Analysis on the heat transfer performance of supercritical liquified natural gas in horizontal tubes during regasification process

The submerged combustion vaporizer (SCV) is an indispensable peak-shaving heat exchanger in the regasification process of liquified natural gas (LNG). This paper mainly studies the trans-critical heat transfer performance of LNG in the horizontal tube of SCV under the convective heating condition. To this end, the conditions of fluid temperature, mass flux, and tube diameter are comprehensively investigated through numerical simulation. Based on the simulation results, the influence of the buoyancy on total and local heat transfer performance is analyzed from the distribution of flow field and thermal-physical property in the boundary layer. The results indicate that the buoyancy leads to a significant difference in convection thermal resistance around the circumference. Tube diameter and mass flux affect the degree of heat transfer strengthening in the lower part and heat transfer deterioration in the upper part of the tube, as well as the occupied circumferential proportion of the corresponding region. Considering the effects of local heat transfer strengthening and deterioration, buoyancy shows an enhancement effect overall on the heat transfer process, especially under the conditions of low mass flux and large diameter. Based on the mechanism analysis of the convective heat transfer, two correlations are proposed to calculate the local convection thermal resistance in the buoyancy strengthening and buoyancy deterioration region, respectively.