An Experimental Study of Contact Coefficients in Paper Drying

The influence of different dryer fabrics on the contact coefficient has been studied experimentally under various conditions. A bench-scale drying apparatus, in which the fabric could be fixed at variable tensions, was used in the experiments. A technique for measuring the heat flux and surface temperatures of the paper sample and the hot surface was developed. Three paper grades were used in the investigation: newsprint, fine paper, and liner The key parameters affecting the heat transfer were found to be the moisture content of the sheet and the hot surface temperature. The applied fabric tension, the number of contact points and the contact area of the fabric did not have significant influence on the heat transfer in the 2-6 kN/m fabric tension range investigated. An extensive review of the literature on contact coefficients was conducted. It showed a very large scattering of results, due mainly to different experimental conditions and techniques.