Flux correction factor

Weisman and Pei applied their approach to data from tubes with nonuniform axial heat flux. They found the predictive scheme to hold without the need for any nonuniform heat flux correction factor. The accuracy of their prediction was only slightly less than that of the W-3 correlation, Eq. (5-106), for the data they examined. 

Figure 8.2. High flux correction factor from film theory.

The parameter 3 in this expression accounts for the nonlinearity of the composition profiles it is, in fact, a high flux correction factor as is [3] in the matrix methods described above. Equation 8.5.18 involves no iteration because the rate factor <1> and the correction factor 3 can be calculated from Eqs. 8.5.15 all we need to know are the boundary conditions y Q and y Q. 

These values are used in the calculation of the mass transfer rate factors form Eqs. 9.3.38, the high flux correction factors from Eqs. 9.3.39 and, hence, new values of the high flux mass transfer coefficients. The cycle of flux-coefficient calculations is repeated and after 10 iterations we obtain the following converged values ... 

The final values of the high flux correction factors 1.009, 3 = 0.9999) confirm... 

The next step is to compute the multicomponent mass transfer coefficients modified for the effect of a nonzero total flux. The total mass flux is needed for the evaluation of the high flux correction factor and is... 

We now turn our attention to the liquid-phase mass transfer rate equation. The high flux correction to the liquid-phase mass transfer coefficient is given by the second part of Eq. 8.2.13. However, its value is sufficiently close to unity to have no impact on the results. Accordingly, we shall set the liquid-phase mass transfer flux correction factor to unity. 

Powers et al. (1988) found that the high flux correction factor is not important in distillation and it has been ignored in rewriting Eqs. 11.5.4 and 11.5.5. 

The vapor-phase high flux correction factor follows as ... 

The final values of the mass transfer rate factor and high flux correction factor are... 

It is obvious that the flux correction factors cannot be ignored in this particular problem. This is likely to be the case in many condensation problems. 

The numerical value of the high flux correction factor is 0.805. Thus, a calculation of... 

Reijnhart et al. (1980) analyzed mass transfer from spills of volatile, single component, liquids into turbulent air streams. As the temperature increases the high flux correction factors become significant due to the increased mass transfer rates. Reconcile the analysis of Reijnhart et al. with the material presented in Chapter 10. Attempt to simulate their experimental results for the evaporation of toluene into air. Note that for spills of multicomponent liquid mixtures, the analysis of Chapter 10 really comes into its own. 

To avoid spurious variations introduced to the result by the iteration, SAND-II applies smoothing to the weighting factors used for the calculation of the flux correction factor Experience has shown that SAND-II is better than either SPECTRA or RDMM. 

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