卧式套管潜热蓄热单元偏心与肋片结构优化模拟

doi:10.19799/j.cnki.2095-4239.2023.0758

摘要/Abstract

摘要：

利用偏心布置增强相变蓄热单元内部自然对流是提高相变蓄热系统性能的新思路，为了更深入地研究偏心布置对相变蓄热系统性能的影响，基于焓-孔隙率法建立了卧式套管相变蓄热单元的三维数学模型，并利用Fluent软件对环形空间相变材料熔化过程进行数值模拟，通过对熔化过程流场、液相率及温度云图的分析，将熔化过程划分为三个阶段：导热主导的初始阶段，随后是自然对流和导热的混合作用的阶段，以及导热再次占主导地位的最终阶段，并将相变材料环形空间划分为两个区域，据此提出新的评价参数“偏心面积比”。结果表明：硬脂酸作为相变材料时较佳的偏心面积比位于16∶1附近，熔化时间相对于同心布置缩短了45.8%，但同时会使蓄热单元?效率略有降低，并且预测对于其他材料，预期的最佳偏心面积比与使用材料的自然对流强度和导热能力之间的比值有直接相关。利用偏心结构与肋片结合的方法进一步强化传热，比较了螺旋肋、十字肋和X形肋三种肋片，发现X形肋具有较佳性能，与相应偏心无肋结构相比熔化时间缩短了36.7%，比螺旋肋和十字肋结构分别缩短了20.3%和7.1%。

关键词: 潜热蓄热, 偏心面积比, 肋片, 强化传热, ?效率

Abstract:

Enhancing natural convection inside a phase change material (PCM) improves the performance of latent heat storage (LHS) systems. To investigate the impact of eccentric arrangement in detail, a three-dimensional numerical model was established for the horizontal double-pipe LHS unit based on the enthalpy-void fraction method, and the melting process of the PCM in annular space was simulated using Fluent software. Analyses of the flow field, temperature, and liquid fraction contours during the melting process lead to the melting process being divided into three stages: the initial stage in which heat conduction predominates, followed by the concurrent action of natural convection and heat conduction, and the final stage in which heat conduction dominates again. The corresponding annular space of PCM can be divided into two regions, and a new evaluation parameter called the "eccentric area ratio" is proposed accordingly. The results showed that the optimal eccentric area ratio is approximately 16∶1 for the PCM stearic acid. The melting time decreases by 45.8% compared with that of the concentric structure, whereas the energy efficiency of the LHS unit decreases slightly. The optimal eccentric area ratio for other materials should be directly related to the ratio of the natural convection intensity to the heat conduction of the material. Combining the eccentric structure with fins further enhances heat transfer. The results show that the X-shaped fins perform best; the melting time decreases by 36.7%, 20.3%, and 7.1% compared with that of the smooth structure, helical fins, and cross-shaped fins, respectively.

Key words: latent heat storage, eccentric area ratio, fin, heat transfer enhancement, exergy efficiency

中图分类号:

TK 02

张璐荻, 周国兵. 卧式套管潜热蓄热单元偏心与肋片结构优化模拟[J]. 储能科学与技术, 2024, 13(3): 1019-1029.

Ludi ZHANG, Guobing ZHOU. Simulated optimization of eccentricity and fin structure of a horizontal double-tube latent heat storage unit[J]. Energy Storage Science and Technology, 2024, 13(3): 1019-1029.

图/表 14

图1

表1

图2

图3

图4

图5

图6

表2

不同偏心面积比对应的偏心距离 y"

偏心面积比 $ε$	偏心距离y/mm
同心布置	0
4∶1	4.49
8∶1	7.69
16∶1	9.92
24∶1	10.86

表2

图7

图8

图9

图10

图11

图12

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物性参数	硬脂酸	水	铜
固体密度，ρ_S/(kg/m³)	965	—	8798
液体密度，ρ_L/(kg/m³)	862	998.2	—
导热系数，k/[W/(m/K)]	0.162	0.670	387.6
相变潜热，L_PCM/(kJ/kg)	220.8	—	—
固相线温度，T_S/K	340.13	—	—
液相线温度，T_L/K	344.05	—	—
固态定压比热容，C_p_S/[kJ/(kg/K)]	2.27	—	0.381
液态定压比热容，C_p_L/[kJ/(kg/K)]	1.76	4.197	—
黏度，μ/[kg/(m/s)]	0.00631	0.0003543	—
热膨胀系数，β/K^-1	0.00005	—	—

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