Thermal Performance Improvement of Phase Change Plates in Underground Refuge Chambers Through Nano-Graphite Particles and Fins

As coal mining operations extend deeper underground, the importance of refuge chambers as temporary shelters for miners grows given the heightened risk of accidents. The severe geothermal conditions in deep mines present significant challenges to temperature regulation within these chambers, potentially subjecting miners to hazardous heat exposure. The utilization of phase change plates (PCPs) presents a promising approach to improving temperature regulation performance. To systematically investigate the enhancement effects of nano-graphite particles (NGPs) and fin structures on the thermal performance of phase change materials (PCMs), this study conducted thermophysical property tests and temperature-controlled melting experiments to analyze the influence of varying NGP concentrations on the thermal characteristics of PCMs, while observing their melting behavior. Four PCP models were designed: base PCM, PCM with NGPs, plate fin, and pin fin. Based on the enthalpy-porosity method, numerical simulations were performed to systematically evaluate the melting kinetics and temperature regulation performance of each design under extended operation conditions. The findings indicate that while NGP doping markedly increases the thermal conductivity and peak melting temperature of the PCM, it also results in a reduction in latent heat capacity. The NGP-enhanced No. 25 paraffin wax (RT25) PCP reduced the surface temperature by 1.02 °C compared to the base material. During extended operation, the NGP-based model outperformed others, maintaining effective temperature regulation for 149.8 h, 13 h longer than the base PCM and exceeding the standard requirement by 53.8 h. This underscores its notable advantages in thermal management. These advancements offer a valuable reference for the utilization of PCP in refuge chambers, thereby augmenting their temperature regulation capabilities.