Evaluating biodegradable alternatives to petroleum-based phase change materials in enclosed cavity heat transfer

Finding biodegradable alternatives to petroleum-based phase change materials (PCMs) is essential for sustainable thermal energy storage. This study presents a numerical investigation comparing paraffin wax (petroleum-based) and beeswax (biodegradable) in two-dimensional enclosed aluminum cavities of varying height-to-width ratios (H/L = 0.5, 1, 2) and heating configurations (bottom and side heating), using finite-element method. A novel viscosity model for each PCM was developed using existing experimental data to improve prediction accuracy. Key features such as convective cell formation, thermal plumes, and viscous fingering were analyzed through time-resolved velocity, temperature, and liquid fraction contours. The results showed that paraffin wax exhibits faster melting due to lower viscosity and thermal conductivity, but also more unstable convective behavior. Beeswax, in contrast, displayed slower yet more uniform melting with greater thermal stability. The highest heat transfer was observed for H/L = 2 due to stronger vertical convection. Bottom heating was more effective in promoting uniform melting compared to side heating, which resulted in thermal stratification. This study demonstrates that biodegradable PCMs like beeswax can offer comparable thermal performance with improved stability, making them viable for sustainable thermal management systems.