Heat and moisture transport in a paper sheet moving over a hot print surface

The generation of moisture-induced deformations during the final use of paper is of concern for the printing industry. Knowing the moisture profiles during printing is a primary step in order to understand such deformations. In this paper we derive a mathematical model to describe the heat and moisture transport in paper, and use this model to study the moisture gradients induced on a paper sheet by a printer from Océ Technologies, which contains a hot print surface. The model regards paper as a porous medium saturated with air, and it considers heat and moisture transport along the length and thickness directions of the sheet. Several physical parameters are determined experimentally; others are taken from literature. The system of coupled differential equations is solved iteratively, and the numerical results are also used to identify the relevant driving forces in the temperature-induced moisture changes in paper.