Drying Uniformity Analysis in a Tray Dryer: An Experimental and Simulation Approach

This study aimed to use a Computational Fluid Dynamics (CFD) simulation of a tray dryer to investigate the possible causes of non-uniformity in the absolute final product humidity after the drying process in an empirically constructed tray dryer. In the experimental part, turmeric, which is the rhizome of a perennial herbaceous plant with interesting properties for the cosmetic and food industries, was dried. Pieces of turmeric with identical dimensions were placed in different zones of the dryer and their initial and final humidity values were empirically measured. In the simulations, the momentum and energy equations were solved with ANSYS software (Student v.17.2). The K-epsilon model was used to model the turbulence and the boundary and process conditions were identical to those used in the experiment. Although the steady-state CFD simulations show a homogenous local temperature distribution in the dryer, the local turbulence intensity profiles display dead zones with low turbulence values. Furthermore, these dead zones are consistent with areas where the product exhibits higher humidity. Low local turbulence values can negatively affect the local mass transfer coefficient, which may explain the experimental results of this study.