High-Rayleigh-number convection of pressurized gases in a horizontal enclosure

High-pressure gases are used to study high-Rayleigh-number Rayleigh-Benard convection in cylindrical horizontal enclosures. The Nusselt-Rayleigh heat transfer relationship is investigated for 1 x 10(9) < Ra < 1.7 x 10(12). Schlieren video images of the flow field are recorded through optical viewports in the pressure vessel. The data set is well correlated by Nu = 0.071Ra (0.328). The schlieren results confirm the existence of a large-scale flow that periodically interrupts the ascending and descending plumes. The intensity of both the plumes and the large-scale flow increases with Rayleigh number.