110 CHEMICAL ENGINEERING VOLUME 1 SOLUTIONS
Compression cycles are shown in Figs 8a and 8b. The former indicates the effect of
various values ofninPVnDconstant and it is seen that the work done is the area under
the temperature – entropy curve. Figure 8b illustrates the three-stage compressor of this
problem. The final temperatureT 2 , found fromT 2 /T 1 DP 2 /P 1
^1 /
, is 390 K. The
dotted lines illustrate the effect of imperfect interstage cooling.
Adiabatic temperature
Rise Temperature,
T
T 2
T 1
n < γ
n > γ
n = γ
n = 1
P 1
P 2
Line of constant
pressure
Work done where
PVn = constant
n < γ
0 Entropy, S
Figure 8a.
0 Entropy (kJ/kg K)
Work
done
stage 3
Work
done
stage 2
Work
done
stage 1
Delivery
Delivery for
imperfect
cooling
Indicates
imperfect cooling
4000 kN/m^21308
428
140
Inlet
283
390
Temperature (K)
Figure 8b.