Numerical study on natural convection heat transfer of supercritical CO2 in an infinite space

A numerical study of natural convection heat transfer from horizontal heating wire to supercritical carbon dioxide (sCO2) in an infinite space was performed. The qw ∼ ∆T curves of sCO2 natural convection heat transfer were calculated in a wide range of parameters, where initial bulk temperature (Tib) and operating pressure (P) varied in the range: 275 K < Tib < 345 K and 7.5 MPa < P < 11 MPa, respectively. Then, we reported from the viewpoint of pseudo-phase transition for supercritical fluids, the characteristics and mechanism of sCO2 natural convection heat transfer were revealed through comparing with qw ∼ ∆T curve of subcritical pool boiling. The similarity between film-like heat transfer at Tw > Tpc for supercritical pressure and film boiling at Tw > Tsat for subcritical pressure was demonstrated. The influence of operating parameters such as Tw, Tib, and P on sCO2 heat transfer was also discussed. For supercritical film-like heat transfer, thermal resistance of film-like which reflects the effect of gas-like film thickness and its thermal conductivity on heat transfer was proposed. Expectedly, the variation of thermal resistance explained successfully the difference of sCO2 heat transfer under different operating parameters. The investigation is of paramount importance in comprehension of sCO2 heat transfer mechanism for designing heat exchanger component in the advanced sCO2 application. © 2024