Investigation of Effective Moisture Diffusivity and Activation Energy in Thin-Layer Drying of White Yam Slices (Dioscorea rotundata): A Study of Solar Drying and Pretreatment Techniques

Abstract:

This research investigates the effective moisture diffusivity (D_eff) and energy activation (E_a) as it affects thin layer drying of white yam (Dioscorea rotundata) slices using hybrid drying system under different parameters. These factors helps researchers and food producers to develop optimized drying processes for yam slices in order to minimize drying time, improve energy efficiency, and maintain high product quality. The experimental analysis highlight the interplay between pretreatments (Blanching, B; Sodium metabisulfite, SNa; Neem bark extract, SNBE and Control, C), drying systems (indirect solar drying: ISD and solar-powered hot-air supplemented drying: SPHSD under 0.8 m/s and 1.2 m/s air velocity, and air temperatures of 50 °C, 60 °C, and 70 °C) and slice thickness (5 and 3 mm) on white yam slices during drying. Important data were obtained using Arduino based data logging system for accuracy. Mass transfer during the entire drying of the yam slices took place entirely in the falling drying rate period and was described using Fourier approach based on Fick’s second equation of diffusion. The result demonstrated that D_eff and E_a is significantly affected by petreatment, slice thicknesses, air velocity and drying system. D_eff increased with rising drying temperature and air velocity. However, SPHSD, at 5 mm thickness exhibited a decrease in D_eff compared to 3 mm with values ranging from 1.647 × 10^-10 to 2.790 × 10^-10 m²/s within the investigated parameters. In contrast, ISD and sun-dried yam slices displayed relatively lower and fluctuating D_eff values (not higher than 1.4 × 10^-10), likely due to intermittency in solar radiation. Specific energy consumption varies from 6184.373 J/kg.K to 4620.571 J/kg.K for different thicknesses, temperature and air velocity. Thermal efficiency values which decreases with increased slice thickness ranges from 52.539 % to 39.347 %. Drying efficiency increases with increased temperature and air velocity for SPHSD (87.020 % to 93.169 %) while ISD has the least at 54.196 %.

• Periodical: Advanced Materials Research (Volume 1185)
• Pages: 75-92
• DOI: https://doi.org/10.4028/p-H58gpP
• Online since: December 2025
• Authors: Oluwafemi Taiwo Aduewa*, Solomon Ajiboye Oyerinde, Patrick Ayoola Olalusi, Samuel Oladele, Simon Gbenga Omotoso
• Keywords: Drying Efficiency, Hybrid Solar Dryer, Moisture Diffusivity, Specific Energy, Thermal Efficiency, White Yam

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