Combined convective and infrared drying of a capillary porous body

This research has resulted in the design and development of an experimental facility to study the combined convective infrared (I.R.) drying process of a capillary porous material (glass beads) in high temperature flow conditions.;A drying front model is also presented and tested with the experimental results in convection drying and for the combined process. The drying time, the bottom temperature evolution, the surface temperature evolution up to the critical point and the overall shape of the drying rate curve were well reproduced by the model. Simulations have also showed that the effect of the diffusion mass flux on the heat and mass transfer coefficients leads to a decrease of the evaporation rate by a maximum of 8% for both the purely convective and combined processes.;The necessity to decrease the heat transfer coefficient for the effect of high mass transfer flux (when convection is combined with I.R. heating) has been demonstrated. Further, the analogy between the transfer of heat and mass expressed in terms of average heat and mass transfer coefficient ratios has been verified to apply when the surface is not contaminated. Experiments have also showed that there is a link between the evaporation temperature and crust formation at the evaporating surface. Moreover, an increase in the heat transfer coefficient was observed when the surface reaches the boiling point and is higher than that of the flowing air. Lastly, it was observed that the critical moisture content is independent of the convective drying parameters, sample thickness and the overall incident heat flux.