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How do the flow conversion coefficients of different gases come from? How does the conversion factor of the mixed gas be calculated?

How do the flow conversion coefficients of different gases come from? How does the conversion factor of the mixed gas be calculated?
The flow conversion factor of a gas theoretically depends on the density and specific heat of the gas in the standard state, and the molecular composition of the gas. For the commonly used one-component gas, the conversion coefficient can be found in the manufacturer's product specification; if the density and specific heat of the gas are known, it can also be calculated by the following basic formula.
The basic formula of the gas mass flow conversion coefficient C:
C=0.3106 N /ρ(Cp)
Where: ρ - the density of the gas
CP - constant pressure specific heat for gas
N - The composition coefficient of the gas molecules (related to the composition of the gas molecules, see the following table)
Gas molecular composition coefficient table
Gas molecule composition Example N Value
Monoatomic Molecules Ar He 1.01
Diatomic Molecules CO N2 1.00
Triatomic molecules CO2 NO2 0.94
Polyatomic molecule NH3 C4H8 0.88
If it is a multi-component mixture (assuming that it consists of n gases), calculate the conversion factor C as follows:
0.3106 [N1 (ω1/ωT )+N2 (ω2/ωT ) + ••• + Nn (ωn/ωT )]
C = ————————————————————————
ρ1Cp1 (ω1/ωT )+ ρ2Cp2 (ω2/ωT )+ ••• + ρnCpn (ωn/ωT)
Among them: ω1 ... ωn - the flow of the corresponding gas
ωT - the flow of mixed gas
Ρ1...ρn——the density of the corresponding gas (see the product datasheet for the values)
CP1...CPn - constant pressure specific heat for the corresponding gas (see the product data sheet for the values)
N1 ... Nn - the molecular composition of the corresponding gas
Note: If the mixing ratio of the mixed gas is not fixed, the conversion factor cannot be calculated.

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