Composite phase change heat storage technology through the composite sensible heat storage and phase change heat storage materials, to avoid the sensible heat storage technology and phase change heat storage technology many shortcomings, has become a hot spot at home and abroad in recent years, but the traditional skeleton materials use natural minerals or their secondary products, large-scale mining or processing will destroy the local ecological environment and consume a large amount of fossil energy, in order to reduce the impact of the above problems on the environment, solid waste can be used to prepare composite phase change heat storage materials.
Calcium carbide slag is acetylene, polyvinyl chloride and other industrial solid waste produced in the production process, China produces more than 50 million tons per year, and the application of calcium carbide slag in the cement industry has been saturated, resulting in a large number of calcium carbide slag open air accumulation, ditch reclamation, serious damage to the local ecological environment, urgent need to explore new resource utilization methods.
In order to absorb industrial solid waste calcium carbide slag on a large scale and prepare low-carbon and low-cost composite phase change heat storage materials, researchers from Beijing University of Civil Engineering and Architecture proposed to use calcium carbide slag as the skeleton material to prepare Na2CO3/calcium carbide slag composite phase change heat storage materials by cold-pressing sintering method, and the specific steps are shown in the figure.
Considering the deformation, surface molten salt leakage and heat storage density, although the heat storage density of sample NC4 is the largest among the three composite phase change heat storage materials, the mass ratio of the composite phase change heat storage material corresponding to sample NC5 is considered to be the optimal ratio.
Subsequently, the team analyzed the macroscopic morphology, heat storage performance, mechanical properties, microscopic morphology, cyclic stability and material component compatibility of the composite phase change heat storage materials.
And mainly obtained the following conclusions:
01
The calcium carbide slag component has good compatibility with Na2CO3, which can replace the traditional natural skeleton material to synthesize Na2CO3/calcium carbide slag composite phase change heat storage materials, and large-scale resource recycling of calcium carbide slag to realize the low-carbon and low-cost preparation of composite phase change heat storage materials.
02
The 52.5% calcium carbide slag and 47.5% phase change material Na2CO3/composite can be used to prepare a composite phase change heat storage material with excellent performance, with no change and no leakage, with a heat storage density of up to 993 J/g, a compressive strength of 22.02 MPa, and a thermal conductivity of 0.62 W/(m•K) within 100~900 °C. After 100 heating/cooling cycles, the heat storage performance of the sample NC5 remained stable.
03
The thickness of the film layer determines the inter-particle force of the skeleton material and the compressive strength of the composite phase change heat storage material, and the composite phase change heat storage material prepared under the optimal mass fraction of the phase change material has the best mechanical properties.
04
The thermal conductivity of the skeleton material particles is the main factor affecting the heat transfer performance of the composite phase change heat storage materials, and the impregnation and adsorption of the phase change materials in the pore structure of the skeleton materials improves the thermal conductivity of the skeleton material particles, thereby improving the heat transfer performance of the composite phase change heat storage materials.
