Multi-objective design of heat-exchanger networks considering several life cycle impacts using a rigorous MILP-based dimensionality reduction technique

This work addresses the optimal design of heat exchanger networks (HENs) considering economic and environmental concerns. The design task is posed in mathematical terms as a multi-objective mixed-integer non-linear programming (MINLP) problem, in which life cycle assessment (LCA) principles are used to quantify the environmental impact. One of the advantages of our approach is that it accounts for the simultaneous minimization of several environmental metrics, as opposed to other models that focus on minimizing a single aggregated indicator. A rigorous dimensionality reduction method based on a mixed-integer linear programming (MILP) formulation is applied to aid the post-optimal analysis of the trade-off solutions. The capabilities of our approach are tested through two examples. We clearly illustrate how the use of a single overall aggregated environmental metric is inadequate in the design of HENs, since it may leave some solutions that are appealing for decision-makers out of the analysis. Our method is aimed at facilitating decision-making at the early stages of the design of HENs.