An experimental and empirical investigation of convective heat transfer for gas-liquid two-phase flow in vertical and horizontal pipes

Scope and method of study. The purpose of this study was to develop a comprehensive convective non-boiling heat transfer correlation during gas-liquid two-phase flow in vertical and horizontal pipes, by evaluating and refining existing models/correlations on the basis of their physical merits and comparisons with the available data from the literature and the collected data from our own experiments. In order to assess the general validity of the existing correlations, 20 identified heat transfer correlations were compared with seven sets of experimental data from the open literature with or without considering the limitations originally suggested by the authors. With the advance knowledge accumulated from the above accomplishments using the previously recommended correlations, a new general heat transfer correlation, which can be applied to turbulent gas-liquid two-phase flow in vertical pipes with different fluid flow patterns and fluid combinations was proposed. In order to develop heat transfer correlation(s) for different flow patterns in a horizontal pipe, a two-phase heat transfer experimental setup covering several different flow patterns in a horizontal pipe was built and air-water heat transfer experimental data were successfully obtained.; Findings and conclusions. A correlation that can be used to predict turbulent two-phase gas-liquid non-boiling heat transfer for a wide range of fluid combinations and several different flow patterns in a vertical pipe was successfully developed using the appropriate forms of parameters quality, void fraction, Prandtl number, and viscosity. Based on the agreements between the observed experimental flow pattern data with a well known flow pattern map from literature, this study proposed a flow pattern map using the mass flow rates of air and water in a horizontal pipe. From the obtained air-water experimental data, the two-phase heat transfer coefficient generally increases as the Reynolds number of gas increases for a fixed liquid Reynolds number since the introduction of gas phase into the liquid stream increases the turbulence level and mixing action in the main stream due to continuous interaction of the two-phases. With minor modification of the constant values, the general correlation developed for turbulent flow in a vertical pipe was successfully applied to the air-water experimental data in a horizontal pipe with good accuracy.