Particulate flow model application

This chapter describes the fundamental principles of heat and mass transfer in gas-solid flows. For most gas-solid flow situations, the temperature inside the solid particle can be approximated to be uniform. The theoretical basis and relevant restrictions of this approximation are briefly presented. The conductive heat transfer due to an elastic collision is introduced. A simple convective heat transfer model, based on the pseudocontinuum assumption for the gas-solid mixture, as well as the limitations of the model applications are discussed. The chapter also describes heat transfer due to radiation of the particulate phase. Specifically, thermal radiation from a single particle, radiation from a particle cloud with multiple scattering effects, and the basic governing equation for general multiparticle radiations are discussed. The discussion of gas phase radiation is, however, excluded because of its complexity, as it is affected by the type of gas components, concentrations, and gas temperatures. Interested readers may refer to Ozisik (1973) for the absorption (or emission) of radiation by gases. The last part of this chapter presents the fundamental principles of mass transfer in gas-solid flows. 

Gas-solid and gas-solid-liquid flows are identified in Technology Vision 2020 The Chemical Industry as critical to developing advanced chemical reactors and separations. Solids handling is a critical technology for chemical manufacture. For companies such as DuPont and Dow Chemical Company, more than 50 percent of the products sold are in a solid/particulate form. This consortium was formed to develop technology to accurately model gas-solid transport in industrial applications. 

The few models discussed here serve to demonstrate the complexity of the problem of attempting to describe the mechanism of particulate deposition in mathematical terms. Much of the difficulty stems from the inability to recognise the importance of specific variables and a lack of understanding of the interaction between the variables. Furthermore the lack of knowledge of the true composition of flow streams and flow conditions in industrial heat exchangers, makes the application of models for design and operation analysis, almost impossible except in all but the simplest examples. In the following section the effect of some of the contributory factors will be demonstrated in relation to some experimental data. 

For die first case study, the particulate filled nanopolymers is studied. An investigation on viscometric flow for particulate filled nanopolymers is presented as the second case study in this chapter. Application of synthetic or natural inorganic fillers is reviewed as the third case study. The next two case studies are devoted to description of a multiscale micromechanical model and plication of cement materials reinforcement with nanoparticles. 

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