Effect of successively variable orientation of piezoelectric fan on heat transfer performance of cylindrical surface

The present study is numerically investigated the effects of successively various location and tilted angle of piezoelectric fan on the heat transfer performance of a uniform heated cylindrical surface by piezoelectric fan. Since the blade vibrates periodically, three dimensional laminar, pseudo-steady-state natural convection flow is assumed. The discrete structure of fluid domain adopts the dynamic meshing scheme to simulate the three-dimensional time-varying geometries of the vibrating blade. Thus, numerical analysis can define precisely the motion of piezoelectric fan along the length of the blade at each time step. The numerical results infer that the heat transfer augmentation by piezoelectric fan is mainly contributed with two factors: One is the scale of produced vortex region by the vibrated blade; the other is the direction of induced jet-like stream impinging to the heat transfer surface. To obtain the optimal heat transfer augmentation, a total of 12 piezoelectric fans with various blade orientations from the bottom section of the cylinder to the flat top surface are evaluated. The cases of P4 ( y / H = 0.625) and P2 ( y / H = 0.375) provide the best heat transfer augmentation ratios 1.92 and 1.41 for the fan tip dimensionless amplitude equal to 2 and 1, respectively. However, the worst heat transfer performances occur at the positions P12 and P11 for dimensionless amplitude equal to 2 and 1.