EXPERIMENTAL STUDY OF THE EFFECT OF DRYER CONFIGURATION ON INTERNAL TEMPERATURE AND MOISTURE PROFILES IN THE SHEET DURING CYCLIC CONTACT DRYING

摘要

Contact drying studies on a laboratory scale are often carried out with static dryingrndevices. This means that the paper sheet is dried against a hot plate, and usually only onrnone side. This brings about some major differences, concerning heat and mass transferrnwhen compared with pilot and production scale processes. Production scale processesrnare usually cyclic, whilst laboratory drying is often static.rnThe objective of this study was to measure the development of temperature andrnmoisture profiles in paper during cyclic drying, both in single-sided and double-sidedrnconfigurations. Moreover, the effect of contact time (machine speed) was examined. Anrnexperimental apparatus for measuring the temperature and moisture profiles during arncyclic drying process was constructed. The experimental apparatus consists of arncomputer based data acquisition and control system, a sample frame with a traversingrnsystem for the sample movement, and two plate surfaces, which are temperaturerncontrolled.rnLaboratory hand sheets prepared from one, three and six layers with total basis weightrnranging from 67 to 430 g/m2 were dried in single- and double-sided configurations.rnCycle duration ranged from 1 to 10 seconds. The results showed that the temperaturernand moisture profiles in the sheet are strongly dependent on the drying configuration.rnCycle duration has a clear effect on the internal temperature development, but only arnsmall effect on the moisture profile.