Carbon neutrality is emerging as an irresistible mission of the times. To realize this, the proportion of renewable energy must be expanded, and ocean energy can be an alternative. OTEC (closed type), one of ocean energy, has the largest theoretical potential among ocean energy. In the case of the closed type of OTEC, two-phase flow may occur in the turbine, and it is necessary to model in CFD (Computational Fluid Dynamics) for more accurate design and analysis. In this study, a non-equilibrium (Non-eq) two-phase model was applied instead of the equilibrium (Eq) model assuming thermodynamic equilibrium. The result was compared and analyzed with single-phase model, two-phase model, and experimental results. In addition, the GCI method was used to estimate the discretization error. As a result of the CFD simulations, the Non-eq model was the most similar to the experimental values compared to the single-phase and Eq model. Qualitatively, the Non-eq model showed some differences in velocity field and mass fraction at spanwise 50 percent. In conclusion, the model estimated to be closest to reality is the Non-eq model, and the rationale for this is estimated quantitatively and qualitatively.