Fluid Mechanics 9th Edition By Frank White (Solutions Manual)

Solutions Manual for
Fluid Mechanics 9 th

Edition By Frank
White (All Chapters
1-11, 100% Original
Verified, A+ Grade)
All Chapters
Arranged Reverse:
11-1

, Chapter 11  Turbomachinery 11-1




Chapter 11  Turbomachinery
P11.1 Describe the geometry and operation of a human peristaltic PDP which is
cherished by every romantic person on earth. How do the two ventricles differ?

Solution: Clearly we are speaking of the human heart, driven periodically by travelling
compression of the heart walls. One ventricle serves the brain and the rest of one’s extremities,
while the other ventricle serves the lungs and promotes oxygenation of the blood. Ans.



P11.2 What would be the technical classification of the following turbomachines:

(a) a household fan  an axial flow fan. Ans. (a)
(b) a windmill  an axial flow turbine. Ans. (b)
(c) an aircraft propeller  an axial flow fan. Ans. (c)
(d) a fuel pump in a car  a positive displacement pump (PDP). Ans. (d)
(e) an eductor  a liquid-jet-pump (special purpose). Ans. (e)
(f) a fluid coupling transmission  a double-impeller energy transmission device. Ans. (f)
(g) a power plant steam turbine  an axial flow turbine. Ans. (g)



P11.3 A PDP can deliver almost any fluid, but there is always a limiting very-high
viscosity for which performance will deteriorate. Can you explain the probable reason?

Solution: High-viscosity fluids take a long time to enter and fill the inlet cavity of a PDP.
Thus a PDP pumping high-viscosity liquid should be run slowly to ensure filling. Ans.



P11.4 Figure P11.4 shows the impeller on a common device which, in operation, turns
as fast as 300,000 r/min. Can you guess what it is and offer a description?




Fig. P11.4

Solution: This turbine, typically only 10 to 12 mm in diameter, drives a dental drill,
using high pressure air from tiny nozzles. Oy! When drilling against a tooth, it typically
runs at 360,000 r/min.
______________________________________________________________________




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, Chapter 11  Turbomachinery 11-2



P11.5 What type of pump is shown in
Fig. P11.5? How does it operate?

Solution: This is a flexible-liner pump.
The rotating eccentric cylinder acts as a
“squeegee.” Ans.

Fig. P11.5



P11.6 Fig. P11.6 shows two points a half-
period apart in the operation of a pump.
What type of pump is this? How does it
work? Sketch your best guess of flow rate
versus time for a few cycles.

Solution: This is a diaphragm pump. As
the center rod moves to the right, opening A
and closing B, the check valves allow A to
fill and B to discharge. Then, when the rod
moves to the left, B fills and A discharges.
Depending upon the exact oscillatory motion
of the center rod, the flow rate is fairly steady,
Fig. P11.6
being higher when the rod is faster. Ans.


P11.7 A piston PDP has a 5-in diameter and a 2-in stroke and operates at 750 rpm with
92% volumetric efficiency. (a) What is the delivery, in gal/min? (b) If the pump delivers
SAE 10W oil at 20C against a head of 50 ft, what horsepower is required when the overall
efficiency is 84%?

Solution: For SAE 10W oil, take   870 kg/m3  1.69 slug/ft3. The volume displaced is

 (5)2 (2)  39.3 in 3 ,
4
 in   1 gal  
3
strokes 
 Q   39.3   3  750  (0.92 efficiency)
 stroke  231 in   min 
or: Q  117 gal/min Ans. (a)
 117 3 
1.69(32.2)  ft /s (50)
gQH  449  ftlbf
Power    846  550  1.54 hp Ans. (b)
 0.84 s




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McGraw-Hill Education.

, Chapter 11  Turbomachinery 11-3



P11.8 An 11-inch-diameter Bell and Gossett pump at best efficiency, running at 1750
r/min and 32.4 brake horsepower, delivers 1050 gal/min of water against a head of 105 ft.
(a) What is its efficiency? (b) What type of pump is this?

Solution: (a) For water take ρg = 62.4 lbf/ft3. Pump efficiency is defined as

(  g)QH (62.4lbf / ft 3 )(.83 ft 3 / s)(105 ft)
    0.86  86% Ans.(a)
bhp (32.4 *550) ft  lbf / s

(b) If you have only progressed as far as the beginning of this chapter, it would be
difficult to name this type of pump, which is centrifugal. You could rule out a PDP – to
pump water with a piston 11 inches in diameter at 1170 r/min would result in a much
higher head than 105 ft. Conversely, H = 105 ft is too high, and Q = 1050 gal/min is too
low, for an axial-flow pump. This pump has a specific speed (Section 11.4) of 1700,
about right for a centrifugal pump.



P11.9 The measured performance of a piston pump when delivering SAE 10W oil at
180F (  910 kg/m3) is shown in the table below. The pump displacement is 45 cm3/r
and the pressure rise is 210 bar. Make some general observations about these data vis-à-
vis Fig. 11.2 and your intuition about PDP behavior.

n, r/min 600 800 1000 1200 1400 1600
Q, m3/s 26.0 34.5 43.0 51.5 60.0 68.5
P, kW 11.5 14.6 17.7 20.8 23.9 27.0
η 80.5 83.8 86.3 88.2 90.0 91.8


Solution: The following are observed:
(a) The discharge Q is almost linearly proportional to speed  and slightly less for the
higher heads (H or p).
(b) The efficiency (volumetric or overall) is nearly independent of speed  and again
slightly less for high p.
(c) The power required is linearly proportional to the speed  and also to the head H
(or p). Ans.




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McGraw-Hill Education.