Comparing the efficiency of Kalina cycle system 11 (KCS11) and Kalina cycle system 111 (KCS111) based on different decision variables. The results were compared with some benchmarks in the literature. From a thermodynamics perspective, and apart from KCS111's complex configuration and high costs, it is more efficient than the base cycle, KCS11.
Kalina cycle system (KCS) is a modified Rankine cycle proposed by Alexander Kalina, which operates with water-ammonia solution instead of pure water. The new mixture's boiling point and temperature change differ from a pure fluid. Apart from being a toxic gas, it is well-established that Ammonia can be integrated into the water without applying any modifications to the cycle. Furthermore, since Ammonia has a lower boiling point than water, the new mixture could take advantage of the temperature difference between the source and sink. Due to this exciting characteristic in capturing the low-temperature heat source's power, the Kalina cycle system can be used in parallel with geothermal sources, solar cells, or even reusing industrial waste heat, e.g., cement kilns.
The inlet fluid is supposed to be at three different temperature levels, very low, low, and intermediate. The decision variables are pressure levels, mass flow rate, and ammonia concentration. Exergy and thermal efficiency are taken as the objective function, and the novel double pressure Kalina cycle and the base Kalina cycle are compared. Results show that the Kalina cycle system named 111 is much more efficient than the base cycle, KCS11. It is also demonstrated that raising the heat source temperature increases the exergy efficiency of the base cycle, KCS11, while the new cycle's exergy efficiency, KCS111a, remains nearly the same. Engineering Equation Solver (EES) has been used to develop the codes.