Enhancement of charging and discharging performance of a latent-heat thermal-energy storage unit using snowflake-shaped fins

doi:10.19799/j.cnki.2095-4239.2021.0541

Abstract

Abstract:

Phase-change heat storage technology can solve the volatility and instability of renewable energy during usage. However, available phase-change materials are challenged by their low thermal conductivity, which results in very slow heat storage/release rates, limiting industrial applications. Based on the fractal structure of snowflake crystals, herein, we propose a new type of fin structure to increase the storage/discharge rates of latent-heat storage units filled with phase-change materials. We performed a full three-dimensional multifield coupled numerical simulation on the heat storage/release process of the units. The results show that compared with longitudinal fins with the same volume, both the heat transfer rate and temperature uniformity are significantly enhanced by snowflake-shaped fins when the heat transfer fluids are under the same flow conditions. Further, for the longitudinal and snowflake-shaped fins, the complete melting/solidification time was reduced by 26.87% and 32.01%, respectively. Although the heat storage/release rate of the heat storage unit is greatly improved, the integral average value of the maximum velocity of the liquid phase change material is decreased by 26.83% during the charging process and increased by 18.00% during the discharging process.

Key words: snowflake fin, latent-heat storage unit, phase-change material, heat storage/release performance, natural convection

CLC Number:

TK 02

Yongxue ZHANG, Zixi WANG, Bohui LU, Shengqi YANG, Hongyu ZHAO. Enhancement of charging and discharging performance of a latent-heat thermal-energy storage unit using snowflake-shaped fins[J]. Energy Storage Science and Technology, 2022, 11(2): 521-530.

Figures/Tables 14

Fig. 1

Fig. 2

Table 1

Table 2

Fig. 3

Fig. 4

Fig. 5

Fig. 6

Fig. 7

Fig. 8

Fig. 9

Fig. 10

Fig. 11

Fig. 12

References 15

1	新华社. 习近平在第七十五届联合国大会一般性辩论上发表重要讲话[EB/OL]. (2020-09-22)[2021-07-16]. http://www.gov.cn/xinwen/2020-09/22/content_5546168.htm.
2	胥义, 刘道平. 固液相变蓄热技术的研究进展[J]. 节能, 2002(12): 3-7.
	XU Y, LIU D P. Research progress of solid-liquid phase change heat storage technology[J]. Energy Conservation, 2002 (12): 3-7.
3	徐治国, 赵长颖, 纪育楠, 等. 中低温相变蓄热的研究进展[J]. 储能科学与技术, 2014, 3(3): 179-190.
	XU Z G, ZHAO C Y, JI Y N, et al. Research progress of phase change heat storage at medium and low temperature[J]. Energy Storage Science and Technology, 2014, 3(3): 179-190.
4	CHEN Y P, WU L Y, ZHANG L. Dynamic behaviors of double emulsion formation in a flow-focusing device[J]. International Journal of Heat & Mass Transfer, 2015, 82: 42-50.
5	ZHANG C B, GAO W, ZHAO Y J, et al. Microfluidic generation of self-contained multicomponent microcapsules for self-healing materials[J]. Applied Physics Letters, 2018, 113(20): 203702.
6	PIZZOLATO A, SHARMA A, GE R H, et al. Maximization of performance in multi-tube latent heat storage-optimization of fins topology, effect of materials selection and flow arrangements[J]. Energy, 2019, 203(2020): 114797.
7	ARICI M, TÜTÜNCÜ E, YILDIZ Ç, et al. Enhancement of PCM melting rate via internal fin and nanoparticles[J]. International Journal of Heat and Mass Transfer, 2020, 156(2020): 119845.
8	ZHOU B, CAI P, CHEN Y P. Interfacial mass transfer of water for fluorobenzene/aqueous solution system in double emulsion[J]. International Journal of Heat and Mass Transfer, 2019, 145(2019): 118690.
9	高轩. Y型纵翅片管式相变蓄热过程模拟与优化[D]. 兰州: 兰州理工大学, 2016.
	GAO X. Simulation and optimization of Y-shaped longitudinal fin tube phase change heat storage process[D]. Lanzhou: Lanzhou University of Technology, 2016.
10	SCIACOVELLI A, GAGLIARDI F, VERDA V. Maximization of performance of a PCM latent heat storage system with innovative fins[J]. Applied Energy, 2015, 137: 707-715.
11	YU C, WU S C, HUANG Y P, et al. Charging performance optimization of a latent heat storage unit with fractal tree-like fins[J]. The Journal of Energy Storage, 2020, 30: 101498.
12	ZHANG C B, LI J, CHEN Y P. Improving the energy discharging performance of a latent heat storage (LHS) unit using fractal-tree-shaped fins[J]. Applied Energy, 2020, 259: 114102.
13	罗新梅, 古家安. 不同长径比的分形肋片强化PCM熔化传热数值分析[J]. 储能科学与技术, 2021, 10(2): 523-533.
	LUO X M, GU J A. Numerical analysis of fractal fins with different aspect ratios to enhance PCM melting heat transfer[J]. Energy Storage Science and Technology, 2021, 10(2): 523-533.
14	LONGEON M, SOUPART A, FOURMIGUÉ J-F, et al. Experimental and numerical study of annular PCM storage in the presence of natural convection[J]. Applied Energy, 2013, 112: 175-184.
15	JI C Z, QIN Z, DUBEY S, et al. Simulation on PCM melting enhancement with double-fin length arrangements in a rectangular enclosure induced by natural convection[J]. International Journal of Heat and Mass Transfer, 2018, 127: 255-265.

属性	石蜡	水	铜
密度/(g/cm³)	880(s)/760(l)	998.2	8960
比热容/[J·(g·K)]	1.8(s)/2.4(l)	4182	402.5
热导率/[W·(m·K)]	0.2(s)/0.1(l)	0.6	389
熔点/℃	28~40	—	—
相变潜热/(J/g)	157	—	—
密度/(g/cm³)	0.86(s)/0.79(l)	—	—
体膨胀系数/K^-1	0.0006	—	—
运动黏度/(m²/s)	3.3×10^-6	^—	^—

项目	储热过程	放热过程
进口温度/℃	52	22
进口速度/(m/s)	0.01	0.01
出口条件	压力出口	压力出口
其他面	绝热	绝热
初始温度/℃	22	52

[1]	Yunqi GUO, Nan SHENG, Chunyu ZHU, Zhonghao RAO. Preparation of Al₂O₃ fibers using a template method， and the investigation of the thermal properties of paraffin phase-change composite [J]. Energy Storage Science and Technology, 2022, 11(2): 511-520.
[2]	Caimei YU, Xuelai ZHANG, Weisan HUA. Research progress of sodium sulfate decahydrate phase changematerial [J]. Energy Storage Science and Technology, 2021, 10(3): 1016-1024.
[3]	Lihui LIU, Yajing MO, Xiaoqin SUN, Jie LI. Thermal storage characteristics and optimization of plate-type phase change energy storage unit [J]. Energy Storage Science and Technology, 2020, 9(6): 1784-1789.
[4]	Yiqian GAO, Yi LIU, Ling LI. Numerical simulation of natural convection melting inside a triangular cavity using Lattice Boltzmann method [J]. Energy Storage Science and Technology, 2020, 9(6): 1798-1805.
[5]	ZHOU Huilin, QIU Yan. Heat storage characteristic and structure optimum inrectangular unit [J]. Energy Storage Science and Technology, 2020, 9(4): 1082-1090.
[6]	ZOU Yong, QIU Rudong, WANG Xia. Simulation study on thermal storage process of paraffin phase change materials [J]. Energy Storage Science and Technology, 2020, 9(1): 101-108.
[7]	YANG Zhishun, CHEN Lihua, XIA Zhenhua. Numerical investigation of the thermal mechanism of the solid-liquid phase changing process [J]. Energy Storage Science and Technology, 2019, 8(6): 1217-1223.
[8]	YANG Cenyu, HU Xiao, LI Yawen, XING Zuoxia, GAO Yunxing, DONG Jiayi, XU Guizhi. Modeling and simulation of phase change material based energy storage system using fluid-solid coupling [J]. Energy Storage Science and Technology, 2019, 8(3): 538-543.
[9]	LU Yuanwei, DU Wenbin, WU Yuting, LI Xiaoli, MA Chongfang. Sensible heat storage in a single tank using molten salt and associated natural convection heat transfer [J]. Energy Storage Science and Technology, 2015, 4(2): 189-193.
[10]	XU Zhiguo, ZHAO Changying, JI Yunan, ZHAO Yao. State-of-the-art of phase-change thermal storage at middle-low temperature [J]. Energy Storage Science and Technology, 2014, 3(3): 179-190.
[11]	LIU Yongkun, TAO Yubing, TANG Zongbin. Numerical study on performance enhancement of latent heat storage unit [J]. Energy Storage Science and Technology, 2014, 3(3): 197-202.