Page 241 - Design and Operation of Heat Exchangers and their Networks

CHAPTER 6

Optimal design of heat exchanger

networks

a
b
Wilfried Roetzel , Xing Luo , Dezhen Chen c
a
Institute of Thermodynamics, Helmut Schmidt University/University of the Federal Armed Forces Hamburg,
Hamburg, Germany
b
Institute of Thermodynamics, Gottfried Wilhelm Leibniz University Hannover, Hannover, Germany
c
Institute of Thermal Energy and Environmental Engineering, Tongji University, Shanghai, China

In many industrial processes, heat exchanger networks are used to transfer
heat among more than two process streams, in which the cold streams are
heated by the hot streams that need to be cooled and vice versa. In this
way, a large amount of heat energy can be recovered from the process
streams, and therefore, the heating and cooling loads from external
sources (hot and cold utilities) can be dramatically reduced. However,
the use of heat exchangers for heat recovery also increases the investment
costs. Therefore, a balance between the utility costs and investment costs
should be established. The optimal design of a heat exchanger network is
to configure a heat recovery system or retrofit an existing network capable
of performing the prescribed tasks at the minimum total annual costs that
are mainly determined by the utility costs and investment costs (Masso
and Rudd, 1969). Because of its structural characteristics, it is also named
as synthesis of heat exchanger networks. The optimal design also deals
with the optimal retrofit design of an existing heat exchanger network
by rematching the process streams; changing the heat exchanger area;
and adding or removing some heat exchangers, heaters, and coolers, so
that the sum of the annual utility costs and retrofitting costs reaches
the minimum.
The available optimization design and synthesis methods can be classified
into three categories: (1) thermodynamic analysis methods with pinch
technology (Linnhoff and Flower, 1978a; Linnhoff et al., 1979); (2) math-
ematical programming methods (Grossmann and Sargent, 1978); and
(3) stochastic or heuristic algorithms such as genetic algorithm (Lewin,
1998), simulated annealing algorithm (Dolan et al., 1989) and particle swarm

Design and Operation of Heat Exchangers and their Networks © 2020 Elsevier Inc.
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