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Evaporation rate and separation factor of molecular distillation in a falling film apparatus


  • Dr.-Ing. Zdzislaw Kawala,

    1. Institute of Chemical Engineering and Heating Equipment, Technical University of Wroclaw, 50-373 Wroclaw, Poland
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  • Prof. Dr.-Ing. Karl Stephan

    1. Institut für Technische Thermodynamik und Thermische Verfahrenstechnik, Universität Stuttgart, Pfaffenwaldring 9, FA 1705, Postfach 1140, D-7000 Stuttgart 80
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During molecular distillation in a falling film apparatus, temperature and concentration of the more volatile components undergo a marked decrease in axial and radial directions, due to the distillation in vacuo. The gradients produce changes in the rate of surface evaporation and separation efficiency along the flow path. A theoretical study of this problem is presented for binary mixtures. The respective differential equations for heat and mass transfer in the liquid film are solved numerically. As the results demonstrate, the aspect ratio of an apparatus should be large when a high separation is required and small when a high distillation rate is more important.

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