Heat transfer to flowing fibre suspensions

Heat transfer measurements were obtained in a special flow loop with various suspensions of chemical pulps. Heat transfer coefficient h(c) values were calculated and are presented graphically as a junction of flow velocity. Systematic differences in h(c) values were obtained at a bulk velocity of 1.0 m/s for various fibre suspensions at 0.4% concentration. The magnitude of heat transfer coefficient h(c) at a fixed flow velocity and fibre concentration was found to correlate well with fibre length, fibre length to perimeter ratio, certain fibre flexibility indicators and actual flexibility measurements, as well as relative fibre number or fibre population. As a consequence, certain paper handsheet properties could also be correlated. The fibre-turbulence mechanisms of heat and momentum transfer are discussed briefly and data are presented to show that both heat transfer coefficient and functional pressure loss reflect changes in fibre characteristics.