Thermal Conductivity of Handsheets, Papers and Model Coating Layers

Abstract

Thermal conductivity of paper is a property of importance in the understanding of conductive heat  transfer in the pulp and paper industry. For example, heat transfer between a paper web and a heated roll in a nip during calendering. Besides, the trends in the calendering area are to replace machine calenders by soft calenders and to replace cotton filled rolls by polymeric rolls in the supercalenders. As a result, temperatures of heated rolls in calenders are increasing constantly. There is a need for measuring thermal conductivity of paper. Some measurement methods and some values of thermal conductivity are available in the literature. But measurement methods are often reserved to specialists and values of conductivity show great variations. This drove us to develop a rapid method to measure the thermal conductivity of semi-insulated films. Our objective was to be able to measure the thermal conductivity of papers, of polymers and of model coating layers–with simplicity and rapidity, if necessary at the expense of the accuracy. Indeed heat transfer calculations often used a lot of restrictive hypotheses and a measurement of the thermal conductivity with an accuracy of less than 10% is quite sufficient.