Minor Losses Report

7/30/2019 Minor Losses Report

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1.Introduction:The energy balance between two points in a pipe can be described by Bernoulli

equation, given by

Head loss hL includes the sum of pipe friction losses hf and all minor losses. Pipe

friction losses are assumed to be negligible in this experiment.

If

h1 & h2 are peizometer readings, hm is the minor losses.

The energy loss which occurs in a pipe fitting (so-called secondary loss) is commonly

expressed in the form:

2.Purpose:To determine the loss factors for flow through a range of pipe fittings including

bends, a contraction, an enlargement and a gate-valve

3.Apparatus:1. Energy Losses in Bends and Fittings Apparatus consists of:

1. Sudden Enlargement

2. Sudden Contraction

3. Long Bend

4. Short Bend

5. Elbow Bend

6. Mitre Bend

7. Gate Valve.

Fig (1): minor losses apparatus

Lhg

Vz

p

g

Vz

p

22

2

22

2

2

11

1

g

VKhm

2

2

g

V

g

Vhhhm

2221

2

2

2

1thenhz

phz

p,2,1 2

21

1

g

VhK m

2/

2


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2. The following dimensions from the equipment are used in the appropriate

calculations.

Internal diameter of pipe: d = 0.0183 m

Internal diameter of pipe at enlargement outlet and contraction inlet :

d = 0.0240 m

3. For the gate valve experiment, pressure difference before and after gate is

measured directly using a pressure gauge. This can then be converted to an

equivalent head loss using the equation: 1 bar = 10.2 m water

4.Procedure:It is not possible to make measurements on all fittings simultaneously and, therefore,

it is necessary to run two separate tests.

PART (A)

1. Set up the losses apparatus on the hydraulic bench so that its base is horizontal by

adjusting the feet on the base plate if necessary. (this is necessary for accurate

height measurements from the manometers). Connect the test rig inlet to the bench

flow supply and run the outlet extension tube to the volumetric tank and secure it

in place.

2. Fully open the gate valve and the outlet flow control valve at the right hand end of

the apparatus.

3. Close the bench flow control valve then start the service pump.

4. Gradually open the bench flow control valve and allow the pipework to fill with

water until all air has been expelled from the pipework.

5. In order to bleed air from pressure tapping points and the manometers close both

the bench valve and the test rig flow control valve and open the air bleed screw

and remove the cap from the adjacent air valve. Connect a length of small bore

tubing from the air valve to the volumetric tank. Now, open the bench valve and

allow flow through the manometers to purge all air from them; then, tighten the

air bleed screw and partly open both the bench valve and the test rig flow control

valve.


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Next, open the air bleed screw slightly to allow air to enter the top of the

manometers, re-tighten the screw when the manometer levels reach a convenient

height.

6. Check that all manometer levels are on scale at the maximum volume flow rate

required (approximately 17 liters/ minute). These levels can be adjusted further by

using the air bleed screw and the hand pump supplies. The air bleed screw

controls the air flow through the air valve, so when using the hand pump, the

bleed screw must be open. To retain the hand pump pressure in the system, the

screw must be closed after pumping.

7. If the levels in the manometer are too high then the hand pump can be used to

pressurise the top manifold. All levels will decrease simultaneously but retain the

appropriate differentials.

If the levels are too low then the hand pump should be disconnected and the air

bleed screw opened briefly to reduce the pressure in the top manifold.

Alternatively the outlet flow control valve can be closed to raise the static pressure

in the system which will raise all levels simultaneously.

If the level in any manometer tube is allowed to drop too low then air will enter

the bottom manifold. If the level in any manometer tube is too high then water

will enter the top manifold and flow into adjacent tubes.

8. Adjust the flow from the bench control valve and, at a given flow rate, take height

readings from all of the manometers after the levels have steadied. In order to

determine the volume flow rate, you should carry out a timed volume collection

using the volumetric tank. This is achieved by closing the ball valve and

measuring (with a stopwatch) time taken to accumulate a known volume of fluid

in the tank, which is read from the sight glass. You should collect fluid for at least

one minute to minimize timing errors. ( note: valve should be kept fully open.)

9. Repeat this procedure to give a total of at least five sets of measurements over a

flow range from approximately 8 - 17 liters per minute.


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PART (B)

10.Clamp off the connecting tubes to the mitre bend pressure tappings (to prevent air

being drawn into the system).

11.Start with the gate valve closed and open fully both the bench valve and the lest

rig flow control valve.

12.open the gate valve by approximately 50% of one turn (after taking up any

backlash).

13.For each of at least 5 flow rates, measure pressure drop across the valve from the

pressure gauge; adjust the flow rate by use of the test rig flow control valve. Once

measurements have started, do not adjust the gale valve. Determine the volume

flow rate by timed collection.

14.Repeat this procedure for the gate valve opened by approximately 70% of one turn

and then approximately 80% of one turn.

5.Data and Results:Table (1): Raw Data for All Fittings Except Gate Valve

Case No. I II III IV V

Volume (L) 13 13 21 24 25

Time (sec) 95.93 75.8 107.06 108.53 93.14

PiezometerReadings(mm)

Enlargement1 243 255 265 276 299

2 248 263 275 289 319

Contraction3 247 262 274 287 317

4 237 245 253 260 276

Long Bend5 246 259 272 284 309

6 244.5 256 267 279 301

Short Bend7 237 245 253 260 277

8 228 231 234 237 243

Elbow

9 220 220 219 219 217

10 206 198 191 183 165

Mitre Bend11 190 175 162 147 115

12 171 145 122 98 43


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Table (2): Raw Data for Gate Valve


50%

Opened

Volume (L) 40 25 24 19 14

Time (sec) 84.12 61.21 67.02 63.49 65.22

GaugeReading

(bar)

Red

(upstream) 1.1 0.79 0.6 0.4 0.2

Black(downstream) 0.09 0.05 0.01 0 0

70%O

pened

Volume (L) 40 40 35 30 25

Time (sec) 57.53 68.04 65.39 64.9 71.4

Gauge

Reading

(bar)

Red(upstream) 0.4 0.3 0.23 0.16 0.09

Black(downstream)

0.02 0.01 0 0 0

80%O

pened

Volume (L) 40 40 40 40 40

Time (sec) 55.45 61.39 67.31 83.97 96.78

Gauge

Reading

(bar)

Red(upstream) 0.2 0.17 0.11 0.08 0.03

Black(downstream)

0.07 0.05 0.02 0 0

Calculations:

Table (3): Minor Head Losses of All Fittings Except Gate Valve


Q (m3/sec) 1.355*10^-4 1.715*10^-4 1.961*10^-4 2.21*10^-4 2.684*10^-4

V (m/s) 0.515 0.652 0.7456 0.840 1.020

V2/2g (m) 0.0135 0.0216 0.0283 0.0359 0.053

MinorHead

Losses(m)

Enlargementh -5*10^-3 -8*10^-3 -10*10^-3 -13*10^-3 -20*10^-3

V12/2g- V2

2/2g 8.93*10^-3 14.34*10^-3 18.73*10^-3 23.8*10^-3 35.1*10^-3

h +V12/2g- V22/2g 3.93*10^-3 6.34*10^-3 8.73*10^-3 10.8*10^-3 15.1*10^-3

Contractionh 10*10^-3 17*10^-3 21*10^-3 27*10^-3 41*10^-3

V12/2g- V2

2/2g -8.93*10^-3 -14.34*10^-3 -18.73*10^-3 -23.8*10^-3 -35.1*10^-3

h +V12/2g- V22/2g 1.07*10^-3 2.66*10^-3 2.27*10^-3 3.2*10^-3 5.9*10^-3

Long Bend 1.5*10^-3 3*10^-3 5*10^-3 5*10^-3 8*10^-3

Short Bend 9*10^-3 14*10^-3 19 *10^-3 23*10^-3 34*10^-3

Elbow 14*10^-3 22 *10^-3 28*10^-3 36 *10^-3 52*10^-3

Miter Bend 19*10^-3 30*10^-3 40*10^-3 49 *10^-3 72*10^-3


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Table (4): Loss Coefficients for All Fittings Except Gate Valve


Q (m3/sec) 1.355*10^-4 1.715*10^-4 1.961*10^-4 2.21*10^-4 2.684*10^-4

V (m/s) 0.515 0.652 0.7456 0.840 1.020

V2/2g (m) 0.0135 0.0216 0.0283 0.0359 0.053

LossCoefficients

Enlargement 0.291 0.293 0.308

Contraction

Long Bend

Short Bend

Elbow

Mitre Bend

Table (5): Equivalent Minor Head Loss and Loss Coefficient for Gate Valve


50%O

pened

Q (m3/sec) 4.75*10^-4 4.08*10^-4 3.58*10^-4 3*10^-4 2.14*10^-4

V (m/sec) 1.8 1.55 1.36 1.14 0.813

V2/2g (m) 0.165 0.122 0.094 0.066 0.0336

Minor Head

Loss (m)1.01 0.74 0.59 0.4 0.2

Loss

Coefficient

70%O

pened

Q (m3/sec) 6.95*10^-4 5.878*10^-4 5.35*10^-4 4.622*10^-4 3.5*10^-4

V (m/sec) 2.642 2.231 2.034 1.756 1.33

V2/2g (m) 0.355 0.253 0.21 0.157 0.09

Minor Head

Loss (m)0.38 0.29 0.23 0.16 0.09

Loss

Coefficient

80%O

p

ened

Q (m3/sec) 7.21*10^-4 6.515*10^-4 5.94*10^-4 4.76*10^-4 4.133*10^-4

V (m/sec) 2.74 2.475 2.258 1.8 1.57

V

2

/2g (m) 0.382 0.3122 0.259 0.165 0.1256Minor Head

Loss (m)0.13 0.12 0.09 0.08 0.03

Loss

Coefficient


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0

0.005

0.01

0.015

0.02

0 0.01 0.02 0.03 0.04 0.05 0.06

MinorLo

ss(m)

Dynamic Head (m)

FIG(2): Dynamic Head Vs Minor Loss

Enlargement h

0

0.001

0.002

0.003

0.004

0.005

0.006

0.007

0 0.01 0.02 0.03 0.04 0.05 0.06

MinorLoss(m)

Dynamic Head (m)

FIG(3):Dynamic Head Vs Minor Loss

Contraction h

0

0.002

0.004

0.006

0.008

0.01

0 0.01 0.02 0.03 0.04 0.05 0.06

Mino

rLoss(m)

Dynamic Head (m)


Long Bend


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0

0.002

0.004

0.006

0.008

0.01

0 0.01 0.02 0.03 0.04 0.05 0.06

Min

orLoss(m)

Dynamic Head (m)

FIG(5):Dynamic Head Vs Minor Loss

Short Bend

0

0.001

0.002

0.003

0.004

0.005

0.006

0 0.01 0.02 0.03 0.04 0.05 0.06

MinorLoss(m)

Dynamic Head (m)


Elbow

0

0.002

0.004

0.006

0.008

0 0.01 0.02 0.03 0.04 0.05 0.06

MinorLoss(m)

Dynamic Head (m)


Miter Bend


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0.28

0.285

0.29

0.295

0.3

0.305

0.31

0 0.01 0.02 0.03 0.04 0.05 0.06

LossC

offiecient

Flow Rate

FIG(8): Head loss agnist dynamic head

Enlargement h

0

0.05

0.1

0.15

0 0.01 0.02 0.03 0.04 0.05 0.06

LossCoffiecient

Flow Rate


Contraction h

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.02 0.04 0.06

LossCoffiecient

Flow Rate


Short Bend


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0

0.05

0.1

0.15

0.2

0 0.01 0.02 0.03 0.04 0.05 0.06

LossCoffiecient

Flow Rate


Long Bend

0.134

0.136

0.138

0.14

0.142

0 0.01 0.02 0.03 0.04 0.05 0.06

LossCoffiecient

Flow Rate


Miter Bend

0.096

0.098

0.1

0.102

0.104

0 0.01 0.02 0.03 0.04 0.05 0.06

LossCoffiecient

Flow Rate


Elbow


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0

0.2

0.4

0.6

0.8

1

1.2

0 0.05 0.1 0.15 0.2

Head

Loss(m)

Dynamic Head (m)

FIG(14): Effect Of Flow Rate on Loss Cofficient

50% Opened

0

0.1

0.2

0.3

0.4

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4

HeadLoss(m)

Dynamic Head (m)

FIG(15): Effect Of Flow Rate on Loss Cofficient

70% Opened

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0 0.1 0.2 0.3 0.4 0.5

HeadLoss(m)

Dynamic Head (m)

FIG(16):Effect Of Flow Rate on Loss Cofficient

80% Opened


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6.Comments:It is recommended to make sure that there is no zero error. And it should to the

experimenter to see and analysis the changes of parameters during the

experiment by engineering sense and make comments.

Minor Losses Report

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