Splattering and Heat Transfer During Impingement of a Turbulent Liquid Jet

Abstract

Splattering and heat transfer due to impingement of an unsubmerged, fully turbulent liquid jet is investigated experimentally and analytically. Heat transfer measurements were made along a uniformly heated surface onto which a jet impacted, and a Phase Doppler Particle Analyzer was used to measure the size, velocity, and concentration of the droplets splattered after impingement. Splattering is found to occur in proportion to the magnitude of surface disturbances to the incoming jet, and it is observed to occur only within a certain radial range, rather than along the entire film surface. A nondimensional group developed from inviscid capillary disturbance analysis of the circular jet successfully scales the splattering data, yielding predictive results for the onset of splattering and for the mass splattered. A momentum integral analysis incorporating the splattering results is used to formulate a prediction of local Nusselt number. Both the prediction and the experimental data reveal that the Nusselt number is enhanced for radial locations immediately following splattering, but falls below the nonsplattering Nusselt number at larger radii. The turbulent heat transfer enhancement upstream of splattering is also characterized.

Radial heat transfer behavior of impinging submerged circular jets

“…Independent of jet Reynolds number and jet type, the present data agree well with the previous experimental results of Refs. [6,7]. Comparisons show that very small differences are perceived for a submerged jet of 0.28% and a free surface jet of 4.33% and these differences are mainly attributed to different initial turbulence intensity at the nozzle exit [10] and radial velocity gradient between them, respectively.…”

“…For comparison, Fig. 1(a) also presents the experimental data of Ma et al [6] for an R113 submerged jet and Lienhard et al [7] for a water free surface jet. As illustrated by squares in the figure, stagnation point heat transfer in this study was enhanced slightly.…”

Delay of wetting propagation during jet impingement quenching for a high temperature surface

“…Heat flux, temperature, and the flow field by flow visualization were studied extensively in those investigations. Some other studies [8][9][10] also performed on free surface jet impingement cooling, have given valuable background information on single phase convection heat transfer. Wetting delay is an important phenomena in jet impingement quenching.…”

Observations of the Character of a Water Jet

“…Possibilities for extending these experiments include the use of different nozzle diameters, different fluids, and non-normal wall impingements. Another interesting aspect of the wall impingement transition experiment, not discussed here, is the opportunity to explore the character of the wall impingement itself as exemplified by the heat transfer studies of Lienhard et al [5]. …”