## 3 Results and Discussion
### Heat Transfer Process of Phase Change Panels  
Figure 8 illustrates the temperature variation curves on both surfaces of phase change panels in experimental groups 1 and 2, with the heat transfer process of experimental group 1 annotated. Due to the rapid temperature changes on the heating surface of the phase change panel and the varying temperature distribution of the PCM at different locations, the temperature change on the non-heating surface is used as the standard for dividing the overall heat transfer process of the phase change panel. From Figure 6, it can be seen that the heat transfer process of the phase change panel is divided into three main stages [27]. Stage one is the sensible heat storage stage in the solid phase before the phase change. During this stage, the PCM on the non-heating side has not yet melted and remains in a solid state. The initial temperature is relatively low and the rate of temperature increase is rapid. For experimental group 1, this stage is located in the OA section of the curve and lasts from 0 to 40 min, while for experimental group 2, it is located in the OB section and lasts from 0 to 60 min. This indicates that experimental group 1 starts the next stage 20 min earlier than experimental group 2. Stage two is the latent heat storage stage during the phase change. In this stage, the PCM partially melts and exists in a solid-liquid coexistence state, resulting in a distinct temperature plateau. The temperature of the PCM rises slowly within the phase change range of 28 \({}^{\circ}\)C to 29 \({}^{\circ}\)C. As the temperature on the heating surface continues to rise, the PCM accelerates its melting. After 160 min, the PCMs inside the panels of both experimental groups 1 and 2 are completely melted, and both groups start the next stage simultaneously. For experimental group 1, this stage is located in the AC section of the curve and lasts from 40 to 160 min, while for experimental group 2, it is located in the BC section and lasts from 60 to 160 min. Figure 8: The temperature variation curves on both surfaces of phase change panels in experimental groups 1 and 2 (the stages are set according to group 1). Stage three is the sensible heat storage stage in the liquid phase after the phase change. In this stage, the PCM is completely melted and remains in a liquid state. The temperature continues to rise, but the rate of temperature increase gradually decreases. For experimental group 1, this stage is located in the CD section of the curve, while for experimental group 2, it is located in the CE section. During this stage, both experimental groups 1 and 2 occur between 160 and 300 min, but the temperature of experimental group 1 is higher than that of experimental group 2. After 300 min, the temperature increase of both the heating and non-heating surfaces of the phase change panels slows down and approaches a critical value. Due to the thermal resistance of the PCM, there is a fixed temperature difference between the heating and non-heating surfaces, and the entire phase change panel eventually reaches thermal equilibrium. In terms of the heating rate, the sensible heat storage phases in both the solid and liquid states are relatively fast. The heating rates during these two phases are primarily influenced by the specific heat capacity, density, and thermal conductivity of the PCM. The driving force for heat transfer is the temperature difference, which is greatest at the initial stage when the temperature difference between the PCM and the heating surface is the largest. As the heating process progresses, the temperature difference gradually decreases, leading to a slowdown in heat transfer. Additionally, the specific heat capacity of liquid paraffin is higher than that of solid paraffin, resulting in a slightly higher heating rate during the solid-phase sensible heat stage compared to the liquid phase.