Scattering, multiple elastic, effect

Charge transfer occurs when particles collide with each other or with a solid wall. For monodispersed dilute suspensions of gas-solid flows, Cheng and Soo (1970) presented a simple model for the charge transfer in a single scattering collision between two elastic particles. They developed an electrostatic theory based on this mechanism, to illustrate the interrelationship between the charging current on a ball probe and the particle mass flux in a dilute gas-solid suspension. This electrostatic ball probe theory was modified to account for the multiple scattering effect in a dense particle suspension [Zhu and Soo, 1992]. 

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. 

G. D. J. Phillies. Suppression of multiple scattering effects in quasi-elastic light... 

G. D. J. Phillies. Suppression of multiple scattering effects in quasi-elastic light scattering by homodyne cross-correlation techniques. J. Chem. Phys., 74 (1981), 260-262. 

Apart from its magnitude, the most interesting characteristic of the elastic cross section is its angular distribution. The measurement of this angular distribution is difficult in the first place it is not easy to measure the scattered neutrons in the presence of neutrons emitted from the source which can be screened from the detector only with difficulty secondly, since relatively large quantities of material are required to give a measurable effect, the experimental results require correction for multiple scattering which usually can only be made on a semi-empirical basis. 

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