EFFECTS OF INTERACTIONS BETWEEN ADJOINING ROWS OF CIRCULAR, FREE-SURFACE JETS ON LOCAL HEAT-TRANSFER FROM THE IMPINGEMENT SURFACE

Experiments have been conducted to obtain single-phase local heat tran sfer coefficient distributions associated with impingement of one or t wo rows of circular, free-surface water jets on a constant heat flux s urface. The nozzle diameter, the centerline-to-centerline distance bet ween nozzles in a row, and the nozzle-to-heater separation distance we re fixed at 4.9, 6.3, and 89.7 mm, respectively. Two row-to-row separa tions (81 and 51 mm) were considered, and nozzle discharge Reynolds nu mbers were varied over the range from 16,800 to 30,400. The interactio n zone created by opposing wall jets from adjacent rows is characteriz ed by an upwelling of spent flow (an interaction fountain) for which l ocal coefficients can approach those of the impingement zones. Interac tions between wall jets associated with nozzles in one row can create sprays that impact the adjoining row with sufficient momentum to induc e a dominant/subordinate row behavior. In this case the interaction zo ne is juxtaposed with the subordinate row, and local coefficients in t he impingement and wall jet regions of the affected row may be signifi cantly enhanced. This result contrasts with the deleterious effects of crossflow reported for submerged jets throughout the literature. Spra y-induced enhancements, as well as interaction zone maxima, increase w ith decreasing row-to-row pitch and with increasing Reynolds number.