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Marwadi Education Foundations Group of Institutions

Faculty of Engineering/Technology

Semester 5 Mechanical Engineering

25 Important Questions for 2nd

Mid sem exam 2013

Subject: Power Plant Engineering (151904)

1. (i) What is the function of stokers? Compare underfeed and overfeed stokers.(ii) Enumerate different types of ash handling systems. Discuss the working of

pneumatic ash handling system.

2. Explain the working of pressurized fluidized bed combustion boiler with help ofneat sketch.

3. (i) Why is draught necessary in a boiler? Compare the natural draught and artificialdraught.

(ii) Determine height of the chimney to produce a static draught of 17 mm of water.

The temperature in the chimney is 300oC and surrounding temperature is 28

oC.The

barometer reads 755 mm of Hg. The value of of characteristic gas constant is 287

J/kgK and that for gases is 255 J/kgK

4. Derive an expression for chimney height in order to obtain a draught of hmm ofwater column if the boiler used m kg of air / kg of fuel. Assume surrounding air

temperature as T1 and flue gas temperature as T2 in degree absolute. Also derive

an expression for the condition of maximum discharge of flue gases through a

chimney.

5. Explain the travelling grate stoker with help of neat sketch6. What are the advantages and Disadvantages of Pulverized coal firing7. Explain the working of Electrostatic precipitator with neat sketch8. Classify various Ash handling system. Explain Pneumatic and steam jet ash handling

system

9. Classify Different types of Fan .Explain why are centrifugal backward curvedbalding normally used for Forced Draft. Fan

10. Compute the required motor capacity needed for F.D. Fan under followingCondition:

Coal rate: 10 tonnes/h

Coal analysis: C78.0, H 3.0, O 3.0, S 1.0,

M 7.0, A 8.0

Excess air: 30 %

Plenum chamber pressure: 180 mm of water gaugeMechanical Efficiency of the Fan : 60%

Room temperature: 300 C

11. A 40 m high chimney is discharging flue gases at 350 C, when the ambienttemperature is 30 C. The quantity of air supplied is 18Kg/Kg of fuel burnt.

Determine

(i) Draught produced in mm of water

(ii) Equivalent draught in m of hot-gas column

(iii) Efficiency of chimney if minimum temperature of artificial draught is 150 C

mean specific heat of flue gases is 1.005K J/Kg K,

(iv)Percentage of heat spent in natural draught system if Calorific value of fuelsupplied is 30600K J/Kg

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Marwadi Education Foundations Group of Institutions

Faculty of Engineering/Technology

Semester 5 Mechanical Engineering

(v) Temperature of chimney gases for maximum discharge in given time and what

will be corresponding draught in mm of water produced.

12. (i) Explain Ball and Race mill with a schematic. State its merits and demerits.(ii)Explain cyclone burner with a schematic. State its merits and demerits.

13.Explain difference between Nuclear fission and Fusion. Discuss Various componentsof Nuclear reactor and its function

14.Explain CANDU type nuclear reactor with neat sketch. Also give advantages anddisadvantages of CANDU reactor

15.Explain with neat sketch Pressurizes water Reactor(PWR) Explain function ofpressurizer in PWR

16.Explain with neat sketch Boiling water Reactor(BWR)17.Explain with neat sketch Gas cooled Reactors18.Write a short note on Fast Breeder Nuclear Reactor19.Explain Open type, Closed type and Mixed type cooling system used in Condensers20.Explain the various types of Jet and Surface condensers in brief21.What is the function of cooling tower? What are the various types of cooling towers?

Explain hyperbolic cooling tower.

22.Write a short note on Mechanical Cooling towers and Cooling ponds23.The air leakage into a surface condenser operating with a steam turbine is estimated84kg/hr. the vacuum near the inlet of air pump is 70mm of Hg when barometer reads

76mm of Hg. The temperature at the inlet of vacuum pump is 20 C. Calculate (i)

Minimum capacity of pump in cu-meters per hour (ii) Dimensions of reciprocating air

pump to remove air if it runs at 200rpm (iii) L:D=3:2 and volumetric efficiency=80% (iv)

Mass of vapour extracted per minute with air

24.The following reading were taken during a test on a surface condenser Meancondenser temperature =35 C , Hot well temperature=30 C, condenser

vacuum=69cm Hg , barometer reading 76cm Hg, condensate collected 16Kg/min.

Cooling water enters at 20 C and leaves at 32.5 C, flow rate being 37500 Kg/hr.

Calculate (i). Mass of air present per cubic meter of condensate (ii). Quality of steam

at condenser inlet (iii). Vacuum efficiency (iv). Condenser efficiency

7/27/2019 2ndMidExam2013_25Important_Questions_PPE__2013_10_14_08_04_42

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Marwadi Education Foundations Group of Institutions

Faculty of Engineering/Technology

Semester 5 Mechanical Engineering

25.A steam turbine of 20,000 kW capacity requires 5 kg of steam per hour per kW. Thequantity of air leakage into the condenser is 1 kg per 1000 kg of steam used by

turbine. The vacuum in the condenser is 70 cm of Hg when the barometer reads 76

cm of Hg. The temperature at the suction of the air pump is 30oC. The surface

condenser used is fitted with a separate condensate pump and air pump.

Find : a) The capacity of the air pump requires per minute. b) The mass of water vapor

carried by air in kg/hr. c) The quantity of cooling water required per minute in tons if the

rise in temperature of water is limited to 8oC. The quantity of steam entering the

condenser is 0.9 dry and there is no under cooling in the condenser. Properties of steam

at 30oC : Absolute Pressure = 0.04325 bar Enthalpy of liquid hf = 125.8 kJ/kg Enthalpy of

evaporation hfg = 2438.1 kJ/kg Specific volume = 32.8 m3/kg