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CEIC2001 Quiz 2 2012
Show all units, reasoning/assumptions, and workings. Be sure to
justify your
assumptions. You may not have to use all the information
provided.
50 minutes, Open book (no electronic material except for UNSW
approved calculators)
1. 30 marks
We want to model drag on a flat plate.
Using dimensional analysis, express the dimensionless drag force
as an arbitrary function
of one or more other relevant dimensionless groups. You need to
show how you derive
the dimensionless groups.
Assume that the relevant parameters are area of the flat plate
(A), drag force (F), density
of the fluid (!), velocity of the fluid (V), and viscosity of
the fluid ().
2. 50 marks
Below is the pipe and pump configuration for transferring 240
L/min of a fluid (vapor
pressure 3.2 kPa, viscosity = 10-3kg/ms, density = 1000 kg/m3)
from a tank to a transferpoint 2. You need to determine the
following:
a)
What is the NPSHA?
b) What is the total dynamic head required for the pump?
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Assumptions:
You have 30 meter of pipe from the tank/reservoir to the pump
and you have 100 meterof pipe from the pump to point 2 (which is at
300 kPa (abs))
The diameter of the pipe is 5 cm and the pipe is made from cast
iron.
The only minor losses to take into account are the
90ostreetelbows (two between the
tank/reservoir and pump and two between the pump and the exit at
point 2).
The reservoir is open to the air at atmospheric pressure (101.3
kPa).
5 m
2 m
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3. 20 marksThe pump performance curve is given from a catalog
for clean water .
The speed of the pump is 3600 rpm and impeller diameter is 100
mm.
a) I have a piping system that gives system resistance (in
meters head)
= 8 + (.0011) Q2Q is in L/min
Which of pump models shown on the graph may be suitable for me
to operate at >45L/min and what would be the operating point?
Explain your reasoning.
b) If the operating point is at the point of best efficiency (as
we try to achieve in our
pump selection and piping design), what type of rotodynamic pump
have youselected in part a)?
