scholarly journals The design of the electromagnetic aluminum mold of periodic action

2021 ◽  
Vol 29 (2) ◽  
pp. 100-116
Author(s):  
Alexander A. Bazarov ◽  
Ashot A. Navasardyan ◽  
Natalya V. Bondareva
Keyword(s):  
Electromagnetic Force ◽  
Internal Heat ◽  
Heat Removal ◽  
Side Surface ◽  
Support Surface ◽  
Cylindrical Shape ◽  
Shape Distortion ◽  
Entire Volume ◽  
Periodic Action ◽  
Internal Sources

This publication discusses a set of issues on computer modeling of electromagnetic and thermal processes in an induction crystallizer of an aluminum melt, in which forces are created between the melt and the inductor coil, compressing the column of liquid material and preventing direct contact of the melt with the crucible walls. In known induction systems using electromagnetic pressure on molten metal, for crystallization, the parameters of the inductor are selected so that, with sufficient force, the temperature does not rise due to internal sources of heat release with sufficient water cooling of the surface. In the proposed work, heat removal mainly occurs through contact with a water-cooled support surface. The aim of the work is to determine the process parameters at which the required electromagnetic force is formed on the melt wall, taking into account the change in the current density at the interface between the solid and liquid phases of aluminum. When determining the parameters of induction crystallizers, the temperature dependences of the thermophysical properties were used. Variants of the inductor realization are investigated, which makes it possible to cover the entire volume of the melt, inside which significant changes in the electrical conductivity of aluminum and the power of internal heat sources are observed. Obtaining a cylindrical shape of the ingot, in contrast to the known electromagnetic crystallizers, is achieved by determining the design of the inductor, which provides a decrease in the repulsive electromagnetic force acting on the side surface of the melt in height. The results of the study showed the possibility of using the crystallizer at various ratios of the height and diameter of the melt column, and the intensity of cooling. The efficiency of the process for aluminum increases with an increase in the radius of the melt column, which also leads to a decrease in shape distortion in the region of the upper end.

Natural Convection in a Cylindrical Porous Enclosure With Internal Heat Generation

1989 ◽  
Vol 111 (4) ◽  
pp. 916-925 ◽  
Author(s):  
V. Prasad ◽  
A. Chui
Keyword(s):  
Nusselt Number ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Aspect Ratio ◽  
Numerical Study ◽  
Vertical Wall ◽  
Internal Heat ◽  
Heat Removal ◽  
Maximum Temperature ◽  
Wall Boundary Conditions

A numerical study is performed on natural convection inside a cylindrical enclosure filled with a volumetrically heated, saturated porous medium for the case when the vertical wall is isothermal and the horizontal walls are either adiabatic or isothermally cooled. When the horizontal walls are insulated, the flow in the cavity is unicellular and the temperature field in upper layers is highly stratified. However, if the top wall is cooled, there may exist a multicellular flow and an unstable thermal stratification in the upper region of the cylinder. Under the influence of weak convection, the maximum temperature in the cavity can be considerably higher than that predicted for pure conduction. The local heat flux on the bounding walls is generally a strong function of the Rayleigh number, the aspect ratio, and the wall boundary conditions. The heat removal on the cold upper surface decreases with the aspect ratio, thereby increasing the Nusselt number on the vertical wall. The effect of Rayleigh number is, however, not straightforward. Several correlations are presented for the maximum cavity temperature and the overall Nusselt number.

scholarly journals MATHEMATICAL MODELS OF HEAT TRANSFER IN ELEMENTS OF TURBO GENERATORS (CONTINUED)

2020 ◽  
Vol 2 (1) ◽  
pp. 21-28
Author(s):  
V. I. Havrysh ◽  
◽  
B. O. Bilinskyi ◽  
O. S. Korol ◽  
R. R. Shkrab ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Temperature Distribution ◽  
Mathematical Models ◽  
Half Space ◽  
Analytical Solutions ◽  
Internal Heat ◽  
Normal Operation ◽  
Cylindrical Shape ◽  
Temperature Regimes

Previously developed [8] and presented new mathematical models for the analysis of temperature regimes in individual elements of turbo generators, which are geometrically described by isotropic half-space and space with an internal heat source of cylindrical shape. Cases are also considered for half-space, when the fuel-releasing cylinder is thin, and for space, when it is heat-sensitive. For this purpose, using the theory of generalized functions, the initial differential equations of thermal conductivity with boundary conditions are written in a convenient form. To solve the obtained boundary value problems of thermal conductivity, the integral Hankel transformation was used, and as a result, analytical solutions in the images were obtained. The inverse Hankel integral transformation was applied to these solutions, which made it possible to obtain the final analytical solutions of the initial problems. The obtained analytical solutions are presented in the form of improper convergent integrals. Computational programs have been developed to determine the numerical values ​​of temperature in the above structures, as well as to analyze the heat transfer in the elements of turbo generators due to different temperature regimes due to heating by internal heat sources concentrated in the cylinder volume. Using these programs, graphs are presented that show the behavior of curves constructed using numerical values ​​of the temperature distribution depending on the spatial radial and axial coordinates. The obtained numerical values ​​of temperature indicate the correspondence of the given mathematical models for determining the temperature distribution to the real physical process. The software also allows you to analyze media with internal heating, concentrated in the spatial figures of the correct geometric shape, in terms of their heat resistance. As a result, it becomes possible to increase it, to determine the allowable temperatures of normal operation of turbo generators, to protect them from overheating, which can cause the destruction of not only individual elements but also the entire structure.

scholarly journals IMPROVING THE HEAT RECOVERY SYSTEM WITH STABILIZATION OF THE THERMAL PROCESSES OF ROTARY KILNS

2020 ◽  
pp. 114-121
Author(s):  
E.А. Geraskina ◽  
◽  
О.І. Khomenko ◽  
N.V. Danichenko ◽  
А.А. Khomenko ◽  
...  
Keyword(s):  
Rotary Kiln ◽  
Building Materials ◽  
Cooling System ◽  
Heat Removal ◽  
Side Surface ◽  
Utilization Efficiency ◽  
Controlled Cooling ◽  
Bypass Line ◽  
Entire Flow ◽  
Rotary Kilns

Abstract. The article is devoted to the problem of increasing the efficiency of using heating systems for industrial and municipal heat supply. The principles of rational cooling of furnaces and building materials are formulated, methods for stabilizing the thermal regime and conditions for the development of functional schemes for furnace units are determined. Rotary kilns under alternating of air temperature, wind speed, sunlight and precipitation lose from the side surface into the environment up to 30% of heat. The adverse effect of these factors negatively affects the thermal condition of the furnace unit with overheating in warm and overcooling in the cold periods of the year, and also reduces the lining stability and product quality. Characteristically, in order to maintain the necessary temperature at the inner surface of the furnace and extend the service life of the lining, the natural cooling of the side surface of the unit is assumed. This is an uncontrollable process with the above mentioned disadvantages. A radical solution to ensure the process requirements and improve utilization efficiency of fuel combustion energy is the organization of controlled cooling of the rotary kiln. One of the schemes providing the necessary heat removal from the furnace surface is a circuit with a recirculation channel. It is based on the reuse of the heating medium flow, the recirculation part of which increases with decreasing outdoor temperature. In the summer settlement mode, the system operates as a direct-flow system and the entire flow enters the consumer systems. In the winter billing period, air flows from the bypass line. Based on the above conditions, dependencies are established for finding the main parameters of the stabilizing cooling system of a rotary kiln, which is used for municipal heating.

scholarly journals Perfection of cooling systems of overhead tuyeres heads of 250-t BOFs

2019 ◽  
Vol 75 (3) ◽  
pp. 327-336
Author(s):  
S. P. Panteikov ◽  
L. M. Uchitel’ ◽  
V. V. Ivko ◽  
Yu. I. Kharchenko ◽  
Yu. P. Makhlai ◽  
...  
Keyword(s):  
Cooling System ◽  
Heat Removal ◽  
Internal Surface ◽  
Side Surface ◽  
Operating Characteristics ◽  
Blow Down ◽  
Cooling Systems ◽  
Nozzle Block ◽  
Heat Removal Efficiency ◽  
Positive Effect

Deterioration of tips cooling as a result of number of nuzzles increase in tuyere heads does not allow to use multinozzle (six and more) overhead tuyeres for increasing of steel melting technical and economical indices and operating characteristics of technological equipment. The main reason of it is as follows: deterioration ofcooling results in over-heating and burnt-outof tips material in the farthest nozzle zone following the overhead tuyeres breakage. To avoid the water stagnant areas in the farthestnozzle zones of the heads cooling route and therefore to increase the overheads oxygen tuyeres of 250-t BOF operation life, a new design of the six-nozzle tuyere head with asymmetric cooling of tips farthest zones elaborated, manufactures and tested. The perfection of the six-nozzle heads cooling system included asymmetric (relating the side surface of the nozzle block) installation behind every nozzle (in the water direction) a guidingblade of special design. It enabled to increase to a maximum degree the heat removal efficiency from the internal surface in the tip farthest zones and had a positive effect on the overhead tuyeres heads resistance. The workability of the proposed design of the six-nozzle tuyere head with asymmetric cooling of farthest zones was confirmed during test-industrial heats at 250-t BOFs of OJSC “Dneprovskysteel-works”. The heats were carried out with oxygen consumption of 800–1200 m 3/min and regime of partial afterburning ofexit gases. The water consumption for tuyeres cooling decrease from 320–340 m 3 /h, at that the  water temperature difference at the tuyere entry and exit varied in the range of 11–16 °C depending on blow-down duration. Application of the new design of the six-nozzle tuyere head with asymmetric farthest zones cooling enabled to increase the sixnozzle heads resistance by a factor 1.287 comparing with six-nozzle heads without farthest zones cooling and by a factor of 3.327 comparing with regular five-nozzle tuyere heads. The effect reached thanks to more rational cooler distribution and increase ofits velocity. The metal pick up of shafts of the six-nozzle tuyere head with asymmetric farthest zones cooling: while the five-nozzle tuyeres were taken off for salamander cutting off after 1–5 heats, the six-nozzle tuyeres were taken off for the salamander cutting off after 79–81 heats. It indicated a higher efficiency of heat running blow-down and slag regimes with application of proposed design of the six-nozzle tuyere head with asymmetric farthest zones cooling.

Influence of vessel dimensions on particles homogenization and heat removing in TMF stirrer

2020 ◽  
Vol 39 (1) ◽  
pp. 125-132
Author(s):  
Shvidkiy Evgeny ◽  
Igor Sokolov ◽  
Kirill Bolotin ◽  
Valery Zakharov
Keyword(s):  
Design Methodology ◽  
Heat Removal ◽  
Side Surface ◽  
Transient Simulation ◽  
Particle Tracing ◽  
Content Type ◽  
Exothermic Reactions ◽  
Finite Element Software ◽  
Traveling Magnetic Field ◽  
Practical Implications

Purpose The purpose of this paper is to determine how the shape of the container affects the efficiency of a traveling magnetic field (TMF) stirring. Design/methodology/approach The modeling approach is based on finite element software Comsol which includes harmonic electromagnetic (EM), transient CFD and particle tracing modules. For evaluating efficiency of stirring the particle, homogenization parameter is used. Findings It has been determined that the use of an elliptical cylinder-shaped vessel allows better heat removal from the side surface and, at the same time, the stirring efficiency does not drop significantly. Practical implications The results of the work can be used in the design of EM stirring installations in which exothermic reactions occur. Originality/value The transient simulation of particle transport in a TMF-driven melt flow gives the opportunity to estimate the efficiency of stirring process in different vessel shapes.

scholarly journals Modelling the Temperature State of Bodies with Internal Heat Sources

2021 ◽  
Vol 2096 (1) ◽  
pp. 012090
Author(s):  
A V Eremin ◽  
K V Gubareva ◽  
A I Popov
Keyword(s):  
Fuel Element ◽  
Internal Heat ◽  
Quadratic Function ◽  
Heat Sources ◽  
Unsteady Temperature ◽  
Temperature State ◽  
Unsteady Temperature Field ◽  
Numerical Analytical Method ◽  
Internal Heat Sources ◽  
Internal Sources

Abstract This article presents the results of the development of a numerical - analytical method for solving the problem of thermal conductivity in a plate fuel element. An unsteady temperature field inside a fuel element is investigated for a given spatial distribution of heat sources. The heat release rate is given by the quadratic function of the coordinate. Modeling the temperature state of bodies with internal heat sources allows you to study the operation of equipment in transient modes, control heating/cooling modes of elements, determine temperature stresses, etc. It is shown in the work that regardless of the power of internal sources of heat, the temperature state is stabilized at a temperature level that depends on the Pomerantsev number.

scholarly journals Closed cycle of air-steam mixture the drying section of paper machine

2019 ◽  
Vol 21 (3) ◽  
pp. 24-31
Author(s):  
V. G. Kazakov ◽  
E. N. Gromova
Keyword(s):  
Heat Recovery ◽  
Internal Heat ◽  
Heat Removal ◽  
Exergy Efficiency ◽  
Thermal Mode ◽  
Paper Machine ◽  
Closed Cycle ◽  
Drying Section ◽  
Almost All ◽  
Condensate System

The energy efficiency of the drying section of paper machine is determined by the technology of heat flows arrangements in it. Paper drying is the most energy-consuming stage of paper production. The thermal mode of the drying section is provided by the steam condensate system which is a part of it. Analysis of exergy increments shows that almost all elements of the drying thermal process are characterized by low exergy efficiency. The main ways for increasing the degree of thermodynamic perfection of the processes occurring in the drying section of the paper machine are identified based on the exergy analysis. It is assumed that the deep internal heat recovery of the steam-air mixture for heating the source air will increase the exergy efficiency of the heat recovery plant and reduce heat removal to the environment. The effectiveness of development and implementation of a closed cycle use of steam-air mixture in the drying section was examined. Building a closed cycle provides that the air mainly has a process duty, that is, it is a transport agent for the transfer of moisture and heat along a closed circuit. The calculations show that the exergy efficiency of the processes in the recovery unit of the drying section of the paper machine of the existing production is 28.6% against 66.29% for the proposed method.

Ceramic High-Temperature Heat-Pipes

2014 ◽  
Author(s):  
Peter Meisel ◽  
Wolfgang Lippmann ◽  
Antonio Hurtado
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Heat Pipe ◽  
Internal Heat ◽  
Heat Removal ◽  
Heat Pipes ◽  
Operating Regime ◽  
Working Fluid ◽  
Stable Operating

Ceramic heat pipes and heat pipe based heat exchangers are tailored for automatically heat removal and heat distribution in thermally, chemically and abrasive high stressed systems. The manufacture of silicon carbide heat pipes was carried out. These were filled with sodium or zinc and sealed by laser brazing using metallic and glassy solder materials. High-temperature performance tests revealed a stable operating regime for both ceramic heat pipes with sodium and zinc as working fluid, respectively. Specifically the heat transferred by a zinc filled heat pipe of 22 mm in diameter and 750 mm in length accounted for 600 W at a temperature difference of 400 K. Notably the internal heat transfer capacity of the working fluid was even higher however, the total heat transfer was limited by the external active heat transfer area of the heat pipe. In order to evaluate the long-term stability of the heat pipes, particularly with respect to the joining seam, manufactured heat pipes are currently being tested in long-term annealing experiments at a temperature of 1000 °C under a variety of corrosive atmospheres.

scholarly journals TRISO fuel thermal simulations in the LS-VHTR

2019 ◽  
Vol 7 (2B) ◽  
Author(s):  
Mario C. Ramos ◽  
Maria E. Scari ◽  
Antonella Lombardi Costa ◽  
Claubia Pereira ◽  
Maria A. F. Veloso
Keyword(s):  
Reactor Core ◽  
Heat Removal ◽  
Cylindrical Shape ◽  
Triso Fuel ◽  
Liquid Salt ◽  
Graphite Matrix ◽  
Homogeneous Models ◽  
Triso Particles ◽  
Thermal Simulations ◽  
Heat Removal System

The liquid-salt-cooled very high-temperature reactor (LS-VHTR) is a reactor that presents very good characteristics in terms of energy production and safety aspects. It uses as fuel the TRISO particles immersed in a graphite matrix with a cylindrical shape called fuel compact, as moderator graphite and as coolant liquid salt Li2BeF4 called Flibe. This work evaluates the thermal hydraulic performance of the heat removal system and the reactor core by performing different simplifications to represent the reactor core and the fuel compact under steady-state conditions, starting the modeling from a single fuel element, until complete the studies with the entire core model developed in the RELAP5-3D code. Two models were considered for representation of the fuel compact, homogeneous and non-homogeneous models, as well as different geometries of the heat structures was considered. The aim to develop several models was to compare the thermal hydraulic characteristics resulting from the construction of a more economical and less discretized model with much more refined models that can lead to more complexes analyzes to representing TRISO effect particles in the fuel compact. The different results found, mainly, for the core temperature distributions are presented and discussed.

Laminar Heat Transfer Behavior of a Phase Change Material Fluid in Microchannels With Staggered Pins

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Satyanarayana Kondle ◽  
Jorge L. Alvarado ◽  
Charles Marsh
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Phase Change ◽  
Phase Change Material ◽  
Single Phase ◽  
Internal Heat ◽  
Heat Removal ◽  
Heat Transfer Fluid ◽  
Change Material ◽  
Phase Fluid

Microchannels have been studied extensively for a variety of heat transfer applications including electronic cooling. Many configurations of microchannels have been studied and compared for their effectiveness in terms of heat removal. Recently, the use of staggered pins in microchannels has gained considerable traction, since they can promote internal flow fluctuations that enhance internal heat transfer. Furthermore, staggered pins in microchannels have shown higher heat removal characteristics because of the continuous breaking and formation of the heat transfer fluid boundary layer. However, they also exhibit higher pressure drop because the pins act as flow obstructions. This paper presents numerical results of two characteristic staggered 100-μm pins (square and circular) in microchannels. The heat transfer performance of a single phase fluid (SPF) in microchannels with staggered pins, and the corresponding pressure drop characteristics are presented. Furthermore, a phase change material (PCM, n-eicosane) fluid was also considered by implementing the effective specific heat capacity model approach to account for the corresponding phase change process of PCM fluid. Comparisons of the heat transfer characteristics of single phase fluid and PCM fluid are presented for two different pin geometries and three different Reynolds numbers. Circular pins were found to be more effective in terms of heat transfer by exhibiting higher Nusselt number. Microchannels with circular pins were also found to have lower pressure drop compared to the square-pin microchannels.

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