Chapter Three: Overview The Gas Correction Factor (GCF)
37
Example
Calculate the GCF for a gas mixture of argon (gas 1) flowing at 150 sccm and nitrogen (gas 2)
flowing at 50 sccm, where:
Argon (Ar) Nitrogen (N
2
)
a
1
= 150 = 0.75 a
2
= 50=0.25
200 200
s
1
= 1.030 s
2
= 1.000
d
1
= 1.782 g/l d
2
= 1.250 g/l
cp
1
= 0.1244 cal/g ° Ccp
2
= 0.2485 cal/g ° C
then:
GCF
M
=
(0.3106) [(0.75)(1.030) + (0.25)(1.000)]
(0.75)(1.782)(0.1244) +(0.25)(1.250)(0.2485)
=
(0.3106) [(0.7725) + (0.25)]
(0.1663) + (0.0777)
=
(0.3106) (1.0225)
0.244
=
0.3176
0.244
GCF
M
= 1.302
How To Read Mass Flow at a Different Reference Temperature
The equations for calculating the GCF assume that the MFC was calibrated at a reference
temperature of 0° C (~273° K). If you want to read the mass flow as if the MFC was calibrated
at a different reference temperature, adjust the calculated GCF value using the following
equation:
Temperature Corrected
GCF
= GCF x
T
T
x
s
where:
T
x
= Reference temperature (° K)
T
s
= 273.15° K (~ equal to 0° C)
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