Learning Objectives

Objective $1$: Interpret information provided on a pump performance curve

Objective $2$:Differentiate between NPSH R and NPSH A

Objective $3$: Explain the vapor pressure of a fluid

Objective $4$: Calculate NPSH A

Problems

Figure $4\mathrm{.}2$ Performance curve for a pump with an impellor diameter of $15\mathrm{.}75-$in operating at $1750$ rpm $.$ The solid black line represents pump performance curve, the solid grey line represents system curve, the dashed line represents the efficiency curve $($read from right vertical axis$),$ the dotted line represents NPSH $,$ and the dash$-$dot line represents the BHP$.$

You have a system with a performance curve defined as $h_p=150+0\mathrm{.}15*Q^{1\mathrm{.}85}$ where $Q$ is in cfs$.$ Sketch the system curve onto the pump performance curve shown in Figure $4\mathrm{.}2($included above$).$ Overlay the system curve onto the pump performance curve and interpret the following data based on the operating point $($where the pump performance and system curve intersect$).$

A$.$ Operating Flowrate $(gpm)=$

B$.$ Operating pump head $(ft)=$

C$.$ Pump efficiency $(\%)=$

D$.$ Net Positive Suction Head Required, $NPS{H}_R(ft)=$

E$.$ Brake Horsepower $($HP$)=$

F$.$ The best efficiency point $($BEP$)$ for this particular pump curve $($gpm where the pump is at it's max efficiency$)=$

To be a good selection, the pump operating point should be $60\%-120\%$ of the BEP flow rate. Is this an appropriate pump for this application? Justify your answer with observations from the provided pump performance curve and system curve equation.

The objective of this problem is to compute the net positive suction head available $($NPSHA$)$ for the system shown on the figure below $($this is similar to Figure $4-1$ in Hydraulic Lessons$).$ The $24-$in diameter pipeline that runs from the suction tank to the pump is $50$ ft long and has a friction factor of $0\mathrm{.}021.$ The tank$\text{'}$s low water level $(LWL)$ has an elevation of $10$ feet, a high water level $($ HWL $)$ of $25$ feet, and the pump elevation is $5$ feet. The design flow rate is $3,177gpm.$ Assume minor losses of one rounded entrance, and one $90-$deg bend $($cast$/$forged$)$ and $T=90F.$ Round your final answer to the nearest tenth of a foot.