Modeling and comparative analysis of solar drying behavior of yam (Rhizoma dioscoreae) slices

Yam (Rhizoma Dioscoreae) is prone to spoilage when stored fresh. Drying is a well-established preservation technique that extends its shelf life. Solar energy, due to its directly usability and environmental friendliness, offers ideal conditions for drying. This study investigates the drying dynamics of yam slices by combining forced convection and solar radiation. Our findings indicate that the solar drying of yam slices follows the Page model, signifying a prototypical slow-drying procedure. Utilizing Fourier and Laplace transformations, which characterizes a typical slow-drying process. Using Fourier and Laplace transformations, the effective moisture diffusion coefficient was evaluated, along with thermodynamic parameters such as activation energy, Gibbs free energy, enthalpy change, and entropy change. The effective diffusivity values obtained through Fourier transform were higher than those derived from the Laplace transformation, with the calculated activation energy being 35 kJ/mol. Thermodynamic parameters were calculated using the Eyring-Polanyi equation, adjusted for temperature based on the effective diffusivity method. The enthalpy change was 92.95 kJ/mol, indicating endothermic behavior during the drying process. The entropy increase was 435.34 J/(K·mol), suggesting increased disorder during drying. The negative Gibbs free energy change indicates a spontaneous drying process. This study provides a reference for optimizing process parameters and developing drying equipment for yam solar dryers.