Local heat/mass transfer phenomena in rotating passage, part 1: Smooth passage

Local heat/mass transfer and flow characteristics in a rotating smooth passage are investigated. Mass transfer experiments are performed to obtain detailed heat/mass transfer coefficients on the leading and trailing surfaces. The passage is modeled after an internal coolant channel of modern gas turbine blades and contains a 180-deg turn. The aspect ratio of the passage is 0.5. The rotational and flow condition is adjusted to five rotation numbers from 0.0 to 0.20 and a fixed Reynolds number of 10 × 10³, respectively. To verify the heat/mass transfer augmentation, internal flow structures are calculated for the same conditions using a commercial code. For the stationary case, the geometry of the 180-deg turn dominantly determines heat/mass transfer and flow characteristics in the turn and in the upstream region of the second pass by generating a pair of counter-rotating vortices. For the rotating case, however, only a single vortex cell is produced close to the leading surface in the turning region because the Coriolis force deflects the radial flow. It subsequently results in heat/mass transfer discrepancy on the leading and trailing surfaces and changes heat/mass transfer characteristics in the second pass significantly. The estimation of the centrifugal buoyancy force effect is conducted, and the results of the mass transfer experiment agree well with those of the heat transfer experiment for low-buoyancy parameters such as a Rayleigh number of 8.8 × 10⁷ and a density ratio Δρ/ρ of 0.043.