Heat Transfer and Thermal Instabilities

An alternative heat transfer model was published by Todd [17], based on a correlation of heat transfer data over a Reynold s number range from 10-3 to 10  

73 Reactive Extrusion for Solvent-Free Processing Facts and Fantasies 

A special complication is formed by thermal inhomogeneities. The polymer follows a circular path in the cross-channel direction, which implies that only a certain amount of polymer passes the thermal boundary layer where it is cooled directly. Therefore, for deep cut channels the heat of reaction in the middle of the channel is difficult to remove. Janeschitz Kriegl [18] compared the thickness of the thermal boundary layer with the channel depth, and identified a criterion for thermal homogeneity in a single-screw extruder. This can be adapted to twin-screw extruders with m thread starts per screw. It may be concluded that thermal inhomogeneities become important if  

If the overall temperature rise is too large to be accepted, some classical solutions can also be applied to reactive extrusion  

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