Preparation and properties of shape-stabilized heat storage phase change materials in solar greenhouse

Octadecane-lauric acid/expanded graphite shape-stabilized phase change materials (OC-LA/EG), which is suitable to heat storage for solar greenhouse production, were prepared by using the eutectic mixture of octadecane (OC) and lauric acid (LA) as phase change material, porous expanded graphite (EG) of high adsorption characteristics as supporting matrix. The structure and properties of the materials were studied by ESEM, DSC and the test of melting and solidification process. As the result, the eutectic mixture can be uniformly absorbed in the worm-like pores of the expanded graphite by capillary forces, which can prevent the eutectic mixture from permeating outwards, and the mass fraction of the eutectic mixture in OC-LA/EG is found to be 80.47%. The phase change temperature and latent heat of OC-LA/EG is 24.12°C and 151.4J/g respectively. Its thermal conductivity are high owing to the large thermal conductivity of graphite, and the time of storing and releasing of the shape-stabilized phase change material obviously becomes shorter than that of the eutectic mixture.