## 4 Simulation Results and Analysis
### Melting Process  
The melting process of phase change materials mainly occurs on the sea level, and the whole process platform is basically in a static state. Therefore, it is a fixed wall-temperature boundary condition, and its boundary temperature is the ocean surface-water temperature.  
Figure 4: Liquid fraction distribution for the cylindrical heat exchanger with diameter of 0.07 m and height of 0.95 m.  
Figure 5: Liquid fraction distribution when seawater temperature is 7 \({}^{\circ}\)C.  
In this paper, 26 \({}^{\circ}\)C is taken. Since the temperature of the platform is gradually increasing during the floating process, the initial temperature of the phase change material during the melting process is set to the melting-point temperature, \(T_{\text{m}}\).  
2.1 The Influence of Different Sizes of Cylindrical Phase change Heat Exchangers on the Melting Process  
From Figures 6 and 7, it can be clearly seen that with the decrease in the outer diameter of the cylinder (i.e., the decrease in the thickness of the phase change material), the phase change melting rate is significantly accelerated, and the total liquid-phase fraction is significantly increased. This is also because the smaller the thickness of the phase change material is, the smaller the thermal resistance is, the stronger the heat transfer is, and the faster the melting process is; in addition, the smaller the outer diameter of the cylinder and the longer the cylinder, the larger the heat transfer surface area and the stronger the heat transfer. The numerical analysis results show that the time required for the two cylindrical phase change heat exchangers with different outer diameters to complete the melting process is 2130 and 520 s, respectively.  
2.2 The Influence of Cylindrical Phase change Heat Exchanger and Cylindrical Phase change Heat Exchanger on the Melting Process  
In the analysis, four cylindrical phase change heat exchangers with a diameter of 0.07 m and a length of 0.95 m were used to install phase change materials, which were equivalent to the volume of the cylindrical phase change heat exchanger.  
Figure 6: Liquid fraction distribution for the cylindrical heat exchanger with outer diameter of 0.3 m and height of 0.45 m.  
Figure 7: Liquid fraction distribution for the cylindrical heat exchanger with outer diameter of 0.26 m and height of 0.95 m.  
Comparing Figures 7 and 8, it can be clearly seen that, under the same phase change time, the total liquid-phase ratio of the cylindrical phase change heat exchanger is significantly larger than the total liquid-phase ratio of the cylindrical phase change heat exchanger. The reason is also that the larger thickness of the phase change material in the cylindrical phase change heat exchanger and the smaller total outer surface of the heat exchange are not conducive to the heat exchange between the phase change material and the outside world. The numerical analysis results show that the time required for the cylindrical phase change heat exchanger to complete the melting process is 3100 s, which is much higher than the 520 s of the cylindrical phase change heat exchanger with the same height, and also higher than any of the cylindrical phase change heat exchangers mentioned above.