Direct contact condensation phenomenon (DCC) is widely used in applications which heat and mass transfer efficiently. In this study, several experiments are conducted to investigate the DCC of steam injected in water flow in a vertical square cross-section pipe. The characteristics of condensation, including steam plume shape and length, average heat transfer coefficient, and average Nusselt number, are studied. The dimensionless steam plume length and average heat transfer coefficient are found in the range of 0.5-5.1 and 0.716-3.131 MW/m(2) K, respectively. Additionally, the influence of effective operating parameters, namely steam mass flux, water temperature, and water flow Reynolds number, on each condensation characteristic is investigated. Using a high-speed camera, three main regimes of steam plume (chugging, oscillatory, and stable jet) are observed. The distribution of these regimes versus flow effective parameters is presented in a three-dimensional condensation regime map. Finally, empirical correlations for a stable steam plume, which show a good agreement with measurements, are suggested to predict each characteristic of DCC of steam jet in water flow. (C) 2018 Elsevier Ltd. All rights reserved.