This is the Multiple Choice Questions Part 8 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 8 of the Series

⇐ MCQ in Power Plant Engineering Part 7 | ME Board Exam

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

351. Calculate the heat transfer per hour through a solid brick wall 6 m long, 2.9 m high, and 225 mm thick, when the outer surface is at 5°C and the inner surface 17°C, the coefficient of thermal conductivity of the brick being 0.6 W/m-K.

A. 2,004.48 kJ

B. 3,004.48 kJ

C. 2,400.48 kJ

D. 3,400.48 kJ

Answer: **Option A**

Explanation:

352. A vertical furnace wall is made up of an inner wall of firebrick 20 cm thick followed by insulating brick 15 cm thick and an outer wall of steel 1 cm thick. The surface temperature of the wall adjacent to the combustion chamber is 1200°C while that of the outer surface of steel is 50°C. The thermal conductivities of the wall material in W/m-K are: firebrick, 10; insulating brick, 0.26; and steel, 45. Neglecting the film resistances and contact resistance of joints, determine the heat loss per sq. m. of wall area.

A. 1.93 W/m^{2 }

B. 2.93 W/m^{2}

C. 1.55 W/m^{2}

D. 2.55 W/m^{2}

Answer: **Option A**

Explanation:

353. A composite wall is made up of an external thickness of brickwork 110 mm thick inside which is a layer of fiberglass 75 mm thick. The fiberglass is faced internally by an insulating board 25 mm thick. The coefficients of thermal conductivity are as follow:

Brickwork 1.5 W/m-K

Fiberglass 0.04 W/m-K

Insulating board 0.06 W/m-K

The surface transfer coefficients of the inside wall is 3.1 W/m^{2}-K while that of the outside wall is 2.5 W/m^{2}-K. Take the internal ambient temperature as 10°C and the external temperature is 27°C. Determine the heat loss through such wall 6m high and 10 m long.

A. 330.10 W

B. 230.10 W

C. 430.10 W

D. 530.10 W

Answer: **Option A**

Explanation:

354. One insulated wall of a cold-storage compartment is 8 m long by 2.5 m high and consists of an outer steel plate 18 mm thick. An inner wood wall is 22.5 m thick. The steel and wood are 90 mm apart to form a cavity which is filled with cork. If the temperature drop across the extreme faces of the composite wall is 15°C. Calculate the heat transfer per hour through the wall and the temperature drop across the thickness of the cork. Take the coefficients of thermal conductivity for steel, cork and wood as 45, 0.045, and 0.18 W/m-K respectively.

A. 408.24 kJ, 12.12°C

B. 708.24 kJ, 11.12°C

C. 608.24 kJ, 13.12°C

D. 508.24 kJ, 14.12°C

Answer: **Option D**

Explanation:

355. A cubical tank of 2 m sides is constructed of metal plate 12 mm and contains water at 75°C. The surrounding air temperature is 16°C. Calculate the overall heat transfer coefficient from water to air. Take the coefficient of thermal conductivity of the metal as 48 W/m-K, the coefficient of heat transfer of water is 2.5 kW/m^{2}-K and the coefficient of heat transfer of the air is 16 W/m^{2}-K.

A. 15.84 W/m^{2}-°C

B.14.84 W/m^{2}-°C

C. 16.84 W/m^{2}-°C

D. 13.84 W/m^{2}-°C

Answer: **Option A**

Explanation:

356. A cold storage compartment is 4.5 m long by 4 m wide by 2.5 m high. The four walls, ceiling and floor are covered to a thickness of 150 mm with insulating material which has a coefficient of thermal conductivity of 5.8 x 10^{-2} W/m-K. Calculate the quantity of heat leaking through the insulation per hour when the outside and inside face temperature of the material is 15°C and -5°C respectively.

A. 2185.44 kJ

B. 2285.44 kJ

C. 3185.44 kJ

D. 4185.44 kJ

Answer: **Option A**

Explanation:

357. A furnace wall consists of 35 cm firebrick (k = 1.557 W/m-K), 12 cm insulating refractory (k = 0.346) and 20 cm common brick (k = 0.692) covered with 7 cm steel plate (k = 45). The temperature at the inner surface of the firebrick is 1,230°C and at the outer face of the steel plate is 60°C. Atmosphere is 27°C. What is the value of the combined coefficient for convection and radiation from the outside wall?

A. 31.13 W/m^{2}-K

B. 30.13 W/m^{2}-K

C. 41.3 W/m^{2}-K

D. 40.13 W/m^{2}-K

Answer: **Option C**

Explanation:

358. Hot gases at 280°C flow on one side of the metal plate 10 mm thickness and air at 35°C flows on the other side. The heat transfer coefficient of the gases is 31.5 W/m^{2}-K and that of the air is 32 W/m^{2}-K. Calculate the over-all heat transfer coefficient.

A. 15.82 W/m^{2}-K

B. 16.82 W/m^{2}-K

C. 14.82 W/m^{2}-K

D. 17.82 W/m^{2}-K

Answer: **Option A**

Explanation:

359. The surface temperature of the hot side of the furnace wall is 1200°C. It is desired to maintain the outside of the wall at 38°C. A 152 mm of refractory silica is used adjacent to the combustion chamber and 10 mm of steel covers the outside. What thickness of insulating bricks is necessary between refractory and steel, if the heat loss should be kept at 788 W/m^{2}? Use k = 13.84 W/m-K for refractory silica; 0.15 for insulating brick, and 45 for steel.

A. 220 mm

B. 240 mm

C. 260 mm

D. 280 mm

Answer: **Option A**

Explanation:

360. An insulated steam pipe located where the ambient temperature is 32°C, has an inside diameter of 50 mm with 10 mm thick wall. The outside diameter of corrugated asbestos insulation is 125 mm and the surface coefficient of still air, ho = 12 W/m^{2}-K. Inside the pipe is steam having a temperature of 150°C with film coefficient hi = 6000 W/m^{2}-K. Thermal conductivity of pipe and asbestos insulation are 45 and 0.12 W/m-K respectively. Determine the heat loss per unit length of pipe.

A. 110 W

B. 120 W

C. 130 W

D. 140 W

Answer: **Option B**

Explanation:

361. How many watts will be radiated from a spherical black body 15 cm in diameter at a temperature of 800°C?

A. 5.34 kW

B. 4.34 kW

C. 6.34 kW

D. 3.34 kW

Answer: **Option A**

Explanation:

362. A wall with an area of 10 m^{2 }is made of a 2 cm thickness of white pine (k = 0.133 W/m-°C) followed by a 10 cm of brick (k = 0.649 W/m-°C). The pine is on the inside where the temperature is 30°C while the outside temperature is 10°C. Assuming equilibrium conditions exist, what is the temperature at the interface between the two metals?

A. 15.65 °C

B. 17.64 °C

C. 18.21 °C

D. 19.31 °C

Answer: **Option D**

Explanation:

363. A counter-flow heat exchanger is designed to heat a fuel oil from 45°C to 100°C while the heating fluid enters at 150°C and leaves at 115°C. Calculate the arithmetic mean temperature difference.

A. 40°C

B. 50°C

C. 60°C

D. 70°C

Answer: **Option C**

Explanation:

364. With three different quantities x, y, and z of the same kind of liquid of temperatures 9, 21 and 38°C respectively, it is found that when x and y are mixed together the resultant temperature is 17°C and when y and z are mixed together the resultant temperature is 28°C. Find the resultant temperature if x and z were mixed.

A. 25.87°C

B. 25.92°C

C. 20.85°C

D. 24.86°C

Answer: **Option B**

Explanation:

365. The journals of a shaft are 380 mm diameter, it runs at 105 rpm and the coefficient of friction between journals and bearings is 0.02. If the average load on the bearings is 200 kN, find the heat generated per minute at the bearings.

A. 501.375 kJ

B. 505.575 kJ

C. 401.375 kJ

D. 501.575 kJ

Answer: **Option A**

Explanation:

366. A reverse Carnot cycle requires 3 Hp and extracts energy from a lake to heat a house. If the house is kept at 70°F and requires 2000 Btu per minute, what is the temperature of the lake?

A. 35.29°F

B. 36.29°F

C. 39.29°F

D. 40.29°F

Answer: **Option B**

Explanation:

367. An oxygen cylinder of volume 2.3 ft3 has a pressure of 2200 psig and is at 70°F. Determine the mass of oxygen in the cylinder.

A. 25.66 lbs.

B. 26.66 lbs.

C. 27.66 lbs.

D. 28.66 lbs.

Answer: **Option D**

Explanation:

368. A group of 50 persons attend a secret meeting in a room which is 12 m wide by 10 m long and a ceiling height of 3 m. The room is completely sealed off and insulated. Each person gives off 150 kCal per hour of heat and occupies a volume of 0.20 m^{3}. The room has an initial pressure of 101.3 kPa and temperature of 16°C. Calculate the room temperature after 10 minutes. Use R = 0.287 kJ/kg-K and Cv = 0.171 kCal/kg-K.

A. 33.1°C

B. 37.7°C

C. 38.7°C

D. 31.7°C

Answer: **Option A**

Explanation:

369. One kilogram of wet steam at a pressure of 8 bar (υ_{g} = 0.2404 m^{3}/kg, υ_{f} = 0.0011148 m^{3}/kg) and dryness of 0.94 is expanded until the pressure is 4 bar (υ_{g} = 0.4625 m^{3}/kg, υ_{f} = 0.0010836 m^{3}/kg). If expansion follows the law PV^{n} = C, where n = 1.12, find the dryness fraction of the steam at the lower pressure.

A. 0.9072

B. 0.4197

C. 0.2260

D. 0.2404

Answer: **Option A**

Explanation:

370. 2.5 liters of superheated steam at 25 bar and 400 C (υ = 0.1252 m^{3}/kg) is expanded in an engine to a pressure of 0.1 bar (υ_{g} = 14.674 m^{3}/kg, υ_{f} = 0.0010102 m^{3}/kg) when its dryness fraction is 0.9. Find the final volume of the steam.

A. 163.74 liters

B. 263.74 liters

C. 363.74 liters

D. 463.74 liters

Answer: **Option B**

Explanation:

371. A 1.5 kg of wet steam at a pressure of 5 bar (h_{f} = 640 kJ/kg, hf_{g} = 2109 kJ/kg) dryness 0.95 is blown into 70 liters of water 12°C (h = 50.4 kJ/kg). Find the final enthalpy of the mixture.

A. 74.80 kJ/kg

B. 84.80 kJ/kg

C. 94.80 kJ/kg

D. 104.80 kJ/kg

Answer: **Option D**

Explanation:

372. A 650 BHP diesel engine uses fuel oil of 28°API gravity, fuel consumption is 0.65 lb/BHP-hr. Cost of fuel is P7.95 per liter. For continuous operation determine the minimum volume of cubical day tank in cm^{3}, ambient temperature is 45° C.

A. 4,372,890 cm^{3}

B. 5,987,909 cm^{3}

C. 5,291,880 cm^{3}

D. 7,352,789 cm^{3}

Answer: **Option C**

Explanation:

373. A typical industrial fuel oil, C_{16}H_{32} with 20% excess air by weight. Assuming complete oxidation of the fuel, calculate the actual air-fuel ratio by weight.

A. 17.56 kg_{air}/kg_{fuel}

B. 15.76 kg_{air}/kg_{fuel}

C. 16.75 kg_{air}/kg_{fuel}

D. 17.65 kg_{air}/kg_{fuel}

Answer: **Option D**

Explanation:

374. Fuel oil in a day tank for use of an industrial boiler is tested with hydrometer. The hydrometer reading indicates a SG = 0.924 when the temperature of the oil in the tank is 35°C. Calculate the higher heating value of the fuel.

A. 43,852.13 kJ/kg

B. 53,852.13 kJ/kg

C. 58,352.13 kJ/kg

D. 48,352.13 kJ/kg

Answer: **Option A**

Explanation:

375. A diesel electric plant supplies energy for Meralco. During a 24 hr Period, the plant consumed 200 gallons of fuel at 28°C and produced 3930 Kw-hr. Industrial fuel used is 28°API and was purchased at P5.50 per liter at 15.6°C. What should the cost of fuel be produce one kw-hr.?

A. P 1.05

B. P 1.10

C. P 1.069

D. P 1.00

Answer: **Option A**

Explanation:

376. A certain coal has the following ultimate analysis:

C = 70.5% S = 3.0% H = 4.5% Ash = 11%

O2 = 6% Moisture = 4% N2 = 1.0%

A stoker fired boiler of 175,000 kg/hr. steaming capacity uses this coal as fuel. Calculate the volume of air in m^{3}/hr. with air at 60°F (15.6°F) and 14.7 psia (101.325 kPa) the coal is burned with 30% excess air. Boiler efficiency is 70% and factor of evaporation of 1.10.

A. 212,861.04 m^{3}/hr

B. 221,861.04 m^{3}/hr

C. 218,261.04 m^{3}/hr

D. 281,261.04 m^{3}/hr

Answer: **Option A**

Explanation:

377. A diesel power plant consumed 1 m3 of fuel with 30°API at 27°C in 24 hrs. Calculate the fuel rate in kg/hr.

A. 36.21

B. 26.25

C. 29.34

D. 39.42

Answer: **Option A**

Explanation:

378. A diesel power plant uses fuel with heating value of 43,000 kJ/kg. What is the density of the fuel at 25°C?

A. 840 kg/m^{3}

B. 873 kg/m^{3}

C. 970 kg/m^{3}

D. 940 kg/m^{3}

Answer: **Option C**

Explanation:

379. A water tube boiler has a capacity of 1000 kg/hr of steam. The factor of evaporation is 1.3, boiler rating is 200%, boiler efficiency is 65% and heating surface area is 0.91 m^{2} per bo.Hp. and the heating value of fuel is 18,400 kCal/kg. The total coal available in the bunker is 50,000 kg. Determine the no. of hrs. to consume the available fuel.

A. 853.36 hrs.

B. 706.57 hrs.

C. 979.46 hrs.

D. 100.75 hrs.

Answer: **Option A**

Explanation:

380. Two boilers are operating steadily on 91,000 kg of coal contained in a bunker. One boiler is producing 1591 kg of steam per hour at 1.2 factor of evaporation and an efficiency of 65% and another boiler produced 1364 kg of steam per hour at 1.15 factor of evaporation and an efficiency of 60%. How many hrs. will the coal in the bunker run the boilers if the heating value of coal is 7,590 kCal/kg?

A. 230.80 hrs.

B. 280.54 hrs.

C. 350.35 hrs.

D. 300.54 hrs.

Answer: **Option A**

Explanation:

381. The heating value of fuel supplied in a boiler is 40,000 kJ/kg. If the factor of evaporation is 1.10 and the actual specific evaporation is 10, what is the efficiency of the boiler?

A. 62.07%

B. 53.08%

C. 78.05%

D. 54.97%

Answer: **Option A**

Explanation:

382. What is the rate of evaporation of a water tube boiler if the factor of evaporation is 1.10, percent rating of 200% and the heating surface area is 250 m^{2}?

A. 7,817.16 kg/hr.

B. 7,898.67 kg/hr.

C. 6,789.45 kg/hr.

D. 5,768.54 kg/hr.

Answer: **Option A**

Explanation:

383. Steam is admitted to the cylinder of an engine in such a manner the average pressure is 120 psi. The diameter of the piston is 10 in. and the length of a stroke is 12 in. What is the Hp of the engine when it is making 300 rpm?

A. 171.4 Hp

B. 175 Hp

C. 173.2 Hp

D. 174.4 Hp

Answer: **Option A**

Explanation:

384. Steam enters a turbine stage with an enthalpy of 3628 kJ/kg at 70 m/s and leaves the same stage with an enthalpy of 2846 kJ/kg and a velocity of 124 m/s. Calculate the power if there are 5 kg/s steam admitted at the turbine throttle?

A. 4597.45 kW

B. 3976.55 kW

C. 3883.81 kW

D. 1675.42 kW

Answer: **Option C**

Explanation:

385. Steam with an enthalpy of 800 kCal/kg enters a nozzle at a velocity of 80 m/s. Find the velocity of the steam at the exit of the nozzle if its enthalpy is reduced to 750 kCal/kg, assuming the nozzle is horizontal and disregarding heat losses. Take g = 9.81 m/s2 and J constant = 427 kg m/kCal.

A. 452.37 m/s

B. 245.45 m/s

C. 651.92 m/s

D. 427.54 m/s

Answer: **Option C**

Explanation:

386. Steam is expanded through a nozzle and the enthalpy drop per kg of steam from the initial pressure to the final pressure of 60 kJ. Neglecting friction, find the velocity of discharge and the exit area of the nozzle to pass 0.20 kg/s if the specific volume of the steam at exit is 1.5 m^{3}/kg.

A. 346.4 m/s, 879 mm^{2}

B. 356.7 m/s, 278 mm^{2}

C. 765.6 m/s, 467 mm^{2}

D. 346.4 m/s, 866 mm^{2}

Answer: **Option D**

Explanation:

387. A 6 MW steam turbine generator power plant has a full-load steam rate of 8 kg/kW-hr. Assuming that no-load steam consumption as 15% of full-load steam consumption, compute for the hourly steam consumption at 75% load, in kg/hr.

A. 37,800 kg/hr.

B. 38,700 kg/hr.

C. 30,780 kg/hr.

D. 30,870 kg/hr.

Answer: **Option A**

Explanation:

388. A 4 kg of air enters a turbine with enthalpy of 600 kJ and velocity of 250 m/s. The enthalpy at exit is 486 kJ and velocity of 170 m/s. What is the work developed if there is a heat loss of 10 kJ?

A. 122.83 kJ

B. 171.2 kJ

C. 80.2 kJ

D. 28.3 kJ

Answer: **Option B**

Explanation:

389. Calculate the drive horsepower for pumping 1703 L/min cold water to a tank suction at 127 mmHg vacuum, delivery at 5.3 kg/cm^{2} ga., both measured close to pump, e_{p} = 0.65.

A. 31.42 Hp

B. 20.42 Hp

C. 35.42 Hp

D. 23.02 Hp

Answer: **Option A**

Explanation:

390. Find the length of a suspension bunker to contain 181 tons of coal without surcharge; width = 4.6 m, depth = 4.3 m. The level capacity of a suspension bunker is 5/8 wdL where: w = width, d = depth and L = length. Density of coal is 800 kg/m^{3}.

A. 18.30 m

B. 15.80 m

C. 17.61 m

D. 12.61 m

Answer: **Option A**

Explanation:

391. A 305 mm x 457 mm four stroke single acting diesel engine is rated at 150 kW at 260 rpm. Fuel consumption at rated load is 0.26 kg/kW-hr with a heating value of 43,912 kJ/kg. Calculate the brake thermal efficiency.

A. 31.63%

B. 41.63%

C. 21.63%

D. 35.63%

Answer: **Option A**

Explanation:

392. The brake thermal efficiency of a 1 MW diesel electric plant is 36%. Find the heat generated by fuel in kW if the generator efficiency is 89%.

A. 3,121.10 kW

B. 3,528.64 kW

C. 4,121.10 kW

D. 4,528.64 kW

Answer: **Option A**

Explanation:

393. In an air-standard Brayton cycle, the compressor receives air at 101.325kPa, 21°C and it leaves at 600 kPa at the rate of 4 kg/s. Determine the turbine work if the temperature of the air entering the turbine is 1000°C.

A. 3000 kW

B. 2701 kW

C. 2028 kW

D. 3500 kW

Answer: **Option C**

Explanation:

394. Kerosene is the fuel of a gas turbine plant: fuel-air ratio, m_{f} = 0.012, T_{3} = 972 K, pressure ratio, r_{p} = 4.5, exhaust to atmosphere. Find the available energy in kJ per kg air flow. Assume k = 1.34 and C_{p} = 1.13.

A. 352.64 kJ/kg

B. 452.64 kJ/kg

C. 252.64 kJ/kg

D. 552.64 kJ/kg

Answer: **Option A**

Explanation:

395. An ideal gas turbine operates with a pressure ratio of 10 and the energy input in the high temperature heat exchanger is 300 kW. Calculate the air flow for temperature limits of 30°C and 1200°C.

A. 0.25 kg/s

B. 0.34 kg/s

C. 0.41 kg/s

D. 0.51 kg/s

Answer: **Option B**

Explanation:

396. In an air-standard Brayton cycle the inlet temperature and pressure are 20°C and 101.325 kPa. The turbine inlet conditions are 1200 kPa and 900°C. Determine the air flow if the turbine produces 12 MW.

A. 21.41 kg/s

B. 20.20 kg/s

C. 19.25 kg/s

D. 18.10 kg/s

Answer: **Option B**

Explanation:

397. A gas turbine power plant operating on the Brayton cycle delivers 15 MW to a standby electric generator. What are the mass flow rate and the volume flow rate of air if the minimum and maximum pressures are 100 kPa and 500 kPa respectively and temperature of 20°C and 1000°C?

A. 31.97 kg/s, 26.88 m^{3}/s

B. 36.98 kg/s, 28.99 m^{3}/s

C. 41.97 kg/s, 26.88 m^{3}/s

D. 46.98kg/s, 28.99 m^{3}/s

Answer: **Option A**

Explanation:

398. In a hydraulic plant the difference in elevation between the surface of the water at intake and the tailrace is 650 ft. when the flow is 90 cfs, the friction loss in the penstock is 65 ft. and the head utilized by the turbine is 500 ft. The mechanical friction in the turbine is 110 Hp, and the leakage loss is 4 cfs. Find the hydraulic efficiency.

A. 87.45%

B. 84.57%

C. 85.47%

D. 78.54%

Answer: **Option C**

Explanation:

399. A hydro-electric power plant consumes 60,000,000 kW-hr per year. What is the net head if the expected flow is 1500 m3/min and over-all efficiency is 63%?

A. 34.34 m

B. 43.43 m

C. 44.33 m

D. 33.44 m

Answer: **Option C**

Explanation:

400. A pelton type turbine has a gross head of 40 m and a friction head loss 6 m. What is the penstock diameter if the penstock length is 90 m and the coefficient of friction head loss is 0.001 (Morse)?

A. 2040 mm

B. 3120 mm

C. 2440 mm

D. 2320 mm

Answer: **Option A**

Explanation:

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