## 2 Thermodynamic Analysis
### System Design  
This study performed a thermodynamic analysis of a marine diesel engine exhaust gas-driven RC for used ships. Technical data, operating data, and heat balance for the marine diesel engine are provided in Tables 4-6, respectively. The values are provided for 100% load [33]. The pump, recuperator, and expander types are a centrifugal pump, a counterflow plate heat exchanger, and an axial turbine. Also, the condenser is seawater-cooled with counterflow and a plate heat exchanger. The designed simple RC system within the scope of this study is illustrated in Figure 1. Simple RC systems in ship engines harness energy recovery by evaluating the hot gases and waste heat emitted from the ship's engine exhaust. When the ship's engine operates, exhaust gases are released at high temperatures. These hot gases are directed into the exhaust gas boiler. The working fluid in the boiler begins to evaporate in this hot environment. The evaporation process signifies the transition of the liquid to the vapor phase and the gaining of expansion potential by the vapor. The resulting vapor expands in a turbine, converting it into mechanical energy. During this expansion phase, the turbine rotates, driving a generator to produce electrical energy. The steam exiting the turbine typically enters a cooling system. In this stage, the vapor is condensed back into the liquid phase. This process ensures that the liquid working fluid returns to the boiler. With the liquid returning to the boiler, the RC system completes a cycle, and the process begins anew. The designed RC with a recuperator system within the scope of this study is provided in Figure 2. Passing the liquid working fluid through the recuperator enhances system efficiency and recovers more energy from waste heat. The hot fluid emitted from the exhaust of the ship's engine enters the exhaust gas boiler. At this stage, the liquid working fluid begins to vaporize, and during the vaporization process, the temperature rises. The recuperator facilitates the heat transfer between the hot vapor-containing fluid and the cold fluid, which will be used later in the system. This process increases system efficiency by recovering waste heat. The energy of the hot vapor is transferred to the working fluid, which cools in the recuperator, condensing some of the vapor back into liquid form. The cooled fluid passing through the recuperator is typically sent back to the exhaust gas boiler with the assistance of a pump. Having regained heat and carrying vaporization potential, \begin{table}
\begin{tabular}{c c} \hline \hline
**Type of Waste Heat** & **Rate of Heat Transfer (kW)** \\ \hline Charge air & 220 \\ Lubricating oil & 85 \\ Exhaust gases & 523 \\ Radiation & 42 \\ Jacket water & 161 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Heat balance at full load for marine diesel engine. Figure 1: Simple RC system. this fluid starts the cycle anew. This process establishes a loop within the system, and passing the liquid working fluid through the recuperator enhances the boiler's efficiency. When returned to the boiler, the liquid passing through the recuperator starts at a lower temperature. However, while recuperators improve efficiency by recovering waste heat, they also introduce additional pressure drops and require more complex control systems, which should be considered in this study. Operations Challenges and Potential Limitations  
The marine diesel engine exhaust heat-driven organic and inorganic Rankine cycle is required to increase the ship's energy efficiency. However, several operational difficulties and possible restrictions are associated with its application in maritime environments. These operational and technological limits are taken into consideration when outlining the challenges and limitations. The [PERSON]'s Research World Fleet Register, the open literature, and ship owners and an engine manufacturer provided the data for the review [18].