The Microelectronics Cooling Impact and Comparison of 2D and 3D Unsteady Effects of a Pair of Opposed Confined Angled Impinging Air Jets

Abstract

The unsteady laminar flow and heat transfer characteristics for a pair of angled confined impinging air jets centered in a channel were studied numerically. The time-averaged heat transfer coefficient for a pair of heat sources centered in the channel was determined, as well as the oscillating jet frequency for the unsteady cases. The present study is a continuation of the authors’ previous investigations, identifying the similarities and differences arising from the expansion to the third dimension. It examines the interaction between the angled jets and the associated impact on the cooling of the heat sources placed on the board at a jet Reynolds number of 100 and 600. Maintaining the inlet jet width, W, at 1 cm, as in the previous studied cases, the interaction between the 45° angled jets leads to the formation of unsteady symmetrical jets that impinge on the two heat sources placed on the board at a Reynolds number of 100. A second case investigates the hydrodynamic interaction between the 45° angled jets at a Reynolds number of 600. In this case the jets interact and form a region of unsteady shear causing the jets to sweep the target board and the heated components placed on it. The nature of this unsteadiness depends on the proximity of the jet inlets, the channel dimensions and the jet Reynolds number. The jet unsteadiness causes the stagnation point locations to sweep back and forth over the impingement region causing the jets to “wash” a larger surface area on the target wall. The relevant trends for the 2D and 3D jet hydrodynamic and thermal fields are further documented by comparing the field plots and the Nusselt numbers on the target walls for the cases under evaluation. Although similar in nature, the unsteady 3D opposite jets produce results that deviate from the 2D unsteady opposite jets. The complex vortex patterns resulting from the jet interaction at various jet inlet locations, as well as the velocity, vorticity and temperature fields for both 2D and 3D cases are thoroughly evaluated.