SAVEETHA SCHOOL OF ENGINEERINGSAVEETHA UNIVERSITY

DEPARTMENT OF MECHANICAL ENGINEERING

ME3407 – MODERN THERMODYNAMICSYear / Sem: IV Department: EEE

UNIT – I BASIC CONCEPTS AND LAWS OF THERMODYNMICS

Part – A Two Marks Questions

1. Define thermodynamics and give some applications.2. Define I) Heat ii) Specific Heat Capacity. 3. Define specific heat capacity at constant volume. 4. Define specific heat capacity at constant pressure. 5. Define I) Work ii) Mechanical work. 6. Define the term system, surrounding and boundaries. 7. Define I) Closed system ii) Open system iii) isolated system. 8. Define intensive and extensive property. 9. Define point and path function. 10. Define internal energy. 11. Define enthalpy. 12. Define thermodynamic equilibrium. 13. State the first and second law of thermodynamics. 14. State zeroth law. 15. Define entropy. 16. Distinguish between isothermal and adiabatic process. 17. Identify the different thermodynamic process. 18. Derive an expression for work done during isothermal process. 19. Explain the second law of thermodynamics. 20. Derive the relationship between Cp, Cv and R. 21. Define steady flow system.

22. Explain the steady flow energy equation. 23. Name the applications of steady flow energy equation. 24. Define control volume. 25. Write down the equation of SFEE. 26. Explain reversible and irreversible process

Part – B (16 Marks questions)1. Derive an equation for SFEE. And apply for various thermal equipments.

2. Air flows steady by a rate of 0.5kg/sec through an air compressor entering at 7m/sec velocity, 100kpa Pressure and 0.95m3/kg specific volume and leaving at 5m/sec, 700kpa and 0.19m3/kg. The internal energy of air leaving is 90kJ/kg greater than that of entering. Cooling water in the compressor absorbs heat from the air at the rate of 58KW.

(a) Compute the rate of shaft work input to the air in KW

(b) Find the ratio of inlet pipe diameter to outlet pipe diameter.

3. In a steady flow process 125kg of work is done by each kg of working fluid. The specific volume, velocity and pressure of the working fluid at inlet as 0.41m3/kg, 15.06 m/sec & 6 bar respectively. The inlet is 31m above the ground and the exhaust pipe is at ground level. The discharge conditions of the working fluid are 0.64m3/kg, 1bar and 263m/s. Find total heat loss between inlet & discharge.

4. Air flows steadily at the rate of 0.5kg/sec through an air compressor entering at 7m/sec velocity, 100Kpa, & 0.19m3/kg. And leaving at 15m/sec, 500kpa and 0.41m3/kg. The internal energy of air leaving is 90kj/kg greater than that of air entering. Cooling water in the compressor jacket absorbs heat from the air at the rate of 58KW.(a) Compute the shaft work input to the air in KW.(b) Find the ratio of inlet pipe diameter to outlet pipe diameter.

5. Air at one bar and 40oC is compressed to one by tenth of its original volume

adiabatically. Determine the final pressure, final temperature and work done on / m3

of air. Take R = 0.287 KJ / KgK. And gamma as 1.4 for air.

6. 0.35 m3 of air at 22oC and under atmospheric pressure is heated under constant

volume at a temperature of 100oC. Assume Cp = 1 KJ / KgK and Cv = 0.7 KJ/Kgk.

Find 1.Mass, 2. The final pressure, 3. Heat transfer, 4. Change in internal energy and

work done.

7. 0.65 Kg of air at 14 bar and 210oC is expanded to four times the final volume

according to the law P.V1.23 = C. Determines 1. The initial and final volume of the

gas, 2. Final temperature and pressure of the gas, 3. Work done, 4. Change in internal

energy, 5. Heat transfer, 6. Change in entropy. Assume R = 287 KJ/KgK.

8. A mass of air in initially at 260oC and 700Kpa and occupies 0.028m3. The air is expanded at constant pressure to 0.084m3. Polytropic process with n=1.5 is then carried out followed by a constant temperature process which complete the cycle. Assume all the process is reversible process.

(a) Sketch the cycle in the PV & TS diagram.

(b) Find the heat received & heat rejected from the cycle…..

(c) Find the efficiency.

9. Air initially at state 1 is at 27 oC, 1.05bar and occupies 0.02m3. It is heated at const. volume to state 2 where its pressure is 4.2 bar it is then cooled at constant pressure to state 3 where its temperature becomes 27 oC.

(a) Sketch the 2 process is T-S dig.

(b) Calculate the net heat transfer.

(c) Calculate net change in entropy.

10. An air compressor draws in air at 1 bar pressure, 0.5 m/kg specific volume and 5 m/sec velocity and delivers at 7 bar pressure, 0.15 m/kg specific volume and 7.5 m/sec velocity .If the enthalpy of air at delivery is 170Kj/kg greater than that at inlet and the rate of airflow is 15kg/min. Estimate the power of the compressor in kW and the ratio of pipe diameter at inlet and outlet. Assume a heat loss of 7300kj/min to the cooling water and surrounding air

11. Establish the Inequlity of Clausius.

12. A heat pump uses water in a river at 6 degree as an energy source and it delivers heat at 65oC to a building. It operates at 65% of its maximum possible COP between these temperatures and is powered by a 1.5 kW motor. What is the heat output to the building?

13. What are the 2 – statements of 2nd law of thermodynamics? Show that the 2 – statements are equivalent.

14. Explain heat pump, heat engine and refrigerator.

15. Explain Carnot theorem.

UNIT – II IC ENGINES AND GAS TURBINES

Part – A Two Marks Questions

1. Define air standard efficiency. 2. List the types of thermodynamic cycles. 3. Define mean effective pressure. 4. State the assumptions in deriving air standard efficiency. 5. Explain Carnot cycle with neat sketch. 6. Explain why the efficiency of Carnot cycle is High. 7. Sketch the p _ V and T _ S diagram for the Otto cycle. 8. Sketch the p _ V and T _ S diagram for the Diesel cycle. 9. Sketch the p _ V and T _ S diagram for the Dual cycle. 10. Distinguish between Otto cycle and Diesel cycle. 11. Explain the effects of Cut off ratio and compression ratio on the efficiency of diesel cycle. 12. Define Explosion ratio.13. Define swept volume and clearance volume. 14. No engine can work on Carnot cycle. Why? 15. Find the percentage increase in efficiency when the compressor ratio for a petrol engine is

raised from 5 to 6. Assume Gamma = 1.4. 16. Calculate the air standard efficiency of an engine working on Otto cycle, if the pressure at the

beginning and the end of compression are 103.5 KN/m2 and 827.5 KN/m2 respectively. Take Gamma = 1.4.

17. Find the air standard efficiency of a diesel cycle engine if the cut off ratio is 6% of the stroke and the clearance is 1/13th of the stroke. Take Gamma = 1.4.

18. How is I.C engines classified? 19. Sketch and name the nomenclature of I.C engine. 20. Write down the major different between S.I engine and C.I engine. 21. Distinguish between four stroke and two-stroke engine. 22. What do you mean by Detonation in I.C engines? 23. Compare open cycle gas turbine and closed cycle gas turbine.24. How are gas turbine classified. 25. What are all the applications of gas turbine?26. Explain how a reheater improves the performance of a gas turbine. 27. Write down the merits and demerits of gas turbine.28. Explain regeneration and reheating. 29. State the advantages of gas turbine over I.C engines.

Part – B (16 Marks questions)1. Explain two stroke SI engine with neat sketch.2. Explain four stroke SI engine with neat sketch.3. Explain two stroke CI engine with neat sketch.4. Explain four stroke CI engine with neat sketch.5. Differentiate SI engine and CI engine. And draw the PV and TS diagram for Otto cycle,

diesel cycle and dual cycle.6. Differentiate two stroke engine and four stroke engine. And draw the PV and TS diagram

for Otto cycle, diesel cycle and dual cycle.7. Derive air standard efficiency for Otto cycle with PV and TS diagram.8. Derive air standard efficiency for Diesel cycle with PV and TS diagram.9. Derive air standard efficiency for Dual cycle with PV and TS diagram.10. Explain brayton cycle with regeneration with PV and TS diagram.

11. Explain brayton cycle with reheat with PV and TS diagram.12. Explain brayton cycle with inter-cooling with PV and TS diagram.13. In an air standard Otto cycle, compression begins at 1bar & 40 oC with a compression

ratio at 7. The heat added is 2500KJ/kg. Find the maximum temperature, maximum pressure of the cycle, work done per kg of air, cycle efficiency and mean effective pressure.

14. An engine working on constant volume cycle has the following data.Clearance volume is 0.04m3, swept volume is 0.13m3, pressure and temperature at the beginning of cycle are 1.15bar and 120oC, Maximum pressure of the cycle is limited to 23bar. Calculate the air standard efficiency, maximum temperature of the cycle and mean effective pressure.

15. In an ideal constant volume cycle the pressure temperature and volume at the beginning of the cycle are 1.2bar, 35oC and 0.5m3 respectively at the end of compression the pressure is 12bar, 315KJ of heat is added per kg of gas, during the const. vol. pressure calculate the pressure temp & vol. of all point also find the air standard efficiency of cycle and mean effective pressure.

16. In an ideal diesel cycle, the temperature at the beginning and end of compression is 57oC & 603oC respectively. The temperature at the beginning & end of expansion is 1950oC & 870 oC respectively. Determine the ideal efficiency of the cycle taken 1.4. If the compression ratio is 14 & the pressure at the beginning of the compression is 1bar calculate maximum pressure.

17. An oil engine working on theoretical diesel cycle has a bore of 200mm & stroke of 300mm compression ratio is 16, cut off takes at 10% of strokes. Find the clearance volume, cut off ratio, expansion ratio and air standard efficiency.

UNIT III STEAM BOILERS AND TURBINES Part – A Two Marks Questions

1. What is the difference between impulse turbine and reaction turbine2. Find the temperature of water at a state where the pressure is 500kPa and the enthalpy

is 2960kJ/kg.3. What is compounding of turbine4. What is mean by sensible heat5. What is mean by latent heat6. What is impulse turbine?7. What is reaction turbine?8. Define dryness fractions9. What are the types of steams.10. Give an example for high pressure boilers.11. Draw simple Rankine cycle.12. Draw the P-V and T-S diagrams for simple Rankine cycle.13. What are the types of compounding?14. What is the difference between boiler accessories and boiler mountings?15. Give few examples for boiler accessories.16. Give few examples for boiler mountings.

Part – B (16 Marks questions)1. What are the different compounding methods of steams turbines? Explain any one

compounding.

2. Explain pressure compounding and velocity compounding with neat sketch.

3. Explain with neat sketch for thermal power plant layout.

4. Dry saturated steam at 10bar expands in a turbine to 0.1 bar. Calculate ideal Rankine

cycle efficiency.

5. During boiler testing 250kg of coal is used to evaporate 2000kg water to produce 0.95

dry steams at 11.5 bar. Feed water temperature is 34oC and calorific value of coal is

29800kJ/Kg. estimate the equivalent evaporation from and at 100oC per kg of coal

and efficiency of the boiler.

6. (i) Explain the process of steam formation with the help of temperature-total heat

group.

(ii) The following observations were made in a boiler trial : Coal used 250 kg of

calorific value 29,800 kj/kg water evaporated 2000 kg , steam pressure 11.5 bar,

dryness fraction of steam 0.95 and feed water temperature 34 C. Calculate the

equivalent evaporation from and at 100 C per kg of coal and efficiency of the boiler.

7. Draw the velocity diagram of an impulse turbine and indicate the various components.

8. Mention the function of pressure gauge, fusible plug, economizer and super heater

used in boilers.

9. Explain boiler accessories and mountings with at least two examples and neat sketch.

10. Explain any one of the high pressure boilers.

11. A simple Rankine cycle steam power plant operates between the temperatures of

260oC and 95oC.The steam is supplied to the turbine at a dry saturated condition. In

the turbine, it expands in an isentropic manner, determine the efficiency of the

Rankine cycle operating between these two temperature limts. Draw the turbine cycle

on h-s and on a T-s diagram.

12. In a De-lavel turbine the steam enters the whee through a nozzle with a velocity of

500 m/s and at an angle of 20° to the direction of motion of the blade.The blade speed

is 200m/s and the exit angle of the moving blade is 25°.Find the inlet angle of the

moving blade, exit velocity of steam and its direction and work done per kg of steam

using velocity diagram.

Unit – IV COMPRESSORS, REFRIGERATION AND AIR CONDITIONING Part – A Two Marks Questions

1. How air compressors are classified 2. With neat sketch explain the working of multistage air compressor. 3. What is intercooler? 4. Write the advantages of rotary air compressor. 5. Distinguish between reciprocating and rotary compressor. 6. Define positive displacement and negative displacement. 7. What are the uses of compressed air? 8. What are all the special features of rotary compressor? 9. Explain the various efficiency of air compressor. 10. Sketch the multi cylinder air compressor. 11. Sketch the axial flow rotary compressor. 12. Compare centrifugal and axial flow compressor. 13. Name the factors in maintenance of compressor and explain any one. 14. Define pressure ratio and clearance ratio. 15. State the merits of multi stage air compressor.16. Define refrigeration17. Define air conditioning 18. Differentiate between refrigeration and air conditioning 19. Distinguish between relative humidity and specific humidity 20. What is subcooling?21. Draw the layout of vapour compression systems22. What is difference between vapour compressions systems and vapour absorptions

systems?23. Explain cooling and dehumidification.24. Define one tonne of refrigeration.25. Draw the layout of summer air conditioning.26. Draw the layout for winter air conditioning.

Part – B (16 Marks questions)

1. With the help of a neat sketch explain summer air-conditioning system.

2. With the help of a neat sketch explain winter air-conditioning system.

3. Discuss the principle of operation axial flow air compressor with a sketch.

4. With the help of p-h diagram explain effect of sub cooling and super heating on vapour

compression refrigeration cycle.

5. (i) Compare reciprocating and rotary air compressors.

(ii) Discuss the principle of operation axial flow air compressor with a sketch.

6. (i)Explain the vapour compression cycle with the help of T-s diagram.

(ii) Define wet bulb temperature, specific humidity, humidification and dehumidification.

7. Discuss the principle of operation axial flow air compressor with a sketch.

8. A single stage reciprocating air compressor takes in 7.5 m/min of air at 1 bar and 30C

and delivers it 5 bar. The clearance 5 percent of the stroke. The expansion and

compression are plytropic with n=1.3.Calculate the temperature of air delivered

volumetric efficiency and power of the compressor.

9. A two stage single acting reciprocating compressor takes in air at the rate of 0.2m3/s.

The intake pressure and temperature of air are 0.1 Mpa and 16°C.The air is compressed

to a final pressure of 0.77 MPa. The intermediate pressure is ideal and inter-cooling is

perfect. The compression index in both the stages is 1.25 and the compressor runs at 600

rpm. Neglecting clearance determine the intermediate pressure , the total volume of each

cylinder, the power required to drive the compressor and the rate of heat rejection in the

intercooler. Take cp=1005 kJ/kg K and R=287 J/kg K.

10. A single acting reciprocating air compressor has cylinder diameter and stroke of 200

mm and 300 mm respectively. The compressor draws air at 1 bar and 27°C and delivers

at 8 bar while running at 100 rpm. Find the indicated power, mass of air delivered per

minute and temperature of the air delivered by the compressor. The compression

follows the law pv1.25=C. Take R as 287 J.kg K.

11. An air compressor receives air 1.05 bar and 14oC and compressor it to 8bar. The temperature of

the air delivered is 150oC. The compression follows the law p.Vn=C. Calculate the value of

index _n_. The delivery rate is 1.4 m3 of free air per min. Ignore temperature changes during

suction and delivery. Find the power saved if the compression takes place isothermally.

UNIT – V HEAT TRANSFER

Part – A Two Marks Questions

1. Define thermal conductivity of a material?2. Write down the Fourier conduction equation:3. Define overall heat transfer coefficient4. State Fourier’s law of heat conduction.5. What is critical thickness of insulation?6. Unit for thermal conductivity is?7. What are the three ways in which heat may be transferred?8. Define efficiency of fin9. Define effectiveness of fin10. Mention four application of fin.11. Define convection.12. State Newton's law of convection.13. What is meant by free or natural convection?14. W hat is forced convection?15. Define emissive power 16. Define monochromatic emissive power 17. What is meant by absorptivity 18. What is meant by reflectivity? 19. What is Black body?20. Define Emissivity. 21. State Wien's displacement law.22. What is meant by gray body?23. Define Radiation.

Part – B (16 Marks questions)1. Derive an expression for heat flow through a hollow sphere with heat transfer

coefficient.

2. Derive an expression for heat flow through a composite wall with heat transfer

coefficient.

3. Derive an expression for heat flow through a composite cylinder with heat transfer

coefficient.

4. A composite wall is made of two slabs with outside surface temperature. Maintained

at 1300oC and 115oC. The 1st slab has a thickness of 500mm and thermal conductivity

of 104W/mk. The thickness and thermal conductivity of 2nd slab are 161mm and

0.35W/mk respectively. Calculate the conduction heat transfer through this composite

wall per unit area.

5. A cold storage room has wall made of 0.23m of brick, on outside 0.08m plastic foam

and finally 1.5cm of wood on the outside, the outside and inside temperature are 22 oC

and -2oC respectively. If the inside and outside heat transfer co-efficient are 29W/m2k

and thermal conductivity of brick, plastic, wood are 0.98, 0.02& 0.17W/mk

respectively. (a) The rate of heat removed by refrigeration, if the total area is 90m2 &

(b) the temperature of the inside surface of the brick.

6. A 1.2m high & 2m wide double plane window consist of two 3mm thick layer of

glass (k=0.78W/mk) repeated by a 12mm width stagnant air gap (k=0.0268W/mk) a

steady state of heat transfer through this double plan window & the temperature of its

inner surface for a day during which the room is maintained at 24oC. While the

temperature of the outdoor is -5oC. Take the convection heat transfer co-efficient on

the inner and outer surface of window to the h1=10W/m2k.and h2=25W/m2k. Find the

heat transfer. And neglect any heat transfer by radiation.

7. Hot air at a temperature of 60 oC is flowing through a steel pipe of 10cm diameter the

pipe is covered with 2 layer of different insulating material of thickness 5cm &3cm

and their corresponding thermal conductivity are 0.23 & 0.27 W/mk. the inside and

outside heat transfer co-efficient are 58 & 12W/m2k. The atmosphere is at 25oC. Find

the rate of heat loss from a 50m length. Neglect the resistance of the steel pipe.

8. When 0.6kg of water/min is passed through a tube of jump. It is found to be heated

from 20 oC to 60oC. The heating is achieved by condensing steam on the surface of the

tube and subsequently the surface temperature of the tube is maintained at 90oC. the

length of the tube required for fully developed flow.

9. Find the loss from the rod of 3mm in and initially long when its base is maintained at

140oC. The conductivity of the material is 150W/mk & the heat transfer co-efficient

on the surface of the rod is 300W/m2k. The temperature of the air surrounding of the

rod is 15oC.

10. A long rod 5cm its base is connected to a wall at 150oC. While the end is projecting

into the room at 20oC. If the temperature of the rod at a distance 20cm apart from the

base is 60oC. The conductivity of the material is 200W/mk. determine the convective

heat transfer co-efficient.

11. A wire of 6mm diameter with 2mm thickness insulation (k=0.11W/mk). If the

convective heat transfer co-efficient between the insulating surface & air is 25W/m2k.

Find the critical thickness of insulation and also find the % change in the heat transfer

rate if the critical radius is used.

12. A steel pipe line has inner diameter 100mm & outer diameter 110mm. Its thermal

conductivity is 50W/mk. It is covered with 2 layer of insulation each 50mm thickness

the thermal conductively of inner insulation is 0.06W/mk & outer is 0.12W/mk

calculate the loos of heat per meter length of pipe & interface temperature between

two layer, if the temp of inside surface of tube is 250deg c. & outside surface of

insulation is 50oC.

13. A thin aluminium sheet with an emissivity of 0.1 on both sides is placed between two

very large parallel plates that are maintained at uniform temperatures T l = 800 K and

T2 = 500 K and have emissivity 0.2 and 0.7 respectively. Determine the net rate of

radiation heat transfer between the two plates per unit surface area of the plates and

compare the result to that without shield.

14. Two large parallel planes with emissivity 0.35 and 0.85 exchange heat by radiation.

The planes are respectively 1073K and 773K. A radiation shield having the emissivity

of 0.04 is placed between them. Find the percentage reduction in radiation heat

exchange and temperature of the shield.