Question

A 38-in pump is installed for the system below. The pipe (100-cm diameter) has a friction factor of 0.012 and a total length of 20 km. Given that Ke = 0.5 (pipe entrance) and Kε = 1.0 (pipe exit). For water at 80 degrees Fahrenheit, estimate the flow rate (in gpm), the power required in horsepower, HP), and the net positive suction head required (in ft) to avoid cavitation for the system when the pump running. Elevation = 180 m Elevation = 150 m 20 km Pump 100 cm The measured performance curves of the pump are shown below: n= 710 r/min 400 NPSH 350 -412-in dia. NPSH, ft 15 88% 10 %98 D +300 38-in dia. %68 Total head, ft 250 -35-in dia. 88% 18 86% 84% 200 1500 bhp 150 1250 bhp 1000 bhp 100 0 4 8 28 12 16 20 24 U.S. gallons per minute x 1000

Answer 1

Solution:- o Given that, Pump The pipe 38 in 100 cm - diameter 11 friction factor = 0.002 Total length 20 km = 0.5 = 10 lower and upper ke pee entrance) kę (pipe ext) fornata 80+ Apply Burnoulli Equation balueen point, and (point) located at Water surfall Elevation reserwop97 tespadfuely. Pil8+ V13/629 +Z1 the since, both point , and 2 are open to atmosphere, priser P8 only atmospheric rence gauge for sure, Pi=8z =0 at surface i8 VI = V2 = 0 Elevation, 27 = 150m and 22 = 180m 32]+V=129 +22+Hf+um velocity neplegible „so, Hp P8 pump head HF Head 108 due to buration HM House manor head los due to entry and state henee, aboue equation reduces to, 0 + 150+ HP = 0 + 180+ HA

HP 30+ Hf - 19.8502 > Hm Also , Hf 84L0%/1m+90) yf= 8 (0-012) (20000 ) 07 (7°4981x15) =) Hf Ako, Hm = (kertory + kenit ) (*/29 A? of pipe (A) = (hu) (1)² = (Tolu) 0)*= 0.78559.m (0.5+1) 02/(2*9-81 x 0-785) 2 *Hm = 0.12402 patting values in Equation in =) Hp = 30 +19.850*+ 0.124.02 30+2002 The above equation is system head ewwe Equatres where a PJ in mils and Hp BS in meter @gal/min) o (ms) Hpm) Hplot) 0 o 8000 30 98.42 114.83 0.50 35 16000 - 50 164 24000 10557 248 7506 91.95 28000 1: 76 301.6 Now plet the system curve on given pump pertamance for 38 Pn ampeller diameter as shown below. cuore

300 250 Np ) Pump performance curve 5-System Curve 200 150 100 0 A000 4000 12000 70000 24000 16000 lepm)

6) NOW, curve and Ne know the point of Intersection of performance curve 78 operating point Hence, operating flowerale = 21000 gpm or 46-62084 Similarly, honšppolver corresponding to operating point 1250 hp NPSH corrisponding to operating point trajt