相变套管式储热系统放冷性能实验研究

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.