Abstract Solar Salt-based nanofluids have attracted significant scientific interest in recent years due to their improved thermal properties, making them strong candidates as thermal energy storage materials and/or heat transfer fluids in CSP plants. There have been reports on increased specific heat due to the addition of nanoparticles, however, there is a lack of comprehensive information on other essential properties affecting the heat transfer, such as the viscosity. This article concerns the rheological behaviour of nanofluids made of Solar Salt (mass percentage at 60% NaNO 3 – 40% KNO 3 ) as the base fluid and silica or alumina nanoparticles as additives. The evolution of these nanofluids viscosity as a function of the shear rate (1–1000 s −1 ) at a temperature range of 250–400 °C was measured and analysed. The impact of the salt purity (refined or industrial grade), the nanoparticle concentration (0.5–1.5 wt%) and the rheometer measuring configuration (coaxial cylinder or parallel plate) are examined. The results showed in general a Newtonian behaviour of the nanofluids with independency of the rheometer configuration. The relationship between the viscosity and the temperature follows an Arrhenius model. The influence of the nanoparticle concentration on the viscosity of the refined grade Solar Salt is analysed according to the Maron-Pierce and Kriegher-Dougherty models for the nanofluids containing alumina and silica nanoparticles respectively, due to their different shape.

中文翻译：

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用于聚光太阳能的基于太阳能盐的纳米流体的流变学。盐纯度、纳米颗粒浓度、温度和流变仪几何形状的影响

摘要 近年来，基于太阳能盐的纳米流体由于其改进的热性能而引起了极大的科学兴趣，使其成为 CSP 工厂中热能储存材料和/或传热流体的有力候选者。有报道称由于添加纳米粒子而导致比热增加，但是，缺乏关于影响传热的其他基本特性（例如粘度）的综合信息。本文涉及由太阳盐（60% NaNO 3 – 40% KNO 3 的质量百分比）作为基液和二氧化硅或氧化铝纳米粒子作为添加剂制成的纳米流体的流变行为。在 250-400°C 的温度范围内，测量并分析了这些纳米流体粘度随剪切速率 (1-1000 s -1 ) 的变化。检查了盐纯度（精制或工业级）、纳米颗粒浓度（0.5-1.5 wt%）和流变仪测量配置（同轴圆柱或平行板）的影响。结果通常表明纳米流体的牛顿行为与流变仪配置无关。粘度和温度之间的关系遵循 Arrhenius 模型。分别根据含有氧化铝和二氧化硅纳米粒子的纳米流体的 Maron-Pierce 和 Kriegher-Dougherty 模型分析了纳米粒子浓度对精制级太阳盐粘度的影响，因为它们的形状不同。结果通常表明纳米流体的牛顿行为与流变仪配置无关。粘度和温度之间的关系遵循 Arrhenius 模型。分别根据含有氧化铝和二氧化硅纳米粒子的纳米流体的 Maron-Pierce 和 Kriegher-Dougherty 模型分析了纳米粒子浓度对精制级太阳盐粘度的影响，因为它们的形状不同。结果通常表明纳米流体的牛顿行为与流变仪配置无关。粘度和温度之间的关系遵循 Arrhenius 模型。分别根据含有氧化铝和二氧化硅纳米粒子的纳米流体的 Maron-Pierce 和 Kriegher-Dougherty 模型分析了纳米粒子浓度对精制级太阳盐粘度的影响，因为它们的形状不同。