添加纳米MgO和SiO_2颗粒对二元碳酸盐(Li_2CO_3-K_2CO_3)比热容的影响

Effect of MgO and SiO_2 nanoparticles on specific heat capacity of binary carbonate eutectic

熔盐作为一种新型传热工质,由于其液体使用范围宽,比热容相对较高,蓄热能力强,已被广泛应用于聚热太阳能电站的储热传热介质,而通过增强熔盐的比热容可以显著提高其储热密度。将纳米Si O_2和MgO颗粒分别均匀分散到二元共晶碳酸盐(Li_2CO_3-K_2CO_3)中,制备出两种稳定的纳米流体,采用差式扫描量热法(DSC)分析纳米颗粒对熔盐比热容的影响。实验结果显示,添加20 nm的纳米颗粒对碳酸盐的比热容有显著影响:通过添加纳米MgO和Si O_2颗粒,纳米熔盐比热容相比基盐分别平均提高了27.5%～34.1%,11%～20.7%。经过多个固-液循环后,测得两种纳米流体的比热容变化率均低于4.31%,且具有良好的热稳定性。采用电子扫描显微镜表征纳米流体的微观结构,纳米流体在固态时的SEM图像显示在熔盐表面形成了特殊的纳米结构。

As a new type of heat storage and heat transfer medium,molten salt has been widely used in concentrating solar power(CSP)system due to its wide working temperature range,relatively high specific and strong heat storage capacity.Increasing the specific heat capacity of the molten salt can significantly increase its heat storage density.Nanofluids were synthesized by dispersing20nm SiO2and MgO particles to binary carbonate eutectic(Li2CO3and K2CO3).The specific heat capacity effect of nanoparticles on molten salt was characterized by DSC measurement.Results show that mass fraction of20nm nanoparticles significantly enhanced the specific heat of binary carbonate eutectic.Compared with the base salt,the average specific heat improved with20nm MgO and SiO2nanoparticles was found to be27.5%-34.1%,11%-20.7%,respectively.The change rate of the specific heat values of the two nanofluids is lower than4.31%after multiple solid-liquid cycles.The molten salt nanofluids showed good thermal stability.The microstructure of nanofluids was characterized by scanning electron microscopy(SEM).The images of nanofluids in solid state showed that special nanostructures were formed on the surface of molten salts.