Numerical simulation of solidification characteristics of graphene nanofluid as phase change material

doi:10.16085/j.issn.1000-6613.2017-0954

Abstract

Abstract: Graphene nanofluid is a promising phase change material for improving the efficiency of cool storage. The solidification characteristics of water based graphene nanofluid were numerically investigated; enthalpy-porosity method was adopted to track the solid-liquid interface; the effects of graphene nanosheet mass fraction, cool storage cavity size and geometry on the solidification time and solid-liquid interface evolution were analyzed. The results showed that the solidification time decreased significantly with the increase of graphene nanosheet mass fraction. In a circular cool storage cavity with a diameter of 72mm, the solidification time for 1.2% graphene nanofluid was 30.1% less than that for the deionized water, which was consistent with the experimental results. With the decrease of circular cavity diameter, the solidification time for graphene nanofluid significantly decreased, but the enhancement effect of thgraphene nanosheet on the solidification was weakened. For the same sectional area, the moving velocity of solid-liquid interface during the solidification in a triangular cavity is larger than that in the circular and square cavities, which indicated that the triangular cavity was more conducive to the promotion of solidification process. For those three types of cavities, the solidification occurred at the bottom of cavity in the initial stage; the solid-liquid interface was similar to the shape of the cavity itself and tended to be circular in the middle and later stages, respectively.

Key words: cool storage, phase change, nanoparticles, graphene, numerical simulation

摘要： 鉴于石墨烯高导热性能的特点，将石墨烯纳米流体作为相变材料有望提高蓄冷效率。本文对水基石墨烯纳米流体相变材料的凝固特性进行了数值研究，采用焓-多孔度法追踪固液相界面，分析了石墨烯纳米片质量分数、蓄冷腔体尺寸和几何形状对凝固时间和相界面演化的影响。结果表明，相变材料凝固所需时间随着石墨烯纳米片质量分数的增大显著降低，对于直径为72mm的圆形蓄冷腔体，质量分数为1.2%的石墨烯纳米流体相变材料与去离子水相比凝固时间降低了30.1%，与已有的实验结果相符；随着圆形蓄冷腔体直径减小，石墨烯纳米流体凝固所需时间显著降低，但石墨烯纳米片对凝固的强化作用减弱；在腔体等截面积的情况下，三角形腔体内凝固过程的相界面移动速率明显大于圆形和方形腔体、更有利于促进凝固过程，3种形状腔体内初期凝固都发生在腔体底部、凝固中期相界面形状与腔体本身形状相似、凝固后期相界面趋近于圆形。

关键词: 蓄冷, 相变, 纳米粒子, 石墨烯, 数值模拟

CLC Number:

TK02

CHEN Chen, PENG Hao. Numerical simulation of solidification characteristics of graphene nanofluid as phase change material[J]. Chemical Industry and Engineering Progress, 2018, 37(02): 681-688.

陈晨, 彭浩. 石墨烯纳米流体相变材料蓄冷特性的数值模拟[J]. 化工进展, 2018, 37(02): 681-688.

References

[1] 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.
[2] 谢望平,汪南,朱冬生,相变材料强化传热研究进展[J]. 化工进展, 2008, 27(2):190-195. XIE W P, WANG N, ZHU D S, et al. Review of heat transfer enhancement of the PCMs[J]. Chemical Industry and Engineering Progress, 2008, 27(2):190-195.
[3] 朱冬生,吴淑英,李新芳,等. 纳米流体工质的基础研究及其蓄冷应用前景[J]. 化工进展, 2008, 27(6):857-860. ZHU D S, WU S Y, LI X F, et al. Fundamental investigation and application prospect of cool storage of nanofluids[J]. Chemical Industry and Engineering Progress, 2008, 27(6):857-860.
[4] METTAAEE E B S, ASSASSA G M R. Thermal conductivity enhancement in a latent heat storage system[J]. Solar Energy, 2007, 81(7):839-845.
[5] ALTOHAMY A A, RABBO M F A, SAKR R Y, et al. Effect of water based Al₂O₃ nanoparticle PCM on cool storage performance[J]. Applied Thermal Engineering, 2015, 84:331-338.
[6] BALANDLN A A, GHOSH S, BAO W, et al. Superior thermal conductivity of single-layer graphene[J]. Nano Letters, 2008, 8(3):902-907.
[7] SATHISHKUMAR A, KUMARESAN V, VELRAJ R. Solidification characteristics of water based graphene nanofluid PCM in a spherical capsule for cool thermal energy storage applications[J]. International Journal of Refrigeration, 2016, 66:73-83.
[8] LI X, CHEN Y, CHENG Z, et al. Ultrahigh specific surface area of graphene for eliminating subcooling of water[J]. Applied Energy, 2014, 130(5):824-829.
[9] 贾莉斯, 彭岚, 陈颖, 等. 水基纳米流体的凝固行为[J]. 功能材料, 2014, 45(9):92-95. JIA L S, PENG F, CHEN Y, et al. Solidification behaviors of water-based nanofluids[J]. Functional Materials, 2014, 45(9):92-95.
[10] 吴淑英,朱冬生,杨硕. Al₂O₃-H₂O纳米流体的相变蓄冷实验研究[J]. 工程热物理学报, 2009, 30(6):981-983. W U S Y, ZHU D S, YANG S. Experimental study on phase change cool storage of Al₂O₃-H₂O nanofluids[J]. Journal of Engineering Thermophysics, 2009, 30(6):981-983.
[11] ARASU A V, MUJUMDAR A S. Numerical study on melting of paraffin wax with Al₂O₃ in a square enclosure[J]. International Communications in Heat and Mass Transfer, 2012, 39(1):8-16.
[12] ARASU A V, SASMITO A P, MUJUMDAR A S. Thermal performance enhancement of paraffin wax with Al₂O₃ and CuO nanoplatelets——a numerical study[J]. Frontiers in Heat and Mass Transfer, 2012, 2(4):043-048.
[13] VAJJHA R S, DAS D K, NAMBURU P K. Numerical study of fluid dynamic and heat transfer performance of Al₂O₃ and CuO nanofluids in the flat tubes of a radiator[J]. International Journal of Heat and Fluid Flow, 2010, 31(4):613-621.
[14] 李新芳,朱冬生. 纳米流体强化相变蓄冷特性的实验研究[J].材料导报, 2009, 23(6):11-13. LI X F, ZHU D S. Experimental study of cold storage characteristics of nanofluids as the phase change material[J]. Materials Review, 2009, 23(6):11-13.
[15] SHARMA R K, GANESAN P, SAHU J N, et al. Numerical study for enhancement of solidification of phase change materials using trapezoidal cavity[J]. Powder Technology, 2014, 268:38-47.
[16] 刘玉东,李夔宁,何钦波,等. 低温纳米复合相变蓄冷材料热物性研究[J]. 工程热物理学报, 2008, 29(1):105-107. LIU Y D, LI K N, HE Q B, et al. Study on thermal properties of low temperature nanocomposites for phase change cool storage[J]. Journal of Engineering Thermophysics, 2008, 29(1):105-107.
[17] MOTAHAR S, ALEMRAJABI A A, KHODABANDEH R. Experimental investigation on heat transfer characteristics during melting of a phase change material with dispersed TiO₂ nanoparticles in a rectangular enclosure[J]. International Journal of Heat and Mass Transfer, 2017, 109:134-146.
[18] ARICI M, TÜTÜNCÜ E, KAN M, et al. Melting of nanoparticle-enhanced paraffin wax in a rectangular enclosure with partially active walls[J]. International Journal of Heat and Mass Transfer, 2017, 104:7-17.
[19] KHODADADI J M, HOSSEINIZADEH S F. Nanoparticle-enhanced phase change materials (NEPCM) with great potential for improved thermal energy storage[J]. International Journal of Heat and Mass Transfer, 2007, 34:534-543.
[20] BRINKMAN H C. The viscosity of concentrated suspensions and solutions[J]. Journal of Chemical Physics, 1952, 20(4):571-571.
[21] VOLLER V R, PRAKASH C. A fixed grid numerical modelling methodology for convection-diffusion mushy region phase-change problems[J]. International Journal of Heat and Mass Transfer, 1987, 30(8):1709-1719.
[22] CHANDRASEKARAN P, CHERALATHAN M, VELRAJ R, et al. Influence of the size of spherical capsule on solidification characteristics of DI (deionized water) water for a cool thermal energy storage system:an experimental study[J]. Energy, 2015, 90:807-813.
[23] GAU C, VISKANTA R. Melting and solidification of a pure metal on a vertical wall[J]. Journal of Heat Transfer, 1986, 108(1):174-181.
[24] BRENT A D, VOLLER V R, REID K J. Enthalpy-porosity technique for modeling convection-diffusion phase change:application to the melting of a pure metal[J]. Numerical Heat Transfer Applications, 1988, 13(3):297-318.
[25] 康亚盟,刁彦华,赵耀华,等. 纳米复合相变蓄热材料的制备与特性[J]. 化工学报, 2016, 67(1):372-379. KAN Y M, DIAO Y H, ZHAO Y H, et al. Preparation and properties of nano composite phase change thermal storage materials[J]. CIESC Journal, 2016, 67(1):372-379.
[26] 丁晴,方昕,闫晨,等. 石墨纳米片尺寸对复合相变材料储热特性的影响[J]. 化工学报, 2015, 66(6):2023-2031. DING Q, FANG X, YAN C, et al. Effects of graphite nanosheet size on thermal storage property of composite PCMs[J], CIESC Journal, 2015, 66(6):2023-2031.
[27] CHANDRASEKARAN P, CHERALATHAN M, KUMARESAN V, et al. Enhanced heat transfer characteristics of water based copper oxide nanofluid PCM (phase change material) in a spherical capsule during solidification for energy efficient cool thermal storage system[J]. Energy, 2014, 72(7):636-642.
[28] ALKAN C, SAR A, KARAIPEKLI A. Preparation thermal properties and thermal reliability of microencapsulated n-eicosane as novel phase change material for thermal energy storage[J]. Energy Conversion and Management, 2011, 52(1):687-692.
[29] DHAIDAN N S. Nanostructures assisted melting of phase change materials in various cavities[J]. Applied Thermal Engineering, 2017, 111:193-212.
[30] MAHDI J M, NSOFOR E C. Solidification of a PCM with nanoparticles in triplex-tube thermal energy storage system[J]. Applied Thermal Engineering, 2016, 108:596-604.