MECH 3300 Assignment # 6
MECH 3300 Assignment # 6
MECH 3300 Assignment # 6
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<strong>MECH</strong> <strong>3300</strong><br />
<strong>Assignment</strong> # 6<br />
Due: April 8 th , 2011, 16:30<br />
1. a) A pump delivers 1500 L/min of water at 20ºC against a pressure rise of 270 kPa.<br />
Kinetic and potential energy changes are negligible. If the driving motor supplies 9<br />
kW, what is the overall efficiency?<br />
b) A 3.5 hp pump delivers 1140 lbf of ethylene glycol at 20ºC in 12 seconds, against a<br />
head of 17 ft. Calculate the efficiency of the pump.<br />
c) A pump delivers gasoline at 20ºC and 12 m 3 /h. At the inlet p 1 = 100 kPa, z 1 = 1 m,<br />
and V 1 = 2 m/s. At the exit p 2 = 500 kPa, z 2 = 4 m, and V 2 = 3 m/s. How much power<br />
is required if the motor efficiency is 75% ?<br />
2. Would the smallest, or the largest, of the seven Taco Inc. pumps presented on the<br />
following figure be better:<br />
a) for producing, near best efficiency, a water flow rate of 600 gpm and a head of<br />
95 ft?<br />
b) At what speed, in rpm, should this pump be run?<br />
c) what input power is required?<br />
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3. The 28-in-diameter pump in the preceding figure, with a rotation speed of 1170 rpm,<br />
is used to pump water at 20ºC through a piping system at 14 000 gpm. (The average<br />
friction factor is 0.018).<br />
a) Determine the required brake horsepower.<br />
b) If there is 65 ft of 12-in-diameter pipe upstream of the pump, how far below<br />
the surface should the pump inlet be placed to avoid cavitation?<br />
4. a) A pump must be designed to deliver 6 m 3 /s of water against a head of 28 m. The<br />
specified shaft speed is 20 r/s. What type of pump do you recommend?<br />
b) A pump is needed to deliver 40 000 gpm of gasoline at 20ºC against a head of 90<br />
ft. Find the impeller size, speed, and brake horsepower needed to pumps from the<br />
following families: (i) Centrifugal pump (Fig. 11.8), or (ii) Axial pump (Fig. 11.13).<br />
Which is the best design in that case?<br />
5. It is proposed to run the pump having the following performance data at 880 rpm (18-<br />
in-diamter centrifugal pump) to pump water at 20ºC through the system presented<br />
below.<br />
Q, gpm 0 2000 4000 6000 8000 10 000<br />
H, ft 92 89 84 78 68 56<br />
P, hp 100 112 130 143 156 163<br />
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The pipe is 20-cm-diameter commercial steel. What flow rate in ft 3 /min will result?<br />
Is this an efficient application?<br />
6. A dam on a river is being sited for a hydraulic turbine. The flow rate is 1500 m 3 /h,<br />
the available head is 24 m, and the turbine speed is to be 480 rpm. Discuss the<br />
estimated turbine size and feasibility for a Francis turbine.<br />
7. a) A Darrieus VAWT in operation in Lumsden, Saskatchewan, that is 32 ft high and<br />
20 ft in diameter sweeps out an area of 432 ft 2 . Estimate the maximum power and the<br />
rotor speed if it is operating in 16 mi/h winds.<br />
b) An American 6-ft diameter multiblade HAWT is used to pump water to a height of<br />
10 ft through 3-in diameter cast iron pipe. If the winds are 12 mi/h, estimate the rate<br />
of water flow in gpm.<br />
c) The commercial Cape Cod Wind Project proposes 130 large wind turbines in<br />
Nantucket Sound, intended to provide 75% of the electric power needs of Cape Cod<br />
and the Islands. The turbine diameter is 328 ft. For an average wind velocity of<br />
14mi/h, what are the best rotation rate and total power output estimates for (i) a<br />
HAWT and (b) a VAWT?<br />
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