experiment 9
TRANSCRIPT
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.