Performance of models to determine flow rate using orifice plates/Desempenho de modelos para determinacao de vazao utilizando placas de orificio.

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Publisher: ATECEL--Associacao Tecnico Cientifica Ernesto Luiz de Oliveira Junior
Document Type: Article
Length: 4,211 words

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Abstract :

This study aimed to evaluate three methodologies for orifice-plate water-flow estimation by quantifying errors in the flow determinations to propose an appropriate measurement range for each evaluated condition. Two orifice-plate models (nominal diameters of 100 and 150 mm) with 50% restriction in the flow section were evaluated. In the theoretical equations, the discharge coefficient was obtained using the Reader-Harris/Gallagher equation (Method 1) and approximated from experimental data using the angular coefficient of a zero-intercept straight line (Method 2). The recommended measurement ranges for errors that were lower than 5% for the 100 and 150 mm plates were 30 to 65 [m.sup.3] [h.sup.-1] and 70 to 130 [m.sup.3] [h.sup.-1] using the theoretical equation and 20 to 65 [m.sup.3] [h.sup.-1] and 40 to 130 [m.sup.3] [h.sup.-1] using the empirical equation, respectively. The Reader-Harris/Gallagher equation (Method 1) adequately estimated the discharge coefficient of the orifice plates; however, the use of empirical equations (Method 3) demonstrated smaller measurement errors and greater rangeability of the evaluated flow meters. Key words: hydrometry, diaphragm, hydraulics Objetivou-se neste estudo avaliar tres metodologias para a estimativa da vazao de agua em placas de orificio, quantificando erros nas determinacoes de vazao a fim de sugerir a faixa de medicao apropriada para cada condicao avaliada. Foram avaliados dois modelos de placa de orificio (diametros nominais 100 e 150 mm) com restricao de 50% em relacao ao diametro nominal. Nas equacoes teoricas, o coeficiente de descarga foi obtido pela equacao de Reader-Harris/Gallagher (Metodo 1) e aproximado a partir de dados experimentais pelo coeficiente angular de uma reta com intercepto igual a zero (Metodo 2). A faixa de medicao recomendada para manter os erros inferiores a 5% para a placa de 100 e 150 mm foi de 30 a 65 [m.sup.3] [h.sup.-1] e de 70 a 130 [m.sup.3] [h.sup.-1] utilizando a equacao teorica e de 20 a 65 [m.sup.3] [h.sup.-1] e de 40 a 130 [m.sup.3] [h.sup.-1] utilizando a equacao empirica, respectivamente. A equacao de Reader-Harris/Gallagher (Metodo 1) estimou adequadamente o coeficiente de descarga dos modelos de placas de orificio, entretanto o uso de equacoes empiricas (Metodo 3) proporcionou menores erros de medicao e maior rangeabilidade dos medidores de vazao avaliados. Palavras-chave: hidrometria, diafragma, hidraulica

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Gale Document Number: GALE|A648142276