The heat transfer, friction factor, and collector efficiency are estimated experimentally for multi-walled carbon nanotubes+Fe₃O₄ hybrid nanofluid flows in a solar flat plate collector under thermosyphon circulation. The combined technique of in-situ growth and chemical coprecipitation was utilized to synthesize the multi-walled carbon nanotubes+Fe₃O₄ hybrid nanoparticles. The experiments were carried out at volume flow rates from 0.1 to 0.75 L/min and various concentrations from 0.05% to 0.3%. The viscosity and thermal conductivity of the hybrid nanofluids were experimentally measured at different temperatures and concentrations. Due to the improved thermophysical properties of the hybrid nanofluids, the collector achieved better thermal efficiency. Results show that the maximum thermal conductivity and viscosity enhancements are 28.46% and 50.4% at 0.3% volume concentration and 60 °C compared to water data. The Nusselt number, heat transfer coefficient, and friction factor are augmented by 18.68%, 39.22%, and 18.91% at 0.3% volume concentration and 60 °C over water data at the maximum solar radiation. The collector thermal efficiency improved by 28.09% at 0.3 vol. % at 13:00 h daytime and a Reynolds number of 1413 over water data. Empirical correlations were developed for friction factor and Nusselt number.

中文翻译：

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热虹吸条件下太阳能平板集热器中MWCNT + Fe3O4 /水杂化纳米流体的热效率，传热和摩擦因子分析

在热虹吸循环下，通过太阳能平板收集器中的多壁碳纳米管+ Fe ₃ O ₄杂化纳米流体流，通过实验估算了传热，摩擦系数和收集器效率。利用原位生长与化学共沉淀相结合的技术合成了多壁碳纳米管+ Fe ₃ O ₄杂化纳米粒子。实验在0.1至0.75 L / min的体积流量和0.05％至0.3％的各种浓度下进行。在不同的温度和浓度下，通过实验测量了混合纳米流体的粘度和热导率。由于杂化纳米流体的改进的热物理性质，收集器获得了更好的热效率。结果表明，与水数据相比，在0.3％的体积浓度和60°C的条件下，最大的热导率和粘度增加分别为28.46％和50.4％。在0.3％的体积浓度和60°C的温度下，相对于最大太阳辐射下的水数据，Nusselt数，传热系数和摩擦系数分别增加了18.68％，39.22％和18.91％。在0.3体积时，集热器的热效率提高了28.09％。％在13：白天00小时，水数据雷诺数为1413。建立了摩擦系数和努塞尔数的经验相关性。