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260 Chapter 5

z 2 = 2.0 + 2.280 = 4.28 m (14.0 ft)

From Table 5.4.1, the stripper-bottom pressure, pi= 1.65 bar (23.9 psia), and
the absorber-top pressure p 2 = 34.8 bar (505 psia). Thus, we can calculate the sec-
ond term in Equation 5.48.
The total-frictional pressure drop in the system is the sum of the pressure
drops caused by the piping and fittings, control valve, interchange^ and air cooler.
Estimates of these loses are listed in Table 5.15. Therefore, the total frictional
pressure drop in the system,

E s + E D = 0.35 + 0.70 + 0.35 + 0.60 = 2.0 bar (29.0 psi)

Now, substitute numerical values into Equation 5.48. In the SI system of
5
2
units gc, is not needed. Because one bar equals IxlO Pascals (N/m ), we have,
after multiplying and dividing the first term in Equation 5.48 by kg,
9.8m (4.28 - 24.0) m-kg (1.65 -34.8) bar IxlO 5 N 1 m 3
2
1 s 2 1 kg 1 1 m -bar 974.0 kg

2.0 bar IxlO 5 N 1 m 3
3
- = -3.391xl0 N-m/kg (-3.217 Btu/lb)
2
1 1 m -bar 974.0kg
3
( -3.391xl0 J/kg) ( -3.217 Btu/lb)
equals one Newton, the first term has units of N-m/kg, as does
Because kg-m/s2
the other terms. The negative sign means that the work is done on the system.
Work done by a system is positive.
According to Table 5.13, the centrifugal pump efficiency depends on the
volumetric flow rate. From Table 5.13, the pump efficiency is 45 %, Therefore,
from Equation 5.49 the pump shaft power,

mW 1 2.08 m 3 974kg 3391 J 1 min

r|p 0.45 1 min 1m 3 1 kg 60 s

5
= 2.544xl0 J/s (254 kW) (341.2 hp)
Assuming that a squirrel-cage electric-motor drive for the pump is selected,
the electric-motor efficiency is determined by interpolating between 100 and
1,000 hp (in Table 5.9). An acccurate determination of the motor efficiency re-

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