## 4 Parameter Sensitivity Analysis
### Condensation Model  
The condensation phenomenon of steam containing noncondensable gas plays an important role in the heat removal process of the containment in a nuclear power plant under an accident condition. As can be seen from Equation (2), the total heat transfer coefficient is affected by both the convective heat transfer coefficient and the condensation heat transfer coefficient, and there are certain differences in the calculation results obtained using the different condensation calculation models. So, it is important to select an accurate condensation model that is suitable for the development of a severe accident analysis code. In this paper, the most widely used experimental correlation models of Uchida [7], Tagami [8] and Dehbi [9] are selected successively to compare with the experimental results and the calculated values of the PISAA code model.  
\[h_{\text{Uchida}}=380.0\bigg{(}\frac{W_{\text{nc}}}{1-W_{\text{nc}}}\bigg{)}^{-0 7} \tag{16}\]  
\[h_{\text{Tagami}}=11.4+284\bigg{(}\frac{1-x_{\text{nc}}}{x_{\text{nc}}}\bigg{)} \tag{17}\]  
\[h_{\text{Dehbi}}=\frac{L^{0.05}[3.7+28.7p-(2483+458.3p)log_{10}W_{\text{nc}}]}{ \big{(}T_{\text{g}}-T_{\text{w}}\big{)}^{0.25}} \tag{18}\]  
where: \(h\)--condensing heat transfer coefficient; \(W_{\text{nc}}\)--noncondensable gas mass fraction; \(\text{x}_{\text{nc}}\)--noncondensable gas volume fraction; \(L\)--characteristic length of condensing wall; \(p\)--pressure; \(T_{\text{g}}\)--gas temperature; \(T_{\text{w}}\)--condensing wall temperature.  
The comparison results are shown in the Figure 5.  
Figure 5: Effect of condensation model on heat transfer coefficient of condensation. (**a**) Vertical condensation wall. (**b**) Horizontal condensation wall.  
The comparison shows that the calculation results of the condensation model based on [PERSON]'s law and the heat/mass transfer analogy principle chosen in this paper are closer to the experimental measurement data from the Wisconsin experiment. The deviation between the calculation results from the Tagami model and the experimental data is the largest, and the accuracy of the Dehbi model is slightly higher than that of Tagami and Uchida, but the deviation is much larger than that of the calculation model used in this paper.  
To analyze the reason, the Uchida and Tagami models only consider the influence of the noncondensable gas fraction on the condensation heat transfer coefficient, and the Dehbi model is further improved, considering the influences of wall length, total pressure and wall subcooling degree on the condensation heat transfer coefficient, but the applicability range of the model is limited, and the factors affecting the mass and heat transfer of condensation, such as the temperature and composition of the gas in the main flow and the interface, are not considered in detail. The calculation model used in the PISAA code considers all the factors mentioned above; therefore, the calculation results are closer to the actual experimental measurements, and at the same time, simulate better.  
The comparison results show that the condensation heat transfer model used in this paper, which is based on simplifying and integrating the mechanism and the experimental correlations, can effectively solve the limitations of the traditional empirical correlations model, and realize the accurate simulation of the condensation heat transfer of steam with noncondensable gas, and the calculation results are more reliable than the results calculated using the pure empirical correlations.