Página 1 dos resultados de 88 itens digitais encontrados em 0.008 segundos

Development of granular structure in Cu/sub 90/Co/sub 10/ ribbons through furnace and current annealing

Silva, F.C.S.; Knobel, Marcelo; Ferrari, Edson Fernando; Denardin, Juliano C.; Miranda, Marines Grande Malcum; Bracho Rodriguez, Gustavo Jesus; Antunes, Arlei Borba; Baibich, Mario Norberto
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Artigo de Revista Científica Formato: application/pdf
ENG
Relevância na Pesquisa
26.06%
On-line measurements of resistance and temperature in melt-spun Cu90Co10 ribbons are made using two different annealing techniques: conventional furnace annealing, and linearly varying current Joule heating. The aim of this paper is to consider the electrical current, flowing through the sample during the annealing, as a possible parameter to control thermal treatment parameters and thus the microstructure of these systems. Although an exact way to obtain the temperature fromthe annealing current remains a difficult task, the on-line changes in resistance with current allows one to identify structural changes in the sample during annealing. Also, because the temperature is found to increase continuously with electrical current, it is possible to calibrate the Joule heating system to precisely determine the annealing temperature.

Analysis of aluminum plates under heating in electrical and natural gas furnaces

Magalhães Sobrinho, Pedro; Carvalho Jr., João A.; Luz Silveira, José; Magalhães Filho, Paulo
Fonte: Elsevier B.V.; Elsevier B.V. Publicador: Elsevier B.V.; Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 975-987
ENG
Relevância na Pesquisa
36.1%
This paper analyzes the thermal storage characteristics of aluminum plates in furnaces during their heating for lamination under two sources of heat: an electrical resistance bank and a combustion process carried out with natural gas. The set of equations to model the furnace under operation with electrical energy, for air as the fluid, is presented. This supports the theoretical analysis for the system under operation with natural gas combustion products. A numerical procedure, using the software ANSYS, is applied to determine the convection heat transfer coefficients for heating by the air flow. Temperatures measured in a plate inside a real furnace are used as parameters to determine these coefficients. Then convection and radiation heat transfer coefficients are determined for the natural gas combustion products. Results are compared, indicating a possible gain of 5.5 h in relation to a 19.5 h period of conventional electrical heating per plate.

Bem-estar dos animais e uso racional de energia eletrica em sistemas de aquecimento para leitões desmamados; Animal welfare and energy saving in heating systems for weaned piglets

Juliana Sarubbi
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 26/02/2009 PT
Relevância na Pesquisa
46.18%
Para que os mecanismos que visam promover condições de bem-estar aos suínos possam ser utilizados, é necessário que se desenvolvam pesquisas para reduzir seus custos e aumentar sua praticidade, possibilitando a sustentabilidade do processo. O aquecimento de leitões em fase de creche e maternidade pode ser trabalhado no sentido de viabilizar a eficiência do uso da energia elétrica sem, no entanto, prejudicar o bem-estar dos suínos. Por meio deste trabalho, objetivou-se comparar três tecnologias de aquecimento para leitões a partir de três semanas de idade, em fase de creche, com relação ao uso de energia elétrica, condições de bem-estar e desempenho dos animais. Estudaram-se três tecnologias de aquecimento: TR - resistências elétricas suspensas, TP - piso aquecido e TA - aquecimento por convecção. O sistema de aquecimento por pisos foi melhor sob o aspecto de uso de energia elétrica. O sistema de aquecimento por resistências elétricas foi o melhor com relação ao atendimento das necessidades térmicas dos animais e o sistema de aquecimento por convecção foi o melhor considerando a resposta produtiva, comportamental e fisiológica dos animais. De maneira geral, atribuindo-se pesos aos aspectos analisados (implantação e operação...

The effects of electrical currents on foods and other biological systems

Vicente, A. A.; Castro, Inês; Pereira, Ricardo
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em //2009 ENG
Relevância na Pesquisa
35.98%
To extend shelf life of food products a heat treatment is generally required. This may be provided through the use of e.g. tubular heat exchangers or scraped surface devices, where heat is generated outside the food and transmitted to it by conduction and/or convection. For products containing particles, e.g. fruit bits, or for highly viscous fluids, the mentioned heat treatments frequently cause overheating of parts of the product in order to achieve proper heat treatment of the products’ cold spot. This fatally leads to losses of nutritional as well as organoleptic properties. In the aseptic processing of these food systems, the application of electric fields (ohmic heating) to the heat treatment of food products is seen has a potential alternative to conventional heating processes, essentially due to the fact that heat is internally generated due to the electrical resistance of foods, thus providing a uniform heating of the product. Our work has been centred in determining the influence of the application of an electric field on food components (enzymes, other proteins, carbohydrates and lipids) and on microorganisms (both vegetative cells and spores). Further, we have also evaluated the effects of electricity on the performance of fermentation systems...

Crystallization kinetics of Fe-B based amorphous alloys studied in-situ using X-rays diffraction and differential scanning calorimetry

Santos,D.R. dos; Santos,D.S. dos
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2001 EN
Relevância na Pesquisa
26.03%
The crystallization processes for the amorphous metallic alloys Fe74B17Si2Ni4Mo3 and Fe86B6Zr7Cu1 (at. %) were investigated using X-rays diffraction measurements performed in-situ during Joule-heating, with simultaneous monitoring of the electrical resistance. We determined the main structural transitions and crystalline phases formed during heating, and correlated these results to the observed resistance variations. As the annealing current is increased, the resistance shows an initial decrease due to stress relaxation, followed by a drop to a minimum value due to massive nucleation and growth of alpha-Fe nanocrystals. Further annealing causes the formation of small fractions of Fe-B, B2Zr or ZrO2, while the resistance increases due to temperature enhancement. In situ XRD measurements allowed the identification of metastable phases, as the gamma-Fe phase which occurs at high temperatures. The exothermal peaks observed in the differential scanning calorimetry (DSC) for each alloy corroborate the results. We also have performed DSC measurements with several heating rates, which allowed the determination of the Avrami exponent and crystallization activation energy for each alloy. The obtained activation energies (362 and 301 kJ/mol for Fe-B-Zr-Cu; 323 kJ/mol for Fe-B-Si-Ni-Mo) are comparable to reported values for amorphous iron alloys...

Temperature dependence of the electrical transport properties in few-layer graphene interconnects

Liu, Yanping; Liu, Zongwen; Lew, Wen Siang; Wang, Qi Jie
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em 25/07/2013 EN
Relevância na Pesquisa
35.93%
We report a systematic investigation of the temperature dependence of electrical resistance behaviours in tri- and four-layer graphene interconnects. Nonlinear current–voltage characteristics were observed at different temperatures, which are attributed to the heating effect. With the resistance curve derivative analysis method, our experimental results suggest that Coulomb interactions play an essential role in our devices. The room temperature measurements further indicate that the graphene layers exhibit the characteristics of semiconductors mainly due to the Coulomb scattering effects. By combining the Coulomb and short-range scattering theory, we derive an analytical model to explain the temperature dependence of the resistance, which agrees well with the experimental results.

A heterojunction bipolar transistor with stepwise allog-graded base : analysis, design, fabrication, and characterization

Konistis, Konstantinos, 1973-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 126 p.; 7006227 bytes; 7022058 bytes; application/pdf; application/pdf
EN_US
Relevância na Pesquisa
35.87%
(cont.) features but the device self-heating turned out to be crucial for the longevity of the base micro-airbridges. The short lifetime of the base micro-airbridges was prohibitive for the realization of high frequency measurements. This work serves as the foundation for the implementation of robust HBT transit-time oscillators with the incorporation of slight modifications in the fabrication process.; This thesis explores the potential benefits of a GaAs-based heterojunction bipolar transistor (HBT) with stepwise alloy-graded base. The step height is slightly greater than the longitidinal optical (LO) phonon energy h[omega]LO in order to facilitate LO-phonon-enhanced forward diffusion of minority carriers in the base. The intuitive theoretical approach of carrier transport in the base, as proposed by other workers for this type of alloy-grading, did not incorporate in detail the various mechanisms of transport. In this work, we solved the Botzmann transport equation (BTE) in one dimension across the base for arbritrary frequencies. Impurity and LO phonon scattering were considered as the dominant scattering mechanisms. The intrinsic and extrinsic elements were combined and a small-signal equivalent circuit was proposed for the evaluation of the high-frequency performance of the device. The unique feature of this HBT is that the base transport factor undergoes a moderate magnitude attenuation and phase delay. By choosing a suitable collector delay...

Vacuum Brazing of Alumina Ceramic to Titanium Using Pure Gold as Filler Metal for Biomedical Implants

Siddiqui, Mohammad S
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica Formato: application/pdf
Relevância na Pesquisa
36%
One of the many promising applications of metal/ceramic joining is in biomedical implantable devices. This work is focused on vacuum brazing of C.P titanium to 96% alumina ceramic using pure gold as the filler metal. A novel method of brazing is developed where resistance heating of C.P titanium is done inside a thermal evaporator using a Ta heating electrode. The design of electrode is optimized using Ansys resistive heating simulations. The materials chosen in this study are biocompatible and have prior history in implantable devices approved by FDA. This research is part of Boston Retinal implant project to make a biocompatible implantable device (www.bostonretina.org). Pure gold braze has been used in the construction of single terminal feedthrough in low density hermetic packages utilizing a single platinum pin brazed to an alumina or sapphire ceramic donut ( brazed to a titanium case or ferrule for many years in implantable pacemakers. Pure gold (99.99%) brazing of 96% alumina ceramic with CP titanium has been performed and evaluated in this dissertation. Brazing has been done by using electrical resistance heating. The 96% alumina ceramic disk was manufactured by high temperature cofired ceramic (HTCC) processing while the Ti ferrule and gold performs were purchased from outside. Hermetic joints having leak rate of the order of 1.6 X 10-8 atm-cc/ sec on a helium leak detector were measured. Alumina ceramics made by HTCC processing were centreless grounded utilizing 800 grit diamond wheel to provide a smooth surface for sputtering of a thin film of Nb. Since pure alumina demonstrates no adhesion or wetting to gold...

Vacuum brazing of alumina ceramic to titanium for biomedical implants using pure gold as the filler metal

Siddiqui, Mohammad S
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
36%
One of the many promising applications of metal/ceramic joining is in biomedical implantable devices. This work is focused on vacuum brazing of C.P titanium to 96% alumina ceramic using pure gold as the filler metal. A novel method of brazing is developed where resistance heating of C.P titanium is done inside a thermal evaporator using a Ta heating electrode. The design of electrode is optimized using Ansys resistive heating simulations. The materials chosen in this study are biocompatible and have prior history in implantable devices approved by FDA. This research is part of Boston Retinal implant project to make a biocompatible implantable device (www.bostonretina.org). ^ Pure gold braze has been used in the construction of single terminal feedthrough in low density hermetic packages utilizing a single platinum pin brazed to an alumina or sapphire ceramic donut (brazed to a titanium case or ferrule for many years in implantable pacemakers. Pure gold (99.99%) brazing of 96% alumina ceramic with CP titanium has been performed and evaluated in this dissertation. Brazing has been done by using electrical resistance heating. The 96% alumina ceramic disk was manufactured by high temperature cofired ceramic (HTCC) processing while the Ti ferrule and gold performs were purchased from outside. Hermetic joints having leak rate of the order of 1.6 × 10-8 atm-cc/ sec on a helium leak detector were measured. ^ Alumina ceramics made by HTCC processing were centreless grounded utilizing 800 grit diamond wheel to provide a smooth surface for sputtering of a thin film of Nb. Since pure alumina demonstrates no adhesion or wetting to gold...

Activated carbon cloth regeneration with electrical resistance heating.

Covington, Brett A.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
35.73%

ELECTRICAL RESISTANCE HEATING OF GROUNDWATER IMPACTED BY CHLORINATED SOLVENTS IN HETEROGENEOUS SAND

Munholland, Jonah
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
66.12%
Remediation of sites impacted by dense nonaqueous phase liquids (DNAPLs) is an ongoing, costly challenge where technological improvement is needed to allow for cost-effective cleanup. Remedial processes using in situ thermal technologies have received increasing attention in recent years. Electrical resistance heating (ERH) is a commonly applied thermal technology in the industry. ERH applications are used at heterogeneous sites, where permeability contrasts can significantly impact the heating process along with the movement of DNAPL and gas phases. To further understand this, a series of intermediate-scale laboratory experiments were completed in a two-dimensional flow cell examining the impacts on subsurface processes occurring during ERH. Groundwater velocity variations within a homogenous coarse sand were shown to limit the heating rates during ERH. Additionally, experiments entailed the heating 270 mL of trichloroethene (TCE), chloroform (CF), and tetrachloroethene (PCE) pools in a medium-grained silica sand with a coarse-grained sand lens located above the DNAPL pools. Spatial and temporal distributions of temperature, gas saturations, and aqueous DNAPL concentrations were collected and observed using a distribution of thermocouples...

Gas Dynamics during Bench-Scale Electrical Resistance Heating of Water, TCE and Dissolved CO2

Hegele, Paul
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
96.17%
In situ thermal treatment (ISTT) applications require successful gas capture for the effective remediation of chlorinated solvent dense non-aqueous phase liquid (DNAPL) source zones. Gas production and transport mechanisms during bench-scale electrical resistance heating (ERH) experiments were examined in this study using a quantitative light transmission visualization method. Processed images during water boiling indicated that gas bubble nucleation, growth and coalescence into a connected steam phase occurred at critical gas saturations of Sgc = 0.233 ± 0.017, which allowed for continuous gas transport out of the heated zone. Critical gas saturations were lower than air-water emergence gas saturations of Sgm = 0.285 ± 0.025, derived from the inflection point of ambient temperature capillary pressure-saturation curves. Coupled electrical current and temperature measurements were identified as a metric to assess gas phase development. Processed images during co-boiling of pooled trichloroethene (TCE) DNAPL and water indicated that discontinuous gas transport occurred above the DNAPL pool. When colder zones were introduced, condensation prevented the development of continuous steam channels and caused redistribution of DNAPL along the vapour front. These results suggest that water boiling temperatures should be targeted throughout the subsurface (i.e....

Laboratory study evaluating electrical resistance heating of pooled trichloroethylene

Martin, Eric John
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado Formato: 9765941 bytes; application/pdf
EN; EN
Relevância na Pesquisa
96.29%
A laboratory scale study was conducted to evaluate the thermal remediation of trichloroethylene (TCE) in a saturated groundwater system using electrical resistance heating (ERH). Two experiments were conducted using a two-dimensional polycarbonate test cell, the first consisting of a single pool of TCE perched above a capillary barrier, the second consisting of two pools of TCE each perched on separate capillary barriers. Temperature data was collected during the heating process from an array of 32 thermocouples located throughout the test cell. Visualization of the vaporization of liquid phase TCE, as well as the upward migration of the produced vapour was recorded using a digital camera. Chemical testing was performed 48 hours after experiment termination to measure post heating soil concentrations. A co-boiling plateau in temperature was found to be a clear and evident earmark of an ongoing phase change in the pooled TCE. Temperature was found to increase more rapidly in the second experiment that included a fully spanning barrier. As temperatures increased above the co-boiling plateau, vapour rise originating from the source zone was observed, and was found to create a high saturation gas zone beneath the upper capillary barrier when no clear pathway was available for it to escape upwards. When the source zones had reached the target temperature of 100°C and the ERH process stopped...

Distributed photomixers

Duerr, Erik Kurt, 1973-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 197 p.; 3610590 bytes; 3573805 bytes; application/pdf; application/pdf
ENG
Relevância na Pesquisa
35.87%
Although the terahertz domain has been explored scientifically, components, especially sources, are needed to enable further exploration of the frequency range. A photomixer generates coherent THz radiation through optical heterodyne down-conversion. A terahertz-frequency beat signal on an optical carrier illuminates an ultrafast photoconductor, modulating the conductance. The time-varying conductance together with a constant voltage bias generates time-varying current at the beat frequency. Low-temperature-grown gallium arsenide (LTG-GaAs) is the photoconductive material of choice, because its short carrier lifetime allows the conductance to be efficiently modulated at THz frequencies. The distributed photomixer described in this thesis is a new style of LTG-GaAs photomixer which uses an optical waveguide to couple the beat signal to an active area whichis large relative to the terahertz wavelength. This large, traveling-wave mode active area distributes the heat load from absorbed optical power and ohmic heating from photocurrent and avoids the RC rolloff associated with a lumped-element photomixer's intrinsic capacitance and the load resistance. The distributed photomixer structure consists of coplanar strips (CPS) fabricated on top of a dielectric strip-loaded waveguide that guides the optical beat.; (cont.) The conductance of a thin layer of LTG-GaAs between the CPS and optical guide is modulated by the weakly coupled optical signal. The THz conductance wave between the dc-biased CPS creates a THz electromagnetic wave which propagates along the CPS. To velocity match the THz and optical waves...

AN EXPERIMENTAL STUDY OF DIATHERMY : IV. EVIDENCE FOR THE PENETRATION OF HIGH FREQUENCY CURRENTS THROUGH THE LIVING BODY.

Christie, Ronald V.; Binger, Carl A. L.
Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 31/10/1927 EN
Relevância na Pesquisa
26.09%
The principles governing the passage of high frequency currents through various conductors have been discussed and exemplified in experiments done on both non-living and living bodies. In Part I it was shown: (1) That the current takes the path of least electrical resistance rather than the shortest path; (2) that maximal heating occurs at the point of greatest concentration of the lines of current flow. In a homogeneous medium with parallel electrodes maximal heat production occurs in those portions of the medium adjoining the electrodes and the heat gradient is from without inward. Under these circumstances maximal heating never occurs at the center. In discussing the localization of heat not only the electrical resistance and current concentration, but also the cooling effect, must be considered. In experiments on the dog's cadaver no evidence of the so called "skin effect" could be demonstrated. This is in contradistinction to the findings of Bettman and Crohn, but the discrepancy is explained on the basis of what we believe to be a technical error in their work. The finding of no "skin effect" is in agreement with the conclusions of Dowse and Iredell, based on both experimental and theoretical considerations. In Part II three types of experiments were performed on the anesthetized dog. The conclusions to be derived from them are these: (1) The heat gradient of the body is reversed during diathermy and heating occurs from without inward; (2) deep heating during diathermy is greater than that which results from the application of local heat to the skin; (3) the lung can be heated by diathermy in spite of simultaneous cooling of the chest wall. These experiments we regard as satisfactory evidence of the passage of the current through the interior of the body.

Resistance switching in polycrystalline NiOx thin film

Kim, Tae-Hyun; Nawaz (Saleh), Muhammad; Kim, Sung-I; Venkatachalam, Dinesh; Belay, Kidane; Burgess, Andrew; Strumpp, Stephan; Elliman, Robert
Fonte: Institute of Electrical and Electronics Engineers (IEEE Inc) Publicador: Institute of Electrical and Electronics Engineers (IEEE Inc)
Tipo: Conference paper
Relevância na Pesquisa
35.73%
Resistive switching properties of polycrystalline NiOx dielectric films are investigated utilizing thermo-chemical model in which a field-induced conductive filament is formed and broken by joule heating.

Unusual resistance-voltage dependence of nanojunctions during electromigration in ultra-high vacuum

Stöffler, D.; Marz, M.; Kießig, B.; Tomanic, T.; Schäfer, R.; Löhneysen, H. v.; Hoffmann-Vogel, R.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 01/11/2014
Relevância na Pesquisa
35.84%
The electrical resistance R of metallic nanocontacts subjected to controlled cyclic electromigration in ultra-high vacuum has been investigated in-situ as a function of applied voltage V. For sufficiently small contacts, i.e., large resistance, a decrease of R(V) while increasing V is observed. This effect is tentatively attributed to the presence of contacts separated by thin vacuum barriers in parallel to ohmic nanocontacts. Simple model calculations indicate that both thermal activation or tunneling can lead to this unusual behavior. We describe our data by a tunneling model whose key parameter, i.e., the tunneling distance, changes because of thermal expansion due to Joule heating and/or electrostatic strain arising from the applied voltage. Oxygen exposure during electromigration prevents the formation of negative R(V) slopes, and at the same time enhances the probability of uncontrolled melting, while other gases show little effects. In addition, indication for field emission has been observed in some samples

Electrical and Thermal Transport in Metallic Single-Wall Carbon Nanotubes on Insulating Substrates

Pop, Eric; Mann, David; Goodson, Kenneth; Dai, Hongjie
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
36.02%
We analyze transport in metallic single-wall carbon nanotubes (SWNTs) on insulating substrates over the bias range up to electrical breakdown in air. To account for Joule self-heating, a temperature-dependent Landauer model for electrical transport is coupled with the heat conduction equation along the nanotube. The electrical breakdown voltage of SWNTs in air is found to scale linearly with their length, approximately as 5 V/um; we use this to deduce a thermal conductance between SWNT and substrate g ~ 0.17 +/- 0.03 W/K/m per tube length, which appears limited by the SWNT-substrate interface rather than the thermal properties of the substrate itself. We examine the phonon scattering mechanisms limiting electron transport, and find the strong temperature dependence of the optical phonon absorption rate to have a remarkable influence on the electrical resistance of micron-length nanotubes. Further analysis reveals that unlike in typical metals, electrons are responsible for less than 15% of the total thermal conductivity of metallic nanotubes around room temperature, and this contribution decreases at high bias or higher temperatures. For interconnect applications of metallic SWNTs, significant self-heating may be avoided if power densities are limited below 5 uW/um...

The origin of hysteresis in resistive switching in magnetite is Joule heating

Fursina, A. A.; Sofin, R. G. S.; Shvets, I. V.; Natelson, D.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 21/05/2009
Relevância na Pesquisa
36.06%
In many transition metal oxides the electrical resistance is observed to undergo dramatic changes induced by large biases. In magnetite, Fe$_3$O$_4$, below the Verwey temperature, an electric field driven transition to a state of lower resistance was recently found, with hysteretic current-voltage response. We report the results of pulsed electrical conduction measurements in epitaxial magnetite thin films. We show that while the high- to low-resistance transition is driven by electric field, the hysteresis observed in $I-V$ curves results from Joule heating in the low resistance state. The shape of the hysteresis loop depends on pulse parameters, and reduces to a hysteresis-free "jump" of the current provided thermal relaxation is rapid compared to the time between voltage pulses. A simple relaxation time thermal model is proposed that captures the essentials of the hysteresis mechanism.; Comment: 7 pages, 6 figures

Development of a mathematical model to determine the temperature distribution in the metal layer and hearth of an electrical resistance smelter

Carlson, Kurt B.
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
56%
A steady-state finite-difference heat transfer mathematical model was derived to determine the temperature distribution in the metal layer and the hearth of a cylindrical electrical-resistance smelter. The temperature distribution is required for the redesign of the refractory materials and their positions in the hearth to insure that the metal layer is kept molten at normal smelting temperatures and that mechanical and structural integrity of the hearth is maintained. An extensive literature search revealed that no previously defined model of this type existed and that consideration of a three-dimensional model was beyond the scope of this work. The literature search also verified that the metal layer and the hearth could be modeled independently of the slag layer. The finite-difference heat transfer model was then developed by defining nine different types of nodes in the model and deriving steady-state heat transfer equations for each type of node. An algorithm was then developed for the solution of the non linear dependent set of simultaneous equations. Beyond the scope of this work, ninety percent of a Fortran 11 77 computer program was written and compiled employing the algorithm. It is recommended that the computer program be finished...