The Superstructure Approach to Heat Exchanger Network Design

Q = heat exchanger duty U = overall heat transfer coefficient A Tlm = logarithmic mean temperature difference 

Note that the A Tmin for the problem must be fixed in order to remain an MILP problem. Fixing A Tmin fixes the composite curves and the temperatures across each enthalpy interval or block. Unfortunately, this would not necessarily lead to the best network, as the initial superstructure was already simplified with many structural options missing. But this can be allowed for by first carrying out the 

A simplified superstructure is first optimized using MILP. 

The major advantage of the superstructure approach to heat exchanger network design is that, in principle, it is capable 

Any Parallel, Series-parallel or Parallel-series Arrangement 

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