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Estudo do perfil de concentração em um preciptador eletrostático do tipo placa-fio
(Universidade Federal de São Carlos, 2004-03-30) Cerda, Edmundo Eduardo Valdés; Coury, José Renato
The different models utilized for the calculation of the collection efficiency of electrostatic precipitators are based in distinct hypotheses about the behavior of the particles inside the equipment. Hence, in one extreme they consider the particles in perfect mixture, in a flat concentration profile in turbulent flow, known as the Deutsch model, and in the other it is assumed a laminar flow without mix. Other authors proposed intermediate theoretical behaviors. However, experimental results are very scarce. Therefore, to know the real behavior inside the precipitator, an experimental method was devised to measure and determine the concentrations of the aerosol and verify which of the proposed behaviors in the literature describe adequately the data. The electrostatic precipitator utilized was of the plate-wire type, in laboratorial scale, with a 0.50 m in length and 0.20 m in width, with 6 discharge electrodes. It was observed that the points of higher concentrations occurred in the duct center and decreased towards the walls. The Deutsch model offered the best description of the experimental profile. However, it was noticed that in the entrance region, a different behavior occurred. Also, it was noticed that, with the increase of the electric field, the concentration decreased both in the center as near the wall, and this variable presented a more significant effect in the concentration than the gas velocity.
Contribuições ao estudo da secagem em um leito pneumático vertical
(Universidade Federal de São Carlos, 2004-03-30) Narimatsu, Cristiane Pirola; Freire, José Teixeira; https://lattes.cnpq.br/2270677706718167
Pneumatic dryers are widely applied in industry, mainly because the transport of particulate material can be performed simultaneously with heating and drying operations. However, the design of such equipment is still based on empirical knowledge and fundamental researches on drying still need further development because few experimental works in literature focus simultaneously the momentum, heat and mass transfer mechanisms involved during a drying process. Therefore, the purpose of this work is to analyze the fluid dynamic and thermal behavior in a vertical pneumatic bed by carrying out experimental investigation and analyzing the variables and parameters involved in the process through correlations available in literature and mathematical models, aiming to contribute for a better understanding of the drying phenomena. In the tests was employed a drying bed made of galvanized iron with diameter of 53.4mm, length of 4.1m. The solids are fed into the tube by a gravitational feeder. The experimental data were obtained for two materials: glass spheres (flat surface and non porous structures) and alumina particles (wrinkled surface and porous structures), both with mean diameter of 3.68mm. From experimental results, it was possible to check the operational behavior of the solids feeder, to estimate the fluid-wall attrition coefficient and to identify the flow regimes by locating the dilute and dense phase regions in curves of pressure gradient versus air velocity. The thermal analysis was accomplished by measuring gas and solids temperature profiles and also by solving the energy balances applied to solid and fluid phases. Therefore, it was possible to compare the experimental and theoretical profiles of gas and solids temperatures and also to determine the gas-solid heat transfer coefficient under different conditions of solid flow rates and air velocity. A comparison between the heat transfer coefficient and pressure drop versus air velocity curves shows that the gas-solid heat transfer coefficients are higher in the transition between the dense and dilute regimes. Concerning the investigation of drying in pneumatic beds, it was observed that it is very difficult to measure precisely the local values of gas and solid moistures and the solids temperature, mainly at dilute flow conditions. Through the simulation of one-dimensional mathematical models from Rocha (1988) and Pelegrina and Crapiste (2001) it was verified that the theoretical profiles of gas and solids temperature and moisture are strongly dependent on the correlations used for estimation of heat transfer coefficients. It can be concluded that further studies on the drying in pneumatic beds require the improvement of experimental techniques and the development of new methodologies aiming the validation of models.
Biologia reprodutiva do cíclídeo neotropical ornamental acará disco, Symphysodon discus Heckel, 1840 (Osteichthyes: Perciformes: Cichlidae)
(Universidade Federal de São Carlos, 2004-03-30) Câmara, Mércia Rocha da; Verani, José Roberto; https://lattes.cnpq.br/0053232138684810; Chellappa, Sathyabama;
The Neotropical cichlid fish red discus, Symphysodon discus Heckel, 1840 originates from the Amazonian basin. Though this species is popularly used in aquaria and is exported as an ornamental fish, it has not been intensively studied. As such, this work was carried out with an objective to study the reproductive biology of this species. Eighty individuals of both sexes of different body sizes and in different stages of gonadal development were used in this study. The gonads were examined macroscopically in order to observe the maturation stages and histological staining was used for microscopic observations. The fecundity, type of spawning and the gonadosomatic index were determined. Aggressive interactions and territoriality between mature males of different body sizes were observed in neutral situation. The results of macroscopic observations of the gonads of both sexes showed the four stages of gonadal development, such as, immature, maturing, mature and partially spent. Microscopic examinations showed five different phases of the ovarian development and four testicular developmental stages. The average fecundity per batch was 536 oocytes. The gonads of the mature females showed all the different phases of oocyte development indicating the multiple spawning habit of this species. The mature males in the reproductive phase manifested aggression, territoriality and defence of territory, exhibiting differences in body size, degree of aggression and capacity of territorial defence. The bigger males were more aggressive than the smaller males. The males with established territories were preferred by the females for courtship.