New transshipment type MINLP model for heat exchanger network synthesis

Abstract

Heat exchanger network (HEN) is one of the most important parts in chemical process industry, owing to its significant advantages of energy recovery. However, models with plentiful HEN structures always result in complex mixed-integer nonlinear programming (MINLP) models with non-convexity of nonlinear constraints, which will cause heavy computational burdens. The computational time of MINLP models and even the feasibility of models without good initial points are still challenging researchers. This paper presents a novel transshipment type model for heat exchanger network synthesis (HENS), which is formulated asa MINLP problem with all linear constraints. Stream splitting, stream by-pass, isothermal and non-isothermal mixing, and recycling flows are all included, while multiple utilities are available in the model. Furthermore, new formulations are presented to calculate the temperature difference of heat exchangers, while a more precise heat exchanger area calculation method by piecewise calculation is developed in the new model. Six literature examples are presented to illustrate the effectiveness and applicability of the proposed model. It is shown that several better results are obtained by the proposed model.