The heat transfer performance of the condensate layer formed by a downward-flowing, dry saturated vapor flowing over an isothermal horizontal tube with wall suction effects is examined. Under the effects of wall suction, the gravity force, the potential flow pressure gradient, and the interfacial shear stress, the local/mean Nusselt numbers of the condensate film are obtained as a function of the Jakob number Ja, the Prandtl number Pr, the Rayleigh number Ra, the two-phase mean Reynolds number Rev, the dimensionless pressure gradient parameter P, and the suction parameter Sw. The results show that the mean Nusselt number increases with increasing Rev and Sw. Furthermore, the dimensionless pressure gradient parameter has a negligible effect on the Nusselt number for Rev ＜ 2 × 10^6, but has a negative effect on the Nusselt number for Rev ≥ 2 × 10^6.
