Preparation And Thermal Performance Research Of Sodium Acetate Trihydrate Composite Phase Change Heat Storage Material

With the rapid development of society, the contradiction between the massive consumption of fossil energy and the worsening environment is becoming more and more obvious. Improving energy utilization is the main method to alleviate the contradiction between energy and environment. Phase change energy storage material is a kind of material that can realize the time-space conversion of thermal energy, which is of great significance to improve the utilization of energy. Sodium acetate trihydrate is a common phase change material, which has a series of advantages, such as large amount of latent heat of phase change, low-cost and wide source. It’s widely used in household heat storage, heat pump, industrial waste heat recovery, etc. However, due to its low thermal conductivity and low heat release rate. Therefore, it is the key to improve the thermal conductivity and the heat transfer rate of the material. Aiming at solving the problem of sodium acetate trihydrate disadvantages, such as its low thermal conductivity and low heat release rate. In this paper, mixed addition method was proposed to improve the thermal conductivity of materials. And researching how different additives affecting the performance, meanwhile doing comparative analysis.In the paper, expanded graphite was used as the material to enhance thermal conductivity, Sodium acetate trihydrate is the phase change heat storage material. Method of melt blending was applied to producing composite phase-change thermal energy storage materials, composed of expanded graphite and Sodium acetate trihydrate. In order to characterized and tested micro morphology and thermal properties of the composite materials, and researching addition amount of expanded graphite, particle size, and the influence of filling different particle sizes mixed on the composite thermal conductivity, microstructure of composites, undercooling, performance of heat storage and latent heat and phase transition temperature, the paper adopting a series of measures, such as using DSC and SEM, setting up heat storage and heat release test system. The results are as follows:1. Expanded graphite appeared agglomeration phenomenon in composite materials and the coefficient of thermal conductivity was lower under the condition of low amount of additives. When the amount of expanded graphite reached to 0.25g, expanded graphite reached the percolation threshold and disperse uniformly in composite materials, the thermal conductivity was 2.32W/(m·k), latent heat of material reduced 3.3% compared with sodium acetate trihydrate matrix, the super-cooling degree of composite stayed a steady value,1.7℃ after multiple cycles, showing perfect cycling performance.2. the 320 mesh expanded graphite had low thermal conductivity and had significant trend to show up agglomeration phenomenon, compared with sodium acetate trihydrate matrix. The largest gap of thermal conductivity between 320 mesh and 50 mesh expanded graphite was 0.30 W/(m·K), However, both of them had the same the phase transition temperature, rage of 56℃-57℃. The gap was shortened to 0.19 W/(m·K) when expanded graphite reach the percolation threshold. The supercooling degree of 320mesh expanded graphite composite materials became lower, the latent heat was 238.234 J/g. Compared with The latent heat of 50mesh expanded graphite composite materials increased by about 9J/g.3. When the 320 mesh to 50 mesh expanded graphite ratio was 3:5, expanded graphite form satisfied thermal conductivity net chain, the thermal conductivity of composite materials became 2.89W/(m·K), Heat storage and heat release time were greatly reduced.320mesh expanded graphite composed little influence on latent heat of composite materials, Phase transition temperature increased about 1℃. The super-cooling degree of composite stayed a steady value, 1.2℃.