Research Papers: Flows in Complex Systems

Pressure-Loss Coefficient of 90 deg Sharp-Angled Miter Elbows

[+] Author and Article Information
Wameedh T. M. Al-Tameemi

Department of Mechanical Engineering,
University of Sheffield,
Sheffield S1 4ET, UK;
Reconstruction and Projects Office,
Ministry of Higher Education and
Scientific Research,
Baghdad, Iraq
e-mail: wtal-tameemi1@sheffield.ac.uk

Pierre Ricco

Department of Mechanical Engineering,
University of Sheffield,
Sheffield S1 4ET, UK
e-mail: p.ricco@sheffield.ac.uk

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received August 26, 2017; final manuscript received December 12, 2017; published online January 30, 2018. Assoc. Editor: Moran Wang.

J. Fluids Eng 140(6), 061102 (Jan 30, 2018) (7 pages) Paper No: FE-17-1534; doi: 10.1115/1.4038986 History: Received August 26, 2017; Revised December 12, 2017

The pressure drop across 90deg sharp-angled miter elbows connecting straight circular pipes is studied in a bespoke experimental facility by using water and air as working fluids flowing in the range of bulk Reynolds number 500<Re<60,000. To the best of our knowledge, the dependence on the Reynolds number of the pressure drop across the miter elbow scaled by the dynamic pressure, i.e., the pressure-loss coefficient K, is reported herein for the first time. The coefficient is shown to decrease sharply with the Reynolds number up to about Re=20,000 and, at higher Reynolds numbers, to approach mildly a constant K=0.9, which is about 20% lower than the currently reported value in the literature. We quantify this relation and the dependence between K and the straight-pipe friction factor at the same Reynolds number through two new empirical correlations, which will be useful for the design of piping systems fitted with these sharp elbows. The pressure drop is also expressed in terms of the scaled equivalent length, i.e., the length of a straight pipe that would produce the same pressure drop as the elbow at the same Reynolds number.

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Fig. 1

Schematic diagram of the experimental facility

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Fig. 2

Schematic diagram of the 90 deg sharp-angled elbow and pressure tap

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Fig. 3

Schematic diagram of the test sections

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Fig. 4

Picture and schematic diagram of the pressure taps

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Fig. 5

Friction factor Cf as a function of the Reynolds number Re for flow through straight pipes

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Fig. 6

Pressure-loss coefficient K for 90 deg sharp-angled elbows as a function of the Reynolds number Re. The symbols are given in Fig. 5.

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Fig. 7

Pressure-loss coefficient K for sharp-angled elbows as a function of Cf

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Fig. 8

Equivalent length to diameter ratio L for sharp-angled elbow as a function of Re. The symbols are given in Fig. 5.

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Fig. 9

Pressure drop relative to the measurement location A along the 11-mm-diameter test section at Re=17,000 for air and water flows. The pressure-loss coefficient K and the scaled equivalent length L are indicated.

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Fig. 10

Air-flow pressure drop at different angles around the pipe periphery at stations C,D,E, and F of the 16-mm-diameter test section at different Reynolds numbers




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