Superheated Steam Drying of Parsley: a Fixed Bed Model for Predicting Drying Performance

Superheated steam drying technique has been known for a long time, but its application to food drying has received little attention. In this work, superheated steam was applied to dry fresh parsley (Petroselinum Cripsum). A mathematical model to simulate this drying process was developed by using mass and energy conservation equations for solid and steam phases. The resulting partial differential equation system was solved by means of a finite difference method. Software Matlab 5.3 for Windows was used for programming the algorithm. The development of the drying kinetics equation, required in the model, was based on thin layer experimental results. The simulation model was used to analyze the influence of different variables (bed height, operating pressure, steam velocity and steam temperature) on solid moisture content, as well as on solid and steam temperature profiles along the bed. Experimental determinations in a fixed bed arrangement were done at different operating pressures (0.07-0.17 kgf/cm), steam temperatures (70-100°C), steam velocities (5-12 m/sec.) and bed heights (thin layer, 2 cm and 10 cm). Solid temperature at the top of the bed and average solid moisture content were measured as drying proceeded. An acceptable agreement between experimental and theoretical average solid moisture contents was obtained. Keywords-Parsley Drying, Superheated Steam, Fixed Bed.