2007 Anna University B.E Mechanical ME- 1251 Thermal Engineering Question paper

Course: B.E Mechanical University: Anna University

Fourth Semester(Regulation 2004) Mechanical EngineeringME 1251- Thermal engineering Part- A (10X2=20 marks)

1. Sketch the Diesel cycle on P-V and T-S planes .2. List out any two assumptions for the analysis of thermodynamic air cycles .3. what is the function of camshaft and crankshaft.4. List out the effects of detonation.5. Define nozzle efficiency.6. Give the working principle of an impulse turbine.7. Define the volumetric efficiency of air compressor.8. What is free air delivered.9. A Carnot refrigerator requires 1.3 kW per tonne of refrigeration to maintain a region at low temperature of -380 C. Determine the COP of the refrigeratorand the higher temperature of the cycle.10. Define dew point temperature.

PART-B (5X16=80 marks)

11. (a) An engine working on otto cycle has a volume of 0.45 m3,pressure 1 barand temperature 300C at the beginning of compression stroke.At the endof compression stroke, the pressure is 11 bar and 210 kj of heat is addedat constant volume.determine

(i) pressures,temperatures and volumes at salient points in the cycle(ii) efficiency(or)

(b) (i) Derive an expression for the air-standard efficiency of a braytoncycle in terms of pressure ratio.(ii) Prove that the pressure ratio for maximum work is a function of thelimiting temperature ratio.12. (a) (i) Explain any four types of classification of internal Combustionengines.(ii) With a neat sketch explain any one type of ignition system.

(or)(b)Following data relates to 4 cylinder,A stroke petrol engine.Air/Fuel ratioby weight 16:1.Calorific value of the fuel = 45200 kj/kg, mechanicalefficiency = 82%. Air standard efficiency = 52%,relative efficiency = 70%volumetric efficiency = 78%,stroke/bone ratio = 1.25 suction conditions =1 bar,250C.Speed=2400rpm power at brakes = 72KW.Calculate

(i) Compression ratio

(ii) Indicated thermal efficiency

(iii) Brake specific fuel consumption and

(iv) Bore and stroke.

13. (a) (i) Derive an expression for the critical pressure ratio in terms of theindex of expansion.

(ii) Dry saturated steam enters a steam nozzle at a pressure of 15 barand is discharged at a pressure of 2.00bar.If the dryness fraction ofdischarge steam is 0.96, what will be the fi9nal velocity of steam.Neglect initial velocity of steam,If 10% of heat drop is lost inFriction, find the percentage reduction in the final velocity.(or)(b) A 50% reaction turbine funning at 400 rpm has the exit angle of the bladesas 200 and the velocity of the steam relative to the blades at the exit is1.35times the mean speed of the blade. The steam flow rate is 8.33 kg/s andat particular stage the specific volume is1.381 m3/kg. calculate for this stage.

(i) a suitable blade height , assuming the rotor mean diameter 12 times theblade height , and(ii) the digram work.

14 (a) (i) Derive an expression for maximum work required for a two stagereciprocating air compressor with perfect inter cooling and neglectingclearance.(ii) A two stage air compressor compresses air from 1bar and 200C to 42bar . if the law of compression is pv1.35 = constant and the inter coolingis perfect. Find per kg of air(1) the work done in compression(2) the mass of cooling water necessary for abstracting the heat in the intercooler, if the temperature rise of the cooling water is 250C.(or)(b) (i) With a neat sketch describe any one type of rotary compressor.(ii) A single stage single acting reciprocating air compressor deliovers 14 m3 offree air per minute from 1bar to7bar. The speed of the compressor is 310rpm .Assuming that compression and expansion follws the law pv1.35=and clearance is 5% of the swept volume, find the diameter and stroke ofthecompressor . take stroke length is 1.5 times the bore dia.

15. (a) A refrigeration system of 10.5 tonnes capacity at an evaporator temperature of-120C and an condenser temperature of 270C is needed in food storage locker .the refrigerant ammonia is sub cooled by 60C before entering the expansionvalve. The vapour is 0.95 dry as it leaves the evaporator coil. The compressionin the compressor is of adiabatic type . Find(i) Condition of vapour at the outlet of the compressor(ii) Condition of the vapour at the entrance of the evaporator(iii) COP(iv) The power required.Neglect valce throttling and clearance effect. (or)

(b) A sling psychrometer in alaboratory test recorded the following readingsDry bulb temperature = 350 CWet bulb temperature = 250 CCalculate the following :(i) specific humidity(ii) relative humidity(iii) vapour density in air(iv) dew point temperature(v) enthalpy of mixture per kg of dry airTake atmospheric pressure = 1.0132 bar.

MODEL PAPER CALSS TEST - I

508METO2 Thermal Engineering - I

Time:1.00 Hour Marks: 20

PART-A (3x2=06 marks) Instructions : Answer all questions 1) Define Thermodynamic System.

2) An ideal gas has a mass of 1.5 kg and occupies 2.5 m3 while at a temperatureof 270 C and a

pressure of 200 KN/m2. Determine the gas constant.

3) Represent the following processes on P-V diagram

( i ) Isothermal Process ( ii ) Isobaric Process

PART- B

Instructions : Answer any TWO questions. Each question carries 07 marks. ( 2 x 7 = 14 )

4 ) A piston – cylinder containing air expands at a constant pressure of 150 KPa from a

temperature of 285 K to a temperature of 550 K. The mass of air is 0.05 kg. Find the heat

transfer, work transfer and change in internal energy during the process. Assume Cp = 1.01

KJ/kg K and Cv = 0.72 KJ/ kg K.

5 ) One kilogram of air is compressed adiabatically so that its pressure increases from 1 bar to

10 bar. The work of 200 KJ is done on the air. Calculate the initial and final temperature of air.

Assume Cv = 0.718KJ/kgK for air and ratio of specific heats 1.4.

6 ) Describe with a neat diagram, the working of a Bomb Calorimeter.

MODEL PAPER CLASS TEST – II

508MET02 Thermal Engineering

Time:1.00 Hour Marks: 20

PART-A ( 3 x 2 = 6 marks) Instructions : Answer all questions

1) Define Combustion. What are the products of combustion?

2) Define a) Latent Heat b ) Sensible Heat

3) Define Refrigeration.

PART-B

Instructions : Answer any TWO questions. Each question carries 07 marks. ( 2 x 7 = 14 Marks )

4) An engine working on Carnot cycle has maximum and minimum temperature of 927 0C and 1270C.

Determine its efficiency and the heat supply per minute when the output is 36KW.

5) 2 kg of steam at a pressure of 800 KPa and 0.8 dry is heated at constant pressure until the final

temperature is 2500C. Determine using steam tables.

a) the heat added b ) change in internal energy

Assume Cp for superheated steam as 2.1 KJ/kgK.

6) An ice plant produces 10 tons of ice per day of 24 hours from water at 25 0C.COP of the plant is

given as 3.5. Calculate the capacity of the compressor if the overall efficiency of the plant is 80%.

Assume specific heat of water as 4.19 KJ/kgK and the latent heat of solidfication of water at 00C as

335KJ/kg.

THERMAL ENGINEERING-II

Subject Code : M-405

Subject Title : Thermal Engineering -IIPeriods/Week: 05 Periods per Semester : 75

UNIT TEST –I

Chapter No Major Topics No. of

PeriodsShort

answer Questions

Essay typeQuestions

1 Internal Combustion Engines 15 2 1

2 Air Compressors 08 1

3 Gas Turbines & Jet Propulsion 8 1

4Elements of Automobile

Engineering(up to 4.6)

05 1

UNIT TEST –II

Chapter No Major Topics No. of

PeriodsShort

answer Questions

Essay typeQuestions

4Elements of Automobile

Engineering(From 4.7 to 4.14)

05 1

5 Steam Boilers 12 1 16 Steam Nozzles 08 17 Steam Turbines 14 1 1

C-09 D.M.E - IV SEMESTER , THERMAL ENGINEERING-II

UNIT TEST –I

MODEL QUESTION PAPER

Marks : 20 .

PART-A

Answer all questions 3x2=6

1. Write any four differences of C I and S I Engines.

2. List different methods of cooling I C Engines.

3. List various components of an automobile

PART – B

Answer any two questions 2 X 7 = 14

4 Explain with line diagram the working of a single Stage reciprocating air compressor.

5 Compare the battery ignition system with magneto ignition system.

6 Represent cycle of operation of a closed cycle type gas turbine on P-V and T-s diagrams

C-09 D.M.E - IV SEMESTER M-405, THERMAL ENGINEERING-II

UNIT TEST –II MODEL QUESTION PAPER

Marks : 20 .

PART-A

Answer all questions 3x2=6

1 . Write the functions of propeller shaft and how it is perform its function2 What are differences between fire tube boilers and water tube boilers ?

3. State the necessity of governing a turbine

PART – B

Answer any two questions 2 X 7 = 14

4. During a test on a boiler the following data were collected

Steam pressure 9.487bar gauge

Steam condition dry and saturated

Feed water temperature 350c

Rate of evaporation 12kg/kg of coal

Calorific value of fuel 37.5X103kJ/kg

Determine the a)thermal efficiency

a) Factor of evaporation

Equivalent evaporation

5. Dry saturated steam enters a convergent nozzle at a pressure of 10 bar and

with a velocity of 90m/s. the exit pressure is 5 bar and steam leaves the

nozzle at a velocity of 435m/s. The friction loss is 10kJ/kg of steam flow.

Determine a) Final condition b) Area at exit if the inlet area is 1260mm2

6. a). Classify of Turbines with examples?

b). Derive formula for work done of a Turbine

BOARD DIPLOMA EXAMINATION(C-09)

MODEL PAPER UNIT TEST - I

M-501 Refrigeration and Air Conditioning

Time:1.00 Hour Marks: 20 PART-A (3x2=06 marks)

Instructions : Answer all questions 4) Define the term Refrigeration5) What are the basic components of a vapour compression Refrigeration system.6) What are desirable properties of refrigerants.

PART-B

Instructions : Answer any TWO questions. Each question carries 07 marks.

4) In an ammonia plant, temperature range is from -100C to 200C. Find C.O.P if vapour

after compression is (a) 0.95 dry (b) dry and (c) super heated to 350C at same

pressure.

t0C hf Hs Фf Фs

-100C 200C

154293.8

14501479.8

0.82961.3285

5.7555.374

5) Explain the principle of operation of an Electrolux refrigerator.

6) Explain the working principle of an air cooled condenser.

BOARD DIPLOMA EXAMINATION(C-09)

MODEL PAPER UNIT TEST - II

M-501 Refrigeration and Air Conditioning

Time:1.00 Hour Marks: 20 PART-A (3x2=06 marks)

Instructions : Answer all questions 1) What are ducts? How do you classify the ducts?2) Define psychrometry?3) What are the components of air conditioning system

PART-B

Instructions : Answer any TWO questions. Each question carries 07 marks.

4) (a) How do you classify the condensers.

(b) Explain working principle of an air cooler

5) (a) Define the terms

i) Dry Bulb Temperature

ii) Wet Bulb Temperature

(b) Explain the principles of winter air conditioning system.

6) How many tons of refrigeration are required to cool 120 m3 of air per minute at 300

DBT and 60% RH to 200 DBT and 80% RH..