Page 321 - Design and Operation of Heat Exchangers and their Networks

Optimal design of heat exchanger networks 307

Example H10C10—cont’d

1100 3150
220 (10.61347) 120 180 75
H5 H1
(25) (30)
1050
2050 800
280 90 190 50
H9 (15) (30) C4
3150
150 40 180 75
C6 H3
(10) (30)
150 40 C7 130 40 C9
(20) (35)
1400 1050
1100
210 120 C8 140 1800 45
(35) H4 (30)
2400
280 120 120 60
H2 C10
(15) (30)
744 1503
1456.201 2246.502
180 60 170 45
H10 H7
(30) (30)
1753
230 40 C1 250 50 C5
(20) (20)
3444 1400
260 120 180 3900 50
(35) C2 H8 (30)
1250 1350
180 55 190 40
H6 C3
(10) (35)
Fig. 6.33 Optimal solution for Example H10C10 (Bohnenstaedt et al., 2014),
TAC¼1,716,695$/yr.
Example H13C7
This large-scale heat exchanger network example was taken from Escobar
and Trierweiler (2013) who used the problem data of Sorsak and Kravanja
(2002) for synthesis of heat exchanger networks comprising different heat
exchanger types, however, with their own equipment cost equation, as is
given in Table 6.34. In this example, the inlet temperature of one of the
hot stream (H13, T out ¼1034.5°C) is higher than the hot utility
temperature (927°C). Consequently, H13 shall be matched with the cold
stream C7, which has the highest target temperature (923.78°C). Using
the monogenetic algorithm (Fieg et al., 2009) and taking the network
configuration of Xiao et al. (2018) for the initial subnetworks, we had
obtained the heat exchanger network better than previous optimal
results. However, we noticed that in the obtained network, H13 is
heated again to reach its target temperature. This is because of the fact
that the monogenetic algorithm is based on the stagewise superstructure
of Yee et al. (1990), in which the utilities are located at the outlets of the
network if necessary. To avoid the reheating of hot streams, we manually
deleted the match H13HU and added the heater before the match of
H13C7. The best network configuration is shown in Fig. 6.34, which
has three independent variables. After local optimization of the three
variables, the TAC reaches to 1,410,649$/yr.
Continued