Heat transfer of rotating rectangular duct with compound scaled roughness and V-ribs at high rotation numbers

Thermal performance of rotating two-pass ribbed square channel with wavy sidewalls

“…Inferring the buoyancy mechanisms in the rotating channels from the mixed free convection driven by earth gravity, the buoyancy effects in the rotating ribbed channels with radially outward and inward flows were previously found analogical to the mixed convection in the static channels with counter and parallel flows respectively [1,2,30]. By normalizing the Nu data collected from the rotating surfaces to the similar non-rotating references (Nu 0 ), it is consistently found that the degrees of Bu effects on Nu/Nu 0 ratios are systematically weakened as Ro increases [8,9,11,12,[15][16][17][18][19][20][21][22][27][28][29]; hence ensuring the interdependent Ro and Bu impacts on heat transfer performances in rotating channels.…”

“…Heat transfer performances of the rotating channels enhanced by ribs with square [1][2][3][4][5][6], rectangular [7][8][9], circular [10], trapezoidal [11], parallelogram [12] and triangular [13] shapes and by concave/convex dimples [14,15], pin-fins [16,17], scaled imprints [18] and wavy endwalls [19] were examined. With compound HTE measures, the endwall HTE properties for the rotating channels using V-ribs with scaled imprints [20], angled ribs with dimples [21] and angled rib-lands with pin-fins [22] are recently studied. In general, the Coriolis force effects induce the sectional vortices with the turbulence production to be respectively promoted and suppressed over the unstable and stable walls [23].…”

“…Such isolated Coriolis force effects generate the peripheral heat transfer decays from the unstable toward the stable walls and are reconfirmed by the heat transfer data converted from the mass transfer test results [24] with diminished buoyancy interaction. Acting by the Coriolis force effects in isolation by increasing Ro, the heat transfer rates over the unstable wall keep increasing from the stationary channel levels; whereas the stable counterparts are initially reduced from the stationary references but followed by the subsequent heat transfer recoveries after Ro exceeding the critical values [1][2][3][4][5][6][8][9][11][12][15][16][17][18][19][20][21][22]. As the near-wall flow structures are considerably affected by the presence of the various types of HTE devices, the Bu impacts on endwall Nu vary with the thermal boundary conditions [25] and the HTE devices [26].…”

Heat transfer of a radially rotating furrowed channel with two opposite skewed sinusoidal wavy walls

“…Whilst the experimental method for measuring the full Nu scans over the rotating surface with the buoyancy effect considered is under investigation, the search for HTE surfaces for turbine rotor blade cooling develops at a good pace. In this respect, the HTE effects attributed to the deepened scales [24] and the compound roughness of V-ribs and scales [25] were previously investigated.…”

“…Although their considerable HTE effects in the rotating channel were realized [24,25], the pressure drop penalties were accordingly generated due to the enhanced turbulences, friction drags and flow separations [26]. As the wavy channels facilitate considerable HTE effects with relatively low pressure drops, the wavy channels propose their potential cooling applications to turbine rotor blades.…”