Presenting and optimization of a novel ammonia‐water combined power and compression cooling system

Abstract

Greenhouse gas emissions and increasing energy consumption motivate researchers toward using waste heat recovery. In the present study, a novel combined cooling and power (CCP) generation system driven by waste heat recovery of a steel factory in northeastern Iran is presented which uses an ammonia-water mixture as the working fluid and consists of a vapor generator, a superheater, a turbine, an expansion valve, a mixer, a compressor, an evaporator, two recuperators, two condensers, and two pumps. In the presented system, a non-isothermal phase change occurs in the vapor generator while an isothermal phase change happens in condensers. To evaluation of the system performance, comprehensive thermodynamic and thermoeconomic analyses are performed. The effects of generator pressure and ammonia concentration on the performance of the cycle are investigated. To satisfy different needs of users, the cycle is optimized by a genetic algorithm for different ratios of power to cooling capacity considering single and multi-objectives and the best values of generator pressure and ammonia concentration are presented for each power to cooling ratio. The results show that based on the multi-objective function, for heat source temperature of 573K the best conditions happen at power to cooling capacity ratio of 0.6, in which the optimum generator pressure and ammonia concentration are 43.87 bar and 79.49%, respectively.