Coupled effects of dome-shaped geometry and inclination on buoyancy-driven flow and melting dynamics in latent heat storage units

Combined effects of enclosure geometry and inclination angle on the melting behavior of coconut oil as a bio-based phase change material (PCM) were numerically assessed. A conventional square enclosure (SQ) and three different dome-shaped enclosures (D1, D2, and D3) with varying dome heights but identical PCM volumes were evaluated at four inclination angles of θ = 0°, 30°, 60°, and 90°. Simulations were conducted using the enthalpy-porosity technique, and the numerical procedure was validated against experimental data. The contour results indicate that the D3 configuration, which has the highest dome, redistributes the circulation in the upper region and facilitates the upward motion of thermal plumes. Quantitatively, tilting the reference SQ from θ = 0° to θ = 90° reduced the melting time from 111 to 49 min, achieving a 55.8% reduction. A corresponding reduction of 52.3% was observed for D3 configuration. Furthermore, at the vertical orientation (θ = 0°), the constant-volume D3 modification reduced the total melting time to 96.5 min, which was 13% lower than that of SQ. Additionally, in the side-heating orientation, SQ required 83.5 min to reach the target energy storage of 280 kJ, whereas D3 reached the same value in 62.5 min, corresponding to a 25.1% reduction in charging time. These outcomes show that the relative benefit of the constant-volume D3 configuration is greater in the side-heating orientation, where natural convection is weaker. Consequently, within the investigated two-dimensional, constant-volume configuration, the combined modification of the top boundary geometry and enclosure width is promising for improving melting and charging performance, particularly in the side-heating orientation.