Aplicação da abordagem euleriana granular multifásica na previsão da transferência de calor e massa na secagem do yacon

Abstract

Yacon (Smallanthus sonchifolius) is a tuberous root with high functional value, whose industrial preservation requires efficient dehydration processes that preserve its bioactive compounds. The computational simulation of this process aims to simultaneously represent the heat and mass transfer of yacon sphere drying. To this end, it was necessary to develop and validate a multiphase Eulerian-Granular approach, via Computational Fluid Dynamics (CFD), to predict the convective drying of yacon spheres. The methodology integrated experimental and numerical stages. Initially, the physical and thermophysical properties of the samples were determined, presenting values consistent with the literature, and used as input parameters in the simulation. Experimental drying for validation was performed in a forced-air tunnel dryer, varying temperatures (50 and 70 °C) and velocities (1 and 3 m s⁻¹), with the 50 °C and 1 m s⁻¹ condition selected for the simulation due to the model's high computational cost. The experimental determination of the convective heat coefficient (h) revealed a critical limitation in modeling focused solely on heat transfer: When using only the energy equation with the calibrated h, the simulated temperature diverged from real behavior, exceeding the wet-bulb temperature by failing to account for evaporative cooling. To bridge this gap, a novel coupling of the Species Transport model was implemented, treating water evaporation as a mass consumption reaction. Results initially reproduced the yacon-water loss curves and water accumulation in the air. It is concluded that the developed method successfully reproduced, initially within the simulated 0.23 s, the fundamental physical mechanisms of evaporation, constituting a novel predictive tool for drying process engineering.