Experimental methods for scale-up

In the Introduction a number of questions were posed which are often asked in connection with model experiments. 

How small can a model be The size of a model depends on the scale-factor Lt/Lm, and on the experimental precision of measurement. Where Ij/f-M = 10, a measurement accuracy of +10% may not suffice. Therefore a larger model-scale will have to be chosen to reduce the scale-factor. 

Is one model-scale sufficient or should tests be carried out on models of different sizes One model-scale is sufficient if the relevant numerical values of the dimensionless numbers necessary to describe the problem (the so-called process point in the pi-space describing the operational condition of the technical plant) can be adjusted by choosing the appropriate process parameters or physical properties of the model material system. If this is not possible, the process characteristics must be determined in models of different sizes, or the process point must be extrapolated from experiments in technical plants of different sizes. 

When must model experiments be carried out exclusively with the original material system Where the material model system is unavailable (e.g., in the case of non-Newtonian fluids) or where the relevant physical properties are unknown (e.g., with foams, sludges, slimes and slurries) the model experiments must be carried out with the original material system. In this case measurements must be performed on models of various sizes. 

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