Numerical investigation on the condensation heat transfer characteristics in tube bundles of LNG intermediate fluid vaporizer

• Main heat transfer mechanisms are summarized at different operating conditions. • Suction effect appears and promotes heat transfer at large wall subcooling. • Three semi-empirical models are compared and a new model for the IFV tube bundle is developed. The intermediate fluid vaporizer (IFV) has various advantages over other liquefied natural gas (LNG) vaporizers and has received increasing attention in recent years. The condensation heat transfer characteristics of the refrigerants outside the LNG tubes are different from those at room temperatures, characterized by a wider range of wall subcooling. In this paper, the vertical dynamic flow and condensation characteristics of propane outside the IFV tube bundle are investigated by a 2D CFD model. The main heat transfer mechanisms are summarized and compared at different operating conditions. At small wall subcooling and droplet mode, it is found that the vapor flow deforms the droplets on the lower tubes. The nearby liquid film becomes thinner and the heat transfer is enhanced. As the condensation rate increases and the tube spacing decreases, the suction effect and the resulting heat transfer enhancement become more pronounced. In addition, the liquid bridge inhibits the heat transfer of the bottom tubes, while it enhances the suction effect. The staggered tube bundle exhibits a higher suction effect and lower inundation effect than the inline tube bundle. Furthermore, the Honda model shows the smallest deviation from the numerical results among the three semi-empirical models, with a mean absolute percentage deviation of 17.1 %. Finally, a new semi-empirical model is developed for the IFV.