纳米TiO_2增强NaNO_3-KNO_3-NaNO_2熔盐的中温储热特性
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摘要
NaNO_3-KNO_3-NaNO_2(Hitec)熔盐作为一种理想的中高温传储热介质,未来有望在太阳能热利用等领域展开广泛应用。但其作为中温储热介质而言,其比热和导热性能相对较低,若能提高其比热和导热系数无疑将在太阳能热利用等实际应用中具有很重要的意义。采用水法技术制备了纳米TiO_2/Hitec熔盐复合储热介质,采用不同的表征技术研究了不同粒径、不同添加量纳米TiO_2颗粒对复合储热介质的比热、导热系数和热稳定性的影响。结果表明:与Hitec熔盐相比,纳米TiO_2颗粒明显提高了熔盐复合储热介质的储热特性。其中25 nm粒径,添加质量分数为0.062 5%纳米TiO_2对Hitec熔盐复合储热介质的比热(提高12%)和导热系数(增大15%)增强显著,同时热稳定性也得到改善。
[Background] NaNO_3-KNO_3-NaNO_2(7%-53%-40% in mass fraction) Hitec molten salt is considered as one of the promising candidate materials for heat transfer and thermal storage media in concentrated solar power(CSP), due to wide work temperature, low vapor pressure and so on. However, the specific thermal capacity of molten salt is relatively low. It will be significant in practical applications by improving the species thermal capacity with some addition into molten salt. [Purpose] The study aims to investigate the effect of various size(25 nm, 40 nm and 100 nm) and addition amount(0.062 5%, 0.5% and 1% in mass fraction) of TiO_2 nanoparticle on the thermal storage properties of Hitec molten salt. [Methods] Differential scanning calorimetry, thermal gravity and laser flash analyzer were used to determine the effect of TiO_2 nanoparticle on the species heat capacity, thermal stability and thermal conductivity of Hitec. [Results & Conclusion] The TiO_2 nanoparticle improves the thermal storage properties of Hitec, compared to origin Hitec. Furthermore, 0.062 5%(mass fraction) addition of TiO_2 nanoparticle with 25 nm size showed the best enhancement of the thermal storage properties of Hitec, where the specific heat capacity and thermal conductivity increased by 12% and 15%, respectively. Moreover, the upper working temperature of NaNO_3-KNO_3-NaNO_2 increased a lot.
[Background] NaNO_3-KNO_3-NaNO_2(7%-53%-40% in mass fraction) Hitec molten salt is considered as one of the promising candidate materials for heat transfer and thermal storage media in concentrated solar power(CSP), due to wide work temperature, low vapor pressure and so on. However, the specific thermal capacity of molten salt is relatively low. It will be significant in practical applications by improving the species thermal capacity with some addition into molten salt. [Purpose] The study aims to investigate the effect of various size(25 nm, 40 nm and 100 nm) and addition amount(0.062 5%, 0.5% and 1% in mass fraction) of TiO_2 nanoparticle on the thermal storage properties of Hitec molten salt. [Methods] Differential scanning calorimetry, thermal gravity and laser flash analyzer were used to determine the effect of TiO_2 nanoparticle on the species heat capacity, thermal stability and thermal conductivity of Hitec. [Results & Conclusion] The TiO_2 nanoparticle improves the thermal storage properties of Hitec, compared to origin Hitec. Furthermore, 0.062 5%(mass fraction) addition of TiO_2 nanoparticle with 25 nm size showed the best enhancement of the thermal storage properties of Hitec, where the specific heat capacity and thermal conductivity increased by 12% and 15%, respectively. Moreover, the upper working temperature of NaNO_3-KNO_3-NaNO_2 increased a lot.
引文
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14 Donghyun S.Specific heat of nanofluids synthesized by dispersing alumina nanoparticles in alkali salt eutectic[J].International Journal of Heat and Mass Transfer,2014,74(07):210?214.DOI:10.1016/j.ijheatmasstransfer.2014.02.066.
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17 Shin D,Banerjee D.Enhanced specific heat of silica nanofluids[J].Journal of Heat Transfer,2011,133(7):024501.DOI:10.1115/1.4002600.
18 Dudda B,Shin D.Effect of nanoparticle dispersion on specific heat capacity of a binary nitrate salt eutectic for concentrated solar power application[J].International Journal of Thermal Sciences,2013,69:37?42.DOI:10.1016/j.ijthermalsci.2013.02.003.
19 Shin D,Banerjee D.Enhanced of specific heat capacity of high-temperature silica-nanofluids synthesized in alkali chloride salt eutectics for solar thermal energy storage applications silica nanofluids[J].International Journal of Heat and Mass Transfer,2010,54:1064?1071.DOI:10.1016/j.ijheatmasstransfer.2010.11.017.
20 Shin D,Banerjee D.Specific heat of nanofluids synthesized by dispersing alumina nanoparticles in alkali salt eutectic[J].International Journal of Heat and Mass Transfer,2014,74:210?214.DOI:10.1016/j.ijheatmasstransfer.2014.02.066.
2 Liu M,Bell S.Review on concentrating solar power plants and new developments in high temperature thermal energy storage technologies[J].Renewable&Sustainable Energy Reviews,2015,53(09):1411?1432.DOI:10.1016/j.rser.2015.09.026.
3 Ignatiev V V,Feynberg O S.Molten-salt reactors:new possibilities,problems,and solutions[J].Atomic Energy,2012,112(3):157?165.DOI:10.1007/s10512-012-9537-2.
4 Piyush S,Matt E,Manohar S.Molten salts for high temperature reactors:university of Wisconsin molten salt corrosion and flow loop experiments-issues identified and path forward[R].Idaho National Laboratory,INL/EXT-10-18090,2010.DOI:10.2172/980798.
5 Bradshaw R W,Siegel N P.Molten nitrate salt development for thermal energy storage in parabolic through solar power system[M].Sandia National Laboratory,ES2008-54174,2008.DOI:10.1115/ES2009-90140.
6 Pelay U,Lou L,Fan Y.Thermal energy storage systems for concentrated solar power plants[J].Renewable Sustain Energy,2013,79(11):82?100.DOI:10.1016/j.pecs.2013.02.001
7江绵恒,徐洪杰,戴志敏.未来先进核裂变能--TMSR核能系统[J].中国科学院院刊,2012,7(3):366?374.DOI:10.3969/J.ISSN.1000-3045.2012.03.01.JIANG Mianheng,XU Hongjie,DAI Zhimin.Advanced fission energy program-TMSR nuclear energy system[J].Bullet in Chinese Academy of Sciences,2012,7(3):366?374.DOI:10.3969/J.ISSN.1000-3045.2012.03.01.
8金愿,张鹏.几种典型熔盐冷却剂的热物性研究[J].核技术,2016,39(5):050604.DOI:10.11889/j.0253-3219.2016.hjs.39.050604.JING Yuan,ZHANG Peng.Research on thermo-physical properties of several typical molten salt coolants[J].Nuclear Techniques,2016,39(5):050604.DOI:10.11889/j.0253-3219.2016.hjs.39.050604.
9阴慧琴.腐蚀产物Cr F3对Li F-Na F-KF熔盐物化性质的影响研究[D].上海:中国科学院上海应用物理研究所,2015.YIN Huiqin.The effect study of corrosion product Cr F3on physic-chemical properties of Li F-Na F-KF[D].Shanghai:Shanghai Institute of Applied Physics,Chinese Academy of Sciences,2015.
10程进辉.传蓄热熔盐的热物性研究[D].上海:中国科学院上海应用物理研究所,2014.CHENG Jinhui.Study on molten salt thermos-physical properties for heat transfer and storage[D].Shanghai:Shanghai Institute of Applied Physics,Chinese Academy of Sciences,2014.
11 Hani T,Donghyun S.Enhanced specific heat capacity of high-temperature molten salt-based nanofluids[J].International Journal of Heat and Mass Transfer,2012,57(02):542?548.DOI:10.1016/j.ijheatmasstransfer.2012.10.062.
12 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 and Mass Transfer,2013,70(03):174?184.DOI:10.1016/j.ijheatmasstransfer.2013.10.078.
13 Bharath D,Donghyun S.Effect of nanoparticle dispersion on specific heat capacity of a binary salt eutectic for concentrated solar power applications[J].International Journal of Heat and Mass Transfer,2013,69(07):37?42.DOI:10.1016/j.ijthermalsci.2013.02.003.
14 Donghyun S.Specific heat of nanofluids synthesized by dispersing alumina nanoparticles in alkali salt eutectic[J].International Journal of Heat and Mass Transfer,2014,74(07):210?214.DOI:10.1016/j.ijheatmasstransfer.2014.02.066.
15 Chen J H,Zhang P,An X H,et al.A device for measuring the density and liquids temperature of molten fluorides for heat transfer and storage[J].Chinese Physics Letters,2013,30(12):126501.DOI:10.1088/0256-307X/30/12/126501.
16 An X H,Chen J H,Yin H Q,et al.Thermal conductivity of high temperature fluoride molten salt determined by laser flash technique[J].International Journal of Heat and Mass Transfer,2015,90:872?877.DOI:10.1016/j.ijheatmasstransfer.2015.07.042.
17 Shin D,Banerjee D.Enhanced specific heat of silica nanofluids[J].Journal of Heat Transfer,2011,133(7):024501.DOI:10.1115/1.4002600.
18 Dudda B,Shin D.Effect of nanoparticle dispersion on specific heat capacity of a binary nitrate salt eutectic for concentrated solar power application[J].International Journal of Thermal Sciences,2013,69:37?42.DOI:10.1016/j.ijthermalsci.2013.02.003.
19 Shin D,Banerjee D.Enhanced of specific heat capacity of high-temperature silica-nanofluids synthesized in alkali chloride salt eutectics for solar thermal energy storage applications silica nanofluids[J].International Journal of Heat and Mass Transfer,2010,54:1064?1071.DOI:10.1016/j.ijheatmasstransfer.2010.11.017.
20 Shin D,Banerjee D.Specific heat of nanofluids synthesized by dispersing alumina nanoparticles in alkali salt eutectic[J].International Journal of Heat and Mass Transfer,2014,74:210?214.DOI:10.1016/j.ijheatmasstransfer.2014.02.066.