Some remarks on renewal models

Abstract A renewal model is proposed for representing the turbulent mass transfer in the vicinity of a wall. In this model it is considered that the elements of fluid which come into contact with the wall at the moment of renewal do not maintain their individuality while they remain into contact with the wall, but a certain part of them (situated further from the solid surface) is renewed by elements from the bulk of the fluid. Starting from this model equations for the mass-transfer coefficient, valid for two extreme cases, are established.