Numerical and experimental investigation of flow patterns in scraped surface heat exchangers

A numerical investigation of a scraped surface heat exchanger was undertaken using the commercial CFD code FLUENT in order to characterize the flow patterns for Newtonian and Non-Newtonian highly viscous fluids where experimental measurements are difficult to obtain. Simulation results were validated with experimental shear rates measured using electrochemical method (Mabit et al., 2003) as well as velocity profiles obtained by PIV. Two different flow configurations were treated separately: first, the inlet bowl not reached by the scraping blades, and second the exchanger itself, with two scraping blades. In the inlet bowl, velocity profiles calculated show a dead zone where clogging can occur. In the exchange part itself, the zone localized between the tip of the blades and the stator has to be studied more carefully. Laminar isothermal steady-state flow was studied in a 2D cross section of the exchanger. Comparison between predictions and experimental measurements gave good agreement.