On Numerical Investigation of Non-dimensional Constant Representing the Occurrence of Secondary Peaks in the Nusselt Distribution Curves

The cooling of the heat sinks in electronic packaging system is generally achieved through the impingement of air jet. Here, the characteristic study of heat dissipation rate is done with by numerically evaluating the radial distribution of Nusselt magnitudes. These profiles are reported for various injection and geometric parameters in the present research. A very contagious look towards these profiles shows the occurrence of secondary and localized rise. However these local rises are observed provided the Nusselt profiles are accurately predicted. To achieve this, the present research takes an effort in numerically simulating a computational domain, analogous to actual experimental conditions. For this, an appropriate turbulence model is selected with its validation with present experimental result, in order to accurately predict the development of flow regime and necessary heat interactions. The computational simulations at lower nozzle-target spacing and higher impinging velocity revels the occurrence of secondary rise in Nusselt profiles. No doubt, the occurrence of such secondary peaks increases the magnitude of area average heat transfer rate. Hence this is of great concerned. A very less light is observed in determining the exact cause and the intervening range for the occurrence of such peaks in the profiles. Looking into which, the current research focuses on the determination of the critical constant and its magnitude within which these peaks exists in the profile. The non dimensional constant representing the critical magnitude is defined as a ratio of diameter based Reynolds number with nozzle - target spacing (Z/d). While the corresponding critical magnitude was approximately investigated to be 6000. However, the mapping of velocity contours at different values of this non-dimensional constant enables the physical understanding of the transition region occurring in the flow profile. A very judicious look towards these contours conveys the occurrence of turbulence flow in near wall region to be responsible for the secondary rise in heat transfer rate.