Abstract The Natural Circulation Loop (NCL) has many applications in nuclear and renewable energy systems including solar heaters and geothermal power derivation. Applying nanofluids in NCL has distinctive advantageous, including higher stability and effectiveness of NCL. The present study is a numerical investigation of a rectangular single-phase natural circulation loop utilizing Water, water-based Al2O3, and TiO2 nanofluids as working fluids. Both steady-state and transient simulations are in good agreement with experimental data. The effects of heating power and nanoparticle concentration on the stability and flow transitions were investigated in this study. Flow rate and heat transfer capacity enhancement were significantly observed by applying nanofluids in NCL compared to Water. The comparison of effectiveness factor, temperature difference over heater, and mass flow rate of NCL utilize different working fluids, revealed thermal performance improvement by particle concentration increment, and this is more considerable for the nanofluids containing bigger particle size.

中文翻译：

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基于纳米流体的自然循环回路的研究

摘要 自然循环回路 (NCL) 在核能和可再生能源系统中有许多应用，包括太阳能加热器和地热发电。在 NCL 中应用纳米流体具有独特的优势，包括更高的 NCL 稳定性和有效性。本研究是对利用水、水基 Al2O3 和 TiO2 纳米流体作为工作流体的矩形单相自然循环回路的数值研究。稳态和瞬态模拟都与实验数据非常吻合。本研究研究了加热功率和纳米颗粒浓度对稳定性和流动转变的影响。与水相比，通过在 NCL 中应用纳米流体，可以显着观察到流速和传热能力的增强。有效性因子的比较，