Just a quick note on an extension of the pump performance curves demonstration that was suggested by Ed Maurer of SCU. The initial demonstration had students calculate the head rise – flow rate relationship for a cheap aquarium pump. Ed extended this with the addition of an inline power meter (such as the Kill A Watt meter). Simply record the power consumed (P in watts) for each flow rate (Q) and pump head rise (Ep=height over which water is pumped plus tubing and exit head loss) . The efficiency can then be calculated as
You can then plot the pump efficiency against flow rate on the same plot as the head rise vs flow rate. When Ed Maurer did this he reported very low efficiency peaking around 20%. This is not terribly surprising as they are cheap pumps (typically only cost around $20).
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