A pump is used to take water out of large lake and deliver it to a farm to be us
ID: 1837929 • Letter: A
Question
A pump is used to take water out of large lake and deliver it to a farm to be used for irrigation. The suction side of the pump is 3 meters above the water surface in the lake and the vertical intake pipe has a diameter of 150 mm.
A. What is the pressure on the suction side of the pump when the flow rate through the system is 0.1 m3/s?
B. What must be assumed about the system and/or fluid for your answer in part a to be valid?
C. If the suction side can operate at a maximum absolute pressure of 100,000 Pa, What is the maximum flow rate that can be pumped out of the lake?
Explanation / Answer
A. Volume rate = rho*A*v = 1000*pi*(0.15/2)^2*v = 0.1
v = 5.6617*10^-3 m/s
now from bernoullis theorem
Po + 0.5*rho*v^2 = P + rho*g*h + 0.5*rho*v^2
P = Po - rho*g*h = 1.1*10^5 - 1000*9.8*3 = 71600 Pa
B. The fluid is incompressible
C. For P = 100,000 Pa
the extra pressure is used for sucking in extra volume of fluid
Extra pressure = 100,000 - 71600 = 28400 Pa = 0.5*rho*v^2
v = 7.5365 m/s
net v = v + 5.6617*10^-3
v = 7.5422 m/s
new flow rate = rho*A*v = 133.214 m^3/s
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