泡沫铜内石蜡凝固的孔隙尺度实验研究

对泡沫铜内石蜡凝固相变进行孔隙尺度实验研究。采用高分辨率相机与红外热像仪对凝固过程相场与温度场进行可视化,并通过热电偶测量石蜡与泡沫铜骨架局部温度以获得相变过程热响应及热非平衡特性。揭示了泡沫铜孔隙内凝固相变中包括固液相界面移动、液态石蜡流动及石蜡体积收缩等多个物理过程。研究表明:在多物理过程交互影响下,泡沫铜可高效扩展凝固相界面、提升样品热响应速率,采用孔隙率为0.974的泡沫铜可将石蜡凝固相变速率提升至2.8倍;泡沫铜能有效避免石蜡凝固过程由体积收缩引起的裂缝问题,消除由其引起的热阻;石蜡与泡沫铜骨架间存在局部热非平衡性,且在相变阶段尤为明显。

Experimental study on solidification of paraffin in copper foam at pore scale

An experimental study is carried out to investigate the solidification phase change of paraffin in high porosity open-cell copper foam at foam pore scale level. Detailed visualizations of phase fields and temperature fields for paraffin-foam and pure paraffin samples are conducted by using HD camera and infrared camera to observe the complex phase change phenomena. The local temperatures of both paraffin and copper foam matrix are measured by thermocouples to obtain the precise thermal response and thermal non-equilibrium information during the phase change process. Results reveal multiple pore-scale physical processes including solid-liquid interface evolution, flow of liquid paraffin and volume contraction of paraffin, involved during the solidification of paraffin in metal foam. It is found that: 1) the adoption of copper foam (with porosity of 0.974) can effectively extend the phase change interface, increase the thermal response rate of the sample tested and achieve significant phase change enhancement (approaching to 2.8 times) of paraffin without reducing too much latent heat storage density; 2) copper foam can avoid the gap caused by the volume shrinkage of paraffin, thus eliminating the gap-induced thermal resistance; 3) there exists inherent thermal non-equilibrium effect between paraffin and copper foam for both the sensible and latent heat absorption stages, and it is influenced by the phase change process remarkably.