混合式填充床熔盐蓄热系统热性能分析

THERMAL PERFORMANCE ANALYSIS OF MOLTEN-SALT HEAT STORAGE SYSTEM IN MIXED PACKED-BED

基于混合扩散中心对称（D—C）模型，考虑自然对流现象对液态相变材料（PCM）导热性能的影响，建立填充床蓄热系统的热力学模型，开发数值计算程序并通过文献实验数据对其进行验证。研究混合式填充床熔盐蓄热系统在工程规模下蓄、放热过程的循环热特性；从温度分布和填充床热装载率分布的角度评价蓄热系统的热力性能；并研究填充床结构对蓄热系统放热时间和系统容量因子的影响规律。结果表明随着总相变填充比例的增加，系统容量因子呈先增大后减小的趋势，系统放热时长则一直增加，且增幅逐渐减小；在一定的总相变填充比例下，存在最优的高、低温相变填充层体积比使系统的放热时长和容量因子达到最大值。

The thermodynamic model of packed-bed heat storage system was built based on mixed dispersion-concentric symmetry （DC） model, considering the effect of natural convection on the thermal conductivity of liquid phase change material （PCM）, developing the numerical calculation program and verifying through literature experimental data. The thermal cycling characteristics of mixed packed bed molten salt heat storage system during the project scale storage and exothermic process were studied. The thermal performance of the heat storage system was evaluated from the temperature distribution and the thermal loading rate distribution of packed bed. The effect of the packed-bed structure on the heat release time and the capacity factor of the heat storage system was studied. The results showed that with the increase of the total phase change filling ratio, the capacity factor of the system first increases and then decreases, while the system exothermic time increases continuously, and the increases gradually reduce; Under certain total phase change filling ratio, there exists optimal volume ratio for high and low temperatures of phase change filling layer which maximizes the exothermic duration and capacity factor of the system.