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首页> 外文期刊>International Journal of Heat and Mass Transfer >Numerical investigation of the heat and mass transfer in a vertical tube evaporator with the three-zone analysis
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Numerical investigation of the heat and mass transfer in a vertical tube evaporator with the three-zone analysis

机译：三区分析法研究立管式蒸发器传热传质

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摘要

A numerical study for the flow, heat and mass transfer characteristics near the inflow region of the vertical evaporating tube with the films flowing down on both the inside and outside tube walls has been carried out. Condensation occurs along the outside wall and evaporation at the free surface of the inside film. The transport equations for momentum and energy are parabolized by the boundary-layer approximation and solved by using the marching technique. In this kind of numerical approach, the accurately predicting the early stage is really important because a small error at the previous step can produce the amplified big error at the next step. To accurately predict the flow at the inflow region of the vertical evaporating tube, the calculation domain of two film flow regions and tube wall is solved simultaneously. The interesting heat transfer characteristics revealed through this three-zone simulation, such as the evaporation delay and the temperature inflection at the very near inflow region are found and discussed along the discrepancy between the inner film inlet temperature and the saturation temperature. The case that the inner film comes in with the saturation temperature shows a good performance. The velocity and temperature fields as well as the amounts of the condensed and evaporated mass in both inner and outer films are predicted for the various conditions.
机译：对垂直蒸发管的流入区域附近的流动，传热和传质特性进行了数值研究，薄膜在管的内壁和外壁上都向下流动。沿外壁发生冷凝，在内膜的自由表面蒸发。动量和能量的传输方程通过边界层近似被抛物线化，并使用行进技术求解。在这种数值方法中，准确预测早期阶段非常重要，因为前一步的小误差会在下一步产生放大的大误差。为了准确地预测垂直蒸发管流入区域的流量，同时求解了两个膜流动区域和管壁的计算域。通过内膜入口温度和饱和温度之间的差异，发现并讨论了通过该三区域模拟揭示的有趣的传热特性，例如蒸发延迟和非常接近流入区域的温度变化。内膜进入饱和温度的情况显示出良好的性能。对于各种条件，预测了内部和外部薄膜中的速度和温度场以及冷凝和蒸发的物质的量。

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