Particle Swarm Optimisation in heat exchanger network synthesis including detailed equipment design

Abstract

Heat exchanger network (HEN) synthesis has been a well-studied subject over the past four decades. Many studies and methodologies have been proposed to recover energy between process streams, minimizing the utilities consumption and the number of heat transfer equipment. Most of these formulations assume constant heat-transfer coefficients and counter current arrangement for all stream matches, which can lead to non-optimal results. In the present contribution an optimisation model for the synthesis of HEN that includes a detailed design for each heat exchanger in the network is proposed. Shell and tube pressure drops and fouling have been considered, as well as mechanical aspects, like shell and tube bundle diameters, internal and external diameter of tubes, number of tubes, number of baffles, baffles spacing, number of shells, tube length, tube pitch, tube arrangement and the fluid allocation in the heat exchanger. Particle Swarm Optimisation approach has been applied to determine the HEN that minimizes the total annual cost, considering capital costs of heat exchangers, energy costs for utilities and pumping duties. The algorithm combines two distinct models, a superstructure simultaneous optimisation model for the HEN synthesis and a model for the detailed equipment design according to TEMA. An illustrative example shows the potential of the method, and optimum HEN configuration with the detailed heat exchangers design was obtained.