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Navegando por Assunto "Viscosity"

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    Caracterização de óleos e gorduras vegetais amazônicas: utilização de modelo para predizer viscosidade
    (Universidade Federal do Pará, 2022-06-03) FREITAS, Joice Silva de; SILVA, Luiza Helena Meller da; http://lattes.cnpq.br/2311121099883170; https://orcid.org/0000-0002-6002-9425
    The Amazon rainforest is rich in oilseed plant species, which have fruits that are attractive due to their economic potential and biological properties. Oils from oleaginous matrices have a unique composition with physicochemical and nutraceutical properties that attract attention as a source of fatty acids. The predictive model is based on the use of mathematical equations that are more comprehensive and less limited than simple linear or polynomial models, and are able to predict a certain property using one or more physicochemical parameters. Thus, this work aimed to use a predictive model to calculate the viscosity of Amazonian oils (açaí, bacaba, tucumã) and fats (cupuaçu, bacuri and tucumã). The samples were physicochemically characterized in terms of acidity index, density, oxidative stability, peroxide, melting point, iodine index, saponification index, fatty acid composition, triacylglycerol composition, solid fat content, atherogenicity index and heterogeneity. Two predictive models were used to obtain the viscosity values of oils and fats, the model using the profile of the mass fraction of polyunsaturated and monounsaturated fatty acids and the model using the iodine and saponification index.The results showed that the oils (patauá, pracaxi, bacaba, açaí, tucumã) had high levels of unsaturated fatty acids, especially oleic acid, which has good thermal stability, while the fats (cupuaçu, bacuri and tucumã) are composed of mainly by saturated fatty acids. The oxidative stability showed that at a temperature of 110 °C, pracaxi oil and cupuaçu fat presented the highest values, while bacaba oil presented a lower value, this low stability value indicates that this sample is more conducive to oxidation. Pracaxi oil showed the highest value for the ratio between hypocholesterolemic and hypercholesterolemic fatty acids (HH), indicating that it is more nutritionally adequate. The studies to predict the regularity of Amazonian oils and fats proposed in this work may contribute to simplifying the evaluation of the physicochemical properties of important regional oleaginous raw materials on which there are no studies, but with growing industrial interest in different areas, in addition of the food area.
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    Estudo da influência da granulometria no comportamento reológico de polpa de bauxita e no fator de atrito
    (Universidade Federal do Pará, 2011-09-14) BRUM, Sebastião Martins; SOUZA, José Antônio da Silva; http://lattes.cnpq.br/6157348947425968; MACÊDO, Emanuel Negrão; http://lattes.cnpq.br/8718370108324505
    This paper presents studies of the rheological characterization and determination of friction factors in three bauxite slurries originating in Miltonia Mine, Paragominas - Para, resulting from operating conditions with different degrees of grinding. Thus, the basic difference between them lies in the size distribution. The goal is to make a proposal to revise the specification of the product particle size (for the bauxite slurry pipeline), allowing a comparison with the slurries of the project (pilot plant) and the current operation (processing plant) and the response to changes, especially, viscosity and friction factors. The slurry proposal incorporates a higher percentage of fines (<10 microns) compared with other slurries. The benefits can earn recovery with the incorporation of this portion of fines, which currently is discarded to the tailings pond. The material was characterized by size analysis of the series Tyler, physical and physical-chemical, electron microscopy (SEM) and X-ray spectrometry energy dispersive (EDS). Testes were conducted in coaxial cylinder viscometer, Searle type, in order to determine the rheological behavior of these slurries, depending on the size distribution and varying the concentration of solids. The rheological properties were measured viscosity, yield stress and also behaviors that show the dependence of viscosity with the time of application of a constant shear rate, verifying through the hysteresis curve, the presence or absence of thixotropy and reopexia. The experimental results showed that for the slurries tested, the particle size and solids concentration are important parameters in determining the viscosity. Tests with these three bauxite slurries of different sizes, were performed at predetermined concentrations, to determine the model whose rheological parameters showed the best correlation coefficients (R2), and the best fits were found using the Herschel-Bulkley model. The friction factors were obtained for formulations involving a logarithmic relationship, using the Law of the Wall as a method of obtaining these expressions apply to non-Newtonian viscoplastic fluid, and compared with those calculated by Dodge and Metzner correlation and found that in general there is agreement between the model studied in the three slurries. The factor analysis of friction in the concentration of 50% solids, which is the concentration of pumping by pipeline, shows that the behavior of the slurries studied is similar, with the best settings for the range from 10,000 to 100,000 Reynolds (average work range for the turbulent flow of the ore pulp, homogeneous and heterogeneous).
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    Influência do teor de cinza volante na reologia de argamassa de assentamento: fabricado com reciclagem de resíduos
    (Universidade Federal do Pará, 2014-02-05) CARDOSO, Dilson Nazareno Pereira; SOUZA, José Antônio da Silva; http://lattes.cnpq.br/6157348947425968; FELIPE, Augusta Maria Paulain Ferreira; http://lattes.cnpq.br/8871741271063047
    The mortars may be considered as a set of solid suspended particles (aggregate), water and binders (cement slurry). Thus, rheological behavior during cure can be influenced by factors such as particle size, composition and content of corporate water. This study investigated the rheological properties of six mortars, depending on the content of fly ash as a pozzolanic activity material, partial replacement of cement. This type of cement used as an aggregate base construction of the residue (RCC) which was characterized by diffraction and fluorescence X- rays. Were formulated for the mortars with addition of rheological tests residue construction (RCC) in proportions of 95, 90, 85, 80, 75 and 70% fly ash (CV) 0, 5, 10, 15, 20 and 25 % to 5 % of ordinary Portland Cement (PC - II and 32), and in each sample was incorporated 35 % water. We used the model VT 550 viscometer with sensor type coaxial cylinders SV1 - Haake temperature of 28 ºC. To evaluate the curing time of the material has scheduled a constant shear rate 53.4 s-1 for 1h and 45 min, with rated torque at intervals of 15min. For the development of flow curves and hysteresis curves, we used the shear rate between 0 and 600 s-1 in the time interval of 120 s. The results showed that the incorporation of fly ash is the main factor for increased torque on the curing time of mortar and behavior change reópetico for thixotropic, the traits analyzed. The experimental data of the proposed formulations are adjusted to the rheological model of Herschel - Bulkley.
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