Heat transfer and pressure drop characteristics of gas-liquid Taylor flows in a mini tube with 1 mm inner tube diameter were investigated numerically using a moving frame of reference method. A CuO/water nanofluid was used as the continuous phase, while nitrogen was adopted as the dispersed phase. The inlet Reynolds number ranged from 250 to 600, and the volume concentration of the CuO particles was in the range of 0% to 3%. The results show that a thicker liquid film and a relatively longer bubble are obtained for Taylor flows with nanofluids compared with those using pure water. The heat transfer process could be divided into three stages with increasing time. At the initial stage, a quick increase of the thermal boundary layer results in a dramatic decrease of the heat transfer coefficient. With increasing time, heat transfer coefficient oscillation is obtained because of the advection of cold liquid from the tube center to the heated wall. With the combined effect of thermal diffusion and recirculation in liquid slugs, the fully developed status of Taylor flow is obtained. Heat transfer coefficients increase with decreasing gas void fraction and with increasing nanoparticle concentration. The overall two-phase pressure gradients increase with increasing nanoparticle concentration and , but with decreasing gas void fraction. The increase in the thermal conductivity and the viscosity of nanofluids is the main reason for heat transfer enhancement and pressure drop penalty.

中文翻译：

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使用 CuO/水纳米流体对垂直毛细管中气液泰勒流的数值研究


使用移动参照系方法对内管直径为 1 mm 的微型管中气液泰勒流的传热和压降特性进行了数值研究。 CuO/水纳米流体用作连续相，而氮气用作分散相。入口雷诺数为250～600，CuO颗粒的体积浓度为0%～3%。结果表明，与使用纯水的泰勒流相比，使用纳米流体的泰勒流获得了更厚的液膜和相对更长的气泡。随着时间的增加，传热过程可分为三个阶段。在初始阶段，热边界层的快速增加导致传热系数急剧下降。随着时间的增加，由于冷液体从管中心向受热管壁平流，传热系数出现振荡。在液塞中热扩散和再循环的综合作用下，获得了泰勒流的充分发展状态。传热系数随着气体空隙率的降低和纳米颗粒浓度的增加而增加。总体两相压力梯度随着纳米粒子浓度和 的增加而增加，但随着气体空隙率的减少而增加。纳米流体导热系数和粘度的增加是传热增强和压降损失的主要原因。