Heat Transfer Analysis of a Bevelled Blade: Experimental and Theoretical, 2000 Coating Conference Proceedings

M. Hyensjo, B. Sunden, D. Eklund--The aim of this study was to clarify the influence of different base papers and pre-coated base papers on the heat transfer in the vicinity of the bevelled blade tip during coating. Several trial runs on a high-speed pilot coater were carried out to study the influence of machine speed, paper grade and blade load (coat weight). A heat conduction analysis for the blade was performed as the blade was cooled both with coating colour and with air. An apparent friction force was defined and introduced assuming that all heat generated under the blade tip is caused by an apparent friction force times the machine speed. A linear correlation between the tip temperature and the apparent friction force was found for a machine speed of 1250 m/min. The conclusion is that the tip temperature can be used as a quantitative measure of the heat generation under the blade. A further interesting result was that a higher surface roughness of the paper led to a higher tip temperature at the same blade load, which indicates that the surface roughness of a paper influences the heat generated under the blade. The theoretical temperature distribution gave an underestimation of the temperature in the blade compared with experimental data, due to the low value assumed for the overall heat transfer coefficient.