Modelling of the heating process massive batch
At technological processes of metallurgy and machine industry is metals heating one of the most important operations have influence on production in term of the efficiency, quality and costs. Charge inner temperature is an important variable in the heating process, because allows to determine the phase of the material treatment (change in the structure of the material). Currently, charge inner temperature is not measured for the following reasons: the design of the furnace (moving charge), destruction of a sensor during the process, the increased cost of furnace operation etc. This article describes a method for modelling the temperature in the charge, which is a steel coil. The method calculates the charge inner temperature by measured charge surface temperature in the annealing process. The resulting accuracy is evaluated by statistical methods.
The analysis of models for indirect measurement of surface temperatures in massive charge
2Analýza modelu pre nepriame meranie povrchovej teploty v masivnej vsadzke In this article are described the models for indirect measurement of the surface temperatures in the steel coil. The indirect measurement of surface temperatures is part of intelligent system of indirect temperature measurement in the steel coil. The major task of this system is to measure massive charge temperatures in the annealing process continuously in time. In the design and creation of these models we used the fact that only one direct measured temperature of the atmosphere was at our disposal – the one under the protection cover. The created and verified models are in the form of difference equations and the surface temperatures depend on the atmospheric temperature only. The system of indirect temperature measurement The task of the system of indirect temperature measurement in massive charge is the indirect measurement of internal temperatures during heat treatment. The system goes out the direct measured quantities and then it provides information about the temperature inside the charge. It’s impossible to obtain this information without destructive measurement. Nowadays we can divide the system of indirect temperature measurement into two basic models (Fig. 1): 1. The model for indirect measurement of surface temperatures, 2. The model for indirect measurement of internal temperatures. Both models are very important in the whole system of the indirect temperatures measurement. The internal temperatures inside the charge are calculated by the elementary balance method, following the surface temperatures. It was necessary to assemble models for indirect measurement of surface temperatures, because these temperatures are not measured directly. The model for indirect temperature measurement of the surface in massive charge calculates surface temperatures (Tsurface). These temperatures are calculated from directly measured temperature of the atmosphere (Tatm) and directly measured temperatures of the etalon (Tetal). The internal temperatures (Tinternal) inside the charge are calculated from indirectly measured temperatures of the surface (Kostur, 2005; Pastor, 2006).
Coefficients for calculating thermodynamic and transport properties of individual species
Libraries of thermodynamic data and transport properties are given for individual species in the form of least-squares coefficients. Values of C(sup 0)(sub p)(T), H(sup 0)(T), and S(sup 0)(T) are available for 1130 solid, liquid, and gaseous species. Viscosity and thermal conductivity data are given for 155 gases. The original C(sup 0)(sub p)(T) values were fit to a fourth-order polynomial with integration constants for H(sup 0)(T) and S(sup 0)(T). For each species the integration constant for H(sup 0)(T) includes the heat of formation. Transport properties have a different functional form. The temperature range for most of the data is 300 to 5000 K, although some of the newer thermodynamic data have a range of 200 to 6000 K. Because the species are mainly possible products of reaction, the data are useful for chemical equilibrium and kinetics computer codes. Much of the data has been distributed for several years with the NASA Lewis equilibrium program CET89. The thermodynamic properties of the reference elements were updated along with about 175 species that involve the elements carbon, hydrogen, oxygen, and nitrogen. These sets of data will be distributed with the NASA Lewis personal computer program for calculating chemical equilibria, CETPC.