Abstract: This paper presents an experimental investigation on the heat transfer characteristics of liquid nitrogen flow boiling in a vertical tube. The variations of wall temperature, fluid temperature, quality, and heat transfer coefficient in the flow direction were analyzed. The effect of heat flux, inlet pressure and mass flux on the flow boiling heat transfer coefficients was examined. Four correlations by Chen, Klimenko, Shah, and Liu-Winterton were adopted to predict the flow boiling heat transfer coefficient. The relative errors in different ranges of heat transfer coefficients were calculated and analyzed to evaluate the correlations under the experimental conditions. The predicted results show that the results calculated with the four correlations are generally lower than the experimental data. The Klimenko correlations are more adaptable under the whole experimental conditions.

Key words: flow boiling, liquid nitrogen, two-phase flow, heat transfer, vaporization

摘要： 实验研究了竖直圆管内液氮流动沸腾传热特性，分析壁面温度、流体温度、干度以及传热系数沿实验段管程的变化规律，考察热通量、质量流量和入口压力对液氮两相流动传热特性的影响。针对实验工况分别采用Chen、Klimenko、Shah以及Liu-Winterton关联式对传热系数进行预测，并将实验结果与预测结果进行比较，对不同传热系数区间内的相对误差进行了计算、分析，以评估实验工况范围内各关联式的准确性。结果表明，在传热系数较大的情况下，4个关联式的预测值普遍低于实验值，在整个实验工况范围内，采用Klimenko关联式预测时误差最小。

关键词: 流动沸腾, 液氮, 两相流, 传热, 汽化