Analysis and prediction of heat transfer deterioration of supercritical pressure cryogenic methane in a vertical tube

Abstract

Developing a compact vaporizer with high thermal efficiency is of great significance to the storage and usage of Liquid Natural Gas (LNG). Numerical simulations were performed to investigate the flow and heat transfer characteristics of supercritical pressure methane in a vertical tube, and primary focus was to reveal the mechanism of two-peak wall temperatures occurrence. Six turbulent models have been confronted with experimental data, and the Renormalization Group (RNG) k-ε model is adopted. When Heat Transfer Deterioration (HTD) occurs, two-peak wall temperatures appear in the upward flow with high mass flux. The phenomenon of two-peak wall temperatures were explained in detail based on radial distributions of velocity and turbulent kinetic energy at different axial positions. The “M”-shape velocity distribution promotes the generation of turbulence in the core region. The reversal of radial flow direction enhances the mixing between hot and cold fluids. A new criterion was proposed for predicting the critical heat flux which causes the onset of HTD in supercritical pressure methane.