奈米熔鹽之比熱

Abstract

熔鹽(molten salt)目前被廣泛的應用於太陽能發電廠，而太陽能發電廠的儲熱能力受限於熔鹽的比熱值，因此熔鹽的比熱值為一非常重要的熱性質。本研究探討加入氧化鋁奈米粒子於熔鹽後(以下簡稱奈米熔鹽)，其奈米熔鹽濃度與奈米粒子尺寸對比熱所造成的影響。本研究使用了13 nm和90 nm的氧化鋁奈米粒子，分別調配1.1 %、3.3 %、5.4 %等不同體積百分濃度之奈米熔鹽來比較。實驗結果發現奈米熔鹽的比熱隨著體積百分濃度上升而下降，同時在相同體積百分濃度下，90 nm之奈米熔鹽所得之比熱高於13 nm之奈米熔鹽。此外，發現實驗結果與現有的理論所預測之比熱不符，因此本研究提出一新的理論模型，此理論模型考慮奈米粒子的表面薄膜層對比熱之影響，根據此新理論模型所得之比熱預測值，更能準確的解釋實驗結果。

Molten salts are extensively used as a thermal energy storage material in solar-thermal power plants nowadays. The energy storage capacity of a solar-thermal power plant is restricted by the specific heat capacity of the molten salt. In this work, the effect of concentration and size of the nanoparticles on the specific heat capacity of the molten salt embedded with the nanoparticles (named as nano-salt) was studied. The nano-salts having alumina nanoparticles of two different sizes (13 nm and 90 nm) and three volume concentrations (1.1 %、3.3 % and 5.4 %) were synthesized. Experimental results show that the specific heat capacity of the nano-salt decreases as the volume concentration increases. Meanwhile, the nano-salts doped with 90 nm alumina nanopartilces have a larger specific heat capacity than that of nano-salts doped with 13 nm alumina nanoparticles. In addition, the predictions from the current existing models have a large difference from the experimental data. Thus, a modified model considering the nanolayer effect on the specific heat capacity of the nano-salt was proposed. The prediction based on this modified model agrees better with the experimental data as compared to the existing models.