Comprehensive analysis and optimization of Kalina-Flash cycles for low-grade heat source

In this paper, two configurations of Kalina-Flash cycles (KFC) are proposed to recover low-grade heat source. The thermodynamic and economic models of Kalina-Flash cycles are established. A numerical simulation is conducted, and a parametric analysis is performed to examine the effect of five key parameters, including separator temperature, separator pressure, ammonia mass fraction of ammonia-water basic solution, flash pressure and pinch-point temperature difference, on the thermodynamic and economic performances of Kalina-Flash cycles. Furthermore, a single-objective optimization and a multi-objective optimization are carried out by genetic algorithm and Non-dominated sorting genetic algorithm-II to obtain the optimum thermodynamic and economic performances. The single-objective optimization results show that the Kalina-Flash cycles can achieve higher exergy efficiency and lower specific investment cost than Kalina cycle does. The multi-objective optimization results of Kalina-Flash cycles present the Pareto frontier solutions, which is a series of optimum solutions for exergy efficiency and total capital investment. The Pareto frontier solutions indicate that Kalina-Flash cycles are superior to Kalina cycle in the aspect of thermodynamic and economic performances.