通过将稳态传质模型和一维电偶腐蚀模型耦合，提出了预测异径管流动加速腐蚀速率的新模型。该模型先由稳态传质模型得到异径管近壁面处的自腐蚀电流密度分布和速度极值点处的自腐蚀电位，而后将极值点处自腐蚀电位代入到一维电偶腐蚀模型中，计算该壁面处的电偶腐蚀电流密度。应用此新模型对某一异径管流动加速腐蚀速率进行计算，发现异径管大端的腐蚀电流密度比小端腐蚀电流密度大两个数量级，据此可以解释台湾某核电站蒸汽冷凝水管线统计得出异径管大端出现最大减薄量的现象。与壁面剪切应力理论和稳态传质理论计算流动加速腐蚀速率分布相比，该模型的计算结果更贴近实际情况。
A new prediction model was proposed to calculate the flow accelerated corrosion (FAC) rate in reducer, which was coupled the steady-state mass transfer model electrochemical theory and one-dimensional galvanic corrosion model. Firstly, the steady-state mass transfer model was used to obtain the distribution of concentration polarization current density and the concentration polarization corrosion potential of velocity extreme point near the wall of reducer. The galvanic corrosion current density was calculated by substituting the potential into one-dimensional galvanic corrosion model. The new model was employed to calculate the reducer; the results showed that the corrosion current density of large-end was larger two orders than that of small-end. Compared with the FAC rate calculated by the wall shear stress theory, presented by Efird and Cheng, or by purely steady-state mass transfer theory, the results obtained by the new model have good agreement with the practical situation which were counted 2000 pipe fittings in Taiwan nuclear power plant by Kuen Ting. The statistical result showed that the large-end of reducer appeared the maximum of reduction of thickness.
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