Steam condensation heat transfer in the rectangular mini-channels under one-side heating conditions

Shell condensers based on mini-channel heat exchangers have attracted growing interest for underwater vehicles due to their high heat flux capability, compactness, and marine compatibility. Accurate prediction of steam condensation under one-side heating is crucial for precise shell condenser design, as conventional symmetric models often fail under asymmetric seawater cooling. This study investigates the steam condensation heat transfer characteristics in the rectangular mini-channels under one-side heating conditions with a hydraulic diameter of 4.8 mm, a mass flux range of 20–200 kg·m⁻²·s⁻¹ and saturation pressure from 140 to 460 kPa. The axial evolution of condensation is systematically examined, and the effects of mass flux, vapor, and saturation pressure on the condensation characteristics are evaluated. It is found that mass flux and vapor quality play dominant roles, whereas the influence of saturation pressure is relatively minor. A modified heat transfer correlation is developed based on the boiling-analogy framework proposed by Shah, in which the effects of one-side heating are implicitly incorporated through experimentally fitted coefficients. The correlation was validated against both the present experimental data and an extended literature database. The final correlation yields a mean absolute error (MAE) of 17.9% over a wide range covering mass fluxes from 25 to 900 kg·m⁻²·s⁻¹, hydraulic diameters of 1–9 mm, and pressures from 140 to 2200 kPa under one-side heating condensation process. The newly developed correlation offers improved prediction accuracy under one-side heating conditions, providing practical guidance for engineering design.