纳米增强型复合相变材料的传热特性

Thermal behavior of the nanoenhanced phase change materials

高导热颗粒常被用来增强相变材料(phase change materials,PCMs)的固有导热性能。为研究纳米颗粒种类、含量和分散剂对纳米增强型复合相变材料(nano-enhanced PCMs, NePCMs)传热过程的影响,本文采用纳米石墨(nano graphite,NG)和纳米椰壳炭(nano coconut shell based-carbon,NC)来提高石蜡的导热性能,使用T型热电偶监测不同边界温度下各复合相变材料熔化过程的温度变化,并用红外热像仪观察整体的温度分布。实验结果表明:纳米颗粒能够增强PCMs的热传递性能,且相同浓度下添加纳米石墨的石蜡传热速率更快,但纳米颗粒在相变过程中易分散不均匀;分散剂能够改善纳米颗粒在PCMs中的分散性能从而增强NePCMs的传热速率,其中用油酸作分散剂时能最大程度促进NePCMs的传热;分散良好的情况下,NePCMs的传热性能随其浓度的增大而增强。

Highly conductive particles have been used to improve the thermal conductivity of phase change materials(PCMs).To investigate the influence of the type and concentration of nano-particles and dispersants on the heat transfer process of PCMs,nano graphite(NG)and nano coconut shell basedcarbon(NC)were used in the study to improve the thermal conductivity of paraffin.Type T thermocouples were used to monitor the temperature variation during melting under different boundary temperatures in a climate chamber.Thermovision tests were conducted to illustrate the temperature distribution.It was found that nano-particles were able to enhance the heat transfer of PCMs.The heat transfer of the PCMs with NG outperformed the PCMs with NC under same concentration.However,the distribution of nano-particles within the PCMs was not uniform.Dispersant,especially oleic acid,was able to improve the distribution of nano-particles,resulting in the improvement of heat transfer of NePCMs.When the nano-particles distributed evenly in the PCMs,the heat transfer rate of NePCMs increased with increasing concentration.