Thermal question bank-2

1. Thermal Engineering MCQs Correct Answer Q1. The relation derived for the total emissive power of the blackbody as a function of wavelength and based of quantum theory is known as a) Kirchoff'slaw b) Stefan-Boltzmannlaw c) Planck'slaw d) noneofthe above Q2. Whichmedium of surrounding is better forfin effectiveness? a) gasmedium b) liquidmedium c) finshave sameeffectivenessinboththe gas and liquidmediums d) noneofthe above Q3. Fouling factor of a heat exchanger can be calculated by a) [Thermal resistanceofheatexchangerwithoutscaling] – [Thermal resistanceof heat exchangerwithscaling] b) [Thermal resistanceofheatexchangerwithscaling] – [Thermal resistanceofheat exchangerwithoutscaling] c) [Thermal resistanceofheatexchangerwithoutscaling] x [Thermal resistanceof heat exchangerwithscaling] d) noneofthe above Q4. When is the arithmetic mean temperature difference of heat exchanger used instead of LMTD? a) whenthe temperature profilesoftwo fluidsofheatexchangeraresloping downwardwithcurve b) whenthe temperature profilesoftwo fluidsofheatexchangerareslopingupward with curve c) whenthe temperature profilesoftwo fluidsofheatexchangerarestraight d) noneofthe above Q5. The convectiveheat transfer coefficientin laminar flow over a flatplate a) Increaseswithdistance b) Increasesifa higherviscosityfluidisused c) Increasesifa denserfluidis used d) Decreaseswithincreaseinfreestream velocity Q6. Freon group of refrigerants are a) Inflammable b) Toxic c) Non-inflammableandtoxic d) Nontoxicandnon-inflammable

2. Q7. The boiling point of ammonia is a) -10.5°C b) -30°C c) -33.3°C d) -77.7°C Q8. Forobtaining high COP, the pressure range of compressor should be a) High b) Low c) Optimum d) Anyvalue Q9. A reversible engine has ideal thermal efficiency of 30%. When it is used as a refrigerating machine withall other conditions unchanged, the coefficientof performance willbe a) 1.33 b) 2.33 c) 3.33 d) 4.33 Q10. Cooling water is required for followingequipment in ammonia absorption plant a) Condenser b) Evaporator c) Absorber d) Condenser,absorberandseparator(rectifier) Q11. The freezing point of sulphur dioxide is a) -56.6°C b) -75.2°C c) -77.7°C d) -135.8°C Q12. Mass flow ratio of NH₃ in comparison to Freon-12 for same refrigeration load and same temperature limits is of the order of a) 1: 1 b) 1: 9 c) 9: 1 d) 1: 3 Q13. In a refrigeration system, the expansion device is connected between the a) Compressorandcondenser b) Condenserandreceiver c) Receiverandevaporator d) Evaporatorandcompressor

3. Q14. The vapour compression refrigerator employs the followingcycle a) Rankine b) Carnot c) ReversedRankine d) ReversedCarnot Q15. In actual air-conditioning applications forR-12 and R-22, and operating at a condenser temperature of 40° C and an evaporator temperature of 5° C, the heat rejection factoris about a) 1 b) 1.25 c) 2.15 d) 5.12 Q16. Rating of a domestic refrigerator is of the order of a) 0.1 ton b) 5 tons c) 10 tons d) 40 tons Q17. A human body feels comfortable when the heat produced by the metabolism of human body is equal to the a) Heat dissipatedto the surroundings b) Heat storedin the humanbody c) Sum of(A) and(B) d) Differenceof(A)and (B) Q18. The bank of tubes at the backof domestic refrigerator is a) Condensertubes b) Evaporatortubes c) Refrigerantcoolingtubes d) Capillarytubes Q19. In a lithium bromide absorption refrigeration system a) Lithiumbromideisused asa refrigerantandwateras an absorbent b) Water is usedas a refrigerantandlithiumbromideasan absorbent c) Ammoniaisusedas a refrigerantandlithiumbromideasan absorbent d) Noneof the above Q20. The condition of refrigerant after passing through the condenser in a vapour compression system is a) Saturatedliquid b) Wet vapour c) Drysaturated vapour d) Superheatedvapour

4. Q.21 Whichis not a boilermounting a) Airpreheater b) Safetyvalves c) Fusibleplug d) Manhole Q.22 In thermal powerplants,coal is transferredfrombunkerto the otherplacesby a) Hoists b) conveyors c) cranes d) lifts Q.23 A thermal electricpowerplantproduces1000MWof power.If the coal releases 900x 107 kJ/hofenergy,then what is the rate at whichheat is rejected fromthe powerplant? a) 500MW b) 1000MW c) 1500MW d) 2000MW Q.24 Thecorrectsequenceoffactorsin orderofdeceasingimportancefor locationofathermal powerplantis a) load,coal,water b) coal,water, load c) Water, load,coal d) water, coal,load Q.25 TheefficiencyofsuperheatRankinecycleishigherthanthat ofsimpleRankine cyclebecause a) Theenthalpyofmain steam is higherforsuperheatcycle b) Themean temperatureof heat additionishigherforsuperheatcycle c) Thetemperatureof steam in the condenserishigh d) Thequalityofstem inthe condenserislow Q.26 In a Rankinecycle,regenerationresultsinhigherefficiencybecause a) Pressureinsidetheboilerincreases b) Heat isadded beforesteamenters the lowpressureturbine c) Averagetemperatureofheat additioninthe boilerincreases d) Total workdeliveredbytheturbineincreases Q.27 For a givenset ofoperatingpressurelimitsofaRankinecycle,the highest, efficiencyoccursfor a) Saturatedcycle b) Superheatedcycle c) Reheatcycle d) Regenerativecycle

5. Q.28 In steam and othervapourcycles,the processofremovingnon-condensableis called a) Scavengingprocess b) Deaerationprocess c) Exhaustprocess d) Condensationprocess Q.29 Thereheat cyclein steam powerplantis mainlyadoptedto a) Improvethermal efficiency b) Decreasethemoisturecontent inlowpressurestagesto a safevalue c) Decreasethecapacity ofcondenser d) Recoversthewaste heat ofboiler Q.30 Employingsuperheatedsteaminturbinesleadsto a) Increasein erosionofblading b) Decreaseinerosionofblading c) No erosioninblading d) No changeinerosionofblading Q.31 A regenerativesteamcyclerenders a) Increasedworkoutputper unit massof steam b) Decreasedworkoutputperunit massof steam c) Increasedthermal efficiency d) Decreasedworkoutputperunit massof steam aswell as increasedthermal efficiency Q.32 In whichone ofthe followingsteamturbines,steamis takenfrom variouspoints alongthe turbine,solelyforfeedwaterheating? a) Extractionturbine b) Bleederturbine c) Regenerativeturbine d) Reheatturbine Q.33 In the bottomingcycleofcogeneration,lowgradewasteheatisused for a) Processing b) Powergeneration c) Feed waterheating d) noneofthe above Q.34 A powerplant, whichusesa gasturbinefollowedbysteamturbineforpower generation,iscalled: a) Toppingcycle b) Bottomingcycle c) Braytoncycle d) Combinedcycle

6. Q.35 In the Rankinecyclelowerlimitonthe condenserpressureisdueto the a) Expansionlimitinturbine b) condensersize c) Airleakageinto the condenser d) temperatureof coolingwater Q.36 Theequivalentevaporation(kg/hr)ofaboilerproducing2000kg/hr ofsteam with enthalpycontentof 2426kJ/kgfromfeedwater at temperature40°C (liquid enthalpy= 168kJ/kg,enthalpyofvaporisationofwaterat 100°C =2258kJ/kg)is a) 2000 b) 2149 c) 1682 d) 1649 Q.37 Boilerratingisusuallydefinedintermsof a) Maximumtemperatureofsteam in Kelvin b) Heat transferrate in kJ/hr c) Heat transferareain m2 d) Steam outputin kg/hr Q.38 Heat is mainlytransferredbyconduction,convectionandradiationin a) Insulatedpipescarryinghotwater b) Refrigeratorfreezer coil c) Boilerfurnaces d) condensationofsteamin a condenser Q.39 MeV is a unitof a) Energy b) Power c) Momentum d) Noneof the above Q.40 CANDUisa type of a) Boiler b) Turbine c) Reactor d) Noneof the above Q.41 Graphiteisused inPHWR as a a) Fuel b) Moderator c) Coolant d) Noneof the above

7. Q.42 Calendriaisa part of a) Boiler b) Turbine c) Reactor d) Noneof the above Q.43 Peak loadplantsareusuallyoperated a) Fora higherfractionoftime b) Fora lessfractionoftime c) Maybe 1 or2, dependingon thesituations d) Noneof the above Q.44 Plant factor(Capacityfactor)is…. a) Ratio ofaverageloadto peakloadforsame time intervals b) Ratio ofpeak loadto averageloadforsame time intervals c) Ratio ofaverageloadto rated capacity d) Noneof the above Q.45 Plant capacityalwaysdesignedto a) greaterthan peak load b) lessthan peakload c) Maybe 1 or2, dependingonthesituations d) Noneof the above Q.46 In a coolingtower,"approach"isthetemperaturedifferencebetweenthe a) hot inletwater andcoldoutlet water b) hot inletwater andWBT c) coldoutletwater and WBT d) DBT andWBT

Thermal question bank-2

Thermal question bank-2

Thermal question bank-2

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