Calculating Mass Flow Rate: Inlet & Outlet

[Sabacca6]

Homework Statement

Inlet
Average Velocity at Inlet = 2.50 m/s
Pressure Abs. = 100 Kpa
Elev = 2.00 m
Inlet tube diameter 12.0 cm
Water density 997 kg/m^3

Outlet
Average velocity at outlet = 8.00 m/s
Elevation = 2.00m

a.) Calculate mass flow rate through the pump
b.) w/ an outlet pressure of 300 kPA what is required rate of shaft work input has 85% efficiency?

Homework Equations

m'=pVA

The Attempt at a Solution

My attempt was to just average the two Ave. velocities and plug into mass flow equation, not correct as I got no points on the HW. Part b.) I could not complete I would think it would involve calculating the change in mechanical, potential, and flow work and then multiplying kW by efficiency super frustrated. please help!

 

[rude man]

1.

The Attempt at a Solution

My attempt was to just average the two Ave. velocities and plug into mass flow equation, not correct as I got no points on the HW.

Not a good idea. Compute the mass flow based on input data. Mass flow out in unit time must be the same as mass flow in, must it not?

Part b.) I could not complete I would think it would involve calculating the change in mechanical, potential, and flow work and then multiplying kW by efficiency super frustrated. please help!

Conservation of energy! What is the energy of 1 sec. worth of flow at the input & at the output.