PipeFriction-v9

# PipeFriction-v9 - MEC616 PF Pipe Friction Lab 2011-JAN-15 1...

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MEC616 PF – Pipe Friction Lab 2011-JAN-15 1. Objective To determine the experimental pipe friction factor, f , for a range of pipe flow rates using four dif- ferent diameter smooth copper pipes and compare the experimental values to theoretical results. 2. Introduction 2.1 Measuring the pipe frictional headloss, h f The Bernoulli energy equation for steady, incompressible flow of a real fluid in a pipe between two points 1 and 2 (see Figure 1) may be written as: p 1 1 V 1 2 2 g z 1 = p 2 2 V 2 2 2 g z 2 h f where p = pressure, = g = fluid weight density, = fluid density, = kinetic energy cor- rection factor, g = gravity, V = average flow velocity, z = elevation, and h f = head loss due to fluid friction. Rearranging and solving for h f yields: h f = p 1 z 1 p 2 z 2 1 V 1 2 − 2 V 2 2 2g For a constant diameter pipe, D 1 = D 2 , therefore V 1 = V 2 and 1 = 2 . Thus the head loss is giv- en by: h f = p 1 z 1 p 2 z 2 Note that neither V or are required in the above formula. For some applications may be required. Typical values are: = 1 for uniform flow, = 2 for laminar flow, and = 1.06 for turbulent flow. For most turbulent flow engineering applications use ≈ 1 . The term p / z represents piezometric head which can be read by a simple piezometric tube or piezometer (see Figure 2). Two piezometers may be combined together to form an inver- ted U-tube manometer which reads the difference in piezometric head between points 1 and 2 (see Figure 3). Thus: h m = p 1 z 1 p 2 z 2 = h f h m h f This means that the head loss, h f , can be read directly from the U-tube manometer. PF - 1

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MEC616 PF – Pipe Friction Lab 2011-JAN-15 2.2 Experimental equation for the friction factor, f The head loss between points 1 and 2 may be predicted by the Darcy-Weisbach equation: h f = f L D V 2 2 g where f = friction factor (dimensionless), L = pipe length between points 1 and 2, D = internal pipe diameter, and V = average pipe velocity. Note that V = Q / A where Q = measured flow rate, and A = D / 2 2 for a circular pipe. Rearranging and solving for f
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