Iterative calculation of local head loss coefficient of emitters in lateral lines/Calculo iterativo do coeficiente de perda de carga localizada de emissores em linhas laterais.

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Publisher: ATECEL--Associacao Tecnico Cientifica Ernesto Luiz de Oliveira Junior
Document Type: Article
Length: 3,623 words

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Abstract :

HIGHLIGHTS: Local head loss data from emitters are scarce and iterative procedures can contribute to obtaining them. The procedure proposed can be run from the input and output pressure of the lateral line. Data obtained in the laboratory tests presented a slight difference from those estimated by the iterative procedure. This study aimed to iteratively set the local head loss coefficient of the Naan[R] micro-sprinkler, model 7110 Hadar, installed in a lateral irrigation line. To evaluate the total head loss along the lateral line, tests were performed using a rigid PVC pipe with an inner diameter of 15.8 mm, 12 m in length, and 24 micro-sprinklers inserted along the pipe, regularly spaced 0.5 m. In the tests carried out for four micro-sprinkler nozzle diameters (0.9, 1.0, 1.1, and 1.2 mm) and six inlet pressure head values (5, 10, 15, 20, 25, and 30 m) in the line, the pressure head difference between inlet and outlet in the pipe and the discharge of each emitter along the pipe were measured. The head loss computation was performed by the step-by-step procedure, starting from the downstream end to the upstream end of the line; since varying the local head loss coefficient values iteratively, the total head loss measured in the tests was equal to the calculated. For the different working conditions of the inlet pressure head and the micro-sprinkler nozzle diameter, the local head loss coefficient had values from 0.051 to 0.169. Relating the discharge values measured and estimated along the lateral line, the confidence coefficient of 0.9991 was verified, and the calculation procedure was considered optimal. Key words: pressure head, emitter discharge, nozzle diameter Este estudo objetivou determinar iterativamente o coeficiente de perda de carga localizada do microaspersor Naan[R], model 7110 Hadar, inserido em linha lateral de irrigacao. Para avaliar a perda de carga total da linha lateral foram realizados ensaios empregando um tubo de PVC rigido com diametro interno de 15,8 mm, 12 m de comprimento e 24 microaspersores inseridos na linha, regularmente espacados em 0,5 m. Nos ensaios, realizados para quatro diametros de bocais do microaspersor (0,9, 1,0, 1,1 e 1,2 mm) e seis pressoes de entrada (5, 10, 15, 20, 25 e 30 m) na linha, foram determinados o diferencial de pressao entre o inicio e o final da tubulacao e a vazao de cada emissor ao longo da tubulacao. O calculo da perda de carga foi realizado do ultimo para o primeiro emissor, pelo metodo trecho a trecho, de modo que, variando iterativamente os valores de coeficiente de perda de carga localizada, a perda de carga total observada nos ensaios fosse igual a estimada. Para as diferentes condicoes operacionais de pressao de entrada e diametro de bocal do microaspersor, os coeficientes de perda de carga localizada apresentaram valores entre 0,051 a 0,169. Ao relacionar os valores de vazao mensurados e estimados ao longo da linha lateral verificou-se indice de confianca igual a 0,9991, classificando o procedimento de calculo como otimo. Palavras-chave: pressao de entrada, vazao do emissor, diametro de bocal

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Gale Document Number: GALE|A659304106