Performance research on modified KCS (Kalina cycle system) 11 without throttle valve

Two modified systems based on a KCS (Kalina cycle system) 11 with a two-phase expander to substitute a throttle valve are proposed. The two-phase expander is located between the regenerator and the absorber in the B-modified cycle and between the separator and the regenerator in the C-modified cycle. A thermodynamic performance analysis of both the original KCS 11 and the modified systems is carried out. The optimization of two key parameters (the concentration of working fluid and the temperature of cooling water) is also conducted. It is shown that the two modified cycles have different performance under the investigated conditions. Results also indicate that the C-modified cycle can obtain better thermodynamic effect than the B-modified cycle. The temperature of cooling water plays an important role in improving the system performance. When the cooling water temperature drops from 303 K to 278 K, the C-modified cycle thermal efficiency can be improved by 27%. - Highlights: • Throttling valve is replaced by a two-phase expander to recover the expansion work. • Thermodynamic performance of two modified cycle systems is very different. • The maximum increase of work output by C-modified cycle compared with KCS (Kalina cycle system) 11 is 9.4%. • The ranges of ammonia content of B-modified cycle are rather larger