Heat transfer due to turbulent annular impinging jet with a bullet extension at the end of the inner blockage rod

Abstract

The flow and thermal behavior of a turbulent annular jet impinging on a flat plane are numerically investigated to examine the effect of extending the inner rod of the annulus beyond the exit plane of the jet. The Fluent commercial code is used for conducting the computations employing the k-ε (Realizable) turbulence model. Three different shapes of the extended annular rod end, viz., cylindrical, conical, and semi-ellipsoidal, are considered. The length of the extended part is taken as 0.5, 1, and 2 times the outer jet diameter. The extension of the annular rod end modifies the flow structure and eliminates the recirculation region at the exit of the annular jet, which noticeably affects the impingement plane heat transfer. Depending on the shape and length of the bullet, the bullet extensions affect the heat transfer differently. Compared to the case without the extension, the conical extension diminishes the heat transfer, the ellipsoidal extension moderately increases the heat transfer, while the cylindrical extension enhances the heat transfer for a larger bullet length (≥1). Also, the location and the magnitude of the peak Nusselt number at the hot impingement surface vary as the shape and length of the extension change.

Keywords

• Jet impingement
• Impinging jet heat transfer
• Annular jet
• Bullet extension of the blockage rod
• Realizable k-ε model