###### Abstract  
Utilizing phase change materials (PCMs) in passive energy-saving wall panels to regulate indoor temperatures during hot seasons can improve people's thermal comfort and reduce the energy consumption of air conditioning systems. This study is based on the hot summer and warm winter climatic characteristics of Hainan. According to local meteorological data and residents' living habits, a suitable phase change temperature of approximately 28 \({}^{\circ}\)C was determined. A composite PCM of paraffin and stearic acid n-butyl ester was prepared and tested for thermal performance. Encased in an aluminum box with non-penetrating aluminum rods to enhance heat transfer, the phase change panel was applied to the inner side of exterior walls. Thermal tests demonstrated that increasing the mass ratio of stearic acid n-butyl ester to paraffin lowers the melting point and latent heat. At a 3:7 mass ratio, the melting point of the composite PCM was 28.30 \({}^{\circ}\)C, and the latent heat was 128.26 \({\rm J/g}\). The 20 mm thick panel maintained a stable phase change process, with unheated surface temperatures between 28 \({}^{\circ}\)C and 29 \({}^{\circ}\)C for up to 180 min. Compared to panels without aluminum rods, those with rods exhibited a 20% longer phase change time, extended heat transfer paths, and reduced liquid-phase convective heat transfer rates, demonstrating improved PCM utilization. Therefore, the phase change panel with non-penetrating aluminum rods exhibits excellent insulation and temperature control properties. composite phase change material; heat transfer enhancement; passive energy-saving wall panels +
Footnote †: journal: Applied  
by 13% in the liquid state. [PERSON] [4] incorporated 2%, 4%, and 6% multi-walled carbon nanotubes (MWCNTs) into paraffin and compared the internal temperatures. The results indicated that as the mass fraction of MWCNTs increased, the temperature rise rate of the composite PCM improved. The composite PCM containing 6% MWCNTs exhibited the best temperature rise effect and thermal performance. [PERSON] [5] found that the melting time of copper foam/paraffin composite PCM was reduced by 20.5% compared to pure paraffin. [PERSON] [6] prepared a composite PCM with a mass ratio of 4:1 between the PCM and expanded graphite using the melt blending method. Its thermal conductivity reached a maximum value of 3.084 W/(m\(\cdot\)K) at 40 \({}^{\circ}\)C. [PERSON] [7] investigated the effect of fin length-to-diameter ratio on the phase change process in a rectangular cavity. They found that fins with a high length-to-diameter ratio exhibited melting and solidification rates that were 16% and 15% faster, respectively, compared to fins with a low length-to-diameter ratio. Currently, heat transfer enhancement methods are mainly divided into three categories: the first method involves adding high thermal conductivity metal nanoparticles or carbon nanotubes to the PCMs; the second method involves combining PCMs with high thermal conductivity porous materials, such as metal foams or expanded graphite; the third method involves incorporating high thermal conductivity metal fins, such as plate-like or needle-like fins, into the PCMs. Adding metal fins can increase the heat transfer area, thereby accelerating convective heat transfer within the PCMs and enhancing the heat storage and release rates. Due to their robust structure and the increasingly mature manufacturing techniques, metal fins have been widely used in various heat exchange devices, such as heat sinks and heat exchangers. To address the issue of liquid phase leakage during the phase change process of solid-liquid PCMs, encapsulation methods have emerged as a key breakthrough for applying this technology in the construction field [8]. [PERSON] [9] mixed the PCM with cement mortar to produce a hybrid mortar. [PERSON] [10] added microencapsulated paraffin to concrete to produce phase change concrete.