CHEMICAL ENGINEERING TRANSACTIONS VOL. 45, 2015 A publication of The Italian Association of Chemical Engineering www.aidic.it/cet Guest Editors: Petar Sabev Varbanov, Jiří Jaromír Klemeš, Sharifah Rafidah Wan Alwi, Jun Yow Yong, Xia Liu Copyright © 2015, AIDIC Servizi S.r.l., ISBN 978-88-95608-36-5; ISSN 2283-9216 DOI: 10.3303/CET1545309 Please cite this article as: Short M., Isafiade A.J., Fraser D.M., Kravanja Z., 2015, Heat exchanger network synthesis including detailed exchanger designs using mathematical programming and heuristics, Chemical Engineering Transactions, 45, 1849-1854 DOI:10.3303/CET1545309 1849 Heat Exchanger Network Synthesis Including Detailed Exchanger Designs Using Mathematical Programming and Heuristics Michael Short a , Adeniyi J. Isafiade* a , Duncan M. Fraser a , Zdravko Kravanja b a Department of Chemical Engineering, University of Cape Town, Private Bag, Rondebosch 7701, South Africa b Faculty of Chemistry and Chemical Engineering, University of Maribor, Slovenia AJ.Isafiade@uct.ac.za The synthesis of heat exchanger networks (HENs) has mainly been done through the use of approximate models for each of the individual heat exchangers that comprises the network. These approximate models do not adequately take into account key parameters such as the overall heat transfer co-efficient, TEMA standards, pressure drops, FT correction factors, and multiple shells. These factors can significantly alter the cost of the network. This paper presents a new methodology for the synthesis of heat exchanger networks using detailed heat exchanger design models that takes into account the aforementioned design parameters. The newly developed method involves the following steps. First, a SYNHEAT (Yee and Grossmann, 1990) MINLP model is solved. The individual exchangers for the resulting network are then designed using heuristics, TEMA standards and the Bell-Delaware method. From the designs obtained for these individual exchangers, correction factors are inserted into the SYNHEAT model that account for changes in overall heat transfer coefficient, TEMA choices, pressure drops, Ft correction factors and the effect of multiple shell passes. The SYNEAT model is then re-run and individual exchangers re-designed and the procedure repeated until convergence is achieved. For each iteration the change in each correction factor is limited to avoid the omission of certain solutions. While the methodology cannot guarantee global optimality it can ensure that the synthesised processes are physically achievable and has also been shown to converge on physically meaningful parameters without the explicit formulation of complicated non-linear equations in the MINLP formulation. 1. Introduction Heat Exchanger Network Synthesis (HENS) is one of the most well-known subjects in Process Integration as it can be used to decrease energy costs and environmental impact of a process through the utilisation of process heat rather than through the use of utilities. HENS has been attempted using a variety of methods, with most methods falling under either sequential approaches, like Pinch Technology, or simultaneous approaches. The simultaneous mathematical programming approach has received the most attention in recent years due to advances in solver capabilities and the ability to simultaneously consider multiple factors relating to the overall cost of the network using mixed-integer non-linear programming (MINLP). The majority of mathematical programming approaches to HENS use a stage-wise superstructure-based model (SYNHEAT) first proposed by Yee and Grossmann (1990) that embeds a large number of possible stream matches into a superstructure that allows for stream splitting and isothermal mixing. This method is very good for considering potential networks, however the NP hard formulation makes it difficult to solve to global optimality with current solvers (Furman and Sahinidis, 2002). The formulation fails to consider details involved in heat exchanger design, such as changing heat transfer coefficients, pumping costs, number of baffles, tube passes, and number of shells, and cannot be extended to include these as the combinatorial nature of the problem combined with the increased non-linearity will result in non-optimal solutions. While the use of constant heat transfer coefficients and the simplifications of ignoring design