Manual

1

THERMAL CONDUCTIVITY BY GUARDED PLATE METHOD

AIM:

To find the thermal conductivity of the specimen by two slab guarded hot

plate method.

APPARATUS REQUIRED:

1. Ammeter

2. Voltmeter

3. Thermocouple

4. Temperature indicator

SPECIFICATIONS:

Thickness of the specimen plate = 0.005 m

Specimen diameter = 0.140 m

Area A = 0.0153 m2

FORMULA USED:

Heat transferred through the specimen

dX

dTKAQ

Where,

Q – Heat transfer rate, w

K – Thermal conductivity of the specimen plate, W/mK

A – Surface area of the test plate, m2

dT – Temperature drop across the specimen, K

dX – Thickness of the specimen = 0.005m

005.0

34 TT

dX

dT

dT

dx

A

QK , W/mK

2

PROCEDURE:

1. Connect the three pin plug to the 230 v, 50 Hz, 15 amps main supply and

switch on the unit.

2. Turn the regulator knob clockwise, set the heat input by fixing the voltmeter

and ammeter readings and note down the heat input Q in the table.

3. Adjust the regulator for guard heater so that the main heater temperature is

less than that of the guard heater temperature.

4. Allow water through the cold plate at a steady rate

5. Allow the unit to attain the steady state condition.

6. When the steady state condition is reached note down the temperature

indicated in the temperature indicators.

7. In the temperature indicator, the temperatures T1, T6 represents the cold plate

temperature, T2, T5 represents the main heater temperature T3, T4 represents

the guard heater temperature T7, T8 represents the water temperature. These

values are noted in the table.

8. Calculate the thermal conductivity of the given specimen by using the given

formula and note the value in the table.

9. Repeat the experiment from step 2 to step 8 by varying the heat input to the

system.

3

The

rma

l

Con

du

ctivity

of

spe

cim

en

K

W/m

K

dT

/dX

Wa

ter

Tem

p

˚C T

8

T7

Gu

ard

he

ate

r

Tem

p

˚C

T4

T3

Ma

in h

ea

ter

Tem

p

˚C

T5

T2

Cold

pla

te

Tem

p

˚C T

6

T1

Q=

VI

Wa

tts

Am

me

ter

Rea

din

g

(am

ps)

I

Vo

ltm

ete

r

Rea

din

g

(va

olts)

V

S

No

TA

BL

E:

4

Figure 1. Two slab guarded hot plate

5

RESULT:

Thus the thermal conductivity of the given specimen was calculated.

6

THERMAL CONDUCTIVITY OF PIPE INSULATION USING LAGGED PIPE

APPARATUS

AIM:

To determine the thermal conductivity of the given insulating material by

using lagged pipe apparatus.

APPARATUS REQUIRED:

1. Ammeter

2. Voltmeter

3. Thermocouple


SPECIFICATIONS:

1. Heater diameter, d1 = 0.02m

2. Heater with asbestos diameter, d2 = 0.04m

3. Heater with asbestos + sawdust diameter, d3 = 0.08m

4. Length, L = 0.50m

FORMULA USED:

Heat transfer rate,

)ln(

)(2

)ln(

)(2

2

3

2

1

2

1

r

r

TLK

r

r

TLK

Q

Where, Q – Heat transfer rate, watts

K1 – Thermal conductivity of asbestos in W/mK

K2 – Thermal conductivity of sawdust in W/mK

L – Length of the pipe, 0. 5 m

ΔT– Temperature difference in K

r1 – Heater radius, 0.01m

r2 – Heater with asbestos, 0.02m

r3 – Radius with asbestos and sawdust, 0.04m

7

Thermal conductivity of asbestos

)(2

ln1

2

1TL

r

rQ

K

Where,

ΔT = Tavg (Heater) – Tavg (Asbestos)

Thermal conductivity of sawdust

)(2

ln2

3

1TL

r

rQ

K

Where,

ΔT = Tavg (Asbestos) – Tavg (Sawdust)

8

PROCEDURE:


switch on the unit.





indicated by the temperature indicators.

5. In the temperature indicator, the temperatures T1, T2, T3 represents the

temperature of the heater, T4, T5, T6 represents the temperature of the

asbestos and T7, T8 represents the temperature of the sawdust lagging by

using the multipoint digital temperature indicator. These values are noted in

the table.

6. Calculate K1 (Thermal conductivity of asbestos) and K2 (Thermal conductivity

of asbestos), by using the given formula and note the value in the table.

7. Repeat the experiment from step 2 to step 6 by varying the heat input to the

system.

9

Sa

w d

ust

K2

W/m

k

Asb

esto

s

K1

W/m

k

Sa

wdu

st

Tem

p

˚C

Tavg

T8

T7

Asb

esto

s T

em

p

˚C

Tavg

T6

T5

T4

Hea

ter

Tem

p.

˚C

Tavg

T3

T2

T1

Q

Wa

tts

Am

me

ter

Rea

din

gs

Am

ps

A

Vo

ltm

ete

r

Rea

din

g

s

Vo

lts

V

S

No

TA

BL

E:

10

Figure 2. Lagged pipe apparatus

11

RESULT:

Thus the thermal conductivity of the given insulating material (Asbestos

and Saw dust) has been calculated.

12

NATURAL CONVECTION HEAT TRANSFER FROM A VERTICAL CYLINDER

AIM:

To determine the actual heat transfer co-efficient and theoretical heat

transfer coefficient by natural convection.

APPARATUS REQUIRED:

1. Voltmeter

2. Ammeter

3. Thermocouple

4. Heater


SPECIFICATION:

Length of the rod, L = 0.50m

Diameter of the rod, D = 0.02m

Thermal conductivity of air at mean film temperature, (Tf), K

Area of the rod, A =DL = 0.0314 m2

FORMULA USED:

Theoretical heat transfer co-efficient (htheoretical)

For laminar flow

Nu = hL /k = 0.59(GrPr) 0.25 for 10 4<GrPr<10 9

For turbulence flow

Nu = hL /k = 0.10(GrPr) 0.33 for 10 9<GrPr<10 12

Where,

Nu - Nusselt Number

h - Heat transfer coefficient, W/m2 K

k – Thermal conductivity of airm W/mK

13

Grashoff number, 2

3

TlgGr

Where,

g – Acceleration due to gravity, 9.81 m/s2

β – Co-efficient of expansion, 273

1

fT

2

TTT s

f

Ts - Surface temperature in ˚C

Tα - Air temperature in ˚C

l – Length = 0.5m

ΔT – Ts - Tα, K

γ – Kinematic Viscosity at mean film temperature (Tf) from HMT data

book

Pr – Prandtl number

Actual heat transfer co-efficient (hact)

TAhQ act

Where,

Q – Heat transfer rate = VI, watts

` hact – Actual heat transfer co-efficient, W/m2K

A = Surface area of the heater = DL = 0.0314 m2

T = Ts - Tα

4

5432 TTTTT

2

61 TTT

Where,

Tω = Surface temperature in ˚C

Tα = Air temperature in ˚C

14

PROCEDURE:


switch on the unit.



3. Keep on the temperature indicator switch in the first position



indicated by the temperature indicators

6. In the temperature indicator, T2, T3, T4 & T5 represents the temperature of the

heater at different points. T1 represent the inlet temperature of the air and T6

represents the outlet temperature of the air. These values are noted in the

table.

7. Calculate the theoretical heat transfer coefficient (h theoretical) and actual heat

transfer coefficient (h actual) by using the given formulas.

8. Repeat the experiment from step2 to step 7 by varying the heat input to the

system.

15

hA

ctu

al

(W/m

2K

)

hT

heore

tica

l

(W/m

2K

)

Ou

tle

t

Tem

p o

f

Air

˚C

T6

Inle

t

Tem

p o

f

Air

˚C

T1

Hea

ter

tem

pe

ratu

re

˚C

T5

T4

T3

T2

Q

Wa

tts

Am

me

ter

Rea

din

g

Am

ps

I

Vo

ltm

ete

r

Rea

din

g

Vo

lts

V

S.

No

TA

BL

E:

16

Figure 3: Natural convection apparatus

17

RESULT: The theoretical and actual heat transfer coefficient has been calculated by

using natural convection apparatus

18

FORCED CONVECTION INSIDE TUBE

AIM:

To determine the actual heat transfer and theoretical heat transfer

coefficient using forced convection.

APPARATUS REQUIRED:

1. Voltmeter

2. Ammeter

3. Thermocouple


5. Blower

6. Manometer

SPECIFICATION:

Diameter of the pipe, d1 – 0.04m

Diameter of the orifice, d2 – 0.02m

Length of the pipe, L – 0.5m

FORMULA USED:

Actual heat transfer co-efficient,

hactual =TA

Q

, w/m2k

Where,

Q - Heat input rate= V x I, Watts

A – Surface area of the pipe = πDL = 0.62 m2

TTT s ˚ C

Ts – Wall temperature, ˚ C

19

4

4321 TTTTTs

Tα – Air temperature, ˚ C

2

65 TTT

Theoretical heat transfer co-efficient, htheoretical

K

hDNu , W/m2k

Where,

Nu – Nusselt number

h – Theoretical heat transfer co-efficient, w/m2k

d – Diameter of pipe, m

k –Thermal conductivity of air at Tf , w/mK (From HMT data book)

Air flow head,

1210

a

whhh

, m

Where,

h1, h2 = Manometer readings, m

ρw = Density of water, 1000 kg/m3

ρa = Density of air, 1.1465 kg/m3

Volume flow of air, 2

2

2

1

21 2...

aa

ghaaCdQv

o

, m3/sec

Where,

Cd = Co-efficient of discharge

a2 = Area of orifice, m2 = 2

24

d

= 3.14 x 10-4 m2

a1 = Area of pipe, m2 = 2

14

d

= 1.25 x 10-3 m2

20

Velocity of air, V = A

QV, m/ sec

Where,

A – Area of pipe, = 2

14

d

= 1.25 m2

Reynolds Number (Re) =

1Vd

Where,

d1 – Diameter of pipe, m

V – Velocity of air, m/sec

- Kinematics viscosity at Tf, m2/sec (From HMT data book)

Nusselt number (NU) = 0.023 (Re) 0.8 (Pr) 0.4

Where,

Pr – prandtl number for air at Tf, m2/sec (From HMT data

book)

Re – Reynolds number

D

KNuhthe

21

PROCEDURE:


switch on the unit.



3. Keep on the temperature indicator switch in the first position



indicated by the temperature indicators

6. In the temperature indicator, T1, T2, T3 & T4 represents the temperature of the

heater at different points. T5 represent the inlet in let temperature of the air

and T6 represents the outlet temperature of the air h1&h2 are the manometer

reading. These values are noted in the table.

7. Calculate the theoretical heat transfer coefficient (h theoretical) and actual heat

transfer coefficient (h actual) for forced convection by using the given formulas.

8. Repeat the experiment from step3 to step7 by varying the heat input to the

system.

22

23

h

W/m

2K

hac

hth

e

Ma

no

me

ter

Rea

din

g

m

h2

h1

Ou

tle

t

Tem

p o

f

Air

˚C

T6

Inle

t

Tem

p o

f

Air

˚C

T5

Hea

ter

tem

pe

ratu

re

(˚C

)

T3

T3

T2

T1

Q

Am

me

ter

Rea

din

g

Am

ps

A

Vo

ltm

ete

r

Rea

din

g

Vo

lts

V

S.N

o

TA

BL

E:

24

Figure 4. Forced convection apparatus

25

RESULT:

The theoretical and actual heat transfer coefficient has been calculated

using forced convection apparatus

26

HEAT TRANSFER FROM PIN-FIN APPARATUS

AIM:

To determine the temperature distribution of a PIN-FIN for forced

convection and to find the FIN efficiency.

APPARATUS REQUIRED:

1. Ammeter

2. Voltmeter

3. Heater

4. Blower

5. Fin specimen

6. Thermocouple


SPECIFICATION:

Duct width, B = 0.150m

Duct height , W = 0.100m

Orifice diameter, do = 0.020m

Orifice coefficient, Cd = 0.6

Fin length , L = 0.145m

Fin diameter, Df = 0.012m

FORMULA USED:

1. Surface temperature CTTTTTTT

Ts o

7

7654321

2. Ambient temperature, Tα = T8 , ˚C

3. Mean film temperature 2

TTsT f , ˚C

27

4. Volume flow rate, ghaACQ sd 2. , sec

3m

Where,

Cd = co-efficient of discharge, 0.6

As = Orifice area = 2

4d

= 1.25 x 10

-3, m

2

ha = Drop in manometric head, m

hha

wa

ρw – Density of water, 1000 kg/m3

ρw – Density of air, 1.14 kg/m3

h – Manometer differential head = h1 - h2, m

5. Velocity of air , BW

QV

. , m/sec

Where,

W = Width, m

B = Breadth, m

6. Reynolds number,

fVdRe

Where,

V = Velocity, m/sec

df = Diameter of fin, m

= Kinematic viscosity at Tf, m2/sec (From HMT data book)

8. Nusselt number, 333.0333.0PrRe989.0 Nu , for 1< Re < 4

333.0385.0PrRe911.0 Nu , for 4< Re < 40

333.0466.0PrRe683.0 Nu , for 40< Re < 4000

333.0618.0PrRe913.0 Nu , for 4000< Re < 40000

333.0805.0PrRe0266.0 Nu , for Re > 40000

Where,

Pr = Prandtl number at Tf (From HMT data book)

28

8. Heat transfer coefficient, fD

kNuh

. , w/m2K

Where,

K =Thermal conductivity at Tf, w/mK

Df = Diameter of the fin, m

9. Fin efficiency, %100)tanh(

mL

mLfin

Where,

kAhPm

p = Perimeter = πDf = 0.0376 m

A = Surface area of the pin fin = πDfL = 5.27 x 10-3 m2

L = Length of the pin fin, m

29

PROCEDURE:

1. Connect the three pin plug to the 230v, 50 Hz, 15 Amps main supply and

switch on the unit.



3. Keep the thermocouple selectors switch in first position.


5. Now switch ON the blower.

6. Set the air flow rate to the system by keeping the valve in 1/4th position.

7. The difference in U tube manometer limb levels h1, h2 is noted in the table.

8. Note down the temperatures by temperature indicator.

9. In the temperature indicator, T1, T2, T3, T4, T5, T6 and T7 represent the

temperature of the fin surface. These values are noted in the table and Tavg is

calculated.

10. Also note down the atmospheric temperature T8 in the table by using

temperature indicator.

11. Thus the fin efficiency is calculated using the given formula.

12. Repeat the experiment from step 2 to step 11 by varying the air flow rate to

1/2, 3/4, and fully opened position.

13. Tabulate the readings and calculate for different conditions.

.

30

TABLE:

S. No Valve

position

Manometer readings

Fin surface Temperature

C

Ambient temperature

C

Efficiency

%

h1 h2 T1 T2 T3 T4 T5 T6 T7 Tavg T8

1 1/4

2 2/4

3 3/4

4 Full open

31

Figure 5. PIN – FIN appararus

32

RESULT:

Thus the temperature distribution is determined and the fin efficiency is

tabulated.

33

DETERMINATION OF STEFAN-BOLTZMAN CONSTANT

AIM

To find out the Stefan-Boltzman constant using concentric hemisphere.

APPARATUS REQUIRED

1. Voltmeter

2. Ammeter

3. Thermocouple

4. Heater


SPECIFICATION

Mass of the disc, m = 0.005 kg

Diameter of the disc, d = 0.025m

Material of the disc = copper

Disc weight = 0.008 kg

Specific heat, Cp = 0.381 Kj/kgk

FORMULA USED

Radiation heat transfer

44

dh TTAQ

44

dh TTA

Q

Where,

- Stefean boltzman constant W/m2K4

- Emissivity of the black body = 1

TmCQ P

m - Mass of the disc, kg

34

Cp – Specific heat of copper = 0.381Kj/KgK

T – dT/dt

dT – Change in temperature, ˚C

dt – Change in time, sec

A - Area of disc, = 2

4d

=4.9 x 10-6 m2

Th - Average temperature of hemisphere, K

5

54321 TTTTTTh

Td - Temperature of disc, K

PROCEDURE

1. Allow the water to flow through the heater unit and through the hemisphere

2. Remove the disc from the bottom of hemisphere.

3. Switch on the heater and allow the hemisphere to reach steady state

temperature.

4. Note down the temperatures T1, T2, T3, T4, and T5 from the temperature

indicator and also note the steady state temperature of the disc T6 (Td).

These values are noted in the table.

5. The average of T1, T2, T3, T4, and T5 is hemisphere temperature.

6. Close the disc from the bottom of the hemisphere.

7. Allow the unit to attain steady state.

8. When the steady state is reached note down the temperature in the table.

9. Calculate the Stefan - boltzman constant by using the given formula.

10. Repeat the experiment from step 3 to step 9 by changing the heat input to the

system.

35

36

TABLE:

Sl.No.

Hemisphere Temperature oC

Average Temp of hemisphere

oC

Time

Steady state

Temp of disc (Td)

oC

Stefen boltzman constant,

σ W/m2K4

T6 T1 T2 T3 T4 T5 Th (secs)

37

Figure 6. Stefan-Boltzman apparatus

38

RESULT Thus the Stefan Boltzman constant of the given concentric hemisphere is calculated.

39

DETERMINATION OF EMMISIVITY OF A GREY SURFACE

AIM

To measure the emissivity of the given test plate surface.

APPARATUS REQUIRED

1. Ammeter

2. Voltmeter

3. Heater

4. Test plate

5. Black body

6. Thermocouple


SPECIFICATION

Diameter of the test plate = 0.150 m

Diameter of the black plate = 0.150 m

FORMULA USED

Emissivity of the test plate,

44

44

CP

CBBB

TT

TTEE

Where,

Emmisivity of black body, EB = 1

Average temperature of block body, Tab = Tb(Avg) + 273, K

Average temperature of polished body, Tpa = Tp(Avg) + 273, K

Temperature of the chamber, TC = T7 + 273, K

40

PROCEDURE

1. Connect the three pin plug to the 230V, 50Hz, 15 amps main supply and

switch on the Unit



3. Keep the thermocouple selectors switch in first position.

4. Keep the toggle switch in position 1. By operating the energy regulators

power will be fed back to black plate.

5. Now keep the toggle switch in position 2 and operate the regulator 2 and feed

power to the test surface.

6. Allow the unit to stabilize.

7. Make sure that the power inputs to the black and test surface are set at equal

values.

8. Turn the thermocouple selector switch clockwise step by step and note down

the temperatures indicated by the temperature indicator.

9. In the temperature indicator the temperatures T1, T2, T3 represents the

polished body temperature, T4, T5, T6 represents the black body temperature

and T7 represents the chamber temperature. These values are noted in the

table.

10. Calculate the emmisivity by using the given formula.

11. Repeat the experiment from step 2 to step 10 by changing the heat input to

the system.

41

Em

issiv

ity

E

Ch

am

ber

Tem

p

˚C

T7

A

ve

rag

e

Tem

p

˚C

Tb(A

vg)

Bla

ck B

ody

Tem

p

˚C

T6

T5

T4

Ave

rag

e

Tem

p

˚C

Tp(A

vg)

Po

lish

ed

Bo

dy

Tem

p

˚C

T3

T2

T1

Q=

VI

Wa

tts

Am

mete

r

Re

ad

ing

Am

ps

I

Vo

ltm

ete

r

Re

ad

ing

Vo

lts

V

S.

No

TA

BL

E:

42

Figure 7. Emmisivity apparatus

43

RESULT The emissivity of the given polished plate was found out and it is tabulated.

44

EFFECTIVENESS OF PARALLEL AND COUNTER FLOW HEAT

EXCHANGER

AIM:

To find the overall heat transfer co-efficient and the effectiveness in

parallel flow and counter flow heat exchanger.

APPARATUS REQUIRED:

1. Heat Exchanger Apparatus


3. Thermocouple

4. Stopwatch

5. Water heater

SPECIFICATION:

Inner copper tube

Inner diameter, d1 = 0.012m

Outer diameter, d2 = 0.015m

Outer GI tube

Inner diameter, d3 = 0.04m

FORMULA REQUIRED:

1. Parallel flow

Heat ttransfer rate, LMTDUAQ

Overall heat transfer co-efficient, ).(LMTDA

QU , W/m2K

Where,

oiphh ThThCmQ . , W

mh – Mass of hot water, kg

45

Cph – Specific heat of hot water = 4.186 Kj/kgK

A – Outer area of inner copper tube = Ld2 = 0.025 m2

LMTD – Logarithmic Mean Temperature difference

0

0

ln

)(

T

T

TTLMTD

i

i

P

ΔTi = Thi - Tci

ΔTo = Tho - Tco

Thi – Hot water inlet temperature, K

Tci – Cold water inlet temperature, K

Tho – Hot water outlet temperature, K

Tco – Cold water outlet temperature, K

2. Counter flow

0

0

ln

)(

T

T

TTLMTD

i

i

C

ΔTi = Thi – Tco

ΔTo = Tho – Tci

Thi – Hot water inlet temperature, K

Tci – Cold water inlet temperature, K

Tho – Hot water outlet temperature, K

Tco – Cold water outlet temperature, K

3. Effectiveness of heat transfer,

For parallel flow,

ii

i

TcTh

ThTh

0

For counter flow,

ii

io

TcTh

TcTc

46

PROCEDURE:

1. Connect water supply at the back of the unit. The inlet water flows through the

geyser and inner pipe of the heat exchanger and flows out.

2. Also the inlet water flows through the annulus gap of the heat exchanger and

flows out.

3. For parallel flow open valve V2, V4 and V5.

4. Control the hot water flow approximately 2lit./min and cold water flow

approximately 5 lit./min.

5. Switch ON the geyser. Allow the temperature to reach steady state.

6. Note temperature T1 and T2 (hot water inlet and outlet temperature

respectively) in the table.

7. Under parallel flow condition T3 is the cold water inlet temperature and T4 is

the cold water outlet temperature. Note the temperature T3 and T4 in the

table.

8. Under counter flow condition T4 is the cold water inlet temperature T3 is the

cold water outlet temperature. Note the temperatures T3 andT4 in the table.

9. Note the time for 1 litre flow of hot and cold water and calculate the mass flow

rate by using the given formula.

10. For counter flow open valve V3, V1 and V5 and repeat the experiment from

step 5 to step 9 and calculate the mass flow rate by using t he given formula.

47

TABLE:

For Parallel Flow:

S No

Hot water, oC Cold water, oC Time taken

for 1 lit. of hot

water flow

(sec)

Time taken for

1 lit. of cold

Water flow

(sec)

Inlet,

Thi

Outlet,

Tho

Inlet,

Tci

Outlet,

Tco

T1 T2 T3 T4

For Counter Flow:

S

No

Hot water, oC Cold water, oC Time taken

for 1 lit. of

hot water

flow

(sec)

Time taken for

1 lit. of cold

Water flow

(sec)

Inlet,

Thi

Outlet,

Tho

Inlet,

Tci

Outlet,

Tco

T1 T2 T3 T4

48

Figure 8. Parallel flow and Counter flow heat exchanger

49

RESULT:

Thus the test on parallel and counter flow heat exchanger is performed

and the overall heat transfer co-efficient and the effectiveness of the heat

exchanger are determined.

50

DETERMINATION OF COP OF A REFRIGERATION SYSTEM

AIM:

To conduct the test on refrigeration test rig with isobutene and propane as

a refrigerant to determine the Coefficient of Performance (COP).

APPARATUS REQUIRED:

1. Refrigeration test rig

2. Thermometer

3. Stopwatch

FORMULA:

1. Co-efficient of performance (Actual)

if

fiw

actualEE

TTQ

inputEnergy

effectnfrigeratioPOC

860

Re)..(

55

if

fiw

EE

TTQ

860

3600

186.455

Where,

C.O.P – Co-efficient of performance

QW – Weight of water in evaporator, kg

T5i – Initial temperature of water, ˚C

T5f – Final temperature of water, ˚C

Ei – Initial energymeter reading, Kwhr

Ef – Final energymeter reading, Kwhr

2. Co-efficient of performance (Theoretical)

From p-h diagram of

Propane – R290 – Chart a

Iso butane – R600a – Chart b

51

(i). Stage1 – Compressor Inlet / Evaporator outlet

2

111

hbhah

Where,

h1 – Enthalpy at temperature T1, Kj/kg

ha1- From propane pressure – enthalpy chart for temperature T1, &

pressure P1

hb1- From iso-butane pressure – enthalpy chart for temperature T1,

& pressure P1

(ii). Stage2 – Compressor outlet

2

222

hbhah

Where,



pressure P2


& pressure P2

(iii). Stage3 – Evaporator inlet (Before throttling)

2

333

hbhah

Where,



pressure P3


& pressure P3

52

(iv). Stage4 – Evaporator inlet (After throttling)

h3 = h4

Where,


12

41..hh

hhPOC lTheoretica

3. Co-efficient of performance (Relative)

ltheoretica

actualrelative

POC

POCPOC

..

....

PROCEDURE:

1. Fill up the evaporator with known quantity of water.

2. After 5 min, when the system attains steady state the initial energy meter

reading is noted and also the water temperature in the evaporator is

noted.

3. After a known period of time say 30 min, note down the energymeter

reading and water temperature. Before noting the water temperature,

physically stir the water to ensure that uniform temperature is attained in

the evaporator.

4. Note down the pressure (P1, P2, P3 and P4), temperature (T1, T2, T3 and

T4) also temperature of water T5 and energymeter reading in the table.

5. Calculate actual COP, theoretical COP and relative COP by using the

given formula.

6. Repeat the experiment from step 3 to step 5 and the readings are noted in

the table.

53

En

erg

ym

ete

r

rea

din

g

Kw

hr

E

Tem

pe

ratu

re

of

wate

r

˚C

T5

Tem

pe

ratu

re

˚C

T4

T3

T2

T1

Pre

ssu

re,

Psig

P4

P3

P2

P1

Tim

e t

ake

n

(min

)

t

S N

o

T

AB

LE

:

1

ba

r =

0.0

694

76

Psig

54

P1 – Compressor inlet/Evaporator outlet

P2 – Compressor outlet/Condenser inlet

P3 – Evaporator inlet (Before throttling)

P4 – Evaporator inlet (After throttling)

V – Compressor changing valve

Figure 9. Refrigeration test rig

Rota

met

er

Fil

ter

Liquid received

stage cylinder

Condenser

Compressor Evaporator

P4

P3

P2

P1

55

RESULT:

Thus, the performance on a refrigeration test rig with isobutene and

propane refrigerant is conducted and the relative Coefficient of Performance was

found out.

56

PERFORMANCE TEST ON TWO STAGE RECIPROCATING AIR

COMPRESSOR

AIM:

To determine the volumetric efficiency of the cylinder at normal

temperature conditions and to draw various performance characteristics curves.

APPARATUS REQUIRED:

Two stage reciprocating air compressor.

SPECIFICATIONS:

Type = Two stage, single acting

Speed , N = 700 rpm

Type of cylinder cooling system = Air cooled

Low pressure cylinder (LP) bore dia, d1 = 89.9 mm

High pressure cylinder (HP) bore dia, d2 = 63 mm

Stroke length, L = 88.9 mm

Max. Pressure = 300 kg/cm2

Orifice diameter, do = 0.01m

Energymeter constant = 200 rev/Kwhr

FORMULA USED:

1. Density of air, aa

aa

TR

P

. , kg/m3

Where,

Pa – Atmospheric pressure = 1.013 x 105 N/m2

Ra – Universal gas constant = 287 J/kgk

` Ta – Room temperature, K

57

2. Pressure head in terms of air column, ha

T

wwa

hh

, m

Where,

w - Density of water = 1000 kg/m3

hw – Head of water column, m

a - Density of air = 1.145 kg/m3

3. Velocity of air through orifice, Va

aa ghV 2 , m/sec

4. Area of orifice, Ao

2

4oo dA

, m2

Where,

do – Orifice diameter, m

58

PROCEDURE:

1. Connect the three pin plug to the 230V, 50Hz, 15 amps main supply and

switch on the Unit

2. The valve is provided at the top of LP and HP cylinders, water drain cock and

the air outlet valves are closed after the motor has gained its speed. The

increase in pressure of air in the receiver tank is indicated by pressure

gauge.

3. The pressure of air is maintained constant to the desired valve say (2kgf/cm2)

by adjusting at the opening of the compressed air outlet valve in the reservoir

manually.

4. The following observations are to be made by keeping reservoir pressure

constant (2 kgf/cm2)

a. Delivery pressure

b. Manometer reading (hw)(pressure difference across orifice)

c. Temperature T1, T2, T3, T4 after attaining the steady state

d. Time taken for 5 revolution of energy meter disc

5. The same procedure is repeated for the observations of other reservoir

pressure (4, 6, 8, 10, 12 kgf/cm2).

6. Then the motor is switched off after releasing the valve provided at the top of

LP and HP cylinders.

7. The Volumetric efficiency, Input power and Cooling factor of the cylinder has

been calculated from the given formula and the performance characteristic

curves are drawn.

GRAPH:

Following graphs are plotted

1. Delivery pressure on X – axis Vs Volumetric efficiency on Y – axis

2. Delivery pressure on X – axis Vs Input power on Y – axis

59

Coo

ling

facto

r

Inp

ut

po

wer

Kw

Vo

l.

Eff

%

Tim

e f

acto

r

for

5 r

ev o

f

en

erg

ym

ete

r

dis

c

se

cs

Tem

pe

ratu

re, T

4

˚C

T3

˚C

T2

˚C

T1

˚C

Ma

no

me

teric

Rea

din

g h

1- h

2

cm

h2

cm

h1

cm

Deliv

ery

pre

ssu

re

Kg

/cm

2

S N

o

T

AB

LE

:

60

RESULT:

The performance test on air compressor was conducted, the results were

tabulated and graphs are drawn for above parameters.

Documents

Manual