Exp#5 Head Loss Due to Friction_2014

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MEHB221 Fluids Mechanics Lab 2014

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Experiment No. 5

HEAD LOSS DUE TO PIPE FRICTION

Objective

To verify that Darcy-Weisbachequation can be used to predict the head loss due to friction

with flow of water through a smooth bore pipe.

Apparatus

Fluid Friction Apparatus, FM100.

Hydraulic Bench, FM110.

Summary of theory

For water flowing through a circular pipe, the head loss due to the friction can be calculated

usingDarcy-Weisbachequation.

h = 4fLu22gd

Or

h = Lu2

2gd

Where

L = length of pipe between tappings (m) = 1m for all pipesd = internal diameter of the pipe (m)

u = mean velocity of water through the pipe (m/s)

g = 9.81 (acceleration due to gravity,m/s2)f = pipe friction coefficient [ (British) 4f = (American) ]

The value of Reynolds number Recan be calculated using this equation:

Re= ud

Where (assume temperature = 20C)

= dynamic viscosity = 1.002 x 10-3kg/m.s = density = 998kg/m3


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Procedures

1. Open fully the flow control valve and inlet isolating valve.2. Make sure that gate valve and globe valve are closed.

3. Switch on the main switch for hydraulic bench and digital pressure indicator.

4.

Open fully the outlet control valve.5. Open the isolating valve for the test pipe No. 1.6. Insert the two manometer tubes (from digital pressure indicator) into the tapping

valve of pipe No. 1.

7. Switch on the pump of hydraulic bench.8. Let the water flow through the system for a while.

9. Note down the reading on the differential pressure indicator.

10.Close the drain, use a stopwatch to time a certain amount of water flowing into the

measuring tank and calculate the flow rate.11.Once it is done, open the drain and let the water flow into the sump tank.

12.Change the flow rate of water by adjusting outlet control valve to get different

differential pressure reading.13.

Again, take the differential pressure reading and measure the flow rate.

14.Obtain at least six readings for various flow rates.

15.Switch off the pump and shut the isolating valve for test pipe No. 1.

16.Repeat the above procedures for test pipe No. 2 (repeat procedures 4 to 14).17.Switch off the pump and shut the isolating valve for test pipe No. 2.

18.Repeat the above procedures for test pipe No. 3.

19.Switch off the pump and shut the isolating valve for test pipe No. 3.20.Switch off the main switch and shut the inlet isolating valve.

Data, Observation and Results

Record the results on the result sheet provided.

Calculate the flow rate (Q), velocity (u) and Reynolds number (Re).

For

Q = V x 10-3T

And

u = 4Qd2

Calculate the friction factor (f) using the following equation then calculate :

For laminar flow f = 16

Re


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For turbulent flow f = 0.079

Re0.25

Calculate the theoretical head loss with the following equation:

h = Lu2

2gd

Calculate the percentage error between the theoretical and experimental values.

Plot the graph of friction factor, f versus Reynolds number, Refor each test pipe inone graph (Graph 1).

Analysis and Discussion

Explain about head loss in pipe (including head loss due to friction).

Comment on the result and compare the theoretical with the experimental values.

Comment on Graph 1 and compare your graph with the moody diagram.

List the possible sources of errors and safety precaution.

Result Sheet

Volume

V[ L ]

Time

T[ s ]

Flow

rate (Q)[ m3/s ]

Velocity

u[ m/s ] Re f

Theoretical

head (hth)[ m H2O ]

Exp. head

loss (hexp)[ mm H2O ]

Exp. head

loss (hexp)[ m H2O ]

Percent

Error[ % ]

Test pipe No. 1 diameter = 0.006 m Pipe length L = 1 m

Test pipe No. 2 diameter = 0.010 m

Test pipe No. 3 diameter = 0.017 m


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Figure 1: Unit Construction for Fluid Friction Measurement Apparatus (Model: FM100)

1. Smooth Bore Pipes (6mm, 10mm, 17mm) 6. Outlet Control Valve

2. Artificial Roughen Pipe (17mm) 7. Inlet Isolating Valve

3. Manometer 8. Sudden Contraction

4. Gate Valve 9. Sudden Enlargement

5. Globe Valve 10. Differential Pressure

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3

2

6

54

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98

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Exp#5 Head Loss Due to Friction_2014