Simulation of the convective drying process with automatic control of surface temperature

• Automatic control of surface temperature prevents overheating of drying matter.
• Thermally sensitive products can be exposed to higher temperature in the first stage of drying.
• A lumped parameter model is proposed to simulate the process.
• Automatic control can be based on the lumped parameter model.

In convective drying of fruits and vegetables the maximum temperature develops at the product surface. Furthermore, heat sensitive products can be subjected to high air temperatures in the first stage of drying where the difference between air temperature and wet bulb temperature of the product is still very high. Automatic control of the surface temperature, avoiding exceeding of the maximum allowable temperature, can guarantee for the best drying results in terms of product quality.In the study presented, a lumped parameter model, based on experimental results, for both the drying process of apple slices as well as the automatic control functionality is proposed. The simulation model shows close correlation with experimental data and can be used to determine optimum control and process parameters for convective drying of apples slices. Application of this strategy leads to a significant decrease of drying time and, potentially, increase of process efficiency and product quality.