Conclusions

In this chapter, I have presented a limiting form of the basic equations of vapour transport that should accurately model the full system for low mass transfer rates. The degree of approximation is quantified by the parameter $\varPhi$. The system is considerably simplified, which will allow us to tackle much more difficult problems in the following chapters.

While the reduced system is only designed for use with low mass transfer rates, in the two examples considered--the narrow cavity limit and mild convection in a square cavity--the overall vapour and energy transport rates predicted are in exact and excellent agreement, respectively, with the results of the full model.

It will be noticed that in passing from the full equations to the present limiting form, the interfacial velocity, the variability of the specific heat capacity in the bulk advective energy flux, and the interdiffusive energy flux all vanish together, provided Sc, $\mbox{\textit{Pr}}_r$ and $\mbox{\textit{Pr}}_I$ are of order unity, as is typical for gas-vapour mixtures.