GATE 2019 ME (ME2) – Question 58
An idealized centrifugal pump has blade outer radius 50 mm, consumes 2 kW and runs at 3000 rpm. Liquid enters axially and exits radially with respect to the impeller. Neglect losses. Find mass flow (kg/s), to two decimal places.
Practise this question in The GATE Grind →
Show answer and explanation
Correct answer: 8 to 8.2
Explanation
Blade speed is $U=2\pi(3000/60)(0.05)=15.70796$ m/s. Axial inlet has zero whirl; radial relative exit gives absolute exit whirl U. Euler specific work is $U^2=246.740$ J/kg. Thus $\dot m=2000/246.740=\mathbf{8.11}$ kg/s.