Formula in Nonmetric Units
Q = 37,980,000 A0.82 (ZT)0.5 / (LC)(M0.5)
Where:
Q = The total required venting capacity, in cubic meters of air per hour at standard conditions of 15.6 °C and 1 atm (cubic feet of air per hour at standard conditions of 60 °F and 14.7 psia);
T = The absolute temperature of the vapor at the venting conditions-degrees Kelvin (°C + 273) [degrees Rankine (°F + 460)];
A = The exposed surface area of tank shell-square meters (square feet);
L = The latent heat of vaporization of the lading-calories per gram (BTU/lb);
Z = The compressibility factor for the vapor (if this factor is unknown, let Z equal 1.0);
M = The molecular weight of vapor;
C = A constant derived from (K), the ratio of specific heats of the vapor. If (K) is unknown, let C = 315.
C = 520[K(2/(K ++ 1))[(K + 1)/(K-1)]]0.5
Where:
K = Cp / Cv
Cp = The specific heat at constant pressure, in -calories per gram degree centigrade (BTU/lb °F.); and
Cv = The specific heat at constant volume, in -calories per gram degree centigrade (BTU/lb °F.).
49 C.F.R. §§178.348-4