Computational fluid dynamics of air flow in a spray dryer containing wall air pressure nozzle
CFD Simulation in spray dryer with wall air pressure nozzle
Abstract
Wall deposition is the main problem in a spray dryer that affects the quality of the powder and decreases the dryer operation. In the current study, the influence of using an air pressure nozzle on the conical section of the dryer chamber was examined by simulation of flow pattern in a pilot plant spray dryer using computational fluid dynamics (CFD) technique and Ansys Fluent software (Ver. 17.0). The governing equations are solved in an axisymmetric geometrical model meshed by quadratic elements. Flow pattern was studied and compared in two conditions: before and after considering air pressure nozzle in the dryer chamber wall. Verification of velocity magnitude revealed that there was a little difference (5 to 7%) between numerical and experimental values and there was a good correlation (R2≥ 95%) between them. Flow pattern in the dryer chamber before considering wall pressure nozzle showed recirculation zones were formed near the top of the junction cylinder part and cone part of the chamber. Adding the wall pressure nozzle in the model caused deflection of inflow towards the dryer wall and extension of chamber central core flow. The simulation results showed deviation of particle deposition from cone section towards the cylinder and ceiling parts of dryer.
