Experimental and Numerical Investigation of the Thermal Performance of Paraffin-Based PCM Encapsulated in Different Metallic Capsules for Solar Water Heating Systems

The current work experimentally and numerically examined the effect of the metal material used for the encapsulation of the latent heat thermal energy storage made of paraffin wax and incorporated in the forced-circulation solar water heating system. Based on the findings obtained, the following conclusions can be drawn: 1.                Charging behaviour of the PCM system was highly affected by the encapsulation material. The higher thermal conductivity of the material decreased conductive thermal resistance, increased heat transfer, and caused the faster PCM melting process. 2.                Aluminium performed the best thermal behaviour compared with the studied materials and reached the highest values of thermal efficiency of the collector (64.3%), stored thermal energy (4320 kJ), and latent heat storage (2200 kJ) due to high thermal conductivity of aluminium. 3.                Cast iron had moderate thermal properties while stainless steel had the lowest values of charging efficiency due to low thermal conductivity of the material and lower heat penetration in the encapsulant. 4.                The developed 3D CFD model effectively predicted the transient thermal behaviour of the system with a good correlation with experimental data (RMSE = 0.82 °C, MAPE = 1.56%, R² = 0.991). 5.                This method of analysis is a robust approach to analyze the encapsulation materials and improve the efficiency of solar thermal energy storage based on PCMs without requiring excessive experimental tests. Future research directions can include studying the cyclic behavior of PCMs over an extended period of time, analyzing the techno-economic performance of various other encapsulating materials, and employing advanced heat transfer augmentation methods such as composite PCMs and metallic foams.

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