Analysis and optimization of thermodynamic performance of single flash-Kalina cycle in power generation
Based on the Kalina cycle,a single-stage geothermal flash-Kalina cycle was proposed,incorporat-ing the principles of cascade utilization theory.By analyzing the thermodynamic properties of the working fluid in the cycle,the system's crucial operating parameters were determined,and thermodynamic performance eval-uation metrics were established.Utilizing the Peng-Robinson state equation and employing software of Aspen HYSYS,the system's thermal efficiency and exergy efficiency were optimized using single-objective optimiza-tion based on the genetic algorithm(GA)and multi-objective optimization based on NSGA-Ⅱ for ammonia mass fractions of 48%,50%,and 52%.Thermodynamic analysis results revealed that the evaporation pressure of the ammonia-water mixture,LNG gasification pressure,natural gas transmission pressure,geothermal water evap-oration pressure,and ammonia mass fraction had a significant impact on the system's thermodynamic perfor-mance.The single-objective optimization results indicated that the maximum thermal efficiency achieved at an ammonia mass fraction of 52%was 34.46%,with a maximum exergy efficiency of 50.65%,representing im-provements of 12.47%and 3.43%,respectively,compared to the initial optimization.Employing the LINMAP decision method,the system's optimal thermal efficiency was found to be 32.14%,with an exergy efficiency of 45.31%.The corresponding values for the ammonia-water mixture evaporation pressure,LNG gasification pres-sure,natural gas transmission pressure,geothermal water evaporation pressure,and ammonia mass fraction were 1 627.80 kPa,3 232.85 kPa,503.40 kPa,582.55 kPa,and 52%,respectively.
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