lab manual mech

1 WM MEC 102Mechanical Sciences II (Mechanical Engineering)

2010-2011

LABORATORY MANUAL

MEC 102

Mechanical Sciences II


2010-2011

Table of content

SL No Experiment Page No

1 To conduct tensile test on mild steel and cast iron specimens. 3

2 To conduct Impact test on mild steel and cast iron specimens. 4 to 5

3 To conduct Torsion test on mild steel and cast iron specimens. 6 to 7

4 To find out stiffness of spring and modulus of rigidity of spring wire material. 8

5 To measure the velocity of flow at different points using a Pitot tube . 9 to 10

6 To measure Coefficient of discharge through venturi meter and orifice meter. 11 to 12

7 To determine the loss coefficient for the pipe fittings. 13 to 15

8 To determine the loss of head in the fitting at the various water flow rates, and

determine losses due to friction in pipes .(Darcy Friction ).

16 to 17

9 To study heat transfer through insulating slab. 18 to 19

10 To study free and forced convection. 20 to 24

11 To find out the Stefan Boltzmann constant. 25 to 26

12 To study the Drop wise and Film wise condensation . 27 to 28


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Experiment: 1

Experiment: To conduct tensile test on Mild steel and cast iron specimens

Equipment to be used: Universal Testing Machine, Specimen of MS & CI, Scale, Vernier caliper

Learning Objective: To provides information related to the strength and ductility of metals under

direct tension stress.

Procedure:Measure the original length and diameter of the specimen. The length may either be

length of gauge section which is marked on the specimen with a preset punch or the local length

of the specimen. Insert the specimen into test machine. Begin the load application and record

load Vs elongation data. Measure elongation values with the help of dividers and a ruler.

Continue the test till fracture occurs. Measure the final length and diameter of specimen.

Scope of results to be reported:

Parameters:

A) Original dimensions:

Length= ----------------------

Diameter= ----------------------

Area= ----------------------

B) Final Dimensions:

Length= -----------------------

Diameter= -----------------------

Area= ------------------------

Plots:

Draw a graph: Stress Vs Strain and identify yeild point, ultimate tensile strength and E and %

elongation and % reduction in area. .

Result:

Average breaking Stress =

1. Ultimate Stress =

2. Average Percentage Elongation =

Cautions:

If the strain measuring device is an extensometer it should be removed before necking begins.


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Measuring deflection on scale carefully and accurately.


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Experiment: 2

Experiment: To conduct impact test on mild steel and cast iron specimens.

Equipment to be used: impact testing machine, Specimen of MS & CI, Steel.

Learning Objective:

An impact test signifies toughness of material that is ability of material to absorb energy during plastic

deformation. Static tension tests of un-notched specimens do not always reveal the susceptibility of a

metal to brittle fracture. This important factor is determined by impact test. Toughness takes into

account both the strength and ductility of the material. Several engineering materials have to withstand

impact or suddenly applied loads while in service.

Procedure:

A) Izod Test:

When the striking hammer (pendulum) in safe test position. Put the steel specimen on impact

testing machine’s anvil in such a way that the notch face the hammer and is 75% inside and

25% above the top surface of the slot .Bring the striking hammer to its top most striking

position unless it is already there and lock it at that position. Bring indicator of the machine to

zero. Release the hammer, It will fall due to gravity and break the specimen through its

momentum, the total energy is not absorbed by the specimen, the indicator stops moving, while

the pendulum falls back. Again bring the hammer to its idle position and back.

B) Charpy Test:

With the striking hammer (pendulum) in safe test positions, put the Steel specimen on impact

testing machine anvil in such a way that the notch faces opposite the hammer. Bring the

striking hammer to its top most striking position. Bring indicator of the machine to

zero.Release the hammer. It will fall due to gravity and break the specimen through its

momentum, the total energy is not absorbed by the specimen. Then it continues to swing. At its

topmost height after breaking the specimen, the indicator stops moving, While the pendulum

falls back. Note the indicator at that topmost final position.


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Scope of results and discussion:

a. For Izod Test:

Note the indicator at the topmost final position. Calculate energy.

b. For Charpy Test:

Note the indicator at the topmost final position. Calculate energy.

Caution:

Measure the dimensions of the specimen carefully.

Hold the specimen firmly.

Take the readings carefully.


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Experiment: 3

Experiment: To conduct Torsion test on mild steel and cast iron specimen.

Equipment to be Used: A Torsion testing Machine, Twist meter for measuring angle of twist, A

steel rule and Vernier caliper or micrometer

Learning Objective:

A torsion test is quite instrumental in determining the value of rigidity (ratio of shear stress to shear

strain) of a metallic specimen. The value of modulus of rigidity can be found out through observations

made during the experiment by using the torsion equation:

Where,

T = Torque applied

Ip = Polar moment of Inertia

C = Modulus of rigidity

I = Gauge length

l = gauge length

In the torque equipment one end of the specimen is held by a fixed support and the other end to a

pulley. The pulley provides the necessary torque to twist the rod by addition of weights (w). The twist

meter attached to the rod gives the angle of twist.

Procedure:

1. Prepare the testing machine by fixing the two twist meters at some constant lengths from fixed

support.

2. Measure the diameter of the pulley and the diameter of the rod and take the average.

3. Set the maximum load pointer to zero.

4. Set the protector to zero for convenience and clamp it by means of knurled screw.

5. Carry out straining by rotating the hand-wheel in either direction.

6. Add weights in the hanger stepwise to get a notable angle of twist for T1 and T2.


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7. Then load out to failure as to cause equal increments of strain reading.

8. Plot a torque- twist (T- θ) graph

9. Read off co-ordinates of a convenient point from the straight line portion of the torque twist (T-

θ) graph and calculate the value of C by using above relation.

Scope of Result and Discussion :

1. Gauge length of the specimen, l = …………

2. Diameter of the specimen, d = …………

3. Polar moment of inertia, Ip = ………….

4. Modulus of rigidity of the given specimen is _________ N/mm2

5. The graph between angle of twist and torque for the given specimen is plotted.

Cautions:

Measure the dimensions of the specimen carefully.

Measure the Angle of twist accurately for the corresponding value of Torque.


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Experiment no 4

Experiment: To determine the stiffness of the spring.

Equipment to be Used: Spring testing machine, Spring specimen, Vernier Caliper, Micrometer.

Learning Objective: To determine the stiffness of the spring.

Procedure:

1. Measure the diameter of the wire of the spring by using the micrometer.

2. Measure the diameter of spring coils by using the venire caliper.

3. Count the number of turns,

4. Insert the spring in the spring testing machine and load the spring by a suitable weight and note

the corresponding axial deflection in tension or compression.

5. Increase the load and take the corresponding axial deflection.

6. Plot a curve between load and deflection. The shape of the curve gives the stiffness of the

spring.

Scope of Results and Discussion :

1. Least Count of Micrometer = ___________________

2. Diameter of Spring wire, d = ___________________

3. Least count of Vernier caliper = ___________________

4. Diameter of the spring coil, D = ___________________

5. Mean coil diameter, Dm = D – d = _______________

6. Number of turns, n = ___________________

7. The value of spring constant of Closed coiled helical spring is ___________ N/mm.

8. Modulus of rigidity is ___________________________

Cautions:

1. Measure the dimensions of spring accurately.

2. Note the deflections accurately.

10 WM MEC 102Mechanical Sciences II (Mechanical

Engineering)

2010-2011

Experiment no 5

PITOT TUBE APPARATUS

Experiment :

To measure the velocity of flow at different points in a pipe.

Apparatus :-

Complete set up of Pitot tube apparatus

Stop Watch

The pitot tube consists of a capillary tube, bent at right angle. The lower end, which is bent

through 90º is directed in the up stream direction. The liquid rises up in the tube due to conversion of

kinetic energy into pressure energy. The velocity is determined by measuring the rise of liquid in the

tube.

Learning objective :-

To find the co-efficient of pitot tube

To find the point velocity at the centre of a tube for different flow rates

To plot velocity profile across the cross section of pipe

Out line of procedure :-

Switch on the Main Power Supply (220 Volts AC, 50 Hz).Switch on the Pump. Operate the

Flow Control Valve to regulate the flow of water in the Test Section. Open the Pressure Taps of

Manometer of related Test section very slowly to avoid the blow of water on manometer fluid. Now

open the Air release Valve provided on the Manometer Slowly to release the air in Manometer. When

there is no air in the manometer, close the Air release valves. Adjust water flow rate in desired with the

help of control valve.Set the Pitot tube at the centre of the Test section. Record the Manometer reading.

Measure the flow of water, discharge through desired test section using stop watch and Measuring

Tank. Now move the Pitot tube up & down on the same flow and note down the manometer readings to

find out the velocity at different points in pipe. Repeat the same procedure for different flow rates of

water operating Control valve and By-Pass valve.

Scope of result and discussion :-

Parameters

Calculate velocity at various points by moving the pitot tube UP & down

calculate coefficient of pitot tube

Plots :- Plot velocity profile

FORMULAE:

Discharge (Q): Velocity ,

Q = A x R V = Q/a (m/s)

t


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Actual Velocity

= Cv √ 2 g H m/s

H = 12.6 x h

Coefficient of Pitot Tube,

Cv = Q

a * √ 2 g H

DATA:

A = Area of measuring tank = 0.1 m2

a = Cross section area of test section/pipe = 13.6

g = Acceleration due to gravity =

9.81 m/sec2

ρm = Density of manometer fluid

ρw = Density of water

h = Manometer difference.

A = Area of Measuring Tank (m2)

R = Rise of Water level in Measuring Tank (m)

t = Time taken for Rise of water level in measuring tank (sec.)

Cv = Coefficient of Pitot Tube

a = Cross section area of Test Section

PRECAUTION

1. Do not run the pump at low voltage i.e. less than 180 Volts.

2. Never fully close the Delivery line and By-Pass line Valves simultaneously.

3. Always keep apparatus free from dust.

4. To prevent closing of moving parts, Run Pump at least once in a fortnight.

5. Frequently Grease/oil the rotating parts, once in three months.

6. Always use clean water.

7. It apparatus will not in use for more than one month, drain the apparatus completely.


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Experiment NO 6

ORIFICEMETER SET UP

Experiment :-

To measure discharge through Orifice meter.

Apparatus :-

The apparatus consists of a Venturi meter, and Orifice meter fitted in pipeline. The pipeline

is taken out from a common inlet. At the down stream end of the pipeline. Separate control valves are

provided to regulate the flow through the Venturi meter and orifice meter to conduct experiment

separately. Pressure tapings are taken out from inlet and throat of Venturi meter, inlet and outlet of

Orifice meter and are connected to a differential manometer. Discharge is measured with the help of

measuring tank and stop watch.


To determine the co-efficient of discharge through Venturi meter & Orifice meter.

To compare the discharge of the venturi meter and orifice meter

Out line of the procedure :-

Switch on the Pump and Operate the Flow Control Valve to regulate the flow of water in the

desired Test Section. Open the Pressure Taps of Manometer of related Test section very slowly to

avoid the blow of water on manometer fluid. Now open the Air release Valve provided on the

Manometer Slowly to release the air in Manometer. When there is no air in the manometer, close the

Air release valves. Adjust water flow rate in desired with the help of control valve. Record the

Manometer reading. Measure the flow of water, discharge through desired test section using stop watch

and Measuring Tank. Repeat the same procedure for different flow rates of water operating Control

valve and By-Pass valve. When experiment is over for one desired test section, open the By-pass Valve

fully then close the flow control valve of running test section and open the Control valve of second

desired test section and Repeat the same procedure for other test section .

Scope of Result and discussion :-

Parameters :-

To calculate the theoretical and actual discharge through a venturi meter and orifice meter and

hence find out the coefficient of discharge .

Plots :- Nil

Formula:-

For Orifice meter:

Theoretical discharge (Qt):

Qth = a1a2 √2gH H = 12.6 x h

√a12 – a2

2


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Actual discharge (Qa): Co- efficient of discharge (Cd):

Qa = A x R Cd = Qa/Qt

t

DATA:

A = 0.1 m2

s = Specific gravity of Hg = 13.6

g = Acceleration due to gravity = 9.81 m/sec2

For Orificemeter:

d1 = Dia inlet of Orificemeter = 25 mm

d2 = Dia. of Orificemeter Plate = 15 mm

a1 = π d12 /4 Area at Inlet of Orificemeter =

a2 = π d22 /4 Area of Orifice Plate =

Where

H = 12.6 x h

h = Pressure difference in m of Hg.

A = Area of Measuring Tank (m2)

R = Rise of Water level in Measuring Tank (m)

t = Time taken for Rise of water level in measuring tank (sec.)

Qa = Actual discharge

Qt = Theoretical discharge

s = Specific gravity of Hg

PRECAUTION

Do not run the pump at low voltage i.e. less than 180 Volts.

Never fully close the Delivery line and By-Pass line Valves simultaneously.

Always keep apparatus free from dust.

To prevent closing of moving parts, Run Pump at least once in a fortnight.

Frequently Grease/oil the rotating parts, once in three months.

Always use clean water.

It apparatus will not in use for more than one month, drain the apparatus completely.


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Experiment no 7

LOSSES DUE TO PIPE FITTINGS

Experiment: To determine the loss co-efficient for the pipe-fittings.

Apparatus: - Pipe fitting set up ,Stop watch

The apparatus consist of a ½ “ bend and elbow, a sudden expansion from ½ “ to I”

sudden contraction from I” to ½ “ and ½ “ ball valve and gate valve. Pressure tapings are provided

at inlet and outlet of these fittings at suitable distance. A differential manometer fitted in the line

gives pressure loss due to fittings. Supply to the pipeline is made through centrifugal pump, which

deliver water from sump tank. The flow of water in pipeline is regulated by means of Control valve

& By-Pass valve. Discharge is measured with the help of measuring tank and stop watch.

Learning Objective:

To determine the loss of head in the pipe fittings at the various water flow rates.

To study various types of pipe fittings

OUT LINE OF PROCEDURE:

Operate the Flow Control Valve to regulate the flow of water in the desired test Section.

Open the Pressure Taps of Manometer of related Test Section Very slowly to avoid the

blow of water on manometer fluid. Now open the Air release Valve provided on the

Manometer. Slowly to release the all in manometer. When there is no air in the manometer.

Close the Air release valves. Adjust water flow rate in desired section with the help on

Control Valve and record the Manometer reading. Measure the flow of water, discharge

through desired test section using Stop Watch and Measuring Tank. Repeat same procedure

for different flow rates of water. Operating Control Valve and By-Pass valve. Repeat the

above for each test section separately .When experiment is over, close all Manometers

Pressure Taps first, Switch off Pump and Power Supply to Panel.

Formulas

Loss of head due to change in cross-section, bends, elbows, valves and fittings of all type fall into the

category of minor losses in pipe lines. In long pipe lines the friction losses are much larger than these

minor losses and hence the latter are often neglected. But in shorter pipelines thief consideration is

necessary for the correct estimate of losses. When there is any type of bend in pipe, the velocity of flow

changes, due to which the separation of the flow from the boundary and also formation of eddies.

Takes place. Thus the energy is lost.

The losses of head due to bend in pipe.

hL = KL x V2

2g

The minor losses in contraction can be expressed as :


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hL = KL x V12

2g

The minor losses in enlargement can be expressed as:

hL = KL x (V1-V2)2

2g

Where

hL = Minor loss or head loss

KL = Loss coefficient

V = Velocity of fluid.

V1 = Velocity of fluid in pipe of small Diameter.

V2 = Velocity of fluid in pipe of large Diameter.

Loss of Head (for Contraction):

hL = KL x V12

2g

Loss Co-efficient:

KL = hL x 2g

V12

Loss of Head (for Expansion):

hL = KL x (V1-V2)2

2g

Change of Kinetic Energy:

C = (V1-V2)2

2g

Discharge:

Q = V

t

Volume:

v = A x R (m3)

Velocity:

V1 = Q (Velocity in ½” Pipe)

a1

V2 = Q (Velocity in 1” Pipe)

a2


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DATA:

A = Area of the measuring tank = 0.1 m2


g = Acceleration due to gravity = 9.81 m/sec2

Where

d1 = Dia of the smaller pipe =

d2 = Dia of the larger pipe =

a1 = Area of Cross section of small dia. pipe =

a2 = Area of Cross section of large dia. pipe =

∆H = 12.6 x h

V1 = Velocity of fluid in pipe of Small Diameter(m).

V2 = Velocity of fluid in pipe of Large Diameter (m).

V = Volume of water collected in measuring tank (m)

R = Rise of water level in measuring tank (m).

t = Time taken for R (sec.)

Scope of result and discussion:-

Parameters: - Find out the loss coefficient of Bend, Elbow, Ball valve ,gate valve

Differentiate between losses due to sudden enlargement and contraction

Plots :- Nil

PRECAUTION & MAINTENANCE INSTRUCTIONS:

1. Do not run the pump at low voltage i.e. less-than 180 volts.

2. Never fully closed, the Delivery line and By-Pas line Valves simultaneously.

3. Always keep apparatus free from dust.

4. To prevent clogging of moving parts. Run Pump at least once in a fortnight.

5. Frequently Grease/Oil the rotating parts, once in three months.

6. Always use clean water.

7. It apparatus will not in use for more than one month drain the apparatus completely.


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Experiment no 8

LOSSES DUE TO PIPE FRICTION

Experiment:-

To determine the loss of head in the fitting at the various water flow rates.

To determine the losses due to friction in pipe.

Apparatus:-

Pipe fitting setup ,Stop watch

Learning objective:-

To determine the loss co-efficient for the pipe fittings.

To determine the friction factor for Darcy –Weisbach equation.

Outline of the procedure:-

After Closing all pressure Taps of Manometer connected to different pipe-fittings. Switch

on the Pump. Operate the Flow Control Valve to regulate the flow of water in the desired

test Section. Open the Pressure Taps of Manometer of related Test Section very slowly to

avoid the blow of water on manometer fluid. Now open the Air release Valve provided on

the Manometer. Slowly to release the all in manometer. When there is no air in the

manometer. Close the Air release valves. Adjust water flow rate in desired section with the

help on Control Valve. Record the Manometer reading. Measure the flow of water,

discharge through desired test section using Stop Watch and Measuring Tank. Repeat same

procedure for different flow rates of water. Operating Control Valve and By-Pass valve.

When experiment is over for one desired test section, open the By-pass Valve fully then

close the flow control valve of running test section and open the Control valve of second

desired test section. When experiment is over, close all Manometers Pressure Taps first

Switch off Pump and Power Supply to Panel.

Formulas:-

Darcy-Weisbach equation is given by:

hf = 4f LV2

2 g d

where

hf = loss of head due to friction

f = Co-efficient of friction

L = distance between pressure point

V = Mean velocity of fluid

d = diameter of pipe

g = Acceleration due to Gravity

Discharge: Volume: Velocity:

Q = V v = A x R (m3) V1 = Q

(Velocity in ½” Pipe)


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a1 a1

V2 = Q (Velocity in 1” Pipe)

a2

DATA:

A = Area of the measuring tank = 0.1 m2


g = Acceleration due to gravity = 9.81

m/sec2

d1 = Dia of the smaller pipe = 12.5 mm

d2 = Dia of the larger pipe = 25 mm

a1 = Area of Cross section of small dia. pipe =

a2 = Area of Cross section of large dia. pipe =

∆H = 12.6 x h

L = Length between two pressure points = 1 m

Scope of result and discussions:-

Parameter: - To find out Darcy friction factor for pipe of 25 mm and 12.5 mm

Plots :- nil

PRECAUTION :-

Do not run the pump at low voltage i.e. less-than 180 volts.

Never fully closed, the Delivery line and By-Pas line Valves simultaneously.

Always keep apparatus free from dust.

To prevent clogging of moving parts. Run Pump at least once in a fortnight.

Frequently Grease/Oil the rotating parts, once in three months.

Always use clean water.

It apparatus will not in use for more than one month drain the apparatus completely.


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Experiment No 9

THERMAL CONDUCTIVITY OF INSULATING SLAB

Experiment :-

To study the heat transfer through insulating slab

Apparatus :- Complete set up of insulating slab apparatus

Stop Watch

The apparatus consists of a heater plate surrounded by a heating ring for stabilizing

the temp. of the primary heater and to prevent heat loss radially around its edges. The primary and

guard heater are made up of Mica sheets. These heaters together form a flat which together with the

upper and lower copper plates and rings form the heater plate assembly. Two thermocouples are used

to measure measure the hot face temp. at the upper and lower central heater assembly copper plates.

Two more thermocouples are used to check balance in both the heater inputs. Specimens are held

between the heater and cooling unit on each side of the apparatus. Thermocouple No.5 and 6 measure

the temperature of the upper cooling plate and lower cooling plate respectively. The heater plate

assembly together with the cooling plates and specimen held in position by 3 vertical studs and nuts on

a base plate. The cooling chamber is a composite assembly of grooved Aluminium casting and

Aluminium cover with entry & exit adapters for water inlet & outlet.

Learning objective

To find out the thermal conductivity of an insulating slab

OUT LINE OF PROCEDURE :

Adjust the heat input to central and guard heater through separate single phase supply line with a

dimmer stat in each line and is adjusted to maintain the desired temp. The guard heater input

is adjusted in such a way that there is no radial heat flow which is checked from

thermocouple readings and is adjusted accordingly. The input to the central heater and the

thermocouple readings are recorded after very 10 minutes till a reasonably steady state

condition is reached. The readings are recorded in the observation table. The final steady

state values are taken for calculations.

Scope of Result and discussion :-

Parameter :- Calculate the thermal conductivity of insulating slab

Identify the difference between insulators and conductors

Plot :- Nil

Data :

Specimen : Dia 180 mm Thickness 12 mm (approx.)

Central Heater : Dia 100 mm sandwiched between copper plates

Ring Guard Heater : Width 35 mm sandwiched between copper rings

Cooling Chamber : Made of Aluminium for water circulation, 2 Nos.

Insulation : Bags filled with glass wool

Control Panel : Digital Voltmeter (0-300 V)


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Digital Ammeter (0-2 A)

Dimmer stat (0-230 V), 2 A (2 Nos.)

Digital Temp. Indicator (0-200º C) with

multi channel switch

ON/OFF switch, mains indicator, etc.

Temperature Sensors : RTD PT-100 type (6 Nos.)

FORMULAE :

Heat Input , Q = V x I (For Central Heater)

As heat is divided into two parts

Qact = Q/2

Area, A = π/4 D2 , m

2 (D=100 mm)

K = Qact x X (X = 12 mm)

A (Th – Tc)

Where,

X = Thickness of the insulating material

Th = Temperature of the hot plate

Tc = Temperature of cold plate

Thermal Conductivity

K = q L . , W/m-K …………………(1)

A (Th – Tc)

where

K = Thermal conductivity of Sample, W/m-K

Q = Heat flow in the specimen, Watts

A = Metering area of the specimen, m

Th = Hot plate temp, ºC

Tc = Cold plate temp, ºC

x = Thickness of the specimen, m

PRECAUTIONS :-

1. Never run the apparatus if the power supply is less than 180 volts and above 230 volts.

2. Use stabilized A.C. single phase supply only.

3. Never switch ON mains power supply before ensuring that all the ON/OFF switches given

on the panel are at OFF position.

4. Keep all the assembly undisturbed.

5. Operate selector switch of temperature indicator gently.

6. Always keep the apparatus free from dust.


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Experiment No 10

HEAT TRANSFER THROUGH A PIN FIN

Experiment :- TO Study free and forced convection

Apparatus:- Complete set up of pin fin apparatus

Stop Watch

A brass fin of circular cross section is fitted along a rectangular duct. The other end of

the duct is connected to the suction side of a blower and the air flows past the fin perpendicular to its

axis. One end of the fin projects outside the duct and is heated by a heater. Temperatures at five points

along the length of the fin are measured by RTD PT-100 type temperature sensors. The flow rate is

measured by an orifice meter fitted on the delivery side of the blower.

Learning Objective :

To study the temp. distribution along the length of a pin fin under free and forced convection

heat transfer.

To study the importance of Prandlts’s No. Grashof No. Nusselt No in heat transfer

Out line of procedure:-

NATURAL OR FREE CONVECTION:-

Start heating the fin by switching ON the heater element and adjust the voltage upto a certain level.

Note down the temp. sensor readings No. 1 to 5.When steady state is reached, record the

final readings of Temp. Sensor No. 1 to 5 and also the ambient temp. readings. i.e. Temp.

Sensor No.6

FORCED CONVECTION

Start heating the fins by switching ON the heater and adjust the dimmer stat voltage and

start the blower and adjust the difference of level in the manometer H. Note down the temp. sensor

readings (1) to (5) at a time interval of 5 minutes. When the steady state is reached, record the final

readings (1) to (5) and also record the ambient temp. readings by (6)Repeat the same experiment with

another H.

Data :

Duct Size : 150 x 100 x 1000 mm

Diameter of the fin : 12.7 mm : Length of the fin :

125 mm

Diameter of the Orifice : 35 mm

Dia. of the delivery Pipe : 70 mm

Coefficient of Discharge, Co : 0.64

Control Panel : Digital Voltmeter

(0-300 V)

Digital Ammeter (0-

2 A)


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Dimmer stat (0-230

V), 2 A

Digital Temp. Indicator (0-200º C)

ON/OFF switch,

mains indicator, etc.

Temperature Sensors : RTD PT-100 type (6 Nos.)


Parameters :- Identify the difference of free and forced convection .

Calculate the temp profile experimentally and verify with theoretical

Plots :- Draw the temp profile

Calculations

Mean Temp. of the Fin, Tm = (T1+ T2+ T3+ T4+ T5)/5

Ambient Air Temp. T6 = Tf = ºC

Mean Fluid Temp. Tmf = (Tm+ Tf)/2

Properties of air at mean fluid temp.

Density, ρ = ____________kg/m3

Viscosity µ = ____________kg/ms

Kinematic Viscosity, ν = ___________m2/sec

Thermal Conductivity, K = ____________kcal/hrmºC

Specific Heat Cp = ____________kcal/kgºC

Prandlts’s No. Pr = Cp µ

K

β = 1/( Tmf + 273.15)

Grashof No. Gf = (g β D3 Δ T)/ ν

2

ΔT = (Tm -Tf)

For Free Convection :

Nusselt No. Nu= 0.53 (Gr Pr)1/4

= h D / kair


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Free convective heat transfer coeff,. h = Nu kair / D

Fin Parameter, m = √h C / kb

A

Thermal Conductivity of brass kb = 95 kcal/hrmºC

Perimeter C = π D

Cross sectional area of fin A = π D2

Fin Dia, D = 12.7 x 10-3

m

Fin Length L = 125 x 10-3

m

Fin effectiveness ε = tan h m L/ mL

Parameter H = h / kb m

Theoretical Temp. Profile within the Fin =

θ/θ0 = [T-Tf]/[Tb-Tf] = [cos h m(L-x)+ H sin h m (L-x)]/[ cos h m L + H sin h mL]

Taking Base Temp. Tb = T1

FOR FORCED CONVECTION:-

Orifice Coefficient Co = 0.64

Volumetric Flow of Air, Q = Co(π/4)d2

√ [ 2g ΔH]

Δ H = [ h (ρw/ρa -1)] m of air

100

Velocity of Air, V = Q/a at ambient fluid temp.

ρw = 1000 kg/m3

ρa = 1.21 kg/m3

Velocity of air at mean fluid temp. (Tmf) = V1 = V x (Tmf + 273.15)/(Tf + 273.15)

Mean Temp. of the Fin, Tm = (T1+ T2+ T3+ T4+ T5)/5

Ambient Air Temp. T6 = Tf = ºC

Mean Fluid Temp. Tmf = (Tm+ Tf)/2


Engineering)

2010-2011

Properties of air at mean fluid temp.

Density, ρ = ____________kg/m3

Viscosity µ = ____________kg/ms

Kinematic Viscosity, ν = µ/ ρ __________ m2/sec

Thermal Conductivity, K = ____________kcal/hrmºC

Specific Heat Cp = ____________kcal/kgºC

Prandlts’s No. Pr = Cp µ

K

Using co-relation for Forced convection:

Nusselt No.Nu = 0.615 (Re)0.466

Nu = h D / Kair

Heat Transfer Coefficient, h = Nu Kair / D

Fin Parameter m = √h C / Kb A

Fin effectiveness ε = tan h m L/ mL

Parameter H = h / kb m

Theoretical Temp. Profile within the Fin =

θ/θ0 = [T-Tf]/[Tb-Tf] = [cos h m(L-x)+ H sin h m (L-x)]/[ cos h m L + H sin h mL]

Taking Base Temp. Tb = T1

Where,

Kb = thermal conductivity of Brass fin

C = Perimeter

Tm = Fin mean temp.

Tf = Fin temp. at any point

X = Distance of sensor at the base of the fin

g = Acc. Due to gavity

D = Fin Diameter


Engineering)

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Gr = Grashof Number

Pr = Prandlt Number

Nu = Nusselt Number

Kair = Air conductivity at mean temp.

h = heat transfer coefficient

m = Fin perimeter

A = Cross sectional are of Fin

L = Fin Length

ε = Fin effectiveness

PRECAUTIONS

Never run the apparatus if the power supply is less than 180 volts and above 230 volts.

Use stabilized A.C. single phase supply only.

Never switch ON mains power supply before ensuring that all the ON/OFF switches given on

the panel are at OFF position.

Keep all the assembly undisturbed.

Operate selector switch of temperature indicator gently.

Always keep the apparatus free from dust.


Engineering)

2010-2011

Experiment No 11

STEFAN BOLTZMANN APPARATUS

Experiment :-

To find out the Stefan Boltzmann constant

Apparatus :-

The apparatus is centered on a flanged copper hemisphere B fixed on a flat non-conducting

plate A. The outer surface of B is enclosed in a metal water jacket used to heat B to some suitable

constant temp. One RTD PT-100 type temperature sensor is attached to the inner wall of hemisphere B

to measure its temperature and to be read by a temperature indicator. The Disc D, which is mounted in

an insulating Bakelite sleeves S is fitted in a hole drilled in the center of the base plate A. A chrome

Alumel temperature sensor is used to measure the temperature of D i.e. TD. The temperature sensor is

mounted on the disc to study the rise of its temperature. When the disc is inserted at the temperature

TD (TD < T) (i.e. the temp. of the enclose) the response of temperature change of disc with time is

used to calculate the Stefan Boltzmann Constant.( Stefan Boltzmann Constant and has the value of

4.88 x 10-8

kcal/hrm2K

4 or 5.67 x 10

-8 W/m

2K

4)


To Study radiation mode of heat transfer

To calculate Stefan Boltzmann constant experimentally and compare it with theoretical

value .

Out line of the procedure :-

Heat the water in the tank by the immersion heater up to a certain temp. The disc D is removed

before pouring the hot water in the jacket. The hot water is poured in the water jacket. The

hemispherical enclosure B and A will come to some uniform temp. in a short time after filling

the hot water in the jacket. The thermal inertia of hot water is quite adequate to prevent

significant cooling in the time required to conduct the experiment. The enclosure will soon

come to equilibrium conditions. The disc, D is now inserted in A at a time when its temp. is TD.

Start noting the temperature change for every 30 sec.


Parameters:

calculate the rise in temp with time (for each 30 s gap ) and find out the slope of graph and

then calculate Stefan Boltzmann constant.

Plot :-

Plot the graph between time (T) Vs temp. (t) and determine the slope (dT/dt)t=0

Formula:-

σ = M.S ((dT/dt)t=0)

AD ( T4 – TD

4 )

Where,


Engineering)

2010-2011

M = Mass of the disc (kg) = ………………….

S = Specific heat of disc = 0.1 kcal/kgºC

AD = Area of the disc = ………………….m2

D = Diameter of the disc =………………….m

T = Final Temp. of the disc ºC

TD = Initial temp. of the disc.ºC

Data:-

Hemispherical enclosure Dia : 200 mm

Suitable sized water jacket for Hemisphere

Base Plate : Bakelite ( 250 mm)

Test Disc Dia : 20 mm

Mass of test Disc : 3 gm

Specific Heat, S of test disc : 0.1 kcal/kg-ºC

Number of temp. sensor mounted on B : 1

Number of temp. sensor mounted on D : 1

Control Panel : Digital Voltmeter

(0-300 V)

Digital Ammeter (0-

2 A)

Dimmer stat (0-230

V), 2 A (2 Nos.)

Digital Temp.

Indicator (0-200º C)

ON/OFF switch,

mains indicator, etc.

Immersion wtarer heater of suitable capacity and tank for hot water, 1.5 Kw

PRECAUTIONS

Never run the apparatus if the power supply is less than 180 volts and above 230 volts.

Use stabilized A.C. single phase supply only.

Never switch ON mains power supply before ensuring that all the ON/OFF switches given on

the panel are at OFF position.


Operate selector switch of temperature indicator gently.



Engineering)

2010-2011

Experiment No 12

Drop Wise Film Wise Condensation

Experiment: To study the heat transfer in the process of condensation .

Apparatus: - Drop wise and film wise apparatus complete set up ,Stop watch

The apparatus consist of a metallic container in which steam generation takes place .The

lower portion houses suitable electric heater for steam generation . A special arrangement is

provided for the container for filling water . The glass cylinder houses two water cooled copper

condensers,one of which is chromium plated to promote drop wise condensation and the other is

in its natural state to give film wise condensation. A connection for pressure gauge is provided

.Separate connections of two condensers for passing water are provided .One Rota meter with

appropriate piping can be used for measuring water flow rate in one of the condensers under test .

A digital temperature indicator provided has multi point connections ,which measures temperatures

of steam ,temp of two condensers ,water inlet and outlet temperature of condenser water flow .

Learning Objective:

To determine the heat transfer coefficient for drop wise and film wise condensation process .

To Differentiate the drop wise and film wise condensation process.

OUT LINE OF PROCEDURE:

Operate the Rota meter Valve to regulate the flow of water in the two condensers .Fill the

water in boiler tank up to desired level and start the heater of boiler .when the desired

pressure is achieved the steam valve is regulated and steam is made to flow through glass

tube containg the condensers. Allow for some time and then note down temp of water inlet

/outlet of both condensers. Measure the condensate formed by using measuring flask verse

time. Repeat same procedure for different flow rates of water, Operating Control Valve and

By-Pass valve. When experiment is over, close all valves .remove left over water from

boiler after switching off the heater . Switch off Pump and Power Supply to Panel.

Specifications :-

Condensers : One chromium plated for drop wise condensation

One natural finish for film wise condensation

Dimensions : 19 mm outer dia, 150 mm length , fabricated from

copper with reverse flow in concentric tubes ,filled with

temp sensors for surface temp measurement

Instrumentation : Temp indicator digital 0-200 with multi channel

switch type RTD PT -100 type

Rota meter for measuring water flow rate

Pressure gauge: Dial type 0-2 kg/cm2

Inside diameter of condenser ,Di = 19 mm

Outside Dia of condenser DO = 17 mm

Length of condenser L = 150 mm

Acceleration due to gravity g = 9.8 mm


Engineering)

2010-2011

Scope of result and discussion:-

Study drop wise and film wise condensation on the two tubes physically .

Precaution :-

Use the stabilize single phase AC supply only.

Never switch on mains power supply before ensuring that all the on/off switches given on the

panel are at off position .

Voltage to heater should be given slowly.


Never run the apparatus if the power supply is less than 180 volts and above 240 volts .

Operate selector switch of temp indicator gently.

Do not start heater supply unless water is filled in the test unit.


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