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INDEX

S.No NAME OF THE EXPERIMENT REMARKS

4 Thermal conductivity on lagged pipe

5Heat Transfer through Pin Fin

[Forced convection]

6 Thermal Conductivity

[by guarded hot plate method]

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THERMAL CONDUCTIVITY ON LAGGED PIPE

AIM :

To determine the Thermal Conductivity and Thermal Resistance of

the given insulating material using the Lagged Pipe Apparatus.

APPRATUS REQUIRED:

The insulation defined as a material, which retards the heat flow with

reasonable effectiveness. Heat is transferred through insulation by

conduction, convection and radiation or by the combination of these three.

There is no insulation, which is 100% effective to prevent the flow of heat

under temperature gradient.

The experimental set up in which the heat is transferred through

i l ti b d ti i d t d i th i t

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Knowing the thermal conductivity of one lagging material the thermal

conductivity of the other insulating material can be found.

FORMULAE:

Heat open rated Q = V x I watts.

Mean temperature = TA = (T1+T2+T3) / 3C= TB = (T4+T5 / 2C= TC = (T6+T7 / 2C

Thermal Resistance:

For Asbestos, RA = (TA TB) / Q K/W

For Saw Dust, RS = (TB TC) / Q K/W

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PROCEDURE:

1. First the test apparatus rig mu.st be switched on, and allowed for few

minutes till the temperature is gradually spread over the cylinder.

2. After few minute, note down the Voltage and Ammeter readings.

3. Regulate the regulator and display the temperature in display panel

for corresponding Intermediate surface temperatures and note down

in the tabular column.

4. Vary the ammeter reading and allow the apparatus for ten minutes

to come to a steady state and tabulate the readings to find out the

thermal conductivity and thermal resistance

5. Repeat this procedure and take three sets of readings.

RESULT

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LAGGED PIPE

SAW DUST

ASBESTOS

HEATER

ASBESTOS

T3

T6

T1

T4 T5

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HEAT TRANSFER THROUGH PIN FIN

FORCED CONVECTION APPARATUS

AIM:

To determine the heat transfer Co-efficient from pin fin by Natural

and Forced Convection using the Pin Fin Apparatus.

DESCRIPTION OF APPARATUS :

Consider a PIN-FIN having the shape of rod whose base is attached

to a wall at a surface temperature Ts, the fin is cooled along the axis by a

fluid at temperature TAMB. The fin has a uniform cross sectional area Ao is

made of material having a uniform thermal conductivity K and the average

h t t f ffi i t b t th f t th fl id W h ll

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w = 1000 kg / m3.3. Velocity flow rate

Q = Cd x A 2gH m3 / sec.Cd = 0.64, A = d2 / 4, (d = 18 mm)

4. Velocity of air V = Q / A

A = duct area = 150 mm x 100 mm

5. Reynolds number

Re = V Deq / Deq = 4A / p A Area of duct, P Perimeter of duct

6. Nusselt number

Nu = C (Re)n (Pr)

1/3

Refer HMT data book P 105 for values of C & n

7 Th ti l h t t f ffi i t

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PIN - FIN APPARATUS

HEATER

T7 T6 T5 T3 T2 T1T4

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THERMAL CONDUCTIVITY

[BY GUARDED HOT PLATE METHOD]

AIM:

To find the thermal conductivity of the test plate

DESCRIPTION OF APPARTUS:

The apparatus consists of a guarded hot plate and cold plate. A

specimen whose thermal conductivity is to be measured is sand witched

between the hot and cold plate. Both hot plate and guard heaters are

heated by electrical heaters. A small trough is attached to the cold plate to

hold coolant water circulation. A similar arrangement is made on the

other side of the heater as shown in the figure. Thermocouples are

attached to measure temperature in between the hot plate and specimen

plate, also cold plate and the specimen plate.

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FORMULAE:

Heat Transfer through the specimen plate at steady state

Q = KA (T / X)

Where,

Q - heat supplied to heater = V * I in Watts

A - Surface area of plate = D2 / 4, D = 250 mm

X - Thickness of test plate = 30 mm.

K - Thermal Conductivity of test plate in W / m-K

T - (TA TB) C.

Where, TA = [ T1 + T2 ] /2 C

TB = [ T3 + T4 ] /2 C

PROCEDURE:

1. The setup consists of a test plate placed about a heater plate and below a

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THERMAL CONDUCTIVITY APPARATUS

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TABULATION: Lagged Pipe Apparatus

Sl.

No.

Voltage(V)Volts

Current(I)Amps

Q=V*

IWatts Thermocouple Reading

(0C)

Thermal Resistance Thermal

Conductivity

T1

0C

T2

0C

T3

0C

T4

0C

T5

0C

T6

0C

T7

0C TA TB TC

Asbestos

RA

K / W

Saw dust

RS

K / W

Asbestos

KA

W/mK

Saw dust

KS

W/mK

1

2

3

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TABULATION: Pin Fin forced convection

Sl.

No.

Voltmeter

reading

Ammeter

reading Thermocouple Reading

(0C)Manometer Reading

VelocityNU havg

DischargeQ

m3 / SecT1

0C

T2

0C

T3

0C

T4

0C

T5

0C h1 h2

1

2

3

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TABULATION: Thermal conductivity by guarded hotplate method

Sl.

No.

Ammeter

R

eading

Vo

ltmeter

Re

ading Thermocouple Reading

(0C)

TA

0C

TB

0C

Thermal

Conductivity

W/mKT1

0C

T2

0C

T3

0C

T4

0C

1

2

3