Phase transfer coefficient

K g Overall gas-phase transfer coefficient in terms of mole fractions kmol/m2s nl-2t- ... 

Ka can be defined as a gas-phase transfer coefficient, independent of the liquid layer, when the boundary concentration of the gas is fixed and independent of the average gas-phase concentration. In this case, the average and local gas-phase mass-transfer coefficients for such gases as sulfur dioxide, nitrogen dioxide, and ozone can be estimated from theoretical and experimental data for deposition of diffusion-range particles. This is done by extending the theory of particle diffusion in a boundary layer to the case in which the dimensionless Schmidt number, v/D, approaches 1 v is the kinematic viscosity of the gas, and D is the molecular diffusivity of the pollutant). Bell s results in a tubular bifurcation model predict that the transfer coefficient depends directly on the... 

The overall mass phase coefficient kgj also depends on the gas and liquid phase transfer coefficients ... 

From Chapter 6 it is clear that depends on C t,, and C. The interfacial concentration is no problem, since it may be calculated from when the gas phase transfer coefficient is known or Njt can be referred directly to as in Eq. 6.3.b-5. Two more relations are required, however, to calculate V, (C )out and (C... 

The partial derivatives in this equation are phase transfer coefficients, Ux and (not to be confused with mass transfer coefficients used in Chapter 7). 

This model was found to give a slightly better fit of the distillation data than did the Bolles-Fair model. It is somewhat more cumbersome to use, however, because of the need to evaluate individual-phase transfer coefficients. 

This shows that the relationship between the individual-phase transfer coefficients and the overall coefficient takes the form of addition of resistances (hence two-resistance theory). In similar fashion, is a measure of q and can be used to define another overall coefficient K... 

To be able to predict sulfur release patterns a non-steady sulfur release model has been developed (4) which is based upon diffusion controlled devolitalization, second order volatiles combustion and shrinking particle char combustion further coal particle and bed heat up and fluid dynamic behaviour like segregation, slugging and bed expansion are taken into account. The model contains no fit parameters most of the variables are based on literature correlations the gas transfer parameters like Sherwood number and bubble-dense phase transfer coefficient have been obtained from coal burnout experiments. In Fig. 4 a result of such a calculation is shown together with the results of a quadruple experiment. The agreement between the calculated and the measured curves is good. 

The individual phase transfer coefficients k, and k g are often of the same order of magnitude. However, the value of Ha can vary over a wide range depending on the nature of species A and the liquid phase. If a gas species is highly soluble in the liquid (Figure 3.3.3 illustrates such a system), has a small value, which makes... 

Equation (3.4.8) relates the overall mass-transfer coefficient Kxg to the individual mass-transfer coefficients kxg and kxi- Relations between the overaU transfer coefficient and the individual phase transfer coefficients for other types of concentration driving gradients are also of considerable use. Consider... 

The various results considered above for a gas-Uquid (or vapor-Uquid) system were obtained for absorption of species A from gas (or vapor) into a liquid. If species A is being stripped from the liquid into gas (or vapor) phase, only the direction of transport changes therefore the flux expressions (3.4.3)-(3.4.6) are changed by a minus sign, as are the concentration profiles in the two phases. However, the relations between the overall transfer coefficient K and the individual phase transfer coefficient k remain unaffected by the direction of transport. 

Further, kcw is the external solution-phase mass-transfer coefficient. At the external solution-resin boundary interface, the resin-phase concentration in equilibrium with Cawi is Car,. The resin-phase mass-transfer expression containing the resin-phase transfer coefficient kyg is... 

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