MICROFICHE REFERENCE LIBFUUW - Cd3wd.com

Multiplying all these efficiencies together produces the overallefficiency (OAE) of the water lifting operation, i.e., the percentageof energy put into the prime mover which will actually be added to thewater.That is,OAF = Effx EffPumpx Effmover transmission' (2.16)In systems using electric power, the OAF is often referred to as wire-to-waterefficiency.2.2.5 Performance CurvesUsing various combinations of the parameters defined above, theperformance of any water lifting device can be described graphically inperformance or characteristic curves. Figure 2.1 showed how an H-Q curveis used to describe a pumping system, i.e., what total head must beproduced to deliver a given discharge through that system. Likewise, anH-Q curve can be used to show at what head(s) a water lifter will delivera specified discharge. Specific curves are given in Chapters 3 and 4 ofvarious types of devices; however, the simple bucket can again serve as agood example. As the height (i.e., head) increases through which aperson must lift a bucket of water, it can be expected that he will beable to deliver less buckets per unit time. So, this water lifter's H-Qcurve may look something like Figure 2.3. Similarly, the variation ofBHP and Eff with Q can be plotted. These performance curves are notlimitedto modern pumps.These four characteristic parameters are often plotted together fora specific device using Q as the common absicissa. A fourth curve,