A preliminary study on enhancement of condensation heat transfer in horizontal tube with a Y-type insert was performed. Installation of the insert was expected to promote the condensation heat transfer for the following reasons: ⅰ) The fate of accumulation of the condensate at the bottom of the tube can be reduced by eliminating the condensate flowing down from the upper part by the insert, which results in a larger effective area for condensation at the lower part of the tube. ⅱ) At the same time, the liquid film newly starts below the wings of the Y-type insert to form a thinner layer, and the thermal resistance is considerably decreased. Under the Nusselt assumption, it was predicted that the size(length) of the condenser tube can be reduced substantially by installing the Y-type insert. More refined analysis and experimental verification are left for the future works.