## 3 Results and Discussion
### Comparison of the ORC\({}_{\text{CTE}}\) System and ORC\({}_{\text{DTE}}\) System
Compared with the optimal condensation temperature, it can be found that the variation range of the optimal evaporation temperature is much wider, which indicates that the influence of heat source temperature on optimal evaporation temperature is greater than that on optimal condensation temperature. Figure 13 shows the variation of turbine efficiency with the increasing heat source temperature. Turbine efficiency decreases with the increasing heat source temperature. The reason is that with the increasing heat source temperature, the optimal evaporation temperature increases faster than the optimal condensation temperature, which leads to the increases in pressure ratio. Thus, turbine efficiency decreases. The variation of the net power output at different heat source temperature is presented in Figure 14. For both ORC\({}_{\text{CTE}}\) system and ORC\({}_{\text{DTE}}\) system, the net power output increases with the increasing heat source temperature. However, the increasing rate of the net power output of ORC\({}_{\text{CTE}}\) system is higher than that of ORC\({}_{\text{DTE}}\) system. The reason is that for ORC\({}_{\text{DTE}}\) system, decreasing turbine efficiency decreases the increasing rate of net power output. Additionally, the net  
Figure 11: Optimal evaporation temperature at different heat source temperature. Figure 10: Distribution of optimal condensation temperature. power output of ORC\({}_{\text{CTE}}\) system is always higher than that of ORC\({}_{\text{DTE}}\) system, and the difference of net power output between the two ORC system becomes larger the increasing heat source temperature, the maximum relative deviation is 11.54%. Figures 15 and 16 show the optimal evaporation temperature and the optimal condensation temperature at different ambient temperatures, respectively. Figure 15 shows the variation of the optimal evaporation temperature with the increasing ambient temperature. The optimal evaporation temperature for the ORC\({}_{\text{DTE}}\) system increases with the increasing ambient temperature, while the optimal evaporation temperature for the ORC\({}_{\text{CTE}}\) system stays at approximately 411 K, which indicates that the ambient temperature has almost no effect on the optimal evaporation temperature for ORC\({}_{\text{CTE}}\) system. Additionally, the optimal evaporation temperature for ORC\({}_{\text{CTE}}\) system is higher than that for ORC\({}_{\text{DTE}}\) system, and the difference decreases gradually with the increasing ambient temperature. Figure 16 shows the variation of the optimal  
Figure 14: Net power output at different heat source temperature. Figure 12: Optimal condensation temperature at different heat source temperature. Figure 13: Turbine efficiency at different heat source temperature. condensation temperature with the increasing ambient temperature. The optimal condensation temperature linearly increases with the increment of ambient temperature. In addition, the optimal condensation temperature for the ORC\({}_{\text{DTE}}\) system is always higher than that for the ORC\({}_{\text{CTE}}\) system, and the difference value stays at approximately 2 K. From Figures 15 and 16, it can also be found that the influence of ambient temperature on the optimal condensation temperature is greater than that on the optimal evaporation temperature. Figure 17 shows the variation of turbine efficiency with the increasing ambient temperature. With the increasing ambient temperature, turbine efficiency almost increases monotonically. From Figures 15 and 16, it can be found that the increasing rate of optimal condensation temperature is greater than that of optimal condensation temperature. Thus the pressure ratio decreases and the turbine efficiency increases accordingly. Figure 18 shows the net power output at different ambient temperatures. The net power output of both ORC systems decreases with the increment of ambient temperature. Moreover, the decreasing rate of the net power output for ORC\({}_{\text{CTE}}\) is higher than that of the ORC\({}_{\text{DTE}}\) system.