Axial diffusion in gas blanketed vapor condensers

A model is given, which permits determination of the height of a zone of mixing between a gas and a vapor in a condenser. The resulting predictive equation is algebraically simple and contains a non-dimensional group, z_i ^*, which should characterize a host of related problems: $$z_i^* = z_i sqrt {frac{{4UDelta T_0 tilde RT_0 }}{{pD_0 Rtilde h_{fg} }}} .$$ Data are presented which verify the mathematical model.