Centrifugal Pump Experiment, Summer 2006
*A new DP cell has been installed so that we can get pressure drop data at higher pump speeds,
and for the larger pump head. The software has not been modified to reflect the new range so
you will have to multiply the pressure drop given on the computer screen by a factor. The
factor is given on the apparatus.
Use the SOP provided in the lab manual for startup, shutdown, and operational
procedures. Lab Assignment:
1) Start apparatus according to the SOP.
2) In order to construct characteristic curves and efficiency curves, you will need to
get data at various impeller speeds and operating points:
a. Adjust rotational speed of the pump (RPM) to the desired value. Starting with
the in-line angled globe valve (flow control valve) wide open, record flow rate
and differential pressure (pump head). Close the flow control valve all the way
and find the “shut off head”. Take measurements at 5 other points evenly
spaced between the two extremes in order to plot the pump curve. Adjust
rotational speed of the pump to a second value and repeat part (a). Keep
repeating until you have full data for at 5 speeds. (approx. 500, and 1000,
1250, 1500, 1750 RPM.)
Data: Record all readings from the computer screen
(you will need to scale the pump head value by a factor
of 5.26)
Report Items:
1) Check a representative sample of computer calculations for efficiencies, pump
horsepower, etc. to make sure they are accurate.
2) Plot pump head vs. flow rate with impeller speed as a parameter (in other words, all
speeds on same plot). Construct plot so as to be as clear and readable as possible.
3) Plot pump efficiency vs. flow rate with speed as a parameter.
4) Make log plots of all unique combinations head, flow, and speeds (from data with valve
wide open). Determine experimental affinity law exponents for the various affinity
“laws” by linear regression of the data in each plot. Compare experimental results to
accepted values to see whether or not yours are significantly different.
5) Discuss how the conditions of any of the above might be used to establish optimal pump
performance.
6) Discuss why your pump efficiency varies with the experimental conditions.
7) Make sure you calculate shaft power and fluid power from torque, RPM, Q, and
H- do not rely on the numbers given on the computer screen.