Phase-change materials (PCMs) are capable of storing or releasing a substantial amount of thermal energy within a small volume through the latent heat of fusion during phase transitions of melting and solidification, i.e., from solid to liquid or vice versa, in a near isothermal process. However, commonly used organic PCMs, such as paraffin wax, exhibit very low thermal conductivity, contributing to an adverse increase in overall thermal resistance and, thus, a slow thermal response. This limitation often becomes a bottleneck for the system from a thermal performance standpoint. To mitigate this issue, the present work explores the fabrication of heat sinks incorporating nano-structured graphitic foams, including carbon foam (CF) and expanded graphite (EG), as well as micro-structured metal foams such as open-cell copper foam (OCCF), all impregnated with a paraffin-based PCM with a melting temperature near 37 °C. This study focuses on applying passive thermal management strategies to design efficient heat sinks capable of maintaining the temperatures of battery modules and electronic circuits within an acceptable thermal safety threshold for small satellites and spacecrafts, exemplified by the OPTIMUS and Pumpkin battery modules designed for CubeSats with a nominal cross-sectional area of almost 4″ × 4″. Temperature responses and average overall thermal resistances for fabricated heat sinks are accordingly assessed and compared in a vacuum chamber to simulate space conditions. Furthermore, the impact of operating pressure on the thermal performances of various heat sinks will be investigated by executing the same tests in both atmospheric and vacuum conditions. The findings demonstrate a superior thermal performance of composite heat sinks integrating carbon foam and copper foam into the paraffin PCM compared to the baseline PCM heat sink under both vacuum and atmospheric operating pressure conditions.
Kabir et al. (Sun,) studied this question.