纳米粒子对熔盐复合蓄热材料热物性的影响
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摘要
为了得到SiO_2纳米粒子含量对SiO_2/NaNO_3-KNO_3/EG复合蓄热材料比热容和热导率的影响,通过机械分散法,采用NaNO_3-KNO_3和不同质量分数(0.1%,0.5%,1%,2%,3%)的SiO_2纳米粒子所形成的熔盐纳米材料作为蓄热材料,膨胀石墨(EG)作为基体材料,制备出纳米SiO_2/NaNO_3-KNO_3/EG复合材料。对复合材料的比热容和热导率进行了测量,同时用扫描电镜对其微观结构特征进行了分析。结果表明,SiO_2纳米粒子的质量分数为1%时,复合材料的平均比热容和热导率分别为3.92 J/(g·K)和8.47 W/(m·K),与其他纳米SiO_2添加比例相比,其比热容和热导率分别提高了1.37～2.17倍和1.7～3.2倍。这是由于复合材料表面会形成高密度的网状结构,这种具有较大比表面积和高表面能的特殊纳米结构可以提高复合材料的比热容和热导率。
In order to study the effects of SiO_2 nanoparticles content on the specific heat capacity and thermal conductivity of nano-SiO_2/NaNO_3-KNO_3/EG composite heat storage materials, a series of nano-SiO_2/NaNO_3-KNO_3/EG composites were prepared by mechanical dispersion method. NaNO_3-KNO_3 and SiO_2 nanoparticles with different mass fractions(0.1%, 0.5%, 1%, 2%, 3%) were used as heat storage materials and expanded graphite(EG)was used as matrix material. Then the specific heat and the thermal diffusivity of composite heat storage materials were measured, and the microstructural characteristics were analyzed by scanning electron microscopy(SEM). The results show that adding 1% of SiO_2 nanoparticles to the composite can significantly affect its average specific heat capacity and thermal conductivity, with a measured value of 3.92 J/(g·K) and 8.47 W/(m·K), respectively, which are1.37—2.17 times and 1.7—3.2 times higher than that of the other similar composites. This is owed to its high density network nanostructure with the large specific surface area and high surface energy which can improve the specific heat capacity and thermal conductivity.
In order to study the effects of SiO_2 nanoparticles content on the specific heat capacity and thermal conductivity of nano-SiO_2/NaNO_3-KNO_3/EG composite heat storage materials, a series of nano-SiO_2/NaNO_3-KNO_3/EG composites were prepared by mechanical dispersion method. NaNO_3-KNO_3 and SiO_2 nanoparticles with different mass fractions(0.1%, 0.5%, 1%, 2%, 3%) were used as heat storage materials and expanded graphite(EG)was used as matrix material. Then the specific heat and the thermal diffusivity of composite heat storage materials were measured, and the microstructural characteristics were analyzed by scanning electron microscopy(SEM). The results show that adding 1% of SiO_2 nanoparticles to the composite can significantly affect its average specific heat capacity and thermal conductivity, with a measured value of 3.92 J/(g·K) and 8.47 W/(m·K), respectively, which are1.37—2.17 times and 1.7—3.2 times higher than that of the other similar composites. This is owed to its high density network nanostructure with the large specific surface area and high surface energy which can improve the specific heat capacity and thermal conductivity.
引文
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[26] Jo B, Banerjee D. Enhanced specific heat capacity of molten saltbased nanomaterials:effects of nanoparticle dispersion and solvent material[J]. Acta Materialia, 2014, 75(9):80-91.
[27] Dudda B, Shin D. Effect of nanoparticle dispersion on specific heat capacity of a binary nitrate salt eutectic for concentrated solar power applications[J]. International Journal of Thermal Sciences, 2013, 69(7):37-42.
[28] Tiznobaik H, Shin D. Enhanced specific heat capacity of hightemperature molten salt-based nanofluids[J]. International Journal of Heat&Mass Transfer, 2013, 57(2):542-548.
[29] Shin D, Banerjee D. Specific heat of nanofluids synthesized by dispersing alumina nanoparticles in alkali salt eutectic[J].International Journal of Heat&Mass Transfer, 2014, 74(5):210-214.
[30] Shin D, Banerjee D. Enhanced thermal properties of SiO2,nanocomposite for solar thermal energy storage applications[J].International Journal of Heat&Mass Transfer, 2015, 84:898-902.
[31] Munyalo M J, Zhang X L. Particle size effect on thermophysical properties of nanofluid and nanofluid based phase change materials:a review[J]. Journal of Molecular Liquids, 2018, 265:77-87.
[2] Price H, Lupfert E, Kearney D, et al. Advances in parabolic trough solar power technology[J]. Journal of Solar Energy Engineering, 2002, 124(2):109-125.
[3] Brown D R, Lamarche J L, Spanner G E. Chemical energy storage system for SEGS solar thermal power plant[C]//International Solar Energy Conference. Honolulu, 1992:92.
[4] Malik D R. Evaluation of composite alumina nanoparticle and nitrate eutectic materials for use in concentrating solar power plants[D]. Texas:Texas A&M University, 2010.
[5] Chieruzzi M, Cerritelli G F, Miliozzi A, et al. Effect of nanoparticles on heat capacity of nanofluids based on molten salts as PCM for thermal energy storage[J]. Nanoscale Research Letters,2013, 8(1):448.
[6] Andreu-Cabedo P, Mondragon R, Hernandez L, et al. Increment of specific heat capacity of solar salt with SiO2nanoparticles[J].Nanoscale Research Letters, 2014, 9(1):582.
[7] Ming X H, Pan C. Optimal concentration of alumina nanoparticles in molten Hitec salt to maximize its specific heat capacity[J].International Journal of Heat&Mass Transfer, 2014, 70(3):174-184.
[8] Zhang L D, Chen X, Wu Y T, et al. Effect of nanoparticle dispersion on enhancing the specific heat capacity of quaternary nitrate for solar thermal energy storage application[J]. Solar Energy Materials&Solar Cells, 2016, 157:808-813.
[9]张璐迪.纳米SiO2-熔盐复合储热材料的制备与热物性研究[D].北京:北京工业大学, 2016.Zhang L D. Experimental study on preparation and thermal properties of composite nano-SiO2molten salt using in thermal energy storage[D]. Beijing:Beijing University of Technology,2016.
[10] Qiao G, Lasfargues M, Alexiadis A, et al. Simulation and experimental study of the specific heat capacity of molten salt based nanofluids[J]. Applied Thermal Engineering, 2017, 111:1517-1522.
[11] Aktay K S D C, Tamme R, Müller-Steinhagen H. Thermal conductivity of high-temperature multicomponent materials with phase change[J]. International Journal of Thermophysics, 2008, 29(2):678-692.
[12] Bauer T, Tamme R, Christ M, et al. PCM-graphite composites for high temperature thermal energy storage[C]//Ecostock. DLR,2006.
[13] Acem Z, Lopez J, Barrio E P D. KNO3/NaNO3–graphite materials for thermal energy storage at high temperature(Ⅰ):Elaboration methods and thermal properties[J]. Applied Thermal Engineering,2010, 30(13):1580-1585.
[14] Lopez J, Acem Z, Barrio E P D. KNO3/NaNO3–graphite materials for thermal energy storage at high temperature(Ⅱ):Phase transition properties[J]. Applied Thermal Engineering, 2010, 30(13):1586-1593.
[15] Xiao X, Zhang P, Li M. Thermal characterization of nitrates and nitrates/expanded graphite mixture phase change materials for solar energy storage[J]. Energy Conversion&Management, 2013,73(73):86-94.
[16]张焘,曾亮,张东.膨胀石墨、石墨烯改善无机盐相变材料热物性能[J].无机盐工业, 2010, 42(5):24-26.Zhang T, Zeng L, Zhang D. Improvement of thermal properties of hybrid inorganic salt phase change materials by expanded graphite and grapheme[J]. Inorganic Chemicals Industry, 2010, 42(5):24-26.
[17] Tian H, Wang W, Ding J, et al. Preparation of binary eutectic chloride/expanded graphite as high-temperature thermal energy storage materials[J]. Solar Energy Materials&Solar Cells, 2016,149:187-194.
[18] Huang Z, Gao X, Xu T, et al. Thermal property measurement and heat storage analysis of LiNO3/KCI-expanded graphite composite phase change material[J]. Applied Energy, 2014, 115:265-271.
[19] Tian H, Wang W, Ding J, et al. Thermal conductivities and characteristics of ternary eutectic chloride/expanded graphite thermal energy storage composites[J]. Applied Energy, 2015, 148:87-92.
[20] Zhou D, Zhao C Y. Experimental investigations on heat transfer in phase change materials(PCMs)embedded in porous materials[J].Applied Thermal Engineering, 2011, 31(5):970-977.
[21] Mohamed S A, Al-Sulaiman F A, Ibrahim N I, et al. A review on current status and challenges of inorganic phase change materials for thermal energy storage systems[J]. Renewable&Sustainable Energy Reviews, 2017, 70:1072-1089.
[22] Zhang P, Xiao X, Ma Z W. A review of the composite phase change materials:fabrication, characterization, mathematical modeling and application to performance enhancement[J]. Applied Energy, 2016, 165:472-510.
[23] Chieruzzi M, Cerritelli G F, Miliozzi A, et al. Heat capacity of nanofluids for solar energy storage produced by dispersing oxide nanoparticles in nitrate salt mixture directly at high temperature[J]. Solar Energy Materials and Solar Cells, 2017, 167:60-69.
[24] Song W L, Lu Y W, Wu Y T, et al. Effect of SiO2nanoparticles on specific heat capacity of low-melting-point eutectic quaternary nitrate salt[J]. Solar Energy Materials&Solar Cells, 2018, 179:66-71.
[25]于强,鹿院卫.硝酸盐/纳米SiO2/EG复合蓄热材料的制备与热性能研究[C]//第四届中国太阳能热发电大会.常州, 2018.Yu Q, Lu Y W. Preparation and thermal properties of nitrate/nano-SiO2/EG composite thermal storage materials[C]//Fourth China Solar Thermal Power Generation Congress. Changzhou,2018.
[26] Jo B, Banerjee D. Enhanced specific heat capacity of molten saltbased nanomaterials:effects of nanoparticle dispersion and solvent material[J]. Acta Materialia, 2014, 75(9):80-91.
[27] Dudda B, Shin D. Effect of nanoparticle dispersion on specific heat capacity of a binary nitrate salt eutectic for concentrated solar power applications[J]. International Journal of Thermal Sciences, 2013, 69(7):37-42.
[28] Tiznobaik H, Shin D. Enhanced specific heat capacity of hightemperature molten salt-based nanofluids[J]. International Journal of Heat&Mass Transfer, 2013, 57(2):542-548.
[29] Shin D, Banerjee D. Specific heat of nanofluids synthesized by dispersing alumina nanoparticles in alkali salt eutectic[J].International Journal of Heat&Mass Transfer, 2014, 74(5):210-214.
[30] Shin D, Banerjee D. Enhanced thermal properties of SiO2,nanocomposite for solar thermal energy storage applications[J].International Journal of Heat&Mass Transfer, 2015, 84:898-902.
[31] Munyalo M J, Zhang X L. Particle size effect on thermophysical properties of nanofluid and nanofluid based phase change materials:a review[J]. Journal of Molecular Liquids, 2018, 265:77-87.