You dont have javascript enabled! Please enable it! MCQ in Power Plant Engineering Part 4 | ME Board Exam

# MCQ in Power Plant Engineering Part 4 | ME Board Exam

This is the Multiple Choice Questions Part 4 of the Series in Power Plant Engineering as one of the Mechanical Engineering topic. In Preparation for the ME Board Exam make sure to expose yourself and familiarize in each and every questions compiled here taken from various sources including but not limited to past Board Exam Questions in Mechanical Engineering field, Mechanical Engineering Books, Journals and other ME References. I assume you are looking for a reviewer that will help you achieve your goal to become a License Mechanical Engineer very soon. Yes, you are in the right place to make your dream come true. Make sure to familiarize each and every questions to increase the chance of passing the Mechanical Board Examination.

#### MCQ Topic Outline included in ME Board Exam Syllabi

• MCQ in Power Plant Elements
• MCQ in Power Plant Design
• MCQ in Industrial Plant Engineering
• MCQ in Industrial Plant Design
• MCQ in Refrigeration Engineering and its Applications
• MCQ in Air Conditioning

#### Continue Practice Exam Test Questions Part 4 of the Series

Choose the letter of the best answer in each questions.

151.ย  Consider a refrigerator whose 40 watts light bulb remains on continuously as a result of a malfunctionย  ofย  theย  switch.ย  Ifย  theย  refrigeratorย  hasย  aย  COPย  ofย  1.3ย  andย  the cost of electricity is 8 centsย  perย  kW-hr,ย  determineย  theย  increase in the energy consumption of the refrigerator and its cost per year if the switch is not fixed.

A. P 49.59

B. P 47.59

C. P 45.59

D. P 43.59

Explanation:

152. A 75 hp motorย  that has an efficiency of 91% is worn out and is replaced by a high-efficiency motor that has an efficiency of 95.4%. Determine the reduction in heat gain of the room due to higher efficiency under full -load conditions.

A. 2.24 kW

B. 2.44 kW

C. 2.64 kW

D. 2.84 kW

Explanation:

153.ย  Aย  householdย  refrigeratorย  that has a power input of 450 watts and a COP of 2.5 is to cool fiveย  largeย  watermelons,ย  10 kg each, to 8ยฐC. If the watermelons are initially at 20ยฐC, determine how long it will take for the refrigerator to cool them. The watermelons can be treated as water whose specific heat is 4.2 kJ/kg-K.

A. 2220 seconds

B. 2230 seconds

C. 2240 seconds

D. 2250 seconds

Explanation:

154.ย  When a man returns to his wall-sealed house on a summer day, he finds that the house is at 32ยฐC. He returns on the air conditioner which cools the entire house to 20ยฐC in 15 minutes. If COPย  isย  2.5,ย  determineย  theย  power drawn by the air conditioner. Assume the entire mass within the house is 800 kg of air for which cvย  = 0.72 kJ/kg-K, cp = 1.0 kJ/kg -K.

A. 1.072 kW

B. 2.072 kW

C. 3.072 kW

D. 4.072 kW

Explanation:

155.ย  Aย  heatย  sourceย  atย  800 Kย  lossesย  2000 kJ of heat to a sink at 500 K. Determine the entropy generated during this process.

A. 1.5 kJ/K

B. 2.5 kJ/K

C. -2.5 kJ/K

D. 4 kJ/K

Explanation:

156.ย  Helium gas is compressed in an adiabatic compressor from an initial state of 14 psia and 50ยฐFย  toย  aย  finalย  temperatureย  ofย  320ยฐFย  inย  aย  reversibleย  manner.ย  Determineย  theย  exitย  pressureย  of Helium.

A. 38.5 psia

B. 40.5 psia

C. 42.5 psia

D. 44.5 psia

Explanation:

157.ย  Airย  passesย  thru a nozzle with efficiency of 90%. The velocity of air at the exit is 600 m/s. Find the actual velocity atย  the exit.

A. 382 m/s

B. 540 m/s

C. 458 m/s

D. 568 m/s

Explanation:

158.ย  A 50 kg block of iron casting at 500 K is thrown into a large lake that is at a temperature of 285ย  K.ย  Theย  ironย  blockย  eventuallyย  reachesย  thermalย  equilibriumย  withย  theย  lakeย  water.ย  Assuming averageย  specific heat of 0.45 kJ/kg -K for the iron, determine the entropy generated during this process.

A. -12.65 kJ/K

B. 16.97 kJ/K

C. 4.32 kJ/K

D. 6.32 kJ/K

Explanation:

159.ย  Aย  windmillย  withย  aย  12ย  mย  diameterย  rotorย  isย  toย  beย  installed at a location where the wind is blowingย  atย  anย  averageย  velocityย  ofย  10 m/s.ย  Usingย  standardย  conditionย  ofย  airย  (1 atm,ย  25ยฐC), determineย  the maximumย  power that can be generated by the windmill.

A. 68 kW

B. 70 kW

C. 72 kW

D. 74 kW

Explanation:

160.ย  Consider a large furnace that can supply heat at a temperature of 2000ยฐR at a steady rate ofย  3000ย  Btu/s.ย  Determineย  theย  energyย  ofย  thisย  energy.ย  Assumeย  anย  environmentย  temperatureย  of 77ยฐF.

A. 2305.19 kW

B. 2315.19 kW

C. 2325.19 kW

D. 2335.19 kW

Explanation:

161. A heat engine receives heat from a source at 1200 K at a rate of 500 kJ/s and rejects the wasteย  heatย  toย  aย  mediumย  atย  300ย  K.ย  Theย  powerย  outputย  of the engine is 180 kW. Determine the irreversibility rate for this process.

A. 190 kW

B. 195 kW

C. 200 kW

D. 205 kW

Explanation:

162.ย  A dealer advertises that he has just received a shipment of electric resistance heaters for residential buildings that have an efficiency of 100 percent. Assuming an indoor temperature of 21ยฐC and outdoorย  temperatureย  of 10ยฐC, determineย  the second lawย  efficiency of these heaters.

A. 8.74%

B. 6.74%

C. 3.74%

D. 4.74%

Explanation:

163. A thermal power plant has a heat rate of 11,363 Btu/kW-hr. Find the thermal efficiency of the plant.

A. 34%

B. 24%

C. 26%

D. 30%

Explanation:

164.ย  A rigid tank contains 2 kmol of N2 and 6 kmol of CO2 gases at 300 K and 115ย  MPa. Find the tank volume using the ideal gas equation.

A. 7.33 m3

B. 5.33 m3

C. 3.33 m3

D. 1.33 m3

Explanation:

165.ย  Aย  sphericalย  balloonย  withย  aย  diameterย  ofย  6ย  mย  isย  filledย  withย  heliumย  atย  20ยฐCย  andย  200ย  kPa. Determine the mole number.

A. 9.28 kmol

B. 10.28 kmol

C. 11.28 kmol

D. 13.28 kmol

Explanation:

166. The air in an automobile tire with a volume of 0.53 ft3 is at 90ยฐF and 20 psig. Determine the amountย  ofย  airย  that must be added to raise the pressure to the recommended value of 30 psig. Assumeย  theย  atmosphericย  pressureย  toย  beย  14.7ย  psiaย  andย  theย  temperatureย  andย  theย  volumeย  to remain constant.

A. 0.026 lb

B. 0.046ย  lb

C. 0.066 lb

D. 0.086 lb

Explanation:

167.ย  A rigid tankย  contains 20 lbmย  of air at 20 psia and 70ยฐF. More air is added to the tank until theย  pressureย  andย  temperatureย  rise to 35 psia and 90ยฐF, respectively. Determine the amount of air added to the tank.

A. 11.73 lb

B. 13.73 lb

C. 15.73 lb

D. 17.73 lb

Explanation:

168.ย  A rigid tank contains 5 kg of an ideal gas at 4 atm and 40ยฐC. Now a valve is opened, and half of mass of the gas is allowed to escape. If the final pressure in the tank is 1.5 atm, the final temperatureย  in the tank is?

A. -38ยฐC

B. -30ยฐC

C. 40ยฐC

D. 53ยฐC

Explanation:

169.ย  Theย  pressureย  ofย  anย  automobile tire is measured to be 200ย  kPa (gage) before the trip end 220ย  kPa (gage)ย  afterย  theย  tripย  atย  aย  locationย  whereย  theย  atmosphericย  pressureย  isย  90 kPa.ย  Ifย  the temperatureย  of the air in the tire before the trip is 25ยฐC, the air temperature after the trip is?

A. 45.6ยฐC

B. 54.8ยฐC

C. 27.5ยฐC

D. 26.7ยฐC

Explanation:

170.ย  Waterย  isย  boilingย  atย  1 atmย  pressureย  inย  aย  stainlessย  steelย  panย  onย  anย  electricย  range.ย  Itย  is observed that 2 kg of liquid water evaporates in 30 min. The rate of heat transfer to the water is?

A. 2.07 kW

B. 0.47 kW

C. 2.51 kW

D. 3.12 kW

Explanation:

171.ย  Considerย  aย  personย  standingย  inย  aย  breezyย  roomย  atย  20ยฐC.ย  Determineย  theย  totalย  rateย  ofย  heat transferย  fromย  thisย  personย  ifย  theย  exposedย  surfaceย  areaย  andย  theย  averageย  outerย  surface temperatureย  ofย  the person are 1.6 m2 and 29ยฐC, respectively, and the convection heat transfer coefficient is 6 W/m2 with emissivity factor of 0.95.

A. 86.40 watts

B. 81.70 watts

C. 198.1 watts

D. 168.1 watts

Explanation:

172.ย  Water is boiler in a pan on a stove at sea level. During 10 minutes of boiling, it is observed that 200 grams of water has evaporated. Then the rate of heat transfer to the water is:

A. 0.84 kJ/min

B. 45.1 kJ/min

C. 41.8 kJ/min

D. 53.5 kJ/min

Explanation:

173.ย  Anย  aluminumย  panย  whoseย  thermalย  conductivityย  isย  237ย  W/m-ยฐCย  hasย  aย  flatย  bottomย  whose diameterย  isย  20 cm and thickness of 0.4 cm. Heat is transferredย  steadily to boiling water in the panย  throughย  itsย  bottomย  at a rate of 500 watts. If the inner surface of the bottom of the pan is 105ยฐC, determineย  the temperatureย  of the surface of the bottomย  of the pan.

A. 95.27ยฐC

B. 105.27ยฐC

C. 115.27ยฐC

D. 125.27ยฐC

Explanation:

174. For heat transfer purposes, a standing man can be modeled as a 30 cm diameter, 170 cm long vertical cylinder with both the top and bottom surfaces insula ted and with the side surface atย  anย  averageย  temperatureย  ofย  34ยฐC.ย  Forย  aย  convectionย  heat transfer coefficient of 15 W/m2 -ยฐC, determineย  the rate of heat loss from this man by convection in an environmentย  at 20ยฐC.

A. 316.46 watts

B. 326.46 watts

C. 336.46 watts

D. 346.46 watts

Explanation:

175.ย  Aย  5ย  cmย  diameterย  sphericalย  ballย  whoseย  surfaceย  isย  maintained at a temperature of 70ยฐC is suspendedย  inย  theย  middleย  ofย  aย  roomย  atย  20ยฐC.ย  Ifย  theย  convectionย  heatย  transferย  coefficientย  isย  15 W/m2 -ยฐCย  andย  theย  emissivityย  ofย  theย  surfaceย  isย  0.8,ย  determineย  theย  totalย  heatย  transferย  fromย  the ball.

A. 23.56 watts

B. 32.77 watts

C. 9.22 watts

D. 43.45 watts

Explanation:

176. A frictionless piston-cylinder device and a rigid tank contain 1.2 kmol of an ideal gas at the same temperature, pressure and volume. Now heat is transferred, and the temperature of both systemsย  isย  raisedย  byย  15ยฐC.ย  Theย  amountย  ofย  extraย  heatย  thatย  mustย  beย  suppliedย  to the gas in the cylinder that is maintained at constant pressure is?

A. 0

B. 50 kJ

C. 100 kJ

D. 150 kJ

Explanation:

177.ย  A supply of 50 kg of chicken at 6ยฐC contained in a box is to be frozen to -18ยฐC in a freezer. Determine the amount of heat that needs to be removed. The latent heat of the chicken is 247 kJ/kg, and its specific heat is 3.32 kJ/kg -ยฐC above freezing and 1.77 kJ/kg -ยฐC below freezing. The containerย  boxย  isย  1.5ย  kg,ย  andย  theย  specificย  heatย  ofย  theย  boxย  materialย  isย  1.4ย  kJ/kg -ยฐC.ย  Alsoย  the freezing temperatureย  of chicken is -2.8ยฐC.

A. 15,206.4 kJ

B. 50.4 kJ

C. 15,156 kJ

D. 1,863 kJ

Explanation:

178.ย  Waterย  isย  beingย  heatedย  inย  aย  closedย  pan on top of a range while being stirred by a paddle wheel.ย  During the process, 30 kJ of heat is transferredย  to the water, and 5 kJ of heat is lost to the surrounding air. The paddle wheel work amounts to 500 N -m. Determine the final energy of the system if its initial energy is 10 kJ.

A. 35.5 kJ

B. 40.5 kJ

C. 25.5 kJ

D. 14.5 kJ

Explanation:

179.ย  Aย  classroomย  thatย  normallyย  containsย  40ย  peopleย  isย  toย  beย  air-conditionedย  withย  windowย  air-conditioning units of 5 kW cooling capacity. A person at rest may be assumed to dissipate heat at a rateย  about 360 kJ/hr. Thereย  are 10 light bulbs in the room, each with a rating of 100 watts. Theย  rateย  ofย  heatย  transferย  to the classroom through the walls and the windows isย ย  estimated to be 15,000ย  kJ/hr.ย  If the room is toย  beย  maintained at a constant temperature of 21ยฐC, determine the numberย  of window air-conditioning units required.

A. 1 units

B. 2 units

C. 3 units

D. 4 units

Explanation:

180.ย  A 4 m x 5 m x 6 m room is to be heated by a baseboard resistance heater. It is desired that the resistance heater be able to raise the air temperature in the room from 7 to 23ยฐC within 15 minutes.ย  Assumingย  noย  heatย  lossesย  fromย  theย  roomย  andย  anย  atmosphericย  pressureย  ofย  100ย  kPa, determine the required power of the resistance heater. Assume constant specific heats at room temperature.

A. 2.34 kW

B. 1.91 kW

C. 4.56 kW

D. 6.34 kW

Explanation:

181.ย  A student living in a 4 m x 6ย  m x 6ย  m dormitory room turns on her 150 watts fan before she leaves the room on a summer day, hoping that the room will be cooler when she comes back in the evening. Assuming all the doors and windows are tightly closed and disregarding any heat transferย  throughย  the walls and the windows, determine the temperature in the room when she comes back 10 hours later. Use specific heat values at room temperature, and assume the room to be at 100ย  kPaย  and 15ยฐC in the morning when she leaves.

A. 28.13ยฐC

B. 38.13ยฐC

C. 48.13ยฐC

D. 58.13ยฐC

Explanation:

182.ย  Aย  piston-cylinder device whose piston is resting on top of a set of stops initially contains 0.50ย  kgย  ofย  heliumย  gasย  atย  100ย  kPaย  andย  25ยฐC.ย  Theย  massย  ofย  theย  pistonย  isย  suchย  thatย  500ย  kPaย  of pressureย  isย  requiredย  toย  raiseย  it.ย  Howย  muchย  heatย  mustย  beย  transferred to the helium before the piston starts rising?

A. 1557.13 kJ

B. 1657.13 kJ

C. 1757.13 kJ

D. 1857.13 kJ

Explanation:

183. In order to cool 1 ton (1000 kg) of water at 20ยฐC in an insulated tank, a person pours 80 kg ofย  iceย  atย  -5ยฐCย  intoย  theย  water.ย  Determineย  theย  finalย  equilibriumย  temperatureย  inย  theย  tank.ย  The meltingย  temperatureย  andย  theย  heatย  ofย  fusionย  ofย  iceย  at atmospheric pressure are 0ยฐC and 333.7 kJ/kg, respectively.

A. 12.43ยฐC

B. 14.43ยฐC

C. 16.43ยฐC

D. 18.43ยฐC

Explanation:

184.ย  Aย  fanย  isย  poweredย  byย  0.5ย  hp motor and delivers air at a rate of 85 m3/min. Determine the highest value for the average velocity of air mobilized by the fan. Take the density of air to be 1.18 kg/m3.

A. 18.23 m/s

B. 21.12 m/s

C. 25.34 m/s

D. 32.23 m/s

Explanation:

185.ย  Anย  Ocean-Thermalย  Energyย  Conversionย  powerย  plantย  generatesย  10,000ย  kWย  usingย  aย  warm surface water inlet temperature of 26ยฐC and cold deep-water temperature of 15ยฐC. On the basis ofย  aย  3ยฐCย  dropย  inย  theย  temperatureย  ofย  theย  warmย  waterย  andย  a 3ยฐC rise in the temperature of the coldย  waterย  dueย  toย  removalย  andย  additionย  ofย  heat,ย  calculateย  theย  powerย  required in kW to pump theย  cold-deepย  waterย  toย  theย  surfaceย  andย  throughย  theย  systemย  heatย  exchangerย  ifย  theย  required pumping pressure increase is 12 kPa. Assume a Carnot cycle efficiency and density of cold water to be 100 kg/m3.

A. 108

B. 250

C. 146

D. 160

Explanation:

186. A plate-type solar energyย  collector with an absorbing surface covered by a glass plate is to receiveย  anย  incidentย  radiationย  ofย  800 W/m2.ย  Theย  glassย  plateย  hasย  aย  reflectivityย  ofย  0.12ย  and a transmissivityย  ofย  0.85.ย  Theย  absorbingย  surfaceย  hasย  anย  absorptivityย  ofย  0.90.ย  Theย  areaย  ofย  the collector is 5 m2. How much solar energy in watts is absorbed by the collector?

A. 2500

B. 2880

C. 3510

D. 3060

Explanation:

187. A tank contains liquid nitrogen at -190ยฐC is suspended in a vacuumย  shell by three stainless steel rods of 0.80 cm in diameter and 3 meters long with a thermal conductivity of 16.3 W/m2 -ยฐC.ย  Ifย  theย  ambientย  airย  outsideย  theย  vacuumย  shellย  isย  15ยฐC,ย  calculateย  theย  magnitudeย  ofย  the conductive heat flow in watts along the support rods.

A. 0.168

B. 0.0587

C. 0.182

D. 0.176

Explanation:

188.ย  Anย  elastic sphere containing gas at 120 kPa has a diameter of 1.0 m. Heating the sphere causesย  itย  toย  expand to a diameter of 1.3 m. During theย  process the pressure is proportional to the sphere diameter. Calculate the work done by the gas in kJ.

A. 41.8

B. 50.6

C. 87.5

D. 35.4

Explanation:

189. An ideal gas with a molecular weight of 7.1 kg/kg mol is compressed from 600 kPa and 280 K to a final specific volume of 0.5 m3/kg. During the process the pressure varies according to P = 620 + 150ฯย  + 95 ฯ2 where p is in kPa and ฯ in m3/kg. Calculate the work of compression in kJ/kg.

A. 32.8

B. 28.7

C. 35.6

D. 33.3

Explanation:

190.ย  Aย  oneย  cubicย  meterย  container containsย  aย  mixtureย  ofย  gasesย  composedย  ofย  0.02ย  kg-molย  of oxygenย  andย  0.04ย  kg-molย  ofย  heliumย  atย  aย  pressureย  ofย  220ย  kPa.ย  Whatย  isย  theย  temperature of this ideal gas mixture in Kelvin?

A. 441

B. 350

C. 400

D. 450

Explanation:

191. Methyl alcohol (CH3OH) is burned with 25% excess air. How much unburned oxygen in kg-moloxygen/kg-molfuel will there be in the products if the combustion is complete?

A. 0.35

B. 0.45

C. 0.37

D. 0.65

Explanation:

192. A 12 DC electricalย  motor draws a current of 15 amps. How much work in kJ does this motor produceย  over a 10-minute period of operation?

A. 108.0

B. 129.6

C. 216.0

D. 318.2

Explanation:

193.ย  A 4 liter (2-liter per revolution atย  standard pressure and temperature) spark ignition engine has a compression ratio of 8 and 2200 kJ/kg heat addition by the fluid combustion. Considering a cold air-standard Otto cycle model, how much power will the engine produce when operating at 2500 rpm?

A. 166.53 hp

B. 73.12 hp

C. 97.4 hp

D. 148 hp

Explanation:

194.ย  A simple Rankine cycle produces 40 MW of power, 50 MW of process heated and rejects 50ย  MWย  ofย  heatย  toย  theย  surroundings.ย  Whatย  isย  theย  utilizationย  factorย  ofย  thisย  cogenerationย  cycle neglecting the pump work?

A. 50%

B. 60%

C. 64%

D. 80%

Explanation:

195.ย  Theย  rateย  ofย  heatย  transferย  to the surroundings from a person at rest is 400 kJ/hr. Suppose that the ventilation system fails in an auditorium containing 120 people and assumingย  that the energy goes into the air of volume 1500 m3 initially at 300 K and 101 kPa, calculate the rate in ยฐC/min of air temperatureย  change.

A. 0.81

B. 0.53

C. 0.63

D. 1.0

Explanation:

196.ย  Anย  insulatedย  boxย  containingย  heliumย  gasย  fallsย  fromย  aย  balloonย  4.5ย  kmย  aboveย  theย  earthโs surface. Calculate the temperature rise in ยฐCย  of the helium when box hits the ground.

A. 15.2

B. 12.6

C. 25.3

D. 14.1

Explanation:

197. Consider two Carnot heat engines operating in series. The first engine receives heat from theย  reservoirย  atย  2400ย  Kย  andย  rejectsย  the waste heat to another reservoir at temperature T. The second engine receives heat by the first one, convert some of it toย  work, and rejects the rest to aย  reservoirย  atย  300ย  K.ย  Ifย  thermalย  efficienciesย  ofย  bothย  enginesย  areย  theย  same,ย  determineย  the temperatureย  T.

A. 849 K

B. 578 K

C. 763 K

D. 978 K

Explanation:

198. An ideal gas mixture consists of 2 kmol of N2 and 6 kmol of CO2. The mass fraction of CO2 is?

A. 0.175

B. 0.250

C. 0.825

D. 0.750

Explanation:

199. An ideal gas mixture consists of 2 kmol of N2 and 6 kmol of CO2. Theย  apparent gas constant of mixture is?

A. 0.208

B. 0.231

C. 0.531

D. 0.825

Explanation:

200.ย  Aย  Carnotย  cycleย  operatesย  betweenย  theย temperatureย limitsย ofย 300 Kย andย 1500 K,ย and producesย 600 kWย  ofย  netย  power.ย  Theย  rateย  ofย  entropyย  changeย  ofย  theย  workingย  fluidย  duringย  heat addition process is ?

A. 0

B. 0.4

C. 0.5

D. 2.0

Explanation:

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