Local Heat Transfer Coefficients Under an Axisymmetric, Single-Phase Liquid Jet

Abstract

The purpose of this investigation was to characterize local heat transfer coefficients for round, single-phase free liquid jets impinging normally against a flat uniform heat flux surface. The problem parameters investigated were jet Reynolds number Re, nozzle-to-plate spacing z, and jet diameter d. A region of near-constant Nusselt number was observed for the region bounded by 0≤r/d≤0.75, where r is the radial distance from the impingement point. The local Nusselt number profiles exhibited a sharp drop for r/d > 0.75, followed by an inflection and a slower decrease there-after. Increasing the nozzle-to-plate spacing generally decreased the heat transfer slightly. The local Nusselt number characteristics were found to be dependent on nozzle diameter. This was explained by the influence of the free-stream velocity gradient on local heat transfer, as predicted in the classical analysis of infinite jet stagnation flow and heat transfer. Correlations for local and average Nusselt numbers reveal an approximate Nusselt number dependence on Re1/3.