Perda de carga em linhas laterais de sistemas de irrigação por gotejamento.

Abstract

The general objective of this work was to study the friction head loss (hf) and local head loss (hl) in irrigation lateral lines, consisting of two specific objectives: (i) Compare several explicit equations to estimate the value of the Darcy friction factor (f), arising from different approaches, for small diameter polyethylene pipes used in lateral lines of drip irrigation systems; and, (ii) Evaluate the influence of obstruction and Reynolds Number (Re) on Kinect head coefficient (k) in polyethylene pies with online emitters. For this, an experimental bench developed for studies of localized irrigation was used to control the system and collect the variables relevant to the study (flow, temperature, total head losses (ht) and (hf). The diameters (D) used in this study were 14.2192, 16.0026 and 18.6009 mm. Equations for estimating f available in the literature were evaluated for the different flow regimes. From hf and ht, hl caused by the obstruction of emitters in the pipe was determined. Four values of k were estimated through different approaches, considering or not the influence of viscous forces, through Re. The pipes studied in this work presented the behavior of smooth pipes. All equations for estimating f used showed correlation coefficients above 0.99. The equations that presented smaller errors have a higher degree of complexity. The definition of the equation for estimating f must consider the degree of complexity of the equation itself. The hl can represent up to 40% of the ht in a lateral line, depending on the flow velocity. The higher D, the lower the hl ht-1 ratio. For Re < 4000, k has an inverse behavior to Re, whereas for Re > 4000, k has a positive relationship with Re. The values of k decreased with the increase of D. The different approaches for determination of k present errors as a function of Re. Values of k showed dependence on Re and the obstruction caused by the emitter. Considering Re in estimating k increases the complexity in equating hl. Equating f and k can present different degrees of complexity, requiring the designer to keep in mind what he is looking for. The equations for f and k can still be adjusted to ensure better and easier sizing of drip irrigation lines.