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Problems on Fluid Machineries and etc., Assignments of Fluid Mechanics

Adamson University (AU)Fluid Mechanics

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Typology: Assignments

2020/2021

Uploaded on 04/22/2021

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PROBLEM SET # 1
1. The power output of a fan is 120 kW with efficiency of 80%. Determine the horsepower
output required by the motor to drive the fan.
2. The static head of a fan is measured to be 160 mm of water gage at an air velocity of 25 m/s.
Find the air power at an air condition of 28°C and 98 kPa with a volume flow rate of 5 m3/s.
3. Determine the horsepower required for a fan delivering 35 ft/sec of air through a 2.3 ft x 3.5
ft duct with a total pressure of 3.5 in water gage. Take density of air to be 0.075 lb/ft3.
4. A fan operating at a standard air condition registered a total static head of 230 mm of water
gage. If the static efficiency is 65% and the fan efficiency is 80% determined the velocity of
air if the volume of air delivered is 6 m3/s. (Let the velocity head to be 35% of the static
head).
5. A fan initially operating at a speed of 380 rpm at an air temperature of 26°C. If the speed is
increased to 460 rpm with 55°C, determine the new head in mm of water gage for an initial
head 190 mm of water gauge.
6. What is the horsepower required for a fan to deliver 230 ft 3/sec of air through a 2.5 ft x 4.5
ft duct under a total pressure of 4.2-in water gage?
7. 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 60°C instead of
30°C, determine the power in kW.
8. A fan has a static head of 110 m at a pressure of 1.5 kg/cm2 and 75°F. If the air velocity is 18
m/s, determine the total equivalent head in mm of water gage.
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PROBLEM SET # 1

  1. The power output of a fan is 120 kW with efficiency of 80%. Determine the horsepower output required by the motor to drive the fan.
  2. The static head of a fan is measured to be 160 mm of water gage at an air velocity of 25 m/s. Find the air power at an air condition of 28°C and 98 kPa with a volume flow rate of 5 m^3 /s.
  3. Determine the horsepower required for a fan delivering 35 ft/sec of air through a 2.3 ft x 3. ft duct with a total pressure of 3.5 in water gage. Take density of air to be 0.075 lb/ft^3.
  4. A fan operating at a standard air condition registered a total static head of 230 mm of water gage. If the static efficiency is 65% and the fan efficiency is 80% determined the velocity of air if the volume of air delivered is 6 m^3 /s. (Let the velocity head to be 35% of the static head).
  5. A fan initially operating at a speed of 380 rpm at an air temperature of 26°C. If the speed is increased to 460 rpm with 55°C, determine the new head in mm of water gage for an initial head 190 mm of water gauge.
  6. What is the horsepower required for a fan to deliver 230 ft^3 /sec of air through a 2.5 ft x 4. ft duct under a total pressure of 4.2-in water gage?
  7. The rating of a fan is 610 m^3 /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 60°C instead of 30°C, determine the power in kW.
  8. A fan has a static head of 110 m at a pressure of 1.5 kg/cm^2 and 75°F. If the air velocity is 18 m/s, determine the total equivalent head in mm of water gage.

PROBLEM SET # 2

  1. An air compressor delivers air at a flow rate of 0.25 m^3 /s with initial pressure of 100 and discharge pressure of 680 kPa. Determine the power of the compressor.
  2. A double acting compressor with 225 mm x 380 mm cylinder runs at 480 rpm with a clearance of 8%, compressor air 7 times its initial pressure. Compute the compressor capacity in cubic feet per minute.
  3. A single stage compressor with initial pressure of 100 kPa and discharge pressure of 850 kPa has a suction volume of 0.3 m^3 /s. Determine the percent decrease in power due to two staging if the compressor process is PV1.33^ = C.
  4. An air compressor takes air at 98 kPa at a rate of 0.4 m^3 /s and delivers it at a pressure of 620 kPa. If the power input to the compressor is 135 kW, find the heat loss in the compressor.
  5. A single stage compressor with a suction pressure of 15 psi discharge at a pressure of 75 psi. If the suction volume is 110 ft^3 /min, determine the horsepower capacity of the motor needed to drive the compressor if the compressor efficiency is 80%.
  6. A two stage compressor has a suction volume of 720 m^3 /hr at 100 kPa and 26°C, the discharge is 700 kPa, determine the heat rejected at the intercooler.
  7. An air compressor takes air at 80 kPa has a suction volume at rate of 0.5 m^3 /s and discharges to 650 kPa. If the power input to the compressor is 120 kW, find the heat loss in the compressor.
  8. A two stage compressor takes air at 98 kPa and 24°C with a volume flow rate of 0. m^3 /s and discharges to 680 kPa. What is the amount of heat rejected at the intercooler?

PROBLEM SET # 3

  1. A centrifugal pump delivers 227 m^3 /hr of water from a source 4 meters below the pump center line to a pressure tank whose pressure is 2.8 kg/cm^2. Friction loss estimates are 2 meters in the suction line and 1 meter in the discharge line. The diameter of the suction pipe is 250 mm and the discharge pipe is 200 mm. Find: a) The water horsepower b) The kW rating of the driving motor if the pump efficiency is 70%
  2. A pump is to deliver 80 galloons/min of water 60^0 C with discharge pressure of 1000 kPg. Suction pressure indicates 50 mmHg vacuum. The diameter of suction and discharge pipes are 5 inches and 4 inches, respectively. If the pump has an efficiency of 70%. Determine the brake horsepower of the pump.
  3. An acceptance test was conducted on a centrifugal pump having a suction pipe 25.4 cm in diameter and a discharge pipe 12.7 cm in diameter. Flow was 186 m^3 /hr of clear cold water. Pressure at suction was 114.3 mmHg vac and discharge pressure was 107 kPg at a point 91 cm above the point where the suction pressure was measured. Input to the pump was 15 hp. a) Determine the pump efficiency b) If the pump runs at 1750 rpm, what net flow, head, and brake hp would be developed and required if the pump speed were increased to 3500 rpm? Assume constant efficiency.
  4. A motor driven pump draws water from an open reservoir A and lifts to an open reservoir B. Suction and discharge pipes are 150 mm pipe and 100 mm inside diameter respectively. The loss of head in the suction line is 3 times the velocity head in the 150 mm pipe and the loss of head in the discharge line is 20 times the velocity head in the 100 mm pipeline.. Water level at reservoir A is at elevation 6 meters and that of reservoir B at elevation 75 m. Pump center line is at elevation 2 m. Overall efficiency of the system is 73%. Discharge is 10 liter/sec. Determine the following;

a. Power input of the motor b. Reading in kPa of the pressure gauges installed just at the outlet and inlet of the pump.

  1. A boiler feed pump receives 40 liters per second at 180^0 C. It operates against a total head of 900 meters with an efficiency of 60%. Determine: a. The enthalpy leaving the pump in kJ/kg b. Power output of the driving motor in kW c. Discharge pressure in kPa if suction pressure of 4 MPa
  2. A plant has installed a single suction centrifugal pump with a discharge of 68 m^3 /hr under 60 m head and running at 1200 rpm. It is proposed to install another pump with double suction but of the same type to operate at 30 m head and deliver 90 m^3 /hr a. Determine the speed of the proposed pump. b. What must be the impeller diameter of the proposed pump if the diameter of the existing pump is 150 mm?
  3. A 40 m^3 /hr pump delivers water to a pressure tank. At the start, the gage reads 138 kPa and then the pump was shut off until the gage reads 276 kPa. The volume of the tank is 160 liter. At 276 kPa the water occupied 2/3 of the tank volume. a) Determine the volume of water that can be taken out until the gage reads 138 kPa. b) If 1 m^3 /hr of water is constantly used, in how many minutes from 138 kPa will the pump run until the gage reads 276 kPa? Ans. a) 30.75 liter, b) 0.058 min.
  4. A pump with a 400 mm diameter suction pipe and 350 mm diameter discharge pipe is to deliver 20,000 liter per minute of 15.6^0 C water. Calculate the pump head in meters if suction gage is 7.5 cm below the pump center line and reads 127 mmHg vacuum and the discharge gage is 45 cm above the pump center line and reads 75 kPa. Ans. H=10.14 m
  5. Water from an open reservoir A at 8m elevation is drawn by a motor driven pump to an open reservoir B at 70 m elevation. The inside diameter of the suction pipe is 200 mm and 150 mm for the discharge pipe. The suction line has a loss of head 3 times that of the velocity head in the in the 200 mm pipe. The discharge line has a loss of head 20 times that of the head in the discharge pipeline. The pump centerline is at 4 m. Overall efficiency of the system is 78% For a discharge rate of 10 li/s, find the power input to the motor and the pressure gages reading installed just at the outlet and inlet of the pump in kPg.
  6. The rate of flow of water in a pump installation is 60.6 kg/s. The intake static gage is 1.22 m below the pump center line and reads 68.95 kPa gage; the discharge static gage is 0.61 m below the pump center line and reads 344.75 kPa gage. The gages are located close to the pump as much as possible. The area of the intake and discharge pipes are; 0.093 m^2 and 0. m^2 respectively. The pump efficiency is 74%. Take density of water equals 1000 kg/m3.^ What is the hydraulic power in kW.
  7. A pump delivers 20 cfm of water having a density of 62 lb/ft^3. The suction and discharge gage reads 5 in .Hg vacuum and 30 psi respectively. The discharge gage is 5 ft above the suction gage. If pump efficiency is 70%, what is the motor power?
  8. In a test of a centrifugal pump driven by an electric motor, the suction pipe is 10 in. in diameter and its gage indicates a partial vacuum of 2.5 ft of water. The discharge pipe is 5 in.