Elster Instromet 2000, Instruction Manual

Page: 34 / 136

Model 2000 Flow Computer Instruction Manual
2.0 GENERAL DESCRIPTION
Model 2000 issue 21 Page No
27
2.4.3. ORIFICE PLATE & VENTURI TUBE MEASUREMENT
The Model 2000 Flow Computer can calculate the Mass flow rate and totals using the method of measuring the differential
pressure across an orifice plate or a Venturi Tube. A number of different calculation methods can be selected and used,
these can be set in the main menu item EDIT or can be set-up using the Model 2000 configuration software. The various
options are as follows;-
In accordance with International standard ISO 5167-1 : 1997/2003 using the Reader Harris/Gallagher equation for
flange, corner or D & D/2 pipe tapings.
In accordance with International standard ISO 5167-1 : 1980 using the Stoltz equation for flange, corner or D & D/2
pipe tappings.
In accordance with International standard AGA3 1994 equations for flange pipe tappings.
In accordance with International standard AGA3 1965 equations for flange pipe tappings.
With a Preset Coefficient of discharge for Venturi applications.
In all cases the Model 2000 will calculate and display Coefficient of discharge, Beta ratio, Reynolds number, Expansion
factor for upstream or downstream tappings and other values used within the calculation of mass flow in accordance with the
equations and calculation methods as specified in the above standards. A facility is provided which gives the option to
calculate or pre-set the dynamic viscosity used within the calculation of Reynolds number. The options are selected using the
parameter Dynamic Viscosity eqn. on the Orifice set-up page and are:-
off No correction
Calc Calculated Dynamic Viscosity (See Equation).
) p 00375 . 0 99625 . 0 (
15 . 273 t
164
1
15 . 273 t
164
1
) 15 . 273 t (
15 . 273 t (
0
0
0 t , p
× + ×
+
+
+
+
×
+
+
µ = µ
Where
µ
0 : Reference dynamic viscosity at ref. temperature t0.
µ
p,t : Dynamic viscosity at flowing conditions.
t : Actual measured temperature in deg C.
t0 : Reference temperature for
µ
0 in deg C.
p : Actual measured pressure in BARA.
For applications where the measurement of Steam flow is required the Venturi Tube type of Model 2000 must be selected in
this case the equations used are for Classical Venturi as defined in International standard ISO 5167-1 : 1997. All
measurement inputs are as required for Orifice plate measurement. The only difference is that Look up tables for Steam
density are used instead of direct measurement.