Numerical analysis on heat transfer of supercritical pressure LNG in serpentine tube

Abstract

In this paper, a numerical model is built considering the structure and operation characteristics of typical submerged combustion vaporizer. Based on this model, the flow and thermal performance of LNG in serpentine tube under supercritical pressure are predicted numerically, the impacts of operation parameters on thermal performance are analyzed, and 8 heat transfer correlations are introduced to evaluate the heat transfer of LNG in serpentine tube, which are compared with that of the simulation results. The simulation results reveal that there is a significant non-uniformity of heat transfer along the serpentine tube, especially in the bend sections, where the turbulent structure is rebuilt on account of the secondary flow and reverse flow resulting from the interaction of thermophysical properties and geometry configuration, leading to the remarkable variation on temperature and heat transfer coefficient. The pressure and heat flux play important roles on thermal performance of LNG under supercritical pressure in serpentine tube especially close to the pseudo-critical region. The simulation data is compared with that of 8 empirical heat transfer correlations, and the contrast results indicate that most of the correlations have just the similar trend with the calculation one, only Yamagata’s correlation proximately conforms with the calculation results in large specific heat region, the reason for the non-conformance is that the correlations are suitable for straight tube without considering the effects caused by geometric configuration of bend region and reverse flow on heat transfer, so an adaptive correlation of serpentine tube is expected for the future studies.