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

⇐ MCQ in Power Plant Engineering Part 3 | ME Board Exam

Choose the letter of the best answer in each questions.

151.  Consider a refrigerator whose 40 watts light bulb remains on continuously as a result of a malfunction  of  the  switch.  If  the  refrigerator  has  a  COP  of  1.3  and  the cost of electricity is 8 cents  per  kW-hr,  determine  the  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

152. A 75 hp motor  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

153.  A  household  refrigerator  that has a power input of 450 watts and a COP of 2.5 is to cool five  large  watermelons,  10 kg each, to 8°C. If the watermelons are initially at 20°C, 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

154.  When a man returns to his wall-sealed house on a summer day, he finds that the house is at 32°C. He returns on the air conditioner which cools the entire house to 20°C in 15 minutes. If COP  is  2.5,  determine  the  power drawn by the air conditioner. Assume the entire mass within the house is 800 kg of air for which c_v  = 0.72 kJ/kg-K, c_p = 1.0 kJ/kg -K.

A. 1.072 kW

B. 2.072 kW

C. 3.072 kW

D. 4.072 kW

155.  A  heat  source  at  800 K  losses  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

156.  Helium gas is compressed in an adiabatic compressor from an initial state of 14 psia and 50°F  to  a  final  temperature  of  320°F  in  a  reversible  manner.  Determine  the  exit  pressure  of Helium.

A. 38.5 psia

B. 40.5 psia

C. 42.5 psia

D. 44.5 psia

157.  Air  passes  thru a nozzle with efficiency of 90%. The velocity of air at the exit is 600 m/s. Find the actual velocity at  the exit.

A. 382 m/s

B. 540 m/s

C. 458 m/s

D. 568 m/s

158.  A 50 kg block of iron casting at 500 K is thrown into a large lake that is at a temperature of 285  K.  The  iron  block  eventually  reaches  thermal  equilibrium  with  the  lake  water.  Assuming average  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

159.  A  windmill  with  a  12  m  diameter  rotor  is  to  be  installed at a location where the wind is blowing  at  an  average  velocity  of  10 m/s.  Using  standard  condition  of  air  (1 atm,  25°C), determine  the maximum  power that can be generated by the windmill.

A. 68 kW

B. 70 kW

C. 72 kW

D. 74 kW

160.  Consider a large furnace that can supply heat at a temperature of 2000°R at a steady rate of  3000  Btu/s.  Determine  the  energy  of  this  energy.  Assume  an  environment  temperature  of 77°F.

A. 2305.19 kW

B. 2315.19 kW

C. 2325.19 kW

D. 2335.19 kW

161. A heat engine receives heat from a source at 1200 K at a rate of 500 kJ/s and rejects the waste  heat  to  a  medium  at  300  K.  The  power  output  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

162.  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 21°C and outdoor  temperature  of 10°C, determine  the second law  efficiency of these heaters.

A. 8.74%

B. 6.74%

C. 3.74%

D. 4.74%

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%

164.  A rigid tank contains 2 kmol of N₂ and 6 kmol of CO₂ gases at 300 K and 115  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

165.  A  spherical  balloon  with  a  diameter  of  6  m  is  filled  with  helium  at  20°C  and  200  kPa. Determine the mole number.

A. 9.28 kmol

B. 10.28 kmol

C. 11.28 kmol

D. 13.28 kmol

166. The air in an automobile tire with a volume of 0.53 ft³ is at 90°F and 20 psig. Determine the amount  of  air  that must be added to raise the pressure to the recommended value of 30 psig. Assume  the  atmospheric  pressure  to  be  14.7  psia  and  the  temperature  and  the  volume  to remain constant.

A. 0.026 lb

B. 0.046  lb

C. 0.066 lb

D. 0.086 lb

167.  A rigid tank  contains 20 lb_m  of air at 20 psia and 70°F. More air is added to the tank until the  pressure  and  temperature  rise to 35 psia and 90°F, 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

168.  A rigid tank contains 5 kg of an ideal gas at 4 atm and 40°C. 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 temperature  in the tank is?

A. -38°C

B. -30°C

C. 40°C

D. 53°C

169.  The  pressure  of  an  automobile tire is measured to be 200  kPa (gage) before the trip end 220  kPa (gage)  after  the  trip  at  a  location  where  the  atmospheric  pressure  is  90 kPa.  If  the temperature  of the air in the tire before the trip is 25°C, the air temperature after the trip is?

A. 45.6°C

B. 54.8°C

C. 27.5°C

D. 26.7°C

170.  Water  is  boiling  at  1 atm  pressure  in  a  stainless  steel  pan  on  an  electric  range.  It  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

171.  Consider  a  person  standing  in  a  breezy  room  at  20°C.  Determine  the  total  rate  of  heat transfer  from  this  person  if  the  exposed  surface  area  and  the  average  outer  surface temperature  of  the person are 1.6 m² and 29°C, 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

172.  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

173.  An  aluminum  pan  whose  thermal  conductivity  is  237  W/m-°C  has  a  flat  bottom  whose diameter  is  20 cm and thickness of 0.4 cm. Heat is transferred  steadily to boiling water in the pan  through  its  bottom  at a rate of 500 watts. If the inner surface of the bottom of the pan is 105°C, determine  the temperature  of the surface of the bottom  of the pan.

A. 95.27°C

B. 105.27°C

C. 115.27°C

D. 125.27°C

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 at  an  average  temperature  of  34°C.  For  a  convection  heat transfer coefficient of 15 W/m² -°C, determine  the rate of heat loss from this man by convection in an environment  at 20°C.

A. 316.46 watts

B. 326.46 watts

C. 336.46 watts

D. 346.46 watts

175.  A  5  cm  diameter  spherical  ball  whose  surface  is  maintained at a temperature of 70°C is suspended  in  the  middle  of  a  room  at  20°C.  If  the  convection  heat  transfer  coefficient  is  15 W/m² -°C  and  the  emissivity  of  the  surface  is  0.8,  determine  the  total  heat  transfer  from  the ball.

A. 23.56 watts

B. 32.77 watts

C. 9.22 watts

D. 43.45 watts

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 systems  is  raised  by  15°C.  The  amount  of  extra  heat  that  must  be  supplied  to the gas in the cylinder that is maintained at constant pressure is?

A. 0

B. 50 kJ

C. 100 kJ

D. 150 kJ

177.  A supply of 50 kg of chicken at 6°C contained in a box is to be frozen to -18°C 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 -°C above freezing and 1.77 kJ/kg -°C below freezing. The container  box  is  1.5  kg,  and  the  specific  heat  of  the  box  material  is  1.4  kJ/kg -°C.  Also  the freezing temperature  of chicken is -2.8°C.

A. 15,206.4 kJ

B. 50.4 kJ

C. 15,156 kJ

D. 1,863 kJ

178.  Water  is  being  heated  in  a  closed  pan on top of a range while being stirred by a paddle wheel.  During the process, 30 kJ of heat is transferred  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

179.  A  classroom  that  normally  contains  40  people  is  to  be  air-conditioned  with  window  air-conditioning units of 5 kW cooling capacity. A person at rest may be assumed to dissipate heat at a rate  about 360 kJ/hr. There  are 10 light bulbs in the room, each with a rating of 100 watts. The  rate  of  heat  transfer  to the classroom through the walls and the windows is   estimated to be 15,000  kJ/hr.  If the room is to  be  maintained at a constant temperature of 21°C, determine the number  of window air-conditioning units required.

A. 1 units

B. 2 units

C. 3 units

D. 4 units

180.  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 23°C within 15 minutes.  Assuming  no  heat  losses  from  the  room  and  an  atmospheric  pressure  of  100  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

181.  A student living in a 4 m x 6  m x 6  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 transfer  through  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 100  kPa  and 15°C in the morning when she leaves.

A. 28.13°C

B. 38.13°C

C. 48.13°C

D. 58.13°C

182.  A  piston-cylinder device whose piston is resting on top of a set of stops initially contains 0.50  kg  of  helium  gas  at  100  kPa  and  25°C.  The  mass  of  the  piston  is  such  that  500  kPa  of pressure  is  required  to  raise  it.  How  much  heat  must  be  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

183. In order to cool 1 ton (1000 kg) of water at 20°C in an insulated tank, a person pours 80 kg of  ice  at  -5°C  into  the  water.  Determine  the  final  equilibrium  temperature  in  the  tank.  The melting  temperature  and  the  heat  of  fusion  of  ice  at atmospheric pressure are 0°C and 333.7 kJ/kg, respectively.

A. 12.43°C

B. 14.43°C

C. 16.43°C

D. 18.43°C

184.  A  fan  is  powered  by  0.5  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

185.  An  Ocean-Thermal  Energy  Conversion  power  plant  generates  10,000  kW  using  a  warm surface water inlet temperature of 26°C and cold deep-water temperature of 15°C. On the basis of  a  3°C  drop  in  the  temperature  of  the  warm  water  and  a 3°C rise in the temperature of the cold  water  due  to  removal  and  addition  of  heat,  calculate  the  power  required in kW to pump the  cold-deep  water  to  the  surface  and  through  the  system  heat  exchanger  if  the  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

186. A plate-type solar energy  collector with an absorbing surface covered by a glass plate is to receive  an  incident  radiation  of  800 W/m².  The  glass  plate  has  a  reflectivity  of  0.12  and a transmissivity  of  0.85.  The  absorbing  surface  has  an  absorptivity  of  0.90.  The  area  of  the collector is 5 m². How much solar energy in watts is absorbed by the collector?

A. 2500

B. 2880

C. 3510

D. 3060

187. A tank contains liquid nitrogen at -190°C is suspended in a vacuum  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 -°C.  If  the  ambient  air  outside  the  vacuum  shell  is  15°C,  calculate  the  magnitude  of  the conductive heat flow in watts along the support rods.

A. 0.168

B. 0.0587

C. 0.182

D. 0.176

188.  An  elastic sphere containing gas at 120 kPa has a diameter of 1.0 m. Heating the sphere causes  it  to  expand to a diameter of 1.3 m. During the  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

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 + 150υ  + 95 υ² where p is in kPa and υ in m³/kg. Calculate the work of compression in kJ/kg.

A. 32.8

B. 28.7

C. 35.6

D. 33.3

190.  A  one  cubic  meter  container contains  a  mixture  of  gases  composed  of  0.02  kg-mol  of oxygen  and  0.04  kg-mol  of  helium  at  a  pressure  of  220  kPa.  What  is  the  temperature of this ideal gas mixture in Kelvin?

A. 441

B. 350

C. 400

D. 450

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

A. 0.35

B. 0.45

C. 0.37

D. 0.65

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

A. 108.0

B. 129.6

C. 216.0

D. 318.2

193.  A 4 liter (2-liter per revolution at  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

194.  A simple Rankine cycle produces 40 MW of power, 50 MW of process heated and rejects 50  MW  of  heat  to  the  surroundings.  What  is  the  utilization  factor  of  this  cogeneration  cycle neglecting the pump work?

A. 50%

B. 60%

C. 64%

D. 80%

195.  The  rate  of  heat  transfer  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 assuming  that the energy goes into the air of volume 1500 m³ initially at 300 K and 101 kPa, calculate the rate in °C/min of air temperature  change.

A. 0.81

B. 0.53

C. 0.63

D. 1.0

196.  An  insulated  box  containing  helium  gas  falls  from  a  balloon  4.5  km  above  the  earth’s surface. Calculate the temperature rise in °C  of the helium when box hits the ground.

A. 15.2

B. 12.6

C. 25.3

D. 14.1

197. Consider two Carnot heat engines operating in series. The first engine receives heat from the  reservoir  at  2400  K  and  rejects  the waste heat to another reservoir at temperature T. The second engine receives heat by the first one, convert some of it to  work, and rejects the rest to a  reservoir  at  300  K.  If  thermal  efficiencies  of  both  engines  are  the  same,  determine  the temperature  T.

A. 849 K

B. 578 K

C. 763 K

D. 978 K

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

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

A. 0.208

B. 0.231

C. 0.531

D. 0.825

200.  A  Carnot  cycle  operates  between  the temperature limits of 300 K and 1500 K, and produces 600 kW  of  net  power.  The  rate  of  entropy  change  of  the  working  fluid  during  heat addition process is ?

A. 0

B. 0.4

C. 0.5

D. 2.0