该文以三套管式相变储热单元为研究对象,首先分析相变材料填充率为30%~80%的单、双管填充模型在储热过程中液相分数和平均温度的变化趋势,对比PCM的总蓄热量、熔化时间和平均蓄热速率;其次,以融化时间和总蓄热量为评价指标,采用熵权法和TOPSIS法对PCM填充率进行评价,确定60%PCM填充率的储热单元储热性能最优,进一步分析PCM温度场和涡量的演变情况,揭示重力驱动自然对流增强传热的机理;此外以60%PCM填充率的单管填充模型为对象,研究PCM径向位置对传热性能的影响。结果表明,随着PCM填充率增大,单位蓄热率下降,总蓄热量增加;当填充率高于40%后,由于单管填充模型内漩涡生成速度快于双管填充模型,漩涡对自然对流起到强化作用,因此单管填充模型储热性能优于双管填充模型。PCM采用靠近外管壁的径向填充方法对漩涡的生成起促进作用,在外管径和PCM填充率不变条件下,PCM径向位置越靠近外管完全融化时间越短,融化性能越好。
Abstract
This study investigates triplex-tube phase change thermal storage units. First, the variation trends of liquid phase fraction and average temperature during the heat storage process for single- and double-tube filled models with phase change material （PCM） filling rates ranging from 30% to 80% are analyzed. The total heat storage capacity, melting time, and average heat storage rate of the PCM are compared. Secondly, using melting time and total heat storage capacity as evaluation metrics, the entropy weight method （EWM） and the Technique for Order Preference by Similarity to Ideal Solution （TOPSIS） method are applied to assess the optimal PCM filling rate. The results show that a 60% PCM filling rate yields the best thermal performance. Further analysis of the temperature field and vorticity evolution reveals the mechanism by which gravity-driven natural convection enhances heat transfer. In addition, a single-tube model with a 60% PCM filling rate is used to study the influence of the radial position of PCM on heat transfer performance. The results indicate that as the PCM filling rate increases, the unit heat storage rate decreases, while the total heat storage capacity increases. When the filling rate exceeds 40%, the vortex generation rate in the single-tube model becomes faster than in the double-tube model, leading to enhanced natural convection by the vortex. Therefore, the single-tube filling model exhibits superior thermal storage performance compared to the double-tube model. Furthermore, a radial PCM filling method closer to the outer tube wall promotes vortex formation. Under constant outer tube diameter and PCM filling rate, the closer the PCM is to the outer tube, the shorter the complete melting time and the better the melting performance.
关键词
储热 /
自然对流 /
相变材料 /
三套管式相变储热单元 /
填充率 /
径向位置
Key words
heat storage /
natural convection /
phase change materials /
triplex-tube phase change thermal energy storage unit /
filling rate /
radial position
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基金
河北省自然科学基金（E2022502017）
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