Problem 10.24 [Difficulty: 3]
Given: Data on suction pump
Find: Plot of performance curves; Best effiiciency point
Solution:
Basic equations: ηp
Ph
Pm
PhρQgH (Note: Software cannot render a dot!)
ρ = 1.94 slug/ft3Fitting a 2nd order polynomial to each set of data we find
H=-0.00759Q2 + 0.390Q + 189. 1
Q (cfm) H (ft) Pm (hp) Ph (hp) η (%) η=-6.31x10-5 Q2 + 0.011 13Q + 0.207
36 190 25 12.9 51.7%
50 195 30 18.4 61.5% Finally, we use Solver to maximize η by varying Q:
74 176 35 24.6 70.4%
88 162 40 27.0 67.4% Q(cfm)
H
(ft) η(%)
125 120 46 28.4 61.7% 88.2 164.5 69.8%
Pump Performance Curve
0
50
100
150
200
250
0 20 40 60 80 100 120 140
Q (c fm)
H (ft)
0%
25%
50%
75%
100%
η (%)
H
η
B
E
P