Lec 7 FLOW IN PIPES Dr Zainab Talib

Lec 7 FLOW IN PIPES Dr. Zainab Talib Al-Sharify Email: zainab_talib 2009@yahoo. com

Summary Ø Lecture 4 Chapter 9 Establishment of flow in pipes § Analytical approach (Moody chart, Darcy law) § Some examples § Tutorial questions

Establishment of flow in pipes Dimensional analysis of the friction problem- incompressible flow

Moody diagram or stanton diagram

A Moody chart and commercial pipes A Moody chart (see below) is used to determine the turbulent flow friction factor from the Reynolds number and the relative roughness of the pipe. If the flow is laminar then the fricton factor is 64/Re. Various typical values of hydraulic roughness (ε) In the moody chart above (ε /D ) is identified with both numerator and denominator in metres (for consistency with all other equations on this page. It is probably more convenient to express both in (mm). i. e a 50 mm cast iron pipe (ε mm; /Dmm ) would simply be (0, 203 /50 ).

Typical Values of L/D for Fittings The losses through fittings are generally evaluated by obtaining K = f. T(L/D) Table of pipe friction values for clean pipe in region of complete turbulence

The K 180 value for a 180 o bend may be derived from the equivalent K 90 which is calculated from the above tables using the equation For laminar fluids with low Re numbers ( "<" 500) the K values obtained using the above are probably very innaccurate. The table below illustrates how this affects the K values

ues for Sudden Expansion-Contraction & Orifice The losses through these fitting are generally evaluated by first obtaining β = d 2 / d 1 Important Note: the resulting K values as tabled below are based on the flow velocity in the larger pipe if the flow velocity in the small pipe is used to evaluate the head loss then the K values tabled below should be multiplied by ( β ) 4 = (d 2 / d 1) 4 http: //www. roymech. co. uk/Related/Fluids_Pipe. html

Table of Ke, Kc & KO against β = d 2 / d 1 Reasonable Velocities of fluid in Pipes

References, for this lecture only 1. Venturi Meters Constructed with Pipe Fittings, Pap-1050, USBR 2. Implementation of Magnetic Meters for Irrigation Volumetric Measurement, ITRC Paper No. P 12 -006 3. List of Flowmeter Vendors https: //www. youtube. com/watch? v=5 BH 4 i. STv 16 Y https: //www. youtube. com/watch? v=n. Ply. Wie. Nvy. I https: //www. khanacademy. org/science/physics/fluid-dynamics/v/fluids-part-7 http: //eleceng. dit. ie/gavin/Instrument/Fluid%20 Flow. pdf

References

Dr. Zainab Talib Al-Sharify Thank you!