## 3 Results and Discussion
### The Simulation Application Effect of Phase Change Panels  
Figure 10 shows the temperature variation curves on both surfaces of phase change panels in experimental groups 3 and 4, with the heat transfer process of experimental group 4 annotated. As illustrated, for experimental group 3, the latent heat storage stage is located in the BD section of the curve and lasts from 120 to 300 min, while for experimental group 4, it is located in the AC section and lasts from 80 to 240 min. This indicates that experimental group 4 completes the solid-phase sensible heat storage stage 40 min earlier than experimental group 3 and reduces the phase change time by 20 min.  
This is because both groups 3 and 4 have aluminum rods, which similarly weaken liquid-phase convective heat transfer. When the heating side is on the welded aluminum rod side, the aluminum rods act as efficient heat transfer paths, accelerating the melting of the PCM in the vicinity of the rods. This reduces the thermal resistance of the solid PCM near the heating surface and increases the overall melting rate of the PCM, thereby shortening the phase change time. Conversely, when the heating side is on the non-welded aluminum rod side, during the entire solid-phase sensible heat storage stage and the initial phase of the latent heat storage stage, the temperature of the PCM near the unheated surface remains relatively low. At these stages, the heat transfer enhancement effect of the aluminum rods is not fully realized, which better utilizes the thermal resistance of the PCM and prolongs the phase change time.  
Therefore, in practical applications of phase change panels, it is advisable to position the phase change panel on the inner side of an exterior wall, with the aluminum rods connected to the side of the panel facing the indoor heat source and not penetrating the PCM. This configuration ensures that the heat transferred through the main structure of the wall is absorbed by the PCM, thereby delaying and reducing the indoor peak temperature.  
As shown in Figure 8, the phase change time for experimental group 1 is 120 min. Under identical conditions, with heating applied to the welded aluminum rod side, the phase change time for experimental group 4 extends to 160 min. This discrepancy arises because the heating temperature for experimental group 1 is higher than that for experimental group 4. In practical applications of phase change panels, it is crucial to incorporate an adequate amount of insulation material to optimize the heat storage performance of the PCM within the wall panels.  
Figure 10: The temperature variation curves on both surfaces of phase change panels in experimental groups 3 and 4 (the stages are set according to group 4).  
Field measurements of building exterior walls in Hainan during the summer indicate that from 9:00 a.m. to 3:00 p.m., with adequate sunlight, the exterior surface temperature of the walls can rise rapidly, exceeding 40 \({}^{\circ}\)C. Due to the insulation layer within the wall, the temperature on the side of the phase change panel near the exterior can reach up to 35 \({}^{\circ}\)C. As shown in Figure 8, the temperature on the interior side of the phase change panel increases slowly, with the rate of increase gradually diminishing. After 120 min, the temperature reaches approximately 28 \({}^{\circ}\)C, at which point the PCM begins to melt. The heat transferred through the main structure of the wall is absorbed by the phase change panel, maintaining the temperature on the interior side between 28 \({}^{\circ}\)C and 29 \({}^{\circ}\)C for up to 180 min. This demonstrates the excellent insulation and temperature control effects of the phase change panel, delaying and reducing the peak indoor temperature, enhancing thermal comfort [28], reducing the usage time of air conditioning [29], and lowering the building's energy consumption.