Fractal theory on drying: A review

Fractal geometry has been widely used in various dried materials and drying processes. This review summarizes the related studies and identifies the opportunities for future investigation. The application of fractal concept on drying can be categorized into describing microscopic and macroscopic structure of material in drying with fractal geometry and theoretical models with fractal theory for drying mechanism. And also, the capillary and network models for drying of capillary porous media are discussed and a fractal tortuous capillary model for drying of capillary porous media is proposed. From the selected examples, it is clear that the fractal theory has many advantages for identifying the complex structure of products and investigating drying mechanism. At last, some comments are made for the current investigations and also some prospects for the future development of this field are pointed out.