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.

Convecção mista em cavidades com fontes de calor aletadas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Heat transfer in laminar flow of non-Newtonian fluids in ducts of elliptical section

Laminar forced convection inside tubes of various cross-section shapes is of interest in the design of a low Reynolds number heat exchanger apparatus. Heat transfer to thermally developing, hydrodynamically developed forced convection inside tubes of simple geometries such as a circular tube, parallel plate, or annular duct has been well studied in the literature and documented in various books, but for elliptical duct there are not much work done. The main assumption used in this work is a laminar flow of a power flow inside elliptical tube, under a boundary condition of first kind with constant physical properties and negligible axial heat diffusion (high Peclet number). To solve the thermally developing problem, we use the generalized integral transform technique (GITT), also known as Sturm-Liouville transform. Actually, such an integral transform is a generalization of the finite Fourier transform where the sine and cosine functions are replaced by more general sets of orthogonal functions. The axes are algebraically transformed from the Cartesian coordinate system to the elliptical coordinate system in order to avoid the irregular shape of the elliptical duct wall. The GITT is then applied to transform and solve the problem and to obtain the once unknown temperature field. Afterward, it is possible to compute and present the quantities of practical interest, such as the bulk fluid temperature, the local Nusselt number and the average Nusselt number for various cross-section aspect ratios. (C) 2006 Elsevier. SAS. All rights reserved.

LAMINAR THERMALLY DEVELOPING FLOW INSIDE RIGHT-ANGULARLY TRIANGULAR DUCTS

An analytical approach based on the generalized integral transform technique is presented, for the solution of laminar forced convection within the thermal entry region of ducts with arbitrarily shaped cross-sections. The analysis is illustrated through consideration of a right triangular duct subjected to constant wall temperature boundary condition. Critical comparisons are made with results available in the literature, from direct numerical approaches. Numerical results for dimensionless average temperature and Nusselt numbers are presented for different apex angles.

Thermally developing forced convection of non-Newtonian fluids inside elliptical ducts

Laminar-forced convection inside tubes of various cross-section shapes is of interest in the design of a low Reynolds number heat exchanger apparatus. Heat transfer to thermally developing, hydrodynamically developed forced convection inside tubes of simple geometries such as a circular tube, parallel plate, or annular duct has been well studied in the literature and documented in various books, but for elliptical duct there are not much work done. The main assumptions used in this work are a non-Newtonian fluid, laminar flow, constant physical properties, and negligible axial heat diffusion (high Peclet number). Most of the previous research in elliptical ducts deal mainly with aspects of fully developed laminar flow forced convection, such as velocity profile, maximum velocity, pressure drop, and heat transfer quantities. In this work, we examine heat transfer in a hydrodynamically developed, thermally developing laminar forced convection flow of fluid inside an elliptical tube under a second kind of a boundary condition. To solve the thermally developing problem, we use the generalized integral transform technique (GITT), also known as Sturm-Liouville transform. Actually, such an integral transform is a generalization of the finite Fourier transform, where the sine and cosine functions are replaced by more general sets of orthogonal functions. The axes are algebraically transformed from the Cartesian coordinate system to the elliptical coordinate system in order to avoid the irregular shape of the elliptical duct wall. The GITT is then applied to transform and solve the problem and to obtain the once unknown temperature field. Afterward, it is possible to compute and present the quantities of practical interest, such as the bulk fluid temperature, the local Nusselt number, and the average Nusselt number for various cross-section aspect ratios.

Aplicação da técnica de elementos finitos na estratificação de armazenadores térmicos com barreiras de meios porosos

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Convecção natural em cavidades triangulares

Pós-graduação em Engenharia Mecânica - FEG

Forced convection to laminar flow of liquid egg yolk in circular and annular ducts

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Numerical and experimental analysis of natural convection in a cavity with flush mounted heat sources on a side wall

This work considers a problem of interest in several technological applications such as the thermal control of electronic equipment. It is also important to study the heat transfer performance of these components under off-normal conditions, such as during failure of cooling fans. The effect of natural convection on the flow and heat transfer in a cavity with two flush mounted heat sources on the left vertical wall, simulating electronic components, is studied numerically and experimentally. The influence of the power distribution, spacing between the heat sources and cavity aspect ratio have been investigated. An analysis of the average Nusselt number of the two heat sources was performed to investigate the behavior of the heat transfer coefficients. The results obtained numerically and experimentally, after an error analysis, showed a good agreement.

Alterações morfológicas de tecido laminar do casco e parâmetros clínicos e laboratoriais de equinos com síndrome cólica letal

As afecções gastrintestinais dos cavalos são agravadas por complicações como a laminite, cuja etiopatogenia está relacionada à degradação da membrana basal do tecido laminar por metaloproteinases (MMPs). A ativação das MMPs pode ocorrer devido à liberação local de citocinas inflamatórias ou enzimas provenientes de leucócitos infiltrados no tecido laminar. O objetivo deste trabalho foi avaliar as alterações morfológicas do tecido laminar de equinos com síndrome cólica letal e sua provável associação com parâmetros clínicos e laboratoriais. Observou-se intensa destruição da arquitetura laminar, principalmente nos animais com alterações físicas e laboratoriais mais acentuadas, como tempo de preenchimento capilar prolongado (TPC), membranas mucosas congestas, taquicardia, hemoconcentração e redução nas contagens de plaquetas e leucócitos. Os resultados sinalizam o provável momento do desenvolvimento de lesões do tecido laminar em equinos com síndrome cólica, no qual é possível adotar medidas preventivas contra a laminite.

Lipocalina associada à gelatinase de neutrófilos (NGAL) e calprotectina no tecido laminar de equinos após obstrução jejunal, tratados ou não com hidrocortisona

A laminite é uma doença podal grave que acomete os equídeos, sendo responsável por intenso sofrimento. Neste estudo foram pesquisadas a presença de calprotectina por meio da imunoistoquímica, e de lipocalina associada à gelatinase de neutrófilos (NGAL), por zimografia, no tecido laminar do casco de equinos após obstrução intestinal. Os animais foram divididos em quatro grupos: Grupo controle (Gc), contendo sete animais normais, sem procedimento cirúrgico; Grupo Instrumentado (Gi), contendo cinco animais, os quais passaram por todo o procedimento cirúrgico sem sofrerem obstrução intestinal; Grupo Não Tratado (Gnt), contendo quatro equinos submetidos a obstrução intestinal do jejuno por distensão de balão intraluminal, sem tratamento; e Grupo Tratado (Gt), contendo quatro equinos submetidos a obstrução intestinal, e tratados preventivamente com hidrocortisona. Houve imunomarcação de calprotectina em todos os grupos experimentais, com aumento nos equinos do grupo distendido em relação ao Gc. Com relação ao NGAL, houve aumento também do Gnt e do Gi em relação ao Gc. O Gt não diferiu dos demais. Conclui-se que a distensão do intestino delgado pode promover acúmulos de leucócitos nos cascos de equinos e que o NGAL é um método viável para se detectar infiltração neutrofílica em equinos. Novos estudos deverão ser realizados para se verificar possível benefício anti-inflamatório da hidrocortisona no casco de equinos com obstrução intestinal.

Generalized linear mixed models for the genetic evaluation of binary reproductive traits: a simulation study

The objective of this study was to evaluate the use of probit and logit link functions for the genetic evaluation of early pregnancy using simulated data. The following simulation/analysis structures were constructed: logit/logit, logit/probit, probit/logit, and probit/probit. The percentages of precocious females were 5, 10, 15, 20, 25 and 30% and were adjusted based on a change in the mean of the latent variable. The parametric heritability (h²) was 0.40. Simulation and genetic evaluation were implemented in the R software. Heritability estimates (ĥ²) were compared with h² using the mean squared error. Pearson correlations between predicted and true breeding values and the percentage of coincidence between true and predicted ranking, considering the 10% of bulls with the highest breeding values (TOP10) were calculated. The mean ĥ² values were under- and overestimated for all percentages of precocious females when logit/probit and probit/logit models used. In addition, the mean squared errors of these models were high when compared with those obtained with the probit/probit and logit/logit models. Considering ĥ², probit/probit and logit/logit were also superior to logit/probit and probit/logit, providing values close to the parametric heritability. Logit/probit and probit/logit presented low Pearson correlations, whereas the correlations obtained with probit/probit and logit/logit ranged from moderate to high. With respect to the TOP10 bulls, logit/probit and probit/logit presented much lower percentages than probit/probit and logit/logit. The genetic parameter estimates and predictions of breeding values of the animals obtained with the logit/logit and probit/probit models were similar. In contrast, the results obtained with probit/logit and logit/probit were not satisfactory. There is need to compare the estimation and prediction ability of logit and probit link functions.

Molecular Identification and Characterization of Ileal and Cecal Fungus Communities in Broilers Given Probiotics, Specific Essential Oil Blends, and Under Mixed Eimeria Infection

Broiler digestive tract fungal communities have gained far less scrutiny than that given corresponding bacterial communities. Attention given poultry-associated fungi have focused primarily on feed-associated toxin-producers, yeast, and yeast products. The current project focused on the use of pyrosequencing and denaturing gradient gel electrophoresis (DGGE) to identify and monitor broiler digestive fungal communities. Eight different treatments were included. Four controls were an Uninfected-Unmedicated Control, an Unmedicated-Infected Control, the antibiotic bacitracin methylene disalicylate plus the ionophore monensin as Positive Control, and the ionophore monensin alone as a Negative Control. Four treatments were two probiotics (BC-30 and Calsporin) and two specific essential oil blends (Crina Poultry Plus and Crina Poultry AF). All chickens except the Unmedicated-Uninfected Control were given, at 15 days of age, a standard oral Eimeria inoculum of sporulated oocysts. Ileal and cecal digesta were collected at pre-Eimeria infection at 14 days of age and at 7 days post-Eimeria infection at 22 days of age. Extracted cecal DNA was analyzed by pyrosequencing to examine the impact of diet supplements and Eimeria infection on individual constituents in the fungal community, while DGGE was used to compare more qualitative changes in ileal and cecal communities. Pyrosequencing identified three phyla, seven classes, eight orders, 13 families, 17 genera, and 23 fungal species. Ileal and cecal DGGE patterns showed fungal communities were clustered mainly into pre- and post-infection patterns. Post-infection Unmedicated-Uninfected patterns were clustered with pre-infection groups demonstrating a strong effect of Eimeria infection on digestive fungal populations. These combined techniques offered added versatility towards unraveling the effects of enteropathogen infection and performance enhancing feed additives on broiler digestive microflora.

Dominance of legume trees alters nutrient relations in mixed species forest restoration plantings within seven years

Failures in reforestation are often attributed to nutrient limitation for tree growth. We compared tree performance and nitrogen and phosphorus relations in adjacent mixed-species plantings of contrasting composition, established for forest restoration on Ultisol soil, originally covered by tropical semi-deciduous Atlantic Forest in Southeast Brazil. Nutrient relations of four tree species occurring in both planting mixtures were compared between a legume-dominated, species-poor direct seeding mixture of early-successional species ("legume mixture"), and a species-diverse, legume-poor mixture of all successional groups ("diverse mixture"). After 7 years, the legume mixture had 6-fold higher abundance of N(2)-fixing trees, 177% higher total tree basal area, 22% lower litter C/N, six-fold higher in situ soil resin-nitrate, and 40% lower in situ soil resin-P, compared to the diverse mixture. In the legume mixture, non-N(2)-fixing legume Schizolobium parahyba (Fabaceae-Caesalpinioideae) had significantly lower proportional N resorption, and both naturally regenerating non-legume trees had significantly higher leaf N concentrations, and higher proportional P resorption, than in the diverse mixture. This demonstrate forms of plastic adjustment in all three non-N(2)-fixing species to diverged nutrient relations between mixtures. By contrast, leaf nutrient relations in N(2)-fixing Enterolobium contortisiliquum (Fabaceae-Mimosoideae) did not respond to planting mixtures. Rapid N accumulation in the legume mixture caused excess soil nitrification over nitrate immobilization and tighter P recycling compared with the diverse mixture. The legume mixture succeeded in accelerating tree growth and canopy closure, but may imply periods of N losses and possibly P limitation. Incorporation of species with efficient nitrate uptake and P mobilization from resistant soil pools offers potential to optimize these tradeoffs.