TLV EF200F-C, Инструкция по эксплуатации

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EF200F-C Technical data
147
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 5
000, periodic vortices are no longer generated and flow rate
measurement is no longer possible.
The Reynolds number is calculated as follows:
A0034291
Re Reynolds number
Q Flow
D
i
Internal diameter of measuring tube (corresponds to dimension K)
µ Dynamic viscosity
ρ Density
The Reynolds number, 5000 together with the density and viscosity of the fluid and the
nominal diameter, is used to calculate the corresponding flow rate.
A0034302
Q
Re = 5000
Flow rate is dependent on the Reynolds number
D
i
Internal diameter of measuring tube (corresponds to dimension K)
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).
The lowest flow velocity that can be measured on account of the signal amplitude v
AmpMin
is derived from the Sensitivity parameter and the steam quality (x) or from the force of
vibrations present (a).
Re
=
4 · Q [m³/s] · ρ[kg/m³]
· D [m] · µ [Pa · s] π
i
Re
=
4 · Q [ft³/s]· ρ[lbm/ft³]
· D [ft] · µ [lbf · s/ ft²] π
i
Q [m /h] =
Re = 5000
³ · 3600 [s/h]
4· ρ [kg/m³]
Q [ /h] =
Re = 5000
³ · 60 [s/min]
4· ρ [lbm/ ³]
5000· π · D
i
[m] · μ · [Pa·s]
5000· π · D
i
[ft] · μ · [lbf·s/ft
2
]