The artificial roughness effect on the thermal performance of a submerged combustion vaporizer

The submerged combustion vaporizer (SCV) is a popular vaporizer used for the peak regulation of liquefied natural gas (LNG) in large cities or as a primary vaporizer in cold regions. Due to the consumption of produced natural gas as a heat source for gasification during SCV operation, the thermal efficiency and gasification rate of SCV must be improved urgently. One of the effective methods to improve the heat transfer of a heating tube is adding artificial roughness inside the tube. Hence, this paper establishes a 3D numerical model of the serpentine heating tube with artificial roughness cubes in SCV and explores the impact of artificial roughness on the heat transfer and thermal performance of SCV. To strengthen the heat transfer between the LNG heating tube and the water bath in the straight tube section and avoid the water freezing outside the tube due to the supercooling at the bend section simultaneously, critical factors, such as the arrangement of artificial roughness, especially on the bend region, and the heat flux obtained from the water bath, are discussed. The results indicate that the artificial roughness positively affects the heat transfer of the LNG heating tube. However, it is better to add the artificial roughness only in the straight section of the serpentine tube to suppress the ice formation on the bend regions. The LNG flow becomes chaotic, and the region of forced convection increases due to artificial roughness and centrifugal force. The serpentine tube with artificial roughness exhibits similar thermal behaviour under different heat fluxes, and its influence on the friction factor and irreversible energy loss is more significant than that of smooth tube. Moreover, the comprehensive evaluation coefficient of the heating tube is enhanced obviously by the artificial roughness, and the outlet temperature of LNG is larger by 17.63% and 16.34% respectively with different configurations of artificial roughness than that of the smooth one under the same heated condition, and the gasification rate is improved significantly.