Question 24 from the 2011 case study, 2 p.m
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24. Use a centrifugal pump to pump water out of a cylindrical pool. The pool has a diameter and depth of 4 meters, and it is filled with clean water. The height of the pump suction inlet centerline above the ground is 0.5 m. The allowable net positive suction head (NPSHr) of the pump is 4 m. Under normal temperature and standard atmospheric pressure, the pressure loss in the inlet piping system is assumed to be 1 m of water column. To prevent cavitation in the pump, a safety factor of 1.3 is adopted. What is the maximum amount of water that this pump can pump out (in m3), among the following values? (A) 38.5 (B) 41.5 (C) 47.7 (D) 50.2 Why isn’t the saturated vapor pressure specified for this question? Are the conditions not lacking? Seeking advice from experts! Thank you!
Normal temperature refers to 20 degrees or 25 degrees – you need to keep this in mind! For example, the calibration of centrifugal pumps is carried out under normal temperature conditions of 20 degrees, so that’s the value to use!:lol
This post was last edited by zwp997 on 2015-6-24 09:51. It’s a difficult problem that was already discussed some time ago.
This post was last edited by yaojin911 on 2015-6-23 at 22:09. The atmospheric pressure is equivalent to 10 meters of water column; the effective pumping head = 10 – 4×1.3 – 0.5 – 1 = 3.3 meters. In other words, the water level can drop by 3.3 meters. Therefore, the amount of water that can be pumped out is S*H = 0.785*4*4*3.3 = 41.45 cubic meters. I’m not sure if this is correct Please give me some advice.
This post was last edited by zwp997 on 2015-6-24 09:53. To find out whether it’s difficult or not, please check my analysis at http://bbs.hcbbs.com/thread-1311022-1-1.html
This post was last edited by Pingdan Shi on 2015-6-24 14:16 (B)41.5