Sensitivity Analysis of Internal Mat Environment during Hot-Pressing
Keywords:Wood composite, hot-pressing, modeling, flakeboard, simulation
The effect of several hot-pressing parameters on the internal mat environment was investigated by using a hot-pressing simulation model. The results were compared to experimental data from laboratory-produced flakeboard. The pressing parameters included initial mat moisture content, final panel density, press platen temperature, and press closing time. The variation of temperature and total gas pressure during the press cycle at six points in the vertical mid-plane of a single layer, random mat structure was predicted with the heat and mass transfer model using the different pressing conditions. Twenty-four boards were manufactured according to the same specifications, and the temperature and internal gas pressure were measured with thermocouples and gas pressure probes at the same six locations. The model consistently predicted the major trends during the hot-pressing operation.
The hot-pressing simulation model used in this study was developed based on fundamental engineering principles. The material physical and transport properties were the best available values from the literature or best estimates based on engineering judgment. A sensitivity study assessed the relative importance of the different transport properties during the hot-pressing process. The sensitivity analysis of the model parameters revealed that the thermal conductivity and gas permeability of the mat have the greatest influence on model results. The assessment of these transport properties experimentally, as a function of mat structure, is highly desirable and can considerably improve future model predictions.
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