The Structure And Performance Of Porous Mineral Based Shape-stabilized Phase Change Materials For Thermal Energy Storage

With the continuous growth of population and the rapid development of economy,energy and environment issues have gradually become the key factors restricting social development.The application of phase change materials(PCMs)in building to realize the storage and release of heat energy is of great significance to reduce building energy consumption.However,there is a shortage of cheap commercial PCMs with suitable phase change temperature.Moreover,there are still some problems hindering its development,such as leakage and low thermal conductivity of PCMs.In this paper,Porous materials like diatomite,mesoporous silica,attapulgite were used as carriers to take advantage of their unique pore structure characteristics,and to prepare non-encapsulated shape-stablized PCMs(ss-PCMs)with adjustable phase change temperature and excellent thermal storage performance.The phase change temperature of the composites can be adjusted between 20 and 30“C,and the enthalpy is between 50 and 80 J/g.After 1000 cycles of cooling and heating,there is no obvious deteriation of phase change performance.The composites have good long-term thermal stability and excellent heat storage and release performance.The research are expected to provide technical support for the low cost and high efficiency application of ss-PCMs in buildings.At the same time,a new way is developed for the high value-added utilization of mineral materials such as diatomite and attapulgite,which has good scientific significance and application prospects for the realization of building energy conservation and the utilization of non-metallic mineral resources.PCMs such as paraffins,fatty acids and PEG with low temperature were studied.The phase change temperature and enthalpy of paraffin are about 10-50? and 160-270 kJ/kg respectively and the binary fatty acids are in the range of-22.6-54.01? and 120.1 J/g-178.7 J/g respectively.The phase change temperature of polyethylene glycol(PEG)with low average molecular weight is about 16-40?.A series of ss-PCMs were prepared with different diatomite,mesoporous silica and attapulgite as carriers by melt infiltration method.The ss-PCMs have good thermal stability without leakage.After 200 and 1000 thermal cycles,the thermal properties have not changed significantly and have good long-term thermal stability.The heat storage and release curve shows that the ss-PCMs have good heat storage and release and temperature regulation performance.The interaction mechanism between porous mineral material carriers and organic PCMs was explored,and the influence of pore structure characteristics on the crystallization behavior of phase change materials was obtained.The results show that the phase change temperature decreases compared with those of pure PCMs,and the vairation is proportional to the interfacial interaction and inversely proportional to the pore size.At the same time,the nano-confinement effect of the carrier material was revealed,and the phase change heat transfer process was analyzed.The effect of MCM-41 on the micro-nano confinement of organic PCMs is enhanced in the order of RT21(-CH3 functional group),CA-PA(-COOH functional group)and PEG600(-OH functional group).'The carriers not only play a supporting frame,but also enhance thermal conductivity and thus strengthen heat transfer process.Ordered pore structure is more conducive to heat conduction.The results provide a theoretical and methodological basis for the controllable preparation,performance control and application of porous mineral ss-PCMs.