导热填充物对石蜡复合相变储热系统传热行为影响的数值模拟

Numerical simulation of the effect of heat conductive fillers on the heat conduction behavior of paraffin phase change energy storage system

采用有限元方法模拟圆柱体潜热蓄热系统中的相变蓄热过程。该模型为:以圆柱体封装装置存储相变物质石蜡,圆柱体中间插入一根热水铜管给相变物质供热,不同数量的铜肋片或者不同质量分数的压缩膨胀石墨用于提高相变传热速率。其中铜肋片沿圆柱体径向方向插入圆柱体内;熔融石蜡经过真空浸渗到压缩膨胀石墨内形成压缩膨胀石墨/石蜡复合材料,然后将复合材料填充到圆柱体内。该模型包括四个物理过程:热传导、流体流动、相变传热和对流传热。模拟结果表明,不同数量的铜肋片以及不同质量分数的压缩膨胀石墨对相变储热速率均有明显提高。添加压缩膨胀石墨比添加铜肋片更经济,传热更均匀。

A cylindrical phase change energy storage system was modeled numerically using the finite element method. The model system was composed of a cylindrical container into the center of which is inserted concentrically a copper pipe carrying hot water. Either copper fins or compressed expanded natural graphite （CENG） were placed as heat-conducting fillers between the container and the pipe for comparison. The former is radially positioned while the latter is randomly filled. The remaining space was filled with paraffin as a phase change energy storage material. Fluid flow, heat conduction and convection, and the paraffin phase change were simulated simultaneously. It was found that the heat transfer performance of the system increases with the number of copper fins when they were used as the filler. The time required to reach heat equilibrium is shortened significantly by increasing the density of the CENG when it was used. CENG is much more effective than copper fins to promote paraffin melting.