## 3 ORC System Structure and Design Parameters  
The arrangement of the evaporator in the flue of the main engine within the ORC system, when used for recovering waste heat from the engine's exhaust gas, poses several drawbacks. Directly heating the working fluid in the evaporator with high-temperature flue gas not only raises the exhaust gas back pressure of the main engine and hampers its efficiency but also facilitates the occurrence of carbon corrosion in the evaporator. Henceforth, in this research paper, the waste heat from the main engine's exhaust gas is recuperated in an indirect manner. To begin, the waste heat from the main engine's exhaust gas is used to power the waste gas boiler, which produces a vast amount of high-temperature water steam. The high-temperature water steam is then used as the ORC system's heat source to heat the working fluid in the evaporator, reducing the detrimental influence of the ORC system evaporator on the main engine's performance. Furthermore, \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Main Engine** & **Exhaust Gas** & **Jacket Water** & **Lubricating Oil** & **Other Kinds of** & **High-Temperature** \\
**Load** & **Waste Heat** & **Waste Heat** & **Waste Heat** & **Waste Heat** & **Steam Heat** \\
**(\%SMCR)** & **kW (Calculation)** & **kW (Query)** & **kW (Query)** & **kW (Calculation)** & **kW (Calculation)** \\ \hline
60 & 6820 & 1840 & 1090 & 2403 & 6138 \\
65 & 7171 & 1930 & 1150 & 2798 & 6454 \\
70 & 7509 & 2030 & 1200 & 3258 & 6758 \\
75 & 7921 & 2130 & 1260 & 3706 & 7129 \\
80 & 8839 & 2220 & 1320 & 4201 & 7955 \\
85 & 8852 & 2320 & 1380 & 4665 & 7967 \\
90 & 9404 & 2420 & 1440 & 5152 & 8464 \\
95 & 10,000 & 2510 & 1500 & 5675 & 9000 \\
100 & 10,716 & 2610 & 1570 & 6136 & 9644 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Amount of various main engine waste heats under different loads. Figure 1: Heat balance analysis diagram of the main engine under different loads. it can ensure the stability of the ORC system's heat source quality, which is beneficial to actual ship application and ORC system operation dependability. Among several possible organic working fluids, R365 mfc offers the advantages of excellent safety, good chemical security, lower ODP and GWP values, and other properties that make it appropriate for waste heat recovery below 200 \({}^{\circ}\)C [19]. As a result, R365 mfc is chosen as the ORC system's circulating working fluid in this investigation. Figure 2a,b illustrate the structure composition of the built basic ORC (BORC) system and warmed (PORC) system. BORC is driven by high-temperature water vapor generated from the ship's exhaust gas boiler, and uses seawater as the cooling water for the system. The liquid mass (R365 mfc) is pressurized and fed into the evaporator by the mass pump, the heat emitted by the high-temperature water vapor is absorbed in the evaporator and turned into a high-temperature, high-pressure gaseous mass, which is expanded into the expander to do work and drive the generator, resulting in the generation of electricity. The gaseous mass from the expander outlet enters the condenser and is cooled and condensed into a liquid mass by the outboard seawater and then enters the storage tank, which is then pressurized by the mass pump and enters the next cycle of power generation. The PORC system differs from the BORC system in that it includes a preheater in front of the evaporator and uses the cylinder liner cooling water to preheat the working mass before it enters the evaporator.