In this work, an indirect solar dryer for drying cassava root chips was modelled and experimentally validated using the environmental conditions of Yaoundé in Cameroon and Yamoussoukro in Ivory Coast. The dryers were operational in natural convection mode. Resolution of the equations was achieved by finite differences and the 4th order of Runge–Kutta methods. A model was proposed for performing heat and mass transfer using thermophysical properties of cassava roots, and the obtained results were satisfactory for all conditions, with moisture content difference of less than 0.2 kg/kg between the experimental and theoretical results. The model showed that the core of the product takes more time to dry, which always prolongs the drying duration. The heat and mass transfer coefficients vary during the entire process of solar drying. The drying kinetics vary during the drying with values lower than 1.2 × 10⁻⁴ kg/(kg.s). The great gradients of humidity were observed in the thickness of the sample with a regular distribution of the temperature each drying time in the thickness of the sample.

In this paper, the thermal behavior of large pieces of wood pyrolysis has been modeled. Two mathematical models coupling heat transfer equations to chemical kinetics were used to predict the pyrolytic degradation of a 25 mm radius wood sample, assumed to be dry in the first model and wet in the second, when heated to 973.15 K. The reactions involved in the pyrolysis process are assumed to be endothermic. The diffusion of bounded water during the process is taken into account in the second model, where the heat transfer equation has been coupled to that of the diffusion of moisture. This model, although simple, provides more information on the drying and pyrolysis processes during the heating of wood, which is its originality. It can therefore be advantageously used to calculate the temperature distribution in a pyrolysis bed. The equations of the two models, discretized by an explicit finite difference method, were solved numerically by a program written in Python. The validation of both models against experimental work in the literature is satisfactory. The two models allow examination of the temperature profile in the radial direction of wood samples and highlighting of the effect of temperature on some thermal, physical and physicochemical characteristics.

This study presents the modeling of wood chips pyrolysis, considering the initial moisture content and taking into account the near-parallelepiped geometry of common wood chips, which is not available among the simulated shapes of wood in the literature. The goal is to extend the research and generate useful data on how different varieties of shapes and initial moisture contents influence wood chips pyrolysis. The effects of temperature and thickness variation on the pressure of volatile products, core temperature, and densities of pyrolysis products were studied. The model was validated with the mass fraction of experimental data obtained from beechwood chips with a density of 700 kg/m³ and thickness of 10 mm–30 mm at 973.15 K–1273.15 K. The mean absolute error (MAE) and mean relative error (MRE) values were, respectively, 0.066 and 10.376% at 973.15 K, and 0.065 and 22.632% at 1273.15 K. High temperature favored the rate of biocharcoal production from the surface to the core, though part of the biocharcoal was lost at the surface.