Across a centrifugal pump, the increase in energy per unit mass of liquid is gdeltah, where g is the gravitational acceleration and deltah is the increase in head. This quantity gdeltah may be a function of the impeller diameter D, the rotational speed N, liquid density rho, and the flow rate Q. A centrifugal pump operating at 2,000 rpm is to be designed to handle a liquid hydrocarbon of specific gravity 0.95. To predict its performance, a half-scale model is to be tested, operating at 750 rpm, pumping a light oil of specific gravity 0.80. The scale model is found to deliver 400 gpm with a head increase of 20 ft. Assuming dynamical similarity, for the full-size pump Q = 8,533 gpm deltah = 569 ft