Micro-Scale Nozzled Jet Heat Transfer Distributions and Flow Field Entrainment Effects Directly on Die

Abstract

The heat transfer distributions and associated flow field characteristics of impinging jets have been studied extensively, but mostly for submerged jet conditions on the hot target wall in confined channels. A review of the literature reveals that fewer studies have been expended for non-submerged single phase jets in confined channels. In this research, a total of 64 distinct CFD RANS simulations of turbulently impinging jets issued from a single circular nozzle and accelerated under an orifice plate comprising twenty tapered micro-scaled nozzles in confined channels at different nozzle to wall separation (1 ≤z/d ≤ 16) distances are examined using Icepak and Fluent - commercial finite-volume solvers to extract intricate details of impinging flow fields on a hot silicon wall. An overall heat transfer coefficient to the order of 170,000 W/m2 °K has been observed on the surface of the silicon using this multiple micro-jet impingement setup. The dielectric fluid jet impinging on a wall is a high power density bare die silicon wall dissipating a non-uniform power of 95 Watts and the heat flux power density is very high in certain regions of the die. Flow field simulations predict recirculating toroidal patterns for each impinging micro-jet on the die, entraining near the outflow which is a behavior that is consistent and concurring with the characteristics of confined flow fields. Large Eddy Simulations are used to predict the flow-field turbulent characteristics of a single circular jet impinging directly on the silicon wall for four significant cases with varying (0.5 ≤; z/d ≤ 2) distances at a Reynolds of 20,000 issued from main nozzle reveal intricate features of flow field distributions including entrainment effects on the bare die hot silicon. Results of flow entrainment, surface temperatures, and heat transfer rates along with average Nusselt numbers at the impinging silicon wall are presented for all the CFD simulations cases collated.