Establishment of the Dimensionless Numbers

On the whole, there are two ways to establish a dimensionless number [8]. The one, which is very simple but also hazardous, consists of building a fraction where the numerator has the same dimension as the denominator. The other, which is more consistent, is obtained by equilibrating the two opposite acting forces which are facing each other, and simplifying afterwards. 

According to the second method [9, 10] selected, let us recall that the dimensionless 

In the same way, the other new dimensionless numbers are established in the following way When the process is controlled by diffusion  

When the process is controlled by convection at the polymer-liquid interface, with a low value of the coefficient of convection, the limiting relationship is obtained by writing that the rate of the agent released in the food is equal to its rate of consumption by the microorganisms  

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