Numerical investigation of the effect of fin inclination on melting dynamics and energy storage in a PCM-filled square enclosure

Phase-change material (PCM) latent-heat storage systems are energy inefficient due to low thermal conductivity, resulting in slow melting and limited capacity. This paper uses numerical analysis to study the effects of fin angle on melting, fluid motion, and net energy storage in a square PCM enclosure. Using a COMSOL Multiphysics enthalpy–porosity model, RT27 PCM was heated by a uniform flux of 1000 W m⁻² while the other walls were adiabatic. Ten configurations were investigated: no fins; one horizontal fin; and fins inclined at 15°, 30°, 45°, and 60°. Heat was input to either the left or right enclosure wall. Temperature and velocity fields were assessed at 1200, 2400, and 3600 seconds to observe the conduction–natural convection transition. Fins at 30–45° always produced the best results. At these angles, broad, essentially uniform isotherms formed early on, and vigorous, cavity-spanning vortices-maintained buoyancy-driven circulation long after melting had begun. By 2400 seconds, these shapes had melted, resulting in a considerably larger liquid fraction than in the horizontal or no-fin cases. By 3600 seconds, substantial melting had occurred. In marked contrast, the 15° fin yielded only moderate benefits, while at 60°, flow was concentrated in thin vertical channels, stifling convection and forming extensive solid PCM areas even after 3600 seconds of heating. Moderate fin inclinations of 30–45° thus offer the best balance of conduction and natural convection, facilitating increased melting rates, increased latent heat utilisation, and more consistent temperature field outcomes. These results provide practical design advice for high-performance PCM storage in building energy control, advanced electronics cooling, and solar thermal systems.