
Q
Re = 5000
Flow rate is dependent on the Reynolds number
D
i
Internal diameter of measuring tube (corresponds to dimension K→ See page 41)
µ
Dynamic viscosity
ρ
Density
The measuring signal must have a certain minimum signal amplitude so that the signals can be
evaluated without any errors. Using the nominal diameter, the corresponding flow can also be
derived from this amplitude. The minimum signal amplitude depends on the setting for the
sensitivity of the DSC sensor (s), the steam quality (x) and the force of the vibrations present (a). The
value mf corresponds to the lowest measurable flow velocity without vibration (no wet steam) at a
density of 1 kg/m
3
(0.0624 lbm/ft^3). The value mf can be set in the range from
6 to 20 m/s (1.8 to 6 ft/s) (factory setting 12 m/s (3.7 ft/s)) with the
Sensitivity
parameter (value
range 1 to 9, factory setting 5).
