Analysis of heat conduction inside the nip of a machine calender for the same and different roll temperatures

Abstract

Calendering is a mechanical leveling and segmenting process at the final stage in many industries, like paper, printing, leather, and textile, where a thin sheet of material passes through the nips formed by two or more rolls in contact. The material composition of rolls varies for different types of calenders. Depending on the quality of products required for the end usage, the rolls can be hard or soft. Furthermore, they may be heated to a certain degree of temperature, using different heat transfer processes, such as induction, hot water passage, or heated oil passage. In this paper, the effect of roll temperature and time of contact (dwell time) on the temperature of newsprint paper in the thickness direction has been discussed using a single hard nip calender (machine calender), when the paper web is inside the calender nip formed by two rolls having the same and different temperature levels. The case of temperature gradient calendering has also been discussed.