KNO_(3)熔盐复合相变材料储热性能调控机理研究

Study on the Control Mechanism of Thermal Storage Performance of KNO_(3)Molten Salt Composite Phase Change Material

本文将热物理性能优异的SWCNT掺杂到KNO_(3)熔盐相变材料中,构建KNO_(3)-SWCNT熔盐复合相变材料的微观物理模型,对KNO_(3)-SWCNT熔盐复合相变材料的储热性能进行分子动力学模拟研究,计算得到了熔盐复合相变材料的微观结构参数和储热性能参数,并采用SWCNT表面电荷修饰的方法调控熔盐复合相变材料的储热性能,并揭示了储热性能调控的微观机理。研究发现,随着SWCNT质量分数fm的增加,熔盐复合相变材料的导热系数增大,而黏度、熔化焓、熔点均降低;随温度的升高,导热系数与黏度均降低;当fm从0增加到4.43%和8.48%时,平均导热系数增强了2.26%和28.01%,熔化焓分别降低32.31%和45.19%,SWCNT表面正电修饰可以改变熔盐复合相变材料的微观结构,增强原子之间的相互作用势能,可对熔盐相变材料的储热性能有效地进行调控,熔盐复合相变材料的导热系数平均增加了21.21%。

In this paper,SWCNT with excellent thermophysical properties is doped into KNO_(3)molten salt,and a microphysical model of KNO_(3)-SWCNT molten salt composite PCM is constructed.Molecular dynamics simulations were conducted on the thermal storage performance of KNO_(3)-SWCNT molten salt composite PCM,and the microstructure parameters and thermal storage performance parameters of the molten salt composite PCM are calculated,the surface charge modification of SWCNT method was used to control the thermal storage performance of molten salt composite PCM,and the micro mechanism of thermal storage performance control was revealed.It is found that with the increase of SWCNT mass fraction f_m,the thermal conductivity of molten salt composite PCM increase,and the viscosity,melting enthalpy,and melting point decrease.With the increase of temperature,the thermal conductivity and viscosity decrease;When f_mincreases from 0to 4.43%and 8.48%,the average thermal conductivity was increased by 2.26%and 28.01%,and the melting enthalpy decreases by 32.31%and 45.19%,respectively.The surface positive modification of SWCNT can change the microstructure of the molten salt composite PCM,so that the potential energy of interaction between atoms was enhanced,and effectively regulate the thermal storage performance of the molten salt PCM.The thermal conductivity of the molten salt composite PCM can be increased by 21.21%on average.