SHROUD HEAT-TRANSFER MEASUREMENTS FROM A ROTATING CAVITY WITH AN AXIAL THROUGHFLOW OF AIR

The paper discusses measurements of heat transfer obtained from the in side surface of the peripheral shroud. The experiments were carried ou t on a rotating cavity, comprising two 0.985-m-dia disks, separated by an axial gap of 0.065 m and bounded at the circumference by a carbon fiber shroud. Tests were conducted with a heated shroud and either unh eated or heated disks. When heated, the disks had the same temperature level and surface temperature distribution. Two different temperature distributions were tested; the surface temperature either increased, or decreased with radius. The effects of disk, shroud, and air tempera ture levels were also studied. Tests were carried out for the range of axial throughflow rates and speeds: 0.0025 less-than-or-equal-to m le ss-than-or-equal-to 0.2 kg/s and 12.5 less-than-or-equal-to OMEGA less -than-or-equal-to 125 rad/s, respectively. Measurements were also made of the temperature of the air inside the cavity. The shroud Nusselt n umbers are found to depend on a Grashof number, which is defined using the centripetal acceleration. Providing the correct reference tempera ture is used, the measured Nusselt numbers also show similarity to tho se predicted by an established correlation for a horizontal plate in a ir. The heat transfer from the shroud is only weakly affected by the d isk surface temperature distribution and temperature level. The heat t ransfer from the shroud appears to be affected by the Rossby number. A significant enhancement to the rotationally induced free convection o ccurs in the regions 2 less-than-or-equal-to Ro less-than-or-equal-to 4 and Ro greater-than-or-equal-to 20. The first of these corresponds t o a region where vortex breakdown has been observed. In the second reg ion, the Rossby number may be sufficiently large for the central throu ghflow to affect the shroud heat transfer directly. Heating the shroud does not appear to affect the heat transfer from the disks significan tly.