Mechanical Engineering Review Online

1. A boiler feed pump operates at 50^oC suction. If the pump efficiency is 80% and requires 30 kW of motor power to drive the pump, calculate the maximum pressure of the boiler could attain, in kPa for a mass of 2.3 kg/s. At 50^oC: v_f=0.0010121 m³/kg, P_sat=12.349 kPa.

a. 10322.38

b. 12557.39

c. 13876.30

d. 10089.22

2. A boiler feed is available at 200^oC. The boiler has a steam generated at 12 kg/s at 5 MPa and 400^oC. Calculate the developed boiler horsepower of turbine. At t=200^oC: hf=852.45 kJ/kg. At P=5MPa and t=200^oC: h=3195.7 kJ/kg

a. 1839.36

b. 2866.36

c. 3987.01

d. 2011.3

3. Water tube boiler has a heating surface area of 520 m². For a developed boiler hp of 940. Determine the percent rating of the boiler.

a. 105.3%

b. 164.5%

c. 189.2%

d. 208.3%

4. The factor of evaporation of the boiler is 1.20 and with a steam rate of 0.75 kg/s. Calculate the developed boiler horsepower.

a. 100.3

b. 179.3

c. 207.0

d. 257.3

5. The percent rating of water tube boiler is 210%, factor of evaporation is 1.15 and heating surface area is 310 m². Determine the rate of evaporation.

a. 6988 kg/hr

b. 8798 kg/hr

c. 7768 kg/hr

d. 9733 kg/hr

6. The actual specific evaporation of a certain boiler is 8.3 and the factor of evaporation is 1.18. Calculate the boiler efficiency if the heating value is 26500 kJ/kg.

a. 73.89%

b. 60.87%

c. 85.38%

d. 83.42%

7. The ASME evaporation units of a boiler is 25,800,325 kJ/hr and the boiler auxiliaries consumes 2.8 MW. Calculate the net boiler efficiency if the heat generated by fuel is 33,000,000 kJ/hr.

a. 37.89%

b. 44.38%

c. 51.89%

d. 47.64%

8. A 160,000 kg of coal is supplied to two boilers. One has a capacity of 360 kg/hr and the other boiler has a capacity of 110 kg/hr. How many days to consume the available fuel?

a. 13

b. 14

c. 15

d. 16

9. A boiler operates at 83.4% efficiency and the mass of steam generated is 998,000 lbs in 5 hrs. The enthalpy of steam is 1380 Btu/lb and the feed is 255 Btu/lb while the fuel used for the boiler has a heating value of 15,980 Btu/lb. Determine the mass of fuel required in short tons per day.

a. 101.3

b. 222.8

c. 202.2

d. 111.3

10. Two boilers are operating steadily on 95,000 kg of coal contained in a bunker. One boiler producing 1650 kg/hr of steam at 1.3 factor of evaporation and an efficiency of 70% and another boiler produces 1560 kg/hr of steam at 1.18 factor of evaporation and efficiency of 65%. How many hours will the coal in the bunker run the boilers if the heating value is 7800 kcal/kg?

a. 200.38

b. 234.97

c. 194.18

d. 266.31

11. A steam engine develops 70 Bhp with saturated steam at 1034.25 kPa absolute and exhaust at 124.11 kPa. Steam consumption is 745.48 kg/hr. Calculate the indicated engine efficiency based on 85% mechanical efficiency, hf at 125.06 kPa is 444.37 kJ/kg and hg at 1049.1 kPa is 2779.9 kJ/kg.

a. 12.7%

b. 15.8%

c. 16.9%

d. 10.1%

12. A double acting steam engine rotates at 250 rpm with a bore and stroke of 320 mm x 480 mm. The mean effective pressure acting the piston is 4.8 kg/cm². Determine the indicated horsepower developed in the cylinder.

a. 203.05

b. 227.87

c. 199.80

d. 237.99

13. Steam enters a steam engine at 2.5 MPa and 240oC and exit at 0.18 MPa. Steam consumption is 1600 kg/hr. Determine the equivalent Rankine efficiency (use steam tables).

a. 15.3%

b. 19.7%

c. 22.3%

d. 17.8%

14. The indicated efficiency of a steam engine is 70%. The engine is 2700 kJ/kg and exit is 2200 kJ/kg. If steam consumption is 3200 kg/hr and the mechanical efficiency is 85%, determine the brake power of the engine.

a. 200.5 kW

b. 197.3 kW

c. 264.4 kW

d. 300.1 kW

15. In a hydro-electric power plant the brake power is 2000 kW running at 460 rpm and net head of 30 m. Determine the specific speed of the turbine.

a. 70.85

b. 76.85

c. 81.35

d. 68.31

16. In a Francis turbine, the pressure gage leading to the turbine casing reads 380 kPa and center of spiral casing is 3.2 m above the tail race. If the velocity of water entering the turbine is 8.5 m/s, what is the net head of the turbine?

a. 45.61 m

b. 38.31 m

c. 48.32 m

d. 33.35 m

17. From a height of 68 m, water flows at the rate of 0.85 m³/s and driving a water turbine connected to an electric generator revolving at 180 rpm. Calculate the power developed by the turbine, in kW if the blade resisting torque due to friction is 550 N-m and the velocity of the water leaving the turbine blades is 4.80 m/s.

a. 546.86

b. 500.35

c. 580.68

d. 602.32

18. A pelton type turbine was installed 30 m below the head gate of the penstock. The head loss due to friction is 10% of the given elevation. The length of the penstock is 85 m and the coefficient of friction is 0.00093 (Morse). Determine the diameter, in meters of the penstock and the power output, in kW.

a. 2.8, 38776.0

b. 3.2, 40221.2

c. 1.6, 35022.2

d. 4.0, 30021.21

19. At a proposed hydro-electric power plant site, the average elevation of head water is 620 m, the tail water elevation is 500 m. The average annual water flow is determined to be equal to that volume flowing through a rectangular channel 3.8m wide and 0.50m deep and average velocity of 6.0 m/s. Assuming the plant will operate 345 days a year, calculate the energy, in kW-hr that the plant site can develop if the hydraulic turbine that will be used has an efficiency of 80% and the generator has 90%. Consider the head work loss of 5% of the available head.

a. 55.3 x 10⁶

b. 60.8 x 10⁶

c. 73.2 x 10⁶

d. 76.0 x 10⁶

20. A turbine running at 450 rpm has a specific speed of 80 rpm and head available is 40 m. If the rating of each turbine installed is 120 kW. How many turbines must be used?

a. 4

b. 5

c. 6

d. 7

21. The available flow of water is 28 m³/s at 42 m elevation. If the hydro-electric power plant is to be installed with a turbine efficiency of 85% and generator efficiency of 90%, what is the maximum power, in kW that the plant could generate?

a. 8021.20

b. 11536.56

c. 8825.47

d. 7235.01

Answer Key (Handwritten)