An industrial batch dryer simulation tool based on the concept of the characteristic drying curve

In this study an industrial batch dryer simulation tool is presented. The numerical model behind the scene is developed using the simulation software Engineering Equation Solver (EES) and compared to measurements from a batch dryer facility in Denmark producing insulation boards. In the constant-rate period, the model computes the average heat and mass transfer coefficients from EES built-in
correlations for the actual flow configuration (rectangular duct flows). The transfer coefficients are used to compute the single stream heat and mass exchange effectiveness, assuming the temperature and moisture content in the material to be invariant in the airflow direction. In the falling-rate period, the concept of the Characteristic Drying Curve (CDC) is used as proposed by Langrish et al. (1991), but modified to account for a possible end-drying rate. Using the CDC both hygroscopic and non-hygroscopic materials may be analyzed by the tool and guidelines for the determination of the CDC coefficients are provided.
The comparison of the simulation tool with measurements shows that the assumption of invariant material properties along the flow direction is doubtful at least for the actual case of interest. However, the tool may be used to analyze overall effects of inlet temperature, volume flow rate, geometry, infiltration etc. on the performance in terms of drying time, heat consumption and blower power.