Abstract Hybrid nanofluids are a novel class of colloidal fluids which have drawn significant attention due to potential tailoring of their thermo-physical properties for heat transfer enhancement by a combination of more than one nano-additive to meet specific requirements of an application. In the present work, ceramic copper oxide/carbon (SiO2-CuO/C) nanoparticles in 80:20 (wt%) composition were prepared by ultrasonic-assisted wet mixing technique. The hybrid nanofluid was formulated by dispersing the nanoparticles into a base fluid mixture of 60:40 (% by mass) glycerol and ethylene glycol (G/EG) using the two-steps method. The influence of nanoparticles on the augmentation of specific heat, thermal conductivity and viscosity was examined in the volume concentration range of 0.5–2.0% in the temperature range of 303.15–353.15 K. The results demonstrate that the synthesized SiO2-CuO/C hybrid nanoparticles enhanced the thermo-physical properties of the base fluid mixture which is higher than using SiO2 alone. In the case of SiO2–G/EG nanofluid, the specific heat capacity decremented by a maximum value of 5.7% whereas the thermal conductivity and viscosity incremented by 6.9% and 1.33-times as compared with G/EG at maximum volume concentration of 2.0% at a temperature of 353.15 K. Comparatively, a reinforcement of 80% SiO2 with 20% CuO/C in G/EG mixture led to thermal conductivity and viscosity enhancement by 26.9% and 1.15-times, respectively with a significant reduction of specific heat by 21.1%. New empirical correlations were proposed based on the experimental data for evaluation of thermophysical properties.

中文翻译：

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基于甘油和乙二醇混合物的 SiO 2 -CuO/C 杂化纳米流体用于增强太阳能传输的性能

摘要 混合纳米流体是一类新型胶体流体，由于其热物理特性的潜在定制，通过组合一种以上的纳米添加剂来增强传热以满足应用的特定要求，因此引起了极大的关注。在目前的工作中，通过超声辅助湿法混合技术制备了 80:20 (wt%) 组成的陶瓷氧化铜/碳 (SiO2-CuO/C) 纳米颗粒。通过使用两步法将纳米颗粒分散到 60:40（质量百分比）甘油和乙二醇 (G/EG) 的基础流体混合物中，配制混合纳米流体。在 303.15-353.15 K 的温度范围内，在 0.5-2.0% 的体积浓度范围内检查了纳米颗粒对比热、热导率和粘度增加的影响。结果表明，合成的 SiO2-CuO/C 混合纳米粒子增强了基液混合物的热物理性能，高于单独使用 SiO2。在 SiO2-G/EG 纳米流体的情况下，与最大体积浓度为 2.0% 的 G/EG 相比，比热容最大降低了 5.7%，而热导率和粘度增加了 6.9% 和 1.33 倍在 353.15 K 的温度下。相比之下，G/EG 混合物中 80% SiO2 和 20% CuO/C 的增强导致热导率和粘度分别提高 26.9% 和 1.15 倍，比热显着降低21.1%。根据实验数据提出了新的经验相关性，用于评估热物理特性。