Papers by Keyword: Heat Flow

Abstract: The cooling of the material during elastic tensile loading is well known as the thermoelastic effect. It is already known that the temperature minimum at the elastic-plastic transition can be used for the determination of the onset of yielding. Conceivable parameters for this have already been presented and investigated. Within this study factors influencing the specimen temperature during tensile loading and unloading are experimentally analyzed to improve the determination approach and the understanding of it. Furthermore, the robustness and repeatability of the measurement and evaluation procedures are analyzed. Therefore, cyclic tensile tests with the mild steel DC06 and the high strength steel CR590Y980T (DP1000) are performed with four PT1000 sensors applied on the specimen. The temperature behavior during elastic loading, elastic-plastic elongation and elastic unloading is separately evaluated. Different strain rates are investigated to better understand the strain-dependent heat development and its influence on the temperature-dependent evaluation. In this way, correlations between strain rate and thermal conduction due to prevailing temperature differences are found and their influence on the temperature-based determination of the onset of yielding is analyzed. Therefore, the yield stress at temperature minimum YS_Tmin as well as an additional yield stress at zero plastic strain YS₀ are evaluated for all experiment settings. In a comprehensive experimental study, the standard deviations are compared and thus conclusions can be drawn about the robustness of the determination methods.

Abstract: The use of metal-polymers in the manufacture of mold-forming parts allows for the significant reduction in price and time used in manufacturing of parts. Using data on the thermal conductivity of metal-polymers in calculations of the cooling system of molds allows calculating the optimal cycle of obtaining the product. The authors propose a method of determining the coefficient of heat transfer of metal-polymers based on a die matrix, filled with aluminum. The chosen equipment or measuring tool by them, allows determining the heat transfer coefficient of the material in use. The values of the coefficient of heat transfer of the material in question, obtained in the course of the research can be use in different databases of applications used for modeling production by injection molding. The described method of determining the coefficient of heat transfer may be repeated for samples of metal-polymers.

Abstract: The purpose of this work is to study the processes of spontaneous combustion of coniferous wood samples using a standard installation for determining the flammability classes of building materials "VSM", the study of the difference in the behavior of wood samples of different species under thermal action.

Abstract: The article describes a power efficient technology, allowing to preserve and maintain the heat content in a continuously cast bar at the production line “Continuous Casting Machine – Rolling Mill”. It considers a possibility of obtaining the maximum heat content in the continuously cast bar by means of rational cooling schedules in the secondary cooling zone. In order to maintain the achieved heat content in the bar, it is proposed to utilize heat insulation of the bar in the air cooling zone prior to its cutting-to-length. The article describes the design of the heat insulating shell in the CCM process scheme and the materials to be used for it. To analyze the interaction of heat flows between the bar and the shell in the heat insulation zone, the author has made a thermal balance of this zone. A mathematical model of the concast bar cooling with due consideration of the heat insulation zone and its implementation by means of numerical methods is described here. The application of numerical simulation has allowed to predict rational cooling schedules for the continuously cast bar and to determine the heat content of the bar at the exit from the continuous casting machine with respect to the heat insulation. According to the results of the simulation, there have been plotted the charts of temperature distribution along the CCM length, comparing the air cooling of the bar and its thermal conditioning in the heat insulation zone. These results confirm the effectiveness of utilizing heat insulation for maintaining the maximum heat content of the bar, which makes it possible to reduce the power costs for its heating prior to the rolling.

Abstract: The process of melt crystallization of the material in a twin-roll mold is considered. An adjoin of heat conduction through variable thickness of wall "rolls wall - hard layer" with a convective heat exchange from two sides problem important for the chemical industry is solved using Fourier method and Duhamel theorem. A theoretical dependence of the thickness of a frozen layer on the physical parameters of the melt and technological parameters of the crystallization process is obtained.

Abstract: It is universally accepted that defects in materials scatter thermal phonons, and that this scattering is the reason why defects reduce the flow of heat relative to the defect-free material. However, ab-initio molecular-dynamics simulations which include defect dynamics show that the interactions between thermal phonons and defects involve the coupling between bulk (delocalized) and defect-related (localized) oscillators. Defects introduce Spatially-Localized Modes (SLMs) which trap thermal phonons for dozens to hundreds of periods of oscillation, much longer than the lifetimes of bulk excitations of the same frequency. When a phonon traps in a SLM, momentum is lost and the decay of localized phonons does not depend on the origin of the excitation but on the availability of receiving modes. This strongly suggests that carefully selected interfaces and/or δ-layers can be used to predict and control the flow of heat.

Abstract: The effect of a moving arc spot on a material of a plasmatron electrode is considered in the present paper. Temperature-dependence of material thermophysical properties is taken into account. Dynamics of temperature and thermal stresses fields are calculated. The characteristic feature of temperatures distribution along radius of an electrode is large gradient of temperatures in a narrow zone near to a surface which can cause large thermostresses and microcracks.

Abstract: The article presents the possibilities for the contemporary application of Styrofoam in the elements of building structures. Having in mind that Styrofoam belongs to a group of highly flammable materials, 5 % of combustion retarder - so called "retardant" - needs to be added to the amount when produced for structural building elements. That kind of Styrofoam is called "self-extinguishing" contrary to "normal" that does not contain that substance. The Article also shows the way in which building elements are constructed (external and interfloor construction), made out of Styrofoam using "Plastbau" technology. A possibility to use exterior wall panels ‘Plastbau’ under weather conditions of Saint-Petersburg has been considered. Temperature distribution along a wall’s section as well as a heat flow going through a building enclosure ‘Plastbau’ have been also analyzed herein.

Abstract: The paper deals with effect of window structure seating depth in window lining on the deformation of thermal field represented by the change in surface temperatures and thermal coupling coefficient. Alternative depths of window structure seating are analysed by the numerical experiment using the computer simulation of thermal field. The objective of analysis is to optimize the window structure seating depth in the existing experimental wall. The effect of deformation amount of thermal field of analyzed contact on the course of surface temperatures and thermal coupling coefficient of the binding has also been analysed.

Abstract: The article presents the monitoring of physical aspects of choices hall objects before reconstruction, which are in poor technical condition. The content of this contribution is the comparison of energy savings in selected hall object, which can be achieved by the refurbishment of envelope structures as against the present state. The article is trying to solve the problem of alternative creating envelope structures for an industrial hall depending on the activity performed inside respective plants, its reconstruction in relation to year energy consumption for heating, taking into account necessary thermal and humidity microclimate of a real workshop.