THE EFFECT OF A SWIRLED ANNULAR JET ON CONVECTIVE HEAT-TRANSFER IN CONFINED COAXIAL JET MIXING

Convective heat transfer data from a confining tube to coaxial, counte r-swirled jets are presented. The inner jet diameter was approximately twice the annular gap dimension. The inner jet swirl number varied fr om zero to 1.2 for a Reynolds number of 60 000. The ratio of annular-t o-inner jet Reynolds numbers varied from 0. 10 to 0.95. For those case s where the annular jet was swirled, its swirl number was approximatel y 1.3. Plots of local Nusselt numbers exhibit minima and maxima corres ponding to the separation and reattachment locations associated with w all-bounded recirculation regions. As inner jet swirl strength was inc reased, the peak Nusselt number was shifted upstream. As the annular f low rate was increased, the near wall recirculation zones were stretch ed and shifted downstream until at sufficiently high annular flow rate s, the zones were no longer in evidence from the heat transfer data. F or low annular flow rates, the addition of swirl to the annular jet di d not ensure an increase in convective heat transfer.