TURBULENCE DISSIPATION IN A FREE-SURFACE JET OF WATER AND ITS EFFECT ON LOCAL IMPINGEMENT HEAT-TRANSFER FROM A HEATED SURFACE .2. LOCAL HEAT-TRANSFER

This paper presents local heat transfer data for a planar, free-surfac e jet of water impinging normal on a uniformly heated surface. The hyd rodynamic conditions of the jet were altered through the use of differ ent nozzle types (parallel-plate and converging) and flow manipulators (wire grid and screens) to investigate the relationship between jet t urbulence and local impingement heat transfer. The flow structures for each of the various nozzle conditions are reported in a companion pap er (Wolf et al., 1995), and results are used in this paper to interpre t their effect on local heat transfer. In addition to qualitative inte rpretations, correlations are developed for both the onset of transiti on to turbulence and the dimensionless convection coefficient at the s tagnation point. Higher levels of jet turbulence are shown to induce t ransition to a turbulent boundary layer at smaller streamwise distance s from the stagnation point. The effect of streamwise turbulence inten sity on the convection coefficient is shown to scale approximately as the one-quarter power.