SevenStar D07 Series - Conversion Factors Introduction

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9.2 Conversion Factors Instruction
MFC and MFM are standard calibrated by N
2
while it’s out of factory. Other gas calibrations can be
approximated by converting of conversion factors of our instruction. While using other gas operating:
One single gas: The conversion factors could find out in the users specification instruction.
A mixture of two or more gases: Assume there is “n” sorts of gases, could calculate the conversion factors C by
the following formula:
Basic Formula： C=0.3106 N /ρ(Cp)
ρ — Density of the gas
Cp — Specific heat of the gas
N — Structure factors of gas-molecule (See Table 5.)
Table 5. Gas-Molecule Composing factors
COMPOSITION EXAMPLE N VALUE
Single atom numerator Ar He 1.01
Double atom numerator CO N
2
1.00
Tree atom numerator CO
2
NO
2
0.94
Multi-atom numerator NH
3
C
4
H
8
0.88
For mixture gases： N =N1 (ω1/ωT )+N2 (ω2/ωT ) + ··· + Nn (ωn/ωT )
Then：
0.3106 [N1 (ω1/ωT) + N2 (ω2/ωT) + ··· + Nn (ωn/ωT)]
C = ————————————————————————
ρ1Cp1 (ω1/ωT )+ ρ2Cp2 (ω2/ωT )+ ··· + ρnCpn (ωn/ωT)
ω
1
…ω
n
— The flow of single gas
ω
T
— The flow of mixture gas
ρ
1
…ρ
n
— The density of single gas
CP
1
…CP
n
—Specific heat of the single gas
N
1
…N
n
—Structure factors of gas-molecule (See Table 5.)
Attention :
1） Standard：Temperature 273.15K (0 ºC ); Air Pressure— 101325 Pa (760mm Hg)
2） Please feel free to contact us if the request gas conversion factors could not be found in our
appendix.