# Energy Analysis of Kalina and Kalina Flash Cycles Driven by Renewable Energy
## 4 Conclusions  
The Kalina flash cycle (KFC) has been recently proposed to recover low-grade heat source. In the present study, exergetical and optimal performance analyses were comparatively conducted for the Kalina cycle (KC) and KFC driven by a hot air stream with 150 \({}^{\circ}\)C and 1 kg/s. The important system parameters for the analysis were flash pressure, basic ammonia fraction, and separator pressure. The dependence of the exergy efficiency and destruction at each component of the systems on these parameters were parametrically investigated. The main findings of the analysis are summarized as follows:  
1. In KFC, flash pressure yielding maximum exergy efficiency exists for each set of ammonia fraction and separator pressure. As flash pressure increases, the exergy destructions of power  
Figure 12: Dependence of (**a**) separate and (**b**) cumulative ratios of exergy consumption on the ammonia mass fraction for \(P_{H}\) = 48 bar in the KC.  
Figure 13: Dependence of (**a**) separate and (**b**) cumulative ratios of exergy consumption on the ammonia mass fraction for \(P_{H}\) = 48 bar in the KFC.  
component and regenerator increase; contrarily, those of the condenser, heat recovery vapor generator (HRVG), and flash vessel decrease. The largest exergy destruction occurs at condenser except when ammonia fraction is low and flash pressure is high; in which case it is largest at the power components.
2. In both the KC and KFC, the ammonia fraction producing maximum net power is higher than that yielding maximum exergy efficiency for each separator pressure. With respect to the change of separator pressure, maxima of net power production and exergy efficiency have a local maximum and local minimum, respectively.
3. As the ammonia fraction increases, exergy destructions of the condenser, HRVG, and coolant exhaust increase, while those of the power components, regenerator, and throttle valve decrease; the exergy efficiency shows decreasing, increasing-decreasing, and increasing behaviors for low, medium, and high separator pressures, respectively.
4. Identifying the most irreversible component depends on separator pressure and ammonia fraction. For low separator pressure, the component where the largest exergy destruction occurs is the condenser irrespective of ammonia fraction. For high separator pressure, however, it shifts from power components, to condenser, and to HRVG as the ammonia fraction increases.
5. The KFC showed superior maxima of net power production and system exergy efficiency compared to basic KC and potential for the recovery of the low-grade heat source.  
Conceptualization, K.H.K. and C.H.H.; methodology, K.H.K.; validation, H.J.K. and C.H.H.; formal analysis, K.H.K.; investigation, C.H.H.; data curation, H.J.K.; writing--original draft preparation, K.H.K.; writing--review and editing, H.J.K. and C.H.H.; funding acquisition, C.H.H. All authors have read and agreed to the published version of the manuscript.  
This research was funded by Kumoh National Institute of Technology.  
This research was supported by Kumoh National Institute of Technology.  
The authors declare no conflict of interest.