掺镁碳酸熔盐液体导热特性
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摘要
为克服碳酸熔盐热导率较低的不足,提出通过向三元碳酸熔盐(Li2CO3-Na2CO3-K2CO3)掺杂金属镁粉来改善导热性能的新思路,采用静态熔融法制备了掺杂1%、2%掺镁碳酸熔盐复合材料。采用扫描电镜-X射线能谱、阿基米德法、差示扫描量热法(DIN比热测试标准)和激光闪光法,分别观察了掺镁碳酸熔盐形貌结构,测量了熔盐和复合熔盐液体的密度、比热容、热扩散系数,最后计算获得复合熔盐液体的热导率。研究结果表明,镁粉的加入改变了纯盐(三元碳酸熔盐)的形貌结构,熔体内形成大量的2~5μm球体颗粒,与纯盐相比,1%掺镁碳酸熔盐液体密度、热扩散系数和热导率都得到增强,液体比热容减小,复合熔盐液体的平均热导率增加了21.67%;2%掺镁碳酸熔盐液体密度、热扩散系数和热导率同样得到增强,虽然复合熔盐液体的比热容减小,但其平均热导率仍然增加了19.07%。1%掺镁碳酸熔盐具有更高的液体密度、热扩散系数和热导率,可作为传热介质在太阳能热发电传蓄热系统推广。
In order to improve the low thermal conductivity performance of carbonate molten salt,it is proposed to dope metal magnesium powder with ternary carbonate molten salt(Li_2CO_3-Na_2CO_3-K_2CO_3) to strengthen the thermal conductivity.The static melting method was used to prepare the composite carbonate salts with 1%(mass) or 2%(mass) magnesium powder.The morphology,structure,liquid density,specific heat capacity,and thermal diffusivity were characterized by the scanning electron microscope-energy dispersive X-ray spectrometer(SEM-EDX),Archimedes method,the differential scanning calorimeter(DIN specific heat measure standard) and the laser flash method,respectively.The thermal conductivity was finally calculated based on the density,specific heat capacity,and thermal diffusivity.The results showed that the introducing of magnesium powder changed the morphology of pure eutectic(ternary carbonate salt),a large number of spherical particles(2—5 μm) were detected in the composite salts.Comparison with the pure eutectic,the liquid density,thermal diffusivity and thermal conductivity of salt compound doped magnesium powder were enhanced,and the liquid specific heat capacity was diminished.The mean thermal conductivity of salt compound doped with 1% or 2% magnesium powder was enhanced by 21.67% and 19.07%,respectively.So,the 1% salt composite should be the promising HTF due to the enhancement of density,thermal diffusivity and thermal conductivity.
In order to improve the low thermal conductivity performance of carbonate molten salt,it is proposed to dope metal magnesium powder with ternary carbonate molten salt(Li_2CO_3-Na_2CO_3-K_2CO_3) to strengthen the thermal conductivity.The static melting method was used to prepare the composite carbonate salts with 1%(mass) or 2%(mass) magnesium powder.The morphology,structure,liquid density,specific heat capacity,and thermal diffusivity were characterized by the scanning electron microscope-energy dispersive X-ray spectrometer(SEM-EDX),Archimedes method,the differential scanning calorimeter(DIN specific heat measure standard) and the laser flash method,respectively.The thermal conductivity was finally calculated based on the density,specific heat capacity,and thermal diffusivity.The results showed that the introducing of magnesium powder changed the morphology of pure eutectic(ternary carbonate salt),a large number of spherical particles(2—5 μm) were detected in the composite salts.Comparison with the pure eutectic,the liquid density,thermal diffusivity and thermal conductivity of salt compound doped magnesium powder were enhanced,and the liquid specific heat capacity was diminished.The mean thermal conductivity of salt compound doped with 1% or 2% magnesium powder was enhanced by 21.67% and 19.07%,respectively.So,the 1% salt composite should be the promising HTF due to the enhancement of density,thermal diffusivity and thermal conductivity.
引文
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[23]BAIK H T,SHIN D.Experimental validation of enhanced heat capacity of ionic liquid-based nanomaterial[J].Applied Physics Letters,2013,102:173906.
[2]盛玲霞,李佳燕,赵豫红.塔式太阳能电站接收器的建模及动态仿真[J].化工学报,2016,67(3):736-742.SHENG L X,LI J Y,ZHAO Y H.Modeling and dynamic simulation of receiver in a solar tower station[J].CIESC Journal,2016,67(3):736-742.
[3]BALGHOUTHI M,TRABELSI S E,AMARA M B,et al.Potential of concentrating solar power(CSP)technology in Tunisia and the possibility of interconnection with Europe[J].Renewable and Sustainable Energy Reviews,2016,56:1227-1248.
[4]VIGNAROOBAN K,XU X H,ARVAY A,et al.Heat transfer fluids for concentrating solar power systems—a review[J].Applied Energy,2015,146:383-396.
[5]LIU M,TAY N S,BELL S,et al.Review on concentrating solar power plants and new developments in high temperature thermal energy storage technologies[J].Renewable and Sustainable Energy Reviews,2016,53:1411-1432.
[6]崔武军,吴玉庭,熊亚选,等.低熔点熔盐蓄热罐内温度分布与散热损失实验[J].化工学报,2014,65(S1):162-167.CUI W J,WU Y T,XIONG Y X,et al.Temperature distribution and heat loss experiments of low melting point molten salt heat storage tank[J].CIESC Journal,2014,65(S1):162-167.
[7]LIU M,SAMAN W,BRUNO F.Review on storage materials and thermal performance enhancement techniques for high temperature phase change thermal storage systems[J].Renewable and Sustainable Energy Reviews,2012,16:2118-2132.
[8]WICAKSONO H,ZHANG X,FUJIWARA S,et al.Measurements of thermal conductivity and thermal diffusivity of molten carbonates[J].The Reports of Institute of Advanced Material Study Kyushu University,2001,15:165-168.
[9]SHIN D,BANERJEE D.Enhanced thermal properties of Si O2nanocomposite for solar thermal energy storage applications[J].International Journal of Heat and Mass Transfer,2015,84:898-902.
[10]OYA T,NOMURA T,TSUBOTA M,et al.Thermal conductivity enhancement of erythritol as PCM by using graphite and nickel particles[J].Applied Thermal Engineering,2013,61:825-828.
[11]WEST R E.High temperature sensible heat storage[J].Energy,1985,10(10):1165-1175.
[12]JORGENSEN G,SCHISSEL P,BURROWS R.Optical properties of high-temperature materials for direct absorption receivers[J].Solar Energy Materials,1985,14(3/4/5):385-394.
[13]COYLE R T,THOMAS T M,SCHISSEL P,et al.Corrosion of selected alloys in eutectic lithium-sodium-potassium carbonate at900℃[R].Golden:Solar Energy Research Institnte,1986.
[14]GHERIBI A E,TORRES J A,CHARTRAND P.Recommended values for the thermal conductivity of molten salts between the melting and boiling points[J].Solar Energy Materials&Solar Cells,2014,126:11-25.
[15]SHIBATA H,OHTA H,YOSHIDA H.Thermal diffusivity of molten carbonates at elevated temperatures[J].High Temperature Material Processes,2002,21(3):139-142.
[16]AN X H,CHENG J H,ZHANG P,et al.Determination and evaluation of the thermo-physical properties of an alkali carbonate eutectic molten salt[J].Faraday Discussions,2016,190:327-338.
[17]OTSUBO S,NAGASAKA Y,NAGASHIMA A.Experimental study on the forced Rayleigh scattering method using CO2 laser(Ⅲ):Measurement of molten single carbonates and their binary and ternary mixtures[J].Nihon Kikai Gakkai Ronbunshu B Hen/Transactions of the Japan Society of Mechanical Engineers Part B,1998,64(619):806-813.
[18]PELTON A D,BALE C W,LIN P L.Calculation of phase diagrams and thermodynamic properties of 14 additive and reciprocal ternary systems containing Li2CO3,Na2CO3,K2CO3,Li2SO4,Na2SO4,K2SO4,Li OH,Na OH,and KOH[J].Canadian Journal of Chemistry,1984,62(3):457-474.
[19]黎文献.镁及镁合金[M].长沙:中南大学出版社,2005:2-8.LI W X.Magnesium and Magnesium Alloys[M].Changsha:Central South University Press,2005:2-8.
[20]徐日瑶.镁冶金学[M].北京:冶金工业出版社,1981:3.XU R Y.Magnesium Metallurgy[M].Beijing:Metallurgical Industry Press,1981:3.
[21]高自省.镁及镁合金防腐与表面强化生产技术[M].北京:冶金工业出版社,2012:1.GAO Z X.Magnesium and Magnesium Alloy Corrosion and Surface Hardening Production Technology[M].Beijing:Metallurgical Industry Press,2012:1.
[22]MIN S,BLUMM J,LINDEMANN A.A new laser flash system for measurement of the thermo-physical properties[J].Thermochimica Acta,2007,455:46-49.
[23]BAIK H T,SHIN D.Experimental validation of enhanced heat capacity of ionic liquid-based nanomaterial[J].Applied Physics Letters,2013,102:173906.