Handouts
LINK: Fans, Blowers and Compressors
Topics:
Fans and Blowers
Fans in Series and Parallel
Compressors
Multi-stage Compressor
Exercises
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1. A two stage compressor has a suction volume of 720 m3/hr at 100 kPa and 26oC, the discharge is 700 kPa, determine the heat rejected at the intercooler. a. 12.1 kW b. 22.4 kW c. 28.3 kW d. 31.2 kW 2. An air compressor takes air at 80 kPa at a rate of 0.5 m3/s and discharges to 650 kPa. If the power input to the compressor is 120 kW, find the heat loss in the compressor. a. 3.3 kW b. 4.2 kW c. 5.2 kW d. 6.8 kW 3. A two stage compressor takes air at 98 kPa and 24oC with a volume flow rate of 0.122 m3/s and discharges to 680 kPa. What is the amount of heat rejected at the intercooler? a. 13.37 kW b. 14.82 kW c. 16.77 kW d. 12.58 kW 4. The piston speed of an air compressor is 155 m/min and the displacement volume is 0.25 m3/s. Find the diameter of the compressor cylinder. a. 504.6 mm b. 551.3 mm c. 489.3 mm d. 587.1 mm 5. A two-stage air compressor has an intercooler pressure of 5 kg/cm2, what is the discharge pressure if the suction pressure is 0.8 kg/cm2. a. 22.1 b. 28.1 c. 36.5 d. 31.3 6. Determine the volume displacement of a double acting compressor that has cylinder dimensions of 52 cm x 65 cm and runs at 660 rpm. a. 4 b. 2 c. 5 d. 3 7. A work of a compressor is 125 kW with a piston displacement of 19 m3/min. find the mean effective pressure. a. 320.1 kPa b. 228.6 kPa c. 394.7 kPa d. 353 kPa 8. An air compressor has a suction condition of 98 kPa, 28oC and 0.22 m3/s. If the surrounding air 100 kPa and 23oC, calculate the free air capacity in m3/s. a. 0.112 b. 0.288 c. 0.315 d. 0.212 9. An air compressor has a suction volume of 0.35 m3/s at 28oC and 101.325 kPa and discharges to 680 kPa. Determine the amount of power saved by the compressor in two staging? b. 13.6 c. 15.8 d. 18.1 10. The initial condition of air is 100 kPa and 24oC and compressed to 550 kPa. The bore and stroke are 365 mm and 370 mm, respectively. If the percent clearance is 8% and runs at 320 rpm, determine the mass flow rate of air at the suction. a. 0.12 b. 0.20 c. 0.31 d. 0.39 11. A 15 hp motor is used to drive an air compressor. The compressor efficiency is 75% and the air is available at 29oC. Find the mass of air needed if the pressure compresses to 7 times the initial pressure. a. 3.2 kg/min b. 2.2 kg/min c. 4.1 kg/min d. 5.1 kg/min 12. The discharge pressure of an air compressor is 6 times the suction pressure. If the volume flow at the suction is 0.6 m3/s, find the power required by the compressor operating at PV1.33=C with a suction pressure of 100 kPa. a. 125 kW b. 281 kW c. 135 kW d. 188 kW 13. An air compressor takes air at 98 kPa and compress it isentropically at 720 kPa. If the volume flow at the discharge is 1.8 m3/s, determine the capacity in cfm. a. 15837 cfm b. 16592 cfm c. 14581 cfm d. 17012 cfm 14. What is the horsepower required for a fan to deliver 230 ft3/sec of air through a 2.5 ft x 4.5 ft duct under a total pressure of 4.2-in water gage? a. 8.81 b. 7.31 c. 6.81 15. The rating of a fan is 610 m3/min when running at 360 rpm and requires 8 kW motor to drive it. If the fan speed is increased to 620 rpm and the air handled becomes 60oC instead of 30oC, determine the power in kW. a. 25.18 b. 39.99 c. 37.18 d. 40.2 16. A fan has a static head of 110 m at a pressure of 1.5 kg/cm2 and 75oF. If the air velocity is 18 m/s, determine the total equivalent head in mm of water gage. a. 125.6 mm b. 145.6 mm c. 155.3 mm d. 175.2 mm 17. The total head of a fan is 220 m and the static pressure is 220 mm of water gage. Find the velocity of air flowing if the density is 1.18 kg/m3. a. 25.6 m/s b. 32.8 m/s c. 20.3 m/s d. 18.3 m/s 18. A fan operating at 28oC and 100 kPa has a static pressure of 280 mm water gage. If the fan will operate at 96oC and 15 psi, determine the new static pressure required. a. 201.6 mm b. 236.1 mm c. 255.2 mmd. 286.0 mm 19. A 55 kW motor is used to drive a fan that has a total head of 130 m at a fan efficiency is 78%. Determine the maximum capacity of the motor needed if air is available at 100 kPa and 28oC. a. 30.1 kW b. 35.4 kW c. 41.7 kW d. 38.3 kW 20. A fan with a suction static pressure of 45 mm of water vacuum and air velocity of 6 m/s has a discharge of 165 mm water gage at a discharge velocity of 9 m/s. Determine the total head of the fan, in mm water gage if air density is 1.18 kg/m3. a. 100.5 mm b. 183.9 mm c. 166.1 mm d. 122.6 mm 21. At 1.190 kg/m3 air density, a fan can develop a brake power of 110 kW. If it will operate at 100 kPa and 36oC, what will be the new brake power needed? a. 104.2 kW b. 164.1 kW c. 155.2 kW d. 184.3 kW 22. A boiler requires 100,000 m3/hr of standard air. The mechanical efficiency of the fan to be installed is 75%. Calculate the size of the driving motor needed assuming that the fan can deliver a pressure head of 165 mm of water gage and outlet velocity of 25 m/s. a. 73.8 kW b. 63.1 kW c. 88.2 kW d. 61.8 kW 23. Determine the air horsepower of an industrial fan that delivers 45 m3/s of air through a 720 mm x 1050 mm duct if the static pressure is 160 mm of water gage and air density is 1.12 kg/m3. a. 70.5 kW b. 73.8 kW c. 82.5 kW d. 68.3 kW |
Fans and Blowers
A steam generator has two FD fan with capacity of 150,000 cfm. Static pressure is 10.5 inches of water. (a) Based on a fan input of 345 hp each, calculate the static efficiency (b) Calculate the capacity, head and brake power requirements for a speed increase of 15%.
SOLUTION:
Air Compressor
A single acting reciprocating air compressor has a clearance value of 10%. Air received at 90 kPa and 29.3 deg C and discharged at 600 kPa. The compression and expansion are polytopic with n=1.28. The pressure drop is 5 kPa at suction and 10 kPa at discharge port. The piston volume displacement of the piston is equal to 7.5x10-3 m3/s. Find (a) mass of air compressed and (b) the required compressor power.
SOLUTION:
