Furness controls FCO432, Руководство пользователя

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Page 28 FCO432 Users Guide Issue 1
Laminar Flow Element Calculation
Calculation of Flow from

P:
gas lfe
std
std
lfe
fs
fs std
r T
T
P
P
P
P
Q Q

1
  


 
Calculation of

P from Flow:
gas
std
lfe
lfe
std
fs
fs
std
r
T
T
P
P
Q
P
Q P

  

  
Where:
std
Q
Volumetric flow rate (flow at standard temperature and pressure) in l/m
fs
Q
Orifice full scale flow in l/min
P

Differential pressure in pascals
fs
P

Orifice full scale differential pressure in pascals
lfe
P
Absolute pressure at the laminar flow element in pascals
std
P
Standard pressure in pascals (normally 101325 pascals).
std
T
Standard temperature in kelvin (273.14 + temperature in °C).
lfe
T
Temperature of gas in laminar flow element in kelvin (273.14 + temperature in °C).
gas
r

Relative viscosity of gas at the operating temperature. This is calculated from the
relative viscosity at 20°C using the following calculation:
 
C
T r
r r
lfe
gas
14 . 293
20
20
 
 

 
Where:
20
r

Relative viscosity of the gas at 20°C (air = 1).
C
= 385. This is a correction factor to approximate tabulated data on viscosity changes with
temperature.
If a measure of mass flow rate is required, refer to the mass flow calculation at the end of the Pitot
Tube Calculation section.