Page 280 - Formulas and Calculations for Petroleum Engineering

Fluid flow and transport phenomena formulas and calculations Chapter 5 273

5.34 Diffusion through a stagnant film

Input(s)
2
D AB : Diffusivity (cm /s)
z 1 : Initial Position (ft)
z 2 : Output Position (ft)
x A1 : Mole Fraction of A1 (g/ft)
x A2 : Mole Fraction of A2 (g/ft)
3
x b : Mole Fraction of B in the Logarithmic Mean of Thermal Concentrations (mol/ft )
3
c: Total Molar Concentration (mol/ft )
Output(s)
2
N: Combined Molar Flux (mol/ft s)

Formula(s)

c D AB x ð A1 x Þ
A2
N ¼
ð z z Þ xðÞ
2 1 b
Reference: Bird, R.B., Stewart, W.E. and Lightfoot, E.N. (2002). Transport Phenomena (Second Ed.). John Wiley & Sons,
Chapter: 18, Page: 548.

5.35 Diffusion through a stagnant gas film

Input(s)
x B1 : Mole Fraction of B1 (fraction)
x B2 : Mole Fraction of B2 (fraction)

Output(s)
x B : Average Value of Mole Fraction of B in the Logarithmic Mean of Thermal Concentrations (fraction)

Formula(s)

x ¼ x x Þ= ln x =x Þ
ð
ð
B B2 B1 B2 B1
Reference: Bird, R.B., Stewart, W.E. and Lightfoot, E.N. (2002). Transport Phenomena (Second Ed.). John Wiley & Sons,
Chapter: 18, Page: 547.

5.36 Diffusion through cleat spacing in coalbed methane reservoirs
Input(s)

s: Coal Cleat Spacing (ft)
t: Desorption Time from the Canister Test (day)

Output(s)
2
D: Diffusion Coefficient (ft /day)