## 1 Introduction
In recent decades, with the development of commercial computing software, many scholars have carried out simulation analysis with computational fluid dynamics (CFD) software on fluid flow fields and obtained expected research results. [PERSON] et al. [19] used the self-similar methodology to describe laminar momentum diffusion, and [PERSON] et al. [20; 21] described laminar passive scalar diffusion with the self-similar methodology. Furthermore, the theory of laminar momentum diffusion is developed, and a wide range of [PERSON] and [PERSON] studies offered generality to the results, in turn providing theoretical support for the experimental results. [PERSON] et al. [22] used the finite volume method to simulate the fuel cell processes and introduced innovative designs to improve the performance of cylindrical polymer fuel cells. Moreover, the condensation heat transfer of a steam-NCG mixture could also be calculated using CFD software. [PERSON] et al. [23] integrated a model for the wall condensation of a steam-NCG gas mixture in the ANSYS CFD code FLUENT, and the predicted heat transfer rate was found to be generally consistent with experimental results. [PERSON] [24] simulated the condensation of water vapor in the presence of NCGs in a vertical cylindrical condenser and proposed a method to address the limitations of the currently used CFD to solve the simulation of flows involving multispecies as well as gas fluids and liquids in separate channels. [PERSON] et al. [25] studied the unsteady hydrodynamic-free convective flow of a viscoelastic incompressible fluid past a vertical porous plate in the presence of a variable suction and provided approximate solutions on velocity and temperature fields, shear stress, and the rate of heat transfer using the perturbation technique. Based on a suitable model, CFD simulation can provide additional details on condensation, which may be more accurate, but more modeling and calculation work is also required. Therefore, the boundary layer theory, which only needs to solve the ordinary differential equation (group), still has analytical and engineering significance and can be used as a simple method to study the condensation of a mixture. Compared with other steam-NCG mixtures, research on the condensation of steam-CO\({}_{2}\) mixtures is very limited. [PERSON] et al. (2016, 2017) studied the condensation of water vapor on different surfaces with high and low concentrations of CO\({}_{2}\). Heat transfer data were different between the steam-CO\({}_{2}\) and steam-air mixture condensation rates in the experiment. [PERSON] et al. (2018) investigated steam condensation on a horizontal tube in the presence of CO\({}_{2}\) with an experiment and obtained condensation heat transfer coefficients for the sub-atmospheric pressure ranging from 5 kPa to 101 kPa. [PERSON] et al. (2019) used Comsol software to simulate the condensation heat transfer and separation of a steam-CO\({}_{2}\) and O\({}_{2}\) mixture in the condenser. This provides some data that serve as the basis for the design of a volumetric heat exchanger (condenser) that is suitable for steam-CO\({}_{2}\) separation in flue gas, thus improving the efficiency of power plants. [PERSON] et al. (2018) studied vapor condensation in the presence of non-condensable gases using CFD simulations and calculated the effects of velocity, surface subcooling, and the molar fraction of non-condensable gases on the heat transfer from steam-air or steam-CO\({}_{2}\) mixtures. However, there is still a gap in the recent study to address before we can meet the engineering application requirements in steam-CO\({}_{2}\) mixture condensation. Based on current studies, CO\({}_{2}\) is usually regarded as an NCG. However, in an engineering application, the solubility of CO\({}_{2}\) is not only different from NH\({}_{3}\), which is miscible with water in any proportion, but also different from NCGs, such as air, He, etc. CO\({}_{2}\) is a slightly soluble gas.