LiCl-KCl熔盐纳米流体结构和热物性的分子动力学模拟

doi:10.19799/j.cnki.2095-4239.2022.0683

摘要/Abstract

摘要：

采用分子动力学方法研究了Al₂O₃纳米颗粒对二元氯化物熔盐LiCl-KCl结构和热物理性能的影响，分析了熔盐纳米流体(Nanofluids，NF)的径向分布函数、配位数N(r)、自扩散系数D、密度、黏度和热导率随纳米颗粒掺杂量和温度的变化规律。结果表明，在700～1400 K温度范围内，随着纳米颗粒掺杂量的增加，径向分布函数g_Li-Cl(r)的第一峰位置逐渐向左移动，且峰高增加，配位数逐渐增大，自扩散系数逐渐减小。熔盐纳米流体的密度、黏度和热导率随温度的升高而降低，随纳米颗粒掺杂量的增加而增加，黏度和热导率最大分别提高了16.83%和4.95%。热物性的变化归因于Al₂O₃纳米颗粒的加入减小了纳米流体中阴阳离子间的距离，增强了缔合作用，使得熔体结构更加致密。

关键词: 熔盐, Al₂O₃, 微观结构, 热物性, 分子动力学

Abstract:

Herein, the molecular dynamics method investigates the effects of Al₂O₃ nanoparticles on the structure and thermophysical properties of binary chloride salt LiCl-KCl. Furthermore, the effect of doping amount and temperature on radial distribution function, coordination number [N(r)], self-diffusion coefficient(D), density, viscosity, and thermal conductivity of nanofluids were analyzed. The results show that in the temperature range of 700～1400 K, with increasing nanoparticles, the first peak position of the radial distribution function g_Li-Cl(r) moves to the left gradually, the peak height and the coordination number increase, and the self-diffusion coefficient decreases gradually. The density, viscosity, and thermal conductivity of nanofluids decreased with increasing temperature but increased with increasing nanoparticles, and the maximum viscosity and thermal conductivity increased by 16.83% and 4.95%, respectively. The change in thermophysical properties was attributed to adding Al₂O₃ nanoparticles that reduced the distance between anions in the nanofluids, enhancing the association effect, and making the melt structure more compact.

Key words: molten salt, Al₂O₃, microstructure, thermophysical property, molecular dynamics

中图分类号:

TK 02

田禾青, 寇朝阳, 周俊杰, 余银生. LiCl-KCl熔盐纳米流体结构和热物性的分子动力学模拟[J]. 储能科学与技术, 2023, 12(3): 654-660.

Heqing TIAN, Zhaoyang KOU, Junjie ZHOU, Yinsheng YU. Molecular dynamics simulation of structure and thermal properties of LiCl-KCl molten salt nanofluids[J]. Energy Storage Science and Technology, 2023, 12(3): 654-660.

图/表 8

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参考文献 27

1	GUDE V G. Energy storage for desalination processes powered by renewable energy and waste heat sources[J]. Applied Energy, 2015, 137: 877-898.
2	MAHDI J M, NSOFOR E C. Solidification enhancement of PCM in a triplex-tube thermal energy storage system with nanoparticles and fins[J]. Applied Energy, 2018, 211: 975-986.
3	SHARMA A, TYAGI V V, CHEN C R, et al. Review on thermal energy storage with phase change materials and applications[J]. Renewable and Sustainable Energy Reviews, 2009, 13(2): 318-345.
4	SAID M A, HASSAN H. Effect of using nanoparticles on the performance of thermal energy storage of phase change material coupled with air-conditioning unit[J]. Energy Conversion and Management, 2018, 171: 903-916.
5	李昭, 李宝让, 崔柳, 等. 高温熔盐基纳米流体热物性的稳定性研究[J]. 储能科学与技术, 2020, 9(6): 1775-1783.
	LI Z, LI B R, CUI L, et al. Stability of the thermal performances of molten salt-based nanofluid[J]. Energy Storage Science and Technology, 2020, 9(6): 1775-1783.
6	WEI X L, YIN Y, QIN B, et al. Preparation and enhanced thermal conductivity of molten salt nanofluids with nearly unaltered viscosity[J]. Renewable Energy, 2020, 145: 2435-2444.
7	HAN D M, GUENE LOUGOU B, XU Y T, et al. Thermal properties characterization of chloride salts/nanoparticles composite phase change material for high-temperature thermal energy storage[J]. Applied Energy, 2020, 264: doi: 10.1016/j.apenergy.2020.114674.
8	HAN D M, LOUGOU B G, SHUAI Y, et al. Study of thermophysical properties of chloride salts doped with CuO nanoparticles for solar thermal energy storage[J]. Solar Energy Materials and Solar Cells, 2022, 234: doi: 10.1016/j.solmat.2021.111432.
9	CHEN X, WU Y T, ZHANG L D, et al. Experimental study on thermophysical properties of molten salt nanofluids prepared by high-temperature melting[J]. Solar Energy Materials and Solar Cells, 2019, 191: 209-217.
10	YU Y S, ZHAO C Y, TAO Y B, et al. Superior thermal energy storage performance of NaCl-SWCNT composite phase change materials: A molecular dynamics approach[J]. Applied Energy, 2021, 290: doi: 10.1016/j.apenergy.2021.116799.
11	XIAN L, CHEN L, TIAN H Q, et al. Enhanced thermal energy storage performance of molten salt for the next generation concentrated solar power plants by SiO₂ nanoparticles: A molecular dynamics study[J]. Applied Energy, 2022, 323: doi: 10.1016/j.apenergy.2022.119555.
12	PAN G C, DING J, WANG W L, et al. Molecular simulations of the thermal and transport properties of alkali chloride salts for high-temperature thermal energy storage[J]. International Journal of Heat and Mass Transfer, 2016, 103: 417-427.
13	FUMI F G, TOSI M P. Ionic sizes and born repulsive parameters in the NaCl-type alkali halides—I[J]. Journal of Physics and Chemistry of Solids, 1964, 25(1): 31-43.
14	姜涛, 王宁, 程长明, 等. LiCl-KCl-CeCl₃熔盐结构与热力学的分子动力学模拟[J]. 物理化学学报, 2016, 32(3): 647-655.
	JIANG T, WANG N, CHENG C M, et al. Molecular dynamics simulation on the structure and thermodynamics of molten LiCl-KCl-CeCl₃[J]. Acta Physico-Chimica Sinica, 2016, 32(3): 647-655.
15	CACCAMO C, DIXON M. Molten alkali-halide mixtures: A molecular-dynamics study of Li/KCl mixtures[J]. Journal of Physics C: Solid State Physics, 1980, 13(10): 1887-1900.
16	LARSEN B, FØRLAND T, SINGER K. A Monte Carlo calculation of thermodynamic properties for the liquid NaCl+KCl mixture[J]. Molecular Physics, 1973, 26(6): 1521-1532.
17	ZHOU W N, YANG Z X, FENG Y H, et al. Insights into the thermophysical properties and heat conduction enhancement of NaCl-Al₂O₃ composite phase change material by molecular dynamics simulation[J]. International Journal of Heat and Mass Transfer, 2022, 198: doi: 10.1016/j.ijheatmasstransfer.2022.123422.
18	XIE W J, DING J, PAN G, et al. Heat and mass transportation properties of binary chloride salt as a high-temperature heat storage and transfer media[J]. Solar Energy Materials and Solar Cells, 2020, 209: doi: 10.1016/j.solmat.2020.110415.
19	MÜLLER-PLATHE F, BORDAT P. Reverse non-equilibrium molecular dynamics[M]//Novel methods in soft matter simulations. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004: 310-326.
20	CUI W Z, SHEN Z J, YANG J G, et al. Molecular dynamics simulation on the microstructure of absorption layer at the liquid-solid interface in nanofluids[J]. International Communications in Heat and Mass Transfer, 2016, 71: 75-85.
21	LI Z, CUI L, LI B R, et al. Enhanced heat conduction in molten salt containing nanoparticles: Insights from molecular dynamics[J]. International Journal of Heat and Mass Transfer, 2020, 153: doi: 10.1016/j.ijheatmasstransfer.2020.119578.
22	SARKAR S, SELVAM R P. Molecular dynamics simulation of effective thermal conductivity and study of enhanced thermal transport mechanism in nanofluids[J]. Journal of Applied Physics, 2007, 102(7): doi: 10.1063/1.2785009.
23	WILLIAMS D F, TOTH L M, CLARNO K T. Assessment of candidate molten salt coolants for the advanced high-temperature reactor[R]. Tennessee: Oak Ridge National Laboratory, 2006.
24	VAN ARTSDALEN E R, YAFFE I S. Electrical conductance and density of molten salt systems: KCl-LiCl, KCl-NaCl and KCl-KI[J]. The Journal of Physical Chemistry, 1955, 59(2): 118-127.
25	王佳, 孙泽, 路贵民, 等. 碱金属氯化物二元熔盐密度的分子动力学模拟研究[J]. 华东理工大学学报(自然科学版), 2016, 42(6): 771-781.
	WANG J, SUN Z, LU G M, et al. Molecular dynamics simulation for the densities of molten binary alkali metal chlorides[J]. Journal of East China University of Science and Technology (Natural Science Edition), 2016, 42(6): 771-781.
26	YU Y S, TAO Y B, ZHAO C Y, et al. Thermal storage performance enhancement and regulation mechanism of KNO₃-SWCNT based composite phase change materials[J]. International Journal of Heat and Mass Transfer, 2021, 181: doi: 10.1016/j.ijheatmasstransfer.2021.121870.
27	ZHANG J, FULLER J, AN Q. Coordination and thermophysical properties of transition metal chloro complexes in LiCl-KCl eutectic[J]. The Journal of Physical Chemistry B, 2021, 125(31): 8876-8887.

Pair	A_ij /(kcal/mol)	ρ_ij /nm	σ_ij /nm	C_ij /(nm⁶·kcal/mol)	D_ij /(nm⁸·kcal/mol)
Li-Li	9.7266	0.03425	0.1632	1.0504×10^-6	0.4317×10^-8
Li-K	7.689	0.03396	0.2279	1.91641×10^-5	1.22097×10^-7
Li-Cl	6.687	0.03425	0.2401	2.87769×10^-5	3.45326×10^-7
K-K	6.0782	0.03367	0.2926	3.49639×10^-4	3.453225×10^-6
K-Cl	4.8626	0.03367	0.3048	6.90645×10^-4	1.050356×10^-5
Cl-Cl	3.6473	0.03402	0.317	1.6757854×10^-3	3.3659592×10^-5
Al-Al	0.066783	0.0068	0.15704	3.23548×10^-4	0
Al-O	0.172715	0.0164	0.26067	7.9621×10^-4	0
O-O	0.276344	0.0263	0.3643	1.959372×10^-3	0

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