Page 212 - Advanced Gas Turbine Cycles

176 Advanced gas turbine cycles

(O.lA', - 0.54)
FESR' = (9.22)
(0.9 + 0.4A',) '
and for $ = 1.5,

1.5(1 + A',)
EUF' = (9.23)
6+Ab '
(0.24Ab - 0.81)
FESR' = (9.24)
(1.35 + 0.6A',)

The values of EUF' and FESR' under the conditions of A', greater than 2.25 are plotted
on the right hand side of Fig. 9.5. Now fuel savings appear for A', > 5.4 with $=
&IF2 = 1.2, and for A', > 3.375 with $ = A',/F2 = 1.5.
But the amount of unused heat now varies with AD and is given by

(QNU)CG/FCG = (314) + &[(W - 1l/4,
(QNU)CG/FCG = (1 8 - A',)/24 for = 1.2,
(QN")cG/Fcc = (9 - &)/12, for $ = 1.5.

These are plotted against AD in Fig. 9.6. Clearly, the calculations lose validity when
-
-
A', = 18 for $ = 1.2, and when A', = 9 for $ = 1.5. However, if the exhaust stack

0 2 4 6 a IO 12 14 16 la 20
(HEAT DEMAND)/(WORK DEMAND)
Fig. 9.6. Unused heat as a function of (heavwork) demand.