Side-stream filtration and cooling for hybrid open-closed circulating cooling water system: Retrofitting and stochastic optimization

Abstract

This study presents a retrofit strategy for traditional open circulating cooling water systems by integrating closed-wet cooling towers (CWCTs) into the side-stream pipeline, creating a hybrid system that combines open and closed loop configurations. To accurately represent the performance of the CWCTs within the retrofitted system, an optimal experimental design is conducted to approximate the multivariate probability distributions by generating a finite set of scenarios across various input variables. These distributions are then propagated through multi-scenario CFD simulations to develop a data-driven reduced-order model (ROM) for the CWCTs. This ROM, combined with simplified models for filtration and the existing open cooling towers, is applied within a two-stage stochastic optimization framework to minimize the investment recovery period under uncertainty. Results from a real-world example show a 5.7% reduction in operational load, 13.7% decrease in makeup water consumption, and 5.4% cost savings, demonstrating the strategy’s effectiveness in balancing water conservation, energy efficiency, and economic viability.