Performance analysis and optimum ammonia-water concentration of basic Kalina cycle

• Cycle efficiency depended on ammonia concentration and evaporator conditions. • Finding ammonia concentration for peak efficiency was complex and time-consuming. • Efficiency peaked under 3000 kPa; over that, increased with ammonia concentration. • A model was developed for promptly determining the optimal ammonia concentration. In analyzing the performance of the basic Kalina cycle with ammonia-water as the working fluid pair, it is necessary to determine the optimal ammonia concentration for maximum efficiency, which requires complex and time-consuming calculations. This study, therefore, investigates the behavior of operating evaporating pressures and temperatures within the ranges of 1000–7000 kPa and 100–150 °C, respectively. It was found that when the evaporating pressure did not exceed 3000 kPa, there was an optimal ammonia concentration that maximized the cycle thermal efficiency at any given evaporating temperature. However, when the pressure exceeded 4000 kPa, no peak thermal efficiency was observed at any evaporating temperature, and thermal efficiency increased with both the evaporating temperature and ammonia concentration. The obtained data will be used to develop new correlations for determining the optimal ammonia concentration at low evaporating pressures and the cycle efficiency for high evaporating pressures at any given ammonia concentration. These equations provide a quick method for determining the appropriate ammonia concentration for specific operating conditions at low evaporating pressures and for assessing cycle efficiency at high evaporating pressures. The findings were consistent with existing literature and simulations using the enthalpy method.