Numerical study on flow field uniformity of a pneumatic dryer

The non-uniformity of the airflow inside the dryer in pneumatic dryer directly affects the humidity non-uniformity at the exit of the cut tobacco, which is of significant importance to the quality of the tobacco manufacturing process. By establishing models of pneumatic dryer with two types of deflector, the unevenness of the airflow inside the dryer under different flow rate distributions of the hot air inlet and tobacco inlet is numerically analysed. The study found that the unevenness of the airflow inside the dryer is influenced by the flow rate distribution of the hot air inlet and tobacco inlet, the arrangement of the deflector and the structure of the equalizing roller. The variation of the coefficient of non-uniformity in the dryers with equidistant and non-equidistant deflector decreases with an increase in the flow rate of the hot air inlet. Under high flow rate conditions of the hot air inlet, the dryer with equidistant distribution plates exhibits higher non-uniformity in the flow field and temperature field. At the hot air inlet air volume of 30,000 m 3 /h-tobacco inlet air volume of 28,000 m 3 /h, the average value of non-uniformity coefficient decreased by more than 10%.