Abstract Three-dimensional natural convection in a cuboid enclosure filled with DWCNTs-water nanofluid is studied. The heat transfer performance due to convective flow of nanofluid inside the enclosure at different temperature differences between side hot and cold walls (ΔT = 20 °C, 30 °C, 40 °C and 50 °C) is analyzed experimentally and numerically. A setup has been manufactured to test the natural convection phenomenon within the enclosure. Moreover, in this work, the utilized nanofluid is prepared, the thermo-physical properties, thermal conductivity and dynamic viscosity, of the nanofluid are measured experimentally by means of modern measuring devices. The DWCNTs-water nanofluid is obtained in different solid volume fraction of 0.01%, 0.02%, 0.05%, 0.1%, 0.2%, and 0.5%, and thermo-physical properties have been measured in all solid volume fraction and temperature range of 300 to 340. The 3D computational study utilizing finite volume approach is performed with similar boundary condition with experimental setup and experimental properties of nanofluid to validate the experimental data. Height, length and depth of the enclosure are equal to 100 mm. the left and right side walls have constant and uniform hot and cold temperature respectively, and the other walls are insulated. The constant temperature of side walls is obtained by water channel supplied by circulating water bathes. The temperature of side walls is measured by nine LM-35 temperature sensors, and the temperature of nanofluid is measured by means of PT100 thermocouples inserting from watertight circular slots from back of enclosure. The numerical and experimental results are compared and a good consistency is observed. The temperature distribution between side walls at the mid-height of the enclosure, average heat transfer coefficient and average Nusselt number are presented for different Rayleigh numbers and solid volume fractions.

中文翻译：

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DWCNTs-水纳米流体填充外壳内三维自然对流传热性能研究——实验与数值分析

摘要 研究了充满DWCNTs-水纳米流体的长方体外壳中的三维自然对流。实验和数值分析了由于外壳内纳米流体在侧热壁和冷壁之间的不同温差（ΔT = 20°C、30°C、40°C和50°C）下对流而产生的传热性能。已经制造了一个装置来测试外壳内的自然对流现象。此外，在这项工作中，制备了所利用的纳米流体，并通过现代测量设备对纳米流体的热物理性质、热导率和动态粘度进行了实验测量。DWCNTs-水纳米流体以0.01%、0.02%、0.05%、0.1%、0.2%和0.5%的不同固体体积分数获得，已在所有固体体积分数和 300 至 340 的温度范围内测量了热物理性质和热物理性质。利用有限体积方法的 3D 计算研究是在与纳米流体的实验设置和实验性质相似的边界条件下进行的，以验证实验数据。外壳的高度、长度和深度等于 100 毫米。左右侧墙分别具有恒定、均匀的冷热温度，其他墙体保温。侧壁的恒温是通过循环水浴提供的水道获得的。侧壁温度由 9 个 LM-35 温度传感器测量，纳米流体的温度通过从外壳背面的防水圆形槽插入的 PT100 热电偶测量。数值和实验结果进行了比较，观察到良好的一致性。给出了不同瑞利数和固体体积分数的外壳中间高度侧壁之间的温度分布、平均传热系数和平均努塞尔数。