Heat transfer enhancement mechanism of phase change heat storage system based on two-dimensional gradient dendritic fins

doi:10.11949/0438-1157.20220669

Abstract

Abstract:

A double-dish photothermal-photoelectric heat storage and power generation system was designed. The heat transfer characteristics of phase change heat storage system were studied. Then the phase change heat storage models of six longitudinal fins, snowflake fins and gradient dendritic fins were established. The Fluent software was used to simulate the heat storage and release process of paraffin. Finally, the heat transfer mechanism of paraffin melting and solidification was analyzed through the change of unsteady heat transfer temperature field and velocity field. The results show that the paraffin melting process is accompanied by the synergistic effect of heat conduction and natural convection, and the convective heat transfer in the solidification process is weak and mainly based on heat conduction. From the perspective of field synergy, the gradient dendritic fins are used to make the spatial temperature distribution more uniform, which can improve the synergy degree of fluid velocity field and temperature field. The melting temperature of paraffin is 315, 340 and 360 K respectively, and the complete melting time is 224, 374 and 703 s respectively. Complete solidification time is 3439, 1089, 842 s. It can be seen that with the increase of melting temperature, the complete melting time increases and the complete solidification time shortens. Therefore, the melting temperature, initial and final temperature of heat storage and release and heat storage capacity should be considered when choosing phase change materials.

Key words: solar energy, phase change heat storage, gradient fins, heat storage and release, heat transfer, field synergy, numerical simulation

摘要：

设计了双碟式光热-光电储热发电系统，针对相变储热系统传热特性进行研究，建立了六纵肋、雪花型肋、梯度树状肋相变储热模型，采用Fluent软件对石蜡蓄释热过程进行模拟。通过非稳态传热温度场和速度场的变化分析石蜡熔化和凝固的传热机理。结果表明，石蜡熔化过程伴随着热传导与自然对流的协同作用，凝固过程对流换热微弱以热传导为主。从场协同的角度分析，采用梯度树状肋使空间温度分布更均匀，可提高流体速度场和温度场的协同程度。石蜡熔化温度分别为315、340、360 K，完全熔化时间依次为224、374、703 s；完全凝固时间依次为3439、1089、842 s。可见，随着熔化温度的升高，完全熔化时间增长，完全凝固时间缩短。因此，在选择相变材料时要综合考虑熔化温度、蓄释热初温和终温及储热量的要求。

关键词: 太阳能, 相变储热, 梯度肋, 蓄释热, 传热, 场协同, 数值模拟

CLC Number:

TK 513.5

Xinyu ZHANG, Xiaohong YANG, Yannan ZHANG, Jiakun XU, Xiao GUO, Rui TIAN. Heat transfer enhancement mechanism of phase change heat storage system based on two-dimensional gradient dendritic fins[J]. CIESC Journal, 2022, 73(10): 4399-4409.

张欣宇, 杨晓宏, 张燕楠, 徐佳锟, 郭枭, 田瑞. 基于二维梯度树状肋相变储热系统强化传热机理[J]. 化工学报, 2022, 73(10): 4399-4409.

Figures/Tables 16

Fig.1 Three-phase change heat storage models and dimensions

Table 1 Thermophysical properties of PCM， aluminum and copper［29］

物理量	数值
物理量	石蜡	铜	铝
密度ρ/(kg/m³)	750	8978	2719
比热容c_p /(J/(kg·K))	2000	381	879
热导率λ /(W/(m·K))	0.2	387.6	202.4
动力黏度μ /(kg/(m·s))	0.001	—	—
体积膨胀系数α/K^-1	0.00085	—	—
相变热Δh/(kJ/kg)	255	—	—
凝固温度T_s/K	315.15	—	—
熔化温度T_l /K	317.15	—	—

Fig.2 Grid system of the computational domain

Fig.3 Verification of grid size and time step independence

Fig.4 Validation of numerical method

Fig.5 The cloud atlas of temperature and liquid fraction of paraffin melting process of three models

Fig.6 The cloud atlas of temperature and liquid fraction of paraffin solidification process of three models

Fig.7 Changes in the liquid fraction of phase change materials during heat storage and release process of three models

Fig.8 Changes in the average temperature of phase change materials during heat storage and release process of three models

Fig.9 Changes in the velocity of phase change materials during heat storage and release process of three models

Fig.10 Changes in the heat flux density during heat storage and release process of three models

Fig.11 Transient changes in synergy number Fc of paraffin field in melting process of three models

Fig.12 Transient changes in synergy number Fc of paraffin field during heat release of three models

Fig.13 Changes in the liquid fraction of paraffin during heat storage and release at different melting temperatures

Fig.14 Changes in the average temperature of paraffin during heat storage and release at different melting temperatures

Fig.15 Changes in the heat release capacity of paraffin at different melting temperatures

References 36

1	Palacios A, Barreneche C, Navarro M E, et al. Thermal energy storage technologies for concentrated solar power—a review from a materials perspective[J]. Renewable Energy, 2020, 156: 1244-1265.
2	Settino J, Sant T, Micallef C, et al. Overview of solar technologies for electricity, heating and cooling production[J]. Renewable and Sustainable Energy Reviews, 2018, 90: 892-909.
3	张欣宇, 杨晓宏, 曹泽宇, 等. 太阳能斯特林混凝土储热系统传热特性研究[J]. 太阳能学报, 2022, 43(5): 213-219.
	Zhang X Y, Yang X H, Cao Z Y, et al. Heat transfer performance of concrete thermal storage system for solar energy striling[J]. Acta Energiae Solaris Sinica, 2022, 43(5): 213-219.
4	Guarino S, Buscemi A, Ciulla G, et al. A dish-stirling solar concentrator coupled to a seasonal thermal energy storage system in the southern Mediterranean Basin: a cogenerative layout hypothesis[J]. Energy Conversion and Management, 2020, 222: 113228.
5	李椿, 王志华, 王建春, 等. 壳管式相变储能换热器性能研究与场协同效应分析[J]. 太阳能学报, 2020, 41(3): 226-233.
	Li C, Wang Z H, Wang J C, et al. Performance study and field synergy analysis of shell and tube phase change energy storage heat exchanger[J]. Acta Energiae Solaris Sinica, 2020, 41(3): 226-233.
6	Ibrahim N I, Al-Sulaiman F A, Rahman S, et al. Heat transfer enhancement of phase change materials for thermal energy storage applications: a critical review[J]. Renewable and Sustainable Energy Reviews, 2017, 74: 26-50.
7	杨超, 徐阳, 郑章靖. 二维梯级多孔强化相变储热装置熔化过程研究[J]. 工程热物理学报, 2021, 42(11): 2946-2953.
	Yang C, Xu Y, Zheng Z J. Study on melting process of latent heat thermal energy storage unit strengthened by two-dimensional graded metal foam[J]. Journal of Engineering Thermophysics, 2021, 42(11): 2946-2953.
8	杨喆, 刘飞, 张涛, 等. TPMS 多孔铝-石蜡复合相变材料蓄热过程数值模拟及实验[J].化工进展, 2022, 41(9): 4918-4927.
	Yang Z, Liu F, Zhang T, et al. Numerical simulation and experiment of heat storage process of TPMS porous aluminum-paraffin composite phase change material[J]. Chemical Industry and Engineering Progress, 2022, 41(9): 4918-4927.
9	Xu Y, Li M J, Zheng Z J, et al. Melting performance enhancement of phase change material by a limited amount of metal foam: configurational optimization and economic assessment[J]. Applied Energy, 2018, 212: 868-880.
10	Khan Z, Khan Z A. Experimental and numerical investigations of nano-additives enhanced paraffin in a shell-and-tube heat exchanger: a comparative study[J]. Applied Thermal Engineering, 2018, 143: 777-790.
11	Yuan Y P, Zhang N, Li T Y, et al. Thermal performance enhancement of palmitic-stearic acid by adding graphene nanoplatelets and expanded graphite for thermal energy storage: a comparative study[J]. Energy, 2016, 97: 488-497.
12	Zhu Z Q, Huang Y K, Hu N, et al. Transient performance of a PCM-based heat sink with a partially filled metal foam: effects of the filling height ratio[J]. Applied Thermal Engineering, 2018, 128: 966-972.
13	王成君, 段志英, 苏琼, 等. 以多级孔碳为支撑基体的复合相变材料在光热转换与存储方面的研究进展[J]. 材料导报, 2020, 34(23): 23074-23080.
	Wang C J, Duan Z Y, Su Q, et al. Research progress in photo-thermal conversion and storage of multistage porous carbon supported composite phase change materials[J]. Materials Reports, 2020, 34(23): 23074-23080.
14	Xu H T, Wang N, Zhang C Y, et al. Optimization on the melting performance of triplex-layer PCMs in a horizontal finned shell and tube thermal energy storage unit[J]. Applied Thermal Engineering, 2020, 176: 115409.
15	Bie Y, Li M, Malekian R, et al. Effect of phase transition temperature and thermal conductivity on the performance of latent heat storage system[J]. Applied Thermal Engineering, 2018, 135: 218-227.
16	Khan L A, Khan M M. Role of orientation of fins in performance enhancement of a latent thermal energy storage unit[J]. Applied Thermal Engineering, 2020, 175: 115408.
17	Yu C, Zhang X, Chen X, et al. Melting performance enhancement of a latent heat storage unit using gradient fins[J]. International Journal of Heat and Mass Transfer, 2020, 150: 119330.
18	Liu X D, Huang Y P, Zhang X, et al. Investigation on charging enhancement of a latent thermal energy storage device with uneven tree-like fins[J]. Applied Thermal Engineering, 2020, 179: 115749.
19	Safari V, Abolghasemi H, Kamkari B. Experimental and numerical investigations of thermal performance enhancement in a latent heat storage heat exchanger using bifurcated and straight fins[J]. Renewable Energy, 2021, 174: 102-121.
20	Huang Y P, Cao D C, Sun D K, et al. Experimental and numerical studies on the heat transfer improvement of a latent heat storage unit using gradient tree-shaped fins[J]. International Journal of Heat and Mass Transfer, 2022, 182: 121920.
21	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.
22	Ma B, Zhang X Y, Wang L, et al. Numerical study on melting performance improvement with fractal tree-shaped fins[J]. Physics of Fluids, 2022, 34(4): 047107.
23	过增元, 黄素逸. 场协同原理与强化传热新技术[M]. 北京: 中国电力出版社, 2004.
	Guo Z Y, Huang S Y. Field Synergy Principle and New Technology of Enhanced Heat Transfer[M]. Beijing: China Electric Power Press, 2004.
24	李志信, 过增元. 对流传热优化的场协同理论[M]. 北京: 科学出版社, 2010.
	Li Z X, Guo Z Y. Field Synergy Theory for Optimization of Convective Heat Transfer[M]. Beijing: Science Press, 2010.
25	陈洁璐. 基于场协同理论的翅片管蒸发器管外强化换热研究[D]. 武汉: 华中科技大学, 2017.
	Chen J L. Study on heat transfer enhancement of fin-and-tube evaporator based on field synergy theory[D]. Wuhan: Huazhong University of Science and Technology, 2017.
26	Gu X, Zheng Z Y, Xiong X C, et al. Heat transfer and flow resistance characteristics of helical baffle heat exchangers with twisted oval tube[J]. Journal of Thermal Science, 2022, 31(2): 370-378.
27	Yao P T, Zhai Y L, Li Z H, et al. Thermal performance analysis of multi-objective optimized microchannels with triangular cavity and rib based on field synergy principle[J]. Case Studies in Thermal Engineering, 2021, 25: 100963.
28	Cui W Z, Mao D X, Lin B, et al. Field synergy analysis on the mechanism of heat transfer enhancement by using nanofluids[J]. Case Studies in Thermal Engineering, 2019, 16: 100554.
29	饶中浩, 刘臣臻. 相变储能实验与分析[M]. 徐州: 中国矿业大学出版社, 2018.
	Rao Z H, Liu C Z. Experiment and Analysis of Phase Change Energy Storage[M]. Xuzhou: China University of Mining & Technology Press, 2018.
30	Vogel J, Felbinger J, Johnson M. Natural convection in high temperature flat plate latent heat thermal energy storage systems[J]. Applied Energy, 2016, 184: 184-196.
31	陶文铨. 传热学[M]. 5版. 北京: 高等教育出版社, 2019.
	Tao W Q. Heat Transfer[M]. 5th ed. Beijing: Higher Education Press, 2019.
32	Vogel J, Thess A. Validation of a numerical model with a benchmark experiment for melting governed by natural convection in latent thermal energy storage[J]. Applied Thermal Engineering, 2019, 148: 147-159.
33	Al-Abidi A A, Mat S B, Sopian K, et al. Review of thermal energy storage for air conditioning systems[J]. Renewable and Sustainable Energy Reviews, 2012, 16(8): 5802-5819.
34	Seddegh S, Wang X L, Henderson A D. A comparative study of thermal behaviour of a horizontal and vertical shell-and-tube energy storage using phase change materials[J]. Applied Thermal Engineering, 2016, 93: 348-358.
35	Duan J, Xiong Y L, Yang D. Study on the effect of multiple spiral fins for improved phase change process[J]. Applied Thermal Engineering, 2020, 169: 114966.
36	Ho J Y, See Y S, Leong K C, et al. An experimental investigation of a PCM-based heat sink enhanced with a topology-optimized tree-like structure[J]. Energy Conversion and Management, 2021, 245: 114608.

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