Improving the airflow distribution in a multi-belt conveyor dryer for spice plants by modifications based on computational fluid dynamics

• Non-uniform drying in belt dryers was studied using computational fluid dynamics.
• The angle of the air distribution flap for both sides of the dryer was optimised.
• The air distribution across the belt was also optimised.
• The optimised airflow over the drying area gave uniform product moisture content.

The problem of uneven drying over the belt width in belt dryers is a consequence of inadequate air distribution leading to decreased throughput and high energy requirements. To achieve system optimisation, computational fluid flow simulations were conducted. A problem was discovered in the air distribution to both sides of the dryer, due to the incorrect angle of an adjustable distribution flap. When the angle was adjusted to 45°, the air mass flows from both sides were equal. Furthermore the air distribution across the belt width was inhomogeneous, studied by measurements of the air temperature and product moisture distribution. The simulation of the airflow led to the addition of air guiding plates. The influence of the guiding plates adjoining the drying chamber was confirmed by the fluid path length of the hot air. The study resulted in an optimised airflow over the drying area and uniform product moisture content.