In this chapter, a numerical simulation is presented to investigate the heat and mass transfer during the volatile organic compounds condensation (mixture of alcohol vapors) particularly n-butanol–propanol, in the presence of non-condensable gas (air) along a vertical tube. The two-dimensional model adopted is based on the two-phase boundary layer equations and considers inertia terms and shear stresses at the liquid–vapor interface. The equations systems that are obtained by using an implicit finite difference method are solved by the Thomas algorithm. The calculation carried out made it possible to determine along the tube, the vapor mass fraction at the outlet, the film liquid thickness, the Nusselt number, and the condensation rate.