LOCAL CONVECTIVE MASS-TRANSFER ON CIRCULAR-CYLINDER WITH TRANSVERSE ANNULAR FINS IN CROSS-FLOW

An experimental study was made of local mass transfer from a circular cylinder, which is situated between two annular fins in a crossflow. L ow turbulence-intensity wind tunnel experiments were conducted over mo derate Reynolds numbers, 33 000 < Re-d < 80 000. Velocity measurements were analyzed to examine the characteristics of the boundary layer, w hich is developed on the flat annular fin. The naphthalene sublimation technique was employed to measure the local convective mass transfer around the circular cylinder. The ratio of the axial gap distance betw een two axial fins (L) to the radial protrusion length of the annular fin (H) was an important experimental parameter, and its range was 0 < L/H < 0.40. The impact of horseshoe vortices on local mass transfer w as scrutinized. For a small gap distance (L/H = 0.05), naphthalene sub limation is intense in the front portion of the cylinder, especially n ear the separation region. When the gap distance is moderate (L/H = 0. 15), the overall character of sublimation shows a more organized patte rn. The influence of horseshoe vortices is substantial. For a large ga p distance (L/H = 0.40), a dominant role of horseshoe vortices near th e corner junction is discernible.