| As the main energy consumption raw materials mainly represented by oil,coal and natural gas are facing increasing risks,the situation of energy supply and demand is worsening.Energy consumption in the field of construction accounts for a large proportion of the world's total energy consumption,and building energy conservation plays a crucial role in alleviating energy shortage.In this work,phase change materials are used as energy storage media incorporated into building cement mortar.Thus,the indoor temperature environment can be improved,the thermal comfort of buildings can be enhanced and the utilization rate of energy can be increased depending on the latent heat storage and release characteristics of phase change materials.In this paper,the inorganic hydrated salt of disodium hydrogen phosphate dodecahydrate with high latent heat,low price and rich source was used as phase change energy storage material.A carbon nanofiber-expanded graphite hybrid structure form-stable phase change material was prepared by physical mixing and impregnation.The results show that carbon nanofibers can effectively improve the heat transfer performance and form-stable ability of hydrated salt phase change materials;DSC indicated a good heat storage capacity of DSP/CNF-EG,the latent heat was 208.9 J g-1and the phase change temperature was 33.7?;the latent heat of the DSP/CNF-EG composite was hardly degraded after 200 thermal cycles,showing a favorable thermal stability.The prepared form-stable hydrated salt phase change material was added to cement mortar according to the mass ratio instead of sand,forming phase change energy storage mortar.Thus,the thermal properties of obtained phase change energy storage mortar was investigated.The result showed the thermal conductivity of phase change energy storage mortar from 1.173 W/m·K decreased to 0.726 W/m·K,the specific heat capacity from 1.263 k J/kg·K increased to 1.621 k J/kg·K compared with those of the control cement mortar;Also,the inner surface temperature peak of the phase change energy storage mortar plate was 5.8?lower than that of the control cement mortar heating-cooling test,and the temperature difference located in the center of the chamber was 1.6?.Furthermore,the temperature time curves of the two measuring points were obviously slower than that of the control cement mortar,showing good temperature regulation performance.The pore structure,bearing capacity and damping performance of phase change energy storage mortar were studied as well.The results showed that the hydrated salt form-stable phase change material had a significant effect on the porosity and macroporous content of cement mortar,the porosity increased from 12.18%to 14.74%,and the porosity of pore larger than 100 nm increased from 51.1%to 63.7%;Due to the significant increase of porosity and macropore content,it also had a great impact on the bearing capacity of phase change energy storage mortar.The compressive strength decreased from 40.9 MPa to 12.5 MPa,and the flexural strength decreased from 7.4MPa to 3.3 MPa,but its strength index still met the application standard of building envelope;The introduction of hydrated salt form-stable phase change material also had a significant improvement on the damping performance of phase change energy storage mortar.The damping factor increased from 0.63 to 1.91,showing the increasement of203.1%,which exhibited that the damping performance was significantly enhanced,thus demonstrating a potential seismic application around building seismic. |
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