Bronkhorst EX-FLOW Mass Flow User Manual
Page 10
BRONKHORST HIGH-TECH B.V.
However, as the accuracy of the factor also depends on viscosity, pressure and temperature, special
attention should be taken for gases in the gas/liquid state where specific heat, density, and viscosity can vary
tremendously. Apply to factory for more detailed information.
For gas mixtures a good approach is the following simplified equation:
1
1
1
2
2
C
V
C
V
C
V
C
mix
n
n
=
+
+
.....
C
mix
= Conversion factor for gasmixture
C
n
= Conversion factor for gas n
V
n
= Volumetric part of gas n in the mixture
Example: Gasmixture contains:
(1) 10%
N
2
C1 = 1.00
(2) 30% Ar
C2 = 1.40
(3) 50%
CH
4
C3 = 0.76
(4) 10% He
C4 = 1.41
1
C
0.10
1.000
0.30
1.40
0.50
0.76
0.10
1.41
1.043
mix
=
+
+
+
=
C
mix
= 0.959
When the original meter has been calibrated on 500
ml
n
/ min N
2
, 100% means:
500 ⋅
=
0.959
1.00
480
ml
n
/ min
mixture.
When the original meter has been calibrated on 500
ml
n
/ min
Argon, then 100% means:
500 ⋅
=
0.959
1.40
343
ml
n
/ min
gas mixture
1.5.1 Software for conversion factor calculation
Bronkhorst High-Tech B.V. gathered the physical properties of over 600 fluids in a database called
FLUIDAT
.
Application software, such as FLUIDAT
on the Net (FOTN), enable the user to calculate accurate
conversion factors, not only at 20°C/1 atm (as shown in the conversion table, App.1) but at any
temperature/pressure combination.
Apply to your distributor for more details of this software.
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