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Survey of available data for pressure loss coefficients, ζ, for elbows and tees of pipework

Although numerous data are available for pressure loss factors for ductwork components, the factors for pipework components have not received the same attention. Gross simplifications and contradictions are found in surveys of available published data from the USA, Britain and continental Europe. Some is repeated from research conducted nearly 70 years ago and extrapolated into areas that were not investigated. It was first necessary to disregard that which is least reliable so as to be able to select what might be considered the most reliable. It is regrettable that it is inevitably necessary to discard data published specifically with the intention of helping engineers; it is hoped that no offence is caused. For laminar flow, data were found that had not appeared in any simplified guide. For turbulent flow, there is a case to be made for a re-investigation of the pressure loss factors that occur with standard manufactured components, since some of the best data are taken from generalised work on larger dimensions artificially roughened to simulate pipework. The only data considered as reliable for tees concern tees made of malleable iron. Until further information is available, it is suggested that this will need to be used also for fittings of other materials. Although data for pipe elbows are size dependent, those for tees are not.