碳纳米管直径对石蜡相变蓄热性能的影响

Effect of Carbon Nanotube Diameter on Phase Change Thermal Energy Storage Properties of Paraffin Wax

针对石蜡导热性差、蓄热效率低等问题,利用含碳材料的高热导性改善石蜡蓄热性能。将8~12 nm、10~20 nm、20~40 nm三种不同直径的碳纳米管粉末,以5%的质量分数加入到石蜡中,研究不同碳纳米管直径对石蜡蓄热性能的影响以及碳纳米管/石蜡复合相变材料各向导热特性。实验结果表明:随着碳纳米管直径的减小,复合相变材料的比热容和潜热值降低,与纯石蜡相比,相变温度约降低1℃,潜热值下降2.6%~3.4%,比热容减小16.2%~16.5%。导热系数及热扩散率提高,缩短了石蜡融化时间,8~12 nm的复合材料融化时间缩短18.2%~46.7%。垂直方向的温度均匀性也得到有效改善。小直径的碳纳米管对石蜡复合相变材料蓄热特性具有较好的改善效果。

To solve the problems of poor thermal conductivity and low thermal energy storage efficiency of paraffin wax,carbon-containing materials with high thermal conductivity are used to improve its thermal energy storage performance.Three carbon nanotube powders with different diameters,8-12 nm,10-20 nm,and 20-40 nm,are added to paraffin wax at a mass fraction of 5%to evaluate the influence of the carbon nanotube diameter on the thermal energy storage properties and the anisotropic thermal conductivity of carbon nanotube/paraffin wax composite phase change material(CPCM).The experimental results show that the specific heat capacity and latent heat value of CPCM decreases as the diameter of the carbon nanotubes decreases.The phase change temperature decreases by approximately 1℃;the latent heat value decreases by 0.5%-3.8%,and the specific heat capacity decreases by 16.2%-16.5%compared with those of pure paraffin wax.The improved thermal conductivity and thermal diffusivity shorten the paraffin wax melting time,and the melting time of 8-12 nm composites is reduced by 18.2%-46.7%.Temperature uniformity in the vertical direction was also effectively improved.At the external measurement points,the temperature fluctuation of 8-12 nm composites was 47.7%compared with pure paraffin,whereas at the internal measurement points,the temperature fluctuation of 10-20 nm was 32.9%of pure paraffin.The diameter of the carbon nanotubes significantly improved the thermal energy storage properties of the CPCM.