Mechanical Engineering Review Online

1. A 25 m³ tank is to be filled with water in one hour by pump. If the pump and motor efficiency is 85% and 80%, respectively and a total head of 25 m, determine the cost of filling one tank for a cost of P0.38/kW-hr.

a. 1.092

b. 0.952

c. 1.951

c.0.513

2. A swimming pool of 11 m x 26 m x 2 m dimension is to filled with water by a pump operating with a total dynamic of 55 m. If the overall motor efficiency is 60% and the energy cost is P0.40/kW-hr, calculate the total cost of energy to fill up the swimming pool.

a. 57.15

b. 59.38

c. 58.30

d. 61.23

3. A boiler feed pump has an inlet and exit enthalpy of 2540 kJ/kg and 2550 kJ/kg, respectively. Determine the velocity of water flowing in the pump.

a. 141.4 m/s

b. 132.5 m/s

c. 152.1 m/s

d. 135.3 m/s

4. The specific speed of a pump is 45 and 610 rpm when delivering a 0.015 m³/s of water, Determine the head developed by the pump.

a. 1341.3

b. 1542.4

c. 1241.6

d. 1388.3

5. A pump with an impeller diameter of 155 mm develops a power of 60 kW at a speed of 350 rpm with a fluid specific gravity of 1.03. If the speed increases to 660 rpm, and impeller is decreased to 120 mm and specific gravity changed to 0.8, what is the new power.

a. 130

b. 145

c. 135

d. 140

6. A 360 mm x 400 mm reciprocating pump is running at 380 rpm. If the percent slip is taken to be 12%, determine the volumetric efficiency of the pump.

a. 78%

b. 66%

c. 85%

d. 88%

7. If the developed power of a pump is 30 kW, determine the percent decrease in power of a pump if the speed is decreased by 45%.

a. 73.2%

b. 52.3%

c. 55%

d. 83.3%

8. The head of a pump is 25 m at 400 rpm, what is the increase in head developed if the speed is increased to 1100 rpm.

a. 164 m

b. 154 m

c. 133 m

d. 170 m

9. A water jet has a diameter of 70 mm and a velocity of 20 m/s. Determine the horsepower exerted by the jet of water.

a. 18.6 hp

b. 20.6 hp

c. 22.3 hp

d. 25.4 hp

10. The suction water level of a reservoir A is 6 m above the pump center line and discharge water level is 55 m above the pump centerline. The discharge of the pump is 0.3 m³/s with a pipe suction diameter of 110 mm and discharge diameter of 95 mm. The total head loss is 45% of the velocity head at suction pipe. Determine the torque developed by the motor shaft if the pump efficiency is 80% and running at 380 rpm.

a. 8.38 kN-m

b. 12.75 kN-m

c. 10.38 kN-m

d. 13.20 kN-m

11. The suction diameter of a pump is 65 mm and reads 2.3 psi vacuum, and the discharge diameter is 53 mm and reads 260 kPag. The suction water level is 6 m above the water pump centerline and discharge water level is 28 m above the pump center line. The total head loss is 2.3 m. If the discharge required is 0.02 m³/s, calculate the horsepower needed to pump water when the pump efficiency is 78%.

a. 15.4

b. 16.5

c. 19.2

d. 18.5

12. A pump has a suction condition of 55 mm Hg vacuum pressure at 110 mm diameter pipe and discharge condition of 260 kPa at 95 mm diameter. The discharge tank is 55 m elevation and the suction is 8 m below the pump center line. If the discharge is 0.25 m³/s, find the pump efficiency for 320 kW brake power.

a. 85%

b. 78%

c. 91%

d. 68%

13. Calculate the power of motor required to pump water at a head of 110 m at a rate of 400 liters per second if the pump efficiency is 75%.

a. 605.5 kW

b. 575.5 kW

c. 629.2 kW

d. 702.1 kW

14. A pump is used to deliver 1200 gallons per minute of water at a head of 120 ft. Determine the water power required.

a. 36.37 hp

b. 28.21 hp

c. 40.28 hp

d. 30.78 hp

15. A pump delivers 4800 gallons per minute of fluid with specific gravity of 0.80 at a head of 120 ft. Determine the horsepower required by the motor if the overall efficiency is 65% and motor efficiency is 85%.

a. 152.2 hp

b. 142.3 hp

c. 162.1

d. 176.9 hp

Answer Key (Handwritten)