Numerical Study of Heat Transfer and Fluid Flow in Multiple turbulent Impinging Jets

ABSTRACT

Impingement flows have been studied extensively for various geometries and configurations, but because of the complexity of the turbulent flow and its strong dependence on the geometry of the flow, further investigation is required to identify the suitable model for specific cases. This paper presents a study of various k–E turbulence models in order to identify the best model for an array of multiple confined impinging slot jets, with exhaust ports in the confinement surface located symmetrically between adjacent jets. Such a configuration is used in a novel drum dryer for black liquor. The “High Reynolds number” turbulence models including the standard k–E model fail to predict heat transfer to impingement surface accurately although they do predict the flow field reasonably well. On the other hand, the “Low Reynolds number” models yield considerably better results for both fluid flow and heat transfer. All computed results are compared with experimental data reponed in the literature. This work was motivated by the need to select an optimal multiple impinging jet configuration for a novel drum dryer for Kraft black liquor. It is also pertinent to impingement dryers for paper, films, textiles etc.

Keywords and Phrases:

• drum dryer
• high–Reynolds model
• impinging jet
• k–Emodel
• low–Reynolds model
• Nusselt number
• superheated steamet
• turbulent flow
• wall function