# Modeling and Key Parameter Interaction Analysis for Ship Central Cooling Systems
## 5 Results and Analysis
### Analysis of Key Parameter Sensitivity and Interaction  
As shown in Table 3, by observing the F-values of each factor, it can be inferred that main engine power, seawater pump speed, seawater temperature, and three-way valve opening had relatively significant effects on system energy consumption. The degree of impact of these important factors on system energy consumption was as follows: main engine power (\(X_{1}\)) > seawater pump speed (\(X_{3}\)) > seawater temperature (\(X_{2}\)) > three-way valve opening (\(X_{4}\)). Notably, the F-value for main engine power (\(X_{1}\)) was considerably larger than those of the other influencing factors, indicating its dominant impact on the energy consumption of the ship's central cooling system. Given that seawater pump speed (\(X_{3}\)) was the most critical adjustable operating parameter among these, and its optimal setting was dependent upon varying load (\(X_{1}\)) and seawater temperature (\(X_{2}\)), implementing precise variable frequency control for the seawater pump, tailored to the load and ambient temperature, represented a core and effective strategy for unlocking the energy-saving potential of this system. Furthermore, the three-way valve opening (\(X_{4}\)) should be synergistically optimized in accordance with the actual operating conditions to achieve optimal overall system energy performance. Figures 4(a) and 4(b) respectively present the response surface and contour plots illustrating the interaction effect of main engine power (\(X_{1}\)) and seawater pump speed (\(X_{3}\)) on system energy consumption. The curvature, gradient of the response surface, and the shape and distribution density of the contour lines intuitively reflected the main effects and interaction strength of each factor. As shown in Figure 4(a), the response surface exhibited a steep increasing gradient along the main engine power (\(X_{1}\)) axis, indicating that within the studied range, \(X_{1}\) was the dominant factor influencing system energy consumption, and its increase will lead to a significant rise in energy consumption. Along the seawater pump speed (\(X_{3}\)) axis, the response surface also showed an increasing trend, but with a relatively gentle gradient, suggesting that while seawater pump speed directly impacted energy consumption, its main effect strength was much weaker than that of the main engine power. From a physical mechanism perspective, the increase in main engine power directly determined the thermal load the system needed to dissipate, which was the primary cause of increased cooling demand and energy consumption. In contrast, an increase in seawater pump speed directly raised the pump's own operating power and the fluid's resistance loss in the pipeline, thereby jointly increasing the total system energy consumption. It is worth noting that when the main engine power was in the higher range, the gradient of the response surface along the seawater pump speed (\(X_{3}\)) axis significantly increased. This indicates that under high load operating conditions, the system's energy consumption becomes highly sensitive to changes in seawater pump speed. The contour plot in Figure 4(b) shows that the contour lines exhibited a distinct elliptical or curved shape, rather than nearly parallel straight lines, revealing a relatively significant interaction between main engine power (\(X_{1}\)) and seawater pump speed (\(X_{3}\)). This interaction implied that the effects of the two factors on energy consumption were not simply linearly additive but rather involved a synergistic effect. Specifically, when both main engine power and seawater pump speed were simultaneously at high levels, the system faced the dual pressures of increased thermal load and sharply increased pump power consumption, leading to a non-linear accelerated growth trend in total system energy consumption. This highlights the necessity of collaborative optimal control under such operating conditions.