dimensionless modeling of thin layer drying process of aloe vera gel

this research, presents mathematical modeling of drying process of aloe vera slices with dimensions of 7×4×0.5±0.1 cm. peeled aloe vera slices with the initial moisture content of 5750% (d.b) were osmosed for 5 hours in nacl solution of 10% and temperature of 40 °c at a constant solution to fruit ratio of 5:1. osmosed and unosmosed aloe vera samples were hot air dried at 55, 70 and 85°c with different air flow rates of 0.015, 0.036 and 0.054 m3/s for 13200s. the moisture content of aloe vera samples were measured over different intervals of drying time (1200, 2400, 6000, 9600, 13200s) for each experiment. the experimental results were used to obtain two different dimensionless models based on buckingham’s pi-theorem for both drying methods. to this end, three independent π terms were identified and then the relation between dependent π term and each independent π term was sought. finally, the dimensionless models incorporating the effect of all the independent π terms on the dependent one derived and evaluated. the rmse, (r2), mrd and mbe for the modeling of osmotic-convective drying method were calculated as 0.0185, 0.99, 0.05 and 0.034, respectively. also these statistical parameters for the convective drying method were as: 0.027, 0.98, 0.061 and 0.051, respectively. therefore the dimensionless models could predict the moisture content of aloe vera samples during drying, properly.