Parallel Diffusion of Moisture in Paper. Part 1:  Steady-State Conditions

A theoretical model describing the steady-state transport of moisture in the thickness direction of a stack of paperboard sheets placed in a diffusion cup that accounts for the parallel diffusion of water vapor in the pore space and of bound water in the fiber phase is presented. The predictions of the model compare favorably with experimental measurements of the moisture transmission rate through a bleached kraft paperboard stack, average moisture content of the stack, relative humidity profile in the stack, and average moisture content of the individual sheets of the stack under steady-state conditions.