Heat-transfer process during hot-pressing of flakeboard

Abstract

Hot-pressing is the main process in flakeboard manufacture. Studies in this field also emphasize the effect on the heat-transfer process of the following factors: hot-pressing temperature, original moisture content (MC), target thickness and target density. In this experiment, dynamic data of changes in temperature in mats can be logged through temperature transducers and a computer data log system. The results of the experiment indicate that the core temperature-time curve can be divided into three stages: a stage of a rapidly rising temperature, a stage of moisture vaporizing and a stage of a slowly increasing temperature. If the hot-pressing temperature or the original MC increases during the first stage, the temperature will increase at an accelerated rate. This rate of acceleration in thin or low-density boards is very high. During the second stage, increasing the hot-pressing temperature or decreasing the original MC can shorten the time used to vaporize moisture. In thin or low-density board, this time period is short. In the third stage the original MC does not affect the rate of temperature increase, while the effect of the other factors is the same as that at the first stage. Given different conditions, vaporization temperature in the mat changes.