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

TLDR: In this article, the authors characterized local heat transfer coefficients for round, single-phase free liquid jets impinging normally against a flat uniform heat flux surface, and found that the local Nusselt number characteristics were dependent on nozzle diameter.

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 problems 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 {le} r/d {le} 0.75, where is the radical 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 shower decrease thereafter. 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 Re{sup 1,3}.