# Energy Analysis of Kalina and Kalina Flash Cycles Driven by Renewable Energy
## 3 Results and Discussion
### Effects of Flash Pressure in Kalina Flash Cycle (KFC)
Consequently, the ratio of TB1 power production to total output decreases, and the effects of flashing on the heat transfers at regenerator and HRVG are reduced. Figure 3 shows the dependence of exergy destruction ratios of condenser (\(Dc\)), flash vessel (\(Df\)), and power components (\(Dw\)) on the flash pressure for ammonia fractions of 40%, 60%, and 80% in KFC. As flash pressure increases, exergy destruction ratio of condenser decreases due to the decreased heat transfer at condenser, and that of the flash vessel decreases because of the declined difference of the separator pressure and flash pressure. But the exergy destruction ratio of power components increases with the increase of flash pressure because the resulting higher pressure drop in turbine 2 enhances power production. When flash pressure is specified, making the mixture richer in ammonia results in an increase of exergy destruction of the condenser and decreases of exergy destruction of the flash vessel and power components. All of them change more slowly against flash pressure as the ammonia fraction increases. Figure 2: Dependence of \(\eta_{ex}\), \(Ds\), and \(Dr\) on the flash pressure for some values of \(x_{b}\). Figure 4 shows the dependence of (a) separate and (b) cumulative ratios of exergy consumption on the flash pressure for the ammonia mass fraction of 40%. As seen from Equation (24), the sum of the exergy efficiency and total exergy destruction ratios equals unity, and the distributions of the exergy efficiency and exergy destruction ratio are usually represented with the band graphs or pie charts. In the cumulative graphs [22; 23], the magnitude of the exergy efficiency or an exergy destruction ratio is denoted as the distance between the non-crossing data lines. Therefore, the cumulative graph for a specified flash pressure corresponds to a single band graph and a cumulative graph can be considered as the two-dimensionally extended band graph for varying values of the flash pressure. Example data of separate and cumulative ratios of exergy consumption for \(x_{b}=40\%\) and \(P_{f}=12\) bar are listed in Table 3, and also numerically illustrated in Figure 4b. A maximum point exists in the exergy efficiency (\(\eta_{ex}\)) curve. As flash pressure increases, exergy destruction ratios of power components (\(Dw\)) and regenerator (\(Dr\)) increase; by contrast, exergy destruction ratios of condenser (\(Dc\)), HRVG (\(Ds\)), and flash vessel (\(Df\)) decrease. The exergy destruction ratios of the rest components (\(Dm\), \(Dv\), \(Dco\)) are lower than 3% and insignificant. Of all components, exergy destruction ratio of flash vessel decreases most rapidly: from 17.2% at 4 bar to 0.3% at 23 bar. The largest exergy destruction occurs in a condenser for flash pressures below 20 bar, and in power components above 20 bar. For example, at flash pressure of 5 bar and \(x_{b}=40\%\), Figure 4 shows that \(\eta_{ex}=29.6\%\), \(Ds=16.1\%\) (second), \(Dr=3.1\%\), \(Dc=22.0\%\) (highest), \(Df=14.5\%\) (third), \(Dv=0.1\%\), \(Dm=0.1\%\), \(Dw=10.8\%\), and \(Dco=2.9\%\). Therefore, the top three sources of exergy destruction are condenser, HRVG, and flash vessel. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Type** & \(\eta_{ex}\) & \(Ds\) & \(Dr\) & \(Dc\) & \(Df\) & \(Dv\) & \(Dm\) & \(Dw\) & \(Dco\) \\ \hline separate & 0.394 & 0.122 & 0.070 & 0.180 & 0.054 & 0.006 & 0.005 & 0.142 & 0.027 \\ cumulative & 0.394 & 0.516 & 0.586 & 0.766 & 0.820 & 0.826 & 0.831 & 0.973 & 1.000 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Example data of separate and cumulative ratios of exergy consumption for \(x_{b}=40\%\) and \(P_{f}=12\) bar. Figure 3: Dependence of \(Dc\), \(Df\), and \(Dw\) on the flash pressure for some values of \(x_{b}\). Figure 5 shows the dependence of (a) separate and (b) cumulative ratios of exergy consumption on the flash pressure for the ammonia mass fraction (\(x_{b}\)) of 60%.