Studies On Falling Film Crystallization Process And Its Numerical Simulation

With the development of aerospace and aeronautic technologies as well as electronic industry, various new polymers with high intensity and special properties are being daily developed and applied in the related fields. However, there remains the main obstacles to obtain polymers with high quality due to the difficulties in manufacturing highly pure materials, for example, because of the existence of a trace of impure substance in medicines, the effect of the medicines can not be accomplished perfectly. Furthermore, many products purer than 99.99% are frequently required with the development of material science and the application of materials. All of these mentioned above have considerably made the need of separation and purification of organic materials distinguished itself. Falling Film Crystallization is a newly developed separation and purification technique with high efficiency, energy saving, lower operating temperature and good environmental suitability. It has been widely used to produce highly or ultra highly pure products to be in use in numerous high and new technology and its applications range from isomer separation, i.e. the separation of substances having same empirical formula, but different chemical and physical properties, to the isolation of individual components of coal-tar, from the production of pure carboxylic acids to the purification of monomers.Falling Film Crystallization involves complicated fluid flow, coupled heat and mass transfer process, during which the falling melt is cooled by the cooling tube wall and the melt adjacent to the tube wall precipitates on the wall a layer of crystal with more component in higher melting point and the melting point of the remaining melt goes down. Hence, the component with high melting point has to be delivered from the bulk melt to the tube wall to ensure crystallization going on so as to achieve the object of separating the component with higher melting point from the melt. Clearly, the critical factor to effectively separating and obtaining highly pure products relies on the good controlling of the complicated heat and mass transfer during Falling Film Crystallization. The dissertation focuses on the study on the mechanism of heat and mass transport by both experiment and numerical simulation. It describes all the work in nine Chapters.Chapter 1 is the preface, in which the advantages and application of the falling film crystallization process are described and the background, development and industrial application of melt crystallization are introduced.Chapter 2 is the reference review in related areas of the dissertation. Part 1 describes the characteristics, application and development as well as domestic and abroad statues of the related studies. Part 2 relates to the numerical simulation of falling film crystallization process, in which abroad and domestic studies and the relevance between falling film crystallization and the transport phenomena occurring in porous media is presented. Part 3 involves the fundamentals of transport phenomena and the application of porous media...