Drying kinetic and shrinkage study of a Hawthorn sample in a vibro fluidized bed dryer using an adsorption system in order to control of inlet air humidity

In this research, drying process and shrinkage of Hawthorn in a laboratory scale was studied. The Hawthorn fruit was dried in a Vibro-Fluidized Bed (VFB) dryer by an air stream with 50, 60 and 70 oC inlet temperatures, and 0.92 and 1.06 m/s inlet velocities and 6.8, 7.5 and 8.2 Hz frequencies using an adsorption system, with silica gel particles as adsorbent media, in order to control the inlet air humidity from about 27 relative percent to 4 relative percent. Results show that the drying time of Hawthorn in VFB dryer in present of control humidity system was reduced significantly as compared to the drying in a VFB dryer without using control humidity system and this reduction is different for various operating conditions. For example, for inlet air velocity and temperature to the dryer equal to 0.92 m/s and 60 oC respectively, the drying time was reduced about 15 percent for device with inlet humidity control system compared to usual conditions. On the other hand, the shrinkage of Hawthorn was affected by inlet air humidity, temperature and velocity in the dryer and the effect of air velocity on the shrinkage of Hawthorn is less than to others. Among proposed mathematical models for drying and shrinkage of fruits, the Logarithmic and Ratti models were selected as the appropriate models for drying kinetic and shrinkage of Hawthorn respectively based on experimental conditions with largest amount of R2 and smallest amount of RMSE.