Energy and exergy analyses of the Kalina system integrated with a two-phase turbine

The Kalina power cycle can be integrated with a two-phase turbine as a substitute for the expansion valve to yield useful mechanical energy. An energy- and exergy-based mathematical model was formulated to analyze and evaluate the performance of the proposed cycle in this study. Independent parameters, including the base ammonia-water solution concentration, separator pressure, temperature difference in the recuperator, and vapor turbine outlet pressure, were used to analyze the sensitivity of efficiencies. The results show that the proposed cycle is efficient in terms of energy and exergy efficiencies. The two-phase turbine power is much larger than the solution pump power, and the exergy destruction of the turbine is much smaller than that of a throttle valve. The effect of the base solution concentration was dominant. At low concentrations, the energy and exergy efficiency improvements were 140 % and 160 %, respectively. At high concentrations, the substitution was not significant because the solution flow rate through the two-phase turbine was negligible. Furthermore, the efficiency enhancement was notable at a high vapor turbine outlet pressure.