## 3 Results and Discussion
### Comparison of the ORC\({}_{\text{CTE}}\) System and ORC\({}_{\text{DTE}}\) System
Therefore, adopting predicted turbine efficiency in the ORC system optimization is necessary, and can enhance the reliability and accuracy of the analysis results. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameters** & **Constant Turbine Efficiency** & **Predicted Turbine Efficiency** \\ \hline Evaporation temperature/K & 411.33 & 406.06 \\ Condensation temperature/K & 306.04 & 307.62 \\ Thermal efficiency & 0.150 & 0.139 \\ Specific investment cost/\$\$ kW\$-1 & 4415.14 & 4426.27 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Final optimal solution for the ORC system with different types of turbine efficiency. Figure 8: Pareto frontier of ORC\({}_{\text{CTE}}\) system and ORC\({}_{\text{DTE}}\) system. Figures 9 and 10 present the distribution of the optimal evaporation temperature and condensation temperature for the ORC\({}_{\text{CTE}}\) system and the ORC\({}_{\text{DTE}}\) system. As mentioned, the ORC\({}_{\text{CTE}}\) system has lower thermal efficiency and a higher specific investment cost than ORC\({}_{\text{DTE}}\) system, as shown in Figures 9 and 10. The optimal evaporation temperature for the ORC\({}_{\text{DTE}}\) system is distributed over a wider range than the ORC\({}_{\text{CTE}}\) system, as shown in Figure 9. For ORC\({}_{\text{DTE}}\) system the optimal evaporation temperature is distributed in the range of 393-412 K; while for ORC\({}_{\text{CTE}}\) system the optimal evaporation temperature is distributed in the range of 397-412 K. As shown in Figure 10, the condensation temperature for the ORC\({}_{\text{DTE}}\) system is distributed in a slightly wider range than the ORC\({}_{\text{CTE}}\) system. For ORC\({}_{\text{CTE}}\) system, most of the condensation temperature is distributed in the range of 303.15-307.5 K; while for ORC\({}_{\text{DTE}}\) system, the condensation temperature is distributed in the range of 303.15-308.5 K. It can be found that the impact of turbine efficiency selection on the evaporation temperature is greater than that on the condensation temperature. Sensitivity Analysis and Comparison of the ORC\({}_{\text{CTE}}\) System and the ORC\({}_{\text{DTE}}\) System  
The heat source temperature and ambient temperature are not constant in practical engineering application. Therefore, in this section, sensitivity analysis with regard to heat source temperature and the ambient temperature is conducted for both ORC systems. Multi-objective optimization is carried out at each operating condition, and the final optimal solution at each operating condition is selected using the aid of ideal point method. Figure 11 shows the variation of the optimal evaporation temperature with the increasing heat source temperature. With the increasing heat source temperature, the optimal evaporation temperature increases. Additionally, the optimal evaporation temperature for ORC\({}_{\text{CTE}}\) system increases faster. The optimal evaporation temperature for the ORC\({}_{\text{CTE}}\) system is higher than that for the ORC\({}_{\text{DTE}}\) system, and the difference between the two ORC systems becomes larger with the increasing evaporation temperature, the maximum difference is 10.44 K. Figure 12 shows the variation of the optimal condensation temperature with the increasing heat source temperature. With the increasing heat source temperature, the optimal condensation temperature increases slightly. The optimal condensation temperature for the ORC\({}_{\text{DTE}}\) system is higher than that for the ORC\({}_{\text{CTE}}\) system. It also can be found  
Figure 9: Distribution of optimal evaporation temperature. that the optimal condensation temperature for the ORC\({}_{\text{CTE}}\) system varies in the range of 305.5-306.5 K, while for ORC\({}_{\text{DTE}}\) system, the optimal condensation temperature varies in the range of 306.5-308.5 K, which is slightly wider.