ESDU 83037: Pressure losses in curved ducts: single bends.

Abstract:

ESDU 83037 gives comprehensive data for the estimation of pressure loss in circular-arc bends taking account of the effects of bend radius ratio and angle, upstream and downstream duct lengths, surface roughness, cross-sectional shape and Reynolds number. The data are in the form of a general equation for which a graphical solution is also provided. For the common case of a 90 degree, smooth bend of circular or square section a direct graphical presentation of pressure loss coefficient is given. Reanalysis of the available information for single and 90 degree composite mitre bends has shown that, contrary to the usual assumption, surface roughness has a significant effect on pressure losses. These data are given graphically in terms of a reference pressure loss coefficient and correction factors for Reynolds number and roughness effect. Approximate data are provided for "standard pipe bends" for use where little detail of the bend geometry is available and sources of data for other bend types (for example, bends where the inner and outer walls are not concentric) are referenced. The effect of guide vanes or splitters in bends is considered and a simple design for use in mitre bends is given. All the information results from correlations of experimental data drawn from a wide range of sources. A practical worked example is included, and data on straight pipe friction factors and effective surface roughness of various pipe materials are given. The method for circular-arc bends is provided as a computer program, ESDUpac A8337.

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Details:

Data Item ESDU 83037
Format:	PDF with software with interactive graphs
Status:	Amendment (D), 01 Jan 2007 Published in Release 2007-01
Previous Releases:	ESDU 83037 Amendment C
ISBN:	978 0 85679 452 0

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ESDUpac A8337

Title	Pressure losses in curved ducts: single bends. Computer program calculating frictional losses for incompressible flow in circular section bends.
Version	1.1

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This Data Item contains 22 interactive graph(s) as listed below.

Graph	Title
Figure 1	Friction factor for straight pipes
Figure 2	Boundary layer between long and short circular-arc bends
Figure 3a	Transition region for flow in long circular-arc bends
Figure 3b	K'_s,G for long, smooth circular-arc bends
Figure 3c	Surface roughness correction factor phi₄ for long circular-arc bends
Figure 4a	K_s,G for short, 90 degree circular-arc bends in laminar flow
Figure 4b	K_s,G for smooth, short circular-arc bends in turbulent flow
Figure 5a	K_b for short circular-arc bends in turbulent flow
Figure 5b	K_C for short, 90 degree circular-arc bends in turbulent flow
Figure 5c	K_d for short, 90 degree circular-arc bends in turbulent flow
Figure 5d - Part 1	Downstream tangent length correction to K'_d for short, 90 degree circular-arc bends
Figure 5d - Part 2	Downstream tangent length correction to K'_d for short, 90 degree circular-arc bends
Figure 5e	Bend angle correction to K'_d for short circular-arc bends
Figure 6a	Basic pressure loss coefficient for single mitre bends
Figure 6b	Basic pressure loss coefficient for composite mitre bends, theta = 90 degrees
Figure 7a	Reynolds number correction for mitre bends (for rough bends use factor Phi₄ also)
Figure 7b	Roughness correction for mitre bends (use factor Phi₁ also)
Figure 7c	Roughness correction for mitre bends (use factor Phi₁ also)
Figure 8a - Part 1	Guide vanes or splitters in circular-sectioned circular-arc bends. Optimum location for one guide vane
Figure 8a - Part 2	Guide vanes or splitters in circular-sectioned circular-arc bends. Optimum location for two guide vanes
Figure 8b	Guide vanes or splitters in circular-sectioned circular-arc bends. Reduction in loss coefficient for vanes at optimum location K_s,G (with vanes) = K_s,G (without vanes) x Phi₆
Figure 9	Approximate K_s,G values for 90 degree standard pipe bend fittings