Power plant engineers today are primarily focused on maximizing the extraction of fuel energy. This objective involves improving the efficiencies of different thermodynamic elements and the overall cycle in terms of both first and second laws of thermodynamics. To achieve this, engineers are employing various techniques aimed at increasing these efficiencies. In the present work, one such technique being utilized is the substitution of water/steam with a different working fluid. By changing the working fluid, engineers aim to optimize the thermodynamic performance of the power plant. In this study, the analysis focuses on the utilization of an ammonia-water mixture combined with Trans critical carbon dioxide in a heat recovery vapor generator. The results of this research reveal that the highest work output and second law efficiency achieved are 1192 kJ/sec and 81.68% respectively. These optimal values are obtained when the topping cycle pressure is set to 50 bar, and the turbine inlet temperatures are 500°C and 300°C for the ammonia-water mixture and Trans critical carbon dioxide respectively. Furthermore, the maximum first law efficiency of 43.57% is observed when the topping cycle pressure is set to 50 bar, the bottoming cycle pressure is set to 160 bar, and the turbine inlet temperature is 300°C. The analysis also reveals that the heat source is responsible for the majority of energy destruction, with a maximum of 1970 kJ/sec of available energy being destroyed at a temperature of 500°C. To achieve the highest values of thermodynamic performance parameters, it is recommended to maintain low pressure in the absorber and condenser. Additionally, the analysis indicates that the cost of electricity generation reaches its peak when the condenser pressure is set at 70 bar, amounting to 0.050 USD/kWh.