Scale-down process mathematical modeling

The foregoing survey was focused on situations where bnlk diffusion processes were rate determining. Such systems are amenable to analysis using an electrochemical approach. Other factors such as transport down pores or cracks, volatilization or melting of the oxide scale may occur and require different analyses but diffusion controlled processes may be mathematically modeled and correlated with the defect chemistry of the corrosion product. These limiting cases provide a guide to understanding the more complex phenomena frequently encountered. 

A second consideration in scaling down a reactive extrusion process concerns the axial temperature profile. Because of the different volume to surface ratio between large-scale and small-scale equipment the cooling capacity of the latter will be far better than in production size machines. To obtain similar axial temperature profiles, the temperature settings of the barrel wall in the small-size extruder should be different from those in the large-size machine. The most convenient situation is, of course, if a reliable mathematical model of the reactive extrusion process is available. An alternative is the use of an approximating heat balance over the extruder ... 

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