Akademik Veri Yönetim Sistemi
Journal of Thermal Analysis and Calorimetry, cilt.150, sa.14, ss.11035-11048, 2025 (SCI-Expanded)
This study presents a novel thermal analysis method that enables the experimental calculation of time-dependent solid, mushy, and liquid phase fractions during the melting process of phase change materials (PCMs) in latent heat thermal energy storage (LHTES) systems. Unlike previous studies that predominantly rely on numerical simulations, the proposed method allows direct and detailed experimental determination of phase transformations using calibrated infrared thermography combined with grouped temperature analysis. This innovation addresses a significant gap in the experimental literature, as accurate temporal mapping of phase distributions is essential for enhancing the thermal performance of LHTES units in practical applications. The method was implemented and evaluated on a cubic LHTES unit filled with A42 paraffin-based PCM under varying heating powers and directions. For this purpose, the mass fractions of solid, mushy, and liquid phases were experimentally calculated in a time-dependent manner for the first time in both bottom-heated and side-heated LHTES systems at heating powers of 30, 40, and 50 W. Using the calculated mass fractions, experimental phase change contours for the PCM melting process were presented for the first time in the literature. The results show that the melting behavior of PCM differs significantly depending on the direction of heating, while similar thermal patterns are observed across different heating powers for the same direction. The formation of unstable mushy zones increases with the dominance of convective currents. At a heating power of 50 W, the complete melting time was found to be 120 min for the bottom-heated LHTES and 180 min for the side-heated LHTES. The maximum mushy fraction reached approximately 12% at 100 min in both configurations; however, this peak occurred near the end of the melting process for the bottom-heated case, and around the midpoint for the side-heated case. The obtained time-dependent temperature distributions and phase fraction contours provide valuable experimental insights into PCM melting behavior and serve as a reliable reference for validating numerical models and guiding future studies focused on improving the performance of LHTES systems.