HELP: jet impingement heat transfer
 

Hello,

I'm trying to make a simulation of a cooling system based on air jet impingement; from a prior assessment, air velocity distributions show good accordance with experimental data but temperatures appear overestimated. In fact, the cold air jet is heated by hot ambient air before it hits the target surface I need to cool; this effect was expected, but I'm very uncertain on its magnitude evaluated by CFD (I 've found that a 4000 ft/min air stream from a circular nozzle with a 0.16 inches diameter increases its temperature from 291 K to 313 K at a distance of 12 inches from its inlet, passing through hot air at 323 K). Since this effect strongly reduces the achievable cooling performance, I would like to have a reference to understand if the obtained results are meaningful.

In particular, I'd like to know any setting which could help to correctly investigate this problem with Fluent 6.3 (e.g. best turbolence model).
Any suggestion will be appreciated.

Regards.