Numerical simulation study on heat storage performance of composite phase-change units based on gradient-porosity metal foam

doi:10.19799/j.cnki.2095-4239.2023.0289

Abstract

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

CLC Number:

TK 02

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