Heat Transfer Model in Calender Nip – Verification From Experimental Data On Agricultural Residue Based Coated Paper

The existing models for heat transfer during calendering were mainly due to Keller, Hemesto and Lamvik, which were applied for calendering of newsprint in hardnip machine calenders. The experimental data of newsprint pilot machine were used for simulation. However, the models were never applied for soft nip calender to check their validity. Besides the derivation of models from basic unsteady heat transfer equation were not shown. In present day, demand for high quality papers both surface sized uncoated and pigment coated requires rewriting extension of above models. Therefore, the present investigation deals with simulation of data obtained for uncoated/coated paper made from agricultural residue pulps (bagasse/wheat straw) under laboratory soft nip calender. The basic heat transfer equation were used along with functional dependence of thermal conductivity, thermal diffusivity, specific heat, density etc. and the extended models have been used for simulation and compared with those of Keller's for constant value of coefficient for coated/ uncoated papers. This model is integrated with nip mechanics model of Hertz.