Laminar flow of soursop juice through concentric annuli: Friction factors and rheology

Laminar axial flow of a pseudoplastic fluid food (soursop, juice) in annular ducts has been experimentally investigated. In the first part of the manuscript, the rheological behavior of soursop juice, being essential for the annular flow analysis, was completely determined from 9.3 to 49.4 degrees Brix and temperatures from 0.4 degrees C to 68.8 degrees C, using a rotational rheometer equipped with coaxial cylinders. In order to test the adequacy of the rheology results, pressure loss data in the laminar pipe flow were collected and then experimental and theoretical friction factors were compared, showing excellent agreement, which indicated the reliability of the Power-Law model for describing the soursop juices. In the second part, pressure loss in annular regions was measured and used to estimate friction factors, which were then compared to those resulted from analytical and semi-analytical equations. The principal contributions of this article are to provide a review on the determination of friction factors-Reynolds number of pseudoplastic fluids in annuli, and also supply extensive new experimental data on the rheological properties and pressure loss of an important shear-thinning fluid food, which is of particular interest for the food engineering process design. (c) 2006 Elsevier Ltd. All rights reserved.

Laminar forced convection to a pseudoplastic fluid food in circular and annular ducts

In this manuscript we investigated experimentally the steady-state heat transfer to an important pseudoplastic fluid food, the soursop juice, flowing in laminar regime through circular and concentric annular ducts. The mean convection heat transfer coefficients, determined by measuring the bulk temperatures before and after the heating sections with constant temperatures of the tube walls, were used to correlate simple new empiric expressions to estimate the average Nusselt number in the thermal entrance of the considered geometries. In addition, the thermophysical properties of the tested fluid food, as well as the rheological behavior, being essential for the heat transfer analyses, were experimentally determined. (c) 2006 Elsevier Ltd. All rights reserved.

Nonlinear parameter estimation in laminar forced convection within a circular sector tube

In this article we examine an inverse heat convection problem of estimating unknown parameters of a parameterized variable boundary heat flux. The physical problem is a hydrodynamically developed, thermally developing, three-dimensional steady state laminar flow of a Newtonian fluid inside a circular sector duct, insulated in the flat walls and subject to unknown wall heat flux at the curved wall. Results are presented for polynomial and sinusoidal trial functions, and the unknown parameters as well as surface heat fluxes are determined. Depending on the nature of the flow, on the position of experimental points the inverse problem sometimes could not be solved. Therefore, an identification condition is defined to specify a condition under which the inverse problem can be solved. Once the parameters have been computed it is possible to obtain the statistical significance of the inverse problem solution. Therefore, approximate confidence bounds based on standard statistical linear procedure, for the estimated parameters, are analyzed and presented.

Relação entre o fluxo luminoso interceptado em diferentes épocas no índice de área foliar de diferentes forrageiras

The objective was to evaluate the leaf area index of six different grasses. The experiment was installed at the Instituto Federal de Tecnologia e Educacao of Uberaba, using a randomized block design with split plots in time. The plots were sown: Brachiaria decumbens cv. Basilisk, Brachiaria brizantha cv. Marandu, Panicum maximum cv. Mombasa, Panicum maximum cv. Tanzania, Brachiaria brizantha cv. Xaraes, Cynodon dactylon hb. Tifton and the plots, ten seasons of evaluation in 10 x 6 factorial arrangement with four replications. Rates of leaf area of each forage at different times of year were evaluated. Compared to other forage species, Panicum maximum had a higher leaf area index when subjected to periodic fertilization and irrigation. Only in the late fall Brachiaria Xaraes IAF had increased, but did not differ significantly from the others.

Efeitos do pentobarbital sódico sobre o fluxo sanguíneo renal. Estudo experimental no cão

In six dogs, previously anesthetized with sodium pentobarbital (30 mg/kg) for surgical preparation, catheterism and monitoring, the action of sodium pentobarbital (7,5 mg/kg) on renal flow was studied. Determinations of mean arterial pressure, venous pressure, cardiac rate, arterio-cava pressure gradient and renal arterial resistance were made. Pentobarbital doesn't change significantly the renal blood flow or any of the other parameters studied, with the exception of venous pressure in the inferior caval vein where the drug produces a significant fall.

Coeficientes de perda de carga em valvulas e acessorios no escoamento laminar de fluidos nao-Newtonianos

Friction loss coefficients for laminar flow of xantan gum solutions (concentrations in the range of 0.1-0.5% by weight) through valves and fittings were experimentally determined. The rheological behavior, studied by means of a concentric cylinder rheometer, was pseudoplastic, being well described by the Ostwald-De Waele model with non-linear correlation coefficients (r) between 0.998 and 0.999. In the pressure drop measurements the following fittings were employed: completely open and half way open ball valve, completely open and half way open angle valve, tee used like coupling, tee used like a 90° elbow, short radius 90° elbow and coupling. The results showed that the friction loss coefficients increased with decreasing generalized Reynolds number. The friction loss coefficients could be well adjusted by a potential model, suggested by Kittredge & Rowley (1957) for Newtonian fluids, K f = A(Re g) -B, with correlation coefficients between 0.837 and 0.999.

Study on transient ice formation of laminar flow inside externally supercooled rectangular duct

The transient process of solidification of laminar liquid flow (water) submitted to super-cooling was investigated both theoretically and experimentally. In this study an alternative analytical formulation and numerical approach were adopted resulting in the unsteady model with temperature dependent thermophysical properties in the solid region. The proposed model is based upon the fundamental equations of energy balance in the solid and liquid regions as well as across the solidification front. The basic equations and the associated boundary and initial conditions were made dimensionless by using the Landau transformation to immobilize the moving front and render the problem to a fixed plane type problem. A laminar velocity profile is admitted in the liquid domain and the resulting equations were discretized using the finite difference approach. The numerical predictions obtained were compared with the available results based on other models and concepts such as Neumann analytical model, the apparent thermal capacity model due to Bonacina and the conventional fixed grid energy model due to Goodrich. To obtain further comparisons and more validation of the model and the numerical solution, an experimental rig was constructed and instrumented permitting very well controlled experimental measurements. The numerical predictions were compared with the experimental results and the agreement was found satisfactory.

Efeito do extrato aquoso de sete-sangrias [Cuphea mesostemon (Koehne) Lourt] sobre o fluxo de água, medido em bexiga urinária de sapo in vitro

The Cuphea mesostemon specie, known as sete-sangrias, is widely used as a diuretic substance in popular medicine. As the toad urinary bladder is an epithelium analogous to the distal nephron of mammals, it is used in order to study the transport water and electrolytes in many laboratories. This preparation permits excellent observation in water flow, from the urinary bladder lumen to the external side or the serosal one (water re-absorption), by means of gravimetrical measures. In the present work the hydrosmotic effect of aqueous extract (AE) of sete-sangrias leaf was studied. A 20% solution was added to the serosal side (S) of the bladder preparation, and the water flow was measured every 15 minutes after that. The results showed that 4mL of AE in the S side, increased the JH20 in a significant manner (p<0,05). This effect had a dose - response shape, with the volumes of 0,2mL, 0,4mL and 0,8mL of AE in the S bath. The hydro-osmotic effect of the anti-diuretic hormone (ADH) was studied as well and a significant stimulation (p<0,05) in the JH2O was observed with the magnitude of 150%. The AE effect was similar to the ADH one, and was not antagonized by this hormone. We concluded that Cuphea possesses an anti-diuretic activity similar to that presented by ADH, in toad urinary bladder, in vitro.

Diferentes procedimentos na determinação de indicadores internos para estimativa de produção fecal e fluxo duodenal de matéria seca em bovinos

Times of in situ incubation (144 and 288h) for determination of internal markers IADF and INDF and the effects of differents procedures (wash or not the nylon bag every 72h incubation) was evaluated in samples of diet, duodenal digesta and cattle feces. The duodenal flow dry matter and fecal production utilizing the internal markers to compare with the external marker chromium oxide there was estimated. The animals were fed with sorgum silage, concentrate or urea. In this experiment, a latin square design was used, in a factorial scheme (two times of incubation × two processing nylon bag). No was observed effect of the incubation time or processing in the internal markers INDF and IADF concentration and the in situ incubation after 144h is adequate to reproduce the indigestible markers fraction in samples. For fecal production estimation, the external marker chromium oxide presented similar result (1.26 kg day-1) as the total fecal collection (1.49 kg day-1). Both the internal markers overestimate the duodenal flow dry matter when compared with the external marker chromium oxide.

Indicadores na estimativa do fluxo de digesta em bovinos de corte

single and double marker methods were compared in seven Nellore steers with average body weight 250 kg, and previously canullated in the rumen and duodenum. The animals were fitted with continuous-infusion pump that administered CoEDTA solutions intraruminally. In addition, a capsule containing Cr 2O 3, and other, containing external n-alkanes C 32, C 36 were inserted into the rumen of each steer. Internal markers indigestible neutral-detergent fiber and acid-detergent fiber (iNDF and iADF after 144 h in situ incubation) and internal n-alkanes C 31, C 33, C 35 were components of the diet. Steers were fed with palisade grass (Brachiaria brizantha cv. marandu) in two age of regrowth, 30 and 60 days. The duodenal flow experimental design was a factorial 2×2×12 while omasal experimental design was a factorial 2×2×4. Markers iNDF, CoEDTA and the combination Co+iNDF were efficacious to estimate duodenal dry matter flow whereas iNDF, iADF and the Co+iADF combination were all efficacious to predict omasal dry matter flow. In conclusion, the double marker method for estimation of omasal and duodenal dry matter flow was the most appropriate considering the ruminal fiber digestibility.

Fluxo de potência trifásico probabilístico para redes de distribuição usando o método de estimação por pontos

In this paper the point estimation method is applied to solve the probabilistic power flow problem for unbalanced three-phase distribution systems. Through the implementation of this method the probability distribution functions of voltages (magnitude and angle) as well as the active and reactive power flows in the branches of the distribution system are determined. Two different approaches of the point estimation method are presented (2m and 2m+1 point schemes). In order to test the proposed methodology, the IEEE 34 and 123 bus test systems are used. The results obtained with both schemes are compared with the ones obtained by a Monte Carlo Simulation (MCS).

Avaliação leucocitária de cães com linfoma submetidos ao protocolo de Madison-Wisconsin pela técnica convencional e citometria de fluxo

Lymphoma is the most common hematopoietic tumor in dogs and one of the malignant tumors with higher occurrence in this species. It is a great experimental model due to its resemblance with the non-Hodgkin lymphoma in humans. Considering the importance of the overall changes that result from to this kind of neoplastic tumor and those due to polichemotherapy this study aimed to evaluate the absolute leukon count and the total count of CD45+ cells in the blood of 25 dogs with lymphoma. Findings were crosschecked since diagnose and then once weekly during the first eight sessions of the Madison-Wisconsin chemotherapic protocol. Total granulocyte, lymphocyte and monocyte counts obtained from a conventional automatic counter and by flow cytometry were compared. Results did not reveal statistically significant changes between the two techniques.

Eficácia de fluridone para o controle de Egeria spp. em caixas d'água e em represa de pequeno porte sem fluxo de água

Pós-graduação em Agronomia (Agricultura) - FCA

Retenção do cátion do sulfato de cobre nos compartimentos biótico e abiótico de mesocosmos com sistema de fluxo contínuo de água

Pós-graduação em Aquicultura - FCAV

Aplicação do método de Newton desacoplado para o fluxo de carga continuado

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)