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Department of Mechanical Engineering

LAB MANUAL

FOR

THERMAL LAB II

DEPT. OF MECHANICAL ENGINEERING

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1

1. COOLING CURVE TEST ON SINGLE CYLINDER FIELDMARSHAL DIESEL ENGINE

AIM

To study the influence of cooling water temperature (outlet temperature) on the efficiency of the engine and plot the graph cooling water temperature Vs Brake thermal efficiency.

TEST RIG DETAILS

BP of the engine = 6HP = 6 x 736 W Bore diameter of the engine = 114.3mm. Stroke length of the engine = 139.7mm. Speed of the engine = 650rpm. Orifice diameter = 20 mm

PRECAUTIONS

Cooling water circulation should never be closed. The temperature of the outlet water should never increase beyond 700C.

PROCEDURE

This test is to be conducted at constant load (half full load) and constant speed. Calculate the load corresponding to half the output of the engine at rated speed. Now start the engine taking all the necessary precaution. Allow the engine to run for few minutes at no load. Now load the engine to half full load, keeping the quantity of cooling water circulation as low as possible. Wait for few minutes till the outlet water temperature becomes steady.

Note the cooling water temperature and also the time for 10cc fuel consumption. Repeat the experiment for different rates of cooling water circulation, keeping the load constant. After the completion of experiment, unload and then stop the engine.


2

FORMULAE

1. Maximum load calculation

Brake power, BP = (2πNT)/60. Watt

Where, N = Speed of the engine in rpm.

T = Torque on the brake drum in Nm = (W1 – W2) R x 9.81Nm.

W1 = weight on hanger + hanger weight in kg. W2 = spring balance reading in kg. R = Radius of brake drum + thickness of rope in meters.

Where,

t = time for 10cc fuel consumption in s Specific weight of diesel = 0.83


Where SAMP

RESU

Best co

INFER

e, TFC = ToCV = CalBP = Brak

PLE GRA

ULT

ooling wa

RENCE

otal fuel colorific valuke power

APH

ater temper

onsumptioue of diesein watts

rature (fro

3

on in kg/hrel = 45.2 X

om graph)

r X 106 J/Kg

=

g.K


4

2. RETARDATION TEST ON SINGLE CYLINDER VERTICAL

DIESEL ENGINE

AIM

To determine the frictional horse power of the engine by conducting retardation test and Plot the graph Rated Speed Vs Retardation Time.

ENGINE DETAILS

Brake Power = 6HP =6 x 736 W Rated Speed = 650 rpm Stroke length = 139.7 mm Bore diameter = 114.3 mm Brake drum Radius = 197 mm

APPARATUS REQUIRED

Stop watch

MAXIMUM LOAD CALCULATION

Maximum brake power; B.P max = 2πNT/60 Watts. Where B.P max = 4.416 KW = 4416 Watts, N = speed of the engine = 650 rpm, T = torque on the engine shaft in Nm = WR in Nm Where W = load on the engine in Kg R = radius of the Brake drum = 197 mm Maximum load in Kg W max = B.P max x60/ (2πNR*9.81)

PROCEDURE

Calculate the load to be applied for the maximum output. Take the following precautions before starting the engine. 1. Check the fuel level 2. Check the lubricating oil level. 3. Check the cooling water circulation. 4. Check whether the engine is on no load. Engine is started at No- load condition and is run at rated speed. The fuel is then cut- off using fuel cut off lever and the time taken for the speed to drop to a


lower lever iexperimload anand fri

FORM

FrictioWhere Mecha

speed is nis engagedment is rend the aboictional po

MULAE

onal powere,

anical EffiWhere, In

noted usingd] and theepeated wove procedower is de

r, F.P. = 2 N= spFrictio

Where,

iciency, Mndicated P

g a stop we engine is

with varioudure is reptermined.

2π N TF / 6peed = 660onal Torqu, t3 = Retat2 = RetarTL = LoaTL = WRWhere,

Mech η = BPower, IP =

5

watch. Thes again br

us lower sppeated and

60 Watts0 rpm ue, TF = Tardation timrdation tim

ad TorqueR* 9.81 Nm

W = LR = Ra

BP/IP = BP + FP

e fuel is agrought bacpeeds. Thd noted th

TL x [t3 /(tme at half

me at No-

m Load on enadius of b

P

gain turnedck to the rhe engine he reading

t2-t3)] N mf load [froload [from

ngine rake drum

d on [fuel rated speeis loaded

gs. Plot the

m m the grap

m the grap

m

cut off ed. The to half

e graph

ph] ph]


6

SAMPLE GRAPH

RESULT

Frictional power of the engine = …………….. W Mechanical efficiency =...................%

INFERENCE


7

3. DETERMINATION OF EFFECTIVENESS OF PARALLEL FLOW AND COUNTER FLOW HEAT

EXCHANGER

OBJECTIVE: To determine the logarithmic mean temperature difference (LMTD), effectiveness and overall heat transfer coefficient for parallel and counter flow heat exchanger. EQUIPMENT:

1. The apparatus consists of a concentric tube heat exchanger. 2. The hot fluid namely hot water is obtained from the Geyser (heater

capacity 3 kW), it flows through the inner tube. 3. The cold fluid i.e. cold water can be admitted at any one of the ends

enabling the heat exchanger to run as a parallel flow or as a counter flow exchanger.

4. Rotameters are used for measuring flow rate of cold and hot water. 5. This can be adjusted by operating the different valves provided. 6. Temperature of the fluid can be measured using thermocouples with

digital display indicator. The outer tube is provided with insulation to minimize the heat loss to the surroundings.

Specimen material - Copper Tube Size of specimen- diameter 12.5mm, length -1500mm Outer shell material G I Size of outer shell diameter- 40 mm BASICS: LOGARITHMIC MEAN TEMPERATURE DIFFERENCE (LMTD): LMTD LMTD = (θ2 – θ1)/ ln(θ2/ θ1)

0C where, θ1 = Thi -Tci, and θ2 = Tho. -Tco for parallel flow heat exchanger θ1 = Tho -Tci , and θ2 = Thi, -Tco for counter flow heat exchanger This is defined as that temperature difference which, if constant, would give the same rate of heat transfer as usually occurs under variable conditions of temperature difference.


8

PRECAUTION: Switch ON the heater only after starting water supply. PROCEDURE:

1. Switch ON the unit panel. 2. Start the flow of cold water through the annulus and maintain the

exchanger as counter flow or parallel flow. 3. Switch ON the geyser provided on the panel & allow water to flow

through the inner tube by regulating the valve. 4. Adjust the flow rate of hot water and cold water by using rotameters &

valves. 5. Keep the flow rate same till steady state conditions are reached. 6. Note down the temperatures on hot and cold water sides. Also note the

flow rate. 7. Repeat the experiment for different flow rates and for different

temperatures. The same method is followed for parallel flow also. OBSERVATIONS:

SI. No

Hot water flow rate cc/s

Cold water flow rate cc/s

Temperature of cold water in °C

Temperature of hot water in °C

Tci Tco Thi Tho

Parallel flow

Counter flow

CALCULATION: Heat transfer from hot water Qh = m„cph (Thi –Tho) W where mh - mass flow rate of hot water kg/s. Cph - Specific heat of hot water = 4186.8 J/kgK


9

Heat gain by the cold fluid Qc = mCpc (Tco – Tci) W where me - Mass flow rate of cold fluid, kg/s Cpc - Specific heat of cold fluid=4186.8 J/kgK Q = (Qh + Qc ) /2 W LMTD = (θ2 – θ1)/ ln(θ2/ θ1)

0C Where θ1 = Thi -Tci, and θ2 = Tho. -Tco for parallel flow heat exchanger θ1 = Tho -Tci , and θ2 = Thi, -Tco for counter flow heat exchanger Overall heat transfer coefficient based on outside surface area of inner tube U0 = Q / A0 LMTD W/m2 K where, Area, A0 = π d0L m2 d0 - Outer diameter of the tube = 0.0125 m L - length of the tube = 1.5 m Effectiveness, ε = ( Thi – Tho) / ( Thi - Tci ) if ch < cc

Effectiveness, ε = ( Tco – Tci) / ( Thi - Tci ) if cc < ch

This is applicable for both parallel and counter flow heat exchanger.

RESULT: INFERENCE:


10

4. DETERMINATION OF COP OF THE REFRIGERATION TEST RIG

AIM

To determine the actual, theoretical and relative COP of refrigerating plant.

APPARATUS

The given Refrigeration Test Rig with refrigerant R-132.

a) Digital indicator b) compressor c) condenser d) Expansion device e) evaporator f) waterchiller

THEORY The system works on vapour compression refrigeration cycle. Theoretical COP = Refrigeration effect = (h1-h4) Work done (h2-h4) Where, h1 = Enthalpy corresponding to P1, and T1, kJ/kg h2 = Enthalpy corresponding to P2, and T2, kJ/kg h4 = Enthalpy corresponding to P2, and T3, kJ/kg P1 and T1- Pressure and Temperature of Refrigerant at inlet of compressor. P2 and T2- Pressure and Temperature of Refrigerant at exit of compressor. T3 -Temperature of Refrigerant at the exit of condenser. Actual COP = Heat removed Actual workdone Heat removed = mCp dT m- mass of water taken in the chiller in kg Cp - specific heat of water dt - drop in temperature of water Actual work input = V x I V- Voltage I - Current Relative COP = Actual COP Theoretical COP

PROCEDURE

1) Fill the chiller with water 2) Switch- On the power


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3) Start the system by switching on the thermostat by opening the corresponding valves depending on solenoid and thermostatic expansion valve or capillary expansion device. 4) Note down the initial energy meter reading El. 5) RecordT1, T2, T3, T4, P1, P 2 , V,I and Rotameter reading. 6) Note down the initial temperature of water Ti. 7) After 30 minutes note down the energy meter reading E2 and Temperature of chilled water Tf.

OBSERVATION Diameter of steel vessel (chiller) d = 0.27 m Length of the water column l =

Initial temp

of water

in chiller Ti (0C)

Voltage V

(volt)

Current I

(A)

Pressure at inlet of the

compressor P1 (psi)

Pressure in the condens

er P2 (psi)

Temp at

inlet of the compressor

T1 (0C)

Temp at

outlet of the

compressor T2

(0C)

Temp at

outlet of the

condenser

T3(0C)

Temp at

outlet of the expansion valve

T4 (0C)

Final temp

of water in the chiller Tf (0C)

Calculations

Actual COP, COP (act) = Heat removed Actual workdone Heat removed Q = mCp dT m- mass of water taken in the chiller in kg = ρV where ρ = density of water = 1000 kg/m3 V = volume of water in the chiller in m3 = π/4*d2*l Cp - specific heat of water = 4.182 kJ/kgK dt - drop in temperature of water in K = Ti- Tf Actual work input = V x I V- Voltage I - Current


12

Theoretical COP = Refrigeration effect = (h1-h4) Work done (h2-h4) Where, h1 = Enthalpy corresponding to P1, and T1, kJ/kg from p-H chart. h2 = Enthalpy corresponding to P2, and T2, kJ/kg from p-H chart. h4 = Enthalpy corresponding to P2, and T3, kJ/kg from p-H chart. P1 and T1- Pressure and Temperature of Refrigerant at inlet of compressor. P2 and T2- Pressure and Temperature of Refrigerant at exit of compressor. T3 -Temperature of Refrigerant at the exit of condenser. Relative COP = Actual COP Theoretical COP

Result Theoretical COP of refrigerator = Actual COP of refrigerator = Relative COP refrigerator = Inference

Block diagram of vapour compression cycle

Expansion

Device

T 2 P 3

3

4 1

Entropy Enthalpy

2

4 1

Condenser

Compressor

Evaporator


13

5. MORSE TEST ON 4 CYLINDER PETROL ENGINE AIM To determine the frictional horse power in each cylinder of a 4 cylinder petrol engine. Also determine the indicated power and mechanical efficiency of the engine. ENGINE DETAILS Brake Power = 7.36 KW Rated Speed = 1500 rpm Stroke length = 75 mm Bore diameter = 68mm Radius of dynamometer wheel = 0.125 m APPARATUS REQUIRED Cylinder cut-off arrangement MAXIMUM LOAD CALCULATION Maximum brake power; B.Pmax = 2πNT/60 Watts. Where B.Pmax = 7.36 KW = 7360 Watts, N = speed of the engine = 1500 rpm, T = torque on the engine shaft in Nm = WR in Nm Where W = load on the engine in Kg R = radius of the dynamometer wheel = 0.125 m Maximum load in Kg W max = B.P max x60/ (2πNR*9.81) PROCEDURE Calculate the load to be applied on the eddy current dynamometer for the maximum output. Take the following precautions before starting the engine. 1. Check the fuel level. 2. Check the lubricating oil level. 3. Check the cooling water circulation. 4. Check whether the engine is on no load. The test is conducted at constant speed with constant fuel supply (the throttle valve is not adjusted). Start the engine using self starter. Engage the engine with dynamometer using the clutch. Allow the engine to run for a few minutes at the rated speed (1500rpm) to attain steady conditions. The engine is loaded to about


14

50% of the maximum load and throttle valve is adjusted to maintain constant speed. Now the voltage to the spark plug of 1st cylinder is cut-off and now the engine is running on the expense of 2nd and 3rd cylinders. The speed is maintained constant by reducing load and the load is noted. Close the circuit of 1st cylinder and the 2nd cylinder is short circuited. Repeat the procedures for other cylinders and note the load on the dynamometer on each case. After completion of the experiment, bring the engine to no load conditions and stop the engine by switching off ignition key. Maintain cooling water circulation for some more time.

FORMULAE Brake power, 1st cylinder cut-off = 2πNT/60 Watts Where N= speed = 1500 rpm T = WR* 9.81 Nm B.P = ...........................Watts Indicated power of 1st cylinder; I.P. 1 = B.P. total – B.P. 1st cylinder cut-off Brake power, 2nd cylinder cut-off = 2πNT/60 Watts Where N= speed = 1500 rpm T = WR* 9.81 Nm


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B.P = ...........................Watts Indicated power of 2nd cylinder; I.P. 2 = B.P. total – B.P. 2nd cylinder cut-off Brake power, 3rd cylinder cut-off = 2πNT/60 Watts Where N= speed = 1500 rpm T = WR* 9.81 Nm B.P = ...........................Watts Indicated power of 3rd cylinder; I.P. 3 = B.P. total – B.P. 3rd cylinder cut-off Indicated power of 4th cylinder; I.P. 4 = B.P. total – B.P. 4th cylinder cut-off Total indicated power; I.P. total = I.P. 1 + I.P. 2 + I.P. 3 Mechanical efficiency; Mech η = B.P. total X 100

I.P. total RESULT Total indicated power = …………….. W Mechanical efficiency =...................% INFERENCE


16

6. LOAD TEST ON 4 STROKE PETROL ENGINE AIM To determine the total fuel consumption, specific fuel consumption, brake mean effective pressure and brake thermal efficiency of the petrol engine at various loads and to plot the following graphs. Brake power output Vs T.F.C Brake power output Vs S.F.C Brake power output Vs B.M.E.P Brake power output Vs Br.Th.efficiency ENGINE DETAILS Brake Power = 7.36 KW Rated Speed = 1500 rpm Stroke length = 75 mm Bore diameter = 68mm Radius of dynamometer wheel = 0.125 m APPARATUS REQUIRED Stopwatch PROCEDURE Calculate the load to be applied on the eddy current dynamometer for the maximum output. Take the following precautions before starting the engine. 1. Check the fuel level. 2. Check the lubricating oil level. 3. Check the cooling water circulation. 4. Check whether the engine is on no load. Start the engine using self starter. Engage the engine with dynamometer using the clutch. Allow the engine to run for a few minutes at the rated speed (1500rpm) to attain steady conditions. Observe time for 10cc fuel consumption. Now load the engine keeping the speed constant. Again wait for a few minutes to attain steady conditions at that load. Observe time for 10cc fuel consumption and actual load acting on the engine. Repeat the procedure for six different loads (from no load to full load). Care must be taken not to overload the engine.


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After completion of the experiment, bring the engine to no load conditions before stopping. Maintain cooling water circulation for some more time. OBSERVATION AND TABULAR COLUMN

MAXIMUM LOAD CALCULATION Maximum brake power; B.Pmax = 2πNT/60 Watts. Where B.Pmax = 7.36 KW = 7360 Watts, N = speed of the engine = 1500 rpm, T = torque on the engine shaft in Nm = WR in Nm Where W = load on the engine in Kg R = radius of the dynamometer wheel = 0.125 m Maximum load in Kg W max = B.P max x60/ (2πNR*9.81) SAMPLE CALCULATIONS (SET NO....) Brake power output; B.P = 2πNT/60 Watts Where N= speed = 1500 rpm T = WR* 9.81 Nm B.P = ...........................Watts Total fuel consumption; T.F.C = (10/t)*(3600/1000)*0.75 Kg /hr Where t = time for 10cc fuel consumption =.................sec


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0.75 = sp. weight of petrol T.F.C = ............................. Kg/hr Specific fuel consumption; S.F.C = T.F.C/ B.P Kg/W hr Where T.F.C = Total fuel consumption in Kg/hr B.P = Brake power in Watts S.F.C =.............................. Kg/W hr Brake mean effective pressure; B.M.E.P = (B.P*60)/ LA(N/2)*n in N/m2 Where B.P = brake power in watts L = stroke length = 0.75 m D = diameter of the cylinder (bore) = 0.68m A = area of the cylinder in m2 = π/4* D2 N = speed = 1500 rpm (N/2 is because of four stroke engine) n = no: of cylinders = 3Nos B.M.E.P =.......................... in N/m2 Brake thermal efficiency; Br.th.η = (B.P*3600)/(T.F.C*C.V) X 100 % Where T.F.C = total fuel consumption in Kg/hr C.V = calorific value of petrol = 43.5 J/Kg K B.P = brake power in Watts Br.Th.η =...............................% RESULT Maximum brake thermal efficiency =...................% INFERENCE


19

7. LOAD TEST ON TWO STAGE AIRCOMPRESSOR. AIM To conduct load test on the two stage reciprocating air compressor and to determine the volumetric efficiency and isometric efficiency at various delivery pressure. Also plot the following graphs. Delivery pressure Vs Volumetric efficiency. Delivery pressure Vs Isothermal efficiency. TEST RIG DETAILS: Working pressure = 12 kgf/cm2. Motor power = 3HP Low pressure cylinder bore diameter, D1 = 90mm. High pressure cylinder bore diameter, D2 = 63mm. Stroke length L = 89.5mm Speed, Nc = 925rpm Diameter of orifice, d = 0.015m Coefficient of discharge of the orifice meter, Cd = 0.6 Energy meter constant, K = 1200 impulse/kwh. Number of impulse on energy meter, n = 10 THEORY: During the downward motion of the piston the pressure inside the cylinder falls below the atmospheric pressure and the inlet valve is opened due to this pressure difference. The air is sucked into the cylinder until the piston reaches the BDC (Bottom dead centre). As the piston starts moving upwards the inlet valve closed and the pressure starts building up continuously until the pressure inside the cylinder is above the pressure of the receiver. Then the delivery valve opens and the air is delivered during the remaining upward motion of the piston to the receiver. At the end of the delivery stoke, small volume of high pressure air left in the clearness space. The high pressure left in the clearness space expands as the piston moves downwards and the pressure of the air falls, until the pressure is just below the atmosphere and then the inlet valve opens and fresh air is sucked in and whole process will repeat.


20

The suction, compression and delivery of air take place within two strokes of the piston or one revolution of the crankshaft. The compression of air from initial pressure to the final pressure in more than one cylinder is known as multistage compression. DESCRIPTION: The compressor basically consists of an electric motor (prime mover), two cylinders namely HP cylinder and LP cylinder. The system is intercooled. Pressure gauges are provided at the both of the HP cylinder and LP cylinder outlets to read the pressures. The AC motor gives input power to the compressor. APPARATUS Manometer, Digital rpm indicator, stopwatch PROCEDURE: 1. The water present if any in the receiver is drained out using the drainage cock. 2. The outlet valve of the receiver is kept open to facilitate starting and then the motor is switched on. 3. When the compressor reaches its normal speed the outlet valve of the receiver is closed and the compressor is allowed to build the required pressure. 4. When the pressure reaches the desired valve, the outlet valve is adjusted so that the delivery pressure remains constant at that pressure. At this point manometer reading, speed of the motor and energy meter readings is noted down. 5. The experiment is repeated for different values of pressures and the above set of reading are noted down. After completing the experiment, switch of the motor and release the air from the receiver.


21

FORMULAE: 1) Initial pressure, P1 = Atmospheric pressure = 1,01,325 N/m2 . 2) Final pressure, P2 = (Gauge pressure x 10 5 ) + Atmospheric pressure N/m2 Where gauge pressure = Pressure gauge reading in Kgf/cm2. 3) Actual volume of air intake per second , Va = Cd A √2gha Where Cd = Coefficient of discharge of orifice meter = 0.60 A = Area of orifice = π d2/4 m2. g = Acceleration due to gravity = 9.81 m/s2 ha= Head difference in terms of air column in meters. = Δh x (density of water /density of air at RTP.) Where, Δh = Difference in level of water in manometer in meters. Density of water ρw = 1000 Kgf/m3. Density of air at RTP ρa = 1.293 X 273 / (273 +t ) Kgf/m3. Where t = Room temperature in 0C.


22

4) Theoretical air intake per second, Vth = π /4 x D12 x L x Nc / 60. Where D1 = Diameter of low pressure cylinder in metres. L = Stroke length in metres Nc= Speed of the compressor in rpm. 5) Volumetric efficiency , η vol = (Va / Vth ) x 100 % Where Va = Actual volume of air delivered in m3/s. Vth = Theoretical air intake in m3/s. 6) Input power , P = (3600 x n) / (K x t) kw Where , K = Energy meter constant = 200 rev/kwh. n = Number of revolutions of energy meter disc. t = Time taken for ’n’ revolution of energy meter disc. Assuming transmission and mechanical losses as 20 %. i.e. Total Input = 0.8 P 7) Isothermal work done = P1 V1 loge P2 /P1 x 10 -3 kJ/s Where P1 = initial pressure or atmospheric pressure in N/ m2 . P2 = final pressure in N/ m2. V1 = Va = Actual air intake in m3/s. 8) Isothermal efficiency , ηiso= (Isothermal work done ) / ( Total Input) x 100 %.

RESULT 1) Maximum Volumetric efficiency of the compressor. 2) Maximum Isothermal efficiency of the compressor. INFERENCE


23

8. PERFORMANCE TEST ON BLOWER

AIM:-

To conduct and evaluate the performance test on the blower by plotting the following performance curve:

a) Total head Vs discharge b) Efficiency Vs discharge c) Input Vs discharge

SPECIFICATIONS

a) Power (P) : 7.5HP or 5.5KW b) Speed (N) : 2900rpm c) Pipe Diameter : 125mm d) Throat Diameter : 75mm e) Co-efficient of Discharge (Cd) : 0.6 f) Impeller Diameter : 500mm g) Motor : 7.5hp or 5.5kw, AC,3phase,440V,

50Hz, Squirrel cage Induction h) Delivery Size : 125x80mm i) Inlet Diameter : 200mm

APPARATUS REQUIRED

a) Centrifugal Air blower test rig b) Stop watch c) Tachometer

PRINCIPLE

The main components of air blower are the impeller and the diffuser. The fresh air enters into the eye of the of impeller. Because of the high rotational speed of the impeller, the air contained in the rotational passage is subjected to centrifugal force which causes air to flow radially outwards. All the mechanical energy driving the impeller is transmitted to fluid stream in the impeller, where it is converted into kinetic energy with a slight pressure rise. Blower is used to discharge higher volume of air at a lower pressure it is used in blast furnace, cupolas, air conditioning plant, etc.


24

OBSERVATION AND TABULATION

FORMULA USED

Atmospheric pressure (Pa) = 1.013 x 105 N/m2

Diameter of pipe (d1) = 125mm

Diameter of throat (d2) = 75mm

Co-efficient of discharge (Cd) = 0.6

a) Static Head (Hs)

Hs =(hsx w)/ a (m)

Where , hs = Static pressure manometer (m)

w=density of water ,1000 (Kg/m3)

a =density of air ,1.18 (Kg/m3)

b) Head causing flow

Ha = (Hwx w)/ a (m)

Sl No

Manometer Reading

(m)

Venturimeter reading

Time for

5 pulse on e/m

t

Head causing

flow h1

Discharge Q

Velocity

of air v

Static pressu

re head Hs

Dynamic head Hd

Total

head H

Power output

Po

Power input

Pi

Efficiency

h1

h2

h1‐h2

h1

h2

h1‐h2

sec m m3/s m/s m m m w w %


25

Where, Hw = Veturimeter reading (m)

w = density of water ,1000 (Kg/m3)

a = density of air ,1.18 (Kg/m3)

mercury = density of mercury (Kg/m3)

c) Discharge (Q)

Q= √

(m3/sec)

Where, Cd =Co-efficient of discharge, 0.6

a1 =Area of cross-section of pipe (m2)

=0.012

a2 =Area of cross-section of throat (m2)

=0.004

g = Acceleration due to gravity (m/s2)

=9.81

Ha = Head causing flow

d) Velocity of air in pipe (V)

V= (m/s)

Where, Q = Discharge (m3/s)

A = Area of cross-section of pipe (m2)

e) Dynamic Head (Hd)

Hd = V (m)

f) Total Head (H) H = Hs+Hd+Z (m) Where, Z= Datum height from suction to delivery (m) =1


26

g) Power output (Po) Po = axgxQxH (w) Where, a = Density of air =1.18 (kg/m3) g = Accelaration due to gravity =9.81 (m/s2) Q= Discharge (m) H = total head (m)

h) Power input (Pi) Pi = (w) Where, n = no of pulse on energy meter m = motor efficiency = 85 (%) t = Time for 5 pulse of energy meter (sec) k = Energy meter constant ,1600 pulse/KWH

i) Efficiency ( )

= 100 (%)

PRECAUTIONS

The following precautions were taken before starting the test

a) Check the test rig is under no load b) Check the level of water in the manometer

PROCEDURE

a) Start the blower at no load condition by keeping the delivery valve closed position

b) Open the delivery valve in full open condition c) Take the manometer readings and the time taken for n number of pulses

of energy meter d) Repeat the experiments by closing the delivery valvegradually e) Finally take the reading at closed condition of delivery valve f) Close the delivery valve and switch off the blower


27

RESULT

The following graph are plotted :

a) Total head Vs discharge b) Efficiency Vs discharge c) Input Vs discharge

Maximum efficiency obtained :

Maximum output :

Maximum value of air discharge :

INFERENCE

The efficiency increases gradually with increase in discharge

The input power increases

Gradually with increase in discharge

The head decreases

Gradually with increase in discharge


28

9. HEAT BALANCE TEST ON SINGLE CYLINDER DIESEL ENGINE

AIM To study the variation of heat losses with load and to plot heat balance chart. TEST RIG DETAILS BP of the engine = 6HP = 6 x 736 W Bore diameter of the engine = 114.3mm. Stroke length of the engine = 139.7mm. Speed of the engine = 650rpm. Orifice diameter = 20 mm APPARATUS REQUIRED Stop watch PROCEDURE

Calculate load to be applied on the engine corresponding to the maximum output. Take all necessary precautions before starting the engine.

Open the cooling water supply valve to the engine and dynamometer. Start the engine by cranking. Allow the engine to run for few minutes at no load to attain steady conditions. After this condition reached, note the following readings. 1. Load (Kg) 2. Time for 10cc fuel consumption (s). 3. Manometer reading (m of H2o). 4. Time for 10 litres of water circulation through the engine jacket (s). 5. Temperature of exhaust gas (0C). 6. Inlet and outlet temperatures of cooling water (0C).

Now change the load to full load. Allow the engine to run for few minutes to attain steady condition and note the above set of readings. After completion of experiment, bring the engine back to no load condition and then stop.


29

OBSERVATIONS AND TABULATION

MAXIMUM LOAD CALCULATION

Brake power, BP = (2πNT)/60. Watt

Where, N = Speed of the engine in rpm.

T = Torque on the brake drum in Nm = (W1 – W2) R x 9.81Nm.

W1 = weight on hanger + hanger weight in kg. W2 = spring balance reading in kg. R = Radius of brake drum + thickness of rope in meters.

FORMULAE 1. Brake power output Brake power output = Wmax X N/ 2.71 Watts Where N = speed = 1500 rpm Wmax = load applied on the engine = .................Kg 2. Heat input Heat input = T.F.C X CV Watts Where T.F.C = Total Fuel Consumption = 10 X 3600 X 0.83 Kg/hr

Sl No

Load Applied

W

Speed of the

Engine

N

Time taken for 10cc of

fuel consumption

t

Cooling water

flow rate

Manometer Readings

Temperature of cooling

water

Temperature of

exhaust gas

t3

Temperature of

inlet air

t4 h1 h2 t1 t2

kg r.p.m. sec m3/s cm cm 0C 0C 0C 0C


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t X 1000 CV = Calorific value of diesel = 45.2 X 106 J/Kg Heat input may be taken as 100% 3. Heat carried away by cooling water Heat carried away by cooling water = m CP ΔT Watts Where m = mass flow rate of cooling water in Kg/s [for 10 Ltrs of water] m = 10/t Kg/s Where t = time for 10 ltrs of water circulation CP = Specific heat of water at constant pressure = 4.186 X 103 J/Kg K ΔT = (T1-T2) = difference of inlet and outlet cooling water temperature in K % of heat loss through cooling water = Heat carried away by cooling water x100% Heat Input 4. Heat loss through exhaust gas Heat carried away by exhaust gas = m CP ΔT Watts Where m = mass flow rate of exhaust gas in Kg/s m = mass flow rate of fuel in Kg/s + mass flow rate of air in Kg/s Mass flow rate of fuel = T.F.C/3600 Kg/s Mass flow rate of air = Volume of air in m3/s (Va) X density of air at RTP (ρa) Volume of air in m3/s (Va) = Cd .a. √2gha m3/s Where Cd = 0.62 A = area of orifice = πd2 /4 m2 D = diameter of orifice = ………mm ha = Manometric head of air column = hw ρw/ρa m of air hw = Manometer difference of water column ρw = density of water = 1000 kg/m3 ρa = density of air at R.T.P = 1.293 X 273 Kg/m3 273+t t = Ambient temperature CP = specific heat of exhaust gas = 1.005 X 103 J/KgK ΔT = (T1-T2) = difference of exhaust gas and room temperature in K % of heat loss through exhaust gas = Heat loss through exhaust gas X 100% Heat input


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5. Unaccounted heat loss (radiation and other losses) Unaccounted heat loss = heat input – (work output + cooling water loss+ exhaust gas loss) watts RESULT Heat equivalent of brake power = Heat carried away by cooling water = Heat carried away by exhaust gas = Unaccounted heat loss = Energy Input = 100 %

INFERENCE


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