套管式相变储热单元储热换热性能的研究

Numerical Simulation of Charging Process for Double Pipe Latent Heat Storage Unit

基于石蜡相变材料,对同心套管式相变储热单元的融化过程进行了二维非稳态数值研究。在考虑自然对流的前提下,对比了内传热管和外传热管储热单元的换热特性,得到了相变材料的温度场分布、流线图和相变界面位置随时间的变化规律,并研究了史蒂芬数、瑞利数对储热换热性能的影响。结果表明,在融化相同体积相变材料前提下,外传热管储热单元可以缩短60.7%的融化时间,换热特性明显优于内传热管式储热单元,这对与变储热装置的优化设计提供参考依据。

Two-dimensional and unsteady-state model for double pipe latent heat storage unit was established by using paraffin wax as the phase change material( PCM). Natural convection was considered in the modeling. The heat transfer from inner and outer tubes in charging process were compared to investigate the heat transfer behavior. Temperature field variation,streamline and the position of phase change interface with time were obtained and discussed. Meanwhile,effects of various factors including Stefan( Ra) number and Rayleigh( Ste) number were also examined. The results show that for the same amount of PCM,the melting time required for heat transfer from outer tube reduces by 60.7%,indicating much better the heat transfer behavior. These simulation results could serve as guidance for the design and optimization of the latent heat storage systems.