7/30/2019 ME1324-Hmt Group 3

1/9

INDEX

S.No NAME OF THE EXPERIMENT REMARKS

7 NATURAL CONVECTION

8

VAPOUR COMPRESSION

REFRIGERATION SYSTEM

9

7/30/2019 ME1324-Hmt Group 3

2/9

NATURAL CONVECTION APPARATUS

AIM:

To determine the theoretical and actual heat transfer co-efficients

using Natural Convection Apparatus

DESCRIPTION OF APPARATUS:

Convection is a mode of heat transfer where by a moving fluid

transfers heat from a surface. When the fluid movement is caused by

density differences in the fluid due to temperature variations, it is called

NATURAL CONVECTION.

This apparatus provides students with a sound introduction to the

features of free convection heat transfer from a heated vertical rod. A

vertical duct is fitted with a heated vertical placed cylinder. Around this

cylinder air gets heated and becomes less dense, causing it to rise. This in

7/30/2019 ME1324-Hmt Group 3

3/9

a. - Density of air, - Kinematic viscosity,b. Pr Prenatal number K Thermal conductivity

5. Grashoffs number, Gr = gTL3/2 where, = 1/ (Tf in Kelvin)and L = 0.45 m

6. Nusselts Number, Nu = 0.53 (Gr Pr) If Gr Pr< 105= 0.56 (Gr Pr) If Gr Pr < 108= 0.13 (Gr Pr ) 1/3 If Gr Pr< 1012

7. Nu = hth L / K

Where, L = Length of rod = 0.45m

K = Thermal conductivity.

8. Heat supply rate, Q = V * I Watts

9. Heat transfer through Radiation, Qr = A ( T4 ([ T6 + T7] / 2)4Where, A = DL, D = 20 mm

10 LMTD ( ) / I ( / )

7/30/2019 ME1324-Hmt Group 3

4/9

11.Actual Heat transfer rate : Qact = Q Qr

Hact = Qact / A * LMTD

PROCEDURE:

1. First switch on the heater, and allow the apparatus to attain steady

state.

2. Then note down the Voltmeter and ammeter readings.

3. Regulate the switch and note down the specimen temperatures

T1,T2,T3,T4 and T5 and note down the inlet air temperature T6 and

exit air temperature T7.

4. Again change the ammeter reading and allow the apparatus for few

minutes to attain steady state and then note down the above readings.

5. Repeat this procedure to take three sets of reading.

6 Th l l t th th ti l h t t f h t t f d t l

7/30/2019 ME1324-Hmt Group 3

5/9

T3

T4

T5

T6

NATURAL CONVECTION

7/30/2019 ME1324-Hmt Group 3

6/9

VAPOUR COMPRESSION REFRIGERATION SYSTEM

AIM: To conduct a Test on vapour compression refrigerator test rig and to calculate the

theoretical COP of Carnot and the efficiency of cycle.

SPECIFICATION:

Refrigerant = FreonCompressor motor = 1/3 HP

Fan = 1/3 HP

Rated voltage = 220 V, Single phase.

Current of 220 V = 3 .1 A

FORMULA:

1. Theoritical COP = h1 h3

h2- h1

2. Actual COP = Refrigeration effect

Energy consumed

7/30/2019 ME1324-Hmt Group 3

7/9

3. Relative COP = Actual COP

Theoretical COP

4. COP of carnot cycle = TminTmax T min

5. Efficiency of cycle = Actual cop 100 %

Carnot COP

PROCEDURE:

1. The required valves are opened and rest are closed.

2. A known mass of water is taken in chiller unit

3. Initial temperature of water is noted

4. Therometers are put inside socket.

5. Unit is started and allowed to run for sterility.

6 Fi l i l d

7/30/2019 ME1324-Hmt Group 3

8/9

TABULATION: Natural convection

Sl.

No.

Voltage(V)Volts

Current(I)Amps

Q=V*IWatts Thermocouple Reading

(0C)

GrPr Nu

Actual

Heat TransferCoefficient

HactW /m2K

Theoretical

Heat TransferCoefficient

HthW /m2K

T1

0C

T2

0C

T3

0C

T4

0C

T5

0C

T6

0C

T7

0C

1

2

3

7/30/2019 ME1324-Hmt Group 3

9/9

S.No

Time

periodt

minutes

Refrigerated Temp Reading

(C)

Time for energy

meter disc

Temp

inchiller

(T f)

C

Pressure

gauge

Jb/in2

Pressure

absolute (bar) TheoreticalCOP

ActualCOP

RelativeCOP

CarnotCOP

Efficiencyof cycle

(%)T1 T2 T3 T4

Compressor

(20 rev)

Fan

(3

rev)

P1 P2 P1 P2