According to the non-equilibrium theory, the condensation starts where the wall temperature drops below the saturation vapor temperature before the average fluid temperature reaches the saturation vapor temperature. Likewise, the condensation process continues after the average fluid temperature drops below the saturation liquid temperature until the highest temperature of a certain cross-sectional profile becomes lower than the saturation liquid temperature. However, there is a lack of prediction methods for subcooled condensation considering the non-equilibrium effects. This paper presents an analysis of the subcooled condensation heat transfer of in-tube flow. The state-of-the-art prediction methods for subcooled condensation are summarized and evaluated, based on the experimental data available in the open literature both for pure fluids and zeotropic mixtures covering a wide range of operating conditions. The mass flux varies from 95 kg·m^-2·s^-1 to 801 kg·m^-2·s^-1, while the subcooling degree ranges from 0 °C to 34 °C. The condensation pressure is varied from 1 MPa to 7 MPa, and the heat flux ranges from 0.1 kW·m^-2 to 205.7 kW·m^-2. In addition, a new heat transfer correlation for the target heat transfer process was developed, achieving a mean absolute percentage error of 15.7 %.