Sun drying of cocoa with firebrick thermal storage materials

Abstract

The thin-layer drying process of N38 cocoa beans using open-sun and a solar drying (SD) system with firebrick heat storage materials (FTSM) has been modeled. The 10 kg capacity force convective SD system was developed and used to carry out the experiments. The choice of the best model was based on a comparison of statistical indicators including determination coefficient (R2), reduced chi-square (χ2), root mean square error (RMSE), sum of square error (SSE), and normalized root mean square error (NRMSE) after fitting the experimental results to 11 common thin layer models in the literature. The results revealed that under open-sun drying and SD processes, the Midilli et al model provided the best drying characteristics of cocoa beans. Therefore, in the experimental context, this model can be assumed to reflect the solar/sun drying behavior of cocoa. The effective diffusivity values for the open-sun and SD of cocoa with FTSMA and FTSMB were 4.25× 10−11, 6.64× 10−11, and 5. 95 × 10−11 m2/s respectively. The predicted pre-exponential factor and activation energy were 5.81 × 10−11 m2/s and 22.79 kJ/mol respectively.