Synthesis of Heat-Integrated Water Networks with Exergo-economic Criteria

This paper considers the exergy analysis of Heat-Integrated Water Networks (HIWNs) rarely addressed in the literature. Two objective functions were analyzed, with the first minimizing the total annualized cost (TAC) and the second minimizing the exergy losses of the network. The exergetic objective function minimizes exergy losses due to non-isothermal mixing, heat exchange, and exergy losses due to friction. The HIWN was optimized under a constant pressure assumption. However, exergy losses due to pressure drops are considered to balance network complexity. The proposed nonlinear programming (NLP) model and iterative solution strategy showed that by using exergetic criteria as an objective function, good solutions could be obtained compared to the solution of the mixed integer nonlinear programming (MINLP) model minimizing the TAC. The advantage is that exergy-based model is an NLP, and cost data for the utilities and equipment are not required.