Numerical Investigation into the Natural Convection of Cryogenic Supercritical Helium in a Spherical Enclosure

As an ideal pressurized gas, helium, especially supercritical helium, has been widely used in the pressurization system of various launch vehicles and spacecraft. This work mainly focuses on the natural convection of cryogenic supercritical helium in a spherical enclosure. Firstly, a three-dimensional numerical model is established and verified with experimental data. Then, the effects of inflation pressure and heating power on the flow and heat transfer characteristics are simulated. At the same time, the relationship between the Rayleigh number and Nusselt number is studied in detail. Finally, an improved natural convection heat transfer correlation modified by introducing the density ratio is obtained. The results show that the increase of the inflation pressure in the cavity is helpful to enhance the natural convection heat transfer of the cryogenic supercritical helium, and the temperature distribution in the cavity tends to be more uniform when the inflation pressure in the cavity increases. As to the improved natural convection heat transfer correlation, the average error between the simulation results and the calculated values is approximately 8%, which can better describe the natural convection heat transfer of cryogenic supercritical helium in the spherical enclosure.