In this work, a more rigorous model of the vapor phase was considered in characterizing the molecular distillation more realistically. The model used here tries to predict the behavior of the molecular distillation in terms of several factors that, in a considerable way, influence the evaporation efficiency, e.g. design of the molecular distillators in relation to the distance between the evaporator and the condenser and their geometries, pressure of the system, and condensation temperature. This model was developed in the literature by several authors. The objective here is to consider it in the DISMOL software (developed by the authors of this work) taking into account the main contributions available. (C) 2000 Elsevier Science Ltd.In this work, a more rigorous model of the vapor phase was considered in characterizing the molecular distillation more realistically. The model used here tries to predict the behavior of the molecular distillation in terms of several factors that, in a considerable way, influence the evaporation efficiency, e.g. design of the molecular distillators in relation to the distance between the evaporator and the condenser and their geometries, pressure of the system, and condensation temperature. This model was developed in the literature by several authors. The objective here is to consider it in the DISMOL software (developed by the authors of this work) taking into account the main contributions available.2402/07/1513091315Batistella, C.B., (1996), M.Sc. thesis. LDPS Campinas-SP, Brasil: UNICAMPBatistella, C.B., Maciel, M.R.W., Modeling, simulation and analysis of molecular distillators: Centrifugal and falling film (1996) Computers & Chemical Engineering, 20 (SUPPL.), pp. S19-S24Bhandarkar, M., Ferron, J.R., Simulation of rarefied vapor flows (1991) Industrial & Engineering Chemistry Research, 30, pp. 998-1007Bird, G.A., Direct simulation and the Boltzmann equation (1970) The Physics of Fluids, 13, pp. 2676-2681Bird, G.A., (1976) Molecular Gas Dynamics, , Oxford, UK: Clarendon PressBird, G.A., (1994) Molecular Gas Dynamics and the Direct Simulation of Gas Flows, , Oxford, UK: Clarendon PressBorgnakke, C., Larsen, P.S., Statistical collision model for Monte Carlo simulation of polyatomic gas mixture (1975) Journal of Computational Physics, 18, pp. 405-420Ferron, J.R., Evaporation and condensation of mixture under rarefied conditions (1986) Industrial & Engineering Chemistry Fundamentals, 25, pp. 594-602Lutisãn, J., Cvengrõs, J., Mean free path of molecules on molecular distillation (1995) Chemical Engineering Journal, 56, pp. 39-50Lutisãn, J., Cvengrõs, J., Effect of inert gas pressure on the molecular distillation process (1995) Separation Science & Technology, 30 (17), pp. 3375-3389Oran, E.S., Oh, C.K., Cybyk, B.Z., Direct simulation Monte Carlo: Recent advances and applications (1998) Annual Review of Fluid Mechanics, 30, p. 403