Pump selection – fluid mechanics
Choose sizes foe the pump suction and discharge piping to yield appropriate velocities, and then use Goulds Pump Catalog data to identify ALL Model MTX 3196 3X4-10, 3X4-10H, 4X6-10, and 4×6-10H centrifugal pumps having suitable combinations of operating speed and impeller diameter capable of delivering a design flow rate Qdesign=400gpm for the system shown in the sketch(see attachment). For Goulds pumps, the model number identities the pump outlet connection diameter, inlet connection diameter, and maximum impeller diameter.
identifying suitable pumps generating two system head-discharge curves:
1. One using the approximate explicit formula for Darcy friction factors from Darcy friction factor file (see attachment), and then Darcy -Weisbach equation to estimate pipe friction losses for new, clean steel pipe;
2. Another using C=100 for computing friction losses for old corroded or scaled pipe using the Hazen-Williams Formula.
In BOTH cases, choose minor loss coefficients to account for the applicable minor losses(assume the suction pipe reducer is a sudden contraction, and the discharge pipe increaser is a sudden expansion). Then, read pump head-discharge data pairs from the given manufacturer’s pump curves and use these data to re-plot pump head-discharge curves superimposed over the system head-discharge curves for all combination of pump model, operating speed, and impeller diameter capable of delivering the specified design flow rate for the given system.
Utilize spreadsheet software for the repetitive calculations involved with generating system head-discharge curves, and for creating “X Y”charts superimposing the appropriate pump head-discharge curves over the system head-discharge curves. There should be 3 or 4 suitable pump model-speed-impeller diameter combinations the can deliver the design flow rate. Then, refer again to the manufacturer’s pump characteristic curves for each suitable pump identifying and tabulating the following information:1.Pump model;2.Operating speed;3.Impeller diameter;4.Total dead at the design flow rate ; 5. Efficiency at the design flow rate;6. Brake horsepower at the design flow rate; 7. Shut-off head.
Create two spreadsheet files to accomplish these tasks:
1. Evaluating Models MTX3x4-10 and -10H having feasible operating speeds and impeller diameter.
2. Once its done, save a copy under a new name and then revise it for evaluating Models MTX 4X6-10 and -10H. Two significantly different pump head-discharge curves, and the two sets of pump outlet and reducers and discharge pipe increasers having different minor loss coefficients. All other minor loss coefficients will be identical in the two spreadsheet files.