A numerical simulation was presented to investigate condensation performance of core tubes in air-cooled condenser (ACC). The simulation had been performed in three iso-sectional tubes varying pattern from flat, oval to round. The local heat transfer coefficient (HTC) under the changes of tube inclination angle (beta), vapor saturated temperature (T-s), vapor-inlet velocity (U), and sub-cool temperature (Delta T-cool) was illustrated to verify the influence of these factors on heat performance of each individual tube. Meanwhile, the comparison on overall heat-flow characteristics among three tubes was also carried out. Regardless of the tube pattern, it was shown that a large beta in 0-30 degrees, a high T-s in 316-342 K, and a great U in 103-195 mks effectively enhanced the local HTC, but a high Delta T-cool in 2-8 K reduced it. A nearly twofold increase in Nusselt number was achieved by the round tube compared to flat and oval tubes in a negligible raise of friction coefficient, meanwhile the flat and oval tubes had very close value of performance evaluation criteria. This study highlighted the tube pattern effect to thermal-hydraulic development on the vapor-side of an ACC finned tube system. (C) 2019 Elsevier Ltd. All rights reserved.