Numerical Simulation of Convective Condensation of Steam with Large Proportion of Non-condensable Gas under High Pressure
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摘要: 为适用于大航深的水下航行器热动力系统中含不凝气体的水蒸气对流冷凝换热现象进行数值仿真。首先通过定义连续性方程、动量方程、组分输运方程和能量方程的源项对冷凝过程进行建模, 仿真了经典Kuhn试验工况以验证数值模型的有效性, 结果与试验数据对比良好, 换热系数最大误差小于20%。在此基础上, 对10 MPa压力下不同比例水蒸气和不凝气体冷凝换热过程进行数值仿真, 在仿真中考虑了冷凝液膜的影响, 从热流密度、液膜厚度、饱和温度及冷凝质量流量4个方面分析了高压下不凝气体对水蒸气对流冷凝换热的影响。仿真结果表明: 当不凝气体质量分数达到30%时, 水蒸气冷凝换热的平均热流密度仅减小50%。与经典文献中常压下含不凝气体的水蒸气冷凝换热研究对比, 可知高压下不凝气体对水蒸气换热的抑制作用被削弱。Abstract: This study simulates the convection condensation heat transfer phenomenon of steam containing non-condensable gas(NCG) in the thermal power system of an underwater vehicle at a large sea depth. First, the condensation process is modeled by defining the source terms of the continuity, momentum, component transport, and energy equations. To verify the validity of the numerical model, classical Kuhn experimental conditions are then simulated, with results matching well with the experimental data. The maximum error of the heat-transfer coefficient is found to be less than 20%. Accordingly, the study then simulates the condensation heat-transfer process of different proportions of steam and NCG under 10 MPa pressure. During the simulation, the effect of the condensed liquid film is considered, and the influence of the NCG on the condensation heat transfer of steam under high pressure is analyzed in terms of heat flow density, liquid film thickness, saturation temperature, and condensation mass flow. Results show that the average heat flux of the steam condensation heat transfer is reduced by 50% until the NCG mass fraction reaches 30%. Finally, the simulation conditions are compared with the research on steam containing NCG under atmospheric pressure, with results showing that the inhibition effect of NCG on steam condensation heat transfer is reduced under high pressure.
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