石蜡/膨胀石墨复合相变储热单元的放热性能

Discharge performance of a thermal energy storage unit with paraffin-expanded graphite composite phase change materials

本工作对石蜡(PA)及石蜡/膨胀石墨(97%PA/3%EG和95%PA/5%EG)复合相变储热材料的热性能进行了探究,考察了不同直径储热单元在干燥介质温度为25℃,风速为0.8 m/s条件下的放热性能。结果表明,在石蜡中添加膨胀石墨后,复合材料导热系数较纯石蜡分别提高了178.10%和214.30%,可以有效改善石蜡的导热性能,缩短放热时间;储热单元直径对放热性能有显著影响,随着石蜡相变储热单元直径的增大,放热时间线性增加;膨胀石墨的添加可以明显缩短放热时间,随膨胀石墨含量的增加,相同直径储热单元的放热时间逐渐缩短;膨胀石墨对储热单元放热性能的改善效果随直径变化而不同,在一定范围内随储热单元直径的增大而效果逐渐显著,达到极值后随直径的增大效果逐渐减弱,本实验条件下,最优储热单元直径在35～50 mm之间。结合实际生产需求,最优直径为35 mm。

Thermal properties of paraffin wax(PA)and paraffin/expanded graphite(97%PA/3%EG and95%PA/5%EG)composite materials were investigated.Heat release performance of thermal energy storage(TES)units with different diameters containing the phase change materials were studied at a drying media temperature of25°C and a media velocity of0.8m·s-1.The results showed that the thermal conductivity of the composites was increased by178.10%and214.30%respectively compared with that of PA,which could shorten the TES unit discharge time.The diameter of the TES unit had a significant effect on the heat release performance.An increase in the diameter of the PA based TES unit leads to a linear increase in the heat release time,whereas an increased EG content reduces the heat release time of the unit for a given TES unit diameter.The effect of EG on the heat release performance of the TES unit increases first and then decreases with increasing diameter,leading to an optimal TES unit diameter of35mm under the conditions of this study.