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Modeling multistream heat exchangers with and without phase changes for simultaneous optimization and heat integration
Author(s) -
Kamath Ravindra S.,
Biegler Lorenz T.,
Grossmann Ignacio E.
Publication year - 2012
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.12565
Subject(s) - heat exchanger , process integration , pinch analysis , computer science , mathematical optimization , minification , representation (politics) , a priori and a posteriori , complementarity (molecular biology) , process (computing) , mathematics , process engineering , mechanical engineering , engineering , politics , political science , law , biology , genetics , philosophy , epistemology , operating system
A new equation‐oriented process model for multistream heat exchangers (MHEX) is presented with a special emphasis on handling phase changes. The model internally uses the pinch concept to ensure the minimum driving force criteria. Streams capable of phase change are split into substreams corresponding to each of the phases. A novel disjunctive representation is proposed that identifies the phases traversed by a stream during heat exchange and assigns appropriate heat loads and temperatures for heat integration. The disjunctive model can be reformulated to avoid Boolean (or integer) variables using inner minimization and complementarity constraints. The model is suitable for optimization studies, particularly when the phases of the streams at the entry and exit of the MHEX are not known a priori. The capability of the model is illustrated using two case studies based on cryogenic applications. © 2011 American Institute of Chemical Engineers AIChE J, 2012