Flow Complex Pipe System

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CHARLES DARWIN UNIVERSITY

SCHOOL OF ENGINEERING AND LOGISTICSFLUID MECHANICS - ENG 243

LABORATORY EXPERIMENT

Losses in a Small Diameter Pipe System

Lecturer: Jim Mitroy

Students Name:

Date of Practical: _________________________

Due Date: _________________________

Name of Group Members: _________________________

_________________________

_________________________

_________________________

Declaration

I declare that the work contained in this report is my own work, andthat it has not been copied from another persons work:

Signed: __________________________________


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Aim

This experiment is to determine energy losses sustained by water

flowing through a piped system that contains bends, suddencontractions, sudden expansions, a valve and a long length of pipe.

Introduction

Flow through a pipeline is always accompanied by an energy loss in the

liquid. We often express this in the form of a pressure head loss. The

magnitude of pressure head loss is dependant upon:

The flow velocity The length to diameter ratio of the pipe work, and the Surface roughness of the pipes

Pressure head losses also occur in fluids flowing through bends and

valves. For contractions and expansions in pipelines, energy loss will

always occur, although the pressure head is seen to increase in the case

of expansions.

Apparatus

In this case we have two separate networks namely a blue circuit and a

red circuit. Here it is required to examine the differing pipe diameters

and fittings to determine the losses incurred, the theoretical/given K

factors versus practical results ofK, and friction factorf.


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The Blue circuit consists of:

a gate valve a standard elbow bend a 90 degree mitre bend, and a straight pipe

The Red circuit consists of:

a Globe valve a sudden expansion a sudden contraction a 150mm radius 90 degree bend a 100mm radius 90 degree bend and a 50mm radius 90 degree bend


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In all cases (except the gate and globe valves) the pressure change across

each of the components is measured by a pair of pressurised piezometer

tubes. In the case of the valves, U tubes containing mercury are used to

measure the pressure difference.

Theory

For an incompressible fluid flowing through a pipe the following

equations apply:

Steady Flow 1 D Continuity = oi MM

The Darcy head loss equationg2

V

d

lfh

2

l =

The loss in a sudden expansion2g

Vh

21

l

2

2

1

1

=

The loss at a sudden contraction2g

Vh

22

l

= where Kis a

dimensionless coefficient that depends on the area ratio given in

Table 1

Table 1 Energy Loss in a Sudden Contraction

A2/A1 0 0.1 0.3 0.5 0.7 0.9 1.0K 0.5 0.4 0.45 0.3 0.2 0.08 0

The energy loss in bend is also given in the form2g

Vh

2

l

= , where

the loss coefficient depends upon the bend radius and pipe radiusand the angle of the bend, see Figure 1


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The head loss due to valve is also given by 2gV

h

2

l

= , where the

loss coefficient is give in Table 2

Table 2 Loss Coefficients in Valves

K Factor Gate Vv Globe Vv

Open 0.2 10 Open 0.9 11

Open 5 12.5

Open 24 50

The readings for the valves involve differential U tube mercurymanometers. Review this theory in order that you understand the

equation for the pressure differential

Procedure

For the Blue Circuit

Start up the pump on the hydraulic bench with the supply valveclosed

Ensure the globe valve is fully closed and the gate valve is fullyopen.

Open the hydraulic bench supply valve fully and obtainmaximum flow through the Blue Circuit.

Record the readings on the piezometer tubes and mercurymanometers.


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Collect a sufficient quantity of water in the weighing tank toensure that the weighing takes place over a minimum period for

60 seconds. (Suggested 30 kg).

For the Red Circuit

Before switching off the pump close both the globe valve and thegate valve. This procedure prevents air gaining access to the

system and so saves time in subsequent setting up.

Close the gate valve, open the globe valve fully and repeat theexperimental procedure that was given for the Blue Circuit.

Results and Circuit Data

Pipe Internal Diameter 17.0 mm

35.7mm

Distance between pressure tappings (straight pipe) 925mm

Bend Radii

Sharp 90 Degree mitre 0mm

Proprietary Elbow 90 Degree 19mm

Smooth 90 Degree bend 50mm

Smooth 90 Degree Bend 100mmSmooth 90 Degree Bend 150mm

Diameters

Expansion 17/35.7mm

Contraction 35.7/17mm


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The readings taken for each type of bend includes a length of straight

pipe. Thus the losses across the bend only, may be accurately determined

by deducting the head loss for section length of straight pipe included in

the piezometer readings for each flow rate. Hence initially determine the

friction factor for the straight section of pipe from the head loss equation.

The straight length equivalent, measured for each fitting:

Mitre elbow 850mm

Proprietary Bend 915mm

50 mm bend 730mm

100mm bend 940mm

150mm bend 900mm

straight length 925mm

Blue Circuit results Table

In the table record the difference in the manometer readings [mm]

Test No Time tocollect30kg [s]

GateValve

STDElbow 90deg

90 degMitre

Straightpipe

1

2

3

4

5


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Red Circuit results Table

In the table record the difference in the manometer readings [mm]

TestNo

Timetocollect30kg[s]

GlobeValve

SuddenExp

SuddenCont

150

mm

Radius

100mmRadius

50

mmRadius

1

2

3

4

5

Requirements

Draw up a graph similar to Moody diagram and comment onresults.

Determine average values of K for each bend and plot againstpublished values shown in theory.

Graph calculated and measured values Compare values of K for both valves against values given in theory. Compare the value of the friction factor for each pipe size and

compare with published figures.

Documents

Flow Complex Pipe System