纳米二氧化硅强化四元溴化盐熔化潜热及热稳定性的实验研究

EXPERIMENT STUDY OF FUSION LATENT HEAT AND THERMAL STABILITY OF NANO-SiO_2 ENHANCING QUAD-BROMIDE SALT

高温熔盐作为一种高效的传热和蓄热工质,其熔点的高低和熔化潜热的大小决定着熔盐的工作温度和相变蓄热能力。以化学纯Na Br、KBr、CaBr_2、LiBr为基盐,按照一定比例配制一种混合四元溴化盐。为改善该混合熔盐的性能,将纳米SiO_2以一定质量分数均匀加入混合溴化盐中,配制得到SiO_2纳米溴化盐。利用同步热分析仪对四元溴化盐和SiO_2纳米溴化盐的熔点和熔化潜热进行实验研究。实验结果表明纳米溴化盐的熔点随纳米SiO_2质量百分含量的增大而缓慢下降,下降幅度在2.5℃以内;熔化潜热随纳米SiO_2质量百分含量的增大呈近似直线规律升高,当纳米SiO_2含量达到1.5%时,该纳米SiO_2溴化盐的熔化潜热达到最大,较四元溴化盐升高了89.6%;纳米SiO_2的添加提高了四元溴化盐的分解温度及热稳定性。

High temperature molten salt, as an efficient material of heat transfer and heat storage, the melting point and fusion latent heat determine its working temperature and phase change heat storage capacity, respectively. The quad- bromide salt mixture is prepared by four kinds of chemically pure salts which are NaBr, KBr, CaBr2 and LiBr with a determined proportion. In order to improve the thermal performance of the quad-bromide salts, nano-SiO2 is added to the quad-bromide salts and so new kinds of nano-SiO2 bromide salts are prepared with different mass fractions of nano-SiO2. Then the method of Simultaneous Thermal Analysis （STA） is used to investigate variations of melting point and fusion latent heat of the nano-bromide salts with different ratios of nano-SiO2. The experimental results show that melting point of nano-bromide salts decreases slow with the increase of the mass fraction of nano-SiO2, the fall range is within 2.5℃. The fusion latent heat of the nano-bromide salts increases linearly with the increase of mass fraction of SiO2, when the mass fraction of nano-SiO2 reaches 1.5%, the fusion latent heat of nano-SiO2 bromide salts mixture reaches maximum, increased 89.6 % compared with the quad-bromide salts mixture. The decomposition temperature and thermal stability of the quad-bromide salts mixture are improved by the addition of nano-SiO2.