HYDRAUL-EXPT#10.docx

8/12/2019 HYDRAUL-EXPT#10.docx

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EXPT.No.11 1

HYDRHYDRAULICS LABORATORY

Experiment No.11Pipe Network Flow Analysis

Pipes normally are run from a common junction so that they can distribute at differentsegments of an area. Problems concerning flow rates and head loss in each of thepipes in parallel are concerns of engineers.

Flow in Pipe SystemIn analyzing flow through two or more parallel pipes, the continuity and energy energyequations must be satisfied:

For continuity, Q = Q 1 + Q 2 + + Q n

For head loss relations. h L = h L1 = h L2 = h Ln

If there are several pipes in parallel, or in series, or in a combination of both, it isconvenient to express the head loss in the pipe system by

hL = kQ x or h L = kLQ x

where k is dependent on the length, diameter, arrangement, fluid properties, androughness of the pipes. The Darcy-Weisbach formula gives the value of x varying from1.75 for smooth pipes to 2.0 for rough pipes at high Reynolds number.

Experimentally, the head loss in parallel connection may be determined. In theory, in

the absence of any machine in any pipe in parallel, the individual head losses for pipesin parallel are equal. For a three-type system this translate to,

hL = h L1 = h L2 = h L3

Under a common elevation, and assuming minor losses as small or negligible, the headloss may be taken as the difference in pressure, P, between two points in each pipe.Similarly, the flow rate on pipe 1, Q 1, added to the flow rate in pipe 2, Q 2, and the flowrate in pipe 3, Q 3, totals the flow rate going in and out of the system, Q in = Q out . Hence,

Q = Q 1 + Q 2 + Q 3

For a steady, incompressible flow,

A1V1 + A 2V2 + A 3V3 = Q in


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EXPT.No.11 2


But; can be considered as a constant kn.

It follows that, in terms of V 1,

A1V1 + A 2 (k1/k2)1/2 V1 + A 3(k1/k3)1/2 V1 = Qin

In the last equation, the value of V 1 can be solved, and similarly the value of Q 1. It alsofollows that velocities 2 and 3 can be solved simultaneously. To check for experimentalerrors, the sum of the flow rate in each pipe must be equal to the computed total flowrate.

I. Experiment Objectives

The objective of this experiment is to verify validity of continuity and head loss relationsin a pipe network in parallel.

II. Materials and Apparatuses Required

The apparatuses necessary to perform this experiment are the following:

- Hydraulic Bench- Pipe Assembly- Stopwatch

III. Procedures

1. Attach the pipe apparatus to the hydraulics bench. Make sure all valves are fullyopen. The outlet valve shall control the pressure in the pipes.

2. A partially open outlet valve will produce greater pressure.3. Turn the hydraulics bench on and allow water to flow into the system.4. Start with a high pressure difference between sections as the initial trial.5. Take note of the readings in the pressure gauges in each pipe.6. Measure the flow rate by taking the time it takes to fill the volumetric tank with 15

liters of water.7. Repeat the procedure for various flow rates and/or pressure differences.


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EXPT.No.11 3


IV. Laboratory Data

Temperature of Water : ___________ Friction factor: _________Nominal diameter of pipes: ___________

Actual diameter of pipes: ____________Length between gauges: ___________

Head loss between two sections.

Trial#

Volume(liters)

Time(sec)

FlowRate

(m 3/s)

PressureReading,pipe1 P1

(N/m 2)

PressureReading,pipe1, P2

(N/m 2)

PressureReading,Pipe2, P1

(N/m 2)


(N/m 2)


(N/m 2)


(N/m 2)

1

2

3

4

5


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EXPT.No.11 4


V. Observations

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VI. Conclusions

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