Orifice and impingement flow fields in confined jet impingement

The flow fields in the orifice and the confinement region of a normally impinging, axisymmetric, confined, and submerged liquid jet were computationally investigated. Numerical predictions were made for orifice diameters of 3.18 and 6.35 mm at several orifice-to-target plate spacings, with turbulent jet Reynolds number ranging from 8500 to 23,000. The commercial finite-volume code FLUENT was used to solve the flow fields using a modified k-epsilon model based on renormalization group theory. The predicted characteristics of the separation region at the entrance of the orifice agree with experiments in the literature. The pressure drop across the orifice was predicted to within 5 percent of proposed empirical correlations based on published experimental data. The computed flow patterns in the confinement region of the impinging jet were in good qualitative agreement with flow visualizations; however, a secondary recirculation zone observed in experiments was not predicted by the models. The results presented for the flow (and pressure drop) in the orifice, as well as that in the confined outflow region, influence heat transfer on the impingement surface and are important considerations in electronics packaging design.