Page 15 - Design and Operation of Heat Exchangers and their Networks

2 Design and operation of heat exchangers and their networks

Exchangers for Energy Transfer Intensification: Low Grade Heat and Fouling Mitiga-
tion by Klemes et al. (2015), CompactHeatExchangers: Selection, Design andOper-
ation by Hesselgreaves et al. (2017), Compact Heat Exchangers: Analysis, Design
and Optimization using FEM and CFD Approach by Ranganayakulu and
Seetharamu (2018), Next Generation Microchannel Heat Exchangers by Ohadi
et al. (2013),and Heat Exchanger Design Handbook by Thulukkanam (2013).
These publications are very useful reference books for readers to understand
the heat exchangers and their design and operation methods and techniques.
For the research and development in design and operation of heat exchangers
and their networks, the reference book VDI W€armeatlas (VDI, 2013)and
its English version VDIHeatAtlas (VDI, 2010) should be the most important
reference book that covers most fields of heat transfer in industrial and engi-
neering applications and presents the interrelationships between basic scientific
methods, experimental techniques, model-based analyses, and their transfer to
technical applications.

1.1 Classification of heat exchangers
According to heat transfer manner, the heat exchanger can be classified into
three groups. One group contains direct contact heat exchangers where the
fluids contact directly (e.g., air-water heat exchanger) or are mixed together
(water-water and water-steam exchangers) to exchange heat. Another group
is recuperative heat exchangers (recuperators) where the fluids flow simul-
taneously through the exchanger in separate paths and exchange heat across
the walls separating the fluids. The third group is called regenerative heat
exchangers (regenerators) in which only a single set of flow channels
through a relatively massive solid matrix exist and the hot and cold fluids
pass through the matrix alternately. When the hot fluid flows through the
matrix (called “hot blow”), heat is transferred from the fluid to the matrix
to heat the solid material of the matrix. In the next period, the cold fluid
passes through the matrix (called “cold blow”), the heat is transferred from
the matrix to the fluid, and the solid material is cooled. If a continuous flow
of fluid is required, a duplicated matrix could be provided with quick-acting
valves to switch the flows periodically. The matrices will then experience the
cold blow and the hot blow periods alternately. In other cases, a single matrix
can be used, and the flows are switched cyclically by rotating the matrix or
moving the flow headers controlling the fluids flowing to and from the
matrix. In heat exchanger networks, regenerators under steady operation
can be regarded as counterflow recuperators. The recuperative heat