The role of convection in drying

Abstract An analytical solution is presented for drying a material from one side. The material intially contains a solid or liquid phase. A quasi-steady model is adopted since the usual drying situation is slow and sensible heating effects are small compared to the latent heat of phase change. The thermal properties are constant and the thermal boundary conditions involve constant temperatures at the following positions: the heated surface, the interface between the dry and frozen regions and the back surface of the material. An ‘exact’ solution is found for the drying rate and temperature distribution in the drying material. A partially numerical solution and an approximate closed form solution are presented for the drying time. All equations are presented in non-dimensional form. For the usual range of parameters involved in drying problems of this type, the results show that the approximate solution for drying time is accurate within 2 per cent. The analysis can be used in a simple manner to extend and check and the validity of the approximate solution.