Analysis of air velocity distribution in a laboratory batch-type tray air dryer by computational fluid dynamics

Abstract

Batch dryers are some of the most widespread equipment used for fruit dehydration. Nevertheless, the optimization of the air distribution inside the drying chamber of a batch dryer remains a very important point, due to its strong effect on drying efficiency as well as the uniformity of the moisture content of the drying products. A new scale laboratory batchtype tray air (BTA) dryer was designed, constructed and evaluated for the drying of several horticultural and agricultural products. The airflow field inside the dryer was studied through a commercial computational fluid dynamics (CFD) package. A threedimensional model for a laboratory BTA dryer was created and the steadystate incompressible, ReynoldsAveraged NavierStokes equations that formulate the flow problem were solved, incorporating standard and RNG k�e turbulence models. In the simulation, the tray, used inside the BTA drying chamber, was modeled as a thin porous media of finite thickness. The simulations for testing the chamber were conducted at an average velocity of 2.9 m/s at ambient temperature. The CFD models were evaluated by comparing the airflow patterns and velocity distributions to the measured data. Numerical simulations and measurements showed that the new scale laboratory BTA dryer is able to produce a sufficiently uniform air distribution throughout the testing chamber of the dryer.