Study on the heat transfer deterioration of supercritical nitrogen in a vertical tube using a pseudo-boiling model

•A pseudo-boiling model is used to study HTD of supercritical nitrogen.•The accumulation of pseudo-vapor film near the wall weakens the heat transfer.•CHF is observed in the simulation and verified by experimental data.•The effects of buoyancy and thermal acceleration are used to study HTD. Heat transfer performance of supercritical cryogenic fluid plays a pivotal role in hypersonic vehicle engine cooling and cryogenic fuel vaporization. Heat transfer becomes highly complicated due to the complex physical properties of supercritical fluids (SFs). Heat transfer deterioration (HTD) occurs in SFs similar to the departure from nucleate boiling of subcritical fluids, resulting in a sudden temperature rise. In this study, a pseudo-boiling model is used to investigate HTD of supercritical nitrogen (SCN2) in vertical tubes. The distribution of the pseudo-vapor phase is analyzed to understand the heat transfer behavior in both normal heat transfer (NHT) and HTD regions. Simulation results show that the accumulated pseudo-vapor film weakens the heat transfer from the wall to the mainstream region, resulting in HTD. The critical heat flux (CHF) of SCN2 is observed in the simulation and verified by experimental data. Further investigation into buoyancy and thermal acceleration elucidates the absence of CHF under large mass flux conditions. The forced convection of high turbulent kinetic energy hinders the accumulation of pseudo-vapor film, resulting in NHT under large mass flux conditions. This paper provides a new approach and insights to investigate HTD of SFs using the pseudo-boiling model.