Modelling and simulation of multi-coupled heat and mass transfer processes: A case study of solar biomass dryer

This research aims to develop and simulate multi-coupled heat and mass transfer models for the solar-biomass drying process of agricultural products. The model took into account all the possible resistances to the transport processes by coupling the diffusion, source, or sink terms of the transport models. A stable numerical solution of the models was achieved by the finite difference method via the Crank-Nicolson scheme with a well-relaxed stability criterion(<< 0.5). The results of the drying simulation yielded drying rate constants of0.0318 -0.03061h(-1), average drying efficiency of 0.129 - 0.145 and drying time of 48-144 h, for solar drying of plantain slices with and without a biomass furnace as a supplementary heat source. The simulated transport variables were used to validate the measured results sequel to the practical Biot numbers (<< 0.1), which accounted for the agreement between the experimental and simulated results. Also, the simulated drying rate constant was in agreement with the Arrhenius postulated evaporation rate constant for the two drying methods. Moreover, the solar-biomass drying of the sliced plantain from the initial moisture of 0.67kg(water)/kg(ds) to the final moisture of 0.15kg(water)/kg(ds) was accomplished within 48 h of continuous drying whereas the solar drying took 144 h of quasi-continuous drying to achieve the same result. The present work suggests the automation or regulation of heat from the biomass furnace to achieve quality drying within a short drying time with higher energy utilization efficiency.