## 3 Results  
### Protted Plant Protection Modules  
The experimental results from the tests described in Section 2.4 are presented in Figure 10. In the first case (100% PLA module), the thermal response was characterized by distinct stages of sensible and latent heat dissipation. The dissipation of sensible heat as the temperature decreased from 22 \({}^{\circ}\)C to the solidification range was observed to take approximately 60 min. During this period, the material exhibited a linear cooling trend that is typical of sensible heat loss. As the system entered the liquid-solid phase transition, the temperature remained stable between 6 \({}^{\circ}\)C and 4 \({}^{\circ}\)C, indicative of the latent heat being released during crystallization. This phase transition lasted for approximately 326 min, demonstrating the material's significant capacity to maintain a near-constant temperature, a behavior that underscores the thermal buffering potential of the PLA module. This latent heat stabilization is critical for applications requiring prolonged thermal regulation without active energy input. Following the completion of the phase change, the temperature of the module continued to drop, ultimately reaching 0 \({}^{\circ}\)C after a total duration of 497 min. This final cooling phase highlights the completion of the solidification process and the resumption of sensible heat dissipation. The extended duration of thermal regulation observed in this experiment underscores the effectiveness of the 100% PLA module in maintaining thermal stability over extended periods, making it a promising candidate for applications where passive temperature control is essential.  
In the second case (PLA-metal module), the dissipation of sensible heat as the temperature dropped from 22 \({}^{\circ}\)C to the solidification range also occurred over a span of approximately 60 min. This similarity in initial cooling behavior between the two modules suggests that the presence of the metal component does not significantly alter the rate of sensible heat loss prior to the phase change. During the liquid-solid phase transition, latent heat stabilized the temperature between 6 \({}^{\circ}\)C and 4 \({}^{\circ}\)C for about 343 min, slightly longer than the 326 min observed for the 100% PLA module. This extended period of thermal stabilization indicates that the addition of metal marginally enhances the module's capacity to regulate temperature during the phase change process. Finally, the temperature of the PLA-metal module reached 0 \({}^{\circ}\)C after 507 min, which is 10 min longer than the time required by the 100% PLA module. This slight improvement in performance is consistent with the expected behavior of composite materials, where the integration of metal could potentially enhance thermal conductivity. The performance of the PLA-metal module, while slightly better than that of the PLA-only module, underscores the limitations imposed by the inherent thermal conductivity of the PCM utilized in the study. The minimal difference in performance between the two modules suggests that variations in module design, specifically through the incorporation of metal, have a limited impact on the overall passive heating capability. This observation highlights that the thermal conductivity of  
Figure 10: Experimentally determined cooling curve of fully 3D-printed PLA and PLA–metal module.  
the PCM is a more critical factor than the choice of insulation and housing materials in determining the effectiveness of passive thermal management systems [21].