Abstract: In order to study the complicated two-phase flow heat transfer process in water bath of liquefied natural gas (LNG) submerged combustion vaporizer (SCV), and simplify the computation of LNG SCV in engineering application, a mathematical model for water bath and LNG vaporization was established after theoretical analysis, based on the theory of heat transfer. This model ignores the effect of flue gas, and simplifies flow field outside the heat transfer tube bundle and temperature and flow fields inside the heat exchange tube bundle. With the new model, actual operational parameters of a LNG SCV were used to calculate the average heat transfer coefficient outside the tube bundle, total heat transfer coefficient, total length and total heat-transfer area of the tube. Then, the derived four parameters were back-calculated depending on heating load and measured water flow velocity outside the tube of the LNG SCV. The results show a deviation of 16.8% between the average heat transfer coefficient outside the tube bundle calculated with this model and the actual parameter. However, deviations in total heat transfer coefficient, total tube length and total heat transfer area are only 6.9%, —7.9% and —7.9%, respectively. Generally, these deviations can meet the demands in engineering calculation. In addition, these results validate the reliability of the model proposed.