Design and optimization of plate heat exchanger networks

Abstract

Abstract Heat transfer enhancement technologies have been widely used in heat exchanger network (HEN) retrofit due to its relatively low retrofit cost. However, for enhancement to be effective, one of the side film coefficients must be controlling on one of the side that presents a higher magnitude. Alternatively, plate heat exchangers (PHE) have relatively small minimum approach temperature and high heat transfer coefficient, and they do not rely on the differences between coefficients. Applying PHE into retrofit design of HEN is considered as an attractive option as it can enhance heat recovery and reduce energy consumption. The first part of this paper proposes an optimal design of two-stream multi-pass plate heat exchangers, including gasket plate heat exchangers and welded plate heat exchangers. An MINLP model is formulated to minimize the total area of a PHE by selecting the best plate geometries, chevron angle and flow arrangement. The second part of this paper presents a new cost-effective methodology of applying the optimized PHE model in HEN retrofit with a fixed network structure. Sensitivity analysis is used to identify the best heat exchangers to replace. A non-linear optimization based model is formulate to deal with downstream effect after replacement. A case study highlights the benefits of the new approach of applying PHE in HEN retrofit.