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COB72 Análise do Escoamento em Tubos Capilares Adiabáticos Considerando o Não-Equilíbrio Hidrodinâmico e Térmico Entre as Fases
A. L. Seixlack(*), A. T. Prata e C. Melo(**)
(*)Depto. de Engenharia Mecânica - FEIS/Unesp - Ilha Solteira - SP - Brasil - E-mail: andre@dem.feis.unesp.br
(**) Depto. de Engenharia Mecânica, NRVA/UFSC - Florianópolis - SC - Brasil - E-mail: melo@nrva.ufsc.br
This work presents a model to simulate the refrigerant flow through capillary tubes, used as expansion devices in refrigeration systems. The governing and constitutive equations, the boundary conditions and the simplifying assumptions are presented and discussed. The two-fluid model, considering the hidrodynamic and thermal non equilibrium between the liquid and vapor phases, is applied to the two-phase flow region. The pressure profiles and the mass flow rates given by the model are compared with experimental data and a good agreement is shown.
Keywords: Capillary tubes, two-phase flow, two-fluid model. Tubos capilares, escoamento bifásico, modelo de dois fluidos.
COB73 EQUAÇÕES CONSTITUTIVAS PARA TUBOS CAPILARES E O SEU IMPACTO SOBRE O DESEMPENHO DO PROGRAMA CAPILAR / CONSTITUTIVE EQUATIONS FOR CAPILLARY TUBES AND THEIR IMPACT ON THE CAPILAR PROGRAM PERFORMANCE
Cláudio Melo (**), Carlos Boabaid Neto (*), Rogério Tadeu Da Silva Ferreira (**)
(*) Escola Técnica Federal de Santa Catarina / UnED-SJ
(**) Universidade Federal de Santa Catarina / Depto. de Engenharia Mecânica / NRVA
CEP 88040-900 - Florianópolis - SC - E.mail: melo@nrva.ufsc.br
This work presents a second version of a numerical model to simulate adiabatic capillary tubes. The constitutive equations employed in the first version of the model are replaced by new ones, derived from experimental work on capillary tubes. Comparisons with experimental data reveal that the second version predicts more accurately the refrigerant flow through adiabatic capillary tubes.
Keywords: Capillary tubes, Expansion, Refrigeration, Tubos capilares, Refrigeração
COB740 CIRCUITO PARA ENSAIOS DE EVAPORADORES/ EVAPORATORS TEST
Marcelo Bianchi(a) & Silvio de Oliveira Jr(a, b)
(a) Instituto de Pesquisas Tecnológicas de São Paulo (IPT) - Av. Prof. Almeida Prado, 532 - Cidade Universitária - CEP 05508-901 - São Paulo - E-mail: mabaet@ipt.br
(b) Escola Politécnica da USP - Departamento de Engenharia Mecânica
This paper describes an experimental apparatus for testing evaporators of residential air conditioning systems. In this test rig it is possible to determine the overall heat transfer coefficient, pressure loss (of air and refrigerant sides) and refrigerating capacity as function of different operating conditions (air flow rate, refrigerant flow rate, evaporating temperature, quality at the evaporator inlet). This test rig can be utilized to characterize the performance of evaporators of room conditioners employing different types of refrigerant fluids and heat enhancement surfaces.
Keywords: evaporator test rig, room conditioners
COB874 ESTUDO DO ESCOAMENTO DE REFRIGERANTES ATRAVÉS DE TUBOS CAPILARES - UMA REVISÃO CRÍTICA / A CRITICISM ON THE STUDIES OF THE FLOW THROUGH CAPILLARY TUBES
Marco A. S. de Paiva, Flavio A. S. Fiorelli, Alberto H. Neto, Otávio de M. Silvares
Some important aspects concerning the mathematical modelling and numerical simulation of the flow through capillary tubes, as treated by several researchers, are usually not presented in details on published papers. This paper presents the phenomena, parameters and variables that mostly governs the flow, performing some insights into them.
Keywords: Capillary tubes, two-phase flow, refrigeration, mathematical modelling, simulation.
COB901 VALIDAÇÃO DE UM MODELO PARA SIMULAÇÃO DE SISTEMAS DE AR CONDICIONADO COM TERMOACUMULAÇÃO / VALIDATION OF A MODEL FOR SIMULATION OF THERMAL STORAGE AIR CONDITIONING SYSTMEMS
Osvaldo José Venturini, Eli silva & Manuel da Silva Valente de Almeida
Escola Federal de Engenharia de Itajubá - Departamento de Engenharia Mecânica
CEP 37500-000 Itajubá - MG Brasil E-mail: venturin@iem.efei.rmg.br
This work presents a model for computational simulation of direct ice-storage air conditioning systems. The model developed is based on the thermodynamics quasi-steady equilibrium process. The results of the simulation are compared with experimental data obtained in the air conditioning laboratory at EFEI.
Keywords: Ar condicionado, termoacumulação, modelo, simulação e validação. Air conditioning, thermal storage, model, simulation and validation
COB1140 MODELO DINÂMICO PARA A LUBRIFICAÇÃO DE PISTÕES EM COMPRESSORES ALTERNATIVOS DE REFRIGERAÇÃO / DYNAMIC MODEL FOR PISTON LUBRICATION IN REFRIGERATION RECIPROCATING COMPRESSORS
Julio Romero Santos Fernandes
GES - Sistemas Fluido Dinâmicos, EMBRAER, 12227-901 São José dos Campos, SP - E-mail: gessfd@embraer.com.br
Alvaro Toubes Prata
Departamento de Engenharia Mecânica, Universidade Federal de Santa Catarina
88040-900 Florianópolis, SC - E-mail: prata@nrva.ufsc.br
Fabian Fagotti
Divisão de Pesquisa Mecânica e Materiais, EMBRACO, 89219-901 Joinville, SC - E-mail: pesqmec@embraco.com.br
A numerical simulation of the piston movement inside the cylinder of a reciprocating compressor is performed. The compressor considered here is a small hermetic compressor employed in domestic refrigerators. For the problem formulation both the axial and the radial piston motion is considered. In operation, the piston moves up and down along the axis of the cylinder, but the radial oscillatory motion in the cylinder bore, despite being usually small, plays a very important role on the compressor performance and reliability. The forces acting on the piston are the hydrodynamic force due to the pressure build up in the oil film (lubrication effects), the force due to the connecting rod, the viscous force associated with the relative motion between the piston and oil, and the force exerted by the gas on the top of the piston. All corresponding moments are also included in the problem formulation of the piston dynamics in order to determine the piston trajectory, velocity and acceleration at each time step. The results explore the effects of several design parameters and operation conditions on the stability of the piston, its sealing performance and friction losses.
Keywords: piston dynamics, piston lubrication, sealing, compressor operation
dinâmica de pistão, lubrificação de pistão, vedação, operação de compressores
COB1284 SIMULAÇÃO DE UM REFRIGERADOR ADSORTIVO REGENERATIVO UTILIZANDO REJEITOS TÉRMICOS/ SIMULATION OF AN ADSORPTION REFRIGERATION REGENERATED BY REJECTED HEAT
José Espínola Jr+#, Jesus Marinaldo Medeiros+# & José Maurício Gurgel*
(+)Escola Técnica Federal de Sergipe/UNED - Aracaju - SE 49056-260
(#)UFPB/CT/CPGEM/LES
(*) UFPB/DTM/CPGEM/Laboratório de Energia Solar, E-mail gurgel@les.ufpb.br, 58059-900 João Pessoa - PB - Brasil
This research presents numerical simulation and a later dimensioning technique for a refrigeration system based on solid sorption, taking advantage of the rejected heat of a stationary internal combustion motor for regeneration. The functioning is based on a chemical reaction between two compounds, one in solid form and the other in liquid form or vapor. The choice of the frigorific pair depends on the desired working temperature for evaporation and also the maximum temperature at which the adsorbent can be reactivated. In order to analyze the influence of the frigorific pair, as well as the optimization of the prototypes, it is necessary to construct a mathematical model which represents correctly the operation of a real system. In this model, the heat equations are solved within the porous medius coupled to the form of heat generation relative to the mass transportation. Computation methods will be used to solve in finite differences.
Keywords: Refrigeration - solid adsorption - porous medius - active carbon - methanol
Adsorção sólida - carvão ativado - refrigeração - leito poroso - metanol
COB1423 SISTEMA FRIGORÍFICO A ADSORÇÃO UTILIZANDO CARVÃO ATIVADO-METANOL COM REGENERAÇÃO POR ENERGIA SOLAR / ADSORPTION SOLAR COOLING SYSTEM USING ACTIVATED CARBON-METHANOL
Antonio Pralon Ferreira Leite
Departamento de Engenharia Mecânica, Centro de Ciências e Tecnologia - UFPB
CEP 58.109-970 Campina Grande-PB, Brasil - E-mail: pralon@lctf.ufpb.br
An analytical model of a new-conception of solid sorption solar cooling system and its numerical simulation are presented. This model accounts instantaneous heat and mass transfers in each component of the machine, during a whole characteristic average day of each month. The innovation of the machine consists in the use of a honeycomb TIM's cover for the solar collector and multitubular configurations for the reactor and the evaporator. The performance of the machine is evaluated utilizing meteorological data for one region of Brazil close to the equator, for the hottest six months. The results are compared with those obtained by modeling the system with a single cover solar collector and those from an experimental study of a prototype with usual components realized in Tunisia. The average net solar COP for the six months was 0.13 for the TIM cover system, corresponding to an ice production going from up to 7 to 10 kg per day per square meter of collector surface, respectively for March and December, with solar irradiations of 20 to 23 MJ/m2.
Keywords: Adsorption, Solar Cooling, Activated Carbon-Methanol, Numerical Simulation
Adsorção, Refrigeração Solar, Carvão Ativado-Metanol, Simulação Numérica