Modeling multicylinder paper drying - Validation of a new simulation program

A mathematical model was developed for the drying of paper in a multi-cylinder drying section. The model is based on the unsteady state, one-dimensional heat conduction equation, which is applied to both the cylinder shell and the paper web. No internal mass transfer phenomena were modeled explicitly. Great emphasis ws placed on finding the proper heat and mass transfer coefficients that are integral parts of the boundary conditions. Based on the mathematical model, a simulation program was developed. In order to verify the simulation output nine different industrial paper dryers were surveyed. These produced different paper grades: newsprint, fine paper, fluting, and paperboard. During a survey, temperatures and moisture contents of both paper and drying air as well as the temperature of the cylinder surface were measured. Seven of the nine cases involved steady-state production, whereas in the remaining two cases the basis weight and machine speed were altered considerably. The model applied just as well to lighter paper grades such as newsprint as to heavier grades such as paperboard. The data predicted by the program compared favorably with the measured data in all nine cases.