Antonio P. de Camargo

Method for determining friction head loss along elastic pipes

Abstract Pipes made of plastic materials are generally used in pipelines and the laterals of irrigation systems. Plastic materials such as polyethylene allow significant changes in pipe cross section due to operating pressure, but traditional equations used for determining head loss do not account for this effect. The purpose of this research was to develop an equation for determining friction head loss along elastic pipes. The equation developed is based on the Darcy–Weisbach equation and focuses on pipe cross-sectional variations caused by pressure effects, hence the name pressure-dependent head loss equation (PDHLE). In addition to the parameters required by the Darcy–Weisbach equation, the PDHLE also considers the modulus of elasticity of the pipe material, the pipe wall thickness, and the internal diameter variation due to operating pressure. The PDHLE resulted in high accuracy in determining the friction head loss of elastic pipes.

Assessment of clogging effects on lateral hydraulics: proposing a monitoring and detection protocol

Ageing of drip irrigation systems due to clogging of emitters is considered the largest maintenance problem in microirrigation and this problem is enhanced in subsurface irrigation systems. Whatever the source of the clogging problem, a methodology for early detection of clogging in the field can be useful in decision-making about deploying cleaning processes (flushing or injection of chemicals) and avoiding replacement of laterals. This work presents a methodology for simulating clogging conditions able to reproduce the effects of clogging on pressure profiles, head loss, and emitters flow rate distribution along a single levelled lateral with constant inlet pressure. This methodology was validated by several experiments conducted under controlled conditions of clogging induced by changes in the flow rate of emitters. The effects of clogging intensity and position on hydraulic parameters of a single lateral were analysed in detail and aspects relating to pressure, head loss, and flow rate measurements were discussed. For a given lateral set-up, it is possible to draw a chart relating flow rate and head loss for various levels and positions of clogging. Assuming that measurements of head loss and flow rate are available, this diagram enables immediate estimation of the level and location of clogging, which is useful for deploying maintenance routines. Finally, a protocol was proposed to detect the level of clogging and estimate its position along a levelled lateral under constant inlet pressure. Although constant lateral inlet pressure is atypical in large agricultural settings, it may occur in greenhouse or experimental settings.

Desenvolvimento de um sistema para o controle do pH da água para microirrigação

ABSTRACT The aim of this work was to develop an electronic system for control of water pH in microirrigation. Thestudy was accomplished in the Hydraulics Laboratory of Biossystems Engineering Department, EscolaSuperior de Agricultura “Luiz de Queiroz” (ESALQ/USP). The water pH control system has a device foracid injection controlled by a solenoid valve. This valve is switched on by electric pulses from amicrocontroller. The system was evaluated for different water pH values (ranging from 6.2 to 9.2) underconstant (264 L h -1 ) and variable flow. The pH was measured immediately on system downstream, andalong the lateral line at 1, 14, 29, and 44 m from the lateral inlet, tests were also accomplished for differentintervals of time. The obtained results proved the efficiency of the system on maintaining water pH indesired range for constant and variable flow conditions. Meaningful temporal or spatial variations alonglateral irrigation line were not observed. Key words: clogging control, ions precipitation, treatment water

Quantificação do erro na determinação da perda contínua de carga em tubos elásticos

The plastics industry and its derivatives, with the help of engineering have improved the quality of materials used for manufacturing pipes, mainly polyethylene. The elasticity of polyethylene tubes allows diameter increases as pressure rises, which is not taken into account by the mathematical equations used to determine the head loss. The purpose of this research was to quantify the errors on head loss determining in elastic tubes as a function of inlet pressure on the lateral line, comparing observed and estimated values by equations recommended in the technical literature. Three samples of polyethylene pipe were evaluated under 9 inlet pressures and 3 flow rate conditions, which corresponds to velocities of 1.0, 1.5 and 2.0 m s-1. Measurements for determining the outside diameter of the tubes were carried out under pressures from 0 to 588.4 kPa incrementing 49.05 kPa each step. For all evaluated conditions it was verified that pressure affects the continuous head loss in elastic tubes and the equations of Darcy-Weisbach, Hazen-Williams, and Flamant overestimate the results.