Рассмотрены вопросы тепло- и массопереноса на первом этапе сушки бумажного полотна, в частности тепло- и массообмен между сушильным цилиндром и бумажным полотном, окружающей средой и бумажным полотном, а также перенос теплоты и влаги в материале. Проанализирована физика процессов, получены уравнения для расчета температуры и влажности крайнего и центрального слоя бумаги при прохождении через сушильный цилиндр и на участке свободного хода.
Drying section of a paper machine is the final stage of dehydration of the paper web and largely affects on many indicators of quality of the finished product. All drying process consists of three successive stages of passing: heating a material, portion of constant drying rate and decreasing drying rate. The analysis of the first stage of drying, heating process is presented in this work. Each part of the process which can be separated into such components: transfer of heat and moisture on the contact portion of the paper web with the drying cylinder, on a plot of a freewheeling and transferring heat and moisture inside the material. For each of them was created a mathematical model wish allows to calculate the temperature and humidity of the paper web. For accurate simulation was made a detail analyze of heat transfer from the drying cylinder to a paper web. Due to the heterogeneity of the temperature field inside the material, the heat transfer is divided into two parts, from the drying cylinder to the material surface and from the surface to the central layer. On the site of a freewheeling, most attention is given to processes of moisture transport from the center of the paper web into the environment through the material and drying the cloth.
As the dryer section consists of a series of repeated cycles, in the work was given the generalized mathematical model that calculates the parameters of paper at the end of each cycle under certain initial parameters of the paper drying cylinder and the ambient air.
The mathematic model, presented in this work, is the first part of the model that describes overall process of drying a paper web on a paper machine. Supplemented by models for areas of constant and falling drying rate, they allow calculating the parameters of the product at any point in its location in the dryer section. On the basis of the general model will be possible to build an optimal automatic control system. Such system will solve the actual task of reducing the cost of the paper web drying process with maintaining the specified quality parameters.
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