ENCIT2012-067 NATURAL CONVECTION IN VERTICAL STORAGE TANKS: CORRELATION FOR HIGH PRANDTL NUMBER - PDF
Rejane de Césaro Oliveski, UNISINOS, Brazil
Abstract: A new dimensionless correlation for the Nusseltnumber associated to cooling processes in vertical storage tanks for high Prandtl number is presented. The correlation depends on the average temperature of the tank and is a function of Rayleigh and Prandtl numbers, aspect ratio and heat transfer coefficient. It can be used to correct the temperature profiles obtained through a global method. A Finite Volume method is employed using a transient two-dimensional model in cylindrical coordinates assuming laminar flow. Thermal losses to the external environment are considered for the all walls (top, bottom and sidewalls) of the tank. Several cases of cooling were simulated, varying the aspect ratio, the cooling rate and the volume of the tank. The temperature fields obtained from numerical simulation are used to obtain the internal coefficient of heat transfer in various configurations. Later, the coefficient of heat transfer and other variables are used in the application of Buckingham theorem to determine the dimensionless groups that represent the cooling process. The correlation is checked with numerical simulations results with good agreement.
Keywords:Natural Convection; Storage Tanks; Buckingham; Correlation.
Presentation Schedule: NO PRESENTATION.
ENCIT2012-205 APPLICATION OF THE DOUBLE INTEGRAL METHOD TO TRANSIENT NONLINEAR HEAT TRANSFER PROBLEMS - PDF
Fábio Santiago, Luiz Fernando Milanez, Unicamp, Brazil
Abstract: The objective of this work is to use the Double Integral Method to solve problems of transient heat transfer in semi-infinite body with a boundary condition of first and second kinds. The validation of the results was performed by comparison with analytical solutions in the literature, and the approximate analytical solutions of the simple integral method. The double integral method is a mathematical technique that can be used to obtain approximate solutions to transient heat transfer problems. This method transforms the non-linear boundary value problem into an initial-value problem, whose solution can often be expressed in a closed analytical form. In the double integral method the partial differential equations are integrated twice, the first integration being performed within the domain and the second along the phenomenological distance. This double integration allows the gradient vector at the surface to be approximated using the Simple Integral Method. Thus improvements can be attained by changing the derivative at the boundary by an integral relation, since the process of differentiation amplifies any difference between the assumed temperature profile and the exact solution.
Keywords:Double Integral Method; Approximate Analytical Solution; Refinement of the Karman-Pohlhausen Method.
Presentation Schedule: Monday, 17:40-18:00. Session: HMT1-2. Presenter: Fábio Santiago.
ENCIT2012-061 A MULTIPHASE MULTICOMPONENT MODELING TO SIMULATE THE HEAT AND MASS TRANSFER PHENOMENA INSIDE THE PELLETS UNDER INDURATION FURNACE PROCESS CONDITIONS - PDF
Flávia de Paula Vitoretti, José Adilson Castro, UFF, Brazil
Abstract: Pelletizing of iron ore fines is an important process used to produce high quality of raw materials for the subsequent reduction processes in the ironmaking industries. The process involves the production of green pellets and subsequent induration on a traveling grate furnace to promote inner partial melt and agglomeration which confer physical and metallurgical proprieties appropriated to the subsequent reduction processes. This work focused on the influence of the inner agglomerate pellet structure on the gas flow, heat and mass transfer due to chemical reactions within the pellets agglomeration under industrial process conditions of the travelling grate furnace. A mathematical modeling based on transport equations of momentum, energy coupled with the rate equation for chemical reactions is proposed. The finite volume method is used to discretize the transport equations of momentum, mass and energy describing the behavior of a pellet in travelling grate furnace. Model predictions are shown for the temperature, gas pressure and solid concentrations along the pellet radius as function of residence time and in-furnace conditions. By using this model is possible to obtain optimized furnace conditions to attain the metallurgical and physical properties with lower energy consumption.
Keywords:Multiphase flow; heat and mass transfer; modeling; induration phenomena.
Presentation Schedule: Monday, 16:20-16:40. Session: HMT1-1. Presenter: Flavia de Paula Vitoretti.
ENCIT2012-343 ANALISYS OF BIOFUELS REACTING FLOWS IN DUCTS - PDF
Vinícius Maron Sauer, Albino José Kalab Leiroz, Marcelo José Colaço, UFRJ, Brazil
Abstract: The present work describes a confined axisymmetric reactive flow in a cylindrical duct. The fuels considered in the analysis are methane and ethanol, with ambient air as oxidant. The thermodynamical and transport properties are admitted dependent on temperature. Finite Volume Method is used to solve the conservation equations and the SIMPLEC algorithym is used to consider velocity-pressure coupling. Chemical reactions are treated with flame sheet model, being the reaction mechanism expressed by an irreversible infinitely fast one step global reaction. Results show a general behavior of the combustion system.
Keywords:Flame-sheet model; Confined laminar diffusion flame; finite volume method.
Presentation Schedule: Thursday, 15:20-15:40. Session: HMT1-3. Presenter: Albino José Kalab Leiroz.
ENCIT2012-371 ENHANCED LUMPED-DIFFERENTIAL FORMULATIONS FOR THERMALLY DEVELOPING FLOW WITH ISOTHERMAL WALL - PDF
Leandro Santos de Barros, Leandro Alcoforado Sphaier, UFF, Brazil
Abstract: This paper shows how enhanced lumping approximation techniques can be employed for calculating the mean stream temperature in thermally developing fluid flow. The adopted methodology consists in transforming the original convection-diffusion partial-differential equations into a simpler one-dimensional form, using approximation rules provided by the Coupled Integral Equations Approach (CIEA). The simpler transformed system can then be directly integrated and analytical solutions for the mean stream temperature can be readily obtained, which implies in a significant reduction the required computational effort. The results calculated with the simplified formulations are then compared with solutions for the original partial-differential problem and very reasonable agreement is seen.
Keywords:laminar flow; forced convection; duct flow; lumped-capacitance analysis.
Presentation Schedule: Monday, 17:20-17:40. Session: HMT1-2. Presenter: Leandro Santos de Barros.
ENCIT2012-001 EVALUATION OF THERMAL RESISTANCE IN COMMERCIAL HEAT SINKS - PDF
Humberto Araujo Machado, IAE, Brazil
Miguel Hiroo Hirata, Newton G. C. Leite, Izabel Cristina Loth de Oliveira, UERJ, Brazil
Abstract: In this work the behavior of the thermal resistance of commercial heat sinks is studied, concerned to the Reynolds number, fin height and thickness. Theoretical and experimental values of the Nusselt number are compared, after measurements in a low speed wind tunnel, specially constructed and equipped for this experiment. Experimental results show strong fin efficiency dependence to the Reynolds number and some geometric parameters. An uncertainty analysis for the thermal resistance estimative indicates that some adjustments are necessary in the temperature measurements in the heating basement. Although the experimental estimative for Nusselt number presented dispersion when compared to the theoretical ones extracted from a correlation, the results were considered coherent with the literature.
Keywords:thermal resistance; heat sink; cross flow.
Presentation Schedule: Monday, 17:00-17:20. Session: HMT1-2. Presenter: Humberto Araujo Machado.
ENCIT2012-063 MODELING AND SIMULATION OF HMT ON NATURAL GAS DEHYDRATION USING SOLID DESICCANTS - PDF
Jorge Duarte Benther, Leandro Alcoforado Sphaier, UFF, Brazil
Abstract: Natural gas is the fastest growing primary energy source and its use is expected to almost double to 2020, providing a relatively more clean fuel for the worldwide energy demand. Some contaminants, such as water vapor, have to be removed before its use. Dehydration of natural gas is of extreme importance to avoid the formation of hydrates and other associated problems. Different dehydration methods exist; however the solid desiccant approach can dehydrate natural gas to levels of water vapor lower than other methods. This paper presents a simple formulation for simulating the dehydration of a wet methane stream flowing though a porous medium composed of hygroscopic particles. The model assumes small resistance to diffusion within particles and takes heat and mass transfer rates into account by employing constant transfer coefficients. The formulation was developed based in the traditional mass and energy conservation principles, considering a one-dimensional transient scenario. A dimensional analysis is also performed and relevant dimensionless groups are introduced. The set of dimensionless parameters are similar to effectiveness-NTU groupings, widely used in heat exchangers. Despite its simplicity, the proposed formulation presents a new contribution since similar analysis is apparently unavailable in the gas dehydration literature. Finally, in order to illustrate the effect of varying the dimensionless groups the formulation is solved using a combined finite-volumes/method-of-lines approach. The results example how the dimensionless parameters can influence the dehydration process.
Keywords:Natural Gas; Adsorption; Dehydration; Solid Desiccant; Dehumidification.
Presentation Schedule: Thursday, 15:00-15:20. Session: HMT1-3. Presenter: Leandro Sphaier.
ENCIT2012-176 FEASIBILITY SPREAD OF THE METHOD OF NUCLEATE BOILING SYSTEMS THERMAL TRANSMITTTERS - PDF
Jeferson Camargo Fukushima, Amarildo Tabone Paschoalini, Márcio Antonio Bazani, Natalia Michelan, UNESP, Brazil
Abstract: The development of cooling systems that can be packaged into electronic boards of telephone exchanges aimed at better control of temperature, because the natural cooling efficiency is not forced to keep the system functional, so it was realized the feasibility of building a system to engage to these circuits, using a refrigerant. This study involves the theoretical analysis of the experimental heat transfer mechanism by boiling in a reservoir of flat plates. The experimental apparatus was adapted for simulating heat exchange in an electronic component, the experiment was used as refrigerant acetone and methylene chloride, aluminum billet heated internally with electrical resistance, specific heat flow ranging from 0 to 100W/cm2.
Keywords:Electronic Cooling Plate; Heat Exchanger for Phase Change; Thermosyphon.
Presentation Schedule: Monday, 18:40-19:00. Session: HMT1-2. Presenter: Edson Del Rio Vieira.
ENCIT2012-294 CONSTRUCTAL DESIGN OF A X-SHAPED CAVITY COOLED BY CONVECTION - PDF
Fernanda Link Garcia, UFRGS, Brazil
Elizaldo Domingues dos Santos, Liércio André Isoldi, FURG, Brazil
Luiz Alberto Oliveira Rocha, UFRGS, Brazil
Abstract: This paper considers the constructal design of a X-shaped cavity cooled by convection. The objective is to minimize the global thermal resistance between the solid body and the ambient. Internal heat generating is distributed uniformly throughout the solid body. The cavity is bathed by a steady stream with constant ambient temperature and convective heat transfer. The outer surfaces of the solid body are adiabatic. The total volume of the body and the total volume of the cavity are fixed, but their lengths can vary. The optimized geometry and performance are reported graphically as functions of the degrees of freedom.
Keywords:constructal design; cavities; heat generation.
Presentation Schedule: Monday, 15:20-15:40. Session: HMT1-1. Presenter: Fernanda Link Garcia.
ENCIT2012-329 SOLUTION OF A GENERAL POPULATION BALANCE EQUATION BY THE LAPLACE TRANSFORM AND PARTICLES FILTER TECHNIQUES - PDF
Clauderino da Silva Batista, Emanuel Negrão Macêdo, João Nazareno Nonato Quaresma, UFPA, Brazil
Helcio Rangel Barreto Orlande, UFRJ, Brazil
Abstract: The Laplace transform technique with numerical inversion was used to solve an integro-partial-differential equation related to the mathematical modeling of the physical problem to study convective processes with birth and death rates of particles or aerosols. Such model is governed by the population balance equation (PBE), in which is taken into account the nucleation, growth and coagulation processes. A Bayesian method was employed to solve the non-linear inverse problem and estimate the size distribution density function, thus predicting the dynamic behavior of the physical system. Specifically the application of the particle filter with resampling algorithm has been applied as a method of solving the problem. From these solutions, numerical results were obtained and compared with those available in previous works in the literature permitting a critical evaluation of the present solution methodology.
Keywords:Population Balance Equation; Laplace transform; Particles filter.
Presentation Schedule: Monday, 16:00-16:20. Session: HMT1-1. Presenter: Clauderino da Silva Batista.
ENCIT2012-372 ANALYSIS OF A CONVECTION-DIFFUSION-REACTION PROBLEM IN A SURFACE-BASED BIOSENSOR USING THE METHOD OF LINES - PDF
Carlos Adriano Moreira da Silva, Emanuel Negrão Macêdo, João Nazareno Nonato Quaresma, UFPA, Brazil
Abstract: The Method of Lines (Mol) was used to study the process of mass transport and binding kinetics of biomolecules on a surface, which was monitored through the technology of an optical biosensor by the technique of surface plasmon resonance (SPR). We consider that the receptors are directly immobilized on the sensor surface, i.e., the reaction in the hydrogel phase of the biosensor is neglected and the hydrogel is treated as a planar surface with the receptors. The mathematical modeling of the problem is accomplished along the flow chamber for the laminar flow, in which occurs diffusion both perpendicular and parallel to sensor surface. Furthermore a reversible chemical reaction between analyte and immobilized reactant takes place on the sensor surface. Together with the mass transport equation, a kinetic equation was used in the case of one-site binding where each receptor unit on the surface can accommodate one analyte molecule. The parameter values used for the simulation were chosen from the literature data that lead to transport-influenced binding kinetics, as well as parameter values where such effects are negligible. Therefore, the mathematical model is proposed to describe the mass transport and kinetics process of biomolecular interactions in the optical biosensor. A computer code in programming language FORTRAN 95/90 was developed to solve the model numerically using the subroutine DIVPAG from the IMSL Library. Numerical results for the average concentration of bound analyte and average free analyte concentration at the sensor surface were computed from data previously reported in the literature for typical cases.
Keywords:Biosensor; Convection-diffusion-reaction model; Mass transport; Method of lines.
Presentation Schedule: Monday, 18:00-18:20. Session: HMT1-2. Presenter: Carlos Adriano Moreira da Silva.
ENCIT2012-374 KINETIC MODELING OF THE EXTRACTION PROCESS OF IRON OXIDE OF THE BAUXITE RESIDUE - PDF
Edilson Marques Magalhães, Emanuel Negrão Macêdo, José Antonio da Silva Souza, João Nazareno Nonato Quaresma, UFPA, Brazil
Abstract: The production of alumina from bauxite using the Bayer process generates the residue known by red mud. This material can be used as a source for concentration and recovery of valuable metals such as titanium. The greatest difficulty of concentrating titanium compounds is the large amount of iron oxide present in red mud > 30\% by weight. This work is divided into two stages: the first covers the development of a mathematical model that represents the kinetic modeling of extraction of iron oxide present in red mud.The second focuses on the use of the model with experimental data from the extraction of iron oxide red mud in order to obtain the essential parameters that will enable a greater understanding of the process of extraction of iron oxide, such as, the activation energy, rate constant of reaction and controlling stage the extraction process.
Keywords:Red mud; Bayer process; Leaching.
Presentation Schedule: Monday, 18:20-18:40. Session: HMT1-2. Presenter: Edilson Marques Magalhães.
ENCIT2012-377 HYPERBOLIC HEAT TRANSFER IN GENERALIZED NEWTONIAN FLUIDS - PDF
Heraldo Silva da Costa Mattos, UFF, Brazil
Rodrigo Araujo Cardoso Dias, ESSS, Brazil
Abstract: The present paper is concerned with the modelling of hyperbolic heat transfer in generalized Newtonian fluids. A general procedure, developed within the framework of thermodynamics of irreversible processes, is proposed to obtain constitutive relations that verify automatically the second law of thermodynamics and the principle of material objectivity. Such a thermodynamic approach allows a rational identification of the terms responsible for the thermomechanical coupling in the heat equation, which is a first step to better understand their influence on the fluid behaviour.
Keywords:hyperbolic heat conduction; finite thermal wave speed; generalized Newtonian fluids; material objectivity; second law of thermodynamics.
Presentation Schedule: Thursday, 14:40-15:00. Session: HMT1-3. Presenter: Heraldo da Costa Mattos.
ENCIT2012-119 EXPERIMENTAL DETERMINATION OF OVERALL HEAT TRANSFER COEFFICIENT ON NON HOMOGENEOUS ELEMENTS - PDF
Luís Mauro Moura, Luís César de Carli Turco, Nathan Mendes, PUCPR, Brazil
Abstract: This work describes the adaptation of a calibrated calorimeter in a calibrated guarded hot box, to perform measurements of the overall heat transfer coefficient in insulating non-homogenous materials. In order to determine the maximum adaptation configuration, the requirements of the ASTM C1363-05 standards for the ``Guarded Hot Box'' method were analyzed, as well as the influence of the measuring instruments used, their uncertainties and the propagation of their errors. After determining the equipment behavior, under working conditions, the sensitivity analysis of the results was evaluated. Thus, it was possible to determine the influence of the elements of the guarded hot box on the results and, also, to calibrate the device in the work range. After the calibration, tests on the overall heat transfer coefficient in typical enveloping materials, fence blocks (not structural concrete bricks) were performed. A representative sample of concrete bricks was built and tested with the equipment and its overall heat transfer coefficient was raised experimentally, using the guarded hot box method.
Keywords:Heat transfer; thermal conductivity; calibrated hot box; overall heat transfer coefficient; fence blocks.
Presentation Schedule: Thursday, 14:20-14:40. Session: HMT1-3. Presenter: Luis Mauro Moura.
ENCIT2012-293 CONSTRUCTAL DESIGN OF T-SHAPED ASSEMBLIES OF FINS COOLING A CYLINDRICAL SOLID BODY - PDF
Roberta Lima Corrêa, UFRGS, Brazil
Liércio André Isoldi, Elizaldo Domingues dos Santos, FURG, Brazil
Luiz Alberto Oliveira Rocha, UFRGS, Brazil
Abstract: This paper considers the constructal design of a T-shaped assembly of fins cooling a cylindrical solid body. The objective is to minimize the global thermal resistance between the solid cylindrical body and the ambient. Internal heat generating is distributed uniformly throughout the solid body. The assemblies of fins are bathed by a steady stream with constant ambient temperature and convective heat transfer. The outer surfaces of the cylindrical body are adiabatic. The total volume of the body and the total volume of the assembly of fins are fixed, but the lengths of the fins can vary. The number of T-shaped assembly of fins, N, and the ratio between the total volume of the assembly of fins and the volume of the cylindrical body, \&\#61542;, are design parameters. The optimized geometry and performance are reported graphically as functions of \&\#61542;, and N.
Keywords:Constructal design; heat generation; cylindrical solid body; T-shaped assembly fins.
Presentation Schedule: Monday, 15:40-16:00. Session: HMT1-1. Presenter: Roberta Lima Corrêa.