Carbon capture and storage is an important way to achieve the “dual-carbon” goal. The exhaust gas of the supercritical water-coal to hydrogen coupled CO_2/H_2O mixed working medium thermal power generation system is low pressure and low-temperature CO_2/H_2O mixed gas. In order to achieve zero carbon emission and heat recovery

condensation separation of CO_2/H_2O is a necessary way. Fluent is used to simulate the condensing heat transfer characteristics of CO_2/H_2O mixture outside the horizontal bifurcation tube bundle. The volume of fluid(VOF) model

the component transport model

and the phase transition model written by the user-defined functions(UDF) are employed to load the mass

energy

and component source terms of the two-phase flow. The formation and development process of the liquid film on the wall surface

and the distribution of streamlines

velocity vectors

and liquid-phase volume fractions in the vicinity of droplets

as well as the effects of velocity

vapor superheat

and noncondensable gas content on the heat transfer coefficients and the thermal resistance of the diffusion layer

are investigated. The results show that

the simulation results are in agreement with the experimental data

and the liquid film thermal resistance hardly varies with the steam superheat but decreases with the increase of CO_2 content

inlet flow rate and total pressure. The thermal resistance of the mixed gas diffusion layer increases with the CO_2 content and steam superheat

and decreases with the increase of inlet flow rate. The total heat transfer coefficient increases with the steam superheat

inlet flow rate and pressure

and decreases with the CO_2 content

and the local condensation heat transfer coefficient is negatively correlated with the liquid film thickness. A new dimensionless correlation formula for heat and mass transfer of condensation is proposed for low pressure CO_2/H_2O condensation process.