CHEMICAL ENGINEERING

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.