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COB39 FREE SURFACE FLOW IN A HELICAL RECTANGULAR DUCT
Eugênio Spanó Rosa, Antonio Carlos Bannwart & Fernando de almeida França
Departamento de Energia, Faculdade de Engenharia Mecânica - UNICAMP
Cx.P. 6122 - CEP 13.083-970 - Campinas, SP - Brasil, E-mail: erosa, bannwart, ffranca@fem.unicamp.br
Free surface flow in rectangular helical ducts is investigated experimentally. A liquid, driven by gravity, describes a descendent trajectory forming a curved free gas-liquid surface due to the centrifugal and gravity forces created by the duct curvature and torsion. The experiments were conducted in two different helical ducts, with liquids' viscosity varying from 1 cP to 150 cP and for duct Reynolds numbers ranging from 40 to 90000 performing a total of 18 experimental runs. The liquid height distributions across the duct were measured using a double wire probe. The results were transformed to an orthogonal system and then integrated across the flow orthogonal cross section to determine the averaged main flow velocity and liquid holdup. The friction factor is determined based on the experimental quantities and a correlation is proposed in the form of correction factors to the existing friction formulae for curved rectangular channels to express the effect of the free surface.
Keywords: Helical ducts, free surface flow, experimental techniques, friction factor, rectangular channel/
Dutos helicoidais, escoamento com superfície livre, técnicas experimentais, fator de atrito, canal retangular
COB48 UMA ANÁLISE DA TEORIA QUASE-ESTACIONÁRIA SOBRE A VAPORIZAÇÃO DE GOTAS, PARA TEMPERATURAS INTERMEDIARIAS /AN ANALYSIS OF THE STEADY-STATE THEORY ABOUT VAPORIZATION OF DROPLLETS FOR INTERMEDIARIES TEMPERATURE
Narciso Angel Ramos Arroyo
Departamento de Engenharia Mecânica, UFSC/CTC , 88.010-970 Florianópolis - SC - Brasil ; e-mail : arroyo@sinmec.ufsc.br
This paper show a revision about the steady-state theory developed of Spalding, Godsave, Goldsmith and Penner. It show that the Lewis number can be obtain for the logarithmic relation of the transfer mass Spalding number and the transfer of heat Spalding number. This work show that intermediaries temperature between 310 K and 700 K, the Lewis number is not equal to the unit. It show experimental results for n-heptane drops in these temperatures range.
Keywords: Combustion, Vaporization , Sprays /Combustão, Vaporização, Sprays
COB52 DIRECT IMAGING OF TWO-PHASE FLOWS BY MEANS OF ELECTRICAL CONDUCTIVITY MEASUREMENTS
Paulo Seleghim Jr. & Antonio Moreira dos Santos
Departamento de Engenharia Mecânica, Escola de Engenharia de São Carlos - USP - Av. Dr. Carlos Botelho, 1465, CEP13560-970
São Carlos - SP - Brasil - E-mail : seleghim@sc.usp.br and asantos@sc.usp.br
In this paper a two-phase flow direct imaging probe is presented. To do so, the electrode configuration is adapted in the sense that an imaged representation of the phase distribution within the probe's sensing volume can be obtained by simply plotting the signals corresponding to peripheral conductivity measurements without numerically reconstructing it from the experimental data. Several transient tests were performed in a two-phase loop aiming to demonstrate the the probe's capability in exhibiting not only large structures such as slugs and plugs, but also some finer details as for instance, the wavy or rugged interface in stratified flow and the drainage of the liquid film in the transition between intermittent and annular flow. The methodology proposed in this work is thus fully adapted to on line process monitoring, which is of crucial importance in order to assure ideal exploitation conditions and safety. It constitutes a simple and inexpensive alternative to tomographic imaging techniques.
Keywords two-phase flow, imaging, visualisation, conductivity
COB67 SEARCH FOR FAVORABLE CONDITIONS OF ATMOSPHERIC Fluidized-Bed Gasification of SUGAR-CANE BAGASSE Through Comprehensive Simulation
Marcio L. de Souza-Santos
IPT-Instituto de Pesquisas Tecnológicas de São Paulo e UNICAMP - Universidade Estadual de Campinas, FEM - Faculdade de Engenharia Mecânica, Departamento de Energia, Cidade Universitária Zeferino Vaz, C. Postal 6122, Campinas, SP 13083-970, Brasil, E-mail: souzasan@fem.unicamp.br
A study to search for the most favorable condition of atmospheric fluidized-bed gasification of sugar-cane bagasse has been possible using a comprehensive computer simulator of fluidized bed equipment. A previous version of the simulation program has been improved to provide more precise results. In addition, the prediction of possible particle segregation in the bed has been implemented. "Cold" efficiency has been chosen as objective function. The following conditions have been set as constants: operational pressure, basic geometry of the reactor, bed height, particle size distribution of bagasse, particle size distribution of alumina (used as inert in the bed), and bagasse dry-basis composition. The parameters left as variables were: bagasse moisture and the oxygen ratio (fraction from the necessary oxidant for total or stoichiometric combustion). Future steps toward a more complete optimization are shown. The results are going to be used on studies of power generation systems employing gas turbine concepts.
Keywords: Fluidized-bed, gasification, simulation, optimization, sugar-cane bagasse
COB68 SEARCH FOR FAVORABLE CONDITIONS OF PRESSURIZED FLUIDIZED-BED GASIFICATION OF SUGAR-CANE BAGASSE THROUGH COMPREHENSIVE SIMULATION
Marcio L. de Souza-Santos
IPT-Instituto de Pesquisas Tecnológicas de São Paulo e UNICAMP - Universidade Estadual de Campinas
FEM - Faculdade de Engenharia Mecânica, Departamento de Energia
Cidade Universitária Zeferino Vaz, C. Postal 6122, Campinas, SP 13083-970, Brasil, E-mail: souzasan@fem.unicamp.br
An updated comprehensive simulator for fluidized-bed equipment has been employed to perform studies aiming the optimization of sugar-cane bagasse gasification. The present work for pressurized systems follows one where the atmospheric option was focused. Improvements on the calculations of physical-chemical properties provided more precise computations for operations at high pressures. Gasification ``Cold'' efficiency has been chosen as the objective function. For this first round of studies, the operational pressure was fixed at 2 MPa. The basic geometry of the reactor, the particle size distribution of the alumina (used as inert in the bed), and the bagasse dry-basis composition are assumed as constants. Bagasse moisture and the injected air mass flow (or oxygen ratio) are left as variables. Detailed data of the reactor internal as well as overall operational conditions are discussed. The results are going to be used on studies of power generation systems employing gas turbine concepts.
Keywords: Fluidized-bed, gasification, simulation, optimization, biomass
COB71 ANALYSIS OF SCALE REDUCTION EFFECTS IN ANNULAR SOLID-LIQUID FLOWS
André Leibsohn Martins & Felipe Santos Liporace
PETROBRAS / CENPES / DIPLOT - Ilha do Fundão Q.7 - Cidade Universitária
CEP 21949-900 Rio de Janeiro, Brasil - E-mail: Aleibsohn@cenpes.petrobras.com.br
This paper presents and discusses results of solids transport experiments run in two different flow loops (5 in OD x 4 in ID and 8 in OD x 7.5 in ID external pipes), built in PETROBRAS Research Center and University of Tulsa, respectively. The tests represent the annular stratified flow of solid - non Newtonian fluid mixtures for different operational parameters, such as: fluid and solid properties, annular eccentricity and inclination and fluid flow rate. Based on the experimental data, several recommendations are drawn about the usefulness of running reduced scale solid-liquid flow experiments and its applicability to real oilwell drilling operations.
Keywords: Petroleum Engineering, Drilling, Dimensional Analysis, Similarity Theory, Pilot Plants.
COB239 UMA ABORDAGEM MULTIESCALA NA SIMULAÇÃO NUMÉRICA DE RESERVATÓRIOS DE PETRÓLEO / A MULTI-SCALE APPROACH IN PETROLEUM NUMERICAL RESERVOIR SIMULATION
Solange da Silva Guedes
Exploração & Produção, Gerência de Reservas e Reservatórios - PETROBRAS, E-mail:solange@dep.fem.unicamp.br
Denis José Schiozer
Departamento de Engenharia de Petróleo - Faculdade de Engenharia Mecânica - UNICAMP
CEP 13083-970 - Cidade Universitária Zeferino Vaz - Campinas - SP -E-mail:denis@dep.fem.unicamp.br
Advances in petroleum reservoir descriptions have provided an amount of data that can not be use directly during the simulations. This detailed geological information must be incorporated into a coarser model during the multiphase fluid flow simulations by means of some upscaling technique. The most used approach are the pseudo relative permeabilities and the more widely used is the Kyte and Berry method. In this paper it is proposed a multi-scale computational model for multiphase flow that implicitly treats the upscaling without using the pseudo functions. By solving a sequence of local problems on the more refined scale it is possible to achieve good agreement between a coarser grid and a more fine grid, without expensive computations on a fine grid model of the whole reservoir. The main characteristic of this new upscaling procedure is to overcome some practical difficulties related the use of traditional pseudo functions. Results of bidimensional two phase flow simulations considering homogeneous and heterogeneous porous media are presented. Three examples compare the results between this approach and the commercial upscaling program PSEUDO, a module of the reservoir simulation software ECLIPSE of Geoquest.
Keywords: Upscaling, Multiphase flow, Numerical simulations, Multi-scale computational model.
COB309 DESENVOLVIMENTO DE UM TERMOSSIFÃO BIFÁSICO PARA UTILIZAÇÃO EM FORNOS DE COCÇÃO / DEVELOPMENT OF A CLOSED TWO-PHASE THERMOSYPHON FOR USE IN BAKERY OVENS
Ricardo D. M. Carvalho L , Márcia H. Mantelli2 , Sérgio Colle2 & José A. S. Lima
1 Departamento de Engenharia Mecânica, Faculdade de Engenharia de Joinville, 89223-100 Joinville, SC
E-mail: dem2rdmc@dcc.fej.udesc.br
2 Departamento de Engenharia Mecânica, Universidade Federal de Santa Catarina, 88000-000 Florianópolis, SC
E-mail: marcia@labsolar.ufsc.br
Electricity-powered ovens are largely employed by bakeries in Brazil, which constitutes a misuse of this form of energy. This is even more so considering that hydroelectric energy resources in the country might be coming close to their limit. The present paper describes the design, manufacture, and testing of thermosyphons to be used in bakery ovens using natural gas as the heat source. The design geometrical parameters, working fluid fill ratio, operation limits, and the two-phase flow pattern are discussed.
Keywords: fornos de cocção, projeto e ensaio de termossifões / bakery ovens, thermosyphon design and testing
COB343 ESTIMATING THE THICKNESS OF THE LIQUID FILM GENERATED BY Y-JET ATOMIZERS
Heraldo da Silva Couto & Demétrio Bastos-Netto
Laboratório Associado de Combustão e Propulsão, Centro Espacial de Cachoeira Paulista – INPE – SP
CEP 12630-000 Cachoeira Paulista, SP, Brasil – E-mail: demetrio@yabae.cptec.inpe.br
Internal mixing twin fluid air blast (Y-jet) atomizers, in which liquid is injected into a mixing chamber with compressed air or steam, are extensively used in industry. It is well known that one of the main design parameters for pre filming blast atomizers is the thickness of the liquid film generated at the discharge orifice. This paper derives an expression for estimating that film thickness assuming that, apart from a small amount of droplets formed by the impact of the liquid on the air stream inside the pre-mixing chamber, the great majority of droplets is generated by the liquid film formed on the pre-mixing chamber wall through the deflection of the liquid jet by the high speed gas stream flowing through the center core of the pre-mixing chamber. That is, this Atomizer, usually classified as an "internal mixing, blast atomizer" behaves instead as a "pre filming blast atomizer". The results compared well with experiments.
Keywords: Atomizers, Y-Jet Atomizers, Liquid Films, Droplets and Sprays
COB505 INFLUÊNCIA DA RAZÃO DE VAZÕES NA TRANSFERÊNCIA DE CALOR DE UM ESCOAMENTO LAMINAR ANULAR DE DOIS LÍQUIDOS IMISCÍVEIS EM TUBOS CURVOS / INFLUENCE OF THE FLOW RATE ON THE HEAT TRANSFER IN THE FLOW OF TWO INMISCIBLE LIQUIDS IN CURVED TUBES
Ricardo Junqueira Silva, Márcio Ziviani & Ramón Molina Valle
Departamento de Engenharia Mecânica, UFMG, Av. Antônio Carlos, 6627
CEP 31.270-910 - Belo Horizonte - MG - Brasil - E-mail: junco@demec.ufmg.br
The present paper reports the influence of the flow rate on the flow and heat transfer in the fully developed region in a steady laminar annular flow of two inmiscible liquids inside horizontal and slightly curved tube with constant circular cross section. The liquids interface was considered without thickness, smooth, circular and concentric to the axis of the duct. The liquids properties were taken constant and calculated based on the mean temperature. The finite volume method was used to solve the mass, momentum and energy conservation equations. The influence of the flow rate on the flow, temperature profile and heat loss have been determined.
Keywords: Curved pipe, annular flow, heat transfer, tubo curvo, escoamento anular, transferência de calor.
COB703 INVESTIGATION OF FLUID DYNAMICS IN PNEUMATIC TRANSPORT WITH SPOUTED BED AND SCREW SOLID FEEDING SYSTEMS
Élcio M. V. Silva, Maria do Carmo Ferreira & José Teixeira Freire
Departamento de Engenharia Química, Universidade Federal de São Carlos - C.P. 676 –CEP 13.569-265 - São Carlos - SP – Brazil
E-mail: mariaf@power.ufscar.br
The use of a spouted bed for feeding solids in a pneumatic transport tube allows for a wide range of operational conditions. However, as the solid flow rates become dependent on the air flow rates, the flow diagrams available in literature for flow regime identification cannot be applied for such a equipment. In present work, fluid dynamic characterization of pneumatic transport with a spouted bed type solid feeding system has been extended by comparing its fluid dynamic behavior with the one provided by using a classical feeder, which allowed for independent variation of gas and solid flow rates. Experimental data of pressure gradients versus air velocities have been obtained using the same transport pipe (4.0 m long and 104.8 mm in diameter) and using both a spouted bed and a screw conveyor as solid feeding devices. Experimental values of the air velocities at the transition from dilute to dense-phase regimes have been obtained for both systems. The data obtained using the screw feeder have been compared with data from literature. Also investigated was the validity of using the correlations for predicting the transition air velocities developed for classical feeders for the data obtained using the spouted bed feeder. The results allow the conclusion that the transition point can be predicted using the same criterion for both systems.
Keywords: Pneumatic transport, solid feeding systems, flow regime identification.
COB886 MASS FLOW IN A TWO-PHASE FLOW WITH BOILING THERMAL SIPHON LOOP / VAZÃO MÁSSICA EM ESCOAMENTO BIFÁSICO COM EBULIÇÃO EM UM CIRCUITO DE TERMOSSIFÃO
Maria Eugênia Vieira, Hugo Leonardo de Brito Buarque & Públio Otávio Oliveira Duarte
Laboratório de Energia Solar, Centro de Tecnologia, Bloco 710, Campus do Pici - UFC
CEP 60455-760 - Fortaleza, Brazil - E-mails: eugenia@les.ufc.br / hugo@les.ufc.br
This work presents a model to determine the total mass flow rate in a two phase flow with boiling closed circuit. This system is used to collect solar energy by the formation of vapor bubbles in a solar collector and to release this energy in condensation by heating a second fluid. The model assumes that the total frictional drop equals the pressure gain due to the difference in gravity in the single phase and the two phase vertical parts of the loop. Using the definition of the void fraction, a second expression could be written and the two equations were solved simultaneously for the void fraction and the total mass rate. The results indicated that the two phase flow was bubbly, what was expected considering the relatively low intensity of the solar flux and the experimental values for the temperature difference between the heated wall and the fluid saturation temperature.
Keywords: Thermal siphon, two-phase flow, mass rate, void fraction / Termossifão, escoamento bifásico, fração de void
COB1119 ANÁLISE DA ACELERAÇÃO EM SISTEMAS DE TRANSPORTE PNEUMÁTICO VERTICAL EM FASE DILUÍDA / ANALYSIS OF THE ACCELERATION IN VERTICAL PNEUMATIC TRANSPORT SYSTEM IN DILUTE PHASE
Napoleón González Benitez & André Luiz Amarante Mesquita
Grupo de Turbomáquinas - Departamento de Engenharia Mecânica - Universidade Federal do Pará
CEP - 66075-900 Guamá, Brasil E-mail: gtdem@amazon.com.br
This work presents a model to analysis the gas-solid vertical flow in dilute phase based on one-dimensional, isothermal and steady-state on balances equation. With this model the length of the acceleration region is calculated and the pressure loss can be analyzed. The results from the present model are confronted with experimental data available in the literature, and a good agreement is observed.
Keywords: Pneumatic Transport/ Transporte Pneumático Dilute Phase/Fase Diluída
Gas-Solid Flow/Escoamento Gás-Sólido Acceleration Region/Região de Aceleração
COB1120 UM MÉTODO PARA A ANÁLISE DE TRANSPORTE PNEUMÁTICO VERTICAL EM FASE DILUÍDA / A METHOD FOR VERTICAL PNEUMATIC TRANSPORT ANALYSIS IN DILUTE PHASE
Napoleón González Benitez & André Luiz Amarante Mesquita
Grupo de Turbomáquinas - Departamento de Engenharia Mecânica - Universidade Federal do Pará
CEP - 66075-900 Guamá, Brasil E-mail: gtdem@amazon.com.br
This work presents a model for the gas-solid vertical flow analysis in dilute phase based on one-dimensional, isothermal and steady-state on balance equation. The model is an extension of some significant works. The results from the present model are confronted with experimental data available in the literature, and a good agreement is observed. The model is consistent and it is concluded that energy losses due the solid friction it is not important face the other loss energy sources.
Keywords: Pneumatic Transport/Transporte Pneumático Dilute Phase/Fase Diluída
Gas-Solid Flow/Escoamento Gás-Sólido
COB1445 TURBULENCE AND PHASE DISTRIBUTION FOR SOLID/LIQUID TWO-PHASE FLOW WITH NEUTRAL BUOYANT PARTICLES
A. Assad1 and R.T Lahey, Jr2
1- Purdue University, School of Mechanical Engineering, West Lafayette, IN 47907-1077. E-mail amir@ecn.purdue.edu
2- Rensselaer Polytechnic Institute, Department of Energy and Environmental Engineering, Troy, New York 12180
Detailed local phase distribution measurements were made for solid/liquid two-phase flows in a horizontal pipe using a state-of-the-art laser Doppler anemometer (LDA) system. The disperse phase consisted of 2 mm neutral buoyant spherical particles. Since these particles had the same density as water particle/liquid slip was eliminated, thus simulating microgravity conditions. The conduit was a 30.6 mm diameter pipe, which was made of a special optically clear material (Fluorinated Ethylene Propylene) with the same index of refraction as water. A set of velocity profiles, turbulence structure and volume fraction distributions were measured for each phase. These experimental results were found to agree quite well with a multidimensional two-fluid model.
Keywords: Two-Phase Flow, Solid-Liquid Flow, Laser Doppler and Turbulence.
COB1446 AN EXPERIMENTAL ANALYSIS OF PRESSURE DROP AND ENTRAINMENT IN ANNULAR FLOW
A. Assad1 , M. de Bertodano2 and Stephen Beus3
Purdue University, School of Mechanical Engineering 1 and School of Nuclear Engineering 2
West Lafayette, IN 47907-1077. E-mail amir@ecn.purdue.edu,
Bettis Atomic Power Laboratory Westinghouse Electric Corporation 3, West Mifflin, PA 15122-0079
The droplet entrainment and the interfacial shear are the most important phenomena that can exist in annular flow. Many of the available data were obtained for atmospheric condition neglecting high pressure effects where surface tension plays an important role. A unique vapor/liquid Freon experiments were designed and utilized to scale and simulate annular two-phase flow for high pressure data. The results were compared with two correlations available where Ishii and Mishima's dimensionless group was able to scale the data remarkably well. The pressure data obtained agreed well with Wallis and Asali's correlation for interfacial shear.
Keywords: Two-Phase Flow, Annular Flow and Vapor/Liquid Freon-113