Encapsulation of paraffin-magnetite, paraffin, and polyethylene glycol in concretes as thermal energy storage

These investigations analyze the encapsulation of phase change materials (PCMs): paraffin-magnetite composite, paraffin, and polyethylene glycol (PEG) in concretes. The research aimed to analyze PCMs as a thermal energy storage medium. The concretes were fabricated using the composition of lightweight aggregate, cement, sand, and water. Copper tubes (diameter of 12.7 mm and length of 50 mm) with various formations were installed in the concretes (50 × 50 × 50 mm). The arrangements of the copper tube consist of four-square, four-cross, and six-rectangular tubes. The concretes were then cured for 28 days at an ambient temperature. The copper tubes were filled with the melting paraffin-magnetite composite, paraffin, and PEG. The PCMs analyses include morphology, melting point, latent heat, thermal conductivity, and melting phase transition. The temperature distributions on the concretes filled with the PCMs were monitored using thermocouples and a data logger. The DSC test suggested the highest melting point of 61.65 °C and latent heat of 161.53 J/g obtained in the PEG sample. Adding magnetite particles in paraffin could improve the thermal conductivity to 0.53 W/m·°C compared to paraffin only (0.32 W/m·°C) and PEG (0.28 W/m·°C). The melting phase behavior on the PCMs was affected by the melting point, latent heat, and thermal conductivity. The highest thermal resistance occurred on the concrete where the copper tube only contributes to the low thermal resistance.