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.

2

3Exp. 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.

4Observation: Circumference of the flywheel = 47 cm Rated speed = 1500 rpm

Sl.N

o.

Eve

nts

Posi

tion

w.r

.t.

the

near

est

dead

cen

tre.

Dis

tanc

e fr

om

the

near

est

dead

cen

tre,

cm

Cra

nk a

ngle

, de

gree

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. N

o.

Spee

d, r

pm Period of

IPO, sec IPC, sec EPO, sec EPC, sec TPO, sec TPC, sec

1 1300

2 1400

3 1500

4 1600

5 1700

5

6Port timing diagram

TPO – TPC → Suction EPC – IDC → Compression IDC – EPO → Power EPO – EPC → Exhaust

7

8Model Calculation :

9

10

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.

12Observation: Circumference of the flywheel = 125 cm Rated speed = 850 rpm

Sl.N

o.

Eve

nts

Posi

tion

w.r

.t th

e ne

ares

t de

ad

cent

re

Dis

tanc

e fr

om th

e ne

ares

t de

ad

cent

re,

cm

Cra

nk

angl

e,

degr

ee

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.N

o.

Spee

d, r

pm

Period of

IVO, sec IVC, sec FIO, sec FIC, sec EVO, sec EVC, sec

1 830

2 840

3 850

4 860

5 870

13Exp. 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.

14Valve timing diagram

15

16Model calculation:

17

18

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.

20Observation:

Type of expansion :

mas

s of

wat

er p

oure

d

Pres

sure

s

Tem

pera

ture

of

ref

rige

rant

Tem

pera

ture

of

wat

er

Ene

rgy

met

er

read

ing

symbols→

m

p1

p2 T1 T2 T3 T4 Tw1 Tw2 E1 E2

units→ kg psi psi 0C 0C 0C 0C 0C 0C kwhr kwhr

21Exp. 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.

22Model calculation:

23Formulae:

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 , 0C

Tw2= final temperature of water , 0C

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 )

24

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 = _____________

26Observation:

Sl.N

o.

Loa

d, W

1

Loa

d ,

W2

Wne

t

spee

d

Tim

e fo

r 10

cc o

f FC

BP

FC

SFC

HI

η b

Uni

ts ↓

Kgf kgf N rpm Sec kw kg/hr kg/ kwhr kJ/s %

1

2

3

4

5

27Exp. 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.

28Model calculation:

29Formulae: 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 , %

30

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.

32Observation:

Sl.N

o.

Loa

d, W

1

Loa

d ,

W2

Wne

t

Tim

e fo

r 20

cc o

f FC

BP IP HI ηmech ηb ηi

Uni

ts ↓

Kgf kgf N Sec kw kw kJ/s % % %

1

2

3

4

5

33Exp. 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.

34Model calculation:

35Formulae: 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 , t = time taken for 20 cc of fuel consumption sp. gr. = specific gravity of diesel = 0.86 c) Specific fuel consumption (SFC) = FC / BP ,kg / kw hr d) Heat input (HI) = [ FC x CV ] / 3600 ,kJ / s 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. 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.

36Observation:

Sl.N

o.

Loa

d , W

1

Loa

d , W

2 Manometer readings

h1 h2 Tim

e fo

r 2

0 cc

of

FC

Tim

e fo

r 2

lts.o

f wat

er

colle

ctio

n

Tem

p. o

f ex

haus

t gas

Tem

p. o

f co

olin

g w

ater

at

out

let

Uin

ts ↓

kgf kgf cm cm sec sec 0C

0C

Tabulation ( Results ) :

Sl.No.

Wnet

HI BP Qcw Qeg Qun

Units → N kJ / s % kw % kJ / s % kJ / s % kJ / s %

37Exp. 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

38Model calculation:

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 sp. gr. = specific gravity of diesel = 0.86 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 ]

40Model calculation:

41 where, ρa at STP = 1.18 ,kg / m3 tR = room temperature , 0C cpg = specific heat of exhaust gases = 1.005 ,kJ / kg K tgo = temperature of exhaust gases , 0C tgi = temperature of atmospheric air , 0C 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

42Heat balance chart:

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.

44Observation:

Sl.N

o.

Vol

tage

Cur

rent

Tim

e fo

r 20

cc o

f F.

C.

FC SFC B.P I.P H.I ηmech ηb ηi

Uni

ts ↓

V A sec. Kg/hr Kg/kwhr kw kw kJ/s % % %

1

2

3

4

5

45Exp. 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: 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 : 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.

46Model calculation:

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 , t = time taken for 20 cc of fuel consumption sp. gr. = specific gravity of diesel = 0.86 c) Specific fuel consumption (SFC) = FC / BP ,kg / kw hr d) Heat input (HI) = [ FC x CV ] / 3600 ,kJ / s 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 ,%

48Model calculation:

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