Condensation heat transfer and two-phase flow in the annular region inside helical tubes were analyzed. The effect of circumferential shear resulted from secondary flow was considered and a physical model of heat transfer was established. Heat transfer coefficients and two-phase flow pressure drops during steam condensation inside helical tubes in the regimes controlled or mainly controlled by shear were measured experimentally. The heat transfer coefficients calculated from the physical model were found to be in good agreement with the experimental results.