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ACFM air to ACFM natural gas 1
- Thread starter TedHy
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1
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TedHy,
In the natural gas industry, we usually refer gas volumes to standard conditions. You can do the conversion in two steps, first you can convert the air flow to standard conditions and then you can calculate the equivalent gas flow.
To correct to standard flow rate, Qs, you need to correct the flowing temperature Ta and pressure Pa to standard T - P conditions using the combined gas laws:
PsQs/TsZs = PaQa/TaZa
where the subscript a refers to actual conditions and the subscript s refers to standard conditions, Z is the compressibility.
Solving for Qs and noting that Zs=1 for Ps << 100 psia
Qs = Ts PaQa/TaZa Ps
Now, you can work out an equivalent gas flow by using a simple valve equation. You can write,
Qs-gas = Cv [√][ (Pa[Δ]P)/ (TaGgas Zgas)]
Qs-air = Cv [√][ (Pa[Δ]P)/ (TaGair Zair)]
Cv , Pa , [Δ]P , and Ta cancel out when you take the ratio Qs-gas / Qs-air. Also note that the flow is assumed to be turbulent so that viscosity does not come into play.
Qs-gas / Qs-air= [√][1/(Ggas Zgas)] / [√][1/(Gair Zair)]
Qs-gas / Qs-air= [√][(Gair Zair)/(Ggas Zgas)]
Gair=1 by definition. If Pa << 100 psia then Zair and Zgas can be taken as 1.0 and
Qs-gas = Qs-air [√][1/Ggas]
Nomenclature:
Qs = Volumetric flow rate at standard conditions.
Ps = Standard pressure.
Ts = Standard temperature.
Zs = Compressibility at standard conditions.
Qa = Volumetric flow rate at actual conditions.
Pa = Actual pressure.
Ta = Actual temperature.
Za = Compressibility at actual conditions.
Zair = Compressibility of air at actual conditions.
Zgas = Compressibility of gas at actual conditions.
Q s-gas = Volumetric flow rate of gas at standard conditions.
Q s-air = Volumetric flow rate of air at standard conditions.
Q a-gas = Volumetric flow rate of gas at actual conditions.
Q a-air = Volumetric flow rate of air at actual conditions.
Cv = Valve constant
[Δ]P = Pressure drop across the component.
Ggas = Specific gravity of gas (density gas/density air).
Gair = Specific gravity of air (density air/density air = 1.0).
In the natural gas industry, we usually refer gas volumes to standard conditions. You can do the conversion in two steps, first you can convert the air flow to standard conditions and then you can calculate the equivalent gas flow.
To correct to standard flow rate, Qs, you need to correct the flowing temperature Ta and pressure Pa to standard T - P conditions using the combined gas laws:
PsQs/TsZs = PaQa/TaZa
where the subscript a refers to actual conditions and the subscript s refers to standard conditions, Z is the compressibility.
Solving for Qs and noting that Zs=1 for Ps << 100 psia
Qs = Ts PaQa/TaZa Ps
Now, you can work out an equivalent gas flow by using a simple valve equation. You can write,
Qs-gas = Cv [√][ (Pa[Δ]P)/ (TaGgas Zgas)]
Qs-air = Cv [√][ (Pa[Δ]P)/ (TaGair Zair)]
Cv , Pa , [Δ]P , and Ta cancel out when you take the ratio Qs-gas / Qs-air. Also note that the flow is assumed to be turbulent so that viscosity does not come into play.
Qs-gas / Qs-air= [√][1/(Ggas Zgas)] / [√][1/(Gair Zair)]
Qs-gas / Qs-air= [√][(Gair Zair)/(Ggas Zgas)]
Gair=1 by definition. If Pa << 100 psia then Zair and Zgas can be taken as 1.0 and
Qs-gas = Qs-air [√][1/Ggas]
Nomenclature:
Qs = Volumetric flow rate at standard conditions.
Ps = Standard pressure.
Ts = Standard temperature.
Zs = Compressibility at standard conditions.
Qa = Volumetric flow rate at actual conditions.
Pa = Actual pressure.
Ta = Actual temperature.
Za = Compressibility at actual conditions.
Zair = Compressibility of air at actual conditions.
Zgas = Compressibility of gas at actual conditions.
Q s-gas = Volumetric flow rate of gas at standard conditions.
Q s-air = Volumetric flow rate of air at standard conditions.
Q a-gas = Volumetric flow rate of gas at actual conditions.
Q a-air = Volumetric flow rate of air at actual conditions.
Cv = Valve constant
[Δ]P = Pressure drop across the component.
Ggas = Specific gravity of gas (density gas/density air).
Gair = Specific gravity of air (density air/density air = 1.0).
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