# 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)  
In this section, a Kalina flash cycle (KFC) driven by a hot air with temperature of 150 \({}^{\circ}\)C and mass flow rate of 1 kg/s is simulated. Table 1 lists the basic system data to be input for simulation, which are taken similar to those of [15; 16] for comparison. Table 2 presents the thermodynamic and flow data at each node of KFC under the basic conditions. Here \(y\) denotes dryness factor which is defined as the ratio of the mass of vapor to the mass of mixture (liquid and vapor), thus \(y=0\) and \(y=1\) denote pure liquid and vapor, respectively. The table shows that for the ammonia mass fraction of basic solution of 60%, the mass fractions of primary and secondary vapors rise to higher than 85%, while those of primary and secondary solutions drop to around 30%; the condensing pressure is 7.54 bar. Figure 2 shows the dependence of the exergy efficiency and exergy destruction ratios of HRV (\(D\)s) and regenerator (\(Dr\)) on the flash pressure for ammonia fractions of 40%, 60%, and 80% in KFC. As flash \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Symbol** & **Description** & **Value** & **Unit** \\ \hline \(T_{\rm s}\) & Source temperature & 150 & \({}^{\circ}\)C \\ \(m_{\rm s}\) & Flow rate of source fluid & 1 & kg/s \\ \(T_{\rm H}\) & Separator temperature & 139.9 & \({}^{\circ}\)C \\ \(P_{\rm H}\) & Separator pressure & 24 & bar \\ \(x_{\rm b}\) & Basic mass fraction of ammonia & 60 & \% \\ \(P_{\rm f}\) & Flash pressure & 15 & bar \\ \(T_{\rm L}\) & Condenser outlet temperature & 40 & \({}^{\circ}\)C \\ \(T_{\rm c}\) & Coolant inlet temperature & 25 & \({}^{\circ}\)C \\ \(T_{\rm co}\) & Coolant outlet temperature & 30 & \({}^{\circ}\)C \\ \(T_{0}\) & Dead state temperature & 25 & \({}^{\circ}\)C \\ \(\Delta T_{\rm pp1}\) & Pinch point temperature difference of HRVG & 10 & \({}^{\circ}\)C \\ \(\Delta T_{\rm pp2}\) & Pinch point temperature difference of regenerator & 8 & \({}^{\circ}\)C \\ \(\eta_{\rm p}\) & Isentropic efficiency of pump & 60 & \% \\ \(\eta_{\rm t}\) & Isentropic efficiency of turbines & 75 & \% \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Base conditions of the system. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**No** & **Fluid** & \(y\) & **x** & **T** & **\(P\)** & **\(h\)** & **s** & **\(e\)** & **\(m\)** \\  & & **(\%)** & **(\({}^{\circ}\)C)** & **(bar)** & **(k/kg)** & **(k/kg-K)** & **(k/kg)** & **(kg/s)** \\ \hline
1 & AW & 0.50 & 60.0 & 139.  
pressure increases, exergy efficiency increases to reach a maximum value and decreases afterwards for \(x_{b}=40\%\). This behavior is the result of competition at turbine 2 between the positive effect that an increased pressure ratio enhances specific work and the negative effect of decreased mass flow rate, with increasing flash pressure. Exergy destruction ratio of regenerator is a monotonically increasing function of flash pressure owing to an enhanced heat transfer at regenerator, while exergy destruction ratio of HRVG monotonically decreases with flash pressure, which is because the working fluid enters HRVG with higher temperature and reduces heat transfer at HRVG. For a given flash pressure, exergy efficiency and exergy destruction ratio of regenerator are higher, but exergy destruction ratio of HRVG is lower for higher ammonia concentrations. The changing slopes of the exergy efficiency, and the ratios of exergy destruction of HRVG and regenerator, with respect to flash pressure are very gradual for the highest value of 80%; this implies that their changing slopes decrease with increasing ammonia concentration. It can be explained as follows. As the ammonia mass fraction becomes higher, the dryness factor of the working fluid at the end of HRVG becomes greater, which leads to higher mass flow rate at TB1 (\(m_{2}\)), and lower mass flow rate to the flash vessel (\(m_{3}\)) [16].