Numerical and experimental study of airflow resistance across an array of sliced food items during drying

Characterization of the airflow across food items involves identification of their viscous and inertial resistances. This paper presents an extensive numerical and experimental study to determine the resistances of food items placed in an array. The experimental study used an array of sliced sweet potato with different initial slice diameters. The airflow resistance of the array was determined from a series of wind tunnel measurements. The sliced arrays were dehydrated and digital images were taken to determine the intermediate array-porosity. The numerical study was based on CFD modeling of the airflow across the disc arrays. In the simulations, the size of each individual disc in the array was gradually decreased to reproduce the array-porosity change similar to the experimental dehydration. The airflow resistance of the array was found to be dominated by inertial effects. The influence of geometrical parameters on the inertial resistance coefficient was also studied. Dimensional analysis showed that the inertial resistance was exponentially decaying with array-porosity. To describe this relationship, a model equation was proposed that fitted very well with both the experimental and numerical results. Finally, the findings of the current study were used in a porous media based modeling and simulation of the momentum transport in the dehydration of an array of sliced food items in a solar dryer.