In order to optimize the design of the submerged combustion vaporizer (SCV), an experimental apparatus was set up to investigate the heat transfer character outside the tube bundle in SCV. Several experiments were conducted using water and CO2 as the heat transfer media in the tubes, respectively. The results indicated that hot air flux, the initial liquid level height and the tube pitch ratio had great influence on the heat transfer coefficient outside the tube bundle (h(o)). Finally, the air flux associated factor beta and height associated factor gamma were introduced to propose a new ho correlation. After verified by experiments using cold water, high pressure CO2 and liquid N-2 as heat transfer media, respectively, it was found that the biggest deviation between the predicted and the experimental values was less than 25%. (C) 2018 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved.