Numerical and experimental investigation of paper drying: Heat and mass transfer with phase change in porous media

The physics of paper drying combines heat and mass transfer with phase change in wet porous media. The drying processes can be modeled with the liquid and vapor mass conservation equation, the liquid–gas mixture mass conservation equation, and the energy conservation equation. The drying model of paper includes the convection and the capillary transport of liquid and the convection and the diffusion transport of gas and vapor. Numerical simulation and experimental investigation of whole paper drying are done on an actual paper machine. The drying parameters in boundary conditions including the temperature of outer surface of the cylinder, the temperature and the relative humidity of the air pocket were measured. The numerical results of paper sheet temperature of the first 26th cylinders and the final moisture content after 78 cylinders agree well with experimental data, which means the drying model is valid to predict the performance of paper drying.