Prior to the 1990s, pressure loss factors of ductwork components had almost invariably been quoted as single values, invariant with either size (diameter) or air speed (Reynolds Number). Unlike pipework components, where size has been known to be a factor for some time, with ductwork components there seemed to have been a tacit assumption that neither size nor velocity would affect the value of the non-dimensional pressure loss factor ζ. Enough data is now available for us to know that this assumption was false. The major part of this paper concerns analysis of experimentally obtained data of the European Report (1992)1 and, where appropriate, comparison with other data. The components analysed are shown in Figure 1.
Pressure loss factor ζ is defined by the relationship:
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Practical application
: This paper places in the public domain the most pertinent data obtained from the European Research Project.1 It will be of particular use to authors of technical guides seeking to have more recently obtained research data. Although this distillation is naturally a considerable simplification of the original data, explanations are given as to why the author felt obliged to reject or massage some of the original data. Where there are misgivings and difficult judgements which had to be made, these are also recorded. Though the data as presented might be more detailed than most guide authors might require, this should be useful to computer software writers. Similarly those researchers using computational fluid dynamics (CFD) software to model reality, will appreciate the detail. In terms of future research the paper shows where reliable results are now established. More importantly perhaps, it shows where there are still some elements of doubt, and a few pitfalls which the researchers of the European Report were not quite diligent enough to avoid.
