Numerical analysis of shell-side thermo-hydraulic performances of submerged combustion vaporizer

Submerged combustion vaporizer belongs to one of the frequently-used and high efficient heat exchanger in the LNG industry chain. In this paper, in order to have a more profound understanding of shell-side thermo-hydraulic performances of submerged combustion vaporizer, an integrated thermal model is built to investigate the direct-contact flue gas and water mixture sweeping across the stagger tube bundle, with the condensation process of superheated water vapor presence. The accuracy of numerical model and method is validated by the experimental test data. On this basis, the unique flow and heat transfer mechanism is firstly analyzed, then variations of the gas hold-up, heat transfer and pressure drop performances with the common operational parameters are systematically studied. Significant results demonstrate that the efficient direct-contact condensation heat transfer process occurs between highly turbulent gas-liquid two-phase flow and tube bundle wall. The distinct and interesting circulating water forms due to the existence of weir, which helps to reduce the fluid boundary layer and strengthens the heat transfer. The water bath efficiently absorbs the sensible heat and latent heat carried by flue gas so that the outlet flue gas temperature almost equals to the water bath temperature. When the gas hold-up is within the scope of 25-45%, the shell-side convective heat transfer ability is obviously enhanced. Finally, in view of the numerical results, a new dimensionless pressure drop correlation and Han model are suggested for the optimum design of submerged combustion vaporizer.