Q = Volumetric flow rate (SCFM = standard cubic feet per minute)
N = Unit conversion factor
C = Discharge coefficient (accounts for energy losses, Reynolds number corrections, pressure tap
locations, etc.)
Y = Gas expansion factor
A1 = Cross-sectional area of mouth
A2 = Cross-sectional area of throat
Zs = Compressibility factor of gas under standard conditions
Zf1 = Compressibility factor of gas under flowing conditions, upstream
Gf = Specific gravity of gas (density compared to ambient air)
T = Absolute temperature of gas
P1 = Upstream pressure (absolute)
P2 = Downstream pressure (absolute)