Thermodynamics lab manual

1
Thermodynamics Laboratory
Observation Note Book
By
Mr.B.Ramesh, M.E.,(Ph.D),
Associate professor,
Department of Mechanical Engineering,
St. Joseph’s College of Engineering,
Jeppiaar Trust, Chennai-119
Ph.D. Research Scholar, College of
Engineering Guindy Campus, Anna
University, Chennai.

3
Exp. No. :
Port timing diagram for
two stroke petrol engine
Date :
Aim: To determine the period of port opening and closing and to draw the port
timing diagram for the two stroke petrol engine.
Apparatus required: i) Measuring tape and ii) Marker.
Procedure:
i) Identify the inlet, exhaust and transfer ports.
ii) Ascertain the correct direction of rotation of the flywheel by observing the correct
sequence of opening and closing of the ports.
iii) Measure the circumference of the flywheel.
iv) Rotate the flywheel in the correct direction and mark the position of IDC and
ODC on the flywheel against a reference point.
v) Rotate the flywheel slowly and mark the position at which the inlet port just
begins to open. Continue the rotation and mark the position at which it closes.
vi) In the same way mark the position of the exhaust port and transfer port opening
and closing.
vii) Measure the circumferential distances between the various markings with respect
to the nearest dead centre.
viii) Tabulate the readings. Determine the period of port opening and closing at rated
speed. Also draw the port timing diagram.
Formulae:
i) Crank angle = [ Arc length / Circumference ] x 3600
ii) Period of port opening(closing) = [ Crank angle / 360] x [ 60 / N ] , seconds
Where, N = Speed in rpm.

4
Observation:
Circumference of the flywheel = 47 cm
Rated speed = 1500 rpm
Sl.No.
Events
Positionw.r.t.
thenearest
deadcentre.
Distancefrom
thenearest
deadcentre,
cm
Crankangle,
degree
1 IPO
After ODC
2 IPC
After IDC
3 EPO
Before ODC
4 TPO
Before ODC
5 TPC
After ODC
6 EPC
After ODC
Sl.No.
Speed,rpm
Period of
IPO, sec IPC, sec EPO, sec EPC, sec TPO, sec TPC, sec
1 1300
2 1400
3 1500
4 1600
5 1700

6
Port timing diagram
TPO – TPC → Suction
EPC – IDC → Compression
IDC – EPO → Power
EPO – EPC → Exhaust

11
Result:
The port timing diagram showing the relative crank angle corresponding to the
opening and closing of inlet, transfer and exhaust port is drawn.
For 1500 rpm,
1. Period of inlet port opening = sec.
2. Period of inlet port closing = sec.
3. Period of exhaust port opening = sec.
4. Period of exhaust port closing = sec.
5. Period of transfer port opening = sec.
6. Period of transfer port closing = sec.
7. Overlap angle = 0
8. Period of overlap angle = sec.

12
Observation:
Circumference of the flywheel = 125 cm
Rated speed = 850 rpmSl.No.
Events
Position
w.r.tthe
nearest
dead
centre
Distance
fromthe
nearest
dead
centre,
cm
Crank
angle,
degree
1
IVO Before TDC
2
IVC After BDC
3
FIS Before TDC
4
FIC After TDC
5
EVO Before BDC
6
EVC After TDC
Sl.No.
Speed,rpm
Period of
IVO, sec IVC, sec FIO, sec FIC, sec EVO, sec EVC, sec
1 830
2 840
3 850
4 860
5 870

13
Exp. No. :
Valve timing diagram
for four stroke diesel engine
Date :
Aim:
To determine the period of valve opening and closing and to draw the timing
diagram for four stroke diesel engine.
Apparatus required : i) Measuring tape and ii) Marker
Description:
A cut model of four stroke diesel engine showing different parts of the engine
viz. piston, piston rings, inlet and exhaust valves, rocker arm , push rod, cams, gears,
connecting rod and crank is provided. A marking corresponding to TDC is provided on
the flywheel. An indicator is provided so that markings can be made against it on the
flywheel.
Procedure:
i) Identify the inlet and exhaust valve. Ascertain correct direction of rotation
of the flywheel by observing the correct sequence of opening and closing of the valves.
ii) Measure the circumference of the flywheel.
iii) Rotate the flywheel in the correct direction and mark the position of TDC
and BDC on the flywheel against a reference point.
iv) Rotate the flywheel slowly and mark the position at which the inlet valve
just begins to open. Continue the rotation and mark the position at which it closes.
v) In the same way, mark the positions of exhaust valve opening and closing.
vi) Measure the circumferential distance between the various marking with
respect to the nearest dead centre.
vii) Tabulate the readings and draw the valve timing diagram and determine
the angle of overlap.
viii) Determine the period of valve opening and closing at the rated speed of
the engine.
Formulae:
i) Crank angle = [ Arc length / Circumference ] x 3600
ii) Period of valve opening(closing) = [ Crank angle / 360] x [ 60 / 2N ] , seconds
Where, N = Speed in rpm.

19
Result:
The valve timing diagram showing the relative crank angle corresponding to
the opening and closing of inlet and exhaust valve is drawn.
For 850 rpm,
1. Period of inlet valve opening = sec.
2. Period of inlet valve closing = sec.
3. Period of exhaust valve opening = sec.
4. Period of exhaust valve closing = sec.
5. Period of fuel injector opening = sec.
6. Period of fuel injector closing = sec.
7. Overlap angle = 0
8. Period of overlap angle = sec.

20
Observation:
Type of expansion :
massof
waterpoured
Pressures
Temperature
ofrefrigerant
Temperature
ofwater
Energy
meter
reading
symbols
→
m p1 p2 T1 T2 T3 T4 Tw1 Tw2 E1 E2
units→ kg psi psi 0
C 0
C 0
C 0
C 0
C 0
C kwhr kwhr

21
Exp. No. :
Performance test on vapour compression
refrigeration system
Date :
Aim:
To conduct a performance test on the given vapour compression
refrigeration system and to determine the co-efficient of performance [Theoretical,
Carnot and Actual COPs].
Apparatus required:
i) Vapour compression refrigeration set up & ii) Thermometers
Description:
In the vapour compression refrigeration test rig, the evaporator coils are
kept in a cubical vessel into which water can be poured. The compressor is of
hermetically sealed type. The condenser is of air cooled type with plate fins. A fan is used
to accelerate the rate of heat rejection from the condenser coils. Expansion can be carried
out either through capillary tube or solenoid valve. An energy meter is provided to
measure the actual work input to the compressor. A voltmeter and an ammeter are also
provided for the same purpose. Pressure gauges are provided to measure the pressures at
salient points. Thermometer pockets are provided to find the temperatures between each
components. A pressure limiting switch is available to cut off the power supply when the
evaporator pressure falls below a preset value.
Procedure:
i) A measured quantity of water is poured into the cubical vessel.
ii) The initial temperature of water is noted.
iii) The initial energy meter reading [ in kwhr ] is noted.
iv) The system is operated for a specified duration, say 45 minutes.
v) The pressure and temperature between each component are noted.
vi) The final temperature of water and final energy meter reading are also
noted.

23
Formulae:
a) Actual refrigerating effect ( REact ) = mcp ( Tw1 - Tw2 ) , kJ
where,
m = mass of water poured , kg
cp = specific heat of water = 4.187 kJ / kg K
Tw1= initial temperature of water , 0
C
Tw2= final temperature of water , 0
C
b) Actual work input, Wact = ( E2 - E1 ) x 3600 , kJ
where,
E2 = final energy meter reading , kwhr
E1 = initial energy meter reading , kwhr
c) Actual co-efficient of performance , COPact = REact / Wact
d) Theoretical co-efficient of performance, COPtheo = ( h1 - h4 ) / ( h2 - h1 )
where,
h1 , h2 , h4 = enthalpy of refrigerant at states 1,2 and 4
e) Carnot co-efficient of performance, COPcarnot = T ’
2 / ( T ’
1 – T ’
2 )
where,
T ’
1 = condensing temperature , K
( saturation temperature at condensing pressure )
T ’
2 = evaporating temperature , K
( saturation temperature at evaporating pressure )

25
Result:
The performance test was conducted on the given vapour compression
refrigeration system and the COPs were calculated.
1. Actual co-efficient of performance , COPact = _____________
2. Theoretical co-efficient of performance , COPtheo = _____________
3. Carnot co-efficient of performance , COPcarnot = _____________

26
Observation:
Sl.No.
Load,W1
Load,
W2
Wnet
speed
Timefor
10ccof
FC
BP
FC
SFC
HI
ηb
Units↓
Kgf kgf N rpm Sec kw kg/hr
kg/
kwhr
kJ/s %
1
2
3
4
5

27
Exp. No. :
Performance test on single cylinder
petrol engine
Date :
Aim :
To conduct a performance test on the given petrol engine and to draw the
following characteristic curves:
a) BP vs SFC & b) BP vs Brake thermal efficiency
Apparatus required:
i) Stop watch & ii) Tachometer
Engine Details:
Type : Single cylinder four stroke petrol engine.
Rated power : 2.2 Kw
Rated speed : 3000 rpm
Effective radius of the brake drum, Reff : 10.9 cm
Description:
The petrol engine is of single cylinder four stroke type. The engine shaft is
coupled to a brake drum for mechanical loading. A graduated tube with a three way valve
is provided to facilitate fuel flow measurement. The exhaust line is connected to a
calorimeter to find out exhaust heat loss. A digital temperature indicator is provided to
find out the temperature of exhaust gas and calorimeter water at inlet and outlet. Cooling
water lines are provided to cool the brake drum.
Procedure:
i) The rated load(full load) of the engine is calculated.
ii) The fuel supply is checked.
iii) The engine is started at no load.
iv) The cooling water line is opened.
v) The time taken for 20 cc of fuel consumption is noted down
and the speed of the engine is also noted.
vi) The engine is loaded in steps of 1 kg.
vii) At each load setting the above readings are noted.
viii) The readings are tabulated neatly.

29
Formulae:
a) Brake Power (BP) = [ 2 π NT ] / 60000 ,kw
where ,
N = Speed in rpm
T = Torque in N-m
= Wnet x Reff
Wnet = (W1 - W2) 9.81
b) Fuel consumption (FC) = [10 x10 -3
x sp.gr. x 3600 ] / t ,kg / hr
where ,
t = time taken for 10 cc of fuel consumption
sp. gr. = specific gravity of petrol = 0.78
c) Specific fuel consumption (SFC) = FC / BP ,kg / kwhr
d) Heat input (HI) = [ FC x CV ] / 3600 ,kJ / s
where,
CV = Calorific value of petrol = 43250 ,kJ/kg
e) Brake thermal efficiency ,ηb = [ BP / HI ] 100 , %

31
Result:
The performance test was conducted on the given petrol engine and the following
characteristic curves were drawn :
i) BP vs SFC and
ii) BP vs Brake thermal efficiency.

32
Observation:
Sl.No.
Load,W1
Load,
W2
Wnet
Timefor
20ccof
FC
BP IP HI ηmech ηb ηi
Units↓
Kgf kgf N Sec kw kw kJ/s % % %
1
2
3
4
5

33
Exp. No. :
Performance test on twin cylinder
diesel engine
Date :
Aim:
To conduct a performance test on the given twin cylinder diesel engine and
to draw the following characteristic curves:
a) Brake power vs Specific fuel consumption
b) Brake power vs Mechanical efficiency
c) Brake power vs Brake thermal efficiency and
d) Brake power vs Indicated thermal efficiency.
Apparatus required: Stop watch
Engine details:
Type : Twin cylinder four stroke diesel engine
Power : 10 HP ( 7.4 kw )
Speed : 1500 rpm
Bore : 87.5 mm
Stroke : 110 mm
Orifice diameter : 23 mm
Effective brake drum radius : 21.5 cm
Description:
The engine is of twin cylinder four stroke type with mechanical loading
arrangement . A graduated tube with two way valve arrangement is provided for fuel
flow measurement. Temperature sensors with analog dial indicators are attached to
cooling water ( inlet and outlet ) and exhaust gas lines. Air is allowed to pass through a
cubical tank to avoid turbulence. An orifice meter with manometer arrangement is
provided to facilitate air flow measurement.
Procedure:
i) The maximum load ( full load ) is calculated from the engine ratings.
ii) The cooling water lines are opened.
iii) The fuel in the tank and the valve ( to allow fuel from the tank ) position
are checked.
iv) The engine is started at no load condition.
v) The time taken for 20 cc of fuel consumption is noted.
vi) The engine is loaded in equal steps ( say 2 kgf ).
vii) The above readings are noted and neatly tabulated.

35
Formulae:
a) Brake Power (BP) = [2 π N T ] / 60000 ,kw
where ,
N = Speed in rpm
T = Torque in N-m
= Wnet x Reff
Wnet = (W1 - W2) 9.81
b) Fuel consumption (FC) = [ 20 x 10 -3
x sp.gr. x 3600 ] / t ,kg / hr
where ,
sp. gr. = specific gravity of diesel = 0.86
c) Specific fuel consumption (SFC) = FC / BP ,kg / kw hr
where ,
CV = Calorific value of diesel = 40,500 ,kJ/kg
e) Brake thermal efficiency ,ηb = [ BP / HI ] x 100 , %
f) Mechanical efficiency, ηmech = [ BP / IP ] x 100 , %
where,
BP = Brake power , kw
IP = Indicated power , kw
= BP + FP
FP = Frictional power , kw
( to be determined from “ BP vs FC ” plot)
g) Indicated thermal efficiency, ηi = [ IP / HI ] x 100 ,%
Result:
The performance test was conducted on the given diesel engine and the following
characteristic curves were drawn.

36
Observation:
Sl.No.
Load,W1
Load,W2
Manometer
readings
h1 h2
Timefor20cc
ofFC
Timefor2
lts.ofwater
collection
Temp.of
exhaustgas
Temp.of
coolingwater
atoutlet
Uints↓
kgf kgf cm cm sec sec 0
C 0
C
Tabulation ( Results ) :
Sl.No. Wnet HI BP Qcw Qeg Qun
Units → N kJ / s % kw % kJ / s % kJ / s % kJ / s %

37
Exp. No. :
Heat balance test on twin cylinder
diesel engine
Date :
Aim:
To conduct heat balance test on the given diesel engine and to draw up a
heat balance sheet showing the proportion of useful work and various losses.
Apparatus required:
i) Stop watch and ii) Tachometer
Engine details:
Type : Twin cylinder four stroke diesel engine
Power : 10 HP ( 7.4 kW )
Speed : 1500 rpm
Bore : 87.5 mm
Stroke : 110 mm
Orifice diameter : 23 mm
Effective brake drum radius : 21.5 cm
Description:
The engine is of twin cylinder four stroke type with mechanical loading
arrangement . A graduated tube with two way valve arrangement is provided for fuel
flow measurement. Temperature sensors with analog dial indicators are attached to
cooling water ( inlet and outlet ) and exhaust gas lines. Air is allowed to pass through a
cubical tank to avoid turbulence. An orifice meter with manometer arrangement is
provided to facilitate air flow measurement.
Procedure:
i) The maximum load ( full load ) is calculated from the engine ratings.
ii) 1/4 , 1/2 and 3/4 of full load are estimated.
iii) The cooling water lines are opened.
iv) The fuel in the tank and the valve ( to allow fuel from the tank ) position
are checked.
v) The engine is started at no load condition.
vi) The time taken for 20 cc of fuel consumption is noted by keeping the right
side knob in closed position.
vii) Supply of fuel from the main tank is ensured after taking the above
reading.
viii) The following readings are also noted:
a) Temperature of cooling water outlet.
b) Temperature of exhaust gas.
c) Manometer readings

39
ix) The engine is loaded ( with 1/4 , 1/2 , 3/4 and full load ) and all the
above readings are noted down.
x) The readings are tabulated neatly.
Formulae:
a) Maximum load , Wmax = [ BPrated x 60000 ] / [ 2π Nrated x Reff x 9.81 ]
( Full load )
where,
BPrated = Rated brake power , kw
Nrated = Rated speed , rpm
Reff = Effective radius of the brake drum
b) Brake power (BP) = [ 2 π NT ] / 60000 ,kw
where ,
N = speed in rpm
T = Torque in N-m
= Wnet x Reff
Wnet = (W1 - W2) 9.81
c) Heat carried away by cooling water , Qcw = mw cpw (tw2 - tw1 )
where,
mw = mass flow rate of cooling water = 2 / t2 ,kg / s
t2 = time for 2 litres of water collection.
cpw = specific heat of water = 4.187 ,kJ / kg K
tw1 = temperature of cooling water at inlet , 0
C
tw2 = temperature of cooling water at outlet, 0
C
d) Heat carried away by exhaust gases, Q eg = mg cpg ( tgo - tgi )
where,
mg = mass flow rate of exhaust gases = mf + ma
mf = mass flow rate of fuel = [ 20 x 10-3
x sp.gr ] / t1
t1 = time taken for 20 cc of fuel consumption
ma = mass flow rate of air = ρaCd Ao 2g ha
where,
Cd = Co efficient of discharge of orifice meter = 0.62
Ao = Area of orifice meter = [π d2
] / 4
d = diameter of orifice
g = 9.81 m/s2
ha = [ (h1 - h2 ) ρw ] / [ρa x 100 ]
where,
h1 , h2 = manometer readings ,cm
ρw = density of water = 1000 ,kg / m3
ρa = density of air at room temperature
= [ (ρa at STP) 273 ] / [ 273 + tR ]

41
where,
ρa at STP = 1.18 ,kg / m3
tR = room temperature , 0
C
cpg = specific heat of exhaust
gases
= 1.005 ,kJ / kg K
tgo = temperature of exhaust
gases , 0
C
tgi = temperature of atmospheric
air , 0
C
e) Heat input ( HI ) = mf x C.V.
where,
mf = mass flow rate of fuel , kg / s
C.V. = calorific value of diesel = 40,500 ,kJ / kg
f) Unaccounted heat loss , Qun = HI - ( BP + Qcw + Qeg ) ,kJ / s

43
Result:
The heat balance test was conducted on the given diesel engine and a heat balance
chart has been drawn up for different load conditions.

44
Observation:Sl.No.
Voltage
Current
Timefor
20ccof
F.C.
FC SFC B.P I.P H.I ηmech ηb ηi
Units↓
V A sec. Kg/hr Kg/kwhr kw kw kJ/s % % %
1
2
3
4
5

45
Exp. No. :
Performance test on
diesel alternator set
Date :
Aim:
To conduct a performance test on the given diesel alternator set and to draw
the following characteristic curves:
d) Brake power vs Indicated thermal efficiency
Apparatus required: Stop watch
Engine details:
Type : Single cylinder four stroke diesel engine
coupled to alternator with water rheostat.
Power : 5 HP ( 3.7 kW )
Speed : 1500 rpm
Maximum allowable current : 10 A
Description:
The engine is of single cylinder four stroke type coupled to an alternator . A water
rheostat is provided for loading the engine electrically. A voltmeter and an ammeter are
provided to note voltage and current in the loaded conditions. A graduated tube with two
way valve arrangement is provided for fuel flow measurement. An energy meter is
provided for noting down the power output of the engine. Temperature sensors with
analog dial indicators are attached to cooling water outlet line and exhaust gas line.
Procedure:
i) The cooling water lines are opened.
ii) The fuel in the tank and the valve (used to allow fuel from tank) position
are checked.
iii) The engine is started at no load.
iv) The time taken for 20 cc of fuel consumption is noted by keeping the right
side knob in closed position.

47
v) Supply of fuel from the main tank is ensured after taking the above
reading.
vi) Voltmeter and ammeter readings are noted down.
vii) The engine is loaded by lowering the upper terminal in the water rheostat.
viii) The required current reading is set.
ix) All the above readings are noted down..
x) The experiment is repeated for different current settings.
xi) The readings are tabulated neatly.
Formulae:
a) Brake Power ( BP ) = [V x I ] / 1000 ,kw
b) Fuel consumption (FC) = [ 20 x 10 -3
x sp.gr. x 3600 ] / t ,kg / hr
where ,
c) Specific fuel consumption (SFC) = FC / BP ,kg / kw hr
where ,
CV = Calorific value of diesel = 40,500 ,kJ/kg
e) Brake thermal efficiency ,ηb = [ BP / HI ] x 100 , %
f) Mechanical efficiency, ηmech = [ BP / IP ] x 100 , %
where,
BP = Brake power , kw
IP = Indicated power , kw
= BP + FP
FP = Frictional power , kw
( to be determined from “ BP vs FC ” plot)
g) Indicated thermal efficiency, ηi = [ IP / HI ] x 100 ,%

49
Result:
The performance test was conducted on the given diesel alternator set and the
following characteristic curves were drawn.

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