Calculating Mass Flow Rate: Inlet & Outlet

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SUMMARY

The discussion focuses on calculating the mass flow rate through a pump using the inlet and outlet parameters provided. The inlet parameters include an average velocity of 2.50 m/s, pressure of 100 kPa, elevation of 2.00 m, and a tube diameter of 12.0 cm, while the outlet has an average velocity of 8.00 m/s and the same elevation. The correct approach to find the mass flow rate involves applying the equation m' = ρVA, ensuring that the mass flow rate in equals the mass flow rate out. Additionally, for part b, the required shaft work input at an outlet pressure of 300 kPa with 85% efficiency must be calculated using conservation of energy principles.

PREREQUISITES
  • Understanding of fluid dynamics principles, specifically mass flow rate calculations.
  • Familiarity with the equation m' = ρVA for mass flow rate.
  • Knowledge of conservation of energy in fluid systems.
  • Basic understanding of pump efficiency and work input calculations.
NEXT STEPS
  • Study the application of the mass flow rate equation m' = ρVA in various fluid dynamics scenarios.
  • Learn about conservation of energy principles in fluid mechanics.
  • Research how to calculate shaft work input and efficiency in pump systems.
  • Explore the effects of pressure and velocity changes on fluid flow in pumps.
USEFUL FOR

Students in mechanical engineering, fluid dynamics professionals, and anyone involved in pump system design and analysis will benefit from this discussion.

Sabacca6
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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!
 
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Sabacca6 said:
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.
 

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