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FIGURE 10.30 Computational simulation of accumulation of gas behind impeller blades (black: 0; white: >0.1) (from Ranade et al., 2001c). Reproduced in colour plate section between pages 210 and 211.

FIGURE 10.30 Computational simulation of accumulation of gas behind impeller blades (black: 0; white: >0.1) (from Ranade et al., 2001c). Reproduced in colour plate section between pages 210 and 211.

it may be necessary to treat the three phases separately. For such systems, it is often necessary to model the motion of solid particles using models based on the kinetic theory of granular flows. Some aspects of this are discussed in Chapter 4. Application of granular flow models to simulate the motion of dispersed solids is discussed in more detail in Chapter 12 for fluidized bed reactors. Dispersion of solid particles in liquid can be simulated using the two-fluid models discussed above (Gosman et al., 1992; Micale et al., 2000). Coalescence break-up models, discussed with reference to gas-liquid flows in Chapter 11, can also be applied to simulate coalescence and break-up processes in gas-liquid and liquid-liquid dispersions (Lane et al., 1999).

In general, it may be concluded that the computational snapshot approach or other equivalent, state of the art CFD models can capture the key features of flow in stirred tank reactors and can be used to make either quantitative (for single-phase or pseudo-homogeneous applications) or semi-quantitative (for complex, multiphase applications) predictions. Possible applications to reactor engineering are discussed below.

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