Investigations of jet to wall spacing effects on heat transfer distributions and flow field characteristics

Abstract

Convective heat transfer by impinging jets is known to yield higher local and area averaged heat transfer coefficients on the hot target surface. Therefore, jet mpingement techniques have been employed historically for turbine blade cooling, external wall of combustors and other high heat flux industrial applications not just because of their efficient heat transport capabilities but also for their ability to dissipate extremely large heat fluxes rapidly, triggering recent efforts to focus the use of liquid impinging jets on mainstream electronic cooling applications. Detailed heat transfer distributions of multiple micro-scaled jets orthogonally impinging on the newlinesurface of a high-power density hot silicon wall is presented. The jets issued from five different impingement configurations are studied - (a) single circular nozzle, (b) dual circular nozzles (c) single inlet system with multiple circular nozzles underneath (d) single inlet system with multiple tapered nozzles underneath and (e) dual inlets system with multiple tapered nozzles underneath to accelerate the flow. Jets are issued from the inlet(s) at four different Reynolds numbers {Re = 8000, 12,000, newline16,000, 20,000}. The spacing between the conical (or tapered) nozzle jets and the bare die silicon wall (z/d) is adjusted to be 4, 8, 12, and 16 jet nozzle diameters away from impinging influence. The impact of varying the nozzle to the silicon wall (z/d) standoff spacing up to 16 nozzle jet diameters and its effects on the junction temperature and the flow fields on the surface of the silicon, specifically the entrainment pattern on the silicon surface, is presented newline newline