What Is the Minimum Power Input to the Pump in This Thermodynamics Problem?

AI Thread Summary
The discussion revolves around calculating the minimum power input to a pump in a thermodynamics problem involving water flow. The pump operates with water entering at 20°C and 100 kPa, flowing at 35 L/s, and exiting at 800 kPa with a discharge height of 6.1 m. The key equation used is derived from the energy balance, focusing on the change in enthalpy and potential energy while neglecting heat transfer and kinetic energy. The participant expresses confusion about determining specific enthalpy values (h1 and h2) and the proper use of thermodynamic tables for compressed liquids. The discussion highlights the importance of understanding the relationships between pressure, flow rates, and energy in pump systems.
Bradracer18
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Homework Statement


HI guys, this is an exam review question from the Fundamentals Engr exam. Not sure how to do it, please help me along so I can learn it too!

Water enters a pump steadily at T1=20°C, p1=100 kPa at a rate of 35 L/s and leaves at p2=800 kPa. The flow velocities at the inlet and the exit are the same, but the pump exit where the discharge pressure is measured at 6.1 m above the inlet section. Neglect Kinetic energy effect. The minimum power input to the pump is:

(a) 34 kW (b) 22 kW (c) 27 kW (d) 52 kW (e) 44 kW

Homework Equations



0 = -W + m\dot{}((h1-h2) + g(z1-z2))

The Attempt at a Solution



Well, I simplified the equation by eliminating Q(heat transfer) and KE. I converted kPA to Mpa by multiplying by .100.

So, p1= .1 MPa, p2= .8MPa. The mass flow rate(m)= converted 35L/s to 0.035m^3/s by multiplying by .001. g is gravity which is 9.81m/s^2. z1= 0m and z2= 6.1m

Basically, not sure how to start this problem out. Not sure how I find my h1 and h2. Maybe I'm not even using the correct equation, but I think I am.

Thank you,
Brad
 
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Okay, I found something else out...but have yet to figure out how to use the tables correctly. I think the water is classified as a compressed liquid, but that's as far as I've gotten.
 
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