Lumped-parameter approach for prediction of drying kinetics in foods

Abstract

Drying kinetics of the product are the most important data required for the design and simulation of air dryers. This essential information can be obtained through simple lab-scale experiments. Nevertheless, due to the uncertainty of the process, specially when dealing with biological materials, all the necessary data at different operating conditions are not usually available. On the other hand, drying kinetic models are either too simple to expect reasonably good predictions, or too complicated to be applied easily. The key assumptions of a previously developed lumped-parameter model for air drying kinetics were revised to examine their application to biological materials. A short cut method has been developed to simulate kinetic curves from a minimum number of experimental data. A simple parameter study was carried out to detect the most important variables that affect the mass transfer Biot number in order to predict kinetics data safely. Experimental (hot air) drying curves for bananas, grapes and mushrooms were obtained in a lab scale dryer, at different air temperatures (50 to 70C) and air velocities (1 to 3 m/s). A comparison between experimental and predicted data was done for different operating conditions.