Optimisation, retrofitting, and variable condition analysis of cooling water networks with improved intermediate main configurations

Abstract The cooling water network is an indispensable process in industrial waste heat treatment. Previous studies primarily focussed on optimisation to reduce total economic costs with less adjustable to variable operating conditions. This study proposes two types of improved intermediate water main configurations to optimise and retrofit cooling water networks. The optimisation target is to reduce the annual total cost, and the retrofitting target is to create the optimal adjustment by not changing the original configuration. An energy-saving strategy that combines main-auxiliary pumps and water turbines is proposed to reduce the extra cost of the static pressure head. The optimal adjustment owing to the variable number of heat exchangers and a static head is analysed. The differential evolution algorithm was applied to solve the optimisation and retrofitting problems. Five configurations were compared through optimisation results and retrofit analysis in a case study. The two configurations proposed in this study have a lower total annual cost and can be retrofitted flexibly with variable working conditions. This study proposes a novel approach for an economic optimisation and retrofitting bottleneck problems.