This is the Multiple Choice Questions Part 5 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 5 of the Series

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

**Choose the letter of the best answer in each questions.**

201. Air in an ideal Diesel cycle is compressed from 3 L to 0.15 L and then it expands during the constant pressure heat addition process to 0.3 L. Under cold air standard conditions, the thermal efficiency of this cycle is?

A. 35%

B. 44%

C. 65%

D. 70%

Answer: **Option C**

Explanation:

202. Helium gas in an ideal Otto cycle is compressed from 20ยฐC and 2 L to 0.25 L and its temperature increases by an additional 800ยฐC during the heat addition process. The temperature of Helium before the expansion process is?

A. 1700ยฐC

B. 1440ยฐC

C. 1240ยฐC

D. 880ยฐC

Answer: **Option A**

Explanation:

203. In an ideal Otto cycle, air is compressed from 1.20 kg/m^{3} and 2.2 L to 0.26 L and the net work output of the cycle is 440 kJ/kg. The mean effective pressure for the cycle is?

A. 612 kPa

B. 599 kPa

C. 528 kPa

D. 416 kPa

Answer: **Option B**

Explanation:

204. An ideal Brayton cycle has a net work output of 150 kJ/kg and backwork ratio of 0.4. if both the turbine and the compressor had an isentropic efficiency of 80%, the net work output of the cycle would be?

A. 60 kJ/kg

B. 75 kJ/kg

C. 98 kJ/kg

D. 120 kJ/kg

Answer: **Option B**

Explanation:

205. Air enters a turbojet engine at 200 m/s at a rate of 20 kg/s and exits at 800 m/s relative to the aircraft. The thrust developed by the engine is?

A. 6 kN

B. 12 kN

C. 16 kN

D. 20 kN

Answer: **Option B**

Explanation:

206. A thermal power has a net power of 10 MW. The backwork ratio of the plant is 0.005. Determine the compressor work.

A. 50.15 kW

B. 50.35 kW

C. 50.25 kW

D. 50.45 kW

Answer: **Option C**

Explanation:

207. A heat engine receives heat from a source at 1200 K at a rate of 500 kJ/s and rejects the wasted heat to a sink at 300 K. If the power output of the engine is 200 kW, the second law efficiency of this heat engine is?

A. 35%

B. 40%

C. 53%

D. 75%

Answer: **Option C**

Explanation:

208. A water reservoir contains 100,000 kg of water at an average elevation of 60 m. The maximum amount of electric power that can be generated from this water is ?

A. 8 kWh

B. 16 kWh

C. 1630 kWh

D. 58,800 kWh

Answer: **Option B**

Explanation:

209. A house is maintained at 22ยฐC in winter by electric resistance heaters. If the outdoor temperature is 5ยฐC, the second law efficiency of the resistance heaters is?

A. 0%

B. 5.8%

C. 34%

D. 77%

Answer: **Option B**

Explanation:

210. A thermoelectric refrigerator that resembles a small ice chest is powered by a car battery, and has a COP of 0.10. If the refrigerator cools a 0.350 L canned drink from 20ยฐC to 4ยฐC in 30 min, determine the average electric power consumed by the thermoelectric refrigerator.

A. 130 watts

B. 110 watts

C. 120 watts

D. 140 watts

Answer: **Option A**

Explanation:

211. A Carnot refrigerator operates in a room in which the temperature is 25ยฐC and consumes 2 kW of power when operating. If the food compartment of the refrigerator is to be maintained at 3ยฐC, determine the rate of heat removal from the food compartment.

A. 1504.8 kJ/min

B. 12.86 kJ/min

C. 1625 kJ/min

D. 9.57 kJ/min

Answer: **Option A**

Explanation:

212. A household refrigerator with EER 8.0 removes heat from the refrigerated space at a rate of 90 kJ/min. Determine the rate of heat transfer to the kitchen air.

A. 101.25 kJ/min

B. 63.05 kJ/min

C. 128.46 kJ/min

D. 80 kJ/min

Answer: **Option C**

Explanation:

213. An air-conditioning system is used to maintain a house at 75ยฐF when the temperature outside is 95ยฐF. The house is gaining the heat through the walls and windows at a rate of 1250 Btu/min, and the heat generation rate within the house from people, lights, and appliances amounts to 350 Btu/min. Determine the minimum power input required for this air-conditioning system.

A. 10.06 hp

B. 1.36 hp

C. 1.41 hp

D. 7.94 hp

Answer: **Option C**

Explanation:

214. A refrigeration system is to cool bread loaves with an average mass of 450 g from 22ยฐC to – 10ยฐC at a rate of 500 loaves per hour by refrigerated air. Taking the average specific and latent heats of bread to be 2.93 kJ/kg-ยฐC and 109.3 kJ/kg, respectively, determine the product load.

A. 541.7 kJ/min

B. 351.6 kJ/min

C. 761.5 kJ/min

D. 409.9 kJ/min

Answer: **Option C**

Explanation:

215. A house that was heated by electric resistance heaters consumed 1200 kWh of electric energy in a winter month. If this house were heated instead by a heat pump that has an average performance factor, PF of 2.4, determine how much money the homeowner would be saved that month. Assume a price of 0.085 $/kWh for electricity.

A. $42.5

B. $59.50

C. $102

D. $97.75

Answer: **Option B**

Explanation:

216. An ammonia simple saturation cycle operates with a suction pressure of 291.6 kPa and a condenser pressure of 1204 kPa develops 15 tons of refrigeration. Determine the theoretical horsepower of the compressor. The following enthalpies have been found: condenser entrance = 1653 kJ/kg, exit = 346.6 kJ/kg; compressor entrance = 1450.2 kJ/kg, exit = 1653 kJ/kg.

A. 7.23 hp

B. 13 hp

C. 15 hp

D. 8.23 hp

Answer: **Option B**

Explanation:

217. An ammonia ice plant operates between a condenser temperature of 35ยฐC and evaporator of -15ยฐC. It produces 10 metric tons of ice per day from water at 30ยฐC to ice at -5ยฐC. Assuming simple saturation cycle, determine the horsepower of the motor if the adiabatic efficiency of the compressor n_{c} = 0.85 and mechanical efficiency n_{m} = 0.95. The specific heat of ice is 2.094 kJ/kg-ยฐC and the latent heat is 335 kJ/kg. From the table for ammonia the following enthalpies are: condenser entrance = 1703 kJ/kg, exit = 366.1 kJ/kg; compressor entrance = 1443.9 kJ/kg, exit = 1703 kJ/kg.

A. 17.68 hp

B. 18.61 hp

C. 15.5 hp

D. 21.9 hp

Answer: **Option D**

Explanation:

218. A Freon 22 air conditioning under standard operating conditions of 35ยฐC condensing and 5ยฐC evaporating temperatures. The volume flow rate entering the compressor is 23.72 L/s. Determine the refrigerating capacity if the refrigerating effect is 164 kJ/kg. From the table for R22 the specific volume at the compressor entrance is 40.46 L/kg.

A. 339.3 TR

B. 79.3 TR

C. 96.4 TR

D. 27.4 TR

Answer: **Option D**

Explanation:

219. The refrigerant volume flow rate at the entrance of compressor were obtained from a test on a twin cylinder, single acting 15 cm x 20 cm, 320 rpm compressor ammonia refrigerating plant to be 33 L/s. Determine the volumetric efficiency of the compressor.

A. 77.65%

B. 87.6%

C. 97.6%

D. 65.65%

Answer: **Option B**

Explanation:

220. A twin cylinder ammonia compressor with volume displacement of 14,726 cm^{3} operates at 300 rpm. Condenser and evaporator pressure are 1200 kPa and 227 kPa respectively. Specific volume of refrigerant at the entrance of compressor is 528.26 L/kg. Compression process is polytropic with n = 1.20 and clearance factor of compressor is 2 percent. Determine the horsepower required.

A. 60 hp

B. 70 hp

C. 80 hp

D. 90 hp

Answer: **Option C**

Explanation:

221. A reversed Carnot has a refrigerating COP of 2.5. Determine the ratio TH/TL.

A. 1.4

B. 1.5

C. 1.25

D. 1.2

Answer: **Option A**

Explanation:

222. Three thousand cubic feet per minute of air are circulated over an air-cooled condenser. If the load on the condenser is 64,800 Btu/hr, compute the temperature rise of the air passing over the condenser. Specific volume of standard air (13.34 ft^{3}/lb).

A. 10ยฐF

B. 15ยฐF

C. 20ยฐF

D. 25ยฐF

Answer: **Option C**

Explanation:

223. Saturated vapor ammonia at -16ยฐC (h_{T} = 1442.60 kJ/kg) leaves the evaporator and enters the compressor at -6ยฐC (h_{1} = 1465 kJ/kg). The refrigerant leaves the condenser as saturated liquid at 40ยฐC (h_{4} = 390.6 kJ/kg) and enters the expansion valve at 35ยฐC (h_{5} = 366.1 kJ/kg). Heat rejected from the condenser amount to 50 kW. The work to compressor is 208 kJ/kg, while the heat loss from compressor is 33 kJ/kg. If 95 kJ/kg of heat are lost in the piping between the compressor discharge and condenser inlet, determine the refrigerating capacity of the system.

A. 49.5 TR

B. 46.61 TR

C. 12.88 TR

D. 13.24 TR

Answer: **Option D**

Explanation:

224. In an actual refrigeration cycle using R12 as working fluid, the refrigerant flow rate is 0.05 kg/s. Vapor enters the expansion valve at 1.15 MPa, 40ยฐC (h = 238.5 kJ/kg) and leaves the evaporator at 175 kPa, -15ยฐC (h = 345 kJ/kg). The electric iput to motor driving the compressor is measured and found 3.0 kW. Motor efficiency at this load 92% and mechanical efficiency 82%. Determine the actual coefficient of performance for this cycle.

A. 1.58

B. 2.36

C. 1.78

D. 1.34

Answer: **Option B**

Explanation:

225. In an ammonia refrigeration system, the temperature in the evaporator is -12ยฐC and the ammonia at the evaporator entry 0.1511 dry while at exit is 0.95 dry. If the rate of ammonia circulation is 5.64 kg/min, determine the refrigerating capacity of the system. Enthalpy of saturated liquid and vapor at -12ยฐC is 144.929 kJ/kg and 1447.74 kJ/kg respectively.

A. 17.82

B. 34.82

C. 27.82

D. 4.82

Answer: **Option C**

Explanation:

226. A two stage cascade vapor compression refrigeration system uses ammonia in the low temperature loop and R-12 in the high-temperature loop. The ammonia provides 15 tons of cooling. If the high-loop temperature requires 10.12 kW compressor power and low loop 15.93 kW, determine the COP of the system.

A. 2.027 TR

B. 5.22 TR

C. 3.314 TR

D. 9.1 TR

Answer: **Option A**

Explanation:

227. When a man returns to his well-sealed house on a summer day, he finds that the house is at 32ยฐC. He turns on the air conditioner, which cools the entire house to 20ยฐC in 15 min. If COP of the air conditioner system is 2.5, determine the power drawn by the air conditioners. Assume the entire mass within the house is equivalent to 800 kg of air for which c = 0.72 kJ/kg – ยฐC.

A. 7.08 kW

B. 3.07 kW

C. 19.2 kW

D. 12.08 kW

Answer: **Option B**

Explanation:

228. It is desired to double the COP of a reversed Carnot engine for cooling from 5.0 by raising the temperature of heat addition while keeping the temperature of heat rejection constant. By what percentage must the temperature of heat addition be raised?

A. 10.1%

B. 9.1%

C. 8.1%

D. 7.1%

Answer: **Option B**

Explanation:

229. An ammonia water-cooled compressor receives the refrigerant at specific volume 62 L/kg. It has a piston displacement rate of 5 m^{3}/min. If a squirrel cage motor running at 1200 rpm drives the compressor and average piston speed is 490 m/min, calculate size of cylinder bore.

A. 20.4 cm

B. 26.0 cm

C. 16.13 cm

D. 13.6 cm

Answer: **Option C**

Explanation:

230. If the initial volume of an ideal gas is compressed the one-half its original volume and to twice its temperature, the pressure:

A. Doubles

B. Quadruples

C. Remains constant

D. Halves

Answer: **Option B**

Explanation:

231. If the gage pressure of a medium is 30 kPa (vacuum) and the atmospheric pressure is 101.3 kPa, the absolute pressure will be?

A. 131.3 kPa

B. -71.3 kPa

C. 71.3 kPa

D. -131.3 kPa

Answer: **Option C**

Explanation:

232. If a particle has a velocity of 4 meters per second and a kinetic energy of 144 Joules, then the mass, in kilograms of this particle must be?

A. 44

B. 16

C. 18

D. 24

Answer: **Option C**

Explanation:

233. A condenser vacuum gauge reads 715 mm Hg when the barometer stands at 757 mm Hg. State the absolute pressure in the condenser in kN/m^{2} or kPa.

A. 5.6 kPa

B. 5.9 kPa

C. 6.5 kPa

D. 5.2 kPa

Answer: **Option A**

Explanation:

234. Determine the force in newton in a piston of 465 mm2 area with a pressure of 0.172 MPa.

A. 65 N

B. 72 N

C. 80 N

D. 111 N

Answer: **Option C**

Explanation:

235. One piston of a hydraulic press has an area of 1 cm^{2}. The other piston has an area of 25 cm^{2}. If a force of 150 N is applied on the smaller piston, what will be the total force on the larger piston if both piston surfaces are on the same level?

A. 6 N

B. 175 N

C. 3750 N

D. 4250 N

Answer: **Option C**

Explanation:

236. The work done on air is 10.86 kJ/kg, determine the compressor power if it is receiving 272 kg/min of air.

A. 36.72 hp

B. 49.23 hp

C. 2954 hp

D. 66 hp

Answer: **Option D**

Explanation:

237. A water tank 18 ft wide, 14 ft long, and 4 ft high, calculate the pressure at the bottom of the tank.

A. 1.733 psi

B. 1.999 psi

C. 2.337 psi

D. 3.773 psi

Answer: **Option A**

Explanation:

238. What is the pressure of 750 mm Hg in kN/m^{2}?

A. 90 kPa

B. 100 kPa

C. 103 kPa

D. 110 kPa

Answer: **Option B**

Explanation:

239. A double purpose tank 18 ft wide, 24 ft long and 4 ft depth is filled with water. What is the weight of water in the tank in long tons?

A. 49 tons

B. 48 tons

C. 54 tons

D. 50 tons

Answer: **Option A**

Explanation:

240. Oil flows through a 16 tube single cooler with a velocity of 2 m/s. The internal diameter of the tube is 30 mm and oil density is 0.85 g_{m}/ml. Find the volume flow in liters per sec.

A. 22.62

B. 32.22

C. 62.22

D. 42.62

Answer: **Option A**

Explanation:

241. A substance temperature was 620ยฐR. What is the temperature in ยฐC?

A. 50.7

B. 45.54

C. 71.11

D. 91.44

Answer: **Option C**

Explanation:

242. An unknown volume of container gas of 1 atmosphere is allowed to expand to another container of 10 m^{3} volume at 500 mmHg at constant temperature. Find the unknown volume.

A. 6.58 m^{3 }

B. 6.75 m^{3}

C. 5.67 m^{3}

D. 7.65 m^{3}

Answer: **Option A**

Explanation:

243. An iron block weighs 5 Newton and has a volume of 200 cm^{3}. What is the density of the block?

A. 2458 kg/m^{3}

B. 2485 kg/m^{3}

C. 2584 kg/m^{3}

D. 2549 kg/m^{3}

Answer: **Option D**

Explanation:

244. If air is at a pressure of 22.22 psia and at a temperature of 800ยฐR, what is the specific volume?

A. 11.3 ft^{3}/lbm

B. 33.1 ft^{3}/lbm

C. 13.3 ft^{3}/lbm

D. 31.3 ft^{3}/lbm

Answer: **Option C**

Explanation:

245. The Specific gravity of mercury is 13.55. What is the specific weight of mercury?

A. 123.9 kN/m^{3}

B. 139.2 kN/m^{3}

C. 132.9 kN/m^{3}

D. 193.2 kN/m^{3}

Answer: **Option C**

Explanation:

246. The equivalent weight of mass 10 kg at a location where the acceleration of gravity is 9.77 m/s^{2}?

A. 97.7 N

B. 79.7 N

C. 77.9 N

D. 977 N

Answer: **Option A**

Explanation:

247. A transportation company specializes in the shipment of pressurized gaseous materials. An order is received from 100 liters of a particular gas at STP (32ยฐF and 1 atm). What minimum volume tank is necessary to transport the gas at 80ยฐF and maximum pressure of 8 atm?

A. 16 liters

B. 14 liters

C. 10 liters

D. 12 liters

Answer: **Option B**

Explanation:

248. 100 g of water are mixed with 150 g of alcohol (density = 790 kg/m^{3}). What is the specific volume of the resulting mixtures, assuming that the fluids mixed completely?

A. 0.82 x 10^{-3} m^{3}/kg

B. 0.88 x 10^{-3} m^{3}/kg

C. 0.63 x 10^{-3} m^{3}/kg

D. 1.16 x 10^{-3} m^{3}/kg

Answer: **Option D**

Explanation:

249. How much does 30 lbm weigh on the moon? (g_{moon} = 5.47 ft/s^{2}).

A. 2.0 lb_{f}

B. 3.2 lb_{f}

C. 3.4 lb_{f}

D. 5.096 lb_{f}

Answer: **Option D**

Explanation:

250. A 10 kg block is raised vertically 3 meters. What is the change in potential energy?

A. 320 J

B. 350 km-m^{2}/s^{2}

C. 294 J

D. 350 N-m

Answer: **Option C**

Explanation:

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