Numerical simulation of drying process of cut tobacco in a cylinder dryer

To analyze the influences of drying conditions inside a cylinder dryer such as temperature and humidity fields and flow field during cut tobacco drying, these parameters were studied via numerical simulation. The accuracy of the simulated results was verified by measuring the air humidity inside the cylinder through a drying experiment, and the influences of the temperature and velocity of hot air at inlet, wall temperature and rotation speed of the cylinder on the moisture distribution inside the cylinder during drying were investigated. The results showed that: 1) The rise of hot air temperature at the inlet accelerated evaporation process. 2) The speedup of hot air velocity at the inlet enhanced moisture evaporation in the front section of the cylinder. However the overall moisture concentration inside the cylinder decreased if the hot air velocity at the inlet was too high. 3) The variation of cylinder wall temperature directly affected cut tobacco's temperature and equilibrium moisture content inside the cylinder, which increased with the rise of cylinder wall temperature. 4) The increase of cylinder rotation speed reduced the residence time of cut tobacco in the cylinder, which was not conducive to cut tobacco drying.