基于梯度孔隙率金属泡沫的复合相变单元储热性能数值模拟

doi:10.19799/j.cnki.2095-4239.2023.0289

摘要/Abstract

摘要：

向相变材料中添加金属泡沫可以解决相变材料低导热率引起的换热效果较差等问题，提高系统的整体蓄热效率。然而，复合相变材料的传热性能受金属泡沫孔隙率分布的影响较显著，为进一步提高相变储能单元的传热性能，本工作基于低孔隙率金属泡沫-相变材料(PCM)复合储能系统，建立了一种新的梯度孔隙率金属泡沫结构，通过数值模拟方法，对蓄热单元熔化过程中的熔化率、储能速率、储能总量进行分析，系统研究了孔隙率沿加热方向负梯度分布、正梯度分布对复合相变材料熔化速度和储热性能的影响。研究结果表明，负梯度孔隙率结构可以进一步提高储能系统的储热效率，其中，孔隙率梯度为0.12(案例S-6)时增强效果最显著。在熔化周期的不同阶段，负梯度孔隙率对复合材料的传热均有不同程度增强，对于S-6，在1000 s、2000 s、2600 s时，熔化率相较于均匀孔隙率结构分别增加了0.67%、2.31%、9.90%；随着孔隙率梯度的增加，相变材料的热性能提高越显著，与均匀孔隙结构相比，改进的负梯度孔隙率结构其完全熔化时间最高可缩短7.32%，储热速率可提高8.02%。对于正梯度孔隙率结构，其对熔化速度没有显著影响，但是储热总量可提高0.49%。

关键词: 金属泡沫, 相变材料, 梯度孔隙率, 数值模拟

Abstract:

This research aimed to improve the heat storage performance of the composite phase-change unit filled with metal foam. The heat transfer performance of composite phase-change materials was significantly affected by the porosity distribution of metal foam. Therefore, a new gradient-porosity metal foam structure was established based on the energy storage system of the phase-change material (PCM) composite prepared from low-porosity metal foam. Then, the melting fraction, thermal energy storage rate, and thermal energy storage of the heat storage unit during the melting process were analyzed through numerical simulations. The effects of negative and positive gradient distributions of porosity along the heating direction on the melting rate and heat storage performance of the PCM composites were systematically studied. The results showed that the negative gradient porosity of the structure could further improve the thermal storage efficiency of the energy storage system. In addition, the enhancement effect was most significant when the porosity gradient was 0.12 (case S-6). For S-6, at 1000, 2000, and 2600 s, the melting rate increased by 0.67%, 2.31%, and 9.90%, respectively, compared with the uniform-pore structure. The complete melting time of the structure with the improved gradient pore could be shortened by up to 7.32%, and the thermal energy storage rate could be increased by 8.02% compared with the uniform-pore structure. The structure with the positive gradient porosity had no significant effect on the melting rate, but the thermal energy storage could be increased by 0.49%.

Key words: metal foam, phase change materials, gradient porosity, numerical simulation

中图分类号:

TK 02

严景好, 李杰, 李一鸣, 孙小琴, 席丽娜, 姜昌伟. 基于梯度孔隙率金属泡沫的复合相变单元储热性能数值模拟[J]. 储能科学与技术, 2023, 12(8): 2424-2434.

Jinghao YAN, Jie LI, Yiming LI, Xiaoqin SUN, Lina XI, Changwei JIANG. Numerical simulation study on heat storage performance of composite phase-change units based on gradient-porosity metal foam[J]. Energy Storage Science and Technology, 2023, 12(8): 2424-2434.

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材料	属性	数值
石蜡R56	比热容/[J/(kg·K)]	2100
	密度/(kg/m³)	840
	导热系数/[W/(m·K))	0.2
	黏度/[kg/(m·s)]	0.003
	热膨胀系数/(1/K)	0.0004
	潜热/(kJ/kg)	120.7
	固相温度/K	323.75
	液相温度/K	339.65
铝	比热容/[J/(kg·K)]	963
	密度/(kg/m³)	2680
	导热系数/[W/(m·K)]	160

结构名称	案例	孔隙率分布 ε 1- ε 2- ε 3	孔隙率梯度
S0	S0	0.75-0.75-0.75	0
S1	S1-1	0.77-0.75-0.73	0.02
	S1-2	0.79-0.75-0.71	0.04
	S1-3	0.81-0.75-0.69	0.06
	S1-4	0.83-0.75-0.67	0.08
	S1-5	0.85-0.75-0.65	0.10
	S1-6	0.87-0.75-0.73	0.12
S2	S2-1	0.73-0.75-0.77	0.02
	S2-2	0.71-0.75-0.79	0.04
	S2-3	0.69-0.75-0.81	0.06
	S2-4	0.67-0.75-0.83	0.08
	S2-5	0.65-0.75-0.85	0.10
	S2-6	0.63-0.75-0.87	0.12

孔隙率 ε	(1/K)/m^-2	C/m^-1	a_sf/m^-1	孔隙率 ε	(1/K)/m^-2	C/m^-1	a_sf/m^-1
0.75	139896005.14	0.22	2318.44	0.77	118933662.48	0.21	2220.98
0.73	163849159.92	0.23	2411.23	0.79	100551161.05	0.20	2117.83
0.71	191281121.83	0.24	2500.10	0.81	84401007.81	0.20	2007.56
0.69	222773470.95	0.25	2585.59	0.83	70188150.07	0.19	1888.21
0.67	259023171.95	0.26	2668.14	0.85	57661167.14	0.18	1757.02
0.65	300868811.03	0.27	2748.09	0.87	46605231.71	0.18	1610.14
0.63	349324572.19	0.29	2825.69

案例	熔化率/%
案例	1000 s	2000 s	2600 s
S0	0.29	54.10	87.27
S1-1	0.33	54.27	87.49
S1-2	0.40	54.50	87.80
S1-3	0.44	54.69	88.10
S1-4	0.57	54.16	88.69
S1-5	0.74	55.73	92.02
S1-6	0.96	56.40	97.19

案例	熔化率/%
案例	1000 s	2000 s	2600 s
S0	0.29	54.10	87.27
S2-1	0.24	53.94	87.07
S2-2	0.20	53.84	86.95
S2-3	0.29	54.58	87.84
S2-4	0.15	53.77	86.90
S2-5	0.43	55.34	88.77
S2-6	0.20	54.35	87.57