96 research outputs found

    CONSTRUCTAL DESIGN APPLIED TO A FINNED CHANNEL UNDER FORCED CONVECTION FLOWS WITH DIFFERENT IMPOSED PRESSURE DROPS

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    This paper aims to numerically study the heat transfer in a two dimensional finned channel under laminar, incompressible and forced convective flow with adiabatic walls. The main purpose is to maximize the convection heat transfer by changing the fin’s dimensions by means of Constructal Design. Numerical computations are performed for different Bejan numbers ranging from 0.182 up to 18.2. For all simulations the Prandlt number is kept constant, Pr = 0.71. The fluid motion throughout the channel is caused by imposition of pressure difference between inlet/outlet surfaces. Concerning heat transfer, it is caused by the difference of temperature between the inlet stream of fluid and the heated fins placed at the channel surfaces. The first fin is positioned in the lower surface of the channel while the second one is placed in the upper one. The problem is submitted to three constraints, the channel area (H × L), area of two fins and occupancy areas for the fins. It is considered here that both fins have the same fraction area (ratio between the fins and occupancy areas) f = 0.2. The problem is submitted to three degrees of freedom: H/L (ratio between height and length of channel), H3/L3 and H4/L4 which represent the ratio between the height and length of the first and second fin, respectively. Here, the second fin remains unchanged, being its dimensions H4/L4 = 2.0, whereas the first one is free to modify its dimensions, H3/L3. The channel dimensions are also constant. The solutions are sought using the conservation equations of mass, momentum and energy being these ones discretized through the Finite Volume Method (FVM). Results showed the importance of Constructal Design application for thermal improvement of the problem. Thermal efficiency differences of 5 times where achieved when comparing the best and worst cases. Other important observation is concerned with the effect of ratio H3/L3 over heat transfer ratio (q) which varied significantly from a case where a pressure drop is imposed in the channel to other case where the driven force is caused by imposition of velocity field at the channel inlet

    Carbon Neutral Brazilian Beef: testing its guidelines through a case study.

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    The Carbon Neutral Brazilian Beef (CNBB) is a new concept for sustainable beef production in the tropics, developed by Embrapa and first reported by Alves et al. (2015). The CNBB concept is based in silvopastoral or agrosilvopastoral systems and requires greenhouse gases emissions to be neutralized, at first, by timber production. Aim of this work is to report the first case study of CNBB application for finishing steers and to present animal performance, beef quality, pasture characteristics, microclimate parameters and carbon balance estimates

    Ovelha pantaneira, um grupamento genético naturalizado do Estado do Mato Grosso do Sul, Brasil.

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    O grupamento genético ovino pantaneiro tem origem no Pantanal, bioma singular que exerce seleção natural intensa nos animais domésticos naturalizados. Devido às condições ambientais reinantes na planície alagada, os ovinos pantaneiros sul-mato-grossenses desenvolveram características adaptativas e produtivas que justificam a sua conservação. Os estudos até o momento concentraram-se nos aspectos morfométricos, para definição de padrões raciais, e no desempenho produtivo (carne, lã, leite, peles, reprodução e sanidade), que resultaram em bons resultados comparados a raças ovinas exóticas. Os estudos de características genéticas, para orientar os programas de seleção e melhoramento, estão em andamento, com o objetivo de complementar os estudos científicos que subsidiam o registro da raça Ovelha Pantaneira

    CONSTRUCTAL DESIGN APPLIED TO A FINNED CHANNEL UNDER FORCED CONVECTION FLOWS WITH DIFFERENT IMPOSED PRESSURE DROPS

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    This paper aims to numerically study the heat transfer in a two dimensional finned channel under laminar, incompressible and forced convective flow with adiabatic walls. The main purpose is to maximize the convection heat transfer by changing the fin’s dimensions by means of Constructal Design. Numerical computations are performed for different Bejan numbers ranging from 0.182 up to 18.2. For all simulations the Prandlt number is kept constant, Pr = 0.71. The fluid motion throughout the channel is caused by imposition of pressure difference between inlet/outlet surfaces. Concerning heat transfer, it is caused by the difference of temperature between the inlet stream of fluid and the heated fins placed at the channel surfaces. The first fin is positioned in the lower surface of the channel while the second one is placed in the upper one. The problem is submitted to three constraints, the channel area (H × L), area of two fins and occupancy areas for the fins. It is considered here that both fins have the same fraction area (ratio between the fins and occupancy areas) f = 0.2. The problem is submitted to three degrees of freedom: H/L (ratio between height and length of channel), H3/L3 and H4/L4 which represent the ratio between the height and length of the first and second fin, respectively. Here, the second fin remains unchanged, being its dimensions H4/L4 = 2.0, whereas the first one is free to modify its dimensions, H3/L3. The channel dimensions are also constant. The solutions are sought using the conservation equations of mass, momentum and energy being these ones discretized through the Finite Volume Method (FVM). Results showed the importance of Constructal Design application for thermal improvement of the problem. Thermal efficiency differences of 5 times where achieved when comparing the best and worst cases. Other important observation is concerned with the effect of ratio H3/L3 over heat transfer ratio (q) which varied significantly from a case where a pressure drop is imposed in the channel to other case where the driven force is caused by imposition of velocity field at the channel inlet

    Características de carcaça de animais mestiços criados em sistemas intensivos.

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    Foram estudados o peso de abate (PA), peso de carcaca fria (PCF) e rendimento de carcaca (RC) de animais pertencentes a quatro grupos geneticos (GG), 1/2 Pardo Suico - 1/2 Nelore (PSN), 1/2 Stabilizer - 1/8 Angus - 3/8 Nelore (STN), 1/2 Canchim - 1/4 Angus - 1/4 Nelore (CAN) e 1/4 Canchin - 1/4 Simental - 1/4 Nelore (CSN). A analise, envolvendo somente os machos, revelou que os animais STN foram os que apresentaram os piores desenpenhos para as tres caracteristicas avaliadas, com medias para PA, PCF e RC iguais a 449 kg, 250 kg e 56%, respectivamente. As medias dessas mesmas caracteristicas para os demais grupos geneticos foram 475 kg, 274 kg e 58%. Entretanto, os animais STN, com os CAN, permaneceram somente 143 dias em confinamento, enquanto os demais foram abatidos apos 180 dias. A comparacao dos desempenhos de femeas intactas e ovariectomizadas revelou diferencas importantes. As femeas ovariectomizadas, alem de apresentarem PA e PCF inferiores, permaneceram, aproximadamente, doze dias a mais em confinamento

    Interação entre procedimentos de castração e manejo alimentar na fase de terminação sobre o desempenho e a qualidade do novilho precoce.

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    Na pecuária de corte a castração é uma prática comum que visa modificar a composição do ganho de peso corporal dos animais. Com o presente estudo objetivou-se avaliar o efeito de diferentes métodos de castração, em pesos e planos nutricionais distintos em novilhos precoces

    Desempenho de bovinos de diferentes grupos genéticos durante a fase de recria em sistema de pastejo.

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    O aumento da demanda mundial de carne bovina e das exigências do mercado consumidor quanto à qualidade do produto têm requerido sistemas de produção mais eficientes e sustentáveis tanto ambiental quanto economicamente e que forneçam carne com melhores características físicas e organolépticas (2). Neste contexto, o sistema precoce de produção vem sendo adotado por atender a tais exigências e trazer maior retorno econômico ao produtor.O resumo deste trabalho foi apresentado na "JORNADA CIENTÍFICA EMBRAPA GADO DE CORTE, 11., 2015, Campo Grande, MS. Anais... Campo Grande: Embrapa Gado de Corte, 2015. 114 p. (Embrapa Gado de Corte. Documentos, 213).

    Efeito da imunocastração e da castração cirúrgica no desempenho de animais da raça Nelore de 30-36 meses de idade.

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    A castração de bovinos possibilita melhoria na qualidade da carcaça e da carne. Entretanto, o método cirúrgico além de ser doloroso gera perda de peso nos dias seguintes a castração. A imunocastração é um método que consiste na utilização de uma vacina que leva a castração e não causa danos ao animal. Objetivou-se avaliar o efeito da imunocastração e da castração cirúrgica no desempenho de bovinos de corte da raça Nelore entre 30-36 meses de idade
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