Appendix B
Equation A-4 — Air Density
Equation A-4 — Air Density
Air Density ( PAIR ) in units of g/cm3, is calculated as follows;
ρair = (0.0004646 x (P − 4990221.6 x U x e(− 5315.56 /(273.15 + t )) ))/ (273.15 + t)
where:
P = Barometric Pressure, (mmHg)
t = Air Temperature, (ºC)
U= Relative Humidity, (%RH)
Nitrogen Density — English Units (0 to 1000 PSIG)
To calculate the density of Nitrogen at pressures from 0 psig to 1000 psig, use the following equation;
DENSITY (lbm / in3 )= (2.826 x 10− 6 ) x P
where;
P = PRESSURE in psi absolute (if P is in gauge, convert it to an absolute value by adding barometric pressure, e.g. P + 14.7 )
Nitrogen Density — English Units (1,000 to 15,000 PSIG)
To calculate the density of Nitrogen at pressures from 1,000 psig to 15,000, use the following equation;
DENSITY (lbm / in3 )= (2.37465 x 10− 4 )+ (2.74396 10− 6 )P − (9.46069 x 10−11 )P2
where;
P = PRESSURE in psi absolute (if P is in gauge, convert it to an absolute value by adding barometric pressure, e.g. P + 14.7 )
