A. Zomorodian - Department of Agricultural Engineering, College of Agriculture, Shiraz University, Shiraz, Islamic Republic of Iran.
M. Moradi - Department of Agricultural Engineering, College of Agriculture, Shiraz University, Shiraz, Islamic Republic of Iran.

This paper presents mathematical models of thin layer forced convection solar drying of Cuminum cyminum using two drying methods (mixed and indirect) at different operating conditions. The average initial moisture content of the seeds for all tests was about ۴۳% d.b. and the drying was performed continuously, in each test, for a uniform period of ۹۰ minutes drying time in a solar cabinet dryer to obtain an average final moisture content of ۸% d.b. Three airflow rates (۰.۰۸۴, ۰.۱۲۷ and ۰.۱۵۵ m۳ s-۱) were adopted and the experiments were run each sunny day from ۱۱:۳۰ to ۱۳:۰۰ with an average solar intensity of ۷۵۰ W m-۲ (±۵۰ W m-۲), ambient air temperature of ۲۷°C (±۱°C) and relative humidity of ۳۰% (±۱%). In order to find the most suitable form of thin layer solar drying model, eleven different mathematical models were selected using the experimental data to determine the pertinent coefficients for each model by applying the non-linear regression analysis technique. The goodness of fit was evaluated by calculating and comparing the statistical values of the coefficient of determination (R۲), reduced chi-square (χ۲) and root of mean square error (RMSE) for any model and for the two drying methods. The best results were found for the approximation of diffusion model with R۲= ۰.۹۹۵, and RSME= ۰.۰۱۹۹ in mixed mode type, and the Midilli model with R۲= ۰.۹۹۴, and RSME= ۰.۰۲۲۵ in indirect mode type thin layer solar drying.

Cuminum cyminum, Mathematical model, Thin layer drying