Preparation And Performance Optimization Of Medium And High Temperature Composite Phase Change Heat Storage Materials Based On Solid Waste

Phase change materials,as a new type of thermal energy storage material,can be used to improve the efficiency of energy utilization such as fossil,water and wind energy,and further make some contribution to the goal of achieving carbon peak and carbon neutralization.The development of phase change materials is limited by the shortcomings of leakage and it is caustic.In order to solve this problem,people use porous mineral matrix materials with high compressive strength and high thermal stability to load phase change materials,composite phase change materials can be prepared to effectively improve the disadvantages of phase change materials such as easy leakage.In this experiment,the composite phase change materials prepared by loading sodium nitrate with two kinds of solid wastes,stone-sawing mud and gold tailings,have good thermal conductivity,thermal diffusion coefficient and energy storage density,which can not only improve the disadvantages of single phase change material such as easy leakage,low thermal conductivity and poor thermal stability,but also explore a new way for the resource utilization of solid wastes.Through extensive experiments,the best formulations of high-performance composite phase change thermal storage materials were explored by using two solid wastes,stone-sawing and gold tailings,and their properties and structures were characterized,and the thermal properties of the two materials were further optimized.The main conclusions are as follows:（1）The stone-sawing mud-based composite phase change materials were successfully sintered and formed at 400°C using saw clay as the substrate.The results showed that the highest loading rate of stone-sawing mud to the phase change material Na NO₃ was 50 wt.%.Under the condition of no leakage of phase change material,the T_M of phase change occurs at 306.78℃,and the enthalpy of phase change is 79.86 J/g,the optimum compressive strength was 23.14 MPa,and the optimum thermal conductivity was 0.696 W/（m·K）.The thermal properties of the composite did not change obviously after 100 cycles of absorption and exothermic heat,and the stone-sawing mud matrix composite phase change material has good thermal stability.（2）In the experiments exploring the loading performance of gold tailings,it was found that the loading capacity of gold tailings was slightly lower than that of stone-sawing mud,reaching only 40 wt.%.However,the composite phase change material of gold tailings has higher mechanical properties with an optimum compressive strength of36.66 Mpa.Under the PCM no leakage of phase change material,the phase transition temperature and enthalpy are 297.96℃and 63.25 J/g respectively,the optimal thermal conductivity of gold tailings composite phase change heat storage material is 0.689W/（m·K）.（3）The optimization of the performance of the stone-sawing mud-based composite phase change thermal storage material by adding graphite,which was found that the optimum thermal conductivity of the composite phase change thermal storage material was improved to 2.421 W/（m·K）after adding graphite and no leakage of the phase change material.The improved optimum thermal conductivity of 2.205 W/（m·K）was obtained by the experiments of performance optimization with the addition of graphite without the leakage of phase change material,which is 336%higher than the thermal conductivity of the gold tailings-based composite phase change material without the addition of graphite;in the absence of the energy storage density of these materials have no significant changes under the condition of no leakage of phase change material.