General Conclusions on the Mathematical Treatment

As already stated in Chapter 1, devoted to the mathematical treatment of the mass transport from a polymer package into a liquid, when this transfer is controlled by diffusion, the following conclusions can be drawn  

Equation (4.28), or rather the more simple Equation (4.30), which is mostly appreciated by the users, perhaps because it looks simpler, can be used only from the first approach in order to get an approximative value of the diffusivity. 

the approximate value of the diffusivity obtained with this simple method shown previously in case 2 with Equation (4.30) can be introduced into Equation (4.24) through the dimensionless number R expressed by the relationship (4.23). Of course, various values of the coefficient h should be tested, by following a trial and error method, and by determining the corresponding values of the in Equation (4.22). 

Finally, when the operations required in the previous sections seems too tedious, the convenient numerical model could be used. 

---