ABSTRACT
Scale-up rules provide the possibility to transfer knowledge obtained on small-scale laboratory equipment to large-scale production units. The principle of scale-up is that equations describing the behavior of process equipment can be written in a dimensionless form. Various theories on the scale-up of single-screw extruders exist. A very consistent and complete scale-up theory was presented by Pearson. Rigorous application of thermal similarity would lead in an extruder to scale-up rules that are hardly applicable in practice. This is especially the case in reactive extrusion, where exothermal reactions cause large temperature differences. Thermal similarity is facilitated by hydrodynamic similarity. Because of the temperature dependence of the reaction rate, chemical similarity can only be obtained if thermal similarity exists. Moreover, when working with nonisothermal reactions, chemical similarity influences thermal similarity. Thermal scale rules are generally based on constant specific energy consumption.
