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Navegando por Assunto "Transferência de massa"

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    Desenvolvimento de um modelo via MEF para análise da dispersão de poluentes em rios, lagos e estuários
    (Universidade Federal do Pará, 2012-03) LIMA, Rômulo Correa; BLANCO, Claudio José Cavalcante; http://lattes.cnpq.br/8319326553139808; MESQUITA, André Luiz Amarante; http://lattes.cnpq.br/1331279630816662
    Freshwater of good quality is a pre-requisite for social and economic development of a given region. Paradoxically, this same development is normally responsible for the pollution of their water sources, through domestic or industrial waste dumping without treatment, or through agricultural activities. In this way, the monitoring and the management of that sources are extremely important for the wellbeing of the people living in that region. Among the possible tools to auxiliary this management is the computational simulation of pollutant transport in the hydro medium. In this context, this work presents a computational procedure for the solution of the 2D advectiondiffusion- reaction equation, which is the basis for all the mass transport models. This process consists in the union of the finite elements and finite difference methods in the discretization of the spatial and temporal components, respectively. This methodology was evaluated with the help of tests with synthetic and real data. First one considered the case of mass transport by pure advection to ensure its stability in cases where the classical formulations fail. Second test simulated the transport of a hypothetical pollutant in a piece of a river and showed the correct effect of the drag due to advection and spreading due to diffusion. The last test evaluated the transport of total phosphorus in Agua Preta Lake from the pumped water of the Guama river and point sources located at the margins of the reservoir. The result of the simulation showed the potential of the algorithm to deal with cases closer to the reality.
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    Desenvolvimento de unidade piloto de transferência de massa gás/líquido: redução da reatividade do resíduo da indústria de alumina através da reação com gases de combustão
    (Universidade Federal do Pará, 2013-02) VENANCIO, Luis Carlos Alves; SOUZA, José Antônio da Silva; http://lattes.cnpq.br/6157348947425968; MACÊDO, Emanuel Negrão; http://lattes.cnpq.br/8718370108324505
    The bauxite refining using the Bayer process produces 0.7 to 2.0 tons of the residue known as red mud and about 1.0 ton of CO2 for each ton of alumina produced. The bauxite residue, although not particularly toxic, poses risks to the environment due to its large volume and reactivity. According to the latest technology, part of the moisture is removed and it is stacked on sealed areas specially constructed. More than 95% of the bauxite residue that has been produced (2.6 Bt until 2007) was discarded, especially in ponds on land. This thesis shows the design, construction and operation of a pilot scale gas liquid mass transfer unity with the objective of testing the reduction of the reactivity of the bauxite residue through a reaction with flue gas. As an additional gain, there is a reduction of carbon dioxide and sulfur dioxide emissions. This unity, with three reactors, was designed in order to consume minimal power, process the effluent as efficiently as possible and minimize the investment cost. Twenty-five experiments were realized with duration from 80 to 520 minutes each. The gases were analyzed at the entry and exit with electrochemical cells and non-dispersive infrared sensors. The pH was monitored during and after the reaction in order to evaluate the short and long-term results as well as the stability of the reactions. It was demonstrated the viability of reacting the bauxite residue with the flue gas from the refinery without previous processing with the stabilization pH reaching 10.5.
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    Desidratação osmótica à vácuo do filé de mapará (Hypophthamus edentatus)
    (Universidade Federal do Pará, 2014-03-28) MACIEL, Renan de Almeida; RODRIGUES, Antonio Manoel da Cruz; http://lattes.cnpq.br/7524720020580309; PENA, Rosinelson da Silva; http://lattes.cnpq.br/3452623210043423
    The aim of this work was to evaluate the process of vacuum osmotic dehydration of mapará fillet (Hypophthamus edentatus). Mapará fillets with dimensions of 5 x 2 x 0.5 cm were subjected to vacuum osmotic dehydration in accordance with a rotational central composite design 24, in which were evaluated the effects of the independent variables temperature, time, vacuum pressure and NaCl concentration on the dependent variables water loss (WL), solids gain (GS) and water activity (aw), order to obtain optimal condition of process with greater PA, lower GS and lower aw. The kinetics of osmotic dehydration of mapará was performed under optimal conditions, where were monitored the parameters PA, GS and aw as a function of process time. The empirical model proposed by Azuara et al. was used to represent the kinetics of mass transfer during the process of osmotic dehydration. The mapará fillet presented 76.70% moisture, 15.57% protein, 5.38% fat and 0.93% ash. The NaCl concentration (linear) was the variable that presented the greatest effect on the dependent variables, being positive on WL and GS and negative about the aw. The models obtained for PA, GS and aw were significant at 95% confidence and showed no significant lack of fit, being useful to predictive purposes. Was determined as optimum condition for the process: NaCl concentration 25%, temperature of 25 ° C and time of 120 min. The model proposed by Azuara et al. showed fit good to the experimental data of PA and GS kinetics of osmotic dehydration of mapará fillet. The fillet mapará had a reduction moisture after osmotic dehydration in optimal conditions, however did not meet the humidity recommended by law for salted fish, since the chloride content increased and attended law for salted fish. In relation the instrumental color were observed, after osmotic dehydration, significant statistically differences in lightness (L *) that decreased, indicating that the mapará darkened and the hue angle (h °) that increased, but still showed a tendency to yellow.
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    Determinação de parâmetros de transferência de massa e de propriedades termodinâmicas na secagem curcuma longa L. usando a técnica de refractance window
    (Universidade Federal do Pará, 2020-12-01) CUNHA, Natasha; RODRIGUES, Antonio Manoel da Cruz; http://lattes.cnpq.br/7524720020580309
    The Curcuma Longa L. rhizomes (CL) presents a significant amount of starchy, lipids, vitamins, minerals and important bioactive compounds. The CL is an aromatic spice with natural dye action. However, these rhizomes are perishable, requiring dehydration treatment. The drying by Refractance Window (RW) is a very effective technique in the dehydration process. As far as we know, no information about dehydration or parameters prediction of mass transfer and thermodynamics of CL using this technique is available in literature. Thus, this study had as objective to determinate mass transfer parameters and thermodynamics properties that control the dehydration process of the Curcuma Longa L. by Refractance Window in different temperatures. (70, 80, 90° C), through applicability of the analytical model developed by Dincer e Dost (1995). It was observed that the dehydration process of the samples occurred in a small period. The unity content in natura was 80.71±1.12% (b.u) and of the dry product varied from 20.81 to 17.34% (b.u). The CL samples submitted to drying with exhaustion obtained a small influence on the drying fees when compared to the samples with no exhaustion. According to the model of Dincer & Dost, diffusivity of moisture varied from 5.21 × 107 m².s-1 to 12.89 × 107m².s-1 without exhaustion and 7.89 × 107 m².s-1 a 19.67 × 107m².s-1 with exhaustion and the mass transfer coefficient varied in the range of 9.79 × 105 to 6.73 × 105 m.s-1 without the exhaustion and 8.86 × 105 a 0.51 × 105 m.s-1 with exhaustion. All the entropy values (ΔS) obtained related to the drying of the CL by RW were negative (ΔS < 0). The study showed that the exhaustion system had a small influence on the mass transfer flee during the drying of the CL sample. The thermodynamics properties pointed to a nom spontaneous process with positive values of enthalpy and free energy of Gibbs, and negative values of entropy.
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    Estudo do processo de salga e secagem de camarão (Litopenaeus vannamei) cultivado no estado do Pará
    (Universidade Federal do Pará, 2011-08-10) CORREA, Ana Cristina Leite; CORRÊA, Nádia Cristina Fernandes
    We conducted the study of two forms of food preservation, salting and drying, the shrimp come from cultivation in the state of Pará. The salting process was conducted in brines with 36% concentrations m/m at 80°C and 38% m/m 100°C, using the shrimp in natura in shell and shelled, with and without agitation to evaluate the influence of these variables in the process. The drying process was carried out in the pre-cooked and salted shrimp at “Fazenda Nossa Senhora de Fátima”, in the municipality of Curuçá/Pará, at temperatures of 60°C, 80°C and 100°C. Regarding the treatment of salting, the factors that most influenced the process were the concentration and agitation; as the drying process, there was less drying time for the 100°C temperature. It proposed a mathematical model of the salting process from Fick's Law. The best fit for the process was carried out with the shrimp headless, shelled, with shaking (R2 = 0.99), effective diffusivity values ranged from 0,9x10-8 the 2,0x10-8. The kinetics of shrimp drying was set with models of Henderson and Pabis, Midilli et al., Newton, Page and Wang and Singh. The Midilli et al. model showed the best fit to the kinetic data drying shrimp at temperatures of 80ºC and 100ºC.
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    Soluções híbridas por transformadas integrais para o escoamento magnetohidrodinâmico com transferência de calor em canais de placas paralelas
    (Universidade Federal do Pará, 2015-06-26) PONTES, Fábio de Andrade; QUARESMA, João Nazareno Nonato; http://lattes.cnpq.br/7826389991864785
    The present study is to analyze the dynamics of the magnetohydrodynamic flow of electrical conductors newtonian fluids within a parallel flat plate channel subjected to a uniform external magnetic field, wherein the mathematical formulation of the model is given in terms of stream-function, obtained from the Navier-Stokes equations and the Energy Equation. The adopted assumptions are steady state, laminar and incompressible flow and constant physical properties. It is also admitted that the external magnetic field applied in the normal direction of flow remains uniform, not being thus influenced by any internal magnetic effect. For the solution of the governing equations, the Generalized Integral Transform Technique (GITT) is applied to this system of partial differential equations and a hybrid solution (numerical and analytical), which is computationally implemented using the programming scientific language FORTRAN 90. In order to illustrate the consistency of the integral transformation, convergence analysis is performed and presented. Results for velocity and temperature fields as well as potential correlates are generated and compared with the literature on the basis of the main parameters of government. An in-depth analysis of parametric sensitivity of the main dimensionless parameters such as the Reynolds number, Hartmann number, Eckert number, electric parameter and Prandtl number for some typical situations is performed.
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    A técnica da transformada integral aplicada em modelos de transporte de massa em meios porosos
    (Universidade Federal do Pará, 2015-02-27) FERREIRA, Josiel Lobato; MACÊDO, Emanuel Negrão; http://lattes.cnpq.br/8718370108324505
    The Generalized Integral Transform Technique (GITT) was used to analyze the process of Super Critical Extraction of β-carotene from carrots, sesame seeds oil, canola oil and priprioca oil. The effects of particle size, pressure and temperature were studied. Furthermore the flux effect on the extraction rate was also investigated. Two models based on mass balance for the bed and the particle were employed trying to describe the process. The obtained results were compared with numerical and experimental results available on literature. In addition, the GITT was also used in modelling and simulating the process of methane reforming with CO2 in a fixed-bed catalytic reactor using a Nickel supported on Alumina ( Ni  - Al2O3 ) catalyst. The temperature effect on the concentration profiles was evaluated. In a similar manner as previously, a mass balance based model was utilised seeking to describe the reforming process. Methane decomposition, reverse Boudoard reactions and gas-water (shift) were considered. Moreover, the results were likewise likened to the literature. The Coupled Integral Equation Approach (CIEA) was applied in both cases to simplify the models in order to eliminate the radial dependence of the governing equations of the particle mass transfer and posterior usage of the GITT. The resulting models were numerically solved using the DIVPAG routine of the IMSL library.
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