Penetration theory assumes that turbulent eddies travel from the bulk of the phase to the interface where they remain constant for a constant exposure time (te). The model correlating KL, mass transfer coefficient and DAB, diffusivity can be expressed as

• KL = 2(DAB/πte)0.25
• KL = 2(DAB/πte)0.5
• KL = 2(DAB/πte)0.75
• KL = 2(DAB/πte)