Estimate gas viscosity across a range of conditions with precision
Featured: Lee-Gonzalez-Eakin, Lucas, Stiel-Thodos
The Lee-Gonzalez-Eakin correlation is an empirical method developed specifically for natural gas systems. It calculates gas viscosity (μg) in centipoise (cP) as:
μg = 10-4 K exp(X ρgY)
where K = (9.4 + 0.02 M) T1.5 / (209 + 19 M + T)
X = 3.5 + 986/T + 0.01 M
Y = 2.4 - 0.2 X
ρg = gas density (g/cm3)
The Lucas method is a generalized correlation that uses reduced temperature (Tr) and pressure (Pr). It first calculates the low-pressure gas viscosity (μ1) then applies a correction factor for high pressure:
μ1 = [0.807 Tr0.618 - 0.357 exp(-0.449 Tr)
+ 0.340 exp(-4.058 Tr) + 0.018] Fp FQ
μ/μ1 = 1 + A PrB / (C PrD + (1 + E PrF)-1)
The Stiel-Thodos correlation is particularly accurate for dense gases and near the critical point. It calculates the residual viscosity (μ - μ1) as:
(μ - μ1) ξ = 1.08 × 10-4 [exp(1.439 ρr) - exp(-1.111 ρr1.858)]
where ξ = Tc1/6 / (M1/2 Pc2/3)
