Papers by Keyword: Thermal Process

Abstract: 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.

Abstract: As industry enters into high-tech society, the use of fossil energies is increasing. The demand of solar photovoltaic cell is increasing and according to this increase, the amount of waste photovoltaic cell will increase, too. However, compared to the increase of photovoltaic facility and technology, research about recycling method of waste photovoltaic cell is slow. Therefore, this study continued research to collect cooper and tin which are valuable metals from cooper ribbon electrode recovered from waste photovoltaic electrode. To effectively separate the coating layer when handling bulk of cooper ribbon electrode, heat treating furnace of hydrodynamic vibrating is developed and tin and cooper which are valuable metals are collected by using Hydro-metallurgical process used with nitric acid. The purity of cooper’s basic materials after heat treatment of hydrodynamic vibrating was 98.88wt.% and the purity of tin and cooper collected from the coating layer was measured as 98.07wt.% and 98.44wt.% each.

Abstract: 4H-SiC defects evolution after thermal processes has been evaluated. Different annealing temperatures have been used to decrease the defect density of epitaxial layer (as stacking faults) and recover the damage occurred after ion implantation. The propagation of defects has been detected by Photoluminescence tool and monitored during the thermal processes. The results show that implants do not affect the surface roughness and how a preliminary annealing process, before ion implantation step, can be useful in order to reduce the SFs density. It shown the effect of tuned thermal process. A kind of defect, generated by implant and subsequent annealing, can be removed by an appropriate thermal budget, while others can increase. A fine tuning of thermal process parameters, temperature and timing, is useful to recover the crystallographic quality of the epilayer and increase the yield of the power device.

Abstract: Coal fly ash is a complex mixture of anthropogenic materials produced during the combustion of pulverised coal in coal fired power plants. They pose environmental concerns that lead to air and water pollution. Effort has been done to reduce the production of coal fly ash or to extract potentially valuable products from coal fly ash, such as cenospheres. Cenospheres are light, low density, thin-walled hollow ceramic microsphere with unique properties. Conventional cenosphere production methods involve the separation of cenospheres from coal fly ash. Due to its small quantities in fly ash (1 % wt.), separation process results in low production of cenospheres. In this work, an attempt by applying a vertical thermal flame (VTF) process is done to produce cenospheres from coal fly ash. Particle size of coal fly ash 63 to 90 μm and 90 to 126 μm are selected to undergo the VTF process. Effect of size of precursor, number of passes through the thermal process, density, morphology and particles size of generated spheres are evaluated. The results show that different sizes of coal fly ash and number of passes through the VTF process affect the morphology of obtained spheres and the overall real density. Further optimization of the VTF process design in terms of heat source and the feeding mechanism are required to increase the transformation of coal fly ash to cenospheres.

Abstract: Among individual techniques of wood treatment, there are highly significant differences in the greenhouse gas balance. Greenhouse gases have, according to the currently adopted global convention, a major impact on global warming and climate change. Nevertheless, there are also sceptical opinions on the scientific basis of such concept. As well as the natural processes of tree growth and the end of their life cycle, the wood processing technologies also affect the balance of greenhouse gases on Earth. The current natural forest without human intervention does not have to reduce greenhouse gas emissions definitely, but can also be the source of their emissions. Also, technological, particularly thermal, processes have different contribution to the production of greenhouse gases. The submitted paper presents the context of warming and cooling of the Earth during its development with a concentration of carbon dioxide in the atmosphere. Further, the indicative greenhouse gas balance, respectively, CO₂ generated at thermal wood processing processes, are analysed.

Abstract: The article contains sub-results from analyses of processes in thermodiagnostics. In this paper we give examples of the response simulation model of thermal processes on the step pulse. It describes a method of applying diagnostics in machine production. The paper describes a method of prediction values of consistently transient events that can be described by a mathematical function. This article focuses on thermal process. This gives some reasonable time to take an appropriate control plot in the desired values of variables borders. The article contains results of the simulation and plot comparison of simulation results with the measured value.

Abstract: Thermal process usually has the characteristics of nonlinearity and uncertainty, so it is difficult to establish the nonlinear model by the traditional method of describing the dynamic mathematical model of thermal process and accurately implement optimal control of thermal process. This paper provides an identification method of thermal process based on relevance vector machine and firefly algorithm, and the modeling results are compared with those by minimal resource allocation network and support vector regression. The simulation results show that the method is effective, and the model has high accuracy and can be directly used in control algorithm based on the model.

Abstract: The examination of the main machining methods applied in manufacturing processes from machine building and based on material removal from workpiece highlights essentially the existence of distinct processes able to generate material. An analysis of certain machining methods able to develop processes of material removal from workpieces was initiated by taking into consideration the principle machining schema and the capacity of generating machined surfaces. One concluded that within distinct machining processes, various phenomena are applied in order to obtain material removal from workpiece.

Abstract: s: The effects of homogenizing treatment and thermal process on microstructures and mechanical properties of Mg-12Li-0.5Al-1Zn alloy (LAZ1201) were studied. The results show that the grains of LAZ1201 alloy are refined evidently and the dynamic recrystallization happens during thermal process. The tensile strength and elongation of the as-cast LAZ1201 are 138MPa and 38%, respectively. In this paper, the best mechanical properties with a maximum tensile strength of 166 MPa and elongation of 50% were achieved by 30% rolling.

Abstract: The article presents the analysis of thermal flows into reactor walls within the semi-operational pyrolytic system. There were hydrodynamic and thermodynamic similarity theories and heat transfer by radiation laws used for the solution of this issue. The entry data for the heat transfer analysis were gained by conducted experiments. The correctness of the resulting values has been verified by measurements. The required reactor parameters, for the required heat intake, have been derived from the analytical results at the end of this article.