Interphase micro-scale

Although particles in two-phase flow are not uniformly distributed, the dense and the dilute phases can be considered, each in its own, as uniform suspensions, and the global system can thus be regarded as consisting of dense clusters dispersed in a broth of separately distributed discrete particles, as shown in Fig. 1. The preceding correlations will therefore be used respectively in the dilute and the dense phases, for calculating micro-scale fluid-particle interaction, and also for evaluating meso-scale interphase interaction between clusters and the broth, as shown in Table I, for CD, CD[ and CD. ... 

The model species, total mass, momentum, and energy continuity equations are similar to those presented in Section 13.7 on fluidized bed reactors. Constant values of the gas and liquid phase densities, viscosities, and diffusivities were assumed, as well as constant values of the interphase mass transfer coefficient and the reaction rate coefficient. The interphase momentum transfer was modelled in terms of the Eotvos number as in Clift et al. [1978]. The Reynolds-Averaged Navier-Stokes approach was taken and a standard Computational Fluid Dynamics solver was used. In the continuous liquid phase, turbulence, that is, fluctuations in the flow field at the micro-scale, was accounted for using a standard single phase k-e model (see Chapter 12). Its applicability has been considered in detail by Sokolichin and Eigenberger [1999]. No turbulence model was used for the dispersed gas phase. Meso-scale fluctuations around the statistically stationary state occur and were explicitly calculated. This requires a transient simulation and sufficiently fine spatial and temporal grids. 

Figure 7.4. (a) Visualizing the interphase considering only the micro-scale. Interphase is a continuum layer with a gradient of properties reflecting variations in its structure. The main role of the micro-scale interphase is to provide stable and effective ineans for stress transfer between inclusions and polymer matrix even under adverse conditions, (b) Visualizing the structure of a micro-composite considering also the nano-scale structural features when the discrete structure of the matrix and inclusions becomes evident [169]... 

Figure 7.5. A typical example of the micro-scale organosilane iuterphases of various composition deposited on glass fibers using various deposition techniques and translation of the phenomenological properties of the interphases into mechanical response of multifiber composites with unidirectionally aligned fibers [96]...

This involves knowledge of chemistry, by the factors distinguishing the micro-kinetics of chemical reactions and macro-kinetics used to describe the physical transport phenomena. The complexity of the chemical system and insufficient knowledge of the details requires that reactions are lumped, and kinetics expressed with the aid of empirical rate constants. Physical effects in chemical reactors are difficult to eliminate from the chemical rate processes. Non-uniformities in the velocity, and temperature profiles, with interphase, intraparticle heat, and mass transfer tend to distort the kinetic data. These make the analyses and scale-up of a reactor more difficult. Reaction rate data obtained from laboratory studies without a proper account of the physical effects can produce erroneous rate expressions. Here, chemical reactor flow models using matliematical expressions show how physical... 

In this chapter, the interphase phenomena in the polymer matrix composites at the micro- and nano-scales are briefly reviewed and thdr main differences are discussed. An approach for modeling mechanical properties of continuous macroscopic bodies considering peculiarities brought about by the discrete nature of the matter at the nano-scale is proposed based on the combination of gradient strain elasticity and chain reptation dynamics. 

Jancar J (2008), Review of the role of the interphase in the control of composite performance on micro- and nano-length scales, J Mater Sci 43 6747-6757. 

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