Head Loss at Pipe Entrance Equations and Calculator

Fluids Flow Engineering
Hydraulic & Pneumatic Design Engineering

Head Loss at Pipe Entrance Equations and Calculator using the head loss coefficient and head loss of a fluid at a smooth bellmouth pipe entrance.

Head Loss at Pipe Entrance

The head loss hLcan be calculated as:

hL= kloss x (um2 / (2 x g) )

Where k loss is the head loss coefficient, (um is the mean flow velocity in the pipe, and g is the gravitational acceleration. kloss is calculated from:

kloss = 235.03x4 - 194.09x3 + 56.739x2 - 7.8163x + 0.50

Where x is the defined as:

x = r / Dh

Where:

r = radius in Meters (m)
Dh = Inside diameter in Meters (m)
um = Flow Velocity m/s
hL = Head Loss (m)
kloss = Head Loss - dimension less
Dh = Diameter Ratio - dimension less

The k loss equation was derived from a curve fit from points when plotted from the following data and are accurate plus/minus 10%:

r / Dh
k loss
0.00
0.5
0.01
0.44
0.02
0.37
0.03
0.31
0.04
0.26
0.05
0.22
0.06
0.2
0.08
0.15
0.10
0.12
0.12
0.09
0.16
0.06
0.20
0.03

References

Roberson, John A. and Crowe, Clayton T., Engineering Fluid Mechanics , 2nd Ed., Rudolf Steiner Press, London.1976. p 360 - 384.

Idel'chik, I E. and Fried, Erwin., Flow Resistance, a Design Guide for Engineers , Taylor & Francis, Washington D.C. 1989. p 52.

ASHRAE. ASHRAE Handbook, 1977 Fundamentals , American Society of Heating, Refrigerating And Air Conditioning Engineers, Inc., New York, 1997. p 32.31.

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