Evaluation of Thin Layer Models for Simulating Drying Kinetics of Black Nightshade Seeds in a Solar-Exhaust Gas Greenhouse Dryer

Abstract

: The current study aimed to use, besides solar, waste heat from exhaust gas of a diesel engine operated for milling of grain, to dry black nightshade seeds. Assessment of thin layer models for simulating drying kinetics of black nightshade seeds was performed in a solar-exhaust gas greenhouse dryer operated on solar; solar-exhaust gas; and exhaust gas modes. In solar mode, seeds took 11 hours to reach a final moisture content of 7.13% (db) from an initial one of 89.34% (db). In solar-exhaust gas mode seeds were dried from an initial moisture content of 92.57% (db) to a final one of 6.07% (db) in 10 hours. In exhaust gas mode it took 14 hours to dry black nightshade seeds from an initial moisture content of 88.84% (db) to a final one of 9.42% (db). Newton, Page, Logarithmic, and Henderson and Pabis thin layer drying models were fitted to experimental data and the best model was selected based on low root mean squared error (RMSE) and interpretation of residual plots. To best explain the prediction of thin layer drying of black nightshade seeds, based on the lowest value of RMSE, Page model was found suitable for solar mode with RMSE of 0.01147206, Logarithmic model was found suitable for both solar-exhaust gas and exhaust gas modes of drying with RMSE of 0.0172098 and 0.02315325 respectively. In conclusion, the thin layer modeling approach can be used to provide design data for a solar-exhaust gas greenhouse dryer.