HEAT-TRANSFER IN COUNTERSWIRLED COAXIAL JET MIXING

Convective heat transfer data are presented for the mixing of two coun terswirled coaxial jets confined by a constant-diameter tube. The inne r jet Reynolds number was 3 x 10(4), its swirl number was 1, and its d iameter was approximately twice the annular gap dimension. Annular jet swirl numbers varied from 0 to 1.2. Annular now rates were characteri zed by a ratio of annular-to-inner jet axial momentum (denoted by MFR) , which was varied from 0 to 8.2. Plots of local Nusselt numbers show minimums and maximums corresponding to the separation and reattachment points associated with wall-bounded recirculation cells. Local heat t ransfer coefficients were found to be a strong function of streamwise position and annular swirl number at low values of MFR, yet at high va lues of MFR, there is minimal streamwise variation in heat transfer co efficient as the mean flow largely dictates heat transfer rates. The p roduct of MFR and annular swirl number is shown to be a key parameter in describing heat transfer enhancement downstream of wall-bounded rec irculation cells. Several quantitative results should be useful to gas turbine combustor design efforts.