BALANCE-EQUATIONS FOR MOLECULAR DISTILLATION

We have derived balanced equations for continuous molecular (short-pat h) distillation of a binary mixture in a falling film evaporator. The relation of heat and mass transfer in liquid films on both the evapora ting and condensing surfaces were taken into account, as well as the m ass transfer in the vapor phase in the distillation gap. Individual ba lance equations were coupled by boundary conditions into a closed set of partial differential equations. By introducing the streams, we have transformed partial differential equations into the simple form of or dinary differential equations. These were solved numerically or approx imately for some selected problems in isothermal (e.g., for turbulent film on evaporation surface) and nonisothermal regimes and for the inf luence of reevaporation from the condenser. These developed mathematic al formulations can be used to model various operational situations in a molecular evaporator or to evaluate the influence of some parameter s on the molecular distillation process.