Thermo-economic optimization design of steam-water organic Rankine cycle with splitting flow

Abstract

Aiming to address the potential scenario of waste heat recovery from a steam-water dual heat source, this paper proposes the thermo-economic models of split-flow dual-loop organic Rankine cycle (SFD-ORC) and split-flow triple-loop organic Rankine cycle (SFT-ORC) systems. The particle swarm optimization (PSO) algorithm is employed for single-objective optimization of the systems, with the goal of maximizing the net power output. The non-dominated sorting genetic algorithm-II (NSGA-II) algorithm is used to find the Pareto frontier by considering both the maximum net power output and the lowest cost of electricity production. The multi-objective optimization parameters are evaluated using the entropy weight method and TOPSIS method. The results show that the hot water split ratio and hot water outlet temperature of the high-pressure loop are higher in multi-objective optimization compared to single-objective optimization. The net output power of the SFT-ORC system after single-objective optimization can be up to 7.9% higher than that of the SFD-ORC system. From an economic perspective, it is recommended to use the SFD-ORC system at a hot water temperature of 85 °C–90 °C. In order to enhance the economic performance of the system, the steam outlet pressure should be as low as possible within the allowable range.