Simulation of Electrical Heating of Materials in Metallic Capacity of Cylindrical Form

Electrical and thermal processes, occurring while heating materials in metallic capacities of cylindrical form, are examined. The peculiarities of those processes are defined, and it is shown that their essence is in the way of distributing the sources of heat, while using different methods of electrical heating, in the change of properties of the heated material under varying temperature and in the course of the process in time. Mathematical model to calculate the thermal process, taking place in the heated material, taking into consideration the changes of its thermal parameters, as well as the character of the controlling electrical actions, is developed. On the basis of differential equation of the process of heating and boundary conditions, difference equations are formed, which allow to solve the task by numerical method. The solution is carried out by the method of passing. Analytical dependences to determine the coefficient of the method of passing, and temperature in the random point of the heated material are obtained. It is proposed to carry out the correction of the thermal parameters of the heated material while calculating the coefficients in the process f the “direct” course of the method of passing. The values of temperature of the material, obtained in the period of the preceding “reverse” course of passing, are taken into consideration with that. The opportunity to concentrate the sources of heat both in the internal and external covers of the installation is realized. The change of intensity of their action in time is possible, and that allows to reproduce a wide range of the controlling actions. Algorithm for task solution on the electronic computer is developed. The example for calculating the thermal process of concrete heating in winter time is considered.

Thermal performance of wooden elements exposed to microwave radiation during treatment of building defects

The paper describes application and theory of microwave radiation and experimental optimization of microwave radiation in relation to its growth of temperature inside and outside of wooden elements. The effect of microwave radiation on building structures is first manifested by vibration of water molecules contained in the material, which leads to a change of the state of matter from liquid to steam, which then evaporates from the wet material. During the transformation of energy from liquid state of matter to steam, heat is generated, therefore, wooden elements heat up. Therefore, the irradiated element, a wooden one in this case, gets dried up. More precisely, the paper assesses the effect of the heating times and distance of heated material from the microwave generator (antenna) and reached temperatures on the surface and inside of the irradiated spruce elements. Individual experiments were performed and results were evaluated for all wooden elements. Wooden samples were divided into two groups. Individual groups were exposed to microwave radiation for different times. In total there were two groups of spruce samples, where individual elements were exposed to identical ambient (outdoor) conditions for a long time.

Numerical simulation of induction heating thick-walled tubes

In the paper is shown the connection of two toolboxes in an Ansys Workbench solution for induction heating. In Ansys Workbench, Maxwell electromagnetism programs and Fluent have been linked. In Maxwell, a simulation of electromagnetic induction was performed, where data on the magnetic field distribution in the heated material was obtained and then transformed into the Fluent program in which the induction heating simulation was performed.

Impact of Pretreatment of Wheat Grain Using Infrared Radiation on Flour Falling Number

The aim of the research was to determine how time of infrared radiation heating of grains influences the falling number of flour gained from wheat variety Waluta and spelled wheat variety Schwabenkorn. Moisture content was determined in the first stage of the study and it was 12% ± 1%. Then grain was moisturized to the moisture of: 14, 16 and 18%. Prepared material was subjected to infrared radiation heating at the temperature of 150°C for 30, 60, 90 and 120 seconds. The heated material was sent to milling, and the falling number was determined. It has been found that the infrared radiation heating of wheat grains prior to milling significantly affects the falling number of flour, which increases with the duration of heating grain.

Temperature profiles in microwave heated solid foods of slab geometry: Influence of process parameters

A simple 1-D mathematical model for prediction of local temperatures in a layer of solid material during microwave heating (Houšová et al. 1998) and a sensitivity analysis were used to evaluate the influence of process and material parameters on vertical temperature profiles in a layer of material during heating. The results of calculations are presented in graphs and discussed. The incident microwave power and heat capacity and density of heated material are parameters with great effect on all local and average temperatures and local and average heating rates. The shape of temperature profile is influenced only to a small extent by a change in the value of applied microwave power and also in the value of heat capacity or density of heated material. The whole profiles shift to higher or lower temperature values when the incident microwave power is changing. The distribution of applied microwave power between the upper and bottom layer surface very much influences the shape of the profile and the values and position of the highest and the lowest temperature in the layer. Depth of penetration and thermal conductivity of heated material influence on the shape of temperature profiles and the temperature spread in the layer (evenness of temperature distribution). Effect of penetration depth also depends on the relation to the layer thickness – its effect increases with the increasing layer thickness. At the low values of penetration depth relative to the layer thickness, an uneven temperature profile is to be expected. Effect of thermal conductivity value on temperature profile depends on the time of heating. Because of a short time of microwave heating, the effect of this parameter on temperature distribution is smaller compared to the conventional heating methods. At the beginning of heating its influence is quite negligible. Temperature of the air surrounding the layer and intensity of heat exchange between the air and layer surface are parameters with only small local effect on temperature distribution.

The Optimization of Heating the Billets in the Mills

The heating of basic material is considered the first step of the plastic hot forming. Most of the „prescriptions” concerning this process are based on practical data and basically they can be limited to the checking of the surface temperature of the billet. The model described in this paper makes it possible to determine the temperature distribution developing inside the billet while the system of the conditions of warm-up can be planned and optimized as a function of the physical parameters of the heated material.