Combining simulation and on-line measurements to determine moisture transport dynamics throughout the heatset offset printing process

• Published in: Applied thermal engineering Vol. 50; no. 1; pp. 1021 - 1028
• Main Authors: Tåg, Carl-Mikael, Rajala, Pasi, Toiviainen, Maunu, Juuti, Mikko, Gane, Patrick A.C.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 10.01.2013; Elsevier
• Subjects: Absorption; Applied sciences; Devices using thermal energy; Dryers; Drying of porous media; Energy; Energy. Thermal use of fuels; Evaporation; Exact sciences and technology; Heatset offset printing; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Moisture measurement; Photography, photographic instruments and techniques; xerography; Physics; Absorption; Moisture measurement; Evaporation; Drying of porous media; Heatset offset printing; Infrared detectors; Printing; Porous materials; Measuring methods; Calibration; Inks; Humidity measurement; Offset printing paper; Drying
• ISSN: 1359-4311
• DOI: 10.1016/j.applthermaleng.2012.08.005

The aim of the study was to explain the transportation of liquid (fountain solution) during transfer to coated paper in the heatset offset printing process, together with the subsequent drying of the printed paper, by using statistical and experimental methods. A coating dispersion, applied as a single coating onto a fine paper substrate, was formulated using a narrow fine particle size distribution natural ground calcium carbonate pigment and a styrene acrylic binder. The moisture variation in the paper during printing was monitored by using online multipoint sensors based on near-infrared diffuse reflectance spectroscopy. Based on the results, a simulation model was created to determine the transfer of liquid thin films in the printing units, the evaporation in the printing units, followed by liquid absorption and evaporation in the heatset offset drying process. An accurate simulation depends on precise determination of the different process parameters that influence these factors. The absolute liquid/moisture amount transferred to the paper showed an increased trend as the paper passed through the application nips, though the proportion varied due to limited capillary absorption capacity properties of the paper. The background evaporation in the printing nips was evaluated with the simulation model as well as the drying stages in the dryer including surface and bulk condensation followed by rapid evaporation and cooling. ► Real-time information of liquid imbibition in a porous medium from multiple locations in the process is obtained. ► Combination of simulations and measured online results reveals liquid transportation during drying. ► Simulations and online data separate absorption to evaporation ratio.