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ME2135_Solution_of_QUIZ_march_2009

# ME2135_Solution_of_QUIZ_march_2009 - 03 March 2009 Metric...

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03 March 2009 Metric Number:________________ Department of Mechanical Engineering National University of Singapore ME 2135 – Fluid Mechanics II– Quiz – Dilip A Shah Time Allocated: 40 Minutes Instructions to Candidates: 1. Answer ALL questions. 2. This quiz is equivalent to 10% of the course total score. 3. Enter only your metric number on the top right corner of this page. 4. You are allowed to refer to your class lecture notes.

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Q.1 Consider two geometrically similar centrifugal pumps. One of the pumps ( pump 2 ) is four times larger than the other ( pump 1 ), i.e. D2 = 4 D1. Both pumps operate at their BEP point. (i) If both pumps pump water and use the same power , estimate the ratio of flow-rates through the two pumps, i.e. Q1 / Q2 . (ii) Compare the rotation rates of the two pumps under these conditions, i.e. N2 / N1 . (4 marks) The non dimensional variables are C Q =Q/ND 3 ; C H =gH/N 2 D 2 and C P =P/ρN 3 D 5 . Given: D 2 = 4D 1 At BEP, C H , C Q and C P will be the same for the two pumps. Also given is P 1 = P 2 .
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