Preparation And Thermal Properties Of Organic Solid-solid Phase Change Materials For Middle And Low Temperature

Thermal energy storage can recycle temporarily unused or excess energy stored by certain media, for solving the energy supply and demand of mismatch between time and space. Phase change materials is an idealized medium, which can store and release energy by the phase transformation behavior. In recent years, low-temperature organic phase change material was a hot research topic, because of its moderate phase change temperature and high phase change latent heat.In this paper, we used active carbon granule(ACG) and expanded graphite(EG) with good absorption and thermal performance as supporting materials, polyethylene glycol(PEG), stearic acid and Paraffin as the main phase change materials. The phase change materials with different component ratio were prepared by melt-blending method based on physical absorption principle. The aging chamber was used to test macroscopic state of composite in the phase change process. Differential scanning calorimeter(DSC), thermo-gravimetry(TG) and thermal conductivity tester were used to execute phase change temperature, enthalpy, thermal stability and conductivity of the composite phase change material, respectively.The results show that low molecules organic materials(stearic acid and paraffin)-EG and/ or ACG composite phase change materials emerge poor form-stable performance. For organic polymer materials(PEG)-EG and/ or ACG composite phase change materials, when the content of ACG or EG is ≥ 16, PEG-based phase change materials present solid in the phase change process. With supporting material content increases, form-stable performance of ACG is stronger than EG.Moreover, with the increase of ACG or EG content, the experimental value of the enthalpy of composite material is lower than theoretical value(In addition to Paraffin/EG, small molecules wax into layer structure of EG to rearrangement.), but it still can be used beyond the scope, phase transition temperature keep substantially constant. When the percentage of supporting materials are equivalent, phase change enthalpy of PEG/EG composite phase change materials are higher than that of PEG/ACG.In additional, ACG and/ or EG can improve thermal conductivity of organic phase change materials, and thermal conductively of the composite phase change materials efficiently increased with ACG and/ or EG content. Notablely, the supporting material content(PEG, Paraffin, stearic acid) of composite phase change materials is equivalent, compared with ACG, EG can remarkable enhance the thermal conductivity of organic phase change material.The EG and/ or ACG can restrains thermal decomposition of organic phase change material and improves the heat resistance of materials. The results were attributed in porous structure of EG and/ or ACG to absorb organic phase change materials and their vapor decomposition...