相变套管式储热系统放冷性能实验研究

搭建了套管式相变储热实验系统，分别填充不同质量分数膨胀石墨与正十五烷制备而成的复合相变材料，对系统进行重复充放冷循环实验。采用有效储热比E_st和储能效率ε来表征系统性能，研究了复合相变材料中换热增强对套管式潜热储能系统放冷性能的影响。结果表明：同Re数下，相变材料热导率为0.14 W·m^-1·K^-1（工况A）放冷结束时间为1770 s，相同Re条件下热导率提升至7.10 W·m^-1·K^-1（工况B）和11.60 W·m^-1·K^-1（工况C）的结束时间分别可缩短77.3%、78.9%；热导率的增加可显著提高系统有效储热比E_st和储能效率ε，热导率从0.14 W·m^-1·K^-1增加到11.60 W·m^-1·K^-1，E_st在层流区、过渡区和湍流区分别可提升33.3%、350.0%及129.6%，ε分别可提升26.8%、52.9%及14.6%；Re的增加使得工况A和工况B中E_st和ε呈现下降趋势，工况C中E_st在Re=4298出现峰值1.62。

Experimental study of phase change sleeve tube thermal storage system performance during charging

In this paper, a casing type phase change heat storage experiment system is set up, which is filled with composite phase change materials made of expanded graphite and n-pentadecane with different mass fractions, and the system is charged and discharged repeatedly . The heat transfer enhancement of the sleeve tube thermal storage system was characterized by effective heat storage ratio E_st and energy storage efficiency ε. The results show that the discharging process was completed by 1770 s (Condition A, k_p =0.14 W·m^-1·K^-1). The completed time for Condition B (k_p =7.10 W·m^-1·K^-1) and Condition C (k_p =11.60 W·m^-1·K^-1) were shortened by 77.3% and 78.9% under the same Reynolds number. E_st and ε of the system increase significantly with the increasing thermal conductivity. As the thermal conductivity increases from 0.14 W·m^-1·K^-1 to 11.60 W·m^-1·K^-1, E_st increased by 33.3%, 350.0% and 129.6% in the laminar region, transition region and turbulent region, and ε increased by 26.8%, 52.9% and 14.6% respectively. However, E_st and ε decrease as Re increases in Condition B and Condition C. E_st in Condition C shows a peak of 1.62 at Re = 4298.