Numerical study of condensation flow regimes in presence of non-condensable gas in minichannels
Numerical study of condensation flow regimes in presence of non-condensable gas in minichannels
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DOI：
10.1016/j.icheatmasstransfer.2019.04.001
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发表时间：
2019-08
影响因子：
7
通讯作者：
Y. Lei;Zhen-qian Chen
中科院分区：
文献类型：
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作者：
Y. Lei;Zhen-qian Chen
对R134a在水平小通道内的流态进行了数值研究。该模型以流体体积法为基础，加入了包括冷凝传质和换热的用户自定义程序。将观测到的纯蒸汽冷凝的环状流、喷射流和间歇流，以及气体混合物冷凝的环状(环状)流、喷射流、环状间歇流和间歇流与实验数据进行了定性的比较。不凝气摩尔浓度较低时的流型与纯蒸汽的流型相似，但环流中气液界面的波动和较高不凝气摩尔浓度的环流-间歇流现象明显。此外，在存在不凝性气体的情况下，发现了较大头部体积和较长颈部的注入流动特征和较大段塞尺寸的间歇性流动特征。在验证流型转变的基础上，分析了不凝性气体摩尔浓度和操作条件对流型转变线的影响。结果表明，在纯蒸汽冷凝时，喷射流动转换点有一个相对不变的固定点，而在NCG存在的情况下，则不同。此外，较低的不凝性气体摩尔浓度、较小的进口气体质量流量和较大的壁面热流密度会导致较早的流型。
A numerical research on flow regime of R134a in horizontal minichannels was conducted. The model was on the basis of the volume of fluid approach, and inserted user-defined routines which cover condensation mass and heat transfer. The observed annular flow, injection flow and intermittent flow of pure steam condensation, and annular (annular-wavy) flow, injection flow, annular-intermittent flow and intermittent flow of gas mixture condensation were qualitatively compared against experimental data. Flow patterns of lower non-condensable gas mole concentration show similar with that of pure steam, while the fluctuation of gas-liquid interface in annular flow and the noticeable annular-intermittent flow of higher non-condensable gas mole concentration were noted. Besides, injection flow characters with larger head volume and longer neck, and intermittent flow characters with larger slug sizes in existence of non-condensable gas were found. Furthermore, the influence of mole concentration of non-condensable gas and operating conditions on flow pattern transition lines were analyzed after validating the flow pattern transition. The results showed that the injection flow transition point has a relative fixed point at pure vapor condensation, while various in presence of NCG. Besides, lower non-condensable gas mole concentration, smaller inlet gas mass flux and larger wall heat flux could lead to earlier flow pattern regime.