pesit, bangalore south campuspesitsouth.pes.edu/pdf/mech/rs/course information and lesson...

PESIT, BANGALORE SOUTH CAMPUS DEPARTMENT of MECHANICAL ENGINEERING

Subject: - APPLIED THERMODYNAMICS Faculty name : Dandapani Subject code : 10ME43 Total No. of Lecture hrs: 52 No. of Lecture hrs/week: 04

Department of Mechanical Engineering, PESIT - BSC 1

Class No

Text/ Reference page Topics to be covered % of syllabus covered

Chapter

Cumulative

1

Unit – 2 T1Page.No.521-570 R1Page.No.487-550

UNIT- 2:- Gas power cycle: Introduction to Air Standard cycles: Carnot cycles, P-V and T-S diagrams, description, efficiencies and mean effective pressures.

11.5 11.5

2 Otto cycles, P-V and T-S diagrams, description, efficiencies and mean effective pressures

3 Diesel cycles, P-V and T-S diagrams, description, efficiencies and mean effective pressures

4 Dual and Stirling cycles, P-V and T-S diagrams, description, efficiencies and mean effective pressures, Comparison of Otto, Diesel and dual cycles.

5 Numerical problems 6 Numerical problems

7

Unit – 5 T2Page.No. 73-92 R1Page.No.70-165

UNIT – 5:- Reciprocating Compressors: Operation of a single stage reciprocating compressors, work input through P-V diagram and steady state steady flow analysis.

11.5 23.0

Effect of clearance and volumetric efficiency. Adiabatic, isothermal and mechanical efficiencies.

08 Numerical problems 09 Numerical problems

10 Multistage compressor, saving in work, optimum intermediate pressure, intercooling, minimum work for compression.

11 Numerical problems 12 Numerical Problems 13

Unit – 3 T2Page.No. 95-111 R1Page.No.165-256

UNIT – 3:- I.C. Engine: Testing of two stroke and four stroke SI and CI engines for performance,

11.5

34.5

14 Related numerical problems, 15 Numerical problems

16 Heat balance, Motoring Method, Willian’s line method, Swinging field dynamometer, Morse test. Numerical problems

17 Numerical problems 18

Numerical problems

19

Unit – 4 T1Page.No.457- 514 R1Page.No. 551-605

UNIT – 4:- Vapour Power Cycles: Carnot vapour power cycles, drawbacks as a reference cycle,

13.5

48

20 Simple Rankine cycle, description, T- S diagram, analysis for performance, comparison of Carnot and Rankine cycles.

21 Effects of pressure and temperature on Rankine cycle performance. Actual vapour power cycles.

22 Ideal and practical regenerative Rankine cycle, open and closed feed water heaters, Reheat Rankine cycle.

23 Numerical problems 24 Numerical problems 25 Numerical problems




26

Unit – 6 T1Page.No.533- 515 T2Page.No.331- 402

UNIT - 6:-Gas turbine and Jet propulsion: Classification of Gas turbines, Analysis of open cycle gas turbine cycle.

13.5

61.5

27 Advantages and disadvantages of closed cycle. 28 Methods to improve thermal efficiency, 29 Jet propulsion and Rocket propulsion 30 Numerical problems 31 Numerical problems 32 Numerical problems

33

Unit –7 T1Page.No.578- 612 R1Page.No.607- 649

UNIT-7:- Refrigeration: Vapour compression refrigeration system; description, analysis.

11.5

73.0

34 refrigerating effect, capacity , power required, units of refrigeration, COP.

35 Refrigerants and their desirable properties. Air cycle refrigeration;

36 Reversed Carnot cycle, reversed Brayton cycle, Vapour absorption refrigeration system, steam jet refrigeration. 37 Numerical problems

38 Numerical problems

39

Unit – 8 T1Page.No.644 - 695 R1Page.No.651- 709

UNIT-8:- Psychometry: Atmospheric air and psychometric properties; Dry bulb temperature, wet bulb temperature, dew point temperature; partial pressures, specific and relative humidities.

13.5 86.5 40 Relation between the two enthalpy and adiabatic saturation

temperature. Construction and use of psychometric chart.

41 The Analysis of various processes; heating, cooling, dehumidifying and humidifying. Adiabatic mixing of moist air

42 Summer and winter air conditioning. 43 Numerical problems 44 Numerical problems

45 Numerical problems

46 Unit –1

R2Page.No.561- 616 R1Page.No.7511- 792

UNIT-1:-Combustion thermodynamics: Theoretical (Stoichiometric) air and excess air for combustion of fuels. Combustion efficiency, adiabatic flow temperature.

13.5 100 47 Mass balance, actual combustion, Exhaust gas analysis. 48 A./ F ratio, Energy balance for a chemical reaction,

49 Enthalpy of formation, enthalpy and internal energy of combustion.

50

Numerical problems

51 Numerical problems 52

Numerical problems




Data Handbooks:

1. Thermodynamic data hand book, B.T. Nijaguna And samuga. 2. Properties of Refrigerant & Psychometric (tables & Charts in SI Units), Dr. S.S. Banwait, Dr. S.C. Laroiya, Birla Pub. Pvt. Ltd., Delhi, 2008

TEXT BOOKS:

1. Basic and Applied Thermodynamics, P.K.Nag, 2nd Ed., Tata McGrawHill Pub. 2002

2. Basic Engineering Thermodynamics, Dr. A.Venkatesh, Universities Press, 2008

REFERENCE BOOKS:

1. Thermodynamics, An Engineering Approach, Yunus A.Cenegal and Michael A.Boles, Tata McGraw Hill publications, 2002

2. Fundamentals of Classical Thermodynamics, G.J.Van Wylen and R.E.Sonntag, Wiley Eastern.

3. Engineering Thermodynamics, J.B.Jones and G.A.Hawkins, John Wileyand Sons. 4. An Introduction to Thermodynamcis, Y.V.C.Rao, Wiley Eastern, 1993,

Unit-1




Unit-2: Gas Power Cycle 1. What is a thermodynamic cycle? 2. What is meant by air standard cycle? 3.. Name the various “gas power cycles". 4. What are the assumptions made for air standard cycle analysis 5. Mention the various processes of the Otto cycle. . 6. Mention the various processes of diesel cycle. 7. Mention the various processes of dual cycle. 9. Define air standard cycle efficiency. 10. Sketch the Carnot cycle on P-V and T-S diagrams and derive an expression for its thermal

efficiency. List the assumptions made. 11. Sketch the Otto cycle on P-V and T-S diagrams and derive an expression for its thermal

efficiency. List the assumptions made. 12. Enumerate the difference b/w Otto and Carnot cycle with P-V and T-S diagrams. 13. Define mean effective pressure as applied to gas power cycles. How it is related to indicate

power of an I.C engine? 14. Define the following terms. (i) Compression ratio (ii) Cut off ratio , (iii) .Expansion ratio 15. Drive and expression for the air standard efficiency of Otto cycle in terms of volume ratio. 16. Drive an expression for the air standard efficiency of Diesel cycle 17. Drive an expression for the air standard efficiency of Dual cycle. 18. Explain the working of 4 stroke cycle Diesel engine. Draw the theoretical and actual PV

diagram.




19. Derive an expression for the air standard efficiency of a cycle which is similar to Otto cycle except that the compression is isothermal in terms of compression ratio, the maximum temperature ratio and the ratio of specific heat.

20. A Carnot cycle works between the temperature limits of 900 K & 300 K and pressure limits of 60 bar and 1 bar. Find

i. The Pressure and temperature at all salient points. ii. Heat supplied & Heat rejected per kg of air.

iii. Work done/kg of air iv. Thermal efficiency of the cycle.

21. The maximum pressure & temperature in a Carnot cycle is limited to 20 bar & 4000C. The ratio of isentropic compression is 6 & isothermal expansion is 1.5, assuming the volume of air at the beginning of isothermal expansion is 0.1 m3. Find

i. The minimum temperature in the cycle. ii. Change in entropy during isothermal expansion process.

iii. Mean thermal efficiency of the cycle. iv. Theoretical power if there are 200 cycles/min. v. Mean Effective Pressure (MEP).

22. In an air standard Carnot cycle heat is transferred to the working fluid at 1110 K & heat is rejected at 273 K. The heat is transfer to the working fluid at 1110 K is 105 KJ/Kg. The minimum pressure in the cycle is 1 bar. Find

i. Thermal efficiency of the cycle. ii. MEP.

23. An inventor claims that the new heat cycle will develop 0.4 KW for a heat addition of 32.5 KJ/min. The temperature of heat source is 1990 K & that of sink is 850 K. Is his claim is possible?

24. The highest compression ratio of Carnot cycle using air as working fluid is fixed as Rc & the lower temperature T1 is also fixed. The isentropic compression ‘r’ is a variable. Show that the required expression for maximum work is given by

(훤 − 1) logRc푟 +

1푟( ) − 1 = 0

25. An engine working on an Otto cycle has a volume of 0.5m3, pressure of 1 bar and a

temperature of 270C at the beginning of the compression stroke. At the end of the compression stroke the pressure is 10 bar. Heat added during constant volume process is 200 KJ/Kg. Determine

i. % clearance. ii. Air standard efficiency.




iii. MEP iv. Ideal power developed by the engine if there are 200 cycles/min.

26. An engine has 200 mm bore and 300 mm stroke, works on Otto cycle with a clearance volume of 0.0016 m3. The initial pressure & temperatures are 1 bar and 60 0C. If the maximum pressure is limited to 24 bar, find

i. Air standard efficiency. ii. Pressure and temperature at all salient points. iii. MEP.

27. In an air standard Otto cycle the maximum and minimum pressures and temperatures are 21 bar, 1.05 bar and 1923K, 311K respectively. Calculate air standard efficiency and compare with Carnot cycle efficiency.

28. For an Otto cycle the upper and lower limits for absolute temperature are T3 and T1 respectively,

i. Show that for the maximum work, the compression ratio should have the value of .

ii. The intermediate temperature is given by T T 29. From the P-V diagram of an engine working on Otto cycle is found that the pressure in the

cylinder after 1/8th of the compression stroke executed is 1.4 bar, and after 5/8th of the compression stroke executed is 3.6 bar. The maximum cycle temperature is limited to 1273K. The temperature at the start of the compression is 27 0C. Determine ,

The compression ratio, Air standard efficiency, The net work output, Specific air consumption(SAC)

30. An air standard Diesel cycle has a compression ratio of 12 and cutoff takes place at 6% of the stroke. Calculate the air standard efficiency of the cycle.

31. 1kg of air is taken through a diesel cycle. Initially the air is at 25oC and 1 bar. The compression ratio is 14 and the heat added is 1850KJ. Calculate the ideal cycle efficiency and the mean effective pressure.

32. Draw the theoretical and actual P.V. diagrams for 4-stroke diesel engine and explain why in practice the actual condition differs from the ideal condition.

33. In an air standard Diesel cycle, the compression ratio is 18, and at the beginning of isentropic compression, the temperature is 27CC and the pressure is 0.1 MPa. 1800 kJ of heat is added at constant pressure. Calculate i) the cut-off ratio, ii) the heat supplied per kg of air iii) the cycle efficiency and iv) mean effective pressure

34. A Dual combustion air standard cycle has a compression ratio of 10. The constant pressure




part of combustion takes place at 40 bar. The highest and the lowest temperature of the cycle are 1725degree C and 27 0 C respectively. The pressure at the beginning of compression is 1 bar. Calculate (I) the pressure and temperature at’ key points of the cycle. (ii) The heat supplied at constant volume, (iii) the heat supplied at constant pressure. (Iv) The heat rejected. (v) The work output. (vi) The efficiency and (vii) mep.

35. In a dual cycle the air is compressed isentropically to 1/14th of its initial volume. At the end of compression heat is added at constant volume till its pressure increases to twice the pressure at the end of compression. Then heat is added at constant pressure till its volume increases to twice the volume after compression. Find the efficiency of the cycle.

36. In engine working on Dual cycle, the temperature and pressure at the beginning of cycle are 90oC and one bar. The compression ratio is 9. The maximum pressure is limited to 68bar and total heat supplied per kg of air is 1750kJ. Determine air standard efficiency and mean effective pressure.

37. A dual combustion air standard cycle has a compression ratio of 10. The constant pressure part of combustion takes place at 40 bar. The highest and the lowest temperatures of the cycle are 1727° C and 27° C respectively. The pressure at the beginning of compression is 1 bar. Calculate (i) the pressures and temperatures at key points of the cycle,(ii)the heat supplied at constant volume, (iii) the heat supplied at constant pressure, (iv) the heat rejected, (v) the work output, (vi) the efficiency and (vii) MEP.

38. An air standard dual cycle has a compression ratio of 16 and compression begins at1.013 bar, 50°C. The maximum pressure is 70 bar. The heat transferred to air at constant pressure is equal to that at constant volume. Estimate the temperatures at the cardinal points of the cycle and the cycle efficiency.

39. An air-standard Dual cycle has a compression ratio of 10. The pressure and temperature at the beginning of compression are I bar and 27°C. The maximum pressure reached is 42 bar and the maximum temperature us 1500oC Determine

i. The temperature at the end of constant volume heat addition ii. Cut-off ratio iii. Work done per kg of air and iv. Net work output per kg Cycle efficiency

Unit 3: Internal Combustion Engines

1. Classify IC engine according to cycle of lubrication system and field of

application. Types of lubrication system 2. List the various components of IC engines. 3. Name the basic thermodynamic cycles of the two types of internal




combustion reciprocating engines. 4. Mention the important requites of liner material. 5. State the purpose of providing piston in IC engines. 6. Define the terms as applied to reciprocating I.C. engines "Mean effective

pressure" and "Compression ratio". 7. What is meant by highest useful compression ratio? 8. What are the types of piston rings? 9. What is the use of connecting rod? 10. What is the use of flywheel? 11. Explain full pressure lubrication system I.C Engine 12. Explain the water cooling system in I.C Engine. 13. Explain the 2 types of Ignition system In 5.1 Engine. 14. Draw and explain the valve timing diagram of 4 strokes Diesel Engine. 15. Draw and explain the port timing diagram of 2stroke Petrol Engine. 16. Following data relates to 4 cylinders, 2 stroke petrol engine. Air/Fuel ratio by weight 16:1. Calorific value of the fuel = 45200 kJ/kg, mechanical efficiency = 82%. Air standard efficiency = 52%, relative efficiency =70% volumetric efficiency = 78%, 17. Stroke/bone ratio = 1.25 suction conditions = 1 bar, 25°C. Speed = 2400 rpm power at brakes = 72 kW. Calculate

(i) Compression ratio. (ii) Indicated thermal efficiency (iii) Brake specific fuel consumption and (iv) Bore and stroke.

18. The following observations were taken during trial on a single cylinder oil engine. Duration of trial = 1 hour

Fuel consumption = 7.6 kg

Total revolutions = 12000

Net brake load = 1.5 kN

Brake drum diameter = 1.83 m

Total cooling water circulated = 550 kg

Inlet temperature of cooling water = 15°C

Outlet temperature of cooling water = 60°C

Temperature of exhausted gases = 300°C

Atmospheric temperature = 20°C




Air consumption = 360 kg

Mean effective pressure = 6 bar

Take the followings

CV. of fuel = 45000 kJ/kg

Cp (for exhaust gases) = 1 kJ/kg-K

Bore = 30 cm

Stroke = 45 cm

Determine:

(i) Brake power (ii) Mechanical efficiency (iii) Indicated thermal efficiency (iv) Draw up the heat balance.

19. The following data refer to a single cylinder four stroke petrol engine:

Compression ratio = 5.6 Mechanical efficiency = 80%

20. An eight cylinder four stroke engine of 9 cm bore and 8 cm stroke has a compression ratio of 7 is tested at 4500 rpm on a dynamometer which has a 54 cm arm. During a ten minute test the dynamometer load reading was 42 kg and the engine consumed 4.4 kg of gasoline having a calorific value of 44 MJ/kg. Air at 27°C and 1 bar was supplied to the carburetor at the rate of 6 kg/mm. Find the following:

(i) Brake Mean Effective Pressure (ii) Specific Fuel Consumption and specific Air Consumption (iii) Relative efficiency (iv)Volumetric efficiency.

21. Determine the size of the fuel orifice to give a 13.5 1 air-fuel ratio, if the venture throat

Brake specific fuel consumption = 0.37 kg/kW h Calorific value of fuel = 44000 kJ/kg Adiabatic index for air = 1.4 Find (i) brake thermal efficiency

(ii) Indicated thermal efficiency iii) Air Standard efficiency




has a 3 cm diameter and the pressure drop in the venturi is 6.5 cm Hg. The air temperature and pressure at carburetor entrance are 1 bar and 27°C respectively. The fuel orifice is at the same level as that of the float chamber. Take density of gasoline as 740 kg/m3 and discharge coefficient as unity. Assume atmospheric pressure to be 76 cm of Hg.

22. A four stroke petrol engine has a piston displacement of 2210 cm3. The compression ratio is 6.4. The fuel consumption is 0.13 kg/mm. The calorific value of fuel is 45000 KJ/kg. The brake power developed while running at 2500 rev/mm is 50.25 KW. Determine the brake mean effective pressure and the relative efficiency based on brake thermal efficiency.

23. During the trial of four stoke, single cylinder oil engine the following observations were recorded: bore = 300 mm; stroke 400 mm; speed 200 rpm; duration of trial = 60 minutes; fuel consumption 7.050 kg: calorific value 14000 kJ/kg; area of indicator diagram 322 mm2 length of indicator diagram 62 mm; spring index = 1.1 bar/mm; dead load on the brake drum = 140 kg; spring balance reading = 5 kg; brake drum diameter = 1600 mm; total weight of cooling water = 495 kg: temperature rise of cooling water = 38°C; temperature of exhaust gases = 300°C: air consumption = 311 kg; specific heat of exhaust gases 1.004 kJ/kg K; specific heat of water = 4.186 kJ/kg K; room temperature 20°C. Determine

i. Brake power ii. Indicated power

iii. Mechanical efficiency iv. Thermal efficiency and draw up a heat balance sheet

24. The following results refer to a test on a petrol engine Indicated power = 30 Kw, Brake power = 26 Kw Engine speed = 1000 rpm Fuel brake power/ hour = 0.35 kg Calorific value of fuel = 43900kj/kg, Calculate

i. Mechanical efficiency ii. Indicated thermal efficiency ii. Brake thermal efficiency

25. A four cylinder 2 stroke cycle petrol engine develops 23.5 kw brake power at 2500 rpm. The mean effective pressure on each piston in 8. 5 bar and mechanical efficiency in 85% Calculate the diameter and stroke of each cylinder assuming the length of stroke equal to 1.5 times the diameter of cylinder.

26. The following data to a particular twin cylinder two stroke diesel engine. Bore 15 cm stroke. 20 cm. speed 400 rpm. Indicated mean effective pressure 4 bar, dead weight on the brake




drum 650 N. spring balance reading 25 N Diameter of the brake drum 1 m .Fuel consumption 0.075 kg/min and calorific value of the fuel is 44500 kj/J kg.

Determine i. Indicated Power

ii. Brake Power iii. Mechanical efficiency iv. Indicated thermal efficiency v. Brake thermal efficiency

Unit 4:-




Unit 5: Reciprocating Air Compressor 1. What is meant by single acting compressor? 2. What is meant by double acting compressor? 3. What is meant by single stage compressor? 4. What is meant by multistage compressor? 5. Define isentropic efficiency 6. Define mean effective pressure. How is it related to in power of an I.C engine. 7. What is meant by free air delivered? 8. Explain how flow of air is controlled in a reciprocating compressor? 9. What factors limit the delivery pressure in reciprocating compressor? 10. Name the methods adopted for increasing isothermal efficiency of reciprocating air

compressor. 11. Why clearance is necessary and what is its effect on the performance of reciprocating

compressor? 12. What is compression ratio? 13. What is meant by inter cooler? 14. Define the terms as applied to reciprocating compressor: Mechanical efficiency, isothermal efficiency, isentropic efficiency. 15. What factors limit the delivery pressure in a reciprocating compressor? 16. Name the methods adopted for increasing isothermal efficiency of reciprocating air

compressor.




17. What are the factors that affect the volumetric efficiency of a reciprocating compressor? 18. Discuss the effect of clearance upon the performance of an air compressor. 19. Differentiate between prefect inter cooling and imperfect inter cooling. 20. Compare reciprocating and rotary compressor. 21. What is the main advantage of inter cooling in multistage reciprocating compressor? 22. Why clearance is necessary in reciprocating compressor? 23. Differentiate positive and non positive displacement compressor? 24. What is the effect of clearance volume on the power required and work done in a

reciprocating air compressor? 25. Drive an expression for the work done by single stage single acting reciprocating air

compressor. 26. Drive an expression for the volumetric efficiency of reciprocating air compressors 27. A single stage single acting air compressor is used to compress air from 1 bar and 22° C to 6

bar according to the law PV1 .25 = C. The compressor runs at 125 rpm and the ratio of stroke length to bore of a cylinder is 1.5. If the power required by the compressor is 20 kW, determine the size of the cylinder.

28. A single stage single acting air compressor is used to compress air from 1.013 bar and 25° C to 7 bar according to law PV 1.3 = C. The bore and stroke of a cylinder are 120mm and 150mm respectively. The compressor runs at 250 rpm .If clearance volume of the cylinder is 5% of stroke volume and the mechanical efficiency of the compressor is 85%, determine volumetric efficiency, power, and mass of air delivered per minute.

29. A two stage singe acting air compressor compresses 2m3 airs from 1 bar and 20° C to 15 bar. The air from the low pressure compressor is cooled to 25° C in the intercooler. Calculate the minimum power required to run the compressor if, the compression follows PV1.25=C and the compressor runs at 400 rpm.

30. The free air delivery of a single cylinder single stage reciprocating air compressor is 2.5m3/min. The ambient air is at STP conditions and delivery pressure is 7 bar. The clearance volume is 5% of the stroke volume and law of compression and expansion is pV1.25=C. If L=1.2D and compressor runs at 150rpm, determine the size of the cylinders.

31. A multi stage air compressor is to be designed to evaluate the pressure from 1 bar to 120 bar. Such that the single stage pressure ratio not to exceed 4. Find (i) Number of stages (ii). Exact stage pressure ratio (iii) Inter stage pressure.

32. Consider a single acting two stage reciprocating air compressor running at 300rpm. Air is

compressed at a rate of 4.5kg/min from 1.013bar and 288K through a pressure ratio of 9 to 1.




Both the stages have same pressure ratio and the index of expansion in both stages is 1.3. Assume a complete inter-cooling, find the indicated power and the cylinder swept volume required. Assume that the clearance volumes of both stages are 5% of their respective swept volumes.

33. A two-cylinder single-acting air compressor is to deliver 16 kg of air per minute at 7 bar from suction conditions 1 bar and 15°C. Clearance may be taken as 4% of stroke volume and the index for both compression and re expansion as 1.3. Compressor is directly coupled to a four-cylinder four-stroke petrol engine which runs at 2000 r.p.m. with a brake mean effective pressure of 5.5bar. Assuming a stroke-broke ratio of 1.2 for both engine and compressor and a mechanical efficiency of 82% for compressor, calculate the required cylinder dimensions.

34. A two stage air compressor compresses air from 1 bar and 20°C to 42 bar. If the law of compression is pv1.3= constant and the inter cooling is perfect. Find per kg of air i). The work done in compression ii). The mass of cooling water necessary for abstracting the heat in the intercooler, if the temperature rise of the cooling water is 25°C.

35. A single stage single acting reciprocating air compressor delivers 14 m3 of free air per minute from 1 bar to 7 bar. The speed of compressor is 310rpm.Assuming that compression and expansion follow the law pv1.35 = constant and clearance is 5% of the swept volume, find the diameter and stroke of the compressor. Take stroke length is 1.5 times the bore diameter.

36. A single acting single stage compressor is belt driven from an electric motor at 400rpm. The cylinder diameter is 15 cm and the stroke is 17.5 cm. The air is compressed from 1 bar to 7 bar and the law of compression PV1.3 = constant. Find the power of the motor, if transmission efficiency is 97% and the mechanical efficiency of the compressor is 90%. Neglect clearance effects.

37. A two-stage double acting air compressor, operating at 200 r.p.m, takes in air at 1.013 bar and 27° C. The size of the L.P. cylinder is 350 x 380 mm, the stroke of H.P. cylinder is the same as that of the L.P. cylinder and the clearance of both the cylinders is 4%. The L.P. cylinder discharges the air at a pressure of 4.052 bar. The air passes through the inter-cooler so that it enters the H.P. cylinder at 27° C and 3.850 bar, finally it is discharged from the compressor at 15.4 bar. The value of n is both cylinders is 1.3. Cp = 1.0035 kJ/kg-K and R = 0.287 kJ/kg-K. Calculate (i). The heat rejected in the inter cooler. (ii).The diameter of H.P. cylinder and (iii). The power required to drive H.P. cylinder.

Unit 6: Gas Turbine And propulsion systems

1. How the gas turbine cycles classified? 2. What are essential components required for the operation of gas turbine cycle and explain

their functionality.




3. Draw the schematic diagram of open cycle gas turbine unit and explain its working along with its merits and demerits.

4. Explain with neat sketch Closed cycle gas turbine plant 5. Explain with neat sketch differences between open cycle gas turbine plant and closed

Cycle turbine plant. 6. Derive the expression for thermal efficiency of a simple gas turbine plant 7. Show that the efficiency of an air standard Brayton cycle is a function of isentropic

pressure ratio. 8. What are different operating variables affect the thermal efficiency of gas turbine power

plant? Explain. 9. Show that the specific output of a simple gas turbine cycle is maximum, when the

pressure ratio is such that the compressor and turbine outlet temperatures are equal. 10. What are different parameters influence the performance of gas turbine cycle. Explain. 11. What is the effect of pressure ratio during compression on the performance of gas turbine

cycle? 12. Draw the schematic layout of gas turbine cycle with regenerator, intercooler and

reheating. Explain salient features. 13. Sketch the ideal regenerative Brayton cycle in two stage compression and expansion with

intercooling and reheating. Mark the salient points on T-s diagrams. 14. Derive the thermal efficiency of gas turbine with multi stage compression with inter-

cooling. 15. What is the influence of isentropic efficiency of compressor and turbine on thermal

efficiency of gas turbine unit? Explain with suitable diagrams. 16. Explain the working of regenerative gas turbine cycle with p-V and T-s diagrams. 17. The minimum and maximum temperature limits in a gas turbine plant are288 K and 1100

K. The pressure limits are 1 bar and 8 bar. Determine the thermal efficiency and work ratio.

18. In a gas turbine power cycle, the pressure ratio is 6 and the maximum cycle temperature is 650 0C. The air enters to the cylinder at 15 0c and the flow rate of air is 12 kg/s. Determine the power developed and thermal efficiency of cycle.

19. A Brayton cycle works between 1 bar, 300 K and 5 bar, 1250 K. There are two stages of compression with perfect intercooling and two stages of expansion with reheating. The work output of first expansion stage being used to drive the two compressors, where the inter-stage pressure is optimized for the compressor. The air from the first stage turbine is again heated to 1250 K and expanded. Calculate the power output of free power turbine and cycle efficiency without and with perfect heat exchanger and compare them. Also




calculate the percentage improvement in the efficiency because of the addition of heat exchangers.

20. A closed cycle gas turbine using Argon as the working fluid has a two compression with perfect inter cooling. The overall pressure ratio is 9 and pressure ratio in each stage is equal. Each stage has an isentropic efficiency of 85%. The turbine is also two stages with equal pressure ratio with inter change reheat to original temperature. Each turbine stage has an isentropic efficiency of 90%. The turbine inlet temperature is 1100K and the compressor inlet is 303K. Find

i. Work done per kg of fluid flow ii. Work ratio

iii. The overall cycle efficiency. iv. The properties of argon are Cp = 0.5207kJ/kg0K, Γ =1.667 and R=0.20813kJ/kg0K

21. A Gas turbine plant works between the temperature limits of 11520 K and 2880 K Isentropic efficiency for compressor and turbines are 0.85 and 0.8 respectively. Determine the optimum pressure ratio for maximum work output and also for maximum Cycle thermal efficiency.

22. Compare the maximum work delivered by an air craft gas turbine which works with two stage compression with inter cooling. The compressor pressure ratio is 4 and the temperature limit is 1000 K, for the given ambient condition 1 bar and 301 K. If the temperature and pressure at 6000 m altitude is -25 0C and 0.5 bar, find the percentage change in network output, efficiency and exhaust gas temperature if the volume flow rate is 2.5 m3/s.

23. In gas turbine plant, operating on joules cycle, maximum and minimum temperatures of 8250C and 27 0C. The pressure ratio is 4.5. Calculate the specific work output, cycle efficiency and work ratio. Assume isentropic efficiency of compressor and turbine 85%and 90% respectively. What is the heat rate in kJ / kW-hr? If the rating of the turbine is 1300kW, what is the mass flow in kg/s. Neglect the mass of fuel Cp =1.005 kJ/kg 0K.

Unit 7: Refrigeration:

1. Name four important properties of a good refrigerant 2. What is the difference between air conditioning and refrigeration? 3. In a vapour compression refrigeration system, where the highest temperature will occur? 4. The vapour absorption system can use low-grade heat energy in the generator. Is true of

false? 6. Name any four commonly used refrigerants. 7. Explain unit of Refrigeration.




8. Why throttle valve is used in place of expansion cylinder for vapour compression refrigerant machine. 9. What are the effects of super heating and sub cooling on .the vapour compression cycle? 10. What are the properties of good refrigerant? 11. Draw neat sketch of simple vapor compression refrigeration

system and explain. 12. A refrigeration system of 10.5 tonnes capacity at an evaporator temperature of -12°C and a

condenser temperature of 27°C is needed in a food storage locker. The refrigerant Ammonia is sub cooled by 6°C before entering the expansion valve. The compression in the compressor is of adiabatic type. Find 1. Condition of vapor at outlet of the compressor. 2. Condition of vapor at the entrance of the evaporator 3.COP & power required.

13. An ammonia refrigerator produces 30 tonnes of ice from and at 0°C in a day of 24 hours. The temperature range in the compressor is from 25°C to 15°C. The vapour is dry saturated at the end of compression and an expansion valve is used. Calculate the coefficient of performance. The properties of the refrigerant are given in the following table

14. A food storage locker requires a refrigerating capacity of 50kW. It works between a

condenser temperature of 35°C and an evaporator temperature of -10°C. The refrigerant is ammonia; It is sub-cooled by 5°C before entering the expansion valve and dry saturated vapour leaving the evaporator. Assuming a single cylinder, single acting compressor operating at 1000 rpm with stroke equal to 1.2 times the bore. Determine The power required and cylinder dimensions, the properties of ammonia are,




Unit 8: Psychometry:-

1. How are air-conditioning systems classified? 2. How does humidity affect human comfort? 3. What are the various sources of heat gain of an air-conditioned space? 4. What do you mean by the term infiltration in heat load calculations? Define

Psychrometry. 5. What is humidification and dehumidification? 6. Define specific humidity. 7. Differentiate absolute humidity and relative humidity. 8. What is effective temperature? 9. Represent the following psychrometric process using skeleton psychrometric chart? 10. Define Relative humidity. 11. Define degree of saturation. 12. What is meant by adiabatic saturation temperature (or) thermodynamic wet bulb

temperature? 13. What is dew point temperature? How it is related to dry bulb and wet bulb temperature at

the saturation condition? 14. What is meant by dry bulb temperature (DBT)? 15. What is meant by wet bulb temperature (WBT)? 16. Define sensible heat and latent heat. 17. Consider a room that contains air at 1 atm., 35oC and 40 percent relative humidity. Using

psychrometric chart, determine (i) the specific humidity (ii) the enthalpy (iii) the wet-bulb temperature (iv) the dew-point temperature, and (v) specific volume of air.

18. An air – water vapour mixture at 0.1MPa, 30oC, 80% RH has a volume of 50m3. Calculate the specific humidity, dew point, wet bulb temperature, mass of dry air and mass of water vapour.

19. Air at 16oC and 25% relative humidity passes through a heater and then through a humidifier to reach final dry bulb temperature of 30oC and 50% relative humidity. Calculative the heat and moisture added to the air. What is the sensible heat factor?

20. Saturated air at 20oC at a rate of 1.16m3/sec is mixed adiabatically with the outside air at 35oC and 50% relative humidity at a rate of 0.5m3/sec. assuming adiabatic mixing condition at 1 atm, determine specific humidity, relative humidity, dry bulb temperature and volume flow rate of the mixture.

21. (a) A sling psychrometer reads 40OC DBT and 36OC WBT. Find the humidity ratio, relative humidity, DPT, specific volume of air, density of air, density of water vapour and enthalpy.




(b) Saturated air at 21OC is passed through a drier so that the final relative humidity is 20%. The air is then passed through a cooler until its final temperature is 21OC without a change in specific humidity. Find (i) The temperature of air after drying process, (ii) the heat rejected in cooling process, (iii) the due point temperature at the end of drying process.

22. 40 m3 of air per minute at 31oC DBT and 18.5oC WBT is passed over the cooling coil whose surface temperature is 4.4oC. The coil cooling capacity is 3.56 tons of refrigeration under the given condition of air. Determine DBT and WBT of the air leaving the cooling coil.

23. A sling psychrometer in a laboratory test recorded the following readings.Dry bulb temperature = 35°C, Wet bulb temperature = 25°C Calculate the following

(i) specific humidity (ii) relative humidity (iii) vapour density in air (iv) dew point temperature and (v) Enthalpy of mixture per kg of dry air Take atmospheric pressure = 1.0132 bar.

24. An office is to be air-conditioned for 50 staff when the outdoor conditions are 30°C DBT and 75% RH if the quantity of air supplied is 0.4m3/min/person, find the following:

(i) Capacity of the cooling coil in tonnes of refrigeration (ii) Capacity of the heating coil in kW (iii). Amount of water vapour removed per hour, Assume that required air inlet conditions are 20°C DBT and 60% RH, Air is conditioned first by cooling and dehumidifying and then by heating.

(iv). If the heating coil surface temperature is 25°C, find the by-pass factor of the heating coil?

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