This is the Multiple Choice Questions Part 10 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 10 of the Series

โ MCQ in Power Plant Engineering Part 9 | ME Board Exam

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

451.ย Specific volume is the number of cubic meters of mixture per kilogram of dry air. If dry air has these following properties: Ra = 287 J/kg-K, T = 303 K, Pa = 99.604 kPa. Solve for the specific volume.

A. 0.873 m^{3}/kg

B. 0.853 m^{3}/kg

C. 0.953 m^{3}/kg

D. 0.783 m^{3}/kg

Answer: **Option A**

Explanation:

452.ย Aย refrigeratingย systemย operatesย on the reversed Carnot Cycle. The higher temperature of theย refrigerantย inย theย systemย isย 120ยฐFย andย theย lowerย isย 10ยฐF.ย The capacity is 20 tons. Neglect losses. Determine the coefficient of performance.

A. 2.732

B. 5.373

C. 7.372

D. 4.273

Answer: **Option D**

Explanation:

453.ย Atย aย pressureย ofย 60ยฐF,ย aย motorbike Ire is inflated to 33 psig. As it is driven along the C -5 road,ย theย temperatureย roseย toย 76ยฐF.ย Assumingย theย volumeย remainsย constant,ย determineย the final gauge pressure.

Given:

P_{1} = 33 psig + 14.7 psig = 47.7 psig

T_{1} = 60ยฐF + 460 = 520ยฐR

T_{2} = 76ยฐF + 460 = 536ยฐR

A. 34.47 psig

B. 49.17 psig

C. 35.00 psig

D. 34.30 psig

Answer: **Option A**

Explanation:

454.ย Steam enters a turbine stage with an enthalpy of 3700 kJ/kg and a velocity of 80 m/s and leavesย withย anย enthalpyย ofย 2864ย kJ/kgย withย a velocity of 12.8 m/s. If the rate of a steam flow throughย the turbineย is 0.44 kg/s, what is the workย done in kW?

A. 365 kW

B. 365.64 kW

C. 366.0 kW

D. 366.50 kW

Answer: **Option B**

Explanation:

455.ย Aluminumย hasย aย specificย heatย ofย 0.902ย J/g -ยฐC.ย Howย muchย heatย isย lostย whenย aย pieceย of aluminumย withย aย massย ofย 23.984ย gย coolsย fromย aย temperatureย ofย 415.0ยฐCย toย aย temperatureย of 22.0ยฐC?

A. 8500 J

B. 6000 J

C. 80000 J

D. 7500 J

Answer: **Option A**

Explanation:

456.ย Ifย theย temperatureย ofย anย airย parcel isย -20.5ยฐC, and its density is 0.690 kg/m^{3}, what is the pressure of the air parcel?

A. 40 kPa

B. 50 kPa

C. 60 kPa

D. 70 kPa

Answer: **Option B**

Explanation:

457.ย A 35.0 mL sample of gas is enclosed in a flask at 22 degrees Celsius. If the flask was placed in an ice bath at 0 degrees Celsius,ย what would the new gas volume be if the pressure is held constant?

A. 34.1 mL

B. 32.1 mL

C. 32.39 mL

D. 33.1 mL

Answer: **Option C**

Explanation:

458.ย A car engine with a power output of 65 hp has a thermal efficiency of 24%. Determine the fuel consumptionย rate of this car if the fuel has a heating value of 19,000 Btu/lb m.

A. 36.28 lb_{m}/hr

B. 37.28 lb_{m}/hr

C. 37.28 lb_{m}/hr

D. 35.30 lb_{m}/hr

Answer: **Option A**

Explanation:

459.ย The thermal efficiency of a Carnot cycle operating between 170ยฐC and 620ยฐC is closest to:

A. 44%

B. 50%

C. 63%

D. 73%

Answer: **Option B**

Explanation:

460.ย Compute the humidity ratio of air at 70% relative humidity and 25ยฐC when the barometric pressure is 101.325 kPa. From the steam tables: P_{sat} @ 34 ยฐCย = 3.169 kPa.

A. 0.014 kg_{water vapor}/kg_{dry air}

B. 0.14 kg_{water vapor}/kg_{dry air}

C. 1.4 kg_{water vapor}/kg_{dry air}

D. 0.0014 kg_{water vapor}/kg_{dry air}

Answer: **Option A**

Explanation:

461.ย A pressure gauge registers 50 psig in a region where the barometer reads 14.8 psia. Find the absolute pressure in kPa.

A. 666.66 kPa

B. 556.66 kPa

C. 446.66 kPa

D. 336.66 kPa

Answer: **Option C**

Explanation:

462.ย Consider 1 kg of air at 32ยฐC that expanded by a reversible polytropic process with n = 1.25 untilย theย pressureย isย halved. Determineย the heat transfer. Specific heat at constant volume for air is 0.1786 kJ/kg-K.

A. 17.02 kJ heat rejected

B. 7.05 kJ heat rejected

C. 17.02 kJ heat added

D. 7.05 kJ heat added

Answer: **Option C**

Explanation:

463.ย A Carnot cycle uses nitrogen (k = 1.399) as the working substance. The heat supplied is 54 kJ and the adiabaticย expansion ratio is 10. Determine the heat rejected.

A. 10 kJ

B. 32.4 kJ

C. 21.6 kJ

D. 54 kJ

Answer: **Option C**

Explanation:

464.ย Aย tankย containsย 20ย kgย ofย airย atย 200 kPa (gage) and 23ยฐC. During the heating process the temperatureย ofย airย rises.ย Forย safetyย purposesย aย technicianย installed a relief -type valve so that pressure of air inside the tank never exceeds 260 kPa (gage). At what air temperature the relief valve will start releasing air?

A. 112ยฐC

B. 92ยฐC

C. 82ยฐC

D. 102ยฐC

Answer: **Option C**

Explanation:

465.ย An air compressor takes in 9 kg/min of air at 98 kPa; ฯ
_{1} = 0.125 m^{3}/kg and discharges it at 680 kPa; ฯ
_{2} = 0.03 m^{3}/kg. The increase of internal energy is 93 kJ/kg and the work done on air is 163ย kJ/kg;ย theย changeย inย potentialย andย kineticย energyย areย neglected.ย Howย muchย heatย is transferred per kg of air?

A. 264.15 kJ/kg

B. 61.85 kJ/kg

C. 288.65 kJ/kg

D. 78.15 kJ/kg

Answer: **Option B**

Explanation:

466.ย During a reversible process, there are abstracted 317 kJ/s from 1.134 kg/s of a certain gas while the temperature remains constant at 26.7ยฐC. For this gas c_{p} = 2.232 and c_{v} = 1.713 kJ/kg-K. The initial pressure is 586 kPa. Determine the final volume flow rate.

A. 0.301 m^{3}/s

B. 0.03 m^{3}/s

C. 0.5 m^{3}/s

D. 0.05 m^{3}/s

Answer: **Option D**

Explanation:

467.ย Flowย ofย waterย inย aย pipeย hasย aย velocityย atย 10ย metersย perย second.ย Determineย theย velocity head of the water.

A. 50.1 meters

B. 5.10 meters

C. 8.20 meters

D. 100 meters

Answer: **Option B**

Explanation:

468.ย Aย Dieselย cycleย hasย aย cut-offย ratioย ofย 2.20ย andย aย compressionย ratioย ofย 10.ย Findย theย cycle efficiency.

A. 55.10%

B. 59.735%

C. 52.23%

D. 62.37%

Answer: **Option C**

Explanation:

469.ย Aย dieselย cycleย hasย anย initialย temperatureย ofย 27ยฐC.ย Ifย theย cut-offย ratioย isย 2.50ย and compression ratio is 12,ย find the maximum cycle temperature.

A. 1634.4ยฐC

B. 1753.44ยฐC

C. 2010.3ยฐC

D. 1983.4ยฐC

Answer: **Option B**

Explanation:

470. A diesel cycle, which takes in air at 1 bar and 26ยฐC, has a compression ratio of 19. Calculate the operating clearance in percent.

A. 8.08

B. 8.56

C. 7.52

D. 5.55

Answer: **Option D**

Explanation:

471.ย Anย Ottoย cycleย hasย anย initialย pressureย ofย 100 kPaย andย hasย aย pressureย ofย 400 kPaย after adiabatic compression. Find the cycle efficiency.

A. 32.70%

B. 34.70%

C. 36.70%

D. 38.70%

Answer: **Option A**

Explanation:

472.ย An Otto cycle has a clearance of 8%ย and heat added of 1000 kJ. Find the heat rejected.

A. 564 kJ

B. 353 kJ

C. 709 kJ

D. 867 kJ

Answer: **Option B**

Explanation:

473. Anย Otto cycle has a heat rejected of 300 kJ and work of 700 kJ. Find the cycle efficiency.

A. 56%

B. 60%

C. 70%

D. 50%

Answer: **Option C**

Explanation:

474.ย An Otto cycle has a pressure ratio of 7. What is the cycle compression ratio?

A. 5.18

B. 6.34

C. 7.34

D. 4.01

Answer: **Option D**

Explanation:

475. Find the power of a rotating shaft which develops a torque of 188 N-m at 1350 rpm.

A. 101.54 hp

B. 53.63 hp

C. 63.35 hp

D. 35.63 hp

Answer: **Option D**

Explanation:

476.ย Determineย theย pressureย exertedย onย aย diverย atย 30 mย belowย theย freeย surfaceย ofย theย sea. Assume a barometric pressure of 101 kPa and the specific gravity of sea water is 1.03.

A. 404 kPa

B. 410 kPa

C. 420 kPa

D. 430 kPa

Answer: **Option A**

Explanation:

477.ย An air compressor has an inlet enthalpy of 35 Btu/lb and an exit enthalpy of 70 Btu/lb. The massย flowย rateย ofย airย isย 3ย lb/s.ย Ifย theย heatย lossย isย 466.62ย Btu/min,ย findย theย workย input to the compressor.

A. 139.59 hp

B. 149.59 hp

C. 159.59 hp

D. 169.59 hp

Answer: **Option C**

Explanation:

478.ย An automobile tire is inflated to 35 psig at 54ยฐF. Afterย being driven, the temperature rises to 80ยฐF. Determine the final gage pressure assuming that the tire is inflexible.

A. 36.51 psig

B. 37.51 psig

C. 38.51 psig

D. 39.51 psig

Answer: **Option B**

Explanation:

479.ย Aย condenserย vacuumย gaugeย readsย 600ย mm Hgย whenย theย barometerย readsย 760ย mm Hg. What is the absolute condenser pressure in bar?

A. 0.0213

B. 0.061

C. 0.213

D. 0.610

Answer: **Option C**

Explanation:

480.ย Water flows in a pipe at the rate of 10 kg/s. If the velocity of flow is 10 m/s, find the pipe diameter.

A. 30.23 mm

B. 35.68 mm

C. 38.39 mm

D. 42.39 mm

Answer: **Option B**

Explanation:

481.ย What is the resulting pressure when one kilogram of air at 104 kPa and 98ยฐC is heated at constant volume to 450ยฐC?

A. 202.67 kPa

B. 194.67 kPa

C. 186.53 kPa

D. 198.65 kPa

Answer: **Option A**

Explanation:

482.ย Determine the degrees of superheat of steam at 101.325 kPa and 170ยฐC.

A. 50ยฐC

B. 70ยฐC

C. 60ยฐC

D. 80ยฐC

Answer: **Option B**

Explanation:

483.ย Calculate the approximate enthalpy of water at 90ยฐC.

A. 366.83 kJ/kg

B. 376.83 kJ/kg

C. 386.83 kJ/kg

D. 396.83 kJ/kg

Answer: **Option B**

Explanation:

484.ย A Carnot cycle operates between 30ยฐC and 350ยฐC. Find the cycle efficiency.

A. 51.36%

B. 63.45%

C. 45.37%

D. 76.45%

Answer: **Option A**

Explanation:

485.ย A Carnot cycle has a maximum temperature of 550ยฐF and minimum temperature of 100ยฐF. If the heat added is 4200 Btu/min, find the horsepowerย outputย of the engine.

A. 34.53

B. 40.56

C. 44.13

D. 65.40

Answer: **Option C**

Explanation:

486.ย Aย Carnotย cycleย hasย aย sinkย temperatureย ofย 100ยฐFย andย aย cycleย efficiencyย ofย 70%.ย Findย the temperatureย of the heat source.

A. 1306.70ยฐF

B. 1406.70ยฐF

C. 1506.70ยฐF

D. 1606.70ยฐF

Answer: **Option B**

Explanation:

487.ย The quality of steam is 20%. This means that:

A. mass of liquid is 20%, mass of vapor is 80%

B. mass of liquid is 20%, mass of vapor is 0%

C. mass of liquid is 80%, mass of vapor is 20%

D. none of these

Answer: **Option C**

Explanation:

488.ย Fiftyย kilogramsย ofย coolingย waterย perย secondย enterย theย condenserย atย 25ยฐCย andย leavesย at 50ยฐC.ย Find the heat carried away by water.

A. 1234.45 kW

B. 5233.75 kW

C. 2340.53 kW

D. 3140.25 kW

Answer: **Option B**

Explanation:

489.ย Tenย kilogramsย perย secondย ofย steam enter the turbine with an enthalpy of 3200 kJ/kg and enter the condenser with an enthalpy of 2500 kJ/kg in a Rankine cycle. If the turbine efficiency is 80% and the generator efficiency is 90%, determine the powerย plant output.

A. 4320 kW

B. 3213 kW

C. 4056 kW

D. 5040 kW

Answer: **Option D**

Explanation:

490.ย Determine the quality of steam in a vessel containing 2 kg of saturated vapor and 8 kg of saturated liquid.

A. 100%

B. 20%

C. 80%

D. 60%

Answer: **Option B**

Explanation:

491.ย The condenser of a reheat power plant rejects heat at the rate of 600 kW. The mass flow rateย ofย coolingย waterย isย 5ย kg/sย andย theย inletย cooling water temperature is 35ยฐC. Calculate the condenser cooling water exit temperature.

A. 43.45ยฐC

B. 53.45ยฐC

C. 63.66ยฐC

D. 74.34ยฐC

Answer: **Option C**

Explanation:

492.ย A heat engine has a thermal efficiency of 50%. How much power does the engine produce when heat is transferred at a rate of 10^{9} kJ/hr?

A. 50 MW

B. 75 MW

C. 139 MW

D. 147 MW

Answer: **Option C**

Explanation:

493.ย Oneย kilogramย ofย airย isย compressedย adiabaticallyย andย inย aย steady-flowย manner.ย The compression efficiency is 80% and the work done on the air is 265 kJ/kg. Compute the heat.

A. 212 kJ/kg

B. 100 kJ/kg

C. 0 kJ/kg

D. 331.25 kJ/kg

Answer: **Option C**

Explanation:

494.ย Three-hundredย kilojoulesย ofย heatย flowย byย conductionย fromย theย outsideย toย theย insideย ofย a coldย storage in one hour. If the temperature and all other conditions are the same, what is the heat flowing through the cold storage room in two hours?

A. 600 kJ

B. 900 kJ

C. 300 kJ

D. 1,200 kJ

Answer: **Option A**

Explanation:

495.ย Determine the density of air at 760 mmHg absolute and 22ยฐC?

A. 1.014 kg/m^{3}

B. 1.316 kg/m^{3}

C. 1.197 kg/m^{3}

D. 1.266 kg/m^{3}

Answer: **Option C**

Explanation:

496.ย A refrigerating machine that isย classified as a one-ton machine has the capacityย to produce a cooling effect of?

A. 3.516 kW

B. 12,000 Btu/hr

C. 211 kJ/min

D. All of these

Answer: **Option D**

Explanation:

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