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- Title
The development of an empirical equation for determining minor losses due to bends in smooth pipes for irrigation system design.
- Authors
Tagwi, D.; Senzanje, A.; Lagerwall, G.
- Abstract
As pipe networks get to shorter lengths or number of bends increases, proportion of losses due to bends increases noticeability, leading to possible over- and under-sizing of pumps, owing to estimations of 30 to 50 pipediameters in length of equivalent straight pipe, 10% to 15% and at times 25% of mainline losses as estimated by designers in industry, especially for low operating pressure systems. Without a thorough knowledge of development of the equivalent length, resistance coefficient and valve flow coefficient method, methods do not offer easy, quick, accurate and precise determination of minor losses as bend parameters change in design processes and is addressed by the developed Empirical Equation. Behavioural patterns due to change of individual bend parameters with pressure drop was obtained from bent pipes, Rc (relative radius of curvature) values 13.545, 27.679 and 79.578, experimentally; Short, Standard and Long radius from published data. Key components defining bends, pipe diameter per radius of curvature, Rc and flow coefficient, bend length per pipe diameter ratio (L/D ratio) were then used to derive the Empirical Equation. Derived equation (based on a theoretical 19.05 mm standard radius, = 0.7395) dynamically determined the best estimate of minor losses due to bend angles 0° to 90° without need of thorough knowledge, finding for pipe diameters outside experimental and published data also eliminating error. Pragmatic basis for derivation catered for constant parameters (easily measured) and unseen or immeasurable parameters, validating equation. Saturation phenomenon for Rc beyond experimental values was identified with confirmation of the difference between Short and Standard radius bends often confused, by close approximation of = 0.8976 at Rc = 0.5. Derived Empirical Equation, based on the resistance coefficient method, can satisfactorily be used as a tool in irrigation system design procedures and software for correctly estimating minor losses.
- Subjects
SYSTEMS design; FLOW coefficient; PRESSURE drop (Fluid dynamics); DIAMETER; ANGLES; IRRIGATION; EQUATIONS; PIPE
- Publication
Agricultural Engineering International: CIGR Journal, 2022, Vol 24, Issue 4, p1
- ISSN
1682-1130
- Publication type
Article