Eur. Phys. J. E (2016) 39: 25
https://doi.org/10.1140/epje/i2016-16025-6

Regular Article

Heat and mass transfer models to understand the drying mechanisms of a porous substrate

¹ Laboratory of Paper Coating and Converting and Center for Functional Materials, Abo Akademi University, Porthaninkatu 3, FI-20500, Åbo/Turku, Finland
² Department of Chemical and Biological Engineering, University of Maine, 5737 Jenness Hall, 04469, Orono, ME, USA
³ School of Chemical Technology, Department of Forest Products Technology, Aalto University, P.O. Box 16300, FI-00076, Aalto, Finland
⁴ Omya International AG, CH-4665, Oftringen, Switzerland

^* e-mail: joel.songok@abo.fi

Received: 8 June 2015
Accepted: 8 January 2016
Published online: 26 February 2016

Abstract

While drying of paper and paper coatings is expensive, with significant energy requirements, the rate controlling mechanisms are not currently fully understood. Two two-dimensional models are used as a first approximation to predict the heat transfer during hot air drying and to evaluate the role of various parameters on the drying rates of porous coatings. The models help determine the structural limiting factors during the drying process, while applying for the first time the recently known values of coating thermal diffusivity. The results indicate that the thermal conductivity of the coating structure is not the controlling factor, but the drying rate is rather determined by the thermal transfer process at the structure surface. This underlines the need for ensuring an efficient thermal transfer from hot air to coating surface during drying, before considering further measures to increase the thermal conductivity of porous coatings.