Flow and heat transfer features of an impinging annular jet

Abstract

This paper presents the results of the comprehensive experimental study of flow and heat transfer of the annular impinging jets. The flow fields were studied using the PIV. To measure heat transfer, the miniature gradient sensors of the heat flux were used under the thermal boundary conditions Tw = const. The experimental conditions were as follows: basic round nozzle had diameter d0 = 17.8 mm; ring nozzles have the same outer diameter and different inner diameters d2 = 12.7 and 9.1 mm. Air was the working medium. The distance between the nozzle and wall (S/d0 = 2, 4 and 6) and air flow rate (Reynolds number for the round nozzle was varied within Re = U0d0/ν0 = 1.2 × 104–3.3 × 104) were varied in experiments. Data obtained for the annular and round jets were compared at the same mass air flow rates. It is shown that replacement of the round nozzle by the annular nozzle leads to an increase in intensity of velocity fluctuations in the axial zone of the jet and heat transfer enhancement in the frontal zone of the obstacle. At that, the value of intensification effect depends on the parameters, characterizing the system.