Low intensity convective drying of non-hygroscopic porous materials of high initial moisture content

The convective air drying of non-hygroscopic porous materials under low intensity and high moisture conditions is analysed. The variation of the moisture diffusivity with local moisture content is taken into account. The effects of the "dry" patches that develop on the product surface during the falling rate period are included. The concept of "enthalpy potential" is used to derive the coupled heat and mass transfer boundary condition at the product surface. Goodman's integral method is used to obtain the solution for the constant rate period. An iterative finite difference scheme is written to solve the heat and moisture transfer equations for the falling rate period. The results are presented in terms of seven dimensionless parameters for a particular case of linear variation of liquid diffusivity. The results show the trend that could be expected in drying practice. © 1976.