Desempenho hidráulico de fitas gotejadoras operando sob diferentes temperaturas da água

Abstract

Hydraulic performance of drip tapes operating in a range of water temperatures Temperature variations influence the properties of water, especially viscosity. This can be a significant factor, which affects the emitters' discharge and consequently the uniformity of application. Studies analyzing drip tape material, types of integrated emitters and manufacturing characteristics are important to understand the sensitivity of these materials when operated in a range of values of water temperature. This experiment was carry outat the Laboratory of Tests of Irrigation Material (LEMI) of the Department of Engineering of Biosystems of the "Luiz de Queiroz" School of Agriculture-ESALQ / USP. Five types of drip tapes were evaluated, with variousintegrated emitters and wall thicknesses. The pressure-flow curves presented the same trend for the evaluated material, however, different values of the parameters K and x were found for each temperature. The CV for all materials evaluating in a range of temperatures presented values in accordance with techinical standards. There was no specific trend of the values of CV neither IQR in relation to the water temperature. For the turbulent flow emitters, the dischargetends to decrease with increasing temperature, but not significantly (p> 0.05). For the continuous emitters of turbulent flow, different responses were obtained, the emitter SilverDrip® the dischargeincreased with the increase of the temperature (p <0,05), while for the emitter Turbo Tape®, the dischargedecreased and the greater variations of flow occurred from 60 kPa (p <0.05). For the emitter molded, the dischargeincreased (p <0.05) as a function of temperature, but the greater variation occurred in the lower pressures. For any of the materials, there was a significant difference (p> 0.05) in the dischargevariation comparingthe wall thicknesses, indicating for the emitters studied, the wall thickness does not influence the dischargesensitivity to temperature variations. The results indicate that the sensitivity of the emitter as a function of the water temperature is associated with the exponentof emitter flow.

Head Loss in Thin-Walled Drip Tapes with Continuous Labyrinth

“…A power-law model (equation (8)) was used to correlate the pipe internal diameter ( D , m) with the pressure head ( H , m). The coefficient values for the pipes studied at 23°C were obtained experimentally in [5]:D=cHd.…”

“…When not pressurized, the pipes tend to be flat and the degree of circularity increases with the working pressure. Due to the material elasticity, the diameter tends to increase to a certain extent as the working pressure is raised [4, 5]. Changes in the flow section geometry affect the flow velocity profiles inside the pipe, interfering in the friction factor and consequently in the head loss.…”

Perda de carga em tubos gotejadores colapsáveis para microirrigação

“…Quando não pressurizados, os tubos tendem a ser planos e o grau de circularidade aumenta com a pressão de trabalho. Devido à elasticidade do material, o diâmetro tende a aumentar até certo limite com o aumento da pressão de trabalho (MELO et al, 2019;ARAÚJO, 2019).…”

“…Para o ajuste manteve-se m = 1,75 para possibilitar a comparação com a equação de Darcy-Weisbach, com f calculado por Blasius.Para relacionar o diâmetro interno do tubo (D, m) com a carga de pressão (H, mca) utilizou-se um modelo potencial (Eq. 12) cujos valores dos coeficientes para os tubos estudados, à temperatura de 23 o C, foram obtidos experimentalmente porAraújo (2019).D = cH d 12 sendo para o tubo Turbo Tape c = 0,0156 e d = 0,013 (r 2 = 0,9968); para o Silver Drip c = 0,0155 e d = 0,007 (r 2 = 0,9962); e para Rain-Bird c = 0,0157 e d = 0,0352 (r 2 = 0,9968). Assumindo-se que o diâmetro do tubo (D) aumenta com a carga de pressão (H) e a perda de carga reduz-se com o aumento do diâmetro, ajustou-se um modelo empírico de perda de carga para o escoamento na forma da Eq.…”

Relações entre características geométricas de gotejadores e dinâmica de obstrução

“…Os diferentes tipos de emissores são apresentados na Figura 1. Tipos de gotejadores utilizados na irrigação localizada: gotejador on-line (a), gotejador in-line (b), gotejador integrado tipo cilíndrico (c), gotejador integrado tipo plano (d)(ARAUJO, 2019)…”