Mass/heat transfer in dimpled two-pass coolant passages with rotation

Mass/heat transfer measurements are made in dimpled (hemispherical depressions) inlet and outlet coolant flow passages using the naphthalene sublimation method. The leading and trailing surfaces are dimpled, while the side walls are kept smooth. Measurements are made at a Reynolds number of 21,000 and for Rotation numbers of 0 and 0.2. The measurements indicate that dimples enhance surface mass/heat transfer. This enhancement is stronger in the inlet passage than in the outlet passage. Peak mass/heat transfer occurs immediately downstream of the dimples, while the minimum mass/heat transfer occurs in the dimple region itself. Higher mass/heat transfer is also observed along the lateral edges of the dimple. The location of the Sherwood number peaks suggest the existence of streamwise vortical structures generated from the leading and lateral edges of the dimples.