基于二维梯度树状肋相变储热系统强化传热机理

设计了双碟式光热-光电储热发电系统，针对相变储热系统传热特性进行研究，建立了六纵肋、雪花型肋、梯度树状肋相变储热模型，采用Fluent软件对石蜡蓄释热过程进行模拟。通过非稳态传热温度场和速度场的变化分析石蜡熔化和凝固的传热机理。结果表明，石蜡熔化过程伴随着热传导与自然对流的协同作用，凝固过程对流换热微弱以热传导为主。从场协同的角度分析，采用梯度树状肋使空间温度分布更均匀，可提高流体速度场和温度场的协同程度。石蜡熔化温度分别为315、340、360 K，完全熔化时间依次为224、374、703 s；完全凝固时间依次为3439、1089、842 s。可见，随着熔化温度的升高，完全熔化时间增长，完全凝固时间缩短。因此，在选择相变材料时要综合考虑熔化温度、蓄释热初温和终温及储热量的要求。

Heat transfer enhancement mechanism of phase change heat storage system based on two-dimensional gradient dendritic fins

A double-dish photothermal-photoelectric heat storage and power generation system was designed. The heat transfer characteristics of phase change heat storage system were studied. Then the phase change heat storage models of six longitudinal fins, snowflake fins and gradient dendritic fins were established. The Fluent software was used to simulate the heat storage and release process of paraffin. Finally, the heat transfer mechanism of paraffin melting and solidification was analyzed through the change of unsteady heat transfer temperature field and velocity field. The results show that the paraffin melting process is accompanied by the synergistic effect of heat conduction and natural convection, and the convective heat transfer in the solidification process is weak and mainly based on heat conduction. From the perspective of field synergy, the gradient dendritic fins are used to make the spatial temperature distribution more uniform, which can improve the synergy degree of fluid velocity field and temperature field. The melting temperature of paraffin is 315, 340 and 360 K respectively, and the complete melting time is 224, 374 and 703 s respectively. Complete solidification time is 3439, 1089, 842 s. It can be seen that with the increase of melting temperature, the complete melting time increases and the complete solidification time shortens. Therefore, the melting temperature, initial and final temperature of heat storage and release and heat storage capacity should be considered when choosing phase change materials.