To investigate the complex phase change behavior in two-phase condensation flow of hydrocarbon mixtures in inclined tubes, a numerical model was developed in Fluent using the Volume of Fluid method combined with the Lee phase change model. A mixing effect correction was incorporated to enhance the simulation accuracy, and its impact on the flow and heat transfer characteristics was systematically evaluated. Numerical simulations were performed and subsequently corrected for mixing effects; the final results show good agreement with classical experimental data. The average deviation of the heat transfer coefficient is −0.76%, while that of the frictional pressure drop is 4.5%. Furthermore, by introducing the swaying-motion equation into the model, the effects of different swaying periods and amplitudes on the heat transfer under swaying conditions are investigated. The results show that shorter swaying periods and larger swaying amplitudes lead to more pronounced fluctuations in the heat transfer coefficient. Within the parameter range considered in this study, the influence on the time averaged heat transfer coefficient does not exceed 25%. This study provides a solid theoretical and data foundation for the design of relevant condensation heat exchangers, thereby supporting the development of the offshore LNG industry and enhancing energy security.