## 5 Result and Discussion
### Thermal Performance  
In Figure 5, the net power output increases with \(T_{\text{g1}}\). The DORC net power output is mainly affected by HTL working fluids, and LTL working fluids have minimal influence on the net power output. When HTL working fluids are the same, the relative deviation ( \(\mid\) maximal net power output\(-\)minimal net power output \(\mid\)/minimal net power output \(\times\) 100%) of the net output power affected by different LTL working fluids is less than 3%. Thus, selecting a suitable HTL working fluid is important. When \(T_{\text{g1}}\) is 523.15-598.15 K, cyclopentane and R1234 ze(E) are used, and the maximal net power output is 56.9-117.3 kW. When \(T_{\text{g1}}\) is 603.15-618.15 K, cyclohexane and R1234 ze(E) are used, and the maximal net power output is 125.6-133.4 kW. When \(T_{\text{g1}}\) is raised to 623.15 K, the HTL and LTL optimal working fluids are benzene and R1234 ze(E), respectively, and the maximal net power output is 142.4 kW. Table 7 presents the optimal working fluids and the corresponding net power outputs. R1234 ze(E) is optimal for LTLs when the HTL working fluids are cyclopentane, cyclohexane, and benzene. \(T_{\text{g1}}\) will not affect the optimal LTL working fluid. When the HTL working fluid is toluene, the PPTD of the condenser/evaporator will be higher than \(\Delta T_{\text{pp2}}\) when R1234 ze(E) is used for the LTL considering the lower limits of the HTL condensation and the LTL evaporation temperatures. Therefore, R245 fa is used for maximizing the net power output. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameters** & **Symbol** & **Value** \\ \hline PPTD of HTL/K & \(\Delta T_{\text{pp1}}\) & 20 \\ PPTD of LTL preheater and & & \\ condenser/evaporator/K & \(\Delta T_{\text{pp2}}\) & 10 \\ PPTD of LTL condenser/K & \(\Delta T_{\text{pp3}}\) & 5 \\ cooling water inlet temperature/K & \(T_{\text{w1}}\) & 298.15 \\ cooling water outlet temperature/K & \(T_{\text{w3}}\) & 303.15 \\ turbine efficiency/\% & \(\eta_{\text{t}}\) & 80 \\ working fluid pump efficiency/\% & \(\eta_{\text{p}}\) & 75 \\ cooling water pump efficiency/\% & \(\eta_{\text{p}\text{pw}}\) & 85 \\ cooling water pump head/m & \(H\) & 20 \\ ambient temperature/K & \(T_{0}\) & 288.15 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: DORC parameters. Figure 5: Effects of \(T_{\text{g1}}\) on the net power output. In Figure 5a, when cyclopentane is used for HTL, the net power output increases with \(T_{\text{g1}}\). The optimal HTL evaporation temperature does not reach the upper limit when \(T_{\text{g1}}\) is 523.15-553.15 K, and the increasing trend of the net power output remains unchanged. The optimal HTL evaporation temperature reaches the upper limit, and the optimal HTL superheat degree is 0 K when \(T_{\text{g1}}\) increases to 558.15 K. The HTL evaporation temperature is suitable for \(T_{\text{g1}}\), and the increment rate of the net power output increases. The evaporation temperature becomes unsuitable for increasing \(T_{\text{g1}}\), and the optimal HTL superheat degree is not 0 K when \(T_{\text{g1}}\) increases to 568.15 K. The increment rate of the net power output decreases. When cyclohexane is used for the HTL, \(T_{\text{g1}}\) is 523.15-598.15 K, the optimal HTL evaporation temperature does not reach the upper limit, and the PPTD of the HTL evaporator is at VPP. The net power output increases with the \(T_{\text{g1}}\). When \(T_{\text{g1}}\) increases to 603.15 K, the PPTD of the HTL evaporator occurs at PPP, \(T_{\text{g3}}\) cannot decrease, and the increment rate of net power output decreases. Figure 5b exhibits that, when benzene is used for HTL and \(T_{\text{g1}}\) is 523.15-613.15 K, the optimal HTL evaporation temperature does not reach the upper limit, and the net power output increases with \(T_{\text{g1}}\).