Research on thermal properties of novel silica nanoparticle/binary nitrate/expanded graphite composite heat storage blocks

Abstract

In order to study the effects of EG (expanded graphite) content and SiO2 nanoparticles on the specific heat and thermal conductivity of nano-SiO2/NaNO3–KNO3/EG composite heat storage materials, a series of nano-SiO2/NaNO3–KNO3/EG composites are prepared by the aqueous solution-ultrasound oscillation method. The nano-SiO2/NaNO3–KNO3 and EG with different mass fractions (5%, 10%, 15% and 20%) are used as heat storage material and matrix material, respectively. The specific heat and thermal conductivity of the composite are measured by STA (Simultaneous Thermal Analysis) and LFA (Laser Flash Apparatus), respectively. The results show that nano-SiO2/NaNO3–KNO3/EG composite exhibits obvious better performance than pure binary nitrate NaNO3–KNO3. With 15 wt% EG, the average specific heat (from 250 °C to 430 °C) and thermal conductivity of the composite are 2.574 J/(g·K) and 6.05 W/(m·K), respectively, which are 1.69 times and 9 times higher than that of pure binary nitrate. After adding 1 wt% nano-SiO2 to NaNO3–KNO3/EG (15 wt%) composite, the average specific heat and thermal conductivity increase by 44% and 60.9%, respectively. From the above results, the composite heat storage materials prepared by adding EG and nano-SiO2 into binary nitrate are considered as promising candidate materials for high heat transfer performance.