Forced convective heat transfer on a horizontal circular cylinder due to multiple impinging circular jets

• Consideration of bank of impinging circular jets with high d/D ratio.
• Results based on more than 100 computational fluid dynamics cases.
• For largest jets, heat transfer decreases with movement away from cylinder axis.
• For smaller jet, heat transfer increases with movement away from cylinder.
• Correlation concisely quantifies heat transfer for parametric range considered.

A computational study is undertaken to investigate convective heat transfer on a horizontal cylinder due to a bank of vertically oriented circular jets. The importance of this study stems from the real-world application of convective cooling of rotary cement kilns by the use of large axial fans. A computational model is developed which considers one spatially-periodic section of the domain, and solutions of the conservation equations combined with an appropriate two-equation turbulence model are obtained using the commercial software Fluent™. The computational model is validated by a comparison to previous studies of a single circular jet impinging on a cylinder. A parametric study is presented which considers the impact on average heat transfer due to: jet-to-cylinder spacing (y/d), axial jet spacing (z/d), jet-to-cylinder diameter ratio (d/D), jet offset from the axial centerline (x/d), and jet Reynolds number. Results of the parametric study show that for jet-to-cylinder ratios of d/D ⩾ 0.23, that movement away from the cylinder axis, increased axial spacing and lateral offset all lead to degradation of heat transfer from the cylinder. For d/D = 0.15, similar degradation occurs, but in part of the parametric space studied, increased distance from the cylinder and lateral offset leads to enhancements of the heat transfer. The complete set of results is presented as a correlation wherein the influence of all parameters studied are included as power-law corrections to the average Nusselt number.