ABSTRACT
In an attempt to develop a low cost by-pass elbow meter for flow monitoring in microirrigation systems, characteristics of by-pass flow across 90[deg] commercial PVC elbows were clarified for the case of diameters ranging from 20mm to 50mm. The by-pass and main flow discharge relationship was found to be linear, this linearity characteristic could be valuable for flow measurements. Metering characteristics of each elbow as a function of the pressure head differential and as a function of the by-pass flow were determined for each elbow.HomePage
When inserting within the by-pass path a high resistance in comparison with the by-pass friction lossses, the by-pass flow rate and main discharge relationship will remain strictly linear and the error in flow metering falls within the range of the by-pass flow meter reading precision. The performance of an elbow meter when calibrated on by-pass flow basis is quite as good as when it is calibrated on the basis of the pressure head difference.
Since the by-pass flow rate is too small in comparisoneith the main flow discharge(1/20 for the case of 30mm elbow with 10mm orifice size), the by-pass elbow meter will use a low flow rate flow meter usually at low cost to give accurately total dischage. By also selecting an appropriate by-pass orfice size, the range of the by-pass flow meter could be adjusted to the desired range.Keywords: by-pass elbow meter, microirrigation