Recycling of Tetra Pak for Space and Water Heating by Blending with Phase Change Materials

Abstract

A rapid rise in demands for thermal comfort in the building sector necessitates higher energy consumption for air conditioning, ventilation, space, and water heating systems. Recently, phase change materials (PCMs) have gained much attention from researchers for passive heating/cooling of space and water. PCM can store/release thermal energy as latent heat during its phase change process isothermally. Moreover, PCM facilitates solar energy harvesting by photothermal conversion and storage. However, major limitations of PCM include low thermal conductivity, leakage during phase change, and lack of photoabsorbance. Therefore, in this study, the shape-stabilized phase change composites were prepared by melt blending of Paraffin Wax (PW), Tetra Pak (TP), and expanded graphite (EG). PW is an organic PCM, widely being studied due to its high enthalpy, availability at various melting points, and chemical and thermal stability. In addition to providing shape stability and thermal conductivity enhancement of PCM, the usage of TP promotes the recycling of TP waste into useful products. The addition of EG contributes to the thermal conductivity increase of 3.6 times that of pure PW. Moreover, the excellent photoabsorption of EG and TP effectively converted the photo energy to thermal energy and stored it as latent heat by PW in the composite. Two types of composites using PW of melting points 44 ℃ and 64 ℃ were exhibited a photothermal conversion and storage efficiency of 80 and 55 %, respectively and which is promising for solar water heating applications.