Question

fluid

Q2: A centrifugal pump with an impeller diameter of 220 mm has to pump 0.02 mº/s of brackish water to an RO unit with following performance data at the best efficiency point: impeller speed =3000 rpm, total head= 68 m, net positive suction head=1.8 m, input power=16 hp. Evaluate the performance of a homologous pump with twice the impeller diameter operating at half the impeller speed. (15 Marks) 2016)

Answer 1

Solution. given impeller diameter of pump, D, = 220 mm volumetric flow rate, ai = 0.02 m/s impeller speed, Ni = 3000 rpm total head sha=68m NPSH, = 1.8m Input power, PB = 16 hp for homologous centrifugal pump QAND Q & NID Q22 N2 D 3 ai 02 -19 ginen # 2 AN D2 = 20, D1 = 1 2*1+)-2x5 0102 m/s - m3/ 0:08 IS.N b = 4x 0.02 m/s 2 similoply point =)) Dh₂ Du our (21² x (+ 12 Ang=sh, = 68 m. so, total head of second homoge logous pump is 68m. Input power to the pump PEXN3DS c PE

PEL PEL (1,9 х (4) PEL PEZ 8x SPE, = 4%, 32. A 1914X/8 4 saavaa Break horse power of homologous кроші - щео) PB & PE Por - PEL 1 4 Pв, PER Por чXPв, з чу 16 е = 6ч р. for homdogous centrifugal Pump NPSH, — Npsuz NPSHI NPSH2 (14) 4 NPSHI 10 NPS Hz NPSH = NPSH, = 1.8m Ars, So, second homologous pump will have the same NPSH = 1.8m