Model for convective drying of carrots for pyrolysis

The effects of air temperature and flowrate on the drying of cylindrical carrot samples, which were blanched, peeled, or unaltered, were investigated in a tunnel dryer. The drying was carried out at 21, 42 and 56 °C, and at air superficial velocities of 0.5, 0.625, 0.75 and 0.95 m/s. The Henderson and Pabis model was used to compare results to previous works, but was deemed inadequate since it did not allow for biomass shrinkage or external mass transfer limitations to be taken into account. A simpler approximation was implemented using Crank’s surface evaporation equations to develop a model able to predict the diffusivity and mass transfer coefficient for the thin-sliced carrot samples, modelled as a slab, while accounting for shrinkage and both internal and external mass transfer limitations. Using this new model, an Arrhenius relation with activation energy of 31.76 kJ/mol successfully described the effect of temperature on the diffusivity.