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THERMAL ENGINEERING LAB II

LIST OF EXPERIMENTS

HEAT TRANSFER

1. Thermal conductivity measurement by guarded plate method

2. Thermal conductivity of pipe insulation using lagged pipe apparatus

3. Natural convection heat transfer from a vertical cylinder

4. Forced convection inside tube

5. Heat transfer from pin-fin (natural & forced convection modes)

6. Determination of Stefan-Boltzmann constant

7. Determination of emissivity of a grey surface

8. Effectiveness of Parallel/counter flow heat exchanger

REFRIGERATION AND AIR CONDITIONING

1. Determination of COP of a refrigeration system

2. Experiments on air-conditioning system

3. Performance test on single/two stage reciprocating air compressor.

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Expt. No : Thermal conductivity measurement by guarded

plate methodDate :

AIM:

To measure the thermal conductivity of the specimen using guarded plate apparatus.PROCEDURE:1.

Before start the experiment check the electrical supply and water supply.2. Switch on the power supply and set the heater input to desire value.3. Wait till the steady state temperature is reached.

4. Note down the following readings5.

Ammeter reading

6.

Voltmeter reading7. Temperature at various points8. Vary the heater input to increase the temperature.

9. Wait till the steady state temperature is reached.

10.

Note down the procedure at different temperature.11.

After complete the readings calculate the thermal conductivity of the specimen.

SPECIFICATION:Material : Copper

Diameter : 125 mmThickness : 3 mm

Guarded plate:Material : copperInner diameter : 140 mm

Outer diameter : 200 mmThickness : 3 mm

Specimen Plate:Material : WoodDiameter : 200 mm

Thickness : 6 mmWater Bath:

Material : Mild steelDiameter : 200 mmHeight : 50 mm

Thermocouple:Type : J Range : 1000 C

TABULATION

SI.NOVoltage

(v)

Current

(amps)

Temperature of circular

plate(C)

Avg.temp

Tc(C)

Temperature of

specimen(C)

Avg.temp

Ts(C)

T1 T2 T3 T4 T5 T6

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FORMULA:Power Input

Q=V A (W) (Since heat flows on either side of the heater)2

Where,

V = voltage in voltsA = Current in Amps

SKETCH OF GAURDED PLATE SETUP

(TC-TS) C

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CALCULATION

RESULT:

Thus the thermal conductivity of the specimen is calculated.

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Expt. No :

Date :

THERMAL CONDUCTIVITY OF PIPE INSULATION

USING LAGGED PIPE APPARATUS

AIM

To conduct calculate the thermal conductivity of saw dust using lagged pipe

apparatus.

PROCEDURE:

1. Before switch on the supply check the electrical supply and set the heaterregulator in

2. minimum position.

3.

Switch on the electrical supply and varry the heater regulator to supplyvoltage to the

4. heater.5. Wait till the steady temperature is reached.

6.Note down the following readings.a. Ammeter reading

b. Voltmeter readingc. Temperature at various points

7. Vary the heater regulator to increase the temperature8. Wait till the steady state temperature is reached

9.

Note the above mentioned readings10.Repeat the procedure at different temperature.

11.Calculate the thermal conductivity of saw dust.

SPECIFICATION:

Heater:Type : Rod

Diameter : 20 mmLength : 500 mmInput : 230 V AC

Asbestos lagging:Inner Diameter : 20 mm

Outer Diameter : 80 mmThermocouple:Type : J

Range : 1000 C

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Cut section of Lagged pipe

T7T8

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CALCULATION

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RESULT:Thus thermal conductivity of saw dust is calculated using lagged pipe apparatus.

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Expt. No :

Date :

Natural convection heat transfer from a vertical cylinder

AIM:

To determine the convective heat transfer coefficient for a heated vertical cylinder innatural convection.PRACTICAL RELEVANCE:

Free or natural convection is the principal mode of heat transfer from transmissionlines, pipes, refrigerating coils, hot radiators, buildings and many other practical situat ions in

everyday life.

PROCEDURE:1.

Note down the specification of all the instruments provided on the panel and also the

length (L) and diameter (D) of the metallic tube.

2.Switch on the heater and heater and adjust the heating rate to a suitable level (VI).

3.

Wait for some time to ensure the unit to reach steady state.

4.

At steady state record the voltage and current readings and the temperature T 4

through T6

5.Repeat the experiment for a different heat rate.

SKETCH OF NATURAL CONVECTION ARRANGEMENT

T6

T5

T4

T3

T2

T1

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TABULATION

S.noVolts

(v)Current(amps)

Temperature along thecylinder

Avg.Temp ofcylinder

TC (C)

Temperature of air

Avg.Tempof air

Ta (C) T2(C)

T3(C)

T4(C)

T5(C)

T1(C)

T6(C)

FORMULA USED:

(i) Experimental

Q=hAT

A= dl

Q=VI

Where,

Q = Heat transfer rate, W

A = Area of heat transfer, m2

h = convective heat transfer coefficient, W/m2

Cd = diameter of vertical cylinder, mm

l = length of vertical cylinder, mm

T = temperature difference(Tc-Ta)

V = Voltage, volts

I = Current, Amps.

(ii) TheoreticalNu=h1/K

Gr = g 13

T/2

Where,Nu = Nusselt number

K = Thermal conductivity, W/mKGr = Grasiffs number

g = Acceleratin due to gravity. m/s2

= coefficient of expansion

= Kinematic viscosity

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CALCULATION

RESULTThus the convection heat transfer coefficient of heated vertical cylinder is

h = W/m

2

K (By experimental)h = W/m2 K (By Theoretical)

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Expt. No :Date :

FORCED CONVECTION INSIDE TUBE

AIM:

To measure heat transfer co-efficient using forced convection method.

PROCEDURE:1. Check electrical supply before start the experiment2. Set the heater input to zero position and then switch on the power supply3. Set the air supply to desire level then set the heater input to desire level

4. Wait till the steady state temperature is reached5. Note the following readings

* Amps rating in ammeter* Voltage in voltmeter* Temperature at various point using temperature indicator

* Manometer reading6. Repeat the procedure at different heater input.

7. After complete the reading calculate the heat transfer co - efficient.

SPECIFICATION:

BlowerPower - 420 wattsSpeed - 2800 rpm

HeaterType - Coil

Power - 500 W

OrificeInlet dia - 40 mm

Orifice dia - 20 mmCopper tube

Diameter - 53 mmLength - 500 mm

SKETCH OF FORCED CONVECTON SET UP

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CALCULATION

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RESULT:Thus the heat transfer co-efficient is measured by using the forced convection method.

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Expt. No :

Date :

Heat transfer from pin-fin (natural & forced convection

modes)AIM:

To determine the fin efficiency using pin - fin apparatus.PROCEDURE:1.

Check the electrical supply and then set the heater input as zero.2. Switch on the power supply and run the blower at minimum speed.3. Set the heater input at desire position.

4. Wait till the steady state temperature is reached.5.

Now note down the following readings.

6.

Temperature at various point using temperature indicator.7. Water level on U - tube manometer.8. Ammeter reading.

9. Voltmeter reading.

10.

Increase the heat supplied by heater using regulator.11.

Wait till the steady state temperature is reached.12.Note the above mentioned readings.13.Repeat the procedure at different temperature.

14.After complete the reading calculate the efficient of the fin.SPECIFICATION:Pin - Fin:

Material : BrassLength : 145 mm

Diameter : 12 mmDistance between

each thermocouple : 20 mmDuct:Width : 150 mm

Height : 100 mmOrifice meter:Inlet diameter : 40 mm

Orifice diameter : 20 mmOutlet diameter : 40 mm

Thermocouple:Type : JRange : 1000

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RESULT:Thus the efficiency of the fin is calculated using pin - fin apparatus.

Type of convection Efficiency Effectiveness

Natural

Forced

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Expt. No :

Date :

DETERMINATION OF STEFAN-BOLTZMANN

CONSTANT

AIM:To calculate the stefan Boltzman constant using stefan - Boltzman apparatus.

PROCEDURE:1. Check the electrical supply and water supply.

2. Supply the water to the heater and then switch on the heater.3.

open the bottom plate of the hemisphere.

4.

Wait till the steady state temperature is reached.5. Now colse the bottom plate of the hemisphere and switch on the buzzer.6. Note sown the temperature at various points.

7. Each time buzzer on note down the temperature at various points.

8.

When bottom plate reaches steady state temperature complete the reading.9.

Draw the graph between time and temperature of the bottom plate find slope dT/dt.10.After complete the reading find stefan boltzman constant.

SPECIFICATION:Hemisphere:Material : Aluminimum

Inner diameter : 140 mmOuter diameter : 200 mm

Water Heater:Power : 3 kW

Capacity : 1 literInput : 230 V ACThermocouple :

Type : JRange : 1000 CSmall Plate:

Material : DigitalInner diameter : 140 mm

Outer diameter : 200 mm

SKETCH OF STEFAN BOLTZMAN APPARATUS

Hot waterline

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TABULATIONSI.NO Hemisphere

Temperature

(C)

Avg Temp ofHemisphere

(C) Th

Bottom platetemperature

(C) T4

Steady statetemperature of

plate Tp

T1 T2 T3

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CALCULATION

GRAPH:Time Vs temperature.

RESULT:Thus stefan Boltzman constant is find using stefan apparatus.

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Expt. No :

Date :

DETERMINATION OF EMISSIVITY OF A GREY SURFACEAIM:To measurement the emissivity of the test plate using emissivity measurement apparatus.

PROCEDURE:

1.

Before start the experiment check the power supply.2. Set the heater regulator in minimum position and then switch on the power supply.3. Wait till steady state temperature reached.

4. Note down the following readings5.

Voltmeter reading6. Ammeter reading

7. Temperature on each thermocouple point.8. Now increase the supply to the heater by using regulator.

9. Wait till the steady state temperature is reached.10.Note down the above mentioned readings.11.Repeat the procedure at different temperature.

12.

Calculate the emissitivity of test plateSPECIFICATION:

Black plate:Material : AluminiumDiameter : 150 mm

Thickness : 3 mmTest plate:

Material : AluminiumDiameter : 150 mmThickness : 3 mm

Heater:Type : Coil

Input : 230 V ACThermocouple:Type : J

Range : 500 CAmmeter:

Type : DigitalRange : 0 - 2 AVoltmeter:

Type : Digital

Range : 0 - 300 V AC

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S.NO

Voltmeter

(V)

Ammeter

(A)

Test p lateTemperature

(C)

Avg.temp

(C)(Tp)

Chambertemp

(C)

(T4)

Test plateTemperature(Tb)

(C)

Avg.temp

(C)(Tb)

Emissivityof test

plate()T1 T2 T3 T5 T6 T7

Formula:

Emissivity of test plate

Formula used:Tb

4-T

4

s=Tp

4-T

4

Where,

s = Emissivity of test surfacesTb = Means temperature black surfaceTp = Means temperature polished surface

T = Ambient temperature T4

CALCULATION

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RESULT:Thus the emissivity of the test plate is measured using emiss ivity measurement apparatus.

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Expt. No :

Date :

EFFECTIVENESS OF PARALLEL/COUNTER FLOW

HEAT EXCHANGER

Experiment - 1:AIM:To calculate heat transfer co-efficient in parallel flow heat exchanger.

PROCEDURE:1. Check electrical supply and water supply.2. Set the heater input to zero position.3. Supply water to hot water pipe and cold water pipe.

4. Open valve2 and valve 4 then close valve1, and valve 3.5. Set the heater input to desire level.

6. Wait till the steady state temperature condition.7. Note the following reading

* Flow rate of hot water and cold water.

* Temperature displayed in temperature indicator.* Ammeter reading

* Voltmeter reading.8. Repeat the procedure at different heater input.9. After complete the reading calculate the heat transfer co-efficient.

Hot Water Tube:Length : 1210 mmDiameter : 28 mm

Cold water Tube

Length : 1210 mmDiameter:18mm

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Mean Temperature of Hot WaterMean Temperature of cold

Water

Mass flow rate of hot water

V h = Volume of hot water in liters

t h= Time taken in hour

h = Density of water at T h [from Data book] kg/m3

Mass flow rate of cold water

Vc = Volume of cold water in litres

tc = Time taken in hour

c = Density of water at Tc [from Data book] kg/m3

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CALCULATION

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RESULT:

Thus heat transfer co-efficient is calculated in parallel flow heat exchanger.

Experiment - 2:

AIM:To calculate heat transfer co-efficient in counter flow heat exchanger.

PROCEDURE:1. Check electrical supply and water supply.2. Set the heater input to zero position.

3. Supply water to hot water pipe and cold water pipe.4. Open valve1 and valve 3 then close valve2, and valve 4.

5. Set the heater input to desire level.6. Wait till the steady state temperature condition.7. Note the following reading

* Flow rate of hot water and cold water.* temperature displayed in temperature indicator.

* Ammeter reading* Voltmeter reading.

8. Repeat the procedure at different heater input.

9. After complete the reading calculate the heat transfer co-efficient.

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Mass flow rate of hot water

Vh = Volume of hot water in litersth= Time taken in hour

h= Density of water at Th [from Data book] kg/m3

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CALCULATION

RESULT:

Thus heat transfer co-efficient is calculated in counter flow heat exchanger.

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Expt. No :

Date :

DETERMINATION OF COP OF A REFRIGERATION

SYSTEMAIM :

To measure COP of the vapor compression refrigeration system.PROCEDURE1. Check the electrical supply and pour water to the evaporator to desire level.2. Switch on the power supply.3. Allow refrigerant to flow through thermo expansion valve or capillary tube.

4. Set the flow to desire level and wait till the steady state temperature is reached.5. Note the following readings.

* Temperature at various points* Pressure indicated on pressure gauge* Power consumption by compressor

* Power consumption by condenser

6. Repeat the procedure at different flow rate.7. After complete the read ingcalculateCOP.

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CALCULATION:

RESULT:Thus the cop of the vapor compression refrigeration system is measured.

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Expt. No :Date :

EXPERIMENTS ON AIR-CONDITIONING SYSTEM

AIM:To determine co-efficient of performance of the air conditioning system.

PROCEDURE:1. Check the electrical supply before start the experiment.

2. Switch ON the power supply and switch ON the condenser coding coil andcompressor.3. Wait till the steady state temperature.

4. Note the following reading* Temperature displayed in the indicator.

* Dry bulb and wet bulb temperature at different location.* Flow rate of refrigerant using rotameter.* Power consumption by the compressor

* Overall power consumption.* Pressure at different points.

5. After complete the reading switch OFF the compressor, condenser and cooling coil.6. Now calculate the co-efficient of performance of the air conditioning system.SPECIFICATION:

Compressor:Type : HermaticCapacity : 2 ton

Refrigerant : R 134 a

Condensor:Power : 75 WSpeed : 1350 rpm

SKETCH OF AIR CONDITIONER TEST RIG

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CALCULATION

RESULT: