Heat and Mass Transfer Measurements for Bio-Substrate Drying Processes

Abstract

The complex process of heat and mass transfer in bio-substrates during convection, vacuum, and thermohygrostat drying was studied. Changes in temperature and moisture content at the center of the wet material were measured before and after the experiment in order to calculate the drying rate (%/h). In the case of convection drying, the inverter frequency within the wind tunnel was set at 10, 20, and 30 Hz (velocities of 2.2, 4, and 6 m/s, respectively). Measurements were then made at 10 and 20 Hz, with temperatures at 50 and 60°C. In the case of vacuum drying, the chamber pressure was set at 0.4, 4.2, and 92 Torr. The thermohygrostat was set at 50°C with humidity levels at 30, 40, and 50%. In conclusion, thermohygrostat is more effective because of the controlled environment, and that drying rate is increased with lower wind velocities and chamber pressures for convection and vacuum drying respectively.