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Thermodynamics lab manual cum observation note book

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### Thermodynamics lab manual

1. 1. 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.
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3. 3. 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. 4. 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
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6. 6. 6 Port timing diagram TPO – TPC → Suction EPC – IDC → Compression IDC – EPO → Power EPO – EPC → Exhaust
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8. 8. 8 Model Calculation :
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11. 11. 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. 12. 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. 13. 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.
14. 14. 14 Valve timing diagram
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16. 16. 16 Model calculation:
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19. 19. 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. 20. 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. 21. 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.
22. 22. 22 Model calculation:
23. 23. 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 )
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25. 25. 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. 26. 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
28. 28. 28 Model calculation:
29. 29. 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 , %
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31. 31. 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. 32. 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. 33. 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.
34. 34. 34 Model calculation:
35. 35. 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 , 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.
36. 36. 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 %