Evaluating Pressure Losses in Drip-Irrigation Lines

In this paper an experimental investigation was carried out to deduce an evaluating procedure of local losses due to the protrusion of emitter barbs into the flow in drip-irrigation lines. Local losses corresponding to different pipe-on line emitter systems were measured for different Reynolds number values. Each pipe-emitter system was characterized by an obstruction index (OI) summarizing the reduction of cross-sectional area of the pipe due to the emitter connection. A power relationship between a characteristic value of the α coefficient, expressing the local losses amount as a fraction of the kinetic height, and the corresponding OI index was deduced. Two evaluating procedures of OI were also compared: an analysis of photographs of the connections obtained by dissecting the pipe at the emitters and the use of a caliper to measure emitter protrusion dimensions. Only the first procedure makes it possible to obtain an estimating criterion of the α coefficient because it takes into account both the characteristics of the emitter connection and the deformation of the pipe surrounding the stem.