Experimental and numerical investigations on heat transfer characteristics of thermal energy storage systems with discontinuous fins: Effect of inclination angle

To address the slow thermal response and uneven temperature distribution caused by the low thermal conductivity of phase change materials, this study experimentally compares the heat storage and release performance of novel discontinuous fins versus conventional straight fins under inclined conditions. Furthermore, it systematically investigates the influence of four inclination angles (45°, 60°, 75°, and 90°) on the melting and solidification processes of the discontinuous-fin configuration. The results show that at an inclination angle of 60°, the discontinuous fins, which enhance natural convection through their contraction-expansion regions, reduce the temperature uniformity coefficient (σ) by 38.5% during melting and by 40.45% during solidification, compared to straight fins. The inclination angle exerts distinct regulatory effects on melting and solidification. For the melting process, dominated by natural convection, the inclination angle plays a significant role: the vertical (90°) case yields the shortest melting time, which is 36.6% shorter than that at 45°; the 60° case achieves the highest temperature response coefficient, while the 45° case offers the best temperature uniformity. For the solidification process, governed primarily by heat conduction, the effect of inclination angle is weaker: the 45° case gives the shortest solidification time, 15% shorter than that at 90°, while the improvement in temperature uniformity is only 3.1%. These findings elucidate the coupled heat transfer mechanism between discontinuous fins and inclination angle, providing a theoretical basis for the design of latent heat thermal energy storage systems under variable operating conditions.