Yokogawa EJX115A - Manual (Page 28)

<5. Parameter Setting>
5-8
IM 01C25T04-01EN
Table 5.3 Symbols
# Symbol Description
1 Nc Unit convert factor
2 Kfactor Basic flow Calculation factor
3 C Discharge Coefficient
4 ε Expansion Factor
5 β Diameter Ratio
6 d Diameter of orifice
7 ρb Base Density on Tb, SPb Condition
8 ρnorm Density on Normal, Standard condition
Example 1: Calculation of Nc
(1) When flow unit is changed.
Nc= (Kg/s) /(Mass Flow unit in use)
Table 5.4 Example of Calculated Nc by Flow Unit
Flow unit Calculation of Nc Nc
kg/s (kg/s) / (kg/s) = (1kg/1s) / (1kg/1s) 1
kg/h (kg/s) / (kg/h) = (1kg/1s) / (1kg/3600s) 3600
lb/s (kg/s) / (lb/s) = (1kg/1s) / (0.4535924kg/1s) 2.204623
lb/h (kg/s) / (lb/h) = (1kg/1s) / (0.4535924kg/3600s) 7936.648
(2) When differential pressure unit is changed.
Nc = (Differential pressure unit)/(Pa)
Table 5.5 Example of Calculated Nc by Differential Pressure Unit
T0502.ai
∆p unit
inH2O@68degF / Pa = 248.6406Pa / 1Pa
Calculation of Nc
248.6406 = 15.76834
Nc
Pa
kPa
inH2O@68degF (Pa) / (Pa) = (1Pa) / (1Pa)
kPa/Pa = 1000Pa / 1Pa 1 = 1
1000 = 31.62278
(3) When both flow unit and differential pressure unit are changed.
Nc =(Kg/s)/(Mass Flow unit of use) × (Differential pressure unit of use)/(Pa)
Example 2: Calculation of Kfactor
Qm unit = kg/s, Differential pressure unit = kPa
Kfactor = /4 × Nc × C/ 1− β 4 × ε × d 2 × 2Чρb
= 0.7853982 Ч 31.62278 Ч 0.6043 / 1−0.1296 Ч 0.984 Ч 0.03162 2 Ч 2Ч1.250380
= 0.02502868
0.02503