Study On Preparation Of Graphite Based Composite Phase Change Materials And Application In Building Energy Conservation

Thermal energy storage technology is very important to improve the energy efficiencyand protect the environment, which is widely used in solar energy utilization, electricity peakvalley shift and the industrial waste heat recovery. The key of thermal energy storage is theutilization of thermal storage material with good performance. Organic phase changematerials (PCM) have advantages of low cost, stability and high storage density. But extantorganic PCM have unresolved problems, such as poor thermal conductivity, unstable chemicalperformance and flammability, which are obstacles for the common application in manyfieldsinvolved. Therefore, people are paying more and more attention to the difficult focus todevelop a new type of thermal energystorage composite PCM.In this paper, Expanded graphite was prepared by the microwave method, and theexpanded graphite based composite PCM were prepared by adsorption, such as lauric acid/EG,butyl stearate /EG and octadecane/EG composite PCM. All the composite PCM werecharacterized by SEM, DSC and XRD. It was shown that, the composite PCM with 90 % oflauric acid or butyl stearate or octadecane in mass ratio was still form-stable; The phasechange temperature of the EG-based composite PCM was similar to that of the pure organicPCM, its latent heat were close to the calculated value based on the mass ratio of the pureorganic PCM in the composite.The thermal storage cement was prepared bymixing butyl stearate /EG composite PCM oroctadecane/EG composite PCM with cement, and the effect of composite PCM on mechanicalproperties and heat transfer performance of the cement were studied. The results showed thatthe addition of composite PCM could reduce the compressive strength, the apparent densityand the thermal conductivity of cement. When the ratio of composite PCM to cement was10% by mass, the apparent density of cement board, the 7 days compressive strength and thethermal conductivitydecreased by10%, 56% and 16% respectively.A cube box was prepared with six cement boards, which contains different amount ofcomposite PCM. The temperature changes were investigated within the cube under thecondition of simulated solar radiation. The results showed that the temperature differencebetween inside and outside the cube became larger and larger with the increase of the contentof the composite PCM in the cement , which proved that PCM have a regulatory function onadjusting temperature of the house and can reduce the building energyconsumption.The thermal storage cement boards containing different amount of octadecane/EGcomposite PCM were put on hot plate. The cold sides temperature of cement boards was detected to study the energy storage function of octadecane/EG composite PCM bycomparing the cold side temperature of different boards. The result showd that the cold sidetemperature decreased with the amount of octadecane/EG composite PCM in the cementincreasing. The results proved that composite PCM have great function in energy storage, andthe more PCM in the buliding materials, the better efficiencyof the energystorage have.