BAE2023 Spring ‘11: Pumps 1. If the centrifugal pump below has a 12” diameter impeller, what is the best efficiency point (capacity, total head, efficiency, hp, NPSHr)? What is the shutoff head? 2. The centrifugal pump represented by the curve in problem 1above has been operating at 250 GPM and has an impeller diameter of 12”. Due to piping reconfiguration and system streamlining on the discharge side of the pump, the pump must work against a reduction of 30’ head. We will need to resize the impeller. Maintaining the same capacity, to what diameter should the impeller be machined? 3. A centrifugal pump is attached to a variable speed drive. The original operating conditions are 100 gpm, 80’ head, 1750 rpm. Using the affinity laws, calculate the speed and horsepower required to gain an additional 25 gpm. The impeller diameter can not be changed. 4. Find the NPSH for the following three systems given on the next page.Problem 4: E-1 friction loss = 3 ft.Atmospheric PressureWater, 80F, Pv=0.5 psia, sea levelA) Suction Lift system15 ft. Pgauge =5 psigPFriction losses = 4ft.10 ft.B) suction from pressurized tankAir PressureWater, 80F, Pv=0.5 psia , sea level n-Butane, 100F, Pv=52.2 psia , sea level, sp. gr. = 0.56Pgauge = 37.5 psigPFriction losses = 2 ft.10 ft.C) suction from liquid at boiling pointAir Pressure5. Given the pump represented by the curve below and the system sketch, find the total head, the capacity or pumping rate, impeller diameter, efficiency, motor size and speed requirement, and NPSHR. Would the NPSHR requirement met? Atmospheric Pressure10 ft7 ft46 ft8 ft.Total of 110 ft. of 2 in. Sch. 40 steel pipe3 regular 90 deg. Threaded elbows2 gate valves - fully open30 ft. of the 110 ft. of steel pipe is on thesuction side along with 1 elbow and 1 gatevalve.Fluid pumped: fresh water, 80F, sea level,Pv = 0.5 psiaDrawing Not
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