Experiment 9

OBSERVATION AND CALCULATIONS:FOR WATER AT 30° C AND 1 ATM:

DENSITY=996kg/m KINEMATIC VISCOSITY=0.802*10^-6 DIAMETER 1=0.0183 m DIAMETER 2=0.0240m Re=ρDV/ʋ

AREA:A = 3.142 D2/ 4 A1= 3.142 (0.0183)2/ 4A1= 2.63 * 10-4 m2

A2=3.142(0.0240)2/4A2=0.000452 m2

For enlargement and contraction:For enlargement and contraction change in area results in an additional pressure head which has been added to head loss readings for enlargement and contraction in the following tables:h’=(V2

2/2g)-(V12/2g)

H1’=(0.3800433792/2*9.81)-(0.2209595962/2*9.81)= 0.00487308 H2’=(0.760086752/2*9.81)-( 0.4419191922/2*9.81)= 0.00019492

Fitting Manometer1

Manometer2

Head Lossh

Total head lossΔh

Volume Time

h₁ h₂ h₁-h₂ h+H1’ V tm m m m m³*E-3 sec

MITRE 2.42 2.18 0.24 0.24 1 10ELBOW 2.8 2.63 0.17 0.17 1 10

SHORT BEND 3 2.88 0.12 0.12 1 10ENLARGEMENT 3.06 3.18 -0.12 -0.1151269 1 10CONTRACTION 3.1 3.02 0.08 0.08487308 1 10

GAUGE VALUE READING= 0 mReynold’s No. Flow Rate Area Velocity Dynamic Head K Flow

Qt A=PI/4*d² V V²/2g Δh/(V²/2g)m³/s m² m/s m

440220.465 0.0001 0.0002631 0.3800433 0.019370203 12.39016 Turbulent440220.465 0.0001 0.0002631 0.3800433 0.019370203 8.776366 Turbulent440220.465 0.0001 0.0002631 0.3800433 0.019370203 6.195082 Turbulent335668.104 0.0001 0.0004525 0.2209595 0.011261957 -10.6552 Turbulent440220.465 0.0001 0.0002631 0.3800433 0.019370203 4.130054 Turbulent H3’=(0.950108442/2*9.81)-( 0.552398992/2*9.81)= 0.000304Fitting Manometer

1Manometer

2Head Loss

hTotal head

lossΔh

Volume Time

h₁ h₂ h₁-h₂ V tm m m m m³ *10^-3 sec

MITRE 1.99 1.46 0.53 0.53 2 10ELBOW 2.75 2.38 0.37 0.37 2 10

SHORT BEND 3.15 2.94 0.21 0.21 2 10ENLARGEMENT 3.25 3.44 -0.19 -0.18980507 2 10CONTRACTION 3.41 3.18 0.23 0.23019492 2 10

GAUGE VALUE READING= 0 mReynold’s No. Flow Rate Area Velocity Dynamic

HeadK Flow

Qt A=PI/4*d² V V²/2g Δh/(V²/2g)m³ m² m/s m

17274251.03 0.0002 0.000263128 0.760086758 0.038740406 13.68081 Turbulent17274251.03 0.0002 0.000263128 0.760086758 0.038740406 9.550752 Turbulent17274251.03 0.0002 0.000263128 0.760086758 0.038740406 5.420697 Turbulent13171616.41 0.0002 0.000452571 0.441919192 0.022523914 -8.43548 Turbulent17274251.03 0.0002 0.000263128 0.76008675 0.038740406 5.936954 Turbulent

Fitting Manometer1

Manometer2

Head Lossh

Total head lossΔh

Volume Time

h₁ h₂ h₁-h₂ V t

m m m m m³*10^-3 secMITRE 2.41 1.78 0.63 0.63 2.5 10ELBOW 3.30 2.86 0.44 0.44 2.5 10

SHORT BEND 3.75 3.50 0.25 0.25 2.5 10ENLARGEMENT 3.95 4.10 -0.15 -0.149695 2.5 10

CONTRACTION 4.05 3.76 0.29 0.290304 2.5 10GAUGE VALVE READING=0 m

Reynold’s No Flow Rate Area Velocity Dynamic Head

K Flow

Qt=V/t A=PI/4*d² V=Q/A V²/2g Δh/(V²/2g)m/s m² m/s m

21592813.79 0.00025 0.000263128 0.950108448 0.048425507

13.00967 Turbulent

21592813.79 0.00025 0.000263128 0.950108448 0.048425507

9.08612 Turbulent

21592813.79 0.00025 0.000263128 0.950108448 0.048425507

5.16256 Turbulent

16464520.52 0.00025 0.000452571 0.55239899 0.028154892

-5.32767 Turbulent

21592813.79 0.00025 0.000263128 0.950108448 0.048425507

5.98857 Turbulent

EXERCISE B: GATE VALVE EXPERIMENT

Rotations of gate valve

Pressure 1 Pressure2

ΔP Δh of water

Volume Time

P₁ P₂ ΔP*10.2 V tBar Bar Bar m m³ sec

1 0.7 1.1 0.4 4.08 0.004 102 1.1 1.62 0.52 5.304 0.003 103 1.62 2.25 0.63 6.426 0.002 10

1. DESCRIBE THE APPARATUS USED IN THIS EXPERIMENT.ANS. Energy Losses in Bends and Fittings Apparatus consists of:

Sudden Enlargement Sudden Contraction Long Bend Short Bend Elbow Bend Mitre Bend

Flow rate through the circuit is controlled by a flow control valve. Pressure tappings in the circuit are connected to a twelve bank manometer, which incorporates an air inlet/outlet valve in the top manifold. An air bleed screw facilitates connection to a hand pump. This enables the levels in the manometer bank to be adjusted to a convenient level to suit the system static pressure. A clamp which closes off the tappings to the mitre bend is introduced when experiments on the valve fitting are required. A differential pressure gauge gives a direct reading of losses through the gate valve.

2. WHAT ARE THE PRACTICAL USES OF STUDYING ENERGY LOSSES IN BEND?ANS. For any process, a certain range of flow rates is permitted for maximum efficiency, if the flow rate drops below that due to energy losses it disrupts the entire process and leads to loss of expenditure and inefficiency. Hence the study of losses occurring in a particular fitting is necessary to obtain required efficiency.

3. FOR EXERCISE A, PLOT GRAPHS OF HEAD LOSS AGAINST DYNAMIC HEAD, AND K AGAINST VOLUME FLOW RATE(QT).

HEAD LOSS AGAINST DYNAMIC HEAD:

Flow Rate

Area VelocityV=QT/A

DynamicHead

Reynold’s number

Flow K

Qt A=PI/4*d² V V²/2g Re=ρDV/ʋ Δh/(V²/2g)m/s m² m/s m

0.0004 0.00026313 1.520173517 0.117784277 34548502.07 Turbulent 34.63959780.0003 0.00026313 1.140130138 0.066253656 25911376.55 Turbulent 61.58150730.0002 0.00026313 0.760086758 0.029446069 17274251.03 Turbulent 138.558391

DYANAMIC HEADV2/2g

TOTAL HEAD LOSShΔ

m

m MITRE ELBOWSHORT BEND CONTRACTION

0.019370203 0.24 0.17 0.12 0.0848730.038740406 0.53 0.37 0.21 0.2301940.048425507 0.63 0.44 0.25 0.290304

DYANAMIC HEADV2/2g

TOTAL HEAD LOSShΔ

mm ENLARGEMENT

0.011261957 -0.115126

0.022523914 -0.189805

0.028154892 -0.149695

0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.05 0.055

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

HEAD LOSS AGAINST DYNAMIC HEAD

MITRE

ELBOW

SHORT BEND

CONTRACTION

ENLARGEMENT

DYNAMIC HEAD

HEAD

LOSS

LOSS COEFFICIENT AGAINST VOLUME FLOW RATE

FLOW RATEm3/sec

LOSS COEFFICIENTK

MITRE ELBOW SHORT BEND ENLARGEMENT CONTRACTION

0.0001 12.3901645 8.77636655 6.19508227 -10.655342 4.130054850.0002 13.6808067 9.55075183 5.42069699 -8.4354789 5.93695384

0.00025 13.0096728 9.08612066 5.16256856 -5.3276709 5.98857953

0.00008

0.0001

0.00012

0.00014

0.00016

0.00018

0.0002

0.00022

0.00024

0.00026

-15

-10

-5

0

5

10

15

20

LOSS COEFFICIENT AGAINST VOLUME FLOW RATE

MITREELBOWSHORT BENDENLARGMENTCONTRACTION

VOLUME FLOW RATE

LOSS

CO

EFFI

CIEN

T

4. FOR EXERCISE B, PLOT GRAPHS OF EQUIVALENT HEAD LOSS AGAINST DYNAMIC HEAD, AND K AGAINST QT.

EQUIVALENT HEAD LOSS AGAINST DYNAMIC HEAD

Head lossΔ h

Dynamic headv2/2g

4.08 0.117784277

5.304 0.066253656

6.426 0.029446069

3 3.5 4 4.5 5 5.5 6 6.5 70

0.02

0.04

0.06

0.08

0.1

0.12

0.14

EQUIVALENT HEAD LOSS AGAINST DYNAMIC HEAD

EQUIVALENT HEAD LOSS

DYN

AM

IC H

EAD

LOSS CO-EFFICIENT “K” AGAINST Q T:

Flow rateQt

m3/s

Loss coefficientK

0.0004 34.6395978

0.0003 80.0559595

0.0002 218.229466

0.00015 0.0002 0.00025 0.0003 0.00035 0.0004 0.000450

50

100

150

200

250

LOSS CO-EFFICIENT “K” AGAINST QT

Flow rateQt

LOSS

CO

-EFF

ICIE

NT

5. COMMENT ON ANY RELATIONSHIP NOTICED. WHAT IS THE DEPENDENCE OF HEAD LOSSES ACROSS PIPE FITTINGS UPON VELOCITY?

ANS. According to the observation table and graphs obtained we can establish that value of K decreases with increase in flow rate for some fittings. Besides this, the head loss in a particular fitting increases with increase in velocity.

6. EXAMINING THE REYNOLD’S NUMBER OBTAINED, ARE THE FLOWS LAMINAR OR TURBULENT?ANS. The Reynolds’ numbers are very high indicating TURBULENT FLOW.

7. IS IT JUSTIFIABLE TO TREAT THE LOSS CO-EFFICIENT AS CONSTANT FOR A GIVEN FITTING?ANS. Yes. It’s justifiable to assume loss-coefficient constant for a given fitting as it varies with velocity, flow rate and head losses.

8. IN EXERCISE B, HOW DOES THE LOSS CO-EFFICIENT FOR A GATE VALVE VARY WITH THE EXTENT OF OPENING THE VALVE?

ANS. The loss coefficient for gate valve increases with decrease in the extent of opening of the valve according to our observation this is also in accordance with the formula for loss coefficient as the flow rate is decreased (the valve is closed) the velocity decrease thus the loss coefficient increases.