# Modeling and Key Parameter Interaction Analysis for Ship Central Cooling Systems
## 3 Calculation Model
### Establishment of the Simulation Model  
In this paper, the central cooling system of a certain type of ship was taken as the research object, and its dynamic simulation model was established in the Simulink environment using the physical network method. The basic parameters for the model's design service speed (100% load) operating condition are detailed in Table 1. The simulation system consisted of a mutually coupled high-temperature fresh water loop, low-temperature fresh water loop, and seawater loop. The high-temperature fresh water loop model mainly included the main engine jacket water heat load model, high-temperature fresh water cooler model, fresh water generator model, and dynamic model of the high-temperature fresh water three-way valve (diverting/mixing). The low-temperature fresh water loop model integrated models of key components, such as the central cooler, main engine air cooler, main engine lubricating oil cooler, low-temperature fresh water diverting three-way valve, and other auxiliary cooling equipment. The seawater loop model mainly included the seawater pump model, central cooler (seawater side) model, piping model, etc. The overall structure of the constructed central cooling system Simulink simulation model is shown in Figure 2.  
\begin{table}
\begin{tabular}{c c c} \hline
**Parameter Category (Quantity/Unit)** & **Parameter Name** & **Design Value** \\ \hline Seawater Pump Set (2) & Single Seawater Pump Flow Rate & 320 m\({}^{3}\)/h \\  & Single Seawater Pump Head & 25 m \\  & Single Seawater Pump Power & 37 kW \\  & Seawater Pump Speed & 1760 rpm \\ \hline Low-Temperature Freshwater Pump Set (2) & Single Low-Temperature Freshwater Pump Flow Rate & 180 m\({}^{3}\)/h \\  & Single Low-Temperature Freshwater Pump Head & 25 m \\  & Single Low-Temperature Freshwater Pump Power & 22 kW \\  & Low-Temperature Freshwater Pump Speed & 1760 rpm \\ \hline \end{tabular}
\end{table}
Table 1: Modeling parameters and benchmark values.  
\begin{table}
\begin{tabular}{c c c} \hline
**Parameter Category (Quantity/Unit)** & **Parameter Name** & **Design Value** \\ \hline High-Temperature Freshwater Pump (1) & High-Temperature Freshwater Pump Flow Rate & 640 m\({}^{3}\)/h \\  & High-Temperature Freshwater Pump Head & 25 m \\  & High-Temperature Freshwater Pump Power & 74 kW \\  & High-Temperature Freshwater Pump Speed & 1760 rpm \\ \hline Plate Heat Exchanger (2) & Central Cooler Heat Transfer Area & 200 m\({}^{2}\) \\ \hline Main Engine (1) & Main Engine Power & 9480 kW \\  & Main Engine Cooling Water Flow Rate & 120 m\({}^{3}\)/h \\ \hline Auxiliary (2) & Single Auxiliary Machine Power & 660 kW \\  & Auxiliary Cooling Water Flow Rate & 120 m\({}^{3}\)/h \\ \hline System Heat Load & Total Heat Load of High-Temperature Freshwater Circuit & 1910 kW \\  & Total Heat Load of Low-Temperature Freshwater Circuit & 4490 kW \\ \hline System Design & Seawater Temperature & 32 \({}^{\circ}\)C \\  & Freshwater Temperature & 36 \({}^{\circ}\)C \\  & Main Engine Jacket Water Cooler Interl Temperature & 80 \({}^{\circ}\)C \\  & Main Engine Jacket Water Cooler Outlet Temperature & 65 \({}^{\circ}\)C \\  & Low-Temperature Freshwater Three-Way Valve Outlet Temperature & 36 \({}^{\circ}\)C \\ \hline \end{tabular}
\end{table}
Table 1: _Cont._  
Figure 2: _Cont._