Mathematical modelling and validation of the drying process in a Chimney-Dependent Solar Crop Dryer

A simulation procedure describing the drying process within a Chimney-Dependent Solar Crop Dryer (CDSCD) has been developed. The simulation follows the authors’ experimental work on the effect of varying drying chamber roof inclination on the ventilation and drying processes, and their work on the development of simulation code to help optimise ventilation in such dryers. The current paper presents the modelling and subsequent validation of the drying process inside the dryer, to come out with a design tool for the CDSCD. The work considers the height of the crop shelf above the drying-chamber base, crop resistance to airflow and the shading on the drying-chamber base and their effects on the drying process. The under-load condition temperatures and velocities are predicted to within a relative difference of 1.5% and 10%, respectively of the observed values. Even though the heat inertia of the physical model causes deviation between the predicted drying path and the observed drying path, the two paths tend to converge at the end of each drying cycle, with a general prediction to within 10% relative difference of the observed crop moisture content. The validation results show that the simulation code can serve as an effective tool for comparing and refining the designs of the CDSCD for optimum drying performance.

► The simulation code predicts temperatures to within 1.5% of recorded data.
► The ventilation is predicted to within 5% accuracy.
► Effects of heat inertia cause the actual drying path to deviate from the simulated path.
► The two paths converge in the end with a final moisture content prediction to within 10%.
► The simulation code can be used to compare and refine the dryer designs for optimum drying performance.